One reason electric and plug-in hybrid vehicles have hit the market with a thud is that there are strings attached: Drivers of models such as the Chevrolet Volt and Nissan Leaf must plug in to recharge the battery.
A number of companies are developing ways to cut the cord, to replenish the battery wirelessly with a mat that sits on the floor. Coils on the underside of the car engage the charger when the car is parked over them. The mats are plugged in while the car isn't.
Automakers and suppliers expect to have the chargers ready for sale around 2015.
"The feedback we see from initial Volt and Leaf buyers is that, 'Gee, these cords get really dirty; gee, these cords get all tangled; what a pain in the neck,' " says Phil Gott, an IHS Automotive analyst specializing in powertrain research. "A wireless charger truly gives you total freedom."
Automakers are looking to such vehicles to comply with regulatory pressure to boost mileage and pare emissions.
Tesla Motors, the electric-car maker that recently delivered its first wholly company-produced sedans, says it's close to announcing a plugged-in "supercharger" network that can re-power one of its cars in less than an hour.
Nissan, Delphi Automotive, Volkswagen's Audi, Toyota, Mitsubishi, Qualcomm, Evatran and Brose Fahrzeugteile GmbH & Co. are among the companies developing wireless chargers.
General Motors, the largest U.S. automaker and maker of the Chevrolet Volt, invested $5 million in a private company called Powermat and was joined by Procter & Gamble and Jay-Z last year. So far, GM says, it's using the technology only to charge smartphones and other devices in the car.
The chargers work one of two ways: by induction, similar to the way the battery on an electric toothbrush charges when it's set back on its base, or by magnetic resonance.
Delphi's charger, using a technology developed by WiTricity, uses a magnetic field to transfer the charge between coils in the mat, about the size of a laptop, and bolted onto the underside of the car, says Randy Su
The charger, using technology developed at the Massachusetts Institute of Technology, can send 3 kilowatts of electricity quickly enough to recharge a battery in about four hours, Sumner says. Two coils are tuned to resonate at the same frequency, creating the connection. Audi, Toyota and Mitsubishi also are working with WiTricity.
The chargers probably will sell for more than $2,000, at least double the price of current charging stations, Sumner says. They are also less efficient. About 10 percent of power is lost in transmission, and the goal is to cut that by half, Sumner says.
Kinks are still being worked out. A charging mat is flat and warm, so how to keep a family cat from napping on one? How does a user keep metal away? A group of engineers from suppliers and automakers has been meeting for a year to solve such problems and develop universal standards, Sumner says.
A test in London is looking at how to embed wireless charging mats in city streets and parking garages, says Andrew Gilbert, Qualcomm executive vice president. Qualcomm is outfitting about 50 electric vehicles with chargers, he says.
"Plug-in is not a bad solution; we just see this as a great opportunity to really improve the experience," Gilbert says. "The power source is the same; it's just whether it goes over the air or a cable."