2022 Model Y 4680 Structural Pack is "Amazing", Says Munro & Associates

Munro & Associates has just released an analysis of the structural pack for Tesla's 4680 battery cells, having just received a 2022 Model Y SR from Giga Texas.

In their analysis, Cory Steuben (President of Munro & Associates) and Julian Aytes (lead engineer) found that the car's front seats are directly mounted onto the structural pack itself, making the structural pack essentially the vehicle's floor itself.

"It's absolutely mind-blowing to be standing under a vehicle on a hoist and have absolutely nothing for the floor structure. To truly understand how amazing it is to see a vehicle with no floor and the seats mounted to the top of the structure on the pack, you have to go back more than years, but decades."

(Source: Munro & Associates)

The structural pack, including the seats and other components mounted to it, weighs 1,198 pounds, which is "incredible because in a couple of the other EVs we have, the batteries will weigh twice that. Just the batteries. No seat, no carpet, no trim."

According to Elon Musk, the structural pack is "the right overall architecture from a physics standpoint, but still far from optimized," which seems to be a modest take on the speed of Tesla's design improvements.

https://twitter.com/x/status/1544511999392071680

Despite minor manufacturing issues found by the team, the Giga Press casting machines, noted as the world's largest high-pressure die casting machines, have done an amazing job at astronomically decreasing both parts and complexity for the structure of the chassis itself.

"At Munro & Associates, we've seen the development of the automotive industry for the past 30 to 40 years. I've come from a background of benchmarking vehicles where you'd have hundreds of stamped parts where this front giga casting is, and hundreds of parts in the back. The level of refinement and integration is incredible. Tesla is not waiting to integrate the casting for multiple mounting features."

Overall, these improvements have come from decades of constant work and continuous improvement on Tesla's end, and it is clear to see why Tesla is so ahead of many other manufacturers in terms of vehicle and battery structure.

Steuben mentions that the next goal for their analysis is to remove the battery cover and be able to know how Tesla is securing the 4680 cells themselves and take a look inside the battery pack itself.

The full breakdown and analysis is linked below.

 

[MP3Mike]

I think when 2170s hit with the Model 3 they quickly (like within six months) were able to charge at V3 speeds while the 18650s were limited to ~200kW (and that I think even took awhile before Tesla software upgraded them).

That has nothing to do with the cells, it had to do with the charge port and the cabling used in the Model S&X that were limited.

 

[ZenRockGarden]

That has nothing to do with the cells, it had to do with the charge port and the cabling used in the Model S&X that were limited.

I'd have to agree here. The 2170 might have an edge on longevity and maybe energy density, but in terms of thermal capacity and power input/output the thousands of tiny 18650's are actually tops - see Plaid for demonstration

 

[sleepydoc]

That has nothing to do with the cells, it had to do with the charge port and the cabling used in the Model S&X that were limited.

Charge speed very much depends on the cells - the internal resistance of the cells affects heat generated during charging which is one of the limiting factors. All things being equal, smaller cells will dissipate heat more quickly because of the larger surface to volume ratio.

Did you mean that Tesla changed other factors besides the battery cells that allowed for faster charging?

 

[MP3Mike]

Did you mean that Tesla changed other factors besides the battery cells that allowed for faster charging?

Yes, they upgraded the charge port and the cabling from the charge port to the battery on the Model S&X to enable the faster than ~190kW charging. I think on the Model S the maximum charging rate varies from 90kW to 250kW depending on what combination of pack internal HV bus, charge port, charge port cabling, etc. (And yes battery cell formulation make a difference, but the 18650s, with the same formulation, will almost always charge faster than the 2170s, when in a similarly sized pack.)

 

[jackmott]

So we have some reports that at least early 4680 cells have no silicon, which hurts density by about 10%. This might explain the weight/range of the new Model Y standard model not showing much sign of weight reduction. But *why* no silicon?

 

[AlanSubie4Life]

but the 18650s, with the same formulation, will almost always charge faster than the 2170s, when in a similarly sized pack

Hopefully (and presumably) the extremely tabful cells of the 4680 disrupt this trend. So many tabs!

 

[ZenRockGarden]

Hopefully (and presumably) the extremely tabful cells of the 4680 disrupt this trend. So many tabs!

Tabs are nice, and help the electrons flow easier. But you still gotta cool the cell, and little thin cells have more surface area to chill on.

 

[AlanSubie4Life]

Tabs are nice, and help the electrons flow easier. But you still gotta cool the cell, and little thin cells have more surface area to chill on.

The cornucopia of tabs should help with that! They are conductive!

But I’m not sure there is any evidence that is the limiting factor for charge rate, anyway. I suspect it might be more to do with the larger cell series resistance for the 2170 and diffusion distances within the cell (got a LOT longer distance to go to get those ions to the right place, so that one part of the cell doesn’t start plating or get overcrowded or whatever), which the many additional tabs of the 4680 are supposed help with.

If you’ve supercharged, it seems that lots of additional heat is actually good. Helps with diffusion perhaps.

Not sure, but I doubt heat is the limiting factor here (for charging).

 

[ZenRockGarden]

The cornucopia of tabs should help with that! They are conductive!

But I’m not sure there is any evidence that is the limiting factor for charge rate, anyway. I suspect it might be more to do with the larger cell series resistance for the 2170 and diffusion distances within the cell (got a LOT longer distance to go to get those ions to the right place, so that one part of the cell doesn’t start plating or get overcrowded or whatever), which the many additional tabs of the 4680 are supposed help with.

If you’ve supercharged, it seems that lots of additional heat is actually good. Helps with diffusion perhaps.

Not sure, but I doubt heat is the limiting factor here (for charging).

If you believe heat is universally good during supercharging, why are the cables liquid cooled, and the cars heat-pump running at max-cool during most of the session?

You do want the pack up to optimal temp, but that's like 80 degrees, not 200....

 

[AlanSubie4Life]

If you believe heat is universally good during supercharging, why are the cables liquid cooled, and the cars heat-pump running at max-cool during most of the session?

That’s a much, much tighter pipe! And a conductive copper cable is a much different beast than a bunch of cells (4416 or 8xxx for 18650) in parallel (which can obviously shed heat over a much larger volume).

As you know, to get maximum charge rate, substantial warming of the pack is typically done. Is it necessary to avoid getting it too warm? Sure. Likes to be just right. No need for it to be hotter than it needs to be to accept all the charge it can take.

I just doubt the internal cell temperature is the limiting factor that makes 2170 not quite as fast as 18650. It doesn’t really make any sense.

but that's like 80 degrees, not 200....

Wasn’t it more like 40-50C?Just check the videos, pretty well documented.

If you believe heat is universally good during supercharging

Where did I say this?

 

[ZenRockGarden]

That’s a much, much tighter pipe! And a conductive copper cable is a much different beast than a bunch of cells (4416 or 8xxx for 18650) in parallel (which can obviously shed heat over a much larger volume).

As you know, to get maximum charge rate, substantial warming of the pack is typically done. Is it necessary to avoid getting it too warm? Sure. Likes to be just right. No need for it to be hotter than it needs to be to accept all the charge it can take.

I just doubt the internal cell temperature is the limiting factor that makes 2170 not quite as fast as 18650. It doesn’t really make any sense.


Wasn’t it more like 40-50C?Just check the videos, pretty well documented.


Where did I say this?

"If you’ve supercharged, it seems that lots of additional heat is actually good"

A modest amount of heat is added to the pack if it's cold in prep for supercharging, but it's actively cooling the pack for most of the session once charging gets going at any interesting rate.

 

[AlanSubie4Life]

If you’ve supercharged, it seems that lots of additional heat is actually good"

Exactly. It’s important to not claim that people said things that those people didn’t say! It confuses things! (See also: context, this is not a thread about charging cables)

Internal cell temp is not the limiting factor here. Makes no sense at all.

My guess: Once it is hot enough to overcome the first rate-limiting factor, it is hot enough, and other rate-limiting factors (likely diffusion-rate related) come into play. Arrhenius equation - Wikipedia

 

[ZenRockGarden]

Exactly. It’s important to not claim that people said things that those people didn’t say! It confuses things! (See also: context, this is not a thread about charging cables)

Internal cell temp is not the limiting factor here. Makes no sense at all.

My guess: Once it is hot enough to overcome the first rate-limiting factor, it is hot enough, and other rate-limiting factors (likely diffusion-rate related) come into play. Arrhenius equation - Wikipedia

I'll just ask one more time - why is my Tesla running the heat pump at max-cooling and venting heat out the front on max-fan for most of the supercharging session if your above assertions are true?

 

[AlanSubie4Life]

I'll just ask one more time - why is my Tesla running the heat pump at max-cooling and venting heat out the front on max-fan for most of the supercharging session if your above assertions are true?

Because it wants to keep the batteries at the optimal temperature, and does not want them to get excessively hot.

Note: it does not follow that higher temperature would lead to slower charge rates (this is my point!). It might well lead to other problems.

My question back to you would be: why does the charge rate taper at ~30%? Why does this happen regardless of whether you just plugged in (when heat would not have built up) or whether you started charging at 5%?

If temperature buildup were the limiting factor for charge rate for a pack preconditioned to the optimal temperature, the onset of taper would occur at a lower % if you plugged in at a lower %. If anything, typically the knee occurs at a slightly higher SOC the longer you have been plugged in below the knee.

 

[ZenRockGarden]

Because it wants to keep the batteries at the optimal temperature, and does not want them to get excessively hot.

And finally we agree that your original statement has flaws: "lots of additional heat is actually good"

 

[AlanSubie4Life]

And finally we agree that your original statement has flaws: "lots of additional heat is actually good"

Context matters. Lots of additional heat is definitely good, likely for the reasons I mentioned in that post. Obviously I did not mean excessive heat.

To the point of this discussion: you still have presented no evidence that excessive internal heating of the cells and the lack of ability to cool them is the limiting factor on charge rate. The key argument supporting that it is not is in my prior post.

 

[drtimhill]

Tabs are nice, and help the electrons flow easier. But you still gotta cool the cell, and little thin cells have more surface area to chill on.

To an extent yes, but the problem is always how to transport that heat away from the cells, so the packing of the cells becomes critical. Also, one of the selling points of the 4680 was the reduced internal resistance which, by definition, reduces the heat generated in the first place.

 

[sleepydoc]

To an extent yes, but the problem is always how to transport that heat away from the cells, so the packing of the cells becomes critical. Also, one of the selling points of the 4680 was the reduced internal resistance which, by definition, reduces the heat generated in the first place.

Exactly - the tabless design allows for a much shorter internal current path in the battery which decreases the internal resistance. this is the key. less heat generation means lower heat dissipation requirements, allowing a larger form factor. I suspect this is also what the origin of the "6x power" claim - the tabless design allows for higher peak current.

 

[AlanSubie4Life]

I suspect this is also what the origin of the "6x power" claim - the tabless design allows for higher peak current.

Not quite, or at least that makes it sound better than it is. It’s equivalent to about 5.5 2170 cells in parallel, so for parity, you want it to be able to deliver 5.5x the power. That would just be keeping up.

That’s harder to do with a normal tabbed cell if you make it bigger (due to internal resistance as you said). But adding a bunch of tabs to the cell (aka tabless) allows you to get back to that point, plus just a little more if they actually hit 6x. 6x is about 10% improvement.

I’m not sure why they didn’t claim a 10% improvement. 6x is just confusing. Talk about the parameters that matter…

 

[sleepydoc]

Not quite, or at least that makes it sound better than it is. It’s equivalent to about 5.5 2170 cells in parallel, so for parity, you want it to be able to deliver 5.5x the power. That would just be keeping up.

That’s harder to do with a normal tabbed cell if you make it bigger (due to internal resistance as you said). But adding a bunch of tabs to the cell (aka tabless) allows you to get back to that point, plus just a little more if they actually hit 6x. 6x is about 10% improvement.

I’m not sure why they didn’t claim a 10% improvement. 6x is just confusing. Talk about the parameters that matter…

power is current times voltage. The voltage of the 4680 cells is the same, so the only way to get more power is by more current. If you're talking about an individual cell, that either means lower resistance or better heat dissipation. The larger form factor actually makes heat dissipation more difficult so lower resistance is the only way to accomplish this.

If you're talking about a battery pack comprised of many cells in parallel it gets more complicated. If the 4680 cells have 5x the energy then a nominally equivalent pack would have 1/5th the number of cells meaning to get an equivalent amount of total current from the pack each 4680 cell would need to supply 5x the current of a 2170 cells. That's just to reach parity.

Tesla was very vague about the 6x power claim since it could have meant that the cost savings would allow more cells per pack at the same cost allowing for more total power, but I doubt it. The only real way to get more power without changing the battery pack configuration would be to have more than 5x the current per cell. Given the vagueness of the 6x power statement, it could well mean that they can get 6x the current per cell, which would give 6x the power for that cell but a more modest 10% gain if you look at the battery pack as a whole. I agree that the 6x power statement was confusing. I'm pretty sure that was phrased like that simply to make it sound better. Lies, damned lies and statistics, right?

More than simply increased power, the significance of this is the decreased power loss in the battery. Lower internal resistance means more less heating at a given current and thus less wasted power. This should mean you can get increased range and or use a smaller battery pack. There are a lot of other variables that go into this, though, so the end result is very much up in the air.