Published on 10 October 2020 |
by Chanan Bos
October 10, 2020 of Chanan Bos
Tesla’s Battery Day wasn’t just full of surprises. As you read through the slides, Tesla has made many product announcements, many of which are still waiting to be discovered. What this article is about is Tesla’s new battery pack.
What most people haven’t realized is that Tesla is ditching its famous battery-powered skateboard design. For the uninitiated, until now, Tesla’s vehicles consisted of the body and a low battery “skateboard” on the bottom that, as Tesla would say, get married together in the factory. We also witnessed the ceremony in person. Originally, the skateboard design was developed because it provided a low center of gravity and strong safety benefits, as well as the ability to quickly replace battery packs instead of just supercharging if Tesla went that route.
As you know, the last part didn’t end up happening. Now Tesla has returned to the drawing board to do something better. However, it wasn’t just Tesla’s habit of successfully reinventing the wheel. The company went back to the drawing board because its 4680-cell battery cream required it. See, in the past, the battery cells weren’t dense enough, so Tesla needed as much room as he could get into the floor. If Tesla were to do this again now, the vehicles would have incredible range, but Tesla would not be able to make many.
Tesla had to solve some problems. First, the company needed to find a way to simplify the battery pack and eliminate modules. Later, without the skateboard, Tesla needed a new way to support the vehicle’s structural integrity. What they ended up doing is turning the luggage into a structure in the same way that an airplane made fuel tank shaped wings rather than wings that have the tanks inside.
In a way, it’s the same trick Tesla applied to the design of his spaceship, where the body itself is part of the fuel tank. It is also not the first time that Elon has applied lessons learned in one company to the products of another. In this case, the solution was a glue (material substance meant pun) which not only acted both as an adhesive and as a flame retardant as in the previous models, but also as a material to reinforce the package. Insert it between two steel sheets and make the battery pack solid and cut resistant. It no longer requires external support. Unlike CATL, which started putting cells directly into the package and deleting modules, this is pretty much a cell-to-vehicle solution, since the battery pack is no longer just a casing, it is part of the vehicle structure.
The new Tesla pack kills more than 2 birds with one stone, though, because there are a couple of other things this new architecture allows. Now, without the battery pack extending to the front and rear of the vehicle, it has even more effective deformation zones and more space. This brings us to another advantage. Sure, that extra room could be left empty and used for more luggage. Or perhaps rather than a larger frunk, the vehicle could get a large HEPA filter that enables bioweapons defense mode. Even with the HEPA filter, there would probably still be a bigger frunk than today. It’s hard to overstate how much extra space there will be, and some of that will likely extend to a larger cabin as well.
The final result? Tesla was going around the bush a bit about how much more effective structural integrity was. On Battery Day, Elon Musk touted it as a good solution for solving the structural integrity problems of convertible vehicles, but he did not directly compare it to internal combustion engine (ICE) vehicles or his existing vehicles. Until a tweet this week, in which Elon – coincidentally, replying to my tweet – made it clear that it is more rigid and an important step forward.
The battery pack will be a bonded structure with cells that provide shear transfer between the upper and lower steel face plates, eliminating most of the core body parts and providing improved torsional rigidity and improved polar moment or inertia. This is an * important * breakthrough.
– Elon Musk (@elonmusk) 7 October 2020
Funny enough, it looks like it didn’t actually answer my question. Or yes? You see, this all ties in a lot to the injection molded casting and patent for a unibody design that we saw over a year ago.
You see, with the new battery pack, Tesla can move on to the next stage with its unibody injection molding ambitions. Ultimately, this will only work if the floor is not part of the unibody, as the completed mold is ejected upward and then lifted from the machine. They don’t need to create a floor for structural integrity, because the battery pack takes on that role. Tesla will likely proceed with this in stages. So, is it a coincidence that, when asked whether Tesla will launch the vehicle’s core as one piece, Elon answers about the revolutionary battery that would make it possible? Well, if you need more convincing, here are some more “coincidences”, starting with a specific excerpt from that patent:
“Such casting machines can reduce the number of actual casting machines or castings required to cast a complete or substantially complete vehicle frame (e.g., to less than six, less than five, less than four, less than three, less than two or one casting machine (s)). “
For the Model Y, or perhaps the $ 25,000 at Giga Berlin Model Placeholder, it is possible that Tesla uses a casting machine as it does for the rear body assembly at Fremont, one for the front counterpart, and then the next step. , the center section of the body, will be added as highlighted in one of the images of the patent.
The most interesting thing is that the way the company currently stamps and welds this part of the body together, at some point it looks exactly like what you see in the image above. Two side panels of exactly that shape are then connected by two roof pillars, a front part separating the hood section from the cabin and the rear. Thanks to the structural battery pack, the body can be melted and pushed up and out of the machine.
Now, back to my tweet, that’s exactly what I was asking. In that tweet, I accidentally wrote “stamp” rather than “cast”, but the fact that Elon replied about the structural battery pack in response to a question regarding the unibody fusion makes me think that Elon was confirming that the structural battery pack is. makes it possible. The patents clearly state that this casting technique could take place in parts, and not just as a single unibody. It is very likely that one is a stepping stone for the other. It’s also quite likely that unibody molding will allow Tesla to make significantly cheaper vehicles, such as the $ 25,000 model placeholder or the eventual ultra-cheap robotaxi discussed in my previous article in this chain of articles on Battery Day.
This article was mostly written before Elon Musk replied to my tweet. At the time, I wrote that the current unibody design will not be implemented until Tesla understands fully autonomous driving and can avoid accidents, as a unibody is much more often unrepairable and therefore expensive to insure. However, Elon also responded to a comment on that tweet of his in which something new was revealed.
Shock absorbing rails can be cut and replaced with a bolt-on part for collision repair
– Elon Musk (@elonmusk) 7 October 2020
This means that repairability is not the limiting factor of the unibody fusion. However, it’s still not something Tesla will implement immediately. There is a possibility that Tesla might introduce it with its low-cost vehicle or low-cost robotaxi, and that would explain why both Giga Berlin and Giga Shanghai can introduce their own different looking vehicles – because it’s just a unibody cast. different based on the same underlying battery architecture and the same fusion technology. At the Fremont factory, we even witnessed how Tesla can change a component in his casting machine to make different components that he stores in the warehouse section of the factory.
In any case, for the foreseeable future, there will still be a factory wedding ceremony, but it won’t be a battery-powered skateboard married to the body. For the intermediate step, it will be the union of the unibody and the structural battery with the front and rear deformation zones, which are also whole but separated from the unibody.
So ultimately, Tesla ditched the skateboarding for its cheaper vehicles, but its replacement, the structural battery pack, not only increases safety and creates more space in the vehicle for other purposes, it also brought the company closer to ‘unibody. molding goal we have seen established in the patent.
So rather than simply eliminating modules and switching to cell-to-pack batteries like CATL did, here Tesla took it a step further and invented a cell-to-body solution by making the battery pack part of the structure rather than a precious cargo. Considering all we know now, when Elon Musk said the Model Y produced at Giga Berlin would be a completely different vehicle, he wasn’t kidding.
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