Validation of Electrical Equivalent Circuit Models for Second-Life Regenerated Lithium-Based Traction Batteries

This study aims to verify and improve the Electrical Equivalent Circuit Model (EECM) for a regenerated VW e-Golf cell and to develop a verification and optimization framework that enhances simulation accuracy. The model is based on an identified set of EESB elements derived from enhanced measurements of the regenerated cell and is compared with the original cell. A global EESB model is implemented in the PLECS environment, comprising a charge/discharge block and a Voc versus SOC evaluation. Parameters are obtained from measurements of the regenerated VW e-Golf cell and augmented with SOC-dependent polynomial relationships for individual model components. The methodology was applied to identify EESB elements for the regenerated VW e-Golf cell and to produce an EESB model aligned with the identification results. Verification compares simulated and experimental curves in critical SOC regions (0–10%, around 30%, and during relaxation) and cross-validates regenerated versus original cells. Results show that SOC-based polynomial estimates extend the valid range of EESB elements to 0–10% SOC and improve agreement with measured trajectories. Optimization reduces the computational load and improves accuracy, particularly in critical SOC regions, supporting a robust verification framework for regenerated battery cells and guiding further research and implementation in BMS and simulation environments.