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Future Proofing Built-In

Discussion in 'Model 3' started by SageBrush, Aug 3, 2017.

  1. SageBrush

    SageBrush Active Member

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    I was thinking about the rash of comparos between the Model 3 and car <xyz> and realized that very little ink has been spilled talking about two interesting benefits the Model 3 has over competitors: A rapidly expanding SC network, and hardware for future L3+ autonomous driving.

    The SC network is well known to forum regulars and Tesla owners but perhaps less so to the other 99%. Compared to the unproven and to a large degree only planned CCS network, SC are well planned, well maintained, and growing rapidly from an already excellent basis. They provide almost complete mitigation against battery capacity loss in the future.

    At least to me, the no less remarkable value in the Model 3 is the AP hardware. While I don't know when level 3 (and perhaps more) autonomy will finally arrive, I'm pretty sure of Level 3 in the next 5 years. At that time the people who bought competitor cars but want autonomy will dump their cars for a pittance and fork over another $40k. Model 3 owners will pay for FSD and carry on.

    Amazing. Value
     
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  2. R.S

    R.S Member

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    The best thing about FSD is that you can upgrade it afterwards. I wouldn't buy it right away, or even worse, select it on a lease. Too much risk that you'll never be able to use it, until your lease ends, or maybe just for a very limited time. And it is $50 a month, for something you might not even be able to use.

    It might be different for people planning to keep their Model 3 for a long time, though.
     
  3. Phrixotrichus

    Phrixotrichus Member

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    As it stands now FSD is just a promise. A promise that you don`t have to buy, which makes it ok.

    I´d be suprised if the 3 ever reached lvl 3 beyond normal highway driving, though.
     
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  4. KarenRei

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    The futureproofing that I want to know about is whether they're futureproofing them to work with Supercharger v3. Which, if you look at their patent apps, may involve A) feeding externally-chilled coolant to the vehicle along with power, to allow for faster heat removal; and B) auto-docking underside charging.

    I wouldn't bet on it, personally, at least in early production. I guess it depends on how close Tesla is to releasing v3. I know the conventional charge port on the M3 is designed to be roomy enough to be swapped out for a larger one if need be. Anyone have any good underside shots?
     
  5. R.S

    R.S Member

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    Surely not. The big pack can't even take 120kW from a regular SC, maybe 80kW. And the low range takes even less power, maybe 60kW. And heat dissipation isn't a problem at those power levels. An Ioniq can take over 60kW, for 20 minutes, up to 80%.

    So the cells are definately the limit here.
     
  6. KarenRei

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    #6 KarenRei, Aug 4, 2017
    Last edited: Aug 4, 2017
    Yes, except that the rate of heat dissipation from cells is proportional to A) the cell temperature, and B) the coolant temperature. The latter will be colder if you're using an external reservoir, potentially much colder. Heat dissipation is the limiting issue in fast charging without hurting longevity; high temperatures during charging shorten cell lifespans.

    [​IMG]


    Ioniq uses pouch cells with a high surface area.

    Heat isn't the only limitation, of course; there's a maximum ion mobility (generally from the electrodes to/from the electrolyte rather than through the electrolyte / across the separator), but li-ion chemistries can be tuned to allow for very high rates if desired. If you exceed the maximum ion mobility for a given cell, the extra energy gets dissipated as, of course, more heat. There will inherently be variation on maximum charge rates between cells, and even within individual cells. So your maximum ability to remove heat still comes into play.

    M3 cells are supposedly the same chemistry but different format relative to the MS/MX - yet charge slower. Heat dissipation and the increased need to preserve longevity on a mass market car are the only logical explanations for that, IMHO.

    Also: if V3 is as per their patent app, it means not having to connect, just driving up to the charger and parking over it. Hence including a port (or easy ability to add one) would be "future-proofing" your ability to connect to such chargers.
     
  7. Saghost

    Saghost Active Member

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    Using extremely cold coolant as a way to speed up charging will only work if you accept substantial temperature variation within the pack (or even within the individual cells.)

    I'm not an expert on the subject, but I would expect those temperature differentials to have adverse affects on cell longevity.
     
  8. KarenRei

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    There's always temperature variation within cells; the core runs hotter than the exterior. You can't just cool a pack with liquid nitrogen and charge at some vastly increased rate, even if you had sufficient ion mobility, because you can't have the exterior of the cells charging at below freezing and plating out lithium metal. But that said, there's still a difference between cooling with ~30°C glycol and ~5°C glycol.
     
  9. R.S

    R.S Member

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    Their patent application contains at least 3 different solutions, some would involve a plug with external coolant being pumped into the car, some don't. Some use liquid as a coolant, some use air, some use a heat dissipation plate that connects to the car.

    And it isn't like a Model 3 can't cool it's pack. It still has a radiator. And the waste heat at 60kW charging should be possible to handle.
     
  10. KarenRei

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    To repeat: "But that said, there's still a difference between cooling with ~30°C glycol and ~5°C glycol". Actually a pretty sizeable difference.
     
  11. Saghost

    Saghost Active Member

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    It really depends on how well you can move heat out of the core of the cell. I could see the 25 degree delta making a big difference, or almost no difference.

    That's why the discussion a few months back about Tesla's single side flexible circuit board connector and bottom of cell heat pipe TMS patent was so interesting - if you can get a good thermal connection to the end of the entire coil of separator without risking a short, you may be able to move a lot of heat out of the core effectively.
     
  12. KarenRei

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    #12 KarenRei, Aug 4, 2017
    Last edited: Aug 4, 2017

    For a given thermal conductivity, the rate of heat flow is linearly proportional to delta-T.
     
  13. R.S

    R.S Member

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    That might be, but it seems that Tesla hasn't future proofed the Model 3 in a way to get 5C glycol into the pack. Unless it has some charge port that went previously unnoticed, like under the car.
     
  14. KarenRei

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    #14 KarenRei, Aug 4, 2017
    Last edited: Aug 4, 2017
    And now we're back to my original post:

     
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  15. BigD0g

    BigD0g Member

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    I don't think they will do anything that requires touching the car, just to many moving parts and all the SC's would be a maintenance nightmare.
     
  16. Saghost

    Saghost Active Member

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    Correct. But we're back to the unknown variables.

    If the thermal conductivity from the hottest part of the cell to the coolant is low, and the allowable temperature differential within the cell is low, you can't safely pump the chilled coolant into the pack, and you can't get a significantly higher charge rate by doing so anyway.
     
  17. KarenRei

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    Why would there be a low "allowable temperature differential" in the cell? There's a minimum temperature, but so long as your coolant is above that temperature, it's not a limit.

    A cylindrical cell is not a big block of anode and cathode material that might undergo stress from a heat differential, it's a coil:

    [​IMG]
    The temperature differential on each layer will be miniscule. The cells swell and contract in normal operation due to temperature changes; this is built into the design.
     
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