Tesla vs NY Times: A deeper look at the data(redmonk.com)
redmonk.com
Tesla vs NY Times: A deeper look at the data
http://redmonk.com/dberkholz/2013/02/14/tesla-vs-ny-times-a-deeper-look-at-the-data/
6 comments
> my current kia rio ... nearly 50mpg
I have to ask about this. The highest EPA estimates (which are notoriously generous) for the 2013 Rio are 37 MPG [1].
[1] http://www.fueleconomy.gov/feg/bymodel/2013_Kia_Rio.shtml
I have to ask about this. The highest EPA estimates (which are notoriously generous) for the 2013 Rio are 37 MPG [1].
[1] http://www.fueleconomy.gov/feg/bymodel/2013_Kia_Rio.shtml
You are correct, and I appreciate you bringing that up. I should have mentioned that I'm averaging around 45mpg and peaking at 50mpg. I don't expect everyone to drive this efficiently, I just happen to enjoy it. But even if I'm a bit more aggressive behind the wheel and loose 10 mpg, I believe my argument is still valid.
That's cool to know -- I guess the Rio can be hypermiled more efficiently than some others. My last car was a BMW 128, and for the life of me I can't beat EPA estimates. I drive a Prius now though, and consistently beat EPA estimates -- even with mostly highway miles.
With a more conservative driving style, it's quite doable to get much better range than those estimates.
It's quite fun, actually!
It's quite fun, actually!
Agreed. My wife's hybrid is rated at 35mpg, but it regularly gets more than 40mpg, sometimes as much as 48mpg.
Of course, if you get really creative... https://secure.drivers.lexus.com/lexusdrivers/magazine/artic...
Of course, if you get really creative... https://secure.drivers.lexus.com/lexusdrivers/magazine/artic...
This isn't a deeper look. It's a shallower look. Didn't Musk say that the estimated range is dependent on speed, and that Broder sped illegally fast for part of the trip? There are other factors, as well.
There may well be something to say about Tesla's estimations being off, but this isn't it.
There may well be something to say about Tesla's estimations being off, but this isn't it.
"Didn't Musk say that the estimated range is dependent on speed"
Did he? Because from this figure, it appears the estimated range is NOT dependent on speed (as, of course, it should be). Notice that the lines are extremely linear, with identical slopes throughout.
If he sped for part of the trip, why don't we see steeper slopes during those times?
So Broder "sped illegally fast." What does this even mean? The speed limit is 55 mph on most highways, but nobody goes at that speed. Can the Tesla range estimator not acknowledge speeds about 55 mpg?
Did he? Because from this figure, it appears the estimated range is NOT dependent on speed (as, of course, it should be). Notice that the lines are extremely linear, with identical slopes throughout.
If he sped for part of the trip, why don't we see steeper slopes during those times?
So Broder "sped illegally fast." What does this even mean? The speed limit is 55 mph on most highways, but nobody goes at that speed. Can the Tesla range estimator not acknowledge speeds about 55 mpg?
> The speed limit is 55 mph on most highways
Really? In this part of the country (pacific northwest) the speed limit on interstates is 60 mph in the city and 70 mph in the country.
Really? In this part of the country (pacific northwest) the speed limit on interstates is 60 mph in the city and 70 mph in the country.
You're right. It looks like 65-75 is common throughout the country. Guess I haven't looked at a posted speed limit in a while.
What the article is explaining can be summarized in this chart: http://i.imgur.com/mNcGdfS.png
But I think this is incorrect:
> In nearly every case, the Tesla gets about 20% fewer miles out of each charge than it estimated.
Musk and Broder 'agree' that the vehicle's actual range was greater than it estimated. Musk's wrote,
> Then he bizarrely states that the screen showed “Est. remaining range: 32 miles” and the car traveled “51 miles," contradicting his own statement... The car actually did an admirable job exceeding its projected range.
As an aside, please disable Tynt on your blog.
But I think this is incorrect:
> In nearly every case, the Tesla gets about 20% fewer miles out of each charge than it estimated.
Musk and Broder 'agree' that the vehicle's actual range was greater than it estimated. Musk's wrote,
> Then he bizarrely states that the screen showed “Est. remaining range: 32 miles” and the car traveled “51 miles," contradicting his own statement... The car actually did an admirable job exceeding its projected range.
As an aside, please disable Tynt on your blog.
> What the article is explaining can be summarized in this chart: http://i.imgur.com/mNcGdfS.png
Precisely, the slope indicates the same thing. Unfortunately the vast majority of a general audience has forgotten what a slope is, so rather than confuse them, I explained it differently.
> Musk and Broder 'agree' that the vehicle's actual range was greater than it estimated.
Isn't that explained by the reserve power noted in Musk's blog?
Precisely, the slope indicates the same thing. Unfortunately the vast majority of a general audience has forgotten what a slope is, so rather than confuse them, I explained it differently.
> Musk and Broder 'agree' that the vehicle's actual range was greater than it estimated.
Isn't that explained by the reserve power noted in Musk's blog?
While the term estimation is by definition not exact, I challenge anyone to find a car on sale that has 100% accurate estimation. It's just not possible.
The point, imho, is that the press is always trying to find a story also where there isn't. Sad for them, this time there's the hard data to support Tesla's facts.
The point, imho, is that the press is always trying to find a story also where there isn't. Sad for them, this time there's the hard data to support Tesla's facts.
Nobody's claiming 100% accurate estimation is the standard. But a consistent 20% error is REALLY bad, if the engineers are trying to design an accurate estimator.
Anyone know if that's typical for batteries in cold weather or is Tesla's exceptionally bad?
Not all batteries - but lithium batteries in general are known for greatly reduced performance in the cold. Take your camera out in the winter some time and you'll find that it'll drain several times faster than normal.
I read a recent interview with a well-known landscape photographer who shoots in the Arctic - he carries a whole bandolier of batteries, kept close to his chest at all times to keep them warm. Apparently in the extreme Arctic cold the batteries are reduced to literally a few dozen shots before dying.
I read a recent interview with a well-known landscape photographer who shoots in the Arctic - he carries a whole bandolier of batteries, kept close to his chest at all times to keep them warm. Apparently in the extreme Arctic cold the batteries are reduced to literally a few dozen shots before dying.
That's why it's called an estimation.
Shouldn’t the estimation be conservative, not generous? Especially in this case?
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It's possible that the estimation is accurate/generous when there is plenty of charge left, and conservative when there is little charge left. This would explain why the car didn't actually die when the range estimate hit zero.
They may make the estimate conservative when there is little charge left so people are more apt to charge up.
They may make the estimate conservative when there is little charge left so people are more apt to charge up.
For what it's worth, my car's fuel gauge appears to do exactly this—no change from full for the first 60-100 miles, and about 2.5 gallons left on "empty." The first quarter tank lasts a good deal longer than the third, at least according to the gauge.
You'd think you wouldn't want to do this with a range estimation because the error's more obvious, but I'm also sure they don't want to sandbag its estimate from a full charge because people will be wondering why they're not seeing the advertised range. I'm sure they do want the car to be able to keep going a little past empty, though, and those spare miles have to come from somewhere.
You'd think you wouldn't want to do this with a range estimation because the error's more obvious, but I'm also sure they don't want to sandbag its estimate from a full charge because people will be wondering why they're not seeing the advertised range. I'm sure they do want the car to be able to keep going a little past empty, though, and those spare miles have to come from somewhere.
If I drove like a typical New Jersey-ian then my range would have been somewhere around 450 miles. With some adjustments (namely going around 65mph at most), I could regularly attain 700+ range. This is an adjustment many people absolutely refuse to make. Once I really learned how to get the most out of my car the milage numbers were unbelievable. When I sold the car my lifetime milage was 68 mpg over 130,000 miles (in nj climate).
I can see why Musk is so frustrated... he gets a reviewer that has no interest whatsoever in understanding the vehicle's prime operating conditions and instead is driving the car like a Hertz rental. When going on a long range trip, it should be obvious that you need to drive conservatively. Use the car's incredible performance for shorter trips so that you are not at risk.
I have no problems with these limitations, and I think they are acceptable. I was quite impressed that the range numbers for Tesla were over 500 miles... my current kia rio can't touch that despite getting nearly 50mpg. I have a feeling the media is never going to "get" electric cars because they don't get conservation.