Tesla has started customer deliveries of its Class 8 all-electric Semi truck, revealing a few new things about its powertrain.
According to the manufacturer, the Tesla Semi "is a beast" with a total power output three times higher than in the case of any diesel truck on the road. However, Tesla does not say the exact peak or continuous power output number.
High power does not surprise us considering that the vehicle's acceleration from 0 to 60 mph (96.5 km/h) is promised to take just 20 seconds (when fully loaded). By the way, fully loaded means 82,000 lbs (37,195 kg) Gross Combination Weight (GCW), because the allowed GCW for BEVs is 2,000 lbs higher than for diesel vehicles - 80,000 lbs.
This is probably why a substantially loaded Tesla Semi was able to easily accelerate when driving uphill on a 6% incline in Donner Pass in the northern Sierra Nevada, as shown in the video (37:30). The vehicle easily passed another semi.
Elon Musk adds that, to some degree, the Tesla Semi drives like a normal truck, although it's bigger and heavier.
Now let's get into details. The Tesla Semi is equipped with a new tri-motor system, which consists of three independent electric motors (compared to four, expected to be used in 2017 when the Semi was announced).
The motors are, of course, used to power the two rear axles - 2nd and 3rd - as the front axle is not powered.
An interesting thing is that the electric motors have carbon-sleeved rotors - just like in the Tesla Model S/Model X Plaid introduced in 2021 (see the presentation of the front motor and two rear motors here). This means that Tesla put everything it had to maximize the output of the drive unit.
Tesla Semi drive units
The first rear axle (or the second axle if you wish) has one electric motor, constantly engaged through a single-speed reduction gear. It's optimized for highway driving.
Meanwhile, the other two electric motors are used at the rear axle to individually power the left and right wheels. Those two motors are optimized for acceleration and torque.
Depending on the circumstance (especially speed and accelerator pedal position), the two rear motors are automatically and seamlessly engaged or disengaged mechanically from the drive axle to minimize energy losses.
Here is how it works:
It's important to note that the Tesla Semi utilized powertrain components borrowed from its other electric vehicles - including electric motors and inverters, the heat pump system and the infotainment system.
Of course, there were modifications, but overall the use of mass produced parts allowed Tesla to achieve a much higher level of reliability compared to an alternative scenario of developing all-new systems for a relatively low-volume vehicle (compared to millions of cars).
The Tesla Semi's powertrain, like in the case of other modern electric vehicles, is fully prepared for intensive recuperation. The company's test has shown that it's possible to go downhill using regenerative braking and have basically cold mechanical brakes at the bottom.
Tesla Semi specs (2022):
- Fully loaded at 82,000 lbs (37,195 kg) Gross Combination Weight
- Range: about 300 miles (483 km) or 500 miles (804 km)
(two battery options)
- Energy Consumption: less than 2 kWh/mile (1.24 kWh/km)
- Estimated battery capacity (based on range and energy consumption): lower than 600 kWh or 1,000 kWh (1 MWh)
- Acceleration 0-60 mph (96.5 km/h): 20 seconds (when fully loaded)
- Speed up a 5% Grade: Highway speed limit
- Powertrain: 3 independent motors (vs. four motors in the initial specs in 2017)
- two electric motors for acceleration at the rear axle (with automatic disengage)
- one electric motor for highway driving at the second axle (constantly engaged)
- carbon-sleeved rotors just like Plaid
- Fast Charging: up to 70% of range in 30 minutes
- Fuel Savings (est.): up to $200,000 over 3 years
Initial prices (at unveiling in 2017):
- Expected Base Price (300 mile range) – $150,000
- Expected Base Price (500 mile range) – $180,000
- Base Reservation – $20,000
- Expected Founders Series Price – $200,000
- Founders Series Reservation – $200,000
* Prices displayed in USD. International pricing will vary.