IDAHO FALLS, Idaho (AP) - Scientists at the Idaho National Laboratory are analyzing whether hybrid vehicles that are converted to be plugged into an electrical outlet for recharging are as efficient in the real world as they are in the laboratory.

The work is being done as part of the U.S. Department of Energy's Advanced Vehicle Testing Activity program, which is placing plug-in cars in a variety of cities around the nation and gathering information from them.

Some 30 cars converted from regular hybrids to plug-ins will be added to fleets in Washington state in the coming months, said Nicole Stricker, an INL spokeswoman.

By the end of the year, the Energy Department plans to have 140 plug-ins for the INL to analyze, including cars in California, Arizona, Hawaii and New York.

"Obviously the more cars, the more data, the more we can fine tune what we're trying to do," Stricker told the Post Register. "We don't have a horse in the race. We don't stand to make any money, whether these things succeed or fail. We're the objective analysts."

Hybrid cars are powered by gasoline and batteries that are recharged by capturing energy from the movement of the vehicle. Plug-in versions come with longer-lasting, more powerful lithium ion batteries that can propel the car as far as 30 miles without using gasoline.

INL analysts will track electricity use, average and top speeds, miles per charge, and how long it takes to recharge the cars.

Stricker said it's unclear how long the study will last.

Tim Murphy, systems manager for INL Energy Storage and Transportation, said the study should help answer whether scientists can develop "larger, high-energy battery systems that are cost-effective and have a long, reliable life."

Part of the equation of converting standard hybrids into plug-ins is the cost, which Murphy said is about $10,000 to $15,000.

The batteries, he said, last eight to 10 years, but "there is very limited data, so there are a lot of unknowns."

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