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12V multiple battery system, how to output 48v to UPS inverter

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  • 12V multiple battery system, how to output 48v to UPS inverter

    I currently have a standard grid tied mains system which runs through a standard inverter, but I have recently been playing around with some extra camping equipment to try and run some household stuff to further reduce my energy bill without investing majorly in new equipment.

    To that end, I have:

    1 x 200W 12V solar panel
    1 x 30A 12/24 solar charge controller
    6 x 12v batteries of different sizes, recovered from self propelled golf buggies
    2 x 1050W continuous UPS inverters without batteries

    I've managed to rejuvenate all the batteries so that they hold a charge of 12.5V or more and have them hooked up in parallel

    My idea is to use the solar to charge the batteries during the day and then through the inverted, run the fride at night when the mains solar system is not feeding the house.

    One of the problems is that the UPS inverter has a 48V input. I could of course hook up the batteries in a combination of parallel and series to get 48V, but I wouldn't know how to charge them. Manual switching is not an option as they are in a hard to reach place and this would be too complicated when I'm not around.

    This is really just messing around with recycled parts, so I'm not really looking and making a huge purchase of equipment, but if there is a reasonable solution, I would be interested.

    Regards,

    Mark


  • #2
    no easy way without buying gear, or moving connections twice a day. sorry
    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


    • #3
      Originally posted by gtr33m View Post
      This is really just messing around with recycled parts, so I'm not really looking and making a huge purchase of equipment, but if there is a reasonable solution, I would be interested.
      Nothing easy. You could do a Rube Goldberg thing with relays to connect them as either a 12V bank or a 48V bank depending on time of day, but the relays to do that (which all have to be rated to the fault current of the system) will not be cheap or simple.

      Comment


      • #4
        I thought of using an Arduino and a bank of relays, but i think the relays would be expensive and the thought of one relay failing to cut over and the resulting fire made me rethink it!

        I think I'll rewire the 12v led downlights to permanently off mains, and maybe hook up a couple of points to run a few 12v devices like routers and modems.

        I've got 6x 8v batteries of unknown condition which i inherited, so I'll keep an eye out for some used 48v panels and maybe set up another Frankenstein system for the fridge or washing machine. I know that ups inverters are not good for motors, but hey they are free and lying around!

        Thanks for qualifying.

        Mark

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        • #5
          Just remember anything you take off grid will cost you 5 to 10 times more than buying power, and makes you a heavy polluter. Now why do you want to do that?
          MSEE, PE

          Comment


          • #6
            Please correct me if I'm wrong, but the statistics of 5 to 10 times is based on the cost of production of materials over life expectancy if the system.

            If you read my post, everything that I'm using has been recovered (UPS with dead batteries and old batteries destined to be recycled) or sitting mostly idle (solar panel used when camping). Even the wiring and interconnects were recovered from the scrap merchant I dropped the old ups batteries off to.

            In this case the expense is my time, which has a very questionable value 😉

            Mark

            Comment


            • #7
              Mark you cannot recover batteries, that is where the cost are at. I am not even talking about the panels, controller, wiring, Inverter, or any hardware, just batteries.
              MSEE, PE

              Comment


              • #8
                What Sunking is saying, is that when batteries die, and are replaced, it's seldom possible to perform any "connect wires to the battery terminals and to a magic box" and "Recover" them. You can likely get them to accept a charge, but they are not likely to hold any meaningful power after a cycle or two.
                But, as you say, no cost, except for your time. I would suggest charging them, and then using a 250W 12V inverter, load the battery down with a 60w light bulb for an hour, and see if it makes it. Then you can sort the good batteries from the duds, and try to do something.
                When building a battery bank, all the batteries in it should be closely matched for capacity, or the "smallest" one will get reverse charged and destroyed when you pull hard from the pack.

                And don't do any of this indoors or near anything flammable - If a battery shorts out, who knows what it will do, burn, explode, or melt a hole in the side and drain the acid out on to your carpet.
                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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