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eT Pe ee
The Automobile
Storage Battery.
Its Care and Repair
Cee ee 98 eee 8h © 1 = Boe
American Bureau of Engineering, Inc. 1018-1024 So. Wabash Avenue, Chicago, Iil., U. S. A.
TE TEE Te SCE Se Te Pe Ue ee DT TE TT TUE PU Ge Te SRD GUST RUD RUD PEP PEGE Te PU UU
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Copyright, 1918, by the
American Bureau of Engineering, Ine.
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PREFIX.
Many books have been written on Storage Batteries used in stationary work, as in electric power stations. These books cover the subject thoroughly. The storage battery, as used on the modern gasoline car, however, is subjected to service which is radically different from that of the battery in stationary work. It is true that the chemical actions are the same in all lead-acid storage batteries, but the design, construction, and operation of the starting and lighting battery aré unique, and require a special description.
This book therefore refers only to the lead-acid type of starting and lighting battery used on the modern gasoline automobile. It is divided into two sections. The first section covers the, théory, design, operating conditions, and care of the battery. The Wil- lard Battery Company, the Electric Storage Battery Company, and the U. S. Light and Heat Corporation kindly contributed most of the illustrations for this section.
The second section deals with the actual work of repairing and rebuilding the storage battery. Much of the material for the text in this section was furnished by Mr. H. E. Peers of Topeka, Kansas, who also supplied: most of the photographs from which the illustrations were made for this section. Mr. Peers is a practical battery man, and has been engaged in actually repair- ing and rebuilding batteries for many years.
The second section will be especially valuable to the battery repairman. All the instructions given have been in actual use for years, and represent the accumulated experiences of one of the most up-to-date battery repair shops in the United States.
Information concerning any of the tools and appliances may be obtained from the American Bureau of Engineering.
O. A. WITTE, Chief Engineer, American Bureau of Engineering.
CONTENTS |
SECTION 1.
Chapter Page 1. INTRODUCTORY 2.2... .. cece ec cee cee ee cece eee neee. 1 2. BATTERIES IN GENERAL........ 0... cL ec ccc cece eee 5 3. CHEMICAL ACTIONS WHICH PRCDUCE ELECTRICITY......... 11 4. HOW CHEMICAL ACTIONS PRODUCE ELECTRICITY......... 17 5. LOSS OF CHARGE IN AN IDLE BATTERY..................... 26 6. THE DISCHARGE PHENOMENA................ 20 cece ee eee 2G 7. THE CHARGE PHENOMENA.......... 0... ccc cece ee ee eens 37 8. CAPACITY OF STORAGE BATTERIUS....................085.. 40 9. INTERNAL RESISTANCE .............. 0. cece ee eee 48
10. BATTERY DISEASES ........ 06. ccc ccc eee ee tenes 51
11. CONDITIONS OF OPERATION............. 0... cece eee ee eee 61
12. HOW TO TAKE CARE OF BATTERY ON THE CAR............ 68
13. MANUFACTURE OF STORAGE BATTERIES.................... 89
SECTION 2. 14, THE WORK SHOP. GENERAL INSTRUCTIONS............... 102
15.
16.
The Workshop. Shop Equipment. Special Work Bench. Shelving. Concerning Light. Charging Methods. Charging Equipment. Double Charging Bench. Motor-Generator Sets. Mercury Arc Rectifier. Electrolytic Rectifier. Discharge Board. Tools and Equipment. The Battery Steamer. The Battery Plate Press. Battery Turntable. The Burning Lead Mold. Tagging Bat- teries. Precautions to Be Taken by the Repairman. Lead Burn- ing. Saving the Sediment. Mixing Electrolyte.
ANALYSIS OF THE CONDITION OF THE BATTERY........... 162
What Is the Trouble? Cutout Adjustments. Battery Trouble Charts. Summary of Work to Be Done on the Battery. When May a Battery Be Left on the Car? When Should a Battery Be Removed from the Car? When Is It Unnecessary to Open the Battery? When Must a Battery Be Opened?
WORK ON THE BATTERY.......... 0... ccc cece ce ee ce ene ee eess 182
Charging Batteries Before Rebuilding. How to Open a Battery. What Must Be Done with the Opened Battery? When to Put in New Plates. When the Old Plates May Be Used Again. Separators. Freeing Shorts. Charging, Washing and Pressing.
Chapter
CONTENTS
Page
Burning on Plates. Reassembling the Elements. Repairing the Case. Putting in New Jars. Putting Elements in Jars. Fill- ing Jars with Electrolyte. Putting on the Covers. Sealing Compounds. Sealing the Battery. Burning in the Connecting Straps with Hydrogen and Oxygen Flame. Burning in the Con- necting Straps with Soldering Irons. Cleaning and Painting the
Case. Charging the Rebuilt Battery. Discharging and Testing.
17. SPECIAL INSTRUCTIONS ......... cee cee eee eeee
Willard Type S Batteries. Ex‘de Batteries.
U. S. L. Batteries.
18. CADMIUM TEST. STORING BATTERIES..... eccecceceeeeues
Prestolite Batteries.
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Section I
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BL BUBUE BRIBE
Theory and Practice
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The Automobile Storage Battery
CHAPTER i. INTRODUCTORY.
Gasoline and electricity have made possible the modern auto- mobile. Each has its work to do in the operation of the ear, and if either fails to perform its duties, the car cannot move. The action of the gasoline, and the mechanisms that control it are comparatively simple, and easily understood, because gasoline is something definite which we can see and feel, and which can be weighed, or measured in gallons. Electricity, on the other hand, is invisible, cannot be poured into cans or tanks, has no odor, and, therefore, nobody knows just what it is. We can only study the effects of electricity, and the wires, coils, and similar apparatus in which it is present. It is for ‘this reason that an air of mystery surrounds electrical things, especially to the man who has not made a special study of the subject.
Without electricity, there would be no gasoline engine, be- cause gasoline itself cannot cause the engine to operate. It is only when the electrical spark explodes or ‘‘ignites*’ the mix- ture of gasoline and air which has been drawn into the engine cylinders that the engine develops power. Thus an elec- trical ignition system has always been an essential part of every gasoline automobile.
The next step in the use of electricity on the automobile con- sisted in the substitution of an electric lighting system for the . inconvenient oil or gas Jamps which were satisfactory as far as the light they gave was concerned, but which had the dis- advantage of requiring whe driver to leave his seat, and bring
1
2 THE AUTOMOBILE STORAGE BATTERY
each lamy" inte lyfe. separately, vften in a strong wind or rain which cohstinied* many ~*matchés,-time, and frequently spoiled | his temper for the remainder of the evening. Electric lamps have none of these disadvantages. They can be controlled from the driver’s seat, can be turned on or off by merely turning or pushing a switch-button, are not affected by wind or rain, do not smoke up the lenses, and do not send a stream of unpleasant odors back to the passengers.
The apparatus used to supply the electricity for the lamps con- sisted of a generator, or a ‘‘storage’’ battery, or both. The gen- erator alone had the disadvantage that the lamps could be used only while the engine was running. The battery, on the other hand, furnished light at all times, but had to be removed from the car frequently, and ‘‘charged.’’ With both the generator and battery, the lights could be turned on whether the engine was running or not, and, furthermore, it was no longer necessary to remove the battery to ‘‘charge,’’ or put new life into it. With a generator and storage battery, moreover, a reliable source of electricity for ignition was provided, and so we find dry batteries and magnetos being discarded in a great many automobiles and ‘battery ignition’’ systems substituted.
The development of electric lighting systems increased the pop- ularity of the automobile, but the mbtor car still] had a great drawback—cranking. Owing to the peculiar features of a gaso- line engine, it must first be put in motion by some external power before it will begin to operate under its own power. This made it necessary for the driver to ‘‘crank’’ the engine, or start it moving, by means of a handle attached to the engine shaft. ' Cranking a large engine is difficult, especially if it is cold, and often results in tired muscles, and soiled clothes and tempers. It also made it impossible for the average woman to drive a car because she did not have the strength necessary to ‘‘crank”’ an engine.
The next step in the perfection of the automobile was naturally the development of an automatic device to crank the engine, and thus make the driving of a car a pleasure rather than a task.
We find, therefore, that in 1912, ‘‘self-starters’’ began to be —
used. These were not all electrical, some used tanks of com-
INTRODUCTORY 3
pressed air, others acetylene, and various mechanical devices, such as the spring starters. The electrical starters, however, proved their superiority immediately, and filled such a long felt want that fully 98% of the various makes of automobiles now have electric starters. The present day motor car, therefore, uses gasoline for the engine only, but uses electricity for igni- tion, starting, lighting, for the horn, cigar lighters, hand warmers on the steering wheel, gasoline vaporizers, and even for shifting speed changing gears, and for the brakes.
Fig. 1. The Battery
On any car that uses an electric lighting and starting system, there are two sources of electricity, the generator and the bat- tery. These must furnish the power for the starting, or ‘‘crank- ing’’ motor, the ignition, the lights, the horn, and the other devices. The demands made upon the generator are compara- tively light and simple, and no severe work is done by it. The battery, on the other hand is called upon to give a much more severe service, that of furnishing the power to crank the engine. It must also perform all the duties of the generator when the engine is not running, since a generator must be in motion in order to produce electricity.
4 THE AUTOMOBILE STORAGE BATTERY
A generator is made of iron, copper, carbon, and insulation. These are all solid substances which can easily be built in any size or Shape, and which undergo very little change as parts of the generator. The battery is made mainly of lead, lead com- pounds, water and sulphuric acid. Here we have liquids as well as solids, which produce electricity by changes in their com- position, resulting in complicated chemical as well as electrical actions.
The battery is, because of its construction and performance, a much abused, neglected piece of apparatus which is but partly understood, even by many electrical experts, for to understand it thoroughly requires a study of chemistry as well as of elec- tricity. Knowledge of the construction and action of a storage battery is not enough to make anyone an expert battery man. He must also know how to regulate the operating conditions so as to obtain the best service from the battery, and he must be able to make complete repairs on any battery no matter what its condition may be.
In the following chapters we shall treat in detail the subjects of electrical and chemical reactions, construction, operation, maintenance, and repair, with the object of making the reader familiar with all phases of battery work, and to lift the veil of mystery from the ‘‘giant who lives in a box.’’
—_$— ie, memento, Di. oP a: cian
. ST OGG |e oe
CHAPTER 2. BATTERIES IN GENERAL.
There are three ways of ‘‘generating”’ electricity; 1. Magnet- ically, 2. Chemically, 3. Thermally. The first method is that used in a generator, in which wires are rotated in a ‘‘field’’ in which magnetic forces act. The second method is that of the battery, and the one in which we are now interested. The third method consists of heating a joint of two different metals and is of no practical importance.
If two unlike metals or conducting substances are placed in a liquid which acts chemically upon one of the substances more than upon the other, an electrical pressure, or ‘‘electromotive’’ force is caused to exist between the two metals or conducting substances. The greater the difference in the chemical activity on the substances, the greater will be the electrical pressure, and if the substances are connected together outside of the liquid by a wire‘or other conductor of electricity, an electric current will flow through the path or ‘‘cireuit’’ consisting of the liquid, the two substances which are immersed in the liquid, and the external wire or conductor. |
As the current flows through the combination of the liquid, and the substances immersed in it, which is called a voltaic ‘‘cell,”’ one or both of the substances undergo chemical changes which con- tinue until one of the substances is entirely changed. These chemical changes produce the electrical pressure which causes the eurrent to flow, and the flow will continue until one or both of the substances are changed entirely. This change due to the chemical action may result in the formation of gases, or of solid compounds. If gases are formed they escape and are lost. If solids are formed, no material is actually lost.
Assuming that one of the conducting substances, or ‘‘elec- trodes,’’ which are immersed in the liquid has been acted upon
5
6 THE AUTOMOBILE STORAGE BATTERY
by the liquid, or ‘‘electrolyte,’’ until no further chemical action can take place, our voltaic cell will no longer be capable of causing a flow of electricity. If none of the substances result- ing from the original chemical action have been lost as gases, it may be possible to reverse the entire set of operations which have taken place. “That is, Suppose we now send a current through the cell from an outside source of electricity, in a. direc- tion which is opposite to that in which the currerit, which was produced by the chemical action between the electrodes and electrolyte, flowed.’ If this current now produces chemical ac- tions between electrodes and electrolyte which are the reverse of those which occurred originally, so that finally we have the electrodes and electrolyte brought back to their original compo- sition and condition, we have the cell just as it was before we used it for the production of an electrical pressuree The cell can now again be used as a source of electricity as long as the electrolyte acts tipon the electrodes, or until it is ‘‘dis- charged’’ and incapable of any further production of electrical pressure. Sending a current through a discharged eell, so as to reverse the chemical actions which brought about the dis- charged condition, is called ‘‘charging’’ the cell.
Cells in which an electrical pressure is produced as soon as-the electrodes are immersed in the electrolyte are called ‘‘primary’’ cells. In these cells it is often impossible, and always unsatis- factory to reverse the chemical action as explained above. Cells whose chemical actions are reversible are called ‘‘storage’’ or ‘‘secondary’’ cells. In the ‘‘storage’’ cells used today, a current must first be sent through the cell in order. to cause the chem- ical changes which result in putting the electrodes and elec- trolyte, in such a condition that they will be capable of pro- ducing an electrical pressure when the chemical changes caused by the current are complete. The cell now possesses all the characteristics of a primary cell, and may be used as a.source of electricity until ‘‘discharged.’’ It may then be ‘‘charged’’ again, and so on, the chemical action in one case causing a flow of current, and a reversed flow of current causing reversed chem- ical actions. .
We see from the above that the ‘‘storage’’ battery does not
BATTERIES IN GENERAL 7
“‘store’’ electricity at all, but changes chemical into electrical energy when ‘‘discharging,’’ and changes electrical into chem- ieal energy when ‘‘charging,’’ the two actions being entirely reversible. The idea of ‘‘storing’’ electricity comes from the fact that if we send a current of electricity through the cell for a certain length of time, we can at a later time draw a current from the cell for almost the same length of time.
Three things are therefore required in a storage cell, the liquid or ‘‘electrolyte’’ and two unlike substances or electrodes, through
4 Complete Cell Fig. 2
which a current of electricity can pass and which are acted upon by the electrolyte with a chemical action that is greater for one substance than the other. In the storage cell used on the auto- mobile to-day for starting and lighting, the electrodes are lead and peroxide of lead, and the electrolyte is a mixture of sulphuric aeid and water. The peroxide of lead electrode is the one upon which the electrolyte has the greater chemical effect, and it is called the positive or ‘‘-++’’ electrode, because when the battery is sending a current through an external circuit, the current
8 THE AUTOMOBILE STORAGE BATTERY
flows from this electrode through the external circuit, and back to the lead electrode, which is called the negative, or ‘‘—” electrode.
When starting and lighting systems were adopted in 1912, storage batteries had been used for many years in electrie power stations. These were, however, large and heavy, and many dif- ficult problems of design had to be solved in order to produce a battery capable of performing the work of cranking the engine, and yet be portable, light, and small enough to occupy only a
Fig. 8. A complete element, consisting of a positive and negative group of plates,
hold-down blocks and separators ready for placing in the hard rubber jars very limited space on the automobile. As a result these condi- tions governing the design, the starting and lighting battery of to-day is in reality ‘‘the giant that lives in a box.’’ The Elec- trie Storage Battery Company estimates that one of its types of batteries, which measures only 125 inches long, 73g wide, and 91% high, and weighs only 6312 pounds, can deliver enough energy to raise itself to a height of 6 miles straight up in the air. It must be able to do its work quickly at all times, and in all sorts of weather, with temperatures ranging from below 0° to 100° Fahrenheit.
BATTERIES IN GENERAL 9
The starting and lighting battery has therefore been designed to withstand severe operating conditions. Looking at such a bat- tery on a car we see a small wooden box in which are placed three or more ‘‘cells,’’ see Fig. 1. Each ‘‘cell’’ has a hard, black rubber top through which two posts of lead project. Bars of lead connect the posts of one cell to those of the next. To one of the posts of each end cell is connected a cable which leads into the car, and through which the current leaves or enters the battery. At the center of each cell is a removable rubber plug covering an opening through which communication is established with the inside of the cell for the purpose of pouring in water, removing some of the elec- trolyte to determine the condition of the battery, or to allow gases formed within the cell to escape. Looking down through this opening we can see the things needed to form a storage battery: the electrolyte, and the electrodes or ‘‘plates’’ as they are called. J£ we should remove the lead bars connecting one cell to another, and take off the black cover, we shall find that the posts which project out of the cells are attached to the plates which are broad and flat, and separated by thin pieces of wood or rubber. If we lift the plates out of the jar we find that they are connected alternately to the two lead posts, and that the two outside ones have a gray color. If we pull the plates out from each other, we find that the plates next to the two outside ones, and all other plates connected to the same lead post as these have a chocolate- _ brown color. If we remove the jar of the cell, we find that it is made of hard rubber. Pouring out the electrolyte we find several ridges which hold the plates off the bottom of the jar. The pock- ets formed by these ridges may contain some soft, muddy sub- stance. Thus we have exposed all the elements of a cell,—posts, plates, ‘‘separators,’’ and electrolyte. The gray colored plates are attached to the ‘‘negative’’ battery post, while the chocolate- brown colored ones are connected to the ‘‘positive’’ battery post. Examination will show that each of the plates consists of a skele- ton metallic framework which is filled with the brown or gray sub- stances. This construction is used to decrease the weight of the battery. The gray filler material is pure lead in a condition called ‘‘spongy lead.’’ The chocolate-brown filler substance is peroxide of lead. a” | |
10 THE AUTOMOBILE STORAGE BATTERY
We have found nothing but two sets of plates,—one of pure lead, the other of peroxide of lead, and the electrolyte of sulphuric acid and water. These produce the heavy current necessary to crank the engine. How this is done,.and what the chemical. ac- tions within the cell are, are described in the next chapter.
CHAPTER 3.
CHEMICAL ACTIONS WHICH PRODUCE ELECTRICITY.
Before explaining what happens within one storage cell, let us look into the early history of the storage battery, and see what a modest beginning the modern heavy duty battery had. Between 1850 and 1860 a man named Plante began his work on the storage battery. His original cell consisted of two plates of metallic lead immersed in dilute sulphuric acid. The acid formed a thin layer of lead sulphate on each plate which soon stopped further action on the lead. If a current was passed through the cell, the lead sulphate on the ‘‘anode’’ or lead plate at which the current entered the cell was changed into peroxide of lead, while the sul- phate on the other lead plate or ‘‘cathode’’ was changed into pure lead in a spongy form. This cell-was allowed to stand for a couple of days and was then ‘‘discharged,’’ lead sulphate being again formed on each plate. Each time this cell was charged, more ‘‘spongy’’ lead and peroxide of lead were formed. These are called the ‘‘active’’ materials, because it is by the chemical action between them and the sulphuric acid that the electricity is pro- duced. Evidently, the more active materials the plates contained, the longer the chemical action between, the acid and active ma- terials could take place, and hence the greater the ‘‘capacity,’’ or amount of electricity furnished by the cell. The process of charging and discharging the battery so as to increase the amount of active material, is called ‘‘forming’’ the plates.
Plante’s method of forming plates was very slow, tedious, and expensive. If the spongy lead, and peroxide of lead could be made quickly from materials which could be spread over the plates, much time and expense could be saved. It was Faure who first suggested such a plan, and gave us the ‘“‘pasted’’ plate of to-day, which consists of a skeleton framework of lead, with the sponge lead and peroxide of lead filling the spaces between the
11
12 THE AUTOMOBILE STORAGE BATTERY
‘‘ribs’’ of the framework. Such plates are known as ‘‘pasted” | plates, and are much lighter and satisfactory than the heavy solid | lead plates of Plante’s. Chapter 13 will describe more fully the processes of manufacturing and pasting the plates.
We know now what constitutes a storage battery, and what the parts are that ‘‘generate’’ the electricity. How is the electricity produced? If we take a battery which has been entirely discharged, so that it is no longer able to cause a flow of current, and examine and test the electrolyte and the materials on the plates, we shall find that the electrolyte is pure water, and both sets of plates composed of white lead sulphate. On the other hand, if we make a similar test and examination of the plates and electrolyte of a battery through which a current has been sent from some outside source, such as a generator, until the current can no longer cause chemical reactions between the plates and electrolyte, we will find that the electrolyte is now eomposed of water and sulphuric acid, the acid comprising about 30%, and the water 70% of the electrolyte. The negative set of plates will be composed of pure lead in a spongy form, while the positive will consist: of peroxide of lead.
It is evident that the chemical changes which have taken place in totally discharging the battery consisted in taking all the acid out of the electrolyte, changing the material of the positive plates from lead peroxide to lead sulphate, and changing the material of the negative plates from pure spongy lead to lead sulphate. Both plates are now composed of the same material, and they are im- mersed in pure water, which has no chemical action upon either plate. Such a combination cannot produce electricity, as ex- plained previously. |
The foregoing description gives the final products of the chem- ical changes that take place in the storage battery. To under- stand the changes themselves requires a more detailed investiga- tion. The substances to be considered in the chemical actions are sulphuric acid, water, pure lead, lead sulphate, and lead © peroxide. With the exception of the pure lead, each of these sub- | stances is a chemical compound, or composed of several elements. Thus sulphuric acid is made up of two parts of hydrogen, which is a gas; one part of sulphur, a solid, and four parts of oxygen,
ee a.
a
CHEMICAL ACTIONS WHICH PRODUCE ELECTRICITY 13
which is also a gas; these combine to form the acid, which is a liquid, and which is for convenience written as H,SO,, H., rep- resenting two parts of hydrogen, S one part of sulphur, and O, four parts of oxygen. Similarly, water a liquid, is made up of two parts of hydrogen and one part of oxygen, represented by the symbol H,0. Lead is not a compound, but an element whose chemical symbol is Pb, taken from the Latin name for lead. Lead sulphate is a solid, and consists of one part of lead, a solid sub- stance, one part of sulphur, another solid substance, and four
' WA ASANO NSS SWANS AANA ¢ ~~
Chemical Action in aStorage Cell During Charge
g
Fig. 4
parts of oxygen, a gas. It is represented chemically by Pb SQ,. Lead peroxide is also a solid, and is made up of one part of lead, and two parts of oxygen. In the chemical changes that take place, the compounds just described are to a certain extent split up into the substances of which they are composed. We thus have lead (Pb), hydrogen (H), oxygen (QO), and sulphur (S), four ele- mentary substances, two of which are solids, and two gases. The sulphur does not separate itself entirely from the substances with which it forms combination of H,SO, and Pb SO,. These com- pounds are split into H, and SO, and Pb and SO, respectively.
14 THE AUTOMOBILE STORAGE BATTERY
That is, the sulphur always remains combined with four parts of oxygen. |
Let us now consider a single storage cell made up of electrolyte, one positive plate, and one negative plate. When this cell is fully charged, or in a condition to produce a current of electricity, the positive plate is made up of peroxide of lead (PbO,), the negative plate of pure lead (Pb), and the electrolyte of sulphuric acid (H,SO,). This is shown diagrammatically in figure 4. The chem- ical changes that take place when the cell is discharging and the final result of the changes are as follows:
(a). At the positive plate: Lead peroxide (PbO,) and sulphuric acid (H,SO,) and two parts of hydrogen (H,) produce two parts of water (2H,O) and one part of lead sulphate (PbSO,). This may also be represented in this way: PbO,+H,S0,+H, = PbSO,-+2H,0.
(b). At the negative plate: Lead (Pb) and Sulphate (SO,) produce lead sulphate PbSO,. This may again be represented by Pb-++SO, — PbSQ,.
From (a) and (b), above, we see that at the positive plate the chemical
water and lead sulphate, whereas only lead sulphate is produced at the nega- tive plate, showing that the positive plate is acted upon to a greater extent by the acid than the negative plate is. The storage cell therefore fulfills the condition necessary to have a current produced, namely, that we must have two unlike substances immersed in a liquid, the chemical action of which is greater upon one substance than upon the other.
Chemical Action ina Storage Cell Durin ; . . Discharge The chemical changes described in Fig. 5 (a) and (b) are not instantaneous.
That is, the lead, lead peroxide, and sulphuric acid of the fully charged cell are not changed into lead sulphate and water as soon as a current begins to pass through the
changes during discharge produce |
a cae tl ———
CHEMICAL ACTIONS WHICH PRODUCE ELECTRICITY 15
cell. This action is a gradual one, small portions of these substances being changed ata time. The greater the current that flows through the cell, the faster will the changes occur. The changes will continue to take place as long as any lead, lead peroxide, and sulphuric acid remain. The faster these are changed into lead sulphate and water, the shorter will be the time that the storage cell can furnish a cur- rent, or the sooner it will be discharged. When the cell is completely discharged, we will have the conditions shown in the lower part of the cell of figure 5.
Taking the cell in its discharged condition, let us now connect the cell to a dynamo and send current through the cell from the positive to the negative plates. This is called ‘‘charging’’ the cell. The lead sulphate and water will now gradually be changed back into lead, lead peroxide, and sulphuric acid. The lead sulphate which is on the negative plate is changed to pure lead; the lead sulphate on the positive plate is changed to lead peroxide, and sul-° phuric acid will be added to the water. The changes at the positive plate may be represented as follows:
Lead sulphate (PbSO,) and water (2H,O) and sulphate (SO,) produce sulphuric acid (2H,SO,) and lead peroxide (PbO,), or
PbSO, + 2H,0 + SO, = 2H,SO, + PbO, Pb + SO, + 2H, + 20 + SO, = 2H,SO, + PbO, (Pb + 20) + (2H, + S80,-+ S0,) = 2H,S0O, + PbO,
The changes at the negative plate may be expressed as follows:
Lead sulphate (PbSO,) and hydrogen (H,) produce sulphuric acid (H,SO,) and lead (Pb), or
PbSO, -+ H, = H,S0, -+ Pb Pb -+ SO, + H, = H,80, + Pb Pb + (SO,-+-H.) = H,80, -+ Pb
These changes produced by sending a eurrent through the cell are also gradual, and will take place faster as the current is made greater. When all the lead sulphate has been used up by the ehemical changes caused by the current, no further charging can _ take place. If we continue to send a current through the cell after it is fully charged, the water will continue to be split up into _hydrogen and oxygen. Since, however, there is no more lead
16 THE AUTOMOBILE STORAGE BATTERY
sulphate left with which the hydrogen and oxygen can combine to form lead, lead peroxide, and sulphuric acid, the hydrogen and oxygen rise to the surface of the electrolyte and escape from the cell. This is known as ‘‘gassing,’’ and is an indication that the eell is fully charged.
CHAPTER 4.
HOW CHEMICAL ACTIONS PRODUCE ELECTRICITY.
In Chapter 3 we studied the chemical changes that occurred in the cell both when the cell was producing a current, and when a current was sent through the cell from a dynamo. But we have not as yet learned how these chemical actions preduce electricity. The fact that the chemical actions produce electricity, and that, on the other hand, electricity produces chemical changes shows that electricity and chemical changes are closely asso-
ciated.
A complete study of the electricity which chemical changes make available would furnish material for a book many times
“" te Cell During Discharge
thicker than this one, as it forms a distinct branch of science known as Electro- Chemistry. A general in- vestigation will be made, however. No chemical change, or chemical reac- tion is supposed to produce electricity, but merely to make it available for use. Thus the storage battery contains the electricity be- fore any chemical change takes place. As soon as the battery circuit is closed through the lamps or starting motor, however, the electric current flows out of the battery at the
positive terminal, and back into the battery at the negative terminal. Where is the electricity, and in what form, and how does the mere closing of the battery circuit cause it to appear?
17
18 THE AUTOMOBILE STORAGE BATTERY
‘When we think of an electric current flowing through a wire, we take it for granted that at any point in the wire the cur- rent is flowing in one direction only, just lke water flowing through a pipe. When, however, a current flows through a
liquid, like the battery electrolyte, it is supposed to be |
flowing both from the positive to the negative, and from the negative to the positive. These currents are carried by the sulphuric acid. As long as this acid is not mixed with water, it cannot carry any current. -When the acid is poured
into the water, it is partly divided into hydrogen (H,) and sulphate (SO,). This happens as soon as the acid and water are _ mixed. The hydrogen has a certain amount of positive elec-
tricity attached to it, and the sulphate a certain amount of neg- ative electricity. Where did the electricity come from? It was in the acid in the first place, but as long as the acid was not separated into hydrogen and sulphate, the positive electricity of the hydrogen neutralized that of the sulphate. The particles which have the electricity attached to them are called ‘‘ions.”’ They are extremely small, and the electricity they carry is spoken of as a positive or a negative ‘‘charge’’ of electricity, or simply ‘‘eharge.’’ We then have a quantity of hydrogen ions which
are carrying positive electricity or have a positive ‘‘charge.”’
Similarly the sulphate ions carry a certain amount of negative electricity, or have a negative ‘‘charge.’’ The ions are entirely unlike the substances as we see them and have different char- acteristics.
Leaving the acid with its ‘‘charges’’ of electricity, let us con- sider the electrodes or plates. Like the acid, the lead and lead peroxide contain certain amounts of electricity, both positive and negative. When the electrodes are immersed in the elec-
trolyte these amounts of positive and negative charges are made ©
available.
At the negative plate, which is composed of pure lead, some of |
the lead separates from the plate, and mixes with the acid in the form of ‘‘ions,”’ each ion carrying a small amount, or charge of electricity. The lead ion leaves a similar and equal amount negative electricity on the lead plate. Only a very few of these lead ions are formed as long as no current passes through the
HOW CHEMICAL ACTIONS PRODUCE ELECTRICITY 19
battery. This is due to the fact that the positive charge on the lead ion and the negative charge on the lead plate have a strong attraction for each other. After a few ions have been formed, the attraction is so strong that no more are formed. Similarly, for the positive plate, small particles of the lead peroxide enter
CHARGED CELL ON OPEN CIRCUIT
Ww ae < y a QO { w a
LEAD PEROXIDE PLATE
Fig. 7
the electrolyte, and take with them certain quantities of nega- tive electricity, or negative charges, leaving the plate with an equal positive charge. As long as the circuit outside the battery is Open, no current can flow, because the negative and positive quantities of electricity, or ‘‘charges’’ on the plates are kept there by the opposite charges on the ions that have entered the
20 THE AUTOMOBILE STORAGE BATTERY
acid. The fact that the minute particles called ‘‘ions”’ carry with them certain quantities of electricity is indicated by writing the signs ‘‘+-’’ and ‘‘—”’ after them. Thus, a lead ion is written (Pb*t), and a lead peroxide ion PbO,”).
Figure 7 shows the conditions described above. At the nega- tive plate is a layer of lead ions which have gone into the acid, carrying positive charges and leaving an equal number of nega-
CELL DISCHARGING
LEAD PLATE
LEAD PEROXIDE PLATE
NPI LPI PI I SIL LI I
+t het ttttettte te ttet
tive charges on the lead plate. Similarly, at the positive plate is a layer of lead peroxide ions which have entered the acid, carrying negative charges, and leaving an equal number of posi- tive charges on the positive plate. The acid itself has been split by the water, into hydrogen ions and sulphate ions, the hydrogen ions carrying positive charges, and the sulphate ions carrying negative charges. The ions of the acid are distributed through- out the electrolyte. As the figure shows, the number of positive
HOW CHEMICAL ACTIONS PRODUCE ELECTRICITY 21
and negative ions are equal, and as they attract each other strongly, they cannot move away from each other, and hence no current can flow.
If we now connect the positive and negative plates together through a starting motor, as shown in figure 8, conditions will be changed. The positive charges on the positive plate will move
0 ) 0 a > A 0) m U -) m -
2)
U U U0 Uv U\/ 7 0 v gicgiicic\lelr\lc\loels HTolololol ol] of of o ollollololollollol_ojio KNSNENENAE ADEN ENON
LEAD SULPHATE PLATE LEAD SULPHATE PLATE
: v v v J W) i)
a O \ Ny O w
Fig. 9
along the wire and through the motor to the negative plate. There they will meet the negative charges. In order that the positive and negative charges on the plates may send a current through the starting motor, the lead ions and the lead peroxide ions must be removed from the surfaces of the plates. Otherwise the attraction of the lead and lead peroxide ions for the charges
22 THE AUTOMOBILE STORAGE BATTERY
on the plate will hold the latter on the plate. Now, each ion has a tendency to move through the acid. As soon as some of the negative charges start to leave the lead plate to go through the motor, the lead ions start to move toward the lead peroxide plate. They have hardly started to move, however, before they meet sul- phate ions from the acid. The sulphate ions and the lead ions combine and form lead sulphate. Similarly, the lead peroxide ions begin to leave the positive plate. They are then split up into lead ions (Pb**) and oxygen ions (20°). This leaves hydrogen ions from the acid, and oxygen ions from the lead peroxide un- accounted for. The two have opposite charges, and hence attract each other, uniting to form water. This gives us lead sulphate and water as the final products of discharging a battery, which agrees with, the equation on page 14.
The lead of a negative plate, and the lead peroxide of the positive plate are called ‘‘active’’ materials. They are not the only substances which ean be used for storage batteries. Many combinations for electrolyte and plates have been tried, but the lead, lead peroxide, and sulphuric acid combination has worked out to be the best combination for practical use. They do not ereate electricity, as was explained above, but the chemical ehanges that take place in the battery readjust the small quanti- ties of electricity or ‘‘charges’’ which are carried by the ‘‘ions”’ so that we are able to force the charges to move through the starting motor, lamps, or other apparatus. The water in the bat- tery causes the ‘‘ions’’ to form as separate particles carrying ‘‘charges.’’ Without water we could not have a battery, as the electricity bound up in the active materials would never be avail- able, because the negative and positive charges neutralize each other ordinarily, and must be separated from each other long enough to be forced to run the starting motor, light the lamps, and furnish current for the ignition. Once the charges are separated, they have a tendency to unite with those of opposite sign. The water prevents a complete reunion of the ions carrying the charges, but the tendency they have to unite gives the voltage, or electromotive force of the battery. When a current is made to flow through the motor, charges are uniting, and a current will continue to flow as long as there are charges available. As soon
q
ee, I ee.
HOW CHEMICAL ACTIONS PRODUCE ELECTRICITY 23
as charges unite through the motor, more are formed in the elec- trolyte from the lead, lead peroxide, and sulphuric acid. When these materials have all been used so that we have only lead sul- phate and water in the battery, no more charges are available, and the battery can no longer produce a current.
In practice, a battery is never discharged until all the lead, lead peroxide, and sulphurie acid are changed into lead sulphate and water. As lead sulphate is formed, it fills up the pores in the plates, and covers the remaining lead and lead peroxide so that they are practically sealed in and made useless. The removal of the sulphate becomes increasingly difficult as more is formed, and, therefore, a battery should not be discharged entirely. This subject will be treated. more completely later.
Charging Discharging
Fig. 10
The battery is now completely discharged. We now send a continuous current through it so that the current enters through the positive terminal, and leaves through the negative terminal, . Fig. 10. This direction of flow is just the reverse of the current produced by the battery in discharging. The current we are send- ing through the battery gradually puts it in a condition in which it can again furnish a current. We saw how the battery produces a current when it is fully charged, that is, when we had a plate of pure lead, a plate of lead peroxide and an electrolyte of acid and water. Now we are starting with two plates of lead sul- phate immersed in water. How does a current charge the bat- tery? .
When a battery is completely discharged, we have lead sul-
24 THE AUTOMOBILE STORAGE BATTERY
phate at each plate,.and water. The water has the power to split the lead sulphate into lead (Pb), and sulphate (SO,). The water itself is separated, to a slight extent, into hydrogen (H,), and oxygen (QO). These parts into which the lead sulphate and water separate each carry a ‘‘charge’’ of electricity, some posi- tive, and some negative. The lead and hydrogen are positive, and the sulphate and oxygen negative. We thus have lead ‘‘ions’’ (Pb*t), sulphate ions (SO, -), hydrogen ions (H,*), and oxygen ions (O°). , As long as the battery is not being charged, the + and — charges attract each other, and no chemical changes occur. When the battery is connected to a generator for charging, the generator produces positive charges on the positive plate, and negative charges on the negative plate. The positive charges on the positive plate will attract all the negatively charged ions, while the negative charges on negative plate will attract all the positively charged ions. As a result, the lead and hydrogen ions start to move toward the negative plate, and the sulphate and oxygen ions toward the positive plate. The Pb** which be- gins to move from the positive to the negative plate meets imme- diately with the 20° and PbO, is formed. This seems to then become PbO,”*. The positive charges on the positive plates attract the PbO, ~, and the latter is deposited on the plate as ordinary lead peroxide. The Pb** at the negative plate, is at- tracted by the negative charges on the negative plate, and since the Pb*t is on the negative plate it is immediately deposited as metallic lead, since the negative and positive charges neutralize one another and take the charge away from the lead. This gives us the changes which occur at the plates so as to give us the lead and lead peroxide of a charged battery. We still need sulphuric acid however. At the positive plate, the sulphate ion meets the hydrogen ion, which is free to travel toward the nega- tive plate, and sulphuric acid is formed. At the negative plate, the sulphate ion starts to move toward the positive plate, but meets the hydrogen ion which is moving toward the negative plate, and sulphurie acid is formed, although half of the acid is always separated into hydrogen and sulphate. This accounts for all the materials.
HOW CHEMICAL ACTIONS PRODUCE ELECTRICITY 25
We have thus taken the battery through a charge and dis- charge, both chemically, and electrically. The actions described for discharge take place faster when a heavy current is drawn from the battery. The speed of the charge actions depends upon the voltage of the generator, the motions of the ions being increased in speed as the voltage is increased. As far as current flow in and out of the battery is concerned, this depends upon the positive and negative charges on the positive and negative plates. When the battery is discharging, these charges will pass into the external circuit with increasing speed as the resistance of the circuit decreases. When the battery is being charged, the charges on the plate attract the charges on the ions, and when the charges reach the plates, the opposite charges on lon and plate neutralize one another. The result of the ions travelling in opposite directions in the electrolyte is to produce a current which seems to flow in only one direction in the external circuit. The ions of the lead, lead peroxide, and lead sulphate all tend to move toward one or the other battery plate, but because they are so few in number, and because there are so many hydrogen and sulphate ions in the electrolyte, they have hardly begun to move before they combine with the ions of the acid to form lead sulphate and water. Hence, the ions of the active plate materials move exceedingly minute distances. Those of the acid, especially the hydrogen ion, move through all parts of the elec- trolyte. The chemical actions take place not only at the out- side surfaces of the plates, but wherever acid, lead or lead perox- ide, or lead sulphate come in contact with each other. We know that the acid soaks in to all parts of the plates, and therefore the actions take place throughout the entire plate. The materials on the plates must therefore be porous in order to allow the acid to soak into them easily.
The “pasted” plate is used almost entirely for starting and lighting service. The plates are not made entirely of the spongy lead and lead peroxide. Neither of these substances are tough enough to be made into plates. They must, therefore, be held in place. We thus find that each plate consists of a skeleton framework of lead, the pastes filling up the spaces between the ribs.
CHAPTER 5. LOSS OF CHARGE IN AN IDLE BATTERY.
Before taking up the study of discharge by drawing a current
from the battery, let us see what happens if a fully charged —
battery is allowed to stand idle on open circuit, that is, with no
wires or cabes attached to its terminals. It has been found that : such a battery will gradually become discharged and that it |
must be given an ocasional ‘‘freshening’’ charge.
Now, as we have learned, when a battery discharges lead sul- phate forms on each plate, and acid is taken from the electro- lyte as the sulphate forms. In our idle battery, therefore, such actions must be taking place. The only difference in this case is that the sulphate forms without any current passing through the battery. The actions at the lead and lead peroxide must, there- fore, be independent of each other. At the lead peroxide plate we have lead peroxide paste, lead grid, and sulphuric acid. These are all the elements needed to produce a storage battery, and as the lead peroxide and the lead are touching each other, each lead peroxide plate really forms a short circuited cell. Why does this plate not discharge itself completely? A certain amount of discharge does take place, and results in a layer of lead sul- phate forming between the lead peroxide and the grid. The sul- phate, having high resistance then protects the lead grid and prevents any further action. This discharge action therefore does not continue, but causes a loss of a certain part of the charge.
At the negative plate, we have pure spongy lead, and the grid. This grid is not composed entirely of lead, but contains a per- eentage of antimony, a metal which makes the grid harder and stronger. There is but very little difference of potential between the spongy lead and the grid. A small amount of lead sulphate does form, however, on the surface of the negative plate. This is due to the action between the spongy lead and the electrolyte.
26
a
LOSS OF CHARGE IN AN IDLE BATTERY 27
Some of the lead combines with the acid to form lead sulphate, but after a small amount has been formed the action is stopped because a balanced chemical condition is soon obtained.
Thus only a small amount of lead sulphate is formed at each plate, and the cell thereby loses only a small part of its charge. In a perfectly constructed battery the discharge would then stop. The only further action which would take place would be the slow evaporation of the water of the electrolyte. As the level of the electrolyte dropped below the tops of the plates, crystalliza- tion and sulphation would take place on the part of the negative plate above the electrolyte. The loss of charge which actually occurs in an idle charged battery is greater than that due to the formation of the small amounts of sulphate on the plates, and the evaporation of the water from the electrolyte.
Does an idle cell discharge itself by decomposing its electro- lyte? We have a difference of potential of about two volts between the lead and lead peroxide plate. Why is the electro- lyte not decomposed by this difference? At first it might seem that the water and acid should be separated into its parts, and hydrogen liberated at the negative plate. As a matter of fact, very little hydrogen gas is set free in an idle charged cell be- eause to do so would require a voltage of about 2.5. At two volts, so little gas is formed that the loss of charge due to it may be neglected entirely.
The greatest loss of charge in an idle battery results from con- ditions arising from the processes of manufacture, internal troubles, and leakage between terminals. The grids of a cell are an alloy of lead and antimony. These are mixed while in a molten condition, and are then allowed to cool. If the cooling is not done properly, or if a poor grade of antimony is used, the resulting grid is not a uniform mixture of antimony and lead. There will be areas of pure lead, with an air hole here and there. The lack of uniformity in the grid material results in a local dis- charge in the grid. This causes-some loss of charge.
If the active material completely fills the spaces between the grids, the acid formed as the cell is charged may not be able to diffuse into the main body of the electrolyte, but forms a small pocket of acid in the plate. This acid will cause a discharge between
28 THE AUTOMOBILE STORAGE BATTERY
paste and grid and a coating of lead sulphate forms on the grid, resulting in a certain loss of charge.
In the process of manufacturing and ‘‘forming’’ plates, graph- ite 1s sometimes used to give porosity to the paste, resulting in local action which causes a loss of charge. In general any metallic impurity in a cell will cause a loss at the lead plate. When a cell is charged, the current causes the metals to deposit on the lead plate. Local cells are formed by the metal- lic impurity, the lead plate, and the acid, and these tiny cells will discharge completely, causing a loss of charge. Such metals include iron, copper, tin, arsenic, antimony, and platmum. Of these, iron is perhaps the most destructive, as it travels back and forth from plate to plate, causing a loss of charge. The ions of this metal absorb an additional amount of electricity at the peroxide plate which they carry to the lead plate and there
lose it. This action is continuous, and even a small amount of |
iron in an idle cell can cause an appreciable loss of charge in one day.
Incomplete removal of forming agents causes some local ac- |
tion in an idle cell which results in a loss of charge. Such sub- stances are supposed to have been removed automatically as the forming process is completed, but some may remain and cause trouble.
Another cause of loss of charge in an idle cell is leakage of current between the terminals on the outside of the battery. Dur- ing charge, the bubbles of gas which escape from the electrolyte carry with them minute quantities of acid which may deposit on
——
the top of the battery and gradually form a thin conducting |
layer of electrolyte through which a current will flow from the positive to the negative terminals. This danger may be avoided by carefully wiping any moisture from the battery. Condensation of moisture from the air, on the top or sides and bottom of a battery will cause the same condition. This will be especially noticeable if a battery is kept in a damp place.
Impurities in any form are therefore to be guarded against. The use of impure acid or water will introduce objectionable substances. Every impurity causes local actions which cause a loss of charge and shorten the life of the battery.
a
—__ er
f-
CHAPTER 6. THE DISCHARGE PHENOMENA.
Considered chemically, the discharge of a storage battery con- sists of the changing of the spongy lead and lead peroxide into lead sulphate, and the abstraction of the acid from the electro- lyte. Considered electrically, the changes are more complex, and require further investigation. The voltage, internal resistance, rate of discharge, capacity, and other features must be considered,
CELL VOLTAGE
IZ 14 15 16 17 18 19 20 3 2 3 TIME OF CHARGE —-MINUTE S&S
Fig. 11
and the effects of changes in one upon the others must be studied. This proceeding is simplified considerably if we consider each point separately. The abstraction of the acid from the electro- lyte gives us the most reliable method of determining the con- dition of charge or discharge in the battery, and must also be studied.
29
30 THE AUTOMOBILE STORAGE BATTERY
Voltage Changes During Discharge. At the end of a charge. and before opening the charging circuit, the voltage of each cell is about 2.6 to 2.7 volts. As soon as the charging circuit is opened, the cell voltage drops rapidly to about 2.1 volts, within three or four minutes. This is due to the formation of a thin layer of lead sulphate on the surface of the negative plate and between the lead peroxide and the metal of the positive plate. Figure 11 shows how the voltage changes during the last eight minutes of charge, and how it drops rapidly as soon as the charging circuit is opened. The final value of the voltage after the charging circuit is opened is about 2.15-2.18 volts. This is more fully explained in
Chapter 7. If a current is drawn from the battery at the instant —
VOLTS 2.2
the charge is stopped, this drop is more rapid. At the beginning ,
of the discharge the voltage has already had a rapid drop from the final voltage on charge, due to the formation of sulphate as explained above. When a current is being drawn from the bat-
tery, the sudden drop is due to the internal resistance of the |
cell, the formation of more sulphate, and the abstracting of the
acid from the electrolyte which fills the pores of the plate. The ©
density of this acid is high just before the discharge is begun. It is diluted rapidly at first, but a balanced condition is reached between the density of the acid in the plates and in the main body of the electrolyte, the acid supply in the plates being main- tained at a lowered density by fresh acid flowing into them from the main body of electrolyte. After the initial drop, the voltage decreases more slowly, the rate of decrease depending on the
THE DISCHARGE PHENOMENA 31
amount of curfent drawn from the battery. The entire process is shown in figure 12. Lead sulphate is being formed on the sur- faces, and in the body of the plates. This sulphate has a higher resistance than the lead or lead peroxide, and the internal resis- tance of the cell rises, and contributes to the drop in voltage. As this sulphate forms in the body of the plates, the acid is used up. At first this acid is easily replaced from the main body of the electrolyte by diffusion. The acid in the main body of the electrolyte is at first comparatively strong, or concentrated, caus- ing a fresh supply of acid to flow into the plates as fast as it is used up in the plates. This results in the acid in the electro- lyte growing weaker, and this, in turn, leads to a constant de- crease in the rate at which the fresh acid flows, or diffuses into the plates. Furthermore, the sulphate, which is more bulky than the lead or lead peroxide fills the pores in the plate, making it more and more difficult for acid to reach the interior of the plate. This increases the rate at which the voltage drops.
The sulphate has another effect. It forms a cover over the paste which has not been acted upon, and makes it practically useless, since the acid is almost unable to penetrate the coating of sulphate. We thus have quantities of active material which are entirely enclosed in sulphate, thereby cutting down the amount of energy which can be taken from the battery. Thus the formation of sulphate throughout each plate and the abstraction of acid from the electrolyte cause the voltage to drop at a con- stantly increasing rate.
Theoretically, the discharge may be continued until the voltage drops to zero, but practically, the discharge should be stopped when the voltage of each cell has dropped to 1.7. If the dis- charge is carried on beyond this point all the spongy lead and lead peroxide have either been changed into lead sulphate, or have been covered up by the sulphate so effectively that they are almost useless. Plates in this condition require a very long charge in order to remove all the sulphate. Another danger arises if the discharge is continued. The lead of the grid is grad- ually changed to lead sulphate, and when the cell is recharged, the sulphate will be changed to spongy lead and lead | peroxide, and the grid is consequently weakened.
32 THE AUTOMOBILE STORAGE BATTERY
The cell voltage will rise somewhat every time the discharge is stopped. This is due to the diffusion of the acid from the main body of electrolyte into the plates, resulting in an increased concentration in the plates. If the discharge is continuous, es- pecially if at a high rate, this rise in voltage will bring the cell up to its normal voltage very quicky on account of the more rapid diffusion of acid which will then take place.
The voltage does not depend upon the area of the plate surface but upon the nature of the active materials and the electrolyte. Hence, although the plates of a cell are gradually being covered with sulphate, the voltage measured when no current is flowing, will fall slowly, and not in proportion to the amount of energy taken out of the cell. It is not until the plates are pretty thoroughly covered with sulphate, thus making it difficult for the acid to reach the active material, that the voltage begins to drop rapidly. This is shown clearly in figure 12, which shows that the cell voltage has dropped only a very small amount when the cell is 50% discharged. With current flowing through the cell, however, the increased internal resistance causes a marked drop in the voltage. Open circuit voltage is not useful, therefore to determine how much energy has been taken from the battery.
Acid Density. The electrolyte of a lead storage battery is a mixture of chemically pure sulphuric acid, and chemically pure water, the acid forming about 30 per cent of the volume of elec- trolyte when the battery is fully discharged. The pure acid
has a ‘‘specific gravity’’ of 1.835, that is, it is 1.835 ag heavy |
as an equal volume of water. The mixture of acid and water has a specific gravity of about 1.300. As the cell discharges, acid is abstracted from the electrolyte, and the weight of the latter must therefore grow less, since there will be less acid in it. The ehange in the weight, or specific gravity of the electrolyte is the best means of determining the state of discharge of a cell, pro- vided that the cell has been used properly. In order that the value of the specific gravity may be used as an indication of the amount of energy in a battery, the history of the battery must be known. Suppose, for instance, that in refilling the bat- tery to replace the water lost by the natural evaporation which occurs in the use of a battery, acid, or a mixture of acid and
- |
THE DISCHARGE PHENOMENA 33
water has been used. This will result in the specific gravity being too high, and the amount of energy in the battery will be less than that indicated by the specific gravity. Again, if pure water is used to replace electrolyte which has been spilled, the specific gravity will be lower than it should be. In a bat- tery which has been discharged to such an extent that much of the paste has been covered by a layer of tough sulphate, or if a@ considerable amount of sulphate and active material has been loosened from the plates and has dropped to the bottom of the
“SEI —|----}—
>
CIFIC GRAVITY
91100
LEAT LEE YET TET
|.
=
TL cette ‘TCE EAE
70 60 5 RCENT CAPACITY IN BATTERY.
Fig. 183
eells, it will be impossible to bring the specific gravity of the elec- trolyte up to 1.300, even though a long charge is given. There must, therefore, be a reasonable degree of certainty that a bat- tery has been properly handled if the specific gravity readings are to be taken as a true indication of the condition of a battery. Where a battery does not give satisfactory service even though the specific gravity readings are satisfactory, the latter are not reliable as indicating the amount of charge in the battery. As long as a discharge current is flowing from the battery, the
34 THE AUTOMOBILE STORAGE BATTERY |
acid within the plates is used up and becomes very much diluted. | Diffusion between the surrounding electrolyte and the acid in
the plates keeps up the supply needed in the plates in order to carry on the chemical changes. When the discharge is first begun, the diffusion of acid into the plates takes place rapidly because there is little sulphate clogging the pores in the paste, and because there is a greater difference betwéen the concentration of acid in the electrolyte and in the plates than will exist as the discharge progresses. As the sulphate begins to form and fill up the pores of the plates, and as more and more acid is abstracted from the elec- trolyte, diffusion takes place more slowly.
If a battery is allowed to stand idle for a short time after a partial discharge, the specific gravity of the electrolyte will de- crease because some of the acid in the electrolyte will gradually flow into the pores of the plates to replace the acid used up while the battery was discharging. Theoretically the discharge can be continued until all the acid has been used up, and the electro- lyte is composed of pure water. Experience has shown, how- ever, that the discharge of the battery should not be continued after the specific gravity of the electrolyte has fallen to 1.150. As far as the electrolyte is concerned, the discharge may be carried farther with safety. The plates determine the point at which the discharge should be stopped. When the specific gravity has dropped from 1.300 to 1.150, so much sulphate has been formed that it fills all the pores in the active material on the plates, and is beginning to form a tough covering over the paste. Figure 13 shows the change in the density of the acid during discharge.
Changes at the Negative Plate. Chemically, the action at the negative plate consists only of the formation of lead sulphate from the spongy lead. The lead sulphate is only slightly soluble in the electrolyte and is precipitated as soon as it 1s formed, leaving hydrogen ions, which then go to the lead peroxide plate to form water with other hydrogen ions and oxygen ions released at the peroxide plate. The sulphate forms more quickly on the surface of the plate than in the inner portions because there is a constant supply of acid available at the surface, whereas the formation of sulphate in the interior of the plate requires that acid diffuse into the pores of the spongy lead to replace that already used
————
THE DISCHARGE PHENOMENA 30
up in the formation of sulphate. In the negative plate, however, the sulphate tends to form more uniformly throughout the mass of the lead, because the spongy lead is more porous than the lead. peroxide, and because the acid is not diluted by the formation of water as in the positive plate. When the discharge has pro- ceeded until the specific gravity of the electrolyte has decreased to 1.150, the sulphate has formed a tough coating over the surface of the plate and has filled the pores of the lead to such an extent that most of the spongy lead that remains is prevented from re- acting with the acid because of the high resistance of the sul- phate covering it. If the discharge is continued beyond this point, the acid begins to attack the grids and form a layer of sulphate on them. Subsequent charge will change this sulphate to spongy lead, thus making the grids weaker by the amount of the lead which formed the sulphate. ,
The sulphate has a greater volume than the lead from which it is formed and there is, therefore, an actual increase in the volume of the paste during discharge. The spongy lead being tough and coherent, this expansion does not cause the paste to fall from the plate, but simply results in a bulging out of mate- rial between the grid bars.
Changes at the Positive Plate. In a fully charged positive plate we have lead peroxide as the active material. This is composed of lead and oxygen. From this fact it is plainly evident that during discharge there is a greater chemical activity at this plate than at the negative plate, since we must find something to com- bine with the oxygen in order that the lead may form lead sul- phate with the acid. In an ideal cell, therefore, the material which undergoes the greater change should be more porous than the material which does not involve as great a chemical reaction. In reality, however, the peroxide is not as porous as the spongy lead, and does not hold together as well.
The final products of the discharge of a positive plate are lead sulphate and water. The lead peroxide must first be reduced to lead, which then combines with the sulphate from the acid to form lead sulphate, while the oxygen from the peroxide combines with the hydrogen of the acid to form water. There is, therefore, a greater activity at this plate than at the lead plate, and the forma-
36 THE AUTOMOBILE STORAGE BATTERY
tion of the water dilutes the acid in and around the plate so that the tendency is for the chemical actions to be retarded. When .the discharge has just begun, the positive plate grows darker in color, showing that the lead sulphate at first forms a definite compound with the lead peroxide. As the discharge progresses, the sulphate begins to form in white scales on the surface of the plate.
The sulphate causes the active material to bulge out because it occupies more space than the peroxide. This causes the lead peroxide at the surface to begin falling to the bottom of the jar in fine dust-like particles, since the peroxide here holds together very poorly.
The abstraction of acid from the electrolyte takes place at both plates, of course, but the positive has an additional handicap on account of the water formed in its pores. Experiments have shown that in order to have the peroxide plate working at its greatest capacity, the density of the electrolyte should be more than 1.300, while the negative has the greatest capacity when the electrolyte has a density of 1.220. The discharge of the bat- tery, therefore, tends to have the negative operating at its great- est capacity, while the conditions at the positive are just oppo- site from what they should be in order to obtain the greatest | eapacity from this plate.
CHAPTER 7. THE CHARGE PHENOMENA.
Voltage. Starting with a battery which has been discharged until its voltage has decreased to 1.7 per cell, we pass a current through it and cause the voltage to rise steadily. Figure 14 shows the changes in voltage during charge. Ordinarily the voltage begins to rise immediately and uniformly. If, however, the bat- tery has been left in a discharged condition for some time, or has been ‘‘over discharged,’’ the voltage rises very rapidly for a fraction of the first minute of charge and then drops rapidly to
j z BS 4 5 HOURS ON CHARGE Fig. 14
the normal value and thereafter begins to rise steadily to the end of the charge. This rise at the beginning of the charge is due to the fact that the density of the acid in the pores of the plates rises rapidly at first, the acid thus formed being prevented from diffusing into the surrounding electrolyte by the coating of sulphate. As soon as this sulphate is broken through, diffusion takes place and the voltage drops.
As shown in Figure 14 the voltage remains almost constant between the points M and N. At N the voltage begins to rise because the charging chemical reactions are taking place farther and farther in the inside parts of the plate, and the concentrated acid formed by the chemical actions in the plates is diffusing
37
38 THE AUTOMOBILE STORAGE BATTERY |
into the main electrolyte. This increases the battery voltage and requires a higher charging voltage.
- At the point marked O, the voltage begins to rise very rapidly. This is due to the fact that the amount of lead sulphate in the | plates is decreasing very rapidly, allowing the battery voltage to rise and thus increasing the charging voltage. Bubbles of gas are now rising through the electrolyte.
At P, the last portions of lead sulphate are removed, acid is no longer being formed, and hydrogen and oxygen gas are formed | rapidly. The gas forces the last of the concentrated acid out of the plates and in fact, equalizes the acid concentration through- out the whole cell, Thus no further changes can take place, and | the voltage becomes constant at R.
Density of Electrolyte. Discharge should be stopped when the density of the electrolyte, as measured with a hydrometer, is 1.150. When we pass a charging current through the battery, acid is produced by the chemical actions which take place in the plates. This gradually diffuses with the main electrolyte and causes the hydrometer to show a higher density than before. This increase in density continues steadily until the battery begins to | ‘‘ovas’’ freely. ‘‘Gassing’’ causes the electrolyte in the plates to mix thoroughly with that surrounding the plates and also in- | creases the volume of the electrolyte and consequently decreases its density.
The progress of the charge is always determined by the density of the electrolyte. For this purpose in automobile batteries, a hydrometer is placed in a glass syringe having a short length of rubber tubing at one end, and a large rubber bulb at the other. The rubber tube is inserted in the cell and enough electrolyte © drawn up into the syringe to float the hydrometer so as to be able to obtain a reading. This subject will be treated more fully in a later chapter.
Changes at Negative Plate. The charging current changes lead sulphate into spongy lead, and acid is formed. The acid is mixed with the diluted electrolyte outside of the plates, resulting in a rise in temperature. This is not objectionable unless the tem- , perature rises to more than 105° F., since the concentrated acid formed in the plates diffuses into the electrolyte more rapidly
THE CHARGE PHENOMENA 39
as the temperature is increased, thus hastening the charging actions. As the charging proceeds the active material shrinks or contracts, and the weight of the plate actually decreases on account of the difference between the weight and volume of the lead sulphate and spongy lead. If the cell has had only a normal discharge and the charge is begun soon after the discharge ended, the charge will proceed quickly and without an excessive rise in temperature. If, however, the cell has been discharged too far, or has been in a discharged condition for some time, the lead sul- phate will not be in a finely divided state as it should be, but will be hard and tough and will have formed an insulating coat- ing over the active material, causing the charging voltage to be high, and the charge will proceed slowly. When most of the lead sulphate has been reduced to spongy lead, the charging current will be greater than is needed to carry on the chemical actions, and will simply decompose the water into hydrogen and oxygen, and the cell ‘‘gasses.’’ Spongy lead is rather tough and coherent, and the bubbles of gas which form in the pores of the negative plate near the end of the charge force their way to the surface without dislodging any of the active material.
Changes at the Positive Plate. When a cell has been dis- charged, a portion of the lead peroxide has been changed to lead sulphate, which has lodged in the pores of the paste and on its surface. During charge, the lead combines with oxygen from the water to form lead peroxide, and acid is formed. This acid dif- fuses into the electrolyte as fast as the amount of sulphate will permit. If the discharge has been carried so far that a consider- able amount of sulphate has formed in the pores and on the sur- face of the plate, the action proceeds very slowly, and unless a moderate charging current is used, gassing begins before the charge is complete, simply because the sulphate cannot absorb the current. The gas bubbles which originate in the interior of the plate force their way to the surface, and in so doing cause numerous fine particles of active material to break off and fall to the bottom of the jar. This happens because the lead per- oxide is a granular, non-coherent substance, with the particles held together very loosely, and the gas breaks off a considerable amount of active material.
CHAPTER 8. CAPACITY OF STORAGE BATTERIES.
The capacity of a storage battery is the amount of electrical energy which can be obtained from it. The unit in which capacity is measured is the ampere-hour. Theoretically, a battery has a capacity of 40 ampere-hours if it furnishes ten amperes for four hours, and if it is unable, at the end of that time, to furnish any more current. If we drew only five amperes from this battery, it should be able to furnish this current for eight hours. Thus, theoretically, the capacity of a battery should be the same, no matter what current is taken from it. That is, the current in amperes, multiplied by the number of hours the battery furnished this current should be constant.
In practice, however, we do not discharge a battery to a lower voltage than 1.7 per cell, on account of the increasing amount of sulphate and the difficulty with which this is subsequently re- moved and changed into lead and lead peroxide. The capacity of a storage battery is therefore measured by the number of ampere hours it ean furnish before its voltage drops below 1.7 per cell. This definition assumes that the discharge is a continuous one, that we start with a fully charged battery and discharge it continu- ously until its voltage drops to 1.7 per cell. |
The factors upon which the capacity of storage batteries depend may be grouped in two main classifications:
1. Design and Construction of Battery. 2. Conditions of Operation. Each classification may be subdivided. Under the Design and Construction we have: (a) Area of plate surface. (b) Quantity, arrangement, and porosity of active mate- rials. 40
CAPACITY OF STORAGE BATTERIES 41
(c) Quantity and strength of electrolyte. (d) Circulation of electrolyte.
These sub-classifications require further explanation. Taking them in order:
(a) Area of Plate Surface. It is evident that the chemical and electrical activity of a battery are greatest at the surface of the plates since the acid and active material are in intimate con- tact here, and a supply of fresh acid is more readily available to replace that which is depleted as the battery is discharged. This is especially true with high rates of discharge, such as are caused in starting automobile engines. Therefore, the capacity of a battery will be greater if the surface area of its plates is increased. With large plate areas a greater amount of acid and active mate- rials are available, and an increse in capacity results.
(b) Quantity, Arrangement, and Porosity of Active Materials. Since the lead and lead peroxide are changed to lead sulphate on discharge, it is evident that the greater the amount of these materials, the longer can the discharge continue, and hence the greater the capacity.
The arrangement of the active materials is also important, since the acid and pastes must be in contact in order to produce electricity. Consequently the capacity will be greater in a battery, all of whose active material is in contact with the acid, than in one in which the acid reaches only a portion of the active materials. It is also important that all parts of the plates carry the same amount of current, in order that the pastes may be used evenly. As a result of these considerations, we find that the active materials are supported on grids of lead, that the plates are made thin, and that they have large surface areas. For heavy discharge currents, such as starting motor currents, it is essential that there be large sur- face areas. Thick plates with smaller surface areas are more suit- able for low discharge rates.
Since the inner portions of the active materials must have a plentiful and an easily renewable supply of acid, the active mate- rials must be porous in order that diffusion may be easy and rapid.
(c) Quantity and Strength of Electrolyte. It is important that there be enough electrolyte in order that the acid may not become exhausted while there is still considerable active material left.
42 THE AUTOMOBILE STORAGE BATTERY
An insufficient supply of electrolyte makes it impossible to obtain the full capacity from a battery. On the other hand, too much electrolyte, due either to filling the battery too full, or to having the plates in a jar that holds too much electrolyte, results in an increase in capacity. There is a danger present however, because with an excess of electrolyte the plates will be discharged before the specific gravity of the electrolyte fails to 1.150. This results in overdischarge of the battery yith its attendant troubles as will be described more fully in a later chapter.
It ig a universal custom to consider a battery discharged when the specific gravity of the electrolyte has dropped to 1.150, and that it is fully charged when the specific gravity of the electro- lyte has risen to 1.300. The condition of the plates is, however, the true indicator of charged or discharged condition. With the correct amount of electrolyte, its specific gravity is 1.150 when the plates have been discharged as far as it is considered safe, and is 1.300 when the plates are fully charged. When electrolyte is therefore poured into a battery, it is essential that it contains the proper proportion of acid and water in order that its specific gravity readings be a true indicator of the condition of the plates as to charge or discharge, and hence show accurately how much energy remains in the eell at any time.
A question which may be considered at this point is why in automobile work a specific gravity of 1.300 is adopted for the electrolyte of a fully charged cell. There are several reasons. The voltage of a battery increases as the specific gravity goes up. Hence, with a higher density, a higher voltage can be obtained. If the density were increased beyond this point, the acid would attack the lead grids and the separators, and considerable corro- sion would result. Another danger of high density is that of sulphation, as explained in a later chapter. Another factor which enters is the resistance of the electrolyte. It is desirable that this be as low as possible. If we should make resistance measure- ments on various mixtures of acid and water, we should find that with a small percentage of acid, the resistance is high. As the amount of acid is increased, the resistance will grow less up to a certain point. Beyond this point, the resistance will increase again aS more acid is added to the mixture. The resistance is
CAPACITY OF STORAGE BATTERIES 43
lowest when the acid forms 30% of the total weight of the electro- lyte. Thus, if the electrolyte is made too strong, the plates and also the separators will be attached by the acid, and the resistance of the electrolyte will also increase. The voltage increases as the proportion of acid is increased, but the other factors limit the concentration. If the electrolyte is diluted, its resistance rises, voltage drops, and the amount of acid is insufficient to give much eapacity. The density of 1.300 i therefore a compromise between the various factors mentioned above. 7
(d) Circulation of Electrolyte. This refers to the passing o electrolyte from one plate to another, and depends upon the ease with which the acid can pass through the pores of the separators. A porous separator allows more energy to be drawn from the battery than a non-porous one.
Considering now the operating conditions, we find several items to be taken into account. The most important are
(e) Rate of discharge. (f) Temperature. :
(e) Rate of Discharge. As mentioned above, the ampere hour rating of a battery is based upon a continuous discharge, starting with a specific gravity of 1.300, and finishing with 1.150. The end of the discharge is also considered to be reached when the voltage per cell has dropped to 1.7. With moderate rates of discharge the acid is abstracted slowly enough to permit the acid from outside the plates to diffuse into the pores of the plates and keep up the supply needed for the chemical actions. With increased rates of discharge the supply of acid is used up so rapidly that the diffusion is not fast enough to hold up the voltage. This fact is shown clearly by tests made to determine the time required to discharge a 100 Amp. Hr., 6 volt battery to 4.5 volts. With a discharge rate of 25 amperes, it required 160 minutes. With a discharge rate of 75 amperes, it required 34 minutes. From this we see that making the discharge rate three times as great caused the battery to be discharged in one fifth the time. These discharges were continuous, however, and if the battery were allowed to rest, the voltage would soon rise sufficiently, to burn the lamps for a number of hours.
The conditions of operation in automobile work are usually
44 THE AUTOMOBILE STORAGE BATTERY
considered severe. In starting the engine, a heavy current is drawn from the battery for a few seconds. The generator starts charging the battery immediately afterward, and the starting energy is soon replaced. As long as the engine runs, there is no load on the battery, as the generator will furnish the. current for the lamps, and also send a slight charge into the battery. If the lamps are not used, the entire generator output is utilized to charge the battery, unless some current is furnished to the ignition system. Overcharge is quite possible.
When the engine is not running, the lamps are the only load on the battery, and there is no charging current. Various drivers have various driving conditions. Some use their starter fre- quently, and make only short runs. Their batteries run down. Other men use the starter very seldom, and take long tours. Their batteries will be overcharged. The best thing that can be done is to set the generator for an output that will keep the battery charged under average conditions.
From the results of actual tests, it may be said that modern lead-acid batteries are not injured in any way by the high dis- charge rate used when a starting motor cranks the engine. It is the rapidity with which fresh acid takes the place of that used in the pores of the active materials that affects the capacity of a battery at high rates, and not any limitation in the plates them- selves. Low rates of discharge should, in fact, be avoided more than the high rates. Battery capacity is affected by discharge rates, only when the discharge is continuous, and the reduction in capacity caused by the high rates of continuous discharge does not oceur if the discharge is an intermittent one, such as is actually the case in automobile work. The tendency now is to design bat- teries to give their rated capacity in very short discharge periods. If conditions should demand it, these batteries would be sold to give their rated capacity while operating intermittently at a rate which would completely discharge them in three or four minutes. The only change necessary for such high rates of dis- eharge is to provide extra heavy terminals to carry the heavy current.
The Society of Automotive Engineers, in January, 1914, adopted
—/
CAPACITY OF STORAGE BATTERIES. 45
a standard method of rating, starting and lighting batteries, as follows: |
‘‘Batteries for combined lighting and starting service shall have two ratings, of which the first shall indicate the lighting ability, and the capacity in ampere hours of the battery when discharged continuously at a 5 ampere rate to a final voltage of 1.8 per cell, the temperature of the battery beginning such discharge being 80°F. The second rating shall indicate starting ability and shall be the rate in amperes at which the battery will discharge for twenty minutes continuously to a final voltage ‘of not less than 1.65 per cell. The temperature of the battery beginning such discharge to be 80°F.”’
The discharge rate required under the average starting con- ditions is higher than that specified above, and would cause the required drop in voltage in about fifteen minutes. In winter, when an engine is cold and stiff, the work required from the bat- tery is even more severe, the discharge rate being equivalent in amperes to probably four or five times the ampere-rating of the battery. On account of the rapid recovery of a battery after a discharge at a very high rate, it seems advisable to allow a bat- tery to discharge to a voltage of 1.0 per cell when cranking an engine which is extremely cold and stiff.
(f) Temperature. Chemical reactions take place much more readily at high temperatures than at low. Furthermore, the active materials are more porous, the electrolyte lighter, and the internal resistance less at higher temperatures. Opposed to this is the fact that at high temperatures, the acid attacks the grids and pastes, and lead sulphate is formed, even though no current is taken from the battery. Other injurious effects are the destructive actions of hot acid on the wooden separators used in most starting and lighting batteries. Greater expansion of paste will also occur, and this expansion is not, in general, uni- form over the surface of the plates. This results in unequal strains and the plates are bent out of shape, or ‘‘buckled.’’ The expansion of the paste will also cause much of it to fall from the plates, and we then have ‘‘shedding.’’
When sulphurie acid is poured into water, a marked tempera- ture rise takes place. When a battery is charged, acid is formed.
46 THE AUTOMOBILE STORAGE BATTERY
and when this mixes with the diluted electrolyte, a temperature rise occurs. In discharging, acid is taken from the electrolyte, and the temperature drops. On charging, therefore, there is danger of overheating, while on discharge, excessive tempera- tures are not likely. Fig. 15 shows the temperature changes on charge and discharge.
Another factor which should be considered in connection with capacity is the age of the battery. New batteries will seldom
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give their rated capacity when received from the manufacturer. This is due to the methods of making the plates. The ‘‘paste’” plates, such as are used in automobiles, are made by applying oxides of lead, mixed with sulphuric acid, to the grids. These oxides must be subjected to a charging current in order to pro- duce the spongy lead and lead peroxide. After the charge, they must be discharged, and then again charged. This is necessary because not all of the oxides are changed to active material on one charge, and repeated charges and discharges are required
CAPACITY OF STORAGE BATTERIES AT
to produce the maximum amount of active materials. Manu- facturers do not charge and discharge a battery a sufficient num- ber of times before sending it out, and after a battery is put into use, its capacity will increase for some time, because more active material is produced during each charge.
When a battery has been in use for some time, a considerable portion of the paste will have fallen from the positive plates, and a decrease in capacity will result. Such a battery will charge faster than a new one because the amount of sulphate which has formed when the battery is discharged is less than in a newer battery. - Hence, the time required to reduce this sulphate will be less, and the battery will ‘‘come up’’ faster on charge.
CHAPTER 9.
INTERNAL RESISTANCE,
The resistance offered by a storage battery to the flow of a current through it results in a loss of voltage, and in heating. Its value should be as low as possible, and, in fact, it is almost negligible even in small batteries, seldom rising above 0.05 ohm. On charge, it causes the charging voltage to be higher and on
discharge causes a loss of voltage. tion in resistance.
Figure 16 shows the varia-
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6 See on 728 GRR an eee eee an oe ee ‘2 CR see eT INTE ELE reer 7 Nee see 2 COON Mo +t | | Soe | TTT PT TT tet PPP Pere ann am ost LETT TTT aan aan ° ' ? id HOURS . . 7 _ @
Fig. 16
The resistance aS measured between the terminals of a cell
is made up of several factors as follows:
1. Grids. This includes the resistance of the terminals, con- necting links, and the framework upon which the active materials are pasted. This is but a small part of the total resistance, and does not undergo any considerable change during charge and discharge. It increases slightly as its temperature goes up.
48
INTERNAL RESISTANCE 49
2. Electrolyte. This refers to the electrolyte between the plates, and varies with the amount of acid and with tempera- ture. As mentioned in the preceding chapter, a mixture of acid and water in which the acid composes thirty per cent of the total weight of electrolyte has the minimum resistance. Diluting or increasing the concentration of the electrolyte will both cause an increase in resistance from the minimum value. The expla- nation probably lies in the degree to which the acid is split up into ‘‘ions’’ of hydrogen (H), and sulphate (SO,). These ‘‘ions’’ earry the current through the electrolyte. Starting with a cer- tain amount of acid, let us see how the ionization progresses. With very concentrated acid, ionization does not take place, and hence, there are no ions to carry current. As we mix the acid with water, ionization occurs. The more water used, the more ions, and hence, the less the resistance, because the number of ions available to carry the current increases. The ionization in- creases to a certain maximum degree, beyond which no more ions are formed. It is probable that an electrolyte containing thirty per cent of acid by weight is at’: its maximum degree of ioniza- tion and hence its lowest resistance. If more water is now added, no more ions are formed. Furthermore, the number of ions per unit volume of electrolyte will now decrease on acccunt of the increased amount of water. There will therefore be fewer ions per unit volume to carry the current, and the resistance of the electrolyte increases.
With an electrolyte of a given concentration, an increase of temperature will cause a decrease in resistance. A decrease in temperature will, of course, cause an increase in resistance. It is true, in general, that the resistance of the electrolyte is about half of the total resistance of the cell. The losses due to this re- sistance generally form only one per cent of the total losses, and are a practically negligible factor.
3. Active Material. This includes the resistance of the pastes and the electrolyte in the pores of the active materials. This varies considerably during charge and discharge. It has been found that the resistance of the peroxide plate changes much more than that of the lead plate. The change in resistance of the positive plate is especially marked near the end of a discharge. The composi-
20 THE AUTOMOBILE STORAGE BATTERY
tion of the attive material, and the contact between it and the grid affect the resistance considerably.
During charge, the current is sent into the cell from an external source. The grids therefore carry most of the current. The active material which first reacts with the acid is that near the
surface of the plate, and the acid formed by the charging current |
mixes readily with the main body of electrolyte. Gradually, the eharging action takes place in the inner portions of the plate, and concentrated acid is formed in the pores of the plate. As the sulphate is removed, however, the acid has little difficulty in mixing with the main body of electrolyte. The change in resistance on the charge is therefore not considerable.
During discharge, the chemical action also begins at the sur- face of the plates and gradually moves inward. In this ease, however, sulphate is formed on the surface first, and it becomes increasingly difficult for the fresh acid from the electrolyte to diffuse into the plates so as to replace the acid which has been
greatly diluted there by the discharge actions. There is therefore |
an increase in resistance because of the dilution of the acid at the point of activity. Unless a cell is discharged too far, however, the increase in resistance is small.
If a battery is allowed to stand idle for a long time it grad- ually discharges itself, as explained in a previous chapter. This is due to the formation of a tough coating of crystallized lead sulphate, which is practically an insulator. These crystals gradu- ally cover and incapsulate the active material. The percentage change is not high, and generally, amounts to a few per cent only. The chief damage caused by the excessive sulphation is
therefore not an increase in resistance, but consists chiefly of mak- |
ing a poor contact between active material and grid, and of re- moving much of the paste from action by covering it.
CHAPTER 10. BATTERY DISEASES.
Storage batteries have their own peculiar troubles which pro- duce injuries that are not always curable. The chief troubles met with are as follows:
1. Sulphation.
2. Loss of capacity.
3. Buckling of plates in battery.
4. Hardening of negative plates when exposed to air.
5. Buckling of positive plates when exposed: to light.
6. Internal discharge. |
These troubles are not entirely independent of one another, since the causes of one of them may include some of the ethers.
1. Sulphation: Many battery men say a battery is sulphated whenever anything is wrong with it. Sulphation is the forma- tion of lead sulphate on the plates. As a battery discharges, it is entirely natural and normal for lead sulphate to form. When the voltage of a battery has dropped to about 1.7 per cell, there is still a considerable portion of active material left, but much of it is covered by sulphate and thus made useless. A normal charge will change this sulphate to active material. If the discharge is continued after the voltage has dropped to 1.7 per cell, so much sulphate has been formed that it is difficult to change it to active material. Moreover, the expansion of the paste which takes place when lead sulphate is formed may be so great that it causes the paste to break off from the plate and fall to the bot- tom of the jar.
If a battery is charged and discharged intermittently, and the discharge is greater than the charge, the battery may never be fully charged, and there will always be sulphate present. If a battery which has been discharged is allowed to stand idle for several months, the sulphate which was formed during the dis-
51
D2 THE AUTOMOBILE STORAGE BATTERY
charge changes. Instead of being finely divided, it now forms crystals which grow by the addition of sulphate from other parts of the plates. These crystals can be reduced to active material only with the greatest difficulty, and often it is impossible to do so.
Another factor which aids in the ‘‘sulphation,’’ is the self- discharge caused by impurities. These cause local actions which partly discharge the battery and add their quotas of sulphate. A completely charged battery can, in an emergency, be left idle for six months without causing an excessive amount of sulphate to form and crystallize.
Usually, most of the sulphate is formed by the chemical actions which produce the electrical energy. Useless chemical action occurs however between paste and electrolyte which result in the formation of lead sulphate even though no current is taken from the battery. Thus a certain amount of sulphate forms on the sur- face of the spongy lead and between the lead peroxide and the positive grids. Since these are entirely normal actions, they can hardly be classified as diseases. If there is too much acid in the electrolyte, or its temperature is allowed to become too high, an abnormal amount of sulphate is formed, because hot concentrated acid is more active chemically than the normal electrolyte.
Over-sulphation is often caused by the loosening of the active material and consequent short circuit between the plates. Sulpha- tion from any cause may result in shedding, buckling, loss of ca- | pacity, loss of efficiency and an increased temperature while charging and discharging. The voltage of a sulphated battery | will be below normal on discharge and above normal on charge.
If the electrolyte is allowed to fall below the tops of the plates, so that the pastes are exposed to the air, the parts thus exposed will gradually sulphate, especially on the negative plates. Some , of the sulphate is formed because the current heats up those parts of the grids which are not covered by acid. This heats the pastes and any acid in them. The sulphate which has been formed by normal discharge will be dissolved on account of the heat, and will then form in erystals as the heat dries up the acid. This will take place on both positive and negative plates. After sulphate has been formed in this way, no more is formed on the positive
BATTERY DISEASES : D3
plate. On the negative plate, however, the sulphate continues to form. This is explained as follows:
The negative paste is spongy lead, which is in an unstable chem- ical condition. The dry spaces between the plates and above the surface of the electrolyte contain definite amounts of sulphur di- oxide (SO,), and sulphur trioxide (SO,), liberated during the chemical reactions of the cell. These unite with the spongy lead to form lead sulphate. The spongy lead first absorbs oxygen from the air and becomes oxidized, then combines with the dioxide and trioxide to form lead sulphate. Gradually the entire nega- tive active material becomes sulphated in this way. The lead peroxide does not sulphate when dry because it is in a stable con- dition. |
Lead sulphate does not form uniformly over the surfaces of the plates as a battery discharges. At the beginning of a discharge it is supposed that the lead sulphate forms chemical compounds. The reason for this belief is that a peroxide plate grows darker at first instead of lighter as we should expect, since lead sulphate is white, and a mixture of lead peroxide and lead sulphate should be lighter than the peroxide alone. After a time, however, patches of the white sulphate appear on the plate surfaces. If only a nor- mal discharge is given, it is not difficult to change this sulphate to active material. If the sulphate is allowed to erystallize, how- ever, it is a very difficult matter. The crystallized sulphate is tcugh, and is a good: insulator. Such a plate must be charged at a low rate, because so much of the active material is covered with the sulphate that the current cannot reach it. Only a small portion of the active material is uncovered and hence in contact with the acid. These parts must carry all the charging current, and if this current is not low, the small patches of active material which must earry the current become very hot, resulting in serious injury to them. Furthermore, if a large charging current is used, the water of the electrolyte is split into hydrogen and oxygen, and gassing results. This causes chips of the sulphate to break off and fall to the bottom of the cell, and thus be removed from action.
Another danger from large charging currents in sulphated plates is that the parts carrying the current will become hotter
o4 THE AUTOMOBILE STORAGE BATTERY
than other parts. This results in an unequal expansion of paste and grids, and the plate may be warped and bent out of shape.
We see, therefore, that the presence of lead sulphate is objec- tionable only when an excessive amount is formed, or when it be- comes crystallized. A small amount of sulphate in the positive plate is desirable, in fact. Lead peroxide does not hold together well, but a small amount of sulphate acts as a cement and binds the particles of the paste together. At the surface of the plate, the sulphate is almost completely removed on charge, and some of the peroxide loses its hold on the plate and falls to | the bottom of the cell. This is called ‘‘shedding’’ of the active material. A battery which is kept slightly undercharged will have a longer life than one which is continually over- charged.
The best remedy for a sulphated battery is to pass a charge of low amperage through the cells for a long time. The charge rate should not be much above 1/25 of the capacity of the bat- tery in ampere-hours and should be continued until the specific gravity has risen to its normal value of 1.280-1.300 and has re- mained eonstant for three or four hours. At this time all of the cells should be gassing rather freely. The length of time required may be from one day to one week of continuous charging or a succession of charges of equivalent time.
2. Loss of Capacity. This subject may be again subdivided, as quite a number of factors must be considered. Some of them are given under the main headings at the beginning of this chap- ter. They are as follows: |
(a) Impurities in Electrolyte. These result in local action and self-discharge. They can sometimes be removed by giving the battery a complete charge, discarding the electrolyte, and putting in new electrolyte of the proper specific gravity to bring it to 1.280-1.300 when fully charged.
(b) Low Gravity of Electrolyte. Low gravity may result from lack of charge, replacing spilled electrolyte or electrolyte which has leaked out through a cracked jar, with water. This condition may be remedied by charging until the cells are gassing freely and no further increase in specific gravity occurs, and then removing some of the electrolyte and adding electrolyte of
BATTERY DISEASES ay)
1.400 gravity. Then give battery a full charge. It may be necessary to empty out the old electrolyte and put in new electro- lyte. If the maximum specific gravity of the old electrolyte was 1.200, use 1.400 electrolyte, and if the old electrolyte has a different strength, vary the specific gravity of the new accord- ingly. ;
(ce) High Gravity of Electrolyte. This is caused by incorrect mixtures of acid and water in preparing electrolyte, and by adding raw acid or electrolyte in making up for loss of elec-
trolyte by evaporation. It results in sulphation, burned separa- tors, or corroded plates, all of which cause a loss of capacity.
(d) Sulphation. This has already been explained.
(e) Pores of Separators Filled With Impurities or Active Ma- terial From Bulged Plates. This prevents circulation of electro- lyte, which hinders chemical action and thus reduces capacity. Generally, a battery in this condition has been neglected or abused. The plates will probably be found to be in need of re- pairs, a subject which will be discussed more fully later.
(f) Bulged Active Material on Negative Plates, Causing Poor Contact Between Paste and Grid. If the lead does not have a granular appearance, or if active material has not been shed to any considerable extent, pressing the plates in a vise or press (see page 215) will remedy the trouble. When the bulged paste has been pressed back into the grids, it will be necessary to charge and discharge the battery several times in order to put the spongy lead in an active condition.
(¢g) lack of Sufficient Charging and Discharging of New Batteries, Batteries Which Have Been Sulphated, and Rebuilt, Batteries With New Plates. This can be remedied generally by eharging and discharging two or three times, and adjusting electrolyte so as to have proper specific gravity by removing some of old electrolyte and adding water or 1.400 electrolyte, as the case may be.
If in doubt as to the battery’s condition, charge it until it gasses freely, and the specific gravity of the electrolyte does not inerease over several hours. Now discharge the battery at one fourth to one fifth of its ampere hour capacity. If, when the battery voltage has dropped to 1.7 per cell, the battery has de-
06 THE AUTOMOBILE STORAGE BATTERY
livered fifty to sixty per cent of its ampere hour capacity, based
on its eight hour rate, the battery should give reasonable service.
If convenient, make the cadmium test (see page 266). If this test shows that the plates of any cell are in a poor condition,
the battery must be opened and the trouble found and repaired |
(see page 187).
(h) Corroded Grids. Caused by nonuniform mixture in alloy of which grids are made, by the chemical action resulting from electrolytic decomposition of highly dilute acid in the pores
of the active material, and by the presence of lead dissolving acids |
or their compounds in the electrolyte. The first condition is hope- less. The second is also, as it occurs in every cell if the dis- charge is carried too far, or if the plates have a thick layer of active material when the rate of discharge is high. If the elec- trolyte contains impurities which attack the lead, the remedy is to pour out the old electrolyte, and put in fresh, which is known to be chemically pure.
Corrosion is also the natural result of the action of the acid on the plates, and is the natural depreciation occurring in the plates. This can be retarded by keeping the specific gravity of the electrolyte slightly below that for full charge. This corro- sion tends to take place most rapidly at the surface of the elec- trolyte, and the damage at this point can be lessened by keep- ing the plates covered with electrolyte, and making the terminal bars and lugs extra large in cross section.
(i) Reversal of Negative Plates. If one cell of a battery has an internal short circuit, or some other defect which causes it to lose its charge, the cell will be discharged before the others which are in series with it, and when this cell is completely discharged, the other cells will send a current through it in a discharge direc- tion, and the negative plates will have a coating of lead perox- ide formed on them, and will assume the characteristics of posi- tive plates.
This reversal may also be the result of charging a battery in the wrong direction, on account of reversed charging connections. The remedy is to charge the battery for a long time in the proper direction. If the reversal was caused by some defect within the cell itself, the cause of the defect should be found and removed.
BATTERY DISEASES o7
Such defects may be internal short circuit, local action caused by impurities, loss of active material, sulphation, ete.
(j) Loss of Active Material, or Shedding. This is a natural action for positive plates, since the lead peroxide is not coherent, and as it expands, on discharge, outer layers are forced off, and fall to the bottom of the jar. Internal short circuits, sulpha- tion, or buckling of the grids will also cause shedding. The posi- tive plate becomes extremely thin and gradually wears out, or ages. Excessive charging rates resulting in violent evolution of gas. This loosens some of the active material and causes it to drop to the bottom of the jar. Normal charging rates will cause shedding in sulphated plates because gassing will take place due to the fact that the plates do not have enough active material exposed to the current to use all the current in producing chem- ical action. A current which is normal for a battery in good condition is therefore excessive for a sulphated battery.
Should the active material be loosened from the grids and fall to the bottom of the cell in large quantities, it will not only result in short circuiting the plates but will also result in a loss of capacity because of the decreased volume of material remaining in the grids. Shedding is usually the result of overcharge or buckling. It is also caused by the addition of raw acid or electro- lyte in place of water. The remedy is to have the plates repasted in a battery repair depot that is equipped for such work. A certain amount of space is left between the bottom of the plates and the bottom of the cells to care for this sediment but if the collection is allowed to grow until it touches the plates, short circuiting will result. The remedy is to have the plates removed and the cells cleaned at intervals of nine months to one year.
(k) Negative Plates Granulated. The spongy lead tends to become granulated and dense in structure, and to lose its porosity so that it resembles ordinary lead. This is a natural and un- avoidable condition, and is simply. the natural ageing of the spongy lead.
The remedy for ths condition is to discharge the battery, re- move the negative plates, place them in a bath of electrolyte of 1.200 specific gravity sulphuric acid, in which sheets of ordinary lead, 1/16 inch thick are also placed. Current is sent through
58 THE AUTOMOBILE STORAGE BATTERY
the combination, entering at the negative plates and leaving at the “‘dummy’’ electrodes of ordinary lead. The spongy lead first turns into lead monoxide (PBO), and then lead peroxide (PBO,). When all the spongy lead has been changed to lead peroxide, the current is reversed. Befcre reversing the current, however, the electrolyte is poured out and new electrolyte used, in order that any impurities in the old electrolyte may not be redeposited on the negative plates. The lead peroxide now changes back to spongy lead, and when the plates are replaced and the battery reassembled, it will be found to have regained the capacity which was lost by the ageing of the spongy lead.
(1) Improperly constructed battery, or one which has been poorly designed. Inferior materials and poor workmanship result in a battery of low capacity.
3. Buckling. This is the bending or twisting of plates, and is caused by unequal expanson of the various parts of the active material. Buckled plates are saucer shaped, the center portions expanding more than the edges on account of being less firmly braced and supported. Any conditions of operation which will cause excessive or non-uniform expansion of active material will result in buckling. These conditions are as follows:
(a) Overdischarge. If discharge is carried too far, the expan- sion of the active material on account of the formation of lead sulphate will bend the grids out of shape, and may even break them.
(b) Continued Operation With Battery In a Discharged Con- dition. When a considerable amount of lead sulphate has formed, and current is still drawn from the battery, those portions of the plate which have the least amount of sulphate will carry all the current, and will therefore become heated and expand. The parts covered with sulphate will not expand, and the result is
that the parts that do expand will twist the plate out of shape. .
A normal rate of discharge may be sufficient to cause buckling in a sulphated. plate. (c) Charging at High Rates. If the charging rate is exces-
oe a va a ve eT
sive, the temperature will rise so high that excessive expansion
will take place. This is usually unequal in the different parts of the plate, and buckling results. With a battery that has been
BATTERY DISEASES 59
over-discharged, the charging current will be carried by those parts of the plates which are the least sulphated. These parts will therefore expand while others will not, and buckling results.
(d) Non-Uniform Distribution of Current Over the Plates. In a battery which has not been over-discharged, buckling may result if the current carried by the various parts of the plate is not uniform on account of faulty design, or careless application of the paste. This is a fault of the manufacturers, and not the operating conditions.
(e) Defective Grid Alloy. If the metals of which the grids are composed are not uniformly mixed throughout the plate, areas of pure lead may be left here and there, with air holes at various points. The electrolyte enters these air holes, attacks the lead and converts the grid partly into active materail. This causes expansion and consequent distortion and buckling.
Buckling will not necessarily cause trouble, and batteries with buckled plates may operate satisfactorily for a long time. If, however, the expansion and twisting has caused much of the active material to break away from the grid, or has loosened the active material from the grids, much of the battery capacity is lost. Another danger is that the lower edges of a plate may press against the separator with sufficient force to cut through it, touch the next plate, and cause a short-circuit, and the battery fails. |
If buckling is caused by defective plates, there is no remedy except to avoid discharging the plate very far, and protect the battery from the effects of light and heat. If over-discharge, or other conditions not resulting from defective plates have caused buckling, and if the active material has not been loosened from the grids, or has not dropped to the bottom of the cell, it is possible to remove the separators, put in boards having same thickness as the separators, and then slowly and carefully compress the plates in a vise until restored to shape. If the buckling has been so excessive that parts of the grids have broken, much paste has been lost, or a short circuit has resulted, the only remedy is to install new plates.
4. Hardening of Negatives. When negative plates are exposed to air, the spongy lead, instead of being soft and finely divided,
60 THE AUTOMOBILE STORAGE BATTERY
erystallizes and oxidizes, and becomes hard. This causes the paste to become heated. The acid which remains in the plate will also heat, and attack the spongy lead. Negative plates should therefore always be immersed in water or weak electrolyte when removed from a battery.
5. Buckling of Positive Plates When Exposed to Light. A phe- nomenon for which no explanation has been found is that positive plates buckle when exposed to light, the side toward the light becoming concave. The positive plates should therefore be kept in a dark box or cupboard when removed from the battery.
6. Internal Discharge. This shows itself by the gradual los: of charge when a fully or partly charged battery is allowed to stand idle. The causes are:
(a) Formation of layer of sulphate between the lead peroxide and the grid. :
(b) Formation of a layer of sulphate on the surface of the negative plate.
(ec) Impurities in plates which form small cells with the active materials and by their discharge take away some of the battery capacity.
These points have already been explained. See page 26.
‘CHAPTER 11. CONDITIONS OF OPERATION.
The starting and lighting equipment of a gasoline automobile consists of three principal parts.
1. The Battery.
2. The Starting Motor.
3. The Dynamo or Generator.
The normal course of operation of this system consists of
(a) Cranking the Engine With the Starting Motor. A switch is operated whereby the battery is connected to the starting motor, causing the latter to put the engine in motion. As soon as the gasoline has begun to vaporize, and is mixed with the correct amount of air, the sparks at the spark plugs ignite the mixtures of air and gasoline which are drawn into the engine cylinders. The engine then operates under its own power. The starting switch is then opened, disconnecting the motor from the battery. As long as the engine now continues to run under its own power, the starting motor is not used. |
(b) Charging the Battery. The current taken by the start- ing motor is a heavy one, and discharges the battery to a con- siderable extent. The energy taken out must therefore be re- placed. This is done by the dynamo. It is important, however, that the dynamo should not be connected to the battery until the engine is operating above a certain minimum speed. This is necessary because a dynamo must develop a voltage which is greater than that of the battery before it can send a current through the battery so as to charge it. In order to develop this voltage, the speed of the dynamo must reach a certain value. Should the dynamo be connected to the battery at a lower speed, its voltage would be less than that of the battery, and instead of the dynamo sending a current through the battery, the battery
61
62 THE AUTOMOBILE STORAGE BATTERY
will send a current through the dynamo, and thus lose more energy.
In most cars, the switch which connects the dynamo to the battery operates automatically, and does not operate until the voltage of the dynamo is slightly greater than that of the bat- tery. It is known as the ‘‘circuit breaker,’’ ‘‘cutout relay,’’ or simply the ‘‘cutout.’’ When the speed of the engine decreases, the voltage developed by the dynamo also decreases, and it becomes necessary to disconnect the dynamo from the battery when the dynamo voltage begins to drop below that of the
battery. This is also done by the eutout. The construction |
cutouts will be explained more fully later. Some cars have no
automatic cutout, but use a hand operated switch. Others have |
both the automatic and the hand operated switches.
(c) Furnishing Current to the Lamps. When the engine is
not running, the battery is the only source of electricity on the
car, and therefore operates the lights. When the engine is in | operation, and the dynamo is sending a current through the — battery, or is ‘‘charging’’ it, the dynamo also supplies the cur- |
rent to operate the lamps.
These conditions of operation seem to be simple enough, and ©
as long as all parts work as they should, no difficulties are en- eountered. In order to obtain satisfactory service, however, 4 number of things must be considered.
Normal Conditions of Operation, Engine Idle.
When the engine is idle and the lamps and all other electrical equipment on the automobile are entirely disconnected from the battery by means of their controlling switches, there should be no current delivered by the battery. When there is no current delivered by the battery under the above ‘conditions, it indicates that there are no shorts or grounds connecting the positive and negative terminals of the battery or between the battery and the terminals of the various switches. It also indicates that the eutout, whether it be mechanical, electro-magnetic or manual, is open and no current is being deliverd by the battery to the dynamo armature. When the battery shows a discharge with
CONDITIONS OF OPERATION 63
all the various controlling switches open, it may be due to grounds, short circuits or improper operation of the cutout. An inspection of the cutout will soon tell whether it is closed or not, and thus eliminate this possible cause of trouble, which reduces the difficulty to a short circuit or ground. A thorough inspection of the circuit will be necessary in order to determine the exact location of this kind of trouble.
It is not advisable to equip an automobile with lamps whose candlepower exceeds that recommended by the manufacturer of the car or equipment maker. If the current delivered by the battery with the lamps turned on exceeds the normal value for that particular car, it may be due to lamps 8f higher candle- power having been substituted for the standard equipment, or shorts and grounds. A short or ground may also be thrown onto the battery circuit when the switches controlling special elec- trical equipment, such as electric gear shifts, horns, trouble lamps, ete., are closed. It is always advisable to test each of these different circuits separately in order to make sure that they are free from shorts and grounds and not drawing an excessive current from the battery when in operation.
Normal Conditions of Operation, Engine Running.
When a manual type of cutout is used the battery and dynamo are connected together through a switch whose opera- tion is controlled by the driver of the car. These switches are of different forms and arrangements, some being combined with the ignition switch, some with the starting switch, while some may operate to a certain extent independent of either the start- ing or ignition switches. With this type of cutout the operation of the dynamo and the adjustment of the regulator controlling the output of the dynamo should be such that the battery will be charging when the engine is running at very low speeds. If this adjustment is not made, it is advisable not to run the engine at very low speeds at any time with the cutout closed, as the voltage of the dynamo will be lower than the voltage of the battery and, hence, the battery will discharge back into the
64 THE AUTOMOBILE STORAGE BATTERY
dynamo. A condition of this kind may be the cause of a dis- charged battery. The car speed at which the battery starts to discharge may be determined by connecting an ammeter in series with the battery and observing its indication as the speed of the engine or car is decreased. The speedometer indication, when the ear is running and the ammeter indicating zero current, corresponds to what might be called the neutral speed; that is, the voltage of the generator and battery are equal and the battery is neither charging nor discharging. This neutral speed should not be excessive, as a high neutral speed means a rela- tively low dynamo voltage, and hence a corresponding decrease in output of the dynamo.
If a mechanical cutout is used its adjustment should be such that the circuit connecting the dynamo and battery is not closed until the speed of the dynamo is sufficient to cause a generated voltage in its armature winding greater than the voltage of the battery. If this cutout closes too soon the battery will discharg when the circuit is first closed and will continue to do so until the speed of the dynamo is ample to cause the generated voltage in its armature winding to be equal to or greater than the voltage of the battery. This type of cutout may be tested by observing the indications of an ammeter connected in series with the bat- tery while the speed of the engine is gradually increased. If the voltage of the dynamo is less than the voltage of the battery when the cutout closes, the ammeter will indicate a discharge from the battery. If the voltage of the dynamo happens to be equal to the voltage of the battery when the circuit is: closed, there will be no indication on the ammeter, but as the speed of the engine is increased, the ammeter will show a gradually in- ereasing charge. If the voltage of the dynamo exceeds the voltage of the battery when the cutout closes, the charging current, aS indicated on the ammeter will not gradually rise from zero to a maximum value with increase of engine speed, but the indication of the ammeter will suddenly jump from zero to a certain value when the cutout closes, depending upon how much the voltage of the dynamo exceeds the voltage of the battery and the resistance of the entire circuit. The indicator
CONDITIONS OF OPERATION 65
then gradually increases from this value to a maximum value with increase in engine speed.
The operation of the electromagnetic cutout should be such that the dynamo and battery are connected together when the voltage of the dynamo is high enough to cause a charging cur- rent to pass through the battery when the voltage of the battery is at its maximum value or the battery is practically fully charged. The value of the charging current at the instant the circuit is closed will depend upon the difference between the voltage of the dynamo and the voltage of the battery. This difference will be greatest when the battery is practically or completely discharged and a minimum value when the battery is fully charged. The operation of the cutout may be determined as described on page 169.
The charging rate must be sufficiently high so that with all lamps turned on and the car running at a speed of about fifteen miles per hour, an ammeter connected at the battery will show some charge in spite of the current being drawn for lighting (lamp load). This does not mean, however, that the charge rate with the lamps turned off should always be equal to the lamp load, because of the variations in dynamo control.
The charge rate with the lamps turned off should never exceed in amperes one-sixth of the total ampere-hour capacity of the battery, and except at extreme high speeds should never exceed one-eighth of this capacity.
General Operating Conditions Which Govern the Action of a Battery.
The greatest drain on the storage battery is the operation of the starting motor. Under no conditions should the starting motor be used to propel the car, as there will undoubtedly be permanent damage done to the battery. Damage due to such treatment may not appear for some time, but it is sure to come if the practice be followed to any extent.
The starting motor should be used as economically as possible, and the engine started only when it is necessary to do so. Care should be exercised in the adjustment of the carburetor and
66 THE AUTOMOBILE STORAGE BATTERY
ignition system so that it will not be necessary to erank the
engine for a considerable period before it will start. A great many drivers have a habit of holding their foot on the starting switch after the engine starts to fire, which results in an unneces- sary discharge of the battery.
The adjustment of the output of some dynamos is such that |
the dynamo very seldom reaches its maximum output due to the fact that the driver may not ordinarily operate the car at a high enough speed, on account of traffic regulations or road con- ditions, to enable the dynamo to develop. its maximum voltage. In such cases the output of the dynamo should be increased when such an adjustment is possible.
In some cases a car may be used almost entirely at night or | at least a large part of the time that it is in use may be at night, |
and in such cases the drain on the battery may be excessive for the amount of charge put into it. The driver should use his
starting motor as sparingly as possible, substitute lamps of lower |
candle power for the ones regularly supplied if such substitution gives ample light for driving purposes, and be careful in the _use of the electric horn and other electrical accessories. In no ease should the charging rate be increased to such an extent by adjusting the regulator that the dynamo or battery will he damaged.
The efficiency of a storage battery is considerably less in cold |
weather than it is in warm weather, and this, coupled with the
fact that the number of hours of darkness during which the car |
is likely to be used is greater in cold weather than in warm, often results in the battery becoming discharged, or failing to carry the load imposed upon it during the winter, even though it oper- ated very satisfactorily during the warm summer months. The engine is always harder to start in cold weather than it is in warm weather, due to the fact that the gasoline does not vaporize as readily and the oil in all the bearings and around the pistons is stiff, making the engines much harder to turn over. In such eases it is often necessary to increase the output of the dynamo during certain months of the year in order to make up for the loss in efficiency and increase in output the battery is called upon to supply.
CONDITIONS OF OPERATION 67
The condition of operation during the warm summer months and long days may on the other hand result in serious damage to the battery on account of excessive charging in proportion to discharge. During the summer. the engine turns over more easily, the battery is much more efficient, the gasoline vaporizes more easily, and the lamps are not used nearly as much as they are in the winter. This condition of over-charging can be relieved to a certain extent by means of a touring switch, by means of which the driver may disconnect the battery from the dynamo, or by turning on all of the lamps with the engine idle and allowing the battery to discharge for a few hours at certain intervals, depending upon the speed at which the car is driven when in use, that is, upon the amount of charge put into the battery.
CHAPTER 12. HOW TO TAKE CARE OF THE BATTERY ON THE CAR.
The manufacturers of Starting and Lighting Equipment have designed their generators, cutouts, and current controlling devices so as to relieve the car owner of as much work as possible in taking care of batteries. The generators on most cars are auto- matically connected to the battery at the proper time, and also disconnected from it as the engine slows down. The amount of current which the dynamo delivers to the battery is automatically prevented from exceeding a certain maximum value. Under the average conditions of driving, a battery is kept in a good con- dition. It is impossible, however, to eliminate entirely the need of attention on the part of the car owner, and battery repairman.
The repairman, especially, should know what charging currents the various makes and types of generators with which the auto- mobiles are equipped should produce. It is a good plan always to put an ammeter in series with the battery, run the engine with the lamps turned off, and measure the charging current which is being delivered to the battery. This should be done on every car that is brought in for repairs. The charging current actually received by the battery should be checked with the current the generator is intended to deliver, and for which the generator is adjusted before the car leaves the factory. If the generator is not delivering the proper current, find out why, and remedy the trouble. Otherwise the battery cannot be expected to do its work satisfactorily, and be fully charged.
The storage battery requires but little attention, and this is the very reason why many batteries are neglected. Motorists often have the impression that because their work in caring for a battery is quite simple, no harm will result if they give the battery no attention whatever. If the battery fails to turn over the engine when the starting switch is closed, then instruction
68
HOW TO TAKE CARE OF BATTERY ON CAR 69
books are studied. Thereafter the motorists pay more attention to the battery. The rules to be observed in caring for a battery on a car are given in the remainder of this chapter. Some of them apply to car owners tlone, while the others are intended for garagemen.
Preparing Battery for Use.
1. Unpacking. If the battery arrived packed, unpack it care- fully, being careful to keep it right side up. Brush off all dirt, excelsior, etc.
2. Inspect for Leakage. Remove the vent plugs and see that the electrolyte covers the plates. Rough handling in shipping
Fig. 17. The Battery Installed
may have cracked one of the jars. If the electrolyte does not cover the plates, or if there is electrolyte around the jars or at the joints in the box, one or more of the jars are probably broken. In this case, take the matter up with the transportation company, or party from whom the battery was received.
3. Installation of the Storage Battery. A special battery com- partment is provided on the automobile in the majority of cases which provides both an electrical and mechanical protection. The
70 THE AUTOMOBILE STORAGE BATTERY
battery must be firmly fastened in a definite position in the battery box or compartment, so as to prevent any movement due to the vibration of the car. Special hooks are usually provided for hold- ing the battery in place by fastening their upper ends in openings or handles on the wooden containing case, their lower ends passing through the bottom of the battery compartment. See Figure 17. A thumb-nut or other adjustment is provided on these hooks by means of which they may be drawn up. It is advisable to place the battery on several small wooden cleats laid on the bottom of
Fig. 18, Battery Short Circuited by a Pair of Pliers
the battery compartment unless such cleats are provided, and then place the battery in such a position in the compartment that there will be an air space on all sides as well as top and bottom. This arrangement gives the maximum mechanical and electrical protection as well as the best ventilation. It is not advisable to use any packing of any kind about the battery, but depend en- tirely upon the hooks to hold it firmly in place. Lack of care in properly securing the battery will undoubtedly result in broken battery jars, broken electrical connections or cracked sealing compound, any one of which may result in serious damage to the
HOW TO TAKE CARE OF BATTERY ON CAR 71
battery and at the same time make the electrical system inop- erative. Under no conditions use the battery compartment in storing tools, oil cans, pieces of wire, etc., as they are likely to jolt around and short cricuit one or more of the cells.
The leads coming into the battery compartment should be long enough so that the terminals on their ends may be easily attached to the terminals of the battery and still have ample slack in the leads so as to prevent the terminals or connections being broken should the battery happen to move. Care should be exercised in making the electrical connections to the battery to see that the surfaces coming into contact are thoroughly cleaned and the area of the contact is as large as possible, which means a minimum resistance. Under no condition connect a copper wire directly to the terminal of a storage battery, as the acid fumes will attack the eopper and start corrosion, which will eventually result in the end of the wire being eaten off entirely and at the same time a badly corroded battery terminal.. If such connections are neces- sary in order to take care of additional circuits and equipment other than the regular equipment, connection may be made to the leads from the battery some distance from the battery or pref- erably at a terminal block when one is provided.
There is room for great improvement in the design of battery terminals and cable connections. The best method has the cables burned directly to the battery posts. This eliminates the possi- bility of corrosion at the connection between the cable and the post. The burned-on cables should be fastened to a terminal block placed on the side of the box. The cables and wires leading to the starting motor and other parts of the car should be fastened to these terminal blocks also. If all batteries were connected in this fashion, much of time spent in the cleaning of terminals, and charging made necessary by loose or corroded connections would be saved.
4, Connection of Battery. The cables attached to the battery lead to the starting motor, dynamo, lighting system, and very frequently the ignition system also. As far as the starting, light- ing, and ignition systems are concerned, it makes no difference which cable is connected to the positive (marked ‘‘P,’’ ‘‘Pos,’’ or ‘19. battery terminal post and which cable is attached to the
72 THE AUTOMOBILE STORAGE BATTERY
negative (marked ‘‘N,’’ ‘‘Neg,’’ or ‘‘—’’) battery terminal post. With some dynamos this is also true. With most dynamos, how- ever, the cable which is attached to the positive battery terminal must lead to the positive dynamo terminal, and the cable which is attached to the negative battery terminal must !ead to the negative dynamo terminal. On many cars, one battery terminal is connected to the iron car frame. In this case the corresponding terminal on the dynamo must also be connected to the iron car frame. The other battery terminal is connected to the remaining dynamo terminal. If it is not known which cable leads to the posi- tive and which to the negative dynamo terminal, the following test may be made:
Fill a tumbler with electrolyte or salt water. Fasten a wire to each cable, insert the wires in the tumbler,
Now start the engine, and run it at a speed corresponding to a car speed of not less than 20 miles per hour.
one of the wires, and.the cable to
the negative dynamo terminal, and should be connected to the negative battery terminal. See Figure 19.
B. Freshening Charge. Battery should be given a charge just before installing on car, or immediately after, at the charging rate stamped on the nameplate. Directions for charging will be given later.
6. Keep Battery and Interior of Battery Box Wiped Clean and Dry. For this purpose use a rag dipped in ammonia or baking soda. Do not bring an open flame near the battery vent holes. The reason for this is that bubbles of hydrogen and oxygen escape from the electrolyte, and the mixture is very explosive.
In ease the electrolyte or water has been spilled on top of the battery, the surface should be rubbed off with a cloth that has been moistened with ammonia water and should then be wiped with a dry cloth.
keeping them at least one inch apart. |
which this wire is attached leads to |
Fine bubbles of gas will collect at |
se"
HOW TO TAKE CARE OF BATTERY ON CAR 73
The battery terminals and other connections must be clean and free from corrosion. Should erystals or cakes of blue-green copper sulphate be found the parts should be washed with a solution of baking soda in hot water and should then be covered with vaseline to prevent further action by the acid.
7. Inspect the Battery Twice a Month in Winter, and Once a Week in Summer, to Make Sure That the Electrolyte Covers the Plates. To do this, remove the filling plugs and look down through the opening, as shown in Figure 20. If a light is necessary for this purpose, use an electric lamp. Never use an open flame, such as @& match or candle. An explosion may result from the gases of the battery. Dur- ing the normal course of op- eration of the battery, water from the electrolyte will evaporate. The acid never evaporates. The surface of the electrolyte should be not less than one half inch above the tops of the plates. A con- venient method of measuring the height of the electrolyte is shown in Figure 21. Insert one end of a short piece of a glass tube, having an open- ing not less than one-eighth inch diameter, through the filling hole, and allow it to "#,,20;,Fraplgine the jae of Bat rest on the upper edge of the See the Height of Solution plates. Then place your finger over the upper end, and withdraw the tube. A column of liquid will remain in the lower end of the tube as shown in the figure, and the height of this column is the same as the height of the electrolyte above the top of the plates in the cell. If this is less than one-half inch, add enough distilled water to bring the electrolyte up to the proper level. Never use well water, spring water, water from a stream, or ordinary faucet water. These contain impurities which will damage the battery if
xe THE AUTOMOBILE STORAGE BATTERY
used. If no distilled water is available, clean rain water, if collected in the country, or melted artificial ice may be used. Rain water in
Fig. 22
the city is seldom pure enough. City atmospheres usually contain ammonia, and other gases which the rain absorbs in falling, making it unfit for use. In winter time, if the air temperature is below freez- ing (32°F), start the engine before adding water, and keep it running for about one hour after the battery begins to ‘‘gas.’’? A good time to add the water is just before starting on a trip, as the engine will then usually be run long enough to
charge the battery, and cause the water to mix thoroughly with the electrolyte. Otherwise, the water, being lighter than the electro-
‘UNSCREW ‘THIs CAP
FILL UP TO THIS POINT:
Fig, 22. Cross Section of Battery, Showing Correct Level of Water
HOW TO TAKE CARE OF BATTERY ON CAR) 75
Ff. 23. Pour Some of the Dis- Fig. 24. Release the Pressure on tilled Water Into a Glass. the Bulb, Thus Drawing Water Squeeze the Air Out of the Up Into the Hydrometer Bulb of the Hydrometer. Put .
Rubber Tip in the Glass
Fig. 25. Insert the Tube in Vent Hole in Center of Battery, and Squeeze the ‘drometer Bulb Until the Cell Is Filled to the Proper Level
6 THE AUTOMOBILE STORAGE BATTERY
Fig. 2B. Release the Pressure on the Bulb and Hold Syringé in Horizontal, Position Prevent Water from Dripping on Battery. Return Excess Water to Glass
Fig. 27. Replace the Screw Plugs and Wipe Dirt and Moisture from Top of Battery
HOW TO TAKE CARE OF BATTERY ON CAR 77
Fig. 28. Showing Battery with Electrolyte too High
Fig. 29. Showing Battery with Electrolyte too Low
78 THE AUTOMOBILE STORAGE BATTERY
lyte, will remain at the top and freeze. Be sure to wipe all water from the battery top after filling. It is essential that distilled water be used for this purpose, and it must be handled carefully so as to keep impurities of any kind out of the water. Never use a metal can for handling water or electrolyte for a battery, but always use a glass or porcelain vessel. The water should be stored in glass bottles, and poured into a porcelain or glass pitcher when it is to be used. A con- venient method of adding the water to the battery is to draw some up in a hydrometer syringe and add the necessary amount to the cell by inserting the rubber tube which is at the lower end into the vent hole and then squeezing the bulb until the required amount has been put into the cell. This is shown pic- torially in Figures 22 to 29 inclusive.
The acid in the electrolyte does not evaporate, and it is very seldom necessary to add acid. Acid is lost when a cell gasses; electrolyte may be spilled; a cracked jar will allow electrolyte to leak out; if too much water is added, the expansion of the electrolyte when the battery is charging may cause it to run over and be lost, or the jolting of the car may cause some of it to be spilled; if a battery is allowed to become badly sulphated, some of the sulphate is never reduced, or drops to the bottom of the cell, and the acid lost in the formation of the sulphate is not regained. Thus it is seldom necessary to add acid. If acid or electrolyte is added instead of water, when no acid is need- ed, the electrolyte will become too strong, and sulphate plates will be the result. If a battery under average driving condi- tions never becomes fully charged, it should be removed from the ear and charged from 8,3 0., ,thls Shows How Eiaies snd
an outside source as explained ing Acid Solution Instead of Water
HOW TO TAKE CARE OF BATTERY ON CAR 79
later. If, after a long continued charge, the battery is still not fully — charged, some of the electrolyte should be removed, fresh electro- lyte having a specific gravity of 1.400 should be added instead of water. This should preferably be done by an experienced battery man.
Care must be used not to fill the battery cells too far above the plates. By looking down through the opening left when the filler plug is removed a second opening may usually be seen, between a half inch and one inch below the top. The level of the liquid should be at this lower hole but should not be brought above it. See Figure 28.
If the battery is filled above this point, the electrolyte will run over the top of the tube, cause a short circuit between the battery terminals, and run down the sides of the box. It may get into the metal battery box and eat out the bottom, as well as rot the wooden battery case.
8. The specific gravity of the electrolyte orm, should be measured every two weeks anda ft'(/(..\'\." permanent record of the readings made for future reference. )
As already explained, the specific gravity of the electrolyte is the ratio of its weight to the weight of an equal volume of water. Acid is heavier than water, and hence the heavier the electrolyte, the more acid it con- tains, and the more nearly it is fully charged. In automobile batteries, a specific gravity of 1.3800-1.250 indicates a fully charged battery. Other readings are as follows:
1.300-1.250—Fully charged.
Se 1,250-1.200—More than half charged. Fig. 31 1.200-1.150—Less than half charged. 1.150 and less—Completely discharged.
For determining the specific gravity, a hydrometer is used. This consists of a small sealed glass tube with an air bulb and a quan- tity of shot at one end, and a graduated scale on the upper end. This scale is marked from 1.100 to 1.300, with various intermediate
80 THE AUTOMOBILE STORAGE BATTERY
markings as shown in Figure 31. If this hydrometer is placed in a liquid, it will sink to a certain depth. In so doing, it will displace a certain volume of the electrolyte, and when it comes to rest, the volume displaced will just be equal to the weight of the hydrometer. It will therefore sink farther in a light liquid than in a heavy one, since it will require a greater volume of the light liquid to equal the weight of the hydrometer. The top mark on the hydrometer scale is therefore 1.100 and the bottom one 1.300.
For convenience in automobile work, the hydrometer is enclosed in a large glass tube having a short length of rubber tubing at its lower end, and a large rubber bulb at the upper end. The combination is called a hydrometer-syringe, or simply hy-
drometer. See Figure 32. In measuring the specific gravity of the electrolyte, the filler plug is removed, the bulb is squeezed {so as to expel the air from it, and the rubber tubing inserted in the hole from which the plug was removed. The pressure on the bulb is now released, and electrolyte is drawn up into the glass tube. The rubber tubing on the hydrometer should not be withdrawn from the cell. When a sufficient amount has entered the tube, the hydrom- eter will float. In taking a reading, there must be no pres- sure on the bulb, and the hy- drometer should be floating
Fig. 33. Taking a Specific Gravity freely and not touching the
Reading walls of the tube. The tube must be held in a vertical position, and the stem of the hydrometer must also be vertical. The reading will be the number on the stem at the surface of the electrolyte in the tube. Thus if the hydrometer sinks in the electrolyte, until the electrolyte comes up to the 1.150 mark on the stem, the specific gravity is 1.150.
HOW TO TAKE CARE OF BATTERY ON CAR. 81
Having taken a reading, the bulb is squeezed so as to return the electrolyte to the cell.
Care should be taken not to spill the electrolyte from the hy- Crometer syringe when testing the gravity. Such moisture on top of the cells tends to cause a short circuit between the terminals and to discharge the battery.
In making tests with the hydrometer the electrolyte should always be returned to the same cell from which it was drawn. Failure to do this will finally result in an increased proportion of acid in one cell and a deficiency of acid in others.
The specific gravity of all cells of a battery should rise and fall together, as the cells are usually connected in Series so that the Same current passes through each cell both on charge and dis- charge. Some batteries are divided into two or more sections which are connected in parallel while the engine is running, and in such cases the cables leading to the different sections should all be of exactly the same length, and the contacts in the switch which connect these sections in parallel should all be clean and tight, If cables of unequal length are used, or if some of the switch contacts are loose and dirty, the sections will not receive equal charging currents, because the resistances of the charging circuits will not be equal. The section having the greatest resistance in its circuit will receive the least amount of charge, and will show lower specific gravity readings than for other sec- tions. In a multiple section battery, there is therefore a tendency for the various sections to receive unequal charges, and for one or more sections to run down continually. An ammeter should be attached with the engine running and the battery charging, first to one section and then to each of the others in turn. The am- meter should be inserted and removed from the circuit while the engine remains running and all conditions must be exactly the same, Otherwise the comparative results will not give reliable indications. It would be better still to use two ammeters at the same time, one on each section of the battery. In case the am- perage of charge should differ by more than 10% between any two sections, the section receiving the low charge rate should be examined for proper height of electrolyte, for the condition of its
82 | THE AUTOMOBILE STORAGE BATTERY
terminals and its connections at the starting switch as described. Should a section have suffered considerably from such lack of charge its voltage will probably have been lowered. With all connections made tight and clean and with the liquid at the proper height in each cell this section may automatically receive a | higher charge until it is brought back to normal. This high | charge results from the comparatively low voltage of the section affected.
30
Fig. 34 Fig. 35 Hydrometer Reading, 1.300 ‘Hydrometer Reading, 1.150
{ In case the car is equipped with such a battery, each section must carry its proper fraction of the load and with lamps turned on or other electrical devices in operation the flow from the sev- eral sections must be the same for each one. An examination should be made to sce that no additional lamps, such as trouble \ finders or body lamps, have been attached on one side of the { battery, also that the horn and other accessories are so connected that they draw from all sections at once.
HOW TO TAKE CARE OF BATTERY ON CAB 83
Some starting systems now being used have not been designed carefully in this respect, one section of the battery having longer cables attached to it than the others. In such systems it is impos- sible for these sections to receive as much charging current as others, even though all connections and switches are in good con- dition. In other systems, all the cells of the battery are in series, and therefore must receive the same charging current, but have lighting wires attached to it at intermediate points, thus dividing the battery into sections for the lighting circuits. If the currents _taken by these circuits are not equal, the battery section supplying the heavier current will run down faster than others. Fortunately, multiple section batteries are not being used to any great extent at present, and troubles due to this cause are disappearing.
If one cell of a battery shows a specific gravity which is de- eidedly lower than that of the other cells in series with it, and if this difference gradually increases, the cell showing the lower gravity has internal trouble. This probably consists of a short circuit. If the electrolyte in this cell falls faster. than that of the other cells, a leaky jar is indicated. The various cells should have specifie gravities within twenty-five points of each other, such as 1.250 and 1.275.
If the entire battery shows a specific gravity below 1.200, it is not receiving enough charge to replace the energy used in starting the engine and supplying current to the lights, or else there is trouble in the battery. The troubles which cause low gravity are given on pages 172 to 174. It is often difficult to determine what charging current should be delivered by the generator. Some generators operate at a constant voltage slightly higher than that of the fully charged battery, and the charging current will change, being higher for a discharged battery than for one that is almost or fully charged. Other generators deliver a con- stant current which is the same regardless of the battery’s con- dition. To give data on this subject is beyond the scope of this book. Complete information is given in the Ambu Charts pub- lished by the American Bureau of Engineering, Ine.
In the constant voltage type of generator, the charging current automatically adjusts itself to the condition of the battery. In the constant current type, the exact value of current for which
84 THE AUTOMOBILE STORAGE BATTERY
the generator is designed and adjusted is determined by the manu- facturer, and is intended to keep a battery charged under the average driving conditions. Individual cases often require that another current value be used. In this case, the output of the generator must be changed. With most generators, a current regulating device is used which may be adjusted so as to give a fairly wide range of current, the exact value chosen being the result of a study of driving conditions and of several trials. The charging current should never be made so large that the tem- perature of the electrolyte in the battery is above 90° Fahrenheit. A dairy thermometer is very useful in determining the tempera- ture. See Figure 36. The thermometer bulb is immersed in the electrolyte above the plates through the filler hole in the tops of the cells. Complete information on generators is given in the Ambu Charts referred to above.
Specific gravity readings should never be taken soon after dis- tilled water has been added to the battery. The water and elec- trolyte do not mix immediately, and such readings will give mis- leading results. The battery should be charged several hours before the readings are taken. It is also a good plan to take a specific gravity reading before adding any water, since accurate results can also be obtained in this way.
If the gravity, before filling, was below 1.150, the battery should be removed from the car and fully charged from an outside source. If the gravity was 1.150 or above the engine should be run at a speed that corresponds to 15 to 20 miles per hour, with- out any lamps turned on, for‘a total of at least twelve hours. This treatment should be continued until the specific gravity of the battery does not show any further rise for two hours. If the gravity was 1.100 or below the charging must be continued for a total of sixty hours or more. If the battery is recharged on the ear, it will be best to substitute lamp bulbs of lower candle power than those regularly used until the gravity comes up to 1.275.
A completely discharged battery will ordinarily take about twenty hours’ charging to bring it up, but if the battery has stood for a considerable length of time in a discharged condition or has been reversed it may take several days to bring the gravity up to normal,
HOW TO TAKE CARE OF BATTERY ON CAR 85
The temperature of the electrolyte affects the specific gravity, since heat causes the electrolyte to expand. If we take any bat- tery or cell and heat it, the electrolyte will expand and its specific gravity will decrease, although its actual strength will be the same, because the actual amount of acid is the same. The change in specific gravity amounts to one point, approximately, for each degree Fahrenheit change. If the electrolyte has a gravity of 1.250 at 70°F, and the temperature is raised to 73°F, the specific gravity of the battery will be 1.249. If the temperature is decreased to 67°F, the spe- cific gravity will be 1.251. Since the change of tempera- ture does not change the actual strength of the electro- lyte, the gravity readings as obtained with the hydrom- eter syringe should be corrected one point for every three degrees change in temperature. Thus 70°F is considered the normal temperature, and one point is added to the electrolyte reading for every three degrees above 70°F. Similarly, one point is subtracted for every three de- grees below 70°F. For convenience of the hydrometer user, a special thermometer has been developed by bat- tery makers. This is shown in Figure 36. It has a special scale mounted beside the regular scale. This scale shows the corrections which must be made when the temperature is not 70°F. Opposite the 70 point on the thermometer is a ‘‘0’’ point on the special scale. This indicates that no correction is to be made. Op- posite the 67° point on the regular scale is a —1, indi- eating that 1 must be subtracted from the hydrometer reading to find what the specific gravity would be if the temperature were 70°F.. Opposite the 73° point on the regular scale is a -++1, indicating that 1 point must be added to reading on the hydrometer, in order to reduce the reading of specific gravity to a temperature of 70°F. Fig. 36
. Special
9. Operating Temperatures. Storage batteries are Thermon- Strongly affected by changes in temperature. Both ex- eter tremely high, and very low temperatures are to be avoided. At low temperatures the electrolyte grows denser, the porosity of plates
ST S.e FLELS. EL
| ee
UE Uo TES Oe EO
pj] jo] Be] S| Bl
86 THE AUTOMOBILE STORAGE BATTERY
and separators decreases, circulation and diffusion of electrolytes are made difficult, chemical actions between plates and acid take place very slowly, and the whole battery becomes sluggish, and acts as if-it were numbed with cold. The voltage and capacity of the battery are lowered. .
As the battery temperature increases, the density of the electro- lyte decreases, the plates and separators become more porous, the internal resistance decreases, circulation and diffusion of electro- lyte take place much more quickly, the chemical actions between plates and electrolyte proceed more rapidly, and the battery voltage and capacity increase. A battery therefore works better at high temperatures.
Excessive temperatures, say over 100°F, are, however, more harmful than low temperatures. Evaporation of the electrolyte takes place very rapidly, the separators are attacked by the hot acid and are ruined, the active materials and plates expand to such an extent that the active materials break away from the grids and the grids warp and buckle. The active materials themselves are burned and made practically useless. The hot acid also attacks the grids and the sponge lead and forms dense layers of sulphate. Such temperatures are therefore extremely dangerous.
A. battery that persistently runs hot, requiring frequent addi- tion of water is either receiving too much charging current, or has internal trouble. The remedy for excessive charge is to de- crease the output of the generator, or to burn the lamps during the day time. Motorists who make long touring trips in which considerable day driving is done, with little use of the starter, experience the most trouble from high temperature. The remedy is either to install a switch with which the generator may be dis- connected from the battery, or to use the lamps as mentioned above.
Internal short-circuits cause excessive temperature rise, both on charge and discharge. Such short circuits usually result from buckled plates which break through the separators, or from an excessive amount of sediment. This sediment consists of active material or lead sulphate which has dropped from the positive plate and fallen to the bottom of the battery jar. All battery jars are provided with ridges which keep the plates raised an inch
HOW TO TAKE CARE OF BATTERY ON.CAR 87
or more from the bottom of the Jar, and which form pockets into which the materials drop. See Figure 22. If these pockets be- come filled, and the sediment reaches the bottom of the plates, internal short circuits result which cause the battery to run down and cause excessive temperatures.
If the electrolyte is allowed to fall below the tops of the plates, the parts of the plates above the acid become dry, and when the battery is charged grow hot. The parts still covered by the acid also become hot because all the charging current is carried by these parts, and the plate surface is less than before. The elec- trolyte will also become hot and boil away. A battery which is thus ‘‘charged while dry’’ deteriorates rapidly, its life being very short. :
Sulphated plates will also grow hot, even with a normal charg- ing current, because only those parts of the active material which are not covered by lead sulphate carry the current, and therefore heat up. This results in buckling and fracture of plates.
If a battery is placed in a hot place on the ear, this heat in addition to that caused by charging will soften the plates and jars, and shorten their life considerably.
In the winter, it is especially important not to allow the battery to become discharged, as there is danger of the electrolyte freez- ing. A fully charged battery will not freeze except at an extremely low temperature. The water expands as it freezes, loosening the active materials, and cracking the grids. As soon as a charging current thaws the battery, active material is loosened, and drops to the bottom of the jars, with the result that the whole battery may disintegrate. Jars may also be cracked by the expansion of the water when a battery freezes.
To avoid freezing, a battery should therefore be kept charged. The temperatures at which electrolyte of various specific gravities freezes are as follows:
Specific Gravity Freezing Pt. Specific Gravity Freezing Pt. 1.020 30°F. 1.170 0°F. 1.060 26°F, 1.220 -28°F. 1.100 21°F. 1.260 -65°R,
1.140 12°F. 1.290 -98°R,
88 THE AUTOMOBILE STORAGE BATTERY
No anti-freeze solution of any kind is required for use in the battery. The addition of alcohol or anything else except pure water to the cells will result in internal damage.
10. Care of Storage Battery When Not in Service. A storage battery may be out of service for a considerable period at certain times of the year, for example, when the automobile is put away during the winter months, and during this time it should not be allowed to stand without attention. When the battery is to be out of service for only three or four weeks, it should be kept well filled with distilled water and given as complete a charge as possi- ble the last few days the car is in service by using the lamps and starting motor very sparingly. The specific gravity of the elec- trolyte should be tested in each cell, and it should be somewhere between 1.270 and 1.300. All connections to the battery should be removed as any slight discharge current will in time completely discharge it, and the possibilities of such an occurrence are to be avoided. If the battery is to be put out of service for several months, it should be given a complete charge by operating the dynamo on the car or by connecting it to an outside charging eircuit. During the out-of-service period, water should be added to the cells every six or eight weeks and the battery given what is called a refreshing charge; that is, the engine should be run until the.cells have been gassing for perhaps one hour, and the battery may then be allowed to stand for another similar period with- out further attention. Water should be added and the battery fully charged before it is put back into service. It may be neces- sary to charge the battery for 40 or 50 hours at one-half the normal raté before it will be fully charged if it has stood for five or six months without being charged. It is desirable to have the temperature of the room where the battery is stored fairly eon- stant and as near 70 degrees Fahrenheit as possible.
| CHAPTER 13. MANUFACTURE OF STORAGE BATTERIES.
To supply the great number of batteries needed for gasoline automobiles, many large companies have been formed and huge factories erected. Each company has its special and secret pro- cesses which it will not reveal to the public. Only a few com- panies supply batteries in any considerable quantities, the great majority of cars being supplied with batteries made by not more than five or six manufacturers. This greatly reduces the number of possible different designs in general use today.
The design and dimensions of batteries vary considerably, but the general constructions are similar. The special processes of the manufacturers are of no special interest to the motoring pub- lic, and only a general description will be given here. .
A starting and lighting battery consists of the following prin- cipal parts:
1. Plates. ; 4. Jars. 2. Separators. 5. Top connectors and. covers. 3. Electrolyte. 6. Case.
Plates. Of the two general types of battery plates, Faure and Plante, the Faure or pasted plate type is used on the great ma- jority of automobiles. In the manufacture of the Faure or pasted plates there are several steps which we shall describe in the order they are carried out.
Moulding the Grid. The grid is a casting made of lead and antimony, about 6 to 10% of antimony being used. This gives a grid which is harder and stronger than pure lead, less liable to deformation, and one which is not affected by the battery acid to any appreciable extent. On the other hand, the grid is more brittle, and more liable to be fractured or broken if the active materials should expand abnormally.
The lead and antimony are melted together, thoroughly mixed,
89
90 THE AUTOMOBILE STORAGE BATTERY
and then poured into the molds. The Willard Co. makes two plates in one casting. The mold resembles a waffle-iron, the plates being molded bottom to bottom. The casting therefore has a lug at each end, and is thus easily handled, the lugs being used to hold the cast- ing in racks during the various processes through which it passes. The casting is not split into two plates until the paste has been
Fig. 37. A Pair of Grids Trimmed and Ready to be Pasted. The Lugs at the Top Are for Burning in to the Connector Straps to Make a Group
applied, and the plates formed and dried. The two parts of the casting are, of course, made into plates of the same polarity. After cooling, the grids are removed from the molds, and cleaned. The rough edges are trimmed off, and the parts polished. The grid is now ready for pasting.
Figure 37 shows a Willard grid ready for pasting. It will be noticed that a heavy lug is at the upper left hand corner. This
Pos, Connecting Strap Neg. Connecting Strap Fig. 38
is later burned into a cross bar, together with other plates, and from this cross bar extends the outer battery terminal to which a battery cable or connecting link is attached. (See figure 38.) Seven vertical stiffening ribs, together with the four heavy ribs at the tops and side, serve to make the plate strong and rigid. It will be noticed that the top and left hand side piece taper away
MANUFACTURE OF STORAGE BATTERIES 91
from the lug. This gives strength and also provides a greater current carrying area near the lug. The amount of current carried by these ribs is greatest near the lug, and grows less toward the right hand end and bottom of the grid.
In the Willard Battery the ribs all run at right angles to one another. This is true of most of the different'makes. In the Philadelphia Diamond grid, these ribs are arranged at smaller angles to each other, so as to form diamond shaped openings. The purpose of the ribs in any grid is to form a rigid supporting frame for the paste, and to distribute the current uniformly to all parts of the paste. The pastes used are weak mechanically, and could not be made into plates without the supporting grids, especially in automobile service, where batteries are often sub- jected to severe jolting.
Fig. 39. A Pair of Formed Plates Ready to be Burned to the Connecting Straps
Pastes. There are many formulas for the active materials. For the positive plates, litharge (PbO), or red lead, (Pb,O,), or a combination of the two is mixed with dilute sulphuric acid. A paste is made which is just thick enough to make it easy to work it into the spaces between the ribs of the grid. For the negative plates litharge (PbO) is generally made into a paste with dilute sulphuric acid.
Various methods and machines are used for making the pastes. Some manufacturers use mixers which resemble the ordinary cement mixer and which are power driven. The lead com- pounds and acid are dumped into the mixers and the latter are then set in motion. Iland rotated drums are also used.
Applying the pastes.. This may be done with the bare hands, or with wooden paddles, or with machines, as in the USL Machine
92 THE AUTOMOBILE STORAGE BATTERY
Pasted Plate. In hand pasting the pastes are worked first into one side of the grid, and then into the other. In machine pasted plates, both sides are filled with the pastes simultaneously. Fig- ure 40 shows a pasting room in a Willard factory. The pastes begin to harden from the time they are mixed, and the pasting is done quickly so as to apply the pastes before they are too stiff to be worked into spaces of the grids.
The freshly pasted plates are now allowed to dry in the air, are put into drying ovens and dried by a hot air blast, or are
Fig. 40. Pasting Room in the Willard Storage Battery Co. Factory
immersed in dilute sulphuric acid for several days. In either ease, the pastes set to a hard mass, this being due to the forma- tion of lead sulphate, which hardens, and cements the particles of the paste. This sulphate becomes crystallized into a firm bind- ing mass without which the pastes would soon fall from the grids. The plates become so hard that they may be pounded on the floor without losing any paste. Both positive and negative plates are allowed to sulphate in this way.
Forming. After the sulphation, or cementing process is com- pleted, the plates are brushed clean, and sent to the forming
MANUFACTURE OF STORAGE BATTERIES 93
room. This is usually a large room containing a number of acid filled tanks, into which the plates are placed. Figure 41 shows a forming room in the Willard factory. Negative and posi: tive plates are arranged very much as they appear in the finished battery. All positives are connected together, as are also the negatives. Current is then passed through the plates for from three to six days so as to change the pastes into sponge lead and lead peroxide; the process being called ‘‘forming”’ the plates. The forming current used varies with the size, design, and make,
Fig- 41. Forming Room in the Willard Storage Battery Co, Factory
the Willard Co. using a current of one-half ampere per plate. The ‘pastes as applied to the grids could not enter into chemical actions with the electrolyte so as to provide electricity for operat- ing a starting motor, or lamps. They must be changed consider- ably before becoming ‘‘active’’ material. The changes they undergo must be produced mainly by an electric current.
At the beginning of the ‘‘forming”’ process, the positive plate contains about 55% of litharge (PbO), 25% of lead peroxide, (PbO,) and 20% of lead sulphate (PbSO,). The lead oxide begins to change to lead peroxide as soon as the forming current is started. The amount of lead sulphate begins to increase, and
24 THE AUTOMOBILE STORAGE BATTERY |
continues to do so for several hours. This is probably caused by the plate becoming more porous, so that the acid is able to reach more oxide, which it changes to sulphate. The sulphate soon changes to lead peroxide, however, and when the forming is completed, the positive plates contain nine per cent of litharge (PbO), 88% of lead peroxide (PbO,), and 3% of lead sulphate (PbSO,). This 3% of lead sulphate probably is never changed into lead peroxide if a battery is used normally, but it remains and acts as a cement to bind the particles of lead peroxide together.
The negative plate cements until it contains 30% of lead sul- |
phate. As soon as the forming current is passed through the neg- atives, lead begins to form immediately, but the amount of sulphate also increases. The amount of sulphate reaches a maximum and turns into spongy lead quite rapidly. The fully formed plate contains but a very small amount of lead sulphate, being com- posed of 98% of metallic lead and 2% of litharge. Very little lead sulphate is left, but the spongy lead is itself a tough, coher- ent substance, which sticks together all over the plate surface. When the forming current is turned off, the positive grids have a chocolate brown color, and negative plates have a slate gray color.
Manufacturers have more complicated methods and formulas in mixing pastes for the plates. Some add organic acids, salts or sugar. These are mixed with the pastes, and are used either to increase the hardness of the paste, or to increase its porosity. Magnesium sulphate is also used for this purpose. These ‘‘form- ing’’ agents generally disappear after the battery has been used for some time.
The sulphate which remains in the positive plate at the sur- face is soon changed to lead peroxide when the battery has been charged several times. The lead peroxide then drops to the bottom of the jars, and the plates are said to be ‘‘shedding.”’
In mixing the paste for the negative plates, magnesium sul- phate, or graphite are added to make the plate more porous. The value of these porosity agents is questionable, and they may, in fact, have a harmful effect upon the plate.
As the forming progresses, the plates are tested from time
MANUFACTURE OF STORAGE BATTERIES 95
to time with a voltmeter, and the cadmium test is also made. (See Page 266.) In this way, the conditions of positive and nega- tive plates are determined separately.
‘When the forming process is complete, the positive plates are rinsed in warm water and allowed to dry in the air. The nega- tive plates are also dried in the air. This results in the spongy lead on the negative plates changing back to litharge (PbO). The plates are now ready to be assembled into cells. ,
Separators.
In batteries used both for starting and for lighting, separa- tors made of specially treated wood are largely used. Lately, however, the Willard Company has adopted an insulator made of
Fig. 42. A Pile of Prepared Wooden Separators Ready to be Put Between the Pos-
itive and Negative Plates to Form the Complete Element a rubber fabric pierced by thousands of cotton threads, each thread being as long as the separator is thick. The electrolyte is carried through these threads from one side of the separator to the other by capillary action, the great number of these threads insuring the rapid diffusion of electrolyte which is necessary in batteries which are subjected to the heavy discharge current required in starting.
In batteries used for lighting or ignition, sheets of rubber in which numerous holes have been drilled are also used, these holes permitting diffusion to take place rapidly enough to per- form the required service satisfactorily, since the currents in- volved are much smaller than in starting motor serivee.
For the wooden separators, porous wood, such as basswood,
96 THE AUTOMOBILE STORAGE BATTERY
cypress, or cedar are used. Redwood has been used to some extent. The wood is cut into strips of the correct thickness. These strips are passed through a grooving machine which cuts the grooves in one side, leaving the other side smooth. The strips are next sawed to the correct size, and are then put in a warm alkaline solution to neutralize any organic acid, such as acetic acid, which the wood naturally contains. Such acids would cause unsatisfactory battery action and damage to the battery. _ The alkali is finally washed out, and the separators given a final trimming. They are now ready for assembling.
Electrolyte.
Little need be said here about the electrolyte, since a. full description is given elsewhere. Acid is received by the battery manufacturer in concentrated form. Its specific gravity is then 1.835. The acid commonly used is made by the ‘‘contact’’ pro- cess, in which sulphur dioxide is oxidized to sulphur trioxide, and then, with the addition of water, changed to sulphuric acid. | The concentrated acid is diluted with distilled water to a_ specific gravity of 1.300.
Jars.
The jars are made of vulcanized rubber. The complete jars are inspected carefully for flaws which might result in a leaky, short lived battery. Across the bottom gums of the jar are several stiff ribs which ex- tend up into the jar so as to provide a substantial support for the plates, and at the same time forming several pockets below the plates in which the sediment re- sulting from shedding of active material from the positive plates accumulates.
Top Connectors and Covers.
The connectors with which the cells are connected to each other are castings of lead, which, in batteries used for starting motors are made extra heavy so as to carry the heavy starting current without overheating. The covers are made of vulean-
Fig, 48
MANUFACTURE OF STORAGE BATTERIES 97
ized rubber, and various manufacturers have developed special designs, their aims being to so construct the covers as to facilitate the escape of gases which result from charging, to provide space for the expansion of the electrolyte, to simplify filling with distilled water, to make leak-proof joints at the terminals and jars, and to simplify the work of making re- pairs.
Fig. 44. Between Cell Link Fig. 45. Term. Link in Perspective
Several designs «re shown below. Figure 22, page 74, shows a Willard construction. The rubber cover is shown in gray at the top of the cell. It is made in one piece, and contains the expansion’ chamber. The method of obtaining a leak-proof joint at the terminals is clearly shown. The sealing compound with which the joint between the cover and jar is made is shown in black at the top.
Sectional View of Cover, Plug in Place. Air Lock (A) In Po- sition to Allow Free Escape of Gas Through Passages (BB)
‘Top View of Cover and Filling Plug, Plug Removed - £
°c 8 a @
Sectional View of Cover, Plug Removed. Alr Passages (BB)
Closed and Air Lock (A) in Position to Prevent Overfilling Fig. 46
98 THE AUTOMOBILE STORAGE BATTERY
Figure 46 shows the Non-Flooding Vent and Filling Plug used — in the ‘‘Exide’’ Battery. This is described by the Electric Storage Battery Company as follows, in one of its bulletins: |
From the illustrations of the vent and filling plug, it will be | seen that they provide both a vented stopper (vents F, G, H) and an automatic device for the preventing of overfilling and flood- ing. In a simple and effective manner, the amount of water that can be put into the cells is limited to the cxact amount needed to replace that lost by evaporation. This is accomplished by means of the hard rubber valve (A) within the battery cover and with which the top of the filing plug (E) engages, as shown in the illustrations. The action of removing the plug (E) turns this valve (A), closing the air passage (BB), and forming an air tight chamber (C) in the top of the cell. When water is poured in, it cannot rise in this air space (C) so as to completely fill the cell, As soon as the proper level is reached, the waiter rises in the filling tube (D) and gives a positive indication that suffi- cient water has been added. Should, however, the filling be con- tinued, the excess will be pure water only, not acid. On re- placing the plug (E), valve (A) is automatically turned, opening
the air passages (BB), leaving
Sectional Views of Cover the air chamber (C) available for
the expansion of the solution,
which occurs when the battery is working.
Fig. 47 shows the top construc- tion, and Figure 48 the method of filling USL batteries. The top is in one piece, and dome shaped so as to give strength, and to provide for an expansion chamber large enough to allow for the greatest expansion of electrolyte which is likely to oc-
; . cur, even in the severest charge. with Bushings and Post Straps The holes through which the ter- minals posts pass each have a
lead-antimony bushing which is flanged and molded in with the rubber so as to form a leak-proof joint. In assembling the battery,
; Z p G
g y) 4 g y y y 4 4
MANUFACTURE OF STORAGE BATTERIES 99
the cover is placed over the posts, and both the post and flange lead- burned to the connecting links. Figures 47 and 48 show clearly the large expansion chamber and the method of filling with distilled water. This is done as follows: A finger is placed over the vent tube shown in Fig- ure 48. The water is then poured in through the fill- ing tube. When the water reaches the bottom ‘of the tube, the air imprisoned in the expansion chamber can no longer escape. Conse- quently the water can rise no higher in this chamber, but simply fills up the tube. Water is added till it reaches the top of the tube. The finger is then removed from the vent tube. This allows the air to escape from the expansion ‘cham- ber. The water will there- fore fall in the filling tube, and rise slightly in the ex- pansion chamber. This con- struction makes it impossi- ble to overfill the battery, _ provided that the finger is held on the vent tube as di- rected.
rere
Cases.
The wooden ease in which the battery cells are ‘placed is usually made of the best grade of white oak, which is kiln dried before being used to make it as nearly acid proof as Possible. The wood is inspected carefully, and all pieces are re-
Fig. 48
100 THE AUTOMOBILE STORAGE BATTERY
jected that are weather-checked, or contain worm-holes or knots. The wood is sawed into various thicknesses, and then cut to the proper lengths and widths. The wood is passed through other machines that cut in the dovetails, put the tongue on the bottom for the joints, stamp on the part number, drill the holes for the serews or bolts holding the handles, cut the grooves for the seal- ing compound, ete. The several pieces are then assembled and glued together, this being done, in the Willard factory, by one
Fig. 49. Battery Box or Case with Handles, It Is Made from Kiln-Dried Oak Lumber and Thickly Coated with Acid-Proof Paint. All Metal Parts, Other Than Lead, Are Lead-Coated to Keep Them from Corrosion by the Acid in the Battery Solution
machine. The finishing touches are then put on, these consisting of cutting the cases to the proper heights, sandpapering the boxes, ete. The cases are then inspected and are ready to be painted.
Asphaltum paint is generally used, the bottoms and tops being
given three coats, and the sides two. The handles are then put on by machinery, and the box is complete, and ready for assem- bling.
Assembling and Finishing.
The first step in the assembly of a battery is to burn the correct number of positive and negative plates to their connecting straps,
MANUFACTURE OF STORAGH BAYTRRIES 101
thus forming the positive an@ negat %< gentipe or ““elements.”” The ‘‘burning”’ consists of melting the straps drfd lugs on the plates together with an oxygen-hydrogen, or oxygeu-acetylene flame so as to form one solid mass of lead. Positive and negative groups are next put together, with the separators between them. The completed groups are placed into the jars which are filled with electrolyte up to the proper points. The covers are put in position on the jars and the sealing compound poured over the joint between cover and jar so as to make a leak-proof joint. Figure 50 shows a cross-section of a completed cell.
nk Sealing P ng ate Ne
Fig. 50
The completed cells are now ‘‘formed”’ again, a current of about one-half ampere per plate being sent through the cell for six to seven days. When the plates have thus been formed again, the negative plate again consists of pure spongy lead, and the positive of lead peroxide. When the second forming is finished, the cells are put in the wooden case, the connecting links burned to the strap posts, nameplate put on, date stamped on, a careful general inspection given, specific gravity again meas- ured, and the battery is ready for use on the car.
CHAPTER 14. THE WORK SHOP. GENERAL INSTRUCTIONS.
The degree of success which the battery repairman attains de- | pends to a considerable extent upon the workshop in which the batteries are handled. It is, of course, desirable to be able to | build your shop, and thus be able to have everything arranged as you wish. If you must work in a rented shop, select a place which has plenty of light and ventilation. The ventilation is especially important on account of the acid fumes from the bat- teries. A shop which receives most of its light from the north is the best, as the light is then more uniform during the day, and the direct rays of the sun are avoided. Figure 51 shows a light,
Fig, 51. ‘Typical Work Room Showing Bench About 84 Inches High, Tanks of Hydrogen and Oxygen for Lead Burning, Hot, Plates for Melting ‘Sealing Cot bound and Hand: Drill-Press for Drilling off Top Connector
102 |
THE WORKSHOP. GENERAL INSTRUCTIONS 103
well ventilated workroom. At least 600 square feet of floor sur- face are needed, a shop 25 feet square being well suited for a small repair business.
The fioor should be in good condition, since acid rots the wood and if the floor is already in a poor condition, the acid will soon eat through it. A tile floor, as described below, is best. A wooden floor should be thoroughly scrubbed, using water to which washing soda has been added. Then give the floor a coat of asphaltum paint, which should be applied very hot so as to flow into all the cracks in the wood. When the first coat is dry, several more coats should be given. Whenever you make a solution of soda for any purpose, do not throw it away when you are through with it. Instead, pour it on the floor where the acid is most likely to be spilled. This will neutralize the acid and prevent it from rotting the wood.
If you can afford to build a shop, make it of brick, with a floor of vitrified brick, or of tile which is not less than two inches thick, and is preferably eight inches square. The seams should not be less than one-elghth inch wide, and not wider than one-fourth. They should be grouted with asphaltum, melted as hot and as thin as possible, (not less than 450°F). This should be poured in the seams. The brick or tile should be heated near the seams before pouring in the asphaltum. When all the seams have been filled, heat them again. After the second heating, the asphaltum may shrink, and it may be necessary to pour in more asphaltum.
If possible, the floor should slope evenly from one end of the room to the other, with a drop of about one inch to the foot. A lead drainage trough and pipe at the lower end of the shop will carry off the acid and electrolyte.
It is a good plan to give all work benches and storage racks and shelves at least two coatings of hot asphaltum paint. This will prevent rotting by the acid.
Shop Equipment.
The exact equipment of any shop will be governed by the size and shape of the shop, and the amount of money available for fitting it up. Six things are absolutely essential. These are:
104 THE AUTOMOBILE STORAGE BATTERY
1, Work benches with vise.
2. Lead burning outfit.
3. Sink with water supply.
4, Charging bench and equipment.
5. Shelving, for storing boxes, plates, jars, tools, burning lead, €. 6.
. Stove for heating sealing compound.
Fig. 62. Suggested Layout for a Small Battery Repair Shop
The arrangement of these parts will depend upon the size and shape of the workshop, and the ideas of the repairman. Figure 52 shows a convenient design for a shop 25 feet square, and figure 53 is from an actual photograph of an up-to-date, pro- gressive small repairshop. Near the door is the desk where the
THE WORKSHOP. GENERAL INSTRUCTIONS 105
»0ok-keeping is done. A table is placed next to it for catalogues, nagazines, etc., and for eating lunch.
The work bench extends across one end of the shop, and is six- een feet long. At one end is a sink, in which the sediment may »e washed out of the jars. Figure 54 is a photograph. The bent dipe extending upward is perforated with a number of 1-16 inch roles. In cleaning out jars, the battery box is inverted over the
Fig. 53. Corner of Workshop, Showing Burning Outfit, Burning Bench and Vises
Pipe. The water supply is controlled by a foot operated valve, so that the box may be held in both hands while it is washed. At the other end of the bench is the lead burning outfit, the use of which is explained later. The bench should be made of lumber two inches thick, and given several coats of hot asphaltum paint.
Special Work Bench.
The cross -shaped, double work bench shown at the ieft in Fig- ure 52 is of a special design, and requires a detailed explanation. The bench is to be used by two men, one sitting at each end, and with the following explanation, you should have little difficulty
106 THE AUTOMOBILE STORAGE BATTERY
in constructing one. Figure 55 is a photograph of this bench, as it has been used for several years. Figure 56 is a drawing giving dimensions. Give the various parts of the bench a good coat of asphaltum paint, not too thick, as you assemble it so as to cover the surfaces which will later be covered by other parts‘
Fig. 54, Sink with Faucet, and Extra Swinging Arm Pipe for Washing Out Jars. Four Inch Paint Brush for Washing Battery Cases and thus be impossible to paint. When completed, give the bench a second coat of asphaltum, and let it dry thoroughly before using.
The bench should have a permanent location so that gas, if available, can be piped to it. Otherwise, a gasoline torch may be used. It is a good plan to have it near a wall or partition where each workman may have, within easy reach, shelves on
THE WORKSHOP. GENERAL INSTRUCTIONS 107
hich are kept labeled boxes with parts for different batteries process of repair and rebuilding. You will note that there are 1 middle of bench, directly in front of each workman, elevated aelves, one for each workman, forming two pockets for tools, > that each may keep his own tools separate, with very little hance of becoming mixed. On the edge of shelves you ean put everal nails and hang any special wrenches, such as Exide lead ut wrench, monkey wrench, a pair of snips, a lead funnel, and
Fig. 55. Double Work Bench
a hammer or two, (bore holes in handles so you can hang up.) Tn each workman’s separate pocket there should be a pair of rubber gloves, four screw drivers, four putty knives,14 and ¥4 inch chisels, 2 pairs bent nosed pliers, 2 or 3 pairs different sizes of gas pliers, a good knife, a wire brush, a lead pencil, some good Tags and as asortment of pieces of boards 144x7% inches, and just long enough to go in between the handles of the different standard makes of batteries. These should be oiled, or a thin film of vaseline spread over them. They are used to even up
108 THE AUTOMOBILE STORAGE BATTERY
the separators in assembling, and also in pressing down the top covers when finishing rebuilding of batteries, as described later. You should also have one piece 114x% inch and one piece 114x!4 inch, each 8 or 10 inches long.
You will find the tool scraper (shown at J in figure 56) to the right of each workman very convenient for removing the
DOUBLE WORK BENCH
Fig. 56
compound sticking to your tools, Always have a box under it to catch the compound. When a battery is on the bench and the workman sitting up to it, straddling battery and bench, he is in the best possible position to open it.
A gas, gasoline, or oil pilot light should be mounted on one side of the two uprights. By using two screw drivers in opening a battery, one can be warming in the flame, while you are using the other.
THE WORKSHOP. GENERAL INSTRUCTIONS 109 Shelving.
The dimensions of the shelving depend upon the nature of the material to be stored. For miscellaneous. parts, such as empty jars, empty boxes, groups of plates, tools, separators, cans of grease, bottles of ammonia, or soda solution, and so on, one inch stock is strong enough. For storing completely assembled batteries, two inch lumber should be used as they must carry
Fig. 67. Typical Stockroom Showing Heavy Shelving Necessary for Storing Batterles
loads of hundreds of pounds. The vertical distance between shelves should be two feet if there is sufficient space, in order to be able to take specific gravity readings without removing the bat- teries from the shelves. A space should be left between batteries for ventilation. Figure 57 shows the type of shelving required.
Concerning Light.
Many battery shops are unfortunately situated in basements. Light is essential to good work, so you must have plenty of
110 THE AUTOMOBILE STORAGE BATTERY
good light and at the right place. For a light that is needed from one end of a bench to the other, to look mto each individual battery, or to take the reading of each individual battery, there is nothing better than a 60 Watt tungsten lamp under a good metal shade, dark on outside and white on inside. |
A unique way to hang a light and have it movable from one end of the bench to the other, is to stretch a wire from one end of the bench to the other. Steel or copper about 10 or 12 B &S gauge may be used. Stretch it about four or five feet above top of bench directly above where the light is most needed. If you have double charging bench, stretch the wire directly above middle of bench. Before fastening wire to support, slip an old fashioned porcelain: knob (or an ordinary thread spool) on the wire. The drop cord is to be tied to this knob or spool at what- ever height you wish the light to hang (a few inches lower than your head is the right height). |
Put the ceiling rosette above middle, endwise of bench; eut your drop cord long enough so that you can slide the ight from one end of bench to the other after being attached to rosette. Put vaseline on the wire so the fumes of gas will not corrode it. This will make the spool slide easily. This gives you a movable, flexible light, with which you will reach any battery on bench for inspection. The work bench light can be rigged up the same way and a 75 or 100 Watt nitrogen lamp used,
Charging Methods.
A man must have food and exercise to retain his health and strength. Moreover, there must be a proper balance between the food and exercise. Unused muscles become stiff and weak, and food alone will not restore their strength. A man who takes more food than his body needs becomes fat, sluggish and diseased. Tf, on the other hand, he works hard, and does not eat a suffi- cient amount of food, his body becomes exhausted, and he is sick, and unable to work. Even when no exercise is taken, the man must have food, or he will die of starvation.
The storage battery is quite human in many respects. It must have the proper amount of food and exercise in order to be
THE. WORKSHOP. GENERAL INSTRUCTIONS 111
in the best of health. It must have food, even though it may be idle; but, on the other hand, it must not have too much food at any time, even though it may be working regularly and using ip energy supplied by the food.
A battery, unlike a man, has no mind to enable it to regulate its food and exercise, and is entirely at the mercy of the ear ywner and garage battery man. When called upon it must work as long as a bit of energy remains, and until it is completely ex- aausted and often hopelessly injured. It must also accept all the food offered to it,,even though the amount is far in excess of that needed to restore the amount of energy used up in doing its work. Since the battery is thus unable to defend itself against any abuse and mistreatment to which it may be subjected, it osecomes necessary for the car owner and repairman to think for the battery, and to treat it as he does his own body, giving it the proper amount of food and exercise.
Electricity is the battery’s food, and you feed the battery when you charge it. The electricity must be digested just as our own food is.- The process of digestion in the battery consists, of the formation of spongy lead and lead peroxide from the lead sulphate. When all the sulphate has been thus changed, the bat- tery has received as much food as it can digest, and if it is given more, the energy of the food will be wasted.
The battery works by using the energy resulting from the di- gestion of the electricity, and it should not be forced to work until its energy is completely exhausted, any more than a man should work until he drops from weariness. A man in such an overworked condition is sick, and requires careful nursing and feeding to restore his health. An overworked battery or starved battery requires slow feeding, because its weakened elements cannot absorb the food or charging current quickly, but must be charged at a low rate.
The feeding of a battery is in the repairman’s hands, and he must see that the battery is not overworked or starved any more than he overworks or starves himself. Thus, charging the bat- tery means more than simply sending a current through it. The eurrent must not be supplied faster than the battery can absorb
112 THE AUTOMOBILE STORAGE BATTERY
it. Batteries of different sizes must not be given the same amount of food any more than men of different sizes must be.
The great majority of battery men have adopted the plan of connecting batteries in series while charging them. This is un- doubtedly the cheapest and most convenient method, but has several disadvantages.
Batteries which have different voltages and capacities require different charging currents, and great care should be taken that the batteries which are connected in series require approximately the same charging currents, and are of the same voltage. Garage- men are often careless in this respect, and the smaller batteries are
PosiTvEe NEGATIVE BATTERY BATT ERY
Fig. 58
POSITIVE CHARGING NEGATIVE CHARGH LINE WwWiRme LINE WIRE
CHARGING BATTERIES IN SERIES | Fig. 59
greatly overcharged and literally ‘‘boiled to death.’’ In charg-. ing, therefore, do not connect batteries of various sizes in series | and send the same charging current through them. The smaller batteries will heat up in their attempt to absorb the heavier current required by the larger batteries, and may be permanently injured.
Furthermore, the batteries should be in approximately the same state of discharge, as shown by the specific gravity readings. If these readings differ considerably among the various batteries, those with the highest readings should be watched carefully, and removed from the circuit when there is no further rise in specific . gravity after all cells are gassing freely. Never start a charge
THE WORKSHOP. GENERAL INSTRUCTIONS 113
at such a high rate that gassing takes place immediately, or before the specific gravity stops rising. |
In connecting a battery to a charging line, always connect the ‘
positive battery to the positive line wire, and connect the nega- tive battery terminal to the negative line wire, figure 58. If you connect a number of batteries in series for charging, connect the positive terminal of one battery to the negative terminal of the next, figure 59. .
Instead of connecting all the cells in series, it is a good plan to have several charging circuits in parallel, and connect enough batteries in series on each circuit to obtain the correct charging eurrent. In this way, batteries of various capacities may be charged at once, each circuit being composed of batteries of ap- proximately the same capacity.
The sum of the voltages of the batteries which are connected in series should never be greater than the voltages of the charg- ing circuit. This would result in the batteries discharging back into the line, instead of being charged.
Charging Equipment.
The apparatus to be employed in charging starting and light- ing batteries depends largely upon the source of electricity which is available. If a 110 volt, direct current supply is used, .the simplest and cheapest apparatus is the charging bench with lamps for resistance, which will be described. Instead of the lamps, a motor-generator set may be used, which has a 110 volt, direct cur- rent motor, and a low voltage generator. ‘Such an outfit is far more expensive than the lamps, however, and has no marked advantages to justify its installation.
Where only alternating current is available, a rectifier or motor- generator must be installed. The rectifier changes the alternating current into a direct current. It may do this by means of a mechanical device, an electrolytic cell, or a tube of mercury vapor. The motor-generator set consists of an alternating cur- rent motor driving a direct current generator. Both the Mercury Arc Rectifier and the Motor-Generator are efficient.
a
114 THE AUTOMOBILE. STORAGE BATTERY Double Charging Bench.
The charging bench, as shown in Figures 60 and 61 is designed to accommodate thirty-two batteries. The bench shown in Fig-
ure 60 has been in actual use for several years. The wiring shown ,
in Figure 62 is somewhat different from that of the bench shown in the photograph, and is intended to furnish any current up to about 30-36 amperes. This type of bench has several advantages. Ist. It occupies a minimum amount of floor space. 2nd. Any number of batteries from 1 to 32 may be charged at
Fig. 60. Double Charging Bench
the same time. Any battery may be disconnected from the charg- ing circuit by throwing up the knife switch for that battery. This will allow the other batteries to continue charging.
3rd. To each switch are attached two 18 inch flexible, No. 8 rubber covered wires, each of which has a hold-fast clip at the free end. These clips are snapped on the battery posts in an instant. This arrangement does away with the unsightly, time- consuming, inefficient method of tying batteries in series with any “odd bits of wire which may be at hand, and after you once use this bench, you will never go back to the old, untidy, haphazard way of charging.
4th. The elevated shelf extending down the center of the bench is convenient for holding jars of distilled water, chalk for
THE WORKSHOP.: GENERAL INSTRUCTIONS 115
marking on the battery what is to be done with it, such as, 1 D.C. for one dead cell, R.B. for rebuild, R.S. for reseal, ete. The hydrometer may also be kept on the shelf.
HW
L668 6 3-9:
BATTERY DOUBLE CHARGING BENCH
. 2 6 ; i | a 3 hes t—+ | i 5 * ow | \ . a} NI | U1 «1 4 iw | E 8 b to é ae ® | o La =| \ | ae 14 ty | (< S Hea}? 0) . \e +—-+ | < ls i Fie I\ ° $ |i 4 | ; % ito
Figure 61 shows the various dimensions in sufficient detail to enable you to build the bench. Give each part a coat of asphal- tum paint before assembling the bench. When you have the bench assembled, give it two coats of hot asphaltum paint, being care-
116 THE AUTOMOBILE STORAGE BATTERY
ful to thoroughly cover all parts. If you want to charge more than 32 batteries at one time extend the bench so as to make it wider, and add more switches.
To do this use lumber of the same thickness as the top, and twelve inches wide. Brace with two by fcurs nailed to the side of the bench.
+32: rh
Fig. 62
Figure 62 shows the wiring diagram, using 36 thirty-two candle power, carbon filament lamps. These give one ampere each on 110 volts. Other sized lamps may be used, depending on the amount of current desired. The switches shown at A, B, C, D,E and F control the various groups of lamps. These may be the or- dinary 10 ampere snap switches, or 10 ampere, single pole, single throw knife switches. Any current from