Lead–Acid Accumulator
A rechargeable cell using lead and lead dioxide electrodes in sulfuric acid.
Formula / equation
Pb + PbO₂ + 2H₂SO₄ ⇌ 2PbSO₄ + 2H₂O
Unit
V
In depth
Each cell delivers about 2 V, so six in series give the familiar 12 V car battery. Both electrodes convert to lead sulfate on discharge and are regenerated on charging. The design is heavy and uses toxic lead but is cheap, reliable and delivers the huge currents a starter motor needs.
Examples in the real world
Measuring a battery's state of charge from the acid density, which falls as sulfuric acid is consumed.