This is further than I've ever gotten with anything but the original hardware/circuit
24 parts total. All easily sourced. Going to need to bring along my laptop and CAN sniffer to monitor what's going on. Possibly write in some extra debugs on the Arduino program to track the process. It "started" the session but didn't actually start sending current - though the current requests come from the car side.
If nothing else, I have to make sure that it's not just shutting down the CAN output - this chip will stop transmitting if it doesn't see any other activity on the CANBus. I'd hope the charger keeps sending frames but if it does not, I might need to make some more changes.
Edit: I need to remember the Due runs 3.3V I/O. I'm going to smoke my CAN1 RX pin without even realizing. So, add 2 resistors to the part count...
Edit2: Confirmed I did NOT kill my secondary CAN RX pin. I now have a voltage divider on that output from the CAN transceiver and I'm just sending raw 3.3V to the TX input since that is high enough to read as logic high for 5V.
This is what I'm working with currently: