Lesson 2/Learning Event 1
To seal the battery after the cell cover is installed, the space between the edges of the cell covers
and the container is filled with an acid-resistant compound. Some form of seal is also used where
the terminal post extends through the cover.
The vent plug (filler cap) contains a small hole to permit the escape of gas formed in the cell. A
series of baffles may be built into the plug so the gas must pass around them in leaving the cell.
The baffles prevent electrolyte from splashing out through the venthole. Also, any mist from the
electrolyte is collected here and returned to the cell.
Batteries designed for use in tactical vehicles are waterproof. The vent plugs will not allow water to
enter the cells during fording operations but will still permit gases to escape. This is done by a
pressure vent valve in the vent plug. The valve closes to external water pressure and opens to
release internal gas pressure.
Electrical power comes from the battery through two TERMINAL POSTS. The posts are tapered,
and the positive terminal is slightly larger than the negative terminal. The cable clamps are also
made in two sizes, to reduce the chances of connecting a battery in reverse.
The cells of the battery are filled with
a mixture of sulfuric acid and distilled water, the electrolyte.
Electrical energy is produced by the
chemical action of the sulfuric acid on the plates. The
electrolyte also serves as a carrier for
the electric current inside the battery. The electrolyte of a
fully charged battery contains about
38 percent sulfuric acid by weight (about 27 percent by