Requested link...
Sure. Its in the FAQ. I'm about the 7th or so example down the list.
https://forum.ih8mud.com/showthread.php?t=104630&highlight=dual+battery+faq
I looked around at the different automatic/isolator options before I did mine. In the end I decided to do a brute force version that requires me to choose how my system is configured on any particular day. The batteries are Optima D31A industrials bought in a matched two pack set. In general...