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Tesla ‘Roadrunner’ cell leak hints that Battery Day will be more insane than expected

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

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Tesla’s Battery Day has been hyped so much that the event will have to include something truly amazing to live up to its expectations. In the lead up to the highly-anticipated event, a leaked image featuring what is supposedly a cell from Tesla’s “Roadrunner” line has emerged. And if the leak proves legitimate, it would appear that Battery Day will not only meet expectations — it will be even more insane than expected. 

The leaked image, which was initially published in a report on Electrek, featured a massive battery cell that was supposedly a product of the Roadrunner line. The publication noted that the image was sent through an anonymous source and confirmed by another independent source. From the get-go, it is evident that the cell is massive, closer in size to a supercapacitor than a traditional battery cell. Initial observations by battery enthusiasts online also point to some radical improvements that such a cell design would bring. 

While Electrek’s sources have mentioned that the Roadrunner cell will feature roughly double the diameter of the 2170 cells that the electric car maker currently uses in the Model 3 and Model Y, Tesla enthusiast @_BRCooper, who is familiar with battery tech, has observed that one of the leaked images had the number “054” printed on its side. If this number represents the cell’s diameter, it would point to Tesla’s Roadrunner cells adopting a 54×98 form factor, which has 10x the volume of a 2170 cell.

As noted by Jordan Giesige of The Limiting Factor channel on YouTube, adopting a 54×98 form factor for its next-generation cells has numerous implications for the entire battery manufacturing process and the performance of Tesla’s vehicles as a whole. With the larger cells, Tesla could produce battery packs that have an order of magnitude fewer cells than before. This would result in the company only using 1/10 the number of rolls, cans, electrolyte fills, and welds compared to its current operations. Such a strategy opens the doors to massive cost reductions that could help bring down the prices of electric cars to a notable degree. 

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But regardless of its actual size, the design of the Roadrunner cell appears to be optimized and designed for a cell-to-pack drop-in setup. Interestingly enough, the leaked image of the Roadrunner cell seems to have a tabless electrode design, which Elon Musk has dubbed is “way more important than it sounds” last year. Provided that the Roadrunner cells are indeed inspired by Tesla’s tabless electrode patent, the new form factor could pave the way to more performance and further reductions in production costs. 

What’s even more notable is that these improvements become possible with just the Roadrunner cell’s new form factor and design. Giesige, for his part, has noted that with the Roadrunner cell’s design and potential 54×98 form factor alone, Tesla may be able to close in on 300 wh/kg before making any significant changes to its battery chemistry. Elon Musk actually mentioned a 30-40% improvement from 250 wh/kg back in 2018, which translates to an improvement to 325-350 wh/kg. Musk’s prediction was considered fantastical by critics then, but as Battery Day approaches and leaks start to emerge about the event, it is starting to look more and more likely that 325-350 wh/kg is feasible. 

Watch a feature on the Roadrunner battery cell leak 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’s Boring Co. Tunnel Vision Challenge ends with a surprise for Louisiana, Maryland and Dallas

The Boring Company stunned three cities today, awarding New Orleans, Baltimore, and Dallas free underground Loop tunnels.

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Elon Musk’s The Boring Company (TBC) announced today that it is building free underground Loop tunnels in three American cities: New Orleans, Louisiana; Baltimore, Maryland; and Dallas, Texas. The company had promised one winner when it launched the Tunnel Vision Challenge in January. After receiving 487 submissions, it selected three, committing to fund and construct all of them pending a feasibility review, entirely at its own expense. For a company that has faced years of skepticism over the gap between its promises and its delivered projects, choosing to expand its commitment rather than narrow it is a notable shift in both scale and accountability.

All three projects will now enter a rigorous, fully funded diligence phase that includes meetings with elected officials, regulators, community and business leaders, geotechnical borings, and a complete investigation of subsurface utilities and infrastructure. TBC confirmed that all costs associated with this diligence process are 100% funded by the company. If all three projects pass feasibility, all three get built. If only one clears the bar, that one gets built. The company’s willingness to fund the due diligence regardless of outcome removes one of the most common early-stage barriers that kills promising infrastructure proposals before they leave a spreadsheet.

Beyond the three winners, TBC announced it will continue working with two additional entrants it found compelling enough to pursue independently: the Hendersonville Utility Tunnel in Hendersonville, Tennessee, and the Morgan’s Wonderland Tunnel in San Antonio, Texas, which would notably serve one of the nation’s premier theme parks built specifically for guests with special needs.

The challenge also coincides with TBC’s most active construction period to date. The company recently began drilling on the Music City Loop near the Tennessee State Capitol in Nashville, and in February it broke ground on a Loop in Dubai. Musk has long argued that the fundamental problem with urban infrastructure is cost and bureaucratic inertia, not engineering. “The key to solving traffic is making going 3D either up or down,” he said in 2018, a conviction now reflected in a company structure built to absorb the financial risk that typically stalls public projects for years.

Music City Loop could highlight The Boring Company’s real disruption

The Tunnel Vision Challenge’s most underappreciated element may be what it produced beyond three winners. Submissions came from individuals, companies, and governments across states including Alaska, Arkansas, Colorado, Kansas, Louisiana, Maryland, New York, and Texas, as well as from international entrants. Musk captured the underlying logic years ago when he said, “Traffic is driving me nuts. I’m going to build a tunnel boring machine and just start digging.” Today, three American cities are counting on exactly that.

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Tesla launches first ‘true’ East Coast V4 Supercharger: here’s what that means

What truly distinguishes this installation from the hundreds of “V4” stalls already scattered across the network? Most existing V4 dispensers, rolled out since 2023, feature welcome upgrades like longer cables, built-in touchscreen displays, integrated credit-card readers for non-Tesla users, and improved ergonomics.

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Credit: Tesla Charging | X

Tesla has launched its first “true” V4 Supercharger on the East Coast, and while that may be sort of confusing, here’s what we mean by that.

Tesla has opened its first true V4 Supercharging station on the East Coast in Kissimmee, Florida, just south of Orlando.

The eight-stall site, powered by an advanced 1.2 MW V4 power cabinet, is capable of delivering up to 500 kW, making it one of only four fully operational 500 kW-capable V4 stations in the United States.

Pricing is dynamic and competitive, as Tesla owners pay $0.40 per kWh during peak hours (8 a.m. to midnight), dropping to an attractive $0.20/kWh off-peak (midnight to 8 a.m.).

Non-Tesla EVs, which can now plug directly into the NACS ports thanks to the open standard, are charged a premium—$0.56/kWh peak and $0.28/kWh off-peak—reflecting Tesla’s strategy to monetize network access while rewarding its own customers.

What’s Makes This a “True” V4 Supercharger

What truly distinguishes this installation from the hundreds of “V4” stalls already scattered across the network? Most existing V4 dispensers, rolled out since 2023, feature welcome upgrades like longer cables, built-in touchscreen displays, integrated credit-card readers for non-Tesla users, and improved ergonomics.

Tesla confirms significant detail regarding V4 Supercharger

However, nearly all of these have been paired with legacy V3 power cabinets. These hybrid setups, sometimes informally called V3.5, deliver charging curves virtually identical to standard V3 stations, typically topping out at 250-325 kW depending on the vehicle and site conditions.

In contrast, Kissimmee’s true V4 architecture incorporates next-generation 1.2 MW power cabinets. These support battery voltages up to 1,000 V (double the 500 V of V3 systems) and can push up to 500 kW per stall.

One compact cabinet efficiently powers all eight stalls, slashing the physical footprint and reportedly keeping deployment costs under $40,000 per stall, far cheaper than earlier designs.

Right now, the primary beneficiary is the Cybertruck, which can achieve dramatically faster charging at low states of charge.

Everyday models like the Model 3 and Model Y see little immediate difference in peak speeds, but the hardware lays the groundwork for future vehicles with higher-voltage batteries.

Tesla launches faster Cybertruck charging at all V4 Superchargers

This milestone signals Tesla’s accelerating push toward a high-power, future-proof Supercharger network.

As true V4 sites multiply, charging times will shrink, grid efficiency will improve, and the entire EV ecosystem, Tesla and non-Tesla alike, will benefit from the infrastructure lead Tesla continues to expand. For drivers in central Florida, the Kissimmee station is more than just another charging stop; it’s a glimpse of the faster, smarter charging era that’s finally arriving.

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Tesla reveals various improvements to the Semi in new piece with Jay Leno

Tesla Chief Designer Franz von Holzhausen and Semi Program Director Dan Priestley joined Leno in a 47-minute segment revealing all of the various things it did to make the Semi even better as it heads toward volume production this year.

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Credit: Jay Leno's Garage | YouTube

Tesla has revealed the various improvements it has made to the Semi with its redesign, which was unveiled late last year, on a new episode of Jay Leno’s Garage.

Tesla Chief Designer Franz von Holzhausen and Semi Program Director Dan Priestley joined Leno in a 47-minute segment revealing all of the various things it did to make the Semi even better as it heads toward volume production this year.

Last year, Tesla revealed it had updated the Semi design to fit the bill of its aesthetic, which, on its other vehicles, includes things like lightbars and a sleeker and more aerodynamic design. The changes were not all to appease the eye, but the drivers who will use the Semi on a daily basis to haul goods regionally as the program gets off the ground running.

Weight Reduction

Priestley revealed almost immediately that Tesla was able to cut out about 1,000 pounds of weight from the Semi compared to the previous version.

This does several things, all of which are positive to the mission of a Class 8 truck, which is to haul goods and obtain more efficient travel to cut down on logistics costs.

Initially, this can increase payload capacity, which is often the biggest value driver for fleets that frequently hit gross vehicle weight limits. Tesla’s early Pilot Program members, like PepsiCo. and Frito-Lay, are large-scale companies. They will benefit from a decreased overall weight.

Lighter vehicles also require less energy to accelerate, climb hills, and maintain highway speeds. This new design has that advantage, and as Leno said in his first drive with the Semi as he hauled another unit behind, “I don’t feel like I’m pulling anything.”

Drag Coefficient

Franz said one of the goals of the Semi was to get the drag coefficient down below that of a Bugatti Veyron. This would increase efficiency tremendously, a major need with a large truck like a Semi.

Drag coefficient is extremely valuable when it comes to electric vehicles, because the displacement of air is incredibly important for range ratings.

Franz said aerodynamic efficiency has been improved by 7 percent compared to the last model. He says the coefficient is around 0.4.

New Features and Improvements

Priestley shed some additional light on the Semi and some of the improvements the company has made under the hood.

These include:

  • Fully Electric Steering Assist
  • Cybertruck actuators are being used for more strength
  • Tesla included a 48-volt architecture
  • Semi will utilize 4680 battery cells, which are designed to last 1 million miles

These changes come after Tesla rolled out the Semi to various companies for its Pilot Program, which yielded tremendous results. Due to the years it has been working with those companies, it knew what things it had to change and what it had to improve upon before selling the Semi openly.

Fleet Data

The fleet data Tesla has gathered from the Pilot Program has been one of the most widely discussed parts of the Semi program.

Franz and Priestley said that there are currently a few hundred Semi units in the real world, and Tesla has gathered 13.5 million miles. One of those units has traveled over 440,000 miles in the years it has been on the road.

Tesla Semi’s latest adoptee will likely encourage more of the same

Pilot Program members have reported an uptime of 95 percent, and Tesla’s maintenance and Service teams have kept things running:

“80% of breakdowns if you have one, are returned back to the customer in less than 24 hours, and half are back in less than 1 hour.”

Demand

Priestley says demand for the Semi has never been higher, and due to the recent political climate and the impact things have had on gas prices, Tesla has never received more inquiries for the Semi than it has recently.

Many companies will be surprised to hear that the Semi Pilot Program has been an overwhelming success. As Tesla begins to build out the infrastructure for the vehicle, it will only benefit the all-electric Class 8 trucks that keep things moving.

CEO Elon Musk said Tesla plans to start high-volume production this year. The company also plans to start deliveries this year.

 

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