Abstract: A capacitor unit with plural double layer capacitors eliminating irregularity in a state of charge of the respective double layer capacitor in the capacitor unit. A capacitor unit, a capacitor unit control method, a capacitor unit control apparatus and a vehicle charging system, wherein a chargeable and dischargeable capacitor unit 1 with plural electronic double layer capacitors 11 connected in series is characterized in that electric double layer capacitors 11 in a higher state of charge is subject to discharge so that a state of charging of the respective electric double layer capacitor 11 may become approximately equal to each other.

Abstract: A capacitor system suitable for charging and discharging of a vehicle such as discharging due to starting of an engine, charging by an alternator, and recharging upon braking. The capacitor system can be a vehicle power source having several connected cells in which ion conductive materials are arranged between a pair of electrode structures with large surface area materials and an electric double layer is formed between the large surface area materials in the electrode structure and an electrolyte of the ion conductive materials. Charging and discharging are controlled for state of charge of the capacitor unit with several connected modules to be within a predetermined range. A minimum charge within the predetermined range is sufficient for the engine to start while a maximum charge within the predetermined range is within a rated voltage of the capacitor unit with several connected modules.