One of the modern conveniences of electronic devices like smartphones or earbuds is wireless charging. As an electric vehicle enthusiast, you may wonder if the same wireless charging can work in electric vehicles. It would be very convenient to charge an electric car without having to handle cables, by simply parking over a charging pad.
Is wireless electric car charging possible?
The answer is yes, electric vehicles can charge wirelessly. The wireless charging found on phones can be scaled up, technically, to handle cars. However, as it happens when scaling things up, the increased power transfer rates make electric vehicle wireless chargers more complex. For example, the thermal losses, safety requirements, costs, and environmental challenges are more intense.
This brings us to how wireless charging can be adapted to work in electric vehicles.
How do wireless electric car chargers work?
Wireless electric car charging uses resonant magnetic induction to transfer energy from a charging pad placed on the floor of the garage, for instance, to another receiving pad that attaches to the car’s underside. The charging pad is usually one square meter in size, while the receiving pad is more compact. Charging speed can vary between 3.3 and 20 kW. The charging takes place when the driver parks the car over the charging pad and the two pads align.
Since the power from the grid is alternating current (AC) but the communication between the two pads is in direct current (DC), the transmitter, which is fixed in place, has to convert the current to DC before transmitting. In the receiver, the direct current may interface directly with the DC battery management system or be converted back to AC to use the same electrical infrastructure used by the plug-in interface.
Electric vehicle wireless charging is versatile. However, is it efficient?
How efficient is wireless electric car charging?
Electric vehicle wireless chargers can be more than 90 percent efficient. However, several challenges have to be overcome. The two biggest challenges are reliability and energy efficiency.
As both the charging and receiving pads are exposed, they are exposed to extreme conditions like high temperatures, humidity, or even physical forces. New materials that can withstand these conditions and still work reliably are needed.
Using a semiconductor with a large bandgap and nominal voltage in the inverter and AC/DC converter in the transmitter/receiver enables more efficient wireless power transfer.
Another way to increase the efficiency of wireless electric car chargers is to design the process to depend less on the orientation of the transmitter and receiver when they couple inductively. This is important because drivers may not be able to position the vehicle in a way that the two pads align perfectly.
The gap between the pads can also affect efficiency. The ideal gap is between 150 mm and 300 mm. However, better placement can be achieved by using a lowering mechanism on the vehicle to bring the receiving pad closer to the charging pad and take care of unevenness on the road surface or floor.
What if road builders get creative with wireless charging pads and put them on the road or other surfaces? Will it work?
Can wireless charging be embedded on road surfaces?
Wireless charging can be built into the road, with a few modifications. With a sensor included, the power transmitter can detect when a vehicle is directly above it. The charging starts when a car arrives and stops when it is driven off, without requiring the intervention of a human.
There are many interesting applications of embedded wireless charging on the road. For example, a Wireless Electric Vehicle Charging System (WEVCS) can be installed at traffic light stops, supermarket car parks, or other highway sections (dynamic WEVCS) so that vehicles receive a charge from the transmitters while driving. Public electric buses can be charged with embedded wireless chargers when they are discharging or loading passengers at bus stops. Taxi fleets can also charge wirelessly when they wait for riders at the taxi rank.
Wireless EV Home Charger
Wireless EV chargers can be installed at home, just like plug-in chargers. The Plugless Power, for instance, uses inductive charging to transfer power, meaning you only have to park over the transmitter and do not have to handle cables before charging your vehicle at home. It is the first 3.3 kW and 7.2 kW wireless chargers on the market. The Plugless Power has a smartphone app that lets you monitor the charging process via notifications.
Wireless charging is a natural step in the evolution of electric vehicles. It is a very convenient and efficient way of charging the battery and can be installed at home, on the road, or in other places where electric vehicles come to rest.