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Hawker battery failure

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

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
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PostPosted: Tue Jan 17, 2006 11:41 am    Post subject: Hawker battery failure Reply with quote

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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