Estimating State of Charge for Lithium Iron Phosphate Batteries with Extended Kalman Filter

Abstract:
Accurate State of Charge (SOC) estimation is paramount for effectively managing Lithium Iron Phosphate (LFP) batteries. Building upon the Extended Kalman Filter (EKF) SOC estimation model by Khanum et al., this study endeavours to develop a comprehensive SOC estimation method by fusing Coulomb Counting (CC), Open Circuit Voltage (OCV), and EKF. The New European Driving Cycle is used to verify the effectiveness of the proposed algorithm. Initial tests showed accurate SOC estimation, but further analysis with offset current exposed significant inaccuracies. With offset current, the EKF functioned similarly to the CC, leading to substantial SOC estimation errors. The findings highlight the complexities of SOC estimation for LFP batteries and show that the suggested fusion method of EKF, despite its promising start, is not robust enough to accommodate the dynamic nature of LFP batteries and offset errors.