关键词: 动力电池；电池不均衡；精准验证；故障诊断；BMS 标定

Abstract: To address the risks of range reduction and thermal runaway caused by imbalance in power battery cells of new energy vehicles, this study takes the severe imbalance fault of model P1AC400 as the research object. A 5 min non-disassembly positioning method is adopted to identify cell #101 as the root cause of the fault. Precision testing instruments such as an internal resistance tester are used for quantitative detection. The measured internal resistance is 26.3 mΩ, the capacity deviation is 15%, and the module voltage difference is 234 mV, with the fault level classified as moderate imbalance. A two-level diagnostic process of "rapid positioning+precise verification" is constructed, and maintenance schemes including graded balancing repair, cell/module replacement, and battery management system (BMS) calibration are formulated. Through full charge-discharge cycles and a 100 km road test, the battery pack voltage difference is stably maintained below 50 mV, and the fault is eliminated. The effectiveness of the graded treatment scheme is verified, providing a theoretical basis and practical reference for fault diagnosis, on-site repair, and routine maintenance of new energy vehicle power batteries. At the same time, it also provides technical support for the cultivation of high-skilled talents in Guizhou's new energy battery materials industry innovation network and the collaborative education of industry-education integration in vocational colleges.

Key words: power battery; battery imbalance; precise verification; fault diagnosis; BMS calibration