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At the North American International Auto Show in Detroit Tesla had many stories to tell. We displayed three cars, each representing a facet of the Tesla story. VIN 1000 embodied a significant production milestone. The Road Trip Roadster, filthy from its drive to Detroit, was a testament to the durability and toughness of our technology. The Model S symbolized Tesla’s future – the ruby red car dazzled media, fans, and industry leaders alike. Peter Rawlinson, Vice President of Vehicle Engineering, met with Engineering TV to talk about the Model S development process.
Watch the video to learn more:
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Nice to have new engineering blog entry.
This wasn’t as good as JB Straubels previous blog, but OTOH I can’t recall any that was better, and this is no worse than usual blogs here. Maybe my expectations were a bit too high.
Still no new info about Type S. Nothing about batteries, car energy usage or practical user experiences about that 17″ touchscreen. I’m very worried about that last one. I really want my controls be usable without looking what you are doing, which that obviously is not, and also how that affects your vision at pitch black night. The less light-sources there are in the cabine at night the better.
I wont be ordering my car before I have some real info about real life range, that touchscreen and car battery durability.
Well, maybe after a few years that info is available. Five or so. Maybe we get Mr Fusion by then
(jokes aside, it is possible that something like Focus Fusion reactor might be possible to build so small that it fits in truck (what is that word…the part of the truck that makes the work, not the cargo). Then you would have practically infinite range for long range trucks).
The touchscreen is overkill – after all the publicity about distracted driving, it is possible that such displays might be illegal by the time the Model S hits the streets. Tesla needs to have a back-up plan, such as a manageable 6″ or 7″ touchscreen for navigation applications, with normal, physical knobs and buttons for standard functions, like A/C, fan, heat, stereo volume, etc., with redundant buttons on the steering wheel. Perhaps hiring some people for developing voice-activation (or licensing the tech from someone else) would provide a permanent work-around so that the details of the physical interface are relatively immaterial.
Otherwise, I think the Model S is awesome, and I look forward to the day in the near future when I am able to comfortably put my money down.
Tom A.
I agree that Type S is gorgeous. One of the most beautiful cars I have ever seen. Better than Roadster for sure. Maybe I get to see one live someday in near future, so that I can see it in practicality point of view. Ground clearance, how good it is to sit on, that sorts of things. I’m a bit big person (180cm, 110kg, with broad shoulders), so many cars in last car show didn’t have enough shoulder room for me to be comfortable. Subaru Impreza WRX had that space, and then there was those clumsy certain-bodypart-extensions that also did have that space, but I don’t need such a vehicle.
Timo: I don’t think they have the info you, and the rest of us, want to know – they only have two fully-operational pre-production units. Tesla probably doesn’t have the 300-mile pack operational yet; there’s probably no user experience studies yet; they even admitted that they are still designing the car – looking for more room in the “boot” and 3cm more headroom in the cabin. In short, the Model S isn’t “done” – it’s not ready for production. I think they are giving all the info that they actually have, or are willing to provide at this stage in the development process. Perhaps the recently-announced IPO will require more transparency.
I am grateful for an update on the engineering blog, though the lack of details and specs is disappointing. However, the design isn’t finished, so I guess there’s only so much we can reasonably expect at this time. Frustrating, but reasonable.
Finally, the truth from Tesla (I just now watched the video) – the Model S design isn’t complete yet. That explains why they haven’t verified the range, 0-60 times, internal dimensions (leg room and head room, size of “trunk” under hood, etc.), traction control results, 300-mile pack testing, etc. There’s no final product to measure/test yet. That explains everything. Once I saw a driveable car, I assumed that it was a production vehicle. I didn’t realize that it was just a prototype.
I agree, Timo, that I would like to see a production vehicle in person so that I could sit in it. I’m 6′4″ and I hear that Elon Musk and other top brass are over 6′ tall as well, so I assume that I’ll be able to fit comfortably, though there’s nothing like sitting in it to be sure. Just about every Japanese vehicle I’ve ever driven is a tight fit, particularly for my legs. That’s also true of the many recent US products. I don’t think that I’ve ever sat in the driver seat of a European vehicle…oh, I drove my uncle’s 525i once…I was still in high school then, so I wasn’t fully grown and I don’t remember how it felt, except that I kept stalling it – the clutch was so smooth that I could not feel when it started to grab.
Anyway, it looks like we’ll just have to wait a little longer for the design to be completed and the subsequent test results and dimensions.
Good luck, Tesla. We’re watching and waiting.
Why does he say that the Roadster Sport has about 240 horsepower? I thought it was more like 288…
Actually the touchscreen is a great idea. I have a Roadster which has a small touchscreen and it works well. Many cars like luxury vehicles from Europe use buttons which have cryptic or no labels due to lack of space and are vary hard to use while you are driving. A touchscreen allows clearly labeled controls for a radio for example that you don’t need to pull out a manual to figure out how to operate. A touch screen Nav system as part of it would be a big improvement over typical button based in car systems. With a touch screen because you can use the entire space for the display instead of button you can for example get a much larger map screen, you can have separate screen for separate functions so there are not dozens of tiny button which are hard to select when you are driving down the road. Really because the ease of use you can do a much better job of keeping you eyes on the road.
Stuart Koford:
Do you look at the touch-screen in your Roadster when you use it? If you do, then it is a bad thing. Optimal situation is that you never ever need to look at any of the controls you are using, and can go by feel or instinct alone. Even looking at speedometer is a risk in traffic (but obviously necessary when you can’t trust a feeling how fast you are really going).
Obviously knots and buttons should be user friendly and basic settings should be usable without looking, which isn’t the case for many cars, but for example basic radio/CD/mp3/whatever volume control is easy with a single knob. Not so easy with touchscreen. You could of course move those basic controls out of the center console and to the steering column. This is probably the safest option, and very useful after you get used to it. But a bit confusing for first time users.
Another concern about 17″ touchscreen is its durability and usability in different conditions and situations like -30C cold or +40C hot, how well it behaves after billion use, how well you can control it with gloves on, how well it withstands small impacts (like for example tossing laptop-backpack to the passenger seat, and part of the pack hits the screen), does it reflect sun for example at some position. etc. etc.
It might be good, and then again it might not. Nobody really knows yet.
Just because it is a 17″ touch screen doesn’t mean that they can’t put some kind of bezel over part of the display to provide “pits” for the various buttons. For all we know the 17″ screen could appear to the user as multiple separate smaller displays.
In any event don’t get too wound up about things before they have shown a production intent car. Remember they only get the screen in the dash on the show car a couple of days before the unveiling!
Has anyone considered tapping off the battery cooling system to heat the cabin during road travel. I understand that the battery system has a water/glycol cooling system.
Another thing about a touch screen: if it goes “down”, you’re SOL — no controls. Impossible to make a screen as robust as a mechanical knob.
That could be a really good idea if it produces enough heat, but I haven’t heard anything. Given how far they have yet to go (the electric motor isn’t even finalized yet, according to the video), they might be working on using the heat from the battery pack as we speak.
I do not know if they do that with the Roadster. Probably not, or we would have heard about it by now.
Andy: good point about the touchscreen – I hadn’t thought about a bezel or the fact that it IS just a prototype. Given all that has been going on about distracted driving, etc., I wouldn’t be surprised if tactile-less interfaces, like the prototype has, will be illegal before the Model S hits the streets.
Besides, the real future is voice-activation with a few redundant buttons for critical things like lights, wipers, stereo volume, A/C, heat, fan speed and cruise control on the steering wheel and column.
Tesla makes, hands down, by far the best EVs on the road today and for several years into the future (based upon concepts and prototypes from the major automakers), but to stay on top, they will need, among other things, to work toward vocal interfaces. “hands-free” is the name of the game for safety as well as convenience (as long as it works).
From an Engineering point of view, how does Tesla ensure the breaks are fully functional during the re-gen process? With the latest press about the Toyota Prius, one helps to wonder what Tesla has done to ensure this type of problems don’t happen on their cars. What are the fail safes and differences from the Tesla safety break system and say another hybrid car on the market? What about the Tesla S model as well; how is that being designed?
The CODA interface is much better – a touch screen of manageable proportions, while having normal, mechanical knobs and buttons for fan, A/C, etc. Their built-in bluetooth, microphone and other various hands-free technology is fantastic.
Very little has been reported by Tesla – does the R, and will the S – have hands-free features, such as bluetooth or equivalent? I’ve read just about everything there is to read about Tesla, from this site to autobloggreen, to wherever, and I can’t answer this question. Can someone? Timo? cablechewer? Brian H? Tesla staff?
Thanks.
Actually, my last comment (which is still “awaiting moderation” at the time of this entry), was kind of dumb – “I’ve read just about everything there is to read about Tesla…” In my defense, I am putting emphasis on “just about”:
Edmunds.com discloses that the Roadster has Bluetooth capabilities for hands-free cell phone use. If I were to peruse the owner’s manual for the Roadster, it would probably say so, as well. It would be reasonable to assume that the base Model S would have Bluetooth and iPod functionality, as well (I would hope so, for a $50k+ vehicle).
Robert;
Tesla Roadster regen braking is basically engine braking when you lift your feet off the accelerator. Brakes are just brakes, no regen there. As reliable as any car with basic brakes (if there is such thing as “basic” for brakes anymore).
What I have read this can be a bit confusing at first, but fantastic when used to. You can drive in traffic with one foot. Your accelerator becomes both: accelerator and deaccelerator and actual brakes are used only for real emergency or when regen is not slowing you fast enough. With one pedal doing both you get a very precise control about your car pace when closing traffic stops.
If regen breaks it basically means that your engine has broken, but you would still have brakes. If brakes break you would still have regen to slow you down.
Frankly, I’m not concerned with the touchscreen, beyond being disappointed at how much attention it’s getting.
I mean, we’re looking at the second iteration of their technology. Sure, the user interface is important, but I’m more concerned with what’s changed under the proverbial hood. I understand that after the fiasco with the transmission, Tesla is reluctant to talk about it, but I want to know if the switch away from a 2-speed transmission would change the balance toward one smaller motor per wheel… what the trade-offs are in the additional control and reduced mechanical complexity (compared to current AWD systems) vs the additional unsprung weight. This is the kind of stuff I’d love to see an engineering blog about.
I’d also love to see something about evaluating emerging battery technologies, but I really doubt we’ll see that.
Ben: I agree that battery tech would be a useful post – I’ll second that! I also will second any motion for details about the motor – according to the video, the traction motor in the Model S is not the same as the Roadster or the Roadster Sport. I, for one, am curious.
As far as the transmission goes, I think you’re behind the times. The single-speed gearbox in the production Roadster has been a huge success, and that’s the exact same design principle they are applying to the Model S. I have neither heard nor read that Tesla has ever considered anything other than the fixed-ratio transmission for the Model S.
To add Bens and Toms posts, I am very curious to hear how that optional 4WD is planned to be made. Two hub-motors in front and one bigger and nastier motor in back?
If hub-motors, have there been any validations or tests yet, and if there are what are the results of those?
Maybe two motors where front motor works just like traditional front-wheel drive cars with some control-electronics making their magic between the engines? Single motor and longer shafts like traditional 4WD?
What about car losses? Wind resistance figures? Rolling resistance figures?
Actually you could post almost all of those figures that Roadster had in JB Straubels excellent blog. Just leave achieved range out. You can estimate car losses pretty accurately without much data. Estimate battery weight and run some test-runs with Roadster drivetrain, and you have estimated pretty much all the losses that that car will have. With slightly better engine and drivetrain efficiency you could get slightly less drivetrain losses, but aerodynamic losses are already fixed with that chassis design, and rolling resistance comes from tires which are not going to develop much combined with car weight, which will not be huge variable, and even drivetrain is already so efficient that it just can’t have much effect in total outcome as long as you stay on efficient RPM range of the engine. Battery weight is perhaps the biggest variable in this. And also the place where EV optimization is in general going to happen in near future.
What you *can’t* have is power figures, acceleration times, battery capacity, handling without knowledge of weight distribution etc things like that.
Battery tech blog would also be very interesting. I have some vague idea what future will give us, but current high-tech battery techs with reasonable prices are more vague area. Single person just can’t browse all battery manufacturers and look at their battery prices/capacities/durability etc versus some other battery manufacturer.
Tom: What I was getting at in my post about the transmission was that maybe instead of having a big electric motor and more conventional drivetrain, it might make sense to switch to in-wheel motors. The reasons to go the way they did, as far as I know, are 1) if you’re planning on a 2-speed transmission, you need one of those per motor, and 2) unsprung weight (electric motors aren’t very heavy, but I don’t know how much of a difference it makes).
There may be factors I don’t know about. I think it would make a good blog.
Will the tesla sedan have an exterior sound system, such as a beeper (like dump trucks or some earth-movers have) to warn pedestrians, as it backs up in, what is otherwise, near silence?
Ben: I see what you mean – the original idea of a 2-speed transmission would have knocked hub motors off the brainstorm list by default.
As far as simplicity goes, hub motors are more complex because there’s more than one, so the control electronics need to be significantly more advanced in order to account for variations, dirt buildup, etc.
With Tesla’s elegant simplicity in every aspect of their drivetrain design, from 1 motor and fixed-ratio gearbox to their brake system being separate from regen activation, I don’t see them going to hub motors any time soon. The added complexity provides more things to go wrong and a higher cost.
I have a feeling that Tesla scrapped the AWD option. It was on their promotional page for the Model S after the reveal, but then it silently disappeared a few months later. I think they dropped it because of the battery pack placement, as well as the need to make the battery swappable. Having a drive shaft go up the middle of the car to drive the front wheels would, I imagine, put a huge monkey wrench into the works. Plus, the added weight, moving parts and such would significantly affect range, just like AWD options drop a few mpg compared to their FWD counterparts.
I’d like to see an AWD feature; however, if Tesla has scrapped the idea for now, I’m not surprised, for at least the reasons of increased complexity, cost and reduced range.
hmmm…with all the concerns about the silence of electric vehicles at low speeds, I would assume that regulations will come out in a year or two that would require some sort of beeping or fake engine noise below a certain forward speed and for reverse.
Given unsprung mass problems and effects from shock and intense vibration on hub motor longevity, are hub motors really a better idea than 4 mechanically separate motors that, while individually driving each wheel are not mounted there, but on the frame and only transmit power through half axles, attached via pairs of “universal” joints? There, only the wheels themselves (and a portion of each half axle/u. joint assembly’s mass) are really the unsprung members. Wheels and axles need not be as delicately built as electric motors, which need careful contact between electrical parts.
Interesting…I hadn’t thought of that. I do agree that hub motors aren’t a good option, regardless.
If they were to do as David suggests, then why not just two motors, one for the front wheels in addition to the rear motor? That would negate the need for the axle bisecting the battery pack, which I posited as a potentially serious hindrance to other aspects of design. Having two motors/reductions would increase complexity and weight, but at least the complexity would be manageable. The second motor would probably need it’s own inverter, but it all could be controlled by a single processor.
If Tesla could develop useful and cost-effective AWD, that would be another leap to stay ahead of the EV curve. I can’t reasonably afford the Model S as is, so it doesn’t make any difference in my personal decision; however, it would be a smart move. It would help compete against Audi’s quattro and everyone else’s equivalents (Mercedes 4-motion; VW has their own version, as does BMW…I forget their trade names).
On a different note, isn’t it a bit odd that the company name, “Tesla”, is not recognized by the built-in spell checker of these comment fields? The webmaster needs to add Tesla to the database.
Hub motors introduce additional electrical / software complexity (see the previous posts on motor control), and reduce mechanical complexity. Since electrical motors themselves are relatively light, and the weight of 4 smaller motors is comparable to 1 larger one of equivalent power, I don’t think we should dismiss it out of hand… after all, since they’re already using a digital motor controller, the additional cost is in development, compared to a higher per-unit cost for the current system. The model S will still be relatively low-volume, in the grand scheme of things, so I don’t know where the break-even point is.
And you’re right: the additional complexity of 4 individually drivable motors is more opportunity for things to go wrong… but it’s also more opportunity to provide functionality that gasoline-powered cars just *can’t*. Kind of like the side-by-side videos in http://www.teslamotors.com/blog4/?p=65 , but more so. I don’t know as much as others about the details, but over the years, we’ve done some very interesting and complex things with rear differentials, all-wheel drive, etc… things that make the system more mechanically complex, and wouldn’t be necessary if we had fine-grained control over each individual wheel.
Anyway, enough soapboxing… I think I’ve made my point, and I’m sure the engineers have already considered all these factors, and many others, and would have made their decision on something this big (affecting so many other aspects of the design) some time ago.
As far as the spell-checking is concerned, that’s probably handled on your end by your browser. I can’t imagine their webmaster wants to transmit a spell-checking database every time someone visits the site.
While it can be fun to do this “armchair engineering”, I will trust the engineers at Tesla Motors to come up with the best
EVs on the market.
Tom A. The spell checker is “built into” your web browser, it isn’t downloaded from Tesla. My web browser, Google Chrome, does recognize “Tesla” with no problem. Google Chrome is a free download from the Google website, and I recommend it highly.
Tom A. ;
Using two motors (one front; one rear) would still require mechanical differentials, with their weight and volume penalties on battery weight and volume and, consequently, maximum range.
The frame supports for the two motors could be central sills (one front and one rear) which only extend between two cross members, there for the purpose. The battery pack need not be bisected.
Ben – good points all around.
Ben, CM – thanks for the spell check info!
Most spell checkers allow you to add any word you wish to the supplementary dictionary. Try right-clicking the word when it’s flagged.
EV 4WD is going to be an interesting technical challenge for anyone who first introduces it. I wonder if Tesla has some cute solution that it thinks might be workable, but isn’t yet sure about.
For spell checking, I rely on my word processor (WordPerfect), on which I always write preliminary drafts, before copying them onto blog sites.
I think I speak for the hundreds if not thousands of us on the EVlist when I offer our sincere condolences on the recent loss of your 3 employees. A tragedy felt by all the members in the EV family.
It boggles the mind that our US DOE gave $450,000,000 (tax dollars) to Tesla who assembles an electric car using off-the shelf components. I have to hand it to Tesla; their marketing persuasion is world class. But aside from the battery technology difference Li-Ion versus SLA.. Tesla EVs have ZERO advantages over the General Motors EV1. And we all know what GM did to all their EV! Cars. What’s even more mind boggling is Dr.Steven Chu Secretary DOE a physicist went along with the deal? Where was Chu’s brain when he looked at the off- the- shelf technologies Telsa use. There batteries are nothing more than energy storage devices, dinosaurs of so-called high-tech……….. Thank you GC
I’m fascinated by Galactic Cannibal’s recent post–can’t say that I understand his thesis, though. One thing with which I do agree” “There (sic) batteries are nothing more than energy storage devices..”. Uh, yeah.
I too am a bit confused about that GC post. Why not give that loan to leading EV manufacturer that has best EV in the world? Tesla has at least two components in their car that are not “off the shelf”: Engine and transmission. I believe that also PEM is their own design. And chassis. So what that leaves for “off the shelf” is …. hmm …. batteries. Actually even that is _as a modules_ Tesla design.
OTOH I do understand his wonder about what’s the great fuss about EV:s in general. They are not new invention. In fact EV is quite a bit older than most people realize, it has been around nearly as long as there has been ICE cars. In fact I don’t think that there are anything revolutionary in techs Tesla uses. What is revolutionary is the fact that this car rivals and beats most comparable priced ICE cars.
What GM did to EV1 is not possible with Tesla. GM leased their cars, Tesla sells them.
Yes, batteries are off the shelf tech and yes they are nothing more than storage devices. So? What else is there that has same Wh/kg ratio and is as easily usable as batteries?
To be honest, I’m not sure the appeal of the touch screen for certain things that are perfectly served with knobs and physical buttons.
I think it’s very cool and helpful for the other features (web browser, GPS nav, pandora, etc) but for something that is perfectly served with a slider and that you, basically, always want immediate access too… I’m not sure the benefit.
Can the touchscreen be effectively used with gloves? I live in a cold climate and routinely get into my car at less than -20 degrees and will want to be able to quickly kick up the heat without taking off my gloves.
It’s true that batteries are “just” energy storage devices… but then again, you could say the same of the hydrogen in a fuel cell – you spend energy to convert it from a low-energy state (such as water) to a high-energy state (like hydrogen and oxygen), and the fuel cell converts it back, releasing the stored energy in the process. Other forms of fuel cell fuel do much the same thing. The energy density is substantially higher than a battery, but the storage process tends to be less efficient.
You could say the same of the gasoline powering an internal combustion engine (or a generator) and be technically correct… but the storage was so long ago, and we don’t have a fast or efficient way of recreating it ourselves, so it just becomes another less-efficient way of generating power than at the plant. And I’m not aware of any other methods of power generation that would be feasible in a mass-produced car – solar comes closest, but that doesn’t generate enough power to run the car continuously, and if you’re going to stop the car to charge when the batteries run out, you may as well just charge at home anyway. I’m also biased against solar because I live in New England.
So really, there are 3 choices for powering an electric car (unless I forgot something, which is always a possibility):
1. Fossil fuel-powered generator, a la Chevy volt – Effectively a hybrid, but without the added complexity of having two drivetrains.
Pros: Uses existing infrastructure; quick refueling. High energy density, relatively low cost. More incremental changes will probably encounter less resistance to adoption.
Cons: Doesn’t stop our dependence on foreign oil. Least efficient (though still more efficient than an internal combustion engine). Higher mechanical complexity may reduce reliability (I’m not sure about that one). Possible weight or noise concerns, depending on implementation.
2. Fuel cell vehicle, such as Honda FCX – Basically uses chemically stored energy as a battery.
Pros: Fast refueling. Low cost per unit of energy stored, particularly for larger tank sizes. Most futuristic-sounding of the three, which may be a draw for some people.
Cons: Almost no existing infrastructure. Fuel cell may not meet peak power requirements, or even sustained ones in performance scenarios. Less efficient means of energy storage.
3. Battery-powered vehicle, such as Tesla Roadster or Model S.
Pros: Most efficient energy storage. Immediately benefits from improvements in power generation on electricity grid. Existing infrastructure can be re-purposed relatively easily.
Cons: Hard to charge quickly. Cost, especially for good range. Weight. Still some stigma attached to electric cars. Maintaining charge (and health) of battery may erode efficiency gains over other solutions.
Energy storage technology isn’t improving as fast as we’d like, but there are changes in the works to address many of the problems listed above. In the end, there are valid reasons for choosing any of these… but right now, in my opinion, Teslas look pretty compelling… if you can afford them.
As far as the improvements over the EV1… I imagine there have been some mechanical improvements, though I can’t say for sure. But even though there hasn’t been a revolutionary improvement in the underlying technology, that doesn’t mean there’s no value in the product. GM looked at the EV1, and decided that they couldn’t manufacture it, have people buy it, and make a profit. How right they were is a matter of some debate, but it’s what they chose to do. Tesla seems to be having better luck so far. Don’t underestimate the difference between building a proof of concept and making it into a viable product.
Timo says true.
“Maybe two motors where front motor works just like traditional front-wheel drive cars with some control-electronics making their magic between the engines? Single motor and longer shafts like traditional 4WD?
What about car losses? Wind resistance figures? Rolling resistance figures?”
Just a thought, but if you could take the Bloom Box from Bloomenergy once the technology gets smaller with a small propane or natrural gas tank to replace some or all of the batteries, this would not only give you more kw but increase mileage and reduce weight of the car.
Will Tesla Motors ever open an new factory on the east coast, maybe Tennessee where the Saturn plant is now located and for sale?
Jason; I very much doubt that that Bloombox can get smaller than high-tech batteries for kW/kg -scale and because of that also mileage will be less. It runs at high temperature which requires insulation and it does need that fuel tank which is pretty heavy and bulky.
You did see the 60minutes video where the inventor lifts up one block of “bloombox”, and says that this is enough for European house? Well, I use about 262Wh / hour an average. Tesla has 180kW power, so you need 687 of those blocks to get same power. It looked that it is about half a liter in size, so that is 343 liters in volume. I bet it did weight over one kg, so for the same power need _without counting fuel tank or insulation_ you get about same size package than Roadster battery.
Also there is no infrastructure for fuels that uses, it lacks the easiness of just plug in when you get home of BEV:s.
It also emits CO2 which is not a good thing, and is very expensive: about hundred times more than batteries.
Just noticed that main page flash-animation now says “236-mile range”. What happened to 244 mile range? EPA changed their test?
Because I know that car itself has not got worse, that change must reflect to something else. Is it “highway speed range”, or is it just EPA test changed?
BTW, performance-specs still say “range 244 miles”.
What is the difference in power consumption if I drove 60mph for 50 miles vs 120mph for 50 miles?
Chris; look here: http://www.teslamotors.com/blog4/?p=70
That’s JB Straubels excellent blog about Roadster power consumption, estimated range and stuff like that.
At 60mph you use 250Wh/mile, at 120mph you use 650Wh/mile. About 2.6 times more.
Note that this same would apply to ICE-cars too, your fuel consumption raises just like that.
Also I think that you overheat engine before you have driven 50miles if you go 120mph, so that is just theoretical. AFAIK that emotor Roadster uses is air-cooled, it would need more efficient cooling system for prolonged near-max RPM usage.
Tesla should consider partnering with Apple or Google to use its Apple or Android operating system for car firmware. It would bring a whole lot of apps that are already written and connectivity, GPS, etc. I love Android, I think Tesla should pick it over Apple.
I want to ask a question. Is there any fuel difference between going with 90kph and 120kph? If so, how can we measure it and why does this difference happening? Thanks.
Even if you ignore the size and weight of the bloom box (of course you can’t, but bear with me), and you budget enough power for an admittedly arbitrary 80 mph sustained (you can use ultracapacitors for peak power requirements), and assuming that the bloom box will provide 1 kW of power for $3000 (the numbers I’ve seen in a quick Google search are generally 1 kW for a “typical” American household)… then it would cost $90,000 just to provide the power. That’s quite a bit more expensive than the $36k it costs (according to Tesla, quoted by Wikipedia) to replace the battery pack today.
If you don’t ignore the size and weight, then as Timo correctly pointed out above, fitting enough power blocks into a car is… enormously challenging, at best. And you still need the fuel tank.
Some people claim that the bloom box is carbon-neutral since the carbon it emits is equal to the carbon that is captured when creating the fuel. Really, it depends on where the fuel comes from… I’m hearing natural gas.
Kemo; getting up to any particular speed costs more energy as the square of the speeds. So accelerating to 120 kph takes (120/90)^2 = 155.6% as much power as getting to 90 kph. Then rolling and wind resistance are also higher by about the same ratio once you are cruising at that speed. So you could expect perhaps 3/4 the efficiency.
I’m sure there are others here who can give you better assessments and numbers, tho’. Just trying to give you an approximate idea.
UK Solar – Scam or just Stupid?
The government is going to pay many times market value for rooftop solar power feeds.
http://www.guardian.co.uk/commentisfree/2010/mar/01/solar-panel-feed-in-tariff
“The government wants everyone to get the same rate of return. So while the electricity you might generate from large wind turbines and hydro plants will earn you 4.5p per kilowatt hour, mini wind turbines get 34p, and solar panels 41p. In other words, the government acknowledges that micro wind and solar PV in the UK are between seven and nine times less cost-effective than the alternatives.”
Kemo, Brian H;
To add Brian H comment; you can quite accurately measure losses car causes at any speed. Basically those are drivetrain losses, rolling resistance, ancillary system losses, and air resistance. At high speeds air resistance is the dominant factor but rolling resistance is quite big one and also quite constant from start to max speed, so at low speeds that is the main factor.
What you can affect most are drivetrain losses and ancillary system losses. Rolling resistance is something that good tires affect quite a lot, but it depends a lot about terrain you are driving too. Weight of the car affects to that most.
Because most of those losses are constant except air resistance, you only need to measure those constant losses by running car in top of…whatsitsname…rolls under car tires so that car does not move. If you have wind tunnel you can measure car CdA (drag coefficient times car frontal area) and calc the air resistance. There are also computer simulators that can do that same, but with less precise results (but those allow simulating whole thing, which means much faster design phase).
That means that car range and so on can be estimated quite accurately before it is even build ready if you just know losses of all the parts. Basically that is just physics and math.
Of course those give you only estimates (though quite accurate ones). You need to run real-life test to do corrections to that estimate. Wind condition and different terrain effects are quite difficult to estimate.
Here is JB Straubels excellent blog about Roadster energy usage:
http://www.teslamotors.com/blog4/?p=70
Assuming 2-wheel steering: on turns/curves, each wheel is taken on its own, separate, track/radius/circumference, with therefore each rotating at its own, separate, speed. Having 4 mechanically independent (not necessarily ELECTRICALLY independent) electric motors driving each wheel, the innermost wheel, which always follows the smallest radius and therefore has the slowest speed, propels the entire vehicle and so needs enough torque for that. Each motor, in this case, needs to be large enough to propel the entire car.
4-wheel steering though (as GM pickup trucks have optionally done, and sedans/roadsters could also) can be designed to always bring both of each side’s wheels, into the same track (with consequentially the same radius and circumference). This keeps each of these 2 wheels rotating at the same speed, sharing the load equally. For this then, motor torque would need only 1/2 the requirement for the whole vehicle.
By the way, since outer wheels coast, only one common speed control is needed.
Incidentally, with each “rear” wheel always precisely following the wheel in “front” of it (in a given direction), traction gets somewhat boosted too.
As commonly used in Diesel-ELECTRIC locomotives, mechanically separate, electric traction motors save a lot of mechanical weight. In mechanical systems, the more bearings there are in gears, etc., the more friction is introduced. In an electric car, reducing such weight and friction could increase range for any given battery technology.
David: I’m not quite sure I follow you as to why, with mechanically independent electric motors on each wheel, only one can drive the car while turning. If there were no feedback from the wheels to the motor controller, then that might be true… but even in that case it could adjust the torque applied to each wheel depending on the position of the steering wheel.
Since there is such feedback, though (needed for traction control, among other things), it should be able to apply a more or less constant amount of torque to each wheel, rather than commanding a given speed.
Come to think of it, with independent electric motors, you should get that to some degree anyway… you don’t control the rpm of the motor directly; you control the amount of power you put into it. So if one motor is going faster, it might accelerate a little less, but it will still provide a significant contribution.
I’m also not sure what you mean by “not necessarily electrically independent”… you really would need to drive each motor independently, to account for variations in manufacturing. It’s a definite problem (and may have figured into their design for a single motor in the model S), but far from unsolvable.
Racing EV.
Just wondering if there is battery chemistry that could allow serious racing. Doesn’t need to be rechargeable.
Something like Le Mans 24h race with lithium-air batteries with battery swapping tech. AFAIK lithium-air has very high energy density, but low power density. If someone makes a racing car with very fast battery swap tech, wouldn’t it be possible to participate that kind of race and actually get some real results.
In Le Mans 24h race you have to change drivers every now and then, and tire changes, refueling etc takes long enough, that very fast battery swap would be possible without losing too much time. It would be interesting to see if BEV is ready to compete ICE in real race.
Blogs are oddly quiet. I posted my previous message partly to see if these still get updated. They do, so reason must be that people do not write here. Which is odd.
Any wild speculations? Ground breaking new discoveries? What technical gizmo do you like in Roadster and what could be done better? Suggestions for Type S based on experience of Roadster? Something?
The link below is to an article about using carbon nanotubes to supply electric power. It claims that they are able to get 10 times the power-to-weight ratio of lithium-ion batteries. They also project that this is only a few years away from being practical. Looks like this is something worth staying on top of.
http://www.msnbc.msn.com/id/35466087/ns/technology_and_science-innovation/
Something I haven’t seen addressed by any EV manufacturers is the effect of electromagnetic fields on the human body. This is somewhat controversial and, as far as I’m concerned, unresolved. Whether or not prolonged exposure to electromagnetic fields can cause cancer or other problems, there is a segment of the population that believes it can or at least might, and placating them may improve marketing. It seems reasonable to me to err on the safe side and provide a Faraday cage surrounding the batteries, motor, drive train, and electronics.
I could be wrong about this, but I believe that simply surrounding these components in conductive sheet metal (copper, aluminum, brass, and/or possibly even steel – which is magnetic as well as conductive) would solve the problem without a major cost or weight penalty. I think this could also work the other way, protecting the electronics against frying if the car is struck by lightning or in the scenario where a nuke is detonated at high altitude with the intent of disrupting electronics rather than causing physical distruction.