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21-70 cell information

Discussion in 'Battery Discussion' started by Rashomon, Aug 1, 2016.

  1. Rashomon

    Rashomon Member

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    Now that Tesla has officially announced the new cell is 21mm by 70mm (21-70 in their naming, 21700 in conventional battery parlance), I'm opening a thread to discuss any known details of it: capacity, discharge rate, weight, etc. Here's what we know currently: almost nothing.
    Samsung recently announced a similar 21700 cell, aimed at the rapidly growing e-bicycle market. The European e-bicycle market alone is around 1.5 million units annually, consuming somewhere around 0.6 gWh of cells, and has been growing at 20 percent compounded for almost a decade. The Samsung 21700 cell is nominally rated at 4.750 Ah, is listed at 3.6 volts nominal, has a max discharge rating of just under 2C, and claimed to weigh 75 grams. Most 18650s are in the range of 45 to 48 grams. Straubel or Musk somewhere along the way mentioned the new 21-70 had 40 percent more energy than the prior 18650 cell, which might put it around 4.8 Ah as well, if they were talking energy and not specific energy.
    Does anyone know anything else?
     
  2. KJD

    KJD Member

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    A 40% improvement would really be amazing. Remember now this is Tesla and sometimes they are a little too optimistic.

    What if when the 21-700 sees final production that its in the range of 30% to 40% increase, as in the 90D becomes the 120D.

    Only thing I know is I want one of these cars. :cool::D
     
  3. Rashomon

    Rashomon Member

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    Keep in mind the cells are bigger and heavier almost in proportion to that 40 percent (if true) energy increase. The pack won't fit the same number of cells as the current S90 pack. We don't know yet what the capacity will be.
     
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  4. rowdy

    rowdy Member

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    46% increase in volume per cell.

    Gigafactory q&a also mentioned a 15% gain with improved cathode/anode developments.

    Need to factor in increased weight of the cells, but there may be improvements to the battery pack/cooling design that can offset this.

    I think quite likely to be a 30-40% range improvement over current 90D. Time will tell....
     
  5. wilheldp

    wilheldp Member

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    75 grams v. 48 grams = 56% increase in weight
    21x70mm v. 18x65mm = 47% increase in volume

    Looks like a 40% increase in power output would be a disappointment.
     
  6. Alketi

    Alketi Member

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  7. GSP

    GSP Member

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    The latest info suggests Tesla and Panasonic are going to the 21700 format instead.

    GSP
     
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  8. Rashomon

    Rashomon Member

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    Very useful info. Perhaps the 21-70 cell will be closer to 5.5 Ah, or even a little better. The new large S/X pack will have fewer cells than the current big pack, but conceivably could reach 115-120 kWh with only a slight weight increase.
     
  9. Alketi

    Alketi Member

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  10. Bangor Bob

    Bangor Bob Member

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    I don't have the spreadsheet anymore, but based on just scaling the dimensions, and assuming a 0.5mm metal case, cells go from 3200mAh to about 4500mAh. That's assuming no improvements in chemistry.

    A block of them 5 feet wide, seven feet long, and 5 cells deep offers 208kWh from just over 10,000 cells. Take some away for cooling passages, naturally. Nice size for a pickup truck though...

    A 75kWh pack needed something like 1800 fewer cells, and a 90kWh pack needed about 2300 fewer. That's going to save some money just in reducing the time spent packing the cells into sheets and wirebonding the fuses.
     
  11. Odebek

    Odebek Don't Panic

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    This plus Autopilot 2.0 is why I decided to lease vs. buy this year.
     
  12. LargeHamCollider

    LargeHamCollider Battery cells != scalable

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    #12 LargeHamCollider, Aug 2, 2016
    Last edited: Aug 2, 2016
    I don't think people should expect 120kwh packs from these new cells, horizontal cell density isnt going to improve much, they both have circular cross sections and existing modules have very tight packing. The additional vertical height is pure bonus though, you'll get a minimum of 70/65 = 7.7% increase in capacity. I'd guess that with chemistry improvements and other tweaks the first 21700 packs have about 15% more capacity giving you a true 100kwh pack. I'd guess this pack gives the S a range of 330-340 miles EPA and the X ~300 miles.

    Edit: Less welcome to some is that larger cell size usually (though new chemistry could mitigate this) means lower power density, don't expect much improved performance for the P100DL.
     
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  13. Rashomon

    Rashomon Member

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    The big pack will be able to fit between 5000 up to maybe 6000 of the 21-70s if it's the least bit similar to current packs. That brackets the capacity to between 90 and 120 kWh depending on exact cell capacity and cell count. The low end isn't very likely. At the high end, the pack ends up quite a bit heavier unless packaging/cooling are a lot lighter/more efficient. If the cells come in at 5.5 Ah or better, the best bet might be a pack around 100-110 kWh that's a little heavier than the current large pack. I wouldn't be shocked if we saw a larger capacity than that next year, but I wouldn't bet on it. I would bet on at least 100 kWh.
     
  14. jdevo2004

    jdevo2004 Member

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    I wonder if the Model S and Model X battery packs can handle the increased 5mm height of the new batteries without modifying the actual vehicle. ;)
     
  15. sandpiper

    sandpiper Active Member

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    I keep wondering if the future P100D that was outed is, in fact, a vehicle with the the first prototype of the 21700 cell battery pack. Clearly they've had test cells from Panasonic Japan for quite some time, and it makes sense to me that they've have them installed in vehicles for testing. Changing cell geometry is more intensive than changing the cell chemistry. The heat generation and cooling characteristics would be quite different, the module geometry would be different, the power distribution would be quite different. They'd want to test this for quite a long while to ensure that the batteries are bulletproof when they hit the street in large numbers.
     
  16. emir-t

    emir-t Member

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    Or they've achieved 100kWh with the good old 18650 cells, only with silicon addition keeping its pace at the anode side. There's strong evidence for this if they've got it approved with European regulators already. They acutally need this in order to spike demand for S and X, as they're catching up with production.

    This would mean great news for the future because it basically means 17% more energy density on the same geometry just with chemistry changes over 4 years. With 21-70 let's round that up to 20% more energy density compared to 2012 18650 cells. So 3.1Ah 2012 18650 cell as base, 40% larger in volume, 20% more dense = 5.2Ah. That's 19Wh assuming the same 3.6V nominal voltage. So a 55kWh Model 3 pack would need around ~2900 cells, and a larger 70kWh pack would need 3684 cells. That's half of what's needed for Model S and X. That's a drastic improvement for pack construction costs, not even accounting for economies of scale and the Gigafactory, yet nothing ground breaking in terms of capacity, charge speed or performance.

    At the end of the day that's the goal with Model 3 anyway. Take S & X, make it affordable. My .02$
     
  17. McKricas

    McKricas New Member

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    One more interesting information on Tesla batteries:
    Tesla’s battery research partner shows potential new path for longer EV range and durability

    This seems almost irrelevant but it's actually a very important thing.

    High-voltage batteries increases the total capacity with very little changes on rest of the battery, including their weight. Depending on the electrolyte used, cell weight can actually decrease if the density of the new electrolyte is lower than the old one.

    I made some calculations using just a 5.94% compound rate in energy density increase for the last 5 years (2012 to 2017) - which seems to me as a reasonable evolution. The new generation of Tesla batteries will have the following specifics:

    Comparing with the 2012 generation of Tesla Batteries:

    What this means is that, if true, this new generation of batteries will allow for:
    - If Tesla wants to maintain the same number of cells per pack in their Model S/X (7104 total cells) they will be able to offer a 175 kWh Pack (although with a 30% weight increase);
    - If Tesla wants to maintain a 90kWh version in their Model S/X, they will only need 4320 cells (40% less) and the total weight of the car will be 19.8% lower (of course, less weight will also mean better range). This could improve even further by redesigning the pack structure making it more lighter with fewer parts (modules even).

    - Model 3 will be far lighter and efficient. A 70 kWh version will only use 2880 cells, will be 46% lighter than current Model S and will allow for at least 310 miles of range. If my calculations are right, for a range of 215 miles a battery pack of just 46 kWh will be enough.

    This could be really quite amazing.
     
  18. scaesare

    scaesare Active Member

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    One teardown video I saw suggested there was about 1/4" of clearance between the floor of the pack and the bottom of the existing 18650 cell modules... that works out to about 6.5mm...
     
  19. emir-t

    emir-t Member

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    Wk057's pack teardowns suggested the cells actually weighed 900lb(400kg) whereas pack shell, coolant tubes, nuts, bolts weighed additionally 300lb(136kg). If they can reduce the amount of adhesive, made a less heavy shell, used less bolts they would have a much slimmer pack. They will have to use less coolant tubes and all because of larger cells and cells will be in less quantity anyway. Also, I think that with years of pack making experience, starting form scratch, they will for sure make a more efficient pack.

    With the new battery pack tech they will use in Model 3, designing a pack with the 21-70 cells would leave about 3.5mm of space at the bottom for the shell, instead of the 6.5mm.
     
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