The setup is exactly the same as discussed above: an EM530 3 phase energy meter (by Carlo Gavazzi) is connected via an FTP cable to the RS485-USB interface by Victron, which is connected to the USB input of the Cerbo GX unit. This installation worked flawlessly for around 7 months, before the communication with the energy meter failed. After reconfiguring the energy meter, checking all the settings, and replacing components, it sometimes makes contact for hours to days and works fine, but then it randomly loses contact again.
We have replaced the energy meter, FTP cable and RS485-USB interface. I also went through all the trouble-shooting steps suggested in the linked discussion. On that page, it was also suggested to replace the Cerbo unit, but it is not discussed whether that resolved the issue.
The energy meter itself does not appear to be the issue; on the display the measurements are shown correctly. I can also connect to the energy meter with my laptop (through the Carlo Gavazzi software), by removing the USB from the Cerbo and plugging it into my laptop. So the FTP cable and RS485-USB interface (which I already replaced) don’t seem to be the problem either.
Are there any other steps I can take? Or would it be possible to link me to the user who posted the original discussion (named “Wattpeak”)? It would be great if I can ask them if and how they ended up resolving this issue.
Not sure if this is the same issue I was having with my Multiplus-II, an ET112 as a grid monitor and an EM111 to monitor solar as it’s quite a different setup.
It would work fine for months and then I would loose connectivity to all my meters. If I reset the VE.bus they would all come back. It only ever seemed to happen in the summer.
I replaced the hub I was using with a StarTech.com 4 Port USB 2.0 Hub with Power Adapter and the problem was fixed.
If you are running over a long cable maybe it’s a similar issue .
Thank you so much for the suggestion! This might very well be the solution.
Initially the RS485/USB interface was connected directly to the Cerbo, but maybe it didn’t deliver enough power to the USB. So now I have placed an externally powered USB hub (I went for 3.0 just to be sure) inbetween, and the issue appears to be resolved.
However, the original setup also sometimes worked for hours on end before failing, so we will only know for sure after testing for a couple of days.
With the USB Hub it appears to be working slightly better, although far from perfect. After installing the hub the connection seemed to be stable, but soon the communication was lost for a period of 4 hours. Then a period of 6 hours where the communication was on-and-off. However since then it seems to be working better: it sometimes misses one logged data point (logged with a frequency of one per minute) but then re-connects automatically and communicates fine.
Since we are only trying to limit quarterly grid offtake values to the contracted power, the communication is likely enough for this purpose. But it is certainly not as consistent as we would expect, or as consistent as it worked for a long period before these issues started. So I’m still open to suggestions!
Mostly thinking out loud …
Anything that takes power from the USB (5v) bus will have to be very forgiving of voltage drops, or handle those drops gracefully.
A powered USB hub often solves or reduces these kinds of issues - the PSU will be capable of much higher currents than the Cerbo is.
There have been issues reported with too many USB devices plugged into a Cerbo, related mostly to how much CPU power the cerbo has to dedicate to each USB device (if they are for example a USB to VE.Direct) but there will also be a limit to how much power the Cerbo can deliver to the USB bus(es).
The RS485 signal is very reliable and resilient, but 5v power over USB is not, so you may be in a situation where the signal is clean and clear, but the receiving device is browning out. If you have some way to graph the 5v from the USB hub, you might see patterns that explain the fault.