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  • Winterizing off grid solar for summer cabin.

    Hello,

    This spring, you guys helped me get the off grid solar back to operable. I inherited the maintenance on this system. I have a small setup. 2, 6v Duracell golf cart batts in series. An MPPT controller and I think about 200 or so watts of panels. It suits our needs of charging phones and some lights just fine (at the moment).

    My question now is about winter storage. This house will be shut down on October 7th and left shuttered up until april/may. What is the best way to shut it down and store it? I can top off the batteries and disconnect them, or I can leave the array/controller connected to maintain them over the winter and disconnect the loads. I know in either scenario I need to make sure they are full (water wise). So what is the best scenario?

    Thanks!

  • #2
    Trickle charge them all the way to the spring. No snow on your panels is a must.

    Comment


    • #3
      Are the batteries Flooded or AGM.
      The issue about leaving them on charge till spring thaw, is every day, the charge controller will attempt to fully recharge the full batteries, with Bulk, 90 min of Absorb and then finally back to Float. You need to set your controller to Float till spring, or you will in a couple months, boil all the water out of your fully charged battery.
      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


      • #4
        They are flooded. I don't think snow is much of a problem, but there will be times when they may be covered. Being right on the ocean, I'm not terribly comfortable about re positioning the panels to shed the snow.

        That was also my concern about the batteries running out of water. I will say that I'm shocked that from April to now, even with the use they have had (which is very little load) I have not needed to add water. I have checked them 3 times, last time being last week and they are all just below the lip of the opening. I'll have to see if and how I can make my controller switch to just float. I imagine there must be a way but I'll admit, I havent played with the settings much.

        Comment


        • #5
          It appears that perhaps I would set up a "user" setting for battery type and use that for winter storage? Any tips on how I would set that up? Or is there another way to do it? My controller is the Acopower 30 amp MPPT.
          Attached Files

          Comment


          • #6
            If you are not using much water currently, you are being to gentle on the batteries, they should need water at least every other month.
            Decide what your batteries manual calls for, FLOAT service , and that voltage is what you set BOOST and FLOAT to. Boost duration can be 10 min. Disable Equalize
            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
              Originally posted by Mike90250 View Post
              If you are not using much water currently, you are being to gentle on the batteries, they should need water at least every other month.
              Decide what your batteries manual calls for, FLOAT service , and that voltage is what you set BOOST and FLOAT to. Boost duration can be 10 min. Disable Equalize
              I do know that I have a lot more battery than I need. The house is empty most of the time with no loads, and even with a full house we might charge 8 or so phones in a day, plus about 4 hours of 4 to 5 amps worth of lighting. My bank is 230 AH at 12v. I did this battery size because very occasionally I will use a small 12v air compressor to fill a tire, or an inverter to charge drill batteries or similar. Hopefully being over sized in my battery bank isn't a problem.

              Thank you for the info on how to program my controller. That sounds pretty straight forward. I'll find that float voltage and create a custom "winter" battery type.

              Comment


              • #8
                Basketcase

                ​​​​​​​Step #1
                ======
                Charge ( Bulk & Absorb ) the batteries until 100% SOC.
                Continue charging until they BUBBLE.

                Step #2
                ======
                Start an EQUALIZE charge.
                Equalize until the SG reading stops rising for two consecutive readings, one hour apart.

                Step #3
                ======
                Set the Charge Controller to FLOAT.


                Do you understand why you cannot skip steps #1 & #2, before you leave for 6 months?
                Last edited by NEOH; 09-21-2017, 07:55 PM.

                Comment


                • #9
                  Originally posted by NEOH View Post
                  Basketcase

                  ​​​​​​​Step #1
                  ======
                  Charge ( Bulk & Absorb ) the batteries until 100% SOC.
                  Continue charging until they BUBBLE.

                  Step #2
                  ======
                  Start an EQUALIZE charge.
                  Equalize until the SG reading stops rising for two consecutive readings, one hour apart.

                  Step #3
                  ======
                  Set the Charge Controller to FLOAT.


                  Do you understand why you cannot skip steps #1 & #2, before you leave for 6 months?

                  I understand why the batteries want to be fully charged, but I do not know the science behind what you are suggesting. I would like to know. I'm not sure I have the kind of control over my charge controller that you are talking about. Maybe I do and I just don't know it.

                  Comment


                  • #10
                    each battery is made of individual cells, inside 1 larger case (cells = number of water refill caps) Over time, they become slightly unbalanced, and need to be Equalized. Or maybe one cell is a bit undercharged, and after 6 months of no charge, it becomes low enough to freeze, or begins to sulfate, thus ruining the entire battery.
                    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


                    • #11
                      Originally posted by Mike90250 View Post
                      each battery is made of individual cells, inside 1 larger case (cells = number of water refill caps) Over time, they become slightly unbalanced, and need to be Equalized. Or maybe one cell is a bit undercharged, and after 6 months of no charge, it becomes low enough to freeze, or begins to sulfate, thus ruining the entire battery.
                      That makes sense, and I understand what an equalize charge does. In this case, I will have the charge controller connected all winter, but at float only. I'll have to see if I can figure out how to force this controller to do an EQ charge. I know it is set to do one automatically every X amount of time, but I'll have to see if I can force it. Worst case, I can connect the generator to them, but that is a PITA because of location.

                      Comment


                      • #12
                        you need to be sure you can DISABLE the automatic EQ for the winter, or it will BBQ your batteries when it tries and fails, and retries the next day and the next and the next
                        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


                        • #13
                          Originally posted by Mike90250 View Post
                          you need to be sure you can DISABLE the automatic EQ for the winter, or it will BBQ your batteries when it tries and fails, and retries the next day and the next and the next
                          IMO it would be better to just bring home the batteries instead of trying to keep them warm and charged through the winter. It might be more work but at least you won't freeze or boil them batteries.

                          Comment


                          • #14
                            Originally posted by SunEagle View Post

                            IMO it would be better to just bring home the batteries instead of trying to keep them warm and charged through the winter. It might be more work but at least you won't freeze or boil them batteries.
                            Its easy enough to disable the EQ setting, and I was planning to. I would like to know what will cause it to BBQ the batteries. Is it the lack of available PV power?

                            I agree that taking them home and tucking them into bed would be an ideal situation, but I have zero intention of dragging them out of the loft, down the trail to the dock, onto the boat, across the bay and then home to my house. My father (who was the caretaker before me) got 6 years out of 12v marine batts in parallel just by disconnecting them and leaving them with whatever charge they had when it was time to leave. When I took over, I began leaving them charging (with the old pwm charge controller from the 90s) for the last 2 years of their life. I have to assume that I can expect similar, if not better performance from 6v batteries in series and a charger that I have some control over. Its a good suggestion to bring them home, and if it were just a camp I drive my truck to, I probably would. In this case its just not practical and hopefully not absolutely necessary.

                            To recap, it seems like the best practical choice is to set all the voltages (bulk, float, etc) to 2.30-2.35 volts per cell (per Deka) and disable the EQ charge. This is AFTER I make sure they are fully charged and filled.

                            Comment


                            • #15
                              What causes a battery to BBQ (from EQ) is that the controller forces a full BULK and ABSORB cycle. THEN it starts the EQ. EQ can only start after Absorb.. But the BBQ part comes along when the sun sets in the winter, and the EQ has not completed (from not enough sun hours in winter days) - So it tries all over again the next day. And the next. All the cycles bubble some electrolyte away daily and pretty soon you need to water the batteries, but you are not there, and so water level falls further and the the exposed plates dry and are ruined. Maybe there will be a couple sunny days and the EQ can finish., and start counting the next 30 day cycle.
                              So for winter, when you are not cycling the batteries, set absorb = Standby Float voltage and no EQ
                              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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