Problems with MP2 10kVA

Q&A and troubleshooting
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1

Hello,
I’m posting here in the hope that you can help me with a problem that I’ve had since the beginning of the system installation. I mention that I’m an installer and I have several systems installed that work without any major problems.

I have a system composed of the following:

  1. A MultiPlus-II 48/10000/140-100/100 inverter
  2. Three SmartSolar MPPT VE.Can 250/85 rev2 solar chargers
  3. A Cerbo Gx
  4. An ET112 Energy Meter mounted on the grid.
  5. Two Lynx Distributor
  6. A Lynx Smart BMS NG
  7. Four LFP-51.2V/100 NG batteries (mounted in parallel)

The cables used for the connections are as follows:
Between Mppt and Lynx, conductors with a section of 35mmp were used.
Between the batteries and Lynx, conductors with a section of 35mmp were used.
Between Lynx and MP2, 95mm2 conductors were used.

The system is mounted in such a way that the whole house is on AC out, but we also provided a bypass method to put the system in parallel (on grid) with the network in case of a failure.

The off grid system works perfectly. The problems occur when connecting to the network.
Issue 1. The system tries to charge the batteries from the grid. I tried to turn off the charger in Ve.Configure, leave Charger on and change only the current to 0, change the maximum current in DVCC to 0…without any effect. As soon as I switch the operating mode from “inverter only” to “on” it starts to draw from the grid and spikes appear on the battery charge part.

Issue 2. The system enters Passthru even at 200W power and no longer draws from the batteries.

Issue 3. The system, at certain times (I noticed that at consumptions of 3-400W) does not want to discharge from the batteries when connected in parallel.

Issue 4. L1 Overload device even at 10A power.

Issue 5. Grid Meter disappears. It is completely random when it happens (it is an error that I have noticed on several systems).

Below I will try to attach pictures and videos of the inverter’s behavior.

I have tried to contact other fellow Victron installers and so far no one has been able to understand what is happening.

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2

A lot of problems.

Is your ET112 working correct or the communications?

Are there errors in the log files (ssh)

3

2 and 5 are probably related.
If the system loses contact with the meter it will enter passthru.
If you don’t need it, or just for a test, try use the internal meter in the multi and see if one aspect normalises.

4

Sadly a lot of issues.

I did set the meter to internal and still the same thing. The only circuit I have before the AC in of the inverter is a service socket so the external meter is not really that important.

The inverter enters Passthru mode regardless of whether the measurement is set as internal or external.

I think the BMS Ng could be the problem or maybe even the Cerbo GX. I want to try replacing them with new units and see if they behave the same. Although as I mentioned in the original post, the system in off grid mode works very well.

5

Check your connection to the grid.

The last time i heard that buzz then collapse sound on the third video/photo it was a bad neutral and poor/corroded line connection to the grid.
Check what voltage you have have between neutral and earth as well.

The other issue (the site we were troubleshooting was three phase) was a weird harmonic from the grid that causes it. And the problem only appeared on one phase of the three.