The one item I added to my MotorHome was two BP65 - smart battery protects 65 amps. I had a “salesman switch” that used a relay (it burned too many watts).. The real reason I got it was so the 12v stuff would not drain my lithium battery. (My rig needed two - yours probably just needs one).
I had installed new agm batteries- used them for a year - took my rig into the shop. It snowed. Because it snowed I left the rig at the shop for a few extra days (so roads would be nice and clear). Unfortunately the small loads ran the batteries down to 4.x volts when I picked up the rig. Recharged them - but the damage was done. Got one more years use - but replaced with lithium. Wanted to make sure there was double backup for killing power. I have them programmed to shutoff at 11.8v and 11.5volts.
I had installed new agm batteries- used them for a year - took my rig into the shop. It snowed. Because it snowed I left the rig at the shop for a few extra days (so roads would be nice and clear). Unfortunately the small loads ran the batteries down to 4.x volts when I picked up the rig. Recharged them - but the damage was done. Got one more years use - but replaced with lithium. Wanted to make sure there was double backup for killing power. I have them programmed to shutoff at 11.8v and 11.5volts.