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How is range calculated?

Discussion in 'Model S: Battery & Charging' started by kirkbauer, Jun 12, 2015.

  1. kirkbauer

    kirkbauer Member

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    Atlanta, GA
    I feel like this must be a FAQ but I couldn't find it anywhere. I don't own the car yet so perhaps this would be obvious if I did.

    So when the car tells you how much range you have, what assumptions does it make on the power consumption? Is it ideal range, or more realistic? Does it adapt to your driving style/energy consumption (either historical or current)?
     
  2. SabrToothSqrl

    SabrToothSqrl Active Member

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    the car (at least mine, a 2wd 85) assumes 300 wH/mile (Watt Hours) per mile.

    you can tell it to display this, which is the EPA rated milage, or you display the other one. lol, I i think the other option is ideal, although I consider rated ideal.

    If you drive 'normally' with traffic, it's not that hard to hit 300 wH/mile. if you drive like me you'll be around 320 or 350. (heavy foot off the line).

    Cold will also impact range.

    With the 85, I've only ever been concerned ONE time driving. and It was mostly my fault for driving 230 miles from one super charger to home, and skipping a charger along the way.
    I partially blame a Nissan GT-R I was pacing around Ocean City, MD. :)

    The car will tell you how much you've used over the last 5,15, 30 miles, and I've gotten up to almost 2,000 wH/mile when playing in the mountains of PA.

    In any case, my daily commute is under 40 miles, and I start each day with a 'full' charge.

    One of the things they don't really tell you on the site is that you'll start each day with a 90% charge. Not 100%. this keeps the battery happy and reduces wear on it.

    I've had no range issues, and LOVE my car SO much, I want another! (P85D next time).

    The thing you have to realize, that many who move to an electric car don't seem to fully appreciate, is that you start every day with a 'full tank'. You don't drive out of your way to the gas station whenever you want. You just go home to work to home to charge. Range isn't an issue when you wake up to a happy charged car :)
     
  3. Cyclone

    Cyclone Active Member

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    SabrToothSqrl got it right on all counts, but I want to elaborate that he is referring to the speedo display's rated range and the battery charging screens rated range. These are range remaining at your current battery level using 300 Wh/mi till empty. Now, the Energy App behaves differently. Rather than using a fixed usage value to estimate rated range, it will average out your past 5/15/30 miles (user selectable) of usage and give an estimated range using that average instead of 300 Wh/mi. Furthermore, if you use the Nav to set a destination, the Energy App's "Trip" display will then also take into account elevation changes and other factors to give an estimate of battery power upon arriving at your destination.
     
  4. kirkbauer

    kirkbauer Member

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    Great information, thanks for the replies everybody!
     
  5. DrumCoder

    DrumCoder Member

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    I've found that the "Rated Range" on my 70D is the equivalent of about 290 Wh/mi. I figured out the math and in order to get 240 miles out of 70kWh, I'd need to average 291 Wh/mi. 215 miles on 63kWh (a 90% charge on a 70D) is the equivalent of about 293 Wh/mi.

    If you look at the Energy tab, it will show you a "Projected Range" based on your average Wh/mi over the last 5/15/30 miles and the current amount of kWh in your battery. That's about the only adaptive stuff it does, but it doesn't reflect that on the speedometer I don't think.

    The math is pretty simple. kWh divided by distance will give you kWh/mi, so you'd move the decimal point three places to get the Wh/mi. Similarly, kWh divided by kWh/mi (move that decimal point three places from the Wh/mi shown) will give you the distance. So, my 70kWh battery at 320 Wh/mi (my current overall average) would only give me 218 miles on a full 100% charge, or 196 miles on a 90% charge.
     
  6. P85_DA

    P85_DA Member

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    I started displaying battery % vs rated miles and find i like that and using projected miles is easier for me to estimate..

    i read somewhere here on forum its % x 2.5 is miles u can drive.... and after using that for last 8k miles find that pretty accurate
     
  7. TexasEV

    TexasEV Active Member

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    The EPA has a test with different types of drive cycles which gives the "rated range", just as it does for city and highway miles/gallon for gasoline cars. And just as with gasoline cars, your mileage may vary. The other range option on the display is "ideal range". Ignore that one. We don't drive in an ideal world.
     

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