
Winter chills limit range of the Tesla Model S electric car - slantyyz
http://news.consumerreports.org/cars/2013/02/tesla-model-s-winter-chills-limit-the-electric-cars-range.html?EXTKEY=I72RSC0
======
potatolicious
Imagine if we listened to the unruly mob here and elsewhere that were calling
for the NYT/Broder's head on a stick.

I recall one very long-winded rant here on HN where a commenter described
Broder as having an axe to grind, a shyster, and concluded his comment with
"Fuck the NYT. Fuck Broder."

All of this, in the grand scheme of the automotive industry, are small
ripples. Tesla will survive this, and electric sales will proceed more or less
unimpeded.

The real takeaway here is _keeping your cool_ and turning off the "mob
outrage" circuit in your brain. The drummed up pitchfork-wielding mob was, in
the end, a more sobering spectacle than any electric car issue.

I must sound like a broken record by now. It seems every month some one-sided
account will splash onto HN's front page, stir up a hornet's nest of
indignation, resulting in long, angry rants and calls for heads to roll.
Inevitably a more balanced picture emerges - but the usual suspects will be
back the next time someone writes a blog post manipulating their outrage.

Whenever a blog post is so _utterly absurd and ridiculous_ that it _demands_
unfettered and unrestrained anger, there is a strong chance you're being
played.

~~~
vor_
I was surprised at the number of people casually accusing Broder of a
conspiracy. Usually, it's the big company representative who gets the vitriol
and the journalist is the underdog good guy, but for some reason, much of the
reaction was opposite from the expected.

~~~
homosaur
That's because Elon Musk is some sort of superhero genius to the many of the
types that lurk here. The Jason Calicanises of the world have all but declared
this guy automobile Jesus.

------
zeteo
>a high portion of freeway driving, which minimizes the opportunity for
regenerative braking, are the most adverse conditions for any electric vehicle

That's a pretty nasty meme and it seems to be spreading. No, people:
regenerative braking _mitigates_ the effects of braking on fuel efficiency! It
doesn't overcome or reverse them. The laws of physics say that driving on the
freeway with no braking is, and will always be, much better for fuel
efficiency, in any conceivable vehicle.

~~~
moultano
Are slower speeds more efficient overall though, such that driving off the
highway could make up for the energy lost to braking? With combustion engines
I had always read that speeds around ~55 are at the crossover point where
increasing wind resistance wins out over increasing engine efficiency, but I'm
wondering if the math works out differently for electric cars?

~~~
seanalltogether
The slowest speed in the highest gear will give you the most bang for your
buck. I'm not sure what kind of gearing the tesla has though since electric
motors are very different beasts to standard combustion engines.

~~~
moultano
<http://en.wikipedia.org/wiki/Tesla_Roadster#Transmission>

It's a fixed gear, so this is actually plausible.

------
redthrowaway
>I exited the freeway, hoping that the lower-speed rural road driving would
allow more regenerative braking and would extend the range.

This is two articles now where the authors, or technicians they're talking to,
seem to think the model S has found away around the laws of thermodynamics. It
has not. Regenerative breaking will not charge your battery any more than you
drained it getting up to that speed in the first place. In fact, by
definition, it will charge the battery _less_. So anyone who thinks the key to
getting more range out of an electric vehicle is to abandon smooth and steady
driving and find a way to slam on the brakes is in for a rude surprise.

~~~
MRSallee
In a car without regenerative braking, city driving will return worse gas
mileage than highway driving. In a car that does have regenerative braking,
city driving will often return higher mileage.

The regen braking isn't the sole source of efficiency gain -- aerodynamic
drag, gearing and engine optimizing are responsible for the "true" gains --
but regen braking makes it more possible to realize the "true" gains because
you're no longer throwing away all of the true gains on braking.

~~~
lutusp
> In a car without regenerative braking, city driving will return worse gas
> mileage than highway driving. In a car that does have regenerative braking,
> city driving will often return higher mileage.

 _The above statement is false_. Regenerative braking in the Tesla (which only
has regenerative braking on the rear wheels) only recovers about 20% of the
energy lost in stopping the car. Accelerating again requires 100% of the car's
final kinetic energy to be provided by the battery. Therefore city driving is
_always_ less efficient than driving at a steady speed unless you're planning
to drive at 90 miles per hour.

All regenerative braking can do is minimize the losses caused by stop-and-go
driving, it is never an improvement over driving at a steady speed at the same
average speed or, for that matter, most higher speeds.

I wish this myth would go away -- by way of some physics education.

> ... you're no longer throwing away all of the true gains on braking.

No, only 80% of them. Which means you would have to drive very fast to equal
the losses of stop-and-go driving.

~~~
cmsmith
I'm no expert on this, but your 20% number seemed pretty low:

According to this, the tesla regenerative braking is just as efficient as the
motor is at acceleration. Result: up to 64% of the original battery energy
returned to the battery.

[http://www.teslamotors.com/blog/magic-tesla-roadster-
regener...](http://www.teslamotors.com/blog/magic-tesla-roadster-regenerative-
braking)

And this page about the Volt suggests that the efficiency might get up to 70%
in some situations.

[http://www.designnews.com/document.asp?doc_id=235313&dfp...](http://www.designnews.com/document.asp?doc_id=235313&dfpPParams=aid_235313&dfpLayout=article)

This is confirmed by measurements which show pretty much all hybrid vehicles
get better mileage in city driving than in highway driving.

~~~
lutusp
> According to this, the tesla regenerative braking is just as efficient as
> the motor is at acceleration.

That's true but misleading. If the motor's combined electrical and mechanical
losses cause only 64% of the battery's energy to propel the car forward, then
by that reasoning, only 64% of the braking energy is made available for
charging.

Let's look at all the factors that influence the outcome:

1\. Both electrical and mechanical losses must be accounted for.

2\. The electrical loss creates a factor of 0.8, the mechanical loss also
create a factor of 0.8. Result 0.64.

3\. On the Tesla, only the rear wheels have regenerative braking, the front
wheels have disc brakes. Factor 0.5, so we are now at 0.32.

4\. During a stop, the car pitches forward onto the front wheels and unloads
the rear wheels, this needs to be taken into account. Factor 0.8 for a total
of 0.2: 26%.

So I stand corrected -- this analysis concludes that the regenerative braking
scheme recovers 26%, not 20%, of the original kinetic energy.

A literature search reveals that the best regenerative braking systems that
involve all four wheels and in which every effort is made to maximize
efficiency, can produce about a 40% energy recovery:

[http://www2.hesston.edu/physics/201112/regenerativeenergy_cw...](http://www2.hesston.edu/physics/201112/regenerativeenergy_cw/paper.html)

A quote: "Since regenerative brakes can only recover about 40% of the energy
we take the recoverable energy and multiply by .4 (Everett, Michael)."

The linked paper goes on to show that 40% is actually overly optimistic for
various practical reasons. But notwithstanding that, we can take the original
40% figure and apply it to the Tesla. By taking into account that only two of
four of the Tesla's wheels have regenerative braking, we arrive at a figure of
20%.

> And this page about the Volt suggests that the efficiency might get up to
> 70% in some situations.

No reputable source makes claims this high _for a full round trip from battery
stored energy to battery stored energy_ (the linked article doesn't try to do
this). Also, the linked chart reports energy recovered in a four-wheel test
and measured before being applied to the battery, not energy delivered to the
battery as stored energy.

> This is confirmed by measurements which show pretty much all hybrid vehicles
> get better mileage in city driving than in highway driving.

That's true, but that doesn't result from regenerative braking. It results
from lower average speeds and reduced wind and mechanical resistance.

Remember that regenerative braking _cannot possibly_ improve on driving at a
steady speed. That would violate some very basic physical principles.

~~~
Someone
_"3. On the Tesla, only the rear wheels have regenerative braking, the front
wheels have disc brakes. Factor 0.5, so we are now at 0.32."_

I would hope that the on board software wouldn't use those front brakes during
light deceleration. Anybody know more about this?

~~~
lutusp
> I would hope that the on board software wouldn't use those front brakes
> during light deceleration.

No, this isn't safe. A car that only allowed one set of wheels to brake would
in some cases spin around dangerously. Safe brakes must apply the same force
on all four (or more) wheels simultaneously.

Remember that the computer can't possibly know if the car is sliding across
black ice, a situation in which the application of even force is an absolute
requirement for a safe stop.

------
YZF
What's with the "regenerative brakes" thing? It seems people think that if you
use the brakes more frequently you'll get more range. The only thing
regenerative braking does is that you'll lose less energy than if you didn't
have it. It's still inefficient to slow down and speed up.

~~~
raverbashing
Yes, the only situation where it would increase your range is if you're going
downhill (for a long stretch) and you're keeping your speed constant using the
brakes

Not sure how Tesla does that (if it does 'engine braking')

And of course that's negated by the fact that you'll be going uphill in the
way back, using more energy

~~~
lutusp
> Not sure how Tesla does that (if it does 'engine braking')

Tesla uses the electric motors that normally propel the car by expending
battery energy, but "in reverse" to generate a small amount of power while
decelerating. It's better than nothing, but it's not as efficient as many
people seem to believe.

> And of course that's negated by the fact that you'll be going uphill in the
> way back, using more energy

Good example -- going downhill with your foot on the brake, recovers 20% of
the car's kinetic energy lost by descending the hill. Going uphill again
requires 100%$ of the required energy from the battery. So it's a net loss of
80% of the total energy represented by climbing and then descending the hill.

------
baddox
Reading all these reviews (and the occasional response from Musk), I'm
surprised by how _complicated_ the accounts seem to be. Just once, I want to
hear "the car predicted x miles remaining, and it turned out to have y miles
remaining." But instead, everything is complicated by multiple readouts
("rated" and "projected"?!), ambient temperature, inside temperature, rate of
speed, terrain, amount of regenerative breaking (by the way, it sounded like
this is another reviewer under the mistaken impression that regenerative
breaking yields a net positive on the battery, which is preposterous), etc.
The cynic in me is tempted to think that Tesla purposefully made the range
estimations complicated to make it difficult to say for sure whether the car
fell short of its estimated range.

~~~
waterlesscloud
Tesla could do themselves a big favor by simplifying the display of range
estimates. And improving their accuracy. It sounds like the kind of thing
where you have to always assume it's a lot less than is being displayed.

How does that help anyone, including Tesla?

------
lutusp
A quote: "As the range indicator sank to 20 remaining miles on the way to
work, I exited the freeway, hoping that the lower-speed rural road driving
_would allow more regenerative braking and would extend the range_."

Where is this stupid idea coming from? It's absolutely false -- regenerative
braking can only reduce losses caused by braking, it doesn't extend the range
of the car compared to driving at a steady speed. Don't expect to gain
anything by choosing stop-and-go driving over steady-speed driving -- it
doesn't work that way.

According to technical estimates, regenerative braking only recovers 20% of
the energy otherwise lost in reducing the car's speed, but gaining that speed
back requires ... wait for it -- 100% of the car's kinetic energy from the
battery. Regenerative braking is better than turning all the car's kinetic
energy into heat, but it has no advantage over maintaining a steady speed.

I wish this myth would go away, preferably by some education in physics.

~~~
raverbashing
But driving at a slower speed uses less energy, so it should (theoretically)
increase the range.

Of course, the energy consumed in 1h of cruise driving is less than 1h of
stop/go "at the same speeds" (YMMV of course)

~~~
lutusp
> But driving at a slower speed uses less energy, so it should (theoretically)
> increase the range.

My comment wasn't about low speeds, it was about stop-and-go driving. Driving
at a steady speed is much more efficient than braking and then accelerating
again.

------
armored_mammal
So it is possible to say something similar while maintaining journalistic
integrity. Surprise surprise.

This is journalism.

Broder's sloppy crap was not.

Note the real issue, not that Mr. NYT's exaggerations and lies were 'close
enough.'

This was never about defending Mr. Hyperbole, AKA Mr. Musk.

It was about a NYT reporter feeling free to take license because it
encapsulated the spirit of the truth or some other lukewarm embrace of poor
reporting.

------
vacri
_and a high portion of freeway driving, which minimizes the opportunity for
regenerative braking, are the most adverse conditions for any electric
vehicle._

Alright, what am I missing? People Who Should Know keep making this strange
claim that you get more energy from regenerative braking than not braking at
all. I don't understand - when you're braking, you're only reclaiming energy
you put there by accelerating in the first place.

I would have thought that freeway driving would be fairly ideal, since you're
at a steady speed and basically only need to overcome air and rolling
resistance, whereas if you're regularly using braking, you're also having to
reaccelerate, plus you're losing energy in the form of heat and possibly
sound.

I get the idea that adding regenerative brakes in the first place will
increase your range, but I don't see why your range would be shorter because
you don't get to brake. Am I missing something somewhere, or am I expecting
too high a knowledge of physics in my car reviewers?

------
vor_
Curious if there will be accusations that Consumer Reports is the latest to
fall to the bribery of the oil and automobile industries, since I was told
last time that the NYT was beholden to them because the NYT sells advertising
space, or something.

~~~
jacques_chester
In respectable newspapers there is a strict separation between the editorial
department and the classifieds and display advertising departments.

In fact, even in less respectable newspapers this is generally true. I worked
at a less respectable newspaper for several years; whenever I wandered into
the editorial area I was treated as being slightly below toenail clippings in
the order of creation.

It's best to think of a newspaper as a device that multiplexes two totally
independent feeds. One feed is ads and classifieds, the other is editorial
material.

Conspiracy theories to the contrary are just embarrassing. Really. Journalists
are tremendously and fiercely proud of themselves (to a fault). Suggesting to
a journalist at a serious newspaper that their writing is biased based on what
the display department did last week is going to get a mix of reactions from
laughter to a punch on the nose for uttering such inflammatory fighting words.

------
RexM
"I decided to risk taking one for the team to determine the Model S real-world
range when it's cold outside and you drive the car as you would any other car,
electric or not."

He explains this as his reasoning for not recharging his car... Regardless of
if it's cold outside, or if the car is powered by electricity, gas, or good
intentions, if the car is telling you that you're running dangerously low on
fuel, why would you not stop and refuel? I feel like stopping and refueling
would be the real-world scenario.

~~~
bryanlarsen
"Why would you not stop and refuel?" Because otherwise I would never have
bothered to read the article. As a potential Tesla owner in a cold climate, I
want to know these things. I want to know how the car will perform if I abuse
it in an emergency, without actually having to abuse it myself as a test.

------
senthilnayagam
"To be clear, cold temperatures, need for cabin heat, and a high portion of
freeway driving, which minimizes the opportunity for regenerative braking, are
the most adverse conditions for any electric vehicle."

usage of "regenerative braking" makes me doubt his tech credentials, not
braking is always more efficient than braking and storing that energy back
into the battery.

I strongly feel this is a proxy article to give a saving grace to New York
Times bungled review.

follow the <https://twitter.com/TeslaRoadTrip> to see how different owners are
driving their Tesla to prove New York times lied

------
Tekker
Living in New England, 45 degrees is not "chilly", it's (at this time of the
year) very nice. Will this car run at, say, 5 below? Cold, as a rule, is not
kind to batteries. Though the tests are enlightening, they show this car is
not destined for cold climates. And that's okay; cold + batteries != good, we
understand that.

That said, if we ever want EVs to "take over" the gas-powered engine industry,
there's a lot of work to do, and we're a far, far, far cry from running long-
range trucks on EV (granted, no one's talking about that now, but that's the
obvious ultimate conclusion).

------
seanp2k2
Why has no one made a practical diesel/electric hybrid car yet? This
technology has been around for /over a century/ (
[http://en.wikipedia.org/wiki/Diesel-
electric_transmission#Sh...](http://en.wikipedia.org/wiki/Diesel-
electric_transmission#Ships) )and I still have not seen a single
diesel/electric hybrid.

Along these same lines, diesel cars aren't popular in America even though they
get better mileage with less-refined fuel. I'm confident that if US auto mfgs
wanted to, they could throw enough money at changing the perception of diesel
as "dirty" in America to really help diesel take off. Why are we ignoring this
perfectly viable, proven, reliable, and ancient technology in favor of battery
packs which create tons of hazardous waste to produce and dispose of?!

~~~
stox
What I would like to see is a Turbine/electric hybrid. It would answer most of
the issues with running a turbine, and be able to burn a very wide range of
fuels.

~~~
lutusp
> What I would like to see is a Turbine/electric hybrid. It would answer most
> of the issues with running a turbine, and be able to burn a very wide range
> of fuels.

One reason this hasn't happened is that the goal is a fuel- and energy-
efficient car, and turbines aren't very fuel efficient compared to piston
engines, a popular misconception to the contrary.

------
jasonlingx
> As the range indicator sank to 20 remaining miles on the way to work, I
> exited the freeway, hoping that the lower-speed rural road driving would
> allow more regenerative braking and would extend the range. I got a little
> "credit" by coasting and hovering on the brake pedal, which was soon
> expended on the hills that followed.

Why do people actually think braking more would conserve energy?! I remember
this being referenced in the NYT article as well...

------
cedricd
What's the deal with this? "I exited the freeway, hoping that the lower-speed
rural road driving would allow more regenerative braking and would extend the
range. I got a little "credit" by coasting and hovering on the brake pedal"

Is there now a pervasive urban myth amongst electric car owners that you can
get free energy from the brakes? Or that you can extend the range in stop and
go driving? The NYT journalist did the same thing. That's just crazy.

------
ZeroGravitas
These electric car reviews are beginning to remind me of Window users
reviewing the Linux Desktop. Particularly this bit:

 _"I considered stopping in Milford, CT, for a quick "supercharge" as I had a
few days earlier, but changed my mind in the spirit of my experiment. I knew
the distance to my office was 55 miles at that point, so I decided to risk
taking one for the team to determine the Model S real-world range when it's
cold outside and you drive the car as you would any other car, electric or
not. Call me a gambler, but I kept cruising and crossed my fingers."_

He intentionally didn't refuel when he had the chance, but believes this is
the same as how he drives a non-electric car. That's insane. But he's so used
to the gasoline paradigm (where you can currently refuel in many more places)
that he doesn't even realise how crazy he is.

As I said, it's not much different from the person reviewing Linux who (in a
Windows mindset) goes looking for downloads of LibreOffice on their website
and ends up trying and failing to compile it from source or some other crazy
thing that no actual Linux user would do.

------
droithomme
Well, obviously the only reasonable explanation here must be that Consumer
Reports is in the pocket of big oil, right, right?

------
cedricd
Interestingly photographers have known about the effects of cold on li-ion
batteries for a long time. It's common to keep your batteries close to your
body to keep them warm when shooting on cold days.

------
kjeldsendk
Another guy that doesn't charge his mobile phone to more than 90%. Excellent!
And even though he didn't "rtfm" the car made it. At least this guy is a
journalist.

------
niggler
Yet another apples to oranges comparison:

Broder: "the temperature was still in the 30s"

Consumer Reports: "45° F"

~~~
Yver
You're the one comparing them.

------
OGinparadise
Consumer Reports are in the pockets of major oil companies. They gave good
ratings to cars using gasoline, so they clearly have a bias toward others.

They drove the car on the cold on purpose instead of waiting for summer to
come.

Tesla has data showing that consumer reports was lying, the temperature wasn't
45 degrees but 44 at least for a three minute period. Would you trust a liar?

</end musk defender at any cost bot> Hacker News is now Elon Musk News.

