A Modified Luenberger Observer for SOC Estimation of Lithium-Ion Battery

State of Charge (SOC) estimation has always been a key issue in the Battery Management System (BMS). This paper proposes a simple modified Luenberger observer to estimate the state of charge of the lithium-ion battery. Nonlinearity of battery equivalent circuit model is approximated at each step. Simulation results show that this simple modified Luenberger observer achieves satisfactory estimation accuracy, while still remains the advantage of low computational complexity. The robustness of this proposed estimation algorithm is demonstrated by Monte-Carlo method, and the estimation output sensitivity to model parameters variations is also revealed through sensitivity analysis.