Fenix 16340 rechargeable battery problem


Newly Enlightened
May 23, 2021
East Anglia, UK
Hi all,
I seem to have a problem with a Fenix 16340 rechargeable Li-ion battery and I'm hoping you may be able to shine some light on it (Pun intended 🔦)
I bought this battery to use with my Fenix E15 so I would be able to recharge it easily and if away from home with its built-in mini-usb socket.
It has worked OK until recently when the E15 will turn off when turbo/level 4 is selected and then will not work at all, until placed momentarily back on charge.

I have tested it today as follows:
I placed the battery in the wall charger until the green light indicated it was full.
I then tested it on my battery charger and it read 4.51V.
I put the battery in the Fenix E15 and cycled through to turbo/level 4 and it very briefly came on & then turned off. It would then not work on any level.
I placed it in battery tester & it showed no reading at all.
I placed it back in the charger and it went straight to green, showing full.
I placed it back in the battery tester and it showed 4.5V
I've tried the E15 with other batteries and all levels work as they should, so I assume the battery is defective, but it seems to work on all other levels except turbo, when it switches off.

If it's beyond saving then fair enough but just wondered if others have had this same problem and if it's a common occurrence.

Thanks for any advice or helpful comments.



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Flashlight Enthusiast
Mar 22, 2013
Southern Ontario
I don’t know very much about these USB rechargeable batteries. But why is it charging to such a high voltage? That battery should only be going to 4.2 V. If the built-in charging circuit and charging it all the way to 4.5 V. Then it’s definitely gone bad.