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200 kWh Roadster Pack: How is Tesla Pulling This Off?
- Thread starter jackbowers
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- Batteries Roadster 2020
Listen, if charging speeds for S3X are to be tripled (per Elon), the cells as used in Model 3 are either going to be done away with, or are just not being utilized to full potential yet (I doubt the latter).
So a 100kWh Roadster pack with 3x as high charging rate, likely will also offer faster discharge rate without overheating issues. The spoils of lower internal resistance chmistries. Rimac gets 1.4MW+ from 120kWh, that's outcome of their mass vs power vs range dilemma, and they are not really bound to a specific cell tech.
Roadster is more expensive than most other cars, so could have externally purchased cells or even pouches. In a $200K+ car, 200kWh will be $20K at the pack level by then again, per Elon). Add a bit for more carbon in stead of aluminum, or higher grade titanium. The battery, if 2170's from Model 3, will NOT be the most expensive part of the car. Or, the car will simply be built for $60K. A more bare Model 3 with more batteries. Fewer seat, windows, window motors, etc, etc.
Roadster is already hitting its specs (and then some) based on the recent test driver interview.
From the Q1 earnings call, they are shooting for more like 2x increase.
Tesla throws cold water on Porsche’s faster charging, says Supercharger to max out at ~250 KW
from Yahoo:
Regarding battery tech:
regarding charging:
If that were truek, then the 3x faster supercharging promised will be with a superior battery chemistry to what the Roadster will get.
You're not likely to see a cell that's great at discharging but slow to charge, or the other way around. It's both about internal resistance as I understand it.
Where was it promised that there will be 3x faster Supercharging. I remember hearing that they were shooting for 2x faster, but not 3x...
Disclaimer, I'm not a battery engineer,
Energy and power tend to be inverses, but not due to ESR. It's the ability of the chemical reactions to occur properly. For instance not plating the electrodes or degrading their surface area. More electrode area gives higher rate, but lower total energy, Non-chemical ESR is minimal and could be overcome with more voltage.
It's 2x, I quoted the conference call discussing this in #323 (second quote block)
Musk was talking long term not 2020 and it's unclear if he was including pack size increases or not
Then, Musk never said that any existing vehicles will be able to take advantage of Supercharger V3. It's safe to assume that at least the new cells can take advantage to some degree but don't assume 250kW at peak.
250kW because that's what Musk mentioned as making sense and since V3 arrives late this year at the soonest and they accelerate expansion afterwards, it's safe to assume that the Roadster with a 200kWh pack, won't be able to do better.
That doesn't suggest major chemistry changes enabling much faster charging and we know Tesla is more focused on cost than charging rates. Another way to look at it, much faster charging would come at a higher cost and lower energy density so they physically couldn't fit a 200kWh pack in the Roadster.
Manufacturing costs have little to do with retail price, even more so for low volume products where you need much higher gross margins to recover R&D. Capital intensity is another factor here, low volume can be done without spending much capital and Tesla needs that.
Rimac wants to sell their cooling technology and their cars are showcasing that technology. Spending $, volume, weight, drag on cooling is not always the best solution. They do claim 0 to 80% in 30 mins so not that fast. The C Two can only do 2 laps at Nurburgring.
Model S peak battery power is 451kW with 100kWh of older cells. The Roadster will need 900-1200kW and Model S doesn't sustain 451 for long. Granted there are a few variables here, cooling efficiency, cooling the motors (with S those heat up first), air intake size , speed per cooling needs and ofc they have the new cells. All in all, even with a a 200kWh pack ,it's not gonna be easy.
A 100kWh version is not gonna happen. They kill perf, range , charging miles per min added, would destroy the balance of the car and they would need to redesign suspension, brakes and wheel alignment +software. And then they sell this for 180k? There wouldn't be demand, the investment would not be recovered, makes no sense. Wouldn't even have better handling since you trade weight for higher center of gravity but the track and wheelbase are not changing.
Weight is an issue when you have constraints like in racing where the tire and wheel dimensions are predetermined. In the real world, you deal with it and everything is a trade-off. And BTW, weight being high is just an alarmist assumption.
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Agree with most.
>The C Two can only do 2 laps at Nurburgring.
Let's just say those 2 laps take up 75% of the nominal 120kWh battery, 90kWh.
It's been reported to be at full bore, no power limitation. With a 1.4MW+ car.
What might average power be over a ~6m30 lap, after regbra and heat losses? Let's throw in 600kW as there is going to be a lot of braking and lifting for corners.
Now, multiply 13/60 minutes with ball park 600kW, and there you have it, 78kWh. Quite close.
Summary: C_Two " only" does two laps (my guess 13 minutes) because it will be outputting a net 5C. Same that current Tesla deliver for around 2 seconds?
The New Roadster COULD do with only a 100kWh battery (and be plenty quick off the line, helped by lower mass), just not with current Tesla cells offering mere single digit seconds at 5C. Double a cell's C rate with altered chemisty doesn't nearly halve the energy density.
Imagine 3x the Ioniq's pack, 3x31kWh. Charging at 3x70kW with ease. That's older tech and really low cost. Doesn't require any imagination. Chevy Volt packs are sparkier still I suppose.
Sure they could have made a slightly lesser car with smaller battery but why do that. Their goal was to take a substantial lead over ICE.
In fact, I think they should make sure the battery is easy to replace and offer higher capacity replacements down the road. That helps a lot with deprecation and buyers will be worried about that with an EV. If they overdimension a bit the electronics and motors, a larger pack could even increase perf and enable faster charging. As volumetric density improves, they could have 300kWh packs in 2025, similar weight and mechanical volume. Actually, in 5-10 years from now, solid state batteries should be available so that would be a nice upgrade. Panasonic just mentioned post 2025 for solid state.Panasonic flags battery cell shortages as Tesla Model 3 output...
And wanna ask about the Rimac, is the 1.4MW something Rimac claims or just derived from horsepower? Asking because I'm wondering if they can actually use all those 1914hp. Makes sense to have ample power on each wheel anytime you might need it but to use all at same time, seems unnecessary and doesn't fit with claimed perf either.
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kW and bhp are the same, just a conversion factor of 1.34 or so.
You can't deliver 1900hp from standstill, the revs are not there.
And maximum torque also can't be put down from the line, lack of traction.
Soon enough the parameters will line up for that power to be utilized, though.
P100D does it at 35mph or so, albeit ever so shortly before turning down the amps?
Example, Koenigseggs are RWD with say 1300-1500hp and can only get it all down at 270kph and up. Wheelspin all the way up to that point. With AWD and if present downforce, the slip limit (in kph) is lowered.
What i was asking is if you got that number by converting or they actually claim it. If peak power draw is bellow what the motors can do (like with Model S), you never get the max horsepower no matter the traction. Anyway they do list 1.4MW on their site so got my answer.
The top speed is way low for the horsepower unless they need to open up air intakes and ruin Cd or they can't quite ever use that total for w/e reason. Or maybe they limit it for safety.
The top speed is way low for the horsepower unless they need to open up air intakes and ruin Cd or they can't quite ever use that total for w/e reason. Or maybe they limit it for safety.
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As the motor spins faster, it produced more back-EMF which counters battery voltage. At peak speed: drag_torque=(pack_voltage - motor_voltage)/motor_resistance*motorCurrentToTorgueTransferRatio.
In other words, unless you have a boost stage in the power path, variable gear box, or a motor wound specifically for the high end (sacrificing low end), the pack is not going to be putting out peak power at top speed.
Horsepower is not only for top speed, it also brings acceleration and indirectly, maximum regen power.
They use a 2-speed gearbox on the rear axle to get a bit better torque curve. Nothing like an 8-speed sportscar gearbox would, but also much less necessary for a super powerful BEV.
While they probably have the powertrain to hit 500kph, gearing to such (say, +15% final drives) would negatively impact both economy and acceleration at all times not actually going 440kph+. Pure waste.
I can't find details on gearing but with the C One they had first gear for torque at low speeds so would assume second gear goes way up.
Acceleration is tires at low speed given the numbers and ok at higher speeds hp but they still don't get anything close to what 1914 could provide.
energy=1/2 x air density so 1.225 x v^3 x Cd x frontal area
Cd listed is 0.28 in low drag mode and maybe they can't sustain it at high power draw. Frontal area got to be under 2m given the car's dimensions.
So you get 1111 hp needed for 300 mph. Add let's say 50hp for rolling resistance, then w/e efficiency losses and you could do it with less than 1500hp.
Neither acceleration nor top speed suggest that they put 1914hp to good use, at any time.
I supposed the weight distribution of the car will screw them at high acceleration. Weight is 48% front and 52% rear but they don't have that flat battery most use with EVs so greater canter of gravity height and load transfer. And they are likely gonna mostly count on rear motors for acceleration as they end up with towards 75% of the load on the rear - an assumption without doing the math. If center of pressure is rear biased too....
So what is this optimized for, torque vectoring and 225-300km/h acceleration? Maybe i am missing something but can't figure out their thinking. Could be that torque vectoring was the focus as it is an asset others don't quite have and gives them a lot of flexibility in customizing riding style.
Acceleration is tires at low speed given the numbers and ok at higher speeds hp but they still don't get anything close to what 1914 could provide.
energy=1/2 x air density so 1.225 x v^3 x Cd x frontal area
Cd listed is 0.28 in low drag mode and maybe they can't sustain it at high power draw. Frontal area got to be under 2m given the car's dimensions.
So you get 1111 hp needed for 300 mph. Add let's say 50hp for rolling resistance, then w/e efficiency losses and you could do it with less than 1500hp.
Neither acceleration nor top speed suggest that they put 1914hp to good use, at any time.
I supposed the weight distribution of the car will screw them at high acceleration. Weight is 48% front and 52% rear but they don't have that flat battery most use with EVs so greater canter of gravity height and load transfer. And they are likely gonna mostly count on rear motors for acceleration as they end up with towards 75% of the load on the rear - an assumption without doing the math. If center of pressure is rear biased too....
So what is this optimized for, torque vectoring and 225-300km/h acceleration? Maybe i am missing something but can't figure out their thinking. Could be that torque vectoring was the focus as it is an asset others don't quite have and gives them a lot of flexibility in customizing riding style.
I disagree, the reason they went to such a large pack is so the car could participate in the standard 50 mile road race.
So I guess this thread has had its day now that Elon has confirmed 200kWh is a result of a double-layer pack?
He says it is 80% Increase over the P100D pack thickness due to single packaging.
Whilst I am excited that he knows the answer and the Roadster is real, I was disappointed to see that he said the pack may be a bit physically smaller with new tech, which implies two things to me:
1. They are still a long way off fisnishing the Roadster design, so I am unlikely to get one before at least 2021
2. They don’t yet HAVE the new tech, otherwise he’d have been more specific.
So I am worried I’ll end up with a Porsche or somethin* when my Model S gets old....
He says it is 80% Increase over the P100D pack thickness due to single packaging.
Whilst I am excited that he knows the answer and the Roadster is real, I was disappointed to see that he said the pack may be a bit physically smaller with new tech, which implies two things to me:
1. They are still a long way off fisnishing the Roadster design, so I am unlikely to get one before at least 2021
2. They don’t yet HAVE the new tech, otherwise he’d have been more specific.
So I am worried I’ll end up with a Porsche or somethin* when my Model S gets old....
1. I don’t think so much the design, they are more concerned with Model 3 ramp up, figuring out Model Y and Semi - it even sounded like the Pickup has more priority. All understadable in terms of sales and market importance...
2.They haven’t build one 200kWh pack, I agree. But at least he didn’t mention some vague battery breakthrough or so. Even though he said two 100kWh packs, I‘m pretty sure that was just a hint on putting two batt layers on top, nothing specific on what type of cell. They would sure use the new Model 3 cells, what reason not to? New housing anyway, less weight, less space.
But yes, all not so much promising for 2020, not even 2021... I‘m gonna stick to my i8 till then
2.They haven’t build one 200kWh pack, I agree. But at least he didn’t mention some vague battery breakthrough or so. Even though he said two 100kWh packs, I‘m pretty sure that was just a hint on putting two batt layers on top, nothing specific on what type of cell. They would sure use the new Model 3 cells, what reason not to? New housing anyway, less weight, less space.
But yes, all not so much promising for 2020, not even 2021... I‘m gonna stick to my i8 till then
Roadster design is less of a deal than Model 3. The car is $250K with 3 simple Model S/X motors it seems. $20K in cells. They can afford to assemble and solder them fully by hand.
To me it means the Roadster will be heavier than Model 3. And NEEDS thrusters to not be a disgrace for the Roadster badge around a corner. But more crucially, Tesla is not about to have a battery breakthrough. World electrification need a 3x energy density increase such as is promised for solid state batteries.
To me it means the Roadster will be heavier than Model 3. And NEEDS thrusters to not be a disgrace for the Roadster badge around a corner. But more crucially, Tesla is not about to have a battery breakthrough. World electrification need a 3x energy density increase such as is promised for solid state batteries.
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