"As soldiers carry more portable electronics, battery weight becomes an issue. On a 72-hour mission in Afghanistan, a US soldier will carry 70 batteries for such devices as night-vision optics, GPS, imaging systems, and communications gear. This adds 20 pounds to a combat load, one-fifth of total weight, says the US Army Research Laboratory (ARL). The load can contribute to fatigue and affect movement during combat. On the cost side, an infantry battalion spends $150,000 per year on batteries, its second-largest expense after munitions, ARL reports.
Sustainable power sources are thus high on the Pentagon’s must-have list of soldier technologies. One promising concept is biomechanical energy harvesting, in which body motion generates electricity. SpringActive Inc. of Tempe, Ariz., is developing such a device, which it calls SPaRK -- Soldier Power Regeneration Kit -- with funding from the Army’s Natick Soldier Research, Development, and Engineering Center in Natick, Mass"
Whole article here:
http://www.designnews.com/author.asp?section_id=1365&doc_id=235935(Pretty cool, imo)