Abstract: An overvoltage control circuit for a reserve battery includes a current limiting resistor connected in series with a thermal-lag type circuit interrupter such as a thermal-lag fuse or circuit breaker. The series combination is connected across a selectively activatable reserve battery which is connected across an electrical load to be energized by the battery. A high current drain through the circuit interrupter and the resistor during an initial activation of the reserve battery is effective to stabilize the output voltage of the battery at a level below a desired working limit of battery potential without an overshoot of the working limit. Subsequently, the current drain operates the circuit interrupter to isolate the limiting resistor to interrupt the current drain and allow the battery output to reach a level approximating the working limit.