Went out the the Barth to do some upkeep (the portable vacation home I always wanted,lol) and found the 12v system dead as a doornail.

Hooked up the charger and set about my repair under the sink.

Could NOT figure out what draw killed those batteries, I had kind of already placed blame in my mind that my wife might have left a closet light on, but no such thing.

Well, while doing my plumbing work, I found that the 'auto fill' solenoid that I de-plumbed last year when it failed, (But never electrically disconnected) must have been tripped in the dark sometime a couple of weeks ago. Since there was no water hookup, and hence no fill alarm to signal it to shut off, it was the drain on my batteries. Sucker was pretty warm to the touch too, glad it didn't start a fire.

Fully disconnected it, and pitched it. Lesson learned, lesson shared.