Patent ID: 8212523

Claim:
A protection device for an assembled cell including a plurality of battery modules connected in series, each of which includes a plurality of secondary batteries connected in series, the protection device comprising: a plurality of protection units provided corresponding one-to-one to a respective one of the battery modules, each of which is connected to a corresponding one of the battery modules through a power supply line including a current detection resistor so as to be fed with a supply current from the corresponding one of the battery modules, wherein each of the protection units is driven by the supply current; and a management unit connected to the protection units in common, wherein each protection unit includes: a voltage measurement unit configured to measure a voltage of the corresponding one of the battery modules; a consumption current measuring unit configured to measure the supply current passing through the detection resistor, wherein the supply current is measured as a consumption current consumed in the corresponding one of the battery modules to obtain measurement data; a communication unit which transmits the measurement data to the management unit and receives setting data from the management unit; a discharging unit which discharges the corresponding battery module to produce a discharge current flowing through the discharge unit; and a control unit configured to control the discharging unit to adjust the discharge current based on the measurement data and the setting data such that a sum total of the consumption current and the discharge current in the protection unit is substantially same as that in the other of the protection units.