When you're heading out for an adventure with a Knog PWR bike light, no matter how big or small, snag the Knog PWR Bank Battery for a sure-fire backup to give you the support you need. This handy battery pack acts as a backup to your light, but can also charge other devices through its USB cord for power on remote journeys. It features a USB port that allows you to plug it in and load it up with life, or plug in your phone for some much-needed life when you hit the top of a ridge and find a little bit of cell signal. The battery packs come in small, medium, and large sizes. The amount of battery life each battery bank will supply varies depending on which light head they are hooked up with, but you can expect the smallest bank to offer just shy of an hour of power to a 1000-lumen head, and the largest to supply several hours of power to a 1000-lumen head, with the medium falling in between with 2 hours of power for a 1000-lumen head. All are capable of supplying sweet life to your phone, GPS device, Garmin, Bluetooth speaker, or head lamp.