Enlarge / Each of those white structures contains lots of batteries that were built for cars. (credit: B2U)

Last week, a company called B2U Storage Solutions announced that it had started operations at a 25 Megawatt-hour battery facility in California. On its own, that isn't really news, as California is adding a lot of battery power. But in this case, the source of the batteries was unusual: Many of them had spent an earlier life powering electric vehicles.

The idea of repurposing electric vehicle batteries has been around for a while. To work in a car, the batteries need to be able to meet certain standards in terms of capacity and rate of discharge, but that performance declines with use. Even after a battery no longer meets the needs of a car, however, it can still store enough energy to be useful on the electric grid. So it was suggested that grid storage might be an intermediate destination between vehicles and recycling.

But there are some significant technical and economic challenges to implementing the idea. So we talked with B2U's CEO, Freeman Hall, to find out why the company decided it was the right time to put the concept into action.