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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: John Roberts {JR} on February 06, 2018, 02:42:24 PM

Title: It's only a battery what could go wrong?
Post by: John Roberts {JR} on February 06, 2018, 02:42:24 PM
Yesterday while assembling drum tuners, (I do occasionally work) I encountered a little drama.

The note sweep sounded a little rough at the bottom of the range, like maybe low voltage, but I had just installed 4 brand new batteries.

I measured across the battery holder and indeed voltage was low, so apart it came. While disassembling it a noticed one battery was unusually hot.

If you look at the image you will see a shiny spot at about 2 o'clock on the - end of the battery where the wire end from the spring contact pierced the insulation wrap around the battery. Apparently the metal casing is positive wrt the floating negative electrode. Piercing through the plastic insulation shorted the cell.

Could have made a mess... while I expect the batteries are pretty safe it was well on its way to melting stuff.

JR
Title: Re: It's only a battery what could go wrong?
Post by: Keith Broughton on February 06, 2018, 03:40:55 PM
Good catch before something bad happened!
I made the mistake of dropping a 9 volt battery in my pocket with some change!
ZIOKS!

"It's just a bunny..."  ;D
Title: Re: It's only a battery what could go wrong?
Post by: David Allred on February 06, 2018, 03:54:28 PM
Good catch before something bad happened!
I made the mistake of dropping a 9 volt battery in my pocket with some change!
ZIOKS!

"It's just a bunny..."  ;D

I was about to make this same comment.  Hot enough to burn.  Definitely a "Whathu?" moment.  Not a casual pocket emptying, for sure.
Title: Re: It's only a battery what could go wrong?
Post by: Jonathan Johnson on February 06, 2018, 04:22:44 PM
Apparently the metal casing is positive wrt the floating negative electrode.

That is correct, sir.

The old carbon-zinc batteries had a negative casing. Alkaline batteries have a positive casing. There's a good reason for that; I don't remember what it is though.
Title: Re: It's only a battery what could go wrong?
Post by: Nathan Riddle on February 07, 2018, 11:37:14 AM
I had this happen in a Senn body pack! It was arcing and the battery was quite hot to the touch!

I really wish they made the battery bodies out of plastic.
Title: Re: It's only a battery what could go wrong?
Post by: Chris Hindle on February 07, 2018, 01:02:10 PM
I had this happen in a Senn body pack! It was arcing and the battery was quite hot to the touch!

I really wish they made the battery bodies out of plastic.

Unless I'm mistaken, the casing IS an electrode.
So, smaller casing, wrapped in plastic - to maintain correct size = less capacity.
Chris.

I used to hand newbies a 9V to "hold on to for a few minutes". Always ended up in a pocket   ;D
Title: Re: It's only a battery what could go wrong?
Post by: John Roberts {JR} on February 07, 2018, 01:15:54 PM
I had this happen in a Senn body pack! It was arcing and the battery was quite hot to the touch!

I really wish they made the battery bodies out of plastic.
Batteries are engineered using very sharp pencils so bom materials are managed tightly.

It seems in hindsight the insulation could be a little thicker on the negative contact end.

I will be more alert during battery insertions for my future.

JR
Title: Re: It's only a battery what could go wrong?
Post by: Mark Oakley on February 07, 2018, 02:48:16 PM
Here's a guy that didn't fare so well:  https://youtu.be/IoAO1S5w7KM

-Mark