The batteries will discharge
relatively slowly. Normally the Batteries are not connected to the Main and APU Battery Busses, unless you do something silly like put the Standby Power switch to BAT. However, the batteries will be connected to the Main HOT and APU HOT Battery Busses.
There are quite a few things on the hot battery busses, but some will be low current, like the clocks, and some things will be running quite nicely on their normal AC power.
The loss of AC 1 will probably keep you rather busy, so don't forget about the Batteries
Rgds.
NSEU