Development and Verification of the Equilibrium Strategy for Batteries in Electric Vehicles

The inconsistency of the cells in a battery pack can affect its lifespan, safety and reliability in the electric vehicles. The balanced system is an effective technique to reduce its inconsistency and improve the operating performance. A hybrid equilibrium strategy based on decision combing battery state-of-charge (SOC) and voltage has been proposed. The battery SOC is estimated through an improved least squares method. An equalization hardware in loop(HIL) platform has been constructed. Based on this HIL platform, equilibrium strategy has been verified under the constant-current-constant-voltage (CCCV) and dynamic-stress-test (DST) conditions. Experimental results indicate that the proposed hybrid equalization strategy can achieve good balance effect and avoid the overcharge and over-discharge of the battery pack at the same time.