Tesla Structural Battery Pack, the good and the bad

Back in September of last year, Tesla had its Battery Day presentation (full video below). In January of this year, Electrek wrote an article about the Tesla structural battery. So why am I writing about this now? The structural battery pack was just a gleam in Elon Musk’s eye at that time, but soon, there will be cars that incorporate the new design. Here’s what you should think about if you’re considering buying a Model S Plaid or a Cybertruck with the structural battery pack.

As Elon said during the presentation, the structural battery pack was inspired by the airline industry. They used to put gas tanks in the wings of airliners. The tanks added weight. More weight meant more fuel needed to fly. Eventually, the aircraft manufacturers figured out that they could save weight if the wings were the gas tanks. They saved weight that way. It’s the same with battery packs. Right now, there are battery cells that are put together in modules. The modules add weight. Then the modules are put together into a large battery pack. That adds more weight. Then all that stuff is put into the structure. More weight means less range.

Tesla engineers figured out that they could save lots of weight if they eliminated modules and if the battery pack was the structure. They do that by making a honeycomb structure with all the wiring and cooling coils inside it. Then they drop in the 4680 cells and epoxy them to the honeycomb structure. For those of you who are not aware, the designation, 4680 refers to the 46mm diameter of the battery cells and the 80mm height of the Tesla cells. Those battery cells are larger than the ones currently in use by all previously made Teslas so they store more power in each cell. For comparison, visualize the current Tesla battery cells being like AA batteries and the 4680 cells being like D batteries. Remember D batteries?

The following picture is from the article in Electrek cited above. You can appreciate the honeycomb pattern of the pack, a structure known for strength and light weight. The coolant loops are built into the sides of the pack.

So saving weight, stronger cells, less of them. More battery, less other stuff. It’s all good, right? Maybe.

Here’s the bad part.

If the car gets in an accident and the battery pack is breached, you can’t just take out the old pack and drop in another pack. That might not matter because chances are pretty good that an accident bad enough to damage the battery pack will total the car. From an individual’s perspective, that’s why you get insurance. But there are other considerations if you care about the environment you’re leaving to my grandchildren.

Batteries should be recycled. So far, they’re not designed for recycling. With technology at its current state, it’s cheaper to mine new materials than it is to recycle the materials from used batteries. The ability to recycle gets worse when the batteries are epoxied into a big honeycomb structure. I’m not a chemical engineer so I can’t offer any suggestions about how battery cells could be designed to make recycling cheaper than mining new materials, but they should be designed that way.

The other bad thing about the structural battery pack is that cells don’t all deteriorate at the same rate. With the current battery packs, bad cells can be detected and switched out for good cells to rejuvenate the range of an old Tesla. That won’t be feasible with the structural battery pack. That may or may not be important. It depends on whether the cells last as long as the rest of the car or not. Time will tell, but it’s something to think about if you plan to keep your car for the million miles that Tesla claims their cars are designed to last.

Here is Tesla's 'Battery Day' presentation. If you care exclusively about the structural battery, you can jump to the 1 hour, 19 minute mark.

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Tesla Starts Rolling Out HW3 Support for FSD to Chinese Employees

Tesla Newswire

Tesla is getting ready to start rolling out FSD support for hardware 3 vehicles in China. Tesla is internally testing what appears to be a build of FSD V12.6 on HW3 vehicles with its employees.

A post on Chinese social media platform Rednote initially shared the software update details and was then shared by Tesla Newswire. We’ve verified that the vehicle in question is a 2023 Model Y, confirming it falls within the HW3 hardware generation.

Tesla initially introduced FSD for HW4/AI4 vehicles in China in late February, making this a surprisingly fast follow-up to extend support to HW3 vehicles. The Chinese rollout of FSD also came just a couple weeks after Tesla introduced FSD in Mexico.

FSD V12.6 Primer

We reviewed FSD V12.6 in depth here, and provided a comparison to FSD V13 here, but here’s the key points you’ll need to know.

FSD V12.6 is Tesla’s latest revision of FSD for HW3 vehicles and it’s is very comparable to FSD V13 in terms of features. It includes 3 speed profiles, Chill, Standard, and Hurry, which control how aggressive FSD is in making lane changes and ensuring it stays at, near, or above the speed limit.

This version of FSD also comes with an improved controller, as well as earlier and more natural lane change decisions, making it far more capable than V12.5 or V12.3 builds.

For Chinese customers getting their first taste of FSD after using Autopilot for years, it’s mindblowing. It can handle city level streets, hanlde turns and traffic control signs and get you to your destination with minimal interventions.

When Does It Release?

Given’s China’s more crowded streets and more complex road layouts, we weren’t sure whether Tesla would introduce support for HW3 vehicles in the market. This news is a positive and encouraging sign, not only for FSD in China, but for all HW3 vehicle owners out there.

Tesla usually releases updates to employees in advance of releasing them to its general customers - providing them with a second chance to find and fix bugs. Usually, once updates make their way to employee vehicles, and barring any major issues, they begin rolling out to customers within one to two weeks.

China currently requires owners to buy FSD, as FSD subscriptions aren’t available in the country yet. If you’re in China and bought FSD on a HW3 vehicle, it may not be long before you have access to FSD.

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A Look at the Tesla Cybertruck’s Crumple Zones [VIDEO]

Not a Tesla App

Tesla’s Cybertruck has officially earned a 5-Star Safety Rating from the NHTSA—an impressive achievement given the vehicle’s design. The achievement demonstrates Tesla’s engineering prowess. As one engineer points out, it wasn’t an easy feat.

Interestingly, the NHTSA only recently disclosed the results, despite the crash tests being completed a while ago. According to Lars Moravy, Tesla’s VP of Vehicle Engineering, the team had been aware of the 5-star rating for quite some time. While the reason for the delay remains unclear, now that the results are public, Tesla’s engineers can finally share how they achieved the rating.

Crumple Zones

Wes Morril, the Cybertruck’s Lead Engineer, wrote about the crash test video on X recently, addressing the claims that the Cybertruck doesn’t have a crumple zone. He also posted a side-by-side video (below) of the engineering analysis and the crash test itself.

Engineered Crash Safety

There’s a lot of engineering precision at play when a Cybertruck is involved in a crash. Unlike traditional crash structures that rely on crash cans and collapse points, the Cybertruck’s front gigacasting is designed to absorb and redirect impact forces in a highly controlled manner.

It all starts with the bumper beam, which crushes within the first few milliseconds of a high-speed impact. At the same time, the vehicle’s sensors rapidly analyze the crash dynamics and determine the optimal deployment of safety restraints, including airbags and seat belt pre-tensioners. These split-second actions are crucial in keeping occupants safe.

As the crash progresses, the vehicle’s structure deforms in a carefully engineered sequence. The drive unit cradle bends, directing the solid drive unit downward and out of the way, allowing the gigacasting to begin absorbing impact forces.

The casting crushes cell by cell, methodically dissipating energy in a controlled manner. This gradual deceleration reduces the g-forces transferred to occupants, making the crash much less severe. As the gigacast begins crushing, the safety restraints are deployed.

As Wes points out in his post - you can see how accurate the virtual analysis and modeling were. The video shows the simulated crash side by side with the real-life crash test and they’re almost identical. All that virtual testing helps provide feedback into the loop to design a better and safer system - one that is uniquely different than any other vehicle on the road.

All the armchair experts claimed the Cybertruck has no crumple zone and I get it, the proportions seem impossible. It was a tough one and there is a lot of engineering that went into it. Let me break it down for you:

Here you can see the large single piece casting in action in a… https://t.co/Jk4X5erTcm pic.twitter.com/24Nmb1bmU5

— Wes (@wmorrill3) February 20, 2025

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