Dell and Sony knew about and discussed manufacturing problems with Sony-made Lithium-Ion batteries as long as ten months ago, but held off on issuing a recall until those flaws were clearly linked to catastrophic failures causing those batteries to catch fire, admits a Sony Electronics spokesman.
Spokesman Rick Clancy said the companies had conversations in October 2005 and again in February 2006. Discussions were about the problem of small metal particles that had contaminated Lithium-Ion battery cells manufactured by Sony, causing batteries to fail and, in some cases, overheat.
As a result of those conversations, Sony made changes to its manufacturing process to minimise the presence and size of the particles in its batteries. However, the company did not recall batteries that it thought might contain the particles because it wasn't clear that they were dangerous, Clancy said.
"We didn't have confirmation of incidents [involving fires] until relatively recently. We received reports, but didn't know if there were environmental situations not related to the systems themselves," he said. "Different measures were taken in February and in October  to further ensure that there were as few of these particles as possible and that they were as small as possible."
On Tuesday, Dell and the US Consumer Product Safety Commission (CPSC) announced they would recall 4.1 million Dell laptop battery packs, citing a fire hazard. The recall covers Dell-branded battery packs that use certain Sony Li-ion battery cells sold through July, 2006. Those batteries were manufactured prior to changes made in February, Clancy said.
Dell spokeswoman Anne Camden declined to comment on the conversations with Sony in October and February, but told Macworld that Dell was "confident that the manufacturing process at Sony has been changed to address this issue. Now our focus is erring on the side of caution to ensure no more incidents occur."
Lithium-Ion batteries are constructed with coated anode and cathode foils separated by thin layers of polymer material, said Dan Doughty, manager of the Advanced Power Sources Research and Development Department at Sandia National Laboratory.
"It looks like a jelly roll. You get a high surface area with thin layers. The thinner they go with the separators, the more room there is for the active material," Doughty said.
The coated layers are wound up on commercial machines to create the individual Li-ion cell, and it's at that stage that contaminants, such as metallic particals, can get embedded in the battery cell. The metallic particles mentioned by Sony and Dell may have been cast off by those commercial machines, he said.
Generally, the polymer separator is very thin - less than 25 micron (one millionth of a metre) thick. If that is punctured by an electrically conductive material, like a metal particle, the battery cell's anode and cathode short circuit, Doughty said.
He said an internal short circuit was "the worst scenario in battery design, because there's nothing you can do to control it," he said. In contrast, manufacturers have a variety of measures to guard the battery contents from external threats, like ambient heat.
Based on its conversations with Dell, Sony strengthened and reinforced the protective barriers and lining of their battery cells to address the danger of metal particles piercing the lining of the cell, Clancy said.
Dell is reported to have known about incidents of laptops overheating, albeit in small numbers, for years. It and CPSC recalled 22,000 laptop batteries in December, 2005, because of overheating problems. Metal particle contamination was the cause behind that recall, as well, said Scott Wolfson, a CPSC spokesman.
Those units were sold between October 2004 and October 2005. Sony declined to characterise the discussions between the companies that took place in October, 2005, and then again in February, except to say that they were "specific to particular cells of batteries in battery packs used in Dell notebooks," Clancy said.
Doughty said Li-ion batteries usually fail "benignly," in what researchers call a "soft short," in which a low current path is created within the battery that causes it to discharge its energy into the cell. However, if a large particle of conductive material penetrates the separator, connecting the anode and cathode, or a small particle of conductive material manages to find just the right position between the anode and cathode, a "hard short" can result in which the battery cell releases all its energy at once, in what's called "thermal runaway."
The key in situations like that is to prevent the reaction from spreading to other cells in the battery pack, which appears to have happened in the now-famous incident in June in Osaka Japan, he said.
But as manufacturers pack more and more power into the Li-ion batteries, the risk of catastrophic failure grows, Doughty said. "The more energy put into it, if things go bad, you lose the ability to have a graceful failure."
Sony says that if its batteries fail, it is usually a benign short circuit that stops the battery from working, Clancy said. "System related issues" that are unique to Dell came into play to cause the fire, he said.
"These Lithium-Ion battery packs are put together based on specifications from the manufacturer," he said. The configuration of the cells in the pack, heat environment, battery charging specifications and proximity to other heat sources in the laptop all vary from manufacturer to manufacturer, Clancy said.
Fujitsu, Toshiba and Hewlett-Packard (HP) said on Thursday that they use Sony Li-ion batteries with their systems, but that the batteries are different from those being recalled by Dell. The companies said they did not see a fire risk for customers and did not plan on doing a battery recall.
"We've worked with Sony to identify whether the cells we used were part of the contaminated batch," said HP spokesman Mike Hockey. "We've not seen any issues whatsoever."
But Doughty said that there's no guarantee that the fire problem with metal particles in the Sony Li-ion cells would be limited to Dell systems. "I'm an R&D guy, but the way I understand it, if you've got an automobile part that's defective in one vehicle, you replace it in other vehicles as well," he said.
The CPSC is in ongoing talks with Sony about its notebook batteries beyond its order with Dell, said Wolfson.
He declined to say which laptop makers the company was working with, or to say whether it would do a broader recall of any Sony batteries with the metal particle contamination problem.
Still, that leaves Sony in a tough place. "They don't know what cells have it and which don't. It could be 1.5 parts per million or 400 per cent of that. You've got to do testing to determine precise failure rate, and when the failure rate is that low, you have to test many, many cells to figure it out," or use probability to determine the likely rate of failure, Doughty said.
The best Sony can do is to enforce strict quality control when making the batteries, especially around the machines that manufacture the Li-ion batteries to make sure no metal flakes are being cast off. Beyond that, the problem is in the hands of regulators, Doughty said.
"CSPC has to do a risk-benefit calculation. You may think the risk is pretty low, but if you have a high severity failure, even if you have a low probability, that can change the calculation," he said.
Wolfson said that CPSC frequently does recalls even when no incidents or injuries have been reported.
"The law allows for companies to carry out recall before the first reports of consumer problems comes in. "It could be six with 4.1 million units or none with 1,000. You still have the ability to do the recall," Wolfson said.
Any company that knows that their product poses a substantial hazard is under federal obligation to report it to CPSC immediately, Wolfson said. However, he declined to say whether metal particle contamination of Li-ion posed such a hazard.
Catastrophic failures of the Li-ion batteries, though rare, can be "very dramatic," Doughty said. "You get a lot of fireworks."
It is not known if Sony discussed these battery dangers with Apple, which uses some Sony batteries in its laptops.