'No ground' fault after charging starts

I have an electrician visiting next week to finally run the supply for OpenEVSE DIY kit. I originally assembled this kit last year and successfully charged my car at that point. I’m using a 230V coil contactor, and so have the (pink) AC RELAY wires connected.

Over the weekend I re-flashed the OpenEVSE controller & ESP32 to the latest versions (v7.0.6 EU & 4.1.1) and then attempted to test charge the car again. Unfortunately within a second of charging starting (State C) the unit shows a “No Ground” fault.

If I disable the “Ground Monitoring” test then the unit works normally and charges the vehicle.

I’m aware the normal causes for this are either missing AC_TEST connections or the OpenEVSE PCB not being grounded. In my case neither seem to apply, unless I’ve missed something! I’ve attached a photo of the wiring whilst it was on my bench, in-case someone can spot where I’ve gone wrong.

The OpenEVSE (v5) PCB is grounded via a cable onto the DIN Rail, which is itself grounded via the Earth Terminal Block - where the supply earth is connected. I have measured 0.2 - 0.3 Ohms continuity between the OpenEVSE PCB ground and the Terminal Block, and the same to the Type 2 Socket Earth.

The AC_TEST (Orange) are in the Type 2 socket conductors in the Grey ferrules, these:
AC_TEST 1 is connected to Contactor Port 2 for Type 2 Live
AC_TEST 2 is connected to Contactor Port 4 for Type 2 Neutral

Is there any further testing that can be done (on the bench) to validate this ground test? Is there a way to force it into State C without a car for example? I don’t have a simulator board, and unfortunately the OEM store is out of stock currently!

It sounds like you have done a thorough job troubleshooting. How are you connecting the EVSE to your mains power? Have you verified that there is a good ground connection to your supply? Maybe try a different socket to be sure.

Assuming there is a good supply ground available and the controller is correctly grounded and the AC test lines are connected, then there it could point to a hardware issue with the controller.

I’m pretty sure we do actually have stock of EV simulators, I’ll get the shop stock updated.

In my photo the EVSE is connected by flex from a bench top plug into the terminal blocks, when testing with my car I had it on the end of a Commando plug. It’s possible I suppose that the earth for the commando cable is damaged - but I’m pretty sure the Tesla UMC would’ve picked that up itself. The electrician will be running a new supply & earth rod in for the permanent install anyway.

I’ve put in an order for the EV simulator, thanks for fixing the store! At least with that I can test it on several plugs inside before the permanent supply is done next week. I can also try downgrading the controller firmware to stock and see if that makes a difference.

Ok great. I don’t think the FW is the issue, since the latest controller FW version has been used in production for quite some time now without any issues.

Received the simulator kit earlier today (although unfortunately the screw terminal was missing), but after testing now on an internal socket I’m still getting exactly the same behaviour.

I was able to definitively confirm though (by measuring at the PCB plug) that the AC_TEST 1 & 2 cables are both showing 240V when the contactor is closed.

It sounds like a hardware fault with the controller, please email [email protected] to organise a replacement.

Thanks Glyn but in this case the controller wasn’t purchased from yourselves - it came as part of the Advanced Kit from the US OpenEVSE store.

The charger is now installed outside and working fine but still only with the Ground Monitoring test disabled. The electrician measured about 30 ohms to ground via the earth rod he’d just fitted, so definitely no issue there.

Is there anything else I can do to troubleshoot this?

Is the North America version (for 120 - 0 - 120 V) different to the ‘export’ version for 240 V with an earthed (or nearly earthed) neutral (TN-S, TN-C or TN-C-S system)?

Did you manage to resolve this issue? What OpenEVSE controller FW version are you running?

No change sadly, for now I have had to leave it with the ground monitoring check disabled. The controller firmware version is v7.0.6 EU, and the ESP32 is on 4.1.1.

I am tempted to look at purchasing another controller to validate it, but given there’s a new wiring harness required it’s not the work of a moment unfortunately.

Where did you obtain this FW from? There has never been a 7.0.6 release, and 7.0.6 does not feature in the changelog! open_evse/CHANGELOG at stable · OpenEVSE/open_evse · GitHub

Doh, sorry Glyn! It is 7.1.6 EU, not 7.0.6. A typo from my earlier message that I reposted without validating again :man_facepalming: It was (at the time) the latest development build from the OpenEVSE Github.

Which version have you linked?


Ah 7.1.6 was a development release marked as a pre-release. There was an issue with the AC pin sampling, causing the GND fault. Our testing indicates that this has now been fixed. 8.2.0 is now the latest stable release. Please confirm if it works for you. Here is the link to 8.2.0.EU, best use this link to download, I’ll remove the FW I attached above to avoid confusion: https://github.com/OpenEVSE/open_evse/releases/download/8.2.0/openevse_eu.hex

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Sounds promising! Will flash 8.2.0 tomorrow and let you know how I get on.

So after two flashes with 8.2.0 EU it is now working normally! :smiley:

Not sure what happened on the first attempt, the controller was responding to RAPI commands but there was no LCD output and it wasn’t detecting the EV. After power cycling and then flashing a second time it came straight up.