Urine-powered battery

We all have heard about using renewable energy to charge batteries, but what about harnessing the power of liquid waste from humans? This battery uses urine to keep itself charged, producing approximately 1.5 volts which is the equivalent of what you find on the standard AA battery. The Pee Battery has a total running life of 90 minutes at the moment, but that can be improved by adjusting the geometry and materials used. This is made possible since urine has plenty of ions that enables the electricity-producing chemical reaction to take place in the battery as well. Other human bodily fluids such as sweat and tears are known to work as well. I can imagine the result of marrying this battery with the Relief Bag, ensuring your cellphone and other gizmos get enough juice despite being stuck in a jam.