Weird behaviour when using multiple VM-3P75CT energy meters

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blieve asked Mar 20, '24

Weird behaviour when using multiple VM-3P75CT energy meters

Hi,

I recently bought 2 VM-3P75CT energy meters to measure the PV power installled on the AC-output of an ESS. So both are in the PV-inverter role.

Both are on the same VE.Can to a Cerbo GX. (they are also connected via the ethernet port but that is not used on the cerbo's config)

I noticed a few things that are not what I expected, I guess also a few of them bugs.

First: in remote console they both show up (so ok), altough one seems to measure only a fraction about what is happening (I still need to investigate this, any ideas are welcome)

In VictronConnect under the cerbo in VRM tab, it shows 2 but 2 times the same name with weird values:

(under the local tab it is ok, because they are also ethernet connected)

In the VRM device list, only one:

On the VRM firmware tab, I need to press scan, 2 or 3 times before both show up (don't know if this is normal behaviour). Altough this morning this seems to be fixed.

Under Modbus TCP services, only 1 shows up (so homeassistant integration also only sees 1)

Same issue in node-red (only 1 available):

Can someone shed a light on this?

Thanx!

Energy Meter

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blieve answered · Mar 21 at 09:54 AM

Apparently a bug in VenusOs sometimes assigning a duplicate VRM instance 0. Victron logged in remotely to do a fix and now it is working as expected.

Will be fixed in a future version

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Modifications Space

Node Red Space

Answer 1 · 2024-03-20T09:15:18Z

duivert answered · Mar 20 at 09:15 AM

did you use VE can terminators on both ends?

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blieve commented · Mar 20 at 09:31 AM

yes, I did

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Answer 2 · 2024-03-20T09:32:54Z

nickdb answered · Mar 20 at 09:32 AM

Don't connect LAN and CAN.

Remove the ethernet and try again.

I am also not sure if the system actually supports two meters in the same PV role. It would be like trying to configure two grid meters. I have asked, hopefully I get an answer.

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blieve commented · Mar 20 at 10:22 AM

Unplugging the LAN didn't make a difference.

Seems that support for 2 is possibly only partially implemented (VRM shows them correctly cummulated, device list in remote console also lists 2, but everywhere else only one pops up)

I don't think I have a strange or uncommon situation with 2 AC coupled PV inverters

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Answer 3 · 2024-03-20T09:55:11Z

blieve answered · Mar 20 at 09:55 AM

The false reading is fixed meanwhile. The CT clamp flipped open overnight apparently.

Tried replacing the RJ45 cables & terminators but same result.

I did noticed now that the one meter that doesn't show has the status led blink red (1 time every 20s or something). Don't know what this mean?

It's in the middle of the canbus chain

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blieve commented · Mar 20 at 10:25 AM

The led code is not in the manual:

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duivert commented · Mar 20 at 10:38 AM

not sure but that just might be the kWh/impuls indication

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blieve duivert commented · Mar 20 at 11:09 AM

you are right, added in yesterdays version apparently:

v1.06 – 19 March 2024

Changes/features added:

Add LED pulse output to indicate energy flow. Default the LED pulses every 10Wh.
Several ethernet related improvements that should help streamlining the firmware update procedure.
Update the bootloader to v1.04 to benefit from the same ethernet improvements as mentioned above.

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Answer 4 · 2024-03-20T14:09:36Z

blieve answered · Mar 20 at 02:09 PM

Seems that they both use VRM instance 0 when on canbus. Using them via modbus gives them id 40 and 41 and does work correctly.

Don't know if this ID can be changed. Would rather have them both on canbus instead of a bit less stable ethernet

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