The design for the power Li-lion battery management system and the prediction of the residual capacity are both rely on the equivalent circuit model of the Li-lion battery, therefore, based on the analysis and comparison of some common equivalent circuit models of the Li-lion battery, many electric charging and discharging tests of the Li-lion battery are conducted in order to analyse the dynamic characters. And double power model based on Thevenin equivalent circuit model are presented and identify the relevant parameters. Building simulation model by using Matlab/Simulink in order tosimulate and verify the double power model. The result shows that double power model can exactly simulate the performance characteristics of the power Li-lion battery and lays foundation for the effective management of the power Li-lion battery．