关键词: 预充继电器；红磷；硅氧烷；接触电阻

Abstract: The pre-charging system of new energy electric vehicles is crucial to vehicle safety. In order to furtherly improve the reliability of the pre-charging system and to propose practical and reliable control measures, this paper analyzes in depth the reasons for the functional failure of the pre-charging system. Through the systematic troubleshooting method, it is found that the abnormally high surface resistance of the contacts of the pre-charging relay is the direct cause of the pre-charging failure. Suction test, computed tomography (CT), microscope inspection, and scanning electron microscope analysis are conducted. The results show that some parts in the battery management system (BMS) have free monomeric phosphorus and volatile silicone, and material migration occurs during high-voltage operation, and the elements of silicon and phosphorus migrate to the surface of the relay contacts, resulting in an abnormally high contact resistance, which ultimately triggers the pre-charging functional failure. The application of this paper concludes that the red phosphorus and siloxane content of BMS system parts needs to be controlled during the design and mass production stage to ensure the reliability of the pre-charging system. The research has strong practical application and reference value.

Key words: Pre-charging relay; Red phosphorus; Silicone; Contact resistance