Hybrid battery-supercapacito storage system for electric city cars

The paper is concerned with the use of hybrid battery-supercapacitor storage systems to extend the range of electric vehicles. For the study case of an electric city car, the paper calculates the relationship between the range of the city car over the ECE 15 cycle and the size of the supercapacitor bank. For this purpose, current drawn by the traction system is determined and the current pulses are supposed to be delivered by the supercapacitor bank to different extents. The range is then calculated by processing the battery current by means of an appropriate battery model. In an attempt to validate the theoretical findings, a hybrid battery-supercapacitor storage system has been designed and set up. The system is built up around a bidirectional DC-DC converter and an electronic control unit. The DC-DC converter interfaces the supercapacitor bank with the DC bus of the storage system. The electronic control unit detects the current drawn by the traction system and controls the DC-DC converter for it to deliver the current pulses to a given extent. Preliminary experimental results are reported, which substantiate the battery model and the design of the storage system.