Hey there, time traveller!
This article was published 26/7/2013 (1226 days ago), so information in it may no longer be current.
The newest source of battery power for your cellphone is both cheap and abundant. Scientists at the University of the West of England in Bristol report microbial fuel cells using human urine can directly power a cellphone battery. As it cascades through a series of fuel cells, hungry bacteria consume it and release electrons, which generate an electrical current. After 24 hours of charging, a Samsung phone stayed alive for 25 minutes -- enough to send texts and make a six-minute call.