Um, excuse me but I need to go, umm, recharge my cellphone.
Physicists in Singapore have succeeded in creating the first paper battery that generates electricity from urine. This new battery will be the perfect power source for cheap, disposable healthcare test-kits for diseases such as diabetes, and could even be used in emergency situations to power a cell phone.From this site we learn that:
The battery unit is made from a layer of paper that is steeped in copper chloride (CuCl) and sandwiched between strips of magnesium and copper. This "sandwich" is then held in place by being laminated, which involves passing the battery unit between a pair of transparent plastic films through a heating roller at 120 degrees Celsius. The final product has dimensions of 60 mm x 30 mm, and a thickness of just 1 mm (a little bit smaller than a credit card).
Using 0.2 ml of urine, they generated a voltage of around 1.5 V with a corresponding maximum power of 1.5 mW.
The capacity of cell phone batteries currently is about 2,000mW.So the average cellphone battery is 2000/1.5 = 1,333 times larger. But if the same ratio holds you would need 1,333 *.2ml = 266 ml or .26 liters to recharge. I think my 6 glasses of water a day ought to be able to handle that. If it works, it would be great for hikers and 3rd world countries where plugging in isn't very easy but, um, relieving oneself is.