Engineers reveal system that could let future EVs charge while driving

7 May 2020

Image: © carloscastilla/

Newly developed technology could one day be scaled up to allow EVs to charge while driving down futuristic motorways.

In the future, users of electric vehicles (EVs) may never need to pull over to charge if a new technology revealed by Stanford researchers comes to fruition. Engineers Shanhui Fan and Sid Assawaworrarit revealed in a study, published to Nature Electronics, that they have taken a big step toward making it practical for EVs to recharge wirelessly while driving down motorways.

While a previous attempt to wirelessly charge objects in motion never made it outside of the lab, the engineers are now confident that their technology could one day be scaled up to power a car moving down a road. For now, however, they believe the system could allow for wireless charging of robots as they move around a warehouse or factory floor.

Wireless chargers that are already on the market today – used to charge mobile phones and small devices – transmit electricity by creating a magnetic field that oscillates a frequency to create a resonating vibration in magnetic coils in the receiving device.

However, the resonant frequency changes if the distance between the source and receiver changes by even a small amount, making it impractical for moving objects.

92pc efficiency

The previous technology developed by the Stanford engineers was only able to able to transmit 10pc of the power flowing through the system.

Now, the researchers have been able to boost the system’s wireless-transmission efficiency to 92pc. The key to this breakthrough, Assawaworrarit explained, was to replace the original amplifier with a far more efficient ‘switch mode’ amplifier.

The prototype technology can transmit 10W of electricity over a distance of a little under a metre, but it should be possible to scale up a system to transmit the hundreds of kilowatts a car would need.

However, while wireless transmission takes just a few milliseconds, it may be limited by how fast the car’s batteries can absorb all of the power. Also, the researchers admitted that it could be many years before it is feasible to embed charging systems into motorways.

“This is a significant step toward a practical and efficient system for wirelessly recharging automobiles and robots, even when they are moving at high speeds,” Shanhui said.

Colm Gorey was a senior journalist with Silicon Republic