The technique of open-circuit potential relaxation from a prior prepolarized state has been employed to study the kinetics of the Pb/PbSO4 electrode in 4.8 M sulphuric acid. The significant features governing the relaxation have been quantitatively analysed to obtain a correlation between state-of-charge of the electrode and its potential-recovery time constant. The effect of immobilizing the electrolyte has also been included due to its relevance in making sealed maintenance-free batteries. The study provides a method for estimating the variation of exchange current density of the Pb/PbSO4 and hydrogen evolution reactions at various states-of-charge with and without added gelling agents.