Question About 4680 Cells

[ajdelange]

The closest car in Teslas line to the CT3 is the Model X Performance. Gets 305 miles with a 100kWh battery. That's 3.05 miles per kWh.

Rivian with its range of 315 miles or so and a 135kWh battery sits at about 2.33 miles/ kWh.

Your 500 mile/ 220 kWh battery is 2.27 miles/ kWh. Thats less efficient than the Rivian. I suspect even the tri motor Cybertruck is going to be lighter and more aerodynamic than the Rivian.

If the Cybertruck splits the difference it would be at about 2.69 miles/ kWh. That would be 190kWh for the tri. The Dual would be about 120kWh.

I'm not suggesting that's what it will be, that's definitely optimistic. Likely it'll be more than that, but 220kWh is about as likely as 160kWh.

Notice... you can make a point, make a post readable, and do so without insulting anyone.

Yes, that's much better. No grammar school insults. And even better than that you actually did some thinking using MATH to come up with an estimate of how big the battery is AND beyond that you even recognize that uncertainty comes into it.

Looking at the MXP with its consumption of 328 Wh/mi, the MXLR+ with its consumption of 282, and the Rivians with theirs of 433 is certainly a reasonable thing to do. But why stop there? There is more information available. ABRP thinks the CT consumption will be 412 and that the Rivians would come in at 432. They came pretty darn close!

Your 500 mile/ 220 kWh battery is 2.27 miles/ kWh. Thats less efficient than the Rivian. I suspect even the tri motor Cybertruck is going to be lighter and more aerodynamic than the Rivian.

I don't have a 500 mile/220 kWh battery. Based on the vehicles we're comparing I'm estimating the consumption at 420 Wh/mi. Note that this is bit conservative relative to ABRP's estimate but still a little less than the RIvian's. We know Rivian's curb weight is 5886 lbs and its GVW 8500. The CT's curb weigh estimates range from 5000 to 6486 lbs and with 3500 lbs payloads GVW would fall between 8487 and 9986 lbs. So we can't grant the CT much advantage for weight. Where it will probably do better is in the drag department.
Anyway that give 500*420 = 210 kWh as my estimate for the battery size based on comparison to other vehicles and ABRP's estimated conumption for the CT.

The next logical step is to see if we can figure out what some of the individual loads are. We know the dimensions of the CT and Musk has put 0.30 out as the holy grail for its drag coefficient. That quicly gets us 168 Wh/mi for the drag load at 60 mph. Likewize assuming the middle of the weight estimate gives us 114 Wh/mi for the rolling resistance load. Assuming 90% drive train efficiency slip of 0.1 and 50 Wh/mi for the inertial load (a WAG) we'd have total comsumption of (168 + 114 + 50)/.81 = 410 Wh/mi.

Now in an adult conversation someone who didn't think 210 is a reasonable estimate would be able to say things like "Hey not so fast! What did you use for a rolling resistance coefficient?" and they say why he thought the value I used (0.01) was unreasonable. Those here who understand something about engineering (and there are several) also understand that an estimate is an estimate subject to uncertainty. Every number in that formula is subject to some uncertainty. Just to make things simple I assumed 10 Wh/mi uncertainty on each of the drag, rolling and inertial loads and an uncertainty of 2% on slip and drive train efficiencies. The following picture shows probable battery sizes based on the loads I calculated and the uncertainties I assigned.

I know this picture will be meaningless to some here but I also know there are some here who understand exactly what it is saying and that is that the pack size will most probably wind up between 185 and 220 kWh, most likely a bit less than 210.

 

[ajdelange]

Whats your frontal area estimate for CT?
(metric works for me)

I found 2.027 m x 1.905 m (w x h)

I'm wondering how much of an effect the ride height has on Cd. Also those exposed tyres are quite large.

A lot to the point that the cars that adjust ride height will lower them at high speed.

 

[ajdelange]

CT3 charging cost is ½ the CT2 charging 3X

Can you explain what that means?

 

[ajdelange]

Can you explain how any of these matter in estimating battery size? If you can we can have an adult conversation about it.

You want me to explain how weight affects range and how battery chemistry affects weight?

No. I wanted you to explain how these things matter in estimating battery size so I could determine whether I could use high school or college level material in explaining how one makes an "engineering estimate" of battery size.

..and I can point you to some 7th grade physics lessons.

I did sort of sense that that's the extent of your STEM exposure. I don't think I can do it at that level but I decided to go ahead anyway as I know there are people on here that have background in this stuff. You can deem it "sand" if you like but they'll understand it.

 

[CyberGus]

I know this picture will be meaningless to some here but I also know there are some here who understand exactly what it is saying

I know this picture will be meaningless to some here but I also know there are some here who understand exactly what it is saying

 

[Ogre]

Yes, that's much better. No grammar school insults. And even better than that you actually did some thinking using MATH to come up with an estimate of how big the battery is AND beyond that you even recognize that uncertainty comes into it.

It is saddening to me that so many people understand Englsh as little as they understand basic science.

The engineers here will understand this.

If you don't understand that math is the sand upon which the house of engineering is built ... you would best remain silent in order to avoid looking foolish.

I know this picture will be meaningless to some here...

Now in an adult conversation someone who didn't think 210 is a reasonable estimate would be able to say things like...

Those here who understand something about engineering...

I did sort of sense that that's the extent of your STEM exposure. I don't think I can do it at that level but I decided to go ahead anyway...

Do you think the constant reminders of how smart you think you are improves the message you are trying to communicate? Because from my side of the keyboard it is just a reminder of how much of an arrogant ass you are. It's pretty ironic seeing it mixed with the way you try to play off like you are taking the higher ground.

Can we just stop with this garbage. Then I will feel compelled to stop calling out the fact that you sound like an arrogant ass. The more you try to sound like a "real engineer", the more you sound like a poser.

You litter nearly every single post with this nonsense. And you can't grasp why people think you are an arrogant ass? You accuse me of being immature? Give it a rest and grow up.

 

[Ogre]

With a 210 kWh battery, the Cybertruck is barely 2% more efficient than the Rivian. Looking at the profiles and the likely weight differences, that still seems on the high side.

Your chart might make some sense if you'd bothered to label the Y axis. It seems to assign a non-zero probability to a 240kWh battery which is just silly.

Likewise, price-wise none of this follows. Current battery costs are ??$155/ kWh?? Even if you assume some pretty big cost reductions and drop the Cybertruck battery cost to $100/ kWh, that puts the 210kW battery at more than 30% of the tri motor Cybertruck price.

What do you think Tesla's cost/ kWh is going to be? $75 less? I know Tesla is projecting some pretty big cost advantages with this process, but I don't think they would have gambled that much on them, particularly not as they are trying to increase margins.

The entire point of the Cybertruck is to create something that is more efficient and more cost effective than the competition. If what you suggest is reality, then Tesla will have failed. In fact worse, it means they planned to fail from the start.

 

[ajdelange]

Sure. It's a picture of a calculator whose owner just multiplied 5*3*19*281.

Just kidding. I was sure it was something like Ramanujan taxi number at first but a quick check of the net reveals its significance.

 

[Ogre]

I did sort of sense that that's the extent of your STEM exposure. I don't think I can do it at that level but I decided to go ahead anyway as I know there are people on here that have background in this stuff.

You are the one who asked a question which was covered in 7th grade physics not me.

 

[ajdelange]

With a 210 kWh battery, the Cybertruck is barely 2% more efficient than the Rivian. Looking at the profiles and the likely weight differences, that still seems on the high side.

OK

Your chart might make some sense if you'd bothered to label the Y axis.

No need. Everypme who can read a histogram knows what those numbers mean.

It seems to assign a non-zero probability to a 240kWh battery which is just silly.

Not to people who understand random variables. Now someone here does look pretty silly but it isn't those of us who have used these tools for hundreds of years against problems like this one. BTW there is nothing stopping you from looking up "histogram" on Wikipedia. I did and I learned something I didn't know. It was invented by Carl Pearson (Pearson's r, PCA, the mode, kurtosis, chi squared...) so I guess I'd have to sau "over a hundred years" rather than "hundreds of years).

Likewise, price-wise none of this follows. Current battery costs are ??$155/ kWh?? Even if you assume some pretty big cost reductions and drop the Cybertruck battery cost to $100/ kWh, that puts the 210kW battery at more than 30% of the tri motor Cybertruck price.

The OP has a chart showing a price reduction per kWh of 56%.

What do you think Tesla's cost/ kWh is going to be? $75 less?

56% of 155 is $86 so yes, I guess so.

I know Tesla is projecting some pretty big cost advantages with this process, but I don't think they would have gambled that much on them, particularly not as they are trying to increase margins.

The entire point of the Cybertruck is to create something that is more efficient and more cost effective than the competition. If what you suggest is reality, then Tesla will have failed. In fact worse, it means they planned to fail from the start.

I'm not suggesting it. Tesla is.

 

[Ogre]

I'm not suggesting it. Tesla is.

No. You suggested the battery pack would be 210kWh not Tesla.

 

[Crissa]

I'm not suggesting it. Tesla is.

Are you guys talking past each other now?

Yes, Tesla suggested their structural battery with 4680 cells would be much cheaper.

No, Tesla didn't suggest there would be any particular kWh capacity battery for the Cybertruck since we don't know it's weight or aerodynamics. We can guess at those, and they're both at least 25% better than Rivian or Ford's.

-Crissa

 

[Zabhawkin]

Sand is a better foundation than those assumptions.
But... https://en.wikipedia.org/wiki/Soil_liquefaction is common in sand plus groundwater.


Seems like you were driving really fast and should've stopped for dinner somewhere and a few kWh. Lunch at a 14-50 will get you almost 10% SoC back.


No.
The 4680 packs in tighter than the 2170 because less wasted space to steel canisters... The bigger circumference is better at a certain pack size. Furthermore, you can get away with putting cooling above and below instead of inside the cell tessellation.



Only smaller packs and lighter vehicles will have a problem with the 4680 cells. Their tessellation will have more wasted space at a certain smaller size.

-Crissa

Yes we were driving fast, most were driving faster. Ignore the time stamps we left in the morning, I forget where we ate but only stopped for half an hour for lunch, no charging available where we ate. I don't have an electric yet, the cyber will be the first if it works out. I was trying to demonstrate that to some of us the 500 mile pack is more important than the loss of some efficiency.

the 2170 packs have a cooling ribbon that runs between the rows of cells, they cool more efficiently through the sides. This lowers packing efficiency. The 4680 cells should cool more efficiently through the top and or bottom which allows the cells to be packed tighter. That and the higher advertised energy density even a smaller pack in a smaller car will benefit from switching to the 4680 cells.

 

[ajdelange]

Whats your frontal area estimate for CT?
(metric works for me)

I found 2.027 m x 1.905 m (w x h)

Boy did I just get a surprise! In an interview with Rivian's Brian Gase he stated that the R1T's Cd is 0.30 - same as Tesla's goal! A quick check of the R1T's frontal dimensions show about 2.0777 x 1.8659 m for a frontal area estimate within 0.4% of the CT's. This means, obviously, that at any particular speed, temperature and humidity the drag loads on the CT and R1T are going to be very close to one another. So they weigh about the same, have about the same drag, will presumably utilize tyres with similar rolling resistance and assuming they have about the same drive train efficiencies we can rough CT Tri battery size at about 135*500/300 = 225 kWh.

 

[JBee]

Boy did I just get a surprise! In an interview with Rivian's Brian Gase he stated that the R1T's Cd is 0.30 - same as Tesla's goal! A quick check of the R1T's frontal dimensions show about 2.0777 x 1.8659 m for a frontal area estimate within 0.4% of the CT's. This means, obviously, that at any particular speed, temperature and humidity the drag loads on the CT and R1T are going to be very close to one another. So they weigh about the same, have about the same drag, will presumably utilize tyres with similar rolling resistance and assuming they have about the same drive train efficiencies we can rough CT Tri battery size at about 135*500/300 = 225 kWh.

Huh thats interesting, especially seeing the R1T does not have a bed cover or particularly good looking rear aero.

But with your aero frontal area are you including the area under the vehicle in your calculation? Your vehicle height is from the ground? Because the CT might be only some 1750mm with the air suspension all the way down for hwy cruise. I can measure up the actual surface area of both if you want in CAD.