Abstract: A thermal battery which includes a plurality of stacked battery cells within a thermally insulated case. Each battery cell includes an anode wafer, a cathode precursor wafer and an electrolyte wafer disposed between them. The electrolyte wafer is solid at room temperature and will become molten at a predetermined temperature. The cathode precursor wafer is of a formulation which is ignitable to supply the necessary heat to cause the electrolyte to become molten. After generation of the heat, the cathode precursor wafer becomes the cathode for the battery cell, thus eliminating the requirement to provide a separate heat wafer for each cell of the battery.