I got my original kit from premium e-cig - it's auto kr8 batteries, usb adapter and wall charger. I bought 2 extra batteries from V4L, and all my cartos are v4L as well. Here's my issue, I have problems sometimes with the cartos not working, i thought it was a battery issue (thought one was dead) I know the batteries are all charged, and i know my cartos are all working, but sometimes I'll put a carto on one battery and it won't work. No vape, doesn't get warm. But i put a different carto on that same battery and it works fine. Or I'll put that same carto on a different battery and it works. What's up? Am I doing something wrong or is this a compatibility issue?