Nasa develops a 'top-up' battery

Nasa has made a technological breakthrough that heralds the end of the rechargeable battery.

Scientists announced that they have developed the first portable, practical fuel cell. Measuring four inches by about eight - roughly the size of two paperback books back to back - it runs on methanol and could be used to power mobile telephones, laptops, and even camcorders.

Instead of recharging a battery for hours when the power runs low, they would need merely a top up of methanol.

The cell produces five watts of electricity - enough to power five mobile telephones simultaneously. It runs at room temperature and its only emissions are water and carbon dioxide.

Until now, sufficiently powerful fuel cells have been too bulky to be practical. Methanol is also safer than the highly explosive hydrogen used in earlier fuel cells.