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Winter chills limit range of the Tesla Model S electric car (consumerreports.org)
85 points by slantyyz 741 days ago | comments



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.

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I'm getting kind of tired of Elon Musk. Last month his crusade was reaming Boeing for their 787 battery problems. This month, someone wrote a bad review of his car (which turned out to be largely factual). Both times, he's on Twitter to talk about himself to anyone who will listen (which is a lot of people, for some reason).

I'm getting a tub of popcorn so I can be adequately prepared for his next crusade. I'm sure that this time it will paint him in a positive light...

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I don't think 'largely factual' is largely factual. The difference between this review and the NYT one is night and day. Omissions, misrepresentation and tone matter - especially in journalism.

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The question here is whether or not you should be an expert to review a car: the author of the Times article did seem confused about some aspects of the car that would not be confusing to an experienced user. Making matters worse were the weather conditions that are extremely unforgiving to an electric car.

So while I wouldn't call it a perfect review, the points it made were relevant. You can't expect people to change cabin temperature settings to be uncomfortable, drive 45mph on the freeway, not drive when it's cold out, and to know the nuances of the car's range estimator. (If the range display says "0 miles", it's reasonable to assume that the battery is dead.)

Remember: the car mostly worked fine, which is a huge coup for electric cars. The article emphasizes the negatives, but the negatives are all things that can be fixed -- many with a simple software upgrade. So on that note, I don't think the review was particularly bad, and I certainly don't think the Times was compensated to make the car look bad, as Musk accuses.

(The article is also a good human factors and UI case study. When customer service and an electronic read-out disagree, one implicitly trusts the read-out more. It happens to airline pilots, too.)

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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.

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It was completely expected. Elon Musk is basically a cult figure for a lot of wannabe "entrepreneurs", so criticism of him or his company is taken very personally and responded to very harshly.

(lest you doubt this, go dig up some of the Boeing 787 threads and see what people were saying about him there -- the level of outright worship of him in the HN comments was more than a little bit scary)

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Elon Musk is idolized by many people here, to a great extent because of Tesla, and when they see Musk make accusations they fall in line. It's more Musk-worshipping than anti-NYT sentiment.

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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.

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I'm not surprised. Don't know if this happens on a global scale, but here in Romania there's a trend of journalists and other media people starting to abuse their power like Broder (supposedly?) did, so for me (not sure about others), a journalist having a strong opinion quickly triggers a bullshit bell.

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There is a psychological label which is useful here: "Naïve Realism"[0].

Basically, everybody assumes that they are correct and that all fair rational people would draw the same conclusions as them given the same information.

When that doesn't happen, it can't be because the person is wrong; their interlocutor must be wrong. If the interlocutor continues to deny that they're wrong, they must be intellectually or morally defective.

That's what's happening here: people are assuming that since Broder doesn't agree with them, he must be deliberately deceitful. You can search any Tesla thread on the net and find the word "liar" or "lies".

Personally I think that Broder made some factual errors but that the big picture -- the battery ran flat in spite of the advice given -- is what matters. Maybe there's an RTFM problem here, maybe there isn't. I don't really care at this point because I happen to know that all new technologies ever have had embarrassing teething problems. When Musk's rockets blow up nobody seems to blame the journalists.

Musk overreacted because it's his baby and because surely anyone who disagrees with the wonderfulness of Tesla must, by the reasoning of Naïve Realism, be intellectually and morally defective.

Sprinkle in the way that humans love to form themselves into tribes, the "hostile media effect" and attitude polarisation and basically we're just hearing the same tunes that are hummed about Microsoft / Google / Obama / Bush / Rails / node.js / whatever.

[0] http://en.wikipedia.org/wiki/Na%C3%AFve_realism_(psychology)

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I was afraid to read yet another depressing shouting match about the Tesla/NYT debacle. Instead I find your comment, which I actually learned something valuable and insightful from.

Thank you for keeping HN great. I am in your debt.

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Here, let me ruin that fuzzy feeling for you with a filename meme:

ohstopityou.jpg

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If Broder made factual errors, then Musk was right to call him on it. It's really as simple as that. Stop fudging and hemming and hawing about psychology and take responsibility.

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The difference is that this article seems to be an accurate account of events whereas Broder's was at best sloppy journalism and more likely outright journalistic malpractice (an attempt to juice up a story to conform to a preconceived plot, little better than tabloid journalism).

No real-world fault of the Tesla justifies a reporter trying to bend the facts or going out of the way to manufacture a story. Broder clearly set out to drain the Tesla and get it on a tow truck, and he tried his damnedest to make that happen.

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> more likely outright journalistic malpractice

That is a heavy charge and the evidence just doesn't support throwing it around so haphazardly. Musk's jumping to that conclusion did this entire discussion a disservice.

Remember, Musk stated as fact that Broder "drove around in circles" for 0.6 miles trying to run the batteries out. His casual accusation on just that point alone makes it hard to take the rest of his analysis (of his company-provided data) without a grain of salt.

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The journalist that did the "original" review was not able to charge his car to 100% I bet that when he charges everything else he understands how it works. It's just not good enough to write a review based on wrong assumptions, especially if you already have a history of not "liking" ev's.

Imagine getting up in the morning, you check your phone, 25% ohh well i am not going to talk a lot to day so says my crystal ball. How many would do that? The NY journalist did his first drive in the Tesla S, and decided to base his drive on his experience, which was zero. Normal people, and other reviewers knew better, better charge to the max when i am actually testing the limits of the car. Not the limits of the reviewers knowledge.

If he had done as he should he would still have been able to write all the negative parts, the drop over night the limits because of the cold etc. it might have been a worthwhile article, like this one.

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Remember, Musk stated as fact that Broder "drove around in circles" for 0.6 miles trying to run the batteries out. His casual accusation on just that point alone makes it hard to take the rest of his analysis (of his company-provided data) without a grain of salt.

I'm posting these without commentary:

http://www.youtube.com/watch?v=-3fO_OHpyYw

http://twitter.com/TeslaRoadTrip/status/302958514245087233

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That backs up Broder completely! Look how inconspicious those chargers are. He said he couldn't find them because they were unlit at night, and this video lends that enormous credibility.

Broder: While Mr. Musk has accused me of doing this to drain the battery, I was in fact driving around the Milford service plaza on Interstate 95, in the dark, trying to find the unlighted and poorly marked Tesla Supercharger.

That someone found the charger faster than him is neither here nor there (it's irrelevant to the review he wrote). His story stands, and Musk's accusations look increasingly like complete libel.

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The video is of someone driving directly to it. The driver ignores the first right in favour of the second then takes an immediate left and right to where the the charger is.

The video makes it seem as if the charger is easy to find, but only if you know where it is already. I can't see how anyone who has never visited that station before would be able to make the same bee-line for the charger without circling the parking lot at least once.

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Since you posted those without commentary it's not clear what I'm supposed to take from that video of someone who was able to find the charger right away.

Again, accusing a journalist of maliciously fabricating anything is a huge deal. It is not something that is taken lightly, and if there's is an inkling of truth to it the folks at the NYT will deal with it and we will know about it.

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Since you posted those without commentary it's not clear what I'm supposed to take from that video of someone who was able to find the charger right away.

Well good, I posted them without commentary for that reason specifically. The goal was to allow you to guide your own thinking.

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They were incredibly hard to see and I can easily see myself driving in circles to find them.

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I wouldn't be surprised if Musk were sued for libel on this point. Were he a journalist, I suppose what he had done could be called journalistic malpractice.

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Broder's review was good journalism because it accurately portrayed the limitations of the Tesla S. Owners expecting to use it in ways similar to a hybrid or relying on Tesla's claims are likely to find themselves with a flatlined battery.

Journalism is not science.

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There was no mob. Just some angry posts on the internet. Please realize most people don't care about random internet comments, or take them seriously. Just something to argue about when we're focused on a story, it's no big deal.

The outrage seemed normal: Broder and Consumer Reports seem to think that leaving the car unplugged overnight is normal or should ever be done. Or they combine 2 days+1 overnight unplugged, and call that a day, knowing that the cold overnight storage sapped the battery.

So either they are acting stupid, or don't really know how to test battery-powered vehicles. Sure, you don't have to follow instructions, but if you don't, you will have problems, no matter what excuse you have about 'testing something'.

If Broder can't remember what happened, farting around for details, he should have been a professional and videotaped at intervals so he could check the facts.

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> "Just something to argue about when we're focused on a story, it's no big deal."

It's a big deal when it labels someone as a liar and a fraudster. It's a big deal when tens of thousands of knee-jerk readers are calling for someone's immediate firing. It's a big deal when someone's entire career is threatened by a bunch of people "not taking things seriously" on the internet.

Not taking things seriously is the problem. People in internet-mob-outrage-mode are flippant, quick to judge, and unreasoned, believing that just because it's a bunch of electrons that there are no consequences.

Hell, this situation in specific is lighter than it could be. On Reddit we've seen in the past vigilantes who turned internet-angry-comments into real-life threats against lives, we've even seen one case where someone committed suicide after being hounded by thousands of "random internet comments" that are (according to you) "no big deal" - the accusation was molestation, btw.

Accusations of fraud are Serious Business(tm) for a journalist - there are real consequences for real people when that is tossed around. Just because you don't take your own words seriously doesn't mean other people don't.

Yours is the worst kind of defense - akin to a bully saying "gosh, I was just horsin' around" when called on the awful things that have been coming out of his mouth.

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Sometimes you have to leave a Tesla unplugged overnight: on a ski trip, in a cold airport parking lot, when traveling and a charger is unavailable, etc.

In addition, the Tesla can lose range even when not parked overnight; it can simply be driven when it is very cold outside.

You can "instruct" people not to do these things, just like Steve Jobs "instructed" people not to hold their iPhones "like that", but you will be ignored.

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Where do you get that CR thinks "that leaving the car unplugged overnight is normal"? The linked-to text says:

> Anyhow, after a seven-hour overnight park (unplugged) and temperatures dropping below freezing, the "rated" range dropped to 65 miles. (Because we're tracking energy poured into the Tesla at our track, I resisted the temptation to top off at home, like a typical owner would.)

That reads to me like CR says that charging at night is the expected normal.

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The issue wasn't with the battery having less capacity when cold. The issue was with Broder's lies.

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Pretty much every "lie" Broder has been accused of making can easily be chalked up to the imperfect nature of human memory. His article has problems and certainly could have done with a bit more accuracy especially given that Musk/Tesla were known to be proactive about reviewers' truthfulness, but I am not comfortable characterizing any of it as a "lie". I'd love to hear any concrete example of him lying though.

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He gave precise numbers that were incorrect, often by a significant margin. He claimed these were from his notes.

Rather than an error of memory, I think it's far, far more likely he just made them up to create an illusion of accuracy that he simply did not do the work to record.

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You're talking about how long he charged for?

You're prepared to take Musk's interpretation of his logs (which we know were wrong about whether the car would move or not - the flat bed operator corroborates Broder) over Broders notes.

I'm familiar enough with logs telling you things different to what you expected to not think it's all that cut and dried. In fact, our QAs use stop watches and keep notes, and we trust those over what the software thinks is happening for certain kinds of issues.

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> Rather than an error of memory, I think it's far, far more likely he just made them up

And it's impossible to tell either way. So clearly the over the top attitude of Musk was unwarranted.

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"I cannot account for the discrepancy, nor for a later stretch in Connecticut where I recall driving about 45 m.p.h., but it may be the result of the car being delivered with 19-inch wheels and all-season tires, not the specified 21-inch wheels and summer tires."

Sure he can.

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If you look at Musk's graphs where the caption says "At no point did broder drive at 45mph" with an arrow pointing to a 50mph segment, the immediately previous (yet short) segment was at 45 mph. There are a few other places where Musk uses quite a bit of poetic license in interpreting the logs, too. I can't say whether or not Broder's notes would have corresponded to this particular segment, but there was indeed a point where he was travelling at 45mph.

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>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.

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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?

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I think the peak is actually closer to 45 for most gasoline-driven cars. It depends on aerodynamics, though. For a big SUV it might be 35. I suppose it could be as high as 55 for a small, highly aerodynamic car.

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Aerodynamics and engine/drive train design.

Aerodynamically, the slower you drive, the more efficient you drive. The exact curve will depend on air pressure, amount of moisture in the air, etc.

For the engine, it is more complicated. You will want to keep its temperature and rpm at ideal levels. rpm and the gearing in the drive train determine what speed(s) that corresponds to (I guess drive train losses will depend a bit on the gearing, too, but that effect should be minimal)

For the two combined, this gets really complicated. Do you drive at the engine-optimal 45 or does the gain due to lower speed offset the loss in engine efficiency at 44? If 44 is more efficient now, will it stay that when it starts to rain? When you enter a different road surface? When your tires heat up and tire pressure increases slightly? When you have a window open?

http://en.wikipedia.org/wiki/Fuel_economy_in_automobiles#Spe... shows how convoluted this can get.

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Yes, efficiency is a monotonic function of speed here (Model S). No crossover point.

http://www.teslamotors.com/goelectric/efficiency

(the graph)

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I'm not sure. The y-axis on this graph is just the rate of power consumption. It doesn't do much for you to use minimal energy while traveling 0 mph.

Efficiency, in terms on miles/gallon, is always a trade-off between traveling fast enough that the overhead of running the vehicle is less significant but slow enough that wind resistance doesn't dominate. There's a sweet spot in there.

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The y-axis has units of [energy]/[distance], I think I'm interpreting it correctly? It seems to take everything into account in there.

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Yeah, I'm definitely confused. I don't understand how a car traveling 0 mph can have a finite value on that graph if the y-axis is [energy]/[distance]. I was hoping the units were [Watts][hours]/[minutes] or something to make everything better.

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I found they have another graph with the same units (written "Wh/mile", so that's unambigious). But it has a different shape, with a minimum at 20-25 mph...

http://www.teslamotors.com/blog/model-s-efficiency-and-range

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Much better. Thank you!

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That graph shows a maximum efficiency at around 22 MPH (for the 85 kWh battery), which makes perfect sense -- any faster and air resistance becomes a factor. Any slower and energy uses apart from propulsion begin to eat away at efficiency -- the computer, lights, air conditioning, heat, and so forth.

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> Yeah, I'm definitely confused. I don't understand how a car traveling 0 mph can have a finite value on that graph if the y-axis is [energy]/[distance].

The car expends energy just sitting at zero MPH -- the computer and lights, air conditioning and heating, things like that. So the graph is correct -- there is an energy expenditure to "go" zero miles per hour.

> I was hoping the units were [Watts][hours]/[minutes] or something to make everything better.

When the speed is zero, it stops mattering which units it's expressed in. :)

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When speed is zero, distance is zero and energy/distance is infinite. Hence the OP questioning how could the graph present a finite value at that point.

Personally, I'd wager they followed the old scientific adage: "If you wish your function to be linear, sample two and only two points".

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> When speed is zero, distance is zero and energy/distance is infinite.

1. Not energy/distance, but energy/speed.

2. Notwithstanding the cart's labeling ("Wh/mi"), its values aren't predicated on a division of energy by speed. "Wh/mi" doesn't literally mean mean "watt-hours divided by miles per hour", it means "the relationship between watt-hours and vehicle miles per hour".

> Personally, I'd wager they followed the old scientific adage: "If you wish your function to be linear, sample two and only two points".

Yes, except the chart isn't linear. Just for fun, here's a polynomial function that matches the chart's results reasonably well:

    f(x) = 0.03165008148658699 * x^2
         + 0.2559872636164877 * x
         + 106.19966024840329
Here's the resulting chart:

http://i.imgur.com/rLmaN90.png

So ... no division by zero. BTW I worked this up with the help of Sage, my current favorite, free math tool:

http://www.sagemath.org/

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I can definitely say that my gas-powered SUV got 19mpg at 55mph for long distance. (Several hours on a rural highway in Wisconsin, using cruise control) It normally gets between 12 and 16 mpg driving around highway and city.

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The comparison is unfair unless you take into account the amount of braking done when driving slowly.

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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.

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http://en.wikipedia.org/wiki/Tesla_Roadster#Transmission

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

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In internal combustion engines with manual transmission be sure not to overdo that, high gear and very low RPMs are bad for the engine/transmission due to high load and minimal oil lubrication, it's also not efficient on fuel, there were local magazine tests done, but I don't have references now sorry.

On an automatic transmission the transmission control module will figure out the gear for you at given conditions (won't let you get too low in the same gear) and what you say will be true.

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Yes, slower speeds are substantially more efficient. It's obviously not linear all the way to zero, but if there's no parasitic load from heat/ac/etc., I think 15-20mph would be more efficient than 55.

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The answer to your first question would seem to be a clear "yes":

http://www.fueleconomy.gov/Feg/bymodel/2012_Toyota_Prius.sht...

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So all these journalists are practically correct, just not being precise about the mechanism. Off highway driving is more efficient, and it is more efficient (relative to a conventional car) due to regenerative breaking. They really should mention that it's more efficient relative to highway driving due to wind resistance.

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But they are saying that with a comparison to fossil fuel powered vehicles in mind aren't they? With a comparative framing it is a perfectly valid statement.

There is an actual head smacking quote in the article where he says he took a country road instead of the highway in hopes of getting more range by taking advantage of regenerative braking... How can an EV car reviewer for Consumer Reports be so ignorant?

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Yeah; this misconception manifesting as "taking the rural roads [will save power]" bothered me too.

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>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.

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I think the source of this is that going at slower speeds is more efficient in the Tesla. It has a fixed gear[1], so you don't gain anything by going faster, you just lose more energy to air friction. If the regenerative breaking performs well enough, it's possible that driving off the highway will be more efficient.

[1]http://en.wikipedia.org/wiki/Tesla_Roadster#Transmission

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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.

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> 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.

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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...

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...

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

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> 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...

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.

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"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?

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> 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.

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The statement is not false, look at EPA gas mileage numbers for hybrids over the last decade.

You're arguing against something I was careful not to say.

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> The statement is not false, look at EPA gas mileage numbers for hybrids over the last decade.

That may be true, but it's not the topic. The topic is how efficient regenerative braking is on the Tesla Model S.

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The topic is HN being critical of authors suggesting that regenerative braking is a net positive.

I suspect that in both the NYT article and in this CR article, the author is mistaken about the role of regenerative braking on fuel efficiency, but they are not incorrect to point to regenerative braking as the enabler of improved fuel efficiency.

Some made up numbers to illustrate the point. I do not know if these apply to the Model S specifically but do apply to other vehicles with regen braking, familiarity with which is likely to have influenced the authors' explanations.

City driving vs. highway driving:

Lower drag: +20% efficiency

Lower engine RPM: +20% efficiency

More stop and go with normal braking: -50% efficiency

More stop and go with regen braking: -50%(.6) = -30% efficiency

= Net city driving with normal braking: -10% efficiency

= Net city driving with regen braking: +10% efficiency

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> The topic is HN being critical of authors suggesting that regenerative braking is a net positive.

But regenerative braking cannot produce net positive energy compared to not braking at all -- that violates basic physical principles.

Regenerative braking is better than no regenerative braking, but regenerative braking is not better than not braking at all. That has been the point all along.

> = Net city driving with regen braking: +10% efficiency

No, not compared to driving at a steady pace. If the scenario you describe were so, it would represent a gain in energy greater than 100%, and that is not possible.

Stop-and-go driving is always less efficient than driving at a steady pace at the same average speed. Regenerative braking can only minimize the loss caused by stop-and-go driving, it can't reverse it -- it can't produce a net gain as you are implying.

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Dude, you're ignoring what I'm saying.

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I'm saying that less drag and less engine speed are giving the fuel efficiency gains. I am saying that, typically, braking wipes out all of those gains and more. I am saying that regenerative braking often reduces the negative impact of braking enough that the gains -- from lower drag and engine speed -- aren't completely undone by braking.

I ride a low-power motorcycle. On the freeway, I get about 50 mpg. On back roads, with braking and generally higher rpm, I get 60+ mpg. For my low-power bike, the drag at freeway speeds takes more effort to overcome than does the varying speed and braking of back road riding.

And that is without regenerative braking. If I had regen braking, I'd get even better economy on back roads.

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No, I'm addressing what you're saying. You tried to say that regenerative braking produced a net advantage, but this is not possible. Here's the source of your error:

> More stop and go with normal braking: -50% efficiency

Wrong value. Apart from the fact that the number is invented, because each stop turns all the car's kinetic energy into heat, the number should be -100%. Either that or perform a full analysis, with a listing of all the factors.

After you recover 20% of the energy with regenerative braking, you end up with -80% instead of -100%.

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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.

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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

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> 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.

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Lack of basic physics knowledge. Shameful really.

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It could also be misleading information from dealers. I've never tried to buy an electric but I can tell you about the astronomical amount of bullshit I've heard from dealers when trying to purchase a normal car.

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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.

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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?

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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.

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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.

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I doubt we'll see any claims of Tesla having logs to disprove the article. CR bought the car and probably didn't sign the waiver giving Tesla access to the car's data.

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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.

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I thought that the issue last time was that Broder was tight with the oil people. I didn't pay that much attention, but it seemed a criticism specific to Broder rather than the NYT at large.

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"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.

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"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.

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In the real world, your route often isn't going to take you past one of Tesla's handful of Superchargers, and a lot of the other charging points are just too slow to be useful for anything but overnight charges.

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Yes, that would be the real-world scenario.

As I understand it, CR were tracking exactly how much they charged the Tesla at their office (in w, I guess). And he didn't want to mess with that. He also wanted to test the "projected range".

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"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

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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).

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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... )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?!

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Diesel-electric vehicles (running the diesel engine all the time to run generators, which in turn run electric motors) have been the standard set-up on railroad locomotives in many parts of the world since before we were born. They are rather big and bulky for automobiles, and that's why they haven't been used much for individual automobile designs.

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Diesel's do not really get better mileage once you consider that diesel fuel has more energy per gallon. Diesel is a little better, but not dramatically so.

And diesel IS dirty. It's really hard to make one that meets emission standards.

And that is the main reason it's not used more often in the US: It's basically impossible to make it clean enough.

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Citroen produce the DS5 Hybrid 4[1] which is a diesel-electric hybrid. I presume it's just not available in the US.

[1]http://www.carmagazine.co.uk/Drives/Search-Results/First-dri...

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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.

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> 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.

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> 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...

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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.

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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.

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

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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.

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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.

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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)

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> 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.

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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.

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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?

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Yet another apples to oranges comparison:

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

Consumer Reports: "45° F"

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You're the one comparing them.

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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.

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