A Lenovo employee displays a ThinkPad notebook computer in February 2006 in Tokyo. (Yahoo.com)  Photo Gallery >>

    The batteries were designed by Lenovo but Sony produced the lithium ion cell. The recall impacts laptops produced from Feburary 2005 to September 2006, according to a Lenovo spokesman.

    PC makers and component suppliers buy the lithium ion battery cells and design batteries around them. The cells can provide several hours of electricity to laptops but the liquid inside them is flammable.

    If a short circuit takes place, a chain chemical reaction can occur that melts the battery or causes the laptop to explode. Lenovo actually inserts technology into its batteries to prevent chain reactions and has contemplated licensing it to others.

    Like the petrol tank in a car, lithium ion batteries in most instances are safe. However, to extend battery life, battery makers have been putting more flammable liquid into these batteries, and making other parts inside the batteries smaller and thinner. This, in turn, increases the potential problem, as it is more likely that thinner materials will come loose and interfere with the proper working of the battery cell.

    It was the fourth recall in recent months involving Sony batteries believed to be defective. In August, Dell asked customers to return 4.1 million faulty laptop batteries and Apple recalled 1.8 million, warning they could catch fire. Last week, Toshiba recalled 340,000 laptop batteries due to a problem that caused laptops to run out of power.

    In the latest recall, Lenovo cited a risk following one confirmed report of a Sony battery overheating and causing a fire that damaged the notebook computer.

    The fire, a Lenovo ThinkPad T43 caught at Los Angeles International Airport earlier this month as the user was boarding a plane, caused enough smoke that a fire extinguisher was needed to put it out. There was minor damage and no injuries. Enditem

    (Agencies)