Samsung has developed a fuel cell capable of powering a personal media player for four hours - almost double the video playback time of the rechargeable batteries that usually ship with such devices.

For now, that is. Samsung said the fuel cell won't go into mass-production until 2008, by which time rechargeable battery technology may have caught up. Still, empty fuel cells will only require a new methanol tank, not a lengthy recharge, and Samsung expects those to become as commonplace as ordinary batteries are today, South Korea's Joong Ang Daily reports.

But don't forget, Toshiba said a few years back it would have PDA- and phone-oriented fuel cells outs by... 2005. Last November, it moved the date back to 2007.

The Samsung cell's cartridges hold 20 cubic centimetres of methanol and are about the half the size of a shot glass - not quite small enough to fit inside, say, a fifth-generation iPod or a Creative Vision:M player. Samsung has its corporate fingers crossed that it can get the size down by the time it's ready to bring the technology to market.

Samsung has been working on fuel cells for some time, spending the equivalent of $3.9m in the last 16 months on the technology, it said. In November 2005, the company announced a notebook-oriented product capable of running for 15 hours. Then, it said the fuel cell would ship in 2007.

Like other methanol fuel cells, the Samsung system uses a catalyst to react methanol and water at the positive electrode. This produces hydrogen and electrons, which combine at the negative electrode with oxygen to create water. The cell has to transfer some of the water back to the anode to continue the reaction and suck the hydrogen across to the cathode to enter into the water-producing reaction. The cell also produces CO₂. ®