Patent ID: 7750607

Claim:
An auxiliary electric power supply for a vehicle, the vehicle comprising an ignition switch and an ignition key operating the ignition switch, the auxiliary electric power supply comprising: a first switch electrically connected to an I/O end; a capacitor bank connected to the first switch, the capacitor bank having: a plurality of series-connected electric double layer capacitors; and a plurality of balanced resistances, each resistance being parallel-connected to each electric double layer capacitor, and having substantively a same resistance value; a discharge resistance connected to the first switch; and a controller controlling the first switch while monitoring voltage of the capacitor bank and an operating state of the ignition key of the vehicle including the auxiliary electric power supply, wherein the controller controls the first switch so as to connect the capacitor bank to the discharge resistance when the ignition switch of the vehicle is turned off, to discharge the capacitor bank and to decrease the voltage of the capacitor bank to a first voltage, at which life deterioration of the electric double layer capacitors is suppressed.