Thermal Modeling of NMC811 Prismatic Battery for Fast Charging Profiles in EV Applications

The thermal management of Li-Ion batteries is essential in battery-powered applications, especially in battery electric vehicles (BEVs), due to the high charge and discharge C rates involved. Designing robust cooling systems for battery packs in BEVs must rely on a high-fidelity thermal model that can track the cells' surface and core temperatures. This paper introduces the development of an accurate lumped thermal model for a high-power NMC811 prismatic battery, the model is based on the equivalent circuit model (ECM). Genetic algorithm optimization was used to fit the surface temperature measurements for multiple charging and discharging profiles on a two-node equivalent model to identify the thermal conductivity and capacitance of the cell. The model is able to estimate the surface temperature of the cell in multiple discharging profiles and drive cycles with a root mean square error (RMSE) as low as 0.1°C, whereas for the fast-charging profiles, that go up to 3.5 C, the RMSE achieved is 0.5°C.