One of the solenoids (inside firewall driver side) is for the starter motor. When it dies, you can hear it clicking with the ignition key on start, but no starter action.
The house battery latching solenoid was back in a driver side compartment before the wet bay.
There are two diode devices on the outside firewall driver side. These feed charge current to your house and chassis batteries. There is also a solenoid in a gray box for jumping your chassis and house batteries.
This info is 1992 related, best I can do and I didn't have an inverter. YMMV.
2013 Allegro Open Road 36LA
2009 Grand Cherokee Limited