Half equations

I found these half equations when searching for info on a lead acid accumilator, the red two was not there until I placed it, was I correct to do so?

Anode:

Pb(s) + SO₄^2-(aq) → PbSO₄(s) + 2e^-

Cathode:

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

Overall:

Pb(s) + PbO₂(s) + 2SO₄^2-(aq) + 4H⁺(aq) → 2PbSO₄(s) + 2H₂O(l)

Also, if anybody has any good links on lead acid accumulators or silver button cells I would really it, thanks.