MADISON, Wis. – The final phase of a high-stakes military contest began this week in the California desert as teams tested battery systems designed to be powerful enough to sustain soldiers' energy needs but light enough for them to wear on their vests.

The million-dollar contest aims to relieve troops who use battery-powered equipment such as night-vision devices and GPS units. The current batteries come with a “heavy” price – they add as much as 20 pounds to soldiers' loads.

The Defense Department hopes to provide lighter batteries that pack a stronger punch, allowing soldiers to carry more equipment. To encourage the development of such power systems the military launched the Wearable Power Prize competition, which culminates with testing and judging within the next two weeks.

The requirements are stiff. The battery system must generate an average of 20 watts of power for 92 straight hours, weigh less than 9 pounds and attach to a soldier's vest.

Troops on average carry enough batteries to produce 150 watts per hour, said John Hopkins, the program manager for the competition. That amount of power can run a standard laptop for 10 hours.

The power system that wins the contest should produce three times that amount – about 480 watts per hour – a mark Hopkins calls aggressive but attainable.

“The bar is high – that was always the intent from the beginning of the competition,” he said. “But clearly we believe it's doable.”

Almost 170 teams entered the competition announced in November. That number was whittled down to the 48 teams who began competing in Twentynine Palms, Calif., on Monday. The three winners will be announced Oct. 4, with first prize worth $1 million, second prize $500,000 and third place $250,000.

The entrants range from large corporations and universities to individuals who ran late-night experiments in their garages after putting the kids to bed.

Rayovac-Remington, the Madison-based division of Spectrum Brands Inc., has a team of 10 engineers who have worked on the project since January.

Team leader Greg Davidson wouldn't reveal many details about their entry but said it built upon the company's lithium-ion research, which has led to batteries for products like high-definition TVs and network printers.

“We're confident we've met all of the requirements,” he said. “But anything can happen on contest day, so yeah, we're a little nervous.”

The contest does not allow the use of hand-cranked power systems. Hopkins said a person can produce about 30 watts of power with two hours of manual cranking but the effort is exhausting.

“The goal here is to give power to soldiers, not extract it from them,” he said.

UltraCell Corp., an entrant based in Livermore, Calif., has made smaller power systems for the military. The firm makes fuel cells, which combine hydrogen gas with oxygen to produce electricity. Whereas a battery eventually runs out of juice, a fuel cell can run as long as fuel is available.

Ian Kaye, UltraCell's director of advanced technology, said it was challenging to meet the contest's dual requirement of tripling the power and halving the weight.

“With the specifications we're given here, it's really pushing the limits for everybody in the power business,” he said. “It's realistic but very aggressive.”

He declined to preview UltraCell's entry except to say it relies upon the company's fuel-cell expertise.

Hopkins, the contest spokesman, said the winners will gain access to top military officials who have purchasing authority. Pentagon officials also will keep an eye out for promising technologies that get disqualified on technicalities, for example if an entry fails to run for 92 straight hours because a wire becomes disconnected after 91 hours.

That's the fear of Mahlon Wilson, a former fuel-cell engineer with the Los Alamos National Laboratory in New Mexico. After he was downsized in January, he used his severance package to finance the 60-hour weeks he invested in a one-man run at the top prize.

Wilson devised a fuel-cell process that runs on methanol. That provides hydrogen as a fuel source and carbon monoxide as a heat source to power the process. But the prototype he's entering is the original one he built and tested, leaving him worried that something might wear out during the competition.

“There's a lot more things that can go wrong than can go right,” said Wilson, who named his company Aviani after his wife's maiden name. He's still buoyed, however, by the idea that his single-person operation granted him the freedom and creativity that his deeper-pocketed competitors may have lacked.

Beyond the military applications of the entries, Hopkins said the newer technologies could eventually trickle into the public sector. Perhaps the know-how generated in the desert could lead to longer-lasting laptop batteries, he speculated, or to products for outdoors enthusiasts or emergency professionals.

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