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Cold weather "loss of power"

Discussion in 'Model S: Battery & Charging' started by tnt1971, Oct 10, 2016.

  1. tnt1971

    tnt1971 Member

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    I have had my car since early March of this year, so I really have not seen real cold weather with the car yet (I am in the NYC area and we rarely see temperatures lower than 20). I generally arrive back at work, where I normally charge, with about 20% SOC, and very rarely less than 15%.

    This morning I saw the cold weather warning as I was pulling into work. It was about 50 degrees today and I had 19% remaining. I forget the exact warning, but it said something to the effect that if it got much colder there could be reduced power. I also noticed that at about 20% power left I lost the very top of the power curve.

    My question is if I could ever just lose range because of the cold, and at what temperature that happens? I know the car uses more in the cold for heat and battery heater and I will use more RMs. That is not my question. I am more concerned that the car would get stuck because I could not get to the lower 20% of the battery. Phrased differently, will the car allow you to use all the RMs down to zero, although at an accelerated rate, or is there a "cliff" where the range could just disappear?
     
  2. jdw

    jdw Member

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    #2 jdw, Oct 10, 2016
    Last edited: Oct 10, 2016
    Some range can temporarily "disappear' when the battery is cold soaked, but it will come back as the battery warms up. Said another way, what the car thinks is zero will change when the battery is cold. Of course, if you can't plug in, it will use some range to warm the battery.

    The car will also limit available power & regen when cold soaked until the battery warms up. This seems to kick in around 45-50 degrees or so.
     
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  3. byan1232

    byan1232 Member

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    If i "preheat" my car, does the average watt/mi higher when driving in cold temperatures? I'm asking because I am planning a road trip to see the fall foliage in VT.
     
  4. bonaire

    bonaire Active Member

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    One key thing regarding EV ownership is the cold weather effect. I suppose this never comes up pre-purchase - we are all eager to buy those EVs but the shortcomings of living in northern climates is not usually discussed.

    Pre-heat off the grid and then you are in better shape than cold-soaking. And if interested, look into the escapades of Mr. John Broder. Don't be a Broder - be educated. Batteries involve chemical reactions - and their favorite temperatures are very much similar to the favorite temperatures of us humans. About 70*F ambient.
     
  5. Joeski1

    Joeski1 Member

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    #5 Joeski1, Oct 10, 2016
    Last edited: Oct 10, 2016
    Flat out you're gonna see a 30% decrease in range.... use the cabin heat or the defogger. much? . I noted the front and side window to fog generously when I run with my seat heat on and about 65 * in the car whenever it drops below 40 or so outside...... ... the pano roof will conduct heat right out of your car in cold weather.... transfer the cold right in... didn't go for it myself

    I preheat the car while attached to the socket to save battery power....

    If you have the cold weather pack that can help because that addresses the worst of it.. a cold steering wheel and fogged or iced glass...

    really... in Ny it can get much colder than 30* esp. in the morning om the drive in unless you garage..

    but really... why would you let your battery run down to 20% on a return drive from work?? Seems risky.. I nevr go with less than two times what I 've found that drive back actually takes...

    if it takes 15%.. I'd make sure I had 31% when I got to work to drive home on...
     
  6. tnt1971

    tnt1971 Member

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    The car is garaged overnight. It rarely gets colder than 55 in the garage.

    Yes, it can get colder but general NYC winter temps are mid 30s during the day and low 20s at night. There is usually a week or two where we see teens at night. We usually only see single digits about once every five years or so, at least close to the City. Go north and west 20 miles or so and I know there is a 10 degree drop.

    I appreciate all the great info but I did not get an answer to the question, probably because I phrased it poorly. my commute to work is 14 miles. I know my usage will be higher in cold, but to be specific, if I left home with, say, 60 miles would there ever be a case where I would not make it? In other words, could the card get down to 45 miles and then all of a sudden lose the remainder of the range because it is 20 degrees out?
     
  7. jdw

    jdw Member

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    Yes, there would be a case where you could not make it.

    Using your numbers, leaving home with a warm battery showing 60 miles, but driving into conditions where actual usage is 50% higher, means arriving at work with 30 miles of range. Then, it's cold out and you freeze your battery, dropping your range to say 20 miles. Then you start driving and the battery heater and cabin heater comes on. Heating the battery both improves the battery range and uses battery power to do so.

    So freezing the battery + warming the battery + cabin heat + driving in slush could equal not enough range to get home.

    Your options would include using range mode which will prevent battery heating at the expense of driving with a cold battery (very little regen), not heating the cabin, driving slowly or charging at work or somewhere else.

    The range loss from a warm battery to a cold battery is temporary, but if you have to warm the battery using the battery, you do lose some range,
     
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  8. scottm

    scottm Active Member

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    #8 scottm, Oct 11, 2016
    Last edited: Oct 11, 2016
    That's an easy question, and thanks for clarifying it that way.

    Simple answer: No. The car will never all of sudden do anything different just because it's cold. Especially as you're driving. You will notice a trending reduction of range when it is cold, and you will be watching rated and estimated range predictions dropping faster than summer time. But no miles "disappear" all of a sudden.

    I drive my Model S in up to 40 degrees below zero, for two winters now... and going into a third. I've see the snowflake on my dash, with warning about cold battery reduced power, no regen, etc.. until the battery heater has a chance to warm it up.

    Awesome car in the snow and ice. Beats my Subaru AWD for wanting to stay on the road. And my Model S is rear wheel drive only.

    Do not worry.

    You live in NY, keep the battery north of 60% whenever you set out even for your commute daily. Use all the cabin heat you want. Heat the car from the App before you leave work to go home. Plug in... do it again the next day.

    Car is in the garage all night... plugged it. At breakfast turn on the cabin heater to treat yourself. That heater power will come from the wall, not your battery. And if the car has dropped a couple % overnight, you can start charging again.. this heats the battery before you set out, again, on shore power.

    FWIW, I'd don't use Range Mode unless I'm on a long road trip in very cold weather.

    Certainly, turn Range Mode OFF when you are parked and charging in the cold.
     
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  9. jdw

    jdw Member

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    Range mode is helpful when you don't want to use battery power to heat the battery when doing a number of short trip/park/short trip/park sequences in the winter when the car is cold soaked. Without range mode on, you would use a lot of energy heating the battery on each short trip, only to have it cool off again when parked.

    Range mode also limits the cabin heating, which can be good from an energy use point of view and bad from a comfort point of view. Also, with Range mode on, it will take a lot longer to warm the battery and get full regen back, as it will mostly use motor heat to do so.

    I often end up toggling it, depending upon the length of the trip and state of charge. There is less benefit to range mode on longer drives in the winter, but it is quite helpful to save energy on short hops when the car is frozen.
     
  10. Doug_G

    Doug_G Lead Moderator

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    • Like x 1
  11. jdw

    jdw Member

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    #11 jdw, Oct 11, 2016
    Last edited: Oct 11, 2016
    I was looking for your post to link to it here, but couldn't find the blogs ... this gives me a chance to say thank you for one of best written, informative and helpful posts on TMC.
     
  12. Doug_G

    Doug_G Lead Moderator

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    Thank you!
     
  13. tnt1971

    tnt1971 Member

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    • Here is my 90% today. 90% of 275.2 is 248 (247.6 to be more precise).
     

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