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 this 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 fast charging to keep the cell at an optimal operational temperature. To this end, an electric-thermal 1D 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 a fast charge profile. In addition, the construction of the 3D model, which represents a scaled version of the full battery pack, is implemented. The heat generation profile calculated by the 1D 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 fast charge when the cells are directly cooled by a dielectric coolant based on real test boundary conditions.
As a result, the maximum cell temperature reached, the maximum cell and module gradient temperature, the coolant pressure drop reached and the heat removed by the coolant are analysed. This analysis determines the optimal cooling scenario to enable the fast charging in safety conditions, enhance the cell ageing due to the reduction of the module gradient and reduce the power cooling consumption.