I realize that there all others out there but this is the one i had on my prior motorhome and now my 3931fb. it has saved me a few times with low voltage that i have had at a few parks during the hot summers. you can see what it protects for on the chart.
https://cdn3.volusion.com/dxylq.nrud...jpg?1443501703
al meyer
3931 fb
az