hard rubber disk below the gas chamber has been lost,
e. Keep vent plugs in place. Do not allow any of
must not be used.
the soda solution to get into the cells. It will neutralize
the electrolyte and lower cell capacity. Sufficient time
h. Vent plugs, when removed, should be placed
bottom side up on the battery covers. When laid right
stops on electrolyte soaked areas, especially on wood
side up, accumulated dirt may be introduced into the
trays, and then immediately rinse off with water at
cell, contaminating the electrolyte, which may in turn
moderate pressure, to remove the soda solution. If
shorten battery life.
soda is allowed to dry on top of the battery, it produces a
i. Cell covers damp with electrolyte may be an
path for current leakage. Allow to air-dry.
indication of clogged vent openings. Damp covers may
f. During a regular monthly inspection, if the top of
also be caused by poorly applied plugs, adding too
a battery is found to be dry but dusty, rinse off with
much water or a break in the seal.
water at a moderate pressure.
g. In freezing weather, after rinsing the top of a
122. Vent Plugs, Rotating
battery, if there is not sufficient time for air drying in the
a. Each time a hydrometer reading is taken, a
shop, use low pressure air to blow off the surplus water.
small amount of electrolyte may be lost. If one cell is
read continuously, its fully charged specific gravity will
h. Do not use steam or high pressure air for
gradually be lowered, resulting in individual low cells.
cleaning or drying as both will remove the protective
grease from the grease ring seal nut on the posts. This
b. To avoid an excessive loss from any one cell,
grease prevents electrolytic corrosion on the copper
use a different cell in each half of the battery every time
lugs, cables, and connector bolts attached to the posts.
a gravity reading is taken.
Steam also tends to remove the protective coating of
c. By the use of a special plug (white porcelain or
paraffin and paint from the woodwork, and may damage
painted), the change in cells can easily be marked and
the sealing between the jar and cover to the extent that
followed. Start with the positive terminal cell in each
resealing might be necessary to prevent loss of
half of the battery, and follow the series circuits until the
negative terminal cell is reached. The special plugs
i. Increase water pressure to wash out battery
should then be returned to the positive terminal cells,
compartment and dirt from under battery trays. This
and the same routine repeated.
helps to prevent grounds.
d. Therefore, after each hydrometer reading
change the white porcelain vent plug to the next cell,
121. Vent Plugs, General
thus moving progressively through the battery circuit so
that all cells will be read and recorded every four
a. Keep the vent plugs securely in place at all
times, except when taking hydrometer readings or
Daily ................... 32 cells ................Check 1 cell in each half battery.
b. All vent plugs are provided with small openings
Daily .................. 56 cells ................Check 1 cell in each half battery.
for the escape of gas.
Weekly ............... 32 cells ................Check 1 cell in each half battery.
Weekly ............... 56 cells ................Check 2 cells in each half battery.
c. Clogged openings may cause sufficient gas
Monthly................ 32 cells ................Check 4 cells in each half battery.
pressure within the cell, to break the seal between the
Monthly................ 56 cells ................Check 7 cells in each half battery.
jar and cover.
d. If these openings are found clogged with dirt,
e. The above procedure will indicate symptoms of
when examined during any inspection, immerse in water
developing trouble in individual cells so that necessary
and thoroughly clean.
corrective action can be taken to avoid serious damage
e. It may be necessary to use a piece of wire to
to the battery or failure to crank diesel engine.
clear the openings.
f. Accumulated gum or grease deposits on the
123. Hydrometer Readings-Specific Gravity
plugs can be removed by cleaning with carbon
a. There is a need for an understanding of the
tetrachloride or cleaning fluid. Remove cleaning fluid
proper method of reading the hydrometer syringe.
with low pressure air.
Unless a uniform method is used a wide variety
g. A cracked vent plug, or one upon which the soft
rubber gasket does not seal tightly, or from which the