Whether you hike, camp, or just drunkenly lie in the sun at Coachella, a solar backpack’s an outlet-free way to juice up your gear. But you might not have upwards of $200 lying around. If you ARE rich in time and patience, Treehugger’s got a tutorial via Instructables for wiring up your own solar bag.
Here’s the gist of it: You attach four encapsulated two-volt/200-milliampere solar panels together, fusing their wires with a soldering iron (you have one of those, right?). When you end up with a positive and negative cable, you connect it to a battery box to charge four NiMH batteries. That part looks pretty tricky -- please don’t electrocute yourself (or get into a soldering gun battle ... that shit burns!).