EKF-Ah Based State of Charge Online Estimation for Lithium-ion Power Battery

One of the most essential and significant aspect of the battery management systems (BMS) is to estimate the state of charge (SOC) accurately, which can provide the judgment basis to system control strategy. In view of the lithium-ion power battery´ s properties and its operation condition in electric vehicles, a new method named EKF-Ah that derives from the extended Kalman filtering (EKF) algorithm and ampere hour counting method is proposed, which has a good performance on SOC estimation in complicated environment and is able to accomplish the requirements on power batteries. Results of tests show that the maximal SOC estimation error is fewer than 6.5%, which validates the feasibility and reliability of the proposed method.