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  • 96V battery configuration

    Hi everybody,
    I need 28.8 kWh storage capacity for my battery bank to run 6 kWp hybrid inverter. I was planning to use 12 GEL battery 24V 100Ah in simple configuration 4 (series) and 3 (parallel) BUT the maximum I can get from supplier is a 12V 200Ah GEL batt.
    I would like to connect the battery like the pics enclosed:
    Battery_bank.jpg
    Is my design correct?
    Any suggestion?
    Thank you

  • #2
    Originally posted by Joe1970 View Post
    Hi everybody,
    I need 28.8 kWh storage capacity for my battery bank to run 6 kWp hybrid inverter. I was planning to use 12 GEL battery 24V 100Ah in simple configuration 4 (series) and 3 (parallel) BUT the maximum I can get from supplier is a 12V 200Ah GEL batt.
    I would like to connect the battery like the pics enclosed:
    [ATTACH]7003[/ATTACH]
    Is my design correct?
    Any suggestion?
    Thank you
    Your design is not correct. Once you have put eight 12V batteries in series to get 96V, you cannot parallel only some of the batteries in the series string to try to get more capacity. Each step in the string must be identical in capacity.

    You can to to a total of 16 batteries, or you can stop at 12.
    If you could find suitable 8V batteries, you could put 12 of them in series to get your 96V.

    Without seeing the exact specifications of the battery type you have selected, you should know that 90+% of GEL type batteries are not suitable for RE use, because the typical GEL battery cannot be charged at a rate higher than C/20, which would not leave enough useful daylight hours in the day to recharge properly.

    Your original idea of using three parallel strings of 24V batteries is also flawed because of the difficultly of keeping the charge and discharge currents balanced among the three strings. It is difficult to keep two parallel battery strings in balance. Three is a lot more difficult.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

    Comment


    • #3
      Originally posted by inetdog View Post
      Your design is not correct. Once you have put eight 12V batteries in series to get 96V, you cannot parallel only some of the batteries in the series string to try to get more capacity. Each step in the string must be identical in capacity.

      You can to to a total of 16 batteries, or you can stop at 12.
      If you could find suitable 8V batteries, you could put 12 of them in series to get your 96V.

      Without seeing the exact specifications of the battery type you have selected, you should know that 90+% of GEL type batteries are not suitable for RE use, because the typical GEL battery cannot be charged at a rate higher than C/20, which would not leave enough useful daylight hours in the day to recharge properly.

      Your original idea of using three parallel strings of 24V batteries is also flawed because of the difficultly of keeping the charge and discharge currents balanced among the three strings. It is difficult to keep two parallel battery strings in balance. Three is a lot more difficult.
      Thank you I understand for the design.
      Now I just update the design with 16 GEL battery 12V 150Ah (8 in series + 8 in series).
      Sorry but I didn't understand what you mean with RE and with c/20?
      The GEL battery have to use in quiet hot area and actually they will be manage by Hybrid 6 kWp inverter using the public grid as backup and a 5 kWp solar power plant. the average sunshine will be about 5.1 hours a day.
      Do you think GEL batt is not the best choise?

      Comment


      • #4
        Originally posted by Joe1970 View Post
        Thank you I understand for the design.
        Now I just update the design with 16 GEL battery 12V 150Ah (8 in series + 8 in series).
        Sorry but I didn't understand what you mean with RE and with c/20?
        RE = Renewable Energy, such as solar PV or wind.
        GEL batteries are found most often in Uninterruptible Power Supplies (UPS) where they will deliver a high load current for an hour or two and then be recharged over 24 hours or more.
        If you have a 100AH battery (at the 20 hour rate) then C/20 is a current of 5A. For most GEL batteries recharging at a higher current than that will cause permanent loss of capacity from bubbles in the electrolyte separating the GEL from the plates.

        Now if you take that 100AH battery down to 50% SOC (State Of Charge) you will need to restore a little more than 50AH to fully recharge.
        If the power source is PV, you will only have at most 5 hours in the day to recharge at full panel power.
        5 hours at 5A will only put back half the capacity used.

        A Floating Lead Acid (FLA) battery can be safely recharged at the ten hour rate (C/10) or 10A for a 100AH battery. In a pinch you can go as high as C/8.
        The Absorbed Glass Mat (AGM) sealed battery type can tolerate a recharge rate of C/4 or higher, making it even better for restoring full charge in a shorter period of time.
        But AGM cost more than FLA for the same capacity and do not last as long. If you also need a very high discharge rate, then AGM may make economic sense compared to an FLA bank of twice the capacity.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

        Comment


        • #5
          Originally posted by inetdog View Post
          RE = Renewable Energy, such as solar PV or wind.
          GEL batteries are found most often in Uninterruptible Power Supplies (UPS) where they will deliver a high load current for an hour or two and then be recharged over 24 hours or more.
          If you have a 100AH battery (at the 20 hour rate) then C/20 is a current of 5A. For most GEL batteries recharging at a higher current than that will cause permanent loss of capacity from bubbles in the electrolyte separating the GEL from the plates.

          Now if you take that 100AH battery down to 50% SOC (State Of Charge) you will need to restore a little more than 50AH to fully recharge.
          If the power source is PV, you will only have at most 5 hours in the day to recharge at full panel power.
          5 hours at 5A will only put back half the capacity used.

          A Floating Lead Acid (FLA) battery can be safely recharged at the ten hour rate (C/10) or 10A for a 100AH battery. In a pinch you can go as high as C/8.
          The Absorbed Glass Mat (AGM) sealed battery type can tolerate a recharge rate of C/4 or higher, making it even better for restoring full charge in a shorter period of time.
          But AGM cost more than FLA for the same capacity and do not last as long. If you also need a very high discharge rate, then AGM may make economic sense compared to an FLA bank of twice the capacity.
          Really thank you very much and sorry for my poor knowledge about battery, just because I always do Grid Tie system.
          Actually I am design the system here in china and of course I need to stay inside a budget.
          So basically I understand your suggestion will be for AGM type, correct?
          I also have as option here Sealed led acid one, but it is better I post the datasheet as soon I will receive!

          Comment


          • #6
            Originally posted by Joe1970 View Post
            Really thank you very much and sorry for my poor knowledge about battery, just because I always do Grid Tie system.
            Actually I am design the system here in china and of course I need to stay inside a budget.
            So basically I understand your suggestion will be for AGM type, correct?
            I also have as option here Sealed led acid one, but it is better I post the datasheet as soon I will receive!
            If you have the space, FLA will be most economical.
            There are only two common types of sealed Lead Acid batteries, AGM and GEL. Any listing for "sealed" that does not tell you which type it is a strong indication that you should not buy from that source.

            At this time, other battery types such as NiFe and Lithium are not suitable for the average user.
            SunnyBoy 3000 US, 18 BP Solar 175B panels.

            Comment


            • #7
              Originally posted by inetdog View Post
              If you have the space, FLA will be most economical.
              There are only two common types of sealed Lead Acid batteries, AGM and GEL. Any listing for "sealed" that does not tell you which type it is a strong indication that you should not buy from that source.

              At this time, other battery types such as NiFe and Lithium are not suitable for the average user.
              This is the datasheet of the "AGM" 12V 150Ah. Actually this supplier do not write clear AGM but just Lead Acid Battery. Really hard to trust....anyway have good price and many told me the quality is acceptable.
              So, 16 of that, 8 in series x 2 line.
              What you think?
              Page1.jpgPage2.jpg

              Comment


              • #8
                Originally posted by Joe1970 View Post
                This is the datasheet of the "AGM" 12V 150Ah. Actually this supplier do not write clear AGM but just Lead Acid Battery. Really hard to trust....anyway have good price and many told me the quality is acceptable.
                So, 16 of that, 8 in series x 2 line.
                What you think?
                [ATTACH]7014[/ATTACH][ATTACH]7015[/ATTACH]
                The performance data looks acceptable. Note that the maximum charge rate is shown on page one as .25C (= C/4). That is good indication that these are AGM rather than GEL batteries.
                But they will not tolerate the C/3 charging rate that one of the earlier posters calculated. With the same charging power but two parallel strings, that would seem to be C/6, which would be fine.
                SunnyBoy 3000 US, 18 BP Solar 175B panels.

                Comment


                • #9
                  Originally posted by inetdog View Post
                  The performance data looks acceptable. Note that the maximum charge rate is shown on page one as .25C (= C/4). That is good indication that these are AGM rather than GEL batteries.
                  But they will not tolerate the C/3 charging rate that one of the earlier posters calculated. With the same charging power but two parallel strings, that would seem to be C/6, which would be fine.
                  Something else about those batteries. That 150Ah rating is for a 10 hour discharge. Most Deep Cycle give an Ah rating over 20 hours.

                  Comment


                  • #10
                    Originally posted by SunEagle View Post
                    Something else about those batteries. That 150Ah rating is for a 10 hour discharge. Most Deep Cycle give an Ah rating over 20 hours.
                    That is a good thing, indicates they are Industrial grade. Bad new could likely be they are used for UPS and not made for cycle service.
                    MSEE, PE

                    Comment


                    • #11
                      Originally posted by Sunking View Post
                      That is a good thing, indicates they are Industrial grade. Bad new could likely be they are used for UPS and not made for cycle service.
                      The data sheet does list cycles versus depth of discharge and if I recall it was over 2000 cycles at 50% DOD. Is that believable? I can't say.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

                      Comment


                      • #12
                        Originally posted by inetdog View Post
                        Is that believable? I can't say.
                        I think you can with a name like Jiangsu. You may not say it, but I know what you think.
                        MSEE, PE

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