This paper represents sizing and design of Hybrid Energy Storage System(HESS) based on theoretical calculations along with power management system for electric vehicle. As proper sizing and design of energy storage system is expected to result into substantial benefits of reduction in cost, increasing lifetime and extension of vehicle range. This paper deals with sizing of dual energy storage system and development of corresponding power management algorithm between energy storage element. Purpose of power management is reduction of stress on battery during transient state by maintaining battery current as constantaspossibleandrecoveryofpowerduringdecelerationby supercapacitor. From experimental result, it is clearly observed that after implementing power management algorithm, battery current is nearly maintain constant i.e battery only supplied average current without facing instantaneous fluctuations and at the other hand this instantaneous current is supplied by supercapacitor.