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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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Tom Büschgens avatar image Tom Büschgens marekp commented ·
With none of the mentioned setups? My understanding of the ESS was that with the EM24, the Multiplus II would provide exactly the amount of Watts (from the battery) as the sum of all 3 phases draw from the grid.


So in a complete 3 phase Multipülus II setup, all MP2 will provide the power (summed up) that is required to keep the meter at zero - it is not that each MP2 tries to balance exactly one phase. That would be inefficient.

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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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