The left Glareshield and center-left Main Instrument Panel (MIP) flood light is powered by the DC Essential Bus. The right Glareshield and center-right MIP flood light is powered by DC1 Norm Bus.
A simplified schematic of the pinouts with a relay connected to control correct behaviour:
When one battery is operating, essential bus services such as the captain side flood lighting will be available.
Unfortunately at the time of this writing, avionic software ProSimA320 does not provide software gates to implement relay control to seperate the different Buses. Jeehell FMGS allows access to these gates using the API (facilitated by the Cockpit Concept relay board).