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Comment by semi-extrinsic | Hacker News Reader

With EVs this problem is getting a lot worse. In latest-gen EVs the battery pack is a stressed member of the frame. Any type of collision that distorts the frame will also imply a deformation of the battery module, which means instant write-off.

So if you think about it - if you first decide you need to go down the "structural battery" route to save cost and weight, you've already lost repairability if the frame is bent. Then moving to a cast frame doesn't really change anything.

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Don't you lose repairability anyway if the frame is significantly bent?

AFAICT the actual batteries inside the "structural battery" are separate much smaller cells [1] that can at least be recovered from the bent frame and reused if undamaged.

Consider four factors: normal car performance, car's safety in a crash, car's repairability after a crash, and car's price. They all work against each other; no wonder that repairability is sacrificed to optimize the other three. (In a military vehicle the price is usually sacrificed instead.)

[1]: https://insideevs.com/news/323682/rare-look-inside-a-tesla-m...

A salvage operation where you harvest raw cells is no where near repairability. That is one step removed from taking a crushed car selling it for scrap metal.

Indeed, not reparability but reusability. The cells are standard and can be readily reused in a variety of ways, unlike a badly bent frame / chassis that can only go to scrap metal.

Maybe batteries will get good enough (hence small enough) to not become a stressed part of the frame in the near future.

This would also lighten EVs, which has a tremendous number of benefits.

The castings and frame are incredibly strong. Or in other words; when those are damaged, the rest of the car is likely beyond economical repair. Even without insurance. Tear it appart for parts.

The battery pack would be bent after the crash if the pack is structural or not.

Do you think just because the pack itself is not structural it just not gone get unharmed?

And by the way, structural pack doesn't mean its not replaceable.

Can you point to any references/examples of this? Not a challenge, but as an EV owner I didn't know this and I'm interested to learn more.

Here is one story from Reuters that is citing GM, Volvo, CATL and BYD doing this, in addition to Tesla.

https://www.reuters.com/business/autos-transportation/next-s...

He's probably referencing Tesla's structural battery packs. Essentially the pack makes up the bottom part of the frame of the car.

https://electrek.co/2021/01/19/tesla-structural-battery-pack...

The Ford Mach-E does the same thing. There's thin box frame rails as part of the traditional ladder frame, and the battery pack actually forms the floorpan and stressed crossmembers. Without the battery pack the frame will deform because there's no lateral reinforcement, making it this weird hybrid of a ladder frame and unibody that it shares with the Model X and Ioniq 5. Most EVs like the Bolt and the Ioniq 6 are unibodies however since they're just designed like regular cars with battery packs shoved where the fuel tank would normally go under the rear seat or rear hatch floor, and the battery pack simply reinforces the floor.

Its not actually the same. People constantly mix things up because the words people use are so wrong.

Structural packs are nothing new, lots of EV always had structural packs.

What Tesla is doing in the newer Model Y (called 'Structural Pack') is actually structural cells. That's the innovation. Where the cells themselves are glued together and sandwiched in a pack. So the cells themselves act as vertical enforcers. The whole back is basically filled with structural foam.

The only other company that is doing something like that is BYD but that is quite different as those are really big Prismatic cells stacked up.

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