Driving to the future of energy storage: Techno-economic analysis of a novel method to recondition second life electric vehicle batteries

The transportation sector is trending towards electrification which means a dramatic change to the availability of used Lithium-ion (Li-ion) batteries which can be reused for grid energy storage systems (ESS). However, second life battery modules can have an imbalanced state of health (SOH) between cells which can reduce battery safety, life, and depth of discharge. This work evaluates the economics of a novel Heterogeneous Unifying Battery (HUB) reconditioning system that cycles battery modules to unify cells' SOH to improve their second life battery performance. The HUB reconditioning cycles can be performed in one of two ways: recondition with grid services or recondition through energy shuffle. The results from this work demonstrate that a simple repurposing process will likely have a lower second life resale price (56 $/kWh) than the HUB system (62 $/kWh) in our baseline scenario; however, in our target scenario the HUB system (34 $/kWh) has a lower resale price than the repurposing system (38 $/kWh). This work also includes an economic analysis for using reconditioned batteries in a grid ESS that was compared to an ESS that is assembled with new Li-ion batteries. Results show that HUB reconditioned ESS require less grid revenue (194 $/kW-year) than new Li-ion ESS (253 $/kW-year). Finally, the HUB reconditioned ESS is shown to be economically feasible in 63% of frequency regulation, 18% of transmission congestion relief, and 16% of demand charge reduction markets but not economically feasible in spin/ non-spin reserve, voltage support, and energy arbitrage markets.