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Float or higher charge voltage for value regulated sealed lead acid battery

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  • Float or higher charge voltage for value regulated sealed lead acid battery

    I am using a 24v system and I have (4) EnerSys PowerSafe 12V190F 180Ah valve regulated sealed lead acid battery which I connect in series and parallel so my battery bank is 24v at 380Ah. I am trying to figure out what is the correct max charge voltage it is suppose to get. The specs on each of the batteries says max float charge voltage per cell is 2.29v which works out to be 13.74v per battery and when you double for 24v that works out to be 27.48v.

    So should I set the max charge voltage to be always 27.48v on my charge controller?
    What if I run down the battery to 23.3v or slightly below 24v sometimes should it still charge up to 27.48v or do I need to go a bit higher sometimes because of the lower discharge?

    Does this battery bank require equalization charge sometimes and if yes how often should it be applied and what is the max charge voltage I should use for equalization charge and how long should it remain on equalization charge?

  • #2
    Many of the AGM batteries out there are designed for UPS/float service. They aren't made for daily cycle service. This may be why you aren't seeing a bulk charge voltage on the label. A lot of people get decent performance with these batteries in part time systems where say in a cabin or RV you don't cycle them on a regular basis.

    Typically AGM batteries don't want as high a charging voltage as a flooded battery wants because they have to recombine the hydrogen gasses back into the electrolyte. If charged at too high a voltage they cant recombine the gas fast enough and will vent and lose electrolyte which cannot be replaced. They all vary in bulk/absorb voltage allowances but usually about 14.4 to 14.6 is safe. Gel batteries are even worse as the gas bubbles will become trapped in the gel electrolyte so they will max out at about 14.2 volts max.

    Generally speaking sealed batteries shouldn't get equalized for the aforementioned reasons. Some Mfg. will call for a periodic slightly higher voltage, "Freshening charge".
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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    • #3
      My charge controller does not allows you to set bulk/absorb then set float voltage. It just allows you to set the pv cut off voltage and whatever voltage you set it at that's where the charge voltage doesn't pass. It will remain at that voltage sending high current into the battery until the current drops down to a small amount and will start to float at that same voltage. So in my case If i set it at the 27.4v will the battery get a full charge? Also what would be the float current going into the battery that would suggest my battery bank is fully charged? My bank is 380Ah so what current or percentage of the 380Ah going into the battery at 27.4v would suggest it is fully charged?

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      • #4
        Your voltage setting is the cut off voltage that your controller holds at for absorb until the amperage drops to whatever it considers full, or it is set at. I don't know exactly how this controller does this. Anyway this setting , like I said would be about 14.4 (12 volt) or 28.8 (24 volt). You should be able to set your float voltage as well. 27.4 volts sounds like the float setting. Amperage at float is minimal. Bulk amperage will be whatever your array can produce. Absorb amperage will gradually reduce to your controllers setting, signaling full battery. At least that's how I see it. Others here may have a different explanation.
        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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        • #5
          So basically if I set my controller to 28.8v is it safe to float charge my value regulated battery at that voltage once the battery temp is @25

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          • #6
            I can answer your questions, but you will not like the answer.

            EnerSys PowerSafe batteries are made for Telecom Float Service. That means that are not designed to be used or cycled. They are used for emergency standby power only. If you cycle them, you will only get 100 to 150 cycles at best. Less than a year. They are the wrong type of battery for the application. They are designed to be Floated at 2.28 @ 20 degree C or 2.265 vpc @ 25 degree C. So at room tems with 12 cells 27.2 to 27.4 volts.
            MSEE, PE

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            • #7
              Originally posted by fabieville View Post
              So basically if I set my controller to 28.8v is it safe to float charge my value regulated battery at that voltage once the battery temp is @25
              No they will go into thermal runaway and self destruct. You have Telecom AGM batteries.
              MSEE, PE

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              • #8
                Would anyone of these charge controller appropriate to use?

                http://www.ebay.com/itm/60A-MPPT-sol...UAAOSwm8VUygAw




                http://www.ebay.com/itm/EPEVER-1210A...3XtuoGkUt8o9qA


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                • #9
                  Would anyone of these charge controller appropriate to use?

                  http://www.ebay.com/itm/60A-MPPT-sol...UAAOSwm8VUygAw

                  http://www.ebay.com/itm/EPEVER-1210A...3XtuoGkUt8o9qA

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                  • #10
                    Stop. ALL of those controllers are a total waste of money, primarily because your batteries are a total waste of money. They are not the right type to use, EXCEPT for floating telcom / backup ups use.

                    Read their own manual and you will see that they are FLOAT charged only at 2.28 to 2.265v per cell. NO higher voltage absorb values!

                    http://www.enersys-emea.com/reserve/...F-002_0209.pdf

                    They are intended for rapid-discharge UPS duty. If you are going to wing it anyway, even medium discharges will destroy them faster than an auto-parts store agm. OR, if you plan to just do "shallow cycling", you have wasted your money again. I suspect these are leftover trash you want to play with.

                    As such, just float charge them only. Don't waste money on an expensive controller, but make sure you can set absorb AND float to the same 27.3v or so value, and has temperature compensation.

                    When new and properly installed, they do a great job at what they were designed to do: provide UPS service for a limited number of cycles. Totally inappropriate for most solar cycling applications.

                    Playing with leftover trash is one thing, but trying to design a system around batteries not designed for it's original purpose is just an expensive goof.

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                    • #11
                      Hey all, long-time listener, first-time caller!

                      I found this thread as I was trying to find the charging specs for the used batteries I just bought: SuperSafe 12T92F. To my dismay after reading this thread I realise that I might have messed up. Can anyone confirm if I've bought float-only-type batteries too? All I could find was the sales documents, which informed me they're VRLA and AGM, 92Ah each (I have two of).

                      It's quite frustrating as I've worked my butt off to study as hard as possible, and haven't stuffed up until potentially now. It's not a huge amount of money lost if so, and if we even get 12 months out of the cells, I'll be in a better position to understand our real-world (and potentially-growing) power demands by then.

                      I'm setting up a small 24v off-grid solution for our bush block in remote Victoria, Australia. We're using two 24VDC solar panels (IMPP 6.99A, VMPP 28.9V - so not true 24v) in series, and a small Victron 100/15 CC & Victron Phoenix 350w inverter. Most of the usage is DC lighting - probably using about 14Ah @ 24VDC per day when we're there.

                      Any advice on the batteries would be hugely appreciated. Thanks.
                      Last edited by tombarton; 09-04-2017, 07:47 AM.

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                      • #12
                        I looked up the Hawker page for it, and it's a Telcom Float service battery. You might get a years worth of gentle use out of it,
                        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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                        • #13
                          Mike thanks so much for that - really appreciate it. I assume the float voltage then is the same for the above battery: 14.4V (28.8V in 24v system)? Should I basically program the victron CC to give it all it has when the sun's out?

                          The system will be well over-specced in terms of solar input, and should replace the daily usage in about an hour (our days go from 1.9 hours of sun a day in winter to 6.6 in summer), so hopefully that'll nurse the batteries for as long as possible. Lesson learned!

                          Cheers, Tom

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                          • #14
                            With sealed batteries, you cannot innovate much, too much charge and you pop the vents, loosing gas (electrolyte) and diminishing your battery capacity, too little and it sulfates. You have to stick with the Mfg's specs.
                            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


                            • #15
                              Thanks Mike. So am I correct in assuming that almost all AGM type batteries are inappropriate for solar storage?

                              My seller is offering to replace what I've bought, but I think all of his used stock is AGM (which makes sense, as it seems the 'used' industry is just on-selling trash UPS storage that's been mandated to be replaced by govt/industry policy every 5 years).

                              He's offering the Lion HZB-12-100 (100ah C20) AGM VRLA. Is this any better? Thanks again for the assistance - I'll give back to the forum where I can in future. Specs look to be:

                              Float: 2.27-2.30 VPC @20 C
                              Cycling: 2.34 @20 C
                              Max. 2.4 VPC Max ripple 3.5% charging V
                              Last edited by tombarton; 09-06-2017, 10:44 PM.

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