A New Method for Identifying the Parameters of the Double Polarization Model of the Li-Ion Battery

The article focuses on modeling the Li-ion cell and the requirements for identifying system parameters. A mathematical model is established representing the nonlinear system of our cell. A Double polarization (DP) model is adapted, which includes terms describing dynamic parameters such as state of charge (SOC), open-circuit voltage (Vocv), Rin, R1, C1, R2, and C2. Subsequently, appropriate battery discharge tests are conducted to identify the model parameters. Initially, the relationship between the SOC and the Vocv is established using the least squares method. The value of Rin is ascertained by cell discharge assays subsequent to the identification of this association. Next, R1, R2, C1, and C2 are determined by utilizing the least squares approach once more to determine the temporal constants τ1 and τ2. Once the different parameters are identified, the established battery model is verified through experimental tests. The obtained error indicates that the mean absolute error (MAE) for modeling is 0.0075 V, and the root mean square error (RMSE) is 0.0113 V. These results demonstrate the high accuracy of our cell model.