After running an Olight S20 for an hour or so last night, I popped the battery (a Samsung ICR18650-30B) into my almost new Xtar VC4. The charger refused to recognize it, although it readily recognized and started charging a Panny 18650B out of another light.
I put the Samsung into a Nitecore i4, and again, no recognition.
Puzzled, I checked the voltage on the Samsung and was surprised to find it at 4.25v! I then put it into an old cheapo 501b to run it down somewhat (out on the deck!) thinking that if it was wanting to have a runaway and popped it’s cork it wouldn’t be doing much damage. Checking it later, it was down to 4.10 and seemingly still healthy, so I ran it down to 3.89 without incident.
Puzzled, I went back to the Xtar and saw that the channels in use (I had later added another cell) showed 4.20 v and were still charging - I popped out the first Panny 18650B I had put in and was shocked to find it at 4.49 v. I have no idea where, or if, it would have stopped, and I don’t know how overcharged that Samsung might have been when I pulled it out of the charger in the first place - but after a good run it was still at 4.25, so it must have been right up there. I suspect I seriously shortened the life of two otherwise very good 18650s.
I won’t be trusting this charger any longer. I guess the moral of the story is, don’t go trusting a charger at all! For now, I’ll go back to the old Nitecore and run it out on the deck when possible. At least the Nitecore always knew enough to stop at 4.18 v.
Any recommendations on a better charger?