One of the primary factors that impede the adoption of electric vehicles (EVs) is the time required for charging, which limits their suitability for long-distance travel. Reducing the charging time would enhance the competitiveness of EVs and address the range anxiety that currently hinders their social acceptance. Nonetheless, the temperature increase that occurs during the charging process can have a detrimental impact on the battery’s lifespan, potentially rendering it non-compliant with warranty requirements or even lead to a safety risk. The EU project ALBATROSS has proposed the development of a novel Direct Liquid Cooling (DLC) battery pack strategy to address the aforementioned issue. In DLC, the coolant is in direct contact with the battery cells, thereby eliminating thermal resistances comparable to those observed in indirect liquid cooling systems where heat transfer occurs through solid interfaces. This direct contact facilitates more rapid and efficient heat dissipation, which is especially crucial under high-power operations as an objective of the project.
This study covers the work done regarding the simulations used in the design process of the Battery Pack Testing strategy to predict the temperature reached by the cells in the battery pack when undergone real operating conditions considering fast charge events. To this end, an electric-thermal model at cell level is developed. Tests at laboratory level are performed at different temperatures to parametrize the electric and thermal equivalent circuit models. The electric-thermal model is applied to calculate the heat generation under WLTC and a fast charge of 2.65C. In addition, the construction of the 3D model, which represents a scaled version of the full battery pack considering 36 cells in a staggered configuration, is implemented. The heat generation profile calculated by the electric-thermal model in the initial phase of the work is then used as the input in the Transient Computational Fluid Dynamic (CFD) simulation of the battery module. The thermal simulation is developed using Ansys Fluent software which permits a coupled analysis, whereby the fluid and heat transfer governing equations are solved simultaneously. Transient CFD simulations are conducted under WLTC discharge and fast charge (up to 2.65C) when the cells are directly cooled by a dielectric coolant based on real test boundary conditions.
As a result, the maximum temperature reached is analysed as well as the cell temperature gradient and the heat removed by the coolant. Through the CFD analysis, the heat rejection rates by the cells and the busbars are investigated to better understand the performance and capability of the module designed. The findings of this study will assist the scientific community in identifying the most effective strategy that allows the fast charge in a battery pack in electric vehicles.