Is lithium ion battery technology still not there?

manufacturer decided to add.

Protection mechanisms don't need no steenkeen printed circuit board.

A simply polymer layer, placed in the end seal, can swell to disconnect the exposed end terminal from the battery proper, if overheated. This is a common physical feature of many types of rechargeable 'dumb' batteries.

Not really popular, because imprecise and tending to disconnect with age/accumulated hours/ambient exposure.

Neither (pcb or polymer) protects against internal-fault-generated heat.

RL

What's the difference, besides playing lawyer with words? If you have masses of two substances that react energetically and exothermically, densely packaged in the same volume, with a deliberately thin separator, expect trouble.

The ideal battery would keep the reactive components separated. A fuel cell, or its liquid equivalent, would keep the reactants in separate tanks and only pipe in what's needed into the reaction space. Something like zinc-air admits one reactant from outside.

Primary batteries tend to be safer than rechargables. I wonder if airplanes could use primary batteries.

Seems like bad economics to ground a fleet of roughly $200 million planes to save about 1000 pounds per.

About 25 years ago or so, the US Navy came up with Hydrogen fuel cells. Not like what we have now, IIRC. They were essentially a gas cylinder with Hydrogen gas in it under pressure, and when fully charged it was like 90 psi, and it dropped in pressure as it discharged. Do not know what the energy density or construction was, and they would likely be pretty heavy unless they used Aluminum cylinders/chambers.

They were certainly a rechargeable design. Don't know if such a thing would be a suitable replacement. Hydrogen is flammable. It would have to be purged in an emergency circumstance.

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Fuel cells are *not* "rechargeable", in the battery sense.

That would be a pretty dumb design since these batteries' whole purpose in life are emergency circumstances.

Though that was never the intent. If they had a certificated and functional substitute that could be installed now to get the aircraft back into the air, no doubt they'd do it, even if the battery weighed

Sylvia.

If they don't have a parallel plan running for NiCads or something, they are betting big time.

I am with John on this one.

Sodium sulphur batteries have been going to be the next great thing since the 1980's. I knew someone who worked on them - they were lethal!

High energy density *is* inherently dangerous - and even more so when both components of the stored chemical energy are kept inside the same physical space as in a battery. Lithium cells are particularly volatile and are well known to have caused trouble in consumer laptops.

Even petrol (US gas) which is an everyday consumer item is very much more dangerous than the average member of the public can grasp. This leads to very sad accidents when people do silly things with it.

Whatever happened to the carbon-sulphur-potassium nitrate battery? I'm sure that would be a magnitude safer than the cobalt based unit my buddies are putting together back in Tucson.

Too much damage to the connected equipment due to excessive power output variation.

Sylvia.

You mean like in gasoline and jet fuel?

The latter do at least require a supply of oxygen before anything untoward can happen, whereas a battery has everything in place to start emitting heat if some internal fault occurs.

An ideal battery chemistry would self-limit its power output when it warms up so that it cannot suffer thermal runaway.

Sylvia.

If you stored LOX in the same tank, then yes, just like that.

And explosives, superheated water, stretched bungee cords, rapidly spinning things, stuff like that.

When planes crash, they tend to incinerate the occupants.

Gasoline in tanks is pretty safe, because the vapors are mostly gasoline (or, lately, nitrogen) and there's no ignition source handy. A high energy battery has all the nasty bits close together.

John Larkin schrieb:

Hello,

NiCads with the same energy stored would be heavier and larger than those lithium cells used before. A reconstruction of the battery compartment and the airplane structure around this compartment may be necessary.

Bye

I think you mean past tense "were" betting big time and cocked it up.

Though the failure mode appears to have been a combo of bad wiring harness and inability of the battery unit to protect itself from bad external connections coupled with the volatile lithium cell chemistry.

Given that laptop and phone makers already knew enough to put defensive failsafe protection into these batteries it seems astonishing that aerospace designers on a civilian plane did not. It isn't like lithium cells have a glowing reputation for reliability and robustness either.

There have been plenty of serious recalls of kit with dodgy lithium batteries where inadequate protection could lead to self immolation!

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batteries.

I am proposing they are inherently damn difficult to do safely. It is a similar concept.

?-)

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I think you have half of a good point with the zinc-air batteries. Good energy density, indefinite shelf life, but one use only. Given the use involved that might not be inappropriate. OTOH at 38,000 feet the air is rather a bit thinner, and the gradient on the way down is noticeable. Designing a zinc-air battery for the required performance with that change in conditions may be very challenging, of course you could add bottled air at altitude, but that carries other problems with it.

?-)

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use bleed air from the jet engines, same as is used for cabin pressure.

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As long as you _have_ engines, why not just use their electrical systems?