It used to be 2x your level. I'm level 111 and just cruised up to 225 banked AAs before I stopped. I didn't get any message about hitting a cap.
Every 5 levels, the AA banked cap increases by 10. So the cap for levels 101-105 is 210, for levels 106-110 is 220, and for levels 111-115 is 230.
Please set the banked AAs to 10x your level to make it much closer to what the ratio of time-to-cap was when they were introduced. Right now AAs are like weeds I have to tend to every half hour.