Battery (All): Terminology: Discharge
WARNING: This page is about a different car, the 2004 Volvo S40, 2003 Volvo S40, 2002 Volvo S40, 2001 Volvo S40, and 2000 Volvo S40. 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 sulphate. Sulphuric 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