BMW Wireless chargingA full recharge of an electric car takes quite some time, and that’s no option when you’re running out of juice during a trip. Siemens and BMW seem to work on a fix, and that’s wireless charging.

Unlike conventional cars with combustion engines, you can’t just go the next station and fill up within 5 minutes.
BMW recently announced the introduction of the BMW i sub-brand, a model line-up to offer mobility solutions for the future. And while the development for the BMW i3 (and BMW i8) continues for the market launch in 2013, there are still some things to consider and some problems to solve to make the idea of electric cars work.

The charging station is connected to the public grid by a primary coil that is completely underground. A secondary coil is attached to the car, and the distance between the two coils is typically between eight and 15 centimeters. When the driver starts the charging process, an electric current begins to flow through the primary coil. The resulting magnetic field induces an electric current in the secondary coil, which recharges the battery.

car's batteries
Electricity is transmitted from the grid through all of the components to the battery at an efficiency of more than 90 percent.The magnetic field is generated only in an exactly predetermined area between the two coils. The system therefore generates a magnetic field whose strength in and around the vehicle is far below the internationally recommended limit of 6.25 microteslas.