JP2014223004A - Power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminatingly identify each of an open state of a voltage detection line and an overcharge state of a power storage unit.SOLUTION: A power storage system has first and second power storage units connected in series. A voltage detection circuit detects a voltage value of each power storage unit by the use of a capacitor connected in parallel with each power storage unit via a voltage detection line. Each power storage unit and the capacitor are connected with a parallel switch, and a controller controls the operation of the switch. A predetermined process is performed to turn the switch corresponding to the first power storage unit from off to on while keeping the switch corresponding to the second power storage unit off. During the predetermined process, if the voltage value (first voltage value) of the first power storage unit detected by the voltage detection circuit is a lower limit value and the voltage value (second voltage value) of the second power storage unit detected by the voltage detection circuit increases, it is determined that the voltage detection line is in an open state.

Description

  The present invention relates to a power storage system that detects voltage values in a plurality of power storage units connected in series.

  In Patent Document 1, in a configuration in which a plurality of battery units are connected in series, the voltage value of each battery unit is detected by connecting the positive terminal and the negative terminal of each battery unit to a voltage detection circuit.

JP 2010-032412 A

  In the configuration described in Patent Document 1, the detection result by the voltage detection circuit is the same when the battery unit is in an overdischarged state and when the wiring connecting the battery unit and the voltage detection circuit is disconnected. May end up. In this case, the detection result of the voltage detection circuit cannot distinguish whether the battery unit is in an overdischarged state or whether the wiring connecting the battery unit and the voltage detection circuit is disconnected.

  The power storage system according to the first invention of the present application includes first and second power storage units connected in series. The voltage detection circuit includes a capacitor connected in parallel with each power storage unit via a voltage detection line, and detects the voltage value of each power storage unit based on the voltage value of the capacitor. A switch is connected in parallel to each power storage unit and capacitor, and the controller controls the operation of the switch.

  Here, the controller keeps the switch corresponding to the second power storage unit off, and performs a predetermined process of switching the switch corresponding to the first power storage unit from off to on. When the predetermined process is performed, the voltage value (first voltage value) of the first power storage unit detected by the voltage detection circuit is the lower limit value, and the voltage value of the second power storage unit detected by the voltage detection circuit ( In response to the increase in the second voltage value), the controller determines that the voltage detection line is in a disconnected state. Specifically, the voltage detection line that is determined to be in the disconnected state is a voltage detection line that is connected to a line that connects the first and second power storage units.

  The first voltage value is the voltage value of the capacitor corresponding to the first power storage unit, and the second voltage value is the voltage value of the capacitor corresponding to the second power storage unit. When the voltage detection line is in a disconnected state, the stored charge of the capacitor corresponding to the first power storage unit can be released by turning on the switch corresponding to the first power storage unit. Accordingly, the first voltage value becomes a lower limit value. Here, if the electric charge is previously stored in the capacitor corresponding to the first power storage unit, the first voltage value is lowered to the lower limit value by turning on the switch corresponding to the first power storage unit.

  If the first power storage unit is not in the overdischarged state, the discharge current of the first power storage unit flows into the capacitor corresponding to the second power storage unit by turning on the switch corresponding to the first power storage unit. . In other words, if the first power storage unit is in an overdischarged state, even if the switch corresponding to the first power storage unit is turned on, the discharge current of the first power storage unit is the capacitor corresponding to the second power storage unit. Do not flow into.

  Thus, if the first power storage unit is not in an overdischarged state, the second voltage value increases. By confirming such behavior of the first voltage value and the second voltage value, it is possible to determine the disconnection state of the voltage detection line while distinguishing the disconnection state of the voltage detection line and the overdischarge state of the power storage unit. That is, by confirming the behavior of the first voltage value and the second voltage value, it is possible to specify that the voltage detection line is in a disconnected state.

  When the first power storage unit is in an overdischarged state, as described above, the discharge current of the first power storage unit does not flow into the capacitor corresponding to the second power storage unit. Accordingly, the second voltage value does not increase. By confirming such behavior of the first voltage value and the second voltage value, it is possible to specify that the voltage detection line is not in a disconnected state and the first power storage unit is in an overdischarged state.

  The power storage system according to the second invention of the present application has the same components as the power storage system according to the first invention of the present application. Here, when the above-described predetermined processing is performed, the voltage value (first voltage value) of the first power storage unit detected by the voltage detection circuit is the lower limit value, and the second power storage detected by the voltage detection circuit. In response to the voltage value (second voltage value) of the unit not increasing, the controller determines that the first power storage unit is in an overdischarged state.

  As described above, when the first power storage unit is in an overdischarged state, the discharge current of the first power storage unit does not flow to the capacitor corresponding to the second power storage unit, and the first voltage value becomes the lower limit value. At the same time, the second voltage value does not increase. Here, if the charge is stored in advance in the capacitor corresponding to the first power storage unit, the first voltage value is reduced to the lower limit value when the predetermined process is performed. If the behavior of the first voltage value and the second voltage value is confirmed, the overdischarge state of the power storage unit can be determined while distinguishing the overdischarge state of the power storage unit and the disconnection state of the voltage detection line.

  When the voltage detection line is in a disconnected state and the switch is turned on by a predetermined process, the accumulated charge of the capacitor connected in parallel with the switch can be discharged. Thereby, since the voltage value of the capacitor approaches 0 [V], the lower limit value described above can be set to approximately 0 [V]. Substantially 0 [V] means that a detection error of the voltage detection circuit is included with respect to 0 [V].

  The switch is used to equalize voltage values in the first and second power storage units. For example, when the voltage value of the first power storage unit is higher than the voltage value of the second power storage unit, the first power storage unit is discharged by turning on only the switch corresponding to the first power storage unit. be able to. Thereby, the voltage value of the 1st electrical storage unit can be reduced, and the voltage value of the 1st electrical storage unit can be made equal to the voltage value of the 2nd electrical storage unit.

It is a figure which shows the structure of a battery system. It is a figure which shows the structure of an assembled battery and a monitoring unit in a battery system. It is a flowchart which shows equalization processing. It is a figure which shows a part of circuit which detects the voltage value of a cell. It is a figure which shows the behavior of a voltage value when a voltage detection line is in a disconnection state. It is a figure which shows the behavior of a voltage value when a cell is in an overdischarge state. It is a flowchart which shows the process which discriminate | determines a disconnection state and an overdischarge state.

  Examples of the present invention will be described below.

  The battery system in Example 1 of this invention is demonstrated using FIG. FIG. 1 is a schematic diagram showing the configuration of the battery system in the present embodiment.

  The battery system shown in FIG. 1 can be mounted on a vehicle. Such vehicles include electric vehicles and hybrid vehicles. An electric vehicle is a vehicle that includes only an assembled battery described later as a power source of the vehicle. A hybrid vehicle is a vehicle provided with a fuel cell, an engine, and the like as a power source for running the vehicle, in addition to an assembled battery described later. In a hybrid vehicle, the assembled battery can be charged using electric power from an external power source. The external power source is a power source (for example, commercial power source) installed outside the vehicle.

  A positive electrode line PL is connected to the positive electrode terminal of the assembled battery 10, and a system main relay SMR1 is provided in the positive electrode line PL. Moreover, the negative electrode line NL is connected to the negative electrode terminal of the assembled battery 10, and the system main relay SMR2 is provided in the negative electrode line NL. System main relays SMR1, SMR2 are switched between on and off in response to a control signal from controller 30. The controller 30 can connect the assembled battery 10 to a load (a booster circuit 22 described later) by switching the system main relays SMR1 and SMR2 from off to on.

  The current sensor 21 detects the current value Ib flowing through the assembled battery 10 and outputs the detection result to the controller 30. In the present embodiment, a positive value is used as the current value Ib when the assembled battery 10 is discharged, and a negative value is used as the current value Ib when the assembled battery 10 is charged. In the present embodiment, the current sensor 21 is provided on the negative electrode line NL, but is not limited thereto. The current sensor 21 only needs to detect the current value Ib flowing through the assembled battery 10. For example, the current sensor 21 can be provided in at least one of the positive electrode line PL and the negative electrode line NL. In addition, a plurality of current sensors 21 can be provided for one of the positive electrode line PL and the negative electrode line NL.

  The assembled battery 10 is connected to the booster circuit 22 via the positive electrode line PL and the negative electrode line NL. The booster circuit 22 boosts the output voltage of the assembled battery 10 and outputs the boosted power to the inverter 23. The inverter 23 converts the DC power output from the booster circuit 22 into AC power, and outputs the AC power to the motor / generator 24. The motor / generator 24 receives AC power from the inverter 23 to generate kinetic energy for running the vehicle. The vehicle can be driven by transmitting the kinetic energy generated by the motor / generator 24 to the wheels.

  When the vehicle is decelerated or the vehicle is stopped, the motor / generator 24 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). Here, also when the vehicle travels downhill, the motor generator 24 converts kinetic energy into electrical energy in order to generate a braking force. The AC power generated by the motor / generator 24 is converted into DC power by the inverter 23. In addition, the booster circuit 22 steps down the output voltage of the inverter 23 and supplies the lowered power to the assembled battery 10. Thereby, regenerative electric power can be stored in the assembled battery 10.

  The controller 30 includes a memory 31, and the memory 31 stores information used when the controller 30 performs a specific process (particularly, a process described in the present embodiment). In this embodiment, the memory 31 is built in the controller 30, but the memory 31 can be provided outside the controller 30.

  Information about on / off of the ignition switch of the vehicle is input to the controller 30. When the ignition switch is switched from OFF to ON, the controller 30 connects the assembled battery 10 to the booster circuit 22 by switching the system main relays SMR1 and SMR2 from OFF to ON. Thereby, the battery system shown in FIG. 1 will be in a starting state (Ready-On).

  On the other hand, when the ignition switch is switched from on to off, the controller 30 cuts off the connection between the assembled battery 10 and the booster circuit 22 by switching the system main relays SMR1 and SMR2 from on to off. Thereby, the battery system shown in FIG. 1 will be in a halt condition (Ready-Off).

  The monitoring unit (corresponding to the voltage detection circuit of the present invention) 40 detects the voltage value Vb of the assembled battery 10 or the voltage value Vb of the single cell included in the assembled battery 10 and outputs the detection result. Output to the controller 30. FIG. 2 shows configurations of the assembled battery 10 and the monitoring unit 40.

  As shown in FIG. 2, the assembled battery 10 includes a plurality of unit cells 11 that are electrically connected in series. The number of unit cells 11 constituting the assembled battery 10 can be appropriately set based on the required output of the assembled battery 10 and the like. As the cell 11, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor can be used instead of the secondary battery.

  In the present embodiment, the monitoring unit 40 detects the voltage value Vb of the single cell (corresponding to the power storage unit of the present invention) 11, but is not limited to this. Specifically, the monitoring unit 40 can detect the voltage value of the battery block (corresponding to the power storage unit of the present invention). Each battery block is configured by a plurality of single cells 11 electrically connected in series, and the assembled battery 10 is configured by connecting the plurality of battery blocks electrically in series. Here, each battery block may include a plurality of single cells 11 electrically connected in parallel.

  The monitoring unit 40 is connected to each unit cell 11 via a plurality of voltage detection lines L1, L2. Here, although omitted in FIG. 2, switches can be provided on the voltage detection lines L <b> 1 and L <b> 2 located between the monitoring unit 40 and the unit cell 11. As this switch, for example, a photo MOS (Metal Oxide Semiconductor) relay can be used.

  The two voltage detection lines L1 are connected to the positive terminal and the negative terminal of the battery pack 10, respectively. The positive terminal of the assembled battery 10 corresponds to the positive terminal of the unit cell 11 positioned at one end of the assembled battery 10 in the circuit configuration of the assembled battery 10 shown in FIG. The negative terminal of the assembled battery 10 corresponds to the negative terminal of the unit cell 11 located at the other end of the assembled battery 10 in the circuit configuration of the assembled battery 10 shown in FIG. In the two unit cells 11 electrically connected in series, the voltage detection line L2 is connected to the negative terminal of one unit cell 11 and the positive terminal of the other unit cell 11.

  Each voltage detection line L1, L2 is provided with a resistance element R11. When a current larger than the allowable current value flows through the resistance element R11, the resistance element R11 is blown, whereby the electrical connection between the monitoring unit 40 and the assembled battery 10 can be cut off. Thereby, it can suppress that an excessive electric current flows into the monitoring unit 40 from the assembled battery 10 (unit cell 11).

  A Zener diode D is electrically connected in parallel to each unit cell 11 via voltage detection lines L1 and L2. The cathode of the Zener diode D is connected to the positive terminal of the unit cell 11, and a resistance element R11 is provided in the current path between the cathode and the positive terminal. The anode of the Zener diode D is connected to the negative terminal of the unit cell 11, and a resistance element R11 is provided in the current path between the anode and the negative terminal.

  The Zener diode D is used for suppressing application of an overvoltage from the assembled battery 10 to the monitoring unit 40. That is, when an overvoltage is applied from the assembled battery 10 to the monitoring unit 40, a current flows through the Zener diode D, thereby preventing the overvoltage from being applied to the monitoring unit 40. Here, the plurality of Zener diodes D are electrically connected in series.

  The voltage detection line L1 is provided with a resistance element R21, and the resistance element R21 is included in the monitoring unit 40. The resistance elements R11 and R21 are electrically connected in series, and the cathode of the Zener diode D is connected to the connection point of the resistance elements R11 and R21. The voltage detection line L2 is branched into two branch lines L21 and L22 inside the monitoring unit 40. The branch line L21 is provided with a resistance element R21, and the branch line L22 is provided with a resistance element R22.

  In the voltage detection line L2, the resistance elements R11 and R21 are electrically connected in series, and the anode of the Zener diode D is connected to the connection point of the resistance elements R11 and R21. In the voltage detection line L2, the resistance elements R11 and R22 are electrically connected in series, and the anode of the Zener diode D is connected to the connection point of the resistance elements R11 and R22.

  A capacitor (flying capacitor) C and a switch SW1 are connected to the voltage detection line L1 and the branch line L22. Specifically, the capacitor C and the switch SW1 are connected to a voltage detection line L1 located between the resistance element R21 and the sampling switch SW21, and a branch line L22 located between the resistance element R22 and the sampling switch SW22. Yes. The sampling switch SW21 is connected to the voltage detection line L1, and the sampling switch SW22 is connected to the branch line L22.

  In addition, regarding the two voltage detection lines L2 connected to the positive electrode terminal and the negative electrode terminal of each unit cell 11, a branch line L21 in one voltage detection line L2 and a branch line L22 in the other voltage detection line L2 include capacitors. C and switch SW1 are connected. Specifically, the capacitor C and the switch SW1 are connected to a branch line L21 located between the resistance element R21 and the sampling switch SW21, and a branch line L22 located between the resistance element R22 and the sampling switch SW22. . Here, the sampling switch SW21 is connected to the branch line L21, and the sampling switch SW22 is connected to the branch line L22.

  The switch SW1 is switched between on and off by receiving a control signal from the controller 30. The switch SW1 can be used to equalize voltage values in all the unit cells 11 constituting the assembled battery 10.

  Specifically, when the voltage value Vb of a specific unit cell 11 is higher than the voltage value Vb of another unit cell 11, the switch SW1 electrically connected in parallel with the specific unit cell 11 is turned on from off. By switching to, the specific unit cell 11 can be discharged. That is, when the switch SW1 is turned on, the discharge current of the specific unit cell 11 can flow through the resistance elements R21 and R22, and the voltage value Vb of the specific unit cell 11 can be reduced. Thereby, the voltage value Vb of the specific single battery 11 can be aligned with the voltage value Vb of the other single battery 11. Here, the process of aligning the variations in the voltage value Vb in the plurality of single cells 11 is referred to as an equalization process.

  Since the capacitor C is electrically connected to the unit cell 11 in parallel via the voltage detection lines L1, L2 or the voltage detection lines L2, L2, the charge stored in the unit cell 11 is stored in the capacitor C. Charged. Thereby, the voltage value of the capacitor C becomes equal to the voltage value Vb of the unit cell 11.

  Sampling switches SW 21 and SW 22 connected to the positive terminal and the negative terminal of each unit cell 11 are connected to a comparator 41. Specifically, the sampling switch SW21 is connected to one input terminal of the comparator 41, and the sampling switch SW22 is connected to the other input terminal of the comparator 41. Here, each sampling switch SW21, SW22 is switched between ON and OFF in response to a control signal from the controller 30. The plurality of sampling switches SW21 and SW22 can be configured by a multiplexer.

  When only the sampling switches SW21 and SW22 corresponding to the specific cell 11 are turned on, the comparator 41 outputs the voltage value Vb of the specific cell 11 (the voltage value of the capacitor C corresponding to the specific cell 11). . Thus, by sequentially turning on the sampling switches SW21 and SW22 corresponding to each unit cell 11, the voltage value Vb of each unit cell 11 can be detected sequentially. The output signal of the comparator 41 is input to the controller 30 after AD conversion. Thereby, the controller 30 can detect the voltage value Vb of each unit cell 11.

  Next, the equalization process will be described with reference to the flowchart shown in FIG. The process shown in FIG. 3 is executed by the controller 30. Moreover, the process (equalization process) shown in FIG. 3 can be performed, for example, while the ignition switch is OFF.

  In step S <b> 101, the controller 30 detects the voltage value Vb of each unit cell 11 based on the output of the monitoring unit 40. As a result, the controller 30 can detect the voltage values Vb of all the cells 11 constituting the assembled battery 10. Here, the voltage value Vb in the plurality of unit cells 11 may vary due to self-discharge of the unit cells 11 or variations in resistance values (internal resistance) in the plurality of unit cells 11.

  In step S102, the controller 30 specifies a voltage value (minimum value) Vb_min based on the voltage values Vb of the plurality of single cells 11 detected in the process of step S101. As described above, the voltage value (minimum value) Vb_min can be specified when there is a variation in the voltage value Vb in the plurality of single cells 11. Further, in step S102, the controller 30 calculates a voltage difference ΔV between the voltage value Vb and the voltage value (minimum value) Vb_min with respect to the other battery cells 11 excluding the cell 11 indicating the voltage value (minimum value) Vb_min.

  In step S103, the controller 30 determines whether or not the voltage difference ΔV calculated in the process of step S102 is greater than or equal to a threshold value ΔV_th. Here, the threshold value ΔV_th is a value for determining whether or not equalization processing is performed, and can be set as appropriate. For example, the threshold value ΔV_th can be set to a value larger than the voltage difference ΔV that can allow variation in the voltage value Vb (due to detection error). Information regarding the threshold value ΔV_th can be stored in the memory 31.

  When the voltage difference ΔV is equal to or greater than the threshold value ΔV_th, the controller 30 determines in step S104 that an equalization process needs to be performed. On the other hand, when the voltage difference ΔV is smaller than the threshold value ΔV_th, the controller 30 determines that it is not necessary to perform equalization processing, and ends the processing shown in FIG. Here, the determination as to whether or not the equalization processing is performed is performed for all the unit cells 11 other than the unit cell 11 indicating the voltage value (minimum value) Vb_min.

  In step S105, the controller 30 discharges the unit cell 11 by switching the switch SW1 included in the monitoring unit 40 from off to on. Here, the unit cell 11 to be discharged is the unit cell 11 determined to require the equalization process in the process of step S104. By discharging the cell 11, the voltage value Vb of the cell 11 decreases and approaches the voltage value (minimum value) Vb_min.

  In step S106, the controller 30 detects the voltage value Vb of each unit cell 11 based on the output of the monitoring unit 40, and determines whether or not the voltage value Vb is equal to or less than the voltage value (minimum value) Vb_min. Here, when the voltage value Vb is equal to or less than the voltage value (minimum value) Vb_min, the controller 30 stops the discharge of the unit cell 11. On the other hand, when the voltage value Vb is higher than the voltage value (minimum value) Vb_min, the controller 30 continues to discharge the single battery 11. With the process shown in FIG. 3, the voltage values Vb of all the cells 11 constituting the assembled battery 10 can be made equal to the voltage value (minimum value) Vb_min.

  FIG. 4 is a diagram showing a part of the configuration shown in FIG. As shown in FIG. 4, the voltage detection line L <b> 2 connected to the negative terminal of the single cell 11-1 and the positive terminal of the single cell 11-2 may be disconnected due to external force or the like. In this case, the capacitors C-1 and C-2 cannot be charged with the electric charges of the single cells 11-1 and 11-2, and the voltage values Vb of the single cells 11-1 and 11-2 are detected. I can't. Here, the unit cell 11-1 corresponds to the first power storage unit in the present invention, and the unit cell 11-2 corresponds to the second power storage unit in the present invention.

  In the configuration shown in FIG. 4, if the voltage detection line L2 connected to the positive terminal of the cell 11-1 is disconnected, the voltage value Vb of the cell 11-1 cannot be detected. Moreover, if the voltage detection line L2 connected to the negative electrode terminal of the single battery 11-2 is disconnected, the voltage value Vb of the single battery 11-2 cannot be detected. In FIG. 4, the disconnected voltage detection line L2 is connected to the negative terminal of the unit cell 11-1 and the positive terminal of the unit cell 11-2.

  The voltage value Vb of the single cells 11-1 and 11-2 detected by the monitoring unit 40 when the voltage detection line L2 is disconnected is the voltage value when the single cells 11-1 and 11-2 are in an overdischarged state. It becomes almost equal to Vb. Thereby, even if the voltage value Vb detected by the monitoring unit 40 is monitored, the disconnection state of the voltage detection line L2 and the overdischarge state of the single cells 11-1 and 11-2 cannot be distinguished.

  Therefore, in this embodiment, as described below, the voltage fluctuations of the cells 11-1 and 11-2 when the switch SW1 included in the monitoring unit 40 is switched from OFF to ON are checked. The disconnection state of the detection line L2 is distinguished from the overdischarge state of the single cells 11-1 and 11-2. This will be specifically described below.

  FIG. 5 shows on / off of the switches SW1-1 and SW1-2 and fluctuations in the voltage values V1 and V2 when the voltage detection line L2 is disconnected as shown in FIG. The horizontal axis shown in FIG. 5 is time. As shown in FIG. 4, the voltage value V1 indicates the voltage value of the capacitor C-1 connected in parallel with the unit cell 11-1 (corresponding to the first voltage value in the present invention), and the voltage value V2 is The voltage value (corresponding to the second voltage value in the present invention) of the capacitor C-2 connected in parallel with the unit cell 11-2 is shown.

  At time t11, the switch SW1-1 is switched from off to on. Here, the switch SW1-2 remains off. When the switch SW1-1 is switched from OFF to ON, the electric charge accumulated in the capacitor C-1 is released, and the voltage value of the capacitor C-1 decreases. That is, in the current path including the capacitor C-1 and the switch SW1-1, the voltage value of the capacitor C-1 decreases due to the current flowing.

  Accordingly, the voltage value V1 decreases from the voltage value V1_a to the voltage value V1_b. When the switch SW1-1 is on, the electric charge stored in the capacitor C-1 is easily released, so that the voltage value of the capacitor C-1 is 0 [V]. Accordingly, the voltage value V1_b becomes substantially 0 [V]. Considering the detection error of the monitoring unit 40, the voltage value V1_b may deviate from 0 [V].

  On the other hand, when the switch SW1-1 is on, the current flowing from the unit cell 11-1 to the switch SW1-1 flows into the capacitor C-2 via the branch lines L22 and L21. That is, the electric charge accumulated in the single cells 11-1 and 11-2 is charged in the capacitor C-2, and the voltage value of the capacitor C-2 increases. Accordingly, the voltage value V2 increases from the voltage value V2_b to the voltage value V2_a. Here, the voltage value V2_b corresponds to the voltage value Vb of the cell 11-2, and the voltage value V2_a corresponds to the sum of the voltage values Vb of the cells 11-1 and 11-2.

  When the switch SW1-1 is switched from on to off at time t12, the voltage value V1 remains the voltage value V1_b, and the voltage value V2 remains the voltage value V2_a. In the case of FIG. 5, since the voltage detection line L2 is disconnected, even if the switch SW1-1 is switched from on to off, the capacitor C-1 is not charged with the electric charge of the unit cell 11-1. Therefore, the voltage value V1 remains the voltage value V1_b.

  Further, since the switch SW1-2 remains off, the electric charges of the single cells 11-1 and 11-2 remain charged in the capacitor C-2. Therefore, the voltage value V2 remains the voltage value V2_a. Note that when the switch SW1-2 is switched from OFF to ON, the charge charged in the capacitor C-2 is released, and the voltage value (voltage value V2) of the capacitor C-2 decreases. Here, since the voltage detection line L2 shown in FIG. 4 is disconnected, the voltage value (voltage value V2) of the capacitor C-2 is substantially 0 [V].

  FIG. 6 shows ON / OFF of the switches SW1-1 and SW1-2 and fluctuations in the voltage values V1 and V2 when only the single battery 11-1 shown in FIG. 4 is in the overdischarge state. FIG. 6 is a diagram corresponding to FIG. 5, and the horizontal axis shown in FIG. 6 is time.

  At time t21, the switch SW1-1 is switched from off to on. Here, the switch SW1-2 remains off. When the switch SW1-1 is switched from OFF to ON, the electric charge accumulated in the capacitor C-1 is released, and the voltage value of the capacitor C-1 decreases. That is, the voltage value V1 decreases from the voltage value V1_a to the voltage value V1_b. Specifically, the voltage value V1_b is approximately 0 [V].

  Here, since the unit cell 11-1 is in an overdischarged state, the voltage value Vb of the unit cell 11-1 is approximately 0 [V]. Before the switch SW1-1 is switched from OFF to ON, when charge is accumulated in the capacitor C-1, the voltage value V1 indicates the voltage value V1_a as shown in FIG. When the switch SW1-1 is switched from off to on, the voltage value V1 decreases from the voltage value V1_a to the voltage value V1_b. Note that if no charge is accumulated in the capacitor C-1 before the switch SW1-1 is switched from OFF to ON, the voltage value V1 remains the voltage value V1_b.

  On the other hand, when the switch SW1-1 is on, as described above, the current flowing from the unit cell 11-1 to the switch SW1-1 flows into the capacitor C-2. Here, when the unit cell 11-1 is in an overdischarged state, there is no current flowing from the unit cell 11-1 to the capacitor C-2. Therefore, the voltage value V2 remains the voltage value V2_b. The voltage value V2_b corresponds to the voltage value Vb of the cell 11-2.

  When the switch SW1-1 is switched from on to off at time t22, the voltage value V1 remains the voltage value V1_b, and the voltage value V2 remains the voltage value V2_a. Since the unit cell 11-1 is in an overdischarged state, there is no charge accumulated in the capacitor C-1 from the unit cell 11-1, and the voltage value of the capacitor C-1 does not increase. Further, since the switch SW1-2 remains off, the voltage value of the capacitor C-2 does not vary, and the voltage value V2 also remains the voltage value V2_b.

  When the behavior of the voltage values V1 and V2 shown in FIG. 5 is compared with the behavior of the voltage values V1 and V2 shown in FIG. 6, the behavior of the voltage value V2 is different from each other. That is, the behavior of the voltage value V2 when the voltage detection line L2 is disconnected is different from the behavior of the voltage value V2 when the unit cell 11 is in an overdischarged state. For this reason, by grasping the behavior of the voltage value V2, the disconnection state of the voltage detection line L2 and the overdischarge state of the unit cell 11 can be distinguished.

  Next, processing for determining the disconnection state of the voltage detection line L2 and the overdischarge state of the unit cell 11 will be described with reference to the flowchart shown in FIG. The process shown in FIG. 7 is executed by the controller 30. Moreover, the process shown in FIG. 7 can be performed with respect to the two unit cells 11 connected in series. The two unit cells 11 correspond to the two unit cells 11-1 and 11-2 shown in FIG. 4, and specifically, the positive terminal of one unit cell 11 is the negative terminal of the other unit cell 11. Are two unit cells 11 when they are connected to each other.

  In step S201, the controller 30 detects voltage values V1 and V2 (see FIG. 4) based on the output of the monitoring unit 40. In step S202, the controller 30 switches the switch SW1 (switch SW1-1 shown in FIG. 4) included in the monitoring unit 40 from off to on. The operation of the switch SW1 here is an operation for determining the disconnection state or the overdischarge state, and is different from the operation for the equalization processing. Note that the switch SW1-2 illustrated in FIG. 4 remains off. Further, other switches SW1 (switches other than the switches SW1-1 and SW1-2) included in the monitoring unit 40 remain off.

  In step S203, the controller 30 detects voltage values V1 and V2 (see FIG. 4) based on the output of the monitoring unit 40. In step S204, the controller 30 compares the voltage value V1 detected in the process of step S201 with the voltage value V1 detected in the process of step S203. Then, the controller 30 determines whether or not the voltage value V1 has decreased after the switch SW1 is turned on by the process of step S202. The decrease in the voltage value V1 here corresponds to the decrease in the voltage value V1 from the voltage value V1_a to the voltage value V1_b, as described with reference to FIGS.

  When the voltage value V1 is decreasing, the controller 30 performs the process of step S205. On the other hand, when the voltage value V1 has not decreased, the controller 30 ends the process shown in FIG. If the voltage detection line L2 is not disconnected, the electric charge of the unit cell 11-1 is charged to the capacitor C-1, and therefore the voltage value of the capacitor C-1 is unlikely to decrease. Further, if the unit cell 11-1 is not in an overdischarged state, the electric charge of the unit cell 11-1 is charged to the capacitor C-1, so that the voltage value of the capacitor C-1 is unlikely to decrease. Therefore, when the voltage value V1 has not decreased, the controller 30 determines that the disconnection state and the overdischarge state have not occurred, and can end the process shown in FIG.

  In step S205, the controller 30 compares the voltage value V2 detected in the process of step S201 with the voltage value V2 detected in the process of step S203. Then, the controller 30 determines whether or not the voltage value V2 has increased after the switch SW1 is turned on by the process of step S202. The increase of the voltage value V2 here corresponds to the increase of the voltage value V2 from the voltage value V2_b to the voltage value V2_a as described with reference to FIG.

  When the voltage value V2 is increasing, the controller 30 determines in step S206 that the voltage detection line L2 is in a disconnected state. On the other hand, when the voltage value V2 has not increased, the controller 30 determines in step S207 that the unit cell 11 (unit cell 11-1 shown in FIG. 4) is in an overdischarged state.

  According to the present embodiment, by confirming the behavior of the voltage values V1 and V2, either the disconnection state or the overdischarge state occurs while distinguishing the disconnection state of the voltage detection line L2 and the overdischarge state of the unit cell 11. You can identify what you are doing. If the disconnection state and the overdischarge state can be distinguished, repair and the like can be performed smoothly.

  When a disconnection state or an overdischarge state is specified, a user or the like can be warned that an abnormality has occurred. Thereby, a user etc. can recognize that abnormality has occurred. Here, in the present embodiment, the content of the abnormality (disconnected state or overdischarge state) can also be specified.

  As a warning means, a display or a speaker can be used. Specifically, information indicating that an abnormality has occurred can be displayed on the display, or information indicating that an abnormality has occurred can be output as a sound from a speaker. Here, the content displayed on the display and the content of the sound output from the speaker can be set as appropriate.

10: assembled battery, 11: single battery (storage unit), 21: current sensor, 22: booster circuit,
23: Inverter, 24: Motor generator, 30: Controller, 31: Memory,
40: monitoring unit (voltage detection circuit), 41: comparator,
R11, R21, R22: resistors, SW1, SW21, SW22: switches,
D: Zener diode, C: capacitor, PL: positive line, NL: negative line
L1, L2: Voltage detection line, L21, L22: Branch line

Claims (8)

First and second power storage units connected in series;
A voltage detection circuit for detecting a voltage value of each power storage unit using a capacitor connected in parallel with each power storage unit via a voltage detection line;
A switch connected in parallel with each power storage unit and the capacitor;
A controller for controlling the operation of the switch,
The controller is
When the predetermined process for switching the switch corresponding to the first power storage unit from OFF to ON is performed while keeping the switch corresponding to the second power storage unit off.
The first voltage value of the first power storage unit detected by the voltage detection circuit is a lower limit value, and the second voltage value of the second power storage unit detected by the voltage detection circuit is increased. And determining that the voltage detection line is in a disconnected state.   When the controller performs the predetermined process, the first voltage value is the lower limit value, and the first power storage unit is in an overdischarged state in response to the second voltage value not increasing. The power storage system according to claim 1, wherein the power storage system is determined.   The controller determines that the voltage detection line is in a disconnected state in response to the first voltage value falling to the lower limit value and the second voltage value rising when the predetermined processing is performed. The power storage system according to claim 1 or 2, wherein:   When the controller performs the predetermined processing, the first power storage unit is in an overdischarged state in response to the first voltage value decreasing to the lower limit value and the second voltage value not increasing. The power storage system according to claim 2, wherein the power storage system is determined to be present. First and second power storage units connected in series;
A voltage detection circuit for detecting a voltage value of each power storage unit using a capacitor connected in parallel with each power storage unit via a voltage detection line;
A switch connected in parallel with each power storage unit and the capacitor;
A controller for controlling the operation of the switch,
The controller is
When the predetermined process for switching the switch corresponding to the first power storage unit from OFF to ON is performed while keeping the switch corresponding to the second power storage unit off.
The first voltage value of the first power storage unit detected by the voltage detection circuit is a lower limit value, and the second voltage value of the second power storage unit detected by the voltage detection circuit does not increase. And determining that the first power storage unit is in an overdischarged state.   When the controller performs the predetermined processing, the first power storage unit is in an overdischarged state in response to the first voltage value decreasing to the lower limit value and the second voltage value not increasing. The power storage system according to claim 5, wherein it is determined that the power storage system is present.   The power storage system according to any one of claims 1 to 6, wherein the lower limit value is approximately 0V.   8. The switch according to claim 1, wherein the switch is used to discharge the power storage units to equalize voltage values in the first and second power storage units. 9. Power storage system.