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Is this a problem?

Discussion in 'Model S' started by RYCO, Aug 26, 2016.

  1. RYCO

    RYCO Member

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    I charged my refreshed S90D to 90% this morning. Drove around, apparently about 150 miles. In this time I used 50 kWh of my 81 kWh (90 charged to 81 kWh or 90%) you see in my picture that I had 20% of my battery left. Am I reading this wrong? 20160826_180123.jpg
     
  2. SDRick

    SDRick Member

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    The 90 kw battery does not have 90 kw usable.
     
  3. hanl1

    hanl1 Member

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    This is perfectly normal. I assume you drone the past 150 miles at relatively high speed, because you have a rated 331wh/mi which is more than the ideal rated wh/mi. I don't remember precisely what the ideal wh/mi is (some 293wh/mi?), but you can use that and your rated miles to roughly estimate the 'reserve' portion of your battery that does not get factored into your rated mileage.
     
  4. RYCO

    RYCO Member

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    #4 RYCO, Aug 27, 2016
    Last edited: Aug 27, 2016
    I'm not really worried about the millage. I'm worried that at the beginning of the day I had 81kwh, and after I used 50 of them, it said I only had 20% left. This ratio should always be right on no matter how hard you drive the car. The kwh used may rise faster the harder you drive, but it should still equal out, right?
     
  5. RYCO

    RYCO Member

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    Anyone want to analyze this and tell me, who doesn't understand electricity and dropped out of high school so no math either, if it all jives? Seems like teslafi says I used more % of my battery than the car says. Screenshot_20160827-084736.png Screenshot_20160827-084747.png
     
  6. mblakele

    mblakele radial cross member

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    #6 mblakele, Aug 27, 2016
    Last edited: Aug 27, 2016
    To start with, I think that 81 kWh is too high. I know how you got there: 90% of 90. But there's an anti-bricking buffer, said to be 4 kWh. Accounting for that, 90% is more like 77-78 kWh.

    That closes the gap a little, but there's another important factor. The trip display only counts power used by the motors. It does not include power used for battery heating and cooling, nor for charging the 12V battery (or so I've read here: seems like an odd design choice). While the car is off the battery will cool down or heat up, depending on conditions. When you start driving again, it has to be brought back to operating temperature and kept there. You're in Arizona and it's August, so battery cooling probably used significant power and that didn't show up on the trip meter.

    Compare this to a single long trip in cooler weather. On a cool Spring morning here in California, my 90D trip meter measured 70.1 kWh while going from 90% to about 3% SoC in one drive. If my math is right, that implies 80-81 kWh usable capacity. Where did the other 9-10 kWh go? My guess is about half is the anti-bricking reserve, and the rest went to warming up the battery at the beginning of the trip and then keeping it at operating temperature.

    Anyway that's my understanding, based mostly on posts here. I welcome correction by better-informed correspondents.
     
    • Like x 1
  7. RYCO

    RYCO Member

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    So, normal in your view. Thanks for the input. Any other opinions?
     
  8. CHG-ON

    CHG-ON Still in love after all these miles

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    I love the Teslafi site. Very handy and informative.

    On the wh/mi topic, I can never get below 300 unless it is a moderate downhill all the way. I try to be conservative. But it ain't workin'!
     
  9. kglad99

    kglad99 Member

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    disregarding your driving efficiency, according to that display, you've used 79% of your energy ~ 49kWh. that's not right unless:

    your full battery = 49kWh/.79 ~ 62kWh
     
  10. RYCO

    RYCO Member

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    Ok. So I should have it checked, right?
     
  11. RYCO

    RYCO Member

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    The trip display only counts power used by the motors. It does not include power used for battery heating and cooling, nor for charging the 12V battery (or so I've read here: seems like an odd design choice). While the car is off the battery will cool down or heat up, depending on conditions. When you start driving again, it has to be brought back to operating temperature and kept there. You're in Arizona and it's August, so battery cooling probably used significant power and that didn't show up on the trip meter.

    Never heard of this before. Can anyone confirm? Not that I dont believe the post, just looking for more info.
     
  12. green1

    green1 Active Member

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    It's confirmed. Run your heat/AC all day long while the vehicle is parked and it won't report ANY power draw, only while driving will it show power draw. Now it's not actually that it doesn't count those systems, but it does only count while driving.
     
  13. thefortunes

    thefortunes Member

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    #13 thefortunes, Dec 1, 2016
    Last edited: Dec 1, 2016
    Just to clarify...when the car is running ALL power use is displayed by the trip display. That is why you can show very high Wh/mi if you are driving in town and the battery is heating/cooling or you are running ac/heat etc...

    It's the vampire losses (battery usage when the car is "off") that do not show on the trip display.

    In your TeslaFI screenshot you lost almost 20 miles in the ~ 7 hours the car was off ("idling" in TeslaFi terms). For some reason your car never went to the lower power state ("sleep" in TeslaFi terms) during this period - could be because it was actively cooling the battery, could be because you have "always connected" on, could be because TeslaFi (or other programs) are pinging the car and aren't allowing it to sleep.
     

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