Plug-in hybrid cars undergo tests

A U.S. energy lab is testing 13 hybrid cars with mileage-boosting batteries that can be plugged into a regular household electrical outlet.

Photo: Plug-in hybrid cars undergo tests

The U.S. Department of Energy demonstration project is aimed at judging the performance of plug-in hybrid electric vehicles in an urban area. Over the next 12 months, 13 converted Toyota Prius cars owned by the city of Seattle, King County, Port of Seattle and the Puget Sound Clean Air Agency will drive the streets of western Washington state in the study by the Idaho National Laboratory.

So far, the cars' mileage per gallon has about doubled after being outfitted with lithium plug-in batteries, to 125 miles per gallon in city driving conditions.

"We've done some testing where we've seen over 200 miles per gallon" under laboratory conditions, said Jim Francfort, who leads the program. "Where you've got a lot of city driving, we're seeing 125 miles per gallon, plus."

Currently, there are 10 versions of hybrid cars available in North America, with versions from Toyota, Honda, Ford, Lexus, Mercury and Mazda. Hybrids generally use power from their gas-fueled engines or generated by braking to charge their batteries to propel them in rush-hour and city traffic; in higher-speed situations like highway driving, the engine kicks in.

The Prius comes from the factory with a 1.3 kilowatt-hour battery pack. INL is testing vehicles that have been given 5 kwh to 10 kwh packs. Scientists hope to reduce the cost of a plug-in hybrid battery to just $3,000 (2,000 EUR) per car.