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Hawker battery failure

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nuckollsr(at)cox.net
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Posted: Sat Jan 14, 2006 1:12 pm Post subject: Hawker battery failure

I have some preliminary feedback from a teardown inspection

that's being done on the battery we received here last year.



http://www.aeroelectric.com/Pictures/Battery/Odyssey_OV



There was zero moisture in the battery although the vent

caps were intact meaning that all water had been converted

to steam and exited the cells via the over-pressure vents.



The swelling on the side suggests that the inter-cell

walls became detached from the outside battery wall or

that they stretched. Given that internal pressures are

limited to the cracking value of the valves. See:



http://www.aeroelectric.com/Pictures/Battery/Odyssey_OV/Odyssey_OV_5.jpg



http://www.aeroelectric.com/Pictures/Battery/Odyssey_OV/Odyssey_OV_6.jpg



http://www.aeroelectric.com/Pictures/Battery/Odyssey_OV/Odyssey_OV_7.jpg



It appears that the cell walls are intact but stretched.

I'm going to see if we can run some tests on those caps

(and on a new battery that hasn't been hot).



This battery was subject to an OV condition for considerable

time and it may be that this damage took several flight

cycles to go this far.



Watch this space.



Bob . . .

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nuckollsr(at)cox.net
Guest

Posted: Tue Jan 17, 2006 11:41 am Post subject: Hawker battery failure

Further investigation into the puffed up battery confirmed

that the inter-cell walls got so hot that the plastic

stretched under pressure and after all the smoke (or should

I say steam?) cleared, the walls between cells was still

intact. They're running some cracking pressure tests on

the vent valves.



It's the opinion of those who've tested a lot more batteries

than I that the event probably didn't take more than 20-30 minutes

under an over-charge current that a 40 to 60A alternator

would be capable of.



There's a new battery qualification document (DO-293) that

calls for 3v per cell at up to 8C amps be applied until

all the steaming is over. No fire allowed, no breaches

of battery case. I'm told that within 10 minutes of

application, RG batteries are steaming vigorously and

that the high energy activity is pretty well over in

30-40 minutes.



Looks like the Hawker would have passed this test okay

and that regulator failure was the proximate cause

of the event with outcome exacerbated by lack of active

notification of an OV condition and/or automatic termination

of the OV event.



Bob . . .

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