Vented Ultrafire - An Edgy-Kation in protected batteries

[skipdashu]

Well today I was eying up a "large" battery case (plastic box) designed to hold 2 x 18650 OR 4 x 16340. I really wanted the box to hold 4 x 18350s.

Put in an AW IMR 18350...

OK, now try a no-name IMR 18350...

Oh good, that works too!
Now for the Ultrafire protected 18350s...

Oh, not so good.


Wonder if I could push it in with a little bit of pressure?





OUCH! This M*&^&F#%$%^* is HOT!



And it got hotter and hotter and hotter...

Who needs an stacked battery mod? I can vent single protected batteries at my desk!

 

[skipdashu]

Should be subtitled "How a protection circuit and an idiot can get together and cause a thermal run-away"! LOL

 

[Creniker]

Crazy I wonder how that happened. Any insight?

 

[skipdashu]

Crazy I wonder how that happened. Any insight?

My best guess is that when I tried to push it into the plastic box the edge of the box crushed that band that runs under the wrapper into the battery casing and shorted (the band is part of the protection circuit as it needs both + and - to operate). That band has a thin film of insulation on the back side of it but I guess I squeezed it too thin. Best guess anyway.

 

[Creniker]

That would make sense. You should unwrap it if you still have it and post some pictures.

Edit: I just saw in your first post the pictures I was looking for. Thanks.

 

[Rocketman]

My best guess is that when I tried to push it into the plastic box the edge of the box crushed that band that runs under the wrapper into the battery casing and shorted (the band is part of the protection circuit as it needs both + and - to operate). That band has a thin film of insulation on the back side of it but I guess I squeezed it too thin. Best guess anyway.

removing the plastic wrapper would tell you if you forced the 'nipple' positive contact off center and it touched the negative cell case (my guess). If the kapton tape under the sense strip was damaged that would show.

The same thing can happen trying to force a cell into a tight charger.



never mind , didn't click on you linked photos

 

[skipdashu]

I didn't peal that off... it melted. I took those pics as soon as it quit bubbling in that coffee mug of water and cooled off. First bubbling was out the + button (larger bubbles) then after that quit there were super small bubbles coming from the edges of the plastic wrap (or so it looked). I took it out of the cup after that. Notice it turned the water yellow.