One Tech Tip: What to know about flying with lithium ion portable battery chargers

Jetting off soon for summer travels? If you're planning on bringing an extra battery charger for your phone or other devices, be aware of the latest rules when taking one on a flight.

Rechargeable lithium-ion portable battery chargers, also known as power banks, come in protective enclosures of various shapes and sizes. They're a handy and popular way for getting more juice when you're on the move.

But after a spate of smoke or fire incidents, U.S. and international aviation authorities have issued new guidelines and airlines have tightened up rules for passengers.

Here's a guide on flying with power banks.

The most important thing to know is that you can't pack lithium battery chargers in your checked luggage. They need to go in your carry-on luggage.

Travelers can generally bring two lithium ion power banks with a capacity of 100 watt hours without needing airline approval. That's more than enough to charge a cellphone several times over.

For non-rechargeable lithium metal batteries, the limit is two grams of lithium per battery. AA and AAA batteries typically contain less than a gram of lithium.

Those limits cover nearly all types of lithium batteries in an average person's electronic devices, according to the the Federal Aviation Authority.

The FAA says newer lithium ion batteries should have a label with the watt hour, or Wh, rating. But if your power bank's energy capacity is listed in milliampere hours, or mAH, you'll need to do some math, or use the FAA's online calculator.

To figure out your battery’s watt-hour rating, take the mAH number, divide it by 1,000 to get ampere hours, and then multiply by the device’s voltage, which is usually 3.7 volts. For example, a battery with 10,000 milliampere hour rating is equal to 10 ampere hours. Multiply that by 3.7 volts and you get 37 watt hours.

Passengers will need airline approval for bigger lithium-ion batteries, with a capacity of 100 to 160 watt hours, such as those used in professional video gear or medical equipment.

Airlines are taking the risk of lithium battery fires seriously after a rash of incidents.

One of the worst happened in January 2025 when a fire broke out on an Air Busan plane waiting to take off from an airport in South Korea, forcing the evacuation of all 176 people aboard.

The FAA lists nine lithium battery air incidents so far this year, including six that involved power banks.

Concerns about the batteries have been enough to disrupt flights even when there were no signs of a problem. Last month, an Easyjet flight from Egypt to Britain diverted to Rome as a precaution after a passenger told the crew that they had a power bank in checked luggage charging a device.

Lithium batteries in a jet's cargo hold pose a danger because if there's smoke or fire, the crew can’t take immediate action to identify and extinguish it, according to the International Air Transport Association, or IATA.

Keeping them in the cabin makes it easier for the crew to stop a potential blaze by using fire-resistant bags and insulated gloves to contain an overheating device.

There's a very low risk that a lithium ion battery will short-circuit and cause a fire, but if it does the hazard it creates is “very horrible," said Paul Christensen, a professor of pure and applied electrochemistry at the University of Newcastle in the United Kingdom.

Lithium batteries can store ”a huge amount of energy in a very small space,” Christensen said. The risk comes when a battery is crushed, overcharged or overheated. That can trigger what’s called “thermal runaway,” a chemical reaction that produces heat and toxic gases, he said.

Christensen recommends checking your power bank for any signs of damage. If it’s bulging or getting very hot when charging, those could be signs it has a problem.

He also advises avoiding cheap power banks from unknown manufacturers, which might not have proper quality controls to prevent defects or contamination. Shoddy lithium batteries can “produce thermal runaway a long time after they’ve been purchased,” he said.

Once you're on board, airlines have strict rules on handling power banks in the passenger cabin.

You can't put it in the overhead bin. Instead you'll have to keep it somewhere you can get it to quickly, such as in the seatback pocket or under the seat in front of you.

Don’t use it to charge other devices during flight, and don't recharge it using the aircraft’s on-board power sockets.

If a battery — or battery-powered device — slips down the side of your seat, don't move the seat to try to get it.

“Seats can crush or damage the battery, which could cause it to overheat or catch fire,” IATA says. Instead, call a cabin crew member because they're trained to retrieve devices safely.

The FAA says individual airlines and international rules could be more restrictive than U.S. regulations, so if in doubt, it’s best to check with your airline. Southwest Airlines, for example, said in April that it would limit passengers to one charger each.

Many carriers have a detailed list of rules for various battery types, including lithium-powered devices like laptops, tablets and e-cigarettes.

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