Newbie. Cabin solar charging while not there.

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  • wine_guyu_3
    Junior Member
    • Sep 2013
    • 7
    #1

    Newbie. Cabin solar charging while not there.

    Hi all.
    I have an off grid cabin
    6 100 watt panels - looking to add 2 more
    4 114 amp hour batteries
    PWM controller

    Can I leave the panels connected for months at a time while I'm not there?
    Should I disconnect 4 of them so I have more of a trickle charger while I'm not there?
    Maybe leave the inverter on while gone (200 mA draw when not in use)?

    Any thoughts would be appreciated.

    Tags: None
    • Mike90250
      Moderator
      • May 2009
      • 16020
      #2
      Do not leave the inverter on

      Can you set your controller to float only ?
      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

        • wine_guyu_3
          Junior Member
          • Sep 2013
          • 7
          #3
          Wouldn't float cause more charge, higher voltage on the batteries?

            Comment

            • sdold
              Moderator
              • Jun 2014
              • 1430
              #4
              Originally posted by wine_guyu_3
              Wouldn't float cause more charge, higher voltage on the batteries?
              If they are lead-acid, either wet AKA "flooded" or sealed AKA "AGM" types, they will benefit by being kept on a float charge so they will stay fully charged. Are they something else, like one of the lithium types?

                Comment

                • wine_guyu_3
                  Junior Member
                  • Sep 2013
                  • 7
                  #5
                  They are flooded, lead acid, deep cycle.
                  Won't leaving them on a float charge for a few months put more strain on them?

                    Comment

                    • chrisski
                      Solar Fanatic
                      • May 2020
                      • 553
                      #6
                      How do you feel about not checking the battery fluids for months?

                      I am doing something similar with my RV, and I decided I'm going to try and remove them and bring them to the house when not in use. System should be done building in a couple weeks. Those batteries are heavy, so I don't know how long that will last.

                      I am new at this, but in AZ I lost a battery a year at the RV from being stored in the sun. Actually every 13 months, so 1 month past warranty. The first one was low fluids, my fault, I never checked it the entire year, the second was my fault also, I did not know about DC loss and extended a small gauge 5 watt trickle charge panel by 25 feet, and it did not deliver enough juice to charge it.

                        Comment

                        • SunEagle
                          Super Moderator
                          • Oct 2012
                          • 15126
                          #7
                          Originally posted by chrisski
                          How do you feel about not checking the battery fluids for months?

                          I am doing something similar with my RV, and I decided I'm going to try and remove them and bring them to the house when not in use. System should be done building in a couple weeks. Those batteries are heavy, so I don't know how long that will last.

                          I am new at this, but in AZ I lost a battery a year at the RV from being stored in the sun. Actually every 13 months, so 1 month past warranty. The first one was low fluids, my fault, I never checked it the entire year, the second was my fault also, I did not know about DC loss and extended a small gauge 5 watt trickle charge panel by 25 feet, and it did not deliver enough juice to charge it.
                          Most RV's have a way to disconnect the battery system from all of the vampire DC loads in the coach while it is being stored. Check to see if your RV has one of those and then a small wattage panel should be able to keep the batteries at float.

                            Comment

                            • Mike90250
                              Moderator
                              • May 2009
                              • 16020
                              #8
                              A battery being on a true "Float" charge, won't be harmed. Happens all the time for emergency EXIT sign lights. But the float voltage must be properly set for the battery. Often batteries have 2 voltages for float:
                              Cycle Duty
                              and
                              Standby Duty.

                              And while you are away, you don't want the battery blasted with a 3 hour absorb cycle daily, when it's not been used, so set the controller to Float.
                              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

                                • sdold
                                  Moderator
                                  • Jun 2014
                                  • 1430
                                  #9
                                  Originally posted by wine_guyu_3
                                  They are flooded, lead acid, deep cycle.
                                  Won't leaving them on a float charge for a few months put more strain on them?
                                  We have hundreds of radio sites with batteries sitting on float charge 24/7, and we see many years of service. As Mike said the manufactures typically give a constant voltage value for float service and another for cycle service. The batteries we use the most are about 13.6V for float and I think they recommend 14.5-15V for constant-voltage in cycled service. But your manufacturer should have specific numbers and probably a graph or formula to compensate for temperature.
                                  Last edited by sdold; 09-09-2020, 12:14 AM.

                                    Comment

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