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Energy Usage Chart

Discussion in 'Model S: User Interface' started by nleggatt, Mar 11, 2013.

  1. nleggatt

    nleggatt Member

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    What the heck is the chart showing? Here's what I know: It shows average kW/km over the past "your selection" km (ie 50km). There is a solid line that shows "Rated" and then a dotted line with "Projected".

    Then when you go down a hill (green regen), the line graph eventually turns green... why?

    I had thought that if I kept the dotted usage line under the solid line for my selected distance (ie 50km) I would be getting the Rated range (as displayed on the dash). This does not appear to be the case in practice

    Didn't get a ton of details during the orientation about this.
     
  2. dashrb

    dashrb Member

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    You're right (typo), it's showing kWh/km (or per mile in the US with our broken measurement system). In short, the vertical axis shows the amount of energy (in kilowatt-hours) you need in order to travel a kilometer. The dotted line shows your average, as you say, over the selected range. The widest range (30 miles in the US) is a good indicator of how much energy you're using on a trip of any significant distance. The dotted line is your average, and the display also shows the "Rated" line (which is 300 kWh/mi in the US). This 300 kWh/mi (US) figure is used to calculate the "Rated Range" in the speedometer area of the dash. If your dotted line is below this Rated line, then you will exceed the rated distance because you're using less energy per mile than the EPA did. (big assumption on my part: does the US EPA rating of 300 kWh/mi appear in the non-US displays (converted to km, of course)?). This graph shows your Projected Mileage based on either "Average" (the dotted line), or "Instantaneous" (the most recent data point on the far-right edge of your graph). This is also selectable above the graph (next to the 3 range selection buttons).

    When you are using less energy per distance traveled, the graph line is plotted lower. When the energy used is less than 0, the graph is painted green (for Good!). You can travel a distance such as a tenth of a km, or even a full km, using a negative amount of energy! Since the battery recaptures energy as the vehicle decelerates, if you are descending a steep hill, or exiting a highway on a long exit ramp, you may regain more energy than you used, resulting in negative energy used.

    I believe in general that your thought process is accurate: if you can keep the dotted usage line under the solid Rated line (again, 300 kWh/mi in the US), then you will exceed the Rated range.
     
  3. nleggatt

    nleggatt Member

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    Thanks Dashrb. I should have taken a picture yesterday (will try next time). I was well below the solid line for my entire 50km (30 miles), but my Rated on the dash still showed a greater distance than the projected on the line graph. That's why I'm soooo confused. Glad to know I'm right in theory though.
     
  4. aviators99

    aviators99 Model S - R140

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    1) Make sure your dash is really showing Rated and not Ideal
    2) Make sure your energy graph is set to Average, and not Instant. Note that a bug in the software makes it reset to Instant every time you leave the car.

    Also, to slightly correct dashrb, rated kWh/mi is between 304 and 305.
     
  5. ken830

    ken830 Model S (Res#P12,447)

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    Why is the rated range based on 300 Wh/mile? Would that give 85 kWh / 300 Wh = 283 miles? But the EPA rated range is 265 miles, which should work out to 85 kWh / 265 miles = 320.7 Wh/mile.
     
  6. gregincal

    gregincal Active Member

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    Almost certainly the projected was set to instant, which is based on the current point of the graph, not the average line. Set it to average and it will reflect the average line.
     
  7. jkirkebo

    jkirkebo Model S P85+ VIN 14420 EU

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    You don't have the whole 85kW available for normal use, there is a buffer below zero. I've heard 307-308Wh/mile for rated. 0,307*265=~81,4kWh available.
     
  8. aviators99

    aviators99 Model S - R140

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    The number passed around on this forum was 5% off for reserve. That's 80,750 / 265 = 304.71. I asked ownership what the Wh/mi I should use to get rated miles, and they told me 305. This seems to jibe.
     
  9. Hans (Amsterdam)

    Hans (Amsterdam) Model S res#3130

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    The kWh/km or actual kW usage that the display is showing: does it include energy used by heater / lights / etc ??
    ( does it show the total of energy that is coming from the battery ? )
     
  10. Zextraterrestrial

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    Yes. Sitting still shows some red on the kw meter
     
  11. Hans (Amsterdam)

    Hans (Amsterdam) Model S res#3130

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    Good. I was driving a demo model S steady on the highway at 100 kmh ( 62 mph) with some headwind ( 3 Beaufort) at 35F and heater on at 68F. (Typical Dutch conditions).
    The display showed 20kW of actual energy usage.
    Which means under these conditions the range could be around 400 km (250 miles).
     
  12. Zextraterrestrial

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    I think with the heater blasting and rear defrost + seat heaters there is something like 8kW of draw but the heat draw usually drops to 1 or 2 kW(or less?) after it reaches equilibrium.

    250mi @ 62mph sound about right to me.

    I never learned the Beaufort scale - neat. something new !
     
  13. Robert.Boston

    Robert.Boston Model S VIN P01536

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    That sounds about right. 3 Beaufort adds about 16 kmh (10 mph) to the apparent speed of the Model S, i.e. from an aerodynamics POV, you were driving at 116 kmh (72 mph) on flat roads. 250 miles of range matches my experience for those conditions. Of course, when you've got that same wind at your back, the situation flips, and the aerodynamics will increase your range. In the Netherlands, it's rare that you would drive hundreds of km straight into the prevailing wind!
     

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