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Inside a Model 3 battery

Posted: Fri, 20 Apr 2018, 20:22
by jonescg
Some of us have been waiting a long time to get a tid-bit of information about how Tesla has put their Model 3 battery packs together. Not because they are necessarily good (although, that they are) but because its always something rather unique.

And that it is :shock:
Model 3 battery5.JPG
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Model 3 battery4.JPG
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Model 3 battery3.JPG
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Model 3 battery2.JPG
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Model 3 battery1.JPG
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Full credit to Autoline Network for the content. Sandy Munroe pulled it apart and took meticulous notes.

Skip ahead to 29 minutes to see the battery, and some discussion either side of it.

Re: Inside a Model 3 battery

Posted: Sat, 21 Apr 2018, 00:03
by antiscab
The modules seem to be getting much larger

Re: Inside a Model 3 battery

Posted: Sat, 21 Apr 2018, 14:19
by jonescg
Some interesting observations:

It appears that the cells are all standing up in the same orientation. The negative busbar (you can see the black pen) has the fusible links connected to the side of the cell can (negative terminal) while the positive terminals are fused to the next busbar along in a similar fashion. I assume this was an effort to make manufacturing easier, as modules that big start to get quite unwieldy when flipping and rotating to terminate the opposite side.

The silicone gel stuff serves to both provide some damping to the cells against vibration, as well as acting as a thermally conductive encapsulant. Robo-pumping the goop into a battery module must be a slow process.

The silicone gloop is then used to form a thermally conductive path between the cells and the cooling loop - which is a large flat cooling plate on the top (and presumably the bottom too). It The cooling inlet tubes are still attached in the last 2 images above.

Elsewhere, there have been discussions about the holdups in the Model 3 production line, and they mentioned 'bandoleers' of cells, glued together and slapped together in the plastic tub. I can see how a CNC trying to ultrasonically weld fuse wire to the sides of the cells would struggle!

The shift to the 21700 cell format doesn't add a huge amount of energy density - the bigger volume of active material relative to the non-active material is hardly worth writing home about. But the larger axial surface area as a result of the new aspect ratio makes axial surface cooling more practical. Moreover, the process of wire-bonding to the outer rim of the cell can for the negative terminal is made easier with the larger cell - seems to have a good 2 mm of edge offset there.

Whole modules of a few thousand cells are risky - one fault and the whole thing is in trouble. They must be confident in their cell QC and wire bonding technique...

Re: Inside a Model 3 battery

Posted: Thu, 26 Apr 2018, 08:39
by jonescg
Looks like the cells are cooled radially - consistent with earlier reports of battery cells being glued to cooling strips like bandoleers. ... teardown-9
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