GoPro Dual Battery Charger for HERO4 

Conveniently charge your HERO4 Black or HERO4 Silver
camera batteries with the Dual Battery Charger, the only GoPro charger that
allows you to charge two HERO4 Black or HERO4 Silver batteries simultaneously.

Featuring USB compatibility, you can power it with most
standard USB power adapters, the GoPro Auto or Wall Charger,1 or a
computer.2 Dual LED indicator lights display the charging status, so you know
when your batteries are ready for action.

Package Include:
GoPro Dual Charger(Does not included Battery)
USB Mini Cable

Charge Two Batteries Simultaneously
Power from Nearly Any USB Source
Dual Charge Status Indicator LEDs
Works for HERO4 Black and Silver edition.
Power Requirements: 5 VDC USB bus power