The demand for hybrid cars like the Toyota Prius has skyrocketed over the last decade, but now the energy-efficient vehicle — best known for reducing carbon footprints and saving money at the gas pump — has a new set of admirers: high-tech car thieves.

They’re targeting the vehicles’ high-powered batteries, which can cost as much as $2,500 to $4,000 to replace, said Bob Curry, president of The Hybrid Shop, which offers training, equipment and marketing resources for hybrid and electric car repair shops across the country.

The battery thefts are centered in San Francisco and New York City, where there are high concentrations of Prius and hybrid cars, according to a statement to Safebee from Toyota.

While the cost of replacing a battery can run several thousand dollars, many of the repair bills are much higher due to damage caused as thieves scramble to disconnect and unbolt the 150-pound batteries. Under normal circumstances it takes a trained hybrid-auto mechanic 20 minutes or more to correctly remove the rear-mounted Prius battery. Battery thieves have to work much faster, typically under cover of darkness, to extract the power cells, which carry potentially lethal charges of up to 200 to 300 volts, say police and Curry.

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Removing a hybrid car battery is definitely not for the Do-It-Yourselfer, says Curry, and these people breaking into cars are taking big risks.

“You can’t fix stupid, especially when people ‘think’ they know what they’re doing,” Curry said. “You can make a mistake and end up six feet under.”

Preventing battery theft

Unfortunately, there’s not much you can do to prevent thieves from targeting a hybrid car. “This is actually more of a law enforcement issue, than an automaker issue,” wrote Toyota in its statement. “The number of incidents is very small and the extraction of a battery in this manner is not so easy to accomplish.”

Prius and hybrid owners can make their batteries harder to steal by having a technician install tamper proof bolts to secure the battery to the vehicle and shield the harnesses in sheet metal, according to Yahoo! Autos.

An easier solution may be changing how you park at night. “If you're going to park, back into a spot at night,” Curry said. “There's no way that a thief can get into a trunk to manipulate the pack out if the car is backed up to something. It would be almost impossible.”

Beware when buying bargain batteries

The market for these stolen batteries appears to be mainly online. While not all NiMH batteries (the kind used in hybrid cars) advertised on classifieds and auction sites online are stolen, some of them may be, according to investigators and industry experts.

Ads on sites like Craigslist offer the batteries for $800 to $1,200 a piece, Curry says, which can add up to thousands of dollars in savings for someone who has a battery nearing the end of its lifespan. However, Curry says buying used batteries may be throwing your money away.

“When you buy batteries on these sites, you have no idea what you're getting,” says Curry. “You could be getting one that's been in a car that has 200,000 miles on it or one with 20,000.” He adds, “If you’re going to buy a couch, you can see it first, but these are sealed battery packs and even if you take the cover off you still don't know what the heck you're getting.”

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And there’s this risk: Buying products from someone on Craigslist usually involves meeting that person and exchanging money for the merchandise. In other words, Curry notes, if the battery is stolen, you could be meeting a criminal face to face.

“Here in Northern Virginia, if you do a Craigslist exchange police recommend you do it at or near a police station.”

Ronald Agrella is a freelance writer and former editor of The Boston Globe’s Boston.com.