You can charge your Hero camera by using either its USB cable or with an external battery charger (sold separately). If you use the single-battery charger, it will take up to three hours for each rechargeable lithium ion batteries and two hours if charging only one at a time. For best performance when fully charged, we recommend storing them in temperatures between 40˚F – 122 ˚F degrees Fahrenheit (-40°C – 50°C) where they are less susceptible to damage from lower quality cells that could cause premature failure of their capacity over time.