Apple's big announcement at Macworld yesterday was not a new iMac, Mini or netbook, all of which had been rumoured, but a battery.

The firm announced a widely expected refresh of its 17in MacBook Pro, with a battery that the firm said will offer eight hours of operation, but which is not removable from the case.

The battery, based on conventional lithium polymer technology commonly found in laptops and mobile phones, has been integrated into the case to make the device thinner while increasing battery life, according to Apple senior vice president of marketing Phil Schiller.

Apple has also introduced a separate chip that monitors the power used by each cell and adjusts the charging current accordingly, which the firm says extends the life of the battery.

The Macworld crowd did not let out its characteristic whoops of excitement when Schiller announced the battery, even when he said that its capacity for 1,000 full recharges - three times the average achieved by other notebooks - would give the average battery a five-year life.

However, one Mac customer from the show floor was sceptical of the claims. " Apple says five years, but for some it might only be two or three," he said. " Look at the way guys like us travel."

Apple will offer a £135 take-back and replacement service for the battery.

The keynote was decidedly low-key this year, being Apple's last following a decision to pull out from the IDG-run show. Other than the MacBook Pro, the company concentrated on enhancements to its iWork package, including a beta version of iwork.com.

The service lets users share iWork files, including those in Microsoft Office format, and to comment on each other's work.

Glaringly absent at Macworld were refreshes of the now ageing Mac Mini and the iMac desktop lines.