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Explain the average and instant projections please...

Discussion in 'Canada' started by hingisfan, Feb 15, 2015.

  1. hingisfan

    hingisfan hingisfan_Mark_V

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    OK, so I understand the 10, 25, and 50km averages, that's easy. But I can't figure out why when I have "instant" selected, the number changes if I press 10, 25, or 50. Isn't instant just the current projected based on current usage? What does the 10, 25, or 50 have to do with that???
     
  2. Spurkey

    Spurkey P04251

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    The 'instant' reading pulls from the graph pixels, not the 'actual-instant' energy usage. When you switch from say 10 to 50, the screen renderer has to average several pixels together in order to draw the line then the 'instant' display pulls from wherever the line hits the edge of the graph. This is not at all clear, nor intuitive, nor helpful in any way.

    I've complained to Tesla about this and their concern is that the line-graph-pixel-averaging may confuse people if the instant reading doesn't line up with where the line graph intersects. I suggest you also raise your concern with your local service department, if enough people complain about it perhaps something will be done about it.
     
  3. jerry33

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

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    The latest 6.1 defaults to average, so it's no longer an issue.
     
  4. HankLloydRight

    HankLloydRight Fluxing

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    Do you have a source for this? That doesn't sound right at all.
     
  5. PoweredByRain

    PoweredByRain Member

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    Quick answer: they are not actually providing an "instant" consumption. There's no such thing possible, when you're talking about consumption per unit distance, because you can't divide by zero. The distance over which they calculate the points appears to be different depending on which scale you're looking at, thus "instant" can be different depending on the scale.

    You can see evidence for my theory by switching graph scales and noting that the graphs actually show different extremes. e.g. if you select the 10 km scale you'll see more extreme highs and lows, because that delta of distance in the computation is smaller than that used for the 25 km or 50 km scale. Try going down a significant hill and look at the difference between the graph for 10 km and that for 50; the 10 will quite quickly show a net regeneration (green) whereas the 50 might not.

    - - - Updated - - -

    If you take what Spurkey said and replace "reading from the graph pixels" with "uses the last calculated energy/distance value" then what he's saying makes a lot more sense.



    In short:
    This confusion as to what "instant" means is caused by Tesla using a different "delta d" depending on the graph scale. But think about what would happen if they didn't do this - then when changing to the 50 km scale you could see a very very noisy graph.
     
  6. HankLloydRight

    HankLloydRight Fluxing

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    I'm thinking that's not really correct either. When switching between "Average" and "Instant" the graph doesn't change, only the calculated Whm/WhKM value on the right side of the graph changes. The graph is always just measured energy usage over the selected last x miles/KM. Each dot on the graph isn't a rolling average over the last x miles/km, which is what you are describing.

    So yeah, Tesla seems to be using a different delta d for the "instant" calculation depending on the selected miles chart, but that doesn't make sense either. Instant is instant... be it the last 1 mile/km or other small amount. That shouldn't change when the X axis changes.
     
  7. SUN-day Driver

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    I have noticed this and it never made any sense why the highs and lows of the past 5 mile display is different than those for the final 5 miles of the greater distance displays. Makes no sense whatsoever unless they do something like you say. They should fix these apparent disparities.
     
  8. jerry33

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

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    No one would miss it if they got rid of it. I suspect it's there due to feeping creatureism.
     
  9. PoweredByRain

    PoweredByRain Member

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    No, that isn't what I'm describing. And you're completely missing the point regarding "instant". What does "instant" energy per unit distance mean? It would be the limit as delta d approaches 0 of energy divided by delta d. i.e. power divided by speed. If you do that calculation frequently you're going to get just a huge scatter graph, not a nicely smoothed graph as is displayed. Judging from how the graph is updated, they calculate the energy used over the last "delta d" - say, 100 m - and draw a line to that point. There simply has to be some averaging in order to get a "reasonable" looking graph. (Whether there's an overlap in the calculations - i.e. points are more frequent than delta d, giving effectively a running average - is a separate question. I don't think they're doing that.)

    Given that, it makes sense to use a different delta d for different ranges, otherwise the graph will not look pretty - for the same reason. Cramming 5 times as many points in the 50 km graph as in the 10 would result in a graph that looks much more spikey.

    The down side of doing it the way they appear to be doing it is the problem described, namely that what's shown as "instant" (which as I say almost certainly isn't) changes depending on the scale of the graph.
     
  10. Spurkey

    Spurkey P04251

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    You explained it more better-er than I did. :) "Instant" in this case corresponds to "last averaged distance value" which can obviously change if the scale changes.

    PoweredByRain isn't talking about a rolling average but each dot *is* averaged over a specific distance depending on the scale selected. Exactly as you say the Wh/km changes when you toggle to "Instant", it's the result of Tesla still performing a small averaging calculation to arrive at the "Instant" value, resulting in confusion.

    Sit in the car whilst in park, set the graph to "Instant", then cycle through the 10, 25, and 50 km modes. This'll make it clear what's going on.
     
  11. Doug_G

    Doug_G Lead Moderator

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    This is all ignoring the fact that the "Instant" display is pretty much useless for any and all purposes...
     
  12. PoweredByRain

    PoweredByRain Member

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    Not true, it has tremendous entertainment value. "Look, we can go 999 km at 80 km/h as long as we keep going down this mountain on an 8% grade!"
     
  13. Doug_G

    Doug_G Lead Moderator

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    I stand by my comment LOL.
     
  14. Spurkey

    Spurkey P04251

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    I wouldn't say that fact is being ignored at all. ;)

     

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