And it isn't a battery, not technically at least. It's a 4-inch-high fuel cell that should last 10 times longer than the batteries it was designed to replace.

Its inventors, founders of a firm called H2Volt, have joined the hunt for one of the technology industry's Holy Grails -- a new power source capable of running the portable electronics products that grow more complex every year.

As phones shoot pictures and download songs, as music players keep calendars and sprout video screens, their thirst for electricity swells. Rechargeable batteries as well as the throwaways that line supermarket check-out aisles have improved, but not fast enough to keep up.

Some companies are trying to keep the battery's basic design while using different chemicals to lengthen its life. Others, such as H2Volt, envision a future running on micro fuel cells, which generate power from small amounts of fuel. The hunt has attracted major tech firms. H2Volt, for instance, is backed by German communications powerhouse Siemens.

"We're going to go from hours on a laptop battery to days. Or from days for a cell phone battery to weeks," said Farshid Arman, a Siemens director of venture technology who sits on H2Volt's board. "There's no sense having wireless applications if you need a wire for energy."

Other companies pursuing their own cells designs include IBM, Motorola and
NEC.

So far, however, the goal of a cheap and powerful micro fuel cell has proven elusive. Toshiba, for example, planned to introduce a fuel cell for laptop computers in 2004. That didn't happen and the cell's release was delayed, again, this year.

Optimists say the fuel cell business is about to take off, with one recent study from research firm NanoMarkets estimating the market to be worth $1.6 billion by 2010. But the products have been notoriously slow to hit store shelves.

"With micro fuel cells, they're always two years off," said Rob Enderle, president of the Enderle Group tech industry analysis firm. "The fact is, we are finally seeing light at the end of the tunnel. People are building prototypes that seem to work."

There's no lack of competition. More than 60 companies are working on micro fuel cells that use methanol, according to a Mountain View company that makes a key piece of such cells. And methanol isn't the only potential fuel being explored.

"Used to be, we'd see 20-piece orders," said James Balcom, chief executive of PolyFuel Inc., which makes thin membranes used inside fuel cells. "We're now seeing 200-piece orders." A typical laptop fuel cell, he said, uses about 10.

Although the need has existed for years, the tech industry's latest incarnation has made it more urgent. Mobile devices that tie into the Internet, play songs and videos, and oh yes, make phone calls draw more power with each new function. A largely glowing review of Apple's new video iPod in the New York Times, for example, noted that the battery died after two hours of videos.

Rechargeable lithium-ion batteries have been the standard for most portable electronics. But the need for more juice has led some companies to tinker with the chemical mix. PowerGenix in San Diego, for example, has developed a battery using nickel and zinc, a change the company says allows its battery to be smaller than competitors' while delivering higher voltage.

Much of the research in the field, however, centers on micro fuel cells, shrunken versions of the same devices that some researchers hope will one day power cars.

Whereas rechargeable batteries store electricity, fuel cells generate it, for as long as their fuel lasts. A fuel cell uses oxygen and hydrogen in a process that takes electrons from the hydrogen, sends them through an external circuit to generate power, and then combines the elements into water.

The difficulty lies in making the devices small and light enough to work with laptops and phones as well as cheap enough to mass produce. Many fuel cells, for example, use platinum as a catalyst -- hardly inexpensive.

Medis Technologies has created a fuel cell that doesn't use platinum. The New York company plans to start selling its disposable Power Pack next year and recently hired a company to build it in a production line capable of cranking out 1.5 million of the devices per month.

Each Power Pack can fully recharge a typical cell phone five or six times, according to the company. Or, if the phone's battery dies, the pack should provide about 20 hours of operation. Medis plans to sell them to mobile-phone companies for about $8 apiece, and those companies will then sell them to customers, Chief Executive Officer Robert Lifton said.

Medis also is developing a version of the power pack for the military. The recent Gulf Coast hurricanes, which knocked out electricity across swaths of the South, have demonstrated the need, Lifton said.

"People have now found out that in disaster areas, it's highly desirable to have some way of powering your cell phone," he said.

H2Volt also wants the Pentagon's business.

The company is working with the U.S. Navy to develop fuel cells for wireless sensing devices. While most fuel cells use liquid chemicals, H2Volt's uses dry fuels, which should make them substantially lighter.

Military sensors probably won't need fuel cells as small as cell phones would require. Focusing first on the military, therefore, should give H2Volt income while the company continues to shrink its product, a strategy the company emphasizes while hitting up venture capitalists.

"If you go out there and say 'I need $500 million, and in three years, you're going to have the teeniest battery,' that's the end of the meeting," said Stefan Heuser, president and chief executive officer of the Siemens Technology-to-Business Center.

The center, based in Berkeley, seeks out and funds research on products that Siemens could one day use, typically spending $300,000 to $800,000 on each project. The center also acts as a kind of incubator -- giving the companies it backs advice on bringing their products to market -- and H2Volt operates out of the center's Berkeley office.

Despite the intense interest in micro fuel cells, some researchers don't see them supplanting conventional batteries in the near future.

"It's still a little ways down the road," said Daniel Doughty, manager of the advanced power source technology group at Sandia National Laboratories. "For small amounts of power, batteries are going to be hard to beat."

A fuel cell is, after all, a device rather than a simple repository for power. It must bring in oxygen and combine fuels at a measured pace, Doughty said. And the mechanics for doing so are hard to shrink while still ensuring reliability, he said.

"All these mechanical systems are difficult when they're miniaturized," Doughty said. "I think these things will happen, but they'll happen for larger devices before they do for cell phones."