Definitely go with an Ego style battery, get away from the Cig style.. your trying to Quit the analogs remember... if you want to keep it small stick with a 650 mAh, and a carto for those stealth vapes.. plenty of vendors out there that offer quality products and have good Customer service, and you have the ECF to turn to when your ready for your next big Upgrade lol, Have fun with it, because it is an Adventure , every day I find a new mod, or tank I just have to try.. !!