I can run my Indulgance @ 7.4 volts but the vape is way hot and it eat's juice at that voltage. Even at 6 volts I find the battery life is short. I find for the best all around performance 3.7V using a 18350/900mAh, & LR atty, or 3.7V with a 18650/2600mAh , & LR atty. provide great vape and battery life, The 18650,s last forever but it dose make the mod about 3 inches longer then using the 18350's.