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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.
Tesla is dominating in the United Kingdom so far through 2025, and with about two weeks left in the year, the Model Y and Model 3 are leading the way.
The Model Y and Model 3 are the two best-selling electric vehicles in the United Kingdom, which is comprised of England, Scotland, Wales, and Northern Ireland, and it’s not particularly close.
According to data gathered by EU-EVs, the Model Y is sitting at 18,890 units for the year, while the Model 3 is slightly behind with 16,361 sales for the year so far.
The next best-selling EV is the Audi Q4 e-tron at 10,287 units, lagging significantly behind but ahead of other models like the BMW i4 and the Audi Q6 e-tron.
GOOD NEWS 🇬🇧 Tesla is absolutely crushing the UK electric vehicle market in 2025 💥
The numbers are in, and the dominance is clear. With an impressive amount of 42,270 vehicles delivered year-to-date, the brand now commands a solid 9.6% market share of the total auto market 🆒… pic.twitter.com/dkiGX9kzd0
— Ming (@tslaming) December 18, 2025
The Model Y has tasted significant success in the global market, but it has dominated in large markets like Europe and the United States.
For years, it’s been a car that has fit the bill of exactly what consumers need: a perfect combination of luxury, space, and sustainability.
Both vehicles are going to see decreases in sales compared to 2024; the Model Y was the best-selling car last year, but it sold 32,610 units in the UK. Meanwhile, the Model 3 had reached 17,272 units, which will keep it right on par with last year.
Tesla sold 50,090 units in the market last year, and it’s about 8,000 units shy of last year’s pace. It also had a stronger market share last year with 13.2 percent of the sales in the market. With two weeks left in 2025, Tesla has a 9.6 percent market share, leading Volkswagen with 8 percent.
The company likely felt some impact from CEO Elon Musk’s involvement with the Trump administration and, more specifically, his role with DOGE. However, it is worth mentioning that some months saw stronger consumer demand than others. For example, sales were up over 20 percent in February. A 14 percent increase followed this in June.
News
Tesla Insurance officially expands to new U.S. state
Tesla’s in-house Insurance program first launched back in late 2019, offering a new way to insure the vehicles that was potentially less expensive and could alleviate a lot of the issues people had with claims, as the company could assess and repair the damage itself.
Tesla Insurance has officially expanded to a new U.S. state, its thirteenth since its launch in 2019.
Tesla has confirmed that its in-house Insurance program has officially made its way to Florida, just two months after the company filed to update its Private Passenger Auto program in the state. It had tried to offer its insurance program to drivers in the state back in 2022, but its launch did not happen.
Instead, Tesla refiled the paperwork back in mid-October, which essentially was the move toward initiating the offering this month.
BREAKING: Tesla Insurance has just officially launched in Florida.
This is the first new state to receive @Tesla Insurance in more than 3 years. In total, Tesla insurance is now available in 13 U.S. states (map in thread below of all the states).
Tesla Insurance in Florida uses… pic.twitter.com/bDwh1IV6gD
— Sawyer Merritt (@SawyerMerritt) December 17, 2025
Tesla’s in-house Insurance program first launched back in late 2019, offering a new way to insure the vehicles that was potentially less expensive and could alleviate a lot of the issues people had with claims, as the company could assess and repair the damage itself.
It has expanded to new states since 2019, but Florida presents a particularly interesting challenge for Tesla, as the company’s entry into the state is particularly noteworthy given its unique insurance landscape, characterized by high premiums due to frequent natural disasters, dense traffic, and a no-fault system.
Annual average premiums for Florida drivers hover around $4,000 per year, well above the national average. Tesla’s insurance program could disrupt this, especially for EV enthusiasts. The state’s growing EV adoption, fueled by incentives and infrastructure development, aligns perfectly with Tesla’s ecosystem.
Moreover, there are more ways to have cars repaired, and features like comprehensive coverage for battery damage and roadside assistance tailored to EVs address those common painpoints that owners have.
However, there are some challenges that still remain. Florida’s susceptibility to hurricanes raises questions about how Tesla will handle claims during disasters.
Looking ahead, Tesla’s expansion of its insurance program signals the company’s ambition to continue vertically integrating its services, including coverage of its vehicles. Reducing dependency on third-party insurers only makes things simpler for the company’s automotive division, as well as for its customers.
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Tesla Full Self-Driving gets sparkling review from South Korean politician
“Having already ridden in an unmanned robotaxi, the novelty wasn’t as strong for me, but it drives just as well as most people do. It already feels like a completed technology, which gives me a lot to think about.”
Tesla Full Self-Driving got its first sparkling review from South Korean politician Lee So-young, a member of the country’s National Assembly, earlier this week.
Lee is a member of the Strategy and Finance Committee in South Korea and is a proponent of sustainable technologies and their applications in both residential and commercial settings. For the first time, Lee was able to utilize Tesla’s Full Self-Driving technology as it launched in the country in late November.
Her thoughts on the suite were complimentary to the suite, stating that “it drives just as well as most people do,” and that “it already feels like a completed technology.”
드디어 오늘, 서울에서 테슬라 FSD 체험 했습니다.
JiDal Papa님의 모델S 협찬에 힘입어^^ 파파님 정말 감사합니다.
국회 -> 망원시장 -> 홍익대 -> 국회 복귀 코스였고요.
이미 무인 로보택시를 타봐서 그런지 신기함은
덜했지만, 웬만한 사람만큼 운전을 잘하네요.이미 완성된 기술이라고… pic.twitter.com/8pAidHBpRG
— 이소영 국회의원 (Soyoung Lee) (@im_soyounglee) December 17, 2025
Her translated post says:
“Finally, today I got to experience Tesla FSD in Seoul. Thanks to the Model S sponsored by JiDal Papa^^, I’m truly grateful to Papa. The route was from the National Assembly -> Mangwon Market -> Hongik University -> back to the National Assembly. Having already ridden in an unmanned robotaxi, the novelty wasn’t as strong for me, but it drives just as well as most people do. It already feels like a completed technology, which gives me a lot to think about. Once it actually spreads into widespread use, I feel like our daily lives are going to change a lot. Even I, with my license gathering dust in a drawer, don’t see much reason to learn to drive a manual anymore.”
Tesla Full Self-Driving officially landed in South Korea in late November, with the initial launch being one of Tesla’s most recent, v14.1.4.
It marked the seventh country in which Tesla was able to enable the driver assistance suite, following the United States, Puerto Rico, Canada, China, Mexico, Australia, and New Zealand.
It is important to see politicians and figures in power try new technologies, especially ones that are widely popular in other regions of the world and could potentially revolutionize how people travel globally.
Tesla dominates in the UK with Model Y and Model 3 leading the way
Tesla Insurance officially expands to new U.S. state
