HIC-LLM: Health-Indicator Consistency Scoring and Optional Evidence-Grounded Large Language Model Reporting

Pack-level state-of-health assessment can conceal the cell that first reaches its lower-voltage limit and constrains a series-connected backup battery string. Cell-level localization is therefore required, but the scarcity of labeled field events and high-resolution telemetry does not support training or validating a supervised, unsupervised, or semi-supervised model. General-purpose language models introduce a separate risk of unsupported causal interpretation. These limitations motivate a two-stage framework: a training-free health-indicator consistency (HIC) score performs all numerical localization through within-event, one-sided median-absolute-deviation normalization, and an optional language model converts only the fixed ranking and structured evidence into an author-audited maintenance report with bounded mechanisms and explicit uncertainty. The primary evidence comprises two capacity-test reports from the same 24-cell, 2-V, 100-Ah pack: a manually terminated reference test and one lower-voltage-limit event. A separate CR-BTM workbook contributes 46 low-current pack-level records and 1104 cell-monitor records, but lacks a unique pack or device identifier, calendar date, capacity integration, and termination reason; it is therefore treated only as a candidate ancillary dataset with compatible measurement characteristics. In the lower-voltage-limit event, Cell #6 reached 1.800 V, released capacity was 86.11 Ah versus 100.46 Ah in the reference event, and HIC ranked Cell #6 first with a score of 7.983, compared with 1.145 for the runner-up. Cell #6 also had the largest lower-tail score at every recorded pre-termination time, including the record approximately 0.57 h before termination. Direct final-voltage and voltage-drop rules also rank Cell #6 first; consequently, the result is an engineering consistency verification of one field-confirmed event, not evidence of predictive superiority or population-level performance.