Identifying Critical Use Cases for a Plug-in Hybrid Electric Vehicle Battery Pack from Thermal and Ageing Perspectives

The current trend towards an increasing electrification of road vehicles brings to life a whole series of unprecedent design issues. Among these, the ageing process that affects the lifetime of lithium-ion based energy storage systems is of particular importance since it turns out to be extremely sensitive to the variation of battery operating conditions normally occurring especially in hybrid electric vehicles (HEVs). This paper aims at analyzing the impact of operating conditions on the predicted lifetime of a parallel-through-the-road plug-in HEV battery both from thermal and ageing perspectives. The retained HEV powertrain architecture is presented first and modeled, and the related energy management system is implemented. Dedicated numerical models are also discussed for the high-voltage battery pack that allow predicting its thermal behavior and cyclic ageing. A wide variety of operating conditions is subsequently simulated including different driving scenarios, ambient temperatures, vehicle payloads, and battery state-of-charge (SOC) conditions. Obtained results highlight considerable impacts of the HEV operating conditions on the battery lifetime even in the advised operating temperature interval ranging from 15°C to 35°C. Moreover, charge-depleting HEV operation and high ambient temperature are identified as the most influencing conditions concerning the criticality of the use case. On the other hand, vehicle payload and specific driving scenario appear to have a reduced impact. Presented results might help engineers to improve the effectiveness of current high-voltage battery temperature control systems to extend the battery lifetime while ensuring improved energy economy.