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Lithium Ion Battery Failures

I’ve had two encounters now with lithium ion batteries that have failed, became thermal runaways, and  ended up venting, exploding and catching fire in the process. Believe me, they can release a crap load of noxious gases and smoke in a short amount of time and start a fire rather easily. It’s not an exceptionally common occurrence but if you don’t play by the rules when dealing with high density batteries it does happen. If any one of the protections used on any level is compromised they can and will go ballistic, and I mean that in the literal sense.

My first encounter with one  of these batteries exploding happened while using a Cree LED flashlight poised over my shoulder and my head stuck in the side of a computer case on the bench. Suddenly there was a loud pop with a flash of light and the next thing I know is that the Cree flashlight was no longer with me and there’s smoke and fumes filling the room. My first thoughts were damn, that thing wasn’t even plugged in, why did that capacitor explode? Of course about that time I was also running for the exit and some fresh air. I grabbed a fresh lung full of air, reentered the room and found one of the 16340 (CR123) batteries venting in the computer case and the other one still on fire behind the bench. I put it out and hit the exhaust fans until things cleared out a bit before returning.

When the batteries exploded it swelled the end cap that holds the LED/heat sink/driver assembly in and blew that and the batteries out the front and the main body of the light ended up on a shelf on the opposite wall. I spent 15 minutes trying to find that part of it. Anyhow, it didn’t damage the threads on the end cap or the case so I put some batteries back in it and it works fine.

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The second time was just the other night and involved a 16340 battery that had been left charging in the shop/boiler room adjacent to the studio and main room in the basement. Suddenly there was a load bang and what sounded and looked like a model rocket engine going off in the other room. This is what I found:

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In the both cases the protection circuits failed resulting in  a thermal runaway condition. The Cree batteries and protection failed under load and a long duty cycle so I’m assuming the sustained current draw had something to do with that failure. As for the second occurrence, that was partly my fault, you should never leave LiOn batteries charging and unattended. Don’t assume the cheap Chinese chargers and the built in battery protection won’t fail because if it does so at the wrong time you can have a big problem on your hands. Also keep in mind that there have been instances where the battery was under neither a load or a charging condition and self destructs, just store your batteries in a safe manner.

The biggest problem I see is the cheap chargers for 18650 and 16340 batteries that are flooding the market. There’s also been instances of knock offs being sold with brand name stickers on them and no protection circuit in them at all. Just buy a good charger and try to watch what you’re buying for batteries.

All the high energy density batteries based on lithium ion are very susceptible to voltage and temperature as well as the curve of the charging cycle. If they don’t operate within a specific window of set conditions you’re going to have problems every time. Here’s a graph that was posted in an article by Electropaedia  showing the acceptable operation limits. You can see the rest of the article HERE or click on the graph for a larger image.

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Keep all this in mind when you’re getting ready to purchase that electric vehicle folks. Do you really one to set on one of these that weighs in at over 3/4 ton?

At any rate just be aware of the inherent dangers involved when using them and try to avoid the cheap Chinese chargers as well as any of the knock off batteries  you might find out there.

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