My favorite portable battery yet, the UNIFUN is the sturdiest pack I've found. This 10400 mAh battery is perfect for use on a bicycle, motorcycle or camping.
I do not trust the charging system on one of my motorcycles, and for long road trips apps like Waze and evidently the podcast player run down my iPhone 6 pretty fast. This pack allows several full recharges of my phone over a multi-day trip. It is also small and tough enough to allow me to put the battery in the handlebar mount, and ride with the two connected. I'm not worried the constant buzzing of my bars, or random rainstorms, will damage the battery.
While slightly larger than its less rugged cousins, this battery will hold up to some adventure. It offers 2 USB charging ports, one a higher speed 5v/2.1A and one the other 1.5v/1A, and a flashlight.