Development and Validation of a Battery Thermal Management Model for Electric Vehicles under Cold Driving

Battery thermal management system (BTMS) significantly improves battery electric vehicle (BEV) performance, especially under cold weather. A tradeoff between battery power consumption and cabin heating performance must be considered in cold driving conditions. This preliminary study aims to develop an integrated battery pack and coolant channel model to predict the thermal behavior of a BEV thermal management system. In this study, we develop and calibrate the physical baseline model with testbench data using finite element and CFD software. First, an electrochemical battery cell 1D model (Pseudo-2D or P2D) is built and calibrated against the cell reference data. An integrated pack model consisting of four modules (each has 23 and 25 bricks and a total of 4416 cells) with coolant flow channels is developed using reference and benchmarked data. Then, the model is calibrated against experimental results from a mass-production, mid-size battery-electric SUV operated under cold driving conditions at a constant vehicle speed of 60 km/h for 5800 sec. The integrated model considers the heat transfer characteristics from cell-to-brick and brick-to-coolant channels. As a result, a thermodynamic model that can predict the average battery temperature rise, temperature changes, and pressure drops of the coolant of the battery pack is constructed. The result shows that the battery pack model can predict the coolant pressure drop of the pack with a mean absolute percentage error (MAPE) of 0.49 % and the coolant temperature rise with a 5.23% MAPE. The calibrated battery pack model can reasonably reproduce the terminal voltage with a MAPE of 0.30%. A 3D-CFD simulation result of the battery brick model is also reported on the cell-to-cell temperature distribution of 46 cells.