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

摘要： 针对新能源汽车动力电池单体不均衡诱发续航缩减及热失控隐患，以某车型 P1AC400 严重不均衡故障为对象，采用 5 min 无拆包定位方法，锁定#101 单体为故障根源。利用内阻 测试仪等精准测试仪器量化检测，实测内阻 26.3 mΩ、容量偏差 15%与模组压差 234 mV，故 障等级判定为中度不均衡故障。通过构建“快速定位+精准验证”两级诊断流程，制定分级均 衡修复、单体/模组更换及电池管理系统（BMS）标定维修方案。经全充放循环与 100 km 路 试验证，电池包压差稳定低于 50 mV，故障消除。验证分级处置方案的有效性，为新能源汽 车动力电池故障诊断、现场维修及日常运维提供理论依据与实操参考，同时也为贵州新能源 电池材料产业创新网络高技能人才培养与职业院校产教融合协同育人提供技术支撑。

关键词: 动力电池；电池不均衡；精准验证；故障诊断；BMS 标定