According to the data sheet, combing two 48v/8000VA Multiplus inverters for parallel operation is not possible,
Could someone please confirm this, I sent a question to a Victron supplier recently who replied saying it was possible?
Thanks.
It can only be done with an external transfer switch and special firmware. This is all well documented in the user manual
The ATS option has it’s own manual and requirements, it is linked from the main manual as well.
All accessible via the download links at the product page.
Surely that is not true parallel operation but switching between either unit. What I require is to increase the output from 8 to 16 kw. The inverters have no ac in only used for inverting dc to ac.
Read the docs.
It moves the AC switching from the multis, externally.
Was originally off grid (generator) only, but on-grid is now supported.
Edit:
If you are fully off grid (no AC IN), then, technically, while not supported you are getting around the internal relay issues and it will work.
The tools don’t prevent you configuring it.
If you have any AC IN sources (genset etc) you will need the ATS.
That’s very interesting and directly relevant to my situation — my system is 100% off-grid with zero AC input to either inverter, which appears to be exactly the scenario you’re describing.
A few follow-up questions if you don’t mind:
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In this off-grid configuration, do both units genuinely share the load equally in real time — i.e. true parallel load sharing giving a combined 16kW output — or is it still essentially one unit active at a time?
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Are you aware of anyone running this configuration reliably long term, and are there any known stability issues or behaviours to watch out for?
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Does a standard firmware update risk breaking the configuration, given it’s unsupported?
For context, my existing unit is a Multiplus-II 48/8000/110-100 running firmware 2621556. I’m trying to make an informed decision between reinstating the second 8kW order, or moving to a single Multiplus-II 48/15000 instead.
Thanks in advance.
I strongly recommend you consult a qualified specialist who can offer a guaranteed and safe solution for your requirements and technical specifications. Parallel configurations, and even a single module for that sort of power, are not a toy. Even if you study all the technical documentation for every Victron products and watch basic courses on installing parallel systems, without experience you’ll face a lot of pitfalls and surprises. So don’t play at Lego.
Good luck
Thanks for your advice, I am aware this is not a “lego” project, as you put it. I have built and installed a fully working Victron system with 4 MPPTs, 42 kw solar panel, built 3 x 14kw lifepo4 battery bank that have worked perfectly for the last 3 years. I agree with you that paralleling inverters is no walk in the park and as Victron advise ,the larger multiplus inverters won’t work in parallel (no ac input so they might actually) as the relays would be open) I am inclined to upgrade cabling and fit a single 15000Va single inverter. Appreciate your comments. Cheers.
You want to increase consumption and you’ll need to sort a fair few things out and make the right decisions, since you don’t have the experience to foresee everything, I’d recommend getting the calculations done by a qualified specialist, let them produce the design for you. That’s assuming you’re confident in your own ability to carry out the installation work and that you have the necessary measuring instruments.
For example, start by understanding the load profile for the planned 15 kVA and whether a single module can handle it. Secondly, you’ll need to upgrade not only the cable wiring but the whole protective automation.
Island systems make the task easier, but that’s one side of the coin, on the other hand, island systems aren’t that simple, especially when it comes to high currents in AC and DC power circuits.
Every project is unique and there are no templates. Sometimes it’s correct to use several modules to reach the desired total power without loading each one up to its maximum.
You do realise that nobody here will give you step‑by‑step instructions? Firstly, that’s wrong from a safety point of view, and secondly it goes against the community rules.
In short, you have two routes, commission a proper design and be confident everything’s correct, or try it yourself and learn the hard way.
Good luck
Thank you for taking the time to reply.
I appreciate your good advice and agree if I could find a qualified specialist here in SW France,
I would be happy to hire them.
Perhaps someone on the forum has advice to who’m I might contact in this region Midi Pyrenees or neighbouring departments?
Thanks again.
Your region is full of system integrators and companies working with Victron products, especially those specialising in off‑grid systems.
Take your pick.
victronenergy.com/where-to-buy
Explain your task to them, clearly state your requirements, invite a specialist to audit the existing installation and request the development of project documentation for scaling the system. I’m sure they won’t turn you down.
Thanks!