Abstract: By improving the efficiency of energy feedback, electric vehicle’s endurance mileage could be prolonged efficiently. The efficiency is affected by motor speed, brake torque, battery pack’s state of charge(SOC) and some other factors. The relationship of energy feedback efficiency and motor speed, brake torque, battery pack’s SOC, battery pack’s temperature is studied by means of electric vehicle(EV) power-train’s performance testing bench. The restriction of motor’s temperature to the maximum brake torque setting is discussed. Working condition range is set according to the real results from an EV. And in this range, the energy feedback efficiency is measured under different motor speeds, brake torques, and battery pack’s SOCs. A prediction model of energy feedback efficiency is developed based on measured data, and the model’s validity is verified by testing results. Energy feedback control strategy for coasting process is developed according to the model, and real vehicle testing result show energy feedback efficiency improvement of the new strategy over the original one, which suggests that this efficiency model can be used to optimize the control strategy at coasting condition.

Key words: Efficiency model, Electric vehicles, Energy feedback efficiency, Influencing factors