Its an expensive option, but you actually want an isolater for your system to have it "right".
Isolaters take a power source and, uh, isolate the power across several loads. Your alternator would feed your isolator, which in turn would charge your vehicle battery and your assy battery while maintaining seperate circuits for them. If you are running a fridge, youll want a bit more than a trickle feeding it for longest component life. Just like you dont drive a 5k rpm all over, dont ask your equipment to operate at its extreme.
Not to say it wont work other ways. If you want to do the trickle, run it straight from the battery.
Wih isolators you can have additional power sources, too. Get a converter and youll be able to plug your jeep into a wall outlet to run your elec system.
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