SAE International released, on October 22, new J2954 wireless charging standard for electric vehicles, which took quite some time (more than a decade) to develop.
According to the official description, it's the first global wireless charging standard that specifies, in a single document, both the electric vehicle- and supply equipment (EVSE) ground-system requirements for wireless charging of electric vehicles. It defines acceptable criteria for interoperability, electromagnetic compatibility, EMF, minimum performance, safety, and testing for wireless power transfer (WPT) of light duty plug-in electric vehicles.
For now the SAE J2954 is only about:
- simple one-way wireless charging ("unidirectional") from the grid to the vehicle
(bidirectional energy transfer may be evaluated for a future standard)
- stationary application (charging while vehicle is not in motion)
(dynamic applications may be considered in the future)
- only above-ground (surface mounted) installations are covered
(flush mounted installations have been discussed but are not yet ready for inclusion)
- both home and public charging
- enables alignment for manual/autonomous parking
Image description: "Functional elements of a Wireless Charging System consist of three major partitions:
(1) the grid-connected converter with its attendant GA coil for power coupling, with a communication link to the vehicle system (the GA);
(2) the vehicle-mounted VA coil with rectification, filtering components, and charging control power electronics necessary for regulation/safety/shutdown when required, with a communications link to the infrastructure side (the VA);
and 3) the secondary energy storage system, battery management system components, and associated modules necessary for in-vehicle communications (CAN, LIN) required for battery SOC, charge rate, and other necessary information (the energy storage system)."
Once the vehicle with a Vehicle Assembly (VA) pad parks over a Ground Assembly (GA) pad - both SAE J2954-compatible - there is a communication handshake and charging begins automatically (no physical connection or any additional actions needed).
There are three power levels of the SAE J2954 wireless charging:
- WPT1: 3.7 kW
- WPT2: 7 kW
- WPT3: 11 kW
There is no WPT4 (22 kW) that was hinted at a few years ago (but maybe it will appear at some point in the future).
We guess that the operating frequency of the magnetic resonance field between the transmitting pad on the ground and a receiving pad remained at 85 kHz (81.39 - 90 kHz). Then it's converted from AC to DC and goes into battery.
At a 10-in. (250-mm) ground clearance, the grid-to-battery efficiency is expected at up to 94%.
- There are three overlapping ranges of vehicle ground clearances from 100 to 250 mm (3.9 to 9.8 in.)
- Parking tolerances are:
- ±75 mm (3.0 in.) in the direction of travel
- ±100 mm (3.9 in.) in the lateral direction