d 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 deg. 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
ou