

Tesla vs NY Times: A deeper look at the data - dsberkholz
http://redmonk.com/dberkholz/2013/02/14/tesla-vs-ny-times-a-deeper-look-at-the-data/

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bstar77
Back when I owned one of the original Honda Insights, it became very obvious
that I would need to adjust my driving habits to fully take advantage of the
car's enormous driving range.

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.

~~~
Domenic_S
> 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>

~~~
bstar77
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.

~~~
Domenic_S
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.

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cryptoz
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.

~~~
freyr
"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?

~~~
loeg
> 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.

~~~
freyr
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.

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rgovostes
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.

~~~
dsberkholz
> 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?

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ccarnino
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.

~~~
freyr
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.

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msrpotus
Anyone know if that's typical for batteries in cold weather or is Tesla's
exceptionally bad?

~~~
potatolicious
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.

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doe88
That's why it's called an _estimation_.

~~~
arrrg
Shouldn’t the estimation be conservative, not generous? Especially in this
case?

~~~
freyr
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.

~~~
LnxPrgr3
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.

