Hydrometer; Battery Temperature - Yale 524150797 Maintenance Manual

2240 YRM 0001

HYDROMETER

NOTE: Some batteries have sealed cells. The specific
gravity of the electrolyte cannot be checked on these
batteries.
Use a hydrometer to measure the specific gravity of
the battery. Make sure there is enough electrolyte in
the battery cells. See Adding Water to Battery in this
section. A high level or low level of the electrolyte can
change the specific gravity measurement. When the
1. HIGH FLOAT MEANS HIGH SPECIFIC GRAVITY.
2. LOW FLOAT MEANS LOW SPECIFIC GRAVITY.

BATTERY TEMPERATURE

The temperature of the electrolyte will change the
reading of the specific gravity. When the temperature
increases approximately 6°C (10°F), the specific
gravity will decrease by 0.003 point. See Figure 15 for
making specific gravity corrections. If the hydrometer
you are using does not have a temperature correction,
you will have to use a thermometer. Special battery
thermometers are available that will indicate the
correction factor directly and add or subtract the
correct number of points. See Figure 16.
NEVER charge a battery at a rate that will raise the
electrolyte temperature above 49°C (120°F). NEVER
let a battery stay discharged for long periods. A
temperature above this amount will damage the
battery. The cells in the center of the battery are
normally at the highest temperature. If the battery
temperature is too hot, make sure the ventilation of the
electrolyte level is low, the percent of sulfuric acid in
the electrolyte increases. When the electrolyte level
decreases by 3 mm (1/8 in.), the specific gravity
measurement can increase by 3 to 5 points.
When you use the hydrometer, make sure there is
enough liquid in the barrel to let the float move freely.
The float must not touch the side, top, or bottom of the
barrel. See Figure 14 for the correct method of reading
the hydrometer.
3. CORRECT METHOD OF READING
HYDROMETER: EYE LEVEL EVEN WITH
SURFACE OF ELECTROLYTE.
Figure 14. Reading Hydrometer
battery is increased and make sure the charge or
discharge rate is not too high. A recommendation for a
battery in service is 8 hours of use (discharge),
followed by 8 hours of charging, followed by 8 hours of
cooling.
To charge the battery, a direct current must pass
through the cells in the opposite direction to the
discharging current. The ampere-hours must be equal
to the discharging ampere-hours plus the energy lost
as heat. This additional amount of charge will vary
according to the battery and the temperature, but the
average additional charge is 12 percent. When the
battery is nearly charged, the final charging must be at
a low rate. A charging rate that is too high will cause
heating in the battery and a high loss of water from the
electrolyte. The charging of the battery must be done
correctly, or the service life of the battery will be
decreased.
Battery Maintenance
11