What solar panel specs are used for calculating voltage loss

Joel_T wrote:
Which solar panel specs are reasonably used for calculating line voltage loss?

The variable is the amps being carried on the wire. So two typical situations are 24-12 with MPPT and 12-12 with PWM

24-12 with MPPT has the panel to controller wire carrying Imp at Vmp while the output controller to battery wire will be at 12-12 and the amps will be output watts divided by battery voltage at the time.

12-12 PWM will have the panel to controller wire carrying the panel Isc and passing that through to the battery with the panel's IV curve showing that amps slight reduction as battery voltage rises to the controller's high set point of say 14.8v For two 12s in parallel you add their Iscs for the combiner-controller path amps