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How long until a m3 100kW retrofit?

Discussion in 'Technical' started by BigD0g, Aug 1, 2017.

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How long to retrofit a M3 100kW pack to an X or S

  1. < 12 months

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  2. 12 - 24 months

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  3. 24 - 36 months

    0 vote(s)
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  4. Never

    100.0%
  1. BigD0g

    BigD0g Member

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    So, I'm sure it's just a matter of time for a M3 to be totaled and it's 100kW pack put up for salvage.
    Which I believe is lighter / more dense then the current 100kW packs, so the question is...

    How long until @wk057 has it retrofitted into his other X or a lucky S?
     
  2. KarenRei

    KarenRei KarenRei KarenRei KarenRei KarenRei KarenRei

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    Where did you get the power output of a M3 pack? And 100kW would be weak in a Model S, their packs deliver hundreds of kW. Or do you mean kWh (energy)? A 100kWh pack wouldn't even fit in a M3, the largest size that fits at present (according to Musk) is 75kWh. M3 packs are going to be lower power than S packs, they supercharge slower, and there's no guarantee that they'll have the same form factor / attachment points. Plus S and X packs have an unlimited mileage warranty.

    I really see no point to this.
     
  3. Hash Browns

    Hash Browns Member

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    I'm not sure where you got the 100kW number from. Did you mean 100kWh from Model S/X?

    I don't have an opinion on your poll, but the unit of energy storage in a battery is kWh "kilowatt-hours," not kW "kilowatts." Kilowatts is a unit of power, where 100kW converts to ~134 horsepower.
     
  4. BigD0g

    BigD0g Member

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    Sorry this got all screwed up and I can't delete it, mod please delete this thread.
     
  5. jkn

    jkn Member

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    Supercharge slower, REALLY? If true, Superchargers queues would get longer. Supercharging speed is limited by capacity of cooling system and amount of heat cell generates. So they can make smaller battery fast to charge. Form factor is different, because car is smaller. Probably connectors also.
     
  6. KarenRei

    KarenRei KarenRei KarenRei KarenRei KarenRei KarenRei

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    Yes, really. 130mi/30 minutes on a 220 mi pack means about 40 minutes to 80%, not 30. Same situation with the long range pack, 170mi/30 minutes on a 310 mi pack.

    They're larger format cells. Heat doesn't leave as quickly. That's always the balance, energy density vs. heat issues.

    You forget that superchargers split power between two vehicles when the station is busy. Charging two Model Ss or Xs from near empty at the same time means a big slowdown for both. With two model 3s there's almost no slowdown at all. Protip: if you have to share a charger with someone, share with a Model 3! ;)
     
  7. jkn

    jkn Member

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    I don't know how many cells 220 mi pack has. I'll say it has n cells. So 310 mi pack has 1.41*n cells. If heat transfer inside cell sets limit, then larger pack should charge 1.41 times faster. 130 * 1.41 = 183 miles in 30 min. There must something else limiting charging speed. My guess is: cooling system of the car.

    If cooling system is only limiting factor then larger back would charge less than 1.41 times power of smaller, because more cells produce more total heat. If I remember correctly, empty cell produces less heat than almost full when charging. Larger pack would charge faster (miles/h), because cells do not fill up so quickly.

    I wont change my mind: Charging speed is limited by cooling capacity of the car.

    Next gen supercharger will fix this.
     
  8. KarenRei

    KarenRei KarenRei KarenRei KarenRei KarenRei KarenRei

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    It charges 1,3x faster, which is close enough. There's many factors that go into determining the safe charging speed, but in general it's roughly linear with the number of cells.

    The supercharger has no bearing on how quickly heat leaves the cells.
     
  9. jkn

    jkn Member

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    Difference between 1.3x and 1.41x is so large, that there must be reason for it. Supercharging speed is one of largest advantages Tesla has over competition.

    They are designing charger that will help remove heat from cells. I don't think I have link marked down anywhere, but principle is simple.

    Of course heat transfer inside of cell is harder to speed up. If that were a problem Tesla would not have changed to larger cells.
     
    • Disagree x 1
  10. KarenRei

    KarenRei KarenRei KarenRei KarenRei KarenRei KarenRei

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    #10 KarenRei, Aug 4, 2017
    Last edited: Aug 4, 2017
    I wouldn't call it large at all. Both variants supercharge significantly slower than S/X, and this is expected because they're larger format cells.

    If you want a faster-charging car, pony up more cash and get an S. If you want a car that starts at $35k, this is what you get.

    You can't remove heat faster from the cells than it can flow from the inside of the cell to the outside of the cell**. I'm sorry, but this is a hard limitation. You have a balance: do you want energy density and lower manufacturing costs, or charge speed and maximum power output? Pick.

    ** The only thing you can improve is lowering the temperature of the coolant, which theoretically a supercharger with an external coolant feed could do. But 1) don't bet your life on such support in the vehicle for a charger that doesn't yet exist, and 2) S will always be faster than 3, due to the smaller format cells. Also, you'd be limited on the extent that you do this; if you cool the exterior of the cells too much (with the interior remaining too heat limited), you hurt cell life even more (charging li-ion cells in freezing conditions is a bad thing). Also, glycol freezes at -13°C anyway, and starts getting viscous before then.
     
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  11. jkn

    jkn Member

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    S will be faster than 3, because it is more expensive. Next gen Roadster will probably be faster than S and based on 3.

    I don't believe 2170 cells are large enough to slow down charging rate. Diameter is 21 mm, so heat must travel less than 10.5 mm. S has cells with 18 mm diameter, so heat must travel less than 9 mm. Not a huge difference.

    Supercharging speed is very important for Tesla. It will increase in future.

    I thought you would figure this out yourself and you did. But I remembered when and where I saw this (because i commented):
     

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