Evaluation of the Effects of Thermal Management on Battery Life in Plug-in Hybrid Electric Vehicles

We develop a simulation model that aims to evaluate the effect of thermal management on battery life. The model consists of two submodels: a thermal model and a battery degradation model. The temperature rise in the battery is calculated using the thermal model, and a temperature profile is obtained under pre-defined driving, charging and stand-by scenarios. The temperature profile and the energy requirement required to achieve a driving profile act as inputs to the degradation sub-model, which is used to predict the battery life. The degradation model is derived from models and test data available in literature, and the model is constructed for aircooled cylindrical LiFePO4 cells based on the Hymotion Prius-conversion configuration. Preliminary results suggest that peak temperatures have the greatest impact on degradation: Thermal management increases life substantially in climates with high peak temperatures (Pheonix) and for more aggressive driving cycles (US06), while thermal management has less influence in climates with lower peak temperatures (Miami) and with gentle driving cycles (UDDS). Use of cabin air vs. outside air for thermal management has minor impact on battery life for the control strategy used, but thermostat control settings are important for lowering peak temperatures and extending battery life