A power module includes double layer capacitors, a voltage booster, a charging circuit, and a switching assembly. In discharging mode, the switching assembly connects the voltage booster to the output of the power module. The voltage booster enhances the voltage of the cells as needed for operation of a load at the output of the module. In charging mode, the switching assembly connects the charging circuit to the output of the module to receive electric energy from an external charger connected to the output of the module. The charging circuit converts the received energy into energy suitable for recharging the cells. In end-of-cycle discharging mode, the switching assembly connects the voltage booster to the charging circuit, causing these devices to loop into each other. Inefficiencies in the voltage booster and the charging circuit dissipate the energy in the cells, rendering the battery fail-safe.