3 ms·

> 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 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

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