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Energy-efficient driving

Energy-efficient driving

I am currently experimenting with ways how to drive my Tesla as energy-efficiently as possible, and I have found a way where preliminary results show a 10% reduction in consumption.

Story: I currently have a loaner, provided by the fantastic Denmark Tesla team, when my 12-V Battery malfunctioned for the 3rd time in 3 weeks - they actually transported a loaner 400 miles to Stockholm and brought down my car for repair - WOW!!

This loaner, though, consumes about 10% more energy than my proper car with identical trips, identical settings and, as far as I can see, identical driving. Because of an imminent long haul this concerned me very much, so I started to think of ways of bringing down the consumption. I got the advice from a Tesla man: drive it as you would drive an ICE.

OK, fine. I have developed a style of driving with ICE:s that invariably beats their own consumption figures (and we all know that they are the "optimal" ones anyway). It is quite easy - roll the car in Neutral as much as circumstances allow.

I tried this with the loaner, and it immediately yielded really good results - minus 10%, from 310 Wh/mile to 278 Wh/mile in 40 degrees F.

The Tesla is built with such a small wind and rolling resistance so that these 2 factors coupled with the huge mass makes the Tesla roll "for ever", especially in a down-slope. If there's just a small decline it doesn't even lose speed.

The gearbox is so well-made that I learned in less than 2 minutes how to change back and forth between Drive and Neutral without anyone noticing anything.

So, if you free-roll and want to lose speed, put it in Drive and engage re-gen. If you want to keep the speed or increase it, just put it in Drive and - well, drive.

The Cruise Control doesn't do this well - it constantly gives small "puffs" of energy and then brakes, for instance when you reach a small hill, and the re-gen cannot be 100% efficient, so you lose more than you gain, whereas, if the hill is small enough, you just roll over it in Neutral or you see it coming and accellerate slightly BEFORE the hill and roll down after it (never accellerate uphill, if it can be avoided).

This car has such eminent rolling features that this can be done without at all disrupting the traffic flow, if applied intelligently (mostly meaning rolling downhill, but also anticipating a traffic jam or light).

I called Tesla and asked them if this could in any way, shape or form damage the car (I am driving a loaner, and I am much more careful with other people's properties than with my own), and the answer from the Danish SC was an unequivocal NO.

My lifetime average consumption (incl. the multiple showing-off accellerations in the beginning - I am only human...) with my proper car is 289 Wh/mile, with the temp has varied between 29 F and 50 F. Applying the free-roll system, I think I will get it down to 260 or thereabouts. Will keep you posted.

Would be interesting to hear, if anyone else has tried this and their experiences.

Robert

shs | October 27, 2013

If one is coasting over a block or more in preparation for stopping, the average speed is likely less than going at "full" speed for a bit longer and then using regen to stop. Slower will always use less energy. Using the brakes will always waste energy.

timgostony | October 27, 2013

First post here, and haven't received my car yet, but I thought I could add a few points.

Cruise control is absolutely the most efficient way of driving if you are on a flat surface.

However, the cruise control is a "dumb" system - it simply checks what your desired speed is, and either adds throttle if you're under it, or removes throttle if you're over it. It doesn't know anything about upcoming hills, traffics, or turns.

The only way you can gain efficiency over the cruise control via coasting is when you, the driver, can predict when you will be served by purposely losing speed.

So, suppose I'm going 70 mph on a flat road, and approaching a hill.

By "manually" driving the car, I might purposefully allow myself to slow to 60 mph on the way up the hill instead of exerting the energy to both keep the car at 70 mph and increase my elevation. On the way down the hill again, I might let the car coast back up to speed, possibly exceeding my original speed, knowing that it is "free" energy gained from the elevation change.

If you simply leave cruise control set at 70mph, it will "stubbornly" try to keep the car going 70 mph up the hill, which wastes a lot of energy. Then, on the way down the hill, as the car's speed increases over 70mph, the car might automatically apply regen, again to keep you at 70mph.

I have to agree with others that fiddling with the gear selector while going at highway speeds is not really a safe solution, especially since the P button turns into an E-brake. If you successfully use this method to coast smoothly on 99 trips, the one time you do accidentally use the E-brake, assuming you don't get into an accident or break anything, you are still going to waste all of the energy you saved on the other 99 trips by burning it up in the tires and brakes.

I propose a better solution, which is to just use cruise control, and lower your target speed as you approach a hill. This applies to ICEs as well. You will get better efficiency, have an easier time focusing on the road, and still be "ready to react" in the event that you do need a quick response (since cruise keeps it in gear and disengages with the brake pedal applied).

Also, a note about efficiency - wind resistance is an incredibly powerful force. Drag increases by the square of the velocity, but power required to overcome drag increases by a cube of the velocity, because not only is the work being done squared, but it is being done over a higher speed.

A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times the work done in half the time requires eight times the power.

Furthermore, some types of batteries actually have lower capacity when current is drawn at a higher rate (Peukert's law). Not sure if this applies to Model S batteries, but either way, going fast takes considerably more energy!

J.T. | October 27, 2013

@tim. Very nice first post. I am no engineer so I'll be watching to see if and how those who are take your figures apart.

Either way, welcome and thanks for participating.

Brian H | October 27, 2013

Twice as much energy, for half as long cancels. Except for the fun. Fun || accel.

ye | October 27, 2013

Brian H, driving twice as fast gets you there in half the time, but uses more than twice the power. So I don't know what you're trying to say.

Brian H | October 27, 2013

J/k.

robert | October 28, 2013

@RZippel

Tut Leid, aber ich bin wirklich nicht Ihrer Meinung.

I don't agree. Any system used is dependent upon how and where it is being used. If used unintelligently, any system will fail and possibly be dangerous.
First of all, the gearbox is so incredibly fast and smoothe that, if a situation occurs, the time it takes to engage or disengage the Drive is shorter than the delay in answering the pedal in any normal ICE car.

Secondly, in a difficult situation, I would opine that in 99,xxx percent of the cases it is a matter of bringing the speed down, not up. For that the regular brakes are fantastic and certainly good enough, re-generation or not. I don't even think that applying the regeneration shortens the ABS braking distance at all.

Thirdly, when free-rolling, I put my foot at the brake pedal, of course without depressing it at all. That fact alone gives me a MUCH faster reaction time for braking than anything else. Only when I break the free-roll to increase/hold speed, do I move the foot. For reducing speed, I just engage drive; since the foot isn't on the gas pedal, the re-generation starts immediately and smoothly - if necessary (almost never) I press brake.

Fourthly I have during 52 years of driving all over the world (and certainly at least 40 times Stockholm-Basel or more South and return) never encountered a situation, where ADDITION of speed would have helped me in the least, but, even so, I would never overtake anyone or be in the left lane at all without having the Drive in. That would be basically very unintelligent and ultimately dangerous, especially, as often in Germany, someone approaches from behing, left blinker on, in 150 mph (250 kmh)(I know, to my eternal shame I was once one of them, in my MB 450 SEL). Therefore, we can happily change the 99,xxx% to 100%.

Therefore, the whole set of assumptions on your part is wrong, and therefore also the conclusions.

Viele Grüße gen Süden - Robert

robert | October 28, 2013

@BrianH

"Yes, that's what I meant and robert didn't get."

Normally I do try to keep my posts in a nice tone and in a way that I hope is conducive to the participants in any of the Fora I visit and participate.
However, I have developed a slight antipathy for some of your posts.

I will stipulate that I no longer am quite as sharp as I was when I founded the Finnish Mensa half a century ago, but, dear BrianH, I will also emphatically state that, barring computers and smart-phones that don't hold much interest for me, I D O G E T I T.
If there is anything I don't get, it is most often, because the reasoning that I am supposed to "get" is fawlty (yes, I am an unashamed John Cleese fan), precisely like the post by Herr Zippel, which you +1:ed (see my post above).

====================

While having it out with you, may I also inform you that a fair proportion of this Forum consists of people that do not have English as their first language - maybe not even second (I know for a fact that English was my 4th) and that I therefore think that your constant floccinaucinihilipilificatious (look it up, lock it up) corrections of others' mistakes are misplaced. Yes, the insulted body doesn't propel in the grave, it turns or even rotates, but it was a fair enough translation from Norwegian, and I don't think that any member of this Forum misunderstood the meaning. If you insist of being a Language Police, why don't you spend some time in correcting your linguistic countrymen in the correct usage of it's (abbreviation) vs its (genitive), something that invariably gets mixed up.

- Daddy, why is Internet so good?
- Well, son, it's its IT:s.

Or start writing posts in any of the 10+ languages I feel comfortable in, and experience the sticky end of the wicket.

Having got that off my chest, let's co-operate to make this into a welcoming and conducive Forum, also for those (incl. many of your countrymen, whencever you come) that do not have a perfect command of the Queen's English, shall we?

Best - Robert

robert | October 28, 2013

Unscientifically, after two short legs, using free-rolling:

Home - ferry to Finland. 32,6 km [20,4 miles] 20 freeway, 6 congested freeway, 6 bumper-to-bumper city). No beam, no A/C. Temp 11 [52]

5,6 kW 182 Wm/km [291 Wh/m].
Take away the first 4,3 km [2,7] for the heating up of Battery.

Rest of Trip: 28,3 [17,7] for 4,4 kW or 155 Wh/k [246 Wh/m]

Energy App, Average: Last 25 km [15] 155 Wh/k [246]
Last 10 km [6]: 138 Wh/k [221 Wh/m]

=================

Ferryboat - home this morning

Including the first 5 km, the relevant data: 160 Wh/k [256 Wh/m]
Excluding the first 5 km: 149 Wh/k [238 Wh/m].

Energy App readins Average: Last 10: 135 Wh/k [216 Wh/m]
Last 25 147 [235]

Speed limits: freeway between 70 and 90 [45 - 56 mph], city 50 [31] (but impossible to hold in that traffic).

Nowhere did I hold up traffic or act as a disturbance. I followed the rhythm, even when it exceeded the given legal limits.

===============

Before anyone tells me that the sample is too small, I agree.

On Thursday I will make the 240-mile trip. I will have a passenger on half the journey and the car will be really packed.

I will produce an exhaustive chart of what happened.

I still believe that the free-rolling system is a safe and very saving feature, if applied with a bit of thought, but let's see after Thursday.

Robert

J.T. | October 28, 2013

@Robert

I am a fan of yours since your very first post. I grow more impressed with your knowledge, experience and demeanor with every new problem (did you get to 84 yet?) and I do believe your character comes through even more when you're pissed off at someone. (By the way it was Amped Realtor who called you OCD, Tam was merely defining it.)

Having said that I am also a big fan of Brian H. He is of the opinion that ESL or ETL or EFL posters appreciate being corrected when they use English incorrectly. I'm not so sure that is true but Brian has said many times that education is his intent.

I am quite sure he has expounded on the usage of its and it's in at least three threads. He has a nice mnemonic for it but I can't remember it right now.

He is quite informed about practically everything, Tesla related or otherwise.

Also, he is damn funny at times, but humor is a high-wire act.

I am rooting for you to get your car back from Copenhagen in top notch condition so you can enjoy it without the constant aggravation you've already endured.

robert | October 28, 2013

Very short answer (at least for me):

Oh dear. I missed that. Apologies to Tam!

I don't believe that foreigners appreciate being corrected in open Fora unless they ask for it. It is a touchy subject, to say the least. I have absolutely nothing against it for myself, since I believe in learning, but I have seen a lot of occasions, when the correctee simply withdrew to stop the embarrassment.

Humour is funny when directed against oneself or non-named others, almost never when someone else has to "foot the bill".

Given the service level and attitude of the Tesla Danes I really have no right to complain, except that I strongly suspect that the loaner has been restricted in some ways, esp. accelleration. I let my brother drive a short while, and of course he floored it. The result was nowhere near what I experienced in my car, but he dropped his jaw. Must check up on that.

Thanks for writing and again Sorry, Tam! - Robert

Thomas N. | October 28, 2013

My mother was an English Professor and I spent my entire life being corrected. I'm quite used to it but I sure can see where somebody would find Brian H's corrections to be both pompous and unwarranted. There seems to be one on every forum I belong to, however, and Facebook also has its share of "grammar police" and "spelling police".

I take it with a grain of salt but then again English is my first language and I'm not very skilled at it much less any additional languages.

I do love my Model S and learn a lot from these forums.

J.T. | October 28, 2013

At least on facebook you're being embarrassed by "friends".

Mathew98 | October 28, 2013

@Robert - I am glad you are experimenting with your new gadget on wheels. Please do so without sacrificing your own safety while driving.

Personally speaking, I tried many hypermiling techniques with my hybrid. It was a self challenge at first but after a few years, all my techniques produced perhaps 10 - 15% extra efficiency. I grew tired of hypermiling in the hybrid after a year or so.

My S60 averages about 415 KW/h since ownership. It doesn't bother me one bit that I'm using about 30% more energy than most of the MS owners.

I drive the MS like the awesome toy that it is. My daily city commute is four hours long but only cover 50 miles. There aren't many opportunities for me to go over 60 mph for more than a few seconds.

I enjoy bolting between traffic lights since there are no other ways for me to create the obnoxious grin otherwise.

I would suggest driving the MS in such manners allow you enjoy the car. It doesn't matter if you set it to cruise control at speed limit or have jack rabbit accelerations at every intersection. The MS is a great ride regardless how you choose to drive it (within safety limitations, of course).

robert | October 28, 2013

@Mathew98

Whatever works for you. I suppose it has to do with why one bought the car - as a beautiful toy or to "save the world".
As I also have said a number or times, we simply don't have charging stations in Sweden, which means that planning and economizing are mandatory, if you want to take the car to anything else but a commute.

I, having been one of the great bad energy-wasters previously, before my daughter (who, incidentally, is quite a bit smarter than I am) started to talk to me in earnest, have completely turned around (I am Robert, and I was an energy-waster. Hello, Robert, comes to mind), and am now investing heavily in trying to make up for past sins. I try to remind myself that, even if the Tesla is a great reduction in emissions, the electricity is generated from something, and that something may NOT be particularly good for the environment. I earnestly believe that we should take the necessary steps voluntarily, before we are going to be forced to (anyone remember the queues for gas in 1973? No?? Short memories).
So I try to save even with an energy-saving vehicle.

Robert

Cindy I II III | October 28, 2013

I tried "N" since yesterday and got better range! But that was just a minor point. The major finding for me was how much more fun I had by having more driving variables. Before MS, my cars were standard shifts. MS simplified it from 3-pedal + 1-stick driving to 1-pedal driving. Now I'm using the shift between N and D on top of the accelerator and break (most of the case I shift to D for break)...

Is it true that such shift is bad for the car? Someone wrote it with no supporting evidence. Does anyone have evidence?

Of course, safety is first. And chances are, I can be tired of it one day.

shs | October 28, 2013

There is that little detail that coasting in Neutral in illegal in most, if not all States in the U.S. at least.

robert | October 28, 2013

@Cindy123

I put that very question to the top technician in Tesla Denmark, and he confirmed that this is perfectly OK. Will not harm the car

But, to be double sure I asked Jerome Guillen, who is Vice president of WW sales, and he answered in the same vein.

I had another stint of 37 miles tonight in pitch dark, 50 degrees F and pouring rain. However I tried, I couldn't get it under 170 Wh/km or 272 Wh/mile, and I have noticed before that the consumption in rain is considerably higher. Probably has to do with rolling resistance, fan to get moisture away from the windshield, wipers going etc.

Robert

robert | October 28, 2013

@shs

Are you totally sure? For how long? That would mean, theoretically, that you can't change gear with a stick shift car, since you are then coasting in Neutral (or having the clutch down, which is the same thing) while changing gears.

Interesting. This is the Swedish State Authorities' Homepage:
Så kör du sparsamt med automatlåda
(This is how you drive unwastingly with automatic transmmission)

Här hittar du fem tips på hur du kan köra sparsamt med automatlåda.

(Here you find 5 hints how to save gas with automatic gearbox)

.
.
.

5.Rulla mer
Automatlådan saknar motorbroms. När du släpper gasen rullar bilen långt. Med god framförhållning släpper du gasen tidigt och utnyttjar rörelseenergin för att spara bränsle.

(5. Free-roll (coast) more. The automatic gear lacks motor brake. When you lift the foot from the gas the car will roll far. With good planning you lift off the gas early and use the kinetic energy to save on fuel).

I find it really odd, if the State Authorities feel so differently about exactly the same thing. And, to be sure, I find the American Law totally incomprehensible, if indeed it is like you say.

Of course there is no legal difference between automatic gearbox and manual.

Robert

shs | October 28, 2013

Robert,

From the CA DMV website. It applies specifically to down grades. I believe there are similar laws in most states.

V C Section 21710 Coasting Prohibited

Coasting Prohibited

21710. The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such vehicle in neutral.

AmpedRealtor | October 28, 2013

How on earth could a law enforcement official determine that someone was driving in neutral? This seems highly unenforceable. What am I missing?

Also, a good attorney could poke a fair number of holes into that CA statute as it applies to an EV.

shs | October 28, 2013

Robert,

When I was learning to drive many years ago in Michigan, I would often coast in Neutral, but then somebody told me it was illegal and dangerous, so I stopped. Years later I encountered this technique in a taxi in Beijing. As soon as the driver saw that he would need to stop for a light, the taxi went into neutral and the ignition, off. If a Chinese taxi driver uses the technique, there is no doubt something to it in terms of saving energy when you need to stop anyway for a traffic light or stop sign.

David Trushin | October 28, 2013

I also believe that people should drive in a manner that suits them. But I do have a few comments

1. regen does not use the brake at all. It is pure motor braking.

2. coasting on some hills may require some drivers to use the brakes to the point where they glaze and can no longer stop the car. This I believe is the motivation behind the no-coasting laws. Enforceable or not, the proof of the pudding is the presence of dead runs on mountain slopes in the Western US and mountainous regions of the east.

3. One question: when you coast Robert, do you attempt to keep your speed constant by braking or do you truly freewheel, no matter what speeds you attain?

robert | October 28, 2013

@David Trushin

There is no fixed answer to that. Obviously every situation is new, and equally obviously I have to adjust my driving to the topography, traffic situation etc. If alone, I would let the car attain the speed it wants to, as that's the whole point of the exercise - to save energy. Whatever I gain helps me get further after the downhill.
I don't use my brakes basically at all. If I need to slow down when coasting, I choose Drive and lift my foot (well, I don't have to, since my foot anyway was on the brake pedal, but without braking). The incredible gearbox lets me do this totally smoothly.
I value my license, so I don't let the car exceed the given speed limits by more than the usual "VAT", unless I am in a situation where everyone else does so (I don't want to interrupt the traffic flow). Of course, if I am alone, well...
I drive in Sweden. We simply don't have roads with that steep gradients as you seemingly do, or the Swiss/Italians/Austrians do. I have driven lots in the Alps. To coast down there would be inviting someone to write my obituary, stat!

Again, any driving cannot follow fixed rules (except the State given ones, like normal traffic rules). One needs to apply some forethought, but I can assure you, that becomes second nature after a while. I have done it for decades, and I invariably beat the Manual-given consumptions. The Swedish State invites this way of driving, and I am perfecting it. The Tesla fantastic free-rolling properties makes this more of a pleasure than ever before, with any car. Why, when I change from Drive to Neutral, it actually feels that the car is accellerating for a split second, like it were tellng me that "back off, dud, I can do this better than you".

What a car!!!!

Robert

robert | October 28, 2013

Oh, before the Language Police arrest me:

"I have driven a lot in the Alps".
"The Tesla fantastic free-rolling properties make..."

Why can't one edit the posts??

Robert

robert | October 28, 2013

@shs

For mountainous roads, I can absolutely see the point in not coasting. But do they forbid just pressing the clutch while the car is in gear?
It is a stupid rule, since it is unenforceable. Any unenforceable law is stupid, since it takes away respect for the law in general. Better would had been a warning sign: Coasting downwards in steep gradients is DANGEROUS.

Robert

Peter85 | October 28, 2013

OK. So My commute is a mere 3.6 miles one-way. Going down to the office on my gentle downhill grade I've enjoyed experimenting with driving longer through slower neighborhood streets before getting on the local highway in an effort to minimize energy consumption. Even done the coasting thing. It's fun! Definitely a game. Though I have to confess, I feel conscious if I'm rolling along gently and an ICE car comes barreling down behind me hitting the brakes because of my slower speed. Don't want to give Tesla a bad name if you know what I mean. Anyway, on my best days, on my way to work, I've consumed about 260 Wh/mile. Of course driving back up the hill after work, I consume quite a bit more so that my round trip averages about 300 Wh/mile on a good day. So my 7 mile round trip consumes about 2.1 kWh when I'm being good. Now where the cookie crumbles for me is that while the car sits in the office parking lot for the whole day (if I don't take her to lunch) she loses 7 rated miles of range or another 2.1kWh just playing with herself. So my actual commute consumption ends up being more like 600 wh/mile!!! Bottom line: drive more for better Wpm but drive less to save the planet. Oh and Elon pleeeeeease fix the vampire drain.

Brian H | October 29, 2013

His, hers, its;
He's, she's, it's.
Infallible.

robert;
The extra step to "re-engage Drive" cannot be as quick as "live" control of the regen function with the foot, feathering the pedal to keep energy flow at 0. Not possible.

Test drives prove nothing; it would take thousands to statistically sample the relevant universe.

Joined Mensa in my late teens; found a few narrowly focussed egos, trying to display their feathers. Got bored and left. Haven't sampled other chapters, but see no evidence of any group contributions.

"Regen" is a unique-enough colloquialism to deserve a place in the list of acceptable key-stroke savers.

Do you honestly resent corrections in your non-native language? That takes brass ones.

ye | October 29, 2013

Robert, are you sure that the Swedish webpage you quoted actually recommends coasting in Neutral? It just says to lift your foot from the gas pedal earlier. It doesn't say to shift into Neutral.

(I don't speak Swedish, so my comments are based on your translation.)

robert | October 29, 2013

@ye.

Yes.

Robert

robert | October 29, 2013

@ye

No. Will check.

Robert

robert | October 29, 2013

@ Brian H.

I feather the gearchange lever in the same way as I feather the brake when coasting. I have at least as good reactions in my hand as in my foot (especially when I occasionally put the latter in my mouth), and the Tesla gearbox is incredibly fast, virtually instantaneous. Having said that, no system is better than the person implementing it, and it needs the driver to actually think about what he/she is doing, until it becomes second nature and is done with the "spine". It may well be that you are right in theory, and so I will not stretch the point. Also I think it is a very moot one.

Oh yes, test drives prove everything, or why do you think that car manufacturers send whole teams (half factories, it sometimes seems) to the North of Sweden in order to test their cars in winter conditions? Test driving under controlled circumstances actually points at problems and very often gives good hints on how to solve them. I try to do my tests in as controlled circumstances as possible (e.g. using the same run with different driving styles to collect data from) and then draw my conclusions, and I know both how to do so as the usual logical pits, into which one may fall when drawing one's conclusions. In any case I only want to prove a tendency, not exact percentages, and that I have done to my absolute satisfaction decades ago. The only question was if those principles also applied to Tesla driving, and, to my satisfaction, they do, and even more so than with an ICE. Then, being a generous soul, I wanted to share my findings with others, who may share my opinion about global energy waste, or simply have a need to get further than they are currently doing on a single charge. The others don't have to read, and, anyway, in the nicest possible way, sod them :-).

I do agree with you about Mensa, but I only said that I founded the Finnish chapter, not that I am an active member.

Regen. Yes, of course it is; my comment was only a (not very clever, I admit) attempt at a small dig at you. You don't leave all that many openings for attacks, even though your statement about test drives certainly is one.

Well, I am going to stick my neck out, since (as already stated) I am a generous person and I want to give you the chance to chop my head off, and state that I don't think that even you, barring sloppy typing, will have a lot of reasons to correct my usage of the English language. Or a number of others for that matter. I also like to add, again as already stated, that I welcome corrections to my language, since I believe in learning as much as possible. However, and having said that, I do know of several instances, when such corrections, whence-, how- and whyever they were made, have been perceived as ad hominem attacks by the correctee, and therefore led to a silencing of same. I personally don't feel that a Forum about the Tesla cars is the right place to disseminate linguistic tuition, especially not, when it is as unasked as possibly called for.

I don't believe in false modesty. And yes, I do polish them daily.

I believe that, after now having made our positions clear, we are going to get on like a Tes.. oooops, house on fire.

Very best - Robert

robert | October 29, 2013

@ye

Have now checked with the highest authorities in Sweden for traffic. Not only is it not forbidden, it comes highly recommended, using one's loaf, of course - not downhill a steep mountain. The reasoning was that they cannot micromanage every driver's possible mistakes - learning how to drive is part of getting one's driver's license. To outlaw something that good for the environment just because one or two idiots shouldn't have got a license in the first place is not on in my country.

"So, yes, by all means, put the car in neutral and try to use the kinetic energy already worked up." was the final recommendation in the telephone call I just ended.

Robert

David Trushin | October 29, 2013

Robert, thanks for the clarification. It now sounds to me like your process is one that essentially does manually what the car does automatically. As you said, you apply more intelligence to yhe process and you seem to get better results. I must admit, though it sounds like a lot of work for small returns. You are already saving the planet by not using gas. But saving 10% more is little compared to paving the way to the future of everybody leaving gasoline behind.

J.T. | October 29, 2013

To outlaw something that good for the environment just because one or two idiots shouldn't have got a license in the first place is not on in my country.

It seems the USA is constantly mired in enacting laws that prohibit people from doing things simply because one or two idiots found a way to do them in such a way that property or life was endangered.

robert | October 29, 2013

@David Trushin

I disagree. If I drive my Tesla 10% more efficiently it is like a fart in Universe, agreed, but the beauty of this is that this driving modus operandi is applicable to all cars. If even a tiny percentage in their Hummers and what-nots started to think what they're doing (noone more zealoty than a convert, right?) and saved 10% on gas, a huge saving on the environment would ensue. The next step is to change to a Tesla, when it becomes affordable, and the final step is to drive said Tesla to its minimum consumption.

I try to be at the last step rather than the first. Like with my house, someone must be the ice-breaker.

And, David, I actually enjoy this. It is a challenge, and I like those.

Robert

hillcountryfun | October 29, 2013

robert@bis.se:

I totally understand and follow the same approach with my Prius. That's why I wish Tesla would add an ECO mode (like the Prius) as it would help me more easily drive with greater efficiency. I can see why Tesla might not want to focus on that feature as it might detract from the high performance luxury image of the Model S but I think they could add it without detracting and folks could use it if they wanted. Also, it could be activated when the pack is down at less than 5% or 10% capacity to help you get to that next SuperCharger. It's probably on the future feature list already just maybe not at a high priority.

Good conversation all -

GeirT | October 29, 2013

@ robert@bis.se

Ref. coasting, I seem to recall the great advantage with the SAAB in the olden days was the "free wheel" that exactly gave you the coasting effect you are talking about.

As to illegail...they even have a law for that in the US??? Jeeezzz!

Tesla-David | October 29, 2013

@Robert
Thanks for posting your driving efficiency ideas. I try and drive my Tesla as efficiently as possible without foregoing the fun that driving this incredible automobile provides, and have averaged around 289 W/mile over last 3,500 miles. I will try coasting in neutral to see how that affects my energy use. I have found that I get much better efficiency on longer commutes, and have great difficulty getting below 300 W/mile on short drives of less than 5 miles. Keep posting your experiences and ideas. I appreciate your concern for reducing impacts to our planet.

robert | October 29, 2013

@Geir T

Oh yes, and I had one and drove it very far. The main idea was that when you lifted the gas foot, the car didn't have any motor brake at all, but kept rolling without your having to change to Neutral.

Was that car outlawed in the US, I wonder?

Robert

robert | October 29, 2013

@Tesla-David

Yes, this is almost certainly because you use a lot of energy to heat up the Battery to a proper level. I always find that the first 2-3 miles - however much I try - have a huge consumption that only my owning a smart-phone could prevent...

As I said, my 240-mile roundtrip (that is, if I get that far) on Thursday will give me all the answers I need.

Best - Robert

Notre | October 29, 2013

I am an addicted coaster and have saved literally tons of gas over the years, but am not so enthusiastic about continuing the practice with the MS.

10% saving is an overestimation in my view compared to regular driving with a gentle right foot and standard regen.

Percentage saved is obviously much less compared to a similar ICE vehicle and the absolute amount of energy saved is at best slight.

Cindy I II III | October 29, 2013

Sorry a little off topic here.

@Brian H, I've always enjoyed your postings. Meanwhile, there's story I will not forget - my high-school best friend wrote me her first letter in English professing our friendship. I took out a red pen, made corrections, and sent it back. She wasn't the same friend that I had ever since. And my intention was totally good thinking she would benefit from my feedback. I suppose human beings have feelings, and I missed it in the name of progress.

Notre | October 29, 2013

I think going down a slope at 80 or 90 kmh with cruise control is more efficient than letting the car roll and gain speed to above 100.

More energy is wasted by increased drag than in regen which I have discovered is surprisingly efficient.

Thomas N. | October 29, 2013

Cindy -

I don't know how that could have been taken any other way! If I were to write somebody a letter in Spanish and profess my feelings about our friendship and they sent it back with red markings all over it with corrections I would never write back again.

Mathew98 | October 29, 2013

@Thomas N. - I'm sure Cindy is his wife's name. Then again, I've been told that I'm wrong quite often. Just ask my boss...

qblack1 | October 30, 2013

P85+

I regularly travel at 325 Wh/mi but I only drive a maximum of 100 miles per day. Every other weekend I will drive out to a sporting event ~125-165 miles. If it is in the 125-130 mile range I find I'm bumping up against the limit of the round trip (250-260) range without any recharging. Accordingly, I try to drive in a very efficient manner, usually using cruise control the vast majority of the way. I've always considered the current cruise control inefficient, as it will regen to keep the speed constant, and then immediately power up the next hill to keep the speed constant.

I tried using the neutral setting when going downhill, and then into drive up hill at the point my speed started to just go down. My initial impression is that this technique is VERY efficient compared to just cruise control. I would regularly have a hard time keeping <300 Wh/mi, but with just one day of using neutral on downhills, I am easily below 285 Wh/mi, which bodes well for range.

FEATURE REQUEST: A button on the steering wheel (not a new one, just a repurposed one), that allows you to toggle regen fully off or on. I find using the yolk drive/neutral select to be kind of a hack, but it works. And on the touch screen you can only select standard or low regen.

280-285 Wh/mi in the rolling hills of Western NC is great! Intermittent neutral coasting seems to be useful. This certainly will increase my range. That being said, by the end of the year, I should have 4-5 superchargers in range, so we'll see how that effects my efficiency...

robert | November 1, 2013

Bumping this for AmpedRealtor

AmpedRealtor | November 1, 2013

Thanks Robert, I'm late to this party...

I have been experimenting more with coasting as well, and have been able to lower my energy usage to about 250 Wh/mi. I have a P85 w/ 19" wheels. I have now switched my display to show ideal range, as I have been getting at least ideal range - usually better - when incorporating a lot of coasting into my driving.

Pasadena-S | November 3, 2013

I've had my S85 for more than a year now, and since I am an engineer interested in efficiency I have tried lots of tricks to improve the Model S efficiency. Clearly, coasting to stop or to adjust down your speed is more efficient than using regen, by that factor of 10-20% that is the "round trip" power loss when using regen.

Since selecting Neutral doesn't really disconnect the gears (there is no transmission); all it does is turn off regen. You accomplish the same thing by "feathering" the accelerator to make the power meter zero.

I think there is a relatively easy software improvement that would address 90% of the need to use Neutral to coast.

Right now, feathering the accelerator is rather difficult. It requires quite a bit of concentration to keep the pedal position at the point where the energy in/out is zero. This is because the sensitivity of the pedal is the same (or, at least "feels" the same) no matter whether you are near zero or heavily accelerating/decelerating. What we need is to flatten the response curve near zero power in/out. That would provide a large "plateau" that would be easier to find with your foot, and on that plateau the responsiveness of the pedal would be decreased. The plateau would be located on the power consumption curve, not speed, and so would adjust for going up and down hills, wind, etc.. And making this position easier to find would reduce the cognitive load of driving efficiently, making it more pleasant and more safe.

Would that plateau dampen the response when you try to accelerate. Sure, a little. So accel or decel would be a bit "mushy" near zero. But who cares about small changes near zero? And you could potentially overcome that effect by using the rate of change of your foot position. The mouse on my PC or Mac does this: it's called, coincidentally, "acceleration", and gives your hand a way to "throw" the cursor while still keeping fine control while moving slowly (i.e., by flattening/steepening the response curve as a function of rate of change of position). Similarly, if you "stomp on the pedal", the rate of change would be high, and the software would respond more quickly.

In summary, I'd like to see Tesla provide a driving setting that would allow for a broader "zero power" range for the "speed request pedal".

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