I got a new nextdoor neighbor a few days ago. He came in late so I didn't introduce myself until the next day when I saw him going from bay to bay with a multimeter in his hand and scratching his head.
After finishing lunch I went out, introduced myself and asked if I could help. He said he lost all 12 volts in his 40'DP coach and described all the things he had done to troubleshoot it. He had installed over 1000 watts of solar with lithium batteries and two inverters himself so I thought I wouldn't be able to help him as that was outside my realm of experience.
All of a sudden I thought of the Salesmen's Switch (Battery Disconnect for the purists.) When I asked him if he had checked it he had a slightly confused look on his face. I told him where to look for it. He climbed up the stairs, flipped the switch and instantly became a much happier man.
He called out to his DW telling her I was a genius. That confused me because no one has EVER called me that before.
I told him I was no genius but I am a member of iRV2.com where people teach you stuff like that.
I still need my Salesmen's Switch because my old satellite antenna turns itself on, usually in the middle of the night, two or three times a year apparently to search for satellites. I have done everything I can think of to kill all power to it but the SS is the only thing that works.
I will probably replace the switch with a guarded toggle switch like is found in many aircraft.