There are two induction coils. One is in the charger, and one is in the device to be charged. The coil in the charging device has alternating current electricity run through it which generates a rapidly alternating magnetic field. When the coil in the charged device is close enough, that alternating magnetic field creates an electric current in it, which is then used to charge the batteries.

This basic process of one coil inducing a current in another is not something new, that's how transformers work. What's new is that the accompanying electronics has gotten very efficient both at the producing side and at the receiving side, and in using the natural magnetic resonance frequencies of the coils.

The device to be charged, of course, has to have the right coil and other electronics. Some are built in, some are built into a special sleeve for the device, and some are even built into the battery pack. This is currently being standardized.

Oddly enough, it was used for electric cars before it was used for personal electronics. It was used by several cars in 1998. It's also quite widely used in electronic toothbrushes because it allows the battery to be completely sealed against water. But the car folks gave up on it after a few years. Now they are looking at it again. The question is whether it can be made as efficient as charging with wires and engineers are arguing on both sides. You don't want to struggle for best mileage and then be wasting electricity in the transfer. With hand held electronics the amounts are too small to matter.

At any rate, the car builders are working on standards in case they get the rest ironed out. I'd just like to see lots of electric cars out there, which should take a few years anyway.

The photo is a MaganaCharge: "Inductive MaganaCharge requires a heavy amount of computer communications to check on number/ type/ capacity/ performance of batteries - limited to GM EV1, Toyota RAV4-EV, Chevy S10 EV and Nissan Alta EV vehicles." Those are old, non-production experimental cars.

Here's the answer right from the horse's mouth. It looks like there could conceivably be one for your car today if someone built it--I'd imagine it would be either a mat you park over or something like a proximity card that you'd park near.

"The Powermat Wireless Charging System provides a simple, fast and efficient way to keep all of your favorite personal electronic devices charged. Enabling your devices with Powermat Receivers allows you to Drop and Charge them on any Powermat Mat to experience wireless charging.

Magnetic Alignment
A magnetic attraction between every Receiver and each access point on every Mat assures that alignment is precise and the most efficient charging will occur.

RFiD Handshake
Communication between the Mat and the Receiver allows the mat to deliver an exact amount of power for the proper length of time so that the transfer of power is safe and efficient and no energy is ever wasted.

Audio Confirmation
A unique sound tells you that a solid connection has been made and your device is charging. A second, similar sound is heard when the device is removed.

Charging Light Indication
Each access point has a corresponding light indicator that informs you that wireless charging is occurring.

Auto Shut Off
When a device reaches full charge, power is shut off to that device. This not only saves energy, but it also prevents overcharging of the device's battery, which can shorten battery life.

Full Charge Check
Once full power is achieved and the Auto Shut Off has occurred to save energy and avoid overcharging the device's battery, the system will monitor the status of the battery.

Industrial Design - Mats
Powermat Mats are designed to work in a wide range of locations and environments. Whether you are looking to charge a single device on an end table or night stand, multiple devices on a desk or countertop or take the ultimate in convenient charging with you on the road, there is a Powermat solution that is right for you and your needs.

Industrial Design - Receivers
Powermat Receivers are designed to perfectly integrate onto or into the devices they will enable to charge wirelessly."

PowerMat is an exciting new wireless charging technology. It was first demonstrated in 2008 and early 2009 and is now available to buy for the home and office.

So what is PowerMat? It is a small device that uses wireless charging to charge your most important gadgets like cellphones (including the iPhone and Blackberry), video games (including the Nintendo DS), and iPod without you having to connect them to a charger or plug them into the wall. The PowerMat itself is, of course, plugged into the wall and connected to mains electricity by a wire, but from then on everything is wireless. You drop your device onto the PowerMat and it gets charged wirelessly, without you having to do anything.

So how does PowerMat wireless charging work?

The technology behind PowerMat is known as 'electromagnetic induction' (or just 'magnetic induction'). Michael Faraday is generally credited with the discovery of the induction phenomenon in 1831 though others were working in the same field at the time.

This electromagnetic induction is officially defined as "the production of voltage across a conductor situated in a changing magnetic field or a conductor moving through a stationary magnetic field" but that does not mean very much to most people. A better way to put it is that it is a means to transfer electrical power using a shared magnetic field.

Consider this arrangement:

1. Put electrical power into a coil of wire

2. This will produce a magnetic field around the coil that affects any metal within the field (as demonstrated by Faraday)

3. Change the field quickly over time and an electric current will be generated in the metal

So what is happening when a PowerMat is charging is that it is generating rapidly changing magnetic fields above the mat; these are converted by receivers on any devices on the mat into electrical power, and so these devices get charged. The magnetic fields and electrical currents are, of course, very small and so they can work on handheld gadgets without being a health risk to humans.

The same technology is used in a huge number of other devices and systems including generators, motors, transformers, some cookers, induction welding, and so on. Perhaps to most people the best known example is in rechargeable electric toothbrushes, where they are familiar with dropping a toothbrush into a 'dock' daily to keep it charged. However they may be unaware that similar systems are also operating in electric guitar pickups, video tape players, and computer graphics tablets.

PowerMat is currently the best known example of a wireless charger but this technology is developing rapidly and soon we will see it in many other applications and products. The PowerMat company itself is planning to extend the technology and feature it in kitchen counters, walls, and other surfaces around the home. One day this technology may be used everywhere and be invisible, it will be so commonplace. Finally we will be freed of the endless tangle of chargers and wires around the home.