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Industry cuts the cord on electric car charging

Lucas Mearian | Oct. 22, 2013
Major stumbling blocks to wireless charging -- power loss and slow recharging time -- need to be worked out

A depiction of HEVO's wireless charging manhole (Source: HEVO Power)

Hayfield pointed out that fast charging and wireless charging are two distinctly different technologies.

"Beyond the longer charge time with wireless... there are many other factors which make its adoption a long term trend," Hayfield said of wireless charging.

Among the obstacles that wireless charging must overcome is that it's currently not in production; it must be added aftermarket. Also, the magnetic coil charging system adds weight and cost the the vehicle, Hayfield said.

"Public trials are really only just beginning now. There are safety and interference issues that must be tested in the real world," she added.

Additionally, while wireless charging is supposed to add a level of convenience for EV owners, "plugging in is not a major problem for most," Hayfield said.

Efficiency is key, size matters
Another drawback to wireless charging is power loss. Transferring electricity through the air between two copper coils means some power will dissipate.

HEVO's wireless charging devices have a power transfer efficiency of more than 85% at 12 inches of separation, according to Stahl.

Eric Giler, WiTricity's CEO, said anything under 90% end-to-end efficiency should not be acceptable.

"Think about it. If you're transferring 10,000 watts, and if you're at 85% efficiency, you're continually wasting 1,500 watts of electricity. Even at 90%, you're still wasting 10,000 watts. That's a lot of energy to waste," he said.

HEVO's Power Station technology comes in three parts: a power transmitter - a coil that can be embedded in the pavement or an object; a receiver in a vehicle and a smartphone app. The app can be used to find wireless charging parking spaces, and can also tell the driver when the vehicle is aligned properly for charging.

HEVO's Power Station transmits at 220-volts with up to 10 kilowatts of power for charging a vehicle. The larger the copper coil, the more power that can be transferred.

WiTricity, originally a research project at MIT, was formed in 2007 after scientists demonstrated they could use two copper coils to create a magnetic field and power a 60-watt light bulb wirelessly. To date, the company has garnered more than $40 million in venture capital funding, the last round being led by Toyota.

Today, the company licenses its technology to equipment makers in the consumer, healthcare, industrial and automotive markets. By far, Giler said, the largest markets are consumer and automotive. Along with Delphi and Toyota, Mitsubishi has also partnered with WiTricity to develop charging pads.

WiTricity's 3,300 watt wireless charging pad (Source: WiTricity).

Mobile technology company Qualcomm has also announced that its Halo wireless charging technology will be used in tests to charge EVs around London and to recharge safety vehicles working on the Formula E car racing circuit.


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