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  • Wiring batteries 2volt to 24volt

    Hi everyone have just joined the forum so may be asking a question that already has been answered. I have just purchased 48 2volt 500amp batteries and would like to wire them into a 24volt 2000amp system . I have connected up 12 into a 12volt bank using a old 12v inverter while I am waiting for the new 24v one. What I am not sure about is that I only have 12v output from using one terminal of the first battery and the other off the opposite terminal on the last battery but I have been told I shouldn't be putting power in to the batteries and drawing it out from the same terminals but these 2 terminals are the only ones which are 12volt . If this is wrong would someone be able to help with a wiring diagram for 12 2volt system staying at 12volts with a power in and a power out connection points and also a wiring diagram for 48 2volt into a 24volt system with a power in and power out . Thank you for any help Regards Dave

  • #2
    If you connected 12 - 2V batteries into a 12V bank then you have 6 in series paralleled to 6 more in series.
    With that parallel set you should have two TWO sets of terminals that are reading 12V

    2000Ah is a heck of a lot for a 24V system. If you can return or cancel that 24V inverter I would recommend doing so and getting a 48V inverter instead.

    you will need 4 parallel strings with your batteries to get 24V but only 2 parallel strings to get 48V
    Both systems will have the same power storage but the 48V one will be more efficient, use smaller wires and be safer overall.
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #3
      Originally posted by ButchDeal View Post
      If you connected 12 - 2V batteries into a 12V bank then you have 6 in series paralleled to 6 more in series.
      With that parallel set you should have two TWO sets of terminals that are reading 12V

      2000Ah is a heck of a lot for a 24V system. If you can return or cancel that 24V inverter I would recommend doing so and getting a 48V inverter instead.

      you will need 4 parallel strings with your batteries to get 24V but only 2 parallel strings to get 48V
      Both systems will have the same power storage but the 48V one will be more efficient, use smaller wires and be safer overall.
      Ditto what Butch said
      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
        And for wiring of two or more parallel batteries or stacks of batteries, see http://www.smartgauge.co.uk/batt_con.
        You generally[B] do[/B] want to charge through the same set of terminals that you discharge, just not the same position on both halves of a parallel set instead of diagonal wiring.
        Last edited by inetdog; 04-10-2019, 05:26 PM.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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        • #5
          Hi thanks for the replies the reason for me to go 24v is the batteries are used if I have a failure I can still use 24v just at a lower amps if I had a total failure I would have a better chance of replacing 24volts of batteries Than a 48v set hope this makes sense . Regards Dave

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          • #6
            Originally posted by Sapphireminer View Post
            Hi thanks for the replies the reason for me to go 24v is the batteries are used if I have a failure I can still use 24v just at a lower amps if I had a total failure I would have a better chance of replacing 24volts of batteries Than a 48v set hope this makes sense . Regards Dave
            It is most likely that a single 2V cell will fail rather than a set of 12 independent batteries. By simply cutting the failed cell/battery out of the series string and adjusting the charger set points down appropriately you would be able to continue near full power operation with 23 batteries instead of 24.
            Replacing just one 24V string from a parallel set is definitely not a good idea since it can lead to premature failure of the "good" string.
            Replacing one cell in a series string with a new unit will have less of a downside, since you will get the full remaining life out of the older batteries.
            Last edited by inetdog; 04-11-2019, 03:30 PM.
            SunnyBoy 3000 US, 18 BP Solar 175B panels.

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            • #7
              Thanks for the info inetdog . Dave

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              • #8
                Hi I already have 28 190w solar panels there output is 44volts can this be boosted to run the 48volt system or is a total upgrade needed thanks Dave

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                • #9
                  Originally posted by inetdog View Post
                  And for wiring of two or more parallel batteries or stacks of batteries, see http://www.smartgauge.co.uk/batt_con.
                  You generally[B] do[/B] want to charge through the same set of terminals that you discharge, just not the same position on both halves of a parallel set instead of diagonal wiring.
                  As far as I can tell the OP is talking about two strings. Is there any advantage of putting sets of two in parallel?. This is commonly done with Lithium but I am unfamiliar with the issues around Lead Acid. The above link suggests this is possible as long as the interconnections are of similar resistance.

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                  • #10
                    Originally posted by Ampster View Post
                    As far as I can tell the OP is talking about two strings. Is there any advantage of putting sets of two in parallel?.
                    OP has 48 batteries at 2v and wants a 24v bank so he is talking about four strings not two in parallel
                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                    • #11
                      Originally posted by Sapphireminer View Post
                      Hi I already have 28 190w solar panels there output is 44volts can this be boosted to run the 48volt system or is a total upgrade needed thanks Dave
                      Yes put them in strings of 3 or 4 and then parallel the strings and connect to MPPT charge controller
                      The number in series will depend in the charge controllers input voltage range.
                      OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                      • #12
                        48V is still a better option. You'll still have two parallel strings at 48V, which will be better to manage than four 24V strings. As Inetdog mentions, of you have one single battery failure, you can simply remove one battery from the string and adjust the voltage. As the voltage increases, this hecomes less problematic. Besides, if you need to remove 1 single failed battery, you'll need to remove three good batteries from the other strings, to balance things out. At 48 volts, this would be only one more battery.
                        Last edited by MichaelK!; 04-14-2019, 02:27 PM.

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                        • #13
                          Hi ButchDeal the MPPT is 60amp 12v to 48v Hi MichaelK my biggest concern is total battery failure meaning end of life or worn out the cost in Australia to replace the batteries in a 48 volt system is in the 18,000 to 20,000 dollar range as against 8,000 to 10,000 on a 24 volt system that is the biggest consideration for me thanks everyone Dave

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                          • #14
                            Originally posted by Sapphireminer View Post
                            Hi ButchDeal the MPPT is 60amp 12v to 48v
                            Charge controllers are rated on the output voltage not the input voltage. So to get higher voltage string the pv modules together in series ( increases voltage)
                            larger battery voltage allows the charge controller to handle more solar wattage.
                            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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                            • #15
                              The controller is 100 volts so I guess that would be 2 sets of 2 44v panels in series then connected in parallel to give 88volts . Thanks Dave

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