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Battery swapping isn't practical with modern electric car design. In most EVs today, the battery is part of the structural frame of the car and can't be removed

Battery swapping isn't practical with modern electric car design. In most EVs today, the battery is part of the structural frame of the car and can't be removed easily. DC fast charging seems like a much more practical solution for the occasional cross country trip

yholio 6y ago
That seems more like a practical engineering decision since battery swap is not yet widespread. There doesn't seem to be anything fundamental that prevents it and in fact Tesla retrofitted the idea for vehicles that were not initially designed with swap in mind. It's either that fast charging attains exceptional safe speeds (i.e less than 5 minutes), or that competitive pressures will force electrics to embrace swap. The current status quo of waiting an hour for a full charge cannot stand on the long term; the lost productivity is so large that it completely dwarfs the costs of implementing the swap networks, so somebody is bound to package it in a consumer friendly product and pocket the profits.
- bluGill 6y ago
  engineering tradeoffs are important. By making the battery part of the car you can put more battery in, and you need less framework around the battery. This means integrated batteries have a larger capacity, and the car is more aerodynamic. (there is also less weight in not having to have a separate frame around the battery, but this is more than outweighed by the fact that you have more heavy batteries which means a heavier frame)
  - yholio 6y ago
    A vehicle without battery that is just standing there on the swap platform waiting to get a fresh pack does not need a structurally sound frame. So while the battery is structurally important, it does not follow that non-swappable batteries are by default of a higher capacity; the same structural elements can be integrated in the swappable battery. The only real margin is the swap hardware and any structural binding parts designed to pass loads towards the battery frame as if it was built in part of the fixed frame. True, it makes no sense to design and include those parts when swap is not on the market, so it's a tradeoff. But is it a salient tradeoff, does it make the car with the built-in battery significantly better? Only very marginally I would say. The same for aerodynamics, there is really only one place to put a large battery pack, it's not like you can gain lots of design liberty by putting an unconventional shape battery in the bumper or in the roof. Swappability of the underside of the car has no impact on aerodynamics.
    - bluGill 6y ago
      The structural needs of each car are different. If the battery can handle them all, then it is overbuilt and you can save enough by not being swapable to make your car cheaper (or give it longer range or some other trade off) so you won't do it. If you have a different battery for each car you can follow your plan, but then the logistics of handling all the different batteries means nobody has the right one for your car in stock. There is only one place to put a large battery pack. However there are lots of places to put a smaller battery back. Or you can have a non-rectangular battery pack in that one place to better fit the room you have. Cars are about compromises, so a standard swapable battery pack will be smaller than the customized for the car one you can make. A tiny economy car doesn't have as much space as a large family car so plan is harmful to families that want to go on vacation as they have to stop more often.

yholio 6y ago

That seems more like a practical engineering decision since battery swap is not yet widespread. There doesn't seem to be anything fundamental that prevents it and in fact Tesla retrofitted the idea for vehicles that were not initially designed with swap in mind. It's either that fast charging attains exceptional safe speeds (i.e less than 5 minutes), or that competitive pressures will force electrics to embrace swap. The current status quo of waiting an hour for a full charge cannot stand on the long term; the lost productivity is so large that it completely dwarfs the costs of implementing the swap networks, so somebody is bound to package it in a consumer friendly product and pocket the profits.

bluGill 6y ago
engineering tradeoffs are important. By making the battery part of the car you can put more battery in, and you need less framework around the battery. This means integrated batteries have a larger capacity, and the car is more aerodynamic. (there is also less weight in not having to have a separate frame around the battery, but this is more than outweighed by the fact that you have more heavy batteries which means a heavier frame)
- yholio 6y ago
  A vehicle without battery that is just standing there on the swap platform waiting to get a fresh pack does not need a structurally sound frame. So while the battery is structurally important, it does not follow that non-swappable batteries are by default of a higher capacity; the same structural elements can be integrated in the swappable battery. The only real margin is the swap hardware and any structural binding parts designed to pass loads towards the battery frame as if it was built in part of the fixed frame. True, it makes no sense to design and include those parts when swap is not on the market, so it's a tradeoff. But is it a salient tradeoff, does it make the car with the built-in battery significantly better? Only very marginally I would say. The same for aerodynamics, there is really only one place to put a large battery pack, it's not like you can gain lots of design liberty by putting an unconventional shape battery in the bumper or in the roof. Swappability of the underside of the car has no impact on aerodynamics.
  - bluGill 6y ago
    The structural needs of each car are different. If the battery can handle them all, then it is overbuilt and you can save enough by not being swapable to make your car cheaper (or give it longer range or some other trade off) so you won't do it. If you have a different battery for each car you can follow your plan, but then the logistics of handling all the different batteries means nobody has the right one for your car in stock. There is only one place to put a large battery pack. However there are lots of places to put a smaller battery back. Or you can have a non-rectangular battery pack in that one place to better fit the room you have. Cars are about compromises, so a standard swapable battery pack will be smaller than the customized for the car one you can make. A tiny economy car doesn't have as much space as a large family car so plan is harmful to families that want to go on vacation as they have to stop more often.