Which airbus ? Are you using a jetway and saw the message about the GSX battery charger in action and this is when that happened ?
That's the only case in which GSX ever interacts with the electrical system and, the only thing it does, is to keep the battery charged, but ONLY if it was below 90% of its voltage, and will only do it until it goes back to 90% so, it has been designed this way precisely for the reason that you *may* used an external power so:
- If you are using the external power, that's like to keep the battery charged until 100% so, if you already have it connected (and the charge is higher than 90%) before calling GSX, the GSX battery charger won't even start.
- If you don't use the external power or another power supply (maybe forgot to use it), and leave the battery to discharge, IF you are connected to a jetway, once it goes below 90%, the GSX charger will start, to prevent it from discharging.
Not sure how keeping the *battery* charged, which is a standard simulation variable available in all planes, could affect an airplane external power, which is instead a custom system, since the simulator doesn't provide with such system.