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Tesla’s ‘Roadrunner’ facility gets a neighbor working on tech beyond the million-mile battery
As the wait for Tesla’s Battery Day continues, more and more speculations are abounding about what the electric car maker might reveal during the highly-anticipated event. Elon Musk has stated that Battery Day’s announcements will be mind-blowing, and based on apparent clues recently observed by the Tesla community, it appears that the CEO may be right on the money.
Recent reports have indicated that Amprius, a battery company currently working on silicon nanowire tech, recently relocated its headquarters to a site that’s just a few hundred feet away from Tesla’s Roadrunner battery facility in Kato Road, Fremont. Considering the firm’s focus, its new headquarters’ rather convenient location, and Elon Musk’s previous references to the use of silicon in batteries, there seems to be a fair chance that Amprius’ move to Fremont may be more than a coincidence.
Amprius notes that it is working on creating silicon nanowires for battery anodes that dramatically improve battery weight and density. The company’s website notes that silicon generally has about 10x the capacity of graphite (carbon), but it has a big drawback in the way that it swells when it’s charged, causing the silicon to fracture. To address this, Amprius utilizes silicon nanowires, which keeps the silicon from fracturing and breaking apart even when it swells.
As noted by EV enthusiast and YouTube host Driving Delta, Elon Musk himself appears to be teasing the use of advanced silicon tech on Twitter last month. In one of his posts, Musk shared some lyrics of the song “Lithium” by Nirvana, whose refrain includes sections that state “I’m not gonna crack.” Granted, Musk may simply be trolling the Tesla community with his posts, but it should be noted that he also talked about the increasing use of silicon anodes five years ago.
“We’re shifting the cell chemistry for the upgrade battery pack to partially use silicon in the anode. This is just a sort of baby step in the direction of using silicon in the anode. We’re still primarily using synthetic graphite, but over time, we’ll be using increasing amounts of silicon in the anode,” Musk noted during a 2015 conference call.
As noted by Amprius’ on its website, the use of 100% silicon paves the way for batteries with the highest energy density, perhaps even at the 500 Wh/kg level. That’s enough to start exploring electric VTOL projects, a topic that Elon Musk has admitted is something that truly interests him. That being said, Professor in Energy Materials and Technologies Ying Shirley Meng, who has made significant contributions to Maxwell Technologies’ battery tech herself, believes that challenges still remain in the use of silicon nanowires.
“We should pay attention to the cost per kg. Even (if) those nanowires work (which I doubt), to produce consistent quality in metric ton scale at 10$ per kg it will be sci-fi for now,” she noted.
Elon Musk, for his part, recently stated that the technology that could allow 400 Wh/kg with a high life cycle and volume production is not too far away. Musk gave a rough timeframe for the technology, stating that such milestones could be achieved in about three to four years.
Tesla’s Battery Day event is expected to introduce the company’s next-generation lithium-ion cells, though speculations suggest that these batteries — which are expected to last a million miles — are based largely on Maxwell Technologies’ dry electrode tech. Maxwell itself has previously noted that it could offer batteries with 300 Wh/kg while stating that it had also identified a path to 500 Wh/kg. With this in mind, it appears that Tesla may already be setting the stage for cells that will likely go even beyond the million-mile battery.
Granted, Amprius’ move to Fremont may be unconnected to Tesla. That being said, the two companies’ goals to align with each other, and Elon Musk’s own references to the use of silicon suggests that Tesla will likely get a lot of value from Amprius’ tech. If speculations prove true, the path to batteries that go even further than the million-mile mark may be feasible in the near future. Such innovations are key to Tesla’s goal of accelerating the transition to sustainable energy, after all.
Watch these recent takes on the Amprius rumors in the videos below.
News
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.
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.
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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Tesla FSD (Supervised) blows away French journalist after test ride
Cadot described FSD as “mind-blowing,” both for the safety of the vehicle’s driving and the “humanity” of its driving behaviors.
Tesla’s Full Self-Driving (Supervised) seems to be making waves in Europe, with French tech journalist Julien Cadot recently sharing a positive first-hand experience from a supervised test drive in France.
Cadot, who tested the system for Numerama after eight years of anticipation since early Autopilot trials, described FSD as “mind-blowing,” both for the safety of the vehicle’s driving and the “humanity” of its driving behaviors.
Julien Cadot’s FSD test in France
Cadot announced his upcoming test on X, writing in French: “I’m going to test Tesla’s FSD for Numerama in France. 8 years I’ve been waiting to relive the sensations of our very first contact with the unbridled Autopilot of the 2016s.” He followed up shortly after with an initial reaction, writing: “I don’t want to spoil too much because as media we were allowed to film everything and I have a huge video coming… But: it’s mind-blowing! Both for safety and for the ‘humanity’ of the choices.”
His later posts detailed FSD’s specific maneuvers that he found particularly compelling. These include the vehicle safely overtaking a delivery truck by inches, something Cadot said he personally would avoid to protect his rims, but FSD handled flawlessly. He also praised FSD’s cyclist overtakes, as the system always maintained the required 1.5-meter distance by encroaching on the opposite lane when clear. Ultimately, Cadot noted FSD’s decision-making prioritized safety and advancement, which is pretty remarkable.
FSD’s ‘human’ edge over Autopilot
When asked if FSD felt light-years ahead of standard Autopilot, Cadot replied: “It’s incomparable, it’s not the same language.” He elaborated on scenarios like bypassing a parked delivery truck across a solid white line, where FSD assessed safety and proceeded just as a human driver might, rather than halting indefinitely. This “humanity” impressed Cadot the most, as it allowed FSD to fluidly navigate real-world chaos like urban Paris traffic.
Tesla is currently hard at work pushing for the rollout of FSD to several European countries. Recent reports have revealed that Tesla has received approval to operate 19 FSD test vehicles on Spain’s roads, though this number could increase as the program develops. As per the Dirección General de Tráfico (DGT), Tesla would be able to operate its FSD fleet on any national route across Spain. Recent job openings also hint at Tesla starting FSD tests in Austria. Apart from this, the company is also holding FSD demonstrations in Germany, France, and Italy.
Tesla Optimus showed off its newest capability as progress on the project continues to accelerate toward an ultimate goal of mass production in the coming years.
Tesla is still developing Optimus and preparing for the first stages of mass production, where units would be sold and shipped to customers. CEO Elon Musk has always marketed the humanoid robot as the biggest product in history, even outside of Tesla, but of all time.
He believes it will eliminate the need to manually perform monotonous tasks, like cleaning, mowing the lawn, and folding laundry.
However, lately, Musk has revealed even bigger plans for Optimus, including the ability to relieve humans of work entirely within the next 20 years.
JUST IN: Elon Musk says working will be ‘optional’ in less than 20 years because of AI and robotics. pic.twitter.com/l3S5kl5HBB
— Watcher.Guru (@WatcherGuru) November 30, 2025
Development at Tesla’s Artificial Intelligence and Robotics teams has progressed, and a new video was shown of the robot taking a light jog with what appeared to be some pretty natural form:
Just set a new PR in the lab pic.twitter.com/8kJ2om7uV7
— Tesla Optimus (@Tesla_Optimus) December 2, 2025
Optimus has also made several public appearances lately, including one at the Neural Information Processing Systems, or NeurIPS Conference. Some spectators shared videos of Optimus’s charging rig, as well as its movements and capabilities, most interestingly, the hand:
You have to hand it to Elon 🤟 pic.twitter.com/fZKDlmGAbe
— Ric Burton · NeurIPS 2025 (@_ricburton) December 2, 2025
The hand, forearm, and fingers have been one of the most evident challenges for Tesla in recent times, especially as it continues to work on its 3rd Generation iteration of Optimus.
Musk said during the Q3 Earnings Call:
“I don’t want to downplay the difficulty, but it’s an incredibly difficult thing, especially to create a hand that is as dexterous and capable as the human hand, which is incredible. The human hand is an incredible thing. The more you study the human hand, the more incredible you realize it is, and why you need four fingers and a thumb, why the fingers have certain degrees of freedom, why the various muscles are of different strengths, and fingers are of different lengths. It turns out that those are all there for a reason.”
The interesting part of the Optimus program so far is the fact that Tesla has made a lot of progress with other portions of the project, like movement, for example, which appears to have come a long way.
However, without a functional hand and fingers, Optimus could be rendered relatively useless, so it is evident that it has to figure this crucial part out first.
Tesla hosts Rome Mayor for first Italian FSD Supervised road demo
Tesla FSD (Supervised) blows away French journalist after test ride
