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RE: Dreamliner batteries - 1/29/2013 4:45 AM   
chuckk2


 

Posts: 380
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Last Login: 6/20/2013
From: Warner Robins, GA, USA
Status: offline 		On our RC Lipo's from a reasonably qualified authority.  (Don't Ask, Don't Tell) 
Max do not exceed voltage 4.23 Vdc per cell (New battery, ideal conditions)
A used cell may be slightly lower.

The currrent density issue may be that the current is not always evenly distributed, and  a very small area may see a much higher than expected current density. 

Some years ago, I stopped at a library that had a good collection of recognized technical references, and due to what I was working on at the time, I ended up really looking into just about all practical batteries (Other than Li batteries) for use on military aircraft over extended temperature ranges.
About all I can say today is that each battery type has it's advantages and disadvantages. Obviously, Li rechargeable batteries are a bit more finicky than other choices.  The more energy you pack into a confined area, the higher the chances that something can go wrong.  The range of battery life spans goes from minutes to decades for more or less off the shelf batteries.  Railroads and phone companies used the really long lived Pb batteries and alternatives, with weapons of various types using the short lifetime batteries.


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RE: Dreamliner batteries - 1/30/2013 4:53 AM   
chuckk2


 

Posts: 380
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Joined: 7/24/2007
Last Login: 6/20/2013
From: Warner Robins, GA, USA
Status: offline 		Gee! Looks like a LiPo in a metal case to me!


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RE: Dreamliner batteries - 1/30/2013 2:32 PM   
nonstoprc



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From: Central, TX, USA
Status: offline 		From the NTSB video, the battery c ell is of type Li-Cobalt, with the operating voltage in the range 2.5-4.025v. Not exactly the lipo cells we use in this hobby.

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RE: Dreamliner batteries - 1/30/2013 8:30 PM   
chuckk2


 

Posts: 380
Score: 106
Joined: 7/24/2007
Last Login: 6/20/2013
From: Warner Robins, GA, USA
Status: offline 		"From the NTSB video" - - Li-Cobalt
At least they gave some useful info.  Last I read, nobody knows, (at least outside of Japan) what really is going on.

Two decades a ago, I had an interesting experience involving two Japanese Mfrs. My then new minivan was causing the front tires to "cup" , with a cupping pattern that, in thirty years, I had never run across.  The vehicle mfr blamed the tire mfr, and the tire mfr was replacing tires like crazy.
The uniqueness was that the problem occurred with a rear wheel drive minivan, and steel rims instead of cast rims.

When all was said and done, it turned out that the real cause was play in the rack and pinion steering assembly, and specifically in the power steering valve inside it. There was a friction/damper assembly that masked the problem, at least for about twenty thousand miles or so. Evidently the cast rims had more mass, and helped damp the vibration.

The vehicle mfr refused to admit to the problem.  I found out that increasing the spring loading of the friction plate (Not a mfr recommended adjustment) would really help, at the possible expense of a shorter rack and pinion life.  The final ah ha came as the result of an accident when the van was rear ended as it was turning.  A gear tooth was broken inside the steering assembly, causing it to momentarily and randomly partially lock.  A replacement assembly from an alternate source did not have the problem.    The minivan had over 200k miles when I finally sold it, and shortly there after, the new owners son wrecked it beyond repair.  My wife, son, and daughters managed to get in accidents several times, and I even hit a deer when we owned it.  Other than the cupping problem, it was a very good vehicle. Sadly, the mfr changed later models to front wheel drive, and to my thinking, ruined it. 


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RE: Dreamliner batteries - 1/30/2013 8:37 PM   
chuckk2


 

Posts: 380
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Joined: 7/24/2007
Last Login: 6/20/2013
From: Warner Robins, GA, USA
Status: offline 		http://en.wikipedia.org/wiki/Lithium-ion_batteries

Evidently, there is a multitude of different chemistry variants of Li-Cobalt batteries.
I wonder which variant is involved.


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RE: Dreamliner batteries - 2/1/2013 5:47 AM   
dirtybird


 

Posts: 4565
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From: San Tan Valley, AZ, USA
Status: offline
quote:

ORIGINAL: chuckk2

On our RC Lipo's from a reasonably qualified authority.  (Don't Ask, Don't Tell) 
Max do not exceed voltage 4.23 Vdc per cell (New battery, ideal conditions)
A used cell may be slightly lower.

The currrent density issue may be that the current is not always evenly distributed, and  a very small area may see a much higher than expected current density. 

Some years ago, I stopped at a library that had a good collection of recognized technical references, and due to what I was working on at the time, I ended up really looking into just about all practical batteries (Other than Li batteries) for use on military aircraft over extended temperature ranges.
About all I can say today is that each battery type has it's advantages and disadvantages. Obviously, Li rechargeable batteries are a bit more finicky than other choices.  The more energy you pack into a confined area, the higher the chances that something can go wrong.  The range of battery life spans goes from minutes to decades for more or less off the shelf batteries.  Railroads and phone companies used the really long lived Pb batteries and alternatives, with weapons of various types using the short lifetime batteries.



As a curiosity I googled submarine batteries. It turns out you can buy one of those. They are 7000 ampere/hours and are guaranteed for 35 years. The cost is more than $3000/cell. It says a bank of them will supply the average household for 45 days. I guess that is what those super paranoids that buy an apartment in an old missile silo have. I wonder what they charge them with.
I doubt that Boeing would be interested.

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RE: Dreamliner batteries - 2/7/2013 11:17 AM   
chuckk2


 

Posts: 380
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Joined: 7/24/2007
Last Login: 6/20/2013
From: Warner Robins, GA, USA
Status: offline 		25 micron aluminum sheets. They must have been deposited on a backing of some type, perhaps with an electron beam in a vacuum?
(Sputter plating) Chemical plating would likely leave undesired residuals.


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RE: Dreamliner batteries - 2/7/2013 1:59 PM   
thailazer



Posts: 768
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From: Ampur Mae TaengChiang Mai, THAILAND
Status: offline 		Not sure if my late night calculations are right, but a 25 micron thick sheet of aluminum would have to be over a meter wide to handle ten amps assuming same current densities as home wiring. Any variability in that sheet would seem problematic as well.

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