While interest over electric vehicles is growing worldwide, comes the question of the thermal management of their battery pack. This requires a detailed knowledge of the electrical behavior of the battery cells and the corresponding temperature evolution during charge and discharge. After this necessary step, cooling solutions can be proposed in order to maintain (i) satisfying operating temperature conditions for the cells, and (ii) admissible temperature differences on each cell of the electric vehicle battery pack.

This paper focuses on two main aspects: the experimental characterization of a Li-ion battery cell during charging/discharging cyclic operations and the design of a solution for advanced thermal management at cell level.

Experiments are conducted in the absence of cooling aid system and provide thermal and electrical insights. The temperature maps are captured via thermal imager and documented for 2C charging and 5C discharging, and related to the voltage curves. The maximum temperature differences on the battery cell surface are obtained in various experimental conditions: ambient environment maintained at 25°C and 40°C, ventilation or no ventilation around the cell.

We develop a numerical model describing the voltage changes and the corresponding generated heat. After validation with the experimental results, we propose a thermally efficient solution consisting in inserting between the cells cold plates made of a constructal architecture liquid cooling system. The architecture of the fluid network is a canopy-to-canopy configuration: The fluid is conducted through a trunk channel to orthogonal branches delineating the tree canopy. The branching ducts are connected to their counterparts which are themselves branches to another fluid collecting trunk. We show that canopy-to-canopy configurations allow to extract most of the non-uniformly generated heat by the battery cell with a small mass flow rate.