Yesterday I commented on how good the 510 worked with the kr808d-1 cartomizer. It was great for awhile then it started tasting burnt so I took the 510 off the passthrough as I thought the power was to great. I was right, with the batteries instead of the passthrough it was great again and I vaped all day untill I got a headache from to much vaping. I have found my setup thats perfect. Now I just need to work on battery life not voltage.