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  • Extremely fast discharging

    Hello friends,

    My system consists of 24v 105ah battery bank sealed lead acid and 1200w inverter.
    Batteries are new with only two charge/discharge cycles no lower than 80%

    I'm turning on the inverter and using only a 450w 220v blender for 10 seconds. The battery is draining extremely fast from 100% to 80% according to the charge controller.
    Battery bank volts are going from 25.7 to 25.3 respectively.

    What should I check ?
    Inverter?
    Batteries ?

  • #2
    I am on my second 24v battery bank. Both would be at about 25.2 in the evenings with the inverter on and light loads and around 24.8 to 25 in the mornings.

    You will get voltage sag when you draw load, especially as you dont have a big bank.

    I assume this is at night or in the morning when there is no sun? are they recovering above 25.3 when you turn the inverter back off.

    Comment


    • #3
      Originally posted by Bala View Post

      I assume this is at night or in the morning when there is no sun? are they recovering above 25.3 when you turn the inverter back off.
      Both.
      i have tried it at night with no sun and yes they recover above 25.3 without load.

      Are the percentage readings false ? Is it better to follow voltage readings?

      And one more thing. 25.7 is over than fully charged. Is that right?

      Comment


      • #4
        from what I have read, mostly on this forum about battery state of charge indicators is basically that they are not good.

        I have had flooded batteries so I could use a Sg readings but I now have sealed batteries. I just use voltage anyway.

        I get a baseline when they are new and I get to know my batteries, usage and weather. I have a voltmeter in the house and based on the reading and if there has been enough sun and my usage I can tell what my state of charge is.

        The charts that give you SOC on V vary from battery type and brand.

        I dont think you have a problem at the moment. Especially as they are recovering after you take the load off. I would just make sure they are getting fully charged each day and see how they go. Note down your usage and V readings and get a base line and see if anything changes. I

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        • #5
          Thank You

          Comment


          • #6
            After some mesaurements I found out that for charge controller 100% is 25.9+.
            At night the battery voltage drops at 25.5 (full for me/external batteryindicator while 81% for the charge cobtroller). Every morning charge controller tries to recharge batteries so as to reach 25.9 v again but in reality are full.

            Could this process ruin my batteries?

            Comment


            • #7
              If they the highest they are getting to each day is 25.9 then that is not correct.

              For example mine do a bulk/absorb at 28.3 and a float of 27.

              They spend most of their life at 28.3 if there is enough sun and sometimes they will go to float at 27

              You need to look at the manufacturers specifications for charging for your batteries.
              .

              Comment


              • #8
                If you can get ahold of a load tester you can test all batteries individually and might find a weak one in the mix.
                2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                • #9
                  Originally posted by Takis View Post
                  After some mesaurements I found out that for charge controller 100% is 25.9+.
                  At night the battery voltage drops at 25.5 (full for me/external batteryindicator while 81% for the charge cobtroller). Every morning charge controller tries to recharge batteries so as to reach 25.9 v again but in reality are full.

                  Could this process ruin my batteries?
                  I have a set of 4 50Ah 12V AGM batteries wired in parallel (stupid idea). They now quickly charge up to 13.3 volts but then self discharge back down to 12.5 volts without any load. Since they are about 4 years old I believe they now are nearing their death and will have to be replace. This time I am going with 2 x 6V 220Ah FLA type wired in series. Hopefully they last longer then the AGM type.

                  I have found by experience that batteries that quickly get charged back to 100% SOC are not reliable to provide anywhere near their rated watt hours. They still work but just aren't what they were when new no matter how I charge them.

                  Comment


                  • #10
                    Originally posted by Bala View Post
                    If they the highest they are getting to each day is 25.9 then that is not correct
                    .
                    Do you mean that is too low?

                    Comment


                    • #11
                      Originally posted by Takis View Post
                      Do you mean that is too low?
                      A 24V FLA battery needs to be charged at about 28V, more or less. 25.9 is way too low of voltage.

                      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


                      • #12
                        Originally posted by Takis View Post

                        Do you mean that is too low?
                        Yes 25.9 is not charging enough.

                        You should be able to get specs for the brand you have.

                        What is the brand and model of battery?

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                        • #13
                          I've varta Lfs 105n dual purpose professional. No manual no specs but width and height. No good choice finally.

                          I've bought them because I'm newbie and there were a cheap (maybe value for money) choice.

                          Comment


                          • #14
                            That are a dual purpose battery so not ideal for cycling.

                            I'm only on my phone so short answer is for a 24v system you can go to 28v safely.

                            You need to replace daily what you have used overnight.

                            What do you have for solar panels.

                            Comment


                            • #15
                              A Canadian solar 24v 320w 45voc ipmax 9.5amps
                              it charges them before 11.00 at the morning.

                              I'm planning to expand to four solar panels like it and buy 4 flooded 6v rolls s290. Not sure about my new choice though.

                              Comment

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