External grid meter dissappears frequently while charging causing Passthru mode

Q&A and troubleshooting
, , , , ,
1

During charging my 3-phase MPII 5000 system switches frequently to Passthru mode. There seems to be a relation between SoC and occurances. This starts to happen more often when the SoC increases. It can happen as often as 30 times per charging cycle.

When debugging this issue I used Node-RED for alarming me. I found that it happens when the connection with my external Grid Meter is lost. This is a CG-EM340. The grid meter works fine otherwise.

So I made an alarm in Node-RED for a frozen power value of the grid meter. This disconnection also only happens during charging, and synchronizes with the Passthru mode perfectly: no disconnection other than during charging. All Passthru’s matched exactly with loss of the grid meter connection.

Therefore I am possitive that Passthru mode is caused by lost connection with the grid meter.

I also found an error message in Modbus/TCP matching the exact time of the last Passthru event and related to Modbus connection to the grid meter:


"Error processing function code 3, unit id 30, start address 2600, quantity 38, src ::ffff 192.168.178.20 Error finding service device type grid at device instance 30"

The grid meter is connected via an official Victron USB-modbus device (so why error message in modbus/tcp???)

There are no other instances with VRM id 30.

The problem started on earlier versions of VenusOS, I don´t exactly know which version. It was present in 3.50/3.52. Right now I am testing 3.60~11. Still there.

Has anyone seen this problem before? Is it a bug? Why only during charging?

1 Like
2

You can try to reproduce that by setting the grid-setpoint to a high positive or negative value.

How long is the RS485 cable?
Is it installed parallel to the power cables?

3

Not that long, more or less 2 meters. It is an original Victron USB-cable. I assume that it is a twisted pair cable.

It is installed next to AC-power cables going to the mains supply over a distance of only 80cm’s. It is not close to DC-power cables. The Victron wiring guide has no topic on RS485

If the RS485 suffers from vincinity to AC-power, why only during charging? During discharging the current is in the same order of magnitude without any disconnection ever. The direction of the energy flow (positive or negative) can not be a factor, can it? Or when idle at a sunny day my 10kWp AC-out connected PV-panels are supplying to the grid even more power at higher currents via the same AC-cables.

The problem resembles Em24 disappears in device list and system goes in passthru mode In this case the grid meter is connected via modbus/TCP instead of USB.

It also resembles Quattro going to Passthrough when it should be Charging In this case the internal grid meter of the Quattro is used.

The resemblence could be a red herring of course.

4

You can try to reproduce that by setting the grid-setpoint to a high positive or negative value.

I could try tomorrow. I was under the impression however, that this setting is ignored in DESS trading mode? Isn´t that correct?