Power bank for travel: what capacity, and is it allowed on the plane?

Most airlines allow power banks in carry-on only, with a limit printed in watt-hours on the battery. Never pack them in checked luggage.

Airline rules and the right capacity are covered in the power bank for travel guide (Arabic), and the capacity comparison is in 20000 vs 10000 mAh.

Brand comparison: Anker vs RAVPower. For iPhone: best power bank for iPhone. Magnetic option: MagSafe-style power bank.

Disclosure: I own Rayan Apple Telecom store.