And now I will throw a monkey wrench into the works.... I have just started making regulated mods but have been making mods using 4 AAA NIMH batteries for a while (thanks Puck). Love these things, no protection needed, buy them at local stores, good for thousands of charge cycles and cheap $10 for 4. 1.2V each (fully charged 1.4V), no charge fall off until drained. Next mod I will use 6 batteries for 7.2V and an 8100 regulator evercool circuit. I have been playing with litium batteries but these things are too expensive and don't last as long unless you get the really expensive ones.