Forty Kilojoule Carbon Double Layer Capacitor
presented at the International Seminar on Double Layer Capacitors and Similar Energy Storage Devices, December 6, 1993
David A. Evans

Abstract

A high performance carbon double-layer capacitor (DLC) was constructed using a five element equivalent circuit model. It was designed for 15, 30, 60, or 120 V operation, depending on buss connections. Activated carbon with sulfuric acid was used to forrn its electrodes. The prototype had a mass of 27.5 kg and a volume of 17 liters. It stored more that 40 kJ of energy.

Power performance was measured using resistance, constant-current, and constant-power loads. Currents as high as 400 A and power levels up to 23 kW were used. The capacitor would reproducibly deliver 5 kW for 4 s, 10 kW for 1.1 s, 15 kW for 0.5 s, or 20 kW for 0.1 s. Voltage imbalance problems were not encountered. Capacitor self-discharge power was below 1 W. The feasibility of this approach was clearly demonstrated. Design and construction details are reported. Methods to further reduce the size and weight of large double layer capacitor power units are described.