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EPA range?

Discussion in 'Model S' started by Yggdrasill, Apr 18, 2012.

  1. Yggdrasill

    Yggdrasill Active Member

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    Can anyone explain how the EPA testing is done, and what the probable outcome of the EPA testing will be?

    I keep hearing about how the EPA has toughened up it's testing, and there's something about multiplying with 0.7.

    Have the Nissan Leaf, Mitsubishi iMiev been tested using the new test protocol?
    Was the Roadster tested using the new protocol?

    Googling it doesn't seem to be helping. I can't quite make sense of it.

    Basically, what I'm wondering is how much discrepancy can one expect between the EPA value and the 55 mph-value? And how will the Model S range compare to the other electric cars on the market?
     
  2. AnOutsider

    AnOutsider S532 # XS27

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    I have no in-depth details of the new process, but yes, the LEAF was tested under the new process and they got 70 miles vs 100 quoted by Nissan. The Fisker Karma got 35 vs the quoted 50. So if Tesla gets about the same, we'd probably see 270, 161 and 112 miles of EPA range for the various packs (which, at its worst, is still better than any other EV on the market). Maybe they'll test with the Aero wheels and we'll only lose 25% :wink:

    The Roadster was on the old test as far as I know.
     
  3. Yggdrasill

    Yggdrasill Active Member

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    #3 Yggdrasill, Apr 18, 2012
    Last edited: Apr 18, 2012
    When it comes to those ratios, I doubt Nissan estimated the 100 mile range based on a constant 55 mph figure. Or did they?

    If they estimated 100 miles based on a constant 35 mph, the EPA range disparity when it comes to the Model S could be much smaller. I'm thinking this depends entirely on how the EPA testing is done, and how nissan did their testing.
     
  4. Doug_G

    Doug_G Lead Moderator

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    I doubt it would go down as much as that. If you applied that math to the Roadster, it would go from 240 miles - which really can do 240 miles at 55 mph - to 168 miles. I gotta say it's better than that in real world driving (unless you like standing on the accelerator...)
     
  5. Thumper

    Thumper Member

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  6. smorgasbord

    smorgasbord Active Member

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    With Roadster I figure 200 miles is the real-world maximum range. I would never plan for more than that, although more is do-able (I think my personal max is 205 with about 19 miles claimed to be remaining). Anyway, 200/245 is about an 18% hit. If the same hit applies to Model S, then the 300 mile, 85kWh Model S can go 245 miles.

    Of course, not knowing the the EPA has in mind, it's hard to say what Model S's official EPA rating will be. Both in terms of range and MPGe.
     
  7. AnOutsider

    AnOutsider S532 # XS27

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    I just applied the .7 that the other companies seemed to have gotten to 300, 230 and 160 to get those numbers, though my math was off on the 300m pack and it should have been 210. If the performance is as fun as I think it will be, I'll probably only realize about 200 real world anyway ;)

    I'm hoping smorgasbord's guess of 18% is closer to the truth.
     
  8. dhrivnak

    dhrivnak Active Member

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    I agree that 200 miles is the maximum useful range. While one can go farther IF the road is flat AND there is no head wind AND no rain AND no HVAC and you don't speed.
     
  9. Andrew Wolfe

    Andrew Wolfe Roadster 472 - S 440

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    The Leaf got 73! Otherwise - I wouldn't have made it home Monday night :mad: I think the original 100 mile number from Nissan was at 50Mph - it was not supposed to reflect highway driving.
     
  10. Doug_G

    Doug_G Lead Moderator

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    I've certainly done more than 200 miles on a single charge, but it's a fair statement that 200 is the usable range unless you're being really careful.
     
  11. stopcrazypp

    stopcrazypp Well-Known Member

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    #11 stopcrazypp, Apr 18, 2012
    Last edited: Apr 19, 2012
    I'll try my best to explain EPA testing. First thing you should understand is that the EPA doesn't actually do the testing. Rather, the manufacturer does the testing using established EPA procedures and reports the numbers to the EPA. The EPA only does a limited amount random testing to ensure manufacturers don't cheat.

    The basic procedure is to strap a car to a dynamometer (aka dyno) and run the car through a couple of standard cycles to get the efficiency numbers. Here's a video of a Roadster doing the testing:
    http://www.youtube.com/watch?v=K6uiAI8k5yk

    You can see all the EPA drive cycles here:
    http://www.epa.gov/nvfel/testing/dynamometer.htm

    Before 2008, EPA 2-cycle test was used. There were only two cycles used to test the car (at 75F / 75 degrees Fahrenheit):
    1) The Federal Test Procedure(FTP) or EPA-75 is used for the "city" mpg number. The FTP uses the Urban Dynamometer Driving Schedule (UDDS) or LA4 or "the city test". The FTP is basically UDDS followed by the first 505 seconds of the UDDS.
    2) The Highway Fuel Economy Driving Schedule (HWFET) is used for the "highway" mpg number.

    After 2008, EPA 5-cycle test was used. 3 new cycles were introduced in addition to the previous 2-cycles:
    1) US06 (part of the "Supplemental FTP") which is basically an aggressive mixed driving cycle (more acceleration than the normal city cycle and higher top speed than the highway cycle).
    2) SC03 (also part of the "Supplemental FTP") which is basically the air conditioner/hot weather version of the first 596 seconds of the UDDS done at 95F.
    3) Cold FTP is the basically the heater/cold weather version of the FTP done at 20F.
    The 5-cycle test is supposed to be pretty close to real world mpg numbers (and in general it is really close).
    http://www.greenercars.org/guide_epameas.htm

    70% or 0.7 Multiplier

    All new cars after 2008 have MPG sticker numbers that reflect the 5-cycle test.
    However, not every car manufacturer could do the 5-cycle test in time (nor did it make much sense to retest all the older unchanged models). This is where the 70% or 0.7 multiplier comes in. The EPA allowed automakers to use the previous results from the 2-cycle test if they multiplied the results by a minimum of 0.7 (some cars used higher multipliers, like 0.76; I'll show an example later). Where the 70% came from is that in general, the 5-cycle mpg numbers turned out to be on average about 70% of the previous 2-cycle numbers.

    The 2-cycle numbers without the multiplier were called unadjusted fuel economy numbers. These are the same numbers used in the CAFE efficiency regulations.

    The 5-cycle numbers (either calculated using the multiplier or from actual testing) were called adjusted fuel economy numbers. The 5-cycle numbers using the multiplier were called derived five cycle, and the ones from actual testing were called vehicle-specific five-cycle. These are used for the mpg numbers on car stickers when you buy a new car.

    I'll discuss how these tests apply to BEVs and PHEVs (both their efficiency and range numbers) in another post.
     
  12. AnOutsider

    AnOutsider S532 # XS27

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    Thanks stopcrazy, super informational (posts like these need to go into a wiki or something)
     
  13. EVNow

    EVNow Active Member

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    Leaf's "100 miles" was the LA4 cycle (or UDDS in the above post). It wasn't a constant speed at all.

    BUT, Leaf's real LA4 cycle number is higher than 100 miles. That is why their combined city + highway number is about 100 miles. That is the one that got the 70% treatment to end up with 73 miles.

    Note that 70% is the max adjustment EPA does. Nissan was hoping for a smaller adjustment - but EPA went with the max adjustment.
     
  14. richkae

    richkae VIN587

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    Nissan could have chosen to do the 5-cycle test instead but did not - is that right?
     
  15. Dan5

    Dan5 Member

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    I think Tesla has some simulation for the Model S, so in theory, you could "guess" at the EPA adjusted based on the average of the simulations. I know they had it at the Model X event, I wish they would post it on their website though. My best guess is that the from my calcs is 280-300 miles/charge. The problem is the sim can't do the aggressive driving part, but you can do top speed.
     
  16. EV_QC

    EV_QC Member

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  17. stopcrazypp

    stopcrazypp Well-Known Member

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    Now for what the EPA numbers actually means for the Model S, other BEVs and PHEVs.

    For BEVs and PHEVs, the MPGe and kWh/100 mile efficiency numbers come from plug-to-wheel. This means the EPA actually measures the electricity taken from the socket, not just the electricity from the battery. Basically the procedure is to have a fully charged car, drive it in the EPA tests, then recharge the car to full again and measure the electricity used. You can see the details in this FOIA request done for the Leaf:
    http://www.mynissanleaf.com/viewtopic.php?f=4&t=2433

    What this means is you can't really figure out the range of the car directly from the efficiency numbers even if you know the battery capacity of the car (56kWh for the Roadster). You have to know the amount of electricity it takes to charge the car from the socket (about 60-70kWh for the Roadster).

    Another thing to know is that the new EPA stickers that show the range of BEVs didn't come out until the 2011 model year.

    New sticker (after 2011):
    EPA_Label_Tesla_Roadster-2_5_119mpge.jpg

    Old Sticker (before 2011):
    sticker-3.jpg

    So before the 2011-2012 time-frame, pretty much anything went in terms of the advertised range of EVs.
    Even today there is really no set requirement for what kind of cycle you use to advertise the range of an EV (kind of like how automakers can choose to use the highway mpg of a car in advertising). However, with the new car sticker actually saying the range explicitly, it becomes harder to use a different number and get away with it.

    Like EVNow mentioned, the 100 mile number advertised for the Leaf is from the LA4/UDDS cycle. After the sticker came out, everyone basically took the 73 mile number in the sticker (which represents the range in the combined cycle) as the official number. The combined cycle is basically 55% city and 45% highway.

    Anyways, from a previous post, the 73 mile number is from multiplying the test results from an EPA 2-cycle test by 70%. They used 76% for the Volt.
    I also show the different amount of combined range for the different test cycles in that post.

    One thing you should notice is that the EPA 2-cycle number for the Roadster is actually 245 miles. But remember how I said stickers for cars that came after 2008 reflected EPA 5-cycle test? Well, apparently that doesn't apply to the Roadster's range number, which still from the 2-cycle test. However, it does appear the 30 kWh/100miles number is from the 5 cycle test (245 miles * 70% = 172 miles, which matches well with the number range number I came up with working from the kWh/100mi number). I suppose this anomaly is from the fact that the Roadster came out before the new stickers came out and during the transitional period between the 2-cycle and 5-cycle tests.

    Now on to the 55mph range. The 55mph came up from the following graph for the Roadster:
    [​IMG]
    http://www.teslamotors.com/blog/roadster-efficiency-and-range

    Notice that at 55mph, the range for the Roadster is basically 245 miles. This is basically exactly the same as the EPA 2-cycle range. So basically you can expect the 2-cycle range to be the same as the range when traveling at a steady 55mph.
     
  18. brianman

    brianman Burrito Founder

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    Thanks for the detailed info, stopcrazypp.

    Clarification: If manufacturers decide to (re)test with 5-cycle, can they choose which number to report to the EPA (actual result, multiplier result) or must they report both?
     
  19. Yggdrasill

    Yggdrasill Active Member

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    Thak you stopcrazypp, that's very informative. Now, is the Model S going to be tested according to EPA5, or is it going to be tested according to EPA2 and adjusted? I assume it's going to be tested according to the EPA5, so the 0.7 factor never actually enters the picture.
     
  20. stopcrazypp

    stopcrazypp Well-Known Member

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    #20 stopcrazypp, Apr 19, 2012
    Last edited: Apr 19, 2012
    Actually a manufacturer would report all their detailed test results and the city and highway is figured out from those test results using an EPA formula (for 2-cycle it was simply those two tests directly, for 5-cycle they factor in the extra 3 cycles).

    So basically if you report your 5-cycle results, then you necessarily already reported your 2-cycle results, since the 5-cycles are inclusive of the original 2-cycles.

    As for which number to use on the sticker, I don't have a direct source, but I assume if the EPA received the 5-cycle numbers already, they would use it, since it would be more accurate than the multiplier (which is just an estimate).

    Starting in the 2012, all car makers have to run the cars through the actual 5-cycle test (no more derived numbers from 2-cycles).
    http://www.caranddriver.com/features/the-truth-about-epa-city-highway-mpg-estimates-measuring-fuel-economy-page-2
     

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