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tc-shark avatar image
tc-shark asked

Multiplus II ESS non essential load wiring help needed

Dear all. Please help me with a question. I have a 3kwp ongrid PV system (with ABB inverter) with excess feed in to grid, and i'll extend the system with a Multiplus II GX 48/3000 and a 48V 180Ah PZS battery pack . My main purpose is to optimize self consumption (with 50-60% of the batteries), and also make my PV system work even in case of a power failure (which is pretty often in our village). I can go pretty low with my essential consumption (fridge+freezer+lights+water pump+ charging tools/phone), because i can heat my house+produce hot water also with wood boiler/stove. In the summertime DHW is produced by solar thermal collector.

I want to separate my non essential loads (electric water heater, and a small heat pump (consuming between 3A-11A), and i don't want to supply them AT ALL from battery backup (i dont' want to discharge my batteries too fast, shortening their lifecycle....).

My question is: if i connect my non essential loads to AC2 output, and during daytime, at a certain moment for example PV array produces 800W, no consumption on AC1, and my water heater on AC2 consumes 2000W, will the MPII try to supply the difference of 1200W from the batteries? Or from the grid? (As I heard, the MP try to assure zero input/output on the measuring point, which in my case is inside the MP, no ET112 energy meter will be used. So i think it will try to use the batteries, instead of taking from the grid, but i am not sure....). This is "version B" from the attached drawing.

Or i better use "version A", and connect my non-essentials parallel to MPII ? Disadvantage would be that i can not monitorize my non essential consumers via Victron portal, but i prefer this, than shortening my batteries lifetime.

victron-ver1.png

Your kind help will be higly appreciated.


John T.

Multiplus-IIESSwiring
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3 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @tc_shark,

You can control the conditions for which the AC-2 output is enabled or disabled. If you do not want to supply the load from there from the battery, then you would be best to program it so that the AC-2 output relay is only closed (making contact) when the battery is between 95-100% full (for example).

Therefor it will not be used to discharge the battery below that, and you will get the benefit of using the PV power to supply them when the battery is full.

If you find the internal relay is activating too often, then either increase the PV power, or the cycle range of the battery.

The MP-II will indeed try to use the battery to bring the grid import to zero. That threshold to which its maximum power is used before importing can also be set though, so for all loads over 1000W (for example) then the grid could provide support.

Internally there is no distinction between AC1 and AC2 output loads, once that contact relay is closed.

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tc-shark avatar image tc-shark commented ·

Dear @Guy Stewart (Victron Community Manager)

Thanks a lot for the answer, i really appreciate that.

Sticking to your example, if i program the "relay of AC2 closed (making contact) when the battery is between 95-100% full", it means that it will supply the loads if the battery is full, and after that it will continue to supply them from the grid, right?

Regarding your second example: " That threshold to which its maximum power is used before importing can also be set though, so for all loads over 1000W (for example) then the grid could provide support." this 1000W (example) refers to AC1 + AC2 together? If I understand well, if i set this limit to 1000W, and i have a load of 1700W (AC1+AC2) and my PV plant is producing 600W at that moment, than the difference until 1000w (400W) will be supplied from the battery backup, and the remaining difference (from 1000w to 1700w) of 700W will be taken out from the grid, right?

Sorry to repeat it, if might be obvious to you :) but i want to be sure i undertood well.


Thanks Guy


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Rob Duthie avatar image
Rob Duthie answered ·

Hi

You need to make sure the ABB PV inverter can be set to micro grid mode to work on the output of the Victron. so you get the PV power than using the battery power.

Regards

Rob D

NZ

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tc-shark avatar image tc-shark commented ·
Thanks Rob, but the question refers to another issue, as described above.... Sticking to the example, will those 1200w taken out from the batteries or from the grid in case A and in case B ?
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Rob Duthie avatar image Rob Duthie tc-shark commented ·
Hi

Yes i can supply from either grid or batteries you just set the inverter power to suit the loads in the ESS mode. Very flexible system the Victron gear,m You will need a color controller, cerbo or raspi to control this.

I have used all three types of control, even setup an assitant to divert surplus Pv power to heat hot water for off grid and on grid appliction works very well.

Regards

Rob D

NZ

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tc-shark avatar image tc-shark Rob Duthie commented ·
Thanks Rob, i'm still not sure about the answer to my original question, i'd be glad if anyone would tell me for sure what i asked: if non-essential loads connected on AC2 output will be powered by solar production (from on grid inverter connected on AC1 output) PLUS power from battery bank OR from grid?
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Rob Duthie avatar image Rob Duthie tc-shark commented ·
Hi

Yes will do.

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tc-shark avatar image
tc-shark answered ·
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