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gary bastin avatar image
gary bastin asked

How to configure grid/solar useage

Hi.. I live off grid. However I have mains available from a large 300kva generator that runs constantly feeding the private estate.

My solar system is quite large for a residential property, I will list here for info.

6kw (max theroteical) panel array although some face east and some face west.

24v 5kw multiplus (4 years old) will not run ess

3 x 150/70 mppts

Color GX

BVM700

12 x 2v battery 600ah

Private Grid is availble

2 back up gensets 1 on auto start and one manual start

Both need to be connected via a manual transfer switch (10kva/6kva)

So.. To minimise battery usage and extend their life I have it set up in the virtual switch to only ignore grid if battery soc drops below 90% or load exceeds 2.5kw


So when those conditions are met the inverter switches to grid, but this then cuts the solar, so it pulls everything from grid. (not the real grid, communal generator)


What I want to happen is this..

Example..

3kw of solar available

Load is 4kw

Grid will have cut in.. But I want it to only assist the solar.. So 3kw from solar and 1kw from grid..

Currently it would pull all the 4kw load from grid. Not an ideal situation because the idea is to reduce my grid consumption. And with a wife that has not adapted to solar it is very frustrating, her iron alone is 2.7kw.


I have tried to figure it out.. But obviously missing something as I am sure the inverter should be able to be configured to do this.

Thanks in advance for your advice.


MultiPlus Quattro Inverter Charger
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2 Answers
wkirby avatar image
wkirby answered ·

A 2.7KW iron!!! I feel your pain. Our house is heated by kerosene, but one person in the house likes "fresh air". So rather than standing outside, she opens the windows even when it's sub zero. We can do 300 litres a month!

Anyway, on to your question.
It seems that the solar chargers' absorb Voltage is lower than the MultiPlus' absorb Voltage setting.
Example: Solar chargers are aiming for 28.4V but the MultiPlus is aiming for 28.8V. Once the MultiPlus forces the battery Voltage beyond 28.4V the solar chargers are going to assume that their job is done and they'll grab a cold beer!

ESS would serve you well. It's a pity that you can't implement ESS, a 300KVA community generator is basically grid (unless everyone jumps on the bandwagon) and ESS backfeed would save the community some diesel.

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JohnC avatar image
JohnC answered ·

Just adding a few thoughts to WKirby's answer, which I concur with.

You could also limit the Muti's input. The min for that model is listed as 3.9A @ 230Vac. That mightn't work so well if the Mrs irons at night..

Maybe even drop your Multi's charge targets to (say) 26.0V, so it will only fire when the pv mppt can't reach float, but still above batt standing V.

A dedicated tinkerer would find this project a great challenge. You probably qualify as one of those already.. :)

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