Wireless EV charger makes debut

London-based HaloIPT is demonstrating its wireless technology on a Citroën Ev'ie electric car at the World Electric Vehicle Symposium in Shenzhen, China, which opened November 5. It first launched the system a week earlier.

Power is transmitted from a charging pad under a road or parking spot to a special receiver pad in the floor of the car, using a technology called inductive power transfer. The charging speed is similar to that of plug-in charging, a company spokesman said.

In a release, the company said the charger is designed to work even when buried under asphalt, submerged in water, or covered in ice and snow. In the future, the company hopes chargers can be embedded in roads so cars can charge during their drive.

That could make smaller batteries practical, the company said, and solve the major problems that currently prevent e-cars from being commercially popular - larger batteries are heavy and very expensive, but smaller batteries limit the range of the car too much.

Inductive power transfer involves using a device called an induction coil that converts electric current into an electromagnetic field.

Another induction coil in a receiver converts the field back into electrical current that can charge the battery. The transmitter and receiver are both tuned to a specific frequency in order to work together, so they are unlikely to interfere with other electronic devices, a company spokesman said.

The technique is already commercially available from companies such as to charge low-powered devices such as cellphones and MP3 players.

Until now, however, the chargers and receivers had to be too close together and too closely aligned to be practical for electric-car charging.

HaloIPT says its system works with a maximum height of 40 centimetres between the charger and receiver, so it is suitable even for use with SUVs. It can be misaligned horizontally by up to 25 centimetres, so the driver doesn't have to park perfectly over the charging pad.

The company plans to build a commercial-scale demonstration of the technology by 2012.

Other companies, such as Watertown, Mass.-based WiTricity are working on similar technology. WiTricity estimated its charging devices could be available in 2014 or 2015 models of electric cars.