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nuckolls.bob(at)aeroelect
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 Posted: Fri Sep 16, 2016 8:21 am Post subject: PC680 Failure Analysis |
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A few weeks ago I received a PC680 battery from
Joe Gores that was presenting intermittent behaviors.
Seems the battery would 'go open' but perhaps with some
external coaxing, prodding, banging, etc . . . it would
come alive.
Got a chance to get on the mill in Wichita last week
and we carved the top off the failed battery for
inspection.
The battery's as-received condition is illustrated
at http://tinyurl.com/zkp45md
There was no evidence of external damage or internal
distress. Terminal voltage as received was zero. I tried
some external forces suggested by Joe to no avail.
Tear-down images are posted at http://tinyurl.com/hspd7kt
A 4-wire ohmmeter was used to check inter-cell
connections http://tinyurl.com/z5wauwc. All execpt the
leftmost interconnect presented sub-milliohm continuity.
The leftmost joint was open circuit.
Prying this joint open . . .
http://tinyurl.com/hcmns8t
. . . revealed a weld fracture wherein the entire
face of the weld exhibits corrosion; there was
no evidence of a metallic bridge across the joint
prior to opening it up.
It appears this failure was a long time in the
making.
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1944
Location: Riley TWP Michigan
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| Posted: Fri Sep 16, 2016 10:18 am Post subject: Re: PC680 Failure Analysis |
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Bob,
I am happy that you found a problem and it was not my imagination. If that broken weld were repaired, I'm sure the battery would crank an engine just fine. The battery was new in 2010. (The sticker with 2016 on it is not the date.) I have not been reimbursed for the postage yet. The post office clerk said that using a flat-rate box saved half the cost of sending in a plain cardboard box.
The lesson to be learned from this is that even though a battery failure is highly unlikely, it can happen. The first symptom (low voltage alarm at idle RPM) occurred while flying, even though the engine cranked just fine.
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Joe Gores |
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kenryan
Joined: 20 Oct 2009
Posts: 429
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| Posted: Fri Sep 16, 2016 10:39 am Post subject: PC680 Failure Analysis |
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I wonder if this battery would have passed the 80% draw down test?
On Fri, Sep 16, 2016 at 8:19 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
A few weeks ago I received a PC680 battery from
Joe Gores that was presenting intermittent behaviors.
Seems the battery would 'go open' but perhaps with some
external coaxing, prodding, banging, etc . . . it would
come alive.
Got a chance to get on the mill in Wichita last week
and we carved the top off the failed battery for
inspection.
The battery's as-received condition is illustrated
at http://tinyurl.com/zkp45md
There was no evidence of external damage or internal
distress. Terminal voltage as received was zero. I tried
some external forces suggested by Joe to no avail.
Tear-down images are posted at http://tinyurl.com/hspd7kt
A 4-wire ohmmeter was used to check inter-cell
connections http://tinyurl.com/z5wauwc. All execpt the
leftmost interconnect presented sub-milliohm continuity.
The leftmost joint was open circuit.
Prying this joint open . . .
http://tinyurl.com/hcmns8t
. . . revealed a weld fracture wherein the entire
face of the weld exhibits corrosion; there was
no evidence of a metallic bridge across the joint
prior to opening it up.
It appears this failure was a long time in the
making.
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Fri Sep 16, 2016 12:06 pm Post subject: PC680 Failure Analysis |
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At 01:35 PM 9/16/2016, you wrote:
| Quote: | | I wonder if this battery would have passed the 80% draw down test? |
Interesting thought. I suppose I could have
tested it right after opening it up . . .
but its been open to atmosphere for quite awhile.
I put a charger on a couple of cells
but they've dried out.
Bob . . .
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