The capacity of a lead acid battery, measured in amp-hours (Ah), represents its ability to deliver a constant current over a specific time. At its core, capacity is determined by
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1. Objective Methods other than capacity tests are increasingly used to assess the state of charge or capacity of stationary lead-acid batteries. Such methods are based on one of the following methods: impedance (AC resistance), admittance (AC conductance).
In this video, applications engineer Barry Bolling uses a GS610 source measure unit to perform a charge-discharge test on a lead acid battery to show how to test lead acid battery capacity. The GS610 is made up of a programmable current and voltage source, a voltmeter, and an ammeter. Each function can be combined into numerous operation modes.
The most accurate way to measure battery capacity is through a discharge test. In this process, the battery is discharged at a known rate (in amps) until it reaches a predefined voltage limit. By multiplying the discharge rate by the time it takes for the battery to reach that limit, you can calculate the battery’s capacity in amp-hours (Ah).
When the battery temperature is not as 25°C, use a barely modified formula utilizing a temperature correction factor (K) from the corresponding IEEE standard. Formula: % Capacity at 25°C = [T a / (T s x K t)] x 100 K t – temperature correction factor based on the applicable IEEE standard.
