HOT NiCd with no charge.

ifoxbox

Newly Enlightened
Joined
May 15, 2006
Messages
99
Hi,

I repair Sonicare toothbrush handles which use NiCd batteries in them. I received an Elite handle that did not work out of the box. I was told that the handle was never used and that it was untouched out of the box. They said that it had been in the closet for a couple of years, and had never been used. Anyway, when I opened the handle to remove the battery, I noticed that the positive end of the battery was black, and the back of the PC board was burnt up. I was just curious, what would make a battery that was just sitting heat up like that?



Here is a picture of the back of the PC board. You can see where the positive end of the battery went, and where it burnt up the surrounding area.

Pcboard.jpg
 

Brlux

Enlightened
Joined
Jan 28, 2003
Messages
400
Location
Mesa, AZ
I once had a generic green wraper MiMH AA cell internaly short out for no reason. It was in a mini mag flashlight that I was werring on my belt and if I recal the cell was an 1800mah and fairly new probably within the first 5 charge cycles. I noticed the smell of something hot and felt a warm sensation on my hip through Jeans and the holser. When I puled the light out it was to hot to hold. I set it aside and waited for it to cool down. there was no blackenin of anything but I think the heat shrink was split.
 

speederino

Enlightened
Joined
Jan 17, 2006
Messages
278
Location
Ohio
I had an alkaline short out internally recently. Picked up the TV remote and noticed it was warm. Figured the cat had been laying on it or something so I proceeded to watch some TV. Noticed a little while later it was still warm. Popped the battery cover and sure enough, one of the AA's was warm. A few hours later it was cold and totally dead. I can't imagine a cell with low internal resistance like a Nicd or nimh doing it....hot potato!
 

ifoxbox

Newly Enlightened
Joined
May 15, 2006
Messages
99
SilverFox said:
Hello Ifoxbox,

Perhaps the cell shorted out...

Tom

Hi Tom,

I think that is probably it, but what do you think would make a NiCd that has supposedly not been used short? This is not the first time I have seen this happen in the new Elite handles. I figure that the battery in the handle had probably been sitting on the store shelf for a few years not being used, and then stored in a closet for a while. Just sitting should not cause a cell to short right?

Thanks!
 

SilverFox

Flashaholic
Joined
Jan 19, 2003
Messages
12,449
Location
Bellingham WA
Hello Ifoxbox,

Cadmium migration has been linked to this, but it usually occurs during extended trickle charging. Self discharge tend to form larger crystals, and it may be that a bump caused damage to the separator.

I have not run across this, so I am just guessing...

Tom
 
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