Originally Posted by RJay
I don't have solar power but in what I've been able to learn is that the higher wattage panels with the higher voltages are more expensive but they are the ones that ensure that the power generated will reach the batteries.
Partly true but the higher voltage panels are also impacted more by any shading of a panel due to the way the load resistance affects the controller.
Panels are made for commercial and residential applications and not RV's. In a large grid array on a roof or out in a field the higher voltage with DC current is important. For a 12' run from a RV roof mounted panel to the controller it is much less important.
There is an exaggerated notion as the gauge wire needed. #8 wire has a resistance of .628 per 1000 feet as compared to #6 at 0.395 per 1000 feet and #4 at 0.248 and #2 at 0.156. The difference for a 30 foot cable run between #8 and #2 is a whooping 0.0141 Ohms. With panels providing 24v output the additional voltage drop using #8 wire for the 30 foot run is going to be all of 0.34 volts or 23.66 volts in total getting to the controller. If you are losing more than that then the problem is in one or more of the connections from the panel to the controller or the controller's grounding.
You can get 10x that amount of resistance from a single badly crimped connector. I put my attention into properly soldered copper terminals using my butane powered portable soldering iron to insure maximum current flow through the connections over the life of the installation.