What happens when lead storage battery is subjected to charging?

Charging of storage battery is the reverse of its discharge. The lead sulphate deposited on electrodes is reduced to lead and oxidised to plumbic oxide, with a net reaction for two faradays.
PbSO₄(s)+2H₂O $\underset{ }{\overset{ }{\rightleftharpoons }}$PbO₂(s)+${\mathrm{SO}}_4^{2-}$(aq) +4H⁺(aq)+2e^-
The cell potential increases during charging. Hence, lead storage battery can be reused.