Your phone battery on a fourteen-hour travel day (and the new power bank rules)

The power bank rules, as of September 2026

The capacity limits are long-standing and set by international regulation:

A typical 20,000 mAh power bank is about 74 Wh, so it is comfortably inside the first band. The Wh figure is printed on the casing; if it is not, the bank should not be flown.

Power banks always go in carry-on, never in checked baggage. That has been true for years.

What changed in 2025 and 2026 is how you may use them in the cabin. After a series of in-flight battery fires, airlines started banning use rather than just carriage:

• Emirates cut passengers to a single power bank under 100 Wh from 1 October 2025.
• Lufthansa Group — Lufthansa, SWISS, Austrian, Brussels, Eurowings, Edelweiss, Air Dolomiti and ITA — moved on 15 January 2026: two power banks per passenger, no in-flight use of any kind, no recharging from aircraft outlets, and nothing stored in an overhead bin.
• United banned overhead-bin storage of power banks from 1 March 2026.
• American and Delta limited passengers to two chargers of 100 Wh or less from 1 May 2026.
• Southwest allows one per passenger, kept within reach.

The common thread across all of them: keep it visible, keep it with you, and do not charge anything from it in flight. Several Asian carriers introduced similar rules in 2025 after a cabin fire.

So charge before you fly, not during

With in-flight power bank use restricted, the plan has to change.

• Charge everything to 100% at home, including the power bank itself.
• Use the seat's USB outlet where there is one — that is unaffected by the power bank rules. Bring the cable; many aircraft supply the socket and not the lead.
• Charge at the gate, not in the air. Most airports now have sockets at every seat in the newer piers, and none at all in the old ones.
• Put the phone in airplane mode as soon as you are on board, even if you are paying for Wi-Fi. A phone hunting for a signal at 11,000 metres is the fastest way to flatten it.

Making a phone last the day

A travel day is the worst case: the phone is off Wi-Fi, in and out of coverage, using GPS, taking photos and being looked at every four minutes.

1. 1

   Airplane mode in the air, and in dead zones · The big one

   A phone with no signal burns battery searching for one at full transmit power. Airplane mode in flight, in tunnels and in deep buildings is worth more than every other setting combined.

2. 2

   Low Power Mode from the start · Not at 20%

   iPhone: Settings → Battery → Low Power Mode. Android: Settings → Battery → Battery Saver. Turning it on at the start of the day is worth two or three hours; turning it on at 20% is worth twenty minutes.

3. 3

   Drop the screen brightness and shorten auto-lock · The second biggest drain

   The screen is the largest single consumer on any modern phone. Auto-brightness plus a 30-second auto-lock does more than any app-level tweak.

4. 4

   Download entertainment instead of streaming · Before you leave

   Streaming over a weak mobile signal is the most expensive thing a phone can do, in both battery and data. Download the film, the playlist and the podcasts at home.

5. 5

   Turn off what is hunting in the background · Ten minutes of setup

   Background app refresh, location for apps that do not need it, and Bluetooth if you are not using headphones. Each is small; together they are an hour.

The cold, and other physics

Lithium batteries lose capacity in the cold — a phone at -5°C can show a much lower percentage than the same phone warm, and may shut down entirely. It is not damaged; put it in an inside pocket and it comes back.

Heat is the one that does real damage. A phone left on a dashboard in Athens in July, or used for navigation in direct sun, will throttle, stop charging and age its battery faster. If it gets hot, take the case off and put it in the shade.

Fast charging is fine occasionally and hard on the battery as a daily habit. Charging to 80% rather than 100% is easier on it — both platforms now have an optimised-charging setting that does this automatically.

What to actually pack