A completely electric vehicle complete with an ‘autopilot’ function to help provide assistance with semi-autonomous driving and safety for truckers over long journeys, the Tesla Semi uses four motors to independently power four wheels across the rear axis. The design has been made in this way to ensure there are no differentials and the truck can gain the most traction control possible for added stability.
This will provide an additional safety feature, preventing the truck from jack-knifing. By taking advantage of its unique electric drivetrain, which includes independent motors for each of the wheels, the truck can sense the distribution of weight across the wheels and actuate the motors or brake them accordingly to maximise traction control. This also allows for automatic correction for thing like over-steer in response to weight shifts. Essentially, the Tesla Semi will do everything in its power to avoid a jack-knifing incident, automatically, without requiring any driver intervention.
In fact, the Tesla Semi has a completely different engine braking system. It has no gears and no gearbox. The four electric motors on the drive axles will use regenerative braking under almost any conditions to provide braking force, something engine-braking in a diesel truck can’t permit as often. As a result, inability to downshift to get engine braking will no longer be a problem.
The electric batteries of the Tesla Semi work in a similar way to those of other Tesla vehicles. When Musk announced the vehicle, he said the truck would be capable of going a distance of between 300 and 500 miles (400 to 800 km) on a single charge, with a 30 minute charging time refilling the batteries up to 80%. While this might seem to lead to increased trip times compared to diesel trucks,
after around 400 km, drivers generally stop for a 30 minute break, so there should be very little difference in travel time.
In fact, the Tesla Semi boasts an acceleration of zero to just under 100 km/h in five seconds, or in 20 seconds when it's fully loaded with a 36 000 kg load, the maximum it can carry on US roads. The four independent motors provide instant traction control, allowing the vehicle to quickly travel up grades and inclines.
All of these features are promising to change the way trucks are built and used in the future. However, the success of electric trucks will rest on the batteries. Due to the size of the vehicle they need to help haul along the road (plus the load it is carrying), the Tesla Semi lithium batteries are very large, starting under the floor below the drivers' feet and extending all the way back to the back set of wheels on the cab. The company is promising big things for battery development, but until the Semi is on the roads, it remains to be seen how game-changing the battery is.
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