I studied that a battery has a minimum voltage level when it is fully discharged. If I connect a load to a fully discharged battery, does the battery continue to deliver power? If for example I connect a resistor to a discharged battery, the power delivered to the resistor is Vmin^2/R, right?
Depending on how "discharged" a battery is, it may continue to provide some power, but depending on the level of discharge, the output voltage will drop rather quickly.
Details will vary but past a point, the battery will literally put out a voltage of 0 V. So your equation is correct, assuming you take into account that Vmin is not constant, but keeps dropping as the battery gets discharged.
The best way to understand this is to treat the "level of discharge" as a "growing resistor" placed in line with the battery. The more the battery discharges, the higher the resistance value. So if your battery is 3.7 V when fully charged (the resistor is let's say 0.1 ohm). But when fully discharged, the resistance may now be 1000 ohm or more, so when you draw power from it, you will only get so much current, and of course, as you draw current, the resistance keeps growing. This is rather simplistic, but hopefully gives an idea of why you can't assume Vmin is fixed.