I just started using two 18650's, first because I got one of those high-powered flashlights [wow!! really bright] that uses one of these and second because these seem to be a real advantage where they can work. Who is using them and for what? My flashlight has a Cree XM-LT6 led. I might have made a mistake in getting unprotected cells, but when I ordered them, LG 2600 mah, I thought protection related mostly to charging, not excessive drain or over-discharge. I can handle the charging OK with my DC constant voltage/constant current power supply, probably better than most li-ion chargers. I probably will buy only protected cells in the future. Lots of reading on charging, discharge rates, shorting, and over-discharge strongly suggest protected cells are much safer and better. Regardless, these are light, pack lots of power, and seem to have lots of advantages over NIMH or nicad, where they work. I also have a led flashlight that takes the typical 3-pack of AAA's, and I found that the case and spring have room to take one 18650 - sweet. I have an RC boat with a nicad battery pack, 7.2V -- two 18650's pack far more power and a lot less weight. I also am making a handlebar mount for the high-powered flashlight so that it can be used as a bicycle light. For the high-powered flashlight, I discovered a backup plan using a CR123A lithium primary cell and a spacer made out of 1/2" copper pipe and end caps. Cool. Other experience from anyone?