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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)

Published

5 years ago

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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. 

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. 

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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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GM CEO Mary Barra says she told Biden to give Tesla and Musk EV credit

“He was crediting me, and I said, ‘Actually, I think a lot of that credit goes to Elon and Tesla…You know me, Andrew. I don’t want to take credit for things.”

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8 hours ago

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December 3, 2025

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General Motors CEO Mary Barra said in a new interview on Wednesday that she told President Joe Biden to credit Tesla and its CEO, Elon Musk, for the widespread electric vehicle transition.

She said she told Biden this after the former President credited her and GM for leading EV efforts in the United States.

During an interview at the New York Times Dealbook Summit with Andrew Ross Sorkin, Barra said she told Biden that crediting her was essentially a mistake, and that Musk and Tesla should have been explicitly mentioned (via Business Insider):

“He was crediting me, and I said, ‘Actually, I think a lot of that credit goes to Elon and Tesla…You know me, Andrew. I don’t want to take credit for things.”

Back in 2021, President Biden visited GM’s “Factory Zero” plant in Detroit, which was the centerpiece of the company’s massive transition to EVs. The former President went on to discuss the EV industry, and claimed that GM and Barra were the true leaders who caused the change:

“In the auto industry, Detroit is leading the world in electric vehicles. You know how critical it is? Mary, I remember talking to you way back in January about the need for America to lead in electric vehicles. I can remember your dramatic announcement that by 2035, GM would be 100% electric. You changed the whole story, Mary. You did, Mary. You electrified the entire automotive industry. I’m serious. You led, and it matters.”

People were baffled by the President’s decision to highlight GM and Barra, and not Tesla and Musk, who truly started the transition to EVs. GM, Ford, and many other companies only followed in the footsteps of Tesla after it started to take market share from them.

Elon Musk and Tesla try to save legacy automakers from Déjà vu

Musk would eventually go on to talk about Biden’s words later on:

“They have so much power over the White House that they can exclude Tesla from an EV Summit. And, in case the first thing, in case that wasn’t enough, then you have President Biden with Mary Barra at a subsequent event, congratulating Mary for having led the EV revolution.”

In Q4 2021, which was shortly after Biden’s comments, Tesla delivered 300,000 EVs. GM delivered just 26.

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Tesla Full Self-Driving shows confident navigation in heavy snow

So far, from what we’ve seen, snow has not been a huge issue for the most recent Full Self-Driving release. It seems to be acting confidently and handling even snow-covered roads with relative ease.

Published

10 hours ago

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December 3, 2025

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Credit: Grok

Tesla Full Self-Driving is getting its first taste of Winter weather for late 2025, as snow is starting to fall all across the United States.

The suite has been vastly improved after Tesla released v14 to many owners with capable hardware, and driving performance, along with overall behavior, has really been something to admire. This is by far the best version of FSD Tesla has ever released, and although there are a handful of regressions with each subsequent release, they are usually cleared up within a week or two.

Tesla is releasing a modified version of FSD v14 for Hardware 3 owners: here’s when

However, adverse weather conditions are something that Tesla will have to confront, as heavy rain, snow, and other interesting situations are bound to occur. In order for the vehicles to be fully autonomous, they will have to go through these scenarios safely and accurately.

One big issue I’ve had, especially in heavy rain, is that the camera vision might be obstructed, which will display messages that certain features’ performance might be degraded.

So far, from what we’ve seen, snow has not been a huge issue for the most recent Full Self-Driving release. It seems to be acting confidently and handling even snow-covered roads with relative ease:

Moving into the winter months, it will be very interesting to see how FSD handles even more concerning conditions, especially with black ice, freezing rain and snow mix, and other things that happen during colder conditions.

We are excited to test it ourselves, but I am waiting for heavy snowfall to make it to Pennsylvania so I can truly push it to the limit.

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Tesla hosts Rome Mayor for first Italian FSD Supervised road demo

The event marked the first time an Italian mayor tested the advanced driver-assistance system in person in Rome’s urban streets.

Published

15 hours ago

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December 3, 2025

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Credit: @andst7/X

Tesla definitely seems to be actively engaging European officials on FSD’s capabilities, with the company hosting Rome Mayor Roberto Gualtieri and Mobility Assessor Eugenio Patanè for a hands-on road demonstration. 

The event marked the first time an Italian mayor tested the advanced driver-assistance system in person in Rome’s urban streets. This comes amid Tesla’s push for FSD’s EU regulatory approvals in the coming year.

Rome officials experience FSD Supervised

Tesla conducted the demo using a Model 3 equipped with Full Self-Driving (Supervised), tackling typical Roman traffic including complex intersections, roundabouts, pedestrian crossings and mixed users like cars, bikes and scooters.

The system showcased AI-based assisted driving, prioritizing safety while maintaining flow. FSD also handled overtakes and lane decisions, though with constant driver supervision.

Investor Andrea Stroppa detailed the event on X, noting the system’s potential to reduce severe collision risks by up to seven times compared to traditional driving, based on Tesla’s data from billions of global fleet miles. The session highlighted FSD’s role as an assistance tool in its Supervised form, not a replacement, with the driver fully responsible at all times.

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Path to European rollout

Tesla has logged over 1 million kilometers of testing across 17 European countries, including Italy, to refine FSD for local conditions. The fact that Rome officials personally tested FSD Supervised bodes well for the program’s approval, as it suggests that key individuals are closely watching Tesla’s efforts and innovations.

Assessor Patanè also highlighted the administration’s interest in technologies that boost road safety and urban travel quality, viewing them as aids for both private and public transport while respecting rules.

Replies on X urged involving Italy’s Transport Ministry to speed approvals, with one user noting, “Great idea to involve the mayor! It would be necessary to involve components of the Ministry of Transport and the government as soon as possible: it’s they who can accelerate the approval of FSD in Italy.”

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