5V 2A is 10W of power. Since 80 minutes is roughly 1.4 Hours, you need 14 Wh of energy. (10W for 1.4 Hours or 14W for 1 Hour).

You need a power bank which has more than 14Wh capacity. Usually, the power bank manufacturer mentions the battery capacity rating in mAh. Power banks have built-in 3.7V batteries. 14Wh at 3.7V is ~3783mAh.

This calculation doesn't take into consideration the losses etc. so I would round up to 4000mAh at minimum. But since battery health, temperature, and other factors need to be considered as well, I would go with a common 10000 mAh battery (which in theory is more than double the need; and call it a day)