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AC drops the rated miles like crazy!

Discussion in 'Model 3: Battery & Charging' started by jgd108, Aug 30, 2018.

  1. jgd108

    jgd108 Member

    Joined:
    Jun 13, 2017
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    Location:
    orange county
    Hi!
    My wife started a job this week and using the M3 for her commute. It's 7mi each way, 14mi total.
    She sits in the car for about an hour during lunch time with AC most of the time (it's been hot, peaks at 90).
    When she comes back it seems like 20mi (!) has vanished. Her consumption is 214W/mi which is great, and energy used is "3KW" which is less than half of what I have to charge for next day..

    I know the car keeps the battery cool during the day, but that doesn't seem to reduce much (maybe 3-4mi at most for 8hrs).
    Is running AC without driving that hard on the battery?

    I keep the car at 70% before she leaves every morning, here's the breakdown in Rated Miles:

    220RM charged (70%)
    213RM after reaching work around 8am
    200RM at 3pm! 13RM for AC??
    198RM at 5pm before leaving work
    186RM at 9pm (before charging at midnight, sorry not sure if it was 188RM when she came back)

    Recap:
    14mi commute..
    220-186 = 34 RM used
    20mi of AC & battery cooling in a day?

    I'm on the "latest" 2018.32.2

    Thx!
     
  2. tjkessler

    tjkessler Member

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    Campbell CA
    In most cars the AC is much less efficient if you are sitting still. Airflow over the hot/condenser side really helps with efficiency.
     
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  3. laxdad

    laxdad Member

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    Not surprised by the 13 miles of range lost from running the AC for an hour. I suspect an ICE vehicle would burn a fair amount of gasoline idling for an hour with the AC on.
     
  4. Derek Kessler

    Derek Kessler Active Member

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    Wait until she sits in the car for an hour with the heat running...
     
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  5. PoitNarf

    PoitNarf The Clown Prince of Crime

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    Ok? Why not stay in the office or go to lunch with one of her new coworkers to get to know them? Sounds like a very lonely lunch hour.
     
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  6. timk225

    timk225 Active Member

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    I like having my lunch hours alone. I don't want to talk to anyone at all during lunchtime. That probably hasn't helped with employability and job security, but I am how I am.

    Someone wrote here a few months ago how they did a test with the AC running constantly, it used 60 miles of range in 5 hours. The fans don't take much power but driving the AC compressor does.
     
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  7. Xenius

    Xenius Member

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    In the S, the AC system takes about 2kW of power draw. So at that rate, sitting still you're going to lose ~6.2 miles an hour (300 w rated, so 3.1 miles/kwh. So 60 miles of range in 5 hours seems about right for the 3 which has a rated 250w/mi. Though I'd have expected more about 2kw/hr * 3.1miles / kwh * 5 hours = 31 miles for an S.

    2kw/hr * 4m/kwh * 5hr = 40 miles of range expected loss for running the AC in a Model 3 over 5 hours.

    Did I math correctly?
     
  8. flashflooder

    flashflooder Member

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    Don't quote me, but I think I've seen usage closer to 4kW for AC in my Model 3.
     
  9. jgd108

    jgd108 Member

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    Thanks guys, you are awesome!

    Deep down I know it's better than running ICE engine for an hour so I don't mind the extra 4kwh she's using.

    And yes eventually she'll be having lunch with her colleagues, just that she's doing a special cleansing diet at the moment :p
     
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  10. Rocky_H

    Rocky_H Active Member

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    Well, you are misstating it:
    Using a large amount of energy is in no way "hard on the battery".
     
  11. Letgo

    Letgo Member

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    Northern Virginia
    I am losing miles like crazy here. 3 miles to work and back and the car drops like 20 miles or so. I am not running ac in car or anything though.

    Charged to 250 miles yesterday and drove 40 miles since then. The charge now shows like 160 miles. I called Tesla and scheduled an appointment but want to know if anyone else had same issue
     
  12. COrocket

    COrocket Member

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    Do you have cabin overheat protection enabled?
     
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  13. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    The A/C can use up to 6 kW of energy in every car that has an electric A/C compressor (there may be exceptions, but I don't know of any). However, because the compressor is variable speed, it normally doesn't run at maximum speed so the actual energy used is far less. What I've found to reduce A/C power drain are:

    1. When the car is parked, open the roof to 15% (if applicable) and/or crack all four windows to let the superheated air out.

    2. Start at a high temperature setting. It will still blow cool air, but the compressor won't run nearly as fast.

    3. Reduce the temperature gradually as the car cools down.

    Tinting the windows and roof will help, though I haven't bothered to have my S tinted.
     
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  14. ecarfan

    ecarfan Well-Known Member

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    No. AC is just a power draw, like the electric drivetrain, the cabin heat, the lights, etc.

    It’s what the battery is for; to provide power to vehicle systems. Use it. :cool:
     
  15. gavine

    gavine Petrol Head turned EV Enthusiast

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    AC shouldn’t use that much, unless you’re not using the auto setting. Auto is most efficient. Too often, people will turn the temperature down to LO and manually adjust the fan speed down. This is extremely inefficient. Use auto and a reasonable temperature (72F maybe) and you’ll find that it only uses about 3 miles per hour.
     
  16. wk057

    wk057 Senior Tinkerer

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    Keep in mind that a rated mile in the 3 is "worth" far less energy (~225 Wh) than in an S/X (~285 to ~370, off the top of my head). So A/C use will consume more rated miles in a 3.

    Let's say you run the A/C at full blast on a hot day for an hour. That'd be somewhere around 4 to 5 kWh, worst case. On a 3, that'll be ~18 rated miles. On a P100D it would be ~12 rated miles.

    I'm actually more worried about winter in the 3. Heating the cabin is going to be a killer.
     
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