ingoldsbyingoldsby Registered Users Posts: 19 ✭✭
 Hi everybody  I have a  question  if anyone  could give me advice  I  have had a problem  with    #2 batteries  on end of  string   I have . #8 ,6volt BATTERIES  hooked in series,   one end of the series call it last 2 batts never charge up like rest of string      I have charged those 2 separately   then put them back into service   sg,1265  have also did  eq      still  doing same thing  those 2 batts at end of string are always lower after 5 hours of absorb at 60.4  temp 64 farenheit  5 hour float 54.4     I then  went and got 2 new SURRETES put them in service with other 6 batts      never guess....     same thing   ,,,  oh forgot I even went as far as changing pos and neg  on string      still those #2  new batts are low in sg      please if anybody  has a clue , love to hear from you   cheers  ,,,,,


  • BB.BB. Super Moderators, Administrators Posts: 28,304 admin
    edited January 2018 #2
    Try swapping the two weak batteries with batteries at the other end of the string.

    For otherwise good battery installations, a few people here have rotated their batteries every few years because the batteries at one end of the string had low charging SG readings over time.

    I don't understand why, but it works for them.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ingoldsbyingoldsby Registered Users Posts: 19 ✭✭
    Hi Bill  my name name is Dennis  and I am glad you have answered  my pleas   again    you are a man of knowledge I do appreciate it       as a you were saying to change end batts     I did  I put 2 new batts and still they dropped in sg and voltage
     I even changed both end cables  other ones were fine  but thought for 40 bucks for new cables would maybe fix problem was wrong  but have two new cables at least lol  any other thing you could think of Bill  *
  • BB.BB. Super Moderators, Administrators Posts: 28,304 admin

    Did you put the new batteries, for example, failed batteries1+2 to location 7+8, and move the existing good batteries to location 1+2 where the failing batteries were? (Swap locations)?

    The only reason i think this could help is if batteries 1+2 average 10-20F hotter than the test of bank (poor ventilation, bad terminal connection getting hot, breast sunny window, etc.).

    Otherwise, are you equalizing the battery bank? This overcharged some cells to bring up weak/low sg cells.

    Some surrett batteries are known for needing quite a bit of equalization. Charging at 60-62 volts (especially in cooler climates). You are looking for roughly 5% rate of charging current (ex: 400 ah bank, 20 amps equalization). Can take many hours or several 1/2 day sessions (don't overheat the bank).

    Watch cells, and if the sg stops rising after 1 hour on all cells, log the temperature corrected sg for each cell. That is now 100% charged.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 2,492 ✭✭✭✭✭
    It does seem strange that the two batteries in a specific location would always be at a lower state of charge in a series string, do you perhaps have a 12V load tapped off those batteries as this would definitely cause such a phenomenon, long shot but a common mistake made.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • ingoldsbyingoldsby Registered Users Posts: 19 ✭✭
    Hi Bill  again thanks for replying I replaced the 2 batts with new  which were 1265  sg ,   thinking they would stay up in sg  they dont ,,,, I will charge them separate  tomorrow  and then do absorb then start eq         batts  never get below 59 farenheit    right now at 62 f    can improper torque values cause  this type of problem?   
  • ingoldsbyingoldsby Registered Users Posts: 19 ✭✭
    Hi McGivor   thanks also for your reply      there is no load  connected to those batts   I have a b.m.k kit and arc remote  wire to the bank     i am stumped    I also replaced those 2 cables  connecting the 2 new batts and still low sg on both batts . fyi ,,,they are always at  the same sg  and voltage ie. Lower than the other full  six batts  
  • BB.BB. Super Moderators, Administrators Posts: 28,304 admin
    Improper torque could, in theory, cause a battery to run hotter--If you run high current (loading or charging) for a while, then use an IR Thermometer or even your hand, and see if any of the terminals/wiring is hot (or warmer than others).

    But if the terminals are clean and reasonably tight, it should not be a major contributor to this issue.

    Note, we are talking about a "hot battery" (10-20F or higher than the rest of the bank) having higher self discharge than the rest of the bank.

    Is this your issue--I have no idea--It just has been seen by several long time members that "rotating" the batteries (say once a year) in a single series string helped keep the batteries happy overall.

    If you had "dirty battery tops (and/or corrosion on the battery) can also cause leakage current. And as McGiver asked--If you have "tapped" 12 volts for some local DC loads from a 24 or 48 volt battery bank will also cause charging imbalance too.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ingoldsbyingoldsby Registered Users Posts: 19 ✭✭
    Hi Bill  I charge  those 2 batts  separately   from series got them up in sg  then introduced them back to series  then charged absorb til all sg were up  then followed  with eq  all seems well  I 'll no more as day go by I guess any way      ,checked for hot cables none hot   temp of batts roughly same ,top of batts clean   I am going to by a torque wrench  to to batts  I will keep you posted ,,  again thank you guys for your input  Bill have a good night  cheers,,,,,
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