Abstract: A water activated primary battery in which each cell includes a cathode manufactured largely from an oxy-halogen material and an anode of aluminum, magnesium, zinc or alloys thereof, the electrodes being separated and insulated from one another by a porous membrane; the main feature of the invention being the sandwich construction of the cells and design of the anode which is perforated to provide access of the electrolyte to the cathode and escape of gas from the cell and dimpled to facilitate uniform compaction of the cathode material and to provide cooling water/electrolyte passageways in each cell.