NYT article: Stalled on the EV Highway

[vfx]

I'm told by Tesla engineers the the car records EVERYTHING.

Don't forget that ICEs gasp for air at sufficient elevation.

 

[Norbert]

We can debate whether it's "mildly" hilly or not, but for I-5N from Tacoma to Bellevue the CC could not keep consumption at or under the Rated for a setting of 53 mph. The human driver can (and did) last night. I kept turning off cruise control because it was losing precious miles in the distance race with my battery. I'd gain by a mile or two, flip to CC and it would reverse (down by a mile or two).

For some sections the 47mph-ish was required, but that's another story.

I don't understand what you can do as a "human driver", that you couldn't do by changing the speed of the cruise control (other than perhaps turning it off downhill, to let the car roll if it wants to go faster).

As I understand it, the benefit of the cruise control is to avoid random slow-down and acceleration.

 

[brianman]

I don't understand what you can do as a "human driver", that you couldn't do by changing the speed of the cruise control (other than perhaps turning it off downhill, to let the car roll if it wants to go faster).

As I understand it, the benefit of the cruise control is to avoid random slow-down and acceleration.

As I've said before, add more flex to the cruise control (as an option/setting).

Maintaining specified speed +/- 1mph (which it seems to try to do) on a hilly highway is constantly in a {spend, regen} cycle with no coasting at all. I've got my energy meter on 5 mi and for certain sections of I-5N it looks like near-perfect sine curve.

 

[pythagoras]

I would offer my sympathies from the other side if EV industry,
But after all the loving superiority expressed by Elon and TMC when Fisker was suffering bad luck and bad press over its launch hiccups, all I can say is:

BWAAAAA!!!!

Welcome to the hell of bad press smacking flatbed photos of your car over all the worlds interwebs!

And good luck with your stock price Monday morning.

Someday soon has prices will double again and the rest of the world will realize their ICE habits are not so convenient either.

 

[stevezzzz]

The other cost is associated with countering the effects of gravity - the car "wants" to roll backward, and holding it against that force requires energy. This cost is constant over time for a given slope, so the more time you spend going up a hill the more energy you expend overcoming gravity. Try it for yourself when it's safe to do so. Find a steep hill and slow to a stop while going up it without using the brake. I find it takes about 10kW to hold steady in my driveway (which is as steep as any hill I'm likely to climb, so it's a slightly exaggerated impact.)

The latter cost will paint a curve like the purple line above: the slower you go, the more energy it costs per mile. At 5mph my driveway would add 2000wh/Mi per mile, so I'm much better off at 50mph where it adds a mere 200Wh/mi, saving me 800wH/mi while only losing a fraction of that to aerodynamic effects. That's pretty huge. So I've stopped crawling up hills and it seems to make a difference in my efficiency ... but I'm prepared to have a flaw in my logic pointed out. I can say that I've seen 8000+Wh/mi attributed to climbing my driveway at a crawl before, so I tend to believe the numbers.

There's obviously a "sweet spot" where other effects cancel out the effect I've described and it varies depending on the slope of the climb. I, too, would love to see that graphed for the Model S.

I think your logic is impeccable, but a typo crept in: I believe you meant to type '...saving me 1800wH/mi' rather than '...saving me 800wH/mi'.

Yes, somebody please give us that graph, or rather that family of graphs, if the data exist...

 

[brianoflondon]

I've written a featured OpEd at the Times of Israel replying to this today drawing on my experience driving the battery switch capable Renault Fluence ZE in Israel.

It may be of interest to some here.

Tesla is selling the wrong story on electric cars

Extract:

The Tesla Model S is a great car. It’s probably the best electric car ever sold. Within its driving range, it’s probably one of the greatest cars you can buy today. If it were here in Israel and I had the money, I’d buy one in a heartbeat. The issue is that Tesla just sells cars.

I’ve written extensively about my electric car conversion and driving in Israel but I have something that Tesla customers don’t have: I can switch batteries all over Israel in five minutes. This makes almost any journey in tiny Israel possible even though the range and battery size in my car are less than one quarter the size of the Tesla. My car is also one quarter the cost.

This easy distance driving comes after huge investment expense by Better Place: they’ve built almost 40 switch stations estimated at a cost of $500k each and I’m paying for these by subscription even though they’re free to use each time. In addition they built state of the art range prediction and route planning into every car.

In contrast, Tesla have started installing a small number of “Supercharger” stations. Tesla is creating corridors along popular routes. California was first with LA to San Francisco and Vegas. These stations can recharge their cars (only the most expensive models with the biggest batteries) for free to about 80% in 30 minutes. A full charge takes an hour. Supercharger stations only cost a fraction of what battery switch stations have cost Better Place to build and operate. They’re little more than high-powered electricity output sockets and are unmanned.

 

[Norbert]

As I've said before, add more flex to the cruise control (as an option/setting).

Maintaining specified speed +/- 1mph (which it seems to try to do) on a hilly highway is constantly in a {spend, regen} cycle with no coasting at all. I've got my energy meter on 5 mi and for certain sections of I-5N it looks like near-perfect sine curve.

I don't think you answered my question. On a hilly highway, you'd turn off cruise control as soon as regen kicks in (downhill), or perhaps a bit earlier when coming to the peak, and turn CC back on once the car has slowed down (level or uphill) to the speed you want to keep going at.

What is it that you can do better than that?

 

[PatP]

I've written a featured OpEd at the Times of Israel replying to this today drawing on my experience driving the battery switch capable Renault Fluence ZE in Israel.

I love your conclusion - so true.

"As soon as we try to pretend they are suitable for everybody now, the whole idea of completely electric transport is tarnished."

This is why we have a Model S AND a Volt. Model S can't work for us as our only car. But for 95% of the time it's way better than any ICE cars.

 

[jerry33]

Thought experiment: two Model S cars start a trip at the same time over the same highway segment, in adjacent lanes (no drafting). One car travels the whole distance on cruise control at a constant speed; the other travels the entire distance at a constant power output, accepting variations in speed due to terrain. Assume that, through some miraculous coincidence, they both arrive at the destination at the same time: which will have consumed less energy, and why? Is the 'winner' always the same car, regardless of the speed traveled or the severity of the terrain?

The problem here is that in real-life the road is never perfectly flat--even in Texas. Cruise control maintains a constant speed so even on a "flat" road there are still ups and downs where the cruise control revs too high on the ascents and slows down too aggressively on the descents.

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While an experienced hypermiler can do a better job than cruise control, it is not good advice to a total newbie. Even Wayne Gerdes at cleanmpg.com recommends new hypermilers use cruise control at first.

Quite right. It took me two years to get my first 60 mpg tank. Now I'm unhappy if it's below 70 mpg.

On level ground, with no stoplights, I expect cruise control to be better than all but perfect drivers.

That has not been my experience. YMMV.

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I don't understand what you can do as a "human driver", that you couldn't do by changing the speed of the cruise control (other than perhaps turning it off downhill, to let the car roll if it wants to go faster).

As I understand it, the benefit of the cruise control is to avoid random slow-down and acceleration.

The problem is the rate of slow-down and acceleration. Cruise control has one rate for each and it applies it every time the speed varies. A driver can vary this rate according to circumstances.

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As I've said before, add more flex to the cruise control (as an option/setting).

That would be a fine idea--I'm all for it. To my knowledge, no one has ever done this in a production vehicle. And I haven't heard of this being seriously investigated by any vehicle manufacturer either.

 

[Norbert]

The problem here is that in real-life the road is never perfectly flat--even in Texas. Cruise control maintains a constant speed so even on a "flat" road there are still ups and downs where the cruise control revs too high on the ascents and slows down too aggressively on the descents.

Sounds like this experience comes from your Prius, though. With an EV, on a road flat enough (and not causing regen), this would seem to be less significant than the accidental slow-down and acceleration which a "human driver" causes (unless constantly watching the speedometer).

 

[brianman]

I don't think you answered my question. On a hilly highway, you'd turn off cruise control as soon as regen kicks in (downhill), or perhaps a bit earlier when coming to the peak, and turn CC back on once the car has slowed down (level or uphill) to the speed you want to keep going at.

What is it that you can do better than that?

That's not cruise control to me. That's like saying "I don't consume any fuel" but putting it in neutral every few minutes.

I'm talking about "press cruise control, don't touch any pedals or knobs for miles at a time" vs. not. Hybrids of manual mixed with cruise control are something different entirely, IMO.

 

[Norbert]

The problem is the rate of slow-down and acceleration. Cruise control has one rate for each and it applies it every time the speed varies. A driver can vary this rate according to circumstances.

This would seem to be a question of the specific cruise control, which in an EV may be easier to program to work smoothly.

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That's not cruise control to me. That's like saying "I don't consume any fuel" but putting it in neutral every few minutes.

I'm talking about "press cruise control, don't touch any pedals or knobs for miles at a time" vs. not. Hybrids of manual mixed with cruise control are something different entirely, IMO.

Alright, thanks. (I was trying to find out if there was something else a human hypermiler would do, that can't be done by turning off cruise control in those situations.)

 

[richkae]

I've written a featured OpEd at the Times of Israel replying to this today drawing on my experience driving the battery switch capable Renault Fluence ZE in Israel.

It may be of interest to some here.

Tesla is selling the wrong story on electric cars

Extract:

The Tesla Model S is a great car. It’s probably the best electric car ever sold. Within its driving range, it’s probably one of the greatest cars you can buy today. If it were here in Israel and I had the money, I’d buy one in a heartbeat. The issue is that Tesla just sells cars.

I’ve written extensively about my electric car conversion and driving in Israel but I have something that Tesla customers don’t have: I can switch batteries all over Israel in five minutes. This makes almost any journey in tiny Israel possible even though the range and battery size in my car are less than one quarter the size of the Tesla. My car is also one quarter the cost.

This easy distance driving comes after huge investment expense by Better Place: they’ve built almost 40 switch stations estimated at a cost of $500k each and I’m paying for these by subscription even though they’re free to use each time. In addition they built state of the art range prediction and route planning into every car.

In contrast, Tesla have started installing a small number of “Supercharger” stations. Tesla is creating corridors along popular routes. California was first with LA to San Francisco and Vegas. These stations can recharge their cars (only the most expensive models with the biggest batteries) for free to about 80% in 30 minutes. A full charge takes an hour. Supercharger stations only cost a fraction of what battery switch stations have cost Better Place to build and operate. They’re little more than high-powered electricity output sockets and are unmanned.

The key part of this statement is "tiny Israel".
The Better Place model may work in Israel, with all of its 8000 square miles but the U.S. is about 400x larger with a population density less than 1/6th. The Tesla strategy works with slowly adding stations over time, but the Better Place one requires an upfront investment several orders of magnitude larger.

 

[jerry33]

Sounds like this experience comes from your Prius, though. With an EV, on a road flat enough (and not causing regen), this would seem to be less significant than the accidental slow-down and acceleration which a "human driver" causes (unless constantly watching the speedometer).

I am willing to be convinced that an EV is different in this regard. The longest I've driven an EV was during the GetAmped tour.

My engineering sense tells me that the faster you accelerate over a given distance, the more energy you use regardless of motive power. I don't doubt that a gas engine will use more potential energy for the same acceleration over a given distance due to the poor efficiency of the gas engine. (e.g. if the electric motor is 90% efficient and the gas motor is 40% efficient, then given it takes 100 mJ to do the acceleration, the electric vehicle will use 111 mJ of electricity, while the gas engine will 250 mJ of gas.)

 

[JRP3]

The key part of this statement is "tiny Israel".
The Better Place model may work in Israel, with all of its 8000 square miles but the U.S. is about 400x larger with a population density less than 1/6th. The Tesla strategy works with slowly adding stations over time, but the Better Place one requires an upfront investment several orders of magnitude larger.

Indeed, not to mention BP is in real trouble and has pulled out of the US, not that it was really ever here. Of course in Israel a Model S could do almost any trip on a single charge, and certainly could do anything reasonable with maybe 3 supercharger locations. Battery swapping is a good "idea" but a poor reality. Funny that as BP continues to have problems and Tesla continues to be successful Brian thinks BP has the answer

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Alright, thanks. (I was trying to find out if there was something else a human hypermiler would do, that can't be done by turning off cruise control in those situations.)

Constantly turning cruise control on and off is not using cruise control. Plus you might waste energy during the transitions if you don't hold the proper throttle position.

- - - Updated - - -

I would offer my sympathies from the other side if EV industry,
But after all the loving superiority expressed by Elon and TMC when Fisker was suffering bad luck and bad press over its launch hiccups, all I can say is:

BWAAAAA!!!!

Welcome to the hell of bad press smacking flatbed photos of your car over all the worlds interwebs!

We've dealt with bad press before, and a reporter who doesn't know how to use the vehicle really isn't in the same league with all the problems Fisker has. I'm afraid your gloating will be short lived.

 

[Norbert]

Constantly turning cruise control on and off is not using cruise control. Plus you might waste energy during the transitions if you don't hold the proper throttle position.

I don't know about an area where you would need to do this constantly (secondary question). The primary question is if otherwise cruise control is better as it avoids accidental speed changes, even for an experienced hypermiler.

 

[brianman]

I don't know about an area where you would need to do this constantly (secondary question).

I-5N between Tacoma and Bellevue.

 

[Norbert]

I've written a featured OpEd at the Times of Israel replying to this today drawing on my experience driving the battery switch capable Renault Fluence ZE in Israel.

It may be of interest to some here.

Tesla is selling the wrong story on electric cars

It doesn't look like battery-switching is going to be an alternative in the US. Certainly not at present. Tesla's main story is to have a good range, and that is the "right story". Fast-charging is currently in its beginning, but it is an important beginning. Important both for current owners, as well as for politics which are always future-oriented. Most experiences with Superchargers are good. The mishaps in the article discussed here don't change that. With sufficient charging, the trip could have been done not only reliably, but also with Superchargers (fast-charging) only, in a fair amount of additional time, even in cold weather. With good heating. The question was only how to know how much charging is needed without a negative experience to learn from. My answer would be to get experience with the car under the given conditions, before attempting a road trip that stretches things to the edge. (Or to have a *really* large buffer in battery range, *and* plan well.)

 

[arg]

I'm reasonably convinced that there is additional cost going up a hill that changes the efficiency curve. There are two additional costs: one for physically lifting the vehicle to a higher elevation, which requires a speed invariant output to increase the vehicle's potential energy. You're going to pay this cost for the climb no matter what speed you drive at ... so we can ignore it for purposes of determining how fast to climb.

This is certainly a constant energy cost, but you can't necessarily ignore it (though I agree the effect will likely be small). The motor's efficiency will be a function of both speed and power. The energy to overcome gravity is delivered by the motor: as you say, for a given height rise this is a constant amount of energy to be delivered at the output of the motor, regardless of speed or anything else. However, the amount of energy removed from the battery is greater than that, depending on the motor's efficiency, and that efficiency varies with speed. Hence the amount of energy removed from the battery to overcome gravity does vary with speed (in addition to the energy needed to achieve that forward speed).

The other cost is associated with countering the effects of gravity - the car "wants" to roll backward, and holding it against that force requires energy. This cost is constant over time for a given slope, so the more time you spend going up a hill the more energy you expend overcoming gravity. Try it for yourself when it's safe to do so. Find a steep hill and slow to a stop while going up it without using the brake. I find it takes about 10kW to hold steady in my driveway (which is as steep as any hill I'm likely to climb, so it's a slightly exaggerated impact.)

This extra cost does not exist. Holding the car stationary against gravitational force does not require energy: you could do this with the friction brakes (as you do when parked on a slope). Energy is expended to achieve motion against that force (energy = force * distance), but that is the constant energy we've already counted above.

The 10kW you measure holding the car against the slope with the motor is simply because motors become extremely inefficient as you approach zero speed (in fact, 0% efficient when stopped). That 10kW is going entirely into heat in the motor/battery/power electronics.

The latter cost will paint a curve like the purple line above: the slower you go, the more energy it costs per mile. At 5mph my driveway would add 2000wh/Mi per mile, so I'm much better off at 50mph where it adds a mere 200Wh/mi, saving me 800wH/mi while only losing a fraction of that to aerodynamic effects. That's pretty huge. So I've stopped crawling up hills and it seems to make a difference in my efficiency ... but I'm prepared to have a flaw in my logic pointed out. I can say that I've seen 8000+Wh/mi attributed to climbing my driveway at a crawl before, so I tend to believe the numbers.

There's obviously a "sweet spot" where other effects cancel out the effect I've described and it varies depending on the slope of the climb. I, too, would love to see that graphed for the Model S.

(... and yes, this is fairly serious thread drift. Perhaps the whole subtropical should be moved?)

To put some numbers on this, the power required to raise a car of mass 2 tonnes going straight up at 0.5 metre/sec is 2000*9.8 * 0.5 = 9800W = 9.8kW. 0.5 metre/sec = 1800 metre/hour = 1.125 miles/hour.

That's 1.125 mph vertically upwards - on a 1% slope, the car would be going at 112.5mph; on a 6% slope it would be going 18.75mph, for an expenditure (ignoring motor efficiency) of just under 10kW. Or another way, doing 50mph up that 1% slope has a vertical component of 0.5mph and so needs 4.35kW to overcome gravity. 4.35kW at 50mph is 4.35kWh per 50 miles = 87Wh/mile. Say for convenience that the motor is 87% efficient, that would give 5kW (=100Wh/mile).

If 50mph on flat ground is 280Wh/mile, that is 280*50 Wh/h = 14kW, so adding an extra 5kW to overcome gravity is a significant amount of extra energy, but on the other hand the change from 14kW to 19kW isn't a big change within the motor's overall power band of 0 to 270kW (0-310kW in the case of MSP), so the efficiency probably doesn't change much.

 

[agelston]

New York Times Article

It's very negative

Stalled on the E.V. Highway - NYTimes.com

Here's my question:

I ran the several sets of range shown on battery/range driven the article gave. See the picture attached for the table. Here's it in text.

To-From	Battery Lost	Range Driven	% of actual range	Type of Driving
Delware-NJ	85	68	80.0%	Regular
Milford-Manhatten	92	72	78.3%	Regular
Milford-Conn	95	73	76.8%	"Slowly"
Manhatten-Milford	70	53	75.7%	Range-maximization

[FONT=arial, sans-serif]It's very weird because the author got significantly more mileage out of the Model S when he drove normally, not at 45 miles an hour in the right lane. Counterintuitive [/FONT]

[FONT=arial, sans-serif]The article stresses that point, making it sound like you will have to drive a tesla slowly to achieve the stated range. In fact, USING THE NUMBERS FROM THE ARTICLE, driving a tesla normally (65 in the middle lane) results in better battery performance. The author fails to point this out, probably because he didn't notice it himself. It completely invalidates the concept that you must drive like a old lady if you want to drive a tesla far. Ironically, if the author did not have range anxiety from the start (as he states) and drive so conservative, the car probably might have made it to Milford. [/FONT]

[FONT=arial, sans-serif]Is the author providing bad numbers? or is it actually possible that driving slowly will burn more battery then driving regularly? possibly because of the added time?[/FONT]