JP6489366B2 - A battery pack monitoring device and battery pack capacity equalization method. - Google Patents

Description

  The present invention relates to a technique for equalizing the capacity of assembled batteries.

  When charging / discharging is repeated for an assembled battery in which a plurality of power storage elements are connected in series, the capacity of each power storage element may vary due to differences in self-discharge of each power storage element. If the capacities of the storage elements vary, there is a risk of overvoltage during charging and the usable capacity of the assembled battery may be reduced. Therefore, conventionally, equalization control for equalizing the capacity is performed by charging and discharging the power storage elements.

  By the way, there exists an element of the characteristic which has a plateau area | region with a small change rate of OCV (open circuit voltage) with respect to SOC (charge condition), such as a lithium ion secondary battery, in an electrical storage element. In the plateau region, since it is difficult to estimate the SOC from the measured value of the OCV, equalization control is executed in the vicinity of full charge with high SOC estimation accuracy (Patent Document 1 below).

JP 2010-88194 A

However, a battery with a wide plateau region has few regions with a large voltage gradient even near full charge, and it is difficult to perform equalization control unless it is actually charged to near full charge.
The present invention has been completed based on the above circumstances, and it is an object of the present invention to suppress capacity imbalance between power storage elements even when the battery is not fully charged or is not fully charged. And

  An assembled battery monitoring device disclosed in the present specification includes a voltage detection unit that individually detects a voltage of each storage element of the assembled battery, a charge / discharge circuit that individually discharges or charges each storage element, and a control unit. And the storage element has two low change regions with a relatively low change rate of the open voltage with respect to the charge state, and a change rate of the open voltage with respect to the charge state is relatively between the two low change regions. The first high change region, and when the two storage elements are divided into two low change regions, the control unit, based on the capacity difference between the end points of the first high change region, A first equalization process is performed to reduce a capacity difference between the two power storage elements by discharging or charging at least one of the two power storage elements.

  An assembled battery monitoring device disclosed in the present specification includes a voltage detection unit that individually detects a voltage of each storage element of the assembled battery, a charge / discharge circuit that individually discharges or charges each storage element, and a control unit. And the storage element has two low change regions with a relatively low change rate of the open voltage with respect to the charge state, and a change rate of the open voltage with respect to the charge state is relatively between the two low change regions. The control unit is configured such that when the one storage element is included in the low change area and the other storage element is included in the first high change area, Discharge or charge at least one of the two power storage elements based on the capacity difference between the capacity of the end point close to the power storage element on the other side in the low change region and the capacity of the power storage element on the other side. A space between the two power storage elements. Performing a second equalization process to reduce the difference in.

  According to the assembled battery monitoring device disclosed in this specification, it is possible to suppress the capacity imbalance between the power storage elements even when the battery is not charged to near full charge or when the frequency of full charge is low.

FIG. 3 is a schematic diagram illustrating a configuration of a battery pack in the first embodiment. Circuit diagram of discharge circuit The graph which shows the SOC-OCV correlation characteristic of a secondary battery The figure which expanded the A section of FIG. 3 (description figure of 1st equalization control) The figure which expanded the A section of FIG. 3 (description figure of 2nd equalization control) The figure which expanded the A section of FIG. 3 (description figure of 2nd equalization control) The figure which expanded the A section of FIG. 3 (description figure of compound equalization control) The figure which expanded the B section of FIG. 3 (description figure of 3rd equalization control) The flowchart figure which shows the process sequence of equalization control In Embodiment 2, when a secondary battery does not have a full charge capacity difference, the graph which shows a SOC-OCV correlation characteristic when a capacity imbalance arises between two secondary batteries The graph which shows a SOC-OCV correlation characteristic in case capacity imbalance arises between two secondary batteries, when there exists a full charge capacity | capacitance difference in a secondary battery. The flowchart figure which shows the switching procedure of the execution pattern of equalization control The graph which shows a SOC-OCV correlation characteristic at the time of performing a 3rd equalization process when there exists a full charge capacity difference between secondary batteries. The graph which shows the special discharge characteristic which discharged the secondary battery after execution of a 3rd equalization process

(Outline of this embodiment)
First, an outline of a battery monitoring apparatus disclosed in the present embodiment will be described. The monitoring device includes two low change regions having a relatively low change rate of the open-circuit voltage with respect to the charged state, and a first high change between the two low change regions having a relatively high change rate of the open-circuit voltage with respect to the charge state. When the storage element (assembled battery) having a region is a monitoring target and the two storage elements are divided into the two low change regions, based on the capacity difference between the end points of the first high change region, A first equalization process is performed to reduce a capacity difference between the two power storage elements by discharging or charging at least one of the two power storage elements.

  Further, when one of the power storage elements is included in the low change region and the other power storage element is included in the first high change region, the side closer to the other power storage element in the low change region. Based on the capacity difference between the capacity of the end point and the capacity of the other power storage element, the difference in capacity between the two power storage elements is obtained by discharging or charging at least one of the two power storage elements. The second equalization process is performed to reduce the.

  According to the monitoring device, when the two power storage elements are divided into two low change regions, the first equalization process is executed. Further, when one power storage element is included in the low change region and the other power storage element is included in the first high change region, the second equalization process is performed. Therefore, even when the battery is not charged to near full charge or when the frequency of full charge is low, the capacity imbalance of the power storage element can be suppressed.

Further, the assembled battery monitoring device disclosed in the present embodiment preferably has the following configuration.
After execution of the first equalization process, when one of the storage elements is included in the low change region and the other storage element is included in the first high change region, the other of the low change regions By discharging or charging at least one of the two power storage elements based on a capacity difference between the capacity of the end point close to the power storage element on the side and the capacity of the power storage element on the other side, the two A second equalization process is performed to reduce the capacity difference between the storage elements. In this configuration, since the first equalization process and the second equalization process are executed in combination, the capacity imbalance of the power storage elements can be further suppressed.

  When the power storage element has a second high change region on the low charge state region side or a third high change region on the high charge state region side than the two low change regions, both of the two power storage elements are When included in the second high change region or the third high change region, discharging or charging a capacity corresponding to a voltage difference between the power storage elements on at least one of the two power storage elements. Thus, a third equalization process is performed to reduce the difference in capacity between the two power storage elements. In this configuration, the third equalization process is executed in the second high change region and the third high change region. Accordingly, it is possible to further suppress the capacity imbalance between the power storage elements.

  When there is no full charge capacity difference between the power storage elements, at least one of the first equalization process and the second equalization process and the third equalization process are executed, and the power storage When there is a full charge capacity difference between the elements, at least one of the first equalization process and the second equalization process, or any of the third equalization processes is performed. Run. In this configuration, the equalization control pattern can be switched according to the presence or absence of the full charge capacity difference.

  In addition, a time difference in timing at which the voltage of the power storage element changes when the power storage element is charged / discharged after execution of any one of the first equalization process to the third equalization process, or The accumulated charge / discharge amount during that time is measured, and the full charge capacity difference between the power storage elements is detected based on the obtained time difference or the accumulated charge / discharge amount. In this configuration, the magnitude of the full charge capacity difference of the power storage element can be detected from the time difference in timing at which the voltage of the power storage element changes or the accumulated charge / discharge amount therebetween.

<Embodiment 1>
The first embodiment will be described with reference to FIGS.
1. Configuration of Battery Pack 20 FIG. 1 is a diagram showing a configuration of the battery pack 20 in the present embodiment. The battery pack 20 of the present embodiment is mounted on, for example, an electric vehicle or a hybrid vehicle, and supplies power to a power source that operates with electric energy.

  As shown in FIG. 1, the battery pack 20 includes an assembled battery 30, a current sensor 40, and a battery manager (hereinafter referred to as BM) 50 that manages the assembled battery 30. The assembled battery 30 includes a plurality of secondary batteries 31 connected in series.

  The secondary battery 31 and the current sensor 40 are connected in series via the wiring 35 and connected to the charger 10 mounted on the electric vehicle or the load 10 such as a power source provided in the electric vehicle or the like. Is done. The charger 10 functions to detect the voltage of the assembled battery 30 and charge the assembled battery 30.

  The current sensor 40 functions to detect the current flowing through the secondary battery 31. The current sensor 40 is configured to measure the current value of the secondary battery 31 at a constant period and transmit data of the measured current measurement value to the control unit 60.

  The battery manager (hereinafter referred to as BM) 50 includes a control unit 60, a discharge circuit 70, a voltage detection circuit 80, and a temperature sensor 95. The secondary battery 31 is an example of a “storage element”, and the BM 50 is an example of a “monitoring device”. The discharge circuit 70 is an example of a “charge / discharge circuit”.

  The discharge circuit 70 is provided in each secondary battery 31. As shown in FIG. 2, the discharge circuit 70 includes a discharge resistor R and a discharge switch SW, and is connected in parallel to the secondary battery 31. The secondary battery 31 can be discharged individually by giving a command from the control unit 60 and turning on the discharge switch SW.

  The voltage detection circuit 80 is connected to both ends of each secondary battery 31 via a detection line, and functions to measure the voltage V of each secondary battery 31 in response to an instruction from the control unit 60. The temperature sensor 95 is a contact type or non-contact type, and functions to measure the temperature D [° C.] of the secondary battery 31. The voltage detection circuit 80 is an example of a “voltage detection unit”.

  The control unit 60 includes a central processing unit (hereinafter referred to as CPU) 61, a memory 63, and a communication unit 65. The controller 60 functions to control the discharge circuit 70 to equalize the capacity [Ah] of each secondary battery 31. The “equalization” includes not only equalizing the capacity [Ah] of the secondary batteries 31 but also reducing the difference in capacity [Ah] between the secondary batteries.

  The memory 63 stores a program for executing a process for equalizing the capacity [Ah] of the secondary battery 31 (an “equalization control execution sequence” described later), data necessary for executing the program, for example, FIG. 3 and the data of the full charge capacity [Ah] of the secondary battery 31 are stored.

  The communication unit 65 is communicably connected to an in-vehicle ECU (Electronic Control Unit) 100 and fulfills a function of communicating with the in-vehicle ECU 100. In addition, the battery pack 20 is provided with an operation unit (not shown) that receives input from the user and a display unit (not shown) that displays the state of the secondary battery 31 and the like.

2. SOC-OCV correlation characteristics and equalization control of secondary battery 31 (a) SOC-OCV correlation characteristics FIG. 3 shows SOC- of secondary battery 31 with the horizontal axis representing SOC [%] and the vertical axis representing OCV [V]. OCV correlation characteristics. As shown in FIG. 3, the secondary battery 31 includes a plurality of charging regions including a low change region in which a change rate of OCV (open voltage) with respect to the SOC (charged state) is relatively low and a relatively high change region. have. Specifically, it has two low change regions L1, L2 and three high change regions H1, H2, H3. As shown in FIG. 3, the low change region L1 is located in the range of SOC31 [%] to SOC62 [%]. The low change region L2 is located in the range of SOC68 [%] to SOC97 [%]. In the low change region L1, the change rate of the OCV with respect to the SOC is very small, and the OCV is 3.3 [V] and is a substantially constant plateau region. The low change region L2 has a very small change rate of the OCV with respect to the SOC, and is a plateau region where the OCV is 3.34 [V] and is substantially constant.

  The first high change region H1 is in the range of SOC 62 [%] to SOC 68 [%], and is located between the two low change regions L1 and L2. The second high change region H2 is in the range of SOC31 [%] or less, and is located on the low SOC side than the low change region L1. The third high change region H3 is in a range of SOC 97 [%] or more, and is located on the higher SOC side than the low change region L2. The first to third high change regions H1 to H3 have a relationship in which the OCV change rate with respect to the SOC (the slope of the graph shown in FIG. 3) is relatively high compared to the low change regions L1 and L2.

  As an example of the secondary battery 31 having the SOC-OCV correlation characteristic of FIG. 3, an iron phosphate lithium ion battery using lithium iron phosphate (LiFePO4) as a positive electrode active material and graphite as a negative electrode active material is illustrated. I can do it.

(B) Determination of Change Area and Equalization Control of Secondary Battery 31 The BM 50 measures the OCV of the secondary battery 31 and determines the change area of each secondary battery 31. For example, when the measured value of OCV is 3.3 [V], it can be determined from the SOC-OCV correlation characteristic shown in FIG. 3 that the secondary battery 31 is included in the low change region L1. When the OCV is 3.31 [V] to 3.33 [V], it can be determined that the secondary battery 31 is included in the first high change region H1. If the OCV is 3.34 [V], it can be determined that the secondary battery 31 is included in the low change region L2.

  And BM50 performs the following equalization control based on the determination result of a change area | region. Hereinafter, the content of the equalization control will be described by taking two secondary batteries 31A and 31B as an example. 4 to 7 are enlarged views of the portion A in FIG. 3, and FIG. 8 is an enlarged view of the portion B in FIG.

<First equalization control>
As shown in FIG. 4, when two secondary batteries 31A and 31B are divided into two low change regions L1 and L2, at least a first high change region is provided between the two secondary batteries 31A and 31B. There is a capacity difference of H1 minutes. That is, as shown in FIG. 4, there is a capacitance difference Ccd [Ah] between the end points c and d of the first high change region H1.

  Therefore, the controller 60 causes the discharge circuit 70 to discharge the secondary battery 31B having the higher OCV by the capacity difference Ccd. By doing so, the capacity difference between the two secondary batteries 31A and 31B is reduced by the capacity difference Ccd compared to before discharge (first equalization control). The capacity difference Ccd can be calculated by multiplying the “SOC difference” between the two points c and d by the “full charge capacity”. In the first equalization control, the discharge amount may be an amount based on the capacity difference Ccd. In addition to discharging the same amount as the capacity difference Ccd as described above, the capacity difference Ccd is increased or decreased by a predetermined ratio. May be discharged.

<Second equalization control>
Further, as shown in FIG. 5, when the two secondary batteries 31A and 31B are divided into the low change region L1 and the first high change region H1, at least between the two secondary batteries 31A and 31B, There is a capacity difference Ccb [Ah] between the capacity of the end point (end point close to the secondary battery 31B) c of the low change region L1 and the capacity of the secondary battery 31B.

  Therefore, the control unit 60 uses the discharge circuit 70 to discharge the secondary battery 31B having the higher OCV by the capacity difference Ccb. In this way, the capacity difference between the two secondary batteries 31A and 31B is reduced by the capacity difference Ccb as compared to before discharging (second equalization control). The capacity difference Ccb can be calculated by multiplying the SOC difference between the end point c and the secondary battery 31B by the “full charge capacity”. Further, the SOC of the secondary battery 31B can be obtained from the OCV of the secondary battery 30B and the SOC-OCV correlation characteristic shown in FIG.

  Further, as shown in FIG. 6, when the two secondary batteries 31A and 31B are divided into the first high change region H1 and the low change region L2, at least between the two secondary batteries 31A and 31B, There is a capacity difference Cad [Ah] between the capacity of the secondary battery 31A and the capacity of the end point (end point close to the secondary battery 31A) d of the low change region L2.

  Therefore, the controller 60 causes the discharge circuit 70 to discharge the secondary battery 31B on the higher OCV side by the capacity difference Cad. By doing so, the capacity difference between the two secondary batteries 31A and 31B is reduced by the capacity difference Cad as compared to before discharging (second equalization control). The capacity difference Cad can be calculated by multiplying the “SOC difference” between the secondary battery 30A and the end point d by “full charge capacity”. Further, the SOC of the secondary battery 31A can be obtained from the OCV of the secondary battery 30A and the SOC-OCV correlation characteristic shown in FIG.

  In the second equalization control, the discharge amount may be an amount based on the capacity differences Ccb, Cad. In addition to discharging the same amount as the capacity differences Ccb, Cad as described above, the capacity differences Ccb, Cad You may discharge the quantity which increased / decreased only by the predetermined ratio.

<Composite equalization control>
In addition, as shown in FIG. 7, when the two secondary batteries 31A and 31B are divided into the first low change region L1 and the first high change region H1 after the execution of the first equalization process, the controller 60 Then, the second equalization process is executed to discharge the secondary battery 31B by the capacity difference Ccb. In this way, the capacity difference between the two secondary batteries 31A and 31B is smaller by the capacity difference (Ccd + Ccb) than before the first equalization control and the second equalization control are executed.

<Third equalization control>
Further, the control unit 60 has a high OCV when both of the two secondary batteries 31A and 31B are included in the second high change region H2 or the third high change region H3 and the OCV values are different from each other by a predetermined value or more. By discharging the secondary battery on the side, the capacities of the two secondary batteries 31A and 31B are equalized. For example, as shown in FIG. 8, when both of the two secondary batteries 31A and 31B are included in the third high change region H3 and the value of the OCV differs by a predetermined value or more, the control unit 60 has two secondary batteries. A capacity difference Cv [Ah] between the batteries 31A and 31B is calculated.

  Then, the secondary battery 31B having the higher OCV is discharged by the obtained capacity difference Cv. In this way, the capacities of the two secondary batteries 31A and 31B can be equalized (third equalization control). The capacity difference Cv can be calculated by multiplying the “SOC difference” of the secondary batteries 31A and 31B by the “full charge capacity”. Further, the SOCs of the secondary batteries 31A and 31B can be obtained from the OCV of the secondary batteries 31A and 31B and the SOC-OCV correlation characteristics shown in FIG.

  In the third equalization control, the discharge amount may be an amount based on the capacity difference Cv. In addition to discharging the same amount as the capacity difference Cv as described above, the capacity difference Cv is increased or decreased by a predetermined ratio. May be discharged.

  In the above description, the equalization control has been described by taking two secondary batteries 31A and 31B as an example. However, the number of secondary batteries 31 may be three or more, and in this case, the secondary battery with the smallest OCV is used. What is necessary is just to perform equalization control between the battery 31 and the other secondary battery 31, respectively.

3. Equalization Control Execution Sequence Next, the equalization control execution sequence will be described. The equalization control execution sequence shown in FIG. 9 includes steps S10 to S70. For example, the equalization control execution sequence is executed at the same time when the BM 50 is started and monitoring of the assembled battery 30 is started.

  When the process starts, the control unit 60 acquires the current value of the secondary battery 31 from the output of the current sensor 40. And the process which compares the acquired electric current value with a threshold value (value which can be considered that an electric current is substantially zero) is performed (S10, S20). During the period in which the current value exceeds the threshold value, NO is determined in S20, so that the processes in S10 and S20 are repeated.

  When the current flowing through the secondary battery 31 can be regarded as substantially zero, a YES determination is made in S20, and the control unit 60 then gives a command to the voltage detection circuit 80 to measure the OCV of each secondary battery 31. (S30).

  Thereafter, the control unit 60 refers to the measured OCV to the SOC-OCV correlation characteristics stored in the memory 63 and performs a process of determining in which change region each secondary battery 31 is included (S40). .

  And if the control part 60 determines the change area | region of each secondary battery 31, it will perform the process which determines whether an equalization process is performed or not (S50). Specifically, in the following cases (1) to (4), it is determined as “execution”, and in other cases, it is determined as “not execute”.

(1) When two secondary batteries 31A and 31B are divided into two low change regions L1 and L2, (2) Two secondary batteries 31A and 31B are divided into the low change region L1 and the first high change region H1. Or when the two secondary batteries 31A and 31B are separated in the first high change region H1 and the low change region L2 (3) The two secondary batteries 31A and 31B are included in the second high change region H2. When the OCV value differs by a predetermined value or more (4) When the second high change region H3 includes two secondary batteries 31A and 31B and the OCV value differs by a predetermined value or more

  And when it corresponds to (1)-(4), the control part 60 gives the instruction | command to the discharge circuit 70, and performs a 1st-3rd equalization process (S60). That is, the first equalization process is executed when the condition corresponds to (1). If (2) applies, the second equalization process is executed. If (3) and (4) apply, the third equalization process is executed.

  Thereafter, the process returns to S10, and the processes after S10 are repeatedly executed. And when it will be in the state applicable to (1)-(4), the control part 60 will give a command to the discharge circuit 70, and will perform a 1st equalization process-a 3rd equalization process. Then, as the BM 50 ends the monitoring of the secondary battery 31, the equalization control execution sequence also ends (S70: YES).

4). Description of Effect The BM 50 of the first embodiment performs equalization control even in an intermediate SOC region (region near the portion A shown in FIG. 3) where the SOC is around 65%. Specifically, when the secondary batteries 31A and 31B are divided into two low change regions L1 and L2, the first equalization process is executed. In addition, when the secondary batteries 31A and 31B are divided into the low change regions L1 and L2 and the high change region H1, the second equalization process is executed. Therefore, the capacity imbalance of the secondary battery 31 can be suppressed even when the battery is not charged to near full charge or when the frequency of full charge is low.

  When the two secondary batteries 31A and 31B are divided into the first low change area L1 and the first high change area H1 after the execution of the first equalization process, the control unit 60 performs the second equalization process. Run. Therefore, the capacity imbalance of the secondary battery 31 can be further suppressed. Further, since the third equalization process is performed in the second high change region H2 and the third high change region H3, it is possible to further suppress the capacity imbalance between the secondary batteries 31.

<Embodiment 2>
A second embodiment will be described with reference to FIGS.
1. Detection of full charge capacity difference When there is no full charge capacity difference between the secondary batteries 31A and 31B, if capacity imbalance occurs between the two secondary batteries 31A and 31B, the SOC-OCV of the two secondary batteries 31A and 31B The correlation characteristic is a relationship in which the position is shifted in the SOC axis direction. For example, when the secondary battery 31B is unbalanced with respect to the secondary battery 31A with a smaller capacity, the secondary battery 31A has an SOC-OCV correlation characteristic of the secondary battery 31A as shown in FIG. The SOC-OCV correlation characteristic has a relationship of moving parallel to the high SOC side along the SOC axis.

  In this case, as shown in FIG. 10, in both the A part (near the intermediate SOC region where the SOC is about 65%) and the B part (near the high SOC region where the SOC is near 97%), the secondary battery 31A is the secondary battery 31A. The OCV is higher than that of the battery 31B.

  Therefore, in the “first equalization process or second equalization process”, the secondary battery 31A side having a high OCV is discharged to reduce the capacity difference between the two secondary batteries 31A and 31B. Also, the “third equalization process” is a process of reducing the capacity difference between the two secondary batteries 31A and 31B by discharging the secondary battery 31A side having a high OCV. Thus, when there is no full charge capacity difference in the secondary batteries 31A and 31B, the same secondary battery 31A is discharged in the equalization process.

  Next, FIG. 11 shows SOC-OCV correlation characteristics when capacity imbalance occurs between the two secondary batteries 31A and 31B when the secondary batteries 31A and 31B have a full charge capacity difference. Note that the secondary battery 31A shown in FIG. 11 is an initial product, and the secondary battery 31B is a deteriorated product (a battery having a reduced full charge capacity compared to the initial product).

  When there is a difference in full charge capacity between the secondary batteries 31A and 31B, when capacity imbalance occurs between the two secondary batteries 31A and 31B, as shown in FIG. 11, part A (an intermediate SOC with an SOC of around 65%) In the vicinity of the area) and B part (in the vicinity of the high SOC area where the SOC is near 97%), the OCV magnitude relationship is switched. That is, in part A, the OCV is higher on the secondary battery 31A side than on the secondary battery 31B side. On the other hand, in part B, the OCV is higher on the secondary battery 31B side than on the secondary battery 31A side.

  Therefore, in the “first equalization process or the second equalization process”, the secondary battery 31A side is discharged to reduce the capacity difference between the two secondary batteries 31A and 31B. On the other hand, the third equalization process is a process of reducing the capacity difference between the two secondary batteries 31A and 31B by discharging the secondary battery 31B side. Thus, when the secondary batteries 31A and 31B have a full charge capacity difference, the different secondary batteries 31A and 31B are discharged in the equalization process.

From the above, it is determined whether the secondary battery 31 discharged in the “first equalization process or the second equalization process” and the secondary battery 31 discharged in the “third equalization process” are the same. Thus, it is possible to determine whether or not there is a full charge capacity difference between the secondary batteries 31A and 31B.
In addition, when there is a full charge capacity difference, the reason why the OCV magnitude relationship is switched between the A portion and the B portion shown in FIG. 11 is that when the iron phosphate lithium ion battery deteriorates, the capacity of the low change region L2 Changes to decrease. Therefore, the magnitude relationship is switched between the A part and the B part depending on the manner of unbalance.

  In the present embodiment, after the equalization process is performed, the discharged secondary battery 31 is stored, and when the equalization process is performed next, the secondary battery 31 is discharged depending on whether the secondary battery 31 to be discharged is the same as the previous time. It is detected whether there is a full charge capacity difference between the batteries 31A and 31B. And the execution pattern of equalization control is switched according to the presence or absence of the full charge capacity difference.

FIG. 12 is a flowchart showing a procedure for switching the execution pattern of equalization control.
The control unit 60 performs a process of determining whether or not the secondary batteries 31A and 31B have a full charge capacity difference by the above method (S100). And when there is no full charge capacity difference, the control part 60 performs a 1st equalization process-a 3rd equalization process according to the case of (1)-(4) similarly to the case of Embodiment 1. (S120).

  On the other hand, when there is a full charge capacity difference, the execution of the first equalization process and the second equalization process is prohibited, and when the condition corresponds to (4), only the third equalization process is executed (S110). Specifically, when two secondary batteries 31A and 31B are included in the third high-change region H3 and the OCV value differs by a predetermined value or more, the secondary battery 31 on the higher OCV side is discharged, The capacities of the two secondary batteries 31A and 31B are equalized.

  By doing so, the following effects can be obtained. As shown in FIG. 11, the degraded secondary battery 31 </ b> B tends to start up faster near the B portion (near the high SOC region where the SOC is near 97%) than the secondary battery 31 </ b> A without degradation. In particular, when the first equalization process and the second equalization process are performed, the tendency may become remarkable, and an overvoltage is likely to occur in the deteriorated secondary battery 31B near the full charge.

  In this regard, in this example, the execution of the first equalization process and the second equalization process is prohibited as described above, and only the third equalization process is executed, so that as shown in FIG. In the change region H3, the capacities of the secondary batteries 31A and 31B are equalized, and the rise of the high SOC region of the SOC-OCV correlation characteristics of the two secondary batteries 31A and 31B is aligned in the B portion, so that an overvoltage is generated. Can be suppressed.

  Further, when the third equalization process is performed when there is a full charge capacity difference between the two secondary batteries 31A and 31B, the full charge capacity difference is caused as a shift in the SOC-OCV correlation characteristic in the A part of FIG. appear. That is, the secondary battery 31B is fully charged between the point P2 where the low change region L2 shifts to the first high change region H1 and the point P3 where the secondary battery 31A moves from the low change region L2 to the first high change region H1. Deviation according to the capacity difference occurs. In addition, the fully charged capacity between the point P4 where the secondary battery 31B shifts from the first high change region H1 to the low change region L1 and the point P5 where the secondary battery 31A moves from the first high change region H1 to the low change region. A shift corresponding to the difference occurs.

  Therefore, after the third equalization process, when the secondary batteries 31A and 31B are discharged, the positional shift between the points P2 and P3 and the points P4 and P5 is the timing when the voltages of the two secondary batteries 31A and 31B change. Appear. Therefore, by detecting the time difference between the timings at which the voltages of the two secondary batteries 31A and 31B change in the vicinity of a predetermined voltage value (around 3.34V in the example of FIG. 14), the full capacity of the secondary batteries 31A and 31B is detected. The magnitude of the charge capacity difference can be detected.

  In the example of FIG. 14, after starting discharging at time t0 after full charge, the voltage of the secondary battery 31B decreases, and the tendency of voltage transition changes (inflection point appears) at time “t1”. . After that, the voltage is approximately 3.34 V and hardly changes, the voltage changes at time “t2”, and thereafter the voltage decreases. In the secondary battery 31A, the voltage decreases after time t0, and the tendency of voltage transition (the inflection point appears) changes at time “t1”. After that, the voltage is approximately 3.34 V, hardly changed, the voltage changes at time “t3”, and thereafter the voltage decreases.

  As shown in FIG. 13, the time “t1” corresponds to the point “P1” at which the secondary batteries 31A and 31B shift from the third high change region H3 to the low change region L2. The time “t2” corresponds to the point “P2” at which the secondary battery 31B moves from the low change region L2 to the first high change region H1, and the time “t3” has the secondary battery 31A in the low change region L2. Corresponds to the point “P3” that moves from the first to the high change region H1.

  Therefore, the magnitude of the full charge capacity difference between the secondary batteries 31A and 31B is detected from the time difference T (t3−t2) between the two points corresponding to the two points P2 and P3 where the position shift occurs due to the full charge capacity difference. I can do it. The control unit 60 performs a process of comparing the detected full charge capacity difference with a specified value. If the full charge capacity difference exceeds the specified value, for example, an error process such as displaying an abnormality is performed.

  In addition, since the time t2 and the time t3 are inflection points at which the tendency of voltage transition changes, the full charge capacity difference between the secondary batteries 31A and 31B is large even by detecting the difference in timing at which the inflection points appear. Can be detected. An inflection point is a point at which a change (the slope of the graph changes) appears in the voltage curve shown in FIG.

In addition to the above, the full charge capacity difference between the secondary batteries 31A and 31B can be detected from the time difference T (t4−t3) between the two points corresponding to the two points P3 and P4. In addition, the magnitude of the full charge amount difference is determined based on the accumulated charge / discharge amounts of the secondary batteries 31A and 31B from the time “t2” corresponding to the point P2 to the time “t3” corresponding to the point P3. You may make it detect.
<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the first and second embodiments, the lithium ion secondary battery 31 is illustrated as an example of the storage element. The power storage element includes two low change regions L1 and L2 having a relatively low OCV change rate with respect to the SOC, and a first change in the OCV change rate with respect to the SOC between the two low change regions L1 and L2. Any battery other than the lithium ion battery may be used as long as it has characteristics having the high change region H1.

  (2) In the first and second embodiments, an example in which the capacities of the two secondary batteries 31 are equalized by discharging the secondary battery 31 on the higher OCV side of the two secondary batteries 31A and 31B. Although shown, the capacity of the two secondary batteries 31 may be equalized by charging the secondary battery 31 on the low OCV side. Moreover, you may make it equalize combining charging and discharging. For example, when the two secondary batteries 31A and 31B are divided into the low change areas L1 and L2, the secondary battery 31B on the low change area L2 side discharges the capacity Ccd / 2, and the secondary battery 31A, 31B has a low change area L1 side. The capacity Ccd / 2 may be charged by the secondary battery 31A.

  (3) In the first and second embodiments, the change values L1, L2, and H1 to H3 of the secondary batteries 31A and 31B are determined using the OCV measurement values. The determination method of the change region may be a method using a voltage curve of the secondary battery 31 at the time of charge / discharge, in addition to a method using the measured value of the OCV.

  That is, for example, when the assembled battery 30 is charged from a state in which the two secondary batteries 31 are included in the low change region L1, the secondary voltage 31 shifts from the low change region L1 to the first high change region H1. The voltage change is detected in the secondary battery 31 at the timing to perform, that is, at the end point c in FIG. Further, a voltage change is detected in the secondary battery 31 at the timing when the secondary voltage 31 shifts from the first high change region H1 to the low change region L2, that is, at the end point d in FIG. Therefore, by determining whether or not the voltage change corresponding to the end point c and the end point d is detected in each of the secondary batteries 31A and 31B, the change areas L1, L2, and H1 of the respective secondary batteries 31A and 31B are determined. It is possible to determine whether it is included. Further, since the end point d and the end point c in FIG. 4 are also inflection points at which the tendency of voltage transition changes, the same determination can be made by detecting the inflection points.

  In addition to the above-described determination method, the voltage of the secondary battery 31 is calculated from the current value obtained from the current sensor 40 and the internal resistance, and in which change region the secondary battery 31 is included based on the magnitude of the calculated voltage. It can also be estimated.

  (4) In the second embodiment, when there is a full charge capacity difference, execution of the first equalization process and the second equalization process is prohibited, and only the third equalization process is executed. However, for example, when the battery is not fully charged or when the secondary battery 31 is unlikely to become overvoltage during charging (charge control is performed for each cell voltage of the secondary battery, not the total voltage of the assembled battery) In contrast to the example of the second embodiment, the first equalization process or the second equalization process may be executed, and the execution of the third equalization process may be prohibited. This also makes it possible to maintain the equalization execution frequency at a high level, and to minimize the capacity imbalance between the secondary batteries 31.

  In addition, when the first equalization process or the second equalization process is executed and the execution of the third equalization process is prohibited, the full charge capacity difference is expressed as a rise deviation in the high SOC region (part B in FIG. 11). appear. Therefore, in this case, the magnitude of the full charge capacity difference can be detected by detecting the deviation of the rising portion from the timing when the voltages of the two secondary batteries 31 change.

  (5) In the second embodiment, whether the secondary battery 31 discharged in the “first equalization process or the second equalization process” and the secondary battery 31 discharged in the “third equalization process” are the same. Thus, it was determined whether or not there is a full charge capacity difference between the secondary batteries 31A and 31B. In addition to this, for example, the presence or absence of a full charge capacity difference may be detected from the size of the internal resistance.

  (6) In Embodiment 1, when it corresponds to (1)-(4), the 1st-3rd equalization process was performed, and it was made not to perform an equalization process in the case other than that. Even when the conditions do not correspond to (1) to (4), if the two secondary batteries 31A and 31B are divided into two different high-change regions H, an equalization process may be performed. For example, when the two secondary batteries 31A and 31B are divided into the first high change region H1 and the third high change region H3, the OCV is measured to calculate the capacity difference between the two secondary batteries 31A and 31B. . And the capacity | capacitance of two secondary battery 31A, 31B can be equalized by discharging only the calculated | required capacity | capacitance difference in the secondary battery with the higher OCV.

  (6) Although the example which provided the current sensor 40 separately from BM50 was shown in Embodiment 1, the structure which includes the current sensor 40 in BM50 may be sufficient.

20 ... Battery pack 31 ... Secondary battery (corresponding to "storage element" of the present invention)
40 ... Current sensor 50 ... Battery manager (corresponding to "monitoring device" of the present invention)
60 ... Control unit 70 ... Discharge circuit (corresponding to "charge / discharge circuit" of the present invention)
80 ... voltage detection circuit (corresponding to "voltage detection part" of the present invention)

Claims (9)

A battery pack monitoring device in which a plurality of storage elements are connected in series,
A voltage detector that individually detects the voltage of each storage element;
A charge / discharge circuit for discharging or charging each of the storage elements individually;
A control unit,
The storage element includes two low change regions having a relatively low change rate of the open circuit voltage with respect to the charged state, and a first high voltage having a relatively high change rate of the open voltage with respect to the charge state between the two low change regions. Has a change area,
When the two storage elements are divided into two low change regions, the control unit,
Based on the capacity difference between the end points of the first high change region, at least one of the two power storage elements is discharged or charged, thereby reducing the capacity difference between the two power storage elements. An assembled battery monitoring device that performs a first equalization process. A battery pack monitoring device in which a plurality of storage elements are connected in series,
A voltage detector that individually detects the voltage of each storage element;
A charge / discharge circuit for discharging or charging each of the storage elements individually;
A control unit,
The storage element includes two low change regions having a relatively low change rate of the open circuit voltage with respect to the charged state, and a first high voltage having a relatively high change rate of the open voltage with respect to the charge state between the two low change regions. Has a change area,
Wherein, of the two of said power storage device, when one of the power storage element is included in the low change region, the electric storage element of the other side are included in the first high-change region,
On the basis of the capacity difference between the capacity of the other side of the storage capacity of the side of the end points closer to the device and the other side of the storage element of the low-change region in which one of the storage element is contained, either at least one of the two power storage devices An assembled battery monitoring apparatus that performs a second equalization process for reducing a capacity difference between the two power storage elements by discharging or charging either side. The assembled battery monitoring device according to claim 1,
Wherein the control unit, after the execution of the first equalization processing, of the two power storage devices are included in one of the storage element is the low change region, the electric storage element of the other side included in the first high-change region If
On the basis of the capacity difference between the capacity of the other side of the storage capacity of the side of the end points closer to the device and the other side of the storage element of the low-change region in which one of the storage element is contained, either at least one of the two power storage devices An assembled battery monitoring device that executes a second equalization process for reducing a difference in capacity between the two power storage elements by discharging or charging one side. A monitoring device according to any one of claims 1 to 3,
In the case where the power storage element has a second high change region on the low charge state region side than the two low change regions, or a third high change region on the high charge state region side,
When both of the two power storage elements are included in the second high change region or the third high change region, the control unit sets a capacity corresponding to a voltage difference between the power storage elements of the two power storage devices. An assembled battery monitoring apparatus that performs a third equalization process for reducing a capacity difference between the two power storage elements by discharging or charging at least one of the two. The assembled battery monitoring device according to claim 4,
In the first equalization process, when the two power storage elements are divided into the two low change regions, at least one of the two power storage devices is based on a capacitance difference between the end points of the first high change region. It is a process of reducing the capacity difference between the two power storage elements by discharging or charging either side,
In the second equalization process, when one of the two power storage elements is included in the low change region and the other power storage element is included in the first high change region, At least one of the two power storage elements based on the capacity difference between the capacity of the end point close to the power storage element on the other side and the capacity of the power storage element on the other side in the low change region including the element Is a process of reducing the difference in capacity between the two power storage elements by discharging or charging
The controller is
Detecting the presence or absence of a full charge capacity difference between the plurality of power storage elements constituting the assembled battery,
If there is no full charge capacity difference between the storage elements,
Performing at least one equalization process of the first equalization process and the second equalization process, and the third equalization process;
If there is a full charge capacity difference between the storage elements,
An assembled battery monitoring device that executes at least one of the first equalization process and the second equalization process or the third equalization process. The assembled battery monitoring device according to claim 5,
The control unit is configured to control the timing at which the voltage of the power storage element changes when the power storage element is charged / discharged after execution of any of the first equalization process to the third equalization process. An assembled battery monitoring device that measures a time difference or a cumulative charge / discharge amount therebetween and detects a full charge capacity difference between the power storage elements based on the obtained time difference or the cumulative charge / discharge amount. A method for equalizing the capacity of a battery pack comprising a plurality of power storage elements connected in series,
The storage element includes two low change regions having a relatively low change rate of the open circuit voltage with respect to the charged state, and a first high voltage having a relatively high change rate of the open voltage with respect to the charge state between the two low change regions. Has a change area,
When the two storage elements are divided into the two low change regions, at least one of the two storage elements is discharged or charged based on a capacity difference between the end points of the first high change region. A capacity equalization method for an assembled battery, wherein the difference in capacity between the two power storage elements is reduced by the first equalization process. A method for equalizing the capacity of a battery pack comprising a plurality of power storage elements connected in series,
The storage element includes two low change regions having a relatively low change rate of the open circuit voltage with respect to the charged state, and a first high voltage having a relatively high change rate of the open voltage with respect to the charge state between the two low change regions. Has a change area,
Of the two said electric storage device, contained in one of the storage element is the low change area, if the storage element on the other side are included in the first high-change region, the low change that includes one storage element A second one that discharges or charges at least one of the two power storage elements based on a capacity difference between a capacity of an end point close to the power storage element on the other side of the region and a capacity of the power storage element on the other side. An assembled battery capacity equalization method for reducing a difference in capacity between the two power storage elements by an equalization process. The battery pack capacity equalizing method according to claim 7,
After execution of the first equalization processing, of the two power storage device, when one of the storage element is the included in the low change area, the electricity storage device of the other side are included in the first high-change region,
On the basis of the capacity difference between the capacity of the other side of the storage capacity of the side of the end points closer to the device and the other side of the storage element of the low-change region in which one of the storage element is contained, either at least one of the two power storage devices A method for equalizing a battery pack, wherein a difference in capacity between the two power storage elements is reduced by a second equalization process for discharging or charging either side.

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