Surprise SG on 2 of 12 cells

shokmanshokman Registered Users Posts: 3
 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 ?


  • BB.BB. Super Moderators, Administrators Posts: 32,999 admin
    Check the section in the Rolls manual on "Corrective Equalization"... Starting at Page 26 of the manual.

    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.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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