When I was preparing for my backpacking trip to Yellowstone, one of my concerns was carrying enough batteries for my headlamp, gps and a way to recharge my iPod. At one point we were on the trail for 8 days straight with no re-supply and I did not really want to carry that much extra weight. Being the cheap pseudo-geek that I am, I did some research and opted to build my own solar battery charger. This is a VERY simple task for anyone that has the slightest bit of soldering knowledge. I found lots of great ideas from the website Instructables.com. From these ideas I ordered a flexible 7.2V panel which is .02 inches thick (yes..2/100ths) and weighs 0.9 ounces.

When I first made it I did not have the pouch and my solder joints were not the best and it failed (solder joint pulled loose). On the second pass, I put a little extra solder on the joint and taped the wire to the back with duct tape. This kept them from moving and solved the issue with the solder joints and covered the wire in shrink tubing (also from radio shack). I added the pouch (something I had found on a hike once and packed out....figure it might be useful one day...) to store the batteries and batter holder. This keeps the pull on the wire down to nothing.

Without the pouch & carabiners the charger weighs in around 1.1 ounces. The pouch & carabiners add about 3 ounces. I use a couple of small carabiners or big safety pins and clip it to the top/back of my pack. If we are stopped for lunch or in camp I will try to lay it in a sunny spot. On a really bright sunny day it will fully charge 4 AA batteries in about 6-8 hours. I found while hiking in the woods, it still charged the batteries in 8-10 hours. It is fairly durable, but still needs some TLC when using it. I was somewhat gentle with it when I would put it in and out of my pack, but you know how packs are still dropped and handled a little on the rough side, especially when scouts are hanging the packs (at Yellowstone you have to hang your entire pack at night, not just your food) and it made it through just fine.

For our hike, I carried 8 AA batteries....2 in my GPS, 2 in my headlamp, 4 in the charger. I would rotate the ones in the charger with other people in my group so we were able to reduce our overall weight by a few ounces. It still works great. We used it at home....figure a little green energy is a good thing. If you are not into soldering and would prefer this work done for you, you can get them pre-made for a few dollars more than the parts. The website I ordered my solar panel from is Siliconsolar.com and you can find pre-made chargers there as well.