High Power DC Coupler to Integrate Second-Life Batteries with Solar and EV Chargers

Energy storage systems, powered by second life electric vehicle (EV) batteries, can achieve low system level cost while contributing to sustainable power grid, domestic manufacturing, and lowering environmental impacts caused by precious metal mining. However, a system integration gap exists between the highly heterogeneous second life battery packs in the 280-410 VDC output voltage range and the solar photovoltaic (PV) and EV charging ranges between 800-1500VDC. Available power converter solutions are cost prohibitive, under-optimized for power and voltage, low efficiency, or not capable of addressing EV battery safety concerns. Smartville aims to fill the gap between these two operating voltages to integrate second life battery packs from EVs for large scale energy storage systems (ESS). Current large-scale DC-DC converter input voltages start at 800VDC and are rated for 100kW or higher and are intended to be used in “new” lithium-ion ESS. In addition, battery packs are designed to operate as stand-alone units in the vehicle with integrated high-voltage interlocks and battery management systems to ensure safety. When repurposing second life EV battery packs to stationary ESS, multiple battery packs will be integrated together, creating new technological challenges to maintain the safety and reliability of a second life ESS. A custom power converter and integrated control system is needed to optimize the cost, safety, and compatibility with typical EV battery packs. During Phase I, Smartville tested multiple system topologies to determine which solution to the power conversion problem would be optimal to bridge the voltage gap. In Phase II, Smartville will develop a proprietary high-power DC-DC converter to match the voltage of the EV packs for integration to solar and EV chargers as well as utilize the technology in our current product. This new technology offers advantages over current products on the market due to having higher efficiency, lower thermal requirements, lower cost, and smaller physical size. Existing products on the market have lower power and do not meet the required voltage ranges, making this solution unique and filling a commercial gap in the market. Phase II will explore different power levels, fixed ratios, and inverter coupling solutions leading to Phase IIB and III to commercialize the product to efficiently repurpose and deploy second life battery solutions with solar and EV chargers. The system-level EV charging application developed and commercialized in Phases II and III will: (1) improve the value proposition of solar generation by integrating low-cost energy storage, (2) provide a low-cost way to mitigate utility demand charges during high power EV charging, and (3) provide a high-value market for second-life EV batteries.