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Help diagnosing J1772 EVMS Fault detection

375 Views 0 Replies 1 Participant Last post by  CantDecide
Hello, I'm having trouble diagnosing a problem with my J1772 charging system. I have a ZEVA EVMS system with a TCCH Elcon 6.6 kw charger and a ~400v battery back. I have tried both with the AVC2.r and ZEVA J1772 interfaces - both seem to work fine, though I'm sticking with the ZEVA interface for now as the relay on the AVC2 seemed to get stuck.

If I plug the charger directly into the wall and trigger the charger, everything seems to charge fine. If I use a J1772 EVMS to trigger the charging, but feed AC voltage via a home built extension cord, this also charges fine.

I noticed when I use a 120v EVSE, I charging seems to work fine up to about 4.1-4.2 amps, then it trips and shuts down. I have one EVSE with some diagnostic fault lights, but when that one trips it just shows "car". Not very helpful.

The AVC2 troubleshooting guide says this:

EVSE faults are usually leakage currents in the car to ground. Disconnect the red and Black power leads from
the vehicle inlet connector to your charger and see if the fault goes away. Then work forward finding the fault
which is likely leakage to ground. Lead acid batteries are notorious for this kind of leakage. Instruments on
the main battery back that are not isolated are another common ground fault.
When I disconnect the AC connection, the EVSEs do not detect a fault. I have lithium batteries, so I am guessing the last sentence above is the key, but I don't know how to go about hunting down this type of problem, and I don't fully understand what it means.

Would this imply some type of short between a BMS cell tap and the 12v vehicle ground? If so, how would I go about finding it?