Regenerative braking system evaluation on a full electric vehicle

Regenerative braking systems for electric vehicles enable the range of the vehicle to be extended, but experience has indicated that the benefits are not always as great as might be expected because of inefficiencies in the power conversion processes. Extra mass and cost can often combine to limit the financial viability of a regenerative braking system. To measure the efficiency of a regenerative braking system, the Tata Ace Electric Vehicle has been tested on a hub-mounted chassis dynamometer, and instrumented to enable calculations for plug-to-wheel efficiency and total range (compared to the same vehicle with little or no regenerative braking). Previously the Tata Ace EV has been tested on the road to optimise the regenerative braking settings for energy recovery. The vehicle's motor controller allows the field map of the motor to be adjusted, giving full control over the deceleration of the vehicle when the accelerator pedal is released (and subsequent levels of recovered energy). By mounting the vehicle to a calibrated dynamometer, these settings can be validated by monitoring range and efficiency under controlled conditions. The vehicle has been driven at constant speeds and also on the urban section of the New European Drive Cycle, with results presented here.