Originally Posted by
slowpacer
I an also on a hunt for 18650 batteries for an older Fenix light. Seems like they have cells that charge directly with a micro usb cable without a need for a charger.
https://www.fenixlighting.com/produc...ble-batteries/
I have 2 Panasonic cells that were left in the battery case for a few months without use and they don't take charge anymore. I don't know much about batteries except for higher mah lasts longer, but wonder if these cells would've still worked if they had protected circuit.
The FENIX site says:
"The high capacity 18650 Li-ion rechargeable batteries each provide protection circuits in the anode to help prevent short circuits,
over charge/discharge and over heating. "
Supposing you stored the PANASONIC cells at a very low state of charge, they could have self-discharged further, to the point where whatever you charge them with will not start charging as it might not be able to do so safely.
The FENIX site states it's protect circuit will prevent "over discharge". Probably that's while something is using the battery - like your bike light. While in use, it will shut off if you try to drain it too much (too far?).
Most likely if you drain the FENIX, then store it for a couple of months, it will not be able to charge either due to self-discharge. Seems like a lot of my bike lights say to charge them before storage and charge every three months.
I'm happy to get into the reasons why lithium cells have these protections baked it, but the ultimate answer is "prevent fire". Secondary answer, "lawyers".