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Tesla battery researcher Jeff Dahn’s tests hint at li-ion cells breaking the 2M-mile barrier

Tesla Gigafactory Nevada battery cell production line (Credit: Super Factories)

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Last year, the electric vehicle community’s attention was caught when Tesla battery researcher Jeff Dahn and his team published a paper revealing that quality lithium-ion batteries have the capability to last 1 million miles if used in EVs. A recent presentation from the respected battery pioneer has now revealed that these findings may actually be conservative, as the batteries that Dahn and his team have been testing are still going strong, and are now on track to pass the 2-million-mile mark.

Dahn’s updated findings were discussed in a recent video conference for energy storage and sustainable engineering. According to Dahn, the “million-mile” batteries that were referred to in the past year’s paper are now going towards 10,000 to 15,000 cycles. Considering that the million-mile cells were cycled 5,000 times, it is starting to become evident that the lithium-ion batteries that Dahn’s team have been testing have the potential capability to last 3.5 million km or over 2 million miles if used in an electric vehicle.

https://twitter.com/facts_tesla/status/1317933952645042176?s=20

Remarkably, the lithium-ion cells that are being cycled by Dahn and his team have shown minimal degradation even at this point. With this in mind, there seems to be a good chance that even the study’s “2-million-mile” cells are capable of lasting even longer. Dahn notes that lithium-ion batteries have reached a point where it is becoming imperative to look into the further applications of advanced battery technology, such as vehicle-to-grid, or massive vehicles like airplanes and ferries.

As noted by the team in its 2019 paper, the lithium-ion batteries that it will be using are NMC532 pouch cells obtained from Li-FUN Technology in China. The NMC532 pouch cells are dry batteries as well, using no electrolytes. Interestingly enough, Tesla’s next-generation 4680 cells that the company revealed at Battery Day also utilize dry battery technology developed from the innovations of Maxwell Technologies, a company that the EV maker acquired.

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Considering that the batteries which Dahn and his team are testing are just cells acquired from Li-FUN Technology in China, there seems to be a pretty good chance that Tesla’s next-generation 4680 cells could exhibit comparable or even superior performance when they are deployed to the company’s fleet of vehicles and energy storage units in the coming years. If these assumptions prove accurate, then Tesla’s next-generation cells may truly be a class above anything that is being used in the market today. Dahn, for his part, noted that Tesla’s battery strategy is sound.

“Tesla is just moving forward at the speed of light. They are upscaling their factories, they know they need Tera Watt Hours for both energy storage and vehicles, and it’s incredibly exciting times,” he said.

Watch Jeff Dahn’s recent talk about his team’s battery findings in the video below.

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Simon is an experienced automotive reporter with a passion for electric cars and clean energy. Fascinated by the world envisioned by Elon Musk, he hopes to make it to Mars (at least as a tourist) someday. For stories or tips--or even to just say a simple hello--send a message to his email, simon@teslarati.com or his handle on X, @ResidentSponge.

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Elon Musk

Elon Musk reveals shocking Tesla Optimus patent detail

What looked promising on paper and in simulations failed to deliver the reliability required for a robot expected to handle delicate tasks like folding laundry, assembling electronics, or assisting in factories and homes.

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Credit: Tesla

Elon Musk revealed a shocking detail on the Tesla Optimus patent that was revealed last week. Despite it being made public for the first time, Musk said the company has already moved on from the design, an incredible truth about the development of new technology: things move fast.

Musk dropped a bombshell about the Tesla Optimus humanoid robot hand patent that was released last week. Musk, candidly replying to a post late at night on X, revealed that what is a new technology to many fans and insiders is actually old news to those developing the tech directly.

“We already changed the design,” Musk said. “This one didn’t actually work.”

Patents, after all, are often viewed as blueprints for future products. Yet Musk revealed that the rolling contact mechanism—intended to provide smooth, low-friction articulation in the fingers—had already been scrapped after real-world testing exposed its shortcomings.

What looked promising on paper and in simulations failed to deliver the reliability required for a robot expected to handle delicate tasks like folding laundry, assembling electronics, or assisting in factories and homes.

The hand has been one of the biggest challenges for Tesla engineers since Optimus development started years ago. Musk has said that there is not enough recognition for how incredible and useful the human hand is, and designing one for a humanoid robot has been the biggest challenge of all.

Tesla is stumped on how to engineer this Optimus part, but they’re close

This moment underscores the persistent engineering hurdles in achieving reliable humanoid hand dexterity. Human fingers are marvels of evolution: 27 bones, intricate tendons, ligaments, and a network of sensors working in perfect harmony. Replicating that in metal and silicon is extraordinarily difficult.

Rolling contacts promised reduced wear and precise motion, but testing likely revealed issues with durability under repeated stress, grip stability on varied surfaces, or the micro-precision needed for fine motor skills.

These aren’t minor tweaks, but instead they represent fundamental challenges that have plagued robotics teams for decades. Even advanced competitors struggle here—hands remain the Achilles’ heel of most humanoids because the margin for error is razor-thin.

A fraction of a millimeter off, and a robot drops a glass or fails to button a shirt.

What makes Musk’s reply remarkable is how it signals Tesla’s direct communication style on prototype limitations. While many companies guard failures behind glossy marketing and vague timelines, Tesla openly shares setbacks.

Musk was forthcoming about the failure of this recent design. This transparency builds trust with investors, engineers, and fans. It shows Tesla treats Optimus development like true science: rapid iteration, rigorous testing, and zero tolerance for hype that doesn’t match reality.

The disclosure from Musk also highlights Tesla’s blistering pace of development. By the time the patents are published, which is often over a year after the initial filing, the technology has already evolved.

Optimus is far from a static product, and it’s a living project advancing weekly.

In the high-stakes race for general-purpose robots, Tesla’s approach stands out. Admitting a finger-joint design “didn’t actually work” isn’t a weakness—it’s confidence.

True innovation demands confronting failure head-on, and Musk just reminded the world that Optimus is being engineered that way. The next version of those hands is already in testing, and it will be better because Tesla isn’t afraid to say what didn’t work.

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Elon Musk

Tesla is sending its humanoid Optimus robot to the Boston Marathon

Tesla’s Optimus robot is heading to the Boston Marathon finish line

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Tesla’s Optimus humanoid robot will be stationed at the Tesla showroom at 888 Boylston Street in Boston, right along the final stretch of the Boston Marathon today, ready to cheer on runners and pose for photos with spectators.

According to a Tesla email shared by content creator Sawyer Merritt on X, Optimus will be at the Boston Boylston Street showroom on April 20, coinciding with Marathon Monday weekend. The Boston Marathon finishes on Boylston Street, and the surrounding area draws hundreds of thousands of spectators along with international broadcast coverage. Placing Optimus there puts it in front of a massive public audience at zero advertising cost.

The Tesla showroom is at 888 Boylston Street, between Gloucester Street and Fairfield Street. The final mile of the marathon runs directly along Boylston Street, with runners passing the big stores before reaching the finish line at Copley Square.

Optimus was first announced at Tesla’s AI Day event on August 19, 2021, when Elon Musk presented a vision for a general-purpose robot designed to take on dangerous, repetitive, and unwanted tasks. In March 2026, Optimus appeared at the Appliance and Electronics World Expo in Shanghai, where on-site staff stated that mass production of the robot could begin by the end of 2026. Before that, it showed up at the Tesla Hollywood Diner opening in July 2025 and at a Miami showroom event in December 2025.

Tesla’s well-calculated display of Optimus gives the public a low-pressure first encounter with a robot that Tesla is preparing  to soon deploy at scale. The company has previously indicated plans to manufacture Optimus robots at its Fremont facility at up to 1 million units annually, with an Optimus production line at Gigafactory Texas targeting 10 million units per year.

Tesla showcases Optimus humanoid robot at AWE 2026 in Shanghai

Musk has said that Optimus “has the potential to be more significant than the vehicle business over time,” and separately that roughly 80 percent of Tesla’s future value will come from the robot program. Whether that holds depends on production execution. For now, Boston gets a preview of what that future looks like, standing at the finish line on Boylston Street while 32,000 runners pass by.

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Tesla expands Unsupervised Robotaxi service to two new cities

This expansion builds directly on Tesla’s existing operations. Robotaxi has been ramping unsupervised rides in Austin for months and maintains activity in the San Francisco Bay Area.

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Credit: Tesla

Tesla has taken a major step forward in its autonomous ride-hailing ambitions.

On April 18, the company’s official Robotaxi account announced that Robotaxi service is now rolling out in Dallas and Houston, Texas. The update signals the rapid scaling of unsupervised autonomous operations in the Lone Star State.

The announcement includes a compelling 14-second video captured from inside a Model Y. Shot from the passenger perspective, the footage shows the vehicle navigating suburban roads in both cities with zero driver intervention, with no Safety Monitor to be seen.

Tesla also shared geofence maps highlighting the initial service areas: a compact zone in Houston covering parts of Willowbrook and Jersey Village, and a similarly defined area in Dallas near Highland Park and central neighborhoods.

This expansion builds directly on Tesla’s existing operations. Robotaxi has been ramping unsupervised rides in Austin for months and maintains activity in the San Francisco Bay Area.

With Dallas and Houston now live, Texas hosts three active hubs—an impressive concentration that triples the company’s Lone Star footprint in just weeks. The move aligns with Tesla’s Q4 2025 earnings guidance, which outlined a broader H1 2026 rollout across seven U.S. cities, including Phoenix, Miami, Orlando, Tampa, and Las Vegas.

Texas offers favorable regulations, high ride-share demand, and relatively straightforward suburban-to-urban driving patterns ideal for early autonomous scaling. While initial geofences appear modest—roughly 25 square miles per city—Tesla has historically expanded these zones quickly as it gathers real-world data.

Tesla confirms Robotaxi expansion plans with new cities and aggressive timeline

Unsupervised operation marks a critical milestone: passengers can summon, ride, and exit without safety drivers, a leap beyond many competitors still requiring human oversight.

For Tesla, the implications are significant. Successful scaling in major metros could accelerate the transition to a fully driverless fleet, unlocking new revenue streams and validating years of Full Self-Driving investment.

Riders gain convenient, potentially lower-cost mobility, while the company edges closer to Elon Musk’s vision of Robotaxis transforming urban transport.

As Tesla pushes into more cities this year, today’s launch in Dallas and Houston underscores its momentum. Hopefully, Tesla will be able to expand unsupervised rides to another U.S. state soon, which will mark yet another chapter in this short-but-encouraging Robotaxi story.

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