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Combine separate arrays or not
#21
Had you thought of leaving one (or both) sets of panels connected to the grid to inverter/s and either;
With one array connected to the grid tie inverter and the second array charging the batteries.
Or
Leaving both arrays connected to the grid tie inverters and AC coupling the batteries.

Do you have many loads during the day that can use power as it’s generated from the grid tie inverters?
Do you have an electric HWS that you can use as a heat battery with an export limiter? They can store a huge amount of energy.

An inverter charger like a Victron Multiplus can be used to export/import limit between the battery and the grid tie inverters, and allow you to island in case of a mains failure.


In you original question, if the arrays are fairly similar in voltage the losses will be negligible if connected in parallel.
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#22
Hello Jon
I am leaving one set of panels connected straight to a grid tie inverter to cover morning loads while battery connected to other inverter is being charged..

My system requires absolutely no backfeed to the grid. I am using limiting inverters (will not allow any backfeed) to accomplish that, so I do not think ac coupling would be good for my circumstance..

I do try to use most of my appliances during peak solar to utilize as much solar as I can.

All 4 of us in the house shower off of the hot water heater only heating for 45 min once a day, I shut off and turn on hot water heater during peak solar.. yes the hot water heater uses 4500w but I cover 3k of that with my inverters during peak solar so I only use 1500w for 45min to heat water daily, so I can’t get much use out of a hot water power storage setup..

I already own 2 gridtie inverters that I been running and just received an outback charge controller,, I plan to purchase a power inverter for offgrid-emergency that I will just just flip a switch to use

Yes I came to the conclusion that the differences between the arrays power output is very minimal so connecting arrays will not be an issue.
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#23
Export limited AC coupling as part of a energy storage system works rather well, obviously requires a suitable inverter/charger - any surplus that would normally have to be curtailed is fed to the battery.
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#24
So there’s no backfeed Sean?
I’m always wanting more ideas for an absolute zero export system for when my inverters die
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#25
Hi Doin it

Sounds like you have a good plan Smile
Is it feasible to put a smaller element in your HWS so it draws a bit less current and run it for a bit longer?
A 2kw element running for 2 hours will let you get all your hot water without any import, to me the little optimisations that are a one of change are the things that make a whole system work, especially if they’re “passive or dumb” and don’t add complexity. A smaller element will also give a bit more headroom against needing to import on lower generation days.

With zero export I’d be even more inclined to AC couple and leave your inverters in place, something like a Multiplus will manage your charging and discharging of the battery to as close to zero import and export as the system is capable of. Multiplus will also handle your islanding.

If you have a few things that are all trying to manage zero export it can be a bit tricky where to put the CTs to get them to work in order of priority.
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#26
Smaller element is a good idea..then my inverters should cover all of the power it’s using,. I’ll have to look into it..

I don’t know to much about ac coupling besides the basics,. I’ll have to look into that aswell.. I’ll most likely have to purchase more components to ac couple which wouldn’t be a problem but I’m doing solar to start saving as much money as quick as possible.. might use ac coupling in the future tho
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