4. OPERATING GUIDE - DISCHARGING
Figure 4-2. Typical discharge curves for SLABs at different rates
The discharge of a lead-acid battery beyond the point of which exhaustion of the cell
is approached can be harmful, as the battery will form a sulfate deposit on its plates.
This is particularly true if the battery is not soon recharged.
4.2
DISCHARGE CAPACITY TESTING
The purpose of a discharge test is to determine the long-term capacity of the
battery. For a lead-acid aircraft battery, for example, the capacity test is the
amount of current which can be delivered for one hour or until the voltage
decreases to 1.5 volts per cell. This is considered the emergency capacity of the
battery. The result of the test will determine whether to accept or reject the battery
and which steps could be taken to electrically recondition the battery.
The amount of electrical capacity available from a fully charged nickel-cadmium or
lead-acid battery is defined by the capacity rating of the battery and is stated in terms
of ampere-hours. Because of internal resistance, the higher the discharge rate (higher
current during a shorter period of time) demanded of a battery, the less usable
capacity it can supply. See Figure 4-2.
CA-1550 CHARGER / ANALYZER - OPERATING MANUAL LI-4159-CML Rev A
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