80 3 X 6 cells two panels battery requirement

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  • knoxgi
    Junior Member
    • Oct 2010
    • 1
    #1

    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!
    Tags: 3x6, cell
    • Jason
      Administrator
      • Dec 2008
      • 990
      #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.

        Comment

        • Mike90250
          Moderator
          • May 2009
          • 16020
          #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

            Comment

            • Jason
              Administrator
              • Dec 2008
              • 990
              #4
              moving this thread to "Building Homemade Solar Panels" forum

                Comment

                • Clean energy seeker
                  Junior Member
                  • Oct 2010
                  • 6
                  #5
                  Originally posted by Mike90250
                  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%.

                    Comment

                    • Mike90250
                      Moderator
                      • May 2009
                      • 16020
                      #6
                      Originally posted by Mike90250
                      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

                        • Clean energy seeker
                          Junior Member
                          • Oct 2010
                          • 6
                          #7
                          Originally posted by Mike90250
                          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.

                            Comment

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