Abstract: A flat cell is sealed along the confronting peripheral inner surfaces of positive and negative terminal plates. A pair of sealing films are disposed on the respective peripheral inner surfaces. Each sealing film is comprised of a first thermoplastic layer composed of maleic acid modified polyethylene thermally secured to the peripheral inner surface, a second intermediate thermoplastic layer composed of high-density polyethylene and a third thermoplastic layer composed of maleic acid modified polyethylene so that the confronting third layers of the pair of sealing films are thermally secured to each other to seal the flat cell.

Abstract: The active cathode material of an alkaline cell is a mixture of monovalent silver oxide and graphite or a compound of which the main ingredient is divalent silver oxide. The active anode material is powdered mercury-indium-zinc alloy mixed with a suitable binder and pressed into formed or gelled state. After almost all of the zinc of the anode material is exhausted during the course of discharge of the cell, a small quantity of indium acts as the anode active material so as to continue to supply current for a period of time but at lower voltage. By detecting the voltage drop, it can be determined that the cell is approaching the end of its useful life.