Battery with over-pressure protection

A battery assembly includes a sealed battery cell container holds a positive and negative electrode and an electrolyte. Deflection-responsive means engages at least one outer face of the container and is responsive to deflection thereof for operating a cut-off switch to break the electrical continuity of the battery assembly. Flat battery cell containers may be stacked in different arrangements within a coupling structure, the arrangements defining either a cavity between the coupling structure and an adjacent container face, or a cavity between faces of adjacent cell containers. A membrane switch received in the cavity is actuated by bulging of a cell container wall. A control circuit operates the cut-off switch in response to actuation of the membrane switch.