Can battery order affect performance?

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Ralph Day
Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
My batteries have been in the same series order for 7 years. I've noticed that the batteries closest to the neg terminal inverter connection point have lower average and lower absolute sg values from the others in the series (especially the one at the pos terminal inv connection point).

Layout is 6 x 8v cs25 Surrette fla's (big ones). I've had to replace 2 cells under warranty, and would like to avoid any further replacements until the entire bank needs doing.

My question is should the order of the battery in the series affect it's life and performance? Should I move the "weak" battery to somewhere else in the bank and see if there's a change in status?

Any and all opinions welcome, recommendations not necessarily acted upon :p

Ralph
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  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #2
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    Re: Can battery order affect performance?

    Mine are in Series and Paralleled in a 12 V bank. I have them numbered and will shuffle them around once a year. Someone once said it doesn't matter on a bank that is only in series, but like you I always notice that the first battery use's more water and seem to go first on my 24 V bank. It's not that much trouble to do, good time to do some maintenance on the terminals.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
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    Re: Can battery order affect performance?

    In a series string, battery position means nothing.

    In parallel, it gets nasty. 2 strings fed on the diagonals, generally works OK, beyone that, you need heavy bussbars, and matched fuses and leads, to get parallel strings to share the load equally. Even a string a couple milli-ohms high or low, will shun or hog the power. The lowest resistance string (the best one) quickly gets aged to the point where it matches the worst string.
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #4
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    Re: Can battery order affect performance?

    So it`s just spooky co-incidence then.

    Thanks
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
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    Re: Can battery order affect performance?
    Ralph Day wrote: »
    So it`s just spooky co-incidence then.
    I'm not so sure its a co-incidence. Didn't you say that you had replaced two cells? Its generally not a good idea to mix old and new cells in a battery bank. Where in your series circuit are the new cells?
    --vtmaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • Ralph Day
    Ralph Day Solar Expert Posts: 1,019 ✭✭✭✭
    #6
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    Re: Can battery order affect performance?

    The new cells are #1 (positive inverter connection point) and #13 just past the mid-way point of 24 cells in total. Their sg values have not been dragged down. They consistently measure 1.280-1.290 while the others are from 1.260-1.270 when full SOC is reached. The new ones are probably being overcharged, or the electrolyte formulation has been changed since 2004.

    Ral;ph
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #7
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    Re: Can battery order affect performance?

    I have a 16 battery string and my only "bad" batt is about 2/3 of the way through the string. Still not horrible, the resting voltage is just slightly lower than the rest.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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