All aux battery related wiring is 2GAGeorge, Can you describe the wiring and fuses that you use for your aux battery setup?
I have one of those same batteries and I am thinking of adding a second one.
What wire gauge from your alternator to your battery bank, fuse sizes for the alternator run, fuse for between batteries, fuse for the inverter?
There's a 80A fuse on the battery hot bus, I had an empty position there. (under the plastic box right off the battery + terminal)
I use a Stinger 80A relay switched with D+ to connect the house and vehicle batteries.
The Stinger 80A relay is to the left.
Then I have a 80A fuse between the relay and the batteries under the passenger seat.
An additional 80A fuse is between the batteries and the inverter
That's my old inverter since replaced.