Issue with J1772 in the Bug

As previously stated in my last post, I did encounter an issue with the J1772 protocol in the Bug. The BMS system I installed, the Orion BMS 2, has built in J1772 capability and simply requires you to hookup the wires to the charge port in the car. Unfortunately, due to the type of charger I was using, this led to error after error and would not allow the BMS to function correctly. I then had to build my own system that would handle the J1772 connectivity.

The parts that need to be handled on the car side, is simply building the network of resistors so that the EVSE is on the same page and knows what is going on. J1772 is essentially a "handshake" between the car and the charging station to make sure all of the factors are in correct order. For my purposes, I simply need to make sure the EVSE knew when it was connected, and the car needed to be able to send a signal to the EVSE when the button is pressed on the plug to cut all power for disconnecting.

In the above schematic, while somewhat complicated, gives you a simplified idea as to how the signaling works. I will explain it more in depth in a later post, but this was the schematic that I had to use when designing my control board. Note, I was wiring a board to control the right side of this diagram, so the "vehicle inlet" and the "vehicle controller" parts.

This was the final board that I came up with, utilizing dual microcontrollers. The second microcontroller should be ignored because this is actually a hybrid board that does two different tasks. But for now, you can see the large network of resistors that makes up the car side of J1772. A microcontroller is simply used to monitor the voltage on one of the J1772 port pins that let you know if the button has been pressed, before disconnecting. This then allows the car to send the signal via the resistors, to the EVSE to cut all power. All of these things happen within just a few milliseconds, faster than the blink of an eye.