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Lead-Acid Storage Batteries
DOE-HDBK-1084-95
MAINTENANCE
Rev. 0
Page 37
Batteries
For an acceptance or performance test, use the following equation to determine battery
capacity:
% capacity at 25ºC (77ºF) = Ta/Ts • 100,
(7)
where
Ta
=
actual time of test to specified terminal voltage
Ts
=
rated time to specified terminal voltage.
ANSI/IEEE Std 450 recommends replacement of a battery if its capacity as determined from
the equation above is less than 80% manufacturer's rating. A capacity of 80% shows that the
battery rate of deterioration is increasing even if there is ample capacity to meet load
requirements. If individual cells are required to be replaced, they should be compatible with
existing cells and tested prior to installation. It is recommended that when one or more
cells/jars are replaced the entire battery string be replaced in order to prevent large
differences in cell impedance. If uncorrected, this may result in unequal charging of the
battery string.
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