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Winter Driving Experiences

Discussion in 'Model S: Driving Dynamics' started by kevincwelch, May 13, 2012.

  1. Norbert

    Norbert TSLA will win

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    Unless you charge at the same time, I suppose. Question would be: if the battery is full, can you start heating and then charging?
     
  2. Doug_G

    Doug_G Lead Moderator

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    Yes, if you drain it a bit.

    - - - Updated - - -

    The Model S does not keep the pack warm. It will only heat the pack if (a) it is charging, (b) you are driving, or (c) if you turn the cabin heat on via the smartphone App.

    You can drive with a cold pack, so you don't have to wait, but it will use a LOT more energy at first while it is heating the pack up. Also regen will be limited or disabled altogether, and if it is cold enough then forward power will also be limited.
     
  3. Norbert

    Norbert TSLA will win

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    #923 Norbert, Feb 26, 2013
    Last edited: Feb 26, 2013
    Thanks for the answers so far! According to the interview above, heating the pack up is partially done with excess heat from the motor, gearbox and inverter. When you say it uses a "LOT" more energy, is this based on observing the rated range display, or the SOC (via custom software)? Or is it a theoretical assumption?

    (Or based on the trip meter energy counter?)

    EDIT: A good amount of energy might be needed to warm up the cabin itself, from low temps, in the beginning.
     
  4. Doug_G

    Doug_G Lead Moderator

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    Nothing based on theory here; this is all empirical. I've been keeping a close eye on how everything behaves.

    When you pull up to a stop light, you can see the energy draw on the power meter. It's 5-6 kW for the pack heater and 5-6 kW for the cabin heater on full power. You can tell one from the other simply by turning off the cabin heating system. (Hard to tell exact numbers as the resolution isn't high and the scale is logarithmic.)

    You can also see it in the Wh/km, but it's hard to calculate a fixed power draw based on that. You can however end up with some pretty big numbers!

    Yes, comparable to the pack heater, but the cabin heats up faster so is not as significant.

    This is all assuming very cold conditions, e.g. -20C. By now we're pretty much out of that stuff for this season.
     
  5. Norbert

    Norbert TSLA will win

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    Ah, if constant when driving at different speeds, this is a good way to measure it. Not too bad, it seems (unless you are at the very limit of your range, of course). If it takes an hour, it would be a range loss of about 16 miles, at -20C. I guess one could still ask a question about the motor excess heat being used: This would be larger when driving at higher speeds, so perhaps the additional draw from the battery is smaller at those speeds? Or it could be heating up faster, with the same draw.
     
  6. montgom626

    montgom626 Active Member

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    Generating heat for any purpose in any EV uses a lot of power

    All EVs, such as the Leaf, Volt and MS use a lot of power when heating the car. Generating heat for any purpose in any EV uses a lot of power.
     
  7. mknox

    mknox Well-Known Member

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    There was some speculation early on that Model S was utilizing a heat pump with resistive backup. 5 or 6 kW would seem to be what a resistive heater would likely need to heat the cabin.
     
  8. RDoc

    RDoc S85D

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    You're right!

    I have no idea what was going on when I was playing with the calculator before, I tried it several times with the same results, but when I just tried it now I got your results as well.
     
  9. Doug_G

    Doug_G Lead Moderator

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    Right. Fortunately it only does that until things warm up. Steady state the power draw is much less.

    - - - Updated - - -

    No doubt losses inside the pack itself contribute to heating, and yes the system can connect the motor/inverter loop to the battery loop (according to Tesla engineers) so it can use waste heat from the motor and inverter to warm the pack. However, there is a large thermal mass there, so when you start up from a cold soak the pack heater runs full blast for some time.

    I've noticed that during highway driving, at extreme cold temperatures (-20C) the pack never fully warms up. It gives you the "please plug me in I'm cold" message when you stop. At some point below -20C, the regen limits stay in effect during highway driving. In those conditions I suspect the pack heater is running continually at low power, because there appears to be a little more range loss. The Model S battery pack has a lot of exposed surface area; no doubt it loses a substantial amount of heat through the bottom.
     
  10. Norbert

    Norbert TSLA will win

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    That's probably where the discussion of thermal protection came in, for the battery pack, that I remember reading about.

    Probably at higher, but still cold, temperatures, perhaps around freezing point (0C or 32F), the effects of using motor heat will be more visible, then.

    In any case, it seems that unless one is connected to a charger, where it is possible to warm up the battery using wall power, one should just start driving.
     
  11. pbrulott

    pbrulott Member

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    And d) when the pack reaches critical temperature (which the TM product specialist didn't want to mention to me and assumed to be between -20C and -26C.
     
  12. Doug_G

    Doug_G Lead Moderator

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    Yes, that is correct. Thanks.

    - - - Updated - - -

    Crazy snow day today. Sticky, way deeper than predicted, ice an inch thick on the heavily traveled roads, the whole nine yards. Took us an hour and a half to get our cars out of the parking lot because the snow plow never showed (they're claiming mechanical problems).

    IMG_1537.JPG
    IMG_1540.JPG
     
  13. Zapped

    Zapped Model S - PURE EV

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    That explains the dotted yellow lines on the speedo/energy meter.
    After driving a while, usually the upper power limit line disappears first and the regen after that.
    Both are coming on after parking for 4+ hours at -2C not plugged in.
     
  14. Raven

    Raven Member

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    I've done a search and skimmed through the 94 pages here but probably still missed it....
    Garage is just above freezing. Before heading out one day I decided to see if preheating the cabin pulled wall power or battery power. The charge was complete before I started heating the cabin. From what I was seeing I was simply losing rated range and "charge complete" was still displayed(although my numbers continued I drop). I switched it to "range charge" on my iPhone in an attempt to kick it in the butt to use wall power. It did nothing. It didn't even initiate charging for max range. It simply continued to draw heat from the battery and rob my range. Am I doing something wrong?
     
  15. mnx

    mnx 2013 P85

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    I always see the car pulling 600W when I activate heating via the smartphone app. This is consistent with what others have seen like Doug_G. (I have my doubts if that is enough to fully power the cabin heater though)... So you are not doing anything wrong. Flipping to range mode and back is enough to get my car topping up however...

     
  16. znino

    znino Member

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    I am posting this here because it is probably related to winter and humidity but I noticed today that a portion of my wheels are developing some serious rust. I am not talking about the disc portion themselves or the inside portion of the discs (where a lot of rust has formed) but rather the part closest to where the center of the wheel is, near the disc. a rounded part that is now very brown (not dirt...checked it after a full wash as well) and like like its rusting. It is not a huge issue I guess but cosmetically it does look awful. If you look at your wheels, do you have the same issue?

    Slide1.jpg
     
  17. hcsharp

    hcsharp Active Member

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    Back here a couple of people said their rotors were not rusting. We've had enough winter now that I've seen a couple of MS with rotors that are rusting pretty good but not as bad as the Roadster. I think they should have used the same tech as the Volt rotors. This is more important on an EV than it is with an ICE.
     
  18. patp

    patp Member

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    Exact same rusting on my car.
     
  19. Doug_G

    Doug_G Lead Moderator

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    I have surface rust as shown in areas that don't contact the pads, but it took quite a while to develop. The rotor surfaces themselves are still pretty clean, and stopping power is good. The Model S rotors are performing WAY better than the Roadster's, which get rusty just from a bit of rain, never mind salt.
     
  20. znino

    znino Member

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    Quite a while to develop lol? We've only had the cars just over two months :).

    I also don't have much on the rotors. The other parts just make it look cosmetically ugly :(
     

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