The battery pack is provided with a rechargeable battery that can be charged,
and a protection device to protect the rechargeable battery when an abnormality
occurs. The protection device is provided with an externally exposed first output
terminal connected to the first electrode of the rechargeable battery, an externally
exposed second output terminal connected to the second electrode of the rechargeable
battery, and an externally exposed third output terminal for signal detection as
output terminals, and a contact switching section that can switch contact when
a rechargeable battery abnormality is detected. The protection device is formed
as a single piece with the output terminals and contact switching section. The
contact switching section has one end connected to the second electrode of the
rechargeable battery, the other end is connected to allow switching between a contact
connected to the second output terminal and a contact connected to the third output
terminal. When no abnormality is detected the other end is connected to the contact
connected to the second output terminal, and when an abnormality is detected the
other end switches to the contact connected to the third output terminal.
