An assembled battery management system has an assembled battery having a plurality of battery modules connected in series, wherein each of the battery modules has a plurality of battery cells connected in series, a connection member that connects the plurality of battery modules, and a battery voltage detection device that detects voltages of the battery cells. The battery voltage detection device has a monitoring section having a voltage detector that detects the voltages of the battery cells, wherein the monitoring section monitors the voltages of the battery cells based on a detection result of the voltage detector, and a plurality of voltage input terminals connected to the monitoring section. Each of the battery modules includes a plurality of voltage detection terminals connected to a positive electrode and a negative electrode of each of the modules as well as connecting points of the battery cells.