Help! I need a quick answer! Almost had a protected AW 18650 go up on me!

[jaundice]

Hi. I need a quick answer. Tonight I almost had an AW protected 18650 go up on me.

I was working on a PVC pipe adaptor to fit 2 18650s in a 2D cell mag. I had made the adaptor, slid the two AW 18650s in it, and it was sitting there with the tailcap OFF for about 20 minutes while I was fiddling with the tailcap spring to make it work. I came back in the house, and picked up the light. It was very warm. Concerned, I pulled the batteries out, and found the top of the first battery charred looking. It was stuck in the PVC adaptor. There was no smoke or flames. There was some sort of "juice" in the bottom of the maglite. I immediately took the the batteries and maglite outside and put them on concrete. I shook the hot 18650 out of the PVC and moved away from it. I poured some water on it to cool it down. The black plastic cover was melted away, exposing the metal strip that I assume is the safety circuit. The cell eventually cooled down, with no smoke or flame. It's sitting outside right now on concrete, away from flammable material.

My burning question is, assuming that some of the "juice" mentioned earlier is electolyte, am I in any danger?

I washed my hands as soon as possible. I read the MSDS for Panasonic LiCO batteries, and it only mentioned that in case of irritation, see your doctor. But I read the MSDS for Lithium hexafluourphosphate, and it says the topical exposure can lead to serious bodily injury or death.

Thanks,

-John

 

[jaundice]

I really have no idea why this near-miss happened tonight. I bought these batteries back in February, and have charged them maybe 3 times. They were sitting in an imcomplete circuit.

One thing: I may have compressed them too much when trying to tighten down the tailcap on the 2D maglite. Mags have a ridiculously strong tailspring. I didn't tighten the tailcap down at all, but I did force it pretty hard trying to engage the threads, before taking the tailcap off and shortening the spring. Could that compression have been too much for the cell, and started a chain reaction?

Thanks,

-John

 

[Sgt. LED]

You're probably fine. How much actually got on your skin?

Possibly compression but do you think you could of scraped any of the cell's protective wrapping off putting them in? Also when was the last time you charged it?

 

[jaundice]

Two final questions: what's the best way to decontaminate the inside of my maglite from the electrolyte inside? I just checked it out, and the "juice" inside didn't evaporate like the water that I poured inside it.

Also, should I ditch the other battery that was next the cell that went hot? It appears fine. The damage to the other cell was at the head, away from the "okay" cell.

Thanks,

-John

 

[jaundice]

Sgt. LED;

Thanks for your reply. No, I don't think I scraped the skin of the cell putting it in; I'm pretty anal about stuff like that. There was no binding when the cell went in the tube. Also, it was sitting in a PVC tube, so there's no chance of an external short circuit.

Only a trace amount got on my skin. I pulled the battery out of the light and then the PVC tube with my bare hands to prevent a worse outcome, but I didn't touch the small puddle in the bottom of my maglite.

The cells are/were fresh. I probably charged them two days ago, but I'd been using them a bit in my ROP low. I would estimate a 50 to 70 percent charge.

-John

 

[LuxLuthor]

My guess is your compression shorted the protection strip, essentially creating a dead short between the positive terminal and the negative battery can up near top of cell. In this instance, you would be bypassing the protection circuit. Look at these photos of protected cells I took apart to see what I mean.

I'm not sure how to safely get deposited lithium cobalt electrolyte out of the flashlight body. Maybe with a wire brush while wearing rubber gloves & goggles, brushing in a way that has no brush spray on you. Don't know how much there is.

The other cell is probably fine and uninvolved in the shorted cell.

 

[Sgt. LED]

AH you're fine on exposure. Not sure what happened with the cell!

Juice clean-up. Nitrile (blue) gloves and eye protection, baking soda to soak it up, flush it out with ammonia based cleanser, then follow with paper towel rub down.

I would keep the other cell if it wasn't hot but I would be sure to keep a good watch on it for the next charging cycle just to be sure.

 

[jaundice]

Thank you, gentlemen. This makes me feel a lot better.

Yes, LuxLuthor, I believe you're right about the dead short. I'm sure glad I bought AW cells and not some cheaper ones. As far as I'm concerned, everything turned out all right.

I'll put baking soda on the electrolyte right now, while it's still liquid. I poured water down the tube, which then dripped through the switch, so I think this will require a full teardown.

I'll keep the other cell. It didn't get hot at all,and the casing is fine. I always charge with the cells in front of me while I surf the web, touching them frequently to detect overheating. I'll keep a double eye on it.

Thanks again,

-John

 

[LuxLuthor]

The most important tool to have when using Li-Ion cells is a DMM (Digital Multi Meter) to check voltage. If you don't have one, you can get cheap at Radio Shack, Sears, etc.

 

[jaundice]

LuxLuthor;

Yes, I have a DMM, and use it religiously when charging or using my cells. I only charge my cells to 4.1v and discharge to 3.6v or so, in order to preserve battery life. Plus, I am running a different set of cells in a Megalenium with a WA1185. I really see the voltage drop in the output, so I recharge long before I hit 3.0v. This cell that went out on me tonight was part of pair taht I was using in my ROP. I keep my cells segregated into groups that are identified by date purchased. They're always charged at the same time after being run down to the same or similar voltages (I use them sometimes in single-cell lights, but always charge them at the same time). Like I said, I'm pretty anal about my cell handling and usage.

Thanks for the advice.

-John

 

[LuxLuthor]

Sounds like you are way ahead of the curve. Congratulations!

Don't freak out too much about that short. As the photos show, there is not a lot of protection between the strip and the can. I would send a PM to AW. He has always been one of the best sellers on CPF, IMHO.

 

[jaundice]

Looking at the facts a day later, I think a major contributing factor is the ridges molded into the bottom of the D mag switch. When I tried to screw the mag tailcap into the body, compressing the batteries, one of the ridges must've compressed the protection circuit strip, causing the short. This is sort of a freak accident that thankfully turned out okay.

As far as I'm concerned, the AW batteries performed as advertised. The PTC vented out the expanding electrolyte, with no flames or smoke.

I'm going back and forth about keeping the unharmed battery. One part of me thinks that the pressure of the mag tailspring, though high, was within spec of the battery, and there was no ridge to pinch the circuit strip, so it should be okay.

Then another part of me thinks that I would gladly pay $12 to avoid a near miss like that in the future, so I should junk it and get a new one.

I'll have to figure out what my final mindset is.

This goes to show that as careful as you can be, accidents can still happen. I think, after I clean out the light, I'm going to build another battery tube, but one that completely holds the batteries with a normal powered spring.

Thanks,

-John

 

[jaundice]

I bought these cells from Lighthound, so I called them this morning, and they took care of it immediately.

Great service, as usual.

-John

 

[LuxLuthor]

Great ending to an initially worrisome story. :thumbsup: to Lighthound.