Modeling the Thermal Behavior of a Lithium-Ion Battery Module for Hybrid Electric Vehicle Applications

The lithium-ion battery (LIB) is a preferred power source for hybrid electric vehicle (HEV) applications due to its outstanding characteristics such as high energy density, modular scalability, long cycle life, and low self-discharge rate among others. In a battery module for HEV applications, an uneven temperature distribution in the module can be created depending on the operating conditions and the types of thermal management. Uneven temperature distribution in a module could cause an electrical imbalance and thus lead to the lower performance and shorter life of battery. It is, therefore, important to calculate accurately the uneven temperature distribution in a battery module in order to achieve the optimum performance and long life of the battery module.

In this work, a modeling is performed to investigate the effect of the operating condition on the thermal behavior of an LIB module. The thermal conductivities of the various compartments of a battery cell are estimated based on the equivalent network of parallel/series thermal resistances of the battery components. The heat generation rate in an LIB cell is calculated by using the modeling results of the potential and current density distribution of a battery cell. The temperature distributions in the LIB module obtained from the modeling are in good agreement with the experimental measurement.

The battery module consisting of 8 prismatic pouch-type LIB cells modeled in this work is shown in Fig. 1. In Fig. 2, the temperature distributions of the LIB cells within the module at a few cross sections along the y direction are shown at the discharge time of 960 s with the discharge rate of 3C for natural convection cooling. The temperatures of the two cells located at the bottom and top of the module are lower than those of the other cells.