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Tesla Semi math
- Thread starter ThomasD
- Start date
android04
Active Member
I haven't seen the video, but I don't think that guy is as qualified to do math in regards to vehicles and EVs as this guy is
Engineering Explained basically validates the math for the Tesla Semi, but he shows that the Semi has just over the bare minimum of what is needed to achieve Tesla's claims, so I think that the Semi can do what Tesla claims, but it needs perfect conditions.
Engineering Explained calculates that the bare minimum with 0.36 drag coefficient, 60 mph, 82k lbs and 0% grade is a 800 kWh battery to get 500 miles. Musk said that the Semi has an efficiency of 1.7 kWh/mile, which would mean a 850 kWh of usable battery (and probably 900 kWh of total battery). In Tesla's 500 mile drive test from Sparks NV to San Diego CA, it went over a mountain range, so not going at 0% grade the whole way, but it was carrying concrete Jersey barriers, which would give it much better aerodynamics than a normal box car trailer, and the California speed limit for large trucks is 55mph, so it was going under 60mph. The Semi achieved 500 miles with 4% battery left at the end, so it didn't do badly, but I suspect that its range would have been a little under 500 miles with a normal box car trailer and 60mph.
Engineering Explained calculates that the minimum power for the cab (without trailer) to go from 0 to 60 in 5 seconds is 750 kW or 1000 HP. The Semi has the same motors as the Model S Plaid, which has 760 kW or 1020 HP.
Engineering Explained calculates that the charger needs 1400 kW, but that is based on the assumption that the Semi would have a 1000 kWh battery. With a 850 kWh battery, I calculate that the Megacharger needs to output 1190 kW. Tesla says that its Megacharger is "1MW+", which is in line with 1190 kW.
Engineering Explained calculates that the bare minimum with 0.36 drag coefficient, 60 mph, 82k lbs and 0% grade is a 800 kWh battery to get 500 miles. Musk said that the Semi has an efficiency of 1.7 kWh/mile, which would mean a 850 kWh of usable battery (and probably 900 kWh of total battery). In Tesla's 500 mile drive test from Sparks NV to San Diego CA, it went over a mountain range, so not going at 0% grade the whole way, but it was carrying concrete Jersey barriers, which would give it much better aerodynamics than a normal box car trailer, and the California speed limit for large trucks is 55mph, so it was going under 60mph. The Semi achieved 500 miles with 4% battery left at the end, so it didn't do badly, but I suspect that its range would have been a little under 500 miles with a normal box car trailer and 60mph.
Engineering Explained calculates that the minimum power for the cab (without trailer) to go from 0 to 60 in 5 seconds is 750 kW or 1000 HP. The Semi has the same motors as the Model S Plaid, which has 760 kW or 1020 HP.
Engineering Explained calculates that the charger needs 1400 kW, but that is based on the assumption that the Semi would have a 1000 kWh battery. With a 850 kWh battery, I calculate that the Megacharger needs to output 1190 kW. Tesla says that its Megacharger is "1MW+", which is in line with 1190 kW.
Minor correction. The 500 mile run didn't go from Sparks, NV, but from Fremont, CA. So not over Donner Pass, but still over Tejon Pass (Grapevine). A Semi pulled the barriers over Donner Pass for that video. The 500 mile run had a box car trailer, and we are less sure about the actual weight (see first few seconds of that video). Box car is likely better aero (smooth, and the tractor already has the cross section) than the barriers (lots of turbulences all along).
As of charging, those numbers are average charge over 30 minutes. We don't know the charging curve, but it may be higher at the beginning, instead of sustained.
As of charging, those numbers are average charge over 30 minutes. We don't know the charging curve, but it may be higher at the beginning, instead of sustained.
