question

yaute avatar image
yaute asked

Communication issue with Energy Meter VM-3P75CT

Since January the VM-3P75CT acted as "AC load", no apparent issue.
Installation overview:
- 3 MultiPlus 5kVA for a 3-phase installation, ESS, firmware v506
- VM-3P75CT firmware v1.05, communication under Modbus TCP/IP
- 2 MPPT 450/100 + BYD

We've just move it as "Grid meter" to be able to do self-consummation for a agricultural workshop (with heavy loads such as welding) and here is the problem:
- With or without charge, the values are inconsistent with a huge standard deviation on each phase => no way to discharge the batteries => SOC at 100%
- The VM-3P75CT is not seen on Remote Console / Setting / Energy meters but seen Remote Console / Setting / Modbus / devices

Is there a way to read the VM-3P75CT log to be able to see if there is some communication errors?

Energy MeterModbus TCP
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4 Answers
Martin (Victron Energy) avatar image
Martin (Victron Energy) answered ·

Hi @Yaute, I've sent you an email.

Edit: It turned out that one of the CT's was broken.

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yaute avatar image
yaute answered ·

Updated post from February 21:
There is a software bug in the management of the energy meter. In fact, once the VM-3P75CT was switched from the "AC load" role to the "grid meter" role, I set "ESS / grid metering" to "ESS / external meter" but changing "ESS / grid setpoint" had no effect. I switched to "ESS / inverter charger" but still no way to modify the network setpoint. I had to remove the VM-3P75CT then I was able to set the network set point.

Note to VE staff, please inform your software team.

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cliff76 avatar image
cliff76 answered ·

Multiplus II GX 5KVA v508, v3.22( GX ), Single Phase, Grid Parallel , ESS


Having exactly the same problems. Running version 1.05 on the Energy Meter...

The Grid Meter wont control ESS properly. At night when no PV generation, ESS is charging the battery from grid, but at a very low charge current of around 1amp. It is not discharging the battery into loads as it should.

Energy Meter is set to role 'Grid meter' , using L1 only. It has been detected by the GX and is reporting Power in and out., connected via modbus.

Optimized (without batteryLife )



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rikvanwesterveld avatar image
rikvanwesterveld answered ·

Yesterday I changed my existing EM24 to a VM-3P75CT and since this swap the system is instable.
The VM-3P75CT is reporting totally incorrect numbers to the VRM! I checked all CT's and they are installed properly regarding current direction.
My ESS system isn't usable right now as the reported grid value is totally different to what my P1 port on the grid meter reports (can be ±3000W difference?!)
Anyone any suggestions what the issue can be?

vm-3p75ct-issue.jpg


vm-3p75ct-issue.jpg (109.3 KiB)
3 comments
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ldoes (Victron Energy) avatar image ldoes (Victron Energy) ♦♦ commented ·

Hi Rik, it seems that there is a large difference between apparent power and real power, especially on L2. This hints at some of the CTs being connected to the wrong phase/port combination. Have you verified that the CTs match their respective voltage terminals?

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rikvanwesterveld avatar image rikvanwesterveld ldoes (Victron Energy) ♦♦ commented ·

I did a recheck and all CT's were connected to the correct ports.

So I removed the meter from the system and went back to the EM24 again, all stable again now. I'll return the VM-3P75CT to Victron as it's not working for me.

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rikvanwesterveld avatar image rikvanwesterveld rikvanwesterveld commented ·

After checking my phases with a Phase rotation meter I found out that L2 and L3 are swapped at the main entrance of the house. After adjusting my setup accordingly all works fine now, including the new VM-3P75CT as grid meter!
My EM24 is now being used as a PV-meter.

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