I had an investment in 901 attys and carts and wanted to step up to a better battery because i too was freaking out when i had to leave the house for more than 6 or so hours. I went with the wicked mega tornado with an adapter and have been very happy. I get all day
vaping with it, and the charging with the usb mega charger takes 2.5 hours or so. Not sure how it does that, but it does, and so far battery life has been great (only using it for about 2 weeks now so we'll see how it goes).