1312 / 1906
ELECTRICAL
10
BATTERY TESTING
Battery testing has two basic elements
1.Visual Inspection
2.State of Charge
a.Specific Gravity
b.Open Circuit Voltage
1. VISUAL INSPECTION
Battery service should begin with a thorough
visual inspection. This inspection may reveal
simple, easily correctable problems.
Check for cracks in the battery container and
broken terminals. Either may allow electrolyte
leakage and warrant battery replacement.
Check for broken cable or connectors. Replace
as needed.
Check for corrosion on terminals and dirt or
acid on the battery top. Clean the terminals –
and battery top with a mixture of water and bak-
ing soda. A battery wire brush tool is required to
remove hard scales if any on the terminals.
Check for a loose battery hold-down or loose
cable connection, clean and tighten as needed.
2
.
STATE OF CHARGE
The state of charge of a battery can be easily
checked in one of two ways
a. Specific Gravity Test
b. Open Circuit Voltage Test
a. Specific Gravity Test Procedure
Wear suitable eye protection.
Remove vent plugs from the battery cells.
Squeeze the hydrometer bulb and insert the
pickup tube into the cell up to the plate’s top.
Slowly release the bulb to draw in only enough
acid to cause the float to rise. Do not remove
the tube from the cell.
Read the specific gravity indicated on the float.
Be sure the float is drifting free, not in contact
with the sides of top of the barrel. Bend down to
read the hydrometer at eye level. Disregard the
sight curvature of liquid on the float.
Record your readings and repeat the procedure
for the remaining cells.
Specific gravity varies with the temperature. If the
electrolyte temperature is substantially above 27
O
C
add seven points (0.007) to the observed specific
gravity reading for every 10
O
C by which the actual
temperature is above 27
O
C. Deduct seven points
per 10
O
C where the observed reading is below
27
O
C to obtain the temperature corrected reading
at 27
O
C.
Eg, for observed gravity 1.240 at 35
O
C, true
gravity is 1.240 + (0.007/10 X 8) = 1.2456 at
27
O
C.
Specific gravity should not be measured immedi-
ately after topping up a cell as the added distilled
water will not have diffused enough and gives a
false reading. A charge for sixty minutes or more
after topping up will mix the electrolyte and allow
accurate readings to be taken.
NOTE
If there is insufficient electrolyte in the cells to ob-
tain a hydrometer reading, tilt the battery at 30 deg
angle to one side to increase the electrolyte over
the plates. If the level is still low, top up all cells
with distilled water and mix by charging the battery
to attain full charge. Then take specific gravity
readings, applying temperature correction if the
battery has become hot due to charging, and con-
tinue according to the battery testing procedure.
b. Open circuit Voltage
A digital multimeter must be used to check the
battery’s Open-circuit voltage.
Turn the headlamps high beam for 30 sec to
remove any surface charge.
Turn the headlamp off, and connect the digital
voltmeter across the battery terminals.
Read the volt in the multimeter. A fully charged
battery will have an open circuit voltage of
12.60V.
DE-MINERALIZED
WATER
TOP
UP
PROCEDURE:
Open the vent caps and look inside the fill
wells.
Check electrolyte level. The minimum level is at
the top of the plates.
If necessary add just enough water to cover the
plates at this time.
Put batteries on a complete charge before add-
ing any additional water
Once charging is completed, open the vent
caps and look inside the fill wells.
Add water until the electrolyte level is 1/8" be-
low the bottom of the fill well.
Clean, replace and tighten all vent caps.