PURPOSE: To lengthen the life of a battery by using grids made of Pb-Sb alloy in cathode plates of cells in which the temperature of electrolyte is increased and grids made of Pb-Ca alloy in cathode plates of other cells.

CONSTITUTION: Grids made of Pb-Sb alloy are used in cathode plates of cells C1, C2, C3 in which the temperature of electrolyte is increased. Thereby, no deformation of grids occurs even when the temperature of cells is high, and a sharp drop in performance caused by the extension of the grid does not appear in these cells. Grids made of Pb-Ca alloy are used in cathode plates in cells C4, C5, C6 in which the temperature of electrolyte is not so high. Therefore, current in content voltage overcharge is small and electrolyte loss in overcharge is decreased compared with cells in which grids made of Pb-Ca alloy are used in all cathode plates.