Screw it, lets waste a holiday morning on Cybertruck pack size
A few key facts:
- Frontal area of 3 m² on the original prototype, if we assume they reduced it a bit, let's go with 2.9 m²
- Rolling coefficient of 0.01 from this
awesome post from Wugz
- Drag coefficient of 0.3
- Motor efficiency of 96%
- 96% gear reduction efficiency for a two stage helical gear set
- Battery and inverter efficiency at lower power are quite close to 100%, 99% for good measure
- 6500 lbs vehicle weight
Total battery to wheels efficiency of 91%
EPA highway test cycle has an average speed of 48 mph, with the data above, this means a 190 kWh pack for 500 miles, if we improve drag coefficient to 0.28, it goes down to 185 kWh
Now, this is just using the average speed of the highway portion, which isn't how the EPA range is calculated, there is multiple tests and involving acceleration and deceleration, but total average speed is much lower, so a pack could be smaller than that and still achieve 500 miles on EPA test cycle
EPA tests vehicles by running them through a series of driving routines, or schedules, that specify vehicle speed for each point in time during the laboratory tests.
www.fueleconomy.gov
To the part that concerns this thread more, 185 kWh @ $100/kWh means $18500 cost for Tesla to make it's pack, they probably aren't at that cost with 4680s yet, but let's think on the future when it's fully ramped up. Add on top the IRA credit of $45/kWh and it costs Tesla $10k
Best case scenario for customers would be for even the 500 miles one to be priced under $80k, so the pack is 1/8 of the vehicle selling price, for the Model Y that ratio is 1/8.3, assuming half of the IRA credits, other half goes to Panasonic
So cost and relative profit to battery pack size, they are on par with each other
If they price the top trim over $80k, which let's be honest, has a high likelihood of happening, at least for a while, that turns into a even better case for the Cybertruck, specially with all the manufacturing efficiencies and cost reductions all other parts and systems also will have
Now, the right way to do this calculation above would be to get the test data from EPA and simulate the whole test cycle, which would likely result in a even smaller pack, but that demands way more time