Hard to say....hold fire
I can only comment if this happened on a B737NG.
1. If the 'Standby Power Off' light illuminates, the QRH gives a few lines on what's wrong. The corrective action is:
STANDBY POWER switch.......BAT
End of checklist.
If there's excessive battery discharge (in the 737) the 'BAT DISCHARGE' light will illuminate. In this case the QRH states the obvious that's there's excessive battery discharge and Note: Fully charged batteries provide a minimum of 60 minutes of standby power.
End of checklist.
The second checklist is your heads up to get on terra firma.
Can any 737 engineers tell me if the STANDBY POWER switch is placed to BAT that the batteries should continue to be charged?
IR