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Aerodynamics Won't Help Range Loss in Cold Weather

Discussion in 'Model 3' started by Matthew Lock, May 4, 2016.

  1. Matthew Lock

    Matthew Lock Member

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    Tesla has said that the base Model 3 will have a battery pack of less than 60 kwh, which is fairly low, but a range of 215 miles since it will have very low drag, lower weight etc. We also know that the cold affects the battery power output, effectively lowering it's capacity. One of my concerns being in Canada, where we have cold winters, is that while having good aerodynamics and low weight and that kind of stuff is great for increasing range without increasing battery size in moderate temperatures, it can't stop the raw loss in available energy in cold weather. Therefore I am thinking that we will experience a greater drop in the range in the winter Any thoughts?
     
  2. Kenypowa

    Kenypowa Member

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    No. Your logic doesn't make sense. A car with good aerodynamics will have better range than another car without, regardless it is +30 or -30.
     
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  3. techmaven

    techmaven Active Member

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    If the range drop is 30% during certain winter conditions, having a smaller battery doesn't mean the range drop is higher, say 35 or 40%. It is still the same range drop.

    You certainly have to buy the vehicle with battery setup that makes sense in your situation. That might be the base battery. That might not be.
     
  4. EinSV

    EinSV Member

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    The battery performance/range will not be as good in cold weather (and is actually higher than the estimated range in hotter weather).

    There is a handy feature on the bottom of the linked page from the Tesla website that can give you some idea of the size of the impact with different temperatures and driving speeds, although it is in the context of the Model S: Model S | Tesla Motors

    If you are planning to regularly drive long distances in very cold weather ordering the larger battery may be worth considering.

    EDIT: I do agree with the posts above that there is no reason to think the range will drop more in a Model 3 than a Model S due to cold weather effects.
     
  5. inspron

    inspron Member

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    Your logic doesn't make sense op. Range drop affects all battery size of the same chemistry equally. So a 30% lost in range is a 30% lost in range regardless of the khw size.
     
  6. ucmndd

    ucmndd Member

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    I don't think there is necessarily a problem with the logic.

    If I'm interpreting the statement correctly, it's that aerodynamics are supposedly playing an increasingly important role in the stated range of the M3 - going a longer distance with less battery capacity.

    Meanwhile, they assume that the other losses associated with cold weather (primarily cabin heating, etc) are fairly static - so those losses will eat up a larger percentage of a smaller battery.

    Maybe, maybe not. At any rate, I don't think it's going to be a big enough difference either way to amount to a hill of beans. Sage advice on these forums seems to indicate that you probably want double the rated miles of your planned trip in extremely cold conditions. That rule of thumb will probably continue to hold true just fine.
     
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  7. Booga

    Booga Member

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    I agree with this.

    If you have to generate X units of heat, then it takes a certain amount of energy to accomplish that. If that amount is the same in the Model S and Model 3 for cabin heating, then it becomes a bigger % of the smaller battery in the M3.

    IMO, it's a valid concern, but also likely one that Tesla is thinking about. They haven't released details on their HVAC, but it makes me wonder if they have something up their sleeve. And/or... the glass roof allows a lot of light to enter creating a little bit of a greenhouse effect and warming up the cabin more than most cars would get.

    I'm not getting the M3 with base range - I need the 300 miles to be comfortable for my highway driving. If I was doing city only and occasionally some highway driving, I'd be okay with 200, but I'm on the highway probably 1/2 the weekends of the year.
     
  8. dhanson865

    dhanson865 Active Member

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    Cold air is denser causing more drag thus aerodynamics are more important in cold weather if you are traveling on highways/interstates.

    Whatever else cold is doing (hardening the tire rubber which increases rolling resistance, making it harder to extract energy from the pack, and so on) it is also affecting aerodynamics.
     
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  9. ucmndd

    ucmndd Member

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    I think you've got that bit backwards.
     
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  10. S'toon

    S'toon Knows where his towel is

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    Correct. That's backwards. That's why winter tires are so important. I learned that lesson, one New Years Eve, well after midnight. I had all season tires on my van, and when the light turned red, I hit the brakes, and slid right through the intersection. Good thing there was no traffic due to it being so late. Winter tires remain soft throughout the winter, offering more traction and therefore better braking.
     
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  11. JeffK

    JeffK Active Member

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    When plugged in you can use climate control via the mobile app and it'll warm up the battery... Once the battery warms up you'll be able to access the energy you say was "lost".
     
  12. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    This is correct. The denser the air, the more important aerodynamics is.
     
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  13. Matthew Lock

    Matthew Lock Member

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    I forgot to include the factors that will actually make this worse, such as driving in high wind, snow accumulation on the ground, needing to use the heater, or lots of stop-go city driving where the aerodynamics won't help. There is just purely less energy available to be used to drive the motor.
     
  14. Dynastar

    Dynastar Member

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    The OP is right to a degree (see what I did there?). Assume the Model 3 HVAC is the same as the model S. To make up some numbers, assume heating takes 100w/mile @ 60mph @ 0F. That might represent a 30% increase on the S, but a 40% increase in the 3. The heating will take up a higher percentage of the battery per mile on the 3 then on the S.
     
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  15. techmaven

    techmaven Active Member

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    The interior volume is smaller in the 3 so the HVAC demands are lower.
     
  16. physicsfita

    physicsfita Member

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    ... to be somewhat offset by the fact that the surface-area-to-volume ratio will be higher -- I'm too tired to do the math to see which one wins out.
     
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  17. SageBrush

    SageBrush Active Member

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    Your physics rationale does not sound right to me but it is true that as temperature drops, so does the battery energy capacity. If you are charging e.g. at home, you can work-around the problem by pre-warming the battery and finishing up shortly before you head out.

    Another cold weather effect however does come into play: the friction of rotating parts and tyres on the road increases by some 20-30% on cold, wet or snowy days. A boxy EV with a bigger battery like the Bolt will have a relative advantage ... but I think will still lose out or tie overall due to the much different Cd's of the two cars.

    Check out this graph for the relative Cd advantage compared to the ~ 15% difference in battery size.
     
  18. sandpiper

    sandpiper Active Member

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    My two cents.... in Canada buy the biggest battery that you can get. A large part of the range drop is from the necessity to use cabin heat. And it's not fun to sit in an unheated car for 3 hours at -25, going 10 below the limit, turning on the defrost for a couple of minutes out of every 15 just to keep the windshield partially clear. I'd sacrifice a lot of bells and whistles to get a big battery.

    At -25C, with proper cabin heat, driving 100km/hr, my P85D, will only go 250km before dead battery. My rated range is 404 km. In the summer, on a good highway, I practically get around 380-400.
     
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  19. SageBrush

    SageBrush Active Member

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    And buy heated seats.
     
  20. Topher

    Topher Energy Curmudgeon

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    Don't bother. It depends mostly on whether you have the HVAC set on fresh or recycled. Use those heated seats...

    Some other very minor effects:
    1) A (physically) smaller battery pack will cool down quicker.
    2) The taller batteries used in the new packs, will cool down slower.
    Both due to that same surface to volume issue.

    Yes, cold sucks, and the better we get at using our energy efficiently the more we will notice that suckage.

    Thank you kindly.
     
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