Cybertruck Range Prediction + Cell Calculation + More [Sources]

[anionic1]

Look, aside from the 4 wheel steering, Tesla seems to be reducing weight. They reduced the size of the truck and changed the bed to plastic as two examples. They removed the 6th seat, but i am thinking that will be an option still. They also havent shown the tailgate ramp again, which also could be an option. With the now well defined casting and body frame system leaning less toward an exoskeleton and some of the oil canning we have seen, i am willing to bet the body panels other than the doors and possibly some on the front are not going to be 3mm. But obviously thats a guess, but they are at least 3x heavier and more costly than a thinner panel.

All this to say, Tesla seems to be trying to keep things simple and my bet would be to keep cost and weight down to hopefully hit their range targets. A 350 mile dual motor is and has been the target. A 500 mile tri motor or quad motor was and is a target. I think tesla gets the need for trucks to tow. And Tesla can definitely figure out where to put additional batteries as needed. So both are very feasible still regardless of whether us internet engineers think we have it figured out.

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[JBee]

You dont need to perfectly stack them although that would not be an issue. And if stacked there is likely going to be a seperator that could transfer unperfectly stacked loads. And generally in a rectangular shape the middle axis is a neutral axis without much force acting on it. The upper and lower diaphragms have the most for acting on them. It is very likely that they will stack the packs.

I'm not certain your statements apply to the double stack structural pack design. Although it's true that having a thicker structure, where the top and bottom chords are separated by a higher web is better, it is only up until material rigidity limits. The problem is that the webbing, in the form of vertical battery cans, is not in line with the forces they are subjected too across the platform, which are diagonal inbetween the chord skins. Being a frame that is subjected to dynamic loads, in particular from load points where forces go through the suspension springs on the corners, the ideal structure would be a top and bottom chord skin with a 3D triangular space frame web.

The structural pack using just the battery cans is only an approximation of that, in that the higher number of cans substitute somewhat for lack of correct structural orientation to transfer the forces. As you point out, the main structure is actually the top and bottom chord skins, in that under load one skin goes into compression and the other into tension, but the web (material inbetween the skins) is purely there to keep the skins exactly above eachother and at the same distance from eachother, and to stop skin deformation and in particular so they cannot shear in relation to eachother. Imagine the rigidity of the triangles of a 3 sided pyramid. Now if you add an intermediary layer, by having two stacked packs, the diagonal forces now have to go through two incorrectly angled web structures, (like offset pyramids) and if the middle skin is bonded correctly to the top and bottom battery stack, it simply transfers the load to the top and bottom skins rendering the middle skin unnecessary.

The reason I'm highlighting this is not to be argumentative, rather to point out that it's highly likely that the foam that is used in between the cells to glue them together is as critical, if not more important to the structural design of the pack than the cells themselves, because it transfers the forces in the right direction better than the cans, and also supports the thin walls of the cans to hold their shape meaning they can sustain larger loads in the wrong direction across them.

This obviously works for a double pack design, but as highlighted above it would be critical in the design to make sure the webbing of the cans and foam are such that they transfer the loads to the corners of the platform where the forces it has to counteract come from the suspension risers. This means that the whole area of the platform needs to be double stacked so that the forces can be picked up on the corners, otherwise if the top pack is shorter or smaller in any way, the load will only be carried by the lower pack alone, and the mass of the top layer would have to be carried by the lower pack too, resulting in a net negative structural benefit of the top stack. This applies to the little add on stacks under the seat as well, which in turn would make the design require more support for the packs, meaning a lower overall mass to kWh ratio.

Now this in itself doesn't make it impossible to do, you could add frame ribbing etc, but it does make it less likely than trying to achieve the required range with a much simpler single layer stack, especially if area wise you can get around 170-180kWh in a single stack, in the floor area in between the front firewall and the midgate wall. That would make a full area double stack would be a whopping 360kWh! Which is excessive and unnecessary to say the least.

If anything a later "long range" version would be the result of Tesla reaching their 4680 energy density goals with improved chemistry and anode/cathode designs etc.

Now if you add the loss of interior space in the cabin, and I must point out here that the rear headroom in the CT is not great even with a single stack, the second stack just makes things worse from a packaging and structural performance perspective. Having two interior fitouts or a false floor, that in itself has to be manufactured, installed and carried by the single stack seems to be a very poor design choice.

 

[ldjessee]

Cybertruck unveiling was Nov 2019.
Battery day was 10 months later, Sept 2020.
The magazine could have been told about a pack stacking the smaller cells, before they realized they decided on a larger cell (4680).

And the structural battery pack is made 'solid' thanks to the resin foam...
So I think double stacking would work with the current methodology using the foam, but if not, I am sure the Tesla engineers can design a structural battery pack that was two layers thick if that is what they needed.

Now, usually there is a bunch of electronics in or on top of the battery pack, so do not forget to account for that in your space allocation.

 

[anionic1]

I'm not certain your statements apply to the double stack structural pack design. Although it's true that having a thicker structure, where the top and bottom chords are separated by a higher web is better, it is only up until material rigidity limits. The problem is that the webbing, in the form of vertical battery cans, is not in line with the forces they are subjected too across the platform, which are diagonal inbetween the chord skins. Being a frame that is subjected to dynamic loads, in particular from load points where forces go through the suspension springs on the corners, the ideal structure would be a top and bottom chord skin with a 3D triangular space frame web.

The structural pack using just the battery cans is only an approximation of that, in that the higher number of cans substitute somewhat for lack of correct structural orientation to transfer the forces. As you point out, the main structure is actually the top and bottom chord skins, in that under load one skin goes into compression and the other into tension, but the web (material inbetween the skins) is purely there to keep the skins exactly above eachother and at the same distance from eachother, and to stop skin deformation and in particular so they cannot shear in relation to eachother. Imagine the rigidity of the triangles of a 3 sided pyramid. Now if you add an intermediary layer, by having two stacked packs, the diagonal forces now have to go through two incorrectly angled web structures, (like offset pyramids) and if the middle skin is bonded correctly to the top and bottom battery stack, it simply transfers the load to the top and bottom skins rendering the middle skin unnecessary.

The reason I'm highlighting this is not to be argumentative, rather to point out that it's highly likely that the foam that is used in between the cells to glue them together is as critical, if not more important to the structural design of the pack than the cells themselves, because it transfers the forces in the right direction better than the cans, and also supports the thin walls of the cans to hold their shape meaning they can sustain larger loads in the wrong direction across them.

This obviously works for a double pack design, but as highlighted above it would be critical in the design to make sure the webbing of the cans and foam are such that they transfer the loads to the corners of the platform where the forces it has to counteract come from the suspension risers. This means that the whole area of the platform needs to be double stacked so that the forces can be picked up on the corners, otherwise if the top pack is shorter or smaller in any way, the load will only be carried by the lower pack alone, and the mass of the top layer would have to be carried by the lower pack too, resulting in a net negative structural benefit of the top stack. This applies to the little add on stacks under the seat as well, which in turn would make the design require more support for the packs, meaning a lower overall mass to kWh ratio.

Now this in itself doesn't make it impossible to do, you could add frame ribbing etc, but it does make it less likely than trying to achieve the required range with a much simpler single layer stack, especially if area wise you can get around 170-180kWh in a single stack, in the floor area in between the front firewall and the midgate wall. That would make a full area double stack would be a whopping 360kWh! Which is excessive and unnecessary to say the least.

If anything a later "long range" version would be the result of Tesla reaching their 4680 energy density goals with improved chemistry and anode/cathode designs etc.

Now if you add the loss of interior space in the cabin, and I must point out here that the rear headroom in the CT is not great even with a single stack, the second stack just makes things worse from a packaging and structural performance perspective. Having two interior fitouts or a false floor, then in itself has to be manufactured, installed and carried by the single stack seems to be a very poor design choice.

 

[JBee]

Sorry I think you didn't post any content to your reply for me to respond to?

 

[JBee]

Cybertruck unveiling was Nov 2019.
Battery day was 10 months later, Sept 2020.
The magazine could have been told about a pack stacking the smaller cells, before they realized they decided on a larger cell (4680).

And the structural battery pack is made 'solid' thanks to the resin foam...
So I think double stacking would work with the current methodology using the foam, but if not, I am sure the Tesla engineers can design a structural battery pack that was two layers thick if that is what they needed.

Now, usually there is a bunch of electronics in or on top of the battery pack, so do not forget to account for that in your space allocation.

This is true to the extent that the foam resin aligns with the diagonal load path between the chord skins. The battery cells are densely packed, meaning that there is not much room between the cell walls for resin, so the rigidity is not given by the resin foam alone, rather the composite nature of the resin holding the cell walls to form a single composite mesh of alternating components. For example: the resin stops the cell walls from bending or twisting, and because of that the cell walls can distribute loads between the top and bottom skin chords, that then act in compression and tension to distribute the load.

The electronics and wiring component is also a good point, and is another good reason not to stack the batteries. There's also all the cooling snakes between the cells etc, each item posing a potential interface problem if not bonded correctly, and thermal expansion issues etc, that could inhibit the creation of a structural pack. This is non-trivial stuff, and goes beyond the simplistic idea, of "we'll just stack another one on top and we'll be good. I genuinely think they will be better off just improving the cell chemistry, or possibly just optimising their grading process to only use the better cells they produce in a batch to create long range packs.

 

[LCS]

Sources:
https://insideevs.com/news/598656/tesla-4680-battery-cell-specs/
https://www.teslaoracle.com/2022/07...ros-teardown-analysis-reveals-deeps-insights/
https://insideevs.com/news/584886/tesla-cyber-rodeo-4680-pack-cutaway-analyzed/
https://teslamotorsclub.com/tmc/threads/investor-engineering-discussions.232418/page-16
https://www.torquenews.com/14093/tesla-18650-2170-and-4680-battery-cell-comparison-basics
https://power-calculation.com/battery-storage-calculator.php

Do we know for a fact that Cybertruck will be 4680 and not 2170 battery cells?

 

[Ogre]

Do we know for a fact that Cybertruck will be 4680 and not 2170 battery cells?

On the earnings call Tesla mentioned the new 4680 “CyberCell” will have 10% higher energy density.

I need to listen to the whole thing, but they called it the CyberCell. Seems like a not so subtle hint.

 

[samroy92]

On the earnings call Tesla mentioned the new 4680 “CyberCell” will have 10% higher energy density.

I need to listen to the whole thing, but they called it the CyberCell. Seems like a not so subtle hint.

Yes and also @LCS the picture of the CT assembly line has the CT frame setup for a structural battery pack which implies confirmed 4680.

 

[pricedm]

On the earnings call Tesla mentioned the new 4680 “CyberCell” will have 10% higher energy density.

I need to listen to the whole thing, but they called it the CyberCell. Seems like a not so subtle hint.

Agree. This is the first time we've heard the term "CyberCell." It was specifically stated to have 10% more energy density during the Q2 earnings call.

I interpreted some of the follow-up comments from Tesla that the developments discussed at Battery Day continue to be aspirational (as of Q2 earnings call) and will not be in production with the initial Cybertruck release. Just my guess/bias from what I heard

 

[CyberGus]

Agree. This is the first time we've heard the term "CyberCell."

I wonder if the cells are triangular

 

[samroy92]

Edit: I am revising my range estimates down due to empirical evidence of UCSD teardown of 4680 cell. I think it is likely that yields on Cybertruck 4680 will be in the 90-100Wh per cell range. This puts pack capacity at 130.5kWh - 152kWh or 326mi-380mi

I think this is still high likelihood. It seems that 100-110Wh per gen2 cell is fairly realistic considering the recent comments on earnings call saying that their latest 4680 cells are 10% increase in energy density.

1450 Cells * 110 Wh = 159,500 Wh, in other words ~159kWh. If we assume 400 Wh/mi of driving efficiency this would give us an estimated EPA range of 397miles.

If Cell capacity is only 100 Wh for Gen1 CT the same calculations would yield: 362 miles of range. Not including range buffers.

 

[RVAC]

They will certainly double stack and not pass the midgate with the batteries. Previous post on the recent BIW images clearly show a deep recess for where the tonneau cover will coil up and prevent the continuation of the battery pack. Also, watching the video of Franz's kids getting in the back seat you can clearly see that there is no significant depression in the floor relative to the door threshold. And images below the vehicle seem to show the lower protective plate about flush with the exterior body panels indicating that pack will be about 8" thick, which lines up relatively close to the double stack idea. Also, the CT will experience some of the largest forces of any of their vehicles due to its size and use. Having a thicker structural pack greatly greatly enhances the structural strength of the pack the formula for the moment of inertia of a rectangle, which i assume the structural pack will resemble in section, is

with b being the width of the pack and d being the thickness of the pack. So you can see that the thickness of the pack exponentially increases the strength of the pack. The stress at any point in the pack is inversely proportional to the moment of inertia. I am 95% sure that we will see a double thick pack that only extends from the front fire wall to the mid gate. Any interest in rerunning the calcs on that area with a couble thick pack?

My bet would be for longer range options that they will add an extra hump of batteries under the seats and possibly around the frunk or that vault in the vault where I am showing in red below. It is very clear that the tonneau cover will be in the location i have shown in blue

Theoretically there is space for a single stack pack to extend past the "midgate", whether it will is a different matter:

 

[Ogre]

I think this is still high likelihood. It seems that 100-110Wh per gen2 cell is fairly realistic considering the recent comments on earnings call saying that their latest 4680 cells are 10% increase in energy density.

1450 Cells * 110 Wh = 159,500 Wh, in other words ~159kWh. If we assume 400 Wh/mi of driving efficiency this would give us an estimated EPA range of 397miles.

If Cell capacity is only 100 Wh for Gen1 CT the same calculations would yield: 362 miles of range. Not including range buffers.

I’ve been hearing rumblings around this 100 kWh/ 350 mile pack size. If they can pull that off it would be a huge win. Given the current predictions for Q4 cell production, that would be around 10,000 trucks for the 4th quarter and quite a few more for the 1st quarter 2024.

The 500 mile range is pretty unlikely at launch right now due to capacity limits.

 

[anionic1]

Theoretically there is space for a single stack pack to extend past the "midgate", whether it will is a different matter:

What they seem to have done, and my best guess would be that they did it to allow the rear window to roll down, is that they seem to have lowered the coil well deeper. I could be off here, but see the image below. Either way, I am sure they will pack as much power as possible in there.

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