Battery (All): Terminology: Discharge
WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
The process where a battery is under load and gives off current. During discharge, the lead on the negative plate and the lead oxide on the positive plate are converted to lead sulfate. Sulfuric acid is consumed and water is formed, reducing the density of the acid.
This reaction can be written:
PbO2 + Pb + 2 H2 SO4 → 2 PbSO4 + 2 H2 O