Indeed, a confluence of events must happen to cause a failure that leads to overheating or fire, according to an explanation issued by Dell. Lithium-ion cells look like a can of soup on the outside. But inside they look sort of like a jelly roll. Two strips of coated metal foil are separated by an insulating layer and wound up in a coil. The coil is placed in a metal can, filled with an electrolyte solution, and sealed."Cells can potentially fail if they get very hot due to external heating or excessive current flow, if they are overcharged, or if a short-circuit occurs between layers of the coil. This last problem was what led to the recall: metal particles, contamination from the manufacturing process, are in very rare cases causing a short-circuit in the cell that leads to a fire," Forrest Norrod, Dells vice president of engineering, wrote in an Aug. 22 posting in Dells Direct2Dell blog.But, given the number of variables involved, "when anybody asserted that they didnt have the problem .then there was an unproven assertion," Kay said. Still, not all ThinkPadsnor Dell or Apple notebooksuse battery cells from Sony. ThinkPads also come with batteries from companies such as Sanyo. Sony is the second-largest battery cell maker in the world, behind Sanyo. Thus any action taken by Lenovo could be relatively limited in scope. Still, the potential for an additional recall shouldnt come as a major surprise, said Richard Shim, an analyst at IDC, in San Mateo, Calif. Shim said he estimates that about 1 million of the potentially problematic Sony-made cells are still in circulation. Given that major computer makers tend to buy from the same suppliers, "If [a problem] hits one of these guys, chances are its going to hit the other guys too," he said. The Consumer Product Safety Commission, in Washington, which worked with both Apple and Dell, declined on Aug. 24 to comment on the possibility of future battery recalls involving Sony or another computer maker. However, Sony, in a statement issued on the same day, said it did not anticipate any additional recalls. "We believe the issue has been addressed to the satisfaction of our customers," Sony said in the Aug. 24 statement. Sony also said in a statement that it has introduced safeguards into its battery manufacturing process to address the contamination problem seen by Apple and Dell and to provide a greater level of safety and security. The battery pack recalls have had some effects. Airlines including Virgin Atlantic have issued restrictions against passengers using their Dell or Apple notebooks, unless the batteries in their machines have been checked by cabin crew. Passengers with machines whose batteries are affected by recalls can operate them only sans battery packs on flights, if power outlets are available, the airlines Web site says. But the potential for additional recalls isnt likely to slow down the red-hot notebook market. Stephen Baker, an analyst with the NPD Group, of Purchase, N.Y., believes that any battery recall will not have long-lasting impact on either the notebook market itself or Lenovo. Lenovo "mostly sells to enterprises and businesses and those companies have procedures in place and ways to manage this," Baker said. "Those big businesses are a lot different than consumers. When you have a company more like an HP or a Dell, the company might have more of sales issue with the consumer." The CPSC and Sony could not immediately be reached for comment. Check out eWEEK.coms for the latest news in desktop and notebook computing.