Second-Life EV Battery Energy Storage for Distribution Grid Applications

Abstract

Electric vehicle batteries are commonly removed from traction service after their available capacity or power capability falls below automotive requirements, even though a substantial amount of useful electrochemical capacity can remain. Second-life deployment provides a pathway for reusing these retired batteries as stationary energy storage for distribution networks. This project presents a second-life EV battery energy storage framework designed to support distribution-grid operation through peak shaving, renewable-power smoothing, load shifting, voltage support, and controlled energy exchange. The proposed system includes battery screening and grading, a second-life battery management system, bidirectional power conversion, an energy management system, distribution-feeder monitoring, and protection functions. Battery state of charge (SOC), state of health (SOH), temperature, voltage, current, and feeder conditions are continuously considered during operation. The controller determines charging and discharging commands according to feeder demand, renewable generation, network limits, and battery operating constraints. The project emphasizes that second-life batteries cannot be treated exactly like new batteries because capacity variation, cell-to-cell differences, ageing history, and reliability must be considered during sizing and control. The resulting architecture provides a structured approach for converting retired EV batteries into a flexible stationary resource for distribution-grid applications.