Daimler Tests Cordless Electric Vehicle Chargers

The inductive chargers could make charging more convenient.

KEVIN BULLIS 

Having a few electric vehicle charging stations here and there isn't a big deal. But if they ever become common in cities, they'll be an eyesore, with their long, tangled black cords clumped onto their sides or sprawling across parking spaces to the outlet on the side of a car. Charging stations could also be a tempting target for vandals.

A much more elegant solution would be to bury inductive chargers under parking spots, a concept that Daimler has started testing. The chargers could be invisible and protected from vandals. And they could make charging easier—just pull into a parking spot, and the car can start charging.

Daimler, along with Conductix-Wampfler, a company based in Germany, has only recently started testing cars equipped with the inductive charging coils. But the initial results look positive.

The system is 90 percent efficient, which isn't as good as charging with a cable, but is better than some other inductive charging systems. The companies say that when you count efficiency losses within the car, the system is almost as good as plugging in.

Daimler has modified a E-Cell plug-in hybrid concept vehicle like this one to allow it to charge without having to plug in. So what will we call plug-in hybrids now? Credit: Daimler

In initial tests, after two or three practice runs, drivers have been able to successfully park their cars so that they're centered over the charging coils.

An object detection system is supposed to avoid the potential problem of the buried coils heating up a piece of metal left on the road. The prototypes are based on a wireless charging system developed for electric buses that has been operating since 2003.

It will be interesting to see how the cost of the system compares to conventional chargers, and whether it will still be necessary to install a post for communications gear, to allow drivers to pay for the charge with their credit cards, for example. Ultimately, cities will have to decide whether the better looks and convenience are worth the sacrifice in energy efficiency.

The company WiTricity is developing chargers that could be more convenient still, charging efficiently at distances greater than is allowed by inductive charging. We featured the technology as one of our 10 Emerging Technologies of 2008.