Fast charging of traction batteries in passenger cars enables comfortable travel with electric vehicles, even over longer distances, without having to oversize the installed batteries for everyday use.
As an enabling technology for fast charging, Kautex presents the implementation of 2-phase immersion cooling, where the traction battery serves as an evaporator in a refrigeration process. The 2-phase immersion cooling enables very high heat transfer rates of 3400 W/m^2*K and at the same time maximizes temperature homogeneity within the battery pack at optimal battery operating temperature. Thus, heat loads at charging rates of more than 6C can be safely and permanently managed by the battery thermal system. The cooling performance of 2-phase immersion cooling can also successfully suppress thermal propagation inside a thermoplastic battery housing. While the introduced 2-phase immersion cooling can dissipate the heat to the environment for temperatures up to 30 °C, the thermal cycle is reversable for efficient battery heating in cold ambient conditions. The implementation of flow boiling heat transfer ensures constant high heat transfer without collapse of the vapor bubbles and consequent cavitation damage.
This paper presents the realization of this technology on the test bench, as well as the integration in a demonstrator vehicle. Also, Kautex presents the integration of this technology in a thermoplastic battery housing, which is designed for manufacturing in an injection molding process to achieve readiness for serial production of the system.