Management device and power supply system
Provided is a controller configured: to calculate, among voltages detected from a plurality of cells, a voltage difference between the voltage detected from one cell of the plurality of cells, the one cell to be detected, and a representative voltage at each of a first time and a second time, the representative voltage based on the voltage detected from at least one cell of the plurality of cells, the at least one cell to be compared; and when a discrepancy between the voltage difference at the first time and the voltage difference at the second time is equal to or more than a threshold, to determine that an abnormality has occurred in the one cell to be detected. The controller refers to a state-of-charge versus open-circuit-voltage (SOC-OCV) curve of the one cell to be detected in accordance with a state-of-health (SOH) of the one cell to be detected, so as to estimate an SOC as initial capacitance reference of the one cell to be detected in correspondence to the voltage detected from the one cell to be detected. The controller introduces a linear function using an SOC as initial capacitance reference as an input variable, using an OCV as an output variable, and having a predetermined inclination, and applies the SOC as initial capacitance reference of the one cell to be detected that the controller has estimated to the linear function, so as to derive an OCV. Then, in place of the voltage detected from the one cell to be detected, the controller uses the OCV that the controller has derived, so as to calculate the voltage difference at the first time and the voltage difference at the second time.
1. A management device comprising:
a voltage detector configured to detect a voltage, the voltage being each of voltages detected from a plurality of cells of a power storage module that are connected in series to each other; and
a controller configured to calculate at each of a first time and a second time, among the voltages detected from the plurality of cells, a voltage difference between (i) the voltage of one cell to be detected among the plurality of cells and (ii) a representative voltage, the representative voltage being based on the voltage of at least one cell to be compared among the plurality of cells; and when a discrepancy between a voltage difference at the first time and the voltage difference at the second time is equal to or more than a threshold, the controller is configured to determine that an abnormality has occurred in the one cell to be detected,
wherein the controller refers to a state-of-charge versus open-circuit-voltage (SOC-OCV) curve of a cell in accordance with a state-of-health (SOH) of the cell, so as to estimate an SOC as initial capacitance reference of the cell in correspondence to the voltage detected from the cell,
the controller introduces a linear function using an SOC as initial capacitance reference as an input variable, using an OCV as an output variable, and the linear function having an inclination predetermined, and applies the SOC as initial capacitance reference of the cell that the controller has estimated to the linear function, so as to derive an OCV, and
in place of the voltage detected from the cell, the controller uses the OCV that the controller has derived, so as to calculate the voltage difference at the first time and the voltage difference at the second time.
2. The management device according to claim 1 , wherein the threshold is set to a value corresponding to a value of the inclination of the linear function.
3. The management device according to claim 1 , wherein the controller excludes a maximum voltage and a minimum voltage among the voltages detected from the plurality of cells, and averages a rest of the voltages detected from the plurality of cells, so as to calculate the representative voltage.
4. The management device according to claim 1 , wherein
the controller calculates, whenever a predetermined period of time has elapsed, the discrepancy between the voltage difference at the first time and the voltage difference at the second time, so as to compare the discrepancy calculated with the threshold, and
when the discrepancy is equal to or more than the threshold for N or more times, where N is an integer of 2 or greater, in x comparisons previously made, where x is an integer of 2 or greater, the controller determines that the abnormality has occurred in the one cell to be detected.
5. A power supply system comprising:
the plurality of cells of a power storage module that are connected in series to each other; and
the management device according to claim 1 , the management device configured to manage the plurality of cells that are connected in series to each other.