> So, here's the story: He is expecting a number at around 100 miles because he thinks he's being more efficient now. He sees 50 miles. On a digital display at a hotel at night, he misreads the 5 as a 9, and this fits with his expectation, so he goes to bed thinking he has 90 miles of range. He wakes up and the Tesla has lost 5 miles of range inexplicably -- but it therefore has become 45 miles, which looks totally different. He calls them up complaining that the Tesla lost half of its charge overnight and some sympathetic tech support describes it as a "software glitch."

Pure gold. Thanks for the laugh.

But hey, let's all pick sides based on our allegiance to ( east or west coast, Tesla or The Times ) and have a nice little monkey dance about who's right or wrong.

No, that's not a log of the temperature reading. They logged the temperature SETPOINT. An important distinction.

I do this all the time, being from cold climates. I jack up the heat at the start of my trip, and then once I get going, I eventually turn the heater off completely.

It's a thermostat controlled temperature, though.

There's no reason to turn it down if it's set to a comfortable temperature, because it will automatically shut down when the proper cabin temp is reached.

Anyone who drives in the cold knows this is wrong. You turn the set point to 90 at the start of the trip, because the built-in logic is going to drive the fans harder when the delta between ambient and set point is higher, and the car will warm up faster. Yes, in theory the software should recognize that. But, in practice.... Nah, forget it. Theory is always wrong.

I agree completely that's what you do in cold weather. I do that every morning with my car. But after 3+ hours in the car, it's pretty unlikely that you'd lower the temperature at that point.

EDIT: Downvotes? Really? If the car's climate control is controlled entirely by a thermostat, then setting the temperature up to 90 will warm it faster when it's cold, but once it's warmed up the cabin, you set the temperature to something comfortable(say, 70). You don't turn it off, because the climate control system is supposed to be doing that automatically.

Hi, I live in Michigan. You do turn it off. Your theory sounds like it could be good on paper, but in reality, humans behave a little differently. Our winters are brutal. At some points in the winter time, it's a horrifying proposition climbing into the icebox that is a car's cabin. Reflexively, many people just crank the heat up as high as it will go and blast the cabin with warm air as soon as it's available. As much as you can, as quickly as possible. What tends to happen then is that at some point, you realize that you're hot. You've been blasting the heat, you weren't paying attention (listening to news/music, concentrating on the road, on your phone, etc)and when it suddenly occurs you you that you don't need the heat to be blasting anymore, it's because you are uncomfortable. You're still in full winter gear in your car, you jacket is smothering you, and the cabin is now hot with you in your coat. People aren't always thinking "Ah, let me just lower the heat to a more comfortable level," they're thinking "OMG turn this thing OFF. Could the climate control handle this in theory? Sure. If human psychology and behavior weren't continually getting in the way.

No telling what any given person would do when you don't have the data, but I can tell you what people do do in reality. They crank it then turn it off.

Also, I'll never purchase another car without heated seats in Michigan again as long as I live here. What was I (not) thinking?

A good controller will blast the heat at max until the temperature gets close to the setpoint, then back it down. Turning it up to 90 does exactly nothing extra for you, but does end up overheating you.

However, not all cars have good temperature controllers. My wife owned a Honda Accord a while back, that was simply awesome at this job. We never, ever changed the setpoint in that car because it just worked great.

The Subaru Forester we have now is much, much worse, and we do end up fiddling with the setpoint because the controller's not doing its job well.

So cranking the air temperature setting beyond the desired air temperature for a while will indeed get the cabin more comfortable quicker.

Nah, forget it. Theory is always wrong. I spend an hour in my car every day. Don't you[1] dare tell me how best to warm it up. Just don't.

[1] To head off the wounded screaming: no, I'm not talking about you personally here. Just the idea of "firmware knows best".

Some cars are really good at this. Some are not. It depends on so many factors, including the egghead quality.

I'm one of those firmware eggheads, btw.

As another example, when I fuel my car from emtpy to full, as soon as I turn the key, the fuel gauge ramps rapidly up to Full. In my wife's car, it finds its way to Full after a minute or so. I don't know, but I'm pretty sure the difference is the filtering algorithm employed. One egghead knew about Kalman filters or similar, and the other didn't.

It's the same with all the other software features in the car. Some had good eggheads on the time, and some didn't. I think it's impossible to buy a car that does every single thing "right", by any single person's definition.

That's funny! Does it also fluctuate when you take sharp turns?

The poster above you has it correct. Climate control cars will not turn up the fans until the engine block heats up. Turning up the temperature does nothing to change this.

Please stop with the attitude and name calling.

That's not "anti-intellectualism", it's called "correct requirements analysis". And it's something I wish more software people knew how to do.

A great deal of people beyond yourself drive fancy cars with climate control, myself included. Your car is a single data point. My car is another. That my car, and other posters cars, behave as we say is enough to show that your generalization is wrong.

It is still all anecdote of course; to really determine truth you would need to do a study of as many cars as possible. Further, there is no theory in such a generalization.

This is where your anti-intellectualism comes in. You repeatedly make false statements about theoretical works: "theory is always wrong". It is almost as though you do not understand the definition of "theory." Additionally, your use of "egghead" when referring to engineers is classic anti-intellectualism. I mean, why not just throw out nerd, geek, or pointdexter too? Using anecdote to support your generalization is another extremely common undesirable behavior.

Please stop.

Jayson Blair.

Actually, I don't think he misread anything, I think it genuinely did read 90 miles exactly like he said it did. Look at the graph on the blog post: http://www.teslamotors.com/sites/default/files/blog_images/r... At the 400 mile mark, right where he stopped for the night, there's an abrupt vertical drop from 90 miles remaining to 20 miles remaining, which exactly matches the journalist's claims.

The .6 mile circle in front of the charging station is completely irrelevant, because it's in front of a freaking charger, which is the best place to see if 0 is actually 0.

EDIT: In this post here: http://news.ycombinator.com/item?id=5219611

There's actually a route to the charger from the highway(if you miss a few turns) that's about... .6 of a mile.

As you can see, there is nothing special about his night stop. The night before, it predicted 79 miles. He ended up going 60 miles before it was out of juice. That's 25% shorter than the prediction, so the car must have lost charge during the night or due to cold weather, right? Well, if you look at the day before, the full charge predicted a range of 242 miles, but he only got 196 miles, which is 20% less than the prediction.

In other words: The predicted range is consistently higher than the actual range.

Sure he did, in the manual and in the instructions given to the driver -- when you stop overnight, plug it in.

http://jalopnik.com/towing-company-the-nyt-tesla-model-s-was....

As the State of Charge log shows, the Model S battery never ran out of energy at any time, including when Broder called the flatbed truck.

It obliquely suggests the car wasn't dead on the road. But it clearly was (or else Musk would be loudly calling it out). It's not the responsibility of the reviewer to figure out whether his car bricked because of an empty battery, or buggy software which mimicked an empty battery (displaying zero range, automatically shutting down).

Straws. You maybe holding some.

EDIT: Two words. Occam's Razor. Your explanation is so tangled that an entire battalion of Viet Cong could hide in it.

But no, you're right, let's assume a long-term New York Times veteran lied in the paper, intentionally. That's a safer explanation in the face of your call for Occam's Razor...

On Feb 8, 4 days before the controversial tesla article, he wrote one about how poorly the Chevrolet Volt & Ford Transit performed. I think he already decided on the tone of the article before he drove the Tesla.

His other articles about oil drilling claim that they help with job creation... you be the judge.

I will tell you this:

Both times I made it into the paper, my feeling while giving the interview was that the reporter was writing the story their way despite what I was saying. I was asked leading questions, questions that asked me to come down on one side or another of a complex issue. I was asked repeatedly the same question in different ways to elicit a response that would support a conclusion I didn't agree with.

My friends confirmed my suspicions when they saw the articles that were written. If you dont think that a significant percentage of the articles you read in the paper are pushing a particular viewpoint despite contrary evidence, I'd like a little of what you are smoking.

Just in case you were asking, one of the reporters I'm talking about works for the New York Times. This is the article I was talking about:

http://www.nytimes.com/2005/11/18/national/18harvard.html?pa...

Since I live in ND, we have lots of oil drilling going on, and the Dec 2012 unemployment rate was 3.2% compared to the national rate of 7.8%; I would find that a factually true statement.

Just because something is factually true in a narrow context does not mean it remains factually true when abstracted to a generality.

When was the last time you saw either one of those?

Oil's biggest advantage (other than the massive amount of energy density) is that the full cost of acquiring it isn't factored into the cost per barrel. Since oil is both a commodity and a strategic resource, the government has committed its full resources in the aim of securing supply.

You can argue if this is or isn't a good thing, but you can't argue the fact that it happens.

The reporter might have been reporting a true statement, but it wasn't informative or even relevant to the discussion about energy technologies. There were plenty of telegraph operators, milkmen, and dockworkers once too. Technological advancement made those jobs redundant or irrelevant.

SO MANY nations enjoy the umbrella of protection that is provided by the unipolar geopolitical environment we live in now.

Why else do you think we've committed our military to the purpose of securing supply?

Sure, we've got a lower cost of living than most places, but I'd argue that we've also got a lower quality of life.

When the oilfield is hot, we have lots of high paying jobs for people. Fortunately for us, it's hot right now. What they'll all do when the current boom dries up, I haven't any idea.

You want to calculate the total employment of all industries enabled by oil and then say that the next barrel of oil is responsible for a proportional number of that total?

What about those industries that use oil only because it's still currently cheaper than its alternatives? What about those industries that are already transitioning away from oil and would barely notice if oil became even more expensive? What about those industries where oil is crucially important, but is a fairly minor cost concern and even a doubling of price wouldn't seriously impact their ability to produce products, profits and employees?

How in the world would we even calculate that out to determine how many jobs would exist or not, based on whether we drill the next oil well?

And how would we calculate where those jobs would exist?

Because, oil being fungible, lower production just drives global price up. And the losers in such scenarios tend to be the poorer people and industries, which tend not to be in the US. (It would take a much larger jump in the price of oil to make the next US job in an oil-reliant industry infeasible, than it would take in, say, the developing world.)

And when we do drill that next well, it just lowers (or keeps low) the existing price of oil, and the primary place we'd expect oil-dependent jobs to be created that would not have otherwise been economically feasible without that cheaper oil, is again in the developing world.

So if you want to say oil is massively important, I agree. I never said otherwise.

But if you want to say that the next oil well will necessarily create lots of US jobs, I continue to disagree on the basis that the next oil well simply doesn't directly add many jobs.

And if you want to say that cheaper oil also tangentially creates jobs, I will again agree, but stipulate that new jobs created only because of that cheaper oil, will overwhelmingly be created outside the US.

So I will continue to disagree that the next oil well in the US will have a large impact on US employment.

Petroleum is so ingrained in our economy, most people would have to make a concerted effort to fart without having used oil products.

Frankly that article reads like "EPA claims some infractions but they are no big deal". I can't imagine anyone reading that article and coming away very critical of Shell.

Is the claim that they are actually doing very well, and he was incorrect in his article? Or that he is biased merely for writing an article based on negative facts?

All of them could be perfectly accurate, incidentally - consider a journalist who investigates 100 stories for every one he publishes and only publishes those that are favorable; while none of the articles would contain actual falsehoods, clearly this is a bias.

Whether that's the case here is a much deeper question that I can't answer from my extremely limited skimming of the available media and this thread.

http://topics.nytimes.com/topics/reference/timestopics/peopl...

That this guy could be repeatedly accused here of being an industry shill reflects much more poorly on hn than on him.

https://maps.google.com/maps?q=milford+travel+plaza&hl=e...

The street view here is outdated but I'm pretty sure you would see them immediately as you exit off the highway and, end to end, the rest area is about 0.25 miles. I don't think there's any other way to accumulate 0.6 miles in this rest stop without driving around in circles.

> let's assume a long-term New York Times veteran lied in the paper

What you are asking us to believe than is that Musk faked all this data. Because if he didn't fake the data, then the NYTimes story still doesn't add up, regardless of speculation on his activities.

Furthermore, you are asking us to believe that numerous other reviews by respectable, veteran reports, were wrong.

Maybe this report is the one man speaking out against a large conspiracy of a company and numerous reporters. But it's on him to prove now.

If anything, I think that some veteran reporters get full of themselves and become unafraid of slanting things according to their biases as they get older. Look at the trouble Dan Rather got into at the end of his career because he was determined to sink George W. Bush.

The main factor that affects someone's likelihood of lying is whether they think they can get away with it. Broder most likely knew that the car was logging data. However, he probably didn't know just how detailed the logging was, and assumed it was too rudimentary to refute the kind of story he was cooking up in his head before he even started the drive.

However, didn't we see that long apology yesterday about how easy it is to lie to yourself and others, even when truth is everything to you? This is why we have double blind medical trials etc. – because people are biased and can't help but lie to keep their preconceptions true.

Driving back and forth in front of the charger doesn't seem quite so crazy given the distances involved. The distance the Tesla logs for is ~0.5 miles at a speed of ~10mph, but that's only 3 minutes of malfeasance, if it's anything at all.

And I'm not sure it's malfeasance -- because it's certainly not led to anything in the report. Maybe he wanted to park and get some food but then remembered that the charging takes a while and did it in opposite order. That could take 3 minutes easily off.

People "risk their livelihood" all the time by lying to their boss, etc. I don't think any complex calculus is necessary to explain why someone would do that.

I know it's mentally exhausting, but when reading anything you have to ask, "what does the author want to be true?" Musk quoted Broder's earlier article:

"Yet the state of the electric car is dismal, the victim of hyped expectations, technological flops, high costs and a hostile political climate.”

so I think we know what it is that Broder wants to be true.

Do you know how many MILLIONS of conventional cars are manufactured a year? Who are the biggest companies in the world? You will be shock that they are energy companies.

There are HUGE economic interest in the outcome of different transportation methods. The salary of a man is nothing compared with the BIILIONS over the table just delaying the future one or two years.

I had a friend whose only job at a big French car company maker was organizing summer experiences for car journalist vacations in Europe. I could not believe that a journalist will accept that, now I understand the reviews you find in most car magazines(You never find anything negative).

There may be speculation about certain facts in the case but there is absolutely no speculation as to the fact that this and every other corporate journalist is under systemic influence. In any other industry it would be plainly obvious that employees understand not to insult, aggrieve or otherwise harm their employers customers, especially by way of prominent national media. Somehow everyone manages to convince themselves that what is obvious is no longer so when it comes to journalists and the MSM.

For example, my car also has an adaptive transmission system that collects data on my driving behavior and uses it to improve when the car chooses to shift. Sometimes folks have the dealer erase this data so the car "re-learns" to shift fo r them.(http://www.bmw.com/com/en/insights/technology/technology_gui...)

Digital displays are obviously better for reading a precise value, but not necessarily an accurate one. To generalize, I would say being off by a a couple percent is more likely when reading an analog display, but off by a factor of two is more likely by misreading a digital one.

http://images.thecarconnection.com/lrg/2012-tesla-model-s-di...

...in which case there is not much of an excuse for that type of thing. On the other hand there is a screen which gives the same information but would be very easy to misread, especially if there were glare:

http://elonmusktesla.wordpress.com/2013/02/12/tesla-model-s-...

But yeah, it's not like I was thinking, some display with LCD/LED style digits where a 5 is just one line away from being a 9. You are very correct in that regard.

a) Lincoln tunnel isn't in NYC's downtown. Even Holland isn't. NYC downtown generally defined as below Canal St. So how NYT reporter drove through it, I have no idea.

b) .5 mile is too short for driving back and forth. I can easily walk .5 mile in under 10 minutes.

c) As the _average_ temp setting was 72F... So the next statement is funny, the NYT reported turned the temperature up to 74F? From what? The average temperature? That doesn't make any sense at all.

The commenter here is guilty of forcing his impressions on the situation in the same way Broder seems to be forcing a slant on the Tesla story. How far you walk is completely irrelevant. I know people who run marathons. They don't spin around a 100 car lot many times.

If the temperature setting in the thermostat increased when he said he decreased it, which is the actual claim, that could be a smoking gun. The only innocent explanation could be that he couldn't see what he was doing while he was driving.

However, there are FAR too many BIG screw-ups and coincidences here for that to make sense. How could a professional journalist be so damn incompetent to:

1. mistake "50" for "90". 2. increase the temperature when he meant to decrease it. 3. start each leg of the journey with less and less energy after filling each time. 4. leave the car unplugged for a good part of the time he claimed to be charging it.

The commenter doth protest too much.

So Musk wrong again.

Yea, too many coincidences with Musk's side of the story.

Musk is trying to be precise, I did exactly to him that he was trying to do to NYT's reporter. And yes, my pedantry was on purpose.

Anyway, to anyone outside of NYC, downtown is where the streets are crazy and one way and lots of business takes place... so, really, by that definition, anywhere below Central Park can be considered 'downtown'... especially if you are uptown.

So Musk made a minor mistake, so the NYT reporter made few minor mistakes. I don't see lies, just two different sides of the same story.

Of course the NYT reporter could have driven downtown and take FDR uptown, but I don't see any prove of that. That would make a little sense if you took Holland, but not Lincoln tunnel.

You're other points are meaningful, though.

Lincoln tunnel though, clearly not downtown.

Downtown / Uptown are directions. Lower Manhattan / Midtown / Upper Manhattan are places.

But Lincoln isn't in Lower/Downtown Manhattan,

http://nymag.com/daily/intelligencer/2013/02/elon-musk-new-y...

We'll just have to wait for this "detailed rebuttal" for more information. This is extremely entertaining.

I read that as "drove in circles for over half a mile." I.e., not really enough to make it conk out.

There are other things in Musk's post that make me worry about Broder's reporting, but not this.

How many times do you see people circling the parking when 20 feet away is a spot to park?

But I don't care, this story is B.S., the guy totally was trying report on his agenda and not the facts.

Tesla's logs show that the range dropped from 90 to 30ish at mile 400.

It shows that Broden was 100% correct.

From looking at these graphs, it doesn't look to me that there's a problem with losing charge, but there may be a problem with how the state of charge is reported as range.

I'm not saying this is what Tesla does, I am just saying that the considerations for the UI in this case are interesting, and maybe there were decisions and behaviors involved that are different than a simple function.

If I look at some mobile devices I have access to:

Dell laptop: estimates time remaining in hours and minutes; in my experience, that estimate isn't reliable.

iPod Touch: the most concrete it gets is a warning "20% battery charge remaining". Is likely to show it multiple times. The display only shows a tiny bar.

iPad (and, I think, the iPhone): goes a bit further; can show a numerical battery percentage.

For both iOS devices, the Settings app also shows a "Time since last charge" section with "Usage" and "Standby" times. It does not dare give a time remaining.

Mobile phone: 5-bar battery full indicator.

Back to the electric car: especially given the short range for a full charge, I understand owners will want a distance remaining estimate, but I would say: if you can't give a reliable one, don't. 'Percentage charge remaining' plus a 'at similar speed and weather, you typically would have stretched this for x miles' indicator, IMO, would be better. And that is even more than a gasoline powered car will give you.

I'm not arguing that the log data shows the complete story in enough detail as to contradict every statement made in the NYT. And one another is susceptible to suggestion.I find it odd however that the few persons above me seem to completely ignore the cabin temperature chart for the sake of their argument.

That's why in my account I have the "expected around 90, saw 50 in bad lighting, misread it as 90" snafu. There is a drop, but not as precipitous as it seems.

What happened at 400 miles is apparently a set of full stops as he pulled in to a parking space to talk on the phone and say "I'm not gonna make it," followed by a short reversal of highway time which ends on the 400 mile mark as he went into Norwich, followed by a lot of stop-and-go driving in Norwich to get to some Tesla charger which the NYT article says is around here:

http://goo.gl/maps/cgctM

I can somewhat imagine his impatience and wish to get going again, if that's the situation.

http://www.nytimes.com/imagepages/2013/02/10/automobiles/10t...

And, the points on Musk's graph at ~399 and ~401 very closely match the reported night-before (90 mile) and morning (25 mile) range readouts.

The big drop, almost like a charging straightline in reverse -- is at mile 400. Some have suggested it's the battery's own self-heater which prevents it from getting too cold; that makes sense, but I'd love to see an official Tesla reference to that effect, if it's sufficient to explain the charge drop.

The drop in "miles of range" is precipitous, but the drop in the actual charge level of the battery is not.

More generally this is a sad day for HN. Attack the argument, don't attack the actor. This isn't CNBC or Fox: attacking credibility doesn't constitute a logical refutation of the nYT piece.

I think HN is doing a fine job of arguing both sides.

It's not that simple. Regen does more than lower the loss; it also allows the energy captured during braking to be re-used on the next acceleration. Regen basically means your effective range is based on your average speed, even if you are doing stop and go driving instead of cruising; you can actually get better range in city driving with regen because your average speed is lower, and lower average speeds are more efficient (because there is less loss from drag and friction). This is why hybrids typically have a higher EPA rated mileage for city driving than for highway driving.

True, but if you don't use regen you are 0% efficient at capturing it. Any positive number is better than zero. I'll have to read through the link you gave to see what the guy's reasoning was, but regen should always increase your range.

Edit: On reading through some of the links available on Google, I suspect that he didn't specifically try to avoid regen, but just drove too slowly and with too gentle acceleration and deceleration for the regen system to kick in. Regen does require a certain minimum speed and rate of deceleration to achieve a net gain in energy; if you try it when the car is going too slowly or decelerating too gently all the energy goes into losses in the electrical system and none goes to the battery. The car's control system should be calibrated to only allow regen to kick in when there will be a net gain.

So in that sense you could say that the less than 100% efficiency means there are times when there's no point in using it. But it never causes a loss of energy; you're never worse off than you would be not using regen. It's just that the car's controls won't bother trying if there's no point.

True, but not compared to the alternative of avoiding stop-and-go urban driving, which I believe was the OP's point.

Metcalf's description does say that he accelerated and decelerated very gently; see my edit to my upthread post. So he was trying to approach the ideal of driving at a steady 25 mph as close as he could. If the car's regen system had had lower losses, regen would have saved him some energy on those unavoidable decel/accel cycles.

No, this is a false choice. The choice should not be between stop-and-go driving, versus speeding along. For a proper evaluation, the tested alternatives should be (a) stop-and-go driving with an average velocity of V, versus (b) driving at a constant velocity of V. In that comparison, a constant velocity is much more efficient. The reason is that regenerative braking cannot recover more than a fraction of the energy lost to braking.

The above is in keeping with the best scientific practice, in which an experiment changes just one thing and keeps everything else the same. So we should choose an average velocity, then compare steady speed and stop-and-go driving at that velocity. In that experiment, steady speed wins.

> Metcalf's description does say that he accelerated and decelerated very gently ...

Doesn't matter. Adding a given amount of energy E to a moving object requires the same expenditure of energy regardless of how quickly or slowly it's done (although in practical examples, fast acceleration is wasteful for reasons outside the simplest explanation of the physics). It's the same with removing energy from a moving object, and it is here that the unavoidable losses in regenerative braking prevent the two cases from being equal.

> So he was trying to approach the ideal of driving at a steady 25 mph as close as he could.

That ideal is only achieved by maintaining a steady speed of 25 MPH, not by stop-and-go driving. It's not clear at this point whether Broder was actually told by someone at Tesla that stop-and-go driving was more efficient or not, but if so, that person needs an education.

> If the car's regen system had had lower losses, regen would have saved him some energy on those unavoidable decel/accel cycles.

Yes, but regenerative braking can only minimize losses, it can't recover all the energy lost to braking. Therefore a steady speed is more efficient.

I completely agree, if you are trying to run a scientific experiment. But if you're driving on real-world roads, you're faced with a different set of choices. As I said, you can't expect to drive 400 miles at a steady speed of 25 mph in the real world.

Adding a given amount of energy E to a moving object requires the same expenditure of energy regardless of how quickly or slowly it's done

I wasn't saying that accelerating/decelerating more gently saves energy. I was saying that it probably prevented the regen system on the car from activating at all, meaning that none of the vehicle's kinetic energy was recaptured. Since he could not avoid stopping and starting again (since you can't drive 400 miles at a steady 25 mph on real-world roads), if it had been possible to reclaim some energy through regen during deceleration, it would have increased his range compared to stopping and starting again with zero regen. That's all I was saying, and it's completely consistent with what you're saying.

It's not clear at this point whether Broder was actually told by someone at Tesla that stop-and-go driving was more efficient or not, but if so, that person needs an education.

Not necessarily, because Broder's choice was not between stop and go driving at an average speed of 25 mph, or driving at a steady 25 mph. It was between stop and go driving in Manhattan (you are not, I trust, claiming that it's possible to drive through Manhattan at a steady 25 mph without stopping), at an average speed of 25 mph or so, and driving on freeways at an average speed of, say, 60 mph. Given that choice, it's entirely possible that the stop and go driving would give more range; the exact tradeoff would depend on details like the vehicle's drag coefficient, rolling friction, efficiency of regen, etc.

A red herring. Whatever speed seems appropriate, steady speed is more efficient than stop-and go driving. My only point is that the advice to intentionally engage in stop-and-go driving is mistaken.

A red herring, because the real-world choice is usually between stop and go driving at a low average speed, and steady-state driving at a high average speed. It's irrelevant to point out that a choice that was not actually available (steady-state driving at a low average speed) would be more efficient.

My only point is that the advice to intentionally engage in stop-and-go driving is mistaken.

Not necessarily, if the actual choice is as I said above. Did you read the last part of my previous post?

That's false, breathtakingly ignorant, and you have completely abandoned the original topic, which is to establish whether the advice given to Broder by Tesla (to engage in stop-and-go driving) would help or hinder battery duration and vehicle range. In point of fact, it would hinder battery duration.

> Not necessarily, if the actual choice is as I said above.

Try to focus on something other than your wish to be "right" in spite of the facts. Stop-and-go driving decreases the range of an electric vehicle, and it was incorrect advice to give to a nontechnical journalist.

Pretend to be a scientist, as hard as you may find that. Consider variables one at a time. The driver wants to maximize distance, so he is not going to travel above a moderate speed (this is proven by the fact that Broder knew this and traveled at a moderate speed after he realized his predicament). What is in question is solely whether stop-and-go driving aids or hinders maximum range. It hinders it -- this is physics 101.

You're kidding, right? The choice Broder had was between driving on a freeway and driving through Manhattan. It was not in any way a choice between stop and go driving and steady-state driving at the same average speed.

Stop-and-go driving decreases the range of an electric vehicle

Compared to steady-state driving at the same average speed, yes. Compared to steady-state driving at a significantly higher average speed, not necessarily.

this is physics 101.

Okay, let's do some physics. The energy required to move a car through a distance D is F * D, where F is the force needed to push the car. For travel at a steady speed, F is given by the following equation:

F = c0 + c1 * v + c2 * v^2

where c0, c1, and c2 are constants that are determined by vehicle and environmental characteristics. (Briefly, c0 is the coefficient of friction between the tires and the road times the weight of the car; c1 is a (usually very small) constant related to the internal friction of rotating parts in the car; c2 is 1/2 rho Cd A, where rho is the air density, Cd is the car's drag coefficient, and A is the car's cross-sectional area. The key is that all of these things can be taken to be constant for the duration of the trip.)

For stop and go driving, F is given by the above formula times a constant e, where e is determined by the efficiency of regen; if e = 1 then regen is 100% efficient and all of the the vehicle's kinetic energy is reclaimed on each decel. If e > 1 then regen only captures a portion of the vehicle's kinetic energy, the portion being 1/e.

So if we compare stop and go driving at an average speed v1 to steady-state driving at an average speed v2, we have

E1 = F1 * D = e (c0 + c1 * v1 + c2 * v1^2) * D

E2 = F2 * D = (c0 + c1 * v2 + c2 * v2^2) * D

If we take v2 = 2 * v1, which is a conservative estimate for Broder's situation (25 mph average speed in the city vs. 50 mph average speed on the freeway), we have

E2 = (c0 + 2 * c1 * v1 + 4 * c2 * v1^2) * D

Now subtract to get the net energy difference:

E2 - E1 = [(1 - e) * c0 + (2 - e) * c1 * v1 + (4 - e) * c2 * v1^2] * D

Regen typically recaptures about 80 percent of a vehicle's kinetic energy, meaning e is about 1.25. So we have

E2 - E1 = [-0.25 * c0 + 0.75 * c1 + v1 + 2.75 * c2 * v1^2] * D

This is going to be positive for any vehicle except a heavy one with a low drag coefficient; practically no vehicles have that. So stop and go driving at 25 mph is going to save energy compared to steady state driving at 50 mph. This is the sort of calculation that I suspect was in the minds of the Tesla people when they told Broder that the stop and go segment in Manhattan was going to give him better range than driving on the freeway.

Look -- stop trying to change the subject. Obviously if Broder wanted to maximize range and with the choice to either engage in stop-and-go driving or drive at a constant speed with the same average speed, physics says drive at a constant speed. Your claim that one can only drive fast or engage in stop-and-go driving is false. If the point is to maximize the car's range, the driver can drive at any speed he cares to. And Broder did just that -- he drove as slowly as necessary to prevent pointless losses of energy.

Do you really think that the police will arrest you if you drive too slow on the freeway? Tell that to a long-haul trucker.

> Regen typically recaptures about 80 percent of a vehicle's kinetic energy

Absolutely false. Source: http://auto.howstuffworks.com/auto-parts/brakes/brake-types/...

Quote: "The miraculous thing about regenerative braking is that it may be able to capture as much as half of that wasted energy and put it back to work."

Source: http://theeestory.ning.com/forum/topics/regenerative-braking...

Quote: "Tesla Motors claims an 87% efficiency for powering the electric motor with the energy in the batteries, and the same efficiency in returning motor power to the batteries via regenerative braking. TM also claims an average 80% mechanical efficiency (this goes down as friction increases at very low speeds), including tire loss. So if I have it right, round trip efficiency from taking electricity out of the battery pack to putting it back in, after regen recovery, would theoretically be .87 x .8 x .8 x .87 = 48.4%. But the Roadster uses regenerative braking only on the rear wheels, so if you actually use the brake pedal (instead of coasting with the regenerative braking on) , then the recovery will be far less. The front disc brakes will absorb most (over half) of the kinetic energy when using the brake pedal, because braking action throws more weight to the front of a car."

Your preliminary assumptions are spectacularly wrong. According to the above, the energy recovered in the Model S is about 20% of that required to get the car to its present speed.

> So if we compare stop and go driving at an average speed v1 to steady-state driving at an average speed v2 ...

Learn about science, and don't post again until you do. Science isolates one variable, the topic of study, and keeps everything else the same to the degree that's practical.

Regenerative braking is much less efficient than driving at a steady pace.

I'm not. The subject is whether or not the Tesla people gave Broder good advice. Obviously that depends on what information he gave them and what they based their advice on. You are basically saying that Broder asked them: "I can drive at 25 mph steady state, or do stop and go driving at an average speed of 25 mph; which will give me better range?" If that were indeed the question he had asked Tesla, you are entirely correct that "stop and go" would have been the wrong answer.

But I believe the question Broder actually asked Tesla was more like: "I can drive at 50 mph on the freeway steady state, or do stop and go driving at an average speed of 25 mph; which will give me better range?" If that was the question he asked Tesla, "stop and go" could have been a correct answer. That's my point.

According to the above, the energy recovered in the Model S is about 20% of that required to get the car to its present speed.

The quote you gave referred to the Roadster; as far as I know the Model S uses regen on all four wheels [Edit: probably not--see below]. That would make it 48.4%, not 20%, assuming there are no other differences between the Roadster and the Model S.

If the correct number is 48.4%, that makes e about 2; so my equation would look like this:

E2 - E1 = [- c0 + 2 * c2 * v1^2] * D

I agree this is less likely to be positive; I would have to see detailed numbers for the Tesla Model S to get a better estimate of c0 and c2. The Tesla people who gave Broder the advice presumably had such detailed data, so they would have been able to make a more accurate calculation of estimated range for each alternative.

Science isolates one variable, the topic of study, and keeps everything else the same to the degree that's practical.

Exactly: to the degree that's practical. Broder was not running a controlled scientific experiment; he was running a real-world test of a vehicle.

[Edit: Looking at the Model S specs on the Tesla web site, they do say it's a rear wheel drive vehicle, and there's no mention of separate regen motors for the front wheels. If so, and if the 20% figure for energy recovery is correct, that would make it extremely unlikely that a calculation like the one I've done would give a positive number. If the Tesla people were basing their response on such a calculation, their numbers for regen energy recovery must be significantly higher than 20%, or they were estimating a significantly higher freeway speed than 50 mph, or (most likely) a combination of the two.]

This isn't Jim telling you about his crazy weekend while you stand around the watercooler, this is a professional journalist writing a story for one of the largest and most well respect news outlets in the world.

To me it looks like he doesn't manage to report the correct numbers even once, he said 55, actually going 60, he said 45, actually going 50.

Is it that hard to read a digital display?

Then you say he mistakes a 50 for a 90, if he has that much trouble with eyesight maybe he shouldn't be test driving cars.

Lets see now, which source seems more credible, the guy who doesn't manage to report a single accurate number, and makes mistakes when reading a digital display... or the company which had the foresight to monitor and log everything in their vehicles right down to the state of the temperature controls.

You make a good argument, but I think you are being far too charitable with someone who is a professional journalist and should have done a better job reporting facts if they want to be seen as credible.

Braking and cruise control are mutually exclusive domains. You can't drive with cruise control in stop-and-go traffic even if you wanted to.

Turning off cruise control on the highway might have some small impact on efficiency, but the cause would not be braking.

edit: recharge as in having a net gain of energy. Even if you roll down a 3-mile mountain with the brakes pushed, you'd only be recovering energy spent on the way up, minus losses.

In contrast slower city driving speeds are more efficient and electric vehicles have a unique benefit in stop and go, low-speed driving due to regenerative braking

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

But the big win is driving at city speeds. I had explained this the other day, but power usage depends approx. on the square of your velocity.

So averaging 30mph in the city would take about 1/4 as much power as averaging 60mph on the highway, all other things being equal.

Normally all other things are not equal, as idling at a city stoplight wastes energy in a gas-powered machine, and pressing the brakes wastes energy in a gas-powered machine.

With an EV idling uses very little energy, and you can reclaim some energy from braking. Braking is still a net loss, but not as much.

Combine the two effects with a 4x power efficiency and it's not at all impossible for a hybrid to get better mileage in city, especially in stop-and-go traffic where the average speed is even lower.

He says the Tesla seems more efficient on county highways than side roads because the losses from accelerating the vehicle's over 4500 pound weight exceed losses from air resistance at those speeds.

So what does Broder have to say about that?

"It happened just the way I described it."

http://wheels.blogs.nytimes.com/2013/02/12/the-charges-are-f...

However I don't understand your part about regenerative braking. From everything I've read, regenerative braking very much is capable of adding charge to the batteries.

Regenerative energy is much more efficient than normal braking; but in any case it's far more efficient to simply stay at the same speed. Stop & go is extremely inefficient with normal brakes, and just inefficient with regenerative brakes.