Wireless EV Charging Explained

With the first batches of electric vehicles just months away from hitting the market, all eyes turn to that part of the EV world called infrastructure. A sort of make it or brake it deal, the existence, or for that matter the lack of charging points to support the rise of the electric vehicles, is perhaps just as important for the industry as the willingness to adopt this alternative means of transportation. The most recent study by Pike Research shows that by the year 2015, some 4.7 million charging points will be installed worldwide. There are currently several big players on this booming market, including AeroVironment, Better Place, Coulomb, ECOtality, GE, Panasonic, Samsung, and Siemens. Their number is likely to rise in the years to come, as the need for charging points will increase as well. For now, most of the technologies aimed at charging the electric vehicles are cable-based, meaning that in order to charge an EV or plug-in hybrid, you need a power cord which to plug into a socket, be it in your house or in the points installed on the road. There is, however, a different approach to charging, one which, in time, may prove to be more convenient for the EV owner. That technology is simply described as wireless charging: it eliminates the need for a power cord and a socket and works based on the inductive power transfer phenomenon, which can currently be seen in electrical transformers. INDUCTIVE POWER TRANSFER
The inductive power transfer phenomenon has been discovered by Andre-Marie Ampere in 1820 and is simply described as the ability of the electric current to produce a magnetic field and transfer it to nearby similar systems. Later in the 1800s, Nicola Tesla experimented with the concept and managed to power lights in the ground at his Colorado Springs experiment station without using any cables.

The concept works a bit like this. When electricity travels through a wire, a magnetic field is generated. That field can be amplified by arranging the wires into a coil. The more loops in the coil, the more powerful the field. That field can be used to power electric systems in the vicinity, without using any cables.

Inductive power transfer has however its limitations. Because of the field's tendency to disperse, it is largely ineffective to place the object you need to recharge at a bigger than reasonable distance.


Although there are several companies currently developing wireless charging systems, only one has decided to launch the system onto the market in 2011. Called Evatran, the company has developed what it calls Plugless Power, a system based on inductive power transfer which will be used to recharge electric vehicles.

The system consists of a Plugless Power vehicle adapter, created to the specs of each electric or plug-in hybrid vehicle model and a fixed Plugless Power station to which the adapter connects and charges the batteries.

Plugless Power is in fact a transformer split in half, with one half located in the power station and one on the vehicle. When the two halves are being brought together, the magnetic field generated by the power station expands to encompass the vehicle's half of the transformer and the batteries begin charging.

To charge the vehicle, all a driver needs to do is pull close to a Plugless Power station. Very close, 2 inches (5
cm) close, to be more precise. When the station detects the car, it aligns a built-in parking block so that the car does not hit the station itself. Once the car has been parked, electricity begins flowing between the two halves of the transformer, charging the battery.

According to the manufacturer, the time needed to recharge the batteries of an EV will be similar to the one required when using a conventional system. Despite the small distance between the car and station, the manufacturer expects a 10 percent efficiency loss, one which, it claims, will not affect however the charging time.


Having no power cord, Plugless Power makes recharging an EV a type of park-and-forget deal. Users will no longer have to go to the car or charging station to pull the cord and they will no longer have to plug the vehicle in.

The system has been developed by Evatran to fit each and any electric vehicle, so that it meets the factory required specs and does not require modifications to be brought to the vehicle's design or electric system.


The system still requires some modifications to be brought to the vehicle, because the vehicle adapter will have to be installed. Although it will probably be approved by the EV manufacturers, being provided as an aftermarket gizmo may cause unrest to some owners.

Also because it is an aftermarket gizmo, the system costs extra. Evatran will charge $800 for the adapter to be fitted onto the vehicle. Not a big price, but still $800 more than when using a regular power cord.
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About the author: Daniel Patrascu
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Daniel loves writing (or so he claims), and he uses this skill to offer readers a "behind the scenes" look at the automotive industry. He also enjoys talking about space exploration and robots, because in his view the only way forward for humanity is away from this planet, in metal bodies.
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