Modeling for lithium-ion battery used in electric vehicles

To improve and better the applicability of lithium-ion battery model in electric vehicles, a new electrochemical-polarization model was put forward for the real-time model-based battery management system and control applications by adding an extra RC network on the basis of the electrochemical model to describe the relaxation effect of the lithium-ion battery, and the open circuit voltage as a function of State of Charge defined by the Nernst model is used in the model to avoid a time-consuming, laborious and even error-prone experiment for specially determining open circuit voltage at several specified SoC values. The model parameters are identified by the least squares method with the experimental data of hybrid power pulse characteristic test on a LiFePO ₄ battery module. Experiments and simulation results show the new electrochemical-polarization model can simulate the dynamics of battery well. By using the proposed model and parameters identification approach, the time-consuming and complex experiments for model parameters' identification and periodical calibration are avoided.