A battery that does not need to be pre-charged, and is very easy to make. It only puts out a moderate amount of juice, but it can run LEDs for hours, and charge up those cell phones (and other things) after the Grid is gone. Ingredients: Aluminum foil, copper foil, paper towels, salt water. That's it. Power starts flowing when you add the salt water. Pretty neat. Super easy. You can make it with scavenged copper roof flashing & Al foil. Invented by Volta around 1800, before Aluminum foil was readily available. History: Voltaic pile - Wikipedia, the free encyclopedia How-2 videos: What got me interested: SALt lamp runs on a glass of water and two teaspoons of salt Enjoy!