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alexm avatar image
alexm asked

First large victron self install noob question

Ive installed only small scale solar but I have some electrical experience otherwise. I'm installing 20x 400w panels on a hillside terraced location and in future also want to connect to feed back into the grid but it's not going to be grid connected for a year or so.

Can I ask if anyone sees anything I've done wrong with my spec and also what MPPT/Charge controller would I need for the Multiplus II 10000/48/230. I would also be looking to setup a 3kw micro hydro turbine in future - if that makes any difference to the charge controller spec?

Thanks very much and sorry for the "please check my homework" nature of this question

screenshot-2024-04-21-at-73510-pm.png

https://imgur.com/a/u1omJWH


Multiplus-IIMPPT Controllersoffgridsolar
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6 Answers
kevgermany avatar image
kevgermany answered ·

You need a separate controller for each array. Or some of the larger controllers with multiple trackers, one per array.

You could wire the two 3 panel arrays as one if they get equal illumination through the day. And are wired identically. But as distance is different, probably not.

Pick the controllers using the Victron online MPPT calculator.

Strongly suggest you get professional advice. You could be making some expensive and dangerous mistakes here.

I'd also say that charge controllers have nothing to do with the multiplus, but everything to do with panels and batteries.

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Duivert NL avatar image
Duivert NL answered ·

I dont think those lg 3 phase ESS batteries are going to work

For victron supported batteries see:

https://www.victronenergy.com/live/battery_compatibility:start


and like kevgermany said, you need more mppts and get help from a proffesional victron dealer on system design

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alexm avatar image
alexm answered ·

@kevgermany: Thank you for this, very insightful, so I guess i need a lot of smaller MPPT/charger controllers instead, do I then combine the inputs into a single DC in or does the Multiplus 2 have a number of inputs?


@duivert : I just saw that list, very restrictive set of batteries on that list, I was also looking at the Strong Energy 23kw CRN5ST-23.5 option but no mention even of Strong as a brand on that list . Does this mean warranty is void if I dont use one from this list?

Noted about the advice from pros, I'm currently just trying to work out the size and costs involved. Installer partners in the area are a luxury as it's up a mountain with a day's drive in or out and I need to do as much of the work myself as I responsibly can or the price will get too steep to consider.

Thanks again for the feedback, very valuable indeed

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Craig Chamberlain avatar image Craig Chamberlain commented ·
It’s probably simpler to think of the MPPTs as primarily being there to charge the battery, and the Multiplus can either be also charging the battery or consuming power from the battery through the inverter to power AC loads. In other words, the battery and its associated bus bars are the common point into which and out of which power flows.


The MPPTs need to be matched to both the battery voltage, which for you I assume will be 48V nominal, and to the power source characteristics (eg. PV string voltage and current). There are a lot of factors involved here so I’m not going to go into it in detail but you fundamentally MUST NOT exceed the MPPT rated voltage under any circumstances, bearing in mind that PV panels have temperature coefficients which generally makes them produce more voltage in colder temps.


There are also current limits that you must not exceed, and even PV parallel strings can only be combined in certain ways before you start needing to add string fuses. In general you can combine two identical strings in parallel without any issues but if you combine three or more strings then you’ll probably need string fuses.

To give you an idea, my own system has 16 x 425w PV panels arranged as two separate arrays of 8 panels. Those 8 panels are arranged as two parallel strings of four panels. My PV open circuit voltage is approx 50V and short circuit current is approx 11A so each array is approx 200V and 22A. Since I’m not going beyond two strings in parallel I don’t need string fuses and 200V is well below the 250V limit of the MPPT 250/60 which I use for each array. My array max power is 6.8kWp and my MPPTs can delivery a total of approx 6.3kW which I have seen many times even in autumn or spring. My inverter is a Multiplus-II 48/5000/70-50 and I have a set of three Pylontech US5000 battery modules connected via a pair of Lynx Power-In modules modified to accept fuses.

As others have mentioned, you really should be encouraged to get professional help, even if that is “remote” help that you pay for by buying the equipment via that dealer. My own dealer has provided invaluable assistance via phone and email without any need to visit in person. You can certainly learn a lot by yourself but unless you are planning to do many installations, or are just really keen to know how everything works, then it’s probably a false economy to invest your time in this compared to hiring a professional.

Good luck with your project, let us know how you get on.

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alexm avatar image alexm Craig Chamberlain commented ·
Thank you Craig,

This is very useful info especially your setup and how you have it setup. Can I ask perhaps a very silly question: are you combining your parallel strings into 2 MPPTs for each arrary or do you have more MPPTs one for each string? Also I assume that there isnt any big difference between your strings? Mine will be on separate terraces prone to potential occlusion by trees and terrain, potentially leaves also.
Saor Alba, Thanks again


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Craig Chamberlain avatar image Craig Chamberlain alexm commented ·
I have a total of 16 PV panels which are all on the same unshaded, south facing roof. All panels are identical and will perform pretty much identically.


I decided to go with two medium sized MPPTs rather than one larger MPPT perhaps with multiple trackers. This was part of a design discussion I had with my Victron supplier and we weighed up the pros and cons of each approach. I liked the fact that my voltages aren't super high as they could be if I went for a larger MPPT. Still high enough to be dangerous of course but not 400V+ as you see on many systems. I also liked the redundancy that having two sub-arrays brings, where a failure on one sub-array won't affect the other sub-array. This also allows me to detect more subtle performance issues because both sub-arrays should perform exactly the same so if they aren't then I know something is wrong.

So, each sub-array consists of 8 panels which are arranged in two strings of 4 panels. So string 1 has four panels in series and string 2 also has four panels in series. These two strings are then combined in parallel which means the voltage is still around 200V but the current is doubled. This combined string then feeds a single MPPT. This arrangement is then duplicated for strings 3 and 4 and fed into the second MPPT.

HTH

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Duivert NL avatar image Duivert NL commented ·
@AlexM If the battery is not on the list, then it means its untested by victron for compatibilty


It doesnt mean it wont work, maybe other users have it working

warranty isnt really an issue

You need more smaller mppts, all dc connections have to go to a lynx or an busbar, multi has one dc connection

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nickdb avatar image
nickdb answered ·

Just a reminder that design topics are not encouraged here. Understand your challenges but your supplier is the place to ask questions for any system of scale, this is particularly important for any newb.

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alexm avatar image
alexm answered ·

@nickdb : sorry it's my first post here. can you point to to where to have an open discussion about system design? my preference would not be in private with someone motivated to sell me something.

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nickdb avatar image nickdb ♦♦ commented ·
No stress, it's not that we want to be difficult but the internet just isn't a great medium for design.

Pointers are fine but broad, check my design type questions, are an issue.

Some pointers.

You would be buying or have bought from a supplier, ideally you chose one that can give guidance, or rather should have before purchasing, a good one won't be trying to squeeze you for more cash.

To self-skill there are many resources, as there are topics on the various aspects you want to know about - poke around via search and you will be able to fill in the gaps.

The MPPT calculator is available on the solar charger product page and will properly size a charger for you based on panel specs.

Run through the free video training at professional.victronenergy.com

Get fully acquainted with the ESS design/manual, the related battery setup guides (google for "victron battery compatibility").

Since you are self-installing, this will be valuable for you and it will answer many questions you might have.

Victron don't support Wind generation on MPPT's, but plenty of people use them this way - there are also existing topics for this that will help.

Once you have had chance to absorb all this there should only be focused questions, which you are welcome to post on new, or existing topics.


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Alexandra avatar image Alexandra ♦ commented ·

@AlexM

Have a discussion in private with said person. Get your design together.

Before purchase come here and get a sanity check. We would be happy to help with that.

Are you panels grouped like that because of roof space and direction? There are too many things to work through over a forum discussion.

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alexm avatar image
alexm answered ·

thanks everyone for your help. I will go through the design thoroughly with whoever I will purchase from. Many thanks again

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