Krap stuffed into a car battery jar is OK for weekend warriors. For off grid boondocking nyet, nein, no. No one can make a flooded car battery nowhere near as good as a flooded golf car battery. Good means easier to charge, more resistant to sulfation, longer lived, more efficient, you name it the car jar battery loses.
Even premium manufacturers like Trojan cannot build a forgiving car jar RV battery. Call them. It's toll free.
Group 24, group 27, and group 31 batteries are weekend-warrior specials.
To each his own -- I'm cheap and lazy...