BMW wants to do away with power cables and have drivers of its i3 and i8 plug-in hybrids using inductive charging pads. The company says that this will be a key step to make driving electric vehicles easier and more pleasant. Prototype systems have reduced the recharging time on an i8 to under two hours.
An agreement with Daimler will see the two companies jointly develop and implement a standardised technology for inductive charging of electric cars and plug-in hybrid vehicles.
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The system consists of two components: a secondary coil in the vehicle floor as well as a base plate with integral primary coil that is located underneath the car, for example on the garage floor. The arrangement of the coils, and consequently of the field pattern, is based on a design derived from their circular shape that is compact, lightweight and helps restrict the magnetic field. Charging is stopped automatically if a foreign body – the family cat, for example – is detected between the two plates.
The target charging rate is 3.6 kW and the system is 90% efficient. This means the high-voltage batteries in many plug-in hybrid vehicles can be fully charged in under three hours. It takes less than two hours to charge the BMW i8 using a fully working prototype of an inductive charging station. BMW says that it is also working on increasing the charging rate to 7 kW.
