200 kWh Roadster Pack: How is Tesla Pulling This Off?

[CarlK]

I used to own a Cayman S. The ride at softer of two settings is about the same as ride of Model X with 22" (the one I own). As for the sports setting you never want to punish yourself on the road with that. You don't get those track performance for nothing. What the Model 3 has done without stiffing up the suspension too much is pretty extraordinary. Initial batch did have a more stiff ride but Tesla changed it after people complaining.

 

[Peteski]

I used to own a Cayman S. The ride at softer of two settings is about the same as ride of Model X with 22" (the one I own). As for the sports setting you never want to punish yourself on the road with that. You don't get those track performance for nothing. What the Model 3 has done without stiffing up the suspension too much is pretty extraordinary. Initial batch did have a more stiff ride but Tesla changed it after people complaining.

The Model 3 is not terribly heavy though, so it's not such a major challenge as it will be on a heavyweight ultra-low ride height car like the Roadster. The Model X has plenty of suspension travel to play with and yet is still a pretty firm ride for its class. I find it acceptable on 20" rims and too harsh for UK roads on 22". Every Porsche I've owned has had a great ride/handling balance. FWIW I think the MS has a great ride too (considerably better than the X actually), but undulating roads can upset it once that mass starts heaving around. Those issues will only be magnified in the heavier Roadster. Of course we don't yet know the weight of the Roadster, but a 200 kWh battery is likely to push it well over 2000 kg, maybe even as high as 2500 kg! But then I've heard people suggesting it might be as light as 1700 kg, but I can't see how that would be feasible given the 1735 kg Nio EP9 with full carbon everything and a sub 100 kWh battery. I notice Tesla are not stating any weight information, which is no surprise!

 

[felixtb]

Perhaps I'm too hung up on the weight because I know how important and fundamental it is to vehicle handling, tyre wear and stress. I'm not only a general engineer, I'm a vehicle dynamicist who has worked at the cutting edge of motorsport for a couple of decades before I decided I preferred being a ski bum, lol. I'm not making this up or making any sort of controversial statements here. This is about as basic as physics gets and if you refuse to see the elephant in the room (close on 1000 kg of battery to haul around at 1-2G) then fair enough!

Your analogy to jet fighters is not very relevant to a car reacting all its forces through 4 little rubber contact patches. Once we move away from that fundamental limitation then weight might play less of a leading role, but we are far from that situation with the Roadster.

Design by first principles is exactly what we do in F1. There is a minimum weight regulation and not one competitive car in the history of the sport has ever started on the grid above that minimum weight. There have certainly been a few setting off below it though, lol.

I basically agree with all that you are saying because IT IS simple physics and you do not even have to be an engineer, physicist or vehicle dynamicist to understand the constraints. However, there is only one unknown, the final weight of the roadster. You are all giving the roadster a hypothetical weight relying on today’s battery chemistry and electric and suspension components. And then adding a standard chassis and maybe carbon body panels........ I would not be so sure of those numbers and material choices before we know more. As has been mentioned there are battery chemistry breakthroughs and packaging changes to consider and then there is the actual construction of the chassis and body panels.... light weight high strength materials have certainly gone down in price due to much greater availability in the last few years. So depending on the methodology of the construction of rhe roadster and WHEN it will finally be built, we could have a weight of anything from ~1600kgs up to ~2200kgs. I for one think that we will be closer to the 1700 mark rather than the 2000kg mark considering the above. And at that weight and power output and low center of gravity it will not be super penalized against some of the more track oriented super cars.... yes it will still have problems against the 919 but then again that car went beyond what was allowed for racing just to break records.......... PS I don’t think we will see our roadsters on the road or track until 2022 at the earliest.....

 

[Peteski]

If it did come in below 1700 kg with a 200 kWh battery that would be truly astonishing! The current EV benchmark Nio EP9 at 1735 kg has a full race carbon tub and bodywork with a sub 100 kWh battery.

 

[Cloxxki]

Tesla promised batteries were going to get cheaper ;-)
By the time the New Roadster arrives with 200kWh, that'll be $20K at the cell level, approaching the same on the pack level unless using fancy wrapping.

200kWh implies that they're to use plain cheap slow 2170's to get both insane range and the power needed to make a mark on the stock supercar drag racing scene. If somehow it's to be a next level battery tech such as triple energy density from a solid state battery, that'd be Earth shattering and high-end car industry devastating. Many have promised such, all have delayed or abandoned it. With a triple density tech, a 100kWh pack the weight of half a Model 3 pack stuck inside a carbon chassis and body, would make for a really light car. New Roadster seems to be getting 3 substantial motors. Could be two Model 3 Performance one in the rear, one Model S/X (rear) Performance version in the front. In a much lighter car, the third motor might not be needed. Or use 4 really little ones. Rimac C-Two has four, in 2 sizes. With a light next level pack, 4 small ones would do the trick. Or even one Model 3 P motor front, one S/X P rear.
The three motors and high power+torque suggest New Roadster will be very. Possibly very heavy. With big enough tires, though, that 1.9 to 0-60mph will be managed. And 250mph is only a matter of 600+kW power and the right gearing for about 20-30 seconds. Plus that 10K wheel torque figure.

 

[ggnykk]

Have you guys look at the detail specs of the Rimac C2 hypercar? (check their website). That thing weigh 4400 Ibs with 2 fewer seats than Tesla and with much less batteries (120 kwh). Not to mention that it is carbon fiber everything including the car tub. There is absolutely no doubt that the new Tesla roadster will be a lot heavier than the Rimac C2, way more than 4400 Ibs for sure. Probably around 5000 Ibs for roadster.

 

[Cloxxki]

Have you guys look at the detail specs of the Rimac C2 hypercar? (check their website). That thing weigh 4400 Ibs with 2 fewer seats than Tesla and with much less batteries (120 kwh). Not to mention that it is carbon fiber everything including the car tub. There is absolutely no doubt that the new Tesla roadster will be a lot heavier than the Rimac C2, way more than 4400 Ibs for sure. Probably around 5000 Ibs for roadster.

It's been my 31 hypercar since it came out. Just stunning in every single way.

Spades for spades, +600lb if you want to swing imperial, for 80kWh would be quite the thing.
Modern supercars strangely are not light. Very high safety standards and reliability are expected. Huge brakes, for instance. Huge rims for fashion reasons.
By keeping it simple, Tesla could save a lot of weight, but how much? If 2170's, it will have 800kg in cells alone. The pack would be closer to 1300kg. Converters are simply heavy. 3 big motors add up.
Without a battery breakthrough, New Roadster will be very heavy indeed. Thing of race stripped Model S's. Still heavy. At only 102kWh.

 

[Peteski]

It's been my 31 hypercar since it came out. Just stunning in every single way.

Spades for spades, +600lb if you want to swing imperial, for 80kWh would be quite the thing.
Modern supercars strangely are not light. Very high safety standards and reliability are expected. Huge brakes, for instance. Huge rims for fashion reasons.
By keeping it simple, Tesla could save a lot of weight, but how much? If 2170's, it will have 800kg in cells alone. The pack would be closer to 1300kg. Converters are simply heavy. 3 big motors add up.
Without a battery breakthrough, New Roadster will be very heavy indeed. Thing of race stripped Model S's. Still heavy. At only 102kWh.

I agree, those who are expecting it to weigh well under 2000 kg with a 200 kWh battery are going to be disappointed. I'm thinking it will be well over 2000 kg and probably closer to 2500 kg with that battery capacity.

For current hypercar EV benchmarks we have the Rimac C2 at 1950 kg and the Nio EP9 at 1735 kg. Both are full cost-no-object carbon construction with considerably smaller batteries. Tesla are not going to make the chassis any lighter than these efforts, more likely heavier given the cost constraints, and then there's the elephant in the room (almost literally) 200 kWh battery.

As a further weight data-point, the Porsche Taycan is also rumoured to weigh around 2000 kg, again with half the battery and probably a more comparable aluminium chassis.

 

[Cloxxki]

New whispers from sources inside or close to Porsche are that they made the Taycan surprisingly efficient that it will suffice with a smaller battery than we are expecting. Making it a lighter car than we are expecting (Panamera Hybrid as an example is not light).
It would be arrogant to hold it against Porsche. They know their cars and they accomplish what they set out to.
So let's think...
Similar or smaller frontal surface than Model 3 (lower), but wider tires, let's say the same power output for constant speeds especially on the highway.
Not exactly some off the shelf motor design (well, maybe off the Rimac shelf who have been at it for a while now). It may well be extremely efficient. Let's say, equal to Model 3's motor, to be conservative.
Model 3 at 81kWh or so gets 334 miles of EPA range. Porsche are aiming much lower. They may well keep it at 70-75kWh and lean on the faster charging which by the way batteries work goes hand in hand with relentless track performance. Low internal resistance cells lose less to heat, less heat means slower rise of temperature. With a decent working temperature range, that allows for hard riding and fast charging. Such cells have been around for ages, now thanks to demand for such, the energy density for a 4C charging cell is going up. Or, the charging rate for a high energy density cell is going up.
A Porsche 4C 75kWh pack may well weigh the same or less than the >1.9C Model 3 81kWh pack.
Two motors, similar power output. Porsche's may well be beefier by a bit as they supposedly can take a beating without overheating too much.
Model 3 is world's safest car? Porsche needs not resort to exotic materials to make a safe car with stiff enough chassis that is the same weight as the Model 3.
If Porsche are serious about this car, it's far from impossible that it will get >250 miles EPA from an 1800kg car which has the full 600hp available, most of the time. With Model 3 already lapping like the original Ferrari 458 Italia, rest assured the Taycan will be a compelling car for anyone with a taste for sportcars and high speed cruising in silence.

 

[ICUDoc]

Nice analysis of the Taycan. I’d be happy to buy it if it were available and as good as you think. But we are stilll waiting for a Model S competitor; the Jag is nearly there, but let’s be honest, the Roadster 2020 is what keeps me looking to the future.

 

[Cloxxki]

Nice analysis of the Taycan. I’d be happy to buy it if it were available and as good as you think. But we are stilll waiting for a Model S competitor; the Jag is nearly there, but let’s be honest, the Roadster 2020 is what keeps me looking to the future.

To me the Roadster is a gimmick. Extremely few people actually need ANY of its standout features. It could well have been on the road for years, had someone committed to make it. Only Tesla had the guts to make a car like this. About as useful to society as the not-a-flamethrower.

 

[ICUDoc]

To me the Roadster is a gimmick. Extremely few people actually need ANY of its standout features. It could well have been on the road for years, had someone committed to make it. Only Tesla had the guts to make a car like this. About as useful to society as the not-a-flamethrower.

NEED is fully irrelevant to most car purchases. We buy with our hearts, not our minds. Otherwise we would all drive Camry Hybrids.
For me, 600 miles of range makes any road trip as easy and quick in a BEV as a petrol car- that’s the main attraction. The super-quick acceleration also a plus, but less important. And the looks are simply fabulous. Three good gimmicks.
Gimmick or not, just hurry up.

 

[Peteski]

New whispers from sources inside or close to Porsche are that they made the Taycan surprisingly efficient that it will suffice with a smaller battery than we are expecting. Making it a lighter car than we are expecting (Panamera Hybrid as an example is not light).
It would be arrogant to hold it against Porsche. They know their cars and they accomplish what they set out to.
So let's think...
Similar or smaller frontal surface than Model 3 (lower), but wider tires, let's say the same power output for constant speeds especially on the highway.
Not exactly some off the shelf motor design (well, maybe off the Rimac shelf who have been at it for a while now). It may well be extremely efficient. Let's say, equal to Model 3's motor, to be conservative.
Model 3 at 81kWh or so gets 334 miles of EPA range. Porsche are aiming much lower. They may well keep it at 70-75kWh and lean on the faster charging which by the way batteries work goes hand in hand with relentless track performance. Low internal resistance cells lose less to heat, less heat means slower rise of temperature. With a decent working temperature range, that allows for hard riding and fast charging. Such cells have been around for ages, now thanks to demand for such, the energy density for a 4C charging cell is going up. Or, the charging rate for a high energy density cell is going up.
A Porsche 4C 75kWh pack may well weigh the same or less than the >1.9C Model 3 81kWh pack.
Two motors, similar power output. Porsche's may well be beefier by a bit as they supposedly can take a beating without overheating too much.
Model 3 is world's safest car? Porsche needs not resort to exotic materials to make a safe car with stiff enough chassis that is the same weight as the Model 3.
If Porsche are serious about this car, it's far from impossible that it will get >250 miles EPA from an 1800kg car which has the full 600hp available, most of the time. With Model 3 already lapping like the original Ferrari 458 Italia, rest assured the Taycan will be a compelling car for anyone with a taste for sportcars and high speed cruising in silence.

Interesting analysis. One thing is for certain, Porsche consider overall weight to be a primary parameter for handling performance! They have stated this themselves on a number of occasions when discussing their future EV plans. So I expect the Taycan will be as light as it possibly can be for the price point. Not that it's going to be a lightweight compared to their ICE equivalents. Mark Webber did mention the increased weight when he drove one of the prototypes a few months ago.

Weight is still the major concern for high performance EVs, especially if handling is high on the priority list and this is where Tesla appear to have lost the plot with the Roadster spec. But their priority with the Roadster is clearly to set straight line acceleration and top speed records, similar to Bugatti's approach with the Veyron and Chiron. The offshoot 600 mile range is also a nice headline grabbing feature. Porsche on the other hand appear to be focusing more on overall road and track performance, with a focus on handling performance. Much as they have done traditionally with their ICE cars. All horses for courses, but as usual in engineering, there is always a compromise to be made and with EVs it all comes down to battery capacity & power vs weight. Just imagine how much sooner ICE would have been killed off IF EVs were intrinsically lighter for the same power and range?! Unfortunately we are not yet in that position, so the best we can do is compromise around those basic variables and the Roadster 2020 appears to be going down the heavyweight path for maximum power and range.

 

[Cloxxki]

Yes, BEV history would have been wildly different if another form of batteries were discovered in the past rather than the future. Great inventions don't always come as evolutionary as Lithium Ion. Someone might have skipped that and gone for a 3x more dense solution in the 1970's. But didn't, at least not bring it to market.

I am not convinced it will be Tesla setting drag and speed records. Rimac C_Two may well beat it to production spec. It's got 80kWh less and similar experience in getting torque down to 4 tires. Likely their 120kWh pack with high power density output is well lighter than Tesla's 200kWh with presumed generic 2170's.
And let no-one miss this detail, Porsche threw A LOT OF CASH to Rimac, getting only 10% in stock, just to skip the line in becoming a tech partner. I sat down with Rimac for a very high profile project, but they immediate said they were booked for many years into the future. This was pre-Porsche deal as far as I know. Parent company VW needed their know-how, badly. And perhaps Pikes Peak was a quick taste for that relationship?

If I were Rimac and wanting to impress with specs, I'd offer a high speed version of the C_Two with a longer gear ratio for all wheels. Prep the chassis for such speeds and shoot for 500kph. The power may well suffice for it, the torque would allow it to be a short enough dash to not get into heat issues.
But Porsche are really good at keeping project under wraps. 919 Evo (faster than an F1 car) was suddenly there. 918 Spyder was suddenly there and journos barely realized how good it was.
Porsche may well already be making the 918 successor, based off the C_Two drivetrain. And they might take that car to the record book, while Mercedes are struggling to make true to there "One" promise of a V6 (and 3 EM's) all straight from F1 to be driven on the road. What a blow to Mercedes that would be, Porsche combining their superior chassis of the (heavy) 918 with a cutting edge BEV drivetrain, 919 Evo like aero, all in a surprisingly light package. Perhaps (likely) no such project exists. But we would not know until they were ready. Tesla sends prophets out ahead of new cars