The company has also made the battery safer by separating several conventional safety measures and by inventing new ones. In existing notebook batteries, the current interrupt device and the thermal fuse are packaged on top of each other in the cell's lid. But by separating these elements from each other, the company has built an extra layer of redundancy into the system. These elements are able to control and cut off the current flow, should the battery begin to overcharge. The company has also devised a new ventilation system to alleviate the pressure and heat before they build to catastrophic levels. With aluminum in its canister, rather than carbon steel or nickel, as is common, the Sonata's shell softens much sooner at high temperatures and then self-destructs with a hiss. More-durable elements like carbon steel, which melts at even higher temperatures than aluminum, exacerbate explosions by letting extraordinary pressure and heat build inside the cell until its breaking point. (This is why conventional laptops emit loud booming cracks when they burn.)

"There is a lot of progress being made in battery technology with different chemistries," says Robert Kanode, president and CEO of Valence Technology, an Austin, TX, startup that manufactures phosphate lithium-ion batteries. His company is a competitor with Boston-Power, but Kanode adds, "We know we will not be standing alone: this will be a huge market with many viable players in it."

Lampe-Onnerud says that Boston-Power is in discussions with most of the world's top-tier notebook makers, including Hewlett-Packard, which over the past two years has worked closely with the company, helping it design battery packs that can be dropped into existing notebooks.

"The Sonata opens up a whole new business model for notebook manufacturers that hasn't been available in the past," says Ifty Ahmed, a general partner with Oak Investment Partners, who worked on the deal. Although notebook makers can presently offer a three-year warranty for a computer, they can't make the same offer on a battery, a component that can cost about 10 percent of a laptop's total value. "The market for warranties is extremely profitable," Ahmed says. "So if you can sell a warranty on the battery for three years, you have a very exciting idea."

Boston-Power says that it is focused on commercializing the Sonata, but it also believes that its patented safety features could eventually be used in lithium-ion batteries for smaller consumer-electronics devices as well as for hybrid electric vehicles.