I am now running a single 31' Northstar AGM for my cranking batter with a hood mounted flexible solar panel that keeps that battery topped off at all times. I removed the other battery under the hood and now use the battery box as an electrical fuse bus base for most of my on-board electrics. I installed 2 Battle Born lithium batteries with 100 amp hours each inside my truck on the floor next to my Goose Gear box and built a cage around them so items don't fall on top of the batteries and short them out. Those are charged by a 200 AMP roof rack mounted rigid solar panel by Renogy. I also installed charging ports in both the front and rear bumpers when garaged. My entire power set up is now rock solid. One last thing, I installed the Victron Connect system to monitor my batteries. Redarc also makes super cool monitoring systems, but very pricey. The Victron shows everything I need to manage my batteries and does so with Bluetooth tech to an app on my phone.
I will say, after 6 years and 3 sets of Northstar 31 AGM's under the hood, I'm not recommending it. I found that when the AGM's run too low, the battery memory goes to hell and wind up needing replacement. They're not cheap. Due to my own error by not turning off my fridge, I ran the batteries too low and ruined them. A pretty normal human error....especially when returning home from a long trip and wanting to relax after unloading. Under hood heat is also an issue. I believe the heat contributed to their short life. I should have gone back to the dealers where I purchased them, but I'm too lazy. In the end, it probably would have saved me at least $1,200.