Decoupling and Diagnosis Method for Early Minor Faults in Electric Vehicle Traction Batteries Based on PatchTSSA

Accurate detection of early minor faults in electric vehicle traction batteries is important for preventing thermal runaway under complex operating conditions. Aging-related capacity degradation and measurement noise can mask the weak voltage distortions caused by early faults, leading to false alarms in data-driven diagnostic models. To improve robustness to these disturbances, this paper develops an early multi-fault decoupling and diagnosis framework based on PatchTSSA, a lightweight Transformer architecture that adapts time-series patching and Token Statistics Self-Attention (TSSA) to battery diagnostic sequences. The framework combines static–dynamic feature fusion with time-series patching to capture both global voltage drift and local morphological gradients. Within this adapted framework, TSSA replaces quadratic dot-product attention with second-order moment pooling, giving linear complexity with respect to the number of tokens and supporting future investigation of embedded Battery Management System (BMS) implementation. A physics-informed fault-injection strategy is used to construct a five-class dataset comprising the healthy state (E00), minor internal short circuit (E01), severe internal short circuit (E02), penetration fault (E03), and sensor drift (E04) from public Center for Advanced Life Cycle Engineering (CALCE) and National Aeronautics and Space Administration (NASA) battery-aging data. Across five raw-cycle-grouped splits and training seeds under 5 mV Gaussian white noise, the complete PatchTSSA configuration achieves 91.5±1.9% overall accuracy, 94.1±1.2% macro recall, and 85.4±5.3% E01 recall for the simulated fault patterns. The direct E01–E04 confusion rate is 0.09±0.20%, whereas the E00-to-E01 false-alarm rate is 15.1±6.9%. CALCE–NASA protocol differences are used only to describe cross-dataset domain shift; no transfer-performance claim is made without a matched capacity-free evaluation. The results indicate the potential of the framework for online fault-pattern discrimination, while validation using real fault data and embedded hardware remains necessary.