The aim of this research is to examine the effect of alloying elements in positive plate composition of a lead-acid battery on its self-discharge and delivered current density in discharge state performances. To elucidate, a positive and negative lead-acid battery plates of two alloys namely Pb–Ca–Ag and Pb–Sb are investigated through electrochemical measurements in battery solution. Higher delivered current density of Pb–Ca–Ag cell in compare with Pb–Sb cell is observed for 25 days of 33 measurement days. The evolution of couple potential for both cases shows that the Pb–Ca–Ag cell potential achieves a value in the potential range of water stability after 25 days while in case of Pb–Sb cell, it remains well beyond the water stability potential domain for 33 days of measurements. Further investigations demonstrate that Pb–Sb cell current density is mainly caused by Pb oxidation reaction on negative plate while both anodic and cathodic polarizations (mixed polarization) are responsible in the case of Pb–Ca–Ag cell.