No matter where you are, you will always be able to charge your Go Pro HERO3 & HERO3+ batteries with the Power Bar Duo When plugged to the mains you can charge 2 batteries & the battery in your camera at the same time On the road it doubles as a power bank with enough juice for another 2 batteries or any other USB (Universal Serial Bus) port device Only compatable with HERO3 & HERO3+ batteries