In about 3 months I will be flying from Estonia (Tallinn) to New York (Newark) via Stockholm (Arlanda) by SAS. I have an Aukey 30000 mAh (~111 Wh) battery bank which I'd like to bring on board with me. I did some research and discovered that batteries over 100 Wh require approval by the airline. On my previous flight from Tallinn on British Airways I wasn't allowed to bring in the battery bank with me, and had to hand it over for storage.
I've contacted SAS customer service and they have given me approval (verbally, over the phone) to bring the battery bank on board in my carry on. They also say it's written somewhere in the booking notes, which the check-in staff would see.
However, how would the staff at airport security in Tallinn and Newark know that I'm permitted to carry it? Can they look up my booking and verify it there, or should I request a written approval from SAS to show security?