Electronics > Projects, Designs, and Technical Stuff

Deliberate Lithium cell overcharging

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ThinkingGrenade:
I need to produce a overcharge condition in some typical 18650 cells (and large Lipo's) for training with our local fire and rescue service. i can pop 1 or 2 18650's with my bench power supply, but i need to do it with 8/10 (or more) cells at the same time. 

- a quick background - I live on the Isle of Man, every year the TT races are held here (google it) and for the last few we have had a race dedicated to Electric bikes (they aint slow) - some of which use a huge bank of 18650's. there was a fire last year that involved one of these packs, and the Fire service want to do some training with some new fire fighting mediums, specifically designed for battery fires

 ) 

 I work for a company that provides fire equipment and i know how to make most things go boom, but im asking you guys, as my experience is limited with this kind of thing......

NiHaoMike:
Connect them all in parallel with a welder. Shouldn't take too long to get some flames.

AG6QR:
It's not my area of expertise, but it sure sounds like fun!

My naive approach would be to first charge them fully with a proper charger to fill them with as much energy as practical.  Then, put three in series, and put them on a big charger intended for car batteries.  If you want to make more go off, wire up multiple parallel combinations of three in series.

Of course take appropriate safety precautions by keeping them far from humans and far from combustibles.

And have the cameras running!

MagicSmoker:
Overdischarge until at least one cell experiences voltage reversal reliably damages all lithium chemistries, but the real fireworks mainly occur during subsequent charging, particularly at currents >1C (e.g. - >4A for a 4Ah cell). However, the LiFePO4 is particularly tolerant of abuse and can take 4C charging in stride so wouldn't be the best choice if you actually want something bad to happen. Any of the Cobalt-containing chemistries should give you the kind of surprise you're looking for, but do make sure you have a blast shield of some sort if using 18650 or larger cells.

KC0PPH:
Go buy an EDF RC airplane that runs off of 6S batteries. Fly the piss out of it for a few days fast charging each time, they should start puffing up pretty quickly (keep throttle wide open). Once they are puffed nicely then put them on a bench supply and charge with as fast of current as you can give em. They will make a spectacular show.

Batteries that are new tend to not be as entertaining to blow up, however well used ones with high IR tend to be exciting.

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