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Tesla ‘Roadrunner’ cell leak hints that Battery Day will be more insane than expected
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.
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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Tesla Energy has introduced the Powerwall Lease in conjunction with Tesla Electric, making the service available in Texas. This new option delivers whole-home backup power using two Powerwall units for a net monthly cost of $35 after credits, accompanied by a low fixed electricity rate.
Under the lease terms, customers pay a one-time order fee of $100. The base lease payment for the two Powerwalls is approximately $122 per month during the first year, subject to a 3 percent annual escalator thereafter. Enrollment in a qualifying Tesla Electric Backup plan or Virtual Power Plant plan provides an $87 monthly credit.
Powerwall Lease is now available with Tesla Electric in Texas
Whole-home backup for $35/month, with a low fixed electricity rate
– Two Powerwalls, $0 installation
– Storm Watch outage protection
– One app to manage it all pic.twitter.com/oTzqc6K3aF— Tesla Energy (@teslaenergy) August 13, 2026
This credit lowers the effective cost to roughly $35 per month plus applicable tax.
Installation of the standard system carries no additional charge. The package features Storm Watch for outage protection and allows complete management through a single Tesla application. The system supplies continuous whole-home backup capability.
The Powerwall system enables households to maintain electricity during severe storms that disrupt the utility grid. When outages occur, the batteries automatically provide seamless backup power to the home.
Tesla announces 100k Powerwalls are participating in Virtual Power Plants
Tesla Storm Watch monitors weather forecasts and ensures the units are fully charged ahead of anticipated severe weather events so that power remains available throughout the disruption, keeping lights, refrigeration, and other essential systems operating without interruption.
Availability is restricted to select Texas locations where retail electric choice exists. Participants must lease exactly two Powerwall units and maintain continuous enrollment with Tesla Electric. Solar panels cannot be included under this particular lease arrangement.
The monthly credit activates automatically once the system is installed, receives permission to operate, and enrollment is confirmed. To retain the credit, customers are required to stay enrolled in Tesla Electric and fulfill all program conditions.
Nonstandard installations that involve electrical upgrades or special permitting may lead to extra expenses and might impact eligibility for the credit, so be sure to check with either your installer or Tesla to ensure you will still qualify.
Elon Musk continues to tease the unveiling event for the Tesla Roadster, a continuing trend that has grown into a bigger game of “When” for fans who have been waiting years for the car to finally enter production.
A video shared on X of the Joe Rogan Experience podcast that Musk appeared on last year, teasing the Roadster unveiling, was shared once again on the social media platform. The poster said the Roadster event will be “unforgettable.”
Musk agreed:
Yes
— Elon Musk (@elonmusk) August 12, 2026
The timing is interesting because just yesterday, Musk said that we will be getting flying cars, and for years, Tesla has hinted that it could develop a SpaceX cold gas thruster package that would help the car float or fly for a short period of time.
It would be reasonable to assume Tesla’s major delays with this unveiling event are likely caused by the company’s need to break the rules and push the envelope on nearly everything. Last July, Lars Moravy, Tesla’s VP of Vehicle Engineering, said:
“Roadster is definitely in development. We did talk about it last Sunday night. We are gearing up for a super cool demo. It’s going to be mind blowing. We showed Elon some cool demos last week of the tech we’ve been working on and he got a little excited.”
The latest updates that Tesla has given us are that the Roadster is in design development, and it did have several potential dates for an unveiling event this year, including April. It was then pushed to August.
However, there are no clues as to when Tesla will be ready, and fans are certainly getting frustrated with the delays.
For what it is worth, Franz von Holzhausen told Jay Leno this week that the event would be “very soon.”
We sure hope.
Lifestyle
Tesla’s driverless Cybercab just passed a big test with State Governor
Florida’s governor rode Tesla’s Cybercab at a closed test track and called the experience impressive.
Florida Governor Ron DeSantis rode in a Tesla Cybercab on a closed test track this week and came away impressed, posting on X that the vehicle “successfully navigated all hazards — a kid running into the street, a crash with police stopping traffic, a Model S cutting us off, etc.” He called the ride “impressive.”
The stop was part of a broader event Monday at SunTrax, a 775 acre state owned proving ground in Auburndale that Florida built specifically to test autonomous and connected vehicles before they reach public roads. Standing next to a gold Cybercab, DeSantis described the car in plain terms: “You go in there and you just sit. You have a screen. There’s no steering wheel, no pedals. Clearly these things could be very beneficial.”
We took a ride on a robotaxi on the Suntrax course and it successfully navigated all hazards — a kid running into the street, a crash with police stopping traffic, a Model S cutting us off, etc.
Impressive! https://t.co/FVAkzFLz3r
— Ron DeSantis (@RonDeSantis) August 11, 2026
DeSantis paired the praise with a caveat that has followed autonomous vehicles since the category existed. “You don’t want to be in an autonomous vehicle and it drives you into a ditch. That would not be good,” he said, framing safety validation as the gate before wider deployment.
SunTrax, the 2.25 mile oval which the state calls the only high speed autonomous vehicle test track in the Southeast, can simulate rain, pedestrian crossings, hills and crowded urban conditions at highway speeds, letting companies push a car past what an early public rollout would risk. Tesla, Waymo and Beep all use the facility, and Florida’s regulatory approach, among the most permissive for autonomous vehicles in the country, doesn’t require a human operator inside a fully autonomous car.
Tesla has reason to want the blessing of Florida and states beyond, as the Cybercab entered volume production at Gigafactory Texas this spring and has since self certified as SAE Level 4 under Texas law. Public road testing so far has kept a safety monitor in the passenger seat, and Florida is where Tesla has been expanding its existing Model Y based Robotaxi service instead, adding Miami in July and then Orlando and Tampa two weeks later. A closed track endorsement from a sitting governor doesn’t change any of that, but it does put Tesla’s newest hardware in front of a state that has already shown it will move fast on rules.
Tesla launches Powerwall Lease for affordable home backup
Elon Musk teases Tesla Roadster unveiling once again
