[ORIGIN M.]

Originally Posted by bradleyland

Water is not an energy source. It is, at best, a component of an electrochemical process; usually as an electrolyte. There has to be another energy source though, because H2O is a stable molecule.

I have a feeling that you're probably referring to the Phinergy battery, which does not "run on water". In the Phinergy air-metal battery, the anode is aluminum, and the cathode is oxygen. The water acts as an electrolyte, which means the reaction can't occur without water, but water is not the source of the energy; aluminum and oxygen are.

Phinergy introduced their battery back at the beginning of 2013, but have yet to bring anything to market. Commentary I've read by chemists express concerns over the deterioration of the anode in an aluminum based chemical reaction because of the extremely hard nature of Al2O3. Once formed on the surface of the aluminum, it has a tendency to prevent further reaction. An obvious problem for chemical engineers to solve, but not necessarily a simple one.

Water and aluminum correct.

There is one major car company that will be using these batteries soon enough.