I watched the Battery Day presentation yesterday. it was a worthwhile exercise, it is very comprehensive and well explained.
One statement from Elon stood out as significant, front and rear castings are needed for a structural battery pack.
Given that Tesla use a special alloy for casting, other car makers seem like years away from being able to do structural packs.
The reason I re-watched is related to Plaid Model S battery pack.
We had some Reddit posts here around 24 hours ago from someone claiming to work on the Model S/X battery pack line.
My understanding was he was implying 18650s will be used in a new pack, and possibly for the Plaid Model S structural pack.
Th Reddit user has since deleted all of their posts and I think their user id, this tends to make them more credible IMO.
But there is no certainty their claims are correct, that they have the full picture, or that I have correctly understood their claims.
Elon confirmed a structural pack and possibly 4680 for Plaid Model S in a twitter exchange along these lines..
Omar::Will Plaid Model S have a structural pack and I assume the power density from 4680 helps.
Elon: Yep.
The Reddit user claimed that posit was misunderstood, Elon definitely confirmed that Plaid Model S has a structural pack and that the power density from 4680 helps. He didn't necessarily confirm the Plaid Model S pack will be built with 4680s, but that is a reasonable conclusion, and the vast majority of people would form that conclusion.
The other evidence for Plaid Model S having 4680s is:-
1) it was included in the Battery Day presentation, however I do not think they detailed what cells it was using.
2) Model S/X were listed in the vehicles specifically as using Nickel-Manganese cells.
However, I still have doubts about whether Model S/X is using Nickel-Manganese cells from Kato Rd Q1 2021.
It is possible Kato Rd is making Nickel-Manganese cells, but they are reserved for supporting the Berlin Model Y ramp.
We know Model Y at Fremont was initially built with a 2-peice rear casting and a non-structural 2170 battery pack.
So that path is possible for Model S/X with a later upgrade to a structural 4680 pack with front and rear castings.
However, the Reddit user claimed to down time was for a new pack architecture..
This may still used with a 2-peice rear casting, but could be a 18650 pack that is capable of structural deployment with front and rear casting. That was my reading of the Reddit user's comments.
However this does raise the question of whether the 18650 cells would need to be tab-less, I think tab-less 18650 and 2170 cells are possible, and that upgrade is worthwhile if these cells have a long term future.
However, I also seem to remember the Rivian pack is built with 2170s and end cooling, I doubt those were tab-less 2170 cells.
Again the Reddit user said something cryptic here about assumptions around cooling not being correct.
If an 18650 structural pack has been built, that may just be an interim step, until Model S/X can migrate to 4680.
However, we can be confident 18650s are available Q1 2021, provided they don't need to be modified for tab-less design. or that production line change can be done.
In this context, when I re-watched the Battery Day, I was looking for specific advantages 4680 cells might deliver over and above cost savings. Higher energy density, lower weight, and faster charging were 3 likely advantages..
Overall I'm reasonably confident about my interpretation of the Reddit users comments, and I think they have part of the picture.
If a Model S/X platform can be adapted to work with a structural 4680 pack, it can certainly use some kind of 18650 pack as an interim solution.
