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24 V LIFEPO4 battery build

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  • 24 V LIFEPO4 battery build

    Hi. First post here. I am putting together a 24 volt LIFEPO4 battery made from 64 recovered e-bike cells (8x8). They are all the same type but differ somewhat on the Ah left in them. Lowest around 9 Ah and highest around 11 Ah. The question is, shall I arrange them so that I have cells with similar Ah in every parallell stack or the opposite, try to mix Ah in every parallell stack so all serial cells have around the same Ah and one dont go out first all the time. I would of course prefer mixed/balanced, but the question is if that is ok for the cells? Thankful for any opinion.

  • #2
    STOP. Right now, and return those used e-bike cells.

    It doesn't matter what chemistry you use, but starting out with used / recovered / gray market / rejects etc are the WORST way to start out, and quite frankly a danger to yourself and others. (Despite LFP being the safest of the lithium chemistries).

    Leave the world of trash collecting to others, and do some more homework first. I really like LFP, but if you start out on the wrong foot with TRASH, you will only learn how to empty your wallet, and become a major target for charlatans.

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    • #3
      only use matched capacity cells in a Li bank. That way, when one cell is low, they all are low, If you have 1, 9ah cell and others are 11ah, there is a very good chance, that the 9ah cell will be reverse charged as you try to get the full life out of the rest of the pack. Reverse charge damages the cell, and you get a nice fire when you recharge it at some random time in the future.
      And who knows what else happened to the cells before you got them

      Conversely, when charging the pack the 9ah cell will fill up first and be overcharged.
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