I'm sure happy I read this thread. I'm a newb and just bought a double Li-ion cell flash light with plans on using an unprotected Panasonic 18650 with a WF139 charger. YIKES! Going to make sure now to get a Voltmeter, AW protected cells and a decent charger like a PILA. My unprotected 18650's well run in My Klarus XT10 now. Thanks guys!!!