Eco Factor: Portable battery made from old aluminum can, saltwater and charcoal.
The billions of batteries discarded every year pose a serious threat to the environment and to the scarce freshwater reserves, which provide potable water to billions of people. Rechargeable batteries do reduce the scare but not as much as environmentalists would really love. Instructables user “Egbertfitzwilly” has posted a nice DIY which allows you to make a battery at home using commonly available materials.
The battery uses a casing made from a recycled aluminum can, electrodes of copper and an electrolyte made from burnt charcoal and a saltwater soaked sponge. The battery can churn out a maximum of 0.5V at 3.6mA, which should be good enough to power a few LEDs in your backyard. Head over to Instructables for the complete DIY instructions.
