I have several of these. They are fantastic for camping trips, and will work decently even when not directly pointed at the sun. I just go "bump" the panel ever couple of hours.
I would suggest you pick up at least one extra charger/battery set, if not more. That way, one pack can always be charging (From the panel) while your device is recharging (From one of the fully-charged battery packs.
Mine will fully charge a pack in a little less than four hours.