Figure 12-4. Battery Cell Elements.
(a) When batteries are operated in tropical
climates, the full-charge specific gravity should be
reduced to a value between 1.2 and 1.225 by dilution
(1) Composition. An electrolyte is a liquid that
with water. Rainwater may be used if distilled water is
conducts electricity readily and is decomposed when an
electric current passes through it. The electrolyte in the
lead-acid storage battery has a specific gravity of 1.28,
(b) At the high temperatures encountered
which means that it is 1.28 times as heavy as water. It is
in the tropics, the acid in the electrolyte is more active
composed of one part of chemically pure sulfuric acid
and a weaker concentration will give satisfactory results
and approximately two and three-fourths parts, by
with less damage to plates and separators.
volume, of distilled water. A small quantity of some
impurity introduced into the acid solution by using impure
(c) When the electrolyte is diluted, a
water might interfere with the chemical action and cause
special tag, giving the full-charge specific gravity, will be
attached to the battery and also a 1-inch white spot will
be painted on the battery top. If the battery is a
(2) Specific Gravity Readings. Specific gravity
nonmilitary type, it may have exposed cell connector
is the ratio of the weight of the same volume of
straps and these will be painted white. Be careful to
chemically pure water at 39F (4C). The specific gravity
readjust the specific gravity before shipping such
of sulfuric acid is 1.835; that is, sulfuric acid is 1.835
batteries to frigid areas.
times heavier than water. The electrolyte of a storage
battery is a mixture of water and sulfuric acid. The
amount of sulfuric acid in the electrolyte changes with the
amount of electrical charge; also, the specific gravity of
(1) A battery container is a receptacle for
the electrolyte changes with the amount of electrical
the cells that make up the battery. It is made of hard
charge. This provides a convenient way of measuring
rubber or a polypropylene plastic, which is resistant to
the degree of charge in a battery. A fully charged battery
acid and mechanical shock.
Most motor vehicle
will have a specific gravity of 1.28 at 80F (26.6C). The
batteries are assembled in one-piece containers (fig. 12-
figure will go higher with a temperature decrease and
lower with a temperature increase.
(3) Tropical Operation.