8kW setup with Multiplus II and Fronius Primo

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casper asked Oct 21, '21

8kW setup with Multiplus II and Fronius Primo

Hi everyone,

I'd like to get some feedback on the following.

I currently have the following setup:

- 3kW Multiplus II
- 3kW Fronius Primo connected to the ACout of the MPII
- 9kWh AGM battery bank
- Grid tied system with the ability to export electricity

This system works great in a grid down scenario where the PV array continues to provide power to the Multiplus II.

I like the simplicity of the setup and am looking at upgrading the system to an 8kW system (both for the Multiplus and Fronius Primo due to the 1:1 rule). I would also be upgrading the battery bank to 18kWh AGM's. The Fronius Primo would be the following model: https://www.springers.com.au/shop/product/primo8-2-1-fronius-primo-8-2-solar-inverter-1437

Question: should I be concerned that this type of setup is too big and should this only be suitable for the smaller setup that I have? I.e. would the Primo be able to throttle back sufficiently if there is only a very small AC load and the batteries are already at 100%? Your thoughts on the battery bank capacity would also be appreciated.

Any other thoughts and comments are also welcome.

Thanks

Multiplus-II Fronius

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Paul commented · Apr 12, 2022 at 02:56 PM

Hi Casper,

Your setup is exactly what I am planning to do.

Is there a script for the Fronius listening to the max accepted power of the MP2??

I am not a computer wizzard so something like a do this then that would be nice.

At the moment running with a MP2 5k, a Cerbo, SmartMPPT 250 with 3p4s panels on it, two EM24 kWh meters and 8kWh of LiFePO4 batteries on 48V.

Will be replacing the 12 panels bij 12 new ones in series on a Fronius Primo 4.0, together with 5 panels on the other side of the roof on MPPT input B.

When grid fails, I have 2 options:

a) rewire the panels in 3p4s on the MPPT250/100 OR

b) add the Fronius on the MP2 output and leth both of them communicate with each other.

Choices choices.....

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Modifications Space

Node Red Space

Answer 1 · 2021-10-21T20:44:06Z

Rob Duthie answered · Oct 21, 2021 at 08:44 PM

Hi

Yes will be OK, if you have the Fronius on the input to the Victron you can have any size grid tied inverter, and the 1:1 rule does not apply. Only on the output of the vcitron it applies.

I have a simlar setup with 21kw of battery and have 3Kw multiplus2 and about 5kw of grid inverters and a DC coupled MPPT charge contoller also set to export.

No power bills for over two years now, and in credit.

Regards

Rob D

NZ

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casper commented · Oct 23, 2021 at 08:18 AM

Hi Rob,

Thanks for your comments. That is re-assuring that I'm on the right path.

Would you be able to elaborate on what else runs from your MP2? Do you cook with gas and heat the home with wood? I assume the 21kWh capacity never runs out for you?

Cheers

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Rob Duthie casper commented · Oct 23, 2021 at 08:27 AM

Hi

We have an all electric house only a pellet burner for winter, I am still grid tied, the thing about a vcitron inverter setup it is easy to change settings on the fly depend what your loads are doing.

I have it set to take care of all the small to normal loads, the inverter does power share very well.

Regards

Rob D

NZ

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