Which power banks you can take on a plane
Hand luggage only
Power banks go in hand luggage, not in the hold. The rule comes from flight safety: a lithium battery is easier to watch in the cabin.
The capacity limit
Most airlines accept batteries up to 100 Wh without approval. Between 100 and 160 Wh you usually need the airline’s approval, and above 160 Wh they are not allowed. Always check your airline’s rules.
From mAh to Wh
Power banks usually state capacity in mAh. For watt-hours, multiply the mAh by the voltage (usually 3.7 V) and divide by 1,000. A 5,000 mAh power bank is about 18.5 Wh, well under the 100 Wh limit.
Why not in the hold
Lithium batteries rarely catch fire, but when they do the heat is intense and the fire hard to put out. In the cabin the crew sees it at once and has the means to deal with it; in the hold nobody would see it in time. That is why international aviation rules require power banks to travel in hand luggage only.
If you have packed a power bank in your checked suitcase by mistake, say so at check-in: you will be asked to move it to your hand luggage.
The limits, step by step
The rules most airlines apply, following IATA's guidance, have three steps. Up to 100 Wh: power banks are allowed in hand luggage without approval; almost every phone power bank falls here. Between 100 and 160 Wh: the airline's approval is needed and usually no more than two are accepted. Over 160 Wh: not allowed on passenger aircraft.
Some airlines are stricter, for example forbidding the use or charging of power banks during the flight. Check your airline's rules before you leave.
How to pack it
Keep the power bank in a hand-luggage pocket where you can find it, not buried at the bottom of the rucksack: at security you may be asked to take it out. Cover the ports or keep it in a pouch, so it does not touch keys or coins that could cause a short circuit.
Do not leave it in the seat-back pocket, and if it gets unusually hot or swells, tell the crew at once.
How much energy you really need
For a flight of a few hours and a day of holiday, a 5,000 mAh pack is usually enough for a partial or full phone recharge, depending on the model. If you are away from a socket for long, a bigger pack helps, but it is heavier too. A 5,000 mAh pack is about 18.5 Wh, well under the 100 Wh limit, and usually weighs around 100–150 g.
For the flight itself, think about earbuds too: engine noise is constant, and active noise cancelling earbuds such as the TESNA Ultra cut it without turning the volume up. They last 8 hours with ANC on plus 32 with the case, enough for a long flight and the trip to the hotel.
What the pack must say on it
At security, the capacity must be readable on the pack: in Wh, or in mAh together with the voltage. A pack with no label, a worn-off label or a home-made one may be refused, because nobody can check that it is under the limit.
Keep the box or a photo of the label if the label on the pack is hard to read. And if the pack is swollen, cracked or bent out of shape, do not take it on a plane at all: take it to a battery collection point.
Chargers and cables
Wall chargers, cables and adapters have no battery, so the power bank rules do not apply to them: they can go in checked luggage too. Still, it is handier to keep them in hand luggage, so you can charge your phone at the airport.
The phone, the laptop and earbuds, the devices with a built-in battery, are also best kept in hand luggage.
Magnetic charging
Some power banks have a magnetic ring that holds a compatible phone while it charges, with no cable. You can use the phone in your hand while it charges, and on the plane you no longer hunt for the cable in your bag.
Magnetic charging is slower than by cable. If boarding is close, use the cable; for a quiet top-up during the flight, where allowed, the magnetic way is more comfortable.
For the flight, see also active noise cancelling earbuds: the TESNA Free7, at 3.9 g a bud, are comfortable even with your head against the headrest.