This paper focuses on the faults of power batteries in new energy vehicles. It first analyzes their core characteristics and systematically elaborates on the application logic and operational key points of three key technologies: on-board real-time diagnosis, offline diagnosis, and intelligent diagnosis. Ultimately, a standardized troubleshooting process is constructed, which includes initial screening, in-depth detection, fault repair, and effect verification. The research aims to provide references for improving the efficiency of power battery fault handling and ensuring the safe operation of new energy vehicles.