Reduced-order thermal modeling of liquid-cooled lithium-ion battery pack for EVs and HEVs

Adequate thermal management is critical to maintain and manage lithium-ion (Li-ion) battery health and performance within Electrical Vehicles (EVs) and Hybrid Electric Vehicles (HEVs). Numerical models can assist in the design and optimization of thermal management systems for battery packs. Compared with distributed models, reduced-order models can predict results with acceptable accuracy and much lower computational cost. Therefore, to provide design insight, reduced-order models are often employed for predicting transient thermal and electrical behaviors of a battery pack. This paper presents the development, validation, and application of a detailed, reduced-order thermal model of a battery pack with liquid cooling. The model described is capable of predicting the average temperature of each individual cell. It was first developed in a general vehicle modeling software environment in which an equivalent circuit model captures the electrical characteristics of each cell. A structural-thermal model captures the heat transfer among the cells, the cooling liquid, as well as temperatures of other components inside the battery pack. Calibration and validation of the model is performed with test data that includes cell state of charge (SOC), terminal voltage, coolant temperature, and cell temperature data.