One of the most abundant things on this planet, essential for life, is water. Water represents the building blocks of nature and it is all around us in one form or another. Even our bodies, 70% of which is made up of water, needs water, both to sustain us as well as act as a medium to transport minerals and nutrients in, out and throughout. Water is not just a chemical cocktail of hydrogen and oxygen. Its chemistry aside, it has other properties too. One of them is its heat properties, it's corrosive properties and its ability to conduct energy, both in form and in chemical composition.
Because of its versatility, and its ability to be restored to it's natural state, water is the ideal medium for many tasks. For instance, not only does our body owe its shape to water, as it fills our cells, it also courses our veins carrying nutrients and other biochemical products as well as oxygen and carbon dioxide. Because of its versatility scientists have begun to seriously consider water as a source of energy as well. As such, the first to reach the market in a useful way, has used water as the main reactant in a AA battery. Regular AA batteries are loaded with chemicals that can be extremely hazardous. The electrolyte that reacts with the zinc or the magnesium in the battery can result in burns when exposed to it.
The water batteries however, have no such problem. Aqua Power System Japan were the first to introduce NOPOPO - an eco-friendly battery that generates No Pollution Power - thus the name NoPoPo. The battery is completely rechargeable and it can be totally recycled. The water used within the battery is regular drinking water. No need for special water like that used in a car battery. In fact, it's not really a battery because it doesn't store the charge, it actually generates it - from water.
NOPOPO, with a shelf life of 20 years, can generate 1.5 volts of electricity and 500 mili-Amperes on a few drops of water. The battery comes with a device that helps to drop the water in to the battery, or you can just place the batter in a cup of drinking water and wait while the water seeps into it. Then just dry the battery and place in the device and the charge is enough to power it up. You can find out more about NOPOPO on their website and buy NOPOPO batteries here.