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Tom Büschgens avatar image
Tom Büschgens asked

2* Multiplus II as ESS in Germany (with 2 batteries) - design question

Hi there,

I want to build an ESS consisting of 2 Multiplus 2 (48V 5000) with two 280Ah batteries - so my main goal is to keep the meter at zero, not so much to gain independance from the grid or to create an UPS for my loads at home.

Currently I am struggeling on "how to design" this ESS correctly. My understanding is that there are 2 options (due to "Schieflast" in Germany paralleling is out of question).

  1. Connect the 2 MP2 as a 3phase system (obviously only creating a 2/3 part of a 3 phase system on L1 and L2). The systems will share both batteries via an appropriate busbar, one Cerbo GX required.
  2. Have two completely separated MP2 installations - one on L1, one on L2 for example. This would requried a Cerbo GX for each. But how will those system align on the grid setpoint?

Option 2 seems easier to wire, with the problem to get the meter info to both Cerbo GX, but I guess using the mqtt-dbus approach that should be manageable. Option 1 would be quite ok for me, if this is supported by Victron.

Happy to hear some suggestions on this one.

Multiplus-II3 phasesplit phase
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marekp avatar image marekp commented ·
@Thomas Bueschgens

Is your house supplied by 3-phase grid?

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Tom Büschgens avatar image Tom Büschgens marekp commented ·

Yes, my place is (as usual in Germany) supplied with 3 phase grid.

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marekp avatar image marekp Tom Büschgens commented ·

@Thomas Bueschgens

It is not possible "to keep the meter at zero" with just two MP-II units, unless there is ZERO consumption on one phase

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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Ist zwar eigentlich nicht von Victron vorgesehen, aber habe ich auch schon Mal bei einem Kunden gemacht, als einer der 3 MultiPlus bei ihm defekt war und zur Reparatur ausgebaut werden musste.

Mit "Split-phase 120°" sollte Option 1 klappen.

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maha avatar image maha commented ·

Wie @Matthias Lange - DE schon schrieb: Du könntest ein 2 Phasen-Splitsystem aufbauen. Das geht problemlos. Ich betreue ein solches System im Echteinsatz...

Da du aber Angst vor "Schieflast" beim 5000er Multi hast, dürfest du den nur in einem 3-phasigen System nutzen! Tatsächlich ist der 5000er für Deutschland aber schon auf 4600VA begrenzt. Es gibt nur noch kein deutsches Zertifikat.

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Tom Büschgens avatar image Tom Büschgens maha commented ·
@MaHa

Thanks for your answer. I am not "afraid" of the "Schieflast", just wanted to mention the topic, because this effectively rules out the parallel setup of 2* Multiplus II - which seemed to be the easier setup when checking the available Victron documentation.

So the 2 phase split system (120°, L1 + L2) will be the way to go.



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marekp avatar image marekp commented ·
@Matthias Lange - DE

Interesting.

Was the meter kept at zero?

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Tom Büschgens avatar image Tom Büschgens commented ·
@Matthias Lange - DE

Thanks for some confirmation.

Just in case: Any other suggestions that are more "Victron Standard"? Or would 3 Multiplus II be the "normal step"?

Again: There will be no phase-sharing loads on any AC out of the Multiplus II.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
@MaHa If I remember correctly it was working as a normal 1-phase or 3-phase system.

I would not have done it if it doesn't work. :)

@Thomas Büschgens Wie gesagt, das ist keine offizielle Konfiguration, die von Victron vorgesehen ist. Da ist immer nur die Rede von 1-phasig oder 3-phasig.

Aber wie auch schon geschrieben, ist mit den 5000er MultiPlus eigentlich nur ein 3-phasiges System zulässig, wegen Schieflast.

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Kaspars avatar image Kaspars commented ·

Wie verdrahten Sie in dieser Split-Phase-120-Grad Option den Neutralleiter? Müssen alle Neutralleiter von AC-out 1 und AC-out 2 beider Wechselrichter kurzgeschlossen werden?

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Tom Büschgens avatar image
Tom Büschgens answered ·

Short feedback: Recommended answer by @Matthias Lange - DE worked perfectly.

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