A Study on Effect of Regenerative Braking on Vehicle Range and Axle Life.

During braking condition in EVs, the braking energy is split between the friction braking & regenerative braking. The friction brake fraction will be lost as heat & regenerative brake fraction is converted into electrical energy. In regeneration mode the amount of energy harnessed depends on the regenerative torque available & the rate at which that torque is achieved. If the regenerative torque is higher and if the rate of achieving that torque is higher, energy harnessed will be higher. But higher regenerative torque & higher rate of torque affect the life of the axle components like bevel gear, crown wheel pinion, spider gear & bearing etc & causes gear failure like gear pitting on coast side if proper regeneration torque maps are not defined. This paper gives an outline on effect of different regenerative braking torque values and their rate on the vehicle range and reliability, failure & life of the axle components. Initially an ideal situation with 100% regeneration torque applicability is assumed, where the motor can generate same amount of positive & negative torque, this is a theoretical case but helps to create a boundary. Then different regenerative braking torque values are studied considering different vehicle speeds & different wheel slips. In the third stage on particular regenerative braking torque value is selected & rate of achieving this torque is factored in. All these test cases are integrated into the simulation model and the effective regenerative energy that can be harnessed was calculated. The effect of these regenerative torque values on the life of the transmission components is calculated. A comparative study is made between all the test cases and best suited regeneration strategy is finalized for implementation on the vehicle. This strategy is scalable for variable loads and variable duty cycles and various vehicles platforms.