In RV park. Now have car to drive. Disconnect RV battery?

Or you can install a BIRD a Bi Directional Isolator Relay Delay

There are some brands that come from the factory with them already installed,Fleetwood products such as mine and some Winnebagos come from the factory with a BIRD and if the battery disconnect,on the power panel, is left on it will connect both batteries when not on shore power or generator.

It operates by sensing the voltages on both batteries.
When either of these voltages exceeds 13.3 volts for
approximately 1 minute, which happens when either battery
is being charged, the control will close the isolator solenoid,
connecting the two batteries together, charging them both.
(Normal charging voltages are from approximately 13.8 to
14.4 volts.)
After the solenoid has been closed, the system continues to
sense the voltage. If the ignition switch is off and the battery
voltage drops below 12.8 volts for approximately 1 minute,
which might occur when the converter is heavily loaded,
the solenoid is opened to prevent the chassis battery from
being discharged by the coach loads. When the voltage goes
above 13.3 volts again for approximately 1 minute, the solenoid
closes again. Thus always keeping the Coach as well as Chassis battery charged. Regardless of the parasitic draws on the chassis battery that run it down while sitting unused.