Next gen Roadster

[WhiteKnight]

The question is: will it have AWD?

Elon has said that the problem they're having now is not the motors but the size of the contact patch. They've got so much power they can't harness it with just two wheels driving the car. So absolutely it will have AWD out of necessity.

Three years from now I wonder if Tesla will incorporate Ultra-Capacitors that will enable a burst of energy sufficient to make the 0-60 or 0-100 run.

I would expect that they do everything possible to keep the weight at a bare minimum by using carbon fiber, aluminum, maybe even titanium. They probably could go up to $150,000 in asking price given that they will be competing against Porsche Turbo S, Lamborghini, Ferrari, Bugatti, etc.

 

[Norbert]

Three years from now I wonder if Tesla will incorporate Ultra-Capacitors that will enable a burst of energy sufficient to make the 0-60 or 0-100 run.

And if regen would also go into the Ultra-Caps first, perhaps that would even improve the cycle life of the main battery.

 

[stopcrazypp]

Elon has said that the problem they're having now is not the motors but the size of the contact patch. They've got so much power they can't harness it with just two wheels driving the car. So absolutely it will have AWD out of necessity.

Three years from now I wonder if Tesla will incorporate Ultra-Capacitors that will enable a burst of energy sufficient to make the 0-60 or 0-100 run.

I also think AWD will be necessary. A large majority of the production cars with 0-60 under 3 seconds have AWD. The ones without AWD are at a disadvantage even with more power because of traction.

I would expect that they do everything possible to keep the weight at a bare minimum by using carbon fiber, aluminum, maybe even titanium. They probably could go up to $150,000 in asking price given that they will be competing against Porsche Turbo S, Lamborghini, Ferrari, Bugatti, etc.

It can go up even much higher. The Turbo S and the GTR are the only ones with 0-60 under 3 seconds and a price tag in the $100-200k range. All the other cars are basically $500k and above.

I think weight reduction is the best approach, but they can go both ways:
extreme weight reduction - like the Caparo, only 1000 lbs
adding a load of batteries for more power - like the Veyron with its W16 engine, weight be damned
or a balance of both - like most of the cars with 0-60 under 3 seconds.

 

[stopcrazypp]

Very unlikely if they stick to the small size Li-Ion cells. They have great energy density but their power density is not suited for a supercar.

I don't think it's unlikely.
You don't need the full brute power of the Veyron if you keep weight reasonable; some good benchmarks:
2012 Porsche Turbo S (0-60 2.7 secs, 530hp/395kW, 3494lbs)
2012 Nissan GT-R (0-60 2.8 secs, 560hp/418kW, 3829lbs)

Target:
440kW (just to have a bit more power than both the GT-R and the Turbo S)
<3500lbs (like the Turbo S)

At 4C, you need a 440kW/4C = 110kWh battery. With the 3100mah cells in the 85kWh Model S being 245Wh/kg and 11.16Wh each, that works out to 450kg/992lb cell weight and 9857 cells. Assuming 6831 cells at 44 grams each (about how much a 2400mah cell would weigh like in the original Roadster), I get 300kg/661lb of cell weight in the Roadster. So that's about 150kg/331lbs of extra cell weight to have a battery with enough power. Given the curb weight of the Roadster Sport 2.5 is 2723lbs, you get 3054lbs in total.

So there's about 450lbs of breathing room for the extra motor/differential (for AWD and roughly double the power of the Roadster Sport motor at 215kW), the larger enclosure/extra interconnects/cooling/etc to accommodate the 3026 extra battery cells, plus beefed up wiring and power electronics to handle the extra power.

If Tesla moved to 3400mah cells rather than the 3100mah cells in the Model S, there would be even more breathing room (40kg/88lbs more to be exact, plus less interconnects and a smaller enclosure because you need less cells).

 

[WarpedOne]

Three years from now I wonder if Tesla will incorporate Ultra-Capacitors that will enable a burst of energy sufficient to make the 0-60 or 0-100 run.

No, UltraCaps are useless for this = bad idea.
Take that $$$, add some more batteries and voila, better range, better average acceleration, lower total cost, higher reliability.

 

[WhiteKnight]

If Tesla moved to 3400mah cells rather than the 3100mah cells in the Model S, there would be even more breathing room (40kg/88lbs more to be exact, plus less interconnects and a smaller enclosure because you need less cells).

It's possible the 4000mAh cells could be in production by then! Seems very do-able!!

 

[dsm363]

It's possible the 4000mAh cells could be in production by then! Seems very do-able!!

Looks like they were going for March 2013 when they announced this in 2009
Panasonic Develops High-Capacity Lithium-Ion Battery Cells That Can Power Laptops and Electric Vehicles | Headquarters News | Panasonic Global
The 4.0 Ah batteries are slightly heavier than the 3.4 Ah batteries

Battery 3.4 Ah: Mass Approx. 46 g
Battery 4.0 Ah: Mass Approx. 54 g
Battery 2.9 Ah: Mass Approx. 44 g

 

[dpeilow]

Yeah the 4Ah has a lower gravimetric energy density than the 3.4 in that 2009 press release. I wonder if that is still the case.

 

[richkae]

Yeah the 4Ah has a lower gravimetric energy density than the 3.4 in that 2009 press release. I wonder if that is still the case.

In the Roadster, the cells are about 75% of the weight of the battery, so you still save weight designing your battery to use fewer cells.

 

[dpeilow]

Not convinced it's that much different (assuming overall weight scales linearly with number of cells).

 

[WhiteKnight]

Model R Facts

Re-reading this post from the beginning and following the links to articles where Elon speaks about the next-gen Roadster there are a couple indisputable facts:

(1) Model R will be 2+2 seating - Elon owns a Porsche 911 Turbo and wants the rear seats. They will be tiny, no doubt, but they will be there and therefore it is not a true "Roadster" according to the definition, which is why I'm calling it the Model R.
(2) Model R will be AWD - Tesla has said over and over that the Model S would be faster if they could drive all 4 wheels instead of the back 2. The Model R will be AWD so that it can be wicked-fast.
(3) Model R wil be based on Bluestar skateboard - It will use Bluestar battery packs and that will necessitate Bluestar dimensions. So a foot shorter than the Model S (104" wheelbase) and a half foot narrower (<60" track). Current Roadster has a track of 58.7" and wheelbase of 95.1" (pick up 9" for the rear seat).

There are a couple other things that I would not label as facts but strongly suspect:

(1) Elon wants it to be the fastest production car in the world from 0-60. So faster than Nissan GT-R, faster than Porsche 911 Turbo S and possibly faster than Bugatti Veyron.
(2) I suspect it will be easy for a 6'5" person to get into and out of and drive. I doubt Franz Holzhausen is going to design something he can't fit into.
(3) It will be much more luxurious because Tesla will find it easier to make it so and it will appeal to more people.
(4) Bluestar is not coming before 2015 so it's doubtful that the Model R will be released before then.
(5) Given the battery pack size relative to size and weight of the car it will have 400+ miles of range (see below)

Final note:
I'm not smart enough to check his math but stopcrazypp Next gen Roadster says the Model R would need a 110 kWh battery (590 hp) to be fastest. With the 4.0 Ah batteries (which dsm363 pointed out will be available in 2013) which have roughly 30% more power than today's 3.1 Ah cells in the 85 kWh pack, but 20% less space in which to fit, it seems like you could get to 85 * .80 * 1.3 = 88 kWh. So the question becomes how do you bridge the gap?

(1) Tesla could add extra batteries in the front and rear trunks (seems highly unlikely).
(2) Perhaps Panasonic comes out with 5.0 Ah cells by 2015 (seems very challenging).
(3) Perhaps there are advances in UltraCapacitors allowing power delivery at greater than 440 kW. These UltraCapacitors would serve as buffers between the car and the battery, helping to maximize battery life and performance at the same time. (don't know if this technologically feasible).
(4) Perhaps they can slash the weight on the Model R to about 3,000 pounds in which case 470 hp might be enough to win the race. (seems the most straightforward).

 

[AnOutsider]

Regarding assumption 4, wasn't it speculated that Model R could come BEFORE bluestar and thus subsidize the development of the platform quicker?

 

[WhiteKnight]

Regarding assumption 4, wasn't it speculated that Model R could come BEFORE bluestar and thus subsidize the development of the platform quicker?

That was speculated however I don't think that is likely for several reasons:

(1) They are going to have to be developed at the same time since they have the same skateboard. If the Model R comes first then it will have significant development costs of its own.
(2) If you sell 1,000 Model Rs for $150,000 per pop and 25% gross margins then that's only $37.5 million. Development of the BlueStar platform will probably cost 10 times that. I think the Model S was about this much.
(3) It's quite possible that following the success of the Model S and Model X that TSLA looks to raise money with another secondary equity offering at which point they will be touting the 200,000 per year Model C (or whatever Bluestar will be called in development). I doubt they will be able to get the cash under the auspices of building a rich man's super-car (certainly won't be able to get a DOE loan).

 

[AnOutsider]

Fair points. I also thought that I remembered seeing an article where Elon said the Roadster's replacement would come in 2014 -- which also fueled discussion. Didn't we have a thread with overall timeline assumptions? (i.e. X in 2013, perhaps convertible or R in 2014 etc?)

*edit* Articles like this one: Tesla Plans New Roadster For 2014 - AutoObserver

So, the Roadster (or Model R) would indeed likely come before bluestar (or Model C).

 

[Norbert]

I'm wondering whether they will use the 4.0h battery announced in 2009, or perhaps a battery more specific to the automotive market, not announced yet.

 

[WarpedOne]

I'm not smart enough to check his math but stopcrazypp Next gen Roadster says the Model R would need a 110 kWh battery (590 hp) to be fastest. With the 4.0 Ah batteries (which dsm363 pointed out will be available in 2013) which have roughly 30% more power than today's 3.1 Ah cells in the 85 kWh pack, but 20% less space in which to fit, it seems like you could get to 85 * .80 * 1.3 = 88 kWh. So the question becomes how do you bridge the gap?

stopcrazypp's base assumption was 4C limit. This is high for "ultra-high-energydensity cells" i.e. top of the line cells. If they use cells a bit more power oriented with a bit lower energy density they won't need 110kWh for 440kW. Allow for 5,5C and 80kWh is enough.

 

[stopcrazypp]

With the 4.0 Ah batteries (which dsm363 pointed out will be available in 2013) which have roughly 30% more power than today's 3.1 Ah cells in the 85 kWh pack, but 20% less space in which to fit, it seems like you could get to 85 * .80 * 1.3 = 88 kWh. So the question becomes how do you bridge the gap?

(1) Tesla could add extra batteries in the front and rear trunks (seems highly unlikely).

I actually think this would be more likely if Tesla does build a version of the R with this kind of power (I imagine Tesla will also make versions with smaller batteries and less power). It's not that hard to do given the batteries are packaged in modules/bricks.

Without knowing how the Bluestar will be configured (aka is it still a skateboard), the concern with a car like the R is if a skateboard still makes sense (since sports cars/super cars tend to have low seating and a low height). A mid-battery design like the Roadster is perfectly fine. It's also possible to add a layer or two of batteries under the rear seats (or the floor area in the rear if it's not a 2+2). That way you still have a relatively flat trunk area to the front seats (rather than having the battery dividing the passenger space and the trunk space). The "frunk" is probably going to be a lot smaller or non-existent in the R if it is AWD. It's just a question of good packaging, nothing too difficult.

I think #4 (weight reduction) is also possible, but requires a lot more effort (and expense) just to have some extra trunk space (likely unused).

 

[stopcrazypp]

stopcrazypp's base assumption was 4C limit. This is high for "ultra-high-energydensity cells" i.e. top of the line cells. If they use cells a bit more power oriented with a bit lower energy density they won't need 110kWh for 440kW. Allow for 5,5C and 80kWh is enough.

The problem with power-oriented cells is lower energy density. So a 80kWh pack of 5.5C cells is going to have more weight/volume than a 80kWh pack of 4C cells. It'll be a challenge to find the perfect balance because I'm not sure there are cells that are just a bit more power oriented (usually they are a lot more power oriented, like 10+C but with 2-4x worse energy density, not really something in between), that might drive the design to the other end (a pack with much less capacity, but with more than the necessary power).

 

[WhiteKnight]

Fair points. I also thought that I remembered seeing an article where Elon said the Roadster's replacement would come in 2014 -- which also fueled discussion. Didn't we have a thread with overall timeline assumptions? (i.e. X in 2013, perhaps convertible or R in 2014 etc?)*edit* Articles like this one: Tesla Plans New Roadster For 2014 - AutoObserverSo, the Roadster (or Model R) would indeed likely come before bluestar (or Model C).

So when I read the Autocar article that Auto Observer references it says the Roadster will be based on the Gen-III platform (Tesla's name for BlueStar) and it will "launch" in 2014. I don't know if that means introduced in 2014 or delivered to customers in 2014. I do know that Tesla recently told investors that Gen-III would come in 2015.

 

[WhiteKnight]

The problem with power-oriented cells is lower energy density. So a 80kWh pack of 5.5C cells is going to have more weight/volume than a 80kWh pack of 4C cells. It'll be a challenge to find the perfect balance because I'm not sure there are cells that are just a bit more power oriented (usually they are a lot more power oriented, like 10+C but with 2-4x worse energy density, not really something in between), that might drive the design to the other end (a pack with much less capacity, but with more than the necessary power).

Maybe they'll use the more power-oriented cells in packs in the trunks for the times when you need a big boost. Similar to my ultra capacitor thoughts on acting like a buffer?