Charging · 4 min

What J1772 is, and why a conversion cares

The SAE coupler on US AC charging. It exists so the wall only sends power when the handle is seated. Numbers live on the PWM note.

30 seconds

J1772 is the plastic coupler on almost every US EV that charges from AC at home. One end is the handle. The other is the inlet on the car. It is not “the charger.” The charger (OBC) lives on the vehicle. The J1772 path is how the station and the car agree it is safe to put mains on the pins.

Why a conversion cares: if you skip a real inlet, you are guessing when 240 V is live. The standard exists so a seated handle can take power and a squeezed latch kills it before the pins slide.

A little more

  • The station (EVSE) is the box on the wall or in the portable brick. It turns AC on and off.
  • The inlet is on the car. A home conversion needs that inlet, not a board sold as a “J1772 controller” that is actually the wall side. See why off-the-shelf J1772 controllers often do not fit.
  • Once you care about how many amps the station is advertising, that is PWM. The numbers live on the pilot, proximity, and PWM note.
  • Pack, cable, and fuse are a different problem. See pack planning.

What people get wrong

  1. Calling the inlet “the charger.”
  2. Wiring a wall-side board into the car.
  3. Treating the handle as a dumb extension cord.

If you want bench depth, go to the PWM note.