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Battery Weight V.S. Acceleration Time

Is it safe to assume that there will be a weight difference between the 160, 230, and 300 mile range battery packs? If so, what will this do to the overall acceleration of the car? The website shows that the Model S will hit 60mph in about 5.6 seconds and can have a range of 300 miles. Could this possibly mean that if one were to purchase a Model S with the 160 mile pack that it may accelerate to 60mph closer to or even under the 5.0 second mark due to less weight? Or do you think that Tesla based their approximate acceleration statistic on the lighter battery pack?

For the record:
Subaru WRX STI: 221 kW / 5.2 sec

that is what new tech may enable :)

think that in the car industry the power increased in 100 years by a factor achieved in computing in less than 10 years; electric motors may just give us a quantum leap !

There's an enormous amount of speculation here based on
very sketchy information. As I recall, the 300 mile battery pack
contains advanced high density batteries. I assumed that the weight of the 300 mile pack would equal that of the 240 mile pack, which will be greater than the 160 mile packs, presumably by roughly 50% (excluding common weight, such as the enclosing metal
envelop, coolant, etc. ). I don't believe that Tesla specifically indicated which battery pack produced the estimated 5.6 second acceleration time. Perhaps it's essentially the same for all three. Obviously a larger battery pack could provide more power, but perhaps the smaller packs can provide just about all the juice the motor could ever consume, and while the larger packs can provide somewhat more, they are also heavier. Notice that the Fisker Karma, using only its small battery pack (probably around 16kWhrs), cannot accelerate faster than 8 seconds, but by running its engine in addition, can get to around 6 seconds. The Fisker weight is said to be 1000 pounds more than the Model S. But if that pack were as large as the 160 mile Tesla pack (around 40 kWhrs) it obviously wouldn't need to turn on the gas engine to generate enough power. This data leads me to believe that the 5.6 second time is probably for the base battery pack option and it's likely that the longer range models don't differ substantially.
A better approach would be to simply ask Tesla engineers. They'll know.

To add fuel to the fire of rampant speculation: I heard or read somewhere, don't remember or I'd post link, that the S super will go 0-60 in 4.4 sec. Dream on, my friends!

I heard or read somewhere, don't remember or I'd post link, that the S super will go 0-60 in 4.4 sec.

This seems to be a popular rumor, 1st hand sources that confirm these numbers would be very welcome. As far as I am concerned, 4.4 seems a plausible figure for a Model S Sport.

The Model S sport is supposedly going to have a 4.4s 0-60. That is probably as good as it's going to get for the 4 door model s.

OK, let's come back in about one year (or when Tesla announces the sports Model S) to see what gives. My prediction remains that AWD implies under 4s 0-60mph, possibly under 3.5s !

Now seriously! 0-60 under 4 s or even 3.5s?

The standard Roadster does 0-60 in 3.9, the Sport in 3,7.

The standard Model S will do 0-60 in 5,6s. To make the Model S Sport do anything near 4s would take quite a leap from the standard model. Since the weight will not change substantially, it will require serious extra power.
It takes a Maserati QP 295kw to get to 60 in 5.6s and the QP GTS 325kw to get there in 5.1s.
Anything under 5s for the Model S Sport would be a very nice accomplishment IMHO.

Careful with all that street racing folks.

It is not power that accelerates a car, it is the torque. That is why Roadster beats cars with twice the power in short drag races even that it isn't lightweight car.

If you double the torque you accelerate twice as fast, assuming you can actually deliver that torque to the ground. Problem is that with that much weight normal tires start to slip before you get the acceleration anywhere near under 4 seconds and all you get is a lot of smoke and burned tires.

OTOH with a lot more torque available you can change gearing for a lot higher top speed without sacrificing acceleration. Car that delivers same torque at 0 that can make tires slip and continues to deliver that same torque to the ground at 60 will burn rubber in 60 if you floor the accelerator.

Timo, that is a very common misconception. Hp is derived from torque.
While torque does help cars get off the line, ultimately if your vehicle does not have much hp, it will be slow.

A very good example; there are 500whp/200wtq imports that will destroy 200whp/500wtq v8 cars.

well, I explained earlier how that could be obtained, assuming the battery is powerful enough :
two motors, so we have double power, double torque, double tire surface (traction) :)

The Maserati QP S and the GTS have the same torque, but the GTS is 0,3s quicker to 60mph, but hey I'm no engineer (unlike some others here). Please educate...

All I know is that when you press the pedal on the right you go faster... and when pressing the pedal on the left doesn´t slow you down, you´re in trouble...

@qwk, torque is direct force that accelerates the car. It is torque that accelerates things. At zero RPM you have zero HP, yet you accelerate. Power doesn't tell the acceleration, it is torque. Directly at tires, with gear ratios used at motor.

Power OTOH does tell the top speed you can achieve (well, maybe, assuming you can hit the top power at the top speed RPM). Low power car is not very fast.

@Nicu, double traction doesn't apply in 4WD, when accelerating rear tires get a lot more traction than front tires. When accelerating really fast front tires may even get airborne.

@Ad van der Meer, GTS has probably a bit shorter gearing or it changes gears that 0.3 second faster (if it is necessary in 0-60, not all ICE cars need gear changes in that).

Yep, I admitted there could be a bit less traction on front wheels but we have to remember that the battery is heavy and the center of gravity is very low (plus extra motor on the front wheels); it may be true that up to 20mph front wheels contribution may be small, above that it's only power an torque that matter.

So I'm not claiming the theoretical 3.2s (estimated from 2x everything plus 300kg for the larger battery and extra motor / PEM / "gearbox"), but only 3.5s-4s !

Timo, Ad, both of you are correct in some way.

Let me try to clear up with some physical background.
Torque is translated into acceleration force by the wheel diameter. Thus, more torque=more acceleration.
Power delivered by the engine is proportional to torque multiplied by RPM.
Neither torque nor power are constant over RPM for any given engine, be it ICE or electric motor (see http://www.teslamotors.com/roadster/technology/motor)

For the first few meters, acceleration is limited by tire grip. That's where traction control cuts in to limit engine power, thus limiting torque. usually, you reach ~1g in the beginning for supercars.

Power needed to accelerate a mass is product of speed x mass x acceleration. Assuming a car mass of 2000kg, acceleration 10m/s², we achieve 10m/s after 1s. We need 200'000 kg m²/s² = 200kW (in SI units) to sustain that acceleration at that point of time. Power lost to drag is neglected here!
10m/s equals 22mph or 36kph, and 200kW equals 268hp.

Constantly accelerating to 27m/s (=60mph) we come out at 540kW = 724hp. Somewhat earlier will be the point where we run out of engine power to keep up that acceleration. The traction limit on acceleration is replaced with a power limit. Assuming constant power delivery by an electric motor, this results in a differential equation to which I haven't looked up the solution yet. For ICE car it is way harder to predict because of it's narrow ideal RPM range.

EV will win drag race over ICE in torque limited acceleration phase. ICE will win in power limited acceleration phase IF it is capable of making up the losses at the start.

And for Model S to reach 4.4s for 0-60mph: I guestimate that a drivetrain in the 400kW area will be needed for that.

I reserved a model S.After your interesting discussion about acceleration, that shows a good knowledge of phisic laws, both theoretical and applied, I hope Tesla will sell me a car, not a dragster

I hope Tesla will sell me a car, not a dragster

The short answer is: Both. :-)

The better answer is: only if you drive it that way.

Hp is efficiency over a certain amount of time.

All the torque in the world will not help you win drag races if you don't have much hp. That being said, vehicles with more torque are much funner to drive, and feel faster on the butt dyno, than a lower torque vehicle with much more hp.

I'm not an engineer, but it seems that you'd want all battery options to have the car handle the same, so all adjustments on the assembly line would be the same for suspension and motor, etc.

This would lead me to keep the battery pack weights the same. So simply adding ballast to adjust each pack option so all weigh the same would seem reasonable.

If this is true, then acceleration and handling would be about the same for all battery pack options, assuming the same voltage and current delivery for each option.

qwk, HP is derived from torque. Without torque you wont have HP either. Those are interchangeable values.

What matters most in drag race is RPM range where you get that torque. That gives you speed. The higher the RPM range the higher is the speed you can still accelerate. In ICE cars that is very clear because they need to use transmission to keep the car in max torque area for accelerations.

In EV it is a bit different matter, there is no transmission to keep your car in max torque area. You just start to accelerate from zero RPM and stop accelerating when you car torque matches friction forces. There too wider RPM range helps, but engine HP doesn't really tell you anything about acceleration because your max acceleration actually starts to drop before you reach the max HP.

Instantaneous torque or hp doesn't really tell you anything, you need to combine RPM range to it in order to get a clear picture what the car capabilities are.

Timo,

I know that hp is derived from torque. The lines always cross at 5252rpm. Like I said before, hp is how efficiently you produce work at a certain rpm.

The reason that ICE cars need high rpm's is that they are the most efficient at coverting fossil fuel energy to work at higher rpm's.

You cannot and will not win drag races with low hp and high torque. Simple physics.

The Model S is not going to turn itself into a Ferrari killer. Lets get that out of the way. If you want to blow the doors off a $500k car or a $2m super car, then you have some wiating to do, and the Model S will NEVER be that car.

The Roadster might get into the low 3 second range, but we talking about Version 3.5 or 4 or higher. Why? Because of this little thing called "The Law of Diminishing Return".

This law states that if spend twice the money, you won't get twice the value. As an exmaple, a $200k car is not twice a good or fast as a $100k car. A $200 blue ray player is not 1/2 as good as $400 blue ray player and in fact only 1 in 1000 would be able to tell the difference in picute quality.

Lets use a real world exmaple, as a chunk of you guys are focused on accelleration and nothing speaks bigger volumnes than drag racing. About 5-10yrs ago the fastest drag racers , top fueler nitromethane drag racers, were doing the quarter mile in 5 seconds and developed almost 3000 horespower from a single V8 engine. Pretty impressive stuff. Today the record is 4.4seconds, but it takes almost 8000 horsepower to get there.

ANY Telsa improvements, like shaving off 1 second in the 0-60, is the stuff of dreams. The best speed freaks in the world took 10yrs to shave off 0.6seconds and it took almost 3x the HP and probably cost well over $50 billion

It is indeed very tempting (and the easy way too) to generalize facts to principles ... like saying "a machine heavier than air cannot fly", "the world is flat", "the universe is infinite" and people much smarter than both of us to power 2 have made this error. Einstein's work was regarded as total failure in the beginnings, just because Newton's principles served us so well for centuries ... they had to be right !

I am talking about your examples with dragsters : they are the extreme edge of an exhausted (pun intended) technology, it is just natural that every improvement comes with very high price, after a long sustained effort.

Just take a look at the Roadster, which is the first version of a new tech, an almost artisanal product by a beginner manufacturer. It is faster (up to some speed) than many much more expensive cars on the road that needed a century of evolution to get where they are today.

You give examples of DVD players ... what about the iPad 2 which is 2x CPU / 9x GPU faster than iPad but only $100 (20%) more expensive (after price cut) ? How is this possible when one year ago it was the pinnacle of mobile tech ? Human intelligence plus hard work plus the right tools / tech can make wonders !

I am not betting on this, I just say it is achievable ! They are surely much better than any of us assessing the need for such a product (family super-sports car ? sounds a bit fishy !) and the effort / money needed to achieve that.

What I bet on (with some $25k invested in TSLA, about half in shares and the other in call options) is that they will deliver a great car in Model S, no price increases and no major delays. Basically, if everything goes well, the profit on those will pay the Model S of my choice in about 2 years time !

In response to the last couple posts, I think that more likely than Tesla making such a supercar, or toward straightshooter, perhaps an approved aftermarket modifier (think Shelby/Ford) may offer some sort of souped up version of the S. I can imagine that with an upgraded rear axle, and reconfiguration of the battery you could probably shave off a second or two (just look at the Roadster). I am not sure that doing this themselves is really beneficial to Tesla for many years (unless it is partly to amuse the engineers!) as they should be working on going in the direction of the higher volume options.

A number of poster's have stated that the 230 and 300 mile options will have different battery chemistries. That doesn't make a lot of sense to me for several reasons:

1. The cost difference between the 160 to 230 is the same as between the 230 and 300.

2. Economies of scale are less effective if you make multiple configurations.

3. The supporting electronics might need to be different, further eliminating commonality and increasing cost of production.

Can anyone post a link referring to different chemistries between ranges?

Given that it's rather unlikely there is any chemistry difference, I would suspect that the 300 mile option would weigh more and would be slower. Tesla consistently leaves out caveats when talking vehicle specs so I suspect it will be lower than the 5.6 number usually given.

If anyone can prove otherwise I'd be interested.

Very old info, but they are not changing their design every few months either
http://www.greentechmedia.com/articles/read/panasonic-set-to-make-batter...

Of course the electronics will adapt to cells, half of their work on it is software. They are building a platform for the future, not carving each model in stone ! That is the difference to the industry of dinosaur juice burners.

@Straight Shooter, not scientifically precise in every respect, but very well said IMO.

@jfeister:

1. The cost difference between the 160 to 230 is the same as between the 230 and 300.

You must not confuse cost with price. What you mean is price, and that is primarily market driven, not necessarily reflecting actual cost.

2. Economies of scale are less effective if you make multiple configurations.

That's true, but if you just keep adding cells of the same kind, the car grows heavier and heavier which does not help with range either. At some point, most of the juice you store in the battery is needed to carry the battery itself... OTOH, a different, more capable battery chemistry may be much more expensive than the simpler one, so up to a certain point the simpler and cheaper technology makes more sense. Customers will only shell out the extra required for the more advanced tech if they are getting something extra in return which they cannot get otherwise. Like an electric car that runs 300 miles at a time.

3. The supporting electronics might need to be different, further eliminating commonality and increasing cost of production.

That may or may not be the case. If it is, just add that to the "economies of scale" clause above and the same argument holds.


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