Tesla Battery Day Thread

[hayden55]

Originally Posted by jakobnev

Well this thread went on a bit of a tangent.

Oooops my bad. Back to it. So by there numbers it looks like we now have a 4680. By comparison to the 2170 (5000mAh max) that means the new cell is up to a 25,000 mAh cell.
Anybody know the exact specs c rating and Ah wise?

[MetroMPG]

What's the deal with the tabs? How is this a breakthrough? I assume because it removes a manufacturing step.

[RedDevil]

The anode, cathode and everything in between are thin layers rolled up inside the cell. If you roll it out it can be over half a meter from end to end.

There is only one tab on the anode and cathode, usually somewhere in the middle of the unrolled strip. So the current in the cell does not just flow from the top of the cell to the bottom (or vice versa), but also up to half a meter sideways through the anode and cathode.

By extending the anode and cathode on either side of the roll and carefully folding them flat the current only has to move up or down the cell and no longer sideways through the anode and cathode. This limits the internal friction in the cell, which increases its efficiency and power output and reduces its cooling needs.

Because the cells now need less cooling they can grow in diameter. This greatly expands the capacity per cell, while the production costs of the cell grow less quickly; so the pack can be made with less and relatively cheap cells which of course further reduces cost.

As a bonus the bigger diameter makes the cells more resistant to lateral deformation, so they can become part of the structural support system. Instead of being embedded in the chassis the battery pack now is a structural part of the chassis.

Not having tabs is a small thing in itself but it enables a string of developments which all combined have a huge impact.

[redpoint5]

https://www.youtube.com/watch?v=jKrFAcNgG40

https://www.youtube.com/watch?v=ieR0...ature=youtu.be

[MetroMPG]

Thanks - that explains the photo of the top of the cell - I assume all those cuts are the "continuous tab" material carefully cut/folded to make electrical contact with the rest in the coil.

[oil pan 4]

Looks heavy.

[freebeard]

This is why at Permalink #24 I asked "Tabless or all-tab." The shortened electric path is key.

As for heavy, ~50% more power per kilogram.

edit for oilpan4: Density vs [what they measure in Coulombs] left as an exercise for the more astute reader.

[oil pan 4]

Power like watts you can get out of it or how many total KWH it holds?
It appears that obsolete 2011 nissan leaf battery tech was was likely able to unleash enough power for a short duration to break stuff.

[hayden55]

Originally Posted by oil pan 4

Power like watts you can get out of it or how many total KWH it holds?
It appears that obsolete 2011 nissan leaf battery tech was was likely able to unleash enough power for a short duration to break stuff.

Energy is Wh normally on batteries. Power is c(A) on cells. Basically its how much energy its rated to flow max and not overheat.

[freebeard]

This seems like an appropriate thread for this:

https://www.youtube.com/watch?v=jhoQlWB_irI

2 million miles if you cycle the batteries 0-100-0% repeatedly. 20-80-20% and they're basically immortal. It raises the question — what happens when the battery outlives the car?

They suggest that the robotaxis will need this. The avenue they don't explore is making a car that lives as long as the battery. I posit that the CyberTruck is the answer to that.