What cable size to use for solar panels?

In respect to voltage drop and lengthy runs of wire, bigger is always better.

The 6B&S will do nicely.

If only a short run then 4mm or 6mm twin core sheathed (not ²mm) is the standard. Most 'loose' panels that are setup on the ground will have 10-20m of 6mm twin sheathed.

You don't need to worry about voltage drop on a solar panel as it is capable of supply in excess of 20V but it is the regulator that controls the voltage. It will drop the panel voltage to around 0.1V higher than battery voltage (at the reg) during boost and absorbtion charges.

Regards
David

My Collyn Rivers book has detailed formulas to work all this out - suggests that 6mm² ISO cable is the go for heavier parts of most solar applications - he suggests you can go smaller of course for lower current sections of the system (to save $ I suppose - in motorhomes etc. a lot of cable could end up being used).

Whatever guage wire you use, make sure it has a 20amp plus capacity minimum. You may never get to the ultimate with your panels, but to be sure, to be sure! May sol be with you!