Performance Characterization and Degradation Modeling of Series-Connected NCR18650GA Battery Modules for Electric Refuse Compactor Vehicles: EIS-Based Thermal Prediction, Weibull Reliability, and BMS Validation

This paper presents a comprehensive characterization and degradation modeling framework for 12-series (12S) and 14-series (14S) NCR18650GA lithium-ion battery modules deployed in electric refuse compactor vehicle (e-RCV) applications. Electrochemical impedance spectroscopy (EIS) is employed to extract equivalent circuit parameters, which are subsequently used to derive heat generation rates and construct a lumped thermal model. The thermal model, validated against experimental discharge data, achieves root-mean-square errors (RMSE) of 1.3°C and 1.4°C for 12S and 14S modules respectively. Cycle life testing of seven individual cells, analyzed via Weibull reliability statistics with maximum likelihood estimation incorporating right-censored data, yields a shape parameter β = 12.7 and scale parameter η = 204 cycles, indicating a wear-out failure mode with low cell-to-cell variability. The B10 reliability life is determined to be 171 cycles under accelerated 1C/1C conditions. Open-circuit voltage (OCV) sensitivity analysis confirms that the NCA chemistry maintains dOCV/dSOC above 4.5 mV/%SOC across the full state-of-charge range, providing a favorable basis for model-based SOC estimation. Module-level discharge characteristics, including BMS state-of-charge accuracy and thermal behavior, are compared between the two configurations. The integrated characterization pipeline—from single-cell EIS to module-level thermal prediction and statistical reliability—provides actionable design metrics for battery management system development, module warranty assessment, and e-RCV fleet management.