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gianmarco avatar image
gianmarco asked

2x Multiplus II (10kVA) connected to the same Cerbo GX, NOT in parallel. Possible?

Good morning.

As title, I'm planning to add another Mp II to the existing system. I don't want a parallel connection between the inverters, both because the parallel configuration is not available for the 10kVA and because I'll use the old inverter to power the everyday utilities and the new inverter to power big loads (well pump and 2 big water heaters) only when there is sun.

Of course, for monitoring ad operational needs, I need to hook up the two inverters to the same cerbo and to the same batteries.

Is possible to do this? I'll be able to see both inverters in the VRM and on the Cerbo GX touch panel?


Thank you and sorry for my broken English.


EDIT

I'm reading that sharing batteries is not recommended. This should not be my first problem, since I'm using lead acid cells with a single Lynx Shunt.

Anyway, I'd like to know why sharing the battery bank between two inverters is not recommended. I've been in the off-grid world just for one year and I'm not an experienced user.

Multiplus-IIcerbo gxoffgridmultiplus in parallel
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nickdb avatar image nickdb ♦♦ commented ·

@gianmarco if you are off-grid, there is now a solution to parallel 10k and above inverters using custom firmware and an external transfer switch.

https://www.victronenergy.com/media/pg/MultiPlus-II_External_Transfer_Switch_application/en/index-en.html

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dognose avatar image
dognose answered ·

Short Answer: no.

If managed in a single system, they need to be configured as a unit, either parallel or split phase.

If they should work independent, you need a isolated GX Device (and dedicated batteries, solar, etc.)

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Fideri avatar image
Fideri answered ·

@gianmarco

Search on this forum. In general, what @dognose said applies. If you can live with only monitoring the primary one, you can apparently connect the second one to the GX via an MK3. For some people, this seems to work. But others, also on this forum, say it doesn't. I haven't tried it, so I can't say either way.

F.

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gianmarco avatar image gianmarco commented ·

Thank you. You are the only one that gave me some hints.

So I should connect the second one via USB interface to the Cerbo USB ports? This will make the inverter to show up in the Cerbo panel and in the VRM?

Thank you.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ gianmarco commented ·

It will be shown in the device list but will not be controlled via DVCC Signals.

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gianmarco avatar image gianmarco Matthias Lange - DE ♦ commented ·

So, no VRM and no Power indication on the cerbo control panel?

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nickdb avatar image
nickdb answered ·

You cannot share batteries between independent systems. Rather do it properly.

As a victron community, we need to encourage systems to be installed in supported ways.

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Fideri avatar image Fideri commented ·


One of the posts about two inverters on one system and connecting them as I described is from a key person in Victron, though that's not in the manual.

F.

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nickdb avatar image nickdb ♦♦ Fideri commented ·

There are many ways to assemble a system. Most of them are not supported in any form, not that it prevents people from doing this.

Will something work (is it possible)? Sure.

Will it work reliably? Maybe

Will you get help when it doesn't? Nope.

Key person or not, connecting multiple systems to a GX is documented, along with its limitations.

Sharing batteries is not.

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Fideri avatar image
Fideri answered ·

My mistake. The manual describes how to connect multiple inverter/chargers to "the same GX device" given the specified limitations. From this, one can reasonably assume that that configuration is supported. Indeed, I have seen posters who have problems with this configuration get guidance from community members and Victron staff via this forum. As far as I can tell, the manual is silent about batteries in this configuration.

So if a person in OP's position chooses to do what the manual says, should they assume (unless I missed it, this point seems to be unspecified) that they need to use a separate battery bank with the second inverter or they are on their own?

F.

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nickdb avatar image nickdb ♦♦ commented ·

If a system is not one, unified, 3-phase, split-phase, parallel or standalone system, then each requires a battery.

You will see the same response to every similar post from the many in-house experts that support this forum.

That is the design/support criteria.

Nothing, electrically, prevents it operating, but if you choose to do so, then you need to accept the risks and related loss of support, and potentially, warranty.

Manuals document the supported configurations, they do not document the unsupported ones, so silence, or lack of an explicit mention does not imply a grey area, or some form of latent support.

If you don't see it documented anywhere, it is safe to conclude you are off-piste, particularly when the guidance here has been consistent in all cases.


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lebtwl avatar image
lebtwl answered ·

It's an older Venus GX device but I've had two multiplus units setup in this way on my boat for a few years now. There are a couple downsides. For example as shown below only one unit will show on the summary screens, but you can see the detailed status and configure both units through the Venus device which is really nice. In my case the second unit is connected via USB by a MK3. The one big downside is that the two multiplus units do not communicate with each other, but in my case they are both managed by a BMS so it's not a big issue for me.2muiltidashboard.png

2multiremoteconf.png


2muiltidashboard.png (146.3 KiB)
2multiremoteconf.png (129.1 KiB)
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nickdb avatar image nickdb ♦♦ commented ·

Nothing wrong with using one GX to access the info on more than one unit, the mk3 is a requirement as documented in the GX.

Only one system will be managed and under DVCC/BMS control, as per the limitations, which for standalone systems is not ideal.

For a small system that may be something that is less of an issue, but for large systems it is more problematic.


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lebtwl avatar image lebtwl nickdb ♦♦ commented ·

Not exactly accurate. Only one will be managed by the VE.bus BMS support. The other(s) can easily be setup and controlled by the two signal BMS assistant. Same as you would for other non-victron charge sources in large systems.

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