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Model 3 Battery Details

Discussion in 'Model 3' started by JeffK, Aug 24, 2017.

  1. JeffK

    JeffK Well-Known Member

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  2. KarenRei

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    #2 KarenRei, Aug 24, 2017
    Last edited: Aug 24, 2017
    Awesome, awesome article!

    My reads:

    1) SR and LR packs are the same voltage. YEAY! They should charge at the same speed on weaker power sources like CHAdeMO.
    2) Lots of cells in parallel in each brick. Good!
    3) Glad to see battery swap die.
    4) I really see no need for passenger sedans to have underside charging, unless they really want to push self-recharging. That really only seems necessary to me when you're talking vehicles that need currents so high that a person couldn't comfortably handle the charge connector. That said, coolant-along-with-charge would be nice, regardless of whether you're talking underside-and-automated charging or side-and-manual charging.
    5) The way that they removed the battery heater really shocked me, but I have to admit, if that heating approach works, it works; Tesla comes up with the most out-of-the-box solutions for things. Just hope that the extra inverter use doesn't reduce longevity.
    6) 3-phase AC charge connector? Awww yeahhhhh!
    7) Trying to understand the charge port connector - it looks like there's 4 lines, which doesn't match the HV diagram.
    8) #11 - compressor inside the pack? Or are those just fuses?
    9) Would be nice to know how they're routing the coolant outside the pack!
     
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  3. R.S

    R.S Member

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    Ok I think I have to be the first to say this, so please brace yourself:

    If the base Model 3 really has 50 kWh, as stated in the article, the cells are worse than the 18650s.

    They only have about 16.8 Wh per cell (50 kWh/2976), where the Model S pack has 12.4 Wh per cell (102 kWh/8256). So about 36% more energy per cell.

    But the cell has 46% more volume, but who cares about volumetric energy density anyways?

    But even if the internals weigh nothing and almost all the weight would be in the cells shell, then it would still weigh 26% more than the 18650 and since the internals weigh something, the cells probably would have a worse gravimetric energy density, too.

    Now add in slower charging and less performance and either the new cell format is just worse than the 18650s, or the pack has more than 50kWh total capacity.
     
  4. JeffK

    JeffK Well-Known Member

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    Where do you get this from?
     
  5. KarenRei

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    #5 KarenRei, Aug 24, 2017
    Last edited: Aug 24, 2017
    @R.S

    1) Just because one calls a pack "50 kWh" doesn't mean it's exactly 50 kWh. It generally means that "usable" power is "around" 50 kWh.

    2) Who cares about energy density, volumetric or gravitmetric, anyway? :) The number 1 parameter that matters in EV packs is $/kWh. The number 2 parameter is longevity. #3 and #4 are power density, both gravimetric and volumetric. As for gravimetric and volumetric energy density, they're a distant #5 and #6. The vehicle comes in at a similar curb weight to other vehicles in its price class, so there's no problem.

    3) Charging rates may be reduced simply because it's a cheaper car and they can't afford as many warranty claims on it, so they don't let you abuse your pack as much as an S and X will.

    4) Reiterating #2 for emphasis: The parameter that really matters is $/kWh. If you have lots of money to throw at an EV for a battery pack that one might consider "better", I recommend getting an S. :)
     
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  6. KarenRei

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    Max supercharging rates are 130mi/30 min and 170mi/30 min for SR and LR, respectively. That's 59% and 55%, respectively, of the pack in half an hour, which is a bit poor performing compared to modern S and X packs when you consider that they'll never be charger-limited. It also looks like the packs may be limiting motor performance, since the 0-60 drops by half a second with the larger pack. But there could be other reasons for that. That said, regardless of chemistry differences, you should expect poorer power performance with large-format cells. Particularly with charging, since it's harder to draw the heat out. But I don't think it's a big practical difference, a lot of people were just hoping that since it's a more efficient vehicle, you'd get more miles per unit time when charging it.
     
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  7. R.S

    R.S Member

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    The slower charging is by looking at the fast charge rate of the LR, 170 miles in 30 minutes. So 47.8% in 30 minutes, while the 100D only takes 27 minutes to get to the same percentage. Surely not much worse, but not better either.



    And Elons Quotes here:
    Elon Musk Says Tesla Model S & X Won't Get New 2170 Cell
     
  8. sandpiper

    sandpiper Active Member

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    It's not surprising in retrospect.

    1. They optimized for cost and durability. With half a million cars out there, a pack problem could be the end of it. They will likely use the S/X as the test bed for new battery chemistries.

    2. I've speculated that the announcement that they're going to stay with 18650s in the S/X was because they determined that the 2170 doesn't perform as well. Again, that makes sense; larger cells are tougher to cool, when under high load.

    Interesting stuff.
     
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  9. JeffK

    JeffK Well-Known Member

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    Check those calcs @R.S and compare to Karen's. The Model 3 gets to a higher percentage of range faster than the P100D in your video.

    Let's compare apples to apples. The base Model 3 charges faster in miles per minute than the Model S 60 and goes 0-60 mph nearly as fast as the older S60 RWD simply due to the weight reduction and more aerodynamic nature of the car.

    The Model 3 can charge nearly as many miles in 30 minutes than has been shown on the older S60 in an hour.
     
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  10. R.S

    R.S Member

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    1) That's what I'm assuming. The car has more than 50kWh total capacity.

    2) Everyone does. If you like to think like Elon and break it down to "first principles" the price directly correlates with the cost. The lighter it gets, the cheaper it gets. Especially in batteries, where materials costs make up a good portion of the final costs, 40% or so of the total pack cost.

    Battery-Graph.png
    3) Could very well be. But I just meant the cell wasn't improved for quicker charging, at least not in a way we could see today. If it were, a reduction in energy density would have totally made sense. Quicker charging, less range to start with needed.

    4)That's true, cost is what matters. That's why energy density isn't parameter number 4, but actually number 1.
     
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  11. KarenRei

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    Yeah, but the older S60s have always been poor-performers at charging. Hence people see this as a step backwards.

    Note how the S85 would have charged even faster had it not been charger limited in the beginning. The M3 is never charger limited.
     
  12. R.S

    R.S Member

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    #12 R.S, Aug 24, 2017
    Last edited: Aug 24, 2017
    But that has nothing to do with the cells, does it? That's like saying the new synthetic leather seats in the Model S are better, because the new P100D is much quicker than the P85.

    The car is more efficient and lighter and therefore it can charge and accelerate quicker, despite maybe having worse cells.

    Another point to mention is that newer Model S/X charge about 15% faster, according to Bjorn:


    Warning: Some people complain that his videos are too long, he knows that, but obviously doesn't care :D

    Edit: Also, if you look at the 60 it reaches 50% at about 28 minutes. IDK which range mode Bjorn used, but it surely isn't EPA range.
     
  13. KarenRei

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    That's not true at all. Lower-cobalt chemistries, for example, are cheaper, but have poorer energy and power density.

    People from Tesla have repeatedly stated that they get companies coming in all the time trying to get Tesla interested in some new chemistry or another. They have all sorts of great specs about its energy density, power density, etc, etc - but Tesla always asks them to cut straight to one thing, often the thing that they want to talk about least: what's the cost per kWh? That matters more than anything else to Tesla.
     
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  14. JeffK

    JeffK Well-Known Member

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    #14 JeffK, Aug 24, 2017
    Last edited: Aug 24, 2017
    Yet, if we compare to the P100D in the video posted above. It gained nearly 51% battey capacity or 160 miles of range in 30 min compared to the 170 by the Model 3 LR.

    The exact performance of the cells doesn't matter nearly as much as real world usage. This is the entire reason they've stopped branding the cars. People get tripped up on the numbers and ignore that in miles/minute a Model 3 LR is charging faster than a P100D as shown in the video. Model 3 LR is more on par with the S100D in miles per minute (due to efficiency/mile, obviously).

    ...and obviously in kWh the larger packs are charging more quickly, but that's not the point I'm making. ;)

    If you go by C rate, the Model 3 LR reaching 54% in 30 minutes unlike the P100D in the video means these cells are outperforming the 18650s in the Model S
     
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  15. KarenRei

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    Haha, Björn is the reason why I'm glad that YouTube has the "double speed" playback option ;)
     
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  16. Rogue one

    Rogue one Member

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    Very interesting about the lack of a pack heater I wonder what this will do for winter range, since the pack heater would typically use a fair amount of power at the beginning of a winter trip.
     
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  17. transpondster

    transpondster Member

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    buy new calculator 170/310 = 55%
     
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  18. R.S

    R.S Member

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    Yea, the 100D wasn't really an improvement over the 90D in terms of low SOC charging.

    But no matter the charging speed discussion, the 2170 cells in the Model 3 seem, at least with the info we have now, not to be a real improvement over the 18650s.

    Battery warranty dropped to levels that can be easily exceeded with a Model S, with similar range. Maximum performance output is lower according to Elon, or at least not an improvement. And energy density is also lower. Now of course there are other factors, too. And some of the before mentioned aren't really proven. I'm not judging here, I get the feeling that we aren't really looking at the whole picture, or even the right picture here.

    That's true, the chemistry could be changed. And that would make comparisons a lot harder. Maybe that's the missing piece? I remember Elon saying the cell is the most energy dense on the market, though. So not sure if the numbers just aren't right...
     
  19. R.S

    R.S Member

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    Damn... Ok very true. I'll give you that ;)

    Maybe someone should double check my initial calculations, too?
     
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  20. Runt8

    Runt8 Member

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    You have to compare the energy use of the dedicated pack heater to the energy used by the power train. I would have thought the dedicated heater would be more efficient, but that’s just a guess. You do save by not having to haul the extra weight of the heater all the time, even when not in use. So even if the power train method of heating is less efficient, you would get longer range when it’s warm.

    Edit - I was assuming preheating before you start driving, but re-reading your post I’m thinking you meant that the heater would be running while driving, in which case the power train would be running anyway and using the waste heat would be pure gain.
     
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