Sony has urged a dozen computer notebook makers to recall more of its batteries that could overheat. With two new recalls late last week – and Dell adding 100,000 more laptops to its recall list, making it 4.2 million – the number of lithium-ion batteries to be replaced now stands at about 7 million.


Sony spokesman Takashi Uehara refused to estimate how much it will cost the embattled company, but media have upped their estimates to half a billion dollars.

At the weekend Toshiba and Fujitsu were the latest to tell customers to return batteries. A day earlier, IBM and Lenovo Group announced a recall of 526,000 batteries. Last month, it was Apple and Dell.

Sony blamed “rare cases” when microscopic metal particles short out other parts of the battery cell. Typically a battery pack will shut down after a short circuit. But occasionally the battery catches fire.

Another Sony spokesman said the battery cells were made using an earlier manufacturing process. He says Sony’s manufacturing process has since added more safeguards to reduce the number of loose particles.

US Consumer Product Safety Commission spokeswoman Julie Vallese said notebook computers are vulnerable because their microprocessors and intense user demands generate a lot of heat.

She said there were about 50 incidents of burning batteries reported in the past five years during which tens of millions of notebooks were sold in the US. The recall deeply embarrasses Sony, which is in the midst of a major overhaul of its operations closuring of plants and divisions and causing job

Newspapers say the cost to Sony is heading towards US$500 million. What makes batteries blow

The Wall Street Journal Online asked Donald Sadoway, a professor of materials chemistry at Massachusetts Institute of Technology, to explain
why lithium-ion batteries sometimes explode in flames. It’s tied up with the chemistry of the liquid electrolyte. In all other batteries, it’s water-based; with lithium it’s a cousin of ethyl alcohol.

In charging the battery, you’ve got the temperature rising. And if the cell expands, the pressure could burst the case, so air enters. With elemental lithium, these conditions could lead to higher and higher temperatures.

“There’s also oxide on the other side of the cell,” the prof says. “You can get to the point where you reach the kindling temperature – and you’ve got an organic liquid there. You’ve got all the ingredients for a candle.”