[NSRCA-discussion] Lipo fire

[David Harmon]

I had forgotten that I have also had a pack with an intermittent wire on the
balance lead of one cell.

I discovered this by accident because I picked up the battery when it was on
charge.

Slight finger pressure would cause the wire to go intermittent so I retired
the pack before something worse happened.

 

David Harmon

Sperry, OK

 

From: NSRCA-discussion [mailto:nsrca-discussion-bounces at lists.nsrca.org] On
Behalf Of Anthony Romano via NSRCA-discussion
Sent: Monday, June 13, 2016 3:38 PM
To: General pattern discussion <nsrca-discussion at lists.nsrca.org>
Subject: Re: [NSRCA-discussion] Lipo fire

 

I have re-soldered a number of balance tab leads on older packs. On some the
wire is a little too stiff and work hardens over time. I was very fortunate
that all it did was prevent it from being charged. Perhaps a good routine
inspection of packs and all connections would be useful.

 

Anthony

 

  _____  

From: NSRCA-discussion <nsrca-discussion-bounces at lists.nsrca.org
<mailto:nsrca-discussion-bounces at lists.nsrca.org> > on behalf of Chris Moon
via NSRCA-discussion <nsrca-discussion at lists.nsrca.org
<mailto:nsrca-discussion at lists.nsrca.org> >
Sent: Monday, June 13, 2016 3:56 PM
To: Robert Green; General pattern discussion
Subject: Re: [NSRCA-discussion] Lipo fire 

 

Glad everyone is ok there Robert.

I have handled and dissected hundreds of different packs during my time in
business, evaluating samples etc and I can say with certainty the weakest
link in our batteries are the balance leads and their connections to the
individual cells. These are very thin wires that typically are spot soldered
to tiny tabs on the cells and crimped into tiny pin connectors. Insulation
of the balance wires inside a pack is usually a thin piece of cellophane
looking tape.There is little to no strain relief for the wires and we handle
and flex them every time they are charged. I have seen many break off and
touch others creating sparks and possibly could have lead to fires if they
were pressed together long enough.  I would bet this is what happened to
Robert's pack.  The batteries themselves must pass through pretty rigorous
testing including being crushed with a metal blade without catching on fire
before they will be transported from China.  These testing documents
accompany every large battery shipment so it is highly unlikely one would
spontaneously combust. With an older pack, it most definitely sounds like an
internal short of balance leads.

Chris

 

 

On 6/13/2016 11:15 AM, Robert Green via NSRCA-discussion wrote:

 

Hey guys wanted to let you know about an incident I had over the weekend
that caused some high concern.  I flew four flights yesterday, then returned
home.  I thought I would go back out later and fly three more, so I charged
three more batteries.  The three batteries on was planning on using, were
flown the previous day, and were not overly discharged.  I took my kids to
the movies as my wife did not want to go, and that turned out to be the best
thing for the family.  One of my 2014 packs decided that it no longer wanted
to live and decided to catch fire all by itself.  I have always thought that
the best time for these to catch fire, would be during the charge cycle.
This incident happened almost an hour after charging the pack.  Keep in mind
that after I charged the pack, there were immediately put into my flight box
for storage until I got back from the movies.  After I took them off the
charger, the batteries did not see warm in any way, cool to the touch.  I
have had these batteries for two and as far as I can remember - they where
not damaged in any way.  Due to my wifes' heroic action, the house did not
catch on fire like my toolbox did.  She brought them out to the drive way
water on them to kill the flames.  I have been pretty cavalier with packs,
leaving them out once they are charged and not putting them in something
safe for storage....those days are done.  If this can happen to a battery
sitting with a stored charge, I will not longer leave my house or family
unprotected.  

 

I bought a safe yesterday, but apparently that may not be the best thing for
them either as the battery give off a gas and they need to breathe.  In
other words if you left them in a safe you may be creating a bomb scenario.
What I did was - several years ago, I bought a metal ammo case.  I removed
3/4 of the rubber around the case allowing for the exchange of air to occur.

 

If any one has any other creative ideas on how they store there lipos,
please contribute to this thread as I think it is important as a community
that we spread the message that this technology which has been proven to be
safe for the most part also can be dangerous.

 

thanks,

 

 

Robert





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