4 ms·

I also really liked the idea, but some specialists have argued it would be hard to provide rigidity. Given the load that heavy trucks have to face, this sounds

by bertil 3y ago

I also really liked the idea, but some specialists have argued it would be hard to provide rigidity. Given the load that heavy trucks have to face, this sounds like a bigger problem for trucks than for cars. I think we should focus on either: - charging on the go if those trucks use highways for long-distance, maybe have self-driving trucks drive at night and charge on the way; or better: - moving that cargo on train lines and using trucks with small batteries for the distance between the nearest train station and the final destination. That opens the possibility of using smaller trucks for many routes, which would really help with road safety, especially in dense areas. Trucks that can pull 15 tons or more are unsafe near children.

deleted 3y ago
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CharlesW 3y ago
> I also really liked the idea, but some specialists have argued it would be hard to provide rigidity. Do you happen to have any pointers to more info on this? I don't understand what would prevent the industry from standardizing on a structural battery pack rigid enough for the use case.
- rektide 3y ago
  Then you overbuild the pack. The criticism of the new EV hummer's pack is an example, and it didn't even need swappability, is just trying to get the batteries to stay adequately in place. https://insideevs.com/news/668428/hummer-ev-battery-teardown-reveals-excessive-complexity-weight/ https://insideevs.com/news/668428/hummer-ev-battery-teardown... Imo rigidity still feels like a semi bullshit gripe though. A lift should be able to rise up under the vehicle and uniformly support the batteries. The vehicle can then let them go. I imagine the batteries more or less suspended underneath the vehicle in this configuration, with a latching mechanism holding them up. Some cross bracing to provide structure. Making sure the batteries stay attached though, that they don't give flying in a crash, is a significant & obvious problem though, now that I think of it.
  - Gibbon1 3y ago
    When I've thought about swappable batteries for trucks it seems like you could locate them between the trailers frame rails. I'm sure there is enough structural meat on the frame rails to support a 4000lb battery. My feeling is whether swappable batteries are viable or not is less of a engineering problem than an accounting and logistics one,
- bertil 3y ago
  rektide is right to point at the need to over-build the pack: you need the car to be rigid without the batteries, essentially, and the battery to be sturdy on its own. You could argue that the car only goes through significant stress when the two are together, but every mechanical engineer is not liking that math. Another argument is what Sandy Monroe [0] think is the biggest one: moving connectors. It’s not just high-energy cables, but possibly coolant, etc. Those will be the first thing to fail. Sandy also mentions the risk of using someone else’s over-worn battery, but that’s more his atrabilar personality than something that could be engineered away: have the platform the battery regularly, even have the car do diagnostic and remove the worst ones from circulation. [0] https://youtu.be/Rb0Ix7UCtpA https://youtu.be/Rb0Ix7UCtpA

by bertil 3y ago

deleted 3y ago

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CharlesW 3y ago

> I also really liked the idea, but some specialists have argued it would be hard to provide rigidity. Do you happen to have any pointers to more info on this? I don't understand what would prevent the industry from standardizing on a structural battery pack rigid enough for the use case.

rektide 3y ago
Then you overbuild the pack. The criticism of the new EV hummer's pack is an example, and it didn't even need swappability, is just trying to get the batteries to stay adequately in place. https://insideevs.com/news/668428/hummer-ev-battery-teardown-reveals-excessive-complexity-weight/ https://insideevs.com/news/668428/hummer-ev-battery-teardown... Imo rigidity still feels like a semi bullshit gripe though. A lift should be able to rise up under the vehicle and uniformly support the batteries. The vehicle can then let them go. I imagine the batteries more or less suspended underneath the vehicle in this configuration, with a latching mechanism holding them up. Some cross bracing to provide structure. Making sure the batteries stay attached though, that they don't give flying in a crash, is a significant & obvious problem though, now that I think of it.
- Gibbon1 3y ago
  When I've thought about swappable batteries for trucks it seems like you could locate them between the trailers frame rails. I'm sure there is enough structural meat on the frame rails to support a 4000lb battery. My feeling is whether swappable batteries are viable or not is less of a engineering problem than an accounting and logistics one,
bertil 3y ago
rektide is right to point at the need to over-build the pack: you need the car to be rigid without the batteries, essentially, and the battery to be sturdy on its own. You could argue that the car only goes through significant stress when the two are together, but every mechanical engineer is not liking that math. Another argument is what Sandy Monroe [0] think is the biggest one: moving connectors. It’s not just high-energy cables, but possibly coolant, etc. Those will be the first thing to fail. Sandy also mentions the risk of using someone else’s over-worn battery, but that’s more his atrabilar personality than something that could be engineered away: have the platform the battery regularly, even have the car do diagnostic and remove the worst ones from circulation. [0] https://youtu.be/Rb0Ix7UCtpA https://youtu.be/Rb0Ix7UCtpA