BATTERY PACK AND ELECTRICAL APPARATUS USING BATTERY PACK

A battery pack which has cell units in which top-side and bottom-side battery cells are connected in series, and is capable of switching the connection state of the cell units, wherein a control unit monitors voltage imbalances between the cell units, and also monitors whether or not a cell unit contact failure has occurred. In order to stop a charging/discharging when a contact failure occurs, a signal (abnormality stoppage signal or charging stoppage signal) for stopping discharge is produced and outputted to the electrical device body-side.