Evening star. [volume] (Washington, D.C.) 1854-1972, 1914-01-25
D|SCHARG|NGBATTERY
AND ACID FORMATION
Casing Of Cell Il Feature Of Charg-
ing Very Little
Regarded.


sulphuric acid In the electrolyte combines
with the lead in the active material on
the plates and forms compound called
lead sulphate. This lead sulphate is form
ed in the same way that sulphuric acid
on the copper wiring or terminals forms
copper sulphate or the acid on the iron
work Of the car forms iron sulphate
In this connection 1t is noticeable that a
comparatively large mass of copper sui
phate or iron sulphate is formed on the
metal work of the car when only a small
quantity of the metal is eaten away.
In the same manner the sulphuric acid
of the electrolyte combines with lead in
the plates. forming lead sulphate. which,
on account Of its increased volume fills
the pores of the active material
This sulphate continues to increase in
quantity and bulk. thereby filling the
pores of the plates. AS the pores of the
plates become thus filled with the sui
phate the free circulation of acid into the
plates is retarded. and, since the acid
cannot then get into the plates fast
enough to maintain the normal action,
the battery becomes less active. as is
indicated by rapid drop in voltage.
Experience teaches that at the normal
discharge rate the voltage will begin to
drop rapidly very soon after reaching
is per cell 1t is therefore advisable to
stop the discharge when the voltage has
dropped as low as II per cell. and bat
terry should not normally be discharged
below this point
During normal discharge the amour:
of acid used from the electrolyte in lead
acid batteries will cause the gravity to
drop 100 to $50 points Thus if the grav-
ity of fully charged cell is 1850 it will
at the end Of discharge be between 1.1S0
and 1.13o. depending upon the type of
cell The battery should be put on charge
before it is discharged below this point.
Electrolyte Becomes Stronger.
To charge cause direct current to pass
through the cells in a direction opposite
to that Of discharge. This current. pass
ing through the cells in the reverse direc-
ton, will reverse the action which took
place in the cells during discharge 1t
will be remembered that during discharge
the acid of the electrolyte went into and
combined with the active material filing
its pores with sulphate and causing the
electrolyte to become weaker. Reversing
the current through this sulphate in the
plates restores the active material to its
original condition and returns the acid to
the electrolyte. Thus, during charge, the
electrolyte gradually becomes stronger as
the Sulphate in the plates decreases. until
no more sulphate remains and all the
acid has been returned to the electrolyte,
when it will be of the same strength as
before the discharge and the same acid
will be ready to be used over again dur
ing the next discharge. Since there is no
loss of acid none should ever be added to
the electrolyte.
Remember this: The acid absorbed by
the plates during discharge is, during
charge, driven from the plates by the
charging
electrolyte.. This is the whole object of
charging
II has been said that every man has
different method of charging a storage
battery, but in fact all methods are essen
TALLY the same in principle; that is. to
pass direct current through the cells In
the right direction. In the use Of this
current there are only two points to be
considered-rate in amperes and time.
The rate in amperes is limited by the
state of discharge. When a battery is
fully discharged. at which time the plates
contain the greatest amount of sulphate,
it can utilize current at the highest rate.
AS the charge progresses and the amount
of sulphate in the plate decreases they
can no longer utilize current at the same
rate, and the current should be reduced
The time at which to reduce the rate is
when the cells begin to give off gas.
The gassing of cell is feature of
charging which has been very little re-
garded but Is of great Importance.
Casing shows at any time whether or
not the charging rate Is too high.
Does Easiest Thing First.
Current passing through an electrolyte
will always do something. 1t will always
do the easiest thing first. When current
is passed through discharged cell the
easiest thing is to decompose sulphate.
AS there is comparatively large
amount of sulphate in fully discharged
cell high rate of current can be used
but as the amount of sulphate decreases
a point will be reached at which there
will not be sufficient sulphate remaining
| in the plates to utilize all the current
passing through. The excess current
will then begin to do the next easiest
| thing. which is to decompose the water
of the electrolyte. producing gas, and,
| therefore, when the cells begin to gas
| freely it indicates that current is being
passed through the cells at too high a
rate and the rate should be lowered