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Modern EV design has the batteries integrated into the structural frame of the car. This is because the batteries are the heaviest part of the car, so you want

Modern EV design has the batteries integrated into the structural frame of the car. This is because the batteries are the heaviest part of the car, so you want them to be close to the ground and secure from impact. This also makes it very inconvenient to replace. Lots of companies (even Tesla) have attempted the replaceable battery concept but none have been able to make it work efficiently.

noja 4y ago
https://www.theengineer.co.uk/content/archive/august-1897-the-london-electrical-cab/ https://www.theengineer.co.uk/content/archive/august-1897-th...
kryptiskt 4y ago
NIO is doing battery swapping at scale in China. Here's a random article about how it works: https://insideevs.com/news/591837/nio-battery-swapping-station-norway-5-minutes/ https://insideevs.com/news/591837/nio-battery-swapping-stati...
cjdell 4y ago
Would it not be significantly easier if we're using 4 or 5 independent modules instead of a giant monolith? Aren't cars routinely lifted into the air when being serviced? I understand that the structure of the car's body may be suboptimal and require extra reinforcement but if we're really serious about EV adoption and reducing battery cost then perhaps a trade-off worth making?
- NickNameNick 4y ago
  If you want the batteries to be removable, I suspect the extra couplings in the water coolant loop would make that problematic.
  - silversmith 4y ago
    Check out how tractor hydraulic attachments handle liquid couplings. And hydraulic systems work at much higher pressure than simple coolant loops.
- chiph 4y ago
  For an EV the main design constraints are aerodynamics and weight. If you need to add additional reinforcement to make up for the battery packs that haven't been installed, you're carrying that weight around all the time and taking a range penalty. So assume your vehicle has 3 packs. You normally run it with just one pack because that's all you need to commute and run errands during the week. When you go visit the relatives in Florida, you install the other two packs to get the additional range. The car needs additional structural elements to meet safety standards when the extra packs aren't installed and they add 5% additional weight. That's weight you're carrying around every day, and that has a range cost. Could it be worth it to swap out the extra structure elements when you install the extra packs, so at least you aren't taking the range penalty while driving long distance? Yes, but the manufacturer isn't going to want the liability of a customer removing what is a passive safety device, and then forgetting to reinstall it when they go back to city travel using only one pack. NHTSA will also have input to this. From what I can tell - the applicable FMVSS is this one that deals with EV side impact protection, electrolyte spills, and electric shock. https://www.nhtsa.gov/document/final-rule-occupant-protection-interior-impact-side-impact-protection-fuel-system https://www.nhtsa.gov/document/final-rule-occupant-protectio...
snotrockets 4y ago
Tesla was never serious about replaceable batteries. They could get more tradeable credits for replaceable batteries, so they told everyone they’ll do that, got the credits for the cars that were supposed to have replaceable batteries, and never followed up with the actual tech.
- signatoremo 4y ago
  I did recall Tesla wasn’t serious about battery swapping but can’t find any information about getting credits for doing that, let alone just announcing it. Can you back that up?
  - marvin 4y ago
    The statement is worded critical of Tesla, but IIRC there's some truth to it. They engineered the Model S to be battery-swappable, and there was some advantage wrt. the regulatory credits to doing so. Can't find a link, but I remember reading it. They rolled out this service to a couple of spots in California, which was probably sufficient for the the credit regime, but ended up not expanding the program further and terminating it after a few quarters. The official explanation was that it was not widely used. https://youtu.be/H5V0vL3nnHY?t=57 https://youtu.be/H5V0vL3nnHY?t=57 There may have been other business reasons. I have no idea what was discussed on the executive level but wouldn't be surprised if they considered some tradeoffs of complexity, costs and customer attractivenes to not be worth it. Honestly, it's very rare that you actually need or strongly prefer to have this kind of service rather than just recharging at 150kW for 15 minutes. So if it adds considerable cost or complexity, I could understand the decision to drop it. A short time later, they started welding an extra metal shield onto the bottom of the Model S, to act as an extra layer of protection against collisions with highway debris that caused some high-profile battery fires. I had the impression that this precluded battery swap, so at that point the business decision must have been made to not expand the program further. If the regulatory incentives was key in the decision to do this and then later drop it, that's a fundamental property of incentives to do something that might not be a good idea in isolation.
    - 4y ago
iforgotpassword 4y ago
We'd only need a compromise here. The concept that failed, afaiu, was batteries you'd swap at the gas station on a trip, which you probably want to take no longer than refilling your good old ICE car took. That seems impractical for several reasons. But if you had a range extension pack that you could add/remove in 30 minutes before a longer trip, maybe that would be more realistic?
kjkjadksj 4y ago
All the more reason to ditch the 5000lb car and go for like a 50lb emoped instead.

noja 4y ago

https://www.theengineer.co.uk/content/archive/august-1897-the-london-electrical-cab/ https://www.theengineer.co.uk/content/archive/august-1897-th...

kryptiskt 4y ago

NIO is doing battery swapping at scale in China. Here's a random article about how it works: https://insideevs.com/news/591837/nio-battery-swapping-station-norway-5-minutes/ https://insideevs.com/news/591837/nio-battery-swapping-stati...

cjdell 4y ago

Would it not be significantly easier if we're using 4 or 5 independent modules instead of a giant monolith? Aren't cars routinely lifted into the air when being serviced? I understand that the structure of the car's body may be suboptimal and require extra reinforcement but if we're really serious about EV adoption and reducing battery cost then perhaps a trade-off worth making?

NickNameNick 4y ago
If you want the batteries to be removable, I suspect the extra couplings in the water coolant loop would make that problematic.
- silversmith 4y ago
  Check out how tractor hydraulic attachments handle liquid couplings. And hydraulic systems work at much higher pressure than simple coolant loops.
chiph 4y ago
For an EV the main design constraints are aerodynamics and weight. If you need to add additional reinforcement to make up for the battery packs that haven't been installed, you're carrying that weight around all the time and taking a range penalty. So assume your vehicle has 3 packs. You normally run it with just one pack because that's all you need to commute and run errands during the week. When you go visit the relatives in Florida, you install the other two packs to get the additional range. The car needs additional structural elements to meet safety standards when the extra packs aren't installed and they add 5% additional weight. That's weight you're carrying around every day, and that has a range cost. Could it be worth it to swap out the extra structure elements when you install the extra packs, so at least you aren't taking the range penalty while driving long distance? Yes, but the manufacturer isn't going to want the liability of a customer removing what is a passive safety device, and then forgetting to reinstall it when they go back to city travel using only one pack. NHTSA will also have input to this. From what I can tell - the applicable FMVSS is this one that deals with EV side impact protection, electrolyte spills, and electric shock. https://www.nhtsa.gov/document/final-rule-occupant-protection-interior-impact-side-impact-protection-fuel-system https://www.nhtsa.gov/document/final-rule-occupant-protectio...

snotrockets 4y ago

Tesla was never serious about replaceable batteries. They could get more tradeable credits for replaceable batteries, so they told everyone they’ll do that, got the credits for the cars that were supposed to have replaceable batteries, and never followed up with the actual tech.

signatoremo 4y ago
I did recall Tesla wasn’t serious about battery swapping but can’t find any information about getting credits for doing that, let alone just announcing it. Can you back that up?
- marvin 4y ago
  The statement is worded critical of Tesla, but IIRC there's some truth to it. They engineered the Model S to be battery-swappable, and there was some advantage wrt. the regulatory credits to doing so. Can't find a link, but I remember reading it. They rolled out this service to a couple of spots in California, which was probably sufficient for the the credit regime, but ended up not expanding the program further and terminating it after a few quarters. The official explanation was that it was not widely used. https://youtu.be/H5V0vL3nnHY?t=57 https://youtu.be/H5V0vL3nnHY?t=57 There may have been other business reasons. I have no idea what was discussed on the executive level but wouldn't be surprised if they considered some tradeoffs of complexity, costs and customer attractivenes to not be worth it. Honestly, it's very rare that you actually need or strongly prefer to have this kind of service rather than just recharging at 150kW for 15 minutes. So if it adds considerable cost or complexity, I could understand the decision to drop it. A short time later, they started welding an extra metal shield onto the bottom of the Model S, to act as an extra layer of protection against collisions with highway debris that caused some high-profile battery fires. I had the impression that this precluded battery swap, so at that point the business decision must have been made to not expand the program further. If the regulatory incentives was key in the decision to do this and then later drop it, that's a fundamental property of incentives to do something that might not be a good idea in isolation.
  - 4y ago

iforgotpassword 4y ago

We'd only need a compromise here. The concept that failed, afaiu, was batteries you'd swap at the gas station on a trip, which you probably want to take no longer than refilling your good old ICE car took. That seems impractical for several reasons. But if you had a range extension pack that you could add/remove in 30 minutes before a longer trip, maybe that would be more realistic?

kjkjadksj 4y ago

All the more reason to ditch the 5000lb car and go for like a 50lb emoped instead.