CARE OF THE BATTERY ON THE CAR.
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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 automatically connected to
the battery at the proper time, and also disconnected from it as the
engine slows down. The amount of current which the generator 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 condition. It is impossible, however, to eliminate
entirely the need of attention on the part of the car owner, and
battery repairman.
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 books are studied.
Thereafter more attention is paid to the battery. The rules to be
observed in taking care of the battery which is in service on the car
are not difficult to observe. It is while on the car that a battery is
damaged, and the damage may be prevented by intelligent consideration
of the battery's housing and living conditions, just as these
conditions are made as good as possible for human beings.
1. Keep the Interior of the Battery Box Clean and Dry. On many cars
the battery is contained in an iron box, or under the seat or
floorboards. This box must be kept dry, and frequent inspection is
necessary to accomplish this. Moisture condenses easily in a metal
box, and if not removed will cause the box to become rusty. Pieces of
rust may fall on top of the battery and cause corrosion and leakage of
current between terminals.
Occasionally, wash the inside of the box with a rag dipped in ammonia,
or a solution of baking soda, and then wipe it dry. A good plan is to
paint the inside of the box with asphaltum paint. This will prevent
rusting, and at the same time will prevent the iron from being
attacked by electrolyte which may be spilled, or may leak from the
battery.
Some batteries are suspended from the car frame under the floor boards
or seat. The iron parts near such batteries should be kept dry and
free from rust. If the battery has a roof of sheet iron placed above
it, this roof should also be kept clean, dry and coated with asphaltum
paint.
[Fig. 27 "Do not drop tools on top of battery"]
2. Put Nothing But the Battery in the Battery Box. If the battery is
contained in an iron box, do not put rags, tools, or anything else of
a similar nature in the battery box. Do not lay pliers across the top
of the battery, as shown in Fig. 27. Such things belong elsewhere. The
battery should have a free air space all around it, Fig. 28. Objects
made of metal will short-circuit the battery and lead to a repair bill.
3. Keep the battery clean and dry. The top of the battery should be
kept free of dirt, dust, and moisture. Dirt may find its way into the
cells and damage the battery. A dirty looking battery is an unsightly
object, and cleanliness should be maintained for the sake of the
appearance of the battery if for no other reason.
Moisture on top of the battery causes a leakage of current between the
terminals of the cells and tends to discharge the battery. Wipe off
all moisture and occasionally go over the tops of the cell connectors,
and terminals with a rag wet with ammonia or a solution of baking
soda. This will neutralize any acid which may be present in the
moisture.
The terminals should be dried and covered with vaseline. This protects
them from being attacked by acid which may be spilled on top of the
battery. If a deposit of a grayish or greenish substance is found on
the battery terminals, handles or cell connectors, the excess should
be scraped off and the parts should then be washed with a hot solution
of baking soda (bicarbonate of soda) until all traces of the substance
have been removed. In scraping off the deposit, care should be taken
not to scrape off any lead from terminals or connectors. After washing
the parts, dry them and cover them with vaseline. The grayish or
greenish substance found on the terminals, connectors, or handles is
the result of "corrosion," or, in other words, the result of the
action of the sulphuric acid in the electrolyte upon some metallic
substance.
[Fig. 28 Battery installed with air space on all sides]
The acid which causes the corrosion may be spilled on the battery
when hydrometer readings are taken. It may also be the result of
filling the cells too full, with subsequent expansion and overflowing
as the temperature of the electrolyte increases during charge. Loose
vent caps may allow electrolyte to be thrown out of the cell by the
motion of the car on the road. A poorly sealed battery allows
electrolyte to be thrown out through the cracks left between the
sealing compound and the jars or posts. The leaks may be caused by the
battery cables not having sufficient slack, and pulling on the
terminals.
The cap which fits over the vent tube at the center of the top of each
cell is pierced by one or more holes through which gases formed within
the cell may escape. These holes must be kept open; otherwise the
pressure of the gases may blow off the top of the cell. If these holes
are found to be clogged with dirt they should be cleaned out
thoroughly.
The wooden battery case should also be kept clean and dry. If the
battery is suspended from the frame of the car, dirt and mud from the
road will gradually cover the case, and this mud should be scraped off
frequently. Occasionally wash the case with a rag wet with ammonia, or
hot baking soda solution. Keep the case, especially along the top
edges, coated with asphaltum or some other acid proof paint.
[Fig. 29 Battery held in place by "hold-down" bolts]
4. The battery must be held down firmly. If the battery is contained
in an iron box mounted on the running-board, or in a compartment in
the body of the car having a door at the side of the running-board, it
is usually fastened in place by long bolts which hook on the handles
or the battery case. These bolts, which are known as "hold-downs,"
generally pass through the running board or compartment, Fig. 29, and
are generally fastened in place by nuts. These nuts should be turned
up so that the battery is held down tight.
Other methods are also used to hold the battery in place, but whatever
the method, it is vital to the battery that it be held down firmly so
that the jolting of the car cannot cause it to move. The battery has
rubber jars which are brittle, and which are easily broken. Even if a
battery is held down firmly, it is jolted about to a considerable
extent, and with a loosely fastened battery, the jars are bound to be
cracked and broken.
5. The cables connected to the battery must have sufficient slack so
that they will not pull on the battery terminals, as this will result
in leaks, and possibly a broken cover.
The terminals on a battery should be in such a position that the
cables may be connected to them easily, and without bending and
twisting them. These cables are heavy and stiff, and once they are
bent or twisted they are put under a strain, and exert a great force
to straighten themselves. This action causes the cables to pull on the
terminals, which become loosened, and cause a leak, or break the cover.
[Fig. 30 Measure height of electrolyte in battery]
6. Inspect the Battery twice every month in Winter, and once a week in
Summer, to make sure that the Electrolyte covers the plates. To do
this, remove the vent caps and look down through the vent tube. If a
light is necessary to determine the level of the electrolyte, use an
electric lamp. Never bring an open flame, such as a match or candle
near the vent tubes of a battery. Explosive gases are formed when a
battery "gasses," and the flame may ignite them, with painful injury
to the face and eyes of the observer as a result. Such an explosion
may also ruin the battery.
During the normal course of operation 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 plate. A convenient method of measuring the height of the
electrolyte is shown in Fig. 30. Insert one end of a short piece of a
glass tube, having an opening not less than one-eighth inch diameter,
through the filling hole, and allow it to rest on the upper edge of
the 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. Fig. 31 shows the
correct height of electrolyte in an Exide cell.
Never add well water, spring water, water from a stream, or ordinary
faucet water. These contain impurities which will damage the battery,
if used. 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.
[Fig. 31 Correct height of electrolyte in Exide cell]
A convenient 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.
In the summer time it makes no difference when water is added. In the
winter time, if the air temperature is below freezing (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 electrolyte, will remain at the top and freeze. Be sure to
wipe off water from the battery top after filling. If battery has been
wet for sometime, wipe it with a rag dampened with ammonia or baking
soda solution to neutralize the acid.
Never add acid to a battery while the battery is on the car. By "acid"
is meant a mixture of sulphuric acid and water. The concentrated acid,
is of course, never used. The level of the electrolyte falls because
of the evaporation of the water which is mixed with the acid in the
electrolyte. The acid does not evaporate. It is therefore evident that
acid should not be added to a cell to replace the water which has
evaporated. Some men believe that a battery may be charged by adding
acid. This is not true, however, because a battery can be charged only
by passing a current through the battery from an outside source. On
the car the generator charges the battery.
It is true that acid is lost, but this is not due to evaporation, but
to the loss of some of the electrolyte from the cell, the lost
electrolyte, of course, carrying some acid with it. Electrolyte 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.
If acid or electrolyte is added instead of water, when no acid is
needed, the electrolyte will become too strong, and sulphated plates
will be the result. If a battery under average driving conditions
never becomes fully charged, it should be removed from the car and
charged from an outside source as explained later. If, after the
specific gravity of the electrolyte stops rising, it is not of the
correct value, some of the electrolyte should be drawn off and
stronger electrolyte added in its place. This should be done only in
the repair shop or charging station.
Care must be taken not to add too much water to a cell, Fig. 32. This
will subsequently cause the electrolyte to overflow and run over the
top of the battery, due to the expansion of the electrolyte as the
charging current raises its temperature. The electrolyte which
overflows is, of course, lost, taking with it acid which will later be
replaced by water as evaporation takes place. The electrolyte will
then be too weak. The electrolyte which overflows will rot the wooden
battery case, and also tend to cause corrosion at the terminals.
If it is necessary to add water very frequently, the battery is
operating at too high a temperature, or else there is a cracked jar.
The high temperature may be due to the battery being charged at too
high a rate, or to the battery being placed near some hot part of the
engine or exhaust pipe. The car manufacturer generally is careful not
to place the battery too near any such hot part. The charging rate may
be measured by connecting an ammeter in series with the battery and
increasing the engine speed until the maximum current is obtained. For
a six volt battery this should rarely exceed 14 amperes. If the
charging, current does not reach a maximum value and then remain
constant, or decrease, but continues to rise as the speed of the
engine, is increased, the regulating device is out of order. An
excessive charging rate will cause continuous gassing if it is much
above normal, and the temperature of the electrolyte will be above
100° F. In this way an excessive charging current may be detected.
[Fig. 32 Cell with level of electrolyte too high]
In hot countries or states, the atmosphere may have such a high
temperature that evaporation will be more rapid than in temperate
climates, and this may necessitate more frequent addition of water.
If one cell requires a more frequent addition of water than the
others, it is probable that the jar of that cell is cracked. Such a
cell will also show a low specific gravity, since electrolyte leaks
out and is replaced by water. A battery which has a leaky jar will
also have a case which is rotted at the bottom and sides. A battery
with a leaky jar must, of course, be removed from the car for repairs.
"Dope" Electrolytes
From time to time within the past two years, various solutions which
are supposed to give a rundown battery a complete charge within five
or ten minutes have been offered to the public. The men selling such
"dope" sometimes give a demonstration which at first sight seems to
prove their claims. This demonstration consists of holding the
starting switch down (with the ignition off) until the battery can no
longer turn over the engine. They then pour the electrolyte out of
the battery, fill it with their "dope," crank the engine by hand, run
it for five minutes, and then get gravity readings of 1.280 or over.
The battery will also crank the engine. Such a charge is merely a
drug-store charge, and the "dope" is generally composed mainly of high
gravity acid, which seemingly puts life into a battery, but in reality
causes great damage, and shortens the life of a battery. The starting
motor test means nothing. The same demonstration could be given with
any battery. The high current drawn by the motor does not discharge
the battery, but merely dilutes the electrolyte which is in the plates
to such an extent that the voltage drops to a point at which the
battery can no longer turn over the starting motor. If any battery
were given a five minutes charge after such a test, the diluted
electrolyte in the plates would be replaced by fresh acid from the
electrolyte and the battery would then easily crank the engine again.
The five minutes of running the engine does not put much charge into
the battery but gives time for the electrolyte to diffuse into the
plates.
Chemical analysis of a number of dope electrolytes has shown that they
consist mainly of high gravity acid, and that this acid is not even
chemically pure, but contains impurities which would ruin a battery
even if the gravity were not too high. The results of some of the
analyses are as follows:
No. 1. 1.260 specific gravity sulphuric acid, 25 parts iron, 13.5
parts chlorine, 12.5, per cent sodium sulphate, 1 per cent nitric acid.
No. 2. 1.335 specific gravity sulphuric acid, large amounts of organic
matter, part of which consisted of acids which attack lead.
No. 3. 1.340 specific gravity sulphuric acid, 15.5 per cent sodium
sulphate.
No. 4. 1.290 specific gravity sulphuric acid, 1.5 per cent sodium
sulphate.
No. 5. 1.300 specific gravity sulphuric acid.
If such "dope" electrolytes are added to a discharged battery, the
subsequent charging of the battery will add more acid to the
electrolyte, the specific gravity of which will then rise much higher
than it should, and the plates and separators are soon ruined.
Do not put faith in any "magic" solution which is supposed to work
wonders. There is only one way to charge a battery, and that is to
send a current through it, and there is only one electrolyte to use,
and that is the standard mixture of distilled water and chemically
pure sulphuric acid.
7. The specific gravity of the electrolyte should be measured every
two weeks and a permanent record of the readings made for future
reference.
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, contains, and
the more nearly it is fully charged. In automobile batteries, a
specific gravity of 1.300-1.280 indicates a fully charged battery.
Generally, a gravity of 1.280 is taken to indicate a fully, charged
cell, and in this book this will be done. Complete readings are as
follows:
1.300-1.280--Fully charged.
1.280-1.200--More than half charged.
1.200-1.150--Less than half charged.
1.150 and less--Completely discharged.
[Fig. 33 and Fig. 34: battery hydrometers]
For determining the specific gravity, a hydrometer is used. This
consists of a small sealed glass tube with an air bulb and a quantity
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 markings as
shown in Fig. 33. 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. Some hydrometers are not marked with
figures that indicate the specific gravity, but are marked with the
words "Charged," "Half Charged," "Discharged," or "Full," "Half Full,"
"Empty," in place of the figures.
The tube must be held in a vertical position, Fig. 35, and the stem of
the hydrometer must be vertical. The reading will be the number on the
stem at the surface of the electrolyte in the tube, Fig. 36. 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.
[Fig. 35 Using hydrometer for reading specific gravity]
For convenience in automobile work, the hydrometer is enclosed in a
large tube of glass or other transparent, acid proof material, 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 hydrometer. See Figure 34. In measuring the specific gravity
of the electrolyte, the vent cap 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 cap 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 of electrolyte has entered the tube, the hydrometer
will float. In taking a reading, there should be no pressure on the
bulb, and the hydrometer should be floating freely and not touching
the walls of the tube. The tube must not be so full of electrolyte
that the upper end of the hydrometer strikes any part of the bulb.
The tube must be held in a vertical position, Fig. 35, and the stem of
the hydrometer must be vertical. The reading will be the number on the
stem at the surface of the electrolyte in the tube, Fig. 36. 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.
If the battery is located in such a position that it is impossible to
hold the hydrometer straight up, the rubber tube may be Pinched shut
with the fingers, after a sufficient quantity of electrolyte has been
drawn from the cell and the hydrometer then removed and held in a
vertical position.
Specific gravity readings should never be taken soon after distilled
water has been added to the battery. The water and electrolyte do not
mix immediately, and such readings will give misleading results. The
battery should be charged several hours before the readings are taken.
It is a good plan to take a specific gravity reading before adding any
water, since accurate results can also be obtained in this way.
[Fig. 36 Hydrometer reading showing cell charged, half-charged,
and discharged]
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 hydrometer
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 discharge.
If one cell of a battery shows a specific gravity which is decidedly
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, and the
battery should be opened for inspection. If the electrolyte in this
cell falls faster than that of the other cells, a leaky jar is
indicated. The various cells should have specific gravities within
fifteen points of each other, such as 1.260 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. Use starter and lights sparingly until the specific
gravity comes up to 1.280-1.300. If the specific gravity is less than
1.150 remove the battery from the car and charge it on the charging
bench, as explained later. The troubles which cause low gravity are
given on pages 321 and 322.
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 constant current which is the same regardless of the
battery's condition.
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 generator current remains constant, and the
voltage changes somewhat to keep the current constant. 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 high that the temperature of
the electrolyte in the battery remains above 90° F. A special
thermometer is very useful in determining the temperature. See Fig.
37. The thermometer bulb is immersed in the electrolyte above the
plates through the filler hole in the tops of the cells.
Batteries used on some of the older cars 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 sections. 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 ammeter 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 amperage 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 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.
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 several
sections must be the same for each one. An examination should be made
to see that no additional lamps, such as trouble lamps 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.
Some starting systems have in the past 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 impossible for these
sections to receive as much charging current as others, even though
all connections and switches are in good condition. 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.
The temperature of the electrolyte affects the specific gravity, since
heat causes the electrolyte to expand. If we take any battery or cell
and heat it, the electrolyte will expand and its specific gravity will
decrease, although the actual amount of acid is the same. The change
in specific gravity amounts to one point, approximately, for every
three degrees Fahrenheit. 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 specific gravity will be 1.251. Since the change of temperature
does not change the actual amount of acid in the electrolyte, the
gravity readings as obtained with the hydrometer 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 degrees below 70°F.
For convenience of the hydrometer user, a special thermometer has been
developed by battery makers. This is shown in Fig. 37. 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.
Opposite the 67° point on the regular scale is a -1, indicating 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. 37 Special thermometer]
8. Storage batteries are strongly affected by changes in temperature.
Both extremely high and very low temperatures are to be avoided. At
low temperatures the electrolyte grows denser, the porosity of plates
and separators decreases, circulation and diffusion of electrolyte 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 electrolyte
decreases, the plates and separators become more porous, the internal
resistance decreases, circulation and diffusion of electrolyte 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 110° F, are, however, more harmful
than low temperatures. Evaporation of the water 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 addition of
water, is either receiving too much charging current, or has internal
trouble. The remedy for excessive charge is to decrease 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 decrease the charging rate or
burn the lamps, even in the day time.
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 or more from the bottom of the
jar, and which form pockets into which the materials drop. See Fig.
10. If these pockets become 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 water will also become
hot and boil away. A battery which is thus "charged while dry"
deteriorates rapidly, its life being very short.
If a battery is placed in a hot place on the car, 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 freezing. 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, the 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.
---------------- ------------ ---------------- ------------
1.000 32 deg. F 1.200 -16 deg. F
1.050 26 deg. F 1.250 -58 deg. F
1.100 18 deg. F 1.280 -92 deg. F
1.150 5 deg. F 1.300 -96 deg. F
9. 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 possible the last few days, the car is
in service by using the lamps and starting motor very sparingly. The
specific gravity of the electrolyte in each cell should be tested, and
it should be somewhere between 1.280 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 generator on the car or by connecting it to an outside
charging circuit. 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 freshening 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 without further
attention. Water should be added and the battery fully charged before
it is put back into service. It is desirable to have the temperature
of the room where the battery is stored fairly constant and as near 70
degrees Fahrenheit as possible.
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