Wireless Charging

Wireless Charging

After three years of work, the SAE International J2954™ Task Force for Wireless Power Transfer (WPT) of Light Duty, Electric and Plug-in Electric Vehicles has finally announced that it will shorten its name OEMs, WPT Suppliers, industry experts and government representatives who make up the Task Force agreed upon two key factors for the Technical Information Report (TIR) on interoperability for the first phase of pre-commercial development.

First is the frequency at which power transfer will be done in wireless charging - 85 kHz nominal.

Jesse Schneider, Chair J2954 Taskforce, said:

“A common frequency of operation for WPT is essential for interoperability. After 3 years of international collaboration and investigation within the team, consensus had been reached on a nominal frequency of operation for the light duty vehicle guideline. The SAE team has determined this nominal frequency of 85 kHz for SAE J2954. This frequency lies within an internationally available “frequency band.”

This 85 kHz frequency is within an internationally available (81.38 - 90.00) kHz band.

We can assume that different manufacturers developed to date devices with different frequencies and that this SAE agreement is some kind of milestone.

The second big thing is that the SAE determined three power classes for light duty vehicles, WPT 1, 2 and 3.  Limits are defined by the maximum input Wireless Power Transfer:

SAE TIR J2954™  WPT Power Class
Classification WPT1 WPT2 WPT3
Private/Public Parking  L.D. Fast Charge
Maximum Input WPT Power Rating 3.7 kW 7.7kW 22 kW

No word on fast wireless charging with power levels of over 100 kW - sometimes used in buses.

Whats next? The Task Force plans to complete the TIR in early 2014. The SAE Technical Information Report will be followed by publication of SAE J2954™ Standard, based on field data confirmation.

"The SAE International Task Force is currently working on completing the remaining interoperability topics, including factors such as the minimum coupling factor “k”, alignment, and coil geometries."