Battery voltage drop

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  • julietgolf
    Junior Member
    • Jun 2016
    • 4
    #1

    Battery voltage drop

    Hi,

    I have a Varta 40ah battery which is connected to a charge controller set to charge the battery to 13.9V and a 50W solar panel. My problem is that when I use a 1 amp led strip, it makes the battery drop to 12.5 in an hour. I use this led strip everynight for 7-8 hours. Is this a problem with my battery? My charge voltage? Or somthing else?

    Jack
    Tags: None
    • Mike90250
      Moderator
      • May 2009
      • 16020
      #2
      can you tell if the battery is getting a full charge ?
      One amp LED is 13w, so either the battery is not fully charged, or it may be sulfated/damaged
      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

        • SunEagle
          Super Moderator
          • Oct 2012
          • 15163
          #3
          Well a 12v battery will stop charging around 13.9v but slowly drop to about 12.8volt after a while which is the normal voltage. It will then go down more based on how much it is used.

          So that 12 watt (1a x 12v = 12watt) LED strip running 8 hours should drop it down a bit and 12.5 volts is about right.

          And if you get 3 to 4 hours of good sunlight that 50 watt panel should recharge the battery back up what you took out overnight by using that 12watt LED.

          So what is your question?

            Comment

            • Sunking
              Solar Fanatic
              • Feb 2010
              • 23301
              #4
              Not enough info to answer. When you run this LED strip is that at night or at least starting at the end of a day? If so nothing is wrong. That is not SAG.

              A rested 12 volt Pb battery at 100% SOC is 12.6 volts. Voltage Sag is when you measure the voltage of the battery before you connect the load say 12.6 volts, and you turn on th eload and the battery voltage drops immediately to say 12.4 volts or less.

              If you were to fuly charger your battery on solar, then did not run anything all night, th enext morning you will read 12.6 volts or fully charged. As soon as the controller shuts off at night, the battery looses the charger and settles from 13.9 Float Voltage on the Controller to 12.6 volts open circuit voltage.
              MSEE, PE

                Comment

                • julietgolf
                  Junior Member
                  • Jun 2016
                  • 4
                  #5
                  The battery gets fully charged to 13.9V with a PWM charge controller and I charge/discharge the battery every day/ night. I only purchased the battery 3 months ago.
                  I was wondering if there may have been a problem with the battery since I have seen other battery's stay at a constant voltage under load.

                  The thing that concerned me that some charts on the internet shows 100% charge to be 12.6v. However, due to the information you have told me, I understand more about the charge of my battery.

                  A final question i would like to ask is what should be the lowest voltage my battery should go to?

                  Thanks
                  Jack

                    Comment

                    • Wy_White_Wolf
                      Solar Fanatic
                      • Oct 2011
                      • 1179
                      #6
                      What type of battery? Gel or AGM the charge voltage should be OK. Sealed LA should be about 14.1. FLA should be about 14.4.

                      Are you getting the 12.5 reading while the light is on?

                      While your panel should be big enough now to run the light for 7 to 8 hours it may be too small come winter. That depends on your location but most places in the US get less than 2.5 hours insolation in the winter. That panel will mot supply enough amperage in the winter to recharge the battery.

                      WWW

                        Comment

                        • julietgolf
                          Junior Member
                          • Jun 2016
                          • 4
                          #7
                          Originally posted by Wy_White_Wolf
                          What type of battery? Gel or AGM the charge voltage should be OK. Sealed LA should be about 14.1. FLA should be about 14.4.

                          Are you getting the 12.5 reading while the light is on?

                          While your panel should be big enough now to run the light for 7 to 8 hours it may be too small come winter. That depends on your location but most places in the US get less than 2.5 hours insolation in the winter. That panel will mot supply enough amperage in the winter to recharge the battery.

                          WWW

                          Im using a Varta A14 Blue Dynamite battery. I think it is a FLA as I can here a liquid sloshing around when i move it. Im getting 12.5v whilst the light is on. And for the solar panel supplying enough current in the winter, I live in the UK and am planning to get another 50W panel.

                          Thanks
                          Jack

                            Comment

                            • Wy_White_Wolf
                              #7.1
                              Wy_White_Wolf commented
                              08-18-2016, 12:34 PM
                              Editing a comment
                              Then if it has caps that you remove to check the electrolyte it's FLA. If not then it's SLA (Sealed Lead Acid).

                              But, being an Automotive starting battery you'll be lucky to get it to last a year. They are not designed to be deep cycled or charge with solar.

                              WWW
                            • julietgolf
                              Junior Member
                              • Jun 2016
                              • 4
                              #8
                              Also, when running 6 amps my battery drains down from 12.6 to 12.0. Is this also normal?

                              Jack

                                Comment

                                • Wy_White_Wolf
                                  #8.1
                                  Wy_White_Wolf commented
                                  08-18-2016, 12:39 PM
                                  Editing a comment
                                  Yes. It's called voltage sag

                                  WWW
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