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Need to split battery bank. Opinions / Suggestions requested

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  • Need to split battery bank. Opinions / Suggestions requested

    Due to space limitations and weight distribution considerations, I really need to be able to split up my battery bank, unless it's a completely unworkable solution.

    It will be a 24V bank, consisting of eight 6-V batteries... two parallel strings of 4 batteries each.

    The two 4-battery strings to be paralleled would need to be separated by a distance of ~ 2 feet, but the distance the cables between each string would have to run is ~ 3 feet. The batteries within each string would be right next to each other, so the series connections would be very short.

    The distance from one string to the inverter would be negligible... it will be mounted within a foot or so of the closest parallel branch.

    Is this a feasible scenario? Will this cause any significant problems with battery balancing, inductance, or any other variables I may not even be thinking of at the moment. If there are problems with this arrangement, are there steps that can be taken to mitigate them?

    Thanks!

  • #2
    With good construction techniques, it's workable.

    Things to watch for
    Both battery banks at the same temperature. The warmer one will fail first
    Check your cable symmetry after installing, apply a large load to the inverter and measure the DC amps of each battery bank, they should be within a couple amps of each other.
    see the smartgauge site http://www.smartgauge.co.uk/batt_con.html for wiring ideas
    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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    • #3
      Thanks for the advice, Mike. That sounds like a plan.

      Maybe I should distance the one string a bit further from the inverter then, as right next to it there would likely be a measurable temp difference compared to the other.

      Comment


      • #4
        Originally posted by magicbus View Post

        Maybe I should distance the one string a bit further from the inverter then, as right next to it there would likely be a measurable temp difference compared to the other.
        That is NOT a good idea. Strings with different lengths of wiring will charge differently, ie: the one with the longer length will not charge as well. However, they could be located in two physically different places if the wiring lengths for both strings were exactly the same. I would rig a switch so that one bank could be isolated from the other if you ever find them becoming inbalanced. Then you could charge each bank separately till they are both at full charge.

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        • #5
          Would it be appreciate to make the conductors for both banks the same length and neatly coil up the excess from the nearer bank?

          Comment


          • #6
            Originally posted by PNW_Steve View Post
            Would it be appreciate to make the conductors for both banks the same length and neatly coil up the excess from the nearer bank?
            Yes.
            SunnyBoy 3000 US, 18 BP Solar 175B panels.

            Comment


            • #7
              Originally posted by PNW_Steve View Post
              Would it be appreciate to make the conductors for both banks the same length and neatly coil up the excess from the nearer bank?
              I appreciate this is a DC application so as long as what's going through them is DC, the answer is yes.

              Comment


              • #8
                Originally posted by J.P.M. View Post

                I appreciate this is a DC application so as long as what's going through them is DC, the answer is yes.
                I think OP is safe. I have not encountered any AC battery banks yet.

                Comment


                • #9
                  Originally posted by PNW_Steve View Post

                  I think OP is safe. I have not encountered any AC battery banks yet.
                  You missed the thread about AC batteries at NAWS !
                  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

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