Lithium-ion battery is one of the most promising candidate for the energy storage system in the automobile industry. In electric vehicles, cells are connected with each other closely due to space constraints, where thermal problem becomes significant during the system operation. Among all parameters, the initial cell inconsistency plays an important role in the changing rules of pack thermal performance. This paper seeks to gain a better understanding of current load and uneven heat redistribution for a lithium-ion battery pack consisted of cells with unequal initial parameter.

This study carries out a multi-physics coupling model for a battery pack consisted of cells with different initial resistance and capacity. A pseudo 2D electro-chemical model coupled with a lumped thermal model is used to describe each cell inside the pack. Based on this cell model, a coupled thermal-electrochemical model for a battery pack is built, which is able to predict the current load distribution and uneven heat generation during the charge and discharge procedure.

Using the coupled electrochemical-thermal model, cell initial parameters’ impact on pack performance was studied, including resistance and capacity inconsistency. Different cell numbers and connection pattern (parallel/series) were also selected to explore the changing mechanisms in load non-uniformity and heat performance.