Repurposing spent electric car batteries is a smart move that can keep them out of the waste stream and provide value to seemingly useless products. This line of thought is gaining believers because it addresses both environmental and economic challenges.
One of the major hurdles holding back the widespread popularity of electric vehicles is their battery cost. The retail price of EVs could be cut drastically if batteries retained a high residual value after they could no longer power electric vehicles, especially if EV batteries were leased separately rather than sold with an electric car. 
Actually, EV batteries should retain high residual values. On average, electric car batteries that cannot hold sufficient charge for motive use can still retain as much as 70 percent of their energy storage capacity, even after eight to 10 years of use powering a car. Several projects are now underway aimed at establishing a secondary battery market for these spent batteries.
Since most EVs battery packs are modular, individual modules could be reconfigured for other applications like powering electric bikes. The most promising application is to integrate several into a ‘grid energy storage box’ to provide temporary power during a utility outage, or to handle peak grid demands.
Nissan North America, working with power-transmission equipment manufacturer. ABB, Sumitomo Corp. of America, and 4R Energy Corporation, is looking at using spent lithium-ion batteries such as those used in the Nissan LEAF. The goal is to use these batteries for energy storage by utility companies and as community power sources. A 50 kilowatt-hour battery storage prototype now under development could power 15 homes for two hours. Nissan already sells a system in Japan that enables the LEAF to serve as a backup electricity storage system for homes.
General Motors, also working with ABB, is investigating applications for the 16 kilowatt-hour lithium-ion battery pack used in the Chevrolet Volt. Again, the emphasis is on using recycled batteries for electrical grid storage and grid load leveling, including use with intermittent renewable energy sources like wind and solar.
In yet another example, Duke Energy is working with ITOCHU Corp. in finding second-life applications for lithium-ion electric vehicle batteries. Duke Energy has a fleet of 80 Think City plug-ins with lithium-ion batteries, so a ready-made supply will be available down the road.