The key success factor of wireless charging for electric vehicles and plug-in hybrid cars is the interoperability. Standardisation of these made interoperability a reality: last year the main automotive companies agreed on a standard called ‘SAE J2954’.
The main parameters that had to be set are the distance between the two coils, the functioning frequency, the alignment tolerance, and of course the charging power. One of the main challenges was also to define requirements and testing procedures to avoid any risk of magnetic field exposure.
The specified guidelines of the SAE J2954 standard are a common frequency of 85 kHz and a power of 3.7 kW to begin with the standard also includes higher power levels (7.7 kW, 11 kW and 22kW). The standardisation of systems working at 3.7 kW and 7.7 kW was tested and validated in 2016. 2017 is given to higher power tests.
The standard also defines an alignment methodology to allow the driver an easy parking and guarantee an efficient charge.
These criteria allow the wireless charge to work properly with a high efficiency over 90%. The efficiency of such a charging system is indeed the same as the efficiency of a charge with wire, even with an important ground clearance.
The main interest of this kind of charging system is its ergonomics: it is much easier for a driver to simply park his car and walk away than to look for a heavy and dusty cable lying on the floor and then plug it in. Furthermore, it is not necessary to charge a plug-in hybrid car since it has a fuel tank, and everyone knows that human beings tendto be lazy, therefore wireless charging system is the solution to guarantee a smart use of the vehicle battery.
Jeanne, Consultant, Leyton France