Passive Solution for Battery Disconnect Unit Thermal Management for Electric Vehicle Fast Charging: Numerical Study and Experimental Validation

Charging time remains a major challenge in the development and adoption of electric vehicles (EVs). The difficulty of locating a charging station, combined with the significant duration required for a full charge, has become an increasingly critical factor influencing consumer decisions. Fast-charging is being progressively implemented not only in newly developed EVs but also retrofitted into existing ones. However, one of the main limitations of fast-charging is the overheating of various components within the vehicle, the charging station, and the charging infrastructure. A key element in this system is the Battery Disconnect Unit (BDU), which is responsible for monitoring, activating, and deactivating the high-voltage battery system. It is crucial to maintain the BDU within safe operating temperatures to prevent overheating and ensure reliable operation. Currently, these components are typically designed for standard charging power. However, as charging power increases and charging time decreases, thermal management becomes more and more important. This paper presents a passive solution to enhance the thermal performance of the BDU, allowing it to handle higher power levels without the need for a complete redesign of the cooling system or the vehicle’s high-voltage power distribution network. The proposed solution is evaluated through a combination of simulations and experimental testing. An initial test campaign is carried out to identify the system's thermal hotspots. The component exhibiting the highest temperature rise is selected for targeted cooling improvement. Its thermal behavior is then modeled using GT-Power software to assess the effectiveness of the proposed passive cooling strategy.