3. OPERATING GUIDE - CHARGING
3
OPERATING GUIDE - CHARGING
3.1
CHARGE CHARACTERISTICS
The constant current charge characteristics of a lead-acid cell with respect to cell
voltage, ampere-hours input, specific gravity and rate of gassing at constant
current can be seen in Figure 3-1.
Figure 3-1. Charge characteristics of a lead-acid cell
As shown by the curve in Figure 3-1 the cell voltage of a discharged battery rises
rapidly when the battery is first placed on charge. The extent of the initial rise
depends on the charging rate. As the charge continues, the voltage rises at a
slower rate and eventually levels off when a full state-of-charge is reached. It can
be seen that the specific gravity reading lags behind the rate of ampere-hour return
during most of the charging cycle. Consequently, the specific gravity is not
indicative of the available ampere-hour capacity until the cell approaches a full-
charge state.
When a battery reaches a full state-of-charge the voltage of the battery will
stabilize and remain constant or decrease. The charging should discontinue at this
stage. A minimum of 100% of previous discharged ampere-hours are required.
In general a vented battery may be charged at any rate that will not produce
excessive gassing or electrolyte temperatures above 115°F (46°C). Sealed lead-
CA-1550 CHARGER / ANALYZER - OPERATING MANUAL LI-4159-CML Rev A
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