I did a write up on my blog somewhere on external USB portable powerbanks. I love em. I use em to vape or to charge any of my other gadgets. If you vape normal resistance with a stick-style 5v manual 510 passthrough, you won't trip the protections circuits. Anything over around 2.4 amps being drawn, will shut the power banks down, as they are designed to do. I have an EZoPower 6600 mAh and 12,000 mAh Powergen.I can vape for weeks on Powergen at 1.8 ohms. Its a good all around thing to have, sorta like a multimeter. Charge your tablet, phone, whatever you can via USB. Good for travel when you can't get to an outlet. Built in flashlight is good for vaping during blackouts.
