At Hannover Messe 2011, Siemens presented a development project for inductive charging (“Contactless Charging of Battery-Electric Vehicles”), developed in cooperation with BMW. In June 2011, the capabilities of this non-contact charging system will be tested in a project funded by the German Environment Ministry and involving several vehicles in Berlin.
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. Electricity is transmitted from the grid through all of the components to the battery at an efficiency of more than 90%.
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.
Starting in May, a prototype with a charging power of 3.6 kW will be tested in an electric vehicle. Beginning in June, the test will be followed by trials in Berlin to determine 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. The system also enables the smart use of energy, whereby the car also serves as a storage unit and most of the energy is surplus electricity from solar and wind power facilities.