Lube-Tech Table 1: Electric vehicle battery thermal management solutions.
That said, a promising solution that is being explored is direct battery cooling using dielectric fluids, the insulating properties of which allow them to be in direct contact with the electrochemical cells. The larger heat-exchange surface area makes it an inherently effective solution. However, its TRL (Technology Readines Level) was very low (<3) during the research process’s early days. It was consequently necessary to work not only on the fluid’s optimisation but also on its application in order to increase its TRL. TotalEnergies also broadened its skill set by working on the battery’s thermal management in its entirety in order to be able to evaluate its performance with great accuracy.
Initial development work was founded on the four areas of focus described in Figure 4 below:
PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
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- The question of Efficiency is a new aspect of the brief for fluid developers. Increasing a system’s efficiency effectively calls for a thorough understanding not only of the fluid and the assembly to be cooled, but also of the entire thermal loop. It is necessary to compare direct cooling systems with existing systems across a variety of criteria (thermal performance, consumption of auxiliaries, onboard mass and volume). Additional thermal management skills were therefore required, and this has been beneficial to the development of all EDU fluids.
- The question of Reliability entails proposing fluids that have a longer life expectancy compared with that of the battery pack itself. The specificity of this development has been the necessity to work on the compatibility of new materials, since the battery packs are not made of elements that are widely used in lubricated circuits. Careful attention was also paid to repelling dampness and achieving stable insulation properties with time.
- The question of Sustainability is always factored in, the aim being to develop high-performance products that have the smallest possible impact on the environment, a consideration that could become a norm in the future.
Figure 4: Areas of focus for the development of battery thermal management fluids.
The four areas of focus in detail: - The question of Performance is directly linked to the thermal properties as described above, thereby necessitating the optimisation of the fluid’s different parameters as specified in the Figure of Merit (FOM) equation.
The objectives listed included numerous new considerations, so it was necessary to acquire new skills and conceive new testing procedures. In order to speed up its work and be more agile, TotalEnergies quickly developed its own test method using rapid prototyping, as described in Figure 5. The rig takes the form of a battery module with dummy PHEV2 cells that incorporate heated cartridges to reproduce the temperature rises encountered when fast charging.
LUBE MAGAZINE NO.168 APRIL 2022
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