Nearly had a fire with 18650's, rubber-banded together

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Jul 2, 2015
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Just got saved by the Universe from a lithium battery fire! My rubber banded 18650 lithium batteries were smoldering and getting hot, but the bin fell by accident and when I picked them up I felt the battery pack with a rubber band were warm and they should not be. Look closer, & I saw that one was already smoldering. Lesson, never rubber band any lithium battery. I really thank that universe.

Note: The cells were not in service or connected


Types of 18650's in a rubber-band:
----------------------
Worst was the Nitecore .. plastic wrap was burned partially.
Soshine Li-on and LIFEPO4's were warm, but wrappers were intact


The Nitecore 18650, under service, had the lowest actual capacity compared to the Soshine's. (I won't be buying Nitecore products again.)
 
Why did you have 18650s in a rubber band?
 
I don't understand what rubber band is all about?
You got a cell internal short circuit due to a fall and high impact. Conclusion: never fall your batteries to save your house.
 
Yes if they were all isolated from load / charge sources, then had to be an internal fault.

No sound bank will have any activity creating any heat while isolated.

Nothing to do with rubber bands.

Probably very worn or even secondhand / recycled scrap cells
 
I like the LiMn chemistry, I've read that its close to LiFePO4 in terms of "safe"
battery packs are as safe as they are handled.
 
markz said:
LiMn chemistry
Pretty sure that is no longer a specific chemistry, may just an umbrella term for one family branch?

INR / NMC vs IMR / LMO are examples of more specific / modern chemistries in that family, and they have very different characteristics from each other.

But wrt risk of thermal runaway, no other widely used chemistry is as safe as LFP. LTO maybe, but too pricey for my taste.

You are correct that riskier cell types should be handled carefully.

Many say only charge / test etc out in the back shed, never inside a living space, never charge unattended, etc.

 
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