Enhancing Second-Life Battery Performance With Dynamic Equalization: A Residential Case Study

The growing demand for energy storage in residential photovoltaic systems highlights the potential of second-life electric vehicle batteries. Their residual capacity offers economic and environmental benefits. However, their cells suffer from a significant capacity mismatch, which reduces the overall usable capacity of the battery. Dynamic equalization appears to be a promising solution to fully exploit the battery capacity. This work aims to present a simulation platform designed to evaluate the benefits of dynamic equalization in second-life batteries used for residential photovoltaic energy storage. Through the simulation platform, various scenarios were simulated based on real production and consumption data collected over a one-year operating period to account for seasonal variations. Simple control algorithms are investigated and compared with an improved one based on a digital twin of the battery. In addition, the effects of the equalization system efficiency, battery size, and cell capacity mismatch on the dynamic equalization behavior are discussed. This study demonstrates that the use of dynamic equalization increases energy utilization by up to 8%, even when the efficiency of the equalization DC-DC converter is as low as 70%. Finally, an economic analysis is performed to compare brand-new lithium-ion batteries and second-life batteries with and without dynamic equalization.