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  • Mike90250
    Moderator
    • May 2009
    • 16020

    #16
    320w (@13v)= 25A
    800A of batteries, needs (5-10% of capacity) to sufficiently bubble the electrolyte, this would be 40 - 80 amps. So, unless you have very long days, to complete the absorb cycle, and get the cells bubbling, you will get stratified electrolyte. Eventually, this will ruin the batteries. You could postpone this by rocking each battery a bit, when you visit them, to stir up the electrolyte, or use a turkey baster to slosh the acid around.
    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

    • Bala
      Solar Fanatic
      • Dec 2010
      • 734

      #17
      Mike re 5% to 10% of battery capacity for charging,

      I have 2250w of panels, 1800ah batteries and 2 40amp controllers.

      So by you equation I have a possible 4.5%, 80 amps, to charge with,

      My batteries charge without using any where near 80amps, probably only really use 2% to 3%

      Am I missing something?

      Comment

      • Sunking
        Solar Fanatic
        • Feb 2010
        • 23301

        #18
        Originally posted by Bala
        Am I missing something?
        Probable. Lead acid batteries really need charged at a C/8 C/10 rate for two reasons.

        1. to make the batteries electrolyte bubble and roll to prevent stratification.

        2. In Solar PV systems the batteries rarely ever get fully charged unless you far less power than the panels can generate each day, or in other words oversize panel wattage. You only get a few hours of productive sun each day anywhere from 1 to 6 hours depending on location and time of year. Most of the better charge controllers are 2 or 3 stage and the process take 10 to 24 hours to completely charge a battery. Most peoples 3 stage charge controllers never make it to the 3rd stage which is called float. Nor can a solar system apply a effective equalization charge. You have to have a generator and a good quality 4-stage charger to EQ a battery.
        MSEE, PE

        Comment

        • Bala
          Solar Fanatic
          • Dec 2010
          • 734

          #19
          My batteries go to float @ 27v no worries, they bubble away all the time.

          Basically I use things like the washing machine, pumps etc when the panels can run those items and hold the batteries in float,

          They are set to boost for 3 min @ 29.4, absorb for 4 hrs @ 28 (they dont absorb every day) then float @ 27v

          eqalize Volt is 31v for 2 hrs as per recommendations, the panels can do this no worries on a good day.

          Perhaps because my batteries only get down maybe 10%, so it does not take much to get them back up?

          Comment

          • Sunking
            Solar Fanatic
            • Feb 2010
            • 23301

            #20
            Originally posted by Bala
            They are set to boost for 3 min @ 29.4, absorb for 4 hrs @ 28 (they dont absorb every day) then float @ 27v
            Huh, this does not compute. I think you meant Bulk rather than boost.

            There no set time frames except for Float and Equalize. Float is indefinite time as you can apply a float voltage charge 24 x 7 x 365. Equalize is a timed constant voltage over charge.

            As for Bulk it is a Constant Current method, and terminates when the battery reaches a set voltage which is appealingly 29.4 volts on your system. Time is not defined in the Bulk charge. It could be only a few minutes with very shallow DOD, or up to several hours for a deeply discharged battery.

            Same goes for the absorption charge as there is no time defined, it takes how ever long it takes. Problem I see in your reply, you state it is a constant voltage of 28 volts which is lower then the Bulk charge. The Absorption charge is a current taper charge and terminates when the battery current reaches 3% of the rated charge. What I am driving at is the Absorption charge voltage has to be equal or greater than Bulk.

            Here is a good link that describes the process.
            MSEE, PE

            Comment

            • Sunking
              Solar Fanatic
              • Feb 2010
              • 23301

              #21
              Originally posted by Bala
              Mike re 5% to 10% of battery capacity for charging,

              I have 2250w of panels, 1800ah batteries and 2 40amp controllers.

              So by you equation I have a possible 4.5%, 80 amps, to charge with,

              My batteries charge without using any where near 80amps, probably only really use 2% to 3%

              Am I missing something?
              Operating at what voltage? 12, 24, or 48?

              Assuming a MPPT

              At 12 volts charge current = 188 amps
              24 volts at 94 amps
              48 volts at 47 amps
              MSEE, PE

              Comment

              • Bala
                Solar Fanatic
                • Dec 2010
                • 734

                #22
                Its called Boost on my system,

                perhaps i did not explain it properly, it is set to Boost/ bulk? daily or if the battery gets below a preset voltage,
                It boosts/bulks until it can hold at 29.4 for 3 minutes then drops to absorb or float,

                I will study the link, thanks,

                sorry if its hyjacking the thread just following on from mikes post

                Comment

                • Bala
                  Solar Fanatic
                  • Dec 2010
                  • 734

                  #23
                  24v system, sorry did not put that in before,

                  Comment

                  • Sunking
                    Solar Fanatic
                    • Feb 2010
                    • 23301

                    #24
                    Originally posted by Bala
                    24v system, sorry did not put that in before,
                    Ok then you are at 94 amps. So with 800 AH batteries you are at roughly 12% rated charge current which is great except for 1 thing. You only have 2 charge controllers rated at 40 amps
                    MSEE, PE

                    Comment

                    • Bala
                      Solar Fanatic
                      • Dec 2010
                      • 734

                      #25
                      We get 2250w / 24 = 94a in theory from the panels

                      i have 2 by 40a charge controllers so 80a in theory avail to charge with,

                      I have 1800ah battery so 1800 x 4.5% = 81a, so have a charge possible of 4.5%

                      Am i just calculating the % wrong?

                      Comment

                      • taxideytis
                        Junior Member
                        • Mar 2011
                        • 5

                        #26
                        So, unless you have very long days, to complete the absorb cycle, and get the cells bubbling, you will get stratified electrolyte. Eventually, this will ruin the batteries. You could postpone this by rocking each battery a bit, when you visit them, to stir up the electrolyte, or use a turkey baster to slosh the acid around.
                        ααα...οκ I do this, when i visit my home, every xmm 20 days. Also this summer i' m going to add 3 or 4 panels ...

                        thanks Mike

                        Comment

                        • bidaw
                          Member
                          • Apr 2011
                          • 46

                          #27
                          Originally posted by Mike90250
                          I know of none. 2 very different sources need 2 different control systems. Maybe someone else has ideas ?? Hello ?? Bueller ? Bueller ?
                          Sorry that I have come late to the party, but I was trolling on You Tube researching this very subject...and came across this.



                          I hope this helps.

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