The invention provides a battery module including an output breaker that ensures safe and prompt installation of batteries in a system. The battery module includes one or more batteries and a case housing the batteries and having output terminals, each output terminal being connected to a positive or negative electrode of the housed battery, the battery module further including means for turning on and off the connection between the output terminal and the positive or negative electrode of the battery. The means for turning on and off the connection may include a contact subjected to making and breaking operations and a screw for making and breaking the contact, the screw having an insulator at an interface with the contact.