Siemens is developing an inductive charging system for electric car batteries.
The non-contact charging technology was developed in cooperation with BMW, and works regardless if the vehicle is stopped for a long or short time.
According to Siemens, the charging systems can be easily incorporated into the environment, making them nearly invisible, with protection against vandalism and wear and tear.
The technology has been developed to such a degree that it will be tested in Berlin, Germany come June 2011.
Siemens claims the project is another step in trying to improve the take-up of electric cars. One big obstacle to the use of electric vehicles is the lack of extensive and reliable charging infrastructure.
Electric cars have to recharge their batteries more often than vehicles with combustion engines need to refuel, but plug-in stations are few and far between, and while there are various efforts to improve charging times, current technologies require some time for batteries to be charged.
Siemens’ work is on charging techniques which are adapted to the needs of drivers and vehicles. Inductive energy transmission concept would make it possible to automatically recharge vehicles such as taxis waiting at cab stands.
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 15cm. 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.
According to Siemens, 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.
This means the generated magnetic field is below the internationally recommended limit of 6.25 microteslas.
The prototype will have a charging power of 3.6kW. The real-life trials in Berlin will help Siemens find out which improvements are needed to integrate the system into series-produced vehicles under real-life conditions and to obtain customer feedback for future customer-oriented charging solutions.
