Yeh id agree that if
U can put aux batt in tray them great.
For me though , I couldn't , I have canopy and sleeping for two. (need room , and didn't want fumes in my sleeping quarters)
Haven't had much trouble with heat tho i do expect my battery won't last quite as long in engine bay as it might in cooler location , but that's a compromise I was happy to make
I had originally had a leaky wet cell deep cycle but found she leaked a lot and I neglected it too often.
Now have a maint free lead acid (n70 tray size , 105ah , 800cca all rounder)
V6 in particular is a very hot engine bay.
My sparky mate just today setup his new 70series ute , he went for same battery in the engine bay. He's got a 40amp dc charger. No smart switch over (overkill really).
There are many ways to skin a cat , that's for sure
Just been at mates place and he's got digital ammeter and dual voltage readouts, my car will be next