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I thought I'd make a dedicated thread for this discussion to share thoughts on how the structural pack design works, in response to discussions on various other threads.

Model Y 4680 Structural pack as reference

These are some pictures I grabbed from Monroes teardown the 4680 to get an idea of the of the side buffer setbacks and dimensions on the MY. I think on the CT we should be able to use the same factors, to at least get to the ball park of the max space available for 4680 under the CT. These side buffers are for side impact protection of the battery packs, and they also offer a progressively rigid side impact protection.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 4680 Pack end


Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 4680 Side Buffer2


Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 4680 Side Buffer


Looks like about 175mm (7") between the cell and the edge of the pack. Which is fairly substantial. It looks like the pack screw holes are inside of the red cabin frame, and it slots up onto the grey cabin frame and cast. The red frame is about another 40mm, so about 215mm (8.5") from the outside wall to the first cell.


Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 4680 Removal



CT Pack cell Area

Using those setbacks I end up with a pink box that looks like the below, and inside that a "naked" 120kWh pack on a single layer that is this big:


Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? CT 4680 Pack




It's pretty clear that a single cell high 120kWh pack does not reach the size capacity limit on the CT floor (which is the pink box around the cells), given that we now know that the battery can also extend under the vault cover in the rear (which is actually a bit further back than the pink box), where the "hump" known as the penthouse also is housed. We also know from the x-ray pictures, that the original battery "could" even extend under the front and in between the front wheel arches as shown by the pink box to the left.

Just for comparison this is what a single layer 185kWh looks like still staying within the same setback bounds as a MY design:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? CT 4680 185 kWh Pack



Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? CT Pack 185kWh o


Now this is "just" naked cell density spacing without any structural or cooling components going through the pack. This could take up an extra 20-30% of the surface area depending on configuration. Especially if there is snake cooling between the cells that also has lines that have to be routed to the front cooling system

Edit: But if that cell cooling is no longer between cells anymore, rather just from the cathode side on the top of the pack. it would mean that it wouldn't add to the cell foot print area (like on 18650/2170). This is proposed here

Because the cells are stacked and attached, by the both top and bottom of the cell, by the structural layers, it would also form more of a structural webbing between the top/bottom layers. It's important to point out that both the cell wall of the cell (which is also a bit thicker than a 2170) and the pink foam that binds the cells together transfer load. The foam also helps maintain the cell wall geometry and stops it from buckling, it's also likely a fire retardant, to reduce fire propagation, and also adds some thermal capability as well.

The MY used 4 packs, which means three internal ribs separating the packs:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 4680 4 Packs




Each separating rib being about 40mm wide (1.5")

So just using the above, it's likely that they could get around 165-175kWh in one single layer, and still stay within the constraints of the pink box. BTW 165kWh at 400Wh/mile is well... around 420miles. :p

Now if we add 20% cell improvement over time we get 500mile range or a 200kWh pack.

But we do so within the same confines of the 165kWh, which fits within the 185kWh footprint shown above, and all without needing a dual layer pack at all.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? Sandwich



This is more important than it might first seem, in that a structural pack is unlikely to ever be dual layer, because both the top and bottom steel "skin" layer of the pack form the structural chord and the battery cells themselves the "core" webbing. Now because the webbing is attached to the two steel layers, they can transfer load from front to rear. This is because like a truss, one layer skin goes into compression, while the opposite skin goes under tension, while the core keeps each skin geometrically separated. The core is compressing the cells, every time the top and bottom skins are subjected to forces.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? Panel Stress


Note this diagram will change depending on where the forces are applied, but the principal of the sandwich structure is the same.

With TWO layers of batteries however, there would have to be a third layer in between them, which in turn means that the lower layer battery will carry the top layer battery, but unless it is pre-tensioned, the top layer won't add much structure, and bottom will carry both as the two panels of cells "slide" over each other.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 19_01_Modified_Warren_forces_DegreeTutors.com_


That's why you don't see many "truss" designs that use two trusses stacked on top of eachother.

This is because with core compression the vertical forces need to make it through both the vertical and diagonal webbing from the very top skin to the very bottom skin (chord). If they don't the top horizontal skin chord can't go into compression and the bottom skin chord can't go into tension (as per above truss loading), which is how load is transferred from one side of the truss to the other to the anchor points (red triangles).

There's also a bunch of cooling, cell terminations, and heat that needs to be considered when double stacking, and in particular assembly times etc. There's also height limits in the rear seat to consider, and the fact that the "cabin frame" would need would need to structurally connect to both the single and double layer pack, using the same cabin frame design. The difference in the skin heights means loads will be significantly different between a double and single layer pack.

Making two cabin frames, and possibly even two casts sounds expensive, just to have a longer range pack, which given the cell area above seems unnecessary anyway. From a battery perspective I seriously doubt we will need, or ever see a double layer "structural" pack. And the CT needs a structural pack for it's cabin design, otherwise there's no point making the pack structural in the first place, otherwise the pack will not have the desired effect of reducing the vehicle mass by displacing other load bearing structures in the vehicle.

You could do some "backpack" style under seat battery storage, but I don't think it is necessary given the space in the 1st layer, and adding cooling and connections to the backpacks is also non-trivial for the extra capacity they provide. Let alone they detract from interior space.

For example in the MY the open space under the front seats is quite generous and allows one to put feet underneath. In the CT the rear seats fold up (like the F150) to make a flat floor loading space as we have seen from the pictures. This is because that penthouse is behind the rear bulkhead under the bed, and not under the rear seat like in the rest of the SEXY range.

Hope this helps visualise what is going on.
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RVAC

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Is it just a problem on my end or are several images not showing up? Anyway thank you for taking the time and drawing it up with CAD, been wondering about the available volume.

But note that cell cooling in the MY teardown is no longer between cells anymore, rather just from the cathode side on the top of the pack. This means it wouldn't add to the cell foot print area (like on 18650/2170)
Cooling strategy on the MY 4680 pack is still between the cells with ribbons like on 2170 and 1850 packs, that hasn't changed so far.
 

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i agree that is it is more difficult, but i dont think it is impossible.. maybe internal support for the middle layer, or just literally sandwich two separate packs together. Or they could do what the hummer did, and have a battery "shelf" in the back, or what i think the Ram did and have a battery "hump" down the middle.
 
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Is it just a problem on my end or are several images not showing up? Anyway thank you for taking the time and drawing it up with CAD, been wondering about the available volume.



Cooling strategy on the MY 4680 pack is still between the cells with ribbons like on 2170 and 1850 packs, that hasn't changed so far.
Which images are not showing up do you know? There are 12 in total.

I grabbed that info on the cell end cooling from:
https://insideevs.com/news/464097/tesla-4680-battery-pack-design-update/

I originally remembered the same with the snake cooling, but after reading that I thought it was from Monroes teardown. I'll add a note.
 


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JBee

JBee

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a bunch aren't showing up for me neither, i only see 5:

1699622174964.png


I can see these 5:
1699622319457.png
Strange they all show in chrome and brave, but not in firefox. I'll re-upload them. Sorry.

Update: They should all work now. Must of corrupted something when I copy pasted it from a PM.
 
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It's pretty clear that a single cell high 120kWh pack does not reach the size capacity limit on the CT floor (which is the pink box around the cells), given that we now know that the battery can also extend under the vault cover in the rear (which is actually a bit further back than the pink box), where the "hump" known as the penthouse also is housed. We also know from the x-ray pictures, that the original battery "could" even extend under the front and in between the front wheel arches as shown by the pink box to the left.
I don't really have the expertise or understanding to question anything you've laid out, other than and with respect to the physical size of space available to the pack itself.

Focusing only on the topic of the physical size of the pack itself, I'm also not going to say anything I have extremely strong feelings about, instead just a back-and-forth towards shning more light on it.

But a few things:

First, I think you need to throw out anything whatsoever about the "X-ray" pictures. That was cartoon sketch from back in 2019, prior to anything definitive or real-world having been imparted on the notional design of the CT or it's frame. Too many things have changed since then for the "X-ray" to provide any reasonably reliable inferences about the actual CT being built today.


Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699626499843


Referencing the above X-ray and some main (but not all) critical differences (aside from it obviously showing the 2019 CT exterior design):

  • it has the penthouse in front, not the rear (as is now the case)
  • it doesn't appear to account for the RWS
  • it doesn't appear to account for rear motors
  • has a totally different suspension (at least lower control arms in front, and almost entirely in rear)
  • it doesn't account for the eventual design of the castings
  • note also, that the width of the pack is interior to inner edges of the front/rear tires (so while it shows a longer pack, it also shows a narrower pack)
  • finally, the above 2019 CT is presumably (per on-screen 2019 stats) a full 8" longer than the current CT (and potentially wider as well)
All-in-all, it just doesn't appear reasonable to rely on the above "X-ray" as being informative of anything relevant to the actual CT?

Next, on the location of the penthouse

I think it's possible you're misreading/remembering what we've heard about the penthouse location.

This is because that penthouse is behind the rear bulkhead under the bed, and not under the rear seat like in the rest of the SEXY range.
What we've heard does not mean necessarily that the penthouse is "behind the rear bulkhead," but rather merely accessible from behind the rear bulkhead. Remembering that the bulkhead is angled inward into the cab (and unfortunately relegated to a 2019 design diagram for initial purposes):

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699628436674


if the penthouse is "under the tonneau assembly", it may be located essentially in the midline of the rear door jam line. Presumably it's only accessible after removal of the tonneau assembly.

Having used the above cartoon of the old (and longer) bed design, it's a rough orientation to the following overlay of the modern CT design:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699628808909


Basically, this would suggest the penthouse/rearmost edge must terminate just before the foremost edge of the rear wheel well.


Turning instead to where the front limits of the pack may be:

It helps to first orient by looking at the underside wheel wells and suspension/motor assemblies relative to the front tires:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699628674522


While the above doesn't show the beginning edge of the pack unfortunately, it show the rearmost edge of the wheel wells (right where the photo cuts off at bottom)

Looking at the cab/casting assembly:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699629539210


The photo above appears to show the likely forward and rearward limits and attachment points of the structural pack. In the front, the rearmost 'lip' of the casting has attachment points and lines up with the inner door jam of the cab frame. In the back, just behind the cab bulkhead, there's a cluster of three attachment points right about where we'd expect the penthouse to be located, which is several inches forward of the rear wheel well, and other points of orientation.

Here are the mentioned attachment points in yellow, with the green lines representing roughly where the align to outward points of the cab frame.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699630021521



Taking these rough outward frame locations of the attachment points, in both cases well within the confines of the front / rear wheel wells:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699630272420


Some other work I need to go do for now, but leaving it roughly at this for present purposes

To add later: there *are* videos of the underside that roughly line up with the above diagram, and now that we know the CT is 223" (and separately that the above crash test photo is a reliable measuring reference with a 143" wheelbase, we can nail down the measurements of this to a pretty good point

will do that later

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699628942298
 

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Which images are not showing up do you know? There are 12 in total.
All good now.

I grabbed that info on the cell end cooling from:
https://insideevs.com/news/464097/tesla-4680-battery-pack-design-update/

I originally remembered the same with the snake cooling, but after reading that I thought it was from Monroes teardown. I'll add a note.
The flat cooling plate strategy was what most people were predicting, however they ended up keeping the tried and true ribbons:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? ribbons
 

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Awesome work

Your dimensions line up with what I came up with also, but mine were a bit more conservative with more margin from the pack to the exterior

148 kWh in a single layer of just cells touching each other and considering the 4680s V1, which now would be 163 kWh

My estimates for pack size and 500 miles are between 169 to 184 kWh, that would mean a per layer at worst case, 92 kWh

There is plenty of room, if we go from that and assume a reasonable amount of space taking by everything on the pack of 30%, it could me a up to 230 kWh pack and 600+ miles of range

If Tesla will do it or not who knows and we need to wait a few more weeks, but they have cells now, actually they have and will have an excess of cells that they need to put somewhere and will have for the foreseeable future, so not totally unlikely
 

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I thought I'd make a dedicated thread for this discussion to share thoughts on how the structural pack design works, in response to discussions on various other threads.

Model Y 4680 Structural pack as reference

These are some pictures I grabbed from Monroes teardown the 4680 to get an idea of the of the side buffer setbacks and dimensions on the MY. I think on the CT we should be able to use the same factors, to at least get to the ball park of the max space available for 4680 under the CT. These side buffers are for side impact protection of the battery packs, and they also offer a progressively rigid side impact protection.

4680 Pack end.png


4680 Side Buffer2.jpg


4680 Side Buffer.jpg


Looks like about 175mm (7") between the cell and the edge of the pack. Which is fairly substantial. It looks like the pack screw holes are inside of the red cabin frame, and it slots up onto the grey cabin frame and cast. The red frame is about another 40mm, so about 215mm (8.5") from the outside wall to the first cell.


4680 Removal.jpg



CT Pack cell Area

Using those setbacks I end up with a pink box that looks like the below, and inside that a "naked" 120kWh pack on a single layer that is this big:


CT 4680 Pack.jpg




It's pretty clear that a single cell high 120kWh pack does not reach the size capacity limit on the CT floor (which is the pink box around the cells), given that we now know that the battery can also extend under the vault cover in the rear (which is actually a bit further back than the pink box), where the "hump" known as the penthouse also is housed. We also know from the x-ray pictures, that the original battery "could" even extend under the front and in between the front wheel arches as shown by the pink box to the left.

Just for comparison this is what a single layer 185kWh looks like still staying within the same setback bounds as a MY design:

CT 4680 185 kWh Pack.jpg



CT Pack 185kWh o.jpg


Now this is "just" naked cell density spacing without any structural or cooling components going through the pack. This could take up an extra 20-30% of the surface area depending on configuration. Especially if there is snake cooling between the cells that also has lines that have to be routed to the front cooling system

Edit: But if that cell cooling is no longer between cells anymore, rather just from the cathode side on the top of the pack. it would mean that it wouldn't add to the cell foot print area (like on 18650/2170). This is proposed here

Because the cells are stacked and attached, by the both top and bottom of the cell, by the structural layers, it would also form more of a structural webbing between the top/bottom layers. It's important to point out that both the cell wall of the cell (which is also a bit thicker than a 2170) and the pink foam that binds the cells together transfer load. The foam also helps maintain the cell wall geometry and stops it from buckling, it's also likely a fire retardant, to reduce fire propagation, and also adds some thermal capability as well.

The MY used 4 packs, which means three internal ribs separating the packs:

4680 4 Packs.jpg




Each separating rib being about 40mm wide (1.5")

So just using the above, it's likely that they could get around 165-175kWh in one single layer, and still stay within the constraints of the pink box. BTW 165kWh at 400Wh/mile is well... around 420miles. :p

Now if we add 20% cell improvement over time we get 500mile range or a 200kWh pack.

But we do so within the same confines of the 165kWh, which fits within the 185kWh footprint shown above, and all without needing a dual layer pack at all.

Sandwich.jpg



This is more important than it might first seem, in that a structural pack is unlikely to ever be dual layer, because both the top and bottom steel "skin" layer of the pack form the structural chord and the battery cells themselves the "core" webbing. Now because the webbing is attached to the two steel layers, they can transfer load from front to rear. This is because like a truss, one layer skin goes into compression, while the opposite skin goes under tension, while the core keeps each skin geometrically separated. The core is compressing the cells, every time the top and bottom skins are subjected to forces.

Panel Stress.png


Note this diagram will change depending on where the forces are applied, but the principal of the sandwich structure is the same.

With TWO layers of batteries however, there would have to be a third layer in between them, which in turn means that the lower layer battery will carry the top layer battery, but unless it is pre-tensioned, the top layer won't add much structure, and bottom will carry both as the two panels of cells "slide" over each other.

19_01_Modified_Warren_forces_DegreeTutors.com_.jpg


That's why you don't see many "truss" designs that use two trusses stacked on top of eachother.

This is because with core compression the vertical forces need to make it through both the vertical and diagonal webbing from the very top skin to the very bottom skin (chord). If they don't the top horizontal skin chord can't go into compression and the bottom skin chord can't go into tension (as per above truss loading), which is how load is transferred from one side of the truss to the other to the anchor points (red triangles).

There's also a bunch of cooling, cell terminations, and heat that needs to be considered when double stacking, and in particular assembly times etc. There's also height limits in the rear seat to consider, and the fact that the "cabin frame" would need would need to structurally connect to both the single and double layer pack, using the same cabin frame design. The difference in the skin heights means loads will be significantly different between a double and single layer pack.

Making two cabin frames, and possibly even two casts sounds expensive, just to have a longer range pack, which given the cell area above seems unnecessary anyway. From a battery perspective I seriously doubt we will need, or ever see a double layer "structural" pack. And the CT needs a structural pack for it's cabin design, otherwise there's no point making the pack structural in the first place, otherwise the pack will not have the desired effect of reducing the vehicle mass by displacing other load bearing structures in the vehicle.

You could do some "backpack" style under seat battery storage, but I don't think it is necessary given the space in the 1st layer, and adding cooling and connections to the backpacks is also non-trivial for the extra capacity they provide. Let alone they detract from interior space.

For example in the MY the open space under the front seats is quite generous and allows one to put feet underneath. In the CT the rear seats fold up (like the F150) to make a flat floor loading space as we have seen from the pictures. This is because that penthouse is behind the rear bulkhead under the bed, and not under the rear seat like in the rest of the SEXY range.

Hope this helps visualise what is going on.
Good stuff. The added height of the 4680 makes double stacked batteries both harder and unnecessary. The team has also worked hard to keep the truck "low", both in actual height and in the positioning of the people, etc inside. I think we'll see pack sizes of around 120kWh and 175kWh eventually.
 


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OK, had a brake to go search up the transport videos that I knew would help key the rough pack size to externals, both forward, rear, and side-to-side:

Front of externals of pack lines up almost exactly with the fender flare rearward edge at its widest point (so further forward than my above diagram, estimate):

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699645292514



Rear of pack lines up with rear fender flare's forwardmost edge at the stainless steel:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699645370212



the pictures alone may make it a bit hard to glance the relative location, but the moving videos (and perspective) make these marks pretty clear, so ive linked the relevant videos here, here, and here.

Similarly, the videos may help visually confirm the edge-to-edge width of the pack, which appears to be a good 8-10" inward, on each side, of the CT's maximum regulatory width of 79.9" at the rear door jam (I'd do more diagraming of this, but I know @JBee has a pretty good mental map of how the 79.9" regulatory width (a) is measured at the fender flare tips, (b) is widest at the rear door jam, and (c) occurs at the beltline, with the width decreasing significantly as the truck approaches the lower 'rock guard' area below the doors)

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699646291195


Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699646303829







So, if we roughly assume the physical pack width is 8"-10" within the max reg width, each side, that results in pack width of = 64"-60" wide

As then for the pack length, here, then, is the adjusted / corrected visual from earlier:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699646521590



Because we now know the wheelbase is 143", and this crash test still is perspective adjusted, we can get a pretty good handle on the above sketch pack length:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699646985949



So, exterior of physical pack length and width (on this work) is approx. 92" Long by 62" wide

So, @JBee curious what you come up with using the above max exterior physical pack dimensions?

I know you're already using an estimate of front/back and side/side buffer interior to the pack, but one other thing I'd suggest considering:

The photos used above to derive the 92" pack length, assume that the front edge visible in photos is true 'pack' edge - it seems possible to me that there is at the front/back of pack not just the buffer you've considered, but also some structural depth for purpose of attachment points. Like beams just interior to the pack front/rear, through which the various attachment hardware is both attached and stabalized.

In any event, in your diagram you have pink boxes for layout, but I don't see any resulting assumed dimension to know how well it correlates to 92"x62"
 

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OK, had a brake to go search up the transport videos that I knew would help key the rough pack size to externals, both forward, rear, and side-to-side:
btw, to find those transport videos I had to go scroll through the last 3 months of @greggertruck 's xwitter posts

that dude has been PROLIFIC

and i didn't realize how much 'spotted' content exists that he doesn’t share with us lowly forum members now that he's moved on to the Dante's next circle of hell

but, if someone's as much as whispered the word 'Cybertruck' into their pillow, I *do* know where to go to find it - thanks @greggertruck

signed,
your hidden family
 
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btw, to find those transport videos I had to go scroll through the last 3 months of @greggertruck 's xwitter posts

that dude has been PROLIFIC

and i didn't realize how much 'spotted' content exists that he doesn’t share with us lowly forum members now that he's moved on to the Dante's next circle of hell

but, if someone's as much as whispered the word 'Cybertruck' into their pillow, I *do* know where to go to find it - thanks @greggertruck

signed,
your hidden family
Love always, appreciate everyone <3 It's been a ride..
 
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Lets do one post/point at a time.

Btw can we use a section number lettering system to make it easier to respond to certain parts of the posts instead of requoting everything, especially on these long ones! :)
(Like 1.A.a or something)

First, I think you need to throw out anything whatsoever about the "X-ray" pictures.
I have no problem doing that whatsoever. I only mentioned it, like I pointed out elsewhere, because in my mind originally, I had the "false" perception that they would never put the pack inside of the wheel wells area because it wasn't worth it. Apparently, I should of kept to that premise and ignored the new input from the x-ray. But...for future reference, I will be more guarded to what I assume they will or will not do, even if initially I was closer to the resulting design. In the case of the CT though I'm happy to ignore the between the wheel well space for battery pack volume given the evidence in your second post.

  • it has the penthouse in front, not the rear (as is now the case)
  • it doesn't appear to account for the RWS
  • it doesn't appear to account for rear motors
  • has a totally different suspension (at least lower control arms in front, and almost entirely in rear)
  • it doesn't account for the eventual design of the castings
  • note also, that the width of the pack is interior to inner edges of the front/rear tires (so while it shows a longer pack, it also shows a narrower pack)
  • finally, the above 2019 CT is presumably (per on-screen 2019 stats) a full 8" longer than the current CT (and potentially wider as well)
All-in-all, it just doesn't appear reasonable to rely on the above "X-ray" as being informative of anything relevant to the actual CT?
Agreed.

Except for the last two points, I'd like to say that:

1) In my drawing of the 125kWh pack it is well within the MY and the x-ray pack edge setback, so the 125kWh pack represented there is still a valid comparison, that also easily fits well within your analisys
2) I'd like to know where the actual dimensions have shifted, and how much of that was a loss of wheelbase


I think it's possible you're misreading/remembering what we've heard about the penthouse location.
Possibly, I was going off the post that stated "from the bed one must reach down past the vault and air tank to get to the battery penthouse".

To me this means a few things:
3) there is no access to the penthouse from inside the cab, because the pack is attached to the rear bulkhead, and there are no panels in the rear cabin to remove to access it
4) that the penthouse is behind the bulkhead for packaging reasons, in that it doesn't take away already limited rear cabin headroom. So only having the pack underneath would make sense, given also the flat floor under the foldup rear seats.
5) We don't really know the penthouse dimensions or configuration. It would make sense given the pack length that all the cooling terminations are dealt with at the front of the pack nearest to the front radiator/HVAC which could make it smaller.
6) Also I'd imagine that some of the switching and electrical terminations might have moved out of the penthouse completely, and either closer to the charge port and rear power outlets, or to the frunk HVAC. This is because any significant sized inverter, say 12kW, actually has some bulk to it, and requires decent cooling as well
7) this leads me to another point why the CT "800V" pack will be split like the Humvee, and that is it is much easier to get from 400V to 240/120v and 48/12V with existing mass produced mosfets/IGBTs than from 800V. There would be a bunch of conversion losses they could avoid by matching the pack to the output
8) I agree that the pack will be inside the front and rear "fender wheelbase"

if the penthouse is "under the tonneau assembly", it may be located essentially in the midline of the rear door jam line. Presumably it's only accessible after removal of the tonneau assembly.
As above in 3) I agree, but I think it is smaller overall and spread out across the full width of the vehicle

Here are the mentioned attachment points in yellow, with the green lines representing roughly where the align to outward points of the cab frame.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699630021521-
Basically, this would suggest the penthouse/rearmost edge must terminate just before the foremost edge of the rear wheel well.
I agree.

9) on the front connection points you can see the ribs that go up the cast from those connection points. These are there to distribute the loads being carried by the pack. This to me looks like the "structural pack" is in fact "more structural" than in the MY setup. Similarly, in the rear it goes into the "arch" of the wheel arch/well, which as we know is a good geometry to take load as well. ;)

I think this is because in the MY it was a mid cycle addition, and as such the cabin did more of the work. whereas in the CT they have "optimized" the cabin (read taken stuff off) to essentially 3 main parts, being the two pressed side frames, and the roof apex cross member.

10) Note on the left side of the cabin in that photo you can see how the two pressed steel parts of the cabin have become separated, revealing the shape of the inside and outside pressed steel frame.

11) This leads me to another question though, and that is if the pack is attached to the rear bulkhead, and how. I am assuming, like in the MY that the pack is bolted to the cabin frame sides along the bottom, otherwise the cabin frame would buckle inwards/outwards under load. Like the top roof apex cross member, the pack is essential to keep the cabin frame orientation and geometry straight, otherwise it would just buckle and come apart like on the other side.

Now how this applies to the attachment to the rear bulkhead, depends on the nature of the bulkhead itself, and if it alone deals with all the forces in that area, without passing anything onto the pack, or if it is attached to the pack as well. If so the question then becomes to what on the pack it can connect to, to transfer load. It is unlikely that they would compromise the homogeneity of the structural "sandwich" of the pack, by introducing a crossmember through the cells, to attach the rear bulkhead too. Together with the location of the rear connection points on the wheel wells, this leads me to believe the rear bulkhead is not attached to the pack in any meaningful load bearing way. If it is, it will only be for compression but not for tension, as it is hard to assemble/disassemble the connection to the bulkhead.

So either the "structural part" of the pack ends there if it is attached to the bulkhead, and with it the cell area, or it goes past the bulkhead to the rear well mounts and ignores the bulkhead. I think it ends at the wheel well points.

Because we now know the wheelbase is 143", and this crash test still is perspective adjusted, we can get a pretty good handle on the above sketch pack length:

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699646985949-



So, exterior of physical pack length and width (on this work) is approx. 92" Long by 62" wide

So, @JBee curious what you come up with using the above max exterior physical pack dimensions?

I know you're already using an estimate of front/back and side/side buffer interior to the pack, but one other thing I'd suggest considering:

The photos used above to derive the 92" pack length, assume that the front edge visible in photos is true 'pack' edge - it seems possible to me that there is at the front/back of pack not just the buffer you've considered, but also some structural depth for purpose of attachment points. Like beams just interior to the pack front/rear, through which the various attachment hardware is both attached and stabilized.

In any event, in your diagram you have pink boxes for layout, but I don't see any resulting assumed dimension to know how well it correlates to 92"x62"
I think these pack dimensions are pretty close to what the CT has in reality.

Note my CAD drawings were not meant to depict "where" the actual pack limits were, rather to visualize the cell area versus the "available" CT floor area.

So with the information above, we can further hone down on how big the CT pack actually is.

Tesla Cybertruck 4680 Structural Battery Pack explained - How does it work? 1699674317375


Honestly I never noticed the CT underbody shot in this photo...if someone would of pointed that out to me earlier it would of been nice...so thanks for that!

This photo alone pretty much gives the pack area outline already. It also confirms various points above and where the pack is attached to the casts.

Based on that I'm happy to draw up a pack in more detail to discuss the details further.

--

Can we share our photo collections somehow? I'd love to see a CT picture repository.
 

ninja6r

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Based on that I'm happy to draw up a pack in more detail to discuss the details further.

--

Can we share our photo collections somehow? I'd love to see a CT picture repository.
Yes please! It would be great to see your analysis on how many cells they can actually fit. I always had a strong feeling they could get enough to push the range over 550 miles
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