CNN
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Several airlines in Asia are tightening rules on carrying lithium batteries on planes following a series of overheating and fire incidents on board.

A portable power bank with a lithium battery has been found to be a possible source of a fire that engulfed an Air Busan plane in January while waiting for takeoff, South Korea’s transport ministry said in a press release, citing the investigation committee and forensic services.

Investigators found “multiple electrical melting marks from the remains of a power bank,” the release said.

Travelers often pack lithium-ion battery power banks to charge their phones, tablets, laptops and cameras on the go. The pocket-sized devices keep gadgets fueled to play games or watch downloaded movies to stay entertained on long-haul flights.

But manufacturer issues, misuse and aging can heighten the risk from the batteries, which use flammable materials, potentially posing a fire danger on flights. More than 500 in-flight lithium battery incidents involving smoke, fire, or extreme heat have been recorded by the US Federal Aviation Administration (FAA) in the past two decades.

South Korea implemented nationwide restrictions that took effect this month, banning passengers from storing power banks and e-cigarettes in overhead cabins on all of the country’s airlines. Passengers can store power banks either in the seat pocket or under the seat.

Charging a power bank on the plane by plugging it into the seat’s USB outlet is also prohibited, according to the new regulations.

“Sockets of a power bank should be covered with friction tape or put in a protective pouch or a plastic bag (eg. zipped bag) so they don’t touch other metals,” the country’s transport ministry said.

Thai Airways announced passengers are no longer allowed to use or charge power banks on flights from March 15, following “incidents of in-flight fires on international airlines, suspected to be linked to power bank usage.”

Starting in April, Singapore Airlines is banning passengers from using power banks to charge phones and personal devices in-flight. Power banks are also not allowed to be charged using aircraft USB ports.

Low-cost carrier Air Asia said it will require passengers to store power banks under the seat or in the seat pocket, and prohibit charging portable electronic devices throughout the flight.

Taiwan’s major carriers, EVA Air, China Airlines, and Uni Air, have also banned the use of portable chargers in-flight.

Hong Kong’s aviation regulator said it will prohibit passengers from using power banks during flights and from storing lithium batteries in the overhead cabins from April 7. The change comes after a Hong Kong Airlines flight from the Chinese city of Hangzhou was forced to divert after a portable charging device reportedly triggered a fire in an overhead compartment.

Lithium-ion batteries are commonly used in power banks due to their high energy density and relatively low cost, according to Chrystal Zhang, associate professor, STEM College at RMIT University. The batteries can store a large amount of power without being excessively bulky, making them a popular choice for high-capacity power banks.

Power banks are essential on long-haul flights, for business travelers, and for anyone relying on mobile devices, since most airports lack sufficient charging stations, Zhang told CNN. Imposing a blanket ban on using them in-flight would inconvenience passengers, she added.

Lithium-ion batteries, such as power banks, should only be packed in carry-on baggage, according to US FAA and Transportation Security Administration (TSA) rules.

In general, most airlines allow each passenger to carry a maximum of two lithium-ion power banks of 100-160 Watt-hour (Wh) into the cabin.

However, most power banks on the market use the unit milliamperes per hour (mAh) to measure the battery’s capacity. So, look for ones that are no more than about 43,000 mAh to comply with most airline rules.

A single 100-Wh (27,000 mAh for a typical 3.7 volt battery) power bank is enough to charge an iPhone 13 Pro Max about three to four times.

But whether you can use them in-flight depends on the airline (and there are also exceptions for portable medical devices).

Here’s what you can bring on your carry-on:

Separately, there are no limits on carrying dry cell alkaline batteries (think Energizer Bunny batteries), according to the FAA, as long as the voltage does not exceed 12 volts and are “protected from damage.” This can be done by leaving the batteries in their retail packaging, covering battery terminals with non-metallic tape or by keeping them in an enclosed plastic bag or protective pouch.

Mobile phones, laptops, drones, smart wearables, as well as electric bikes, electric scooters and EVs are all powered by lithium-ion batteries. These batteries can overheat as a result of a phenomenon known as “thermal runaway,” a chain reaction which can lead to a fire or catastrophic explosion.

Lithium-ion batteries, which are used in power banks, are filled with materials which are highly reactive and highly flammable, according to Sonya Brown, senior lecturer in aerospace design at the University of New South Wales (UNSW) in Australia.

“Lithium batteries could act as an ignition source themselves, or as a source of fuel for a fire initiated elsewhere. The potential risk as an ignition source is increased when lithium batteries are damaged, swollen, include manufacturing defects, are over-charged or over-heated,” she told CNN.

Brown also said accidental contact with other battery terminals “can cause unintended discharge” and suggests power banks and spare batteries be taped with a non-conductive material or packed separately to avoid coming into contact with other metals.

She also recommends passengers inspect their power banks before traveling for any signs of swelling or external damage and consider disposing of them according to local regulations if there is anything that appears unusual.