OK I have a big ego so writing this is against all normal tendencies. I thought I knew better - but one battery in my many dozens was not labeled right and caused this mess and a warning not to repeat it should be passed on.

I was getting ready to go flying today and noticed one of the small (what I thought was a 6 cell pack of 250mah nicads) was swelling a little on the charger - at least the blue shrink wrap that completely covered the pack was swelling.

I thought interesting - I have seen it happen before with nicads that got too hot and leaked gasses causing the heat shrink to swell. I had completely covered the pack with a blue heat shrink that I normally used for nicads and nimh packs and had folded over the ends which sealed the battery. But the pack wasn't hot, just barely warm to the touch. I was going to toss it in the kitchen trash can but decided to let out the gases. I had done this several times before with old nicad packs several years ago. They just went a mild pfffff and nothing else.

I figured it would make sure a dead nicad pack was thrown into the trash - so - standing in the middle of my kitchen I touched the point of my pocket knife (sharp) into the shrink wrap a little sidewise just far enough to let a bit of gas out but not touch a cell and - whow! - Firey gasses and sparks began to spew out about a foot (luckily not toward me).

I instantly dropped the battery on the kitchen floor (not going to hold a fire spitting device of any kind and linoleum was cheap compared to skin) and thought - hummmm, must not be a nicad - a genius a work no doubt!

Then I thought - I wonder how long this will go on and why didn't I have a bucket of sand handy! I thought about using our kitchen fire extinguisher but by then I figured it was a lipoly and thought containing the fire was the best bet.

I threw a real heavy cloth kitchen rug/carpet (one of those thick kind made of cloth scraps) over the flaming spewing smoking mass and thought, OK, but it might set the rug on fire so I followed with several pans of water over that - knowing that water was not normally a good thing.

The reason for the water was that it made for a lot of cold wet soggy mass over the flames which should help cool the whole mess faster than it was burning and would constrain what ever was happening.

The rate of flame and smoke before throwing the rug over the battery was pretty impressive. This was not gently venting flame - it was a rapid burn but not an explosion - I think due to the melting of the covering materials.

The heavy wet soggy rug did work very effectively in constraining the flames and smoke. However bout then the fire alarms went off. Let there be no doubt there is a lot of smoke involved in the process even though the wet rug did constrain the smoke after it was on the cell.

Finally things calmed down and my wife and I stood there looking at each other in silence. Words were a bit anti-climatic and none needed to be said. We both knew I had lucked out again.

Now the floor and mess is cleaned but we now have the mess shown in the photo! Based on leftovers on the floor it was apparently a two cell Lipoly of about 700mah size. Luckily we have extra floor stuff and can just cut it out and replace it. The thought of it exploding while in my hand is very scarey.

Now as to why it happened. I think I had replaced the outer heat shrink wrap last year and had apparently gotten distracted in the middle of the job and used the wrong color heat shrink. All the lipoly I have are normally pink, silver or red. I always use blue heat shrink on nicads and nimh and since the pack was blue, I assumed it was a nicad when charging this year for the first time. Too many months between actions and no labeling to warn me.

I didn't notice the difference in cell structural shape in the real small pack probably due to the thick heat shrink. Since the pack was covered completely the normal silver and shape of the lipoly cells weren't apparent. I have many dozens of various shapes and sizes of nicads and nimh so the shape didn't arouse any immediate flags.

I was attending the charging but made a wrong assumption in cell type and it resulted in that I saw it when the cell was barely warm and just a little swollen. The bottom line never charge any battery unattended and if they swell, even a little, no matter what you think the type might be, get it out of the house.

Oh yeah, don't poke the swollen pack with a knife unless you are way out of the house and the knife is on the end of a long stick.

A cheap lesson.

Ben

Originally Posted by Ben Lanterman

The rate of flame and smoke before throwing the rug over the battery was pretty impressive. This was not gently venting flame - it was a rapid burn but not an explosion - I think due to the melting of the covering materials.

Ben

Ben,

The rapid burn is from the electrolyte in the cell burning not the covering materials.

You did the smart thing by quickly dropping the battery.

Chuck

Sorry to hear of your misfortune, Ben.
Cheap lesson, it could have been much worse. Someone I fly with recently caught their motel room on fire. It too was extinguished with minor damage.

Don't throw those NiCads in the trash. RECYCLE

I plugged a puffed pack up to a car battery charger and tried to blow up each cell of the 3 cell pack..

I certainly got them to swell and puff and finally got them to catch fire...

Glad yours didn't turn into a major catastrophy..

Ben, people often "instinctively" do the right things in a crisis.
Water cools things down and represses the flamability of surrounding materials.

Another point: A 2s 700mah LiPo is a relatively small pack. A 3S 2100 contains six time the potential energy and a 3S is by no means a big pack, these days.

Let's charge them outdoors in an open area.

- RD

Originally Posted by Steve Guinn

Don't throw those NiCads in the trash. RECYCLE

Yep, Steve is right, recycle, we don't want that cadmium in the nature....

Nope. We must mine all the cadmium out of them rocks and turn it into Nicads and use them forever.

Same with Uranium, lead and all the other stuff the earth is made for. Its not natural to have a planet made of that stuff.

Thanks for reporting that incident Ben. There are several lessons in your message which will be of value to other modelers.

Ben, your detailed description will be helpful to many people. Thanks for overcoming your "big ego" and sharing this in the interests of helping others. We should all have this same attitude.

Another important point is that if you use a charger like the GP's Triton be sure you have the correct battery type selected before charging. One afternoon I put a 3s 1020 pack on the charger. In a rush and with poor lighting in the shop I set the charger to PB (lead acid) rather than Lipo. When I come back later the charger had kicked off but not before swelling the pack. Discharged and scraped the pack. Hopefully lesson learned.

Originally Posted by rcelectfly

Ben,

The rapid burn is from the electrolyte in the cell burning not the covering materials.

Chuck

Agreed. I was thinking that the covering melting allowed the gases to escape as they burned, as opposed to being confined in a small "hot box" like the ammo box tests I had read about.

I am starting to think about the batteries like a cup of gasoline covered with a plate of glass. It can be perfectly sealed and safe until the top is bumped off by a careless action.

I shutter to think about what the 3200mah lipolys I have might do. No wonder things burn down. Extra smoke detectors in the garage and hobby room would seem a good idea also. They do work when there is still enough oxygen to get out of the house.

Originally Posted by Ben Lanterman

I shutter to think about what the 3200mah lipolys I have might do. No wonder things burn down. Extra smoke detectors in the garage and hobby room would seem a good idea also. They do work when there is still enough oxygen to get out of the house.

And I have several 4S3P 6000 packs in my collection. I wonder about the type of fire they would generate!

Wiz

Vintage,

a little facetiousness? There are many things in nature that I don't care to have near.
How about I send you all my spent NiCads as fertilizer for your vegetable garden?

Renal failure, anyone?

Wow.. no safety Nazi's got on my case about purposely blowing some up.. You guys are alright by me, no matter what anyone else might say about ya!

Lipo just helped my truck burn down about 3 weeks ago.. Here is the post.. Check it out..

Glad you are OK. I use to be a Floor guy so that would be easy to fix or replace it all. You can just cut the bad Squares out and put new ones in. Just double cut the vinyl to get a perfect fit. If you need more instrunctions just PM me and I will be glad to help you.. GLAD you were not hurt...

LATER

Oh yea here is the post..

http://www.rcgroups.com/forums/showthread.php?t=368758