The cell density of the NCR18650A (in 85kWh pack) is (note I'm using prismatic volume so not cylindrical): 3.6V*3.1Ah / 45.5g = 0.245 Wh/g 3.6V*3.1Ah / (18.6mm*18.6mm*65.2mm) = 0.495mWh/(mm^3) http://industrial.panasonic.com/www-cgi/jvcr13pz.cgi?E+BA+3+ACA4001+NCR18650A+7+WW The cell density of the SCiB is: 2.4V*4.2Ah / 155g = 0.065 Wh/g 2.4V*4.2Ah / (62mm*95mm*13mm) = 0.132mWh/(mm^3) http://www.toshiba.com/ind/data/tag_files/SCiB_Brochure_5383.pdf So SCiB pack of the same capacity would be 3.79x cell weight and 3.75x cell volume of the NCR18650A, so even a 40kWh SCiB pack with have about 1.8x the cell weight/volume of the 85kWh pack. The SCiB does save some weight/volume from not requiring liquid cooling, but I doubt the cooling system used by Tesla takes up half the volume and weight of the 85kWh pack. In general, I'm guessing a A123 cell (like the APR18650) is a better match. It keeps the same form factor and is better than the SCiB cells in density (A123 pack of same capacity would be 2.63x weight, 2.88x volume vs NCR18650A): 3.3V*1.1Ah / 39g = 0.093 Wh/g 3.3V*1.1Ah / (18mm*18mm*65mm) = 0.172/(mm^3) http://www.a123rc.com/goods-102-Nano-Phosphate+LiFePO4+Original+A123+APR+18650+M1A+Cell.html And what's this talk about 1C? There's no doubt the 40kWh pack can charge at 1C safely (40kW), since the 85kWh pack can charge at that rate (there's some slight chemistry differences, but in general lithium cobalt 18650s are cycle tested from 0.5-1.0C charging rate, so 1C shouldn't be an issue for most cells). I thought this was already established in previous discussions. The argument was over whether it can safely charge at 90kW ("supercharger" speeds); that's 2.25C. I'm pretty sure even if that can be safely done, it's going to severely effect the life because that's twice the charging rate of the cycle test. And even that 1C rate only gives the 40kWh pack 80k miles life (corresponding to the typical 500 full cycles * 160 miles); Tesla gets the other 20k miles (125 full cycles more) by treating the pack better than the cycle test does.