The Lawrence Livermore National Laboratory in the US recently demonstrated a prototype fuel cell power source that is small enough for wireless devices such as notebooks, PDAs and mobile phones. This may sound trivial, but it means that people who lug spare batteries around for their computers could find they don't have to do so in the future.

Fuel cells are not quite like batteries, being more akin to miniature power stations. A more rigorous definition would be "an electric cell in which chemical energy from fuel oxidation is converted directly to electrical energy in a continuous process".

Early products based on this technology are said to last three times longer than batteries, and this advantage is projected to grow to 15 times longer in the future.

The Lawrence Livermore mini fuel cell uses highly concentrated methanol fuel supplied from a replaceable cartridge. Unlike batteries, fuel cells don't run down, they run out. So besides the capital cost of the fuel cell itself, users would have to add the running cost of refuelling the cartridge, somewhat like refilling a cigarette lighter.

Nevertheless, The Lawrence Livermore researchers predict that fuel cells will eventually displace lithium-based battery technology currently used in mobile phones, handhelds and notebooks.

While this column was being written, Toyota announced its plans to become the first car maker to produce a commercial vehicle powered by a fuel cell. It plans to start selling the FCHV-4 in Tokyo next year, with its fuel cell running on hydrogen supplied from a pressurised tank. The fuel cell will power electric motors to provide the actual driving power.

Hydrogen refuelling stations are already being built around Tokyo in readiness, although anyone who remembers the Hindenburg incident may well shake their heads at the thought of this development.

Globally, the market for rechargeable batteries is predicted to be worth nearly $6bn by 2004. At present, lithium-ion batteries are the dominant battery technology, and the lithium-ion polymer variety are increasingly used in handhelds. Lithium-ion polymer batteries can be moulded to fit the shape of the device they are powering - a break with the tradition of devices having to be shaped to contain the batteries.

It was only a year ago that Toshiba unveiled its own Advanced Lithium Batteries (ALB), based on lithium-ion polymer technology. This hybrid battery technology appears to combine the flexible shaping of lithium-ion polymer technology with the energy density of current lithium-ion designs. These batteries are used in products such as Ericsson's T28 World Phone and Toshiba's own recently launched Portege 2000 ultra-portable notebook.

The notebook with the longest battery life we've seen is Samsung's NV5500TX notebook, which lasted six hours and 15 minutes with a high capacity lithium-ion battery in IT Week Labs tests.

If you're desperate to put in a full day's work while flying to the US, then the technology is already nearly here. However, if fuel cells designed for notebooks and PDAs arrive, then it will become far easier for us to work while away from the mains. I just can't wait.