The Ministry of Economy, Trade and Industry, after two years of speculating fires in Japan involved iPod nanos, confirmed Tuesday that the fires were caused by Apple's music players.
Ministry officials said public-safety investigators examining the fires believe lithium-ion batteries may have caused the iPod nanos to overheat. The ministry said Apple is aware of 14 additional cases in Japan of iPod batteries overheating.
"We are not in the position to speculate on the outcome of the investigation," Hiroyuki Yoshitsune, a Ministry official, told Agence France Press. "But after several incidents like these, it would be appropriate for Apple to take some measures to raise the public's awareness."
Lithium-ion batteries, found in many computers and mobile phones, have a higher power density than nickel-based batteries, according to Apple. This higher power provides a longer battery life. Apple warns on its Web site that iPod owners should keep the music players out of the sun or a hot because heat will degrade the battery's performance.
Investigating the Cause
It is not clear whether the iPod nanos believed to have caused the fires were basking in the sun. Short-circuiting a lithium-ion battery can cause it to ignite or explode.
Officials have pointed to four specific models as the cause of the incidents -- MA004J/A, MA005J/A, MA009J/A and MA107J/A. More than 1.8 million of these players were sold in Japan between September 2005 and September 2006, according to published reports.
Quasi-government safety officials and Apple, according to published reports, will work together to find the specific cause of the overheating. Ministry officials are also asking Apple to improve its technology to avoid any additional fires.
Batteries a Cause for Concern
Lithium-Ion batteries have been the core problem behind many technological recalls in recent years.
In late 2006 Sony Energy Device Corp. in Japan recalled all its lithium-ion batteries used in Apple, Dell and Toshiba notebook computers. Nokia also recalled in 2007 more than 40 million lithium-ion batteries. The batteries, made by Japan-based Matsushita Battery Industrial between December 2005 and September 2006 were considered dangerous because they could overheat while charging.
In August 2007, Lenovo also recalled hundreds of thousands of ThinkPads because the installed lithium-ion batteries manufactured by Japan-based Sanyo Electric were a fire hazard.
Lithium-ion batteries are considered dangerous because lithium ion is not water-based, according to published reports by Donald Sadoway, a battery expert and professor at the Massachusetts Institute of Technology. Because one of the three components in the battery -- the electrolyte -- is an organic liquid similar to alcohol, it is flammable. Sadoway has suggested using polymer electrolytes to avoid this problem.
So with all the recalls, why are so many PDAs, laptops and other devices made with these batteries?
For one, they are lightweight. Lithium-ion batteries are made with lightweight lithium and carbon. These batteries also hold more electricity compared to nickel batteries and lead-acid batteries. And only one percent of all lithium-ion batteries manufactured have been the subject of a recall, according to reports.