Cell cap assembly having frangible tab disconnect mechanism

A cell pressure control system is disclosed which includes a conductive frangible tab which tears in response to a defined pressure. The frangible tab is affixed at one position to a stationary member and at another position to a deflection member which deflects in response to increasing internal cell pressure. When the cell pressure increases to a dangerous level, the deflection member exerts sufficient pressure on the frangible tab to cause it to break. When the tab breaks, the cell goes to open circuit, thus reducing the danger of continued pressure build up. If the cell's internal pressure continues to increase even after the pressure contact is opened, a second stage of the pressure control mechanism may be activated. Specifically, a pressure rupturable region in the above-mentioned deflection member will rupture and release the cell's internal pressure.