I haven't ever used the 18650 batteries so I can't speak to that. On another note, if the light only has one LED, I don't see how 1800 Lumens is even possible. According to the datasheet from Cree, the XM-L line of LEDs, "...can deliver 1000 lumens..." unless I am reading it wrong. The data sheet I found was here: http://www.cree.com/~/media/Files/Cr...g/XLampXML.pdf