Some of the things water batteries can power, they last years and need only plain water. You can also get a copy of how to make them at this link as well. http://www.youtube.com/watch?v=5sqgPk3snj8 (http://www.youtube.com/watch?v=5sqgPk3snj8)
To be more exact: 8-page pdf priced $8.99 to download. To power some LEDs.
http://www.lulu.com/shop/stephen-dickens/how-to-make-homemade-batteries-with-plain-water-that-last-years/ebook/product-20199028.html;jsessionid=817ACB095C884E15EFBC2E86B4625D68