3D FEA Thermal Modeling with Experimentally Measured Loss Gradient of Large Format Ultra-Fast Charging Battery Module Used for EVs 2022-01-0711

A large amount of heat is generated in electric vehicle battery packs during high rate charging, resulting in the need for effective cooling methods. In this paper, a prototype liquid cooled large format Lithium-ion battery module is modeled and tested. Experiments are conducted on the module, which includes 31Ah NMC/Graphite pouch battery cells sandwiched by a foam thermal pad and heat sinks on both sides. The module is instrumented with twenty T-type thermocouples to measure thermal characteristics including the cell and foam surface temperature, heat flux distribution, and the heat generation from batteries under up to 5C rate ultra-fast charging. Constant power loss tests are also performed in which battery loss can be directly measured. A method for measuring the loss distribution across the surface is demonstrated, and the loss gradient is applied in FEA thermal models. 3D steady-state and transient-state FEA models are developed using ANSYS and validated against the experimental data. It is observed that for a 5C charging test with 20°C coolant temperature, the measured temperature on the cell surface is 24.3°C while the model predicts 23.8°C, an error of just 0.5°C. The loss is also found to vary about 30% across the surface of the cell, and this loss variation is included in the FEA modeling. The presented measurements, modeling, and validation give understanding into the design and optimization of lithium ion battery packs and thermal management strategies.