KR808D-1 passtrough doesn't has battery and delivering an astonishing 5.4-5.7V from USB port on my desktop PC.
I'm using a standard 808 cartomizer (came with kit). VG juice is too thick to use with this kind of voltage.
The voltage reading you are getting Is not your true Vapping voltage. You wold have to have your carto or atomizer attached to see what voltage you are getting with a load. You could use a high wattage (10 Watt 2.8 ohm should work) resistor that matches your carto's Ohms ratting to test the voltage however. Also with a little bit of math you can figure out how many watts and amps you are pulling through your Motherboard. I plan on making a stop at Rabbid Snatch (a.k.a Radio Shack) to pick one up to test some of my batteries.
I have to give credit to another thread for reminding me of this even though I should have remembered my self. It's just been a lot of years since I have done any component level work.
(Edit) Gotta love Pluck and Chuck trouble shooting these days.
(Edit II) Please be very careful not to short your leads when testing!