Patent ID: 8754654

Claim:
A power supply device comprising a plurality of battery units, each of the battery units comprising: a battery block that includes a plurality of battery cells serially connected to each other; a voltage detecting circuit that detects the voltages of the battery cells, which constitute the battery block, through voltage detection lines; a power supply circuit that supplies electric power for operating the voltage detecting circuit from the battery block; and a disconnection detecting circuit that detects disconnection of the voltage detection lines based on the detection voltages of the battery cells, which are detected by the voltage detecting circuit, wherein the battery blocks of the battery units are serially connected to each other to constitute a battery pack, at least one of the battery blocks of the battery units includes an unbalance resistor that is connected to the battery block to increase the power consumption of the battery block so that a current flows in the voltage detection line that is connected to a node between the battery block and an adjacent block of the battery block, which is connected next to the battery block to which the unbalance resistor connected, and the unbalance resistor has a preset value of resistance that allows flow of a bypass current thereby bypassing the power supply circuit through the unbalance resistor, the bypass current being larger than a variation of consumption currents flowing through the power supply circuit, the variation being caused by individual differences of the power supply circuit.