Modeling and Control of Second-Life Batteries for Fast Charging Stations

Paper in proceeding, 2025

Rapid growth of electric vehicles has increased the demand for fast charging infrastructure, posing new challenges to grid stability and energy management. Meanwhile, the reuse of second-life batteries (SLBs) offers a sustainable approach to battery retirement, mitigating environmental impact and reducing costs. This paper presents a comprehensive framework for modeling and controlling SLBs in DC fast charging stations. A second-order RC equivalent circuit model is developed to characterize the performance of fresh and aged battery modules, and is further scaled to represent full battery packs. Buck-boost DC/DC converters are designed to regulate the DC bus voltage for multiple battery packs with different states of health (SoH), employing dual PI control loops for current and voltage. To enhance transient performance, a disturbance compensation loop is incorporated. In addition, a current allocation strategy based on real-time SoH estimation is proposed to reduce stress on weaker packs and promote more uniform degradation. The simulation results verify the effectiveness of the proposed approach in improving voltage stability and extending battery lifetime, highlighting the feasibility of SLB deployment in fast charging applications.