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  • batteries drained

    I setup a small solar setup on a floating dock that powers 3 led lamps (about 24 watts total) when turned on. The system uses 2 marine batteries that I hoped would maintain a full charge for use with a trolling motor. I setup the system in the spring of 2018 with essentially no load on it since the inverter that powers the lamps has an on/off switch and stays on off. I've checked on the system about twice per month over the last 8 months and all has looked ok - batteries at 100% and lights work when turned on. However, when I checked this week, the charge controller displayed a battery discharge error and both batteries (wired in parallel) were dead with zero charge. I also noticed some corrosion on the positive terminal connection of the lead battery. I'm thinking that only a dead short in the system could drain two 200 Ah batteries with no load over about a 3 week period. The 30 watt solar panel appears ok as it's I'm seeing 21.2 volts and 1.35 amps. If the panel diode battery current block had failed, I would think that the panel itself would have failed.- any ideas on this problem. See setup below :

    SolarConfig.JPG

  • #2
    Short answer is apply 12V to the batteries and use a clamp on ammeter to see where the
    current is going. In several weeks, it would only take a couple amps to flatten the batteries.
    A straight out DC disconnect would remove the inverter, but sometimes a low power circuit
    is supposed to turn off transistors, so an internal failure could do it. Bruce Roe

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    • #3
      Originally posted by bob20 View Post
      I'm thinking that only a dead short in the system could drain two 200 Ah batteries with no load over about a 3 week period.
      A dead short would drain it in minutes. A tiny drain (less than an amp) over 3 weeks will kill those batteries dead.

      Corrosion indicates some galvanic path to ground, although it's usually less than an amp.

      Check your charge controller and make sure it is outputting the right current.

      Comment


      • #4
        Well, when the battery started discharging could have been anytime from when I noticed the error or 3 weeks ago when I last noticed that is was ok. So, it's only guess as to how much current over what time period . There has been more overcast than sunny days lately, so a slow drain with little or no charging could have killed them. One of the batteries charged, but the other would not take a charge. I plan to hook it back up with the good battery, solar panel and controller , but leave the inverter and lamps out, and add shunts and meters to monitor battery discharge and solar charge..

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        • #5
          I have two sets of 200W portable rigid cells with diodes and controllers. Both charge up my 3x100Ah deep cycle batteries in bright sunlight but seem to draw the batteries down again when the sun moves around. If I follow the sun with the cells this doesn't happen.
          Overnight will draw the batteries down.
          I am judging this by the meters in the RV, Volts and percent capacity. Appreciate these may not be the most accurate.
          I assumed this was diode failure when I first noticed the issue, but now beginning to wonder.
          Appreciate some guidance on this. Would a DC-DC converter stop this?
          Thanks

          Comment


          • #6
            Originally posted by Steve101 View Post
            I have two sets of 200W portable rigid cells with diodes and controllers. Both charge up my 3x100Ah deep cycle batteries in bright sunlight but seem to draw the batteries down again when the sun moves around. If I follow the sun with the cells this doesn't happen.
            Overnight will draw the batteries down.
            I am judging this by the meters in the RV, Volts and percent capacity. Appreciate these may not be the most accurate.
            I assumed this was diode failure when I first noticed the issue, but now beginning to wonder.
            Appreciate some guidance on this. Would a DC-DC converter stop this?
            Thanks
            1) diodes - Never needed when using a good charge controller. Expect losses of nearly a volt across them, reducing power to your battery.

            2) 300 ah of batteries needs a charging source of 30A to maintain battery health

            3) batteries being rapidly drawn down indicates either End of Life of the battery, or excessive loads




            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


            • #7
              Thanks for the guidance.
              Batteries are near new.
              The situation described is with no load connected during maintenance charging between trips.
              I first noticed this on another RV with 200 Ah batteries in same circumstances.
              Solar cells are nothing special from camping shop and connect direct through an Anderson plug.
              For 30A output I would need both sets of cells in direct sunlight - correct?
              I can bypass the diodes and charge controllers and connect through a Redarc that has two inputs and one output. Has the benefit of remote battery monitoring.
              Would this make sense?

              Comment


              • #8
                Near new batteries can be destroyed in weeks.

                400w of panels @15V could give 26A in the very best lab conditions. In real life, flat on a roof, I'd expect only 10-15A PV panels only work in full direct sun.

                200w panels are likely not 18Vmp, and you will need a MPPT controller . What are the specs on the stickers on the panels ? Vmp, Voc, Imp, Isc ?

                Batteries while charging, should be around 15V. After charging, resting, should be 12.5 v @ ~72F

                voltchart1.gif



                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


                • #9
                  Hi, Thanks.
                  There are two panels in the 200W solar. One has its own diode and is then parallel wired across the second and then into a 10A controller (light for 200W?) No other data on the controller.

                  Both panels are same and have following sticker data each.
                  PM 100WP
                  VOC 22.1 V
                  ISC 5.88 A
                  VMP 18.3 V
                  IMP 5.46 A
                  Vmax 1000 VDC

                  The other unit
                  Each has its own diode and is then parallel wired into a "solariser" controller (light for 200W?) No other data on the controller.

                  Both panels are same and there is a single sticker for the pair.
                  PM 200WP
                  VOC 21 V
                  ISC 12.22 A
                  VMP 18.0 V
                  IMP 11.12 A
                  Vmax 1000 VDC

                  Your table tells me that percent charge reading in my panel follows the voltage listed.

                  I guess the panels are average but usable but probably need a better controller and to have all four operating (and more) to keep charging.

                  For now I will use mains at home through a charger.




                  Comment


                  • #10
                    Originally posted by Mike90250
                    Batteries while charging, should be around 15V. After charging, resting, should be 12.5 v @ ~72F

                    voltchart1.gif
                    Would a small maintainer, say 1A, shift the expected at rest voltage a lot? Bruce Roe

                    Comment


                    • #11
                      Originally posted by bcroe View Post

                      Would a small maintainer, say 1A, shift the expected at rest voltage a lot? Bruce Roe
                      Yes and no. If you define the at rest voltage to mean neither charging nor discharging for at least four hours (longer is better) then using a maintainer will not affect the at rest voltage. If you really mean the no load voltage, then having a maintainer will certainly affect that.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

                      Comment

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