Well I've got the batteries in and have been vaping for a few hours. I don't know but it seems like I'm getting a bit better vape at 8-9 watts with the stacked batteries than the single 18650, more vapor and a little warmer hit. I switched over to mode one and tried at 4.5 volts and it was too damn hot of a vape for me but tons of vapor. BTW I'm using a 1.5 ohm cartomizer, 5ml tank. Back to RMS2 mode and at 9 watts it's a great vape. Now when I check the ohms on the device it's telling me my carto is 1.7 ohms, with the 18650 it reads 1.5 ohm true reading. The screen light is much brighter could almost use as a small flashlight. Battery cap won't screw on all the way (button tops) not a big deal. Battery cap not getting warm when vaping. Vamo reads 8.2 volts fully charged. I vaped a little heavy for a bit and pulled the batteries and they were not warm at all. So far so good, have the batteries marked so I can rotate top to bottom after every charge and keep them in a pair. When I get my other set of 18350's I will use these for mini mode single 18350 when I take to work. I'd just like to say I'm very happy with my Vamo, it's the absolute best mod on the market for the price. Like it so much have a SS Vamo on the way with some vivi nova heads. Ordered the SS Vamo and vivi nova's from Vapor Break $29.99 for the Vamo and $6 a piece for the viva nova's can't beat that price.