I guess this is proof I'm a know-nothing when it comes to electricity.
How many disconnect switches do I need and which posts do I put it/them on?
Coach has four batteries, in parallel if I remember my high school teaching.
There is a third (and lighter) negative cable to the coach at the two-dot post.
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DC & Mac
2019 Vista LX 35F (Cayenne)
"The Okiebago"