Daimler and Conductix-Wampfler are collaborating on a research project on the wireless inductive charging of electric vehicles co-funded by Germany’s Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit, BMU). The main target of the project is a safe, automotive-grade charging system with maximum efficiency and minimum weight and package.
The two project prototypes, built using the B-Class E-CELL with range extender, are equipped with an electronic rectifier and a collector coil integrated into the underbody cover. Main components on the infrastructure side are the supplying electronics and the charging coil, which was realized in two variants: above- and below-ground.
Besides the wireless energy transfer, the other functional aspects are the wireless communication between infrastructure and car; the driver assistance function for “driving onto the position above the charging coil”; the automatic start of the charging process; and the vehicle identification.
The inductive transfer components were designed with automotive specific requirements and optimized in packaging and weight. Conductix-Wampfler—which has experience with inductive power transfer in manufacturing automation as well as on from the wireless charging of electric busses in Genoa and Turin, which have been in operation since 2003—developed all components of the system.
Daimler defined the functions of the charging system on the car’s side and developed the assistance system for driver support. The coil integration within the underbody cover of the cars was designed and supplied by Röchling Automotive.
After the prototype vehicles had been built the complete system was mechanically and electrically integrated and taken into operation as a whole. Two inductive charging stations are in the field and are intensively used for the everyday-tests.
First results confirm the considerable gain of comfort in comparison with cable-based charging and that inductive charging is suitable in principle. Further potential optimization regarding package, weight and integration in future vehicle model lines was identified and will accordingly be further developed.
There was an evaluation of the first “driving-experiences” with study participants who had to “drive onto the optimum charging position”. After two or three exercise runs this could be well achieved supported by parking assistance functions. The system tolerates smaller deviations within the range of a few centimeters without noteworthy loss of charging efficiency or transferable power. Also, the system showed already good results regarding electromagnetic compatibility. Future engineering work will seek to optimize this as well as to improve efficiency and to develop solutions for a series production application.
The partners are also evaluating new common projects with potential inductive charging applications in small commercial vehicles and buses. The results of the current tests are important to national and international standardization activities, with the aim to guarantee interoperability of inductive charging systems of different suppliers and vehicle manufacturers.