A redundant battery power supply with combined battery charge indication which incorporates a main cell, conductively coupled to the supply bus which powers the load when activated, and a predictive cell, coupled to the bus by an optional diode which becomes forward biased when the main cell voltage drops below the predictive cell voltage. If the main cell becomes discharged, the predictive cell powers the bus. Each cell is coupled to a voltage comparator which compares the cell output voltage to a common reference voltage. When a cell voltage drops below the reference voltage, the corresponding comparator output goes low. The output of the two comparators are combined by a logical AND gate which controls a flashing light. When both the main cell and predictive cell have voltages greater than the reference voltage, the light flashes, but when either cell (or both) has a voltage less than the reference voltage, the light does not flash. The power for the flashing light is provided solely by the predictive cell.