After performing a long haul flight in the PMDG 777 and switching from APU power to ground power for the turn around, it is protocol to leave the battery on when connected to ground power, or is the battery turned off? I've read the manual but it does not specify this area of the secure and shutdown process. 

Thanks,

Rajan F

You wouldn't turn the battery off unless you were trying to turn the plane off completely.

58 minutes ago, Captain Kevin said:

You wouldn't turn the battery off unless you were trying to turn the plane off completely.

I guess it's the last resort of electrical power in case other sources of electrical power fail, enough at least to power the avionics and radios for a little while?

Thank y'all so much for the quick response. It makes sense that it would stay on during the turn around time, even when connected to a GPU. 

Battery gets turned off in cases when the plane won't be flown for long periods of time.  Usually when the plane is parked  off ground power not at a gate. It prevents discharge over time.

On 5/4/2020 at 3:17 AM, Captain Kevin said:

You wouldn't turn the battery off unless you were trying to turn the plane off completely.

Switching the battery off with external AC power connected wouldn't turn off power. It just isolates the battery. The TRUs would provide DC power. It would probably shut down the APU if that was running though.

It varies by aircraft model, but generally batteries are always kept “on” when running on APU or ground power. In the CRJ, (and probably most large aircraft), the batteries are not actually connected to the DC power buses as long as the TRUs are active, but need to be ready to take over immediately if external or APU power fails. Depending on aircraft model, this may preserve IRU alignment and any preflight FMS programming that may have been accomplished (if an external power interruption is only momentary). With batteries “off” the aircraft would go completely dark, and all preflight actions would have to start from square one.