D-UKF based state of health estimation for 18650 type lithium battery

An accurate estimation method of State of Health (SOH) for lithium battery is presented in this paper. The battery model is improved based on equivalent circuit model and battery internal electrochemical characteristics. In our study, Double Unscented Kalman Filtering (D-UKF) algorithm is designed to calculate State of Charge (SOC) and SOH at the same time. The main feature is the battery SOH estimation model is derived based on battery internal resistances. Two filters defined as UKF1 and UKF2 are working together to calculate the real-value of SOC and Ohmic resistance to obtain the accurate SOH value. The experimental results indicate that our new battery model considers different value of battery internal resistances on different working condition. Besides, our study verifies the performance and feasibility of new estimation method based on D-UKF.