In the study of an electric vehicle (EV), an energy storage system which combines a battery and an electric double layer capacitor (EDLC) has been proposed. Introducing of EDLCs to an EV drive system, energy management become more efficient in term of using regenerative braking energy and saving battery energy. In this study, we propose a series or parallel changeover system using a battery and an EDLC for a small EV. This system can change over the composition of electric sources which battery and the EDLC bank in series or parallel depending on the voltage level of EDLC bank. The operating voltage range of EDLC bank is expanded from maximum to zero by the proposed system. In order to confirm the merit of the proposed method, two prototype EVs that one has a conventional DC-DC converter system and the other has the proposed changeover system are prepared and measured on automobile racing circuit. The effectiveness of proposed changeover system be verified and presented by experimental results.