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

SwTslaGrl

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Oct 23, 2016
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Sweden
200kWh at 06:08 in the 16 november 2017 unveil video,

r2-unveil.jpg
 
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Krash

Data Technician
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Apr 18, 2017
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Why would they list it as 10,000 newton meters of torque? No one knows what a newton meter is or how to relate to it. Use FOOT POUNDS, Tesla!!!
Actually some of us in the US are more familiar with Nm. The bigger issue is the use of wheel torque instead of motor torque. 10000 divided by 10:1 gear ratio divided by 3 motors is 300Nm (221ft pounds) which is pretty docile by tesla standards. I realize the car may need 7:1 ratio to reach 250mph.
 
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Cloxxki

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Aug 20, 2016
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Tesla isn't doing the 200 kWh pack for the 1.9 second 0-60 dash. They're doing it for the 250 mph top speed.
Such a slippery car only needs about 500 kW to reach/maintain 250 mph. Look at McLaren's F1. With better cooling, a 100 kWh Tesla battery ought to be able to do that. Note than Rimac is quoting faster for their 120 kWh C-Two.
 

jackbowers

Jack Bowers
Aug 23, 2009
275
461
Such a slippery car only needs about 500 kW to reach/maintain 250 mph. Look at McLaren's F1. With better cooling, a 100 kWh Tesla battery ought to be able to do that. Note than Rimac is quoting faster for their 120 kWh C-Two.

Yes, but to make the gas car smackdown real requires an ability to sustain 400 km/hr for 15-20 minutes (something gasoline supercars cannot do without running their tanks dry), as well as delivering range that exceeds gas cars at normal driving speeds. That can't be done with a 100 kWh pack.
 
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Cloxxki

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Aug 20, 2016
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Rotterdam
Yes, but to make the gas car smackdown real requires an ability to sustain 400 km/hr for 15-20 minutes (something gasoline supercars cannot do without running their tanks dry), as well as delivering range that exceeds gas cars at normal driving speeds. That can't be done with a 100 kWh pack.
Yes, it really bummed me out the other day that my Bugatti ran out of gas 15 minutes into my 400 kph cruise.
At a realistic 10 kW/min, New Roadster might maintain it for 20 minutes.
Then again, which Tesla ever ran nearly that long at half its peak power? Go drive at 275 kW with your P100D and see how long it lasts. I might be wrong.
 
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Peteski

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Oct 2, 2017
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You can't directly compare car weight of Roadster with ICE cars because of its low center of gravity. Lateral weight is bad for handling but vertical weight is actually good. Just think air wings if you don't see it. The weight of battery pack that sits low contributes more to vertical weight than to lateral weight. 4,000lb may not be all that bad not to mention there are plenty of 4.000 lb supercars in the world.

Please don't take this the wrong way, but this is poor use of terminology. Mass is the correct term you need to be using here (not weight) and mass is definitely the enemy when it comes to performance and handling. A low centre of gravity is a good thing, as it reduces dynamic weight transfer both in cornering and braking. But this is merely mitigating the effect of increased total mass, which is still fundamentally a bad thing - which is why every serious racing car ever produced aims to minimise mass (within the technical regulations, which often state a minimum mass/weight). In this case we are talking about many hundreds of kgs of additional mass with a 200 kWh battery. Not some trivial amount!

Aerodynamic downforce should not be confused with mass/weight either. Downforce creates additional vertical force on the wheels with no associated mass to react. So with downforce you get additional tyre grip without having to support any significant additional mass. The main downside being aerodynamic drag, which can be mitigated with active aerodynamic surfaces. Again downforce can be used to improve the high speed handling and braking performance in a very heavy car, but you have to be very careful with overall tyre loading otherwise you can get into serious trouble!

So just to be clear, adding any mass to a car reduces its lateral grip potential and braking ability. Mass also reduces acceleration, although probably not a big issue in this case! Aerodynamic downforce increases lateral and longitudinal grip, but only significantly at higher speeds. Both mass and downforce add to tyre loading, which could be a limiting factor for high speed runs and serious track use - expect to chew through tyres like crazy in this car!
 

jackbowers

Jack Bowers
Aug 23, 2009
275
461
Yes, it really bummed me out the other day that my Bugatti ran out of gas 15 minutes into my 400 kph cruise.
At a realistic 10 kW/min, New Roadster might maintain it for 20 minutes.
Then again, which Tesla ever ran nearly that long at half its peak power? Go drive at 275 kW with your P100D and see how long it lasts. I might be wrong.

I don't think there's any easy way to get the P100D to draw 275 kW continuously. Its top speed is 250 kph, and it takes less than 150 kW to sustain that speed.

Still, there are practical benefits of having a 200 kWh pack - on the Autobahn, and when driving in the less populated areas of North America. Elon reiterated in this week's shareholder meeting that the main reason Tesla is doing the 2020 Roadster is to prove that an electric car can outperform a gas car in *every* category.
 

Peteski

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Oct 2, 2017
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UK, Milton Keynes
I don't think there's any easy way to get the P100D to draw 275 kW continuously. Its top speed is 250 kph, and it takes less than 150 kW to sustain that speed.

Still, there are practical benefits of having a 200 kWh pack - on the Autobahn, and when driving in the less populated areas of North America. Elon reiterated in this week's shareholder meeting that the main reason Tesla is doing the 2020 Roadster is to prove that an electric car can outperform a gas car in *every* category.

I think the 200 kWh pack is more of a PR exercise than something people will actually want. Of course everyone would want the 600 mile or whatever range IF there was no weight penalty associated, but how many people would actually prefer a 300 mile range with 500 kg less battery weight? Especially in a focused sports car like this. I can see why they are doing it to prove a point, but I'm not convinced it's in the best interests of those who are actually buying the car. Until they offer a smaller pack I'm not going to buy one anyway. I don't need a 600 mile range in a car like the Roadster and I certainly don't want the weight!
 
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J1mbo

Active Member
Aug 20, 2013
1,609
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UK
I think the 200 kWh pack is more of a PR exercise than something people will actually want. Of course everyone would want the 600 mile or whatever range IF there was no weight penalty associated, but how many people would actually prefer a 300 mile range with 500 kg less battery weight? Especially in a focused sports car like this. I can see why they are doing it to prove a point, but I'm not convinced it's in the best interests of those who are actually buying the car. Until they offer a smaller pack I'm not going to buy one anyway. I don't need a 600 mile range in a car like the Roadster and I certainly don't want the weight!

I think they need the bigger battery to get the performance specs. The 600 mile range is a side effect and in some ways it is icing on the cake.

Wouldn't like to be the tyre guy on this project - haul a 2+ tonne car to 60 in < 1.9s, then cruise at 250 mph AND last for more than 600 miles before replacement! ;)

I wonder if they'll cost $30,000 a set to replace like the Veyron...
 

gregd

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Dec 31, 2014
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Wouldn't like to be the tyre guy on this project - haul a 2+ tonne car to 60 in < 1.9s, then cruise at 250 mph AND last for more than 600 miles before replacement! ;)

I wonder if they'll cost $30,000 a set to replace like the Veyron...
I think I heard / read somewhere that a set of tires would be about $1,200 US. No clue how long they'd last, but these certainly aren't going to be for Touring.
 
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Peteski

Active Member
Oct 2, 2017
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UK, Milton Keynes
I think they need the bigger battery to get the performance specs. The 600 mile range is a side effect and in some ways it is icing on the cake.

Wouldn't like to be the tyre guy on this project - haul a 2+ tonne car to 60 in < 1.9s, then cruise at 250 mph AND last for more than 600 miles before replacement! ;)

I wonder if they'll cost $30,000 a set to replace like the Veyron...

I thought that too, but I'm not convinced. I think it was as much about being bigger and better. Just listen to the crowd cheer at the event when Elon says 200 kWh! People don't always think through what that actually means i.e. a heavy assed battery! I must admit it took me a couple of days to realise the consequence.

Even if a smaller battery meant slightly less straight line performance I'd still take the trade off in handling any time. I would be happy with a 2 sec 0-60, sub 200 mph top end and 300 mile range!
 

CarlK

Active Member
Mar 23, 2013
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SF Bay Area
Lighter is of course better but that is not the only factor. I've heard 4000 lb weight of the Roadster mentioned but could not verify it. That is not even as heavy as the Bugatti Chiron. More importantly with low CoG the Roadster sure will be able to handle better than those supercars of equal weight. Heavier weight contributes to both vertical force and lateral force. The former is actually good. Only the later would degrade handling. However the same weight sitting low has less leverage and contributes less to the lateral force than weight at higher level. That's why instead of reducing engine weight, which is hard to do, those supercars would make the engine to sit as low as possible (but still not low as Roadster's battery). That's also the reason why when some cars that could only use partial light weight materials they would put an aluminum hood before they put aluminum fenders. Anyway you can't equal a heavy battery sitting very low to a heavy ICE up high.

Another thing is of course electronic assist. Modern electronics can do a lot to fix natural mechanical deficiencies. Take the 911 for example it has the worst weight distribution imaginable and it shows when the car is drove to the extreme. But that's before Porsche added electronic controls to make the car as drivable as anything either on the road or on the track. There is no doubt the Roadster will have the most advanced computer assisted steering control we have ever seen. Rest assured Tesla knows how to get this thing done right.
 
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kbM3

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May 22, 2017
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Orlando
Please don't take this the wrong way, but this is poor use of terminology. Mass is the correct term you need to be using here (not weight) and mass is definitely the enemy when it comes to performance and handling.

Don’t take this the wrong way, but mass and weight are proportional and easily convertible when gravity is constant (like on earth):

Weight = mass * gravity.

Mass is no better a term than weight.
 

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