In electric vehicles, thermal management of a battery pack is becoming critical as both excessive and low temperature may affect the overall battery life and even trigger disastrous damage to a battery pack. Therefore, estimating the temperature distribution and its variation over time is an essential requirement to ensure safe and provide design guidance for control strategy.

This study carries out a transient thermal model to predict the thermal behavior of a square lithium-ion battery pack with liquid cooling thermal management system. Different from Equivalent thermal circuit (ETC) model, which can only predict a lumped temperature of a battery cell, a one-dimensional thermal model was built in this study to estimate the temperature distribution throughout the cell and its variation over time according to the structural feature and the liquid cooling mode.

The model is based on the Green function method, capable of calculating one-dimensional thermal dynamics and achieving high accuracy with low calculation requirements, making it suitable for real-time control. A second order equivalent circuit model was used in the approach to predict the dynamics of the cell voltage and SOC in relation with the current. Then the electric model is coupled with a lumped thermal model to describe the dynamics of internal temperature distribution of one cell. Based on this cell model, a coupled flow-electro-thermal model for a battery pack was built, which was able to predict the uneven heat generation during the charge and discharge procedure under different cooling conditions.

3D CFD calculation was conducted for the model calibration and validation results are presented to support the proposed modeling approach.