From my time on the A320:
BATTERIES ............................ 25.5V/AUTO
If the aircraft has not been supplied with electrical power for 6 hours or more, perform the following check:
- BATT 1 and 2 ......................CHECK OFF
- BATT 1 and 2 VOLTAGE ........CHECK BOVE 25.5V
(Battery voltage above 25.5V ensures a charge above 50%
. If battery voltage is below 25.5V a charging cycle of 20 minutes is required
- BATT 1 and 2 ...................... AUTO
- EXT POWER ..........................ON
This would imply that battery removal is not required (on the A320 family) and that after a 20 minute charge cycle all is legal to dispatch, and that should you suffer a complete electrical failure the batteries will have the required level of charge to see you ok for 30 minutes.
That's my interpretation. Now back on Boeings and nothing so explicit in our manuals.