24v panel to 36v battery bank

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  • bbells
    Junior Member
    • May 2016
    • 21

    24v panel to 36v battery bank

    Ok, this isn't about what you think. I have several 24v solar panels. And several PWM 12/24v controllers. But, only room for one panel on my next project - A solar golf cart (not for golf).
    I know I can use more than one charge controller on a bank of batteries. But, can I use more than one on different groups of batteries in the series?
    Clarification: 36v battery bank. 6 golf cart batteries, 6v each, in series. Lets call them batteries 1,2,3,4,5,6.
    Question: From 1 solar panel can I use a 24v charge controller on batteries 1,2,3,4 and then a 12v controller on 5,6? I am thinking no because the 12v would have about 40% less wattage, but i am not sure.
    If that doesn't work,
    Can I use 3 12v controllers from the same panel, 1 on batteries 1 and 2. 1 on batteries 3 and 4. And 1 on batteries 5 and 6?
    Thanks for your help. I am retired and just getting into a new project. Oh, my home will be 100% solar by the end of July!!
  • SunEagle
    Super Moderator
    • Oct 2012
    • 15123

    #2
    Short answer. No.

    Long answer. Once the batteries (1 - 6) have been connected together as a complete 36v system you can't equally charge them using multiple chargers wired to different batteries in the same system.

    You will have to figure out how to either increase the pv voltage to about 42v going to the CC or use some other way to charge a 36v battery.

    Comment

    • bbells
      Junior Member
      • May 2016
      • 21

      #3
      So, the problem would be that the charge controllers probably have one common lead between the panel inputs and the battery outputs. This would mean that the controllers would short out due to being connected at the positive of one battery which is connected to the negative of another battery/controller. So, the only ways to make it work would be, an isolation circuit for the panel output (not going to happen), a charge switch that would go from one battery to the next after x amount of time. Or, a converter on the panels to bring the voltage up. The under load voltage on the 24v panel is just a little shy of what the 36v bank needs.

      Comment

      • bbells
        Junior Member
        • May 2016
        • 21

        #4
        Oh, I accidentally left one line out. It seems to me any kind of switch would disconnect the battery when switching (of course). Therefore the panel being connected to the controller without a battery would probably fry the controller when switched. Starting to look like I will need to have 2 panels with a 10 inch overhang on the roof of the cart. No big deal. At least I didn't get to the point of frying components. Always an interesting time on a project.

        Comment

        • littleharbor
          Solar Fanatic
          • Jan 2016
          • 1998

          #5
          Why don't you get a 96 cell high voltage solar panel and a controller that does 36 volt batteries.
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

          Comment

          • Sunking
            Solar Fanatic
            • Feb 2010
            • 23301

            #6
            Forget a PWM Controller. Never going to work. I build racing golf carts as a hobby, so do not expect solar to do much battery charging. They only increase your range. Not enough power to recharge a 36 volt golf cart battery in any meaningful amount of time. Just not possible unless you have a week to recharge.

            Anyway there is only one product out there that will work whether you like it or not. Genasun 36/48 volt Golf Cart MPPT Charge Boost Controller. It can take up to 325 watt 12 or 24 volt panels. It will do exactly what you want and the only game in town period.

            Best answer you are going to get anywhere.
            Last edited by Sunking; 07-04-2017, 08:20 PM.
            MSEE, PE

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