There are so many different kinds of batteries, but here is what you need to know:
Connections
This refers to the connection between the battery (at the top) and the cartomizer (at the bottom). It is just a connection and does not make a difference on how well anything smokes, but simply denotes which parts are compatible with each other. I have used 3 different connection types: 808, 510, and EGo. The 808 is what I started with, and what I think most people will be most comfortable starting with. You can get different colors and styles for each to match your personality and vaping style.
Power
Unlike a battery’s connection, the battery’s power does make a difference in your vaping experience. The higher the capacity, the longer you can smoke before recharging it. As with colors and styles, each battery type comes in assorted power capacities, referencing the length of the battery (mm) or the actual capacity (mAh). For example, if you get the Volt 65mm battery, you are looking at it lasting about 4 hours of vaping time. I call them the ‘shorts’. The Volt 78mm are going to last you longer (about 6-8 hours). They are like having ‘longs’ as far as the size. I recommend people start with the 78mm because of how much longer it lasts, while still being thin. Generally speaking, any battery rated in mm will be smaller capacity than any battery rated in mAh.
You can get batteries that last much much longer, but they are not going to be the pencil sizes, they will be a bit thicker. For example, the Volt X2 comes in 650mAh (they last about 2 days for me), 900mAh (they last about 2-4 days), and 1300mAh (a week or longer). I like using higher capacity batteries so I don’t have to recharge them so much.
Pass-Throughs
These are batteries that you can charge while you are using them. This is especially nice when you only have one battery with you, because if it dies, you can still use it as long as you are close to a computer or power outlet.
Happy Vaping everyone