Simulation of second-order RC equivalent circuit model of lithium battery based on variable resistance and capacitance

With the rise of the electric vehicle industry, as the power source of electric vehicles, lithium battery has become a research hotspot. The state of charge (SOC) estimation and modelling of lithium battery are studied in this paper. The ampere-hour (Ah) integration method based on external characteristics is analyzed, and the open-circuit voltage (OCV) method is studied. The two methods are combined to estimate SOC. Considering the accuracy and complexity of the model, the second-order RC equivalent circuit model of lithium battery is selected. Pulse discharge and exponential fitting of lithium battery are used to obtain corresponding parameters. The simulation is carried out by using fixed resistance capacitance and variable resistance capacitor respectively. The accuracy of variable resistance and capacitance model is 2.9%, which verifies the validity of the proposed model.