The Problem With Stowing Lithium-Ion Batteries on Planes

A ban on most electronics in the cabins of some U.S.-bound flights may be aimed at thwarting terrorist attacks, but it also raises questions about the safest place to stow devices with lithium-ion batteries on airplanes.

The Department of Homeland Security announced Tuesday that laptops and other large electronic devices won't be allowed in the passenger cabins of direct flights to the U.S. from 10 airports in the Middle East and North Africa. The move is in response to intelligence reports that terrorists are looking for new ways to place explosives in electronic devices on airplanes.

Passengers on these flights will now be required to pack devices in their checked luggage. Yet because the lithium-ion batteries in laptops occasionally—though rarely—burst into flames, the new rule raises the question: Is it dangerous to store hundreds of laptops in suitcases in the hold of an airplane?

The issue has been studied extensively by aviation safety experts over the past few years. And there is an emerging body of opinion that, yes, it is somewhat safer if laptops and similar devices are kept in the passenger compartment rather than the cargo hold.

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Why? For one thing, if a laptop catches fire in the cabin, it will be noticed immediately and steps can be taken to put it out. And though there are fire safety systems in the hold of an airplane, they aren't well-equipped to deal with the type of fire that lithium-ion batteries generate.

“There’s a balance here,” says John Cox, a former pilot and CEO of Safety Operating Systems, an aviation consulting firm. “As we put lithium-ion batteries in cargo holds, they are no longer in an area where the crew can deal with them if they do catch fire. And the fire suppression systems using only [the common extinguishant] halon have not proven to be effective on lithium-ion fires.”

If a battery-powered device were to catch fire in the cargo hold, the halon in the onboard suppression system might extinguish the flames, but the battery would continue to heat up, potentially causing other fires.

“If you have a cargo hold with numerous lithium batteries, once one goes and starts that heating process, it can propagate to further devices,” Cox says. “You have this reignition.”

Cox adds that the Federal Aviation Administration "is in a very, very difficult situation.” He acknowledges the challenge in weighing the threat of terrorism against the threat of an in-flight battery fire. “I would like to see the risk analysis, but, at this point, I think that we’ve mitigated some risk and introduced some other.”

In a briefing Monday night, senior administration officials acknowledged that moving lithium-ion batteries from the passenger cabin to an airplane’s hold did create some hazard.

“Lithium-ion batteries are a known safety risk,” says Karen Walker, editor of Air Transport World, an airline industry trade publication. “If they catch fire, it’s a very intense heat. And fire and aircraft don’t mix very well.”

When a battery malfunctions, according to Consumer Reports chief scientific officer James Dickerson, it’s usually because the membranes that separate the charges in the battery are breached, which creates a short circuit and generates a sudden release of energy. That violent burst of energy causes the battery to reach temperatures approaching 1,000° F, potentially destabilizing nearby batteries, creating a condition known as thermal runaway.

Lithium-ion batteries have been in the news in recent months, with spectacular videos popping up on YouTube of various devices—ranging from hoverboards to a pair of headphones—bursting into flames. Last fall, the FAA banned the Samsung Galaxy Note7 smartphone from U.S. flights after it was recalled because of reports of fires and explosions.

But it's important to keep the dangers in perspective, given that millions of devices powered by rechargeable lithium-ion batteries are put to use every day.

“The frequency (of fires) is quite small compared to the number of batteries in use, but it still is a potential hazard,” says Dickerson, an expert on battery science. He adds that nonrechargeable batteries, such as the AA and AAA cells you might find in a remote control, do not pose the same threats for consumers.

Last year the FAA warned that transporting pallets of lithium-ion or nonrechargeable lithium-metal batteries in the cargo holds of planes could cause a “catastrophic explosion” if a single cell were to catch fire. Although stopping short of an outright ban, the agency warned against packing large numbers of batteries together—because of the dangers of thermal runaway—and cautioned that the batteries should be kept separated from other hazardous materials.

The International Civil Aviation Organization (ICAO), affiliated with the United Nations, last year banned the shipping of lithium-ion batteries as cargo on passenger aircraft because of the safety concerns. As with the FAA's restrictions, the move dealt only with commercial cargo, not the electronics devices carried onboard or stowed beneath the plane by passengers.

Though passengers on domestic flights are currently allowed to pack devices containing lithium-ion or lithium-metal batteries in carry-on or checked luggage, the FAA requires that spare batteries—those not installed in a device—be limited to carry-on bags because of the potential for a battery with unprotected electrodes to come in contact with a loose metal object and short out, causing it to ignite.

The FAA on Tuesday deferred comment to the DHS. The ICAO issued a statement acknowledging the need to continually address emerging threats, citing the importance of "finding an effective balance between safety and security approaches."

According to administration officials, the DHS is working with the FAA and airlines to determine the best way to implement the new travel restrictions. The State Department has been in contact with the eight countries with airports affected by the measures.

Smartphones and medical devices belonging to passengers and electronics devices carried by a plane’s crew are exempt from the ban. Officials say there’s no end date for the restrictions. They are continuing to evaluate intelligence, leaving the door open for the new security measures to expand to other airports.

The move currently affects flights coming from specific airports in Jordan, Egypt, Turkey, Saudi Arabia, Kuwait, Morocco, Qatar, and the United Arab Emirates. Nine foreign airlines and about 50 flights daily to the U.S. will be affected. No U.S.-based airlines are on the list because none currently offer nonstop service from the affected airports to the U.S.

Britain announced a similar ban Tuesday.

The U.S. changes officially went into effect at 3 a.m. Eastern time Tuesday, and airlines have 96 hours to comply. Those who don’t could see their clearance to land in the U.S. revoked, the officials said.