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Order of Cells....does it matter?

Discussion in 'Gen 2 Prius Technical Discussion' started by lamtech, May 4, 2014.

  1. lamtech

    lamtech New Member

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    I'm rebuilding my 2nd generation 07 prius battery and I bought all the battery chargers and everything and tested out all my cells using:

    Charge at 5 amps up to 7250mAhr
    Discharge at .7 aMhr down to 6 volts
    DSCH<CHG for 3 cycles.
    Other settings: I set the timer limit to 720 minute cut off. I also set the cool down period to 5 minutes.

    courtesy of ryousideways

    All my cells are charging up great except for 4. I went on ebay, bought 4 remanufactured cells that states it been balanced and fully charged. So I took out the bad and put in the new and did another 1 cycle test on the new cells. All the new cells are testing out low roughly charging up to 2000-3000mAh.

    I marked down the order of these cells 1-28 and 4, 8, 17, and 21 were bad. So replacing just these cells came out with still low results. So what I'm doing is pushing all the good cells together (everyone charged to 7250aMh) and have the last 4 low ones together and doing another cycle run with them.

    My question is: does the position of the cells really matter or did I just purchase 4 bad cells from ebay?
     
    #1 lamtech, May 4, 2014
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  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The physical position of the modules does not matter, each module should behave similarly and if not, you know it is bad.

    You might contact the eBay seller, describe your testing procedure, and see what the response is.
     
    #2 Patrick Wong, May 4, 2014
  3. jdenenberg

    jdenenberg EE Professor

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    It is not the charging capacity, you need to look at the discharge capacity to review the status of your modules.

    JeffD
     
    #3 jdenenberg, May 4, 2014
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  4. Mendel Leisk

    Mendel Leisk Senior Member

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    I'm totally out of my league, but I did read here: it's not a bad idea to rotate the positions, basically: move the cells near the centre out to the ends, and move the ends into the middle. The logic being that the end cells take more abuse, temperature/charging extremes? Something like that, but wait for someone who actually knows something to confirm, lol.
     
    #4 Mendel Leisk, May 4, 2014
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  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Actually the concept is that the modules at the center of the pack would tend to overheat more than the modules at the ends.
     
    #5 Patrick Wong, May 4, 2014
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  6. flxcon

    flxcon Junior Member

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    correct, modules near closed to air flow will be less hot all the time than the one at the end, heat is taken to exhaust and the modules closed to hv computer will get the hottest air. Simple logic. ="Mendel Leisk, post: 2003285, member: 69191"]I'm totally out of my league, but I did read here: it's not a bad idea to rotate the positions, basically: move the cells near the centre out to the ends, and move the ends into the middle. The logic being that the end cells take more abuse, temperature/charging extremes? Something like that, but wait for someone who actually knows something to confirm, lol.[/quote]
    That I
     
    #6 flxcon, May 4, 2014
  7. lamtech

    lamtech New Member

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    Alright, I understand the answer to my question and know a bit more about it. Can you guys give me a 2nd opinion on may data to make sure I'm changing the right ones out. My initial post had the wrong ones that I needed to change but the right ones is on the data list:
    Cell # Volts
    1 7.87 Charge 4621mAh 5654mAh 5756mAh
    Discharge 7250mAh 7250mAh 7250mAh
    2 7.87 Charge 4679mAh 5669mAh 5779mAh
    Discharge 7250mAh 7250mAh 7250mAh
    3 7.87 Charge 4458mAh 5825mAh 5886mAh
    Discharge 7250mAh 7250mAh 7250mAh
    4 7.93 Charge 1998mAh 2214mAh 2240mAh
    Discharge 3813mAh 3812mAh 3569mAh
    5 7.87 Charge 94mAh 5892mAh 5939mAh
    Discharge 7250mAh 7250mAh 7250mAh
    6 7.86 Charge 2101mAh 5748mAh 5832mAh
    Discharge 7250mAh 7250mAh 7250mAh
    7 7.86 Charge 773mAh 5780mAh 5846mAh
    Discharge 7250mAh 7250mAh 7250mAh
    8 7.87 Charge 2128mAh 5697mAh 5790mAh
    Discharge 7250mAh 7250mAh 7250mAh
    9 7.86 Charge 4186mAh 5708mAh 5834mAh
    Discharge 7250mAh 7251mAh 7250mAh
    10 7.94 Charge 1415mAh 1492mAh 1588mAh
    Discharge 2834mAh 2713mAh 3304mAh
    11 8.06 Charge 4128mAh 5430mAh 5607mAh
    Discharge 7250mAh 7250mAh 7250mAh
    12 7.97 Charge 3647mAh 5625mAh 5695mAh
    Discharge 7250mAh 7250mAh 7250mAh
    13 7.86 Charge 2089mAh 5699mAh 5816mAh
    Discharge 7250mAh 7250mAh 7250mAh
    14 7.87 Charge 2102mAh 5652mAh 5805mAh
    Discharge 7250mAh 7250mAh 7250mAh
    15 7.87 Charge 2071mAh 5586mAh 5780mAh
    Discharge 7250mAh 7250mAh 7250mAh
    16 7.86 Charge 5056mAh 5656mAh 5762mAh
    Discharge 7250mAh 7250mAh 7250mAh
    17 7.87 Charge 2153mAh 5616mAh 5670mAh
    Discharge 7250mAh 7250mAh 7250mAh
    18 7.9 Charge 1932mAh 2601mAh 3065mAh
    Discharge 4552mAh 5162mAh 5042mAh
    19 7.86 Charge 2095mAh 4750mAh 5131mAh
    Discharge 7245mAh 7250mAh 7250mAh
    20 7.97 Charge 1943mAh 5269mAh 5378mAh
    Discharge 7250mAh 7250mAh 7250mAh
    21 7.91 Charge 1713mAh 2443mAh 2532mAh
    Discharge 3692mAh 4058mAh 4425mAh
    22 7.86 Charge 2089mAh 5597mAh 5488mAh
    Discharge 7250mAh 7250mAh 7250mAh
    23 7.86 Charge 2050mAh 5702mAh 5892mAh
    Discharge 7251mAh 7251mAh 7250mAh
    24 7.86 Charge 2125mAh 5743mAh 5765mAh
    Discharge 7250mAh 7250mAh 7250mAh
    25 7.87 Charge 4285mAh 5846mAh 5868mAh
    Discharge 7250mAh 7250mAh 7250mAh
    26 7.86 Charge 4556mAh 5685mAh 5774mAh
    Discharge 7250mAh 7250mAh 7250mAh
    27 7.95 Charge 3924mAh 4538mAh 4639mAh
    Discharge 6271mAh 6511mAh 6527mAh
    28 7.86 Charge 255mAh 5767mAh 5788mAh
    Discharge 7250mAh 7250mAh 7250mAh


    I'm thinking module 4, 10, 18, and 21 are the main culprits and possible 27. A second opinion would be great. Thanks,
     

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    #7 lamtech, May 4, 2014
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  8. nh7o

    nh7o Off grid since 1980

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    I agree, even though 27 seems to coming up. However, it is not worth taking a chance at this point, so I would replace 27 now, rather than in the coming months as others have ended up doing.

    Thanks for doing this and adding to the knowledge base.
     
    #8 nh7o, May 4, 2014
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I am wondering how many miles were logged on the OP's battery, since it has 4-5 bad modules.
     
    #9 Patrick Wong, May 4, 2014
  10. lamtech

    lamtech New Member

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    101,500.....1500 more than the warranty...
     
    #10 lamtech, May 4, 2014
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  11. MTL_hihy

    MTL_hihy Active Member

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    I agree, given the current state of the rest of your battery pack without question you should be changing out any modules returning less than 5,000 mAh (ideally 5,500 min) after being fully charged. This will ensure your modules are well matched and you won't need to do this again anytime soon. As stated above the lower capacity modules need to go on the outside of the pack while the highest capacity should be shifted towards the center. Make sure to also try and even out the block capacities as best you can too.
     
    #11 MTL_hihy, May 5, 2014
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