An Afterlife for the Electric Car

Advocates of electric cars and renewable energy have talked for years about repackaging the battery packs built for cars as home energy storage devices once they can no longer hold enough charge to run a vehicle. On Wednesday, ABB and General Motors announced that they were trying out just that idea with the battery packs of five Chevy Volts.

When it is new, the Volt battery pack holds 16 kilowatt-hours. The prototype announced by the two companies promises a capacity of about 10 kilowatt-hours per pack, with five packs lashed together in an array that is supposed to provide two hours of electricity for three to five average houses. For the demonstration, the unit was providing lighting and audiovisual equipment in a structure in San Francisco where the experiment was announced.

The batteries were hardly challenged. In the Volt, each pack is supposed to provide up to 111 kilowatts of power, the watt being a measure of how fast the electricity is delivered. In this case, the five batteries delivered only 2.5 kilowatts, or less than half their original capacity. Using the batteries at low power could extend their lives.

The idea behind the prototype is two-fold: to provide a market for past-their-prime batteries, giving them a resale value that will lower their cost of ownership, and providing distributed storage that could be used to shore up weak spots on the grid or to absorb energy from intermittent sources like solar panels and wind machines and deliver it in a steady stream suitable for the power grid.

ABB believes the installation could also be useful in a neighborhood with a lot of electric cars. The electricity needed to charge those vehicles could come into the area in a steady stream, and be stored by the battery pack and tapped at high speed whenever needed. In that function, the battery pack would resemble the tank on a toilet, which fills slowly but is available for quick discharge.


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