How Tesla's Regenerative Braking Works

By Kevin Armstrong
Tesla offers three stopping modes
Tesla offers three stopping modes
Not a Tesla App

Braking is essential to the driving experience, but not all systems are created equal. A regenerative braking system (RBS) is the most significant difference people notice the first time they operate an electric vehicle.

Regen, as commonly referred to, makes it possible to drive a Tesla and never touch the brake pedal (along with some brake blending for slow speeds), not only reducing wear and tear on braking components but putting energy back into the battery. There are some estimates that regenerative braking can add 10 percent more range and extend the life of braking mechanisms by more than 50 percent.

What is Tesla's Regenerative Braking?

Unlike traditional brakes, which rely on friction to stop the wheels from turning, regenerative braking uses the vehicle's electric motor to create resistance to slow down the vehicle. In addition to slowing the vehicle down without the use of brakes, the motor running in reverse acts as a generator and captures the kinetic energy that would typically be lost as heat and converts it into electrical energy, thereby increasing your vehicle's range.

How to Activate Regen in a Tesla

In a Tesla, the regenerative braking system is activated by lifting your foot off the accelerator. The more you ease off the accelerator, the stronger the braking force and the more energy is captured.

Tesla's Power Meter (Regen bar)

Tesla's power meter, also known as the regen bar or line
Tesla's power meter, also known as the regen bar or line
Not a Tesla App

All Teslas feature a power meter either in the instrument cluster (Model S and X) or the center screen (Model 3 and Y) that displays the amount of energy being captured through regenerative braking, or the amount of energy being used by accelerating the vehicle.

The center of the line is considered neutral. Anything to the left of the center point means energy is being captured, while anything to the right means that energy is being used.

The further the line grows to the left, the greater the amount of regenerative braking is taking place, and the more it moves to the right, the greater the amount of power is being used.

The regenerative braking line is green, while the power line is black (or white when in dark mode). You may occasionally also see a gray line on the left side. This will appear if the vehicle has the 'Apply Brakes When Regenerative Braking Is Limited' feature turned on. This feature introduces a consistent braking experience when lifting your foot off the accelerator pedal when regenerative braking is limited.

You may also see the gray line appear on the left side of the power meter if the vehicle is in Autopilot. This helps the driver understand when the vehicle is using regenerative braking or physical brakes to slow down.

How Does Regenerative Braking Work?

Without getting too deep into Physics, kinetic energy is energy in motion. Therefore, anytime a car slows down, the kinetic energy that is produced has to go somewhere. With traditional brakes, that is heat from abrasion generated from the brake pads squeezing the rotors. But this energy can be used in a different way. In the words of a Tesla engineer, "kinetic energy stored in a moving vehicle is related to the mass and speed of the vehicle by the equation E = ½mv²."

You can see this equation play out every time you drive your Tesla by looking at the vehicle's power meter.

The motor controller manages the torque of the motor. This action helps with both driving and regenerative braking. The position of the accelerator pedal tells the motor controller how much torque is needed. The motor controller then changes this into a voltage or current that produces the correct torque. The rotating force can be positive or negative. When it is negative, it means the vehicle is slowing down, and energy is returned to the battery.

Regenerative Braking Explained

Regenerative Braking Extends the Life of Your Brakes

One of the benefits of regenerative braking is that it can help to lengthen the life of your brakes. Regenerative braking slows the car reducing the work of your traditional braking system. In fact, Tesla estimates that their cars experience 50 percent less brake wear than conventional gasoline cars. Elon Musk predicted that Tesla's Semi would have brake pads that would "literally last forever" because the regenerative system would save those pieces from being used extensively.

It's estimated that regenerative braking captures up to 70 percent of the kinetic energy usually lost during braking and is put back into the battery. As described above, that energy can then extend the range between needing to charge.

Does Regenerative Braking Activate Your Brake Lights?

During regenerative braking, Tesla will still activate the brake lights when the vehicle is slowing down, even if the brakes aren't being used at all. Tesla determines whether to turn on your brake lights based on your vehicle's rate of deceleration. If you're unsure if your brake lights are on, look at your Tesla screen, the car in the display shows the brake lights lit up when the brake lights are activated.

Levels of Regenerative Braking

It's important to note that regenerative braking cannot be turned off. There are two regenerative braking modes for 2020 and older models — low and standard. Tesla recommends that you use standard to maximize your vehicle's range. At some point in 2020, that choice was taken away, presumably to use all the benefits of regenerative braking all the time. However, there were some concerns, as regenerative braking can slow down the car rapidly; therefore limiting traction, the vehicle could slide. Tesla has this warning on its website: In snowy or icy conditions, Model S may experience loss of traction during regenerative braking.

Tire Configuration

The company also notes that installing winter tires may temporarily reduce regen. But the vehicle's systems are constantly recalibrating, so the feel of the vehicle will return to what the driver is used to after a few miles or trips.

You can speed up the calibration process by selecting the type of tires your vehicle is using. To select the type of tires your vehicle is using navigate to Controls > Service > Wheel & Tire Configuration > Tires and choose the appropriate tire type.

Regenerative Braking Limited or Reduced

Regenerative braking is not available or can be limited during certain conditions. If this happens, you may see a dotted line in the vehicle's power meter. If the battery is fully charged, there is nowhere for the kinetic energy to go. Consequently, regen won't work. It also has limited usage during cold weather due to a cold battery. In these cases, you can choose to activate 'Apply Brakes When Regenerative Braking Is Limited' to provide a consistent slow down experience. Tesla stated, "Your car can now automatically apply regular brakes for consistent deceleration when regenerative braking is limited due to battery temperature or state of charge." But the company did leave this as a preference, and the option can be turned off. You can activate it under Controls > Pedals & Steering.

Stopping Modes

Regenerative braking works best at certain speeds, if you're traveling too slow, regenerative braking may be limited or not available at all.

In a Tesla, your vehicle will use regenerative braking whenever you lift your foot off the accelerator pedal. However, if you're using Tesla's 'Hold' stopping mode, which allows you to drive with a single pedal most of the time, the vehicle will automatically blend in the vehicle's brakes when traveling 4 MPH (6.5 KPH) or slower.

If you're using Tesla's 'Creep' or 'Roll' stopping modes, the vehicle will never apply the brakes when lifting your foot off the accelerate, which means the vehicle will continue to roll at slow speeds when regenerative braking is no longer effect.

A Brief History of Regenerative Braking

Tesla used regenerative braking in its first car — The Roadster, in 2008. A year later, the same mechanics of the system were implemented in Formula 1. It is called KERS, which stands for Kinetic Energy Recovery System. It provides such a horsepower boost that it was banned for a season before being regulated the following year. However, this advanced system dates back to the late 1800s.

The Sprague Electric Railway and Motor Company is the earliest known use of the technology in 1886. General Electric used regen in 1936 in its locomotives, and Oerlikon, a Swiss company utilized some components of the system in its gyrobus. The Amitron, a concept electric car created by the American Motor Car Company included regenerative braking in its designs. Toyota introduced the technology to its brand with the Prius Hybrid in 1997 and GM's EV1 had regen when the company sent the cars to the crusher.

Regenerative braking is now a staple of the electric vehicle experience, not only reducing maintenance costs but also improving the vehicle's range and letting drivers accelerate and slow down with a single pedal.

Tesla Preparing to Expand Robotaxi Geofence As Validation Vehicles Spotted

By Karan Singh
Not a Tesla App

Tesla appears to be preparing to expand its Robotaxi geofence in Austin, Texas, with numerous engineering vehicles taking to the road. One of the most interesting sights, between the short and tall LiDAR rigs, was a Cybertruck validation vehicle, which we don’t often see.

Tesla’s expansion is moving the Robotaxi Network into downtown Austin, a dense urban environment that is currently outside the geofence. It appears Tesla is content with the latest builds of Robotaxi FSD and is ready to take on urban traffic.

The inclusion of a Cybertruck in the validation fleet is noteworthy, as the rest of the vehicles are Model Ys. This suggests that Tesla may be addressing two challenges simultaneously: expanding its service area while also addressing the FSD gap between the Cybertruck and other HW4 Tesla vehicles.

Using LiDAR

Recent sightings have shown a fleet of Tesla vehicles, equipped with rooftop validation sensor rigs, running routes throughout downtown Austin and across the South Congress Bridge. While these rigs include LiDAR, it’s not a sign that Tesla is abandoning its vision-only approach.

Instead, Tesla uses the high-fidelity data from the LiDAR as a ground truth measurement to validate and improve the performance of its cameras. In short, it essentially uses the LiDAR measurements as the actual distances and then compares the distances determined in vision-only to the LiDAR measurements. This allows Tesla to tweak and improve its vision system without needing LiDAR.

Additionally, the validation vehicles are likely scouting for the new, pre-determined, selectable pick-up locations that have just rolled out as part of the Robotaxi app.

Expanding the Geofence

This data collection in a new, complex environment right outside the Robotaxi geofence is an indicator that plans to expand the geofence. Tesla has previously indicated that they intend to roll out more vehicles and expand the geofence slowly. Given that their operational envelope includes the entire Austin Metro Area, we can expect more locations to open up gradually.

Once they expand the operational radius to include downtown Austin, they will likely also have to considerably increase the number of Robotaxis active in the fleet at any given time. Early-access riders are already saying that the wait time for a Robotaxi is too long, with them sometimes having to wait 15 minutes to be picked up.

With a larger service area, we expect Tesla to also increase the number of vehicles and the number of invited riders to try out the service.

After all, Tesla’s goal is to expand the Robotaxi Network to multiple cities within the United States by the end of 2025. Tesla has already been running an employees-only program in California, and we’ve seen validation vehicles as far away as Boston and New Jersey, on the other side of the country.

Cyber FSD Lagging Behind

One of the most significant details from these recent sightings is the presence of a Cybertruck. Cybertruck’s FSD builds have famously lagged behind the builds available on the rest of Tesla’s HW4 fleet. Key features that were expected never fully materialized for the Cybertruck, and the list of missing features is quite extensive.

  • Start FSD from Park

  • Improved Controller

  • Reverse on FSD

  • Actually Smart Summon

It may not look like a lot, but if you drive a Cybertruck on FSD and then hop in any of the rest of Tesla’s HW4 vehicles, you’ll notice a distinct difference. This is especially evident on highways, where the Cybertruck tends to drift out of the lane, often crossing over the lane markings.

We previously released an exclusive mentioning that a well-positioned internal source confirmed with us that a new FSD build for the Cybertruck was upcoming, but we never ended up receiving that particular build, only a point release to V13.2.9. The AI team’s focus had clearly shifted to getting the latest Robotaxi builds running and validated, and while a flagship, the Cybertruck fleet was small and new, and really a secondary task.

The Cybertruck’s larger size, steer-by-wire, rear-wheel steering, and different camera placements likely present a bigger set of challenges for FSD. Deploying it now as a validation vehicle in a complex environment like downtown Austin suggests that Tesla is finally gathering the specific data needed to bring the Cybertruck’s capabilities up to par. This focused effort is likely the necessary step to refine FSD’s handling of the Cybertruck before they begin rolling out new public builds.

When?

Once Tesla’s validation is complete, we can probably expect the Robotaxi Network to expand its borders for the first time in the coming days or weeks. However, we’ll likely see more signs of the expansion, such as Robotaxi vehicles driving themselves around the area, before the expansion actually happens.

Hopefully, the Cybertruck will also learn from its older siblings and receive the rest of its much-needed FSD features, alongside an FSD update for the entire fleet.

Tesla Updates Robotaxi App: Adds Adjustable Pick Up Locations, Shows Wait Time and More [VIDEO]

By Karan Singh
Nic Cruz Patane

Tesla is rolling out a fairly big update for its iOS and early-access-only Robotaxi app, delivering a suite of improvements that address user feedback from the initial launch last month. The update improves the user experience with increased flexibility, more information, and overall design polish.

The most prominent feature in this update is that Tesla now allows you to adjust your pickup location. Once a Robotaxi arrives at your pickup location, you have 15 minutes to start the ride. The app will now display the remaining time your Robotaxi will wait for you, counting down from 15:00. The wait time is also shown in the iOS Live Activity if your phone is on the lock screen.

How Adjustable Pickups Work

We previously speculated that Tesla had predetermined pickup locations, as the pickup location wasn’t always where the user was. Now, with the ability to adjust the pickup location, we can clearly see that Tesla has specific locations where users can be picked up.

Rather than allowing users to drop a pin anywhere on the map, the new feature works by having the user drag the map to their desired area. The app then presents a list of nearby, predetermined locations to choose from. Once a user selects a spot from this curated list, they hit “Confirm.” The pickup site can also be changed while the vehicle is en route.

This specific implementation raises an interesting question: Why limit users to predetermined spots? The answer likely lies in how Tesla utilizes fleet data to improve its service.

Release Notes

While the app is still only available on iOS through Apple’s TestFlight program, invited users can download and update the app.

Tesla included these release notes in update 25.7.0 of the Robotaxi app:

  • You can now adjust pickup location

  • Display the remaining wait time at pickup in the app and Live Activity

  • Design improvements

  • Bug fixes and stability improvements

Nic Cruz Patane

Why Predetermined Pick Up Spots?

The use of predetermined pickup points is less of a limitation and more of a feature. These curated locations are almost certainly spots that Tesla’s fleet data has identified as optimal and safe for an autonomous vehicle to perform a pickup or drop-off.

This suggests that Tesla is methodically “mapping” its service area not just for calibration and validation of FSD builds but also to help perform the first and last 50-foot interactions that are critical to a safe and smooth ride-hailing experience.

An optimal pickup point likely has several key characteristics identified by the fleet, including:

  • A safe and clear pull-away area away from traffic

  • Good visibility for cameras, free of obstructions

  • Easy entry and exit paths for an autonomous vehicle

This change to pick-up locations reveals how Tesla’s Robotaxi Network is more than just Unsupervised FSD. There are a lot of moving parts, many of which Tesla recently implemented, and others that likely still need to be implemented, such as automated charging.

Frequent Updates

This latest update delivers a much-needed feature for adjusting pickup locations, but it also gives us a view into exactly what Tesla is doing with all the data it is collecting with its validation vehicles rolling around Austin, alongside its Robotaxi fleet.

Tesla is quickly iterating on its app and presumably the vehicle’s software to build a reliable and predictable network, using data to perfect every aspect of the experience, from the moment you hail the ride to the moment you step out of the car.

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