Originally Posted by GearHd6
Thanks for the solar info!
What is considered a good size wire? My battery is on the tongue and the converter is all the way at the rear. That's probably not an ideal setup to begin with.
I would bet that you currently have #8 or #6 cables from your rear converter to the batteries. All of your normal 12 v loads go through those cables and I am sure that there are things in your unit that can draw at least 20 amps of DC. If you are installing a reasonable solar solution, say 2 100 watt panels, you will never supply more than 11 amps (two 100 to 150 watt panels in parallel) from a solar controller at 12 to 15 volts. Might not sound like much but it goes on for hours and hours...as long as the sun is out. If you locate your solar controller next to your converter and use the existing wiring, you should have plenty of capacity since a #6 wire set would lose you less than 1% from the solar system.
Now, if you use a Trimetric meter and its companion SC-2030 solar controller, the controller will be monitoring the voltage at the batteries
since it gets its information from the Trimetric over a data cable. So if it wants to do a boost charge to 14.5 volts and there is a .3 volt drop in the cables, it will get the battery voltage data as if it measured it right at the battery terminals, since that is where the Trimetric is connected and the controller will boost the voltage until the batteries see 14.5 volts, overcoming any losses in the cables! You should also get the accessory temperature probe and mount it near the batteries since the controller adjusts it charging parameters to allow for the battery temperature.
The only time that you would be supplying 11 amps (two panels) is in full sun, with the panels well aligned to the south, the ambient temperature below 50 to 70 degrees and the batteries at a low state of charge. As the temperature rises, the panels put out less current. There is plenty of voltage available to overcome your 1 to 3% loss from the cables and the controller will adjust accordingly. Other times the current will be lower since the batteries are coming up to full charge or the sun is lower in the sky or an at poor angle to the panels.
Bottom line, I am sure that if your cables can supply the RV or TT with sufficient DC power, they are fine as is for adding a solar solution.
You should, however, use 10 GA PV cables from the panels to the controller.