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  • bucephalis
    Junior Member
    • Jul 2013
    • 1

    #1

    Newbie, new house

    Hello. I'm just starting a new house, in the country. I've always been interested in going solar, and I was going to build the house (on a 400 acre farm) and later add the solar. Interested in grid tied. But I was just given (yup!) 48 LiFePo4 cells, 3.2v 200a each. They are unused. I have an opportunity to get a pure sinewave inverter as well, so I guess I'll go ahead and hook up. I've designed the house with a concrete walled room for batteries, etc., but the panels are going to be stand-alone, not on the house. So one basic design question first...should I put the batteries close to the panel, or in the house. I'll have some questions later on the inverter, haven't seen it yet, but I can have any one of several, from a 7000 w 240/120 v pure sine inverter, a 5600 pure sine 240/120 system that is 24v 23a, to a 3600 pure sine 220v (I think) 30amp 12v. With a little time there may be other choices. Don't have any more info on them yet. Oh, and a 10,000W 240/120 24v.

    It's about a 5000 sq foot 2 story, fireplaces arranged as alternate heat, digitally wired and wireless, heavily built. Clear southern exposure. Going to need some advice!!
  • Sunking
    Solar Fanatic
    • Feb 2010
    • 23301

    #2
    Go grid tied, you will be very sorry going off-grid solar especially with LiPo. The batteries will be destroyed in a year or two, and cost several thousands to replace. There no Charge Controllers for LiPo with BMS.

    Even withy using lead acid i fyou go off-grid you are looking at paying 10 times more for electricity the rest of your life in 5 year up front cash cost replacing batteries. Save yourself that pain, expense, and misery, go grid tied.
    MSEE, PE

    Comment

    • gpearce52
      Junior Member
      • Aug 2014
      • 3

      #3
      Originally posted by Sunking
      Go grid tied, you will be very sorry going off-grid solar especially with LiPo. The batteries will be destroyed in a year or two, and cost several thousands to replace. There no Charge Controllers for LiPo with BMS.

      Even withy using lead acid i fyou go off-grid you are looking at paying 10 times more for electricity the rest of your life in 5 year up front cash cost replacing batteries. Save yourself that pain, expense, and misery, go grid tied.
      Why do you believe the LiFePO4s will be destroyed in a year or two, reasons would be invaluable.

      Comment

      • Sunking
        Solar Fanatic
        • Feb 2010
        • 23301

        #4
        Originally posted by gpearce52
        Why do you believe the LiFePO4s will be destroyed in a year or two, reasons would be invaluable.
        That is two year old info. LiPo would not be the right choice. You would be wanting to use LFP aka LiFePO4. Cost for LFP have dropped to the 35 to 40 cents per watt hour. Depending on how you treat them around 2000 cycles. Still not competitive with high end FLA batteries but getting closer. It takes roughly 80 AH of LFP to equal 100 AH of FLA assuming discharge rate no greater than C/20. A good quality 5 year 12 volt 100 AH FLA will cost you roughly $250 to $275. A low end LFP 12 volt 80 AH will cost you around $330 to $400. Both perform the same amount of work and last just about the same.

        Having said that things change when you start discharging at higher than C/20 and the advantage swings to LFP. Example EV's that discharge at 1C and higher. Not it takes as much as a 400 AH flooded battery to = 100 AH LFP.
        MSEE, PE

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