Methods Of Charging - Yale 524150797 Maintenance Manual

Battery Maintenance
Figure 18. Specific Gravity Compared to Charging

Methods of Charging

There are three methods of charging a battery.
1. GRADUAL CHARGE. This method uses a solid-
state automatic battery charger. The charging rate
begins at 20 to 25 amps/100 amp-hours and
decreases to less than 5 amps/100 amp-hours
when the battery is 80 percent charged. The
charging current decreases when the voltage
across the cell increases during the charging
cycle shown in Figure 19. The increase in the
voltage from the charger is approximately the
same as the increase in the specific gravity in the
cells.
Figure 19. Specific Gravity Compared to Charging
2. MODIFIED CONSTANT VOLTAGE. This method
uses a generator to generate a constant voltage
that is controlled by a resistor. When the charging
current decreases, the voltage across the resistor
14
Time
Time
increases. The increasing voltage across the
resistor causes an increasing voltage at the
battery terminals. The charging is similar to the
gradual charge. The resistor must be correctly
set, or the charging rate will be wrong. The typical
graphs for a modified constant voltage charger
are shown in Figure 20.
3. TWO-RATE CHARGE. This method also uses a
high charging rate at the beginning followed by a
lower rate. Two resistors control the charging
rate. One resistor controls the charging rate at the
beginning of the cycle and a second resistor
reduces the charging rate when the voltage in the
cells reaches 2.37 volts. A relay automatically
controls the second resistor. The two-rate
charging cycle is shown in Figure 21.
Figure 20. Modified Constant Voltage Charger
Figure 21. Two-Rate Charging Cycle
2240 YRM 0001