Battery makers are charging up for a future of computing on the go as a new generation of mobile devices takes over from traditional desk-bound PCs.

The battery boom is coming as slimmer laptops, some weighing as little as 1.2Kg, are expected to overtake traditional computers in unit sales by 2009 in developed markets like the US, according to market research company IDC. Strong growth for other portable devices, such as game and music players, handheld devices and mobile phones, is also expected to propel battery sales as manufacturers look to squeeze out more life from their products.

The move to mobility should lift major manufacturers such as Sony, Sanyo, Matsushita (Panasonic), Toshiba and Motorola, as well as second-tier players like LG Electronics and a growing number of Chinese companies, such as BYD, analysts said. Further down the food chain, the boom is expected to propel a new group of aftermarket players to the forefront as demand grows for batteries to replace those that come with a product after they lose their re-chargeability.

In a world where weight and battery life are key influences on buying decisions, the race is on to find newer and lighter technologies that can run longer on a single charge.

"There are developments being made in improving capacity, but these are more evolutionary than revolutionary, and there doesn't seem to be a major breakthrough on the horizon," said Alan Brown an analyst at Gartner Inc.

Most non-disposable batteries in portable devices use lithium-ion technology, which can power an average laptop for up to six hours on a single charge and a cellular telephone for several days. But those numbers can drop sharply for heavy users, or energy-sapping functions like watching DVDs or bright screen resolutions for computers.

Dell, the world's biggest computer maker, is keeping its eye on new technologies that could extend the battery life of its laptops, said Asian marketing director David Schmook. But change has been slow to come.

"Lithium ion is what we have up and down our product line," he said. "The core technology hasn't changed in several years."

A new kind of battery just entering the market, lithium polymer, can wring about 10 per cent to 20 per cent more life than lithium ion, said Howard Tseng, global product manager for Burnaby International Technology, one of Taiwan's biggest aftermarket battery makers. Burnaby's clients include IBM. But these new batteries are around 50 per cent more expensive, said Tseng at his firm's booth from the floor of Computex, the world's second-biggest computer show, in Taipei, Taiwan.

As a specialist in the fast-growing market for replacement notebook batteries, Burnaby has recently embarked on a major expansion campaign that includes the opening of offices in Germany, Japan, Canada and the US.

The company, whose rivals include PortaPower and Battery Technology also hopes to make an initial public offering in the next one to two years, said David Wu, Europe branch management operator.

While they remain focused on lithium technology, Burnaby, Dell and other industry players are keeping close watch on newer fuel cells being developed on an experimental basis. Such cells, more often associated with cars, use hydrogen or other fuels for energy and are refilled rather than recharged.

Wu said a fuel-cell prototype on display at a recent trade show was about four times larger than today's typical laptop battery, which is about the size of a ledger book. But it also was said to run for up to an entire day, he said.

A Taiwan-based company called Antig is also developing fuel cells that would be the size of a CD-ROM drive, said Gartner's Brown. Toshiba has also developed a cell for use in PCs.

"But pricing, size and availability of refuelling cartridges are still likely to be an issue," he said, adding that it's unlikely fuel cells would be a viable option within five years.