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Am I the only one who thinks range should be advertised as M per kWh?

Discussion in 'Model S: Battery & Charging' started by AMPd, Feb 12, 2013.

  1. AMPd

    AMPd Active Member

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    Or miles per 10 kilowatts, instead of advertising the range of the battery
    that way you won't have people complaining when they don't get 300 miles while driving 75 mph

    You don't see too many ice car manufacturers advertise tank range, (some mentioned the tank range) but its usually MPG and when people get lower mpg than advertised they don't really notice it because of how quick and easy it is to fill up at a gas station

    I don't know I'm just a bit annoyed at some people's stupidity when it comes to electric cars (I'm looking at you NYT reporter)
     
  2. Puyallup Bill

    Puyallup Bill Member

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    Well, I probably have to disagree a bit. Miles per kWh is fine for folks like us who have some awareness of EVs, but I don't think it means much for the average, not necessarily stupid, automobile buyer. When I am questioned about the LEAF, the top three questions are: 1) How far can you go on a charge? 2) How long does it take to charge? 3) How do you charge it?

    I suspect if you advertise an EV with a 25 kWh battery and 5 miles per kWh, Joe is going to immediately expect 125 miles range, but we know that is probably quite optimistic. Because conditions vary, and because no manufacturer is going to allow users to get the last kWh out of the battery.
     
  3. AMPd

    AMPd Active Member

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    I suppose
    I was just thinking at least now the burden will be on the driver to achieve the necessary efficiency to get the advertised range and with the huge energy monitor it shouldn't be too hard
    Its not hard now, but people still seem to forget the laws of physics when it comes to electric cars

    Although even now its still up to the driver to achieve the efficiency needed, but I guess they don't pay attention or don't do the math and are left with fever than advertised miles
     
  4. smorgasbord

    smorgasbord Active Member

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    #4 smorgasbord, Feb 12, 2013
    Last edited: Feb 12, 2013
    That's optimistic because you don't get 5 miles per kWh. You get about 2.5 miles/kWh (according to the EPA). So the 85kWh battery gets you 213 miles.

    Works pretty well, actually.

    EDIT: That said, Range is the important number when driving, as that tells you how far you can go before you need to charge. the MpkWh thing is just to compare car efficiencies, much like MPG is to compare ICE efficiencies. But, you don't use MPG when driving, you use your gas gauge to see how far you can go before filling the tank.

    Telsa just needs to drop the 55MPH Range thing. As I posted in another thread, it's like Stereo amperage ratings in the 1970s. No-one uses peak to peak instantaneous anymore - it's all RMS sustained. Same should be true for Range. Use EPA for comparison and a baseline "Ideal" miles so you don't have to talk in percentages, but use Estimated based on previous driving.

    Actually, Estimated should be based on where you've told your GPS you're going. Then it can figure out whether it's freeway or side roads or city and adjust accordingly. Since what you've been driving on may not be what you will be driving on.
     
  5. EarlyAdopter

    EarlyAdopter Active Member

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    I'm with the OP on this. The measure used to gauge efficiency should go down with inefficient driving, not up.
     
  6. MikeC

    MikeC Active Member

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    And elevation, traffic, and temperature. That will be awesome.
     
  7. Bipo

    Bipo Member

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    Well... Here in Europe we use to measure fuel consumption in litres per 100 km, so the lower the better. Hence, I'd rather use kwh per 100 km, than miles (or km) per kWh.
     
  8. ElSupreme

    ElSupreme Model S 03182

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    I responded to this same question in another thread. In summary Energy/Distance is much better to use that Distance/Energy.

    I like what Tesla has done.

     
  9. mknox

    mknox Well-Known Member

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    ...and I disagreed in that other thread :smile:

    I very much prefer Distance/Energy. I can relate to and visualize a gallon of gas or kWh of electricity. Knowing how far that unit of energy will take me makes perfect sense in my brain. Here in Canada they express consumption as l/100 km which seems awkward to me. I rarely ever drive exactly 100 km and knowing how many litres that driving precisely 100 km will cost me is of little value.

    To each his/her own, I guess!
     
  10. mnx

    mnx 2013 P85

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    Yup, you've expressed your disdain for the metric system in several posts. If I were born in the US or as old as you, then I'd probably agree. :)

     
  11. Ardie

    Ardie Member

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    My ActiveE lists energy used as, say 3.3 kWh per mile. Fine for my own evil calculations.

    But when I talk to other non-electified folk, I tell them that:
    a) it goes about 100 miles on a charge, and
    b) it takes about 4 hours to go from empty to full, and
    c) it costs me about $3.50 in electricity for that 100 miles.

    The hundred miles for less than what they pay for a gallon of gas usually grabs 'em.

    -- Ardie
    "So, how many miles per gallon does your car get?"
     
  12. mknox

    mknox Well-Known Member

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    Aside from the fact that the state forced me to learn and use a new language against my will, I still think km/litre makes more sense than the arbitrary litres/100 km measurement that the SI system utilizes. Why 100 km, why not 1000 km and call it litres/Megameters? We buy fuel in units of litres, and knowing how far the litre of gas will take us is what's relevant.

    Oh, and I am old and I was born in the US :smile:
     
  13. mnx

    mnx 2013 P85

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    Yeah I guessed you were old, but I remembered you were born on the US from some of your posts. :)

    100km was chosen obviously because it gave nice easy #'s... Perhaps mL/km would have made more sense???

    I dunno, I don't care how far a litre or gallon of gas will take me. I do however like to compare the fuel economy ratings between cars, and L/100km is better suited to that.
     
  14. ElSupreme

    ElSupreme Model S 03182

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    Heh. The only thing different between you is a 'ko'. Just thought that was a bit weird.
     
  15. Bipo

    Bipo Member

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    In Italy and Japan is usual to tell comsuption in kilometres per litre... Anyway I think litres per 100 km is easier to do numbers: 300 km trip at 8 L/100km equals 24 litres.
     
  16. mknox

    mknox Well-Known Member

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    Must be the way my brain works, 'cause it is exactly the opposite for me. The litre or gallon of fuel (or the kWh of electricity) is the commodity... I can visualize it... I know how much it costs. The variable between cars is how far that much fuel will take me. I know that 30 MPG is better than 20 MPG since that unit of energy will take me 10 miles further. Pretty easy comparison.

    Sure, L/100 km can be used as a comparator, but it just seems arbitrary with no way to sense what it means in the real world. Neither exactly 100 km nor the odd number of litres of fuel are something that I can easily relate to.

    Fortunately, I can do math and whatever the method, I'll just re-work it into my preferred method (in fact, I use an iPhone database app to log and do exactly that when I fill my car up each time).
     
  17. tezco

    tezco Sig P85

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    #17 tezco, Feb 13, 2013
    Last edited: Feb 13, 2013
    Automobile owners are so used to mpg, it doesn't make sense to me to change to energy/distance measurements now. EPA doesn't go the Tesla route either.

    Manufacturer with the largest sales to date (Nissan Leaf) also uses miles/kWh. Tesla could easily make this a user selectable choice.

    As a driver in a colder climate, I also like the Leaf's instantaneous display of your climate system's energy use. When it hits 4,000 watts I know that my real range is much less than what is indicated by what we like to call the GOM (the Leaf "Guess-O-Meter").
     
  18. brianman

    brianman Burrito Founder

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    I prefer no scale factors at all: L/m.

    Random opinion.
     
  19. dsm363

    dsm363 Roadster + Sig Model S

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    For comparing costs, gallons/100 miles or kWh/100miles makes it easier. If you ask someone the difference in cost to drive 100 miles comparing a 20 mpg car and a 50 mpg car, they'll break out a calculator. Do that same comparison with 5 gallons/100 miles and 2 gallons/100 miles then the math is easier to do at a glance (to me at least).
     
  20. GSP

    GSP Member

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    EPA now has US Gal/100 mi ratings, in addition to the old mpg ratings, for exactly this reason. This is not an SI vs English unit trade off, it is how to understand the cost of 1 mpg better. An increase of 1 mpg is extremely large for a 5 mpg bus, but trivial for a 50 mpg Prius. The math is much more intuitive with gal/100 mi ratings.

    GSP
     

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