Dreamliners at Paine Field in Everett, Wash. The F.A.A. has ordered the planes, the newest jetliners made by Boeing, to be grounded until a potential problem with lithium-ion batteries is resolved.

Powerful and lightweight, lithium-ion batteries are the perfect power source for modern gadgets. But ubiquitous as they are, their short history has also been fraught with problems — they have caught fire in cellphones, laptop computers and electric cars, and even destroyed a small Navy submarine.

Now, federal investigators are trying to determine why a lithium-ion battery caught fire in Boeing’s long-awaited787 Dreamliner last week, and they have grounded the planes until they figure it out.

While Boeing officials insist that the failure never endangered passengers or the plane’s integrity, the prospect that batteries would leak flammable fluids and smoke on flights packed with passengers has opened perhaps the most unnerving chapter in the technology’s relatively short life.

For Boeing, the development of the 787 represented a push into new technology and energy efficiency, and the company staked much of its future on the plane. It turned to the new batteries for many of the same reasons that Silicon Valley and Detroit have: they pack a lot of energy in a small package and, unlike older batteries, can be charged rapidly and frequently without loss of power.

Even though the safety standards are higher in aviation than most other industries, federal regulators decided in 2007 to approve Boeing’s use of lithium-ion batteries for the first time in one of its passenger jets. But the agency also required the company to take a series of steps, among them to keep pressure from building in the batteries and toxic gases from escaping.

Just as in the early days of aviation, “you cannot do pioneering work without assuming some risk,” said Hans Weber, president of Tecop, an aviation consulting firm. “In today’s world, we don’t have to pay the price of pioneering with death anymore, but we have to accept the fact we will have some incidents.”

Still, safeguards for lithium-ion batteries have progressed to the point that a fire on an airplane should never have happened, said Sanjeev Mukerjee, a chemistry professor at Northeastern University and an expert on batteries.

“If a battery of that size catches fire, then a whole bunch of mechanisms didn’t work,” Mr. Mukerjee said. “Whoever is making that battery is doing a really bad job.”

It is still not clear what caused the battery fire last week in Boston, about 30 minutes after a Japan Airlines 787 landed from Tokyo and passengers had gotten off the plane. The cleaning crew noticed smoke seeping into the cabin, and it took firefighters 40 minutes to put out the battery fire in the electrical bay in the back of the plane.

On Wednesday, a 787 had to make an emergency landing in Japan after pilots received a smoke alarm. Officials found that a battery in the front of the plane was charred and swollen. Chemicals appeared to have leaked, and black discolorations on the plane suggested that there had been smoke inside.

Investigators are considering a variety of causes, though it might be months before they pinpoint what went wrong and how to solve it. The problem could be in the basic design of the batteries, the units that charge them or in an undetected manufacturing flaw, experts said.

“It might not be the underlying technology; it might be the design of this particular unit,” said Robert A. McKenzie, an electrical engineer and an aviation lawyer.

Other industries have found out the hard way that minor imperfections in lithium-ion batteries can cause big problems. In 2006, Lenovo, IBM, Dell and Apple all recalled laptops because of concerns about the hazards of lithium-ion batteries manufactured by Sony.

General Motors last year announced a series of enhancements to its electric car, the Chevrolet Volt, after two lithium-ion batteries caught fire days after a crash test.

While those fires were started under extraordinary conditions — and did not involve Volt owners — General Motors nonetheless reacted swiftly to the negative publicity and bolstered the structure and cooling system to protect the battery further in the event of a serious accident.

And about four years ago, Toyota considered switching to lithium-ion batteries for its popular Prius hybrid but decided to stick with an older chemistry, nickel-metal hydride. The reason was cost, said John Hanson, a spokesman for the company.

“It isn’t so much the elements inside of it, it’s because the manufacturing process for lithium batteries is much more complicated,” he said. “Lithium batteries do have special requirements.”

The military has also had mishaps. In late 2008, a mini-submarine designed to carry Navy SEALs to shore was destroyed when its lithium-ion battery exploded as it was being charged.

The dangers of these types of batteries were also well known in the aviation industry. Dozens of fires had broken out on cargo and passenger planes as computer batteries heated up.

These accidents prompted regulators to limit the transport of these batteries in passenger planes and freighters planes.

Despite all these problems, Boeing still saw enough benefits in the new battery technology. But Boeing’s request to use it for the Dreamliner set off some alarm bells, particularly with pilots, who were concerned about the risk of fires during flight and the ability of flight crews to extinguish it rapidly. At the time, the Air Line Pilots Association warned that theF.A.A. should stress that “preventing a fire and not reacting to one, if one occurs, is critical.”

But Boeing officials said they felt they understood the potential hazards, and they built a system with multiple layers of protection that they said would keep the batteries from overheating and would contain any problem. In case any fumes or flames escaped, Boeing said, the pressurized air system would help keep smoke out of the cabin and vent it outside the plane.

After the problems occurred in the last couple of weeks, however, Boeing engineers were clearly surprised. In addition to trying to figure out why the batteries overheated, Boeing and the F.A.A. now also realized the heat was so intense that it appeared to burn through the battery containers.

Still, even former safety officials who have frequently criticized the F.A.A. say that as the 787 paves the way for airplanes to be more fuel efficient, it made sense for Boeing to shift to the latest battery technology.

“It was a bit of a judgment call,” said John Goglia, a former member of the National Transportation Safety Board. “But I think I would have gone with the new technology myself, because you don’t make any advances if you stay with the same old equipment.”

He said the decision to set conditions on Boeing’s use of the batteries was like saying, “You’re on probation on those issues.” But once the second lithium-ion battery problem happened, that “upped the ante” and forced the F.A.A. to ground the 787s.

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