Effective charging method for ultracapacitors

Abstract

One of the advantages of ultracapacitors is its high power capability, which is applicable for high rate of charging and discharging operation like motor starting and regenerative braking of an electric vehicle. This paper presents a new charging method for ultracapacitors. Comparing with batteries, ultracapacitor can accept a wide range of charging current and can be fully charged within a few minutes. Common chargers for ultracapacitors are usually equipped with current transducers and closed loop circuitry for current control, which are expensive and complicated. The proposed circuit consists of a minimum number of components. It does not require any current transducer or dedicated voltage/current control circuitry. A simple open-loop control system is applicable for the whole charging stage. It is free of stability problem and protects itself from being overloaded by ultracapacitor with zero initial charge. This paper presents the design and operation of the hardware circuit. Both simulation and experimental results are included.