PURPOSE: To quickly and stably transmit heat generated from a plate group to a bimetal by providing a charging and discharging external terminal plate directly on a thermal protector in such a manner that one side of an internal connection terminal of the thermal protector has direct contact with the partition wall of an adjacent cell.

CONSTITUTION: A thermal protector 3 has an anode-side external terminal plate 3d insert-molded in a substrate 3e, a bimetal 3c attached to the substrate 3e and a moving plate 3b arranged in opposition thereto. When a battery is overcharged, heat generated from a plate group is transmitted to the moving plate 3b connected to a terminal 3a via a partition wall 1a in a battery jar 1 and an internal connection terminal 3a to push up the moving plate 3b while rebounding the bimetal 3c. In this way, the contact of the terminal plate 3d with the moving plate 3b is released to stably shut off a current in a short time.