I Order You To Pee On This Battery, Soldier

If you think your gear runs out of juice at inopportune moments, consider the infantrymen of the world, whose lives depend on their gadgets maintaining a charge. Thus the MetalCell, a magnesium-based battery that charges with salt water. Or urine.

The MetalCell, developed by engineers in South Korea, is an update on the Baghdad Battery, a device originating in Mesopotamia nearly 2000 years ago that is thought to be one of the first technologies to create voltage.

The updated version produces a charge when sodium—from soldiers' rations or their bodily fluids—reacts with the magnesium plates inside the battery's rugged box. The researchers claim that it can keep a laptop going for four hours on the initial charge, with additional sodium generating more juice. Barring any stage fright, that is. [PopSci]