The Danger of Stupidity - Li-Po Fire

[Breaktru]

So I built this really cool scaled down, very compact mod. I was real proud of the way it turned out and how I squeezed all of it into a cool aluminum case with (2) 1000mah Li-po 20C batteries totaling  to 2000mah. Well until I started to put the LAST screw in. Whamo! I pierced the top battery shell and instant smoke. I placed it outside and it continued to spew for what seemed like 20 min.

Here is the melted mess below all was lost.................

[mamu]

oh.my.gosh.  That royally sucks, breaktru.

Chin up... just a do over.  Hope you have parts to make another as it looks like a really cool mod.  Maybe dremel off some of the length of the screw?

[been there]

Or the luck of the Gods , you could have missed the battery's by a hair and been vapeing with a little movement could of made contact and Boom. It's all in how you look at things .

[CraigHB]

LiPos are like that.  They're only encased in thick foil and they're easy to puncture.  They reliably fry when that happens.  Well, good thing it didn't go up fast in your hand or something.  Sorry to hear you lost your mod.  Careful there.

[Breaktru]

oh.my.gosh.  That royally sucks, breaktru.

Chin up... just a do over.  Hope you have parts to make another as it looks like a really cool mod.  Maybe dremel off some of the length of the screw?

Yeah I have to cut down the screws a bit on the next one.
Damm, it was a real PIA getting the DNA screen in being it's a closed type box.  I do have extra parts.

Or the luck of the Gods , you could have missed the battery's by a hair and been vapeing with a little movement could of made contact and Boom. It's all in how you look at things .

Yup. That could have happened. Lucky I guess.

LiPos are like that.  They're only encased in thick foil and they're easy to puncture.  They reliably fry when that happens.  Well, good thing it didn't go up fast in your hand or something.  Sorry to hear you lost your mod.  Careful there.

Thanks Craig. I'm going to clear my head before starting over. I just barely touched the foil w/ the screw which is rather flat ended and not pointed.

[mamu]

...I just barely touched the foil w/ the screw which is rather flat ended and not pointed.

Is it possible for screws to have conductivity?  Or maybe interference between the metal case and the lipoly batt in conjunction with the screw?

Maybe putting a piece of electrical tape over that area of the lipoly batt would help so it would be isolated.

[Breaktru]

Is it possible for screws to have conductivity?  Or maybe interference between the metal case and the lipoly batt in conjunction with the screw?

Maybe putting a piece of electrical tape over that area of the lipoly batt would help so it would be isolated.

The circuitry is isolated from the case. I ran a separate neg wire and the screws are isolated by way of the plastic end caps. Looking at the battery the screw did pierce the foil.

[CraigHB]

Li-Ion batteries are made with many layers of thin foil with a thin plastic sheet insulating them.  If anything compromises the insulation between the sheets of foil, the cell shorts internally which causes a "runaway thermal condition" as it's technically defined.  Crushing or puncturing the cell can cause that to happen.  The difference with the round cells is they have a hard sheet metal enclosure so they're pretty resistant to external stress, but the same thing can happen to them.

When using LiPos you have to provide physical protection for the cell thorugh the enclosure so you have to consider that when using them.  Just saying since people are using them for mods and may not be aware of how vulnerable they are to external stress.  They can handle a lot of pressure if spread out evenly across the cell, but they're especially vulnerable to punctures or large pressures applied to a small area.

[Breaktru]

@CraigHB
This was my first Li-Po failure. I'm surprised that there weren't more with the way I've been stuffing them in to the tightest spaces filling the enclosures with not a mm to spare.

I admire the way that you design and layout your components and battery to fit precisely but I'm more of a "I got these parts and this case and I'm going to make it fit" kinda guy 

[CraigHB]

The trick is to design the enclosure so any external pressure gets applied to the cell over a wide area.  LiPos can take pretty large compressions when spread out perpendicular to the foil layers.  One thing I do is pad the cell with a few layers of masking then Kapton tape to provide some heat and stress tolerance.  The Kapton tape provides heat resistance (from a faulty PCB) and the masking tape provides some compression relief.

Anything pointy inside the enclosure for a LiPo cell is a definite no-no.  The LiPo should be secured as uniformly as possible inside the enclosure.

I've blown a couple cells being careless in building mods, it happens.  Just the hazard of working with these cells on the bench all the time.  Know where your fire extinguishers are.  Haven't had to break one out, but I've had to dispose of one or two cells in a fire safe manner.  Dont' get too miffed by it.  It just makes you realize, "yes Li-Ion cells can be hazardous."

[Visus]

Wow just noticed this post.

Truly gives respect to the power of  batts.  I blew a hole in my finger being stupid a few months back witha 180 mah lipo stuffing it in a case for fit.  Instant ashed finger-tip that took forever to heal.

 

[nosmo ke]

'Tis but a scratch!

[BEATNIK]

     Glad you both are okay.