A lead storage battery consists of a lead anode, a grid of lead packed with lead oxide (PbO₂) as the cathode, and a 38% solution of sulphuric acid (H₂SO₄) as an electrolyte.

When the battery is in use, the following cell reactions take place:

At anode: Pb(s) + SO₄^2-(aq) → PbSO₄(s) + 2e^-

At cathode: PbO₂(s) + SO₄^2-(aq) + 4H⁺(aq) + 2e^- → PbSO₄(s) + 2H₂O(l)

The overall cell reaction is given by,

Pb(s) + PbO₂(s) + 2H₂SO₄(aq) → 2PbSO₄(s) + 2H₂O(l)

When a battery is charged, the reverse of all these reactions takes place.

Hence, on charging, PbSO₄(s) present at the anode and cathode is converted into and respectively.