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Float voltage for Rolls S-550

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  • #16
    It's a balancing act. Undercharge sulfates batteries. Overcharge causes positive plate corrosion and lots of water consumption. Water usage is easy to deal with , at 50 cents a gallon for good DI water.

    I believe 90% of early battery failures are from undercharge/sulfation. Overcharge is much less common, mostly because you need a lot of solar PV to overcharge batteries in just 7 hours.

    Water usage is a good guideline, if you track usage by cell. When charging starts using lots of water, you have just surpassed the sweet spot. Undercharged uses little water. Barely charged uses more, over charged you go crazy trying to keep them watered.

    If you don't have time to add another half hour to absorb, raise the bulk & absorb voltage .2V and see if that helps after a couple days. If not add more voltage to cram more charge into the cells in s shorter period of time. Don't violate any max charge rate spec from the factory though.

    Batteries have to be fully charged before EQ (which is a slight overcharge) can begin.
    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



    • #17
      I understand the above but what my question is : when you say to stop absorb at 3% of C, is that like 12A on a 420AH battery? Seems like it should go longer... I run absorb down to about 5A and the SG is about right.

      I add water about every 2 or 3 weeks which seems about right.