make sure (as with any dual or triple 18650 mod) you use 'married' batteries... buy as a pair, charge together, use together, and rotate them. Also don't use the USB port for charging.
won't do it as evenly and Joyetech don't recommend using batteries that are 0.3V or more apart. Perosnally I only charge single 18650 mods (like the vaporshark rDNA 40 ) via USB. for the rest it is a Nitecore D4 intellicharger
make sure (as with any dual or triple 18650 mod) you use 'married' batteries... buy as a pair, charge together, use together, and rotate them. Also don't use the USB port for charging.