Ageing mitigation of 21700 Li-ion cylindrical batteries for heavy duty BEVs through forced air and immersion cooling strategies in Nordic climate zones

A Battery Electric Vehicle (BEV) pack requires an intelligent and integrated arrangement of the thermal management system (TMS). While previous studies have investigated TMSs independently, we here make a comparative analysis between air and immersion TMSs tailored for both sub-zero and peak summer temperatures, mimicking Nordic climate zones. A parametric sweep of flow and thermal design parameters using laminar and turbulent flow regimes is performed. These ambient conditions and loading pattern corresponding to a heavy BEV constitute the basis of the comparison. The analysis is based on various well-defined key performance indicators. Moreover, the air based TMS requires high Re flows to give the best performance, while immersion TMS can perform well in a laminar range. It was deduced that low Re (126) and high Re (>3000) may not give better thermal performance, and it is therefore crucial to design the TMS within the proposed flow and thermal design sets. In contrast to previous work, where the main focus has been on the cooling efficiency or steady-state performances, this work extends the horizon to investigate the effect of these TMSs on ageing behaviour to quantify long-term benefits on battery reliability and safety. The coupled ageing-thermal battery model was simulated for 1000 cycles for different cases, showcasing 3.4 % improvement in SOH for immersion TMS compared to the air based TMS. Thus, the climate resilient TMS aids in heat management, and the coupled model is thereby shown to help estimate the battery SOH. • Effect of Nordic climate conditions on 21700 cylindrical cells is studied. • High-fidelity physics-based coupled 1-D to 3-D thermal battery model is utilized. • Thermal and flow design parameters are investigated for air and immersion TMS. • Heating and cooling capabilities are investigated for both TMSs. • Parametric sweep includes 234 cases comparing laminar and turbulent flows.