How to calculate the heat dissipated by a battery pack?
The battery heat is generated in the internal resistance of each cell and all the connections (i.e. terminal welding spots, metal foils, wires, connectors, etc.). You'll need an estimation of these, in order to calculate the total battery power to be dissipated (P=R*I^2).

Considering your data to make an example, with a 1C discharge current (5.75A per cell) and estimating, let's say, a resistance of 50mOhm per cell, each cell is contrubuting 1.65W of dissipated power (Pcell=0.05*5.75*5.75), and the total dissipated power for the battery is Ptot=1.65*720=1190W.

As the real battery current, you can consider the mean discharge current during normal cruising on flat road, which is usually constant speed and quite low current. But take also into account the peak current the battery needs to deliver, for example during acceleration or regenerative braking or climbing. In particular, during the two latter cases, the current value can be high for a prolonged amout of time.