I modified an O scale RS-3 to run on either track power or battery power. My layout is around the ceiling and sometimes I don't use it for awhile so the track does get dirty. I also updated the lighting in the locomotive and the cab lights are track power only so I can see how clean the track is by watching it run around the layout
Now once I switch to battery power, the locomotive just runs with no control. I only use it to clean the track.