Abstract: An electric energy source includes a battery, a positive and a negative booster clamps coupled to the battery for coupling the battery to the vehicle battery, and a device for selectively coupling the battery to the positive and the negative booster clamps when the positive and the negative booster clamps are correctly coupled to the vehicle battery. The battery may supply the energy to the booster clamps when the booster clamps are correctly coupled to the vehicle battery, and will not supply the energy when the clamps are wrongly coupled to the vehicle battery.

Abstract: A rechargeable/portable multi-voltage DC power supply includes an Ni-Cd rechargeable battery set connected to a switching power supply converting circuit, a pulse width modulation circuit, and a filter circuit for providing a regulated output voltage from the filter circuit. A button switch cooperates with a selection circuit and a feedback ratio circuit for selecting a specific output voltage from a plurality of available output voltages. A plurality of light emitting diodes are connected to the selection circuit for indicating the value of the output voltage.