PURPOSE: To make α-PbO2 to be developed preferentially in the interface between a grid made of a lead-calcium system alloy and an active material during the charge of a battery, and prevent any generation of lead sulfate in the former interface which might be caused during the discharge by increaing the thickness of the active material which covers the grid.

CONSTITUTION: A lead-calcium binary alloy or a lead-calcium-tin ternary alloy is used as a positive grid for a lead acid battery, which has a thickness (a) of over 1.2mm. The positive grid is packed with a positive active material 2 to make a positive plate, so that the positive plate has a thickness (b) of 2.0∼3.0mm. Owing to the above constitution, the diffusion of electrolyte into the interface between the grid and the active material 2 is retarded, and the pH of the above interface is maintained high. Consequently, α-PbO2 can be produced preferentially in the above interface during the charge, and any generation of lead sulfate in the above interface can be prevented during the discharge.