Checking the condition of the battery by testing
the state of charge.
O F T H E
BATTERY.Battery maintenance should always
begin with a thorough visual inspection. Look for signs
of corrosion on or around the battery, signs of leakage,
a cracked case or top, missing caps, and loose or
missing hold-down clamps.
CHECKING ELECTROLYTE LEVEL AND
ADDING WATER.On vent cap batteries, the
electrolyte level can be checked by removing the caps.
Some batteries have a fill ring which indicates the
electrolyte level. The electrolyte should be even with
the fill ring. If there is no fill ring, the electrolyte
should be high enough to cover the tops of the plates.
Some batteries have an electrolyte-level indicator
(Delco Eye). This gives a color code visual indication
of the electrolyte level, with black indicating that the
level is okay and white meaning a low level.
If the electrolyte level in the battery is low, fill the
cells to the correct level with DISTILLED WATER
(purified water). Distilled water should be used
because it does not contain the impurities found in tap
water. Tap water contains many chemicals that reduce
battery life. The chemicals contaminate the electrolyte
and collect in the bottom of the battery case. If enough
contaminates collect in the bottom of the case, the cell
plates SHORT OUT, ruining the battery.
If water must be added at frequent intervals, the
charging system may be overcharging the battery. A
faulty charging system can force excessive current into
the battery. Battery gassing can then remove water
from the battery.
Maintenance-free batteries do NOT need periodic
electrolyte service under normal conditions. It is
designed to operate for long periods without loss of
C L E A N I N G T H E B A T T E R Y A N D
TERMINALS.If the top of the battery is dirty,
using a stiff bristle brush, wash it down with a mixture
of baking soda and water. This action will neutralize
and remove the acid-dirt mixture. Be careful not to
allow cleaning solution to enter the battery.
To clean the terminals, remove the cables and
inspect the terminal posts to see if they are deformed or
broken. Clean the terminal posts and the inside
surfaces of the cable clamps with a cleaning tool before
replacing them on the terminal posts.
Do NOT use a scraper or knife to clean
battery terminals. This action removes too
much metal and can ruin the terminal
When reinstalling the cables, coat the terminals
with petroleum or white grease. This will keep acid
fumes off the connections and keep them from
corroding again. Tighten the terminals just enough to
secure the connection. Overtightening will strip the
cable bolt threads.
CHECKING BATTERY CONDITION.
When measuring battery charge, you check the
condition of the electrolyte and the battery plates. As a
battery becomes discharged, its electrolyte has a larger
percentage of water. Thus the electrolyte of a
discharged battery will have a lower specific gravity
number than a fully charged battery. This rise and drop
in specific gravity can be used to check the charge in a
battery. There are several ways to check the state of
charge of a battery.
Nonmaintenance-free batteries can have the state of
charge checked with a hydrometer. The hydrometer tests
specific gravity of the electrolyte. It is fast and simple to
use. There are three types of hydrometersthe float
type, the ball type, and needle type.
To use a FLOAT TYPE HYDROMETER, squeeze
and hold the bulb. Then immerse the other end of the
hydrometer in the electrolyte. Then release the bulb.
This action will fill the hydrometer with electrolyte.
Hold the hydrometer even with your line of sight and
compare the numbers on the hydrometer with the top of
Most float type hydrometers are NOT temperature
correcting. However, the new models will have a built-
in thermometer and a conversion chart that allow you
to calculate the correct temperature.
The BALL TYPE HYDROMETER is becoming
more popular because you do not have to use a
temperature conversion chart. The balls allow for a
change in temperature when submersed in electrolyte.
This allows for any temperature offset.
To use a ball type hydrometer, draw electrolyte
into the hydrometer with the rubber bulb at the top.
Then note the number of balls floating in the
electrolyte. Instructions on or with the hydrometer will
tell you whether the battery is fully charged or