State estimation is the process of extracting the value of a hidden state from indirect, inaccurate and uncertain measurements of the system. This tutorial describes the process for the state of charge (SOC) estimation of Li-Ion cells using an equivalent circuit model. It helps students create and run a SOC estimation strategy based on the 3rd-order R-RC model in MATLAB-Simulink. The tutorial starts with a general overview of state estimation using the extended Kalman filter (EKF) , and the novel smooth variable structure filter (SVSF)  method. Thereafter, it presents applications of the EKF and the SVSF method for SOC estimation of a Li-Ion cell using the 3rd-order R-RC model and input-output (current-terminal voltage) data. Finally, it compares the performance of these estimators where the 3rd-order R-RC model is subjected to uncertainties on the initial SOC estimation, and parameters of the model.
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