TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Power draw during pre-heating

Discussion in 'Model S: Battery & Charging' started by Brass Guy, Nov 28, 2014.

  1. Brass Guy

    Brass Guy Member

    Joined:
    Jan 5, 2014
    Messages:
    505
    Location:
    Stoughton, MA
    I was curious how much power would be drawn from "shore" if I wasn't charging, but preheating the battery and interior. I didn't need much range today (and forgot to plug in yesterday). I started pre-heating, went out to the car, set the charge at 60%, made sure range mode was off, and plugged it in. I was quite surprised at what I saw: 9kW! It was right around the freezing mark outide.
    IMAG0204.jpg

    So I'd be interested if anybody with dual chargers and HPWC has done the same experiment, since mine pretty much ramped up to its capacity. (Voltage was lower than usual this morning, I don't know why.)
     
  2. apacheguy

    apacheguy Sig 255, VIN 320

    Joined:
    Oct 21, 2012
    Messages:
    3,725
    Location:
    So Cal
    Interesting experiment. I could've sworn the max HVAC usage was ~6 kW.
     
  3. swegman

    swegman Member

    Joined:
    Mar 27, 2012
    Messages:
    962
    I noticed today that preheating (with no charging) was drawing 29 Amps at about 234 Volts. In this regard, I've noticed that for the last week, the car has been indicating the line voltage as being between 230 and 234 Volts, whereas during the summer it was between 239 and 245 Voltage when charging at 40 Amps. Don't know why there is the voltage drop.
     
  4. Brass Guy

    Brass Guy Member

    Joined:
    Jan 5, 2014
    Messages:
    505
    Location:
    Stoughton, MA
    I have a fairly long run with #6 wire, and usually drop about 10V at 40A, but start out at about 245V before it ramps up.
    I'm more interested in the power draw. Does anybody see more than 10kW preheating?
     
  5. mknox

    mknox Well-Known Member

    Joined:
    Aug 7, 2012
    Messages:
    8,568
    Location:
    Toronto, ON
    I currently have a 20 amp / 240 volt outlet in my garage and have my car's charging set to 16 amps. If I pre-heat in the winter I use all of that 16 amps plus draw down the battery a little bit. Not ideal, but better than all of the pre-heating power coming from the battery.
     
  6. swegman

    swegman Member

    Joined:
    Mar 27, 2012
    Messages:
    962
    I have 2 gauge wire, and as i said, my pre-heating drew 29A of shore power.
     
  7. Brass Guy

    Brass Guy Member

    Joined:
    Jan 5, 2014
    Messages:
    505
    Location:
    Stoughton, MA
    The power draw from preheating tapers. (Sort of like supercharging.:smile:) To catch it at its maximum, you'd have to catch it fairly early on. Most of the time nobody does this because you preheat so you don't have to go out to a cold car.

    29A is still pretty high though, usually when I get to the car it has tapered to 6A or so.
     
  8. bonaire

    bonaire Active Member

    Joined:
    Aug 24, 2013
    Messages:
    1,524
    Location:
    USA
    swegman, does your neighborhood or general area have homes with houses heated primarily by electricity? Usually a voltage drop is environmental, based on your neighborhood's substation demand. For me, our neighborhood is primarily Propane heating (tanks) and the electricity does not dip much in the winter. I get 121V on the wall socket all the time.
     
  9. swegman

    swegman Member

    Joined:
    Mar 27, 2012
    Messages:
    962
    My house is on several geothermal systems, which is basically a heat pump that uses underground water for heating and cooling rather than ambient air. The energy usage of this system is pretty constant year round. The other homes in my neighborhood are on oil or regular heat pump/resistive heating. Not sure what each house exactly uses. There was no gas on my block until I built my house and had a gas line installed (used for cooking, dryer, gas fireplace and backup heating). Most of the homes in my area were built in the 1940's to 1960's, except for my home (built 19 years ago) and 2 other houses. Plus there is a house that is currently having a large addition(several thousand sq ft) added at the present time, but don't know what type of heating system they are installing.
     
  10. invisik

    invisik Member

    Joined:
    Mar 13, 2014
    Messages:
    620
    Location:
    Minneapolis
    About 17 amps seems to be my typical maximum draw during pre-heating in above-zero temperatures.

    -m
     

Share This Page