question

salvun avatar image
salvun asked

MultiPlus 2 3PHase system to grow over time

Hello everyone, I hope this question has not already been asked to many times.


I want to quickly state that I do have a lot of electrical experience. As I am a trained electrician by trade. So this is not coming from the mind of a untrained individual.


So I own my own machine shop since a few years. As I made a career change and started my own business. The thing that bugs me is that we use a lot of power. Well over 20MW per year and I have been really looking into running my workshop here as much as possible of solar and off grid as I can. Since we have plenty of roof space still available and land to put solar on (Already have 20Kw Solar installed. This is the legal grid connected maximum if you want to avoid tons of red tape.)
There are a lot of legal limitations to grid tied solar setups, and the coming "Peak usage" charges are really pushing me into doing this.

My current setup:

3Phase +N 63Amp grid connection (Meter 1)

  • 7,5Kw 3Phase screw compressor
  • 25Kw max. 3Phase CNC Mill #1 (Usually 5kw or less. But 22Kw motor with Ramp-up draw)
  • 25Kw max. 3Phase CNC Mill #2 (Usually 5kw or less. But 22Kw motor with Ramp-up draw)
  • 5Kw max. 3Phase CNC Mill#3
  • AC units to climate control the shop.

    3Phase +N 32Amp grid connection (Meter 2)
  • House (Basic usage)
  • Office (Lighting mostly)
  • Servers (1.2Kw Servers)
  • Warehouse (Lighting and forklift charger)


Both meters are on the same property and the ultimate goal is to have the entire property on a Victron system with battery's charged as much as possible from solar. With a grid "Trickle" charge as a backup.

Since this entire plan would require a very expensive system to get going. Making me lean to build into this slowly and buying units section by section.
My idea to start was to order 3 Multiplus 2 5000VA setup in 3phase to get started with a couple of 4.8kwH battery packs. Allowing me to setup a smaller system to learn and gain experience by slowly moving loads onto this starter system.
This would be setup in a dedicated technical room with AC housing all the battery's and solar controllers.

Then as things grow, add more Multiplus 2 units. From what I read it would need to be all 5000VA units to grow the system by a set of 3 units at a time. With a goal of having 4 sets in total (12 inverters total.)

Any expansion would always be done in sets of 3 units to keep the entire system symmetrical at all times.


The main question now, does this seem workable. Especially with the time in between adding more Multiplus units. Or is it WAY more recommended to just jump into financial pit and get 3 15000VA units of the bat.

I do like the idea of having more individual units a lot more, since the system can be grown with better up front cost distribution and it looks more robust since if a single 5000VA unit fails, it will not take down the entire microgrid compared to having a single big unit per phase


The reason I want to ask this here and not to a local reseller, is to avoid financial bias from the reseller to try and just push a more expensive option.

Thank you so much for reading and providing some feedback if possible.
-Pieter

Multiplus-IImultiplus in parallelmicrogrid
4 comments
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Alexandra avatar image Alexandra ♦ commented ·
@Salvun

Since you have three phase power needs. You would ideally to start with a three phase system.

Since you want to build up, separation of dB loads would be the only way.

Adding to the system can get tricky depending on your time frame a good distributor could accommodate this if you have a timeline, they reserve stock for you.

But you possibly might find out that you end up with several systems for each section rather than one big central system. Unless you have access to finance?

Maybe start with your office section since it is a much smaller system.

The main section on the surface looks like min a 60kw system with rough maths to cater for surge. So both three phase and parallel.

You can't mix and match different inverter sizes (and to some degree age) either. So if you start with 5s you are set the whole way like that which will make a very complicated install in the end (wiring wise). You are more likely to have failures, one inverter will still take out the whole system by the way (no matter how big or small, as once programmed they are one unit/system. One off means all off. And you can't ESS off asymmetric systems.

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salvun avatar image salvun Alexandra ♦ commented ·
It would 100% be started with a 3Phase system.

The current plan was to buy 3 units of the MP2 5000VA setup in 3phase to start the system.

According to the specsheets, the surge ratings on the units seem to be really large and able to handle the milling machines ramp up.

And the units would still be grid connected, but limit the grid draw. So that the system can help reduce peak draws from the grid.


Any expansion would be with 3 units to keep the system symmetrical!


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Alexandra avatar image Alexandra ♦ salvun commented ·

So right off the bat sizing a system where the peak is outside of nominal rating is a mistake.

Derating and a bunch of other factors a newer installer will miss. As Nick mentioned - there are alot of little details....

As an electrician you know as motors age as well.... then there is always the bearing fail scenario... it is now more than just providing power. It is understanding the system (including the consumers) as a whole. Things almost never work as they appear on the info plate.

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matt1309 avatar image matt1309 commented ·
Hi @Salvun


Others have already commented on the issue of running systems in parallel/three phase with different age/revision models.

My only comment was a suggestion to maybe look into DIY LiFePO4 in the view of saving money.

Given your experience the learning curve would be somewhat minimal. You could also then look into purchasing non EV grade cells to save a little. Of course you need the relevant safety systems as these cells are not perfect/EV grade, however i find for home use you dont see the difference.

Given the anticipated large scale size of the system it could be a big saver (and also just a fun challenge). Happy to share further details if that's something you're interested in. (I've got designs for 60kwh pack, current only filled with 30kwh due to cost of cells), you could easily make the case with your shop by the sound of things. Ordering sheet metal was a large cost for me when i built mine. Very scalable design so could easily get to 120kwh if needed.

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2 Answers
nickdb avatar image
nickdb answered ·

The challenge with systems like this is rarely the wiring. It is understanding the tech, configuration, customisation etc.

For a complex system like this you really want to do the free training and read every config guide imaginable.

If not, you’re likely to expect one thing and experience another. This forum is really not for design work, especially of complex systems.

There are many unhappy posts from people who had expertise but not the experience of working on systems like this. Doing the research will avoid this.

The devil is in the detail, and there is a lot of detail.

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nickdb avatar image
nickdb answered ·

I am going to be a spoilsport and close off this topic.

We really don't encourage complex system design, as per t's and c's of the community.

I would suggest you engage a qualified Victron tech, or speak to a distie/supplier in your region for official help.

https://www.victronenergy.com/where-to-buy

Sales managers contact info in your region is also available on the main site.

Alternatively, to DIY, sign up for free at professional.victronenergy.com and follow the online certification.

Read wiring unlimited, the ESS design manual, the parallel and 3 phase system setup guide and the Cerbo manual for some good background.

Specific queries, if not already available via search on the forum, can easily be answered here.

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