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bwilson4web
User Rank
Gold
Good; Fast; Cheap - pick two
bwilson4web   3/19/2013 7:41:26 AM
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Prevention is key and adding weight by embedding the cells in a heavier structure, does not scale well. If the same solution were used for the fuel, the plane might not get off the ground.

Prevention is key and requires mastery of the battery failure mode(s). But that takes time and testing in field conditions and this is seldom cheap or fast.

I am sympathetic to the need to get the planes flying again. But I won't be surprised when a battery problem happens again even if contained. I'll ride in the plane as the other advances are more than enough to mitigate this unsettled battery.

I would like to see more articles about high-energy battery risks and not limited to just lithium based chemistries.

Bob Wilson

Ralphy Boy
User Rank
Platinum
Re: Sounds like a Bandaid
Ralphy Boy   3/19/2013 12:22:25 AM
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lol... Of course knowing Scotty he'll make due by diverting the excess heat to the shields, thereby saving the Dream Liner, and keeping the passengers from having to miss the movie.

TJ McDermott
User Rank
Blogger
Re: Sounds like a Bandaid
TJ McDermott   3/19/2013 12:16:00 AM
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Ralphy Boy, how about slightly different spin on your 'when all else fails':

"Captain, we're approaching critical temperatures!  We have to eject the warp core now!"

D Hambley
User Rank
Silver
No tests with an actual battery!
D Hambley   3/18/2013 9:47:53 PM
NO RATINGS
I read in AW&ST that Securaplane didn't test their charger with an actual battery. They used a simulated electrical load instead. That's fine IF the real load acts just like that described in the spec from Boeing. However, is was also reported that the actual power discharge of the battery was not at the constant rate which Boeing specified to Securaplane. In fact, the actual load had large changes and reversals in short periods of time. Obviously, the engineers at Securaplane could not be expected to design this charger by "guessing" what the load characteristics were like. I'm disturbed by the lack of information flow here. I bet the engineers at Securaplane were disturbed about this years ago.


What is the "root cause" of the failure which Boeing can learn from? Answer: The root cause is not paying more attention to the technical flow of information between tier 2 and 3 subcontractors. It's not going to happen if it's not contractually required.

Ralphy Boy
User Rank
Platinum
Re: Thermal Management
Ralphy Boy   3/18/2013 9:20:00 PM
NO RATINGS
None of our lith-ion battery packs are for commercially aircraft... but we still have an engineer spending massive amounts of computer time analyzing heat propagation and ways to keep one cell going thermal from taking the rest with it. Design changes that mostly avoid active cooling are being researched.

It's what we will have to rely on until they find a way to have all that energy available per-cell but not have anything flammable in the pack...

Charles Murray
User Rank
Blogger
Re: Boeing 787 battery safe?
Charles Murray   3/18/2013 7:22:28 PM
NO RATINGS
The auxiliary power unit battery provides power to start the APU in ground and flight operations. The main battery provides power to start "selected electrical equipment." Boeing says that both batteries are used only for short periods of time to provide power when the engines aren't running. The 787 also has six primary electrical generators.

vandamme
User Rank
Silver
Where have I heard these assurances before
vandamme   3/18/2013 7:10:07 PM
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"God himself could not sink this ship."

William K.
User Rank
Platinum
The new battery enclosure.
William K.   3/18/2013 6:56:40 PM
NO RATINGS
It does look like the folks at Boeing have come up with a whole lot of things to reduce the risks, with the biggest one being reducing the voltage. It does look like excessive charging is what leads to the worst problems, so perhaps they will be OK now.

As for what to do if the battery pack fails? Many planes can function to some degree using the engine powered alternators, while many others have ab APU, (Auxuilliary Power Unit) to serve as backup for the backups.

And Hey!, we live with dangerous thins all of the time. A race car engine may deliver  1000 horsepower, or more, and sit only inches from the driver. And mostly there is never a problem. And we all hear about it whenever there is a problem, don't we.

battery brain
User Rank
Iron
Re: Boeing 787 battery safe?
battery brain   3/18/2013 6:02:12 PM
For your information,

I was deeply involved at Lux Aviation, one of the pioneers of "trying to make lithium main ship batteries tamed".  During 2008 and 2009 we had discovered the need to separate the cells 30AH Lithium Polymer TRI metal cells (7 in series) to prevent propagation of cells combustion.  We determined that we needed a insulated space as wide or wider than the cell itself.  This would have distroyed our envelope, not to mention the weight advantage our major aircraft manufacturer was using as the reason for the Lithiumbattery.

Next, we knew through testing that the cells' would produce their own oxygen after being approximately 120C so we tried a unique idea (we thought).  We built a sealed case for the battery, then bled the earth's atmosphere out and replace it with pressurized Argon gas (which is inert) and then charged a cell inside the sealed box to point of ignition and as Sandia Labs already know----the damn thing still wooshed (as I call it) to approximately 50-70% of that which we would see in normal earth's atmosphere.  Again, no cigar!

We finally came up with a sniffer that would detect the gas from the electrolyte that emitted from the perforated case of the cell, which "always" preceded ignition.  This detector was used to immediately stop the charging WHICH WE ALWAYS FOUND AS THE REASON FOR BATTERY DISTRUCTION.  We, in over 3 years of battery testing found a single case of a battery taking off in and of itself.  This is consistant with what the laptop people and the EV people have experienced.  The number we believe is still the "one chance in a million flight hours for cell probability.  By the way, my name is on the patent for the "sniffer" as well as (5) other patents that came out of our extensive work in attempting to tame the beast.  The trick is in prevention, detection and "redundant sensing having no chance for latent failures.

Richard Lukso, Consutant

Battery Systems Specialist

Charging-safety-reliability analysis

 

Ralphy Boy
User Rank
Platinum
Re: Sounds like a Bandaid
Ralphy Boy   3/18/2013 5:46:34 PM
Okay, now I'll post what I was thinking while reading last week's installment of the continuing saga of Boeing's Lucky Battery Near Disaster(s)...

They need to have the battery fitted with a parachute and build the little sucker an ejection seat.

Call it the 'when all else fails Band-Aid'.

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