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  • #16
    Originally posted by secessus View Post

    AGM doesn't have the problem EQ is meant to address (stratifying liquid electrolyte in stationary use) but if if the voltage is tolerable (according to the battery mfg) it's a non-issue.




    It's meant as a workaround for controllers that move to Float prematurely. That scenario is most likely with: deep-cycled lead-chemistry batts (FLA, AGM)
    periods of incomplete charging (poor insolation?)
    old or injured batteries
    max charging rates, as this tends to shorten Bulk and lengthen Absorption requirements


    Not useful (and perhaps harmful) when: batteries are sitting on shore power or otherwise not deeply discharged regularly
    charging lithium, as Li doesn't like to sit at 100% SoC
    using non-deepcycle, lead batteries (box store "hybrid", marine, automotive), which are more susceptible to grid corrosion from long periods of higher voltage.

    The easiest way to tell if the batts would benefit from longer Absorption is If the tail/trailing/end/finishing Amps aren't coming down to manufacturer recommendations (.5A/100Ah of capacity, for example). If the batteries are fully fed by the end of the CC's normal Absorption program then more absorption won't do anything useful for the battery. Caveat: If using PWM then running at the higher Vbatt will increase power harvest somewhat.
    Thanks! I really like eternal absorption, my battery is old and the normal three stages charge seems to leave it undercharged (my charger won't go past the 2 hours for abs stage), I'm going to use eternal abs at Vabs=Vfloat=14,2V, that way it won't get so hot and won't loose so much water.

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    • #17
      Originally posted by wdc View Post
      Thanks! I really like eternal absorption, my battery is old and the normal three stages charge seems to leave it undercharged (my charger won't go past the 2 hours for abs stage), I'm going to use eternal abs at Vabs=Vfloat=14,2V, that way it won't get so hot and won't loose so much water.
      Beg your pardon. Set in that manner is what I call Maximum Smoke. Essentially you have set the charger to a very simple CC/CV charger set to 14.2 volts. Bulk is the CC phase, and CV is he Absorb stage. Here is where you are dead wrong. At 14.2 volts is above the gassing stage voltage as that is the idea of the Absrob stage forcing current into the battery at elevated voltages. It does the exact opposite. It uses a lot of water, heats the batteries up, and accelerates grid corrosion. So leaving the voltage elevated after the batteries are saturated signaled by current tapering off, only does damage.

      So be careful with that. Most solar systems are undersized, and you would require to run Max Smoke just to try to keep up. But a system with proper panel wattage would need to lower voltages or shorten Absorb times. Unfortunately most solar charge controllers only control Absorb by time which is the wrong element. You terminate Absord by a current trigger when current drops to 3% of C. Solar does not have that luxury of time waiting for it to happen as Absorb can take 6 to 10 hours. Ironic huh?
      Last edited by Sunking; 09-23-2020, 10:31 PM.
      MSEE, PE

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      • #18
        > So leaving the voltage elevated after the batteries are saturated signaled by current tapering off,


        Agreed; we are talking about situations where taper isn't complete when the controller drops to float. In his case, 120mins Abs duration is hardcoded into the controller.



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        • #19
          Usually, an external shunt is needed to be able to split battery current, from daytime loads. Otherwise, 5 min after absorb starts, and the fridge shuts off, there is a large decrease in output amps, but not to the battery , and you would not want to fool the controller into stopping early
          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


          • #20
            Thanks everybody, I wonder if a charge controller exist that switch to float based on current and not time? I only use my battery at night so that kind of CC would be very useful to me.

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            • #21
              The do exist. the MidnightSolar Classic is one. BUT you need an external current sense gadget (Whiz Bang Jr) so your controller can measure battery current only, not any loads that happen to be running at the time,
              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


              • #22
                Originally posted by Mike90250 View Post
                The do exist. the MidnightSolar Classic is one. BUT you need an external current sense gadget (Whiz Bang Jr) so your controller can measure battery current only, not any loads that happen to be running at the time,
                Mike when I read this lead me to an incorrect conclusion. Perhaps it is me or the way it was worded left me with the impression the shunt would need to be in-line with the battery. It can certainly be in the battery leg, but not required. It can be as easily on the load side of the battery measuring load current and still measure battery current. You have a current node, with three nodes You have the charge controller supplying current in one direction only. You have the battery, and current can flow in either direction of positive or negative.. Third node is the Load and one direction only.

                You only need to know what 2 of the three nodes are to know what all three currents. Example we have shunts in the Controller and Load. Controller = 10 amps, Load = 2 amps. Battery = Controller - Load = 10 - 2 = 8 Amps charging current to batteries. Or say Controller = 10 Amps, Load = 20 Amps. 10 - 20 = -10 amps discharging the battery.

                So knowing only the Controler output current does not tell you much. You do not know where it is going.Conclusion; battery swings both ways.
                Last edited by Sunking; 09-25-2020, 10:08 PM.
                MSEE, PE

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                • #23
                  The instructions for the install of the current monitor is to put it into the battery feed. Apparently the decode logic is set for reading that.
                  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


                  • #24
                    Thanks, it's a shame most CC can't rely on endamps to end absorption stage, at least they should allow the user to control the time for that stage, I wonder why they keep it at 2 hours and no 3 at least. Everyday I'm more convinced that solar power is too variable to achieve full charge in most days, even with lots of panels there will be cloudy and rainy days when less expected.

                    My battery is dying, it has been working for 7 years now (5 in a friend's truck and 2 with me and solar) and I will change it next March, this will be its last summer with me. And I'm switching to AGM, I want to try something new and here, in winter, it gets very cold, I think AGM's are better with cold than FLA. My eyes are on a Ritar 100Ah DC AGM battery, it's expensive for my pocket but what the hell, If I take care of it could last at least 5 years, if that should happen, I'm fine. Also I have my AC power to avoid getting down beyond 50% DOD, so I'm covered in that regard.

                    Thanks again, for your patience and generosity.

                    Comment


                    • #25
                      End amps is a feature. Time of absorb should always be adjustable, or at least dynamic to match the time in Bulk. A fixed time is a low end controller
                      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


                      • #26
                        Thanks, I have some questions but I don't think they deserve their own topic so I'll write them down here:

                        1) If 13,5 to 13,8 are known to be float voltages and 14,2 to 14,6 are known to be absorb ones, what would you think to be a "best of both worlds" voltage for most of the typical deep cycle batteries? I'm looking to keep my battery from losing water and, at the same time, give at least some degree of the benefit of absortion (getting the battery as close to 100% SOC as it can be), do you think such a thing is possible?

                        2) What contributes most to water loss in a battery, high voltages or surrounding temperature? I moved my battery to a cooler place and found that the vents "make noise" when the charging voltage is about 14,3 ~14,4V. Now I wonder if there is any benefit from keeping the battery cooler than before, my highest temperatures now are 34ºC and before were 40ºC, still I'd like to know your opinion about volts versus heat when it comes to water loss.

                        I know this questions could be sort of "nitpicking" but I can't help it, I'm curious and I like better to hear from personnal experiences than to read theory from a text, thanks!

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                        • #27
                          > "Vents make noise"

                          Is this a sealed battery and you hear hissing gas escaping, or a flooded battery with gas bubbles gurgling up thru the cells ?

                          The FLOAT voltage is not supposed to gas, or only very little. Are you storing this battery or using it ?
                          Cold temps lower the chemical activity, so LA batteries (flooded or sealed) need HIGHER voltage when cold, but that should not create more gassing

                          Higher volts at normal temps will cause more gassing

                          Warm batteries might "evaporate" more water, but only a few drops a week

                          Battery plated exposed to air, are damaged and will never be "active" in a battery again. Batteries undercharged become sulfated and loose capacity
                          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
                            Originally posted by Mike90250 View Post
                            > "Vents make noise"

                            Is this a sealed battery and you hear hissing gas escaping, or a flooded battery with gas bubbles gurgling up thru the cells ?

                            The FLOAT voltage is not supposed to gas, or only very little. Are you storing this battery or using it ?
                            Cold temps lower the chemical activity, so LA batteries (flooded or sealed) need HIGHER voltage when cold, but that should not create more gassing

                            Higher volts at normal temps will cause more gassing

                            Warm batteries might "evaporate" more water, but only a few drops a week

                            Battery plated exposed to air, are damaged and will never be "active" in a battery again. Batteries undercharged become sulfated and loose capacity
                            Thanks! I forgot to tell the main features of my system, sorry!

                            It's a very old flooded battery, a white semi-transparent one, with twisting vents, but the sound I hear I don't think is bubbles gurgling up because I've seen those bubbles and they are small, I think the sound comes from the vents, I guess is some kind of mechanicsm that opens and then closes itself. It's not a constant sound, it happens at irregular intervals.

                            I'm cycling-using this battery, it gets discharged every night to lit up the bulbs in my house, they all are 12V led bulbs and there are about 40 of them, but I use at most 10 at a time.

                            I really can't expect to get anything more from this old battery, but I want to learn by experience all I can before I buy a new one.

                            I have another question: If bulk stage is constant current but the max current from the panels are only achieved at noon, how "constant" is the current that goes to the battery from dawn til noon?

                            Thanks!

                            Comment


                            • #29
                              Originally posted by wdc View Post
                              ...........................
                              I have another question: If bulk stage is constant current but the max current from the panels are only achieved at noon, how "constant" is the current that goes to the battery from dawn til noon? Thanks!
                              And that's the trouble with "easy generalizations" . Bulk is "max available current" . Then when the batteries are partly full and reach the absorb voltage,
                              Then you enter the "Constant Voltage" stage. Here's a chart of the Voltage and load amps on my "average day".
                              Voltage rises, then my timer turns on the main water pump till tanks are full ( 1500 gallons, roughly, daily) At some point you can see the battery voltage hit Absorb, and then it drops to the float (non-gassing voltage) [ about 14:30] I have 5kw of PV so I can be assured of reaching full daily in the winter.


                              XW_Chart_Feb1-2018.jpg
                              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


                              • #30
                                Wow, that's a cool chart! what do you use your water for? clearly you and I use solar power in a very different way, I hope someday I could rely solely on RE to feed my house, I very much like extracting water from the ground but I never have had the determination (or the need) to do that. Thanks for your patience.

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