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Panasonic Completing 3 New Cell Production Lines At Tesla's Gigafactory (arstechnica.com)
An anonymous reader quotes a report from Ars Technica: In a Tuesday interview with Bloomberg, the head of Panasonic's Automotive Division said that the company was on track to complete an additional three battery-cell production lines at Tesla's Nevada Gigafactory before the end of this year. That puts the expansion ahead of schedule for completion. Panasonic is a joint owner of the Gigafactory. The company provides the "2170" battery cells that go into a Model 3 battery pack. Tesla packages those cells to complete the pack. In the interview, Panasonic automotive executive Yoshio Ito told Bloomberg that "the bottleneck for Model 3 production has been our batteries." Ito added, "they just want us to make as many as possible."
In short, more battery cells rolling off more lines at the Gigafactory are good for Model 3 production only if the manufacturing process gets smoother. There's evidence that this is happening, as the company was able to sell more than 28,000 Model 3s in the second quarter of 2018, albeit at the slight expense of Model S and Model X production. The three new Panasonic lines will bring the number of cell-producing lines up to 13, Bloomberg wrote. Ito told the news service that Tesla is currently using all of its Gigafactory capacity to produce vehicle batteries, despite initially planning to reserve 30 percent of its capacity to build stationary storage batteries like Powerwalls and Powerpacks. That has played out in long-delayed Powerwall installations.
In short, more battery cells rolling off more lines at the Gigafactory are good for Model 3 production only if the manufacturing process gets smoother. There's evidence that this is happening, as the company was able to sell more than 28,000 Model 3s in the second quarter of 2018, albeit at the slight expense of Model S and Model X production. The three new Panasonic lines will bring the number of cell-producing lines up to 13, Bloomberg wrote. Ito told the news service that Tesla is currently using all of its Gigafactory capacity to produce vehicle batteries, despite initially planning to reserve 30 percent of its capacity to build stationary storage batteries like Powerwalls and Powerpacks. That has played out in long-delayed Powerwall installations.
Most everything (for a long time) used/uses 18650 battery cells which are 18mm in diameter and 65mm in height. 21700 battery cells (AKA "2170") are 21mm in diameter, 70mm in height and only made specifically for electric vehicles.
TL;DR: image comparison.
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Tesla has among the highest pack energy densities in the industry, so your notion about the weight of the packaging killing them obviously doesn't ring true.
The Model 3 packs are put together like giant motherboards. The cells are literally bonded to 2 meter-long PCBs. I doubt you'd argue that all of the bonding that motherboard manufacturers do (capacitors, resistors, etc) is some prohibitive cost ;) The bonds on the cells in the 3 are very thin wires that double as fuses; if a cell short circuits, it melts its wire bonds. Because there are so many cells in a brick, it's easy for current to be routed past it. You can't do this with large prismatic cells, at least not as effectively.
As for technical reasons for going with small cylindrical cells, there's a couple of them. One is the resilience against failure aspect mentioned above; Tesla packs are designed to allow for cell failures with only a trivial impact on the owner. The other is that they offer a high surface area to volume ratio. This is critical for cooling, mainly during supercharging. Tesla has prioritized effective removal of heat, as they offer much higher charge rates than everyone else.
Note that there's a common myth that the S and X packs "overheat" during sustained high power driving, and this is why the S and X can't do sustained track duty. This is incorrect; pack temperature is always kept down and does not correspond with throttling. As can be seen from CAN bus readings, throttling corresponds directly with motor temperature. S and X use (inefficient) induction motors. 3, by contrast, uses a much more efficient PMSRM and sees only mild throttling (similar to that experienced in many modern performance gas cars) in sustained track usage.
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