A lumped-parameter electro-thermal model for cylindrical batteries

Combining several existing lumped-parameter models, this paper presents an electro-thermal model for cylindrical batteries. The model consists of two sub-models, an equivalent-circuit electrical model and a two-state thermal model which are coupled through heat generation and temperature dependence of the electrical parameters. The computationally efficient 5-state model captures the state of charge (SOC), terminal voltage, surface temperature and the often neglected core temperature of a battery for wide range of operating conditions. The proposed parameterization scheme allows separate identification of the electric and thermal sub-models, greatly reducing the complexity of the parameterization process. The methodology is applied to a LiFePO4/graphite battery. Comparison with the electrochemical impedance spectroscopy data clarifies the frequency range of the model fidelity. The model is further validated with two drive-cycle tests, covering SOC range 25%-100%, temperature 5 °C-38 °C, and maximum C-rate of 22C.