A Novel Electro-Thermal Coupled State-of-Charge Estimation Method for High-Rate Lithium-Ion Battery Applications

Abstract

The increasing electrification of large-scale industrial equipment, such as heavy-duty electric mining trucks, necessitates precise state-of-charge (SOC) estimation for lithium-ion batteries under high-rate operations. This is challenging due to the significant electro-thermal coupling effect at high discharge rates. This study introduces a novel SOC estimation method that incorporates electro-thermal coupling to enhance accuracy and robustness. An electrochemical-thermal coupling model is developed to capture interactions between electrochemical reactions and internal heat generation. Subsequently, a reduced-order electro-thermal coupling model is formulated to enable real-time co-estimation of SOC and internal temperature. An electro-thermal SOC estimator based on the Extended Kalman Filter (EKF) is then designed. The proposed method's performance is validated using diverse test profiles with varying initial SOC values. Experimental results show exceptional accuracy and robustness, with a mean absolute error of 3.044% and a root mean square error of 4.658% in the challenging 15 C high-rate pulse discharge test, despite a 40% initial SOC error. This approach significantly outperforms the conventional EKF-only method, offering improved SOC estimation accuracy for high-rate applications.