I have my controller in a water tight utility box mounted to the battery box. I used 10awg wire between the controller and battery. I use 50 amp plug similar to this DEFEND INDUST 50A 6-10 Gauge Universal Battery Connect Quick Disconnect Wire Harness Plugs with Handle for Winch Auto Car Trailer Driver Electrical Devices,2Pcs
https://www.amazon.com/dp/B07T723RT9..._hXXhEbCQZ11HZ to connect the solar panel, just keep it lube with dielectric grease and capped when not being used.