Experimental investigation of a vehicle-scale immersion cooling battery thermal management system for high-energy-density battery packs under cooling and heating conditions

Immersion cooling battery thermal management systems (BTMSs) are attracting increasing attention due to their superior thermal performance and promising application in electric vehicles (EVs). In this study, a full-scale EV-level immersion cooling experimental platform was constructed to comprehensively evaluate both cooling and heating performance. The investigated 30.7 kWh battery pack consists of 48 high-nickel lithium-ion cells, with an average volumetric heat generation rate of 186,360 W m−3 during 3C charging. Under a flow rate of 10 L min−1 and an initial ambient temperature of 40 °C, the battery pack's maximum temperature reached 55.4 °C during 3C fast charging, remaining within the safety threshold. Regarding heating performance, a top-inlet/bottom-outlet flow configuration yielded a 46.48% improvement in heating rate (1.04 °C·min−1) compared to the conventional bottom-inlet configuration and reduced the maximum intra-pack temperature difference at the end of heating to 3.9 °C—a 59.38% reduction. In terms of operating pressure, the battery pack maintained internal pressures below 20 kPa at 10 L min−1, providing valuable insights for structural strength design. For flow resistance, the pressure drop across the immersion-cooled battery pack was measured at 2.32 kPa under cooling conditions, while the chiller contributed approximately 70% of the total system pressure loss. This study offers critical guidance for the design and optimization of EV-scale immersion cooling BTMSs, promoting their practical implementation in next-generation electric mobility solutions.