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Battery math

Discussion in 'Model X: Battery & Charging' started by manyarg, Aug 26, 2018.

  1. manyarg

    manyarg Member

    Joined:
    Apr 5, 2018
    Messages:
    23
    Location:
    Seattle WA
    Hi all,

    I got a Model X 75D a couple of months back and about a month ago I had a Dashcam installed on the same weekend since I got a software udpate. After that weekend I noticed that my Miles were dropping faster than before. Meaning I started with 196 miles and after driving only 8 with an average Wh/mi < 312 (The rated Wh/mi) I would lose approximately 12 miles of range. After 2 weeks I changed to % instead of miles to try and get a better sense of what is going on.

    Over the last two weeks I've noticed the following average consumption for my daily commute: ~6 Kwh (From the trip consumption metric) = ~10% battery drain. If this were actually true, then my actual battery capacity would be closer to 60 Kwh than to 70 Kwh.

    Do any of you know if my dashcam could be introducing an additional drain that the car is unable to track while driving? Do any other X75D owners have noticed similar Kwh to % ratios?
     
  2. Johan

    Johan Funds for M3 secured. Contingent on wife aproval.

    Joined:
    Feb 9, 2012
    Messages:
    7,182
    Location:
    Drammen, Norway
    It's not the dashcam - the energy it uses is a drop in the ocean compared to driving and HVAC.
     
    • Like x 1
  3. dhrivnak

    dhrivnak Active Member

    Joined:
    Jan 8, 2011
    Messages:
    3,678
    Location:
    NE Tennessee
    I would be surprised but you should be able to disconnect for a few days to see.
     
  4. tpham07

    tpham07 Active Member

    Joined:
    Mar 21, 2017
    Messages:
    1,972
    Location:
    Rhode Island
    things like these is why tesla stop advertising battery pack sizes on the model 3. Too many guessing games involved. a 75kwh battery is a 75kwh battery, not 60kwh...

    a 75kwh battery has about 72kwh usable.

    You can't go off your car's measurements of kwh used to determine the actual amount of energy you used. there are lots of power draining functions that do not calculate into consumption. Battery cooling/heating is a major one.

    Phantom drain from always connected is another one, so is cabin overheat. etc.
     
    • Like x 3
  5. DCGOO

    DCGOO Member

    Joined:
    Nov 24, 2015
    Messages:
    978
    Location:
    Indianapolis, IN
    There are many reasons for “miles” to drop. Switch the display to % battery, and things will make a lot more sense. Even with % displayed you will find it drops a percent or two overnight, but it is quite consistent. I have a dash cam, a Linux computer, an Internet router with cellular modem and a 2-way radio (ham) installed and running 24/7. Still drops a % or two overnight, same as with nothing extra powered.

    If you absolutely need to know the predicted range, use the energy graph. It is much more accurate because it includes your recent driving history into its calculation. It still cannot predict the future, but if you are a reasonably consistent driver, your history (last 5,15 or 30 miles) is a reasonable guess at the future. The fuel tank metric in miles is a useless guess.
     
    • Like x 1

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