[Elecraft] ECOM scare -- FW: Soldering lesson

[Jim Miller]

It has been a long time but... I had a battery in my pocket (not sure any
more but probably a 9v), no change in the pocket and do not remember what it
was that caused the problem (probably my knife) but something apparently
shorted the terminals and I felt uncomfortable, jostled my pocket, then
warm, then hot and HAD to get whatever it was out.  I burned my hand. The
battery got MUCH hotter even after it was out.  It would have caused a
serious burn to my leg had I not removed it.  I could only describe the
situation as an avalanche failure inside the battery.

I will not forget that experience and never put batteries in my pocket of
where they can short any longer.  

73, Jim KG0KP

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Don
Wilhelm
Sent: Saturday, February 18, 2017 6:01 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] ECOM scare -- FW: Soldering lesson

I was involved in product testing in my former career.
One large computing machine which I worked on had a backup battery
consisting of 4 AA cells, which no-one thought would be a problem, but
during environmental testing at shipping extremes, condensation formed and
created leakage paths.  It was a hard sell to convince management and many
engineers that AA cells could cause a problem.

The following action was to do extensive testing in the power systems lab in
which several destructive tests were performed, which included shorting the
battery pack terminals.

It is amazing how much current those "lowly" AA cells can produce in a
shorted situation.  Under short conditions, they are just as powerful as any
other battery, but the duration of the huge current discharge is shorter
than for larger batteries.

Lesson I learned is to be careful with any battery.  High density battery
chemistries make the short circuit discharge duration longer and can cause
more damage.

73,
Don W3FPR

On 2/18/2017 6:25 PM, Rick WA6NHC wrote:

> Don't forget that some of the battery packs we commonly use now 
> (LiFePo4 is my example) are capable of tremendous current (mine are 
> 'fused' by a BMS at 100 amps).
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