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Wouldn't a quick battery replacement "gas station like" network make all these concerns obsolete? You drive into a "battery station", a robot switches batterie

Wouldn't a quick battery replacement "gas station like" network make all these concerns obsolete? You drive into a "battery station", a robot switches batteries underneath the car, done.

xvector 5y ago
Even so, there is a clear benefit to not having to stop at said gas station so often.
babesh 5y ago
There is a Chinese company doing this. Tesla unveiled the concept years ago but decided not to do it. There are multiple reasons that battery replacement is not as good as it seems. Charging stations can be built in more locations and more densely than battery swapping locations. This is because you need to store those batteries somewhere and there is more space and machinery involved in swapping. So you trade off queueing time for charging time. Charging stations are most likely cheaper to build and maintain because of the space and machinery requirements. A battery swapping station is more vulnerable to supply imbalances. Charging stations meet demand at charging rate. Charging stations can be more easily made universal. Unless you mandate a common battery form factor, that won’t be the case for battery replacement. This means that charging stations can scale with the whole EV industry. Swapping introduces inefficiencies to the car. You need at least a little additional structure which is weight. The below article does point to advantages but again not what may first expect: cheaper initial cost for car, off peak charging time. Also note the industry standards. https://www.cnet.com/roadshow/news/china-ev-swappable-battery-standards-approved/ https://www.cnet.com/roadshow/news/china-ev-swappable-batter...
- woleium 5y ago
  why not have both? I have an external portable battery pack for my phone, why can't I attach a portable rented battery to the tow hook of my car?
  - babesh 5y ago
    Today’s EVs are in some ways a hack. The energy contained in the battery is far less than in a tank of gasoline. To achieve range, most EVs are more aerodynamic than your average ICE car. Towing a battery out back would be horrible for aerodynamics and thus horrible for range. Furthermore, EVs achieve good EPA ranges by doing better in city driving where they can recover energy via regenerative braking. They do worse at highway speeds since air resistance increases superlinearly with speed. Towing something bad for aerodynamics at highway speeds would be doubly horrible. Lithium batteries must be kept within a temperature range. Too hot and they combust because the liquid electrolyte is flammable. They generate waste heat when discharging. If you don’t get rid of that heat, your battery will combust. That is why EVs have heating and cooling systems for the battery. Your towed battery, if you are extracting power from it directly, will need that. Phones deal with too much heat by shutting down or throttling CPU speed. Some EVs have crawl mode but not for excess heat AFAIK. Just buy an EV with more range. I think the Chinese standards could allow for different amounts of energy contained by the battery. For example, you can use different battery chemistries with the same form factor (nickel vs iron). In other words, there are additional costs borne by an EV with a towed battery beyond what you would have with an external battery pack for your phone.
    - babesh 5y ago
      Oh, another tidbit of understanding has to do with the size of the battery. Volume grows with the cube but surface area grows with the square. Therefore, a smaller battery would be easier to cool or may not need any cooling. A larger battery would need it. An EV car battery is a magnitudes larger than your cell phone battery. It is supposedly why elephants have big ears. Cooling.
      - woleium 5y ago
        Interesting, thank you. :) I guess in the long term an induction lane on the highway would make most sense then.
542354234235 5y ago
If everyone were driving new, perfectly maintained vehicles, this might work. But in the real world, an automated system that can move around huge battery packs, remove and install them correctly, and do so consistently and reliably with all the variability of regular people’s cars is an engineering nightmare. That type of system is already introducing a ton mechanical complexity and failure points, which is the opposite of one of the selling points of BEVs, lower maintenance cost and higher reliability. The system has to work at basically 100% reliability for it to be realistic. If your gas car had a 1% chance of not being able to fill up, and you had to bring it into the shop to find out what part of a complex gas cap system wasn’t functioning properly, that’s probably not a car you would buy. Then there is standardization. Distributing batteries based on the individual vehicle shape and size is hugely beneficial. Forcing it into a standard removable “pack” brick would reduce capacity, handling, etc. And are you going to regulate all cars use the same pack? Otherwise every car manufacturer would have to build out their own battery pack stations across the country and you would have to find your car brand station. Also, the whole idea of driving your fuel down, then going and refilling it all at once is a very ICE vehicle thing. 90% of people use their cars for daily commuting between home and work/shopping/activities and back home. If your car refuels every night and you start each day with 300 miles of range, why would you need to stop anywhere to refuel? Obviously this doesn’t cover all scenarios, but the roadtrip is a pretty small use case.

Wouldn't a quick battery replacement "gas station like" network make all these concerns obsolete? You drive into a "battery station", a robot switches batteries underneath the car, done.

xvector 5y ago

Even so, there is a clear benefit to not having to stop at said gas station so often.

babesh 5y ago

There is a Chinese company doing this. Tesla unveiled the concept years ago but decided not to do it. There are multiple reasons that battery replacement is not as good as it seems. Charging stations can be built in more locations and more densely than battery swapping locations. This is because you need to store those batteries somewhere and there is more space and machinery involved in swapping. So you trade off queueing time for charging time. Charging stations are most likely cheaper to build and maintain because of the space and machinery requirements. A battery swapping station is more vulnerable to supply imbalances. Charging stations meet demand at charging rate. Charging stations can be more easily made universal. Unless you mandate a common battery form factor, that won’t be the case for battery replacement. This means that charging stations can scale with the whole EV industry. Swapping introduces inefficiencies to the car. You need at least a little additional structure which is weight. The below article does point to advantages but again not what may first expect: cheaper initial cost for car, off peak charging time. Also note the industry standards. https://www.cnet.com/roadshow/news/china-ev-swappable-battery-standards-approved/ https://www.cnet.com/roadshow/news/china-ev-swappable-batter...

woleium 5y ago
why not have both? I have an external portable battery pack for my phone, why can't I attach a portable rented battery to the tow hook of my car?
- babesh 5y ago
  Today’s EVs are in some ways a hack. The energy contained in the battery is far less than in a tank of gasoline. To achieve range, most EVs are more aerodynamic than your average ICE car. Towing a battery out back would be horrible for aerodynamics and thus horrible for range. Furthermore, EVs achieve good EPA ranges by doing better in city driving where they can recover energy via regenerative braking. They do worse at highway speeds since air resistance increases superlinearly with speed. Towing something bad for aerodynamics at highway speeds would be doubly horrible. Lithium batteries must be kept within a temperature range. Too hot and they combust because the liquid electrolyte is flammable. They generate waste heat when discharging. If you don’t get rid of that heat, your battery will combust. That is why EVs have heating and cooling systems for the battery. Your towed battery, if you are extracting power from it directly, will need that. Phones deal with too much heat by shutting down or throttling CPU speed. Some EVs have crawl mode but not for excess heat AFAIK. Just buy an EV with more range. I think the Chinese standards could allow for different amounts of energy contained by the battery. For example, you can use different battery chemistries with the same form factor (nickel vs iron). In other words, there are additional costs borne by an EV with a towed battery beyond what you would have with an external battery pack for your phone.
  - babesh 5y ago
    Oh, another tidbit of understanding has to do with the size of the battery. Volume grows with the cube but surface area grows with the square. Therefore, a smaller battery would be easier to cool or may not need any cooling. A larger battery would need it. An EV car battery is a magnitudes larger than your cell phone battery. It is supposedly why elephants have big ears. Cooling.
    - woleium 5y ago
      Interesting, thank you. :) I guess in the long term an induction lane on the highway would make most sense then.

542354234235 5y ago

If everyone were driving new, perfectly maintained vehicles, this might work. But in the real world, an automated system that can move around huge battery packs, remove and install them correctly, and do so consistently and reliably with all the variability of regular people’s cars is an engineering nightmare. That type of system is already introducing a ton mechanical complexity and failure points, which is the opposite of one of the selling points of BEVs, lower maintenance cost and higher reliability. The system has to work at basically 100% reliability for it to be realistic. If your gas car had a 1% chance of not being able to fill up, and you had to bring it into the shop to find out what part of a complex gas cap system wasn’t functioning properly, that’s probably not a car you would buy. Then there is standardization. Distributing batteries based on the individual vehicle shape and size is hugely beneficial. Forcing it into a standard removable “pack” brick would reduce capacity, handling, etc. And are you going to regulate all cars use the same pack? Otherwise every car manufacturer would have to build out their own battery pack stations across the country and you would have to find your car brand station. Also, the whole idea of driving your fuel down, then going and refilling it all at once is a very ICE vehicle thing. 90% of people use their cars for daily commuting between home and work/shopping/activities and back home. If your car refuels every night and you start each day with 300 miles of range, why would you need to stop anywhere to refuel? Obviously this doesn’t cover all scenarios, but the roadtrip is a pretty small use case.