Hi Ian and all fixers,
This is my BBP condition:
-The charging red-LED doesn't turn on when it should: charger connected, battery not full.
-The ac adapter led is on, and there is output electricity (18V)
So i did:
-Opened the bottom cover, and unplugged the battery from charging PCB
-Connected the ac adapter and the speaker can turn on without battery!
Im not sure if a bad battery could interfere with ac adapter only mode, but definitely you can try with no battery. Trial and error until isolate the buggy part.
Kind,
G