I have acquired a 24W monocrystalline solar panel to charge my portable battery pack while on the move. This panel will be able to charge all devices I carry on a regular basis with nothing but some sunlight!
Info on the panel itself. Rated at 24W with nominal 17.6v DC, 1.36A output.
I have installed a switching regulator in the back of the panel, where the connections would normally be wired straight to the array of cells. This regulates the voltage down to a constant 13.8v to provide more compatibility with 12v charging equipment. I have tested the output of the panel in late day sun, at 1.27A.