Patent ID: 7742885

Claim:
A vehicle power supply device comprising: a capacitor unit including a plurality of capacitors storing auxiliary power; a temperature sensor detecting a temperature of the capacitor unit; a charge circuit charging electric power to the capacitor unit; a capacitor-unit current detector detecting a current value of the capacitor unit; a capacitor-unit voltage detector detecting a voltage value of the capacitor unit; a controller electrically connected to the temperature sensor, the charge circuit, the capacitor-unit current detector, and the capacitor-unit voltage detector, the controller obtaining an internal resistance value and a capacitance value of the capacitor unit from the voltage value and the current value; a storage storing a correction calculation formula and a plurality of degradation determination formulas, the correction calculation formula being used to perform the correction calculation of the internal resistance value and the capacitance value in accordance with the temperature in order to obtain a corrected calculated value of internal resistance and a corrected calculated value of capacitance, and the plurality of degradation determination formulas corresponding to numerical ranges of the corrected calculated value of capacitance and being used to calculate an internal resistance standard value from the corrected calculated value of capacitance; and a determination unit determining a degradation level of the capacitor unit based on at least one of the internal resistance standard value and the corrected calculated value of capacitance.