Wireless electric vehicle charging explained

Since many of us now charge our smartphones and earphones without cables, placing them on a wireless charging pad at the end of each day, an obvious question from electric car drivers presents itself – can we do the same with an EV?

At a technical level, the answer is yes. Electric cars use the same lithium-ion battery technology as devices like smartphones, so if equipped accordingly their batteries could also be charged without plugging in a bulky cable. Handy if it's raining, or for on-street parking where installing chargers at the roadside isn't convenient.

It is still early days for wireless EV charging, but progress is being made on numerous fronts. Vehicle manufacturers like BMW have already experimented with the technology, and today there are trials already in operation where specially-equipped cars can be charged wirelessly in public parking spaces.

There's even a car about to go on sale, the Genesis GV60, that has wireless charging hardware fitted, ahead of a pilot kicking off in 2022.

How does wireless electric vehicle charging work?

Charging cars without wires works in a similar way to the wireless phone charger you might already own, just on a bigger scale.

You might have noticed how you can lift your phone very slightly off its charger without stopping the flow of electricity - wireless car chargers work in the same way, but at a distance measured in inches instead of millimeters.

In both cases, the technology required is called inductive charging. This is where electricity is transferred through an air gap from one magnetic coil in the charger to a second fitted to the smartphone or car. All you have to do is park in the right place, to ensure both coils are aligned, then charging can begin.

One EV wireless charging trial happening right now, run by a charging company called Char.gy, is a 12-month trial that kicked off in the UK in October 2021 that will eventually see 10 wireless charging pads installed into parking spaces across the county of Buckinghamshire.

The first is located in Marlow, 35 miles west of London, and can be used by a fleet of 10 Renault Zoe cars modified to work with the wireless chargers.

Char.gy said when the trial began: "This infrastructure means no charging cable – potentially hazardous for other road or pavement users – and no lamp-post charging and is only activated when an EV parks over it."

Similar inductive charging technology has been in use by the #7 bus route in Milton Keynes, UK since 2014, wirelessly topping up the battery for 10 minutes at the start and end of the service's 15-mile route.

In a similar fashion, Nottingham, UK began a wireless charging trial for electric taxis. In this case, 10 taxis were fitted with inductive charging technology, which they used to top up their batteries while parked at certain ranks and waiting for their next fare.

This is a common theme when talking about wireless EV charging – a little-and-often approach, instead of the quicker but less frequent use of fast plug-in chargers.

As for installing such a charger in the home, a US firm called Plugless Power (formerly Plugless) is working on its third-generation inductive EV charger, due in 2022.

These are designed to work with a US domestic 240V output, fit to existing cars, and the company claims power can be delivered through an air gap of up to 12 inches, meaning wireless charging of taller vehicles like SUVs and trucks could be possible.

Plugless Power says its upcoming third-generation wireless charger has a target price of $3,500, plus installation, and it is working on chargers for the European market too.

Which cars can be charged wirelessly today?

Currently, it is the charger manufacturers that are making both the chargers and the hardware needed to give an EV inductive charging. Some vehicle manufacturers have expressed interest in adding inductive charging as standard, with BMW running a trial with its 5 Series 530e iPerformance hybrid in 2018.

The trial began in Germany and expanded to the US in 2019, with a small group of California residents invited to lease a 530e hybrid with wireless home charger for 36 months.

Power is transmitted over an air gap of three inches and is delivered with 85 percent efficiency. It has a charging power of 3.2kW, which is enough to fill the battery in 3.5 hours.

Genesis is also working on inductive charging, and is making the feature available as an option on the new GV60 EV. Genesis claims the optional inductive charger will refill the SUV’s 77.4kWh battery more quickly than a typical home wall charger.

Genesis is quoting a full charge of the 280-mile vehicle in six hours, compared to 10 hours via a conventional wall charger.

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The inductive hardware comes from charging specialist WiTricity, but buyers will have to buy the actual charger, to be fitted into the floor of their garage, themselves.

Genesis says the feature will only be available in South Korea initially, and the inductive charging system won't be activated on vehicles until late-2022.

Speaking of WiTricity, the Massachusetts-based firm was established in 2007 and has worked on wireless charging technology ever since. The VC-backed startup acquired Qualcomm's Halo inductive charging technology in early-2019, with Qualcomm becoming a minority shareholder in WiTricity.

WiTricity claims it can charge wirelessly with a power efficiency of between 90 and 93 percent at a rate of between 3.6kWh and over 11kWh, and across a distance of between 10 and 25cm.

Qualcomm has previously said how its halo technology could charge wirelessly at up to 22kW, suggesting WiTricity is keeping plenty in reserve.

Charging while driving

This is the holy grail of electric car technology; the ability to power a car as it drives over chargers embedded into the surface of the road.

As part of its development of the Halo system, Qualcomm proved in 2017 that charging while driving is possible, even with the vehicle traveling at up to 70mph.

Underneath the regular-looking road surface of its 100-meter test track, Qualcomm installed a wireless charging system capable of sending power to a fleet of specially modified Renault Kangoo electric vans, each fitted with two 10kW charging pads.

Fast-forward to 2021, and while public roads can't yet charge electric vehicles, the US states of Michigan and Indiana are both keen to implement the technology.

Most recently, Michigan governor Gretchen Whitmer said in October 2021 how a one-mile stretch of road would be chosen to run a vehicle charging pilot.

As with in-pavement charging trials in Indiana, the exact location (and a timeframe) hasn’t been disclosed. Such trials are also taking place in Israel and Norway.

Crucial for autonomous cars

It doesn't take much imagination to see how useful such a road would be for autonomous cars of the future.

Instead of robotic taxis taking themselves to the charger every few hours - or, even worse, requiring a human to jump in and take them - they would be constantly charged from the road as they drive along.

It's sometimes easy to dismiss wireless charging as a gimmick – after all, you don't really need to charge your phone without a cable. Similarly, jumping out and plugging in an electric car only takes a few seconds.

But if chargers can be embedded into the roads – something WiTricity, Plugless Power and others clearly want to make a commercial success – then the impact could be revolutionary.