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60Kwh Battery?

Discussion in 'Model S: Battery & Charging' started by okashira, Jan 26, 2015.

  1. okashira

    okashira Member

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    Has anyone opened a 60kwh pack?

    My research shows the 60kwh pack has 14 modules. But that would be 73kwh if they are the same modules as the 85.

    So, either...
    1.) there are fewer cells (empty places) in the modules
    2.) the 60kwh car uses completely different cells, e.g. 2.6Ah cells.
    3.) The 60kwh pack is way overbuilt

    #2 would explain the higher efficiency. Lower capacity cell would likely have lower internal resistance, thus more efficient under load.

    #3 is not possible, based on reported voltages when dead/charged.

    It's either 1 or 2. I'm leaning to 2. since 2.6ah cells would likely be considerably cheaper.


    The NHTSA photos of a 60kwh pack appear to show "empty spots" for cells, however, they are only missing from some modules. This wouldnt work. You'd need to remove the same # of cells from each parallel back or the back would be horribly imbalanced.
    I am guessing the missing cells in those pictures are sharpy marks, black tape, or since its a non functional car they put in some wonky modules.
     
  2. nwdiver

    nwdiver Active Member

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    *The following comments are evidence-based speculation*

    I know that solar cells off the same line often have slightly different power levels... they are tested and segregated. Higher power cells are put into higher power modules. That's why the same solar module is usually available in slightly different power levels. It's possible that the same effect occurs with battery cells...
     
  3. okashira

    okashira Member

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    #3 okashira, Jan 26, 2015
    Last edited: Jan 26, 2015
    That is true for 18650's too.
    But never to the extent of 3.2/3.3Ah (like the 85kwh cells) vs 2.6 Ah.

    And indeed, they are also binned by internal resistance (thus power capability.)

    With panasonic, I am sure the variances are 2% or less for capacity.
     
  4. Saghost

    Saghost Active Member

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    I'm pretty sure I saw some pictures in a thread a while back showing 60 kWh modules, with groups of cells missing from the pattern.
     
  5. okashira

    okashira Member

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    I referred to that in the OP.
     
  6. kennybobby

    kennybobby Member

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    #6 kennybobby, Jan 26, 2015
    Last edited: Jan 27, 2015
    Panasonic indicates their NNP technology cells have an energy of about 11.1 to 12.2 W-hrs at a nominal 3.6V depending upon the cell capacity. Using 11.96 W-hrs as determined from the 85kWh pack (85kWh/7104 cells = 11.96 Wh), then a 60kWh pack would consist of 60kWh/11.96 = 5040 of the 3.3 A-hr cells, or 5376 of the 3.1 A-hr cells.

    So 14 modules in the M60 would be a 84s60p or 84s64p pack depending upon whether the S60 and S85 use the same cells or not.

    Seems odd to think they would use different cells but that's what it appears to me with the NHTSA pack (if 10 empty spaces), 84s64p, 3.1 A-hr cells at nominal 3.6V...
     
  7. wk057

    wk057 Senior Tinkerer

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    From what I understand the 60kWh pack's modules are just not bricks of 444 cells and have dummy cells in ~14 spaces for each of the 6 groups in each module.
     
  8. kennybobby

    kennybobby Member

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    That would make sense then of using the same cell in both the 60 and 85kWh packs, 84s60p and 96s74p with ~3.3 A-hr cell, nominal 3.6V and energy of 11.96 W-hr.
     
  9. okashira

    okashira Member

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    #9 okashira, Jan 27, 2015
    Last edited: Jan 27, 2015
    Panasonic's 3.1 Ah NNP cell is pretty outdated by now and not the best in terms of impedance. It's unlikely Tesla is using it.
    Again, if you look at the NHTSA picture, the "missing cells" are NOT consistant across the modules, which wouldn't work...

    You do have a good point... while it's certainty not 100% that Tesla is using NNP cells for the 60, it's highly likely. The Roadster cells aren't NNP (well, except the upgraded pack) but that pack is quite old now.
    And there aren't any 2.6Ah NNP cells.

    Thanks for the reply. From what do you derive your understanding?
     
  10. wk057

    wk057 Senior Tinkerer

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    I've seen a 60kWh pack opened (not the NHTSA). The dummy cells appear to be black or white and aren't all easily visible in the NHTSA photos.
     

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