Effect of Moisture and Temperature on the Insulating Performance of an EV Battery Thermal Fluid

As electric vehicles become increasingly popular, there is a growing emphasis on innovating their technology, evidenced by the interest surrounding novel thermal management techniques like immersion cooling. Unlike conventional thermal management methods, immersion cooling involves submerging active components directly into a thermal fluid, necessitating an insulating fluid. It offers improved thermal management, which can enable faster charging and extended battery life. The insulating performance of such a fluid depends on various factors, including temperature and moisture content. Therefore, it is crucial to quantify these factors to provide a comprehensive understanding of their impact on fluid properties. While quantifying temperature is straightforward, moisture content in a fluid can be expressed in different ways, namely absolute water content and relative saturation. The relative saturation value is derived from the absolute and the maximum water content at a specific temperature, proving more representative than the absolute value, as the maximum water content can vary significantly with temperature and among different fluid chemistries. With these parameters quantified, a closer examination of insulating performance is possible, in this case focusing specifically on DC resistivity. Following the IEC 60247 standard, the DC resistivity of an EV battery fluid at different temperatures and moisture levels are measured. The results showed that the DC resistivity of the fluid decreases with the increase of temperature or moisture level.