If you don't have an external battery charger, get one! It makes so much of a difference in battery life compared to a usb charging removable batteries in the mod. This cost
Buy Vape Battery + Charger | Quick Delivery | Order Now - LA Rush
Best 18650 Battery Chargers for Vaping (2-Bay & 4-Bay Chargers)
eGo USB Charger Cord 510 Connection - Central Vapors
HoneyStick USB Charger for 510 Vape Pen Batteries
XTAR MC2 2-bay USB Portable Li-ion Battery Charger with Cable - Charges 18650, 18500, 14500, 16340, 26650
Everything You Need to Know About the 18650 Battery