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How to calculate how many miles of range based on kWh?

Discussion in 'Model S' started by AmericanPharoh, Aug 15, 2017.

  1. AmericanPharoh

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    I'm going to be on a road trip, one of my stops will be at a ChargePoint for 2 hours @ 6.6 kW, giving me 13.2 kWh of charge. How many miles will this get me in my Tesla Model S 75D?
     
  2. steveho

    steveho Member

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    About 45-50. 13,200 / 270 = 48 miles. That's assuming you drive about 270 wh/mi.
     
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  3. WARP 10

    WARP 10 Member

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    After around 13000 miles, I find my average usage is around 310wH/mi. Rarely could get 270 (assuming average highway speed of 75) without a good tailwind or no uphill at all. So I would figure 13,200/310 = 42+
     
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  4. ChadS

    ChadS Petroleum is for sissies

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    There is also likely to be some charging overhead. And the car may have to heat/cool the battery. Or the cabin if you stay in the car. So 13.2kWh would be best-case, I would not count on that much.
     
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  5. kort677

    kort677 Active Member

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    at an L2 charger 18 miles per hour would be about the best you could expect to get. L2 charging for me is only for extreme emergencies and overnight stops. if there are SpCs along your route I would use those before using an L2
     
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  6. AmericanPharoh

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    Yup, I've got over 30,000 miles on my car, don't expect to get anywhere near 270kW/mi. I'm hovering closer to 300 kW/mi.
     
  7. ulrichw

    ulrichw Member

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    Those letters after the numbers actually matter - I believe you mean 300 Wh/mi - or 300 Watt-hours per mile.

    You had the units correct in your first post - you're adding 16.6 kWh - or 16.6 kilo Watt hours. (kilo means a thousand, as you probably know, so that's equivalent 16,600 Wh)

    To answer your question, you need to figure out how many miles you can go per kWh.

    Since you know how many Wh you use per mile, you can get there by simply inverting your number:

    mi/kWh = 1 / (kWh/mi)

    300 Wh/mi is .3 kWh/mi - inverting that: 1/.3 = 3.33 mi. per kWh

    (Divide by 1,000 if you want to do the math in Wh - i.e., .00333 mi per Wh - that's about 176 feet)
     
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  8. bob_p

    bob_p Active Member

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    Our S 100D has around 6500 miles on it already, driving a combination of urban streets and highways - our lifetime average is 307 Wh/mi. Assuming we actually have 100Kwh in the battery pack, that would give us about 325 miles of range at 100%, and 260 miles if we kept the charge between 10-90%.

    That means our S 100D would get about 43 miles with 13.2Kwh - if we're driving in average conditions - better in ideal conditions - and worse in bad conditions (high winds, heavy traffic, start/stop driving, elevation changes, rain/snow, cold or very hot temperatures, ...).

    Rather than display the ideal or rated range, what might be interesting would be a 3rd option - predicted range, which could be the range based on recent driving energy consumption (last 1000 miles?). That might be much more interesting to have than using the rated or ideal ranges, which likely don't reflect most people's driving habits (either higher or lower).
     
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  9. AmericanPharoh

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    I would like to see a predicted range option!
     
  10. TIppy

    TIppy Active Member

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    #10 TIppy, Aug 19, 2017
    Last edited: Aug 19, 2017
    On the epa document for the model 3, they had to use 89.404 kwh to charge the car to it's capacity of 78.270 kwh. So only about 87.5 % of the energy makes it into the battery. 13.2 kwh * 0.875 = 11.55 kwh into the battery.

    Subtract 2.1 wh per foot increase in altitude from the 11.55 kwh. Add 1.85 wh (1.6 wh if using regen) per foot to the 11.55 kwh if you are losing altitude. So if your destination is 1000 ft higher, you would subtract 2.1 kwh from the 11.55 kwh. Then your range is the kwh divided by the kwh per mile for your chosen speed.

    For level ground, no a/c and no wind, this is the range for various speeds.

    MPH, KW, KWH / mile, Miles

    55, 11.8147, 0.2148, 53.7679
    60, 14.2318, 0.2372, 48.6938
    65, 16.9874, 0.2613, 44.1945
    70, 20.1080, 0.2873, 40.2079
    75, 23.6200, 0.3149, 36.6744
    80, 27.5500, 0.3444, 33.5390

    For the case where you gain 1000 ft in altitude and are driving at 70 mph:

    11.55 kwh - 2.1kwh = 9.45 kwh
    9.45 kwh / 0.2873 kwh / mile = 32.9 miles
     
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  11. TIppy

    TIppy Active Member

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    #11 TIppy, Aug 20, 2017
    Last edited: Aug 20, 2017
    I measured the power required to run the car and a/c while it is parked for camping. It's about 1350 watts. To see how this affects the range, it must be added to the KW from the above post. Here are a couple of examples using 11.55 kwh:

    MPH, KW, KWH / mile, Miles

    55, 13.1647, 0.2394, 48.2540
    80, 29.9000, 0.3613, 31.9723

    So, at 55 mph you lose about 5.5 miles, and at 80 mph you lose 1.5 miles.
     
  12. mkjayakumar

    mkjayakumar Active Member

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    This is great. Thank you.

    On the last line I think you made an unit error stating 0.2873 kWh/mile. It should be wh/mile.

    Also, can you tell me how you arrived at an efficiency of 0.2873 wh/mile? For S85 or 75M3?
     
  13. TIppy

    TIppy Active Member

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    It's 287.3 wh/mile or 0.2873 kwh/mile.

    This is for a Model S 75D, using the drag data from the epa report. It should be more or less the same for any Model S.
    To get the kwh / mile, divide the KW (20.1080) by the speed (70 mph).
     
  14. fsch

    fsch Member

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    You actually have something like that from the graph of the consumption of the last 10, 25, 50 km. The number is written at the right of the graph, which already gives a good idea. Could ask Tesla to add more distance options.
     
  15. cpa

    cpa Active Member

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    That is true, and it is a pretty good indicator if the terrain is flat. However, it is useless when driving up a long incline, as the program assumes that your drive will continue at an incline indefinitely. Similarly, on a long descent, it assumes that you will have a virtual infinite range.

    I have crossed the Sierra many times. Especially going east to west, those first 30-40 miles of elevation gain are steep and a battery indicator of 75% might reflect fewer than 70-80 miles remaining at the current usage of 600+ wh/mile. Thirty miles beyond the summit will show 250+ miles of range and the battery indicator has maybe dropped to 72%.

    What would be better in my opinion would be to combine the trip graph information with the historical usage on the energy screen. Do a sort of overlay so that we can see what the car is estimating the various usage to be at various points along our journey that are based upon our recent driving style blended with the expected usage 50-100 miles down the road.
     
  16. mkjayakumar

    mkjayakumar Active Member

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    Oops my bad.

    Thanks for all your detailed analysis. Appreciated.
     
  17. TIppy

    TIppy Active Member

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    No problem, and you're welcome.
     
  18. TIppy

    TIppy Active Member

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    Here's the same info for the Model 3.

    Subtract 1.74 wh per foot increase in altitude from the 11.55 kwh. Add 1.52 wh (1.33 wh if using regen) per foot to the 11.55 kwh if you are losing altitude. So if your destination is 1000 ft higher, you would subtract 1.74 kwh from the 11.55 kwh. Then your range is the kwh divided by the kwh per mile for your chosen speed.

    For level ground, no a/c and no wind, this is the range for various speeds.

    MPH, KW, KWH / mile, Miles

    55, 10.3555, 0.1883, 61.3444
    60, 12.5053, 0.2084, 55.4165
    65, 14.9756, 0.2304, 50.1316
    70, 17.7938, 0.2542, 45.4371
    75, 20.9874, 0.2798, 41.2747
    80, 24.5840, 0.3073, 37.5855

    For the case where you gain 1000 ft in altitude and are driving at 70 mph:

    11.55 kwh - 1.74kwh = 9.81 kwh
    9.81 kwh / 0.2542 kwh / mile = 38.6 miles
     
  19. ShockOnT

    ShockOnT Quickish

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    The 75D is one of the most efficient Model S models.
    I'm averaging 177 Wh/km, about 285 Wh/mile.
    To be safe, assume 333 Wh/mile, or 3 miles per kWh.
     
  20. clostridium

    clostridium Member

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    You get that on the center display when you display efficiency.
     

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