What's in a cheap Chinese 18650??- Mtbr.com
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  1. #1
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    What's in a cheap Chinese 18650??

    I recently was gifted a flashlight that came with an 18650. I immediately noticed it was quite a bit lighter than some of my other 18650s. Also despite being labeled 3500mAh, it actually only reported ~1400mAh on my hobby charger. Shrink wrap on it also said "Short circuit, over charge, and discharge protection". Despite that, it was still discharging at 2V on my test rig.

    Since it was obviously a POS, I decided to see what was inside.

    What's in a cheap Chinese 18650??-18650.jpg

    In the lathe to cut the end off. Despite being down to ~2V it still made cute little sparks when a cutting chip from the case (-) would touch the positive terminal.

    What's in a cheap Chinese 18650??-18650-1.jpg

    Hmmm, where's the protection PCB? Musta forgot to stick one in there.

    What's in a cheap Chinese 18650??-18650-2.jpg

    Here's the "jelly roll" compared to the case. Notice that it is a lot shorter, like about 13mm? It also has a 10mm hole in the middle. Good 18650s are much more tightly packed.

    So the answer: A lot of air, hot air at that.
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

  2. #2
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    That's really scary, especially since seeing a bunch of those vape exploding battery videos.

    -Jeremy

  3. #3
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    Quote Originally Posted by Tunnelrat81 View Post
    That's really scary, especially since seeing a bunch of those vape exploding battery videos.
    The thing that bugs me most is the battery was labeled as having a protection circuit when it really did not. Someone putting this on a defective charger or a charger for something other than Li-Ion could have a nice firestarter.

    It did not seem like a short circuit would cause trouble. I shorted it across my ammeter and on a dead short it only produced ~2.5A for a few seconds then dropped rapidly. Pretty high internal resistance.

    All in all, an utter POS.

    I may dissect the light next time I am looking for a laugh. I can already say that despite claims of being a Cree XML T6 emitter, it really is a Latticebright or other XML clone. It is fairly bright though with a good battery in it. I'd never trust it for riding or important usage without a teardown and rework of any shoddy assembly though.
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

  4. #4
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    See Disassembly of GTL batteries of HKJ at his web page. Very similar to your findings. Also this might be interesting to someone: Information

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