JP2012069405A - Electrical storage device abnormal condition detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, if a capacity reduced electrical storage element and an internally shorted electrical storage element are contained in one electrical storage block, a detected voltage of the electrical storage block may be equal to a voltage of an electrical storage block which contains only normal electrical storage elements.SOLUTION: A device for detecting an abnormal state of an electrical storage device which is comprised of plural electrical storage blocks (12) electrically connected in series and respectively containing plural electrical storage elements (11) includes a voltage sensor (20) for detecting a voltage between terminals of each electrical storage block and a controller (30) for detecting an abnormal state of electrical storage elements based on the output of the voltage sensor. The controller charges/discharges the electrical storage device while changing current values under a condition that a voltage difference between plural electrical storage blocks be generated and, when the voltage difference is detected based on the output of the voltage sensor, detects that an electrical storage element in a capacity deteriorated state and an electrical storage element in an internally shorted state are contained in the electrical storage block.

Description

  The present invention relates to a power storage system capable of detecting capacity deterioration and an internal short circuit of a power storage element.

  When detecting the voltages of a plurality of single cells, as shown in FIG. 12, the four single cells 100 are divided into two blocks 101a and 101b, and the voltage between the terminals of each block 101a and 101b is detected by the voltage sensor 102. There is something to do. The voltage value detected by the voltage sensor 102 is the sum V2 of the voltage values V1 of the two unit cells 100 included in each of the blocks 101a and 101b. By providing the voltage sensor 102 for each of the blocks 101a and 101b, the number of voltage sensors 102 can be reduced as compared with the case where the voltage sensor 102 is provided for each cell 100.

JP 2009-276169 A JP 2001-526877 A Japanese Patent Laid-Open No. 06-197475 Japanese Patent Laid-Open No. 11-55866

  An internal short circuit may occur due to deterioration of the unit cell. Specifically, a short circuit may occur when the positive electrode plate and the negative electrode plate are in contact with each other inside the unit cell, or when metal is deposited inside the unit cell. If an internal short circuit occurs, the voltage of the cell will decrease. On the other hand, the capacity of the unit cell may be reduced by repeatedly charging and discharging the unit cell. When the capacity of the unit cell decreases, the voltage of the unit cell is likely to increase due to charging.

  In one block 101b, when the internal short-circuited unit cell 100 and the capacity-reduced unit cell 100 are included, although the voltage of each unit cell 100 is different, the voltage of the block 101b is the normal unit cell 100. It may be equal to the voltage of the configured block 101a.

  As shown in FIG. 13, since the two unit cells 100 constituting the block 101a are normal, the voltage of the two unit cells 100 increases from the voltage value V1 shown in FIG. 12 to the voltage value V3 by charging. . On the other hand, in the block 101b, since an internal short circuit has occurred in one unit cell 100, the voltage of the unit cell 100 decreases from the voltage value V1 shown in FIG. 12 to the voltage value V4 even if charging is performed. . Moreover, since the capacity | capacitance reduction has generate | occur | produced in the other unit cell 100 contained in the block 101b, the voltage of the unit cell 100 rises from the voltage value V1 to the voltage value V5 by charging.

  In the case shown in FIG. 13, the terminal voltage of the block 101a is a voltage value V6 (= V3 + V3), and the terminal voltage of the block 101b is a voltage value V7 (= V4 + V5). Depending on the voltage values V3, V4, and V5, the voltage values V6 and V7 may be equal. In this case, the block 101b is treated as being equivalent to the block 101a configured with the normal unit cell 100, despite the presence of the internal short-circuit unit cell 100 and the capacity-reduced unit cell 100. . That is, it cannot be detected that an internal short circuit and a capacity drop have occurred.

  A first invention of the present application is a detection device that detects an abnormal state of a power storage device in which a plurality of power storage blocks each including a plurality of power storage elements are electrically connected in series, and detects a voltage between terminals of each power storage block And a controller that detects an abnormal state of the power storage element based on the output of the voltage sensor. The controller charges and discharges the power storage device while changing the current value under conditions that generate a voltage difference between the plurality of power storage blocks, and detects a voltage difference based on the output of the voltage sensor. It is detected that a degraded storage element and an internal short-circuit storage element are included.

  Here, the controller can generate a voltage difference by changing the amplitude of the periodically changing current in an increasing direction. Further, the controller can generate a voltage difference by changing the current value in constant current charging.

  A second invention of the present application is a detection method for detecting an abnormal state of a power storage device in which a plurality of power storage blocks each including a plurality of power storage elements is electrically connected in series, and a voltage difference between the plurality of power storage blocks When the voltage difference is detected based on the output of the voltage sensor for detecting the voltage between the terminals of each power storage block while charging / discharging the power storage device while changing the current value under the condition of generating It is detected that the storage element in the capacity deterioration state and the storage element in the internal short circuit state are included.

  According to the present invention, by changing the current value, a voltage difference is generated between a power storage block including a normal power storage element and a power storage block including a power storage element in a capacity degraded state and a power storage element in an internal short-circuit state. It can be made easier. For this reason, it is possible to easily detect the voltage difference using the voltage sensor, and based on the detection of the voltage difference, the storage element in the capacity deterioration state and the storage element in the internal short circuit state are included in one storage block. Can be detected.

It is a figure which shows the structure of the battery system which is Example 1. FIG. It is a figure which shows the change of SOC when a normal battery, a capacity fall battery, and an internal short circuit battery are charged. It is a figure which shows the relationship between SOC in a single battery, and internal resistance. It is the schematic which shows the component which determines the block voltage in a normal battery block and an abnormal battery block. It is a figure which shows the waveform of charging / discharging electric current. It is a figure which shows the change of the block voltage in a normal battery block and an abnormal battery block. It is a figure which shows the waveform of charging / discharging electric current. It is a figure which shows the change of the block voltage in a normal battery block and an abnormal battery block. It is the schematic which shows the component which determines the block voltage in a normal battery block and an abnormal battery block. It is a flowchart which shows the process for detecting generation | occurrence | production of an internal short circuit and a capacity | capacitance fall. It is a figure which shows the change of a voltage when a normal battery, a capacity fall battery, and an internal short circuit battery are charged. It is a figure explaining a voltage change when the cell of an internal short circuit and the cell of a capacity fall are contained in one block which performs voltage detection. It is a figure explaining a voltage change when the cell of an internal short circuit and the cell of a capacity fall are contained in one block which performs voltage detection.

  Examples of the present invention will be described below.

  A battery system that is Embodiment 1 of the present invention will be described with reference to FIG. The assembled battery (power storage device) 10 includes a plurality of single cells (power storage elements) 11 electrically connected in series, and is connected to a load. For example, when the assembled battery 10 is mounted on a vehicle, a motor / generator can be used as a load. Vehicles include hybrid cars and electric cars. A hybrid vehicle is a vehicle that uses an internal combustion engine or a fuel cell in addition to the assembled battery 10 as a power source for running the vehicle. An electric vehicle is a vehicle using only the assembled battery 10 as a power source.

  The motor / generator converts the electrical energy supplied from the assembled battery 10 into kinetic energy used for running the vehicle. Kinetic energy generated by the motor / generator is transmitted to the wheels via a power transmission mechanism. On the other hand, the motor / generator converts kinetic energy generated during braking of the vehicle into electric energy and supplies the electric energy to the assembled battery 10. A booster circuit or an inverter can be disposed between the assembled battery 10 and the motor / generator. If the booster circuit is used, the output voltage of the assembled battery 10 can be raised before being supplied to the motor / generator. If an inverter is used, an AC motor can be used as the motor / generator.

  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. Further, in this embodiment, all the unit cells 11 are electrically connected in series to constitute the assembled battery 10. However, a plurality of unit cells 11 electrically connected in parallel are connected to the assembled battery 10. It may be included. 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 (capacitor) can be used instead of the secondary battery.

  The plurality of single cells 11 constituting the assembled battery 10 are divided into a plurality of blocks (hereinafter referred to as battery blocks) 12, and the plurality of battery blocks (storage blocks) 12 are electrically connected in series. . Each battery block 12 is composed of two unit cells 11 electrically connected in series, and the number of unit cells 11 constituting the battery block 12 is the same in all the battery blocks 12.

  In the present embodiment, one battery block 12 is constituted by two unit cells 11, but the present invention is not limited to this. That is, the number of the single cells 11 constituting the battery block 12 can be set as appropriate, and one battery block 12 can be constituted by three or more single cells 11.

  A voltage sensor 20 is electrically connected in parallel to each battery block 12, and the voltage sensor 20 is used to detect the voltage of the battery block 12. The output signal of the voltage sensor 20 is input to the controller 30, and the controller 30 detects the voltage of the battery block 12 based on the signal from the voltage sensor 20. The controller 30 controls charging / discharging of the assembled battery 10.

  In the battery system of the present embodiment, it is possible to detect that one battery block 12 includes an internal short-circuited cell 11 and a capacity-reduced cell 11. This will be specifically described below.

  FIG. 2 shows a change in SOC (State Of Charge) when the capacity-reduced unit cell 11, the internal short-circuit unit cell 11, and the normal unit cell 11 are charged with a constant current. Here, the normal unit cell 11 is a unit cell 11 in which no capacity reduction or internal short circuit occurs.

  The unit cell 11 with reduced capacity has a higher SOC change rate than the normal unit cell 11 and is likely to be overcharged. On the other hand, in the internal short-circuited cell 11, even if charging is performed, the SOC is difficult to increase, and depending on the current value at the time of charging, the SOC may decrease and overdischarge may occur.

  FIG. 3 shows the relationship between the SOC of the unit cell 11 and the internal resistance of the unit cell 11. As shown in FIG. 3, overcharge occurs in a region where the SOC is high, and the internal resistance of the unit cell 11 tends to increase. Moreover, in the area | region where SOC is low, it becomes overdischarge and the internal resistance of the cell 11 tends to rise. For this reason, the unit cell 11 with reduced capacity or the unit cell 11 with internal short circuit has a larger internal resistance than the normal unit cell 11.

  Next, a battery block (referred to as a normal battery block) 12 constituted only by a normal battery 11 and a battery block (referred to as an abnormal battery block) 12 including a capacity-reduced battery 11 and an internal short-circuited battery 11 The relationship will be described.

  As shown in FIG. 4, the normal battery block 12 is composed of two normal unit cells C1 and C2, and the block voltage of the normal cell block 12 is the open circuit voltage OCV (C1) and the internal resistance in the unit cell C1. It is determined by IR (C1), open circuit voltage OCV (C2) and internal resistance IR (C2) in unit cell C2.

  On the other hand, the abnormal battery block 12 is composed of a unit cell C3 in which a capacity drop has occurred and a unit cell C4 in which an internal short circuit has occurred. The block voltage of abnormal battery block 12 is determined by open voltage OCV (C3) and internal resistance IR (C3) in single battery C3, and open voltage OCV (C4) and internal resistance IR (C4) in single battery C4. .

  As described with reference to FIG. 13, even if the voltage values of the cells C <b> 3 and C <b> 4 are different from each other, the block voltage of the abnormal battery block 12 may be substantially equal to the block voltage of the normal battery block 12. In FIG. 4, the difference between the block voltage of the normal battery block 12 and the block voltage of the abnormal battery block 12 is indicated by ΔV1, but when the voltage difference ΔV1 approaches zero, based on the output of the voltage sensor 20, The voltage difference ΔV1 cannot be detected, and the normal battery block 12 and the abnormal battery block 12 cannot be distinguished.

  In this embodiment, paying attention to the fact that the internal resistances of the cells C3 and C4 are larger than the internal resistances of the cells C1 and C2, based on the output (block voltage) of the voltage sensor 20, the normal battery block 12 and the abnormal battery. Block 12 can be easily distinguished. Specifically, the difference between the block voltage of the normal battery block 12 and the block voltage of the abnormal battery block 12 is widened in a state where the block voltage is periodically changed by periodically changing the current value. I have to. If the block voltage difference is widened, the normal battery block 12 and the abnormal battery block 12 can be easily distinguished.

When charging is performed while changing the current in the cycle shown in FIG. 5, the block voltages of the normal battery block 12 and the abnormal battery block 12 exhibit the behavior shown in FIG. In the current waveform shown in FIG. 5, the average value is set to I ₁ [A], the amplitude is set to I ₁ [A], and the period is set to t _S seconds. As shown in FIG. 6, at a predetermined timing _{t 1,} a block voltage _{V BA} of the normal cell blocks 12, the difference between the block voltage _{V BB} of abnormal battery block 12 is a [Delta] V1.

On the other hand, when charging is performed while changing the current in the cycle shown in FIG. 7, the block voltages of the battery block 12A and the battery block 12B exhibit the behavior shown in FIG. In the current waveform shown in FIG. 7, the average value is set to I ₁ [A], the amplitude is set to I ₂ [A], and the period is set to t _S seconds. Amplitude _{I 2} is larger than the amplitude _{I 1.} As shown in FIG. 8, at a predetermined timing _{t 1,} a block voltage _{V BA} of the normal cell blocks 12, the difference between the block voltage _{V BB} of abnormal battery block 12 is a [Delta] V2.

  In the present embodiment, the charge / discharge current has the waveform shown in FIG. 7, but the present invention is not limited to this, and any waveform may be used as long as it changes periodically.

FIG. 9 shows the relationship between the block voltage V _BA of the normal battery block 12 and the block voltage V _BB of the abnormal battery block 12 in the state shown in FIG. As described with reference to FIGS. 2 and 3, the abnormal battery block 12 (reduced capacity cell C3 and internal short circuit cell C4) has an internal capacity compared to the normal battery block 12 (normal batteries C1 and C2). The resistance IR component increases. For this reason, when the amplitude of the current waveform is increased from I ₁ to I ₂ , the amplitude of the block voltage V _BB can be increased.

If the amplitude of the block voltage V _BB is increased, the difference between the block voltage V _BA and the block voltage V _BB can be widened. That is, the voltage difference ΔV2 shown in FIG. 8 can be made larger than the voltage difference ΔV1 shown in FIG. Thus, the controller 30 can easily detect the difference between the block voltage V _BA and the block voltage V _BB based on the output of the voltage sensor 20. When a difference between the block voltages is detected, it can be determined that one battery block 12 includes the capacity-reduced unit cell 11 and the internal short-circuit unit cell 11.

  In the example shown in FIGS. 6 and 8, the case where the unit cell 11 is charged has been described, but the present invention can also be applied to the case where the unit cell 11 is discharged. In this case, the average value of the current is a negative value in FIGS.

  Note that the amplitude of the current can be set as appropriate. That is, a state in which the difference between the block voltage of the abnormal battery block and the block voltage of the normal battery block can be easily detected. The technical idea of the present embodiment is to increase the difference between the block voltage of the abnormal battery block and the block voltage of the normal battery block so that the voltage difference is easily detected as the current amplitude is increased.

  The processing of the controller 30 in the present embodiment will be described using the flowchart shown in FIG. The process illustrated in FIG. 10 can be performed, for example, when the block voltages indicate the same value in the plurality of battery blocks 12. Also, a mode for performing the process shown in FIG. 10 is prepared, and the process shown in FIG. 10 can be started when this mode is set.

  The controller 30 sets the amplitude and period of the current waveform (S101), and starts charging / discharging the assembled battery 10 (S102). The controller 30 monitors the block voltage of each battery block 12 based on the output of the voltage sensor 20 (S103). Here, the controller 30 determines whether or not the difference between the block voltages can be detected (S104), and when the difference between the block voltages is detected, the battery block 12 includes a single battery 11 with a reduced capacity and a single internal short circuit. It is determined that the battery 11 is included (S105). If the block voltage difference cannot be detected, this process is terminated.

  When it is determined that a capacity drop or an internal short circuit has occurred in the single battery 11, charging / discharging of the battery pack 10 can be limited. Specifically, charging / discharging of the assembled battery 10 can be prohibited. Moreover, the upper limit (voltage or electric power) used by charging / discharging control of the assembled battery 10 can be made small. On the other hand, in the battery system shown in FIG. 1, a display may be provided to display on the display or the like that there is a possibility that a capacity drop or an internal short circuit has occurred.

  According to this embodiment, it is possible to widen the difference between the block voltage of the normal battery block 12 and the block voltage of the abnormal battery block 12 only by changing the amplitude of the current waveform in the increasing direction. It is possible to easily detect and distinguish the normal battery block 12 and the abnormal battery block 12. Further, the difference in block voltage between the normal battery block 12 and the abnormal battery block 12 can be detected without improving the detection accuracy of the voltage sensor 20.

  A battery system that is Embodiment 2 of the present invention will be described. About the same member as the member demonstrated in Example 1, the same code | symbol is used and detailed description is abbreviate | omitted.

  As described in Example 1 (FIG. 2), in the unit cell 11 with reduced capacity and the normal unit cell 11, the SOC increases as charging progresses, and the rate of change in SOC in the unit cell 11 with reduced capacity is: It becomes larger than the rate of change of SOC in the normal unit cell 11. In addition, the internal short-circuit cell 11 is not easily charged, and the SOC change rate in the internal short-circuit cell 11 is smaller than the SOC change rate in the normal cell 11.

  Depending on the SOC behavior of the internal short-circuit cell 11 and the capacity-reduced cell 11, the SOC behavior in the battery block 12 including only the normal cell 11, the internal short-circuit cell 11, and the capacity-reduced cell 11. In some cases, the SOC behavior of the battery block 12 that includes In other words, as shown in FIG. 11, even if the voltage value of the capacity-reduced unit cell 11 and the voltage value of the unit cell 11 of the internal resistance are different from each other, the block voltage of the abnormal battery block 12 is the normal battery block. May be equal to 12 block voltages. In this case, even if the block voltage is detected based on the output of the voltage sensor 20, the abnormal state (capacity drop or internal short circuit) of the unit cell 11 cannot be detected.

  In this embodiment, the normal battery block 12 and the abnormal battery block are distinguished from each other by changing the current value when performing constant current charging. This will be specifically described below.

  When the current value of the charging current is changed, the behavior of the voltage (or SOC) in the capacity-reduced unit cell 11 changes, and the behavior of the voltage (or SOC) in the internal short-circuit unit 11 changes. For example, in FIG. 2, if the current value is increased, the rate of change of SOC can be increased.

  By changing the voltage behavior in the capacity-reduced cell 11 and the voltage behavior in the internal short-circuit cell 11, the block voltage can be made different between the normal battery block 12 and the abnormal battery block 12. That is, by changing the current value, it is possible to generate a state in which the difference between the block voltages can be detected. If the difference between the block voltages can be detected, it can be detected that the single battery block 12 includes the capacity-reduced unit cell 11 and the internal short-circuit unit cell 11 as in the first embodiment.

  In the present embodiment, the current value can be changed as appropriate. That is, it suffices if a difference in the block voltage can be generated between the normal battery block 12 and the abnormal battery block 12 by changing the current value. For example, the current value can be increased stepwise or decreased stepwise. Moreover, the process which raises an electric current value and the process which reduces an electric current value can also be performed at random. In this case, it is necessary to change the current value so as to have different values.

  Even if there is no difference in the block voltage in the plurality of battery blocks 12, when a difference occurs in the block voltage by changing the current value, the capacity-reducing cell 11 and the internal It can be detected that the short-circuit cell 11 is included.

10: assembled battery (power storage device) 11: single battery (power storage element)
12: Battery block (power storage block) 20: Voltage sensor 30: Controller 100: Single battery 101a, 101b: Battery block 102: Voltage sensor

Claims (6)

A detection device that detects an abnormal state of a power storage device in which a plurality of power storage blocks each including a plurality of power storage elements is electrically connected in series,
A voltage sensor for detecting a voltage between terminals of each power storage block;
A controller that detects an abnormal state of the power storage element based on the output of the voltage sensor;
The controller charges and discharges the power storage device while changing a current value under a condition for generating a voltage difference between the plurality of power storage blocks, and detects the voltage difference based on the output of the voltage sensor. A detection apparatus that detects that the storage element in a capacity deterioration state and the storage element in an internal short-circuit state are included in the storage block.   The detection device according to claim 1, wherein the controller generates the voltage difference by changing an amplitude of a periodically changing current in an increasing direction.   The detection device according to claim 1, wherein the controller generates the voltage difference by changing a current value in constant current charging. A detection method for detecting an abnormal state of a power storage device in which a plurality of power storage blocks each including a plurality of power storage elements are electrically connected in series,
Based on the output of a voltage sensor for charging and discharging the power storage device while changing a current value under a condition that generates a voltage difference between the plurality of power storage blocks, and detecting a voltage between terminals of each power storage block When the voltage difference is detected, it is detected that the storage element in the capacity deterioration state and the storage element in the internal short circuit state are included in the storage block.   The detection method according to claim 4, wherein the voltage difference is generated by changing an amplitude of a periodically changing current in an increasing direction. The detection method according to claim 4, wherein the voltage difference is generated by changing a current value in constant current charging.

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