Analysis of Discharge Performance of LiFePO4 Battery Based on Electrical Circuit Model

The open circuit voltage (OCV) and internal resistance of battery cells are important indications for the operation of power systems. The relationships of the OCV and internal resistance between the state of charge (SOC) of a battery are nonlinear. In order to investigate such relationships, this paper uses the equivalent electrical circuit model to characterize the discharge behavior of the LiFePO4 batteries, and also uses the curve fitting method to establish the mathematical functions of the variation of OCV and internal resistance. In this research, various types of batteries (such as cycled, aged, and heated) are introduced into the analysis and comparison. Besides, according to the adopted battery model and the built curve functions, the simulations of the performance of the test batteries at various discharge currents are compared with the experimental data. Finally, a method to estimate the cycling conditions of batteries is proposed in this thesis.