Going to do a test at Death Valley soon and will see if I really need an additional 50 or 60 watts. May get by with only needing 30 watts and Renogy has a 30watt panel with 15ft cable and alligator clips at the ends for only $65. That may be the cheap way out. No need to get a 20 or 30 amp controller and the existing wiring is adequate. Yes, I can buy all kinds of things to make it more efficient. We will see???
I am surprised that the Renogy 30 watt panel doesn't need a controller and hooks directly to the batteries.