Yggdrasill
Active Member
I'm not so sure the amount of cells is unchanged. The new PW2 battery pack seems to be roughly 700 x 700 mm. With ideal cell packing, 90.69% of the 490,000 mm^2 area will be filled by the area of the cells.I've been trying to find dimensions of the Powerack 1 and compare them to the dimensions of PowerPack 2 ever since PP 2 was introduced. The reason is that such a comparison would allow to ascertain what kind of improvement in chemistry is there in the new GF produced cells.
Finally, Internets cooperated, and I was able to find dimensions and weight info for the PP1 and compare it to the newly published specs for the PP2. The results just blew my mind. Let's just note that the competition is NOT worrying me sick at this point.
PP1 W x D x H: 966mm x 1321mm x 2185mm Weight: 1720kg Energy Capacity: 95 kWh (AC)
PP2 W x D x H: 822mm x 1308mm x 2185mm Weight: 1622kg Energy Capacity: 210 kWh (AC)
So, as a complete surprise and in spite of all speculations that 2-fold increase in capacity was partially attributable to an increase in PP2 dimensions as compared to PP1, the actual dimensions AND weight of PP2 are LESS than PP1.
Here is my hypothesis on what it means to the improvements in chemistry for the GF produced cells:
Let's see how long it will take Electrek, Teslarati, et al. to pick up information in this post.
- Due to improvements in cooling architecture (I keep promising to post my research on the subject for a while, but life events conspired against it - will try to get to posting it over this weekend), the same quantity of 2170 cells as there were 18650 cells in each pod. This allowed for an increase in energy capacity of each pod by (70 x 21^2) / (65 x 18^2) = 46.58%
- PP2 has the same quantity of pods as PP1 - 16
- Since energy capacity of PP2 increased by a factor of 210 / 95 = 2.21, the new cell chemistry improvement is responsible for at least 2.21 / 1.4658 = 50.77% improvement in volumetric and gravimetric energy density (neglecting slight reductions in dimensions and weight of PP2)
- We do not know whether materials in the new chemistry cells are more expensive than in the 18650 cells, but it appears that there will be very significant cell level cost reduction due to chemistry improvement on top of the at least 30% reduction due to economy of scale. It looks like 2018 pack level cost of below $100/kWh for TE products is a given.
A 21-70 cell has an area of 346 mm^2, so that means the absolute maximum number of cells is 1284. This means that every cell is touching six other cells. If we assume there's a 2 mm gap between each cell, each cell occupies 491 mm, and the maximum number of cells is 905.
The previous powerwall had 888 cells. So, okay, it's plausible, given a pretty ideal arrangement of cells.
Looking at the active material, the 21-70s should have roughly 1 - (69 x pi x 10^2) / (64 x pi x 8.5^2) = 49.3% more active material per cell than the 18650s. So, if the number of cells was identical, we would expect an improvement of around 49.3%, with no improvement due to chemistry.
And we also know the P100D is using the new pack architecture. Here, the improvement was something like 1 - 100 / 85 = 17.7%. If we assume the improvement due to length comes on top of this, the total improvement due to the pack architecture and cell format should be 1 - (100 / 85) x (69 / 64) = 26.9%
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