I am very much considering doing this Nintendo DS Lite hack myself. In short, you wire solar panels to your DS (4 or so small, high quality panels) and then let your DS charge in front of a window that has sun light. No more wasting power by plugging your DS into the wall. Apparently this works pretty well too.

One problem, however, is that the DS will be slightly more bulky. This isn’t a problem for some people, but for those who have a case on their DS (I have a bulky Nerf Armor Case) it may make it too annoying to stick in your pocket. Because of this, consider making your solar panels detachable. This is probably for the best anyway, seeing as how they panels may get bumped around if in your pocket. Click the below link for a DIY (do it yourself) guide on attaching solar panels to your DS lite. If you have another DS type, such as the DSi or DS normal, then things may be slightly different, but overall the same.

Source: Instructables