g Acid Instead of Water. The sulphuric acid in the electrolyte
is a heavy, oily liquid that does not evaporate. It is only the water
in the electrolyte which evaporates. Therefore, when the level of the
electrolyte falls, only water should be added to bring the electrolyte
to the correct height. There are, however, many car owners who still
believe that a battery may be charged by adding acid when the level of
the electrolyte falls. Batteries in which this is done then contain
too much acid. This leads to two troubles. The first is that the
readings taken with a hydrometer will then be misleading. A specific
gravity of 1.150 is always taken to indicate that a battery is
discharged, and a specific gravity of 1.280 that a battery is charged.
These two values of specific gravity indicate a discharged and charged
condition of the battery ONLY WHEN THE PROPORTION OF ACID IN THE
ELECTROLYTE IS CORRECT. It is the condition of the plates, and not the
specific gravity of the electrolyte which determines when a battery is
either charged or discharged. With the correct proportion of acid in
the electrolyte, the specific gravity of the electrolyte is 1.150 when
the plates are discharged and 1.280 when the plates are charged, and
that is why specific gravity readings are generally used as an
indication of the condition of the battery.

If there is too much acid in the electrolyte, the plates will be in a
discharged condition before the specific gravity of the electrolyte
drops to 1.150, and will not be in a charged condition until after the
specific gravity has risen beyond the usual value. As a result of
these facts a battery may be over-discharged, and never fully charged,
this resulting in the formation of sulphate.

The second trouble caused by adding acid to the electrolyte is that
the acid will then be too concentrated and attacks both plates and
separators. This will cause the plates to become sulphated, and the
separators rotted.

7. Overheating. This was explained in Chapter 9. See page 66.

Buckling

Buckling is the bending or twisting of plates due to unequal expansion
of the different parts of the plate, Figs. 207 and 208. It is natural
and unavoidable for plates to expand. As a battery discharges, lead
sulphate forms. This sulphate occupies more space than the lead
peroxide and spongy lead, and the active materials expand. Heat
expands both active materials and grids. As long as all parts of a
plate expand equ