battery/solar powered solution

Hello. I am looking into purchasing a beagle board.

What is the best solution for making a beagle board portable, with a
reasonable battery life? My project will only reqire a usb wifi dongle
on the beagleboard, no other addons.

My main focus is building low voltage peak power trackers:

I have an 8 watt solar panel which rolls up and weighs 3 ounces.