Research on the output characteristics and SOC estimation method of lithium-ion batteries over a wide range of operating temperature conditions

With the rapid growth of the EV market, the use of lithium-ion batteries (LIBs) has increased significantly. However, the safety of these battery systems remains a concern. Accurate estimation of the state of charge (SOC) is crucial to enhance battery safety and longevity. In this paper, the impact of temperature on LIB performance is investigated and it is found that temperature variations can lead to inaccurate SOC estimation. To address this issue, LIB performance and capacity degradation at different operating temperatures are experimentally studied, and Electrochemical impedance spectroscopy (EIS) characteristics are analyzed. Based on the analysis results, an SOC estimation method, combining recursive least squares with forgetting factor (FFRLS) and adaptive extended Kalman filtering (AEKF) with temperature compensation, is proposed in the study. This method is tested respectively at 0 °C, 25 °C and 45 °C, demonstrating the feasibility and higher prediction accuracy of the proposed method across a wide temperature range.