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re: Boeing should never say never
adornao   3/12/2014 4:50:10 AM
Software is something that isn't being investigated by news or companies involved as the reports make little to no mention of the BMU internal to the battery and since the CPU and firmware were obviously totally fried in the fire the only thing we know is that it never opened the protection circuit and the thermal sensing failed to detect cell 6 failing. The battery charger firmware is the only thing they seem to have fixed by making it a smart charger (not dumping 45A's into a lithum battery which is a bit of an insane fast charge current if you ask me for a 1V drop).

Everyone is focusing on the hardware and electronics without looking at the software while at the same time everyone is jumping on Toyota's case when the hardware makes it irrelevent as to the quality of the software. These lithum batteries are the last line of defense on the 787 for emergency power and having such poor reliablity and clearly defective design is scary to say the least. Even my laptop can sense a bad cell and the boeing 787 doesn't interface battery balance with the charging system directly (the safety circuit can only inhibit charging) this is bad design through and through as most lithum chargers are smart and ensure even cell charging throughout battery pack charging and without direct balance voltages the battery charger has to hope the battery balancer inside the battery works.

It would be far safer if the battery had a charger balance system and a indepdent battery balance monitor instead of tasking the monitor with the balance function.



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re: Boeing should never say never
52634   4/30/2013 4:54:17 PM
I think the Boeing fix(es) are the wrong approach and are risky. Reason why: Saw a documentary the other day on a fault on Boeing777 plane, that resulted in a British Airways plane landing short of the runway (crash landing). Pilots managed to land it without any fatalities, but it was a very near miss. The aircraft crash investigators thought they would have the answers quickly, but it actually took them over 1 year to REPRODUCE THE FAULT and implement the RIGHT fix. When the autopilot landing the 777 requested more power, both engines responded with less power! That caused the incident. After much work, the investigators concluded it must be ice clogging the fuel lines that starved the engines of fuel. When they recreated the temperatures experienced by that particular flight, they found at vey cold temperatures (-30C) hardly any ice formed. At higher temperature (-20C) then much more ice formed and it stuck to the fuel line pipes. Still, this did not create the problem. ONLY when a sudden increase in fuel demanded was issued, did the ice get knocked off the pipe walls and land onto the intake of the heating system, that is designed to heat the fuel before sending it to the engines. This heater had a number of small pipes sticking up at varying heights and the ice got stuck there! Re-designing to make the pipes all stick up the same amount solve the problem. The issue is this: no engineer looking at those pipes suspected a problem. It was only REPRODUCING THE FAULT in their test arena did they understand the ONE, simple fix that was actually needed. Imagine if they had taken the Boeing approach and just implemented a scatter-gun of "fixes" - would they have included the one crucial fix? I think not.

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re: Boeing should never say never
Bert22306   3/20/2013 7:32:35 PM
I'm not sure that I understand why it should be surprising that managers and PR folk speak in non-engineering terms? How is this surprising? If the press get their stories from management and PR people, that's the lingo they will hear - every time. If the new packaging has reduced the risk of smoke or fire to something lower than that associated with other batteries in use, then surely that has to be acceptable. Even if people aren't conscious of it, they take risks from the time they are conceived.

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re: Boeing should never say never
EVVJSK0   3/20/2013 7:17:48 PM
It would be interesting to know if 1) batteries were produced in U.S. or another country. This may speak as to quality not only of test batteries , but also Production 2) If altitude/cabin pressurization testing (at least in a pressuritzation chamber) was done. I have not read a lot on the details of the failure and the testing methodology, but many folks have said that these batteries were prone to problems. It would be interesting to know how much QC and Testing was done to try and mitigate the final product problems. Parts Search

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