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Solar panels and deep cycle batteries

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  • gll

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    Right. We were talking about the 'micro-inverters' attached to each panel - like the integrated ones you spoke of. Again, if those things require a source of power, other than what the panel itself could provide, it would surprise me.
    They do... It's the safety mechanism that prevents backfeeding in a grid down situation.

    Essentially, you could put a 220v plug on a micro-inverter solar panel and plug it into your wall to feed the grid, until the grid goes down, then nothing...

    A hybrid inverter cuts power to grid when switching to battery power for the same reason.
    Texas SOT
     

    MountainGirl

    Never underestimate the abilities of an old woman.
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    The advantage to having excess generation is that you'll have more power on cloudy days...

    The way I first dealt with the generation to storage mismatch is with manual switches to cutoff one or two of my 10 panel 3kw strings when there is excess sun.

    Then later, to automate, I added current sensing relays to two strings that are controlled by the current in the primary string, shutting those down as required to maintain a max total output current for battery charging in an off-grid situation..

    YES!

    You just outlined well the problem with trying to use a grid-tie mismatched setup for a grid-down event. Thank you. The solutions you've described might not be easy for those whose skillsets are elsewhere.

    I intentionally had a small mismatch on the mountain - to cover expanding uses that were unknowable at the time - and the result was power coming down while overcast, and still enough extra I was able to change out the propane HW heater for a 20gal 110 unit.

    EDIT: I need to clarify, here. The panels and battery bank was not mismatched. What WAS mismatched was the size of the whole system to our existing needs. It was bigger than what we needed - for potential use increase.
     
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    MountainGirl

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    They do... It's the safety mechanism that prevents backfeeding in a grid down situation.

    Essentially, you could put a 220v plug on a micro-inverter solar panel and plug it into your wall to feed the grid, until the grid goes down, then nothing...

    A hybrid inverter cuts power to grid when switching to battery power for the same reason.
    If one is grid-tied, there's already an interlock (transfer switch) in the setup to prevent any backflow, from any source. That'd be paramount for the grid provider.
     

    gll

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    YES!

    You just outlined well the problem with trying to use a grid-tie mismatched setup for a grid-down event. Thank you. The solutions you've described might not be easy for those whose skillsets are elsewhere.

    I intentionally had a small mismatch on the mountain - to cover expanding uses that were unknowable at the time - and the result was power coming down while overcast, and still enough extra I was able to change out the propane HW heater for a 20gal 110 unit.
    Solar panels being relatively inexpensive, I like the idea of solar direct water heating for SHTF is appealing, with the caveat that heated water wouldn't always be available...

    I have a 10gal WH appended to my solar direct well pump system that heats quickly in good sun... used it to bath my old dog Thursday... SHTF, I could get a hot shower on sunny days.
     

    gll

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    If one is grid-tied, there's already an interlock (transfer switch) in the setup to prevent any backflow, from any source. That'd be paramount for the grid provider.
    In a micro-inverter grid-tied system the interlock is in the inverters, really, just like it is in a line inverter.

    I don't have any other transfer switch.
     

    MountainGirl

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    MG, I didn't read all the specs, but wonder if buying up to those LiFePO4 cells gets you a lot more charge cycles? That would be worth something, if so.
    It would be, yes. I like the lithium iron over the lithium ion any day, for safety reasons, if nothing else.

    LOL which reminds me - I read back through this whole thread yesterday...and one of the posts spoke about some guy who stored all his batts on a wire rack in a closet...and I thought, man I hope those were AGMs and not lead acid!! :laughing:
     
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    MountainGirl

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    In a micro-inverter grid-tied system the interlock is in the inverters, really, just like it is in a line inverter.

    I don't have any other transfer switch.
    Oops, I wasn't clear, sorry. The transfer switches we had/have (one on the house in Katy, one out here) to hook up the gen (no solar involved) - had/has a 'lock-out' function to disable any path to the grid.
     
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    gll

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    MG, I didn't read all the specs, but wonder if buying up to those LiFePO4 cells gets you a lot more charge cycles? That would be worth something, if so.

    It would be, yes. I like the lithium iron over the lithium ion any day, for safety reasons, if nothing else.

    LOL which reminds me - I read back through this whole thread yesterday...and one of the posts spoke about some guy who stored all his batts on a wire rack in a closet...and I thought, man I hope those were AGMs and not lead acid!! :laughing:
    SOK Battery | 100Ah 48v | User-Serviceable Rack Mount Battery

    48 Volt (51.2 Nominal) 100Ah, 5.12 kWh, LiFePO4
    10 Year Full Warranty & 20 Year Typical Lifespan
    Cells rated for 80% Capacity after 4000 Cycles, 100% DOD @1C Rate
    Typical capacity at 80% DOD @.5C Rate is over 7000 Cycles


    I think these "server rack" batteries are the way to go over 12v when looking at LiFePO4...
     

    gll

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    Not until I add more batteries. I have room AC units I can still use though.
    Your powerwall does all the work of providing grid-down power... Obviously, you could add another, but to do any other battery setup, you would have to add a hybrid inverter, right?
     

    MountainGirl

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    ^^ Not laughin at you @gll
    Just the inevitable hoops.
    And not really laughing, either.
    It doesn't need to be so complicated.

    Time for some shine. :D
     

    no2gates

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    Your powerwall does all the work of providing grid-down power... Obviously, you could add another, but to do any other battery setup, you would have to add a hybrid inverter, right?
    Already have the inverter in addition to the Powerwall. All I would need to do it add additional powerwalls to the system. I'll wait a few years until the price comes down (they're hard to get now).
    If the power goes out, the battery kicks in for everything that is on that battery backed up panel, which is almost everything except the HVAC system and hot water heater, washer/dryer,
     

    MountainGirl

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    Already have the inverter in addition to the Powerwall. All I would need to do it add additional powerwalls to the system. I'll wait a few years until the price comes down (they're hard to get now).
    If the power goes out, the battery kicks in for everything that is on that battery backed up panel, which is almost everything except the HVAC system and hot water heater, washer/dryer,
    Sub panel then, good idea. Hope those Powerwalls are still available when you want them though I dont know why you'd think the price will come down...

    We had a Generlink installed here to hook up the 30amp dual/fuel gen - and we'll shut off all the Main panel circuits except those that power the freezer & one kitchen outlet. Easy peasy, lol.

    Might still do a full solar backup, now that everything else is in place. It would be a lot of fun to do another one. :)
     

    MountainGirl

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    MG, I didn't read all the specs, but wonder if buying up to those LiFePO4 cells gets you a lot more charge cycles? That would be worth something, if so.
    Hi, not ignoring you, had chops & shine for lunch, just waiting for it to wear off a bit so what i look at makes sense. :)
     

    Tnhawk

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    Sub panel then, good idea. Hope those Powerwalls are still available when you want them though I dont know why you'd think the price will come down...

    We had a Generlink installed here to hook up the 30amp dual/fuel gen - and we'll shut off all the Main panel circuits except those that power the freezer & one kitchen outlet. Easy peasy, lol.

    Might still do a full solar backup, now that everything else is in place. It would be a lot of fun to do another one. :)
    I'll hope to have a Generlink installed in the house in Savannah before I move my generator from TN.
     

    gll

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    Wow reading all of this about grid tie is making my head hurt!!! It appears that the grid providers make it as difficult as possible. Glad I am totally off gird, with no chance of ever getting on, running my mini splits and my electric hot water heaters ;)
    Getting my grid-tied system approved by my co-op was actually very easy... Two guys came out, switched off my main breaker, told me to switch my solar array on, then tested for voltage my side of the main breaker... No voltage... OK!

    The complication for me was trying to turn my grid-tied system into a hybrid system that can go off-grid...

    Hybrid inverters solve that handily, if you plan ahead.
     

    MountainGirl

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    Wow reading all of this about grid tie is making my head hurt!!! It appears that the grid providers make it as difficult as possible. Glad I am totally off gird, with no chance of ever getting on, running my mini splits and my electric hot water heaters ;)
    That might depend on the grid provider - our co-op (SamHoustonElectricalCo-op) promotes it, encourages it. Again, though, one really needs to read the fine print in the grids documents... to see what you're agreeing to as far as what all access they will have to your power.

    Also. Having an off-grid, or even a backup solar system for grid-down, may not be the best choice for everyone; each circumstance is different. For example. If your house is in the middle of the city, or even in the burbs, it might be better to be in a similar situation as the homes around you - rather than being the only place around with power. Again, circumstances matter. In that example ^^ having a small solar inverter (like the Oupes) would give the city-dweller a chance to at least make a cup of coffee, charge a cell phone, etc... as the whole portable unit & panels can be brought inside and protected.

    For those of us out in the boonies, though, it's a whole 'nother thang. :D
     

    MountainGirl

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    MG, I didn't read all the specs, but wonder if buying up to those LiFePO4 cells gets you a lot more charge cycles? That would be worth something, if so.

    It would be worth something, indeed. At our age (we're both old, lol) 3-5000 deep cycles will do the trick.. for with the right quantity, and keeping them balanced, they'll last longer than we will. :laughing:

    This is them: $874
     
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