It's kind of a mopar...2017 Cherokee starting system issue
Search for a wiring diagram.
Chilton's manual would probably work
Never saw a setup like that.
My guess is there is an isolator some where in the system. Other wise both batteries would drain if the headlights were left on for example.
Rvs with 2 batteries have an isolator.
There is a possibility that the isolator fried in the jump start attempt so now it's not charging the small battery.
Just spitballing here.