FoxEss H3 with Runnci Yun Modbus to RS485 Adapter - Problem with connection

[NintendoTito]

Hello everyone,

I hope someone here at the source can help me with my problem. The following text has already been posted in the Home Assistant forum, but I have not received any feedback there. I have already connected the cables again, restarted the Pi4 with Home Assistant OS several times, but the problem persists.

After a few minutes the connection breaks off, an entity is only displayed and says:
Modbus Error: [Connection] Failed to connect[ModbusSerialClient pollserial:///dev/ttyUSB0:0]

The problem is described below:

I created a Modbus to RS485 connection using the Runcci Yun USB adapter. Cables neatly tinned and carefully connected.

The good news: It worked, I installed the integration via HACS, “played through” the configuration wizard and the data appeared. Daily production, total consumption etc.

However, Hacs pointed out that a restart was due.

Since then it no longer worked, I got the following message:
Modbus Error: [Connection] Failed to connect[ModbusSerialClient pollserial:///dev/ttyUSB0:0]

I then unplugged the USB adapter and plugged it back in and the values appeared again. But that probably only lasted half an hour, then the connection was lost again.

The problem remains. USB out and back in, data is displayed, then after a few minutes connection gone, no data displayed except
Modbus Error: [Connection] Failed to connect[ModbusSerialClient pollserial:///dev/ttyUSB0:0]

I then tried it once or twice more and then I had a moment of shock: it had apparently shot the entire Home Assistant. No more access to the Yaml, all entities gone. No access to backups (at least the local backups, I still have some online). Even a restart via the interface was not possible. Fortunately, when I disconnected the Pi4 from the power supply and reconnected it, everything still worked.

Could the Modbus RUNCCI connector have caused a short? Anything else would be a strange coincidence.

[NintendoTito]

@nathanmarlor Am I doing something wrong or is the device defective?

I would be very happy about help

[FozzieUK]

Not sure whether it is the same problem, but I have found the RUNNCI usb adapter to be very poor quality - I know the earlier ones worked ok but i've had friends buy them in 2024 and they fail after a few minutes, restart and it works for a few minutes - move the adapter to a known good system and it fails after a few minutes - move a known working RUNNCI adapter to the faulty system and it works. In fact of the 3 they bought from amazon last year each was faulty.

They bought this adapter https://github.com/nathanmarlor/foxess_modbus/wiki/DSD-TECH-SH-U10 and it worked straight away and has been working since.

[NintendoTito]

Mmh, that would of course be annoying. Can you tell me which contacts I should connect the two cables to on the DS Tech? It seems to have 4 contacts, but there are no instructions.

[FozzieUK]