Reduce Solar Panel Current
Solar panels are not current rated by what they DO output but by the maximum current they CAN output if you provide the correct load.
It would be extremely rare to have a 5V, 80 W panel.
Panels of that wattage are almost invariable of a higher rated voltage.
However, if we assume that you do then the 5V would probably be 5V Vmp = voltage at maximum power in full rated insolation (solar illumination).
The maximum current it COULD output at rated voltage would then be
I = P/V = 80/5 = 16A.
This corresponds to a load of R = V/I = 5/16 = 0.375 Ohms.
To draw only 8A at 5V the load would need to be R = V/I = 5/8 = 0.625 Ohms.
Note that this does NOT entail adding a resistor in series with the load but changing the load resistor.
If the panel is operated at lower than its rated load in full sun the voltage will rise to slightly above 5V.
It is likely that this does not cover your real question. If you explain in more detail what you are trying to achieve it will help us to help you.