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tekochip
User Rank
Platinum
Re: Boeing 787 battery safe?
tekochip   3/20/2013 8:22:29 AM
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Thanks Battery Brain.  I seem to remember reading an article that the military no longer charges lithium batteries to 100%, they keep them at around 90% .

Charles Murray
User Rank
Blogger
Re: Boeing 787 battery safe?
Charles Murray   3/20/2013 7:50:45 PM
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I think the rule of thumb in the auto industry, tekochip, is to keep the battery between 20% and 80%. Below 20% is too deep a discharge, above 80% risks overcharging. That's why some of the battery packs end up being so big.

ltron
User Rank
Gold
Additional comments by Sinnett
ltron   3/21/2013 12:10:16 AM
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Sinnett also said that although Oxygen is rereleased if the temperature gets high enough, testing revealed that the amount was insufficient to support combustion for anything but a short puff.

He also contended that neither plane experienced a fire since it was not possible. Further, the fire department report could not substantiate a fire. What was said was that a small area looked white on a thermal imager. It was claimed that the white area in question turned out to be an electrical connector on the outside that did suffer considerable damage.

Basically the whole "Thermal Runaway" issue sounds like a red herring. Too many experts out trying to make a buck if you ask me.


robatnorcross
User Rank
Gold
Re: Boeing 787 battery safe?
robatnorcross   3/21/2013 5:26:29 PM
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RIIIGHT! And the Titanic was UNsinkable and the Winecoff Hotel (Atlanta) was firePROOF.

This is surely pissing in the face of Mr. Murphy who everyone who reads this blog should be very familiar with by now.

Phil Pearce
User Rank
Silver
A Safe Solution
Phil Pearce   3/21/2013 5:33:56 PM
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We recently contacted Boeing with details of a system that is able to prevent thermal runaway by monitoring the cells and detecting any physical instability including swelling or ballooning of one or more of the cells in a lithium-ion battery pack.  By implementing this means of detection we were able to successfully develop a viable solution that is able to prevent the onset of thermal runaway and combustion before it ever occurs. 

Unlike typical battery management systems which at best only monitor voltage, temperature, and current conditions of the battery, this new system is able to detect and protect at a far earlier stage from the potential dangers caused by the volatile nature of lithium-based battery cells by measuring and monitoring any minimal changes, in a 3 dimensional space, the physical dimensions of one or more of the battery cells within the pack.  This dimensional deformation which leads to ballooning or swelling of any of the unstable cells within a battery pack is detected before Thermal Runaway and combustion of any cell occurs.

Whether they implement this solution or not is probably down to the accountants!

phil.pearce@ieee.org

 

Charles Murray
User Rank
Blogger
Re: Eliminates the Possibility
Charles Murray   3/26/2013 6:13:25 PM
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Bill, thank you for making a comment that has made all of us think a little more deeply about this subject. In one short assessment, you've eloquently captured what many engineers felt but struggled to put into words. I first saw your comment on a Saturday morning and couldn't get the words out of head for the next several hours. Your comparison is right on the money, especially topped off by the perfect Mark Twain quote. Very well said.

williamlweaver
User Rank
Platinum
Re: Eliminates the Possibility
williamlweaver   3/26/2013 6:45:05 PM
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Thanks for your very kind words, Chuck. It's too bad that my eloquence no longer has any effect on my wife...  =]


"NEVER" is a strong pet peeve of mine with my students. Unless they want to hear me drone on about how long "never" and "ever" actually is and how quickly the environment can make their solutions obsolete, they learn to avoid using qualitative speech when quantitative speech is required.

Jack Rupert, PE
User Rank
Platinum
Re: Eliminates the Possibility
Jack Rupert, PE   3/27/2013 3:09:01 PM
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williamlweaver - When I read that headline, my first thought was "ever? yeah, right!"  Nothing is that good.  Did you ever write up your discussion of ever/never?  I would be interested in reading that.

williamlweaver
User Rank
Platinum
Re: Eliminates the Possibility
williamlweaver   3/27/2013 5:40:55 PM
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Thanks for the chuckle, Jack. Your use of "ever" in your comment speaks directly to my sense of humor. I have not yet ordered any electrons on the topic of "ever/never", but your comment is strong motivation to grab a soap box and capture my rant. So I guess to answer your question of "Did you ever..." I guess that makes the answer "Yes. But not yet."  =]

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