Can Electric Vehicles Lose the Plug?
Posted by keelynet on September 9, 2010
Companies working on plug-free “proximity” chargers, which rely on magnetic induction, think they can solve this. Such chargers require no plugging–someone who owned an electric car would simply have to pull the car into a spot above a charging pad.
However, this convenience comes with a cost–10 percent or more of the power can be lost during charging. Induction chargers are already used to power electric toothbrushes, medical implants, and some portable electronics.
Inductive charging also plays a major role in electrical transformers used on the grid. The Plugless Power system has three main parts: a tower that plugs into the wall and converts electricity into the right frequency for the charger; a shoe-box sized, 25- to 30-pound adapter that has to be mounted to the front of a car chassis; and a long, flat pad that sits on the ground beneath a car.
The floor pad and the vehicle adapter both contain metal coils; when a car pulls up to the floor pad, the coils inside the pad move until they’re within two to three inches of the coils in the vehicle adapter.
The charger requires this alignment process, which is guided by magnetic sensors, to account for people parking slightly to the right or left of a parking space, and because the system has to be mounted in different locations depending on the car model.
When the coils are aligned, electricity flowing in the charging tower creates a strong magnetic field in the pad’s coils, and this magnetic field induces an electrical current to flow in the coils mounted on the car.
Evatran and other companies developing wireless charging systems say the plugless chargers work just as fast as the kind that require a cord. The difference is that plugless versions need more electricity to provide the same level of charging, and some energy is lost during transmission.
The Plugfree Power products will transfer about 90 percent of the electricity from the wall to the battery, whereas a cable transfers effectively all of it. According to Evatran, this translates to an additional $.005 per mile compared to plugged versions. Or, to put it another way, $5 for every 1,000 miles. – Full Article Source
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