SAE J1772 Charger Interface

Owned by Pei Liang Guo
Feb 25, 2018

The motor interface board will also responsible for communicating with the charger or the electric vehicle supply equipment (EVSE) via the the SAE J1772 signal protocol. The charger informs the the vehicle about the state of the electrical supply and the current rating. The vehicle indicates the electrical connection is established and requests air ventilation if necessary.

Signal Functions

  • Verifies that the vehicle is present and connected
    • The vehicle uses a 2.74-kohm resistor to indicate charge is physically connected to the vehicle
  • Permits energization/de-energization of the supply
    • The vehicle engages another 1.3-kohm resistor to indicate ready to accept energy
  • Transmits supply equipment current rating to the vehicle
    • Reads a PWM signal 
  • Monitors the presence of the equipment ground
  • Establishes vehicle ventilation requirements (will not implement)
    • This is meant for battery that emits hazardous or toxic gases during charging
  • Optional proximity detection (probably will not implement)

Suggestions from the SAE Specifications

  • The diode should have a reverse voltage rating of at least 100 V
  • The contractor output can rise from 0 to 170 V in a few nanoseconds
  • Transients from lightning strikes and other high energy sources may be coupled through the cable.
    • Transient protection is recommended for both charger and the vehicle

AC Level 1 vs AC Level 2 Charging

  • Level 1
    • 120V AC, maximum current of 16A
    • Connect to the common household NEMA 5-15P plug
  • Level 2
    • 208 to 240V AC, maximum current of 80A
    • Dedicated AC EV supply equipment