How many have flashlights that use the 18650 Li-ion batteries?
I just got a new LED light (a gift) and found 8 of these batteries in an old laptop battery pack that are still good but look like unprotected batteries.
I did some research and found that you have to be really careful with the unprotected batteries (don’t run below about 3V to 2.5V and don’t leave in the cheap chargers after they are charged). The protected batteries have a PCB at the end and a conductor that runs the length of the battery that you can feel underneath the covering.
It looks like my Keenwin light has the protection built in to prevent draining the batteries too far even though its not advertised that way. It also has a smart charger built in that uses a USB cord.