Model Identification of Lithium-Ion Batteries Considering Current-Rate Effects on battery impedance

A novel model identification method for lithium ion batteries considering current-rate dependence of the impedance is proposed. In this work, it is found that current-rate is a significant factor affecting battery impedance besides SOC (state-of-charge) and ambient temperature. From the viewpoint of engineering practice, a series of charging and discharging tests are conducted firstly. Though integral transformation, the linear regression method is used to acquire parameters in the electrical circuit model instead of the traditional nonlinear fitting approaches. Then, the relationships between battery impedance and current-rate are analyzed thoroughly. Results show that considering current-rate effects can improve the accuracy of model identification significantly especially for the batteries operating under dynamic loading profiles. Finally, some simulation experiments are designed to further demonstrate the improvement of model accuracy with current-rate consideration.