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State of charge tracking is tricky even for lithium ion batteries. I worked on it for a bit as part of a solar car competition. Usually it involves a mix of cou

State of charge tracking is tricky even for lithium ion batteries. I worked on it for a bit as part of a solar car competition. Usually it involves a mix of coulomb counting and voltage measurements. IIRC, a handful of laptops and consumer electronics have trained neural networks to assist in estimating SOC. As far as aircraft goes, it's sufficient to put a lower bound on the remaining charge. Realistically, the poor (abysmal, really) energy density of batteries pretty much precludes their usage in any serious aircraft. For sustainable air flight I'm more optimistic about syngas or hydrogen.

m463 6y ago
I've always wondered about those one-use aluminum-air batteries one guy was developing. (search for tevor jackson aluminum air battery) They might be more palatable for aircraft.
- manfredo 6y ago
  Batteries are fundamentally unsuitable for aircraft. The energy density is easily an order of magnitude lower than thermochemical fuels: https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3AEnergy_density.svg https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3... Furthermore batteries don't get lighter as their charge is expended, as opposed to fuel that gets burned off. This means a plane powered by batteries has to land with the same mass of fuel as it does when it takes off. Many aircraft are worse at decelerating themselves than accelerating. This means they can actually take off with more mass than they can land, thus extending their range. This can't happen for battery powered planes. Hydrogen powered planes is less far fetched than it seems. The Soviets built a prototype: https://en.m.wikipedia.org/wiki/Tupolev_Tu-155 https://en.m.wikipedia.org/wiki/Tupolev_Tu-155 Cryogenic storage of hydrogen is less difficult than it seems. Because the engines are constantly drawing fuel from the fuel tank, the tank's pressure is constantly dropping which cools it down. Most of the difficulty around hydrogen storage is in long term storage where hydrogen permitting through the vessel is a concern. The main challenge for applying it to aircraft is being able to make a vessel light enough and in a form factor suitable for planes, namely fitting it in the wing.
  - qzw 6y ago
    Ah, simply have separable battery modules that you drop from the plane as their charge is depleted. Put pop-out wings on them and use gps guidence so that they glide back to recovery centers on the ground, which you've had the foresight (and funding) to build in sufficient density along any likely route your plane might operate. Problem solved. I'm joking, mostly.
    - m463 6y ago
      Periodically they would fall over landing on the recovery barge and explode, but that's to be expected. :) (and your idea is brilliant, it should jokingly be called "blue ice")
  - m463 6y ago
    I could make the argument that fuels that burn are unsuitable for automobiles which crash into each other frequently. But yeah, I think it would need lots of development to get battery technology to do something like a ny-tokyo flight. It might only work for short hop service. I guess that's how it has worked for battery electric trucks. The first one basically did short, known routes around town with lots of stop/start. That controlled the parameters and made it feasible. I don't know if battery powered trucks will ever replace long-haul trucks unless batteries get lots better or charging gets really fast.
    - toast0 6y ago
      > I could make the argument that fuels that burn are unsuitable for automobiles which crash into each other frequently. Lithium ion batteries don't like crashing into each other either. The article mentioned that lithium sulfide batteries degrade differently than lithium ion, so fires as a result of heavy use may be reduced, but fires as a result of unscheduled disassembly seem likely, and could be worse than fuel --- you can dump fuel or circle to use it up, but you can't (probably) dump batteries, so you're always going to have lithium available. Not sure if the lithium sulfur compounds are less flamible than the compounds found in lithium ion.
    - faeyanpiraat 6y ago
faeyanpiraat 6y ago
I wonder if changing battery packs by drones in-flight would be feasible

m463 6y ago

I've always wondered about those one-use aluminum-air batteries one guy was developing. (search for tevor jackson aluminum air battery) They might be more palatable for aircraft.

manfredo 6y ago
Batteries are fundamentally unsuitable for aircraft. The energy density is easily an order of magnitude lower than thermochemical fuels: https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3AEnergy_density.svg https://en.m.wikipedia.org/wiki/Energy_density#/media/File%3... Furthermore batteries don't get lighter as their charge is expended, as opposed to fuel that gets burned off. This means a plane powered by batteries has to land with the same mass of fuel as it does when it takes off. Many aircraft are worse at decelerating themselves than accelerating. This means they can actually take off with more mass than they can land, thus extending their range. This can't happen for battery powered planes. Hydrogen powered planes is less far fetched than it seems. The Soviets built a prototype: https://en.m.wikipedia.org/wiki/Tupolev_Tu-155 https://en.m.wikipedia.org/wiki/Tupolev_Tu-155 Cryogenic storage of hydrogen is less difficult than it seems. Because the engines are constantly drawing fuel from the fuel tank, the tank's pressure is constantly dropping which cools it down. Most of the difficulty around hydrogen storage is in long term storage where hydrogen permitting through the vessel is a concern. The main challenge for applying it to aircraft is being able to make a vessel light enough and in a form factor suitable for planes, namely fitting it in the wing.
- qzw 6y ago
  Ah, simply have separable battery modules that you drop from the plane as their charge is depleted. Put pop-out wings on them and use gps guidence so that they glide back to recovery centers on the ground, which you've had the foresight (and funding) to build in sufficient density along any likely route your plane might operate. Problem solved. I'm joking, mostly.
  - m463 6y ago
    Periodically they would fall over landing on the recovery barge and explode, but that's to be expected. :) (and your idea is brilliant, it should jokingly be called "blue ice")
- m463 6y ago
  I could make the argument that fuels that burn are unsuitable for automobiles which crash into each other frequently. But yeah, I think it would need lots of development to get battery technology to do something like a ny-tokyo flight. It might only work for short hop service. I guess that's how it has worked for battery electric trucks. The first one basically did short, known routes around town with lots of stop/start. That controlled the parameters and made it feasible. I don't know if battery powered trucks will ever replace long-haul trucks unless batteries get lots better or charging gets really fast.
  - toast0 6y ago
    > I could make the argument that fuels that burn are unsuitable for automobiles which crash into each other frequently. Lithium ion batteries don't like crashing into each other either. The article mentioned that lithium sulfide batteries degrade differently than lithium ion, so fires as a result of heavy use may be reduced, but fires as a result of unscheduled disassembly seem likely, and could be worse than fuel --- you can dump fuel or circle to use it up, but you can't (probably) dump batteries, so you're always going to have lithium available. Not sure if the lithium sulfur compounds are less flamible than the compounds found in lithium ion.
  - faeyanpiraat 6y ago

faeyanpiraat 6y ago

I wonder if changing battery packs by drones in-flight would be feasible