January 29, 2022

how do the brakes of the Tesla Model 3 work?

A major traffic accident left many injured in Paris. It involved a Tesla Model 3. According to initial reports, a technical failure of the brakes could be involved. Tesla nevertheless defended itself after analyzing the first technical data. And precisely … how do the brakes of the Tesla Model 3 work?

Tesla Model 3

Tesla Model 3 // Source: Frandroid

What used to be a news item seems to become a much bigger deal. Last Saturday, December 11, 2021, there was a terrible traffic accident in the 13th arrondissement of Paris, at avenue d’Ivry and at the intersection of rue de Tolbiac. In total, this accident caused 7 absolute emergencies and 3 relative according to AFP.

#Paris Grave #accident traffic in the 13th arrondissement.
A driver of #taxi would have lost control of his vehicle mowing down several people in its path.
5 absolute emergencies, 3 relative emergencies (PP) pic.twitter.com/nZQeyGkhm2

– Stephanie Roy (@Steph_Roy_) December 11, 2021

The first information was reported by the mayor Jérôme Coumet. According to him, a taxi, and more specifically a Tesla Model 3, crashed into a vehicle and destroyed a traffic light. In the meantime, the driver had hit a cyclist and rushed into a glass container and a Vélib ‘station. The glass container exploded, causing debris to be thrown on passers-by who were around.

Tesla defends itself, G7 suspend its taxis Tesla

According to testimonies, the driver lost control of his vehicle. Mayor Jérôme Coumet explained to the press that “the accelerator got stuck,” according to him, also citing a clutch problem. The driver of the car assured that the brake pedal would not have worked, rendering the vehicle uncontrollable. The investigation was entrusted to the Forensic Accident Treatment Service (STJA) to determine the exact circumstances of this accident.

Source: Le Parisien

Source: Le Parisien

Tesla quickly communicated the analysis of the collected data. According to the automaker, the accident was of human origin. According to Le Parisien, no technical failure was noted. In addition, Tesla clarified that its electric cars are not equipped with a clutch.

The G7 company has shut down its Tesla taxis after a serious accident in Paris on Saturday, the group’s communication confirmed to the#AFP today pic.twitter.com/mlx0Q5FMRF

– Agence France-Presse (@afpfr) December 14, 2021

The company G7 has however decided to suspend its Tesla, there are 37 in total on its network. The taxi platform explains that it took this decision as a precaution, it is awaiting the first conclusions.

How do Tesla’s brakes work?

Tesla uses electric disc brakes, manufactured by Brembo, for most of its vehicles. Tesla vehicles also use their electric motors for braking as they generate power and slow the car down. This is called regenerative braking.

Disc brakes

These are brakes similar to those of the vast majority of new vehicles, whether electric or thermal. These disc brakes use a high strength polished steel disc with louvers in the center for cooling. The disc has a caliper that holds the brake pads on both sides. When hydraulic pressure forces the caliper to close, the ceramic brake pads cause friction and slow the car down.

The disc brakes of a Model 3

The disc brakes of a Model 3

Electric brakes have several advantages over hydraulic systems. One of the most obvious advantages is that unlike hydraulic systems, which use fluid and high pressure lines, an electrical system never leaks. No fluid change or rust problem. This avoids a complex maintenance system, no purging or pressure testing is necessary.

These electric brakes are controlled with precision directly from the on-board computer. There is no intermediary between the brake and the system, mainly to optimize precision and controllability.

And what happens if there is a battery problem? Even with a power problem, the brakes still work in theory. This is because the vehicle’s security systems operate with a different battery (the 12 Volt battery) from that of the main power supply, which means that it operates independently of the overall charge level of the car. This system is probably more reliable than traditional hydraulic brakes because it eliminates many points of mechanical failure.

Regenerative braking

So when do you use regenerative braking instead of conventional brakes? Normally, all movement energy during braking is wasted by the brake pads and discs as heat.

Tesla uses special motors in the front wheels, and more specifically an induction motor, which was designed by Nikola Tesla. This motor is cut off during acceleration, it is activated during deceleration. The car’s momentum spins the magnets to generate energy. It’s a neat way to harness wasted energy, extend service intervals, lower maintenance costs, and increase car efficiency.

This news item has been widely shared. A Model 3 was towed for 2 kilometers at 25 km / h. This allowed him to recover 15 kilometers of autonomy.

This news item has been widely shared. A Model 3 was towed for 2 kilometers at 25 km / h. This allowed him to recover 15 kilometers of autonomy.

Regenerative braking is useful and especially strong on Tesla cars. It is typically used to slow down on the freeway when you see traffic in the distance, slow down on exit ramps, or when approaching a traffic light. These are also the situations where the brake pads wear out very quickly.

When using the conventional brake, the brake pads heat up and the brake discs become deformed when heated over an extended period of time. Regenerative braking therefore has a double advantage. It prevents the brake pads from being worn out in many cases and generates energy for the batteries in the process. Few figures are communicated, one evokes a rate between 60 and 80% of the kinetic energy recovered thanks to this system.

Autonomous emergency braking

The Tesla Model 3s are also equipped with an Advanced Emergency Braking System (AEBS). This is a device allowing sudden deceleration to be triggered in the event of an obstacle being detected. It is a system which will become compulsory in Europe on recent vehicles, it should not be confused with emergency braking (this amplifies the action on the driver’s pedal).

Tesla AEB saves the dog. pic.twitter.com/aEo43wV5nC

— Ray4Tesla⚡️🚘☀️🔋 (@ray4tesla) April 13, 2021

Last April, it was this system that saved a dog’s life, as you can see in the video in the tweet above. Note that this system is independent of Autopilot. The Autopilot is able to avoid an obstacle by maneuvering the car while the AEBS acts only on the brakes. In addition, it is triggered only in a certain speed range (from 10 to 60 km / h, the scope of use was set by the UN) and its deceleration is limited. In the severe accident described above, the car was traveling above 100 km / h.

In October 2020, a news item showed that this system was not infallible. The driver of a Model S lost control of his vehicle and was unable to avoid colliding with two pedestrians on the sidewalk. “A mad 30 m race during which he tore nine posts and damaged the front of a hairdressing salon”, specifies Numerama.

If the theory suggests that AEBS is a technology supposed to prevent all accidents, in practice there can always be biases. It is based on sensors responsible for monitoring the surroundings and designed to alert the driver to the presence of an obstacle. Tesla says in its user manual that there are factors that can prevent the technology from working normally. What to understand: You don’t always have to depend on AEBS to avoid the worst.

In this video produced by the Univers Tesla channel, we can see several scenarios and failures of the system. In the reviews, other owners indicate that the AEBS operates at speeds below 50 km / h.

A precedent in China

In April 2021, Tesla has already been heavily criticized in China. The automaker has faced criticism regarding both the safety and quality of its electric vehicles. As Reuters reports, a Tesla customer made a scene at the Shanghai auto show.

She was complaining about how Tesla had handled her complaints about faulty brakes. She climbed into a Tesla Model 3 while wearing a t-shirt that read “The brakes don’t work”. Tesla defended itself, according to the automaker, no technical problem had been detected on the vehicle in question.


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