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80 3 X 6 cells two panels battery requirement

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  • 80 3 X 6 cells two panels battery requirement

    I am planning to build two panels with 36 3 X6 cells for each panel, what battery I should choose? this will be for an off grid power. thanks!

  • #2
    Hello and welcome to Solar Panel Talk!

    I moved your post to a separate thread. Thanks for joining! Someone should be with you shortly.

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    • #3
      Battery sizing.

      First, determine your loads. Then you only want the nightly load to deplete 20% of your battery. So that gives you a size.

      Then you want your solar to be able to recharge the battery from 50% dead to full, in one day, running all the normal loads too.

      And the charger needs to be able to supply about 10% of the battery's capacity rating, to insure a well agitated electrolyte.

      Then you must assume that your will get only 80% of the spec output of the cells.

      Now you can order the cells and build your panel.
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

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      • #4
        moving this thread to "Building Homemade Solar Panels" forum

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        • #5
          Originally posted by Mike90250 View Post
          Battery sizing.

          First, determine your loads. Then you only want the nightly load to deplete 20% of your battery. So that gives you a size.

          Then you want your solar to be able to recharge the battery from 50% dead to full, in one day, running all the normal loads too.

          And the charger needs to be able to supply about 10% of the battery's capacity rating, to insure a well agitated electrolyte.

          Then you must assume that your will get only 80% of the spec output of the cells.



          Now you can order the cells and build your panel.
          Mike that was very helpful. I try to not discharge my battery no more than 15% ( somewhere around 12.5v) because it takes too long to recharge it back to full. It seems like the deeper the discharge, the slower the rate of recharge too.

          I assume when you say dead battery, you mean discharged 20%.

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          • #6
            Originally posted by Mike90250 View Post
            Then you want your solar to be able to recharge the battery from 50% dead to full, in one day, running all the normal loads too.
            I'm allowing for 20% discharge from full, daily. If you have 2 cloudy days, you are now down 40 or 50% from full. When you go below 50%, it really begins to impact the lifetime of the batteries, so you don't want to plan on regular 50% drawdowns.
            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

            solar: http://tinyurl.com/LMR-Solar
            gen: http://tinyurl.com/LMR-Lister

            Comment


            • #7
              Originally posted by Mike90250 View Post
              I'm allowing for 20% discharge from full, daily. If you have 2 cloudy days, you are now down 40 or 50% from full. When you go below 50%, it really begins to impact the lifetime of the batteries, so you don't want to plan on regular 50% drawdowns.
              My charge controller shuts me off at 11v loaded, so if the battery were measured in unloaded voltage, it would probably be, 20% discharge and off it goes. Good feature.

              The advise on the 10% match of the battery to solar panel amperage output sounds good. So I guess if I had a 100ah battery, I would need at least 10a coming in from the panels to get the battery solution boiling good enough to keep the battery in good shape.

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