Yes, you can have a power bank in your carry-on luggage. Power banks must not go in check-in luggage under any circumstances.
Power banks are managed as if they were spare batteries.
Some types of batteries can’t be taken onto planes because there are risks with them exploding, catching fire, leaking acid or caustic chemicals, harming people and property. Power banks present a significant risk, particularly when they are used to recharge other devices.
For more information on the risks associated with lithium batteries please read the Lithium Batteries - The Good, The Bad, and The Ugly(external link) article.
You will be asked to relinquish all dangerous or prohibited items found in your carry-on luggage. If you refuse:
We x-ray bags going on planes to make sure there is nothing dangerous in them. If something comes up on the x-ray that needs checking, the bag will be opened, searched and any dangerous or prohibited item will be removed.