In order to establish a more accurate battery equivalent model, the polarization circuit of the existing PNGV equivalent model is
extended to characterize the polarization characteristics of the battery better. The double exponential fitting method is used in the
parameter identification to improve the accuracy of parameter identification of battery equivalent model. With the results of hybrid
pulse power characterization experiment, the parameters of improved model are identified. And obtain the functional relationship
between parameters and state of charge through fitting. At last, a real-time simulation model is established. The simulation results
show that the error value between the simulation model voltage and the actual voltage is less than 1.2%, the model accuracy is high.
This lays the foundation for the estimation of the state of charge of the lithium battery in the follow-up work.