Apple this morning launched a voluntary worldwide 15-inch PowerBook G4 battery exchange programme to deal with 28,000 potentially faulty units.

An internal short of the batteries can cause them to overheat, posing a fire hazard. The units were made by LG Chem in South Korea. Apple is replacing the batteries at no charge.

The company says it has received just four reports of the batteries overheating and that no injuries have been reported, in the interests of customers, however: "Apple urges you to stop using your battery and to order a replacement battery immediately. If you continue to use your battery, do not leave it unattended and check for signs of overheating," the company warns.

How to identify affllicted batteries

Not all PowerBooks and no iBooks are reportedly affected. The recalled units were sold worldwide from January 2004 until August 2004 for use with 15-inch G4 PowerBooks.

The recalled batteries have the Model Number: A1045 and serial numbers that begin with: HQ404, HQ405, HQ406, HQ407, or HQ408.

"Batteries with the affected serial numbers contain cells that were manufactured by LG Chem of South Korea during the last week of December 2003 only," Apple adds.

If your battery serial number does not match those listed above, you do not have to exchange your battery.

Further information is available on Apple's Web site.