Announcement

Collapse
No announcement yet.

How much water should I add to old AGM battery?

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by davethedrummer View Post
    I have a total of 8 batteries so I went ahead and added 30ml of water per cell (that was yesterday). Tried to charge them up a bit (they got about 4kwh) today in a string of 4 batteries. 4 of them showed voltages of 16-19V while charging so those are no good. Kept rotating the bad ones out and of the remaining 4, one of them is giving me 15V, the other 3 seem be charging normally.

    Disconnected them now and will test again tomorrow morning after which time I will charge them individually and do further testing.

    Don't really know if the water did anything but hey it's worth a try rather than dumping them.
    Reading SOC without LOAD can be deceiving a batt looks great till load is applied: no load 12.8-13v after load applied 10.5-12+-v
    soc2.JPGsoc1.JPG

    Comment


    • #17
      Bear in mind that AGM batteries are 99% saturated with electrolyte. They are designed to be non spill able, in the event that a case gets cracked the electrolyte is supposed to stay suspended in the matting. Adding water seems like it would dilute the electrolyte to a lower specific gravity than a fully charged battery would like to see.
      2.2kw Suntech mono, Classic 200, NEW Trace SW4024

      Comment


      • #18
        Originally posted by littleharbor View Post
        Bear in mind that AGM batteries are 99% saturated with electrolyte. They are designed to be non spill able, in the event that a case gets cracked the electrolyte is supposed to stay suspended in the matting. Adding water seems like it would dilute the electrolyte to a lower specific gravity than a fully charged battery would like to see.
        That's why I decided to only add 30ml, thought that might be a similar amount that might have gassed off over the years...?

        Comment


        • #19
          Originally posted by davethedrummer View Post

          That's why I decided to only add 30ml, thought that might be a similar amount that might have gassed off over the years...?
          Ideally a Valve Regulated Lead Acid (VRLA) battery will be charged at a low enough rate that no water will be "boiled off" to a pressure greater than the operating pressure of the valve. Once you have removed (or damaged the integrity of) the valve cap or caps you no longer have VRLA. The pressure is necessary to cause catalytic re-conversion of the elemental oxygen and hydrogen back to water inside each cell.
          SunnyBoy 3000 US, 18 BP Solar 175B panels.

          Comment


          • #20
            Originally posted by inetdog View Post
            Ideally a Valve Regulated Lead Acid (VRLA) battery will be charged at a low enough rate that no water will be "boiled off" to a pressure greater than the operating pressure of the valve. Once you have removed (or damaged the integrity of) the valve cap or caps you no longer have VRLA. The pressure is necessary to cause catalytic re-conversion of the elemental oxygen and hydrogen back to water inside each cell.
            I guess you can't really see from the pictures but the caps are made of very soft and elastic rubber that is less than 1mm thick. I seriously doubt those caps would withstand any kind of pressure. There are no valves that I can see, unless they are calling those flimsy little caps valves? Seems like a bit of a stretch of the term.

            Maybe this is an older design? Would be interesting to see if the "valves" on the new Northstar batteries are also just thin rubber caps.

            Comment


            • #21
              Quit kicking a dead horse and wasting our time. The batteries are Boat Anchors. Geez you do not even know VRLA = AGM. Northstar batteries are made for Telecom and completely useless for cycle service. So stop wasting our time and get rid of them at your local recycle center.
              MSEE, PE

              Comment


              • #22
                So one out of the 8 batteries has been revived. Charging and discharging perfectly without large voltage drops under load. Was hoping for a slightly better result but overall I'm very happy that I tried this out.

                Comment


                • #23
                  Originally posted by davethedrummer View Post
                  So one out of the 8 batteries has been revived. Charging and discharging perfectly without large voltage drops under load. Was hoping for a slightly better result but overall I'm very happy that I tried this out.
                  Once you have defeated the pressure relief valves, the battery will no longer be able to recombine the hydrogen and oxygen gas produced by electrolysis during normal charging. That means that you will soon have to add water again instead of having a sealed, maintenance-free battery. The volume of electrolyte compared to capacity is far smaller than in an equivalent FLA cell.
                  SunnyBoy 3000 US, 18 BP Solar 175B panels.

                  Comment


                  • #24
                    I did ask before about NorthStar Red. There are some resellers of used NS red. Ignorant PV users beleive that the SoH of these dumped batteries is 100% cause they show them pictures like this.

                    Can anyone explain me how is it possible that such kind of measuring tool can show a SoH of 100%?
                    Attached Files

                    Comment


                    • #25
                      Originally posted by GeorgeF View Post
                      I did ask before about NorthStar Red. There are some resellers of used NS red. Ignorant PV users beleive that the SoH of these dumped batteries is 100% cause they show them pictures like this.

                      Can anyone explain me how is it possible that such kind of measuring tool can show a SoH of 100%?
                      Depending on the type of instrument some of the quality battery testers can measure the voltage of the battery under load. Just for clarity that 100% is the SOH not the SOC.

                      Comment


                      • #26
                        Originally posted by GeorgeF View Post
                        I did ask before about NorthStar Red. There are some resellers of used NS red. Ignorant PV users beleive that the SoH of these dumped batteries is 100% cause they show them pictures like this.

                        Can anyone explain me how is it possible that such kind of measuring tool can show a SoH of 100%?
                        I am deeply concerned about the 1000A and 1815A figures on the screen of the battery tester. I suppose those are intended to represent some sort of current capability at a specified voltage drop (short circuit???). But there is no way that the clip on leads shown could carry even 1/10 of that current for any significant time. The tester may be applying a very brief high current pulse which will not overheat the wires, but the lead resistance and clip to terminal resistance should make that measurement very unreliable. Or else it is applying a small current (say 10A), measuring the voltage drop, and extrapolating it to higher current.
                        Note also that knowing that the battery can deliver power in the form of some very high current for a short period of time is not necessarily an indication that it has the capacity to deliver energy in the form of watt-hours, over a longer period of time.
                        In short, despite what the person who tested your batteries said, they may only be able to deliver some small fraction of their original rated energy before dropping the voltage to an unusable level.

                        And the SOC level shown is almost certainly just an estimate based on the open circuit voltage. Not to be taken seriously.
                        SunnyBoy 3000 US, 18 BP Solar 175B panels.

                        Comment


                        • #27
                          And,
                          how can such a tester defines the SoH in regard of degration, corrosion etc...???

                          Comment


                          • #28
                            Originally posted by GeorgeF View Post
                            And,
                            how can such a tester defines the SoH in regard of degration, corrosion etc...???
                            Only to the extent that the deficiency in the battery increases the internal impedance of the battery.
                            SunnyBoy 3000 US, 18 BP Solar 175B panels.

                            Comment


                            • #29
                              Originally posted by inetdog View Post

                              Once you have defeated the pressure relief valves, the battery will no longer be able to recombine the hydrogen and oxygen gas produced by electrolysis during normal charging. That means that you will soon have to add water again instead of having a sealed, maintenance-free battery. The volume of electrolyte compared to capacity is far smaller than in an equivalent FLA cell.
                              Like I said before, these aren't actual valves, they are just flimsy little rubber caps that provide basically no pressure resistance. Anyways I'm not expecting it to suddenly be like a new battery but for now it works and I saved a bunch of money by not having to replace it (at least in the short term).

                              Comment


                              • #30
                                Originally posted by davethedrummer View Post

                                I guess you can't really see from the pictures but the caps are made of very soft and elastic rubber that is less than 1mm thick. I seriously doubt those caps would withstand any kind of pressure. There are no valves that I can see, unless they are calling those flimsy little caps valves? Seems like a bit of a stretch of the term.

                                Maybe this is an older design? Would be interesting to see if the "valves" on the new Northstar batteries are also just thin rubber caps.
                                Have you considered the effect on the "flimsy little valve caps" of the plastic cover which you removed to expose them? When constrained from the top from simply popping off, I expect that the rubber caps could provide a very controlled pressure relief function.
                                SunnyBoy 3000 US, 18 BP Solar 175B panels.

                                Comment

                                Working...
                                X