TechnicallyWell offered some good general ideas of what to expect.
That being said... It depends on the "power bank's" input port. Some smaller ones only accept 1A input, others 2A, and others QuickCharge 2.0 or 3.0. And you have to consider the "power bank's" capacity. Obviously all things being equal, larger capacity takes longer to charge.
Here are some examples...
My Anker PowerCore 20100 Portable Charger ( https://www.anker.com/products/A1271012 ) accepts 2A input. It usually takes about 9-10hrs to charge using a 2A or greater wall charger.
My older an Anker 2nd Gen Astro3 12800mAh take about 7hrs to charge. I don't recall if this only accepted 1A or if it actually accepted 2A (I always used 2A wall chargers, or my iPad charger).
I have an Anker PowerCore+ 10050 w/QC2.0 (older model of this one -> https://www.anker.com/products/A1311011 ) which supports Quick Charge 2.0 INPUT to recharge the PowerCore+, it charges in about 3 or 4hrs when using a QC2.0/3.0 wall charger. Using a standard 2A charger, or a multi-port charger capable of 2.4A, it takes a little over 7hrs to charge.
That being said, for ALL of my "Power Banks", I expect to require charging them over night.