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Nav Energy Usage Calculations

Discussion in 'Model S: Battery & Charging' started by kirkbauer, Sep 21, 2015.

  1. kirkbauer

    kirkbauer Member

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    Sorry if this is the wrong subforum, this was my best guess as to where it belongs. Also sorry if some of this is a FAQ but I had no luck finding details.

    So I'm curious as to what the energy planner (Trip tab of the energy app) uses to calculate energy usage. I definitely know it calculates elevation changes. But it also seems to consider speed limit, or even more interesting I think it uses my configured amount over the speed limit. Specifically, I have my speed alarm set to 14mph over which is what speed I mostly drive at and my energy consumption matched the estimated consumption pretty closely. If it used the speed limit (typically about 70mph on my last trip) instead of my actual speed (typically 84mph) it should have way undercalculated my energy usage, right?

    I wonder if it considers temperature and/or climate control? And does it changes its numbers if you enable/disable ranged mode? It doesn't seem to.

    It would be interesting to see the values that are used to calculate the energy usage and ideally even to tweak them (e.g. a what-if tool). So it says I'll get there with 5% remaining, but perhaps I can turn on range mode and set my speed to 4mph over and see what the effect is.

    Obviously being able to set up waypoints would be really helpful too, like being able to add a stop between here and the next supercharger, or remove a specific supercharger from the planned route, etc.
     
  2. Max*

    Max* Autopilot != Autonomous

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    I beleive it uses the average speed traveled on the road, not anything related to your speed limit.

    I have mine at 0mph over (just so I don't have to do any mental math). And I drive about 10-15mph over on long trips, and I arrive with surplus. By your theory I should arrive with a lower percentage than the gray line, and that never happens.
     
  3. kirkbauer

    kirkbauer Member

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    Good to know, Max, and that makes perfect sense. It would certainly still be interesting to have a what-if mode where you could adjust your speed relative to the speed limit or average speed to see the effect on battery usage.
     
  4. Polly Wog

    Polly Wog Member

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    #4 Polly Wog, Sep 22, 2015
    Last edited: Sep 22, 2015
    Unless they have recently changed the nav energy estimator, which I doubt, it does not take into account your projected speed, but indeed uses the average speed - to a limit. It actually caps it at 68 mph, so on a highway where the speed limit is much higher, say 75 or 80, it tends to grossly underestimate your usage, unless you go less than 70. I'm not sure how Max* gets away with going 15 mph over without it being inaccurate. Maybe he always has a tailwind? :smile:
     
  5. Max*

    Max* Autopilot != Autonomous

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    I'm not sure where you got your numbers from?

    Doubt it about the tailwind, lol. I always do around 70-80mph on trips. Speed limit is 55-65 around here. At 70mph I'm ALWAYS above the projection. At 75mph I'm usually pretty close to the prediction. At 80mph I'm rarely above the prediction.

    It could be a climate thing. I've had my car for 3 months (summer) and about 9k miles on it. Or it could be that in the northeast we don't have 70-80mph speed limits.
     
  6. kirkbauer

    kirkbauer Member

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    That's interesting because I just did 500+ miles mostly over 80mph (with range mode) and arrived no more than 3 percent lower than the original estimate, so it is really being conservative (assuming high energy usage) if it is estimating based on 68mph.
     
  7. Polly Wog

    Polly Wog Member

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    @Max*, I had seen the "cap" confirmed in a post in another thread, but I couldn't say who our member was that received confirmation of it. For myself, I personally confirmed it by extensive driving on Interstate 40 in New Mexico and Arizona, where the speed limit is 75 mph. The nav's projected arrival times were based on a speed of 68 mph, over stretches that were 75 and didn't have slow downs. The energy planner estimated accordingly.
     
  8. mknox

    mknox Well-Known Member

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    I have not been so lucky. Discussed over in this thread.
     
  9. apacheguy

    apacheguy Sig 255, VIN 320

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    My understanding was that it always defaults to the speed limit. Only when you begin driving does it adjust to account for the increased draw resulting from higher speeds and climate. Speaking of climate, I don't believe it looks up weather stations along the route. Elon said it does but I've seen no evidence of this.
     
  10. Max*

    Max* Autopilot != Autonomous

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    I doubt it. I always go above the speed limit, and I always arrive at or better than the nav trip prediction.

    Someone mentioned that it defaults to the average speed on the road (not the speed limit), similar to evtripplanner, this I could believe to be accurate.
     

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