Since I have never used rechargeable batteries...
I ordered a flashlight that can use either 3 x AA batteries, or 1 x 26650 rechargeable battery. I intend to use only the AA's. But I wonder if using 26650 would make it much brighter than using AA's? (and probably lasting longer)
I suggest using eneloops AA or AAA since you don't know a lot about rechargeable.
The 26650 cell is a very powerful lion battery and very dangerous cell if you don't know what you're doing. Read here if you'd like to know more.
http://www.candlepowerforums.com/vb/...000mA-exploded
That being said there are plenty of 3 x AA, 4 x AA, 6 x AA and so on flashlights that can be just as powerful as a single lion 18650 or 26650 cell. Which unit did you buy?