Battery theory is summarized below.
Battery Theory Summary
The purpose of a battery is to store chemical energy and to convert this
chemical energy into electrical energy when the need arises.
A voltaic cell develops a potential difference when electrodes of two different
metals are immersed in an electrolyte. One electrode accumulates a positive
charge. The potential difference is due to the difference in charge between
the two electrodes.
The chemical equation for a lead-acid battery during discharge is:
The chemical equation for a lead-acid battery during charge is:
When a lead-acid battery is discharged, electrolyte and the active material on
the plates of the battery are consumed to produce water and lead sulphate.
When a lead-acid battery is charged, electrical energy is added to the battery,
causing the water and lead sulphate to be consumed and produce electrolyte
and active material.
Since specific gravity of a lead-acid battery decreases proportionally during
discharge, the value of specific gravity at any given time is an approximate
indication of the batterys state of charge.