A few months ago my laptop suddenly became totally dependent on mains power. The system's lithium ion battery had stopped working properly. In fact, it seemed to be acting more like a large capacitor, holding enough juice for about five minutes.

Given that my laptop was fairly long in the tooth I didn't hold out much hope of finding a replacement battery pack on the vendor's site. Sure enough, I couldn't find one - and I suspect third-party vendors probably wouldn't be able to help either.

Many users may be glad to see the back of lithium ion battery packs precisely because of problems like this; but are we any nearer to a replacement technology?

The future of laptop power appears to be fuel cells, and Casio has just released a polymer fuel cell that has been reported to be able to power a laptop for anywhere between eight and 16 hours.

Unfortunately this fuel cell has fallen foul of the Japanese regulators who don't want what they see as a small potential bomb being carried on airplanes - though people routinely take butane cigarette lighters or even litre bottles of duty-free spirits on plane journeys. Casio hopes to surmount such obstacles in the next few years.

Until then, notebook users will just have to rely on some of the tried and trusted techniques for extending usable life, like optimising the power management settings, fitting an extended-life battery or even having a fully-charged hot-spare standing by. Some manufacturers extend battery life by the simple expedient of fitting a heavier battery with a higher power rating. The average battery is usually rated at about 3.5 amp hours (Ah), but Canadian firm Electrovaya has batteries rated at 8Ah fitted to some of its Tablet PC models.

Tests in IT Week Labs have shown that laptops employing Intel's Centrino technology are among the most power-efficient designs. Intel also claims that laptops built with the latest Centrino processor, Dothan, extend battery life by an extra 10 percent.

What about alternative power sources? Well, I think we can safely discount wind, wave, and nuclear power. Solar powered laptops may well be able to augment the battery pack, but maybe only for people working outdoors in the Sahara.

How about a wind-up charger, like those clockwork radios you can buy? Well, imagine a thrusting sales executive turning up to a meeting, then halfway through the presentation saying, "Hang on a minute chaps, I've just got to wind up my laptop."

I considered whether the IEEE 802.3af standard for powering devices via the Ethernet cable could be used, but since this only delivers about a third of an amp, it wouldn't make much of a dent - even the most frugal ultraportables require a couple of amps at least.

Perhaps the answer was indicated at Intel's developer forum in San Jose earlier this year. The chip giant unveiled details of low-temperature polysilicon (LTPS) technology, which puts display circuitry directly onto the screen substrate, allowing brighter and more power-efficient LCD panels.

Combine this technology with a fuel cell, and we may finally get a laptop realistically going for a full eight hours.