Eleaf are the go to brand for built in battery and quality. This device is the new version of the Eleaf IStick 80W which utilizes the same battery life (5000mAh) and its all built in. Charging via USB type c for quick charging makes this a very good contender for a powerful mod without external batteries.
 
Specs:
5000mAh built in battery
USB Type C
510 Thread
Variable Wattage
 
Box Contents:
1x Eleaf IStick I Power 2 mod
1x Charging Cable
1x User Manual