I am just guessing here as I am as new to the RV thing as you but that looks like the solenoid that connects the battery to the converter. Mine has a switch at the side door that is labeled battery connect/disconnect. Just for giggles have someone activate your switch and listen to see if that's it. You can hear mine close anywhere in the coach if its quite
I am learning all the systems like you and if you can locate the components they are all fairly simple. I have worked on aircraft for 40 years but since there are no diagrams for my coach you have to pull panels and trace things down.