steve,lem,flt detent
Steve..
Classics can have a dc plug in the e&e for an external supply.
LEM..
Starting an apu with a low battery can be risky.
Sure the battery will suffer but the apu is at greater risk.
flt detent..
Not across all variants but the NG's I am familair with (-800's) have just the one battery for powering the buses.(barring the backup in P6 to close some valves )