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Faro
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Battery Container Contributing To Li-Ion Failure?

Fri Jan 18, 2013 3:57 pm

Any moving electric charge will produce an electromagnetic field.

I wonder whether the container which serves as fire/leak shield for Li-ion batteries may be reflecting back into the battery the (strong) electromagnetic fields which are produced by the movement of lithium ions within it. Depending on the 3D geometry of the container, such retro-reflection may become amplified and focused on a local point within the battery. If such is the case, this point may become susceptible to heat damage and maybe ultimately lead to thermal runaway.

Is this shielding container metallic in the first place? If yes, it is designed to preclude retro-reflection of electromagnetic radiation produced internally by the battery?


Faro

[Edited 2013-01-18 07:59:30]
The chalice not my son
 
nomadd22
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RE: Battery Container Contributing To Li-Ion Failure?

Fri Jan 18, 2013 4:18 pm

DC current through a relatively straight path isn't going to produce that much of a field. I don't know if they have something as simple as a large filter cap to keep high speed current pulses out of the battery.
But, it must be either something like that, where field conditions don't match lab conditions or the batteries being used are different than the ones that were tested. I'd think they would have had a full size pack in the the same boxes they'd be using in the plane being tortured under all possible environments for certification.
Anon
 
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Faro
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RE: Battery Container Contributing To Li-Ion Failure?

Fri Jan 18, 2013 5:08 pm

Quoting nomadd22 (Reply 1):
DC current through a relatively straight path isn't going to produce that much of a field.

The EM field will however peak as the current goes from nil to full discharge current. Given the power of the APU batteries, I dare say that the peak EM field on initial discharge could be quite significant.


Faro
The chalice not my son
 
nomadd22
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RE: Battery Container Contributing To Li-Ion Failure?

Fri Jan 18, 2013 7:41 pm

Quoting faro (Reply 2):
Quoting nomadd22 (Reply 1):
DC current through a relatively straight path isn't going to produce that much of a field.

The EM field will however peak as the current goes from nil to full discharge current. Given the power of the APU batteries, I dare say that the peak EM field on initial discharge could be quite significant.


Faro

That's what I meant regarding the filter cap. It slows down the rise and fall time of the current changes and reduces the fields caused by such quite a bit.

And, hey Faro. Good to be arguing with you again.
Anon
 
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Faro
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RE: Battery Container Contributing To Li-Ion Failure?

Fri Jan 18, 2013 8:31 pm

Always a pleasure nomad, good to see you too   ; this battery thing has me really trumped, something major is messing up its bowels...really hope they sort it out soon.


Faro
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