I thought for sure an estimate of the Gen III battery pack had been done by someone, but not finding any through a search, I went ahead with my own back-of-envelope calculations based on the conversations of this thread. Please troubleshoot and/or improve upon these numbers as my number-crunching skills are not anywhere near CapOp's.
My estimate is fairly straightforward, simply taking 85% of the Model S battery packs due to the quoted 20% size reduction of Gen III and allowing that some elements like power electronics, chargers, airbags, etc. don’t scale linearly but are closer to constant. This may be conservative from the standpoint of Gen III being a more modest car with less range expectation, but I don’t think Tesla wants to skimp on the range (they dumped the 40kWh Model S after all), and the 200mi range quoted for Gen III is only slightly less than the 208 mi EPA certified rating of the Model S 60kWh pack.
Model S Battery Packs (estimated)
Rated Size
| Size w/buffer (1.05X)
| Range (est./cert.)
| Cell Type
| #Cells
|
60 kWh
| 64 kWh
| 230/208
| 3100 mAh @3.6V
| 5735
|
85 kWh
| 89.25 kWh
| 300/265
| 3100 mAh @3.6V
| 7997
|
Gen III Battery Packs (extrapolated from 85% size of Model S as per 20% size/weight reduction)
Rated Size
(Model S x.85)
| Size w/buffer (1.05X)
| Range (est./cert.)
| Cell Type
| #Cells
|
51 kWh
| 50.4 kWh
| 230/208
| 3400 mAh @3.6V
| 4118
|
| | | 4000 mAh @3.6V
| 3500
|
72.25 kWh
| 75.9 kWh
| 300/265
| 3400 mAh @3.6V
| 6197
|
| | | 4000 mAh @3.6V
| 5268
|
I started with a direct 80% weight reduction (48kwH/68kWh) but moved to 85% to be more conservative. I wonder though if it can’t in fact reach 80% because one, the Model S may have some luxury features which add weight that Gen III will forgo; two, the engineers may find more weight savings through everything they’re learning from the S/X platform; and three, most significantly the weight savings of the batteries will be greater if the more powerful 3400 and 4000mAh cells do not weigh proportionally more than the 3100mAh cells they will replace.
It does suggest that even if the cost of cells remains the same, the combined gains of next generation cells with weight savings of a smaller platform start to have significant effects on battery size, and in turn total cost.