I do a lot of camping, and something a very commonly do (as I would assume a lot of people might) is bring along a cell phone, iPod, etc. On short camping trips I generally tend to buy a 24 pack of batteries and just use that with a USB charger, but on longer camping trips (usually about a week) I'll eat through those batteries within a few days. What's a cheaper solution to charge my stuff, as well as keep it as light and cost efficient as possible? (and the ability to get a full AC charging port would be great too).