Can I travel with a rechargeable external battery (power bank)?

YES, you can travel with your power bank provided its rated capacity does not exceed 100 Wh.

Please note the following:

• You must always carry it in your hand luggage. 
• You may carry a maximum of 20 spare batteries, each with a maximum capacity of 100 Wh.
• They must be individually protected to prevent short circuits. You can do this, for example, by using the original packaging, covering the battery with adhesive tape, or storing it separately in a protective bag or case.
• During the flight, it is recommended that you place them under the seat in front of you or in the seat pocket.

You can find further information in this Passenger Information document