Hi Captain,
My understanding is a little different from yours.
Firstly, the main battery charger reverts to a "TR" mode following completion of the primary charge cycle, (reverts to a constant voltage mode), and powers all the loads connected to the battery and hot battery busses.
So all loads would be supported at this stage.
As I understand it, the BAT DISCHARGE light only comes on when there is a high discharge from the primary battery, (like starting the APU), so this one won't come on if the battery internally fails.
The standby power only comes on automatically if either AC transfer bus 1 or the source of power to DC bus 1 is lost. AC bus 1 is normally powered by IDG 1, and subsequently powers, via TRU 1, DC bus 1. So the standby bus will not automatically initiate.
By the way, the ONLY time the auxiliary battery is connected to the aircraft system is when standby power is in use, it is not used for any other purpose.
All those things, clocks etc, I would think would all remain powered.
The main problem, as I see it, would be the reduction of standby power capability from the normal 60 minutes, to something around half that, depending on what effect the failed battery would have on the auxiliary battery, since it would be still connected in the system (assuming the BAT switch is ON).
Thats about all I can think of off the top of the head, please if anyone can 'shoot me down' (bad choice of words) regarding these thoughts, please go ahead, I'm sure I too will learn something here!
Cheers
