Actually, the Bilge pump is wired from the DC panel, which gets shut off as well! Perhaps not smart, but it was like that when i bought the boat a couple of years ago.
My bilge was quite dirty / oily after years of neglect, and I did not want a permanently wired / auto bige pump, that would put out oily water.
I now have the bilge to a pretty clean state, so I could likely rethink this now.
However, I have a traditional stuffing box / hose in good repair, and close all 3 seacocks if I am going off the boat for more than an hour, etc, so, for me, I don't really see the need for a directly wired / auto bilge pump.
Back to the original question, where else could that other wire go, from the common battery switch post???
PS. Bill - my Iota 45 amp charger has been working well. Great recommendation, and great price as well.