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  • #16
    Originally posted by GeorgeF View Post
    Thanks again for all replies. Internetdog, if already reach aborb stage, no matter the DoD, is the duration of absorbtion till till 100%SoC always the same?

    The advises or algorithm of Sunking in serveral posts I did follow and I think to pass bulk is not much of a problem in a tropical country. Like he said somewhere, if I have to choose between undercharging or overcharging i will choose slightly overcharging.
    Definitely choose slight overcharge over slight undercharge.
    In theory, if the battery temperature and working capacity are the same, the time to finish charging after hitting the Absorb threshold should be at least similar.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #17
      Can we say that in general due to the lack of sunhours it is impossible to reach 100% SoC if we only charge with PV no matter the PV capacity, even with ideal weather condition if we daily discharge at least 10%?
      Last edited by GeorgeF; 02-20-2019, 11:48 AM. Reason: Typing error

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      • #18
        Originally posted by GeorgeF View Post
        Can we say that in general due to the lack of sunhours it is impossible to reach 100% SoC if we only charge with PV no matter the PV capacity, even with ideal weather condition if we daily discharge at least 10%?
        No. There are always exceptions. I'm overpaneled. 2 Pole mount arrays, 2 charge controllers. I'm in the sticks, something fails, I'm DOA. So I have redundancy and reach float often before noon, on days I have sun. I use NiFe batteries so I don't worry about undercharge, only about enough to get to the next time I need to run the generator.

        The issue arises with a properly balanced and designed system, and then you get the new, bigger TV and sat dish. And then the wife wants the deep freeze for the elk. Your loads have now grown beyond the design of the system and the batteries don't reach full all the time. Even half the time is OK.

        You have to manage your loads, and see how your batteries are faring. Here's an excerpt from my daily logs:
        ( I manually enter all this from the internal logs from my gear, daily )

        Sample_Log.jpg


        You can see, depending on the weather, the daily harvest is all over the charts. I use a combination of the minimum battery voltage in the morning, and the Absorb time, to help me decide if I'm going to run the generator.

        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

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        • #19
          Originally posted by GeorgeF View Post
          Can we say that in general due to the lack of sunhours it is impossible to reach 100% SoC if we only charge with PV no matter the PV capacity, even with ideal weather condition if we daily discharge at least 10%?
          You most certainly can get a battery-bank up to 100% SOC using solar panels.

          The problem is that batteries at 100% SOC, after a few months will become wonky. Their discharge rates will change and the charge will not last as long as it should.

          It is not about reaching 100% SOC. The problem lies instead in equalizing the cells. You need to boil the water once a month, to keep the battery cells in optimum performance.

          Using solar panels, it is nearly impossible to do an equalize charge.
          4400w, Midnite Classic 150 charge-controller.

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          • #20
            Organic farmer, according to you with MPPT its hard to perform an equalize charge. Do you use an ac 4 stage charger instead?

            1. Can an ac-charger do an eq charge?
            2. Is it not so that you first have to try to charge as full as possible before discharging and during the charge you in fact also desulfate?

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            • #21
              Originally posted by GeorgeF View Post
              ...
              ...
              2. Is it not so that you first have to try to charge as full as possible before discharging and during the charge you in fact also desulfate?
              That is an interesting semantic question. During any charging operation you convert lead sulfate on one plate to metallic lead and increase the concentration of the sulfuric acid electrolyte.
              But sulfation normally refers to the slow conversion of lead sulfate on the plate from its original spongy state which can easily be reversed by charging to a hard crystaline state which does not easily participate in the charging reaction. In that normal sense of the word, neither normal charging nor equalization bring about desulfation. They just prevent sulfation from happening.
              There are a wide range of opinions and anecdotal experimental studies of electrical and chemical ways to actually desulfate a lead acid battery, and I will not go into them right now.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #22
                Originally posted by GeorgeF View Post
                Organic farmer, according to you with MPPT its hard to perform an equalize charge. Do you use an ac 4 stage charger instead?

                1. Can an ac-charger do an eq charge?
                2. Is it not so that you first have to try to charge as full as possible before discharging and during the charge you in fact also desulfate?
                Last summer when I discovered that my Specific Gravities were wildly scattered, I was never able to get the Midnite Classic Charge-controller to perform an equalize.

                I had to pull individual batteries out from the battery-bank and boil them individually.

                My battery-bank is 48vdc, for a separate charger to do an equalize on the entire battery-bank, I would need an AC charger that can do 62.5volts.


                4400w, Midnite Classic 150 charge-controller.

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                • #23
                  I invested in a (high end) consumer multi-volt charger, 6/12/24 volts for about $335. At the 24 volt-30 Amps selection, the best is can do is just over 27 volts, which is about floating voltage. There are warehouse commercial chargers that can do an equalization, but their cost is prohibitive for the typical consumer.

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                  • #24
                    Generally, when you need to EQ the batteries, you try to get the back up to as full as charge as possible. Plan the EQ for the 2nd or 3 sunny day in a row. configure your absorb the day prior, for longer, or as long as possible to get the batteries charged.

                    The morning of EQ day, use your generator to Bulk the batteries and get them into Absorb. Keep your loads minimal, you will need all the power you can harvest. You should time things so you finish Absorb by Noon.

                    When you complete Absorb, initiate the EQ cycle. By 2pm you will start to loose sunshine and the EQ may stop.

                    There are many tutorials about what to do during the EQ cycle, such as monitoring battery tempatures and checking Specific Gravity and when to stop.

                    But the batteries have to be FULLY CHARGED before you can start EQ, Charge them the day before, minimize loads for the interim, and bulk & absorb with generator, to allow the solar to handle the EQ. EQ doesn't take a lot of power, it's a high voltage charge, and it's wasteful of generator fuel to perform EQ on generator power.
                    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


                    • #25
                      Originally posted by organic farmer View Post

                      Last summer when I discovered that my Specific Gravities were wildly scattered, I was never able to get the Midnite Classic Charge-controller to perform an equalize.

                      I had to pull individual batteries out from the battery-bank and boil them individually.

                      My battery-bank is 48vdc, for a separate charger to do an equalize on the entire battery-bank, I would need an AC charger that can do 62.5volts.

                      Your 48 volts Inverter is not a charger as well? Because most of the name brand 48 volts Inverters are also chargers like my old Magnum 4448PAE and my new XW6848 inverters also chargers. I can set the charger to 64 volts to EQ the battery bank with grid or generator.

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                      • #26
                        Batteryuniversity gives this info. I have agm non gel.

                        According to them gel, and in part also agm, can NOT be fully charged. Does this mean that i never can reach 100% SoC, even if i use ac charger?
                        Attached Files

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                        • #27
                          No, you CAN easily reach fully charged. You must however, quickly throttle back the charging when full, to prevent gassing and loosing electrolyte. Cheap chargers cannot always accomplish this.
                          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


                          • #28
                            Ok Mike, thanks for your reply.

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                            • #29
                              Originally posted by inetdog View Post
                              A much more accurate statement is that when using PV alone for recharging you do not typically have time for a classic Bulk/Absorb/Float charging scenario. Instead you need to run the Bulk stage to as high a current as the batteries can take and your PV can supply. Then push the Absorb portion of the charge cycle as hard as you can, because you will not have time in the day to use a small fraction of the PV potential for an extended time to finish the charging process with true Float.
                              Although this is an old thread, permit me to ask more questions especially about absorb:
                              ive been reading some info, also Rolls Surrette info, that the internal resistance (Ri) during absorb increases while as I understood Ri lead acid decreases near or @ fsoc.
                              ​​​​​​
                              Can someone please explain?
                              ​​
                              ​​​

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