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aquacheck asked

Multiplus-II does not charge on low mains voltage

Hi Community.

I have an unusual problem (2 actually). Running MP-II's coupled with Fronius Primo. Modbus TCP control with Cerbo. (edit, for clarity the Fronius is on the OUTPUT of the Victron)

Living with very unreliable grid, so I have set the mains voltage very wide (down to 180V disconnect, 200V reconnect on a 230V grid).

First issue I see is the MP-II will not charge the batteries when the mains goes below about 200V. Worse still: it exports all the solar and only a very small trickle to the battery. SOC limit set well above current SOC. limits are turned off. Also tried scheduled charge, but seems to ignore that.

Second is: when the voltage is just below 180V (disconnected, and voltage stays below the reconnect voltage) it holds the Fronius in Zero Export (like its expecting to connect, but the voltage does not pass threshold). I have checked it does not shift the output frequency, so it must be either pausing coms or throttling the Fronius. Just sits there indefinitely and depletes the batteries. Fronius set up MG50 according to victron recommendation.

Any one else have this situation?

Multiplus-IIFroniusmicrogrid
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Paul B avatar image Paul B commented ·
have you updated to the latest firmware and then the lattest assistants
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aquacheck avatar image aquacheck Paul B commented ·
yes all up to date - first thing i checked
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aquacheck avatar image aquacheck aquacheck commented ·

Hi Paul, your post :"Multiplus 48/5000 with PV installed 4.5Kw output hz keeps changing and shutting PV" seems suspiciously similar to what i see with the low mains volts.(I have 2xMP-II/5000 + 8kW Fronius. SOC also as low as 30%)

If there is mains volts present (with the AC-IN relay open) I get the system shutting down the Fronius. (possibly "ignore AC-In only opens the relay, but doesn't shut down the sensing logic??). My main difference is I don't get the frequency shift, so either is stops comms with Fronius - in which case it will shut down due to TCP coms failure, or it actually tells the Fronius to stop via MODBUS TCP.

Its causing so much drama i have now installed a remote control CB to cut the mains when below 180V (and yes, we have mains sitting at times at 160 to 180V)

Thoughts?

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Alexandra avatar image Alexandra ♦ aquacheck commented ·
Could also be a networking issue.

I have seen routers and switches have hiccups with power changes.

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Alex Pescaru answered ·

Isn't Fronius an AC coupled inverter?

Meaning, as long as it doesn't see a "reliable" grid, it doesn't function/export?

And that grid below 180V (second issue), could be an unreliable grid for Fronius, so it my be a Fronius decision to not export...

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aquacheck avatar image aquacheck commented ·
Hi Alex, yes it is, but in this case i follow the Victron setup for microgrid, meaning the Fronius will not see the grid until Victron closes the relay. So no the Fronius in this case sees the 230V from the Victron. Victron (cerbo) definitely shuts down Fronius and keeps it shut down indefinitely in while in that limbo state state
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