Surprise SG on 2 of 12 cells

shokman
shokman Registered Users Posts: 15 ✭✭
in Old Battery Tech Discussions #1
 A quick history on 4  S550 rolls Surette batteries .  Installed March 2019 in a 12 V configuration SG readings approximately every 3 to 4 months.  Readings are generally taken in the morning and are usually 1.200 to 1.240 . I have rarely seen .010 differences and commonly.005.  However today I was in the hole  and decided to check one cell as I randomly do and lo and behold it was 1.220 which I did not expect as it was the end of a good day of sun so I checked another one and lo and behold it was 1.265 😳  so I checked them all  and they were all between 1.260 and 1.270 except for two which were on different batteries. So of course my question is is this something to worry about ? I will of coarse be watching them now but unfortunately I will be away for several days. Is this a sign I need to do an equalizer?  Because these are on two different batteries can I discount corroded terminals ?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Check the section in the Rolls manual on "Corrective Equalization"... Starting at Page 26 of the manual.

    https://www.rollsbattery.com/wp-content/uploads/2019/11/Rolls-Battery-User-Manual.pdf

    Flooded Cell Lead acid battery cell SG can drift. EQ charging is basically bringing the battery up to full charge, then using somethink like 2.5% to 5% rate of charge to do controlled over charging of the full cells (basically gassing the 100% SoC cells) and charging the "low" SG cells... You continue EQ charging until all cells stop rising SG--The "new full charge" value. Or stop if the battery(ies) overheat and need to cool down... Then start corrective EQ the next day again.

    It may take multiple Discharge/Charge cycles with corrective EQ charging to bring all cells backup.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • shokman
    shokman Registered Users Posts: 15 ✭✭
    #3
     So now that I have been struggling to bring these two cells up I have a bunch of questions about chargers. Because I have not been at the lake house very much this winter I have only had the opportunity to get my batterys  to an equalize stage twice now and only for a couple of hours as the only way I can get voltage up to 15.5 is with sunshine so I do use an Iota charger 3hrs before sun up and hope to finish full charge before noon then into eq mode. Still have a 30 point deficit on my 2 problem cells. My ? about chargers is. Is there not a charger that will allow me to charge at the high voltage called for by Rolls. Or is there some way to input power through my classic 150 from a generator so I can control voltage settings. Or if I was to run the Iota long enough to keep sg at 1.265 for a long period of time would I accomplish the same goal ?
    Marc
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #4

    How much charging current do you have available?

    One possibility, especially if you have "low charging current" (closer to 5% or less vs 10%+ for your 490 AH @ 12 volt battery bank) would be to put the "weak cells/batteries" in one 2x series battery string and just charge that one bank with the smaller battery charger/solar charger... That way you could get by with a 20-40+ amp charger vs needing a 2x larger charger for parallel strings.

    Then you can get 5% - 10% rate of charge from your solar controller on the reduced capacity bank.

    On your IOTA charger--The older/simpler designs had a 10 turn pot that can adjust the output voltage... The 10 turn pot may look like this (blue, vertical or horizontal):



    You need to take the outer cover off the charger to access the trim pot.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • shokman
    shokman Registered Users Posts: 15 ✭✭
    #5
    Thanks Bill ! Just seeing your post now, I have 2 iota 30 amp chargers that I run together with the parallel smart thingy. Hard to tell if that is a screw type mechanism on top to adjust.  I’m not at the lake house right now but I’ll open one up next time I’m out there. If I don’t have the pot is there any other way to control the voltage out put ? I will try the two battery set up also as I should clean up the terminals regardless. I’m going to guess the chargers were bought about 5-6 yrs ago if that helps
    marc
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    edited February 2023 #6
    You are very welcome... I am not sure that is a photo of an Iota or not... Just to give you an idea of what you are looking for.
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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