In four or five years, the batteries in the roughly one and a quarter million electric vehicles currently on the road will start to decline and will have to be replaced. So what will we do with all those batteries that have such much life still in them, but are no longer suitable for cars? Two researchers believe second-life batteries could cost as little as $49 per usable kilowatt-hour to repurpose for storing energy in the grid. That is very cheap compared to the current new stationary battery price today that sits around $300 per kilowatt-hour.