There is a quick and easy way to determine approximately how much usage time you will get out of a portable power station with any given appliance. You simply take the Watt Hours of the power bank and divide that number by the Watts of the tool or appliance.
For example, if you have a 50 watt appliance and a 300Wh power bank, you simply divide 300 / 50 and you get 6 hours of run time.
Of course the actual numbers are going to vary wildly depending on a number of features, but this theoretical approximation is usually enough to get a good idea of whether any particular power source will be enough for your purpose.