CoyoteJim
Well-known member
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- Nov 19, 2019
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- Carmichael
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- Model 3, i3, Zero DS, F-250, CT & Aptera res
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- #1
We all have seen the patent UI mock-ups - 610 miles of range! Shocking, surprising? Even unbelievable? Just a random number in a mockup? How does the CT get there in a package that weighs the same (or less) than a Ford ICE F-150 and cost $70k (or less)?
Elon had stated in the reveal that they didn't "cheat" with the Cybertruck - they stayed within the dimensions and weight of the F-150 which weighs 5700 lbs max. (8) If you take the F-150 body and frame as a reference, it weighs 5150 lbs (current F-150 weight + 700 lbs for steel and subtracting 1250 lbs of powertrain weight).(1) Elon has stated that the CT will be a stressed-skin design and use a three-piece casting process for the frame with a structural battery pack using the new 4680 cells. Switching a body and frame to a unibody build results in a typical weight savings of 25%.(2) I think we can expect a similar weight reduction for the stressed-skin design, which would bring the body/frame weight down to 3863 lbs. If we subtract that from the max weight allowed for the truck (5700 lbs) we get 1837 lbs left for batteries and drivetrain. Subtracting 70 lbs for the drivetrain leaves 1767 lbs for batteries.(3)
Unfortunately Tesla has not released weight info on the 4680 cell, but it has been estimated that 1416 2170 cells occupying a volume of 1.1*10^8 mm3 and weighing 1060 lbs can be replaced by 960 4680 cells with a similar volume of 1.28*10^8 mm3 and estimated to weigh as much as 40% less.(5) This is for the Model Y and the CT will be a wider and longer vehicle. So if we increase the battery volume by 100% we would end up with 1,920 4680 cells and still potentially be under 1767 lbs. The estimated kWh would go to 200 kWh. A 100 kWh in the Model X 100D provides a range of 325 miles with 2170 batteries.(6) Increasing the kWh to 200 (while still keeping the car weight the same 5700 lbs) could increase the range to 570 miles (200 kWh / 351 Wh per mile). Using 200 kWh of more efficient 4680 cells in a vehicle the same weight should increase the range by 16% or to 660 miles. (7)
The problem here seems not to be weight but the increased size of the battery. Can a battery volume of 2.56*10^8 mm3 be fit into the middle structural component of the CT? That volume would translate into dimensions that would be, for example, 60" L x 52" W x 5" H. It seems like that could be incorporated into the center casting of the CT but I can't say for sure.
The other problem seems like it would be the cost to produce as that is a lot of 4680 batteries. However, Elon and Sandy Munro have stated that switching to 4680 batteries can reduce production cost by 50% per kWh.(7) Sandy has also stated that switching to a three-piece casting process could cut production costs by 1/3.(9)
**UPDATE** I need to make a correction - in using the Model X as a surrogate for the CT I forgot to factor in the efficiency penalty that the CT would have over the Model X due to the difference in cd values. The Model X has a cd of .24 and the CT should have a cd of .30 (per Elon’s tweet). I don’t have a source, but as best as I can glean from different examples (10) this would equate to about a 15% penalty in efficiency. (This would not be the percentage difference between the two values but the measured effect.) So with a 200 kWh battery, all other things being the same, the range would be calculated as 495 miles (200 kWh / 404 Wh per mile) and with the 16% efficiency gain from the 4680 cells the calculated range would end up at 575 miles.
My math or interpretation of my source data could be wildly off here, so I am open to valid critical review. (No, I am not an engineer, but personal attacks based on my vocation I don’t believe are relevant. In fact, in these forums it would be appreciated if we just leave personal attacks and insults off the table.)
Sources:
(1) https://www.torquenews.com/106/ford-breaks-down-2015-f150-weight-savings
(2) https://link.springer.com/article/10.1007/s42452-019-0733-8
(3) https://chargedevs.com/newswire/elo...io-is-the-challenge-with-ac-induction-motors/
(4) https://enrg.io/tesla-battery-weight-overview-all-models/#:~:text=Model X – 1200 Pounds*
(5) https://techtricity.substack.com/p/the-4680-cell
(6) https://insideevs.com/news/355282/2019-tesla-model-x-epa-ratings-compared/
(7) https://www.teslarati.com/tesla-4680-cell-pack-breakdown-video/
(8) The Cybertruck has been registered as Class 2b (8501-10,000 lbs GVWR). This means the max weight of the truck has to be 10,000 minus it's max payload, which for the CT is 3500 lbs. So the Cybertruck cannot weigh more than 6500 lbs empty. https://electrek.co/2019/12/13/tesla-cybertruck-medium-duty-vehicle-carb/
(9)
(10) https://aia.springeropen.com/articles/10.1186/s42774-020-00054-7/tables/2
Elon had stated in the reveal that they didn't "cheat" with the Cybertruck - they stayed within the dimensions and weight of the F-150 which weighs 5700 lbs max. (8) If you take the F-150 body and frame as a reference, it weighs 5150 lbs (current F-150 weight + 700 lbs for steel and subtracting 1250 lbs of powertrain weight).(1) Elon has stated that the CT will be a stressed-skin design and use a three-piece casting process for the frame with a structural battery pack using the new 4680 cells. Switching a body and frame to a unibody build results in a typical weight savings of 25%.(2) I think we can expect a similar weight reduction for the stressed-skin design, which would bring the body/frame weight down to 3863 lbs. If we subtract that from the max weight allowed for the truck (5700 lbs) we get 1837 lbs left for batteries and drivetrain. Subtracting 70 lbs for the drivetrain leaves 1767 lbs for batteries.(3)
Unfortunately Tesla has not released weight info on the 4680 cell, but it has been estimated that 1416 2170 cells occupying a volume of 1.1*10^8 mm3 and weighing 1060 lbs can be replaced by 960 4680 cells with a similar volume of 1.28*10^8 mm3 and estimated to weigh as much as 40% less.(5) This is for the Model Y and the CT will be a wider and longer vehicle. So if we increase the battery volume by 100% we would end up with 1,920 4680 cells and still potentially be under 1767 lbs. The estimated kWh would go to 200 kWh. A 100 kWh in the Model X 100D provides a range of 325 miles with 2170 batteries.(6) Increasing the kWh to 200 (while still keeping the car weight the same 5700 lbs) could increase the range to 570 miles (200 kWh / 351 Wh per mile). Using 200 kWh of more efficient 4680 cells in a vehicle the same weight should increase the range by 16% or to 660 miles. (7)
The problem here seems not to be weight but the increased size of the battery. Can a battery volume of 2.56*10^8 mm3 be fit into the middle structural component of the CT? That volume would translate into dimensions that would be, for example, 60" L x 52" W x 5" H. It seems like that could be incorporated into the center casting of the CT but I can't say for sure.
The other problem seems like it would be the cost to produce as that is a lot of 4680 batteries. However, Elon and Sandy Munro have stated that switching to 4680 batteries can reduce production cost by 50% per kWh.(7) Sandy has also stated that switching to a three-piece casting process could cut production costs by 1/3.(9)
**UPDATE** I need to make a correction - in using the Model X as a surrogate for the CT I forgot to factor in the efficiency penalty that the CT would have over the Model X due to the difference in cd values. The Model X has a cd of .24 and the CT should have a cd of .30 (per Elon’s tweet). I don’t have a source, but as best as I can glean from different examples (10) this would equate to about a 15% penalty in efficiency. (This would not be the percentage difference between the two values but the measured effect.) So with a 200 kWh battery, all other things being the same, the range would be calculated as 495 miles (200 kWh / 404 Wh per mile) and with the 16% efficiency gain from the 4680 cells the calculated range would end up at 575 miles.
My math or interpretation of my source data could be wildly off here, so I am open to valid critical review. (No, I am not an engineer, but personal attacks based on my vocation I don’t believe are relevant. In fact, in these forums it would be appreciated if we just leave personal attacks and insults off the table.)
Sources:
(1) https://www.torquenews.com/106/ford-breaks-down-2015-f150-weight-savings
(2) https://link.springer.com/article/10.1007/s42452-019-0733-8
(3) https://chargedevs.com/newswire/elo...io-is-the-challenge-with-ac-induction-motors/
(4) https://enrg.io/tesla-battery-weight-overview-all-models/#:~:text=Model X – 1200 Pounds*
(5) https://techtricity.substack.com/p/the-4680-cell
(6) https://insideevs.com/news/355282/2019-tesla-model-x-epa-ratings-compared/
(7) https://www.teslarati.com/tesla-4680-cell-pack-breakdown-video/
(8) The Cybertruck has been registered as Class 2b (8501-10,000 lbs GVWR). This means the max weight of the truck has to be 10,000 minus it's max payload, which for the CT is 3500 lbs. So the Cybertruck cannot weigh more than 6500 lbs empty. https://electrek.co/2019/12/13/tesla-cybertruck-medium-duty-vehicle-carb/
(9)
(10) https://aia.springeropen.com/articles/10.1186/s42774-020-00054-7/tables/2
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