PURPOSE: To obtain a battery of long durability while increasing mechanical strength of a rolled plate of a Pb-Ca series alloy and suppressing its elongation by giving a cold rolling process at a specific pressing-down rate and a heat treatment process at a specific temperature to the continuously cast and rolled plate of lead alloy containing specific amounts of Ca and Sn respectively.

CONSTITUTION: A cold rolling process at a pressing-down rate 20∼65% and a heat treatment at 120∼130°C are given to a continuously cast and rolled plate of lead alloy consisting of Ca 0.05∼0.1m/o, Sn 0.5∼2.0m/o and the rest Pb. An alloy composition having the content of Ca or Sn out of said range causes a drop in strength. Further, in either case of the pressing-down rate under 20% or exceeding 65%, the endurance power (tensile strength) drops, while in the case of a heat treatment temperature under 120°C or over 130°C, the mechanical strength drops in either case. The heat treatment is desirably performed usually about for 30∼60min.