I built it with a USB first and it wouldn't vape at all, even tried on a 2.1 amp usb 2.0 charger from the wall. I checked the connections with a LED and saw that there was voltage (I have no multimeter right now) Then I scraped the USB because I was reading online that it only put out .5 amps, and I went with a PSP charger that was 5v and 2000ma and I tried my dual coil tank thats only 1.8ohm (I know that was stupid now) the tank vaped good for maybe 3 pulls then died. All my other carts are around 2ohm and none of them will produce any vap at all.