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Inaccurate meter

Discussion in 'Model S: Battery & Charging' started by leshore, May 7, 2014.

  1. leshore

    leshore Member

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    Southern California
    Curious...how accurate is the power consumption readout on the Trip Meter? How accurate is SCE's Meter? As illustrated below, since I took delivery of my Model S on April 19, the car has consumed 270.6 kWh. My ev-dedicated SCE meter shows that I have drawn 316 kWh. A difference of 45.4 kWh. Why such a difference? Where is the discrepancy? At first I thought last night's charge, which has not yet been used. However I drove fewer than 30 miles yesterday, and the 45.4 kWh translates to approx. 139 miles. SCE says to check next month's bill, and if it still is off substantially, they will check the meter. Has anyone else experienced this?
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  2. snooper77

    snooper77 Member

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    Charging losses obviously, about 15%, that's to be expected.
     
  3. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    It's actually remarkably consistent. The power used, as reported in the car, only shows battery power used when the car is "On." The AC charger in the car is about 90% efficient; 270 kWh/90% is 300 kWh. The rest is power used when the car is off, "vampire load." This also includes turning on climate control with the App while the car is "Off." 16 kWh in 18 days to feed the vampire is very plausible.

    Welcome to Tesla energy accounting...
     
  4. bonnie

    bonnie Oil is for sissies.

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    (mod note - fixed typo in thread name)
     
  5. leshore

    leshore Member

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    That explains it. I didn't realize that the trip meter only displays energy used while the car is on. Thank you, Cottonwood.

    - - - Updated - - -

    Thank you, Bonnie, for fixing the typo.
     
  6. ThosEM

    ThosEM Space Weatherman

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    Annapolis, MD
    It is pretty well documented that the rectifiers on board the Model S have about 85% efficiency, though I can't point to specifics off the top of my head. Your numbers are consistent with that. All the internal reporting is with respect to the actual power transferred from the battery.
     
  7. miimura

    miimura Active Member

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    In addition, the car is showing the energy taken out of the battery. Your electric meter shows the energy required to fill the battery. The two figures you showed are in exactly the expected ratio.
     

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