Join Date: Jun 2016
Location: Orange County, CA
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
The question is - how many amps are going from the panels to the charge controller, and how long a cable run is it? Remember that cable run length is measured for the round trip, i.e. there and back, not just one way. There's plenty of cable gauge calculators online to know what to use.
FYI, each half of my PV produces 34A at 30V, and after the individual panels' 10AWG outputs are 12A-fused and combined they use 4AWG welding cable to connect to the 50A input breakers before the charge controllers. If in doubt, go bigger. Without sounding too sexist, cables should be short and fat! And use proper lugs and a good lug crimper tool for a reliable connection. Definitely no mickeymousing when dealing with potentially fatal currents, even when they're at low voltage.