For my Epic 4g I was able to buy 2 batteries and a charger for less than $8 on Amazon. The charger even has a USB port on the bottom so you can charge an extern

For my Epic 4g I was able to buy 2 batteries and a charger for less than $8 on Amazon. The charger even has a USB port on the bottom so you can charge an external battery and your phone at the same time. I find it not too inconvenient to just keep a couple backup batteries around at all times.