I'm weary of getting my batteries from amazon or ebay. I like to make sure I'm getting them from a reputable bendor like Altsmoke.com etc. Batteries are what will make or break your mod as a pipe bomb or a great vaping pleasure. Of course this is just my opinion.
Great advise for "loose batteries" that you put in a mod.
I too suggest buying from
reputable e-cig vendors such as AltSmoke, Discount Vapors, My Vapor Store, etc. Buy only
name brand Joyetech Twist or
Vision Spinner ego batteries. BTW, "ego" is merely a type of battery, not a brand name. Buying "generic" ego batteries is always going to be hit or miss...mostly miss.
However, I have bought a lot of "other vape gear", mostly "rebuildables" on Ebay with great success. The key is doing you research before buying, knowing what you are getting, and reading comments from others who have purchased from the seller.