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85kWh?

Discussion in 'Model S: Battery & Charging' started by CZguy, Nov 17, 2015.

  1. CZguy

    CZguy Member

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    Hi guys,

    I recently made a long trip including a few full-empty legs (easy to do in Germany where you adapt your speed for to reach next Supercharger!). I noticed that on the "meters" on the dashboard, the amount of energy consumed is around 75 kWh when approaching zero remaining distance. I expected it would be ca 85kWh as I have P85D. Is it that the meter only counts miles but not the other energy usage, such as heating? Or is the 10 or so kWh a reserve so that the battery does not drain completely and does not ruin itself?

    Apologize if this was discussed previously.

    Thanks!
     
  2. kaneda

    kaneda Member

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    I beleive the consensus si that the available power is around 77kWh on a 85 batterie pack.
     
  3. David99

    David99 Active Member

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    Yes there have been many other discussions about it. The usable capacity is about 76-77 kWh on a new car with an 85 battery. People who have taken a Tesla battery apart and measured directly the cells confirmed that it doesn't add up to 85.
     
  4. CHG-ON

    CHG-ON Still in love after all these miles

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    Battery heating also takes a big chunk out of range when cold.
     
  5. David99

    David99 Active Member

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    It is included in the energy calculation as long as you drive, though.
     
  6. scaesare

    scaesare Active Member

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    Do you have a reference for this?

    I've seen some discussion as to what voltage range Tesla utilizes, but not sure anything that "confirmed that it doesn't add up to 85"
     
  7. Lanber

    Lanber Member

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    How it all adds up is a black art.

    Bottom line is Tesla isnt letting us use the full battery capasity. Top charging is 4.2 Volts, you can get more energy into it by charging to 4.35V but it costs batterylife.
    Same in bottom, Tesla cuts at a certian voltage. There is still electricity left below to save battery from becoming an expensive boatanchor.

    Battery may well be 85kwh. We only get to play with 76,5kwh before it says 0, then it`s luck and sircumstances that means how much further than that you go before you get "pull over safely"
     
  8. MartinScorpio

    MartinScorpio Member

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    #8 MartinScorpio, Nov 21, 2015
    Last edited: Nov 21, 2015
    Tesla uses a zero mile protection of roughly 5kwh so you can keep going for a bit after the dash says Charge Now, and there is a 4kwh so called 'brick' protection to prevent discharging to the point of permanently damaging the battery. ergo, useable energy is 76kwh. teslabattery.png
     
  9. rlang59

    rlang59 Member

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    That graphic is not official and from what I understand is not correct.
     
  10. jerry33

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

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    That's my understanding too. It was done when the current battery was the "A" battery, and there have been many changes in the past three years.
     
  11. scottm

    scottm Active Member

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    oh no!!! THE GRAPHIC THAT WON'T DIE!!
     
  12. sillydriver

    sillydriver Member

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    I've always kept the battery meter on percent rather than miles of range, since I don't trust the range calculation. Doing this it has been obvious that 100% battery charge does not correspond to 85kWh. This became much easier to measure with software v7.0, which has a trip odometer display for each individual trip segment. The calculation involves multiplying miles driven by Wh/mi to get the Wh (kWh) for the segment and dividing by the change in the % charge for the segment. Recording the charge % right at the beginning and end of each segment means that no vampire losses are included, which would distort the numbers. I tracked this in a spreadsheet for over a dozen separate segments and the conclusion is that on average, 100% to 0% on my particular P85D with its particular battery is 73kWh +/- about 2kWh. The car has about 4k miles on it. The results for each segment vary by more because the meter rounds the percent charge to the nearest percentage point, so a segment that registers a 5% consumption of charge may have a significant error. The other source of error would be non-linearity in the % charge meter: none of the segments involved charges over 90% or under 20% and most were in the 50 to 88 range.

    While my 73 kWh is not out of line with the 76 kWh in the graphic, it is disappointing. My driving averages 320 Wh/mi, although it is starting to get worse now that it's getting cold. 73 and 320 imply a 228 mi real-world range from 100% to 0%, although I imagine I would do a fair bit better in a single trip at steady speed and if I put range mode on.
     

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