Design And Function: Discharge
WARNING: This page is about a different car, the 2010 Volvo V70, 2009 Volvo V70, and 2008 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.
The process during discharge
- Negative plate: Pure lead is converted to lead sulfate
- Electrolyte: The sulfuric acid is converted to water
- Positive plate: Lead oxide is converted to lead sulfate
- Power consuming components.
During discharge, the lead in the negative plate is converted to lead sulfate (PbSO4 ).
The lead dioxide (PbO2 ) in the positive plate is also converted to lead sulfate. During the discharge process, sulfuric acid (H2 SO4 ) is consumed while water (H2 O) is created. This reduces the density of the electrolyte.
The density drops throughout the discharge process and can be gauged to determine the condition of the battery. The electrolyte in a fully charged battery has a density of 1.28 g/cm3 . The density of the electrolyte in a fully discharged battery is 1.10 g/cm3 .