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Apples to apples? Rolls batteries

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  • Apples to apples? Rolls batteries

    48v battery bank, 546ah. I can get there 3 ways with the Rolls 5000 series batteries: 4-cs-17ps, 6-cs-17ps, 8-cs-17p. 4V, 6V, 8V, respectively. Pulling prices from an arbitrary website pricing for the entire bank is $8140, $7655, $7748. Price is for batteries alone, sans shipping. Obviously the number of cells for the entire bank remains the same. Space requirements for the bank not being a factor, is there any reason to choose one bank over the other? It's essentially the same battery, I'm assuming the same plates, just cell count and battery case differ. I would think an 8v bank with less wiring would be more practical but the battery bank should behave the same regardless?

  • #2
    Originally posted by jtbartlett View Post
    I'm assuming the same plates, just cell count and battery case differ. I would think an 8v bank with less wiring would be more practical
    There is the same amount of "wiring", but in the higher voltage batteries more of the "wiring" is internal to the battery. My personal preference, (if price were the same) would be the lower voltage cells. My reason is that I would be able to measure the voltage of fewer cells at a time. Also, in the event of a bad battery, I might be able to swap out the bad battery at lower cost than a higher voltage battery.

    If you use 2 volt cells, you even have the option of simply removing a bad cell and lowering the charge parameters on your controller and lowering the low voltage disconnect on your inverter.

    --mapmaker
    ob 3524, FM60, ePanel, 4 L16, 4 x 235 watt panels

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    • #3
      Originally posted by jtbartlett View Post
      I would think an 8v bank with less wiring would be more practical but the battery bank should behave the same regardless?
      Correct you are. It is fewer eggs in the basket to go wrong. Most problems are from improper installation of battery cabling. Fewer terminations means fewer possible problems. Don't take this wrong but most DIY's have no clue how to make a proper termination. This is mostly due to two facts.
      • Lack of training, experience and understanding.
      • Use the wrong tools. Tooling to terminate heavy gauge cables is very expensive running into the thousands of dollars. DIY's are ignorant about it and do not have access to it.


      Just one slightly bad connection can lead to a fire.
      MSEE, PE

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      • #4
        Originally posted by mapmaker View Post
        There is the same amount of "wiring", but in the higher voltage batteries more of the "wiring" is internal to the battery. My personal preference, (if price were the same) would be the lower voltage cells. My reason is that I would be able to measure the voltage of fewer cells at a time. Also, in the event of a bad battery, I might be able to swap out the bad battery at lower cost than a higher voltage battery.
        Except these are Surrette 5000's. There's no such thing as a "bad" battery. They are identical to a forklift battery and have individually replaceable cells. So you have one that drops a cell - pop the top off it, unbolt the bad "jar" and drop in a new one.

        Edit:
        I sort of agree with Sunking - get the 8's and reduce your number of cabled interconnects. The reason I say "sort of" is because the lower voltage ones are easier to move, so it depends on your utility room situation. The 8's are heavier than hell. We got 12's here and they're REALLY heavier than hell. We grunted, drank beer, dragged, shoved, drank beer, swore, drank beer, pryed, drank beer and finally got 'em to where they needed to be for the last 7 years. They haven't been moved since.

        Rule of thumb with Surrette 5000's; the more volts they got, the more beer it takes to move 'em. The ones with more volts are cheaper to buy, but you have to budget in the required beer and then it's a wash.
        off-grid in Northern Wisconsin for 14 years

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        • #5
          Originally posted by ChrisOlson View Post
          Except these are Surrette 5000's. There's no such thing as a "bad" battery. They are identical to a forklift battery and have individually replaceable cells. So you have one that drops a cell - pop the top off it, unbolt the bad "jar" and drop in a new one.

          Edit:
          I sort of agree with Sunking - get the 8's and reduce your number of cabled interconnects. The reason I say "sort of" is because the lower voltage ones are easier to move, so it depends on your utility room situation. The 8's are heavier than hell. We got 12's here and they're REALLY heavier than hell. We grunted, drank beer, dragged, shoved, drank beer, swore, drank beer, pryed, drank beer and finally got 'em to where they needed to be for the last 7 years. They haven't been moved since.

          Rule of thumb with Surrette 5000's; the more volts they got, the more beer it takes to move 'em. The ones with more volts are cheaper to buy, but you have to budget in the required beer and then it's a wash.
          Chris you are right about the weight, but that is once in a 5 to 7 year chore. Inter-cell connections will eat DIY lunch if they do not buy factory made cables.
          MSEE, PE

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          • #6
            Originally posted by ChrisOlson View Post
            Except these are Surrette 5000's. There's no such thing as a "bad" battery. They are identical to a forklift battery and have individually replaceable cells. So you have one that drops a cell - pop the top off it, unbolt the bad "jar" and drop in a new one.

            Edit:
            I sort of agree with Sunking - get the 8's and reduce your number of cabled interconnects. The reason I say "sort of" is because the lower voltage ones are easier to move, so it depends on your utility room situation. The 8's are heavier than hell. We got 12's here and they're REALLY heavier than hell. We grunted, drank beer, dragged, shoved, drank beer, swore, drank beer, pryed, drank beer and finally got 'em to where they needed to be for the last 7 years. They haven't been moved since.

            Rule of thumb with Surrette 5000's; the more volts they got, the more beer it takes to move 'em. The ones with more volts are cheaper to buy, but you have to budget in the required beer and then it's a wash.
            Don't forget about the cost of aspirin for them aching backs.

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