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

As was said, you need to be more specific with your question.

"Line loss" is directly related to the resistance of the conductor AND the current carried.

If you meant something else, let's start over.

I believe he is asking about cable losses but most voltage loss calculators assume 12V, 24V etc. We all know our panels do not put out 12V or 24V. They put out 17-18Vmp and 27-35 Vmp. So is your question, Should we be using Vmp when sizing our cable? I don't know. I think most just 12V and size for 3% or less loss from PV to controller and 1% or less from controller to battery.

The link mentioned above allows for specific voltage/amperage so in that case, I would tend to use Vmp and Imp from the PV array.

If I am close to the 3% margin I'll lean to going one size larger to account for possible connection losses.

If you are asking about cable losses, none. That is a separate and unrelated (to the panel) spec.

You can find wire resistance loss calculators all over on Google tho.

HERE's ONE