NOVELTY - The battery assembly (1000) has unit cell wirings (111-113) that are configured to provide one connection for a unit cell (101). Multiple unit cells are configured to connect in the connection. A cut-off device (100) is attached to one of the unit cells and provided with a fuse circuit (10) configured to disconnect the connection by heat produced in a heater circuit (20). Power supply wirings (121,122) are configured to supply the heater circuit of the cut-off device with the electric power.    USE - Battery assembly including lithium-ion battery, lithium-ion polymer battery, nickel-cadmium battery, nickel metal hydride battery, vanadium battery, lead-acid battery, sodium-sulfur battery, for electric vehicle and used in power grid system incorporating sustainable power generation system such as solar battery system or wind power generation system.    ADVANTAGE - The electrical isolation of all unit cells at the time of recovery or recycling is achieved due to the parallel connection of heater circuits. The safety for recovery and recycling of battery assembly is improved by applying the electrical power to the heater circuits. The electrical conductivity of the heater is also easily controlled. The short-circuit condition of the heater circuit is prevented, since the electrical resistance is maintained by the insulator. The unit cell is prevented from the abnormal raising of temperature due to the cut-off device. The fusing of cut-off device is possible at abnormal operations. The battery assembly is user convenient, since the heater circuit can be connected or disconnected easily. Since the commercially available components are used for the fuse circuit, the insulation tube, and the heating wire, the manufacturing cost can be reduced.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a unit cell;    (2) a cut-off device; and    (3) a method of disconnecting the unit cells.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit diagram of the battery assembly.    Fuse circuit (10)    Heater circuit (20)    Cut-off device (100)    Unit cell (101)    Unit cell wirings (111-113)    Power supply wirings (121,122)    Battery assembly (1000)