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luke-1 asked

ESS Planning - EasySolar II GX - Open Questions

Dear Victron Community!


I own 3 PV panels (2x Maysun Solar MS370MB-60H, 370Wp und 1x Sonnenkraft 425 Wp HC (bifacial)) which I would like to expand with a DIY LiFePo4 battery. I currently have two microinverters with the Maysun panels, but I would likely discard them.


The panels have the following specifications:


 2x Maysun Solar MS370MB-60H, 370Wp 1x Sonnenkraft 425 Wp HC (bifacial))
Nominal current 10.82 A 13,37 A
Nominal voltage 34.2 V 31,80 V
Short-circuit current 11.37 A 13,85
Open-circuit voltage 41.3 V 38,35


Instead, I was considering using a VictronEnergy EasySolar-II 24/3000/70-32 MPPT 250/70 GX and dimensioning the battery with 8S EVE Prismatischen Zellen as a 24V System (Daly 120A BMS)

The 3000W power of the EasySolar combined with about 8kWh of storage would actually be perfect, as far as I have observed over the past few months.

However, while going through all the datasheets and manuals, I unfortunately encountered some uncertainties that are still troubling me, and I couldn't find any solid information. I would appreciate any answers!

If there are any unclear points about my setup, or if more details are needed, please feel free to ask!


  • Panel input voltage for the MPPT controller: According to the Victron manual (Chapter 6.1) , the voltage must be +5V above the battery voltage to enable charging. My original idea was to connect the 3 panels individually to the EasySolar, but according to the Victron MPPT Calculator, this doesn't seem to work. Which voltages are being compared here? Maximum charging voltage 3.8V per cell and the nominal voltage of the panels? I fear that I can't connect the single Sonnenkraft panel in series with the other two due to the different parameters, right? I'm unsure how I could use the 3 panels to satisfy the MPPT controller.


  • The second question is regarding the connection of the EasySolar to the grid: I don't need island mode and it's enough if I always operate it in grid-parallel mode. So, I would connect the input to one of my grid phases. According to the wiring diagram, I actually wouldn't need an output, since the input is connected to the output in grid-parallel operation anyway. In the end, I would otherwise connect the output to the house grid as well - but that would essentially be the same line, right? I find the Victron documentation absolutely inadequate at this point. Alternatively, I would have to connect all my consumers to the output and essentially pass the house grid through the Victron. However, that would not be structurally easy to do. Connecting a 3000W capable line to the house grid via input would be much easier.


So, it should look like this:

ess.jpg


I hope everything is clear - I would really appreciate your inputs. Unfortunately, I couldn't find concrete answers to my questions, although I think I'm probably not the only one feeling a bit lost here.

Best regards from Austria,

Luke


MPPT ControllersEasySolar All-in-One
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2 Answers
kevgermany avatar image
kevgermany answered ·

I can't comment on ESS.

On the panels, key things if you're mixing different panels one one MPPT are current and voltage at max power. Either the currents need to be close, or the voltages need to be close.

Effectively based on assumptions from what you've given, you have a few options

  • Retain the microinverters
  • Buy a second MPPT
  • Ditch the incompatible Sonnenkraft panel.

Given that you have cold winters, make sure you check the Voc at your coldest temps does not exceed the max input voltage of the controller.


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luke-1 avatar image luke-1 commented ·
Thanks @kevgermany!

That makes sense. I could put at least one existing microinverter to the single Sonnenkraft panel and acept that this panel won't charge the battery but will at least pretty much satisfy my base load (and waste small portion). For no additional costs.

And for the two Maysun panels, I can daisy chain to reach the EasySolar required MPPT voltage - but I'll double check the maximum voltage on the coldest days, thanks for your hint!

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Duivert NL avatar image
Duivert NL answered ·

You have a few options:

Use the microinverters (if they support frequency shifting) a et 112 and a multiplus 2 GX

Use 2 mppt’s and a multiplus 2 GX

Or use the easysolar GX and the 2 matching panels and use a mppt for the 3th panel


Also follow kevgermany’s advice on the panels voc

2/3 panels on 8kw battery is a bit small, if the battery is to empty you will never get it full again with pv

Your question about grid connection, parallel is an option

I suggest you read these manuals:

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

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

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luke-1 avatar image luke-1 commented ·

Thanks for your answer @Duivert NL

I think I understood all the options and possible solutions for my Panel mismatch, thanks!


Regarding the parallel grid connection:

I've read all the manuals that I could find and none seemed to cover my particular question if wiring ONLY to ACC-in is also feasible. I've seen some pictures on the web of connected devices, but it's unfortunately also NOT covered in the explicit AC-connection section of the manual. :-(


Lastly, regarding your doubts about 8kw battery:

On a sunny day, I'm wasting ~3kWh with only the two panes (740wpeak). So, if I'm not or almost not at home, I can charge the 8kW battery almost fully within two days. Additionally to that I'll use a flexible energy tariff which could enable me to charge the battery at certain times almost for free of charge from the grid. I plan to do that whenever the battery < 50%ish and the sun forecast is bad.

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