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Preheating without using power from charger?

Discussion in 'Model S: Battery & Charging' started by Jocce, Apr 11, 2017.

  1. Jocce

    Jocce Member

    Joined:
    Oct 31, 2015
    Messages:
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    Location:
    Sverige
    Is it possible to have the Charging Cable attached, and preheat, without taking power from the Cable (Type 2)?

    Finally I have a Charging station at my home (Apartment-building), after a year with the car!

    So it's good that I can charge the Car. Though I have better prices at charging at other locations (Read: I have a very nice employer that gives me free power ;) ), SO because I'm cheap even though buying an expensive Tesla I want to keep the charging at home to a minimum.

    So when I preheat I want the car to use the battery, not the charge cable.
    I tried unlocking the charging cable in the app, but after a while it locks again and starts using the power from the cable again.

    So any Ideas?


    /Jocce
     
  2. ig_epower

    ig_epower Member

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    Location:
    Oakville
    How long do you intend to preheat the car? The software automatically times out in 30 minutes. I find even on the coldest days, 15 - 20 min is enough to warm the cabin and even melt the frost. if I have any snow accumulation on my windshield, I find the 30 minutes to be adequate. Assuming I am drawing about 6 KW of power for the heater at my maximum electrical rate of $0.18/KWH, that means about 6*0.18/0.5=$0.54/day.

    If I preheat before 7a (which is the cheap rate cut off with my provider), the cost is $0.09/kwh or 27 cents/day. I don't think this will break the bank for me. A 4 month winter of doing this pre-heat ritual would cost me $65 (CDN)/year. In reality, I probably only preheat 1/3 of the time so we are talking about $22/year.

    That is a small price to pay for the comfort of not scrapping my windshield and getting into a comfortable cabin in my opinion (other opinions will obviously vary).
     
    • Informative x 1
  3. tga

    tga Supporting Member

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    I was going to suggest trying to dial back the charge limit to a value well below the current battery state of charge before turning on preheat.

    I tried that, but after turning on the preheat, the relay in the UMC clicked on and the LED's started strobing, even if I wasn't charging.
     
  4. Jocce

    Jocce Member

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    I'm not saying it's expensive, but since I charge for free at work that's cheaper.
    I've been running the preheat for a year (or at least in the colder season) but not having the possibility to charge.

    So IF there is a way to solve it, that would be great. But if there is not, well yes, then it's not expensive but free is cheaper ;)


    /Jocce
     
  5. tga

    tga Supporting Member

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    If your commute is short, just preheat on battery and charge at work. You don't need to preheat on AC unless you're trying to avoid using up some of your charge.
     
  6. Jocce

    Jocce Member

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    Yes, this is exactly what I want to do, but if the cable is attached, it will use the power from the cable instead of battery. So with cable attached, how do I use ONLY battery for Preheating?


    /Jocce
     
  7. tga

    tga Supporting Member

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    There doesn't seem to be a way to do it. Either preheat off the battery and charge at work, or charge and preheat at home.

    How long is your commute? If it's short, you can do all your charging at work/preheat off battery. If it's long, and you need to charge at home, then the percentage of power used for preheat vs charging is probably in the noise, anyway.
     
  8. ig_epower

    ig_epower Member

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    Perhaps what I don't understand is why the OP has to plug the car in at home if charging can occur at work. I am at my office for 8 hours - plenty of time to charge at work (assuming it is not at 110 VAC).
     
    • Like x 2
  9. Gforce1

    Gforce1 Member

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    Not an owner yet so I can't try this myself but what would happen if you lowered the charge level before turning on the preheat? Would it draw from the battery down to the new charge level or still continue to draw from the charge cable and maintain whatever level it was already charged to?
     
  10. kingjamez

    kingjamez Member

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    Fairfax, VA
    Firstly, I'm amazed that the OP can afford a Model S and yet is worried about the dramatically small cost of energy for pre-heating in comparison to charging.

    Lets say the absolute maximum draw is around 7kW for 30 minutes for a preheat == 3.5kWh Using Sweden's average cost of 0.19 Euro/kWh your looking at saving 0.66 Euro's at maximum. Likely much less as your car warms up and the power draw drops.

    Secondly, if you don't want to use your home power, then why are you plugged in?

    -Jim
     
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