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Cabin or battery heating sometimes powered only by 12V battery?

Discussion in 'Model S: Battery & Charging' started by Matias, Feb 12, 2017.

  1. Matias

    Matias Active Member

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    Apr 2, 2014
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    Location:
    Finland
    Is cabin or battery heating sometimes powered by 12V battery and not by main battery? I suspect this because when I enter my car and it has cabin heating on I sometimes hear the clear click sound which I believe is the main battery contactors closing. So this would suggest, that the main battery is not online even at least the cabin heater is on. Is this true?
     
  2. scaesare

    scaesare Well-Known Member

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    Mar 14, 2013
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    Location:
    NoVA
    No. Those heaters are only HV powered.

    The fans are 12v though.. .so those could run with the HV contactors disengaged if the cabin was already up to temp.

    Also are you connected to shore power? The car will draw preconditioning power there if it can. While I've never explicitly tested it, I suspect that the car can keep the HV out of the loop in that scenario.
     
    • Informative x 1
  3. Matias

    Matias Active Member

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    Last time when I heard main contactors click on with preheating, car was not plugged. But it is possible, that cabin had allready reached the target temperature.
     
  4. mknox

    mknox Well-Known Member

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    Location:
    Toronto, ON
    Nope. Fans only. I can speak from experience: A couple of years ago, my main HV contactors blew out when I was on my way home one cold winter day. I lost the traction motor and heat, but all of the usual 12v stuff stayed on, including the HVAC fan.
     
    • Informative x 1

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