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    Custom LiFePO4 battery pack project

    Hello,
    I purchased 24 LiFePO4 8AH cells on Ali to do a 36V 16AH battery pack (2 parallel 12 serial)
    and I received stuf with weird signs of wear...

    I was hopping to buy cells that would give me 1000 charges cycle and now I wonder how many charges cycle I would have with these cells

    I also wonder where these cells come from... what can I learn from the lines on the tab on the picture with 8 cells

    and what is the piece looking like flexible pcb on the lower cells on the 3 cells picture...

    Phil
    Montreal Canada


    Sorry for previous post in visitor's topic... I had not found this 'batteries Lipo topic' ... I am new here...

    Also, btw, almost all LiFePO4 sellers on Ali use deliveries with signature... and I now suspect that this is because people would not acknowledge delivery of what is obviously old recycled cells... Consumer's protection is not very good on Ali... there is a big language and technical barrier with them...
    LiFePO4 pouch quality ? 2 dates code ! tab history ?

    #2
    I would check the internal resistance, even if the cells look crummy on the outside, the cell might be brand new inside. You need a good RC charger that will measure internal resistance to do this.

    Pouch cells are just that, pouch cells and they look like crap when taken out of their fancy shiny manufacturer wrapping.

    G.
    Alpha One 6000W tadpole e-Trike (Cyclone): https://www.youtube.com/watch?v=oFC8MRwvgUM
    Alpha Two Cyclone 3000W tadpole e-Trike: https://www.youtube.com/watch?v=fkakVw8yY8E
    Electric Cyclone 3000W eBike "power mod": https://www.youtube.com/watch?v=_weSmz_h3Ig

    Comment


      #3
      Thank you for the advice gman1971,

      I checked the internal resistance of a random sample of 4 cells charged to their 3.28V/3.3 V with the DC load method and 4 -wire connection on the lugs...

      The test currant was 0.8 Amp charging and 1.45 Amp discharging

      The results under charge test versus discharge test were coherent...

      The measured internal resistance were between 5.2 milli ohm and 7.8 milli ohm.

      Good or Bad ?

      Comment


        #4
        For a brand new LiPo cell (not LiFePo) those would be in the ragged edge of acceptable, most brand new LiPo cells have under 5.0 mOhm, usually under 2.0 for most of the decent stuff I've seen... new, of course (my MultiStar 16,000 packs were all between 0.3-0.7 mOhm IR. But for LiFePo I cannot say for sure.
        Alpha One 6000W tadpole e-Trike (Cyclone): https://www.youtube.com/watch?v=oFC8MRwvgUM
        Alpha Two Cyclone 3000W tadpole e-Trike: https://www.youtube.com/watch?v=fkakVw8yY8E
        Electric Cyclone 3000W eBike "power mod": https://www.youtube.com/watch?v=_weSmz_h3Ig

        Comment


          #5
          Thank you gman1971, the seller had specified them under 3 milli ohm

          He does a lot of battery pack... a more discreet way to recycle old cells !

          Comment


            #6
            5 mOhm is not bad, anything above 25-30 mOhm IIRC in LiPos is usually done...
            Alpha One 6000W tadpole e-Trike (Cyclone): https://www.youtube.com/watch?v=oFC8MRwvgUM
            Alpha Two Cyclone 3000W tadpole e-Trike: https://www.youtube.com/watch?v=fkakVw8yY8E
            Electric Cyclone 3000W eBike "power mod": https://www.youtube.com/watch?v=_weSmz_h3Ig

            Comment

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