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Thread: Cold Weather Range

  1. #11
    Roadster 919, S 2006 Doug_G's Avatar
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    Quote Originally Posted by dhrivnak View Post
    I do think it is more due to running cabin heat that anything else. I go from about 250w/mile to 300w/mile running the heat. So my results are very similart to Doug_G.
    Clearly running the heater full blast can add 50 Wh/mile, but that data was taken with the heat OFF.

  2. #12
    Happy Model S Owner
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    Thanks for the cold weather range testing.

  3. #13
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    Quote Originally Posted by Doug_G View Post
    Aero 54.1 Wh/km
    Tires 34.8 Wh/km
    Anciliary 2.1 Wh/km
    Drivetrain 47.9 Wh/km
    Total 138.9 Wh/km

    The point here is that at this speed, aerodynamic drag is NOT dominant. Drivetrain losses are almost the same.

    Let's assume the aero goes up by 9.3% due to the denser air. That's only an extra 5 Wh/km. I'm seeing about 20 Wh/km. Where is the rest going?
    Both tire drag and drivetrain drag will go up in cold weather as well. Tires are less flexible so "bounce" back less readily. Grease / gear lube is also thicker when cold.

    Quote Originally Posted by Doug_G View Post
    I'm wondering if the loss was due to the rolling resistance of the winter tires. Does anyone have any experience with that?
    Depends highly on the tires in question. The PriusChat guys have varying results, but Nokian tires in particular seem to have low rolling resistance and typically nearly match the stock all-seasons. I would imagine that similar Nokians would at least match the sticky stock Roadster rubber in rolling resistance.

  4. #14
    Roadster 919, S 2006 Doug_G's Avatar
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    I'm running the Pirelli winter tires. I just did a second road trip, with similar results to the first one. The temperature was not quite as cold this time, and the pack was also warmer when I first set out. I'm really thinking the range difference is mainly due to the winter tires, not the temperature.

    On both trips the VDS reported higher-than-normal power consumption at first - 200 Wh/km versus 170 Wh/km after the No-Regen light went out. I was maintaining the exact same speed. Is this a Range mode thing? I must confess that on previous road trips I've not looked closely at the power consumption early on.

  5. #15
    About the heat: someone found that blocking the passenger vent greatly increased the driver's comfort, without affecting the passenger noticeably. Should translate into lower power drain.

  6. #16
    V4663
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    Quote Originally Posted by Brian H View Post
    About the heat: someone found that blocking the passenger vent greatly increased the driver's comfort, without affecting the passenger noticeably. Should translate into lower power drain.
    I did this and while it helped the driver's side head, I had an overheating situation where the heater shut down completely while my car was sitting still for a few minutes with the heater on. I have since removed the passenger side blocking, and have had no further overheating problems. I would not recommend blocking this completely.

    David

  7. #17
    Hmm, does turning the heat down save electricity? ... or do you really need to shut the heat off completely?

    With an ICE vehicle, the knob controls the rate of flow of engine coolant, which is vastly different from what is happening in an EV. The Roadster is using 400 V for the heater, but does it throttle the current or pulse-width modulate it when you turn down the cold/hot knob below full? Would the heater use any power at all if turned on with the knob rotated fully counter-clockwise?

  8. #18
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    Quote Originally Posted by S-2000 Roadster View Post
    Hmm, does turning the heat down save electricity? ... or do you really need to shut the heat off completely?

    With an ICE vehicle, the knob controls the rate of flow of engine coolant, which is vastly different from what is happening in an EV. The Roadster is using 400 V for the heater, but does it throttle the current or pulse-width modulate it when you turn down the cold/hot knob below full? Would the heater use any power at all if turned on with the knob rotated fully counter-clockwise?
    Yes, the Roadster does regulate the power to the heater based on knob setting just as it will vary the speed of the A/C compressor to regulate cooling level based on the knob position. I believe the heat is more of a thermostatically controlled on/off cycle rather then a PWM control but I am not certain.

  9. #19
    Roadster 919, S 2006 Doug_G's Avatar
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    Quote Originally Posted by donauker View Post
    Yes, the Roadster does regulate the power to the heater based on knob setting just as it will vary the speed of the A/C compressor to regulate cooling level based on the knob position. I believe the heat is more of a thermostatically controlled on/off cycle rather then a PWM control but I am not certain.
    The heater power level definitely can ramp up and down; I think it actually is PWM controlled.

    Also note the maximum amount of heat it will provide depends on the fan setting. (I recently noticed that one of the firmware upgrades appears to have changed this behavior somewhat, but I haven't explored that yet.)

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