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Understanding Wh/Mi - Range

Discussion in 'Model X: Battery & Charging' started by ALLMYNE, May 10, 2017.

  1. ALLMYNE

    ALLMYNE Member

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    Hello from a new MX100D owner
    I run 22's for wheels and I'm trying to best understand how to calculate distance for future trips
    So far I have accumulated 650 miles while registering 390wh/mi, 254kwh
    Am I doing the match right if I calculate:
    650 miles / 2.54 = 256 miles total range @ 390wh/mi?
    Not sure if there is a better, easier, more accurate way to calculate actual miles based on wh/mi
    Thank you!
     
  2. HankLloydRight

    HankLloydRight Fluxing

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    Here's how I would do it for Model S.

    Adjust as necessary, as the assumptions would be different.

    First, what's your rated range in miles at a 100% charge?

    For me, it's currently 250 miles on my P85D.

    Model S rated range assumes 300 wh/m, Model X maybe different, I don't know what it is.

    So.. 250 miles * 300 wh/m= 75000 wh (or 75 kWh available total energy in my P85D).

    Then 75,000 wh / 390 wh/mile == 192 miles.

    So I can assume that on a 100% charge, going 390 wh/m, I can expect to go 192 miles.

    But my average wh/m is about 330-340, so realistically, I can get 220 miles on a full charge to zero charge.

    So just figure out what your 100% charge is (in rated miles) and that the wh/m assumption is for Model X for calculating rated miles.
     
  3. wdolson

    wdolson Supporting Member

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    390 Wh/Mi seems pretty high, have you been driving aggressively (lots of launches)? I know the X gets worse energy use numbers than the S and you have 22 inch wheels, which also consume more energy. This time of year I've been getting around 290 Wh/Mi with my S90D (climate system is usually off because the weather has been in the 60s F lately), in the winter it was around 320 Wh/Mi.

    The way you do these things is divide or multiply to get the units right. You are looking for Miles range and you have a number in Wh/Mi and another in KWh. 100 KWh is 100,000 Wh. If you want a result in Miles, take the Wh number and divide by the Wh/Mi number, that cancels out the Wh and puts the Mi on top.

    So 100,000/390 = 256 miles range. You got close to the right answer but your units were Mi/100 KWh, which is not what you were looking for.
     
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  4. ALLMYNE

    ALLMYNE Member

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    Ahhh, that is a very simple way to calculate it and I appreciate it
     
  5. HankLloydRight

    HankLloydRight Fluxing

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    But just be aware that's assuming you have exactly 100 usable kWh in your battery. We know that Tesla has a small reserve of a few kWh to not brick the battery at 0kWh and that the badge marketing doesn't really reflect the actual kWh in the battery (could be more or less than 100 kwh). Using the 100% rated miles method includes these differences, unless you're just looking for a ballpark figure, then use 100kWh.
     
  6. ALLMYNE

    ALLMYNE Member

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    Understand.....makes sense......appreciate your help
     
  7. Racerx22b

    Racerx22b Member

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    MX P100D, 22s, Florida driving, AC on, Rear AC off, Sport mode, Range mode on 50% of time, just drive it (don't try to hypermile and don't launch it everyday (just a few times). Probably 1000 highway miles around 78mph.

    Total miles 3500

    Avg 441Kwh
     
  8. wdolson

    wdolson Supporting Member

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    A trick I learned in Chemistry class many moons ago. It's helped me figure out the math on quite a few things over the years.

    I believe wk057 found the 100 KWh pack had 102 KWh of actual capacity, but of course, not all of it is usable because of the anti-bricking reserve. The 100 KWh pack is the first large pack Tesla has made that has at least the advertised capacity. The 85 pack was closer to 80 and the 90 closer to 85.
     
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  9. rhumbliner

    rhumbliner Member

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  10. verygreen

    verygreen Curious member

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    I think you misread him (or I misunderstood you).
    What he says is that THE CAR assumes 342Wh/mi when calculating remaining miles left (in rated miles). So it basically gets the remaining battery charge (in watts) and divides that by 342. (conversely if you multiply remaining miles by 342, you'd arrive at remaining charge +-342).
    For non-perfromance Model X 100D rated miles are 324Wh/mi.

    But since everybody's driving style and conditions are different (And 22" wheels certainly have an impact on usage), knowing YOUR rated miles would allow you to calculate remaining range yourself were you so inclined (or can use the NAV's calculations that do use some historical data).
     
  11. rhumbliner

    rhumbliner Member

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    I did not see that @wk057 posted the figure used for a non-performance MX. I don't know where the 324 Wh/mi came from. His discussion was pertinent to determining the true battery capacity, not determining your range on any given day. As you correctly pointed out, it depends upon a lot of different factors. Tesla's nav system takes into account distance and elevation but not wind or temperature and EVTripPlanner tries to adjust for temperature and speed.
     
  12. verygreen

    verygreen Curious member

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    When he made that post, there was no MX 100D "in the wild". Now there is so we know the rated number - the car knows it internally so you can query it.
     
  13. carteriii

    carteriii Member

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    @ALLMYNE As you read more of these forums and gain more first-hand experience, you'll find that your wh/mile will change based on a LOT of different factors, including/especially the temperature and speed you drive (cold & fast/freeway driving => much higher energy usage). I mention this only so you don't accidentally assume too much while it's new to you. Be conservative if your estimates until you get a better feel for this yourself.
     

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