SAE J2954 information

SAE J2954 is a standard for wireless power transfer (WPT) for electric vehicles led by SAE International. It defines three classes of charging speed, WPT 1, 2 and 3, at a maximum of 3.7 kW, 7.7 kW and 11 kW, respectively. This makes it comparable to medium-speed wired charging standards like the common SAE J1772 system.^[a] A much more powerful WPT9 is being defined in J2954/2 for 500 kW charging for heavy-duty vehicles which have the room necessary to mount the larger induction plate.^[2]

The system works along similar principles as inductive charging, but uses the resonant inductive coupling concept with a demonstrated efficiency of around 85%. This makes it similar to wired chargers, where the higher theoretical efficiency is offset somewhat by necessary isolation systems that prevent high-current back-feeding, systems that the air-gapped J2954 does not require. Best-in-class medium-speed chargers are around 94%.

Development of the underlying resonance transfer concept was developed by Marin Soljačić at the Massachusetts Institute of Technology (MIT) and then spun-off as WiTricity in 2007. WiTricity has led the SAE standardization efforts, which began in 2012 and have undergone two Recommended Practice releases as of 2019^[update]. The final standard was published in 2020. WiTricity predicts that J2954 chargers will be available as add-on features beginning around 2022.

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