Experimental Study and State of Charge Estimation of A123 Li-Ion Cylindrical Cell Using Passivity Observer in Different Temperatures

Accurate estimation of State of Charge (SoC) in lithium-ion batteries (LIBs) is vital for effective energy management, particularly under varying temperatures. This study develops a temperature-dependent passivity observer for SoC estimation using the Lyapunov and linear matrix inequality (LMI) approaches, applying passivity theory for the first time. Using a thermal chamber, SoC measurements were taken at 0°C, 25°C, and 50°C. By integrating temperature effects into the observer framework, we significantly improved SoC estimation accuracy. Extensive simulations and experimental validation demonstrated superior performance over traditional methods. This advancement promotes more efficient and reliable battery management systems (BMS), optimizing LIB usage in various electric vehicle (EV) applications.