Hi guys, recently I have seen a video of susumu suzuki that shows a water activated battery. In the video, susumu mixes 2 powders and compresses them. Surfing on the net, I has found that these powders are magnesium and carbon. These cells can give energy from water but the worse thing is that they have only 2 or 3 recharging cycles.
http://www.crunchgear.com/2007/09/06/nopopo-batteries-run-off-liquids/
http://www.youtube.com/watch?v=B601aMfBirw