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[Alan Stewart]

Here is a nice youtube video at the EEV blog about the 4680 cell. A guy who actually knows a little bit about electronics and is mildly impressed.

If the ideas behind the 4680 cell format are so obvious why has it taken a number of decades for anyone to implement them? Many innovations are obvious after the fact, physics is just physics. Brilliance is in seeing how to take best advantage of physics, and in the case of commercial products, costs also. The largest barrier to EV adoption is cost.

This guy is not considering the financial and manufacturing aspects of the 4680, which is the primary reason for the design. 5x energy implies 1/5 as many cells are required to make a battery pack of a given capacity, a great reduction in manufacturing and quality control operations and parts counts and thus, costs. There are also possible benefits in reliability. 6x power is significant because a battery pack of a given capacity will be capable of 20% more power, which also has implications for potential charge rates and charging times. The 16% range increase is a result of weight savings for a battery pack of a given capacity, so smaller battery pack can be used to achieve the same range goal, again reducing vehicle cost.

The primary commercial and practical significance of a battery cell design is the battery pack design it enables.

[Alan Stewart]

The Tesla Battery Day presentation is focused is on how to scale up battery production and decrease battery costs, not on the 4680 cell design or EV range.

https://tesla-share.thron.com/content/?id=96ea71cf-8fda-4648-a62c-753af436c3b6&pkey=S1dbei4

[Crissa]

If the ideas behind the 4680 cell format are so obvious why has it taken a number of decades for anyone to implement them?

Well...

The spending to many the continuous or tabless cell just didn't make economic sense to small cells, which is where the vast majority of cylindrical cells are used.  It wasn't just the tabless idea, you also need more precise cell manufacture.  Usually saving money in manufacture is about adapting to a less precise but cheaper method.

For larger cells, it made sense to just make larger cells instead of slowly ramping up.  Remember, pretty much only Tesla decided to use cylindrical cells as a good atomic unit for larger batteries.  This is because just building a large battery was sort-of cheaper than making many small ones.  But small ones can be made fast and cheap... But have you seen how complex Tesla battery packs were?

Obvious doesn't mean 'there is money to do it' because often the inobvious part is 'how much will this save me vs the investment to make it so?'

-Crissa

[Alan Stewart]

Please don't fall into the trap of thinking that manufacturing costs will be the same for both cells. The 4680 cell will requires 5-6 times the raw materials of 21700 cell. Mining costs for materials that much higher for each 4680 cell. There will be some savings in machines required to make the cells but will that be a game changer? I still don't see what would be that cost reduction game changer.

The cost savings is in decrease in the reduction in the number of cells to make a battery pack of a given capacity. One-fifth as many parts and manufacturing operations saves money. Tesla moved to 2170 for the Model 3/Y to save money, per Elon Musk. It’s battery pack cost that matters in the end, not cell cost.

[Crissa]

Most of the per-cell cost is manufacturing it.  More cells, more cost.  That's why GM went with large prismatic cells, to lower the per-cell cost.

-Crissa

[Alan Stewart]

The new visualization from Tesla shows how they’ll be packing the cells closer together and eliminating the cooling ribbon of current battery packs. Probably the cell bottoms will be fully glued to the cooling plate and the interstices between cells also filled with glue to make a very solid honeycomb-like structural component. Sandy Munro thinks they’ll use manifolds welded to the positive and negative contacts at the top of the cells.

https://insideevs.com/news/456644/tesla-shows-4860-cells-and-pack/