Parameters identification using experimental measurements for equivalent circuit Lithium-Ion cell models

Battery modelling is important for the development of efficient battery management systems (BMS), different studies on behaviour under various operating conditions, and the prediction of the batteries lifetime. The focus of this paper is on the experimental measurements on Lithium-Ion (Li-Ion) cells for the parameter identification of Equivalent Electrical Circuit Models (ECM). Depending on model accuracy, a trade-off has to be made between a simple and a complex model of the cell. A simple model is not suitable for accurately simulate the cell dynamics while a complex model is computationally expensive. Different types of equivalent circuit models are proposed in literature; first- and second-order resistor-capacitor (RC) models for Li-Ion cells are studied comparatively in this paper. Equivalent circuit parameters are identified, experimentally, and models of the cells are implemented in Matlab/Simulink. The outputs of the models are compared with actual data to calculate the error. In the models, the parameters dependency on the temperature and the age of the cell are neglected. The simulation results show that in constant current pulse discharge, the Root Mean Square Error (RMSE) expressed as a percentage for the first-order RC model is 2.78% and for the second-order RC model is 1.96%. These results are obtained without any optimization of the parameters.