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I cannot believe no-one has yet managed to come up with a figure for the mass of a single 2170 cell.

Discussion in 'Battery Discussion' started by JKolodziejski, Jun 12, 2018.

  1. JKolodziejski

    JKolodziejski Member

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    #1 JKolodziejski, Jun 12, 2018
    Last edited: Jun 12, 2018
    After furtively searching for it, all across the EV news sites and all the breakdowns so far, despite the very cells obviously being physically separable and in the hands of people analysing the battery pack (Mmmmmph! Hmmm! THIS picture), nobody has seemingly bothered to measure the cell mass itself.

    And, no, the battery pack specific energy density alone isn't good enough and volumetric battery pack energy density means even less.

    Reason I am asking this is because the battery pack mass is variable and does not actually give an indication of the underlying technology.

    it's really quite important if one wants to compare to what LG are doing, and if Elon was stretching it when he says "so and so improvement"

    The cells are known to have circa 18.23 Wh - that's 80.5 kWh divided by 4416 cells.

    Depending on whether this cell is 60 to 75 grams determines specific energies that are surprisingly variable, from 243 Wh/kg to 304 Wh/kg

    It's really irritating. Is there some weird NDA thing going on? Can someone cough up for once?
     
  2. GregRF

    GregRF Squirrel Power

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    From the EVTV teardown we learned that the difference between the two modules is 16lbs (207lb for 25s vs 191lb 23s). So if each series group has 46 cells (4416/96s) in parallel that would make 92 cells that weigh 16lbs, so roughly 79 grams per cell.

    Not sure what else is different between the two module types, but my guess would be that would be the upper bound of cell weight.
     
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  3. JKolodziejski

    JKolodziejski Member

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    Good find but the modules themselves are different lengths. The ones with more cells have more structure and vice versa, however the 79 grams figure does give an upper bound.
     
  4. Electroman

    Electroman Well-Known Member

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    with 18.23 Wh/cell and one cell is 79 grams (upper bound) --> that comes to 230 Wh/Kg (Lower bound).

    Most likely around 250 Wh/Kg. Okay but not great.
     
  5. Brando

    Brando Active Member

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    Google searches are your friend - finding your truth isn't always easy. try for yourself. not helpful? sorry.
    - Weight Without washer 68.0 ± 1.0 g
    https://www.batteryspace.com/prod-specs/11514.pdf
     
  6. gilscales

    gilscales Active Member

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    I did see a figure of 69 grams for a 2170 Samsung, if LG is 68 +or- 1 then we are very close at approx. 68 or 69 grams, cannot see the Panasonic cell much different from the others but I do find it strange that no one has mentioned the individual cell weight yet.

    At 68 or 69 Grams, that's 264 to 268 wh/kg, how does that compare to the 18650's?
     
  7. GregRF

    GregRF Squirrel Power

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    According to EVTV 70 grams
    [​IMG]
     
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  8. Cosmacelf

    Cosmacelf Well-Known Member

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    According to this article, the 18650s were at 254 Wh/kg. Let’s just call it the same, since we don’t have a source where the same person does the same measurements on the two cells.

    We do know the cells have changed quite a bit in that they use far less cobalt, and probably more silicon in the anode. These changes have more to do with cost than performance.

    Remember, the number 1 goal in battery tech is reducing costs. You can do that through better performance, but you can also achieve that through cheaper materials and better battery pack integration, which is what Tesla seems to be doing.
     
  9. GregRF

    GregRF Squirrel Power

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    According to this post:
    Battery cell energy density: from 240 to 247 Wh/kg (18650, 2170), 3% increase
    pack level energy density: from 126.7 to 159.5, Wh/kg, 25.9% increase
     
  10. Electroman

    Electroman Well-Known Member

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    ultimately pack level density is what matters
     
  11. Cosmacelf

    Cosmacelf Well-Known Member

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    Ultimately battery pack level cost is what matters. I’m being glib, but overall volume and weight of the pack doesn’t matter nearly so much as does $/kWh of the pack. As I said above, at the cell level, Tesla/Panasonic hasn’t improved much going from 18650 to 2170 cells in terms of volumetric or gravimetric density, but I’ll bet they improved a bunch in $/kWh.
     
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  12. Brando

    Brando Active Member

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    cost and range is what matters to buyers - obviously
     
  13. Kanting

    Kanting Member

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    Wow the cell casing saves a lot of mass for the pack and saves some cost building the pack as well. not sure how the longevity or degradation goes, considering in a bigger pack and without pack heater.
     
  14. Cosmacelf

    Cosmacelf Well-Known Member

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    The Model 3 pack does have a pack heater.
     
  15. Cosmacelf

    Cosmacelf Well-Known Member

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    Cute. The article I linked to above was posted in 2016, and it was making a case for more advanced battery technologies than what Tesla had. It linked to a French company that was using solid state batteries. I just clicked on that link and the French company is now out of business. Promises, promises...
     
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