At the present status of electric vehicle (EV) technologies, none of the available energy sources can solely fulfill all the demands of EVs to enable them to compete with gasoline powered vehicles. In this paper, an energy management system, adopting the so-called hybridization of energy sources, is proposed to coordinate multiple energy sources for EVs. Hence, the unique advantages of various EV energy sources dan be fully utilized, leading to optimized fuel economy while fulfilling the expected driving range and maintaining other EV performances. The proposed optimization is performed by tuning two ratios, namely the mass ratio and the hybridization ratio. (C) 2001 Elsevier Science Ltd. All rights reserved.