Battery management apparatus and method

Abstract

To provide a battery management device and method that improve estimation accuracy of SOC of a battery including a plurality of battery cells while suppressing deterioration of efficiency and limitation on an application object.SOLUTION: A battery management device manages a battery including a plurality of battery cells in which a change in OCV relative to a change in SOC is small in a first SOC range while a change in OCV relative to a change in SOC is large in a second SOC range. The battery management device is configured to: accumulate a current flowing in each battery cell to calculate the SOC of each battery cell; when the calculated SOC has stayed in the first SOC range for a predetermined period or more, control a plurality of cell balancing circuits in such a way that the SOC of a target battery cell selected from the plurality of battery cells falls within the second SOC range; and calculate the SOC of the target battery cell based on a relation between the SOC and the OCV in the second SOC range and correct the SOC of each battery cell by the amount of correction based on the calculated SOC.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a battery management apparatus and method for managing a battery including a plurality of battery cells. [Background technology]

[0002] Conventionally, a hybrid vehicle (HEV, PHEV) is known that has a battery including an equalization circuit that reduces the variation in SOC of each battery unit by selectively discharging a plurality of battery units connected in series and a battery unit with a relatively high remaining capacity, and a control device that manages the battery (see, for example, Patent Document 1). Each battery unit of the hybrid vehicle includes one or more battery cells that are olivine iron-based lithium-ion secondary batteries. In such an olivine iron-based lithium-ion secondary battery, the change characteristic of the OCV (open circuit voltage) with respect to the SOC of the battery has a first region where the change in OCV exceeds a threshold value with respect to the change in SOC, and a second region (plateau region) where the change in OCV does not exceed the threshold value with respect to the change in SOC. In addition, when the estimated value of the SOC of the battery belongs to the second region, the control device that manages the battery estimates the SOC by integrating the current input and output to and from the battery. Furthermore, when the period during which the estimated value of the battery SOC belongs to the second region exceeds a predetermined period, the control device changes the amount of power consumed by the motor and the amount of power generated by the generator driven by the engine so that the SOC of the battery temporarily belongs to the first region. The control device then uses an estimation method based on an internal reaction model to determine the OCV from the battery voltage and derives the SOC corresponding to the OCV. This reduces the error in the estimated value of the SOC caused by the error of the current sensor that detects the current, and makes the estimated value closer to the true SOC value. Furthermore, before activating the equalization circuit to equalize the SOC of the multiple battery units, the control device estimates the SOC using the estimation method based on an internal reaction model by making the SOC of the battery temporarily belong to the first region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-283922 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a hybrid vehicle including an engine and a generator as described above, the SOC (estimated value) of the battery can be forced to shift from the second region to the first region by changing the power consumption by the motor and the power generation by the generator driven by the engine. However, if the power consumption by the motor and the power generation by the generator are changed to change the SOC of the battery, the efficiency of the entire vehicle may decrease. In addition, in an electric vehicle that does not include a generator driven by an engine, it is practically impossible to force the SOC of the battery to shift from the second region to the first region even if the above control device is used. Therefore, the above conventional control device still has a problem in that the target of application is limited.

[0005] Therefore, the main objective of the present disclosure is to improve the estimation accuracy of the SOC of a battery including multiple battery cells in which the amount of change in OCV relative to the amount of change in SOC is small in a first SOC range and the amount of change in OCV relative to the amount of change in SOC is large in a second SOC range, while suppressing deterioration in efficiency and limitation of applicable targets. [Means for solving the problem]

[0006] The battery management device disclosed herein is a battery management device that manages a battery including a plurality of battery cells in which a change in OCV relative to a change in SOC becomes small in a first SOC range and a change in OCV relative to a change in SOC becomes large in a second SOC range, and includes a plurality of cell balancing circuits that charge at least one of the battery cells with discharge power from at least one of the battery cells, a SOC calculation unit that calculates the SOC of each of the plurality of battery cells by integrating a current flowing through the battery cells, a cell balancing control unit that controls the plurality of cell balancing circuits so that the SOC of a target battery cell, which is one of the plurality of battery cells, falls within the second SOC range when the residence time of the SOC calculated by the SOC calculation unit in the first SOC range becomes equal to or longer than a predetermined period of time, and a SOC correction unit that derives the SOC of the target battery cell based on a relationship between SOC and OCV in the second SOC range, calculates a correction amount based on the derived SOC, and corrects the SOC of each of the plurality of battery cells using the correction amount.

[0007] The battery management device of the present disclosure manages a battery including a plurality of battery cells in which the change in OCV relative to the change in SOC is small in a first SOC range and the change in OCV relative to the change in SOC is large in a second SOC range. The battery management device also includes a plurality of cell balancing circuits that charge at least one of the battery cells with discharge power from at least one of the battery cells. The battery management device further integrates a current flowing through the battery cells to calculate the SOC of each of the plurality of battery cells, and controls the plurality of cell balancing circuits so that the SOC of a target battery cell, which is one of the plurality of battery cells, falls within a second SOC range when the calculated SOC is within the first SOC range for a predetermined period of time or longer. The battery management device then derives the SOC of the target battery cell based on the relationship between the SOC and the OCV in the second SOC range, calculates a correction amount based on the derived SOC, and corrects the SOC of each of the plurality of battery cells using the correction amount. This allows the SOC of the target battery cell to be shifted to the second SOC range using multiple cell balance circuits while significantly reducing the loss of electrical energy in the battery (multiple battery cells). In addition, it is possible to accurately derive the SOC of the target battery cell based on the relationship between the SOC and OCV in the second SOC range, and to properly calculate the SOC correction amount of each battery cell from the SOC of the target battery cell. Furthermore, it is not necessary to use a power device that consumes the battery's power and a generator that generates power to shift the SOC of the target battery cell to the second SOC range. Therefore, it is possible to suppress deterioration in efficiency in the application target of the battery management device and to expand the application range of the battery management device. As a result, according to the battery management device of the present disclosure, it is possible to improve the estimation accuracy of the SOC of a battery including multiple battery cells in which the change in OCV relative to the change in SOC is small in the first SOC range and the change in OCV relative to the change in SOC is large in the second SOC range, while suppressing deterioration in efficiency and limiting the application target.

[0008] Furthermore, the cell balancing control unit may control the cell balancing circuits to restore electrical energy exchanged between the target battery cell and the other battery cells after the SOC of the target battery cell based on the relationship between the SOC and OCV is derived by the SOC correction unit, thereby making it possible to suppress a determination that the SOC of the target battery cell has reached a separately set upper limit SOC or lower limit SOC after the SOC of the target battery cell has been shifted to a second SOC range.

[0009] Furthermore, the cell balance control unit may select the battery cell to be the target battery cell from among the plurality of battery cells so that the same battery cell is not consecutively selected as the target battery cell, thereby making it possible to suppress deterioration of a specific battery cell that is constantly selected as the target battery cell.

[0010] The SOC correction unit may calculate the correction amount for each of the plurality of battery cells based on a difference between an SOC calculated by the SOC calculation unit while the target battery cell is being charged or discharged by the plurality of cell balancing circuits and an SOC based on a relationship between the SOC and an OCV, thereby making it possible to properly calculate the correction amount for each of the plurality of battery cells.

[0011] Furthermore, the SOC calculation unit may be configured to estimate the SOC of each of the battery cells lower when the retention time is equal to or longer than a first period shorter than the predetermined period and shorter than the predetermined period, compared to when the retention time is shorter than the first period. In this way, when the SOC of the target battery cell is shifted to a second SOC range that is lower than the first SOC range, the minimum value of the SOC of the battery cells appears to have decreased to a certain degree immediately before the shift. As a result, even if the SOC of the target battery cell that has been shifted to the second SOC range is notified to the user, it is possible to prevent the user from feeling uncomfortable that the SOC of the battery has decreased more rapidly than expected.

[0012] The battery cell may be a lithium iron phosphate secondary battery. However, the battery cell of the battery managed by the battery management device of the present disclosure may be a battery other than a lithium iron phosphate secondary battery, as long as the battery cell has a small change in OCV relative to the change in SOC in a first SOC range and a large change in OCV relative to the change in SOC in a second SOC range.

[0013] Furthermore, the battery may be mounted on an electric vehicle that does not include an engine and a generator driven by the engine. In other words, the battery management device of the present disclosure can improve the estimation accuracy of the battery SOC without using a power device that consumes the battery power and a generator that generates the power, and is therefore extremely useful for managing a battery mounted on an electric vehicle.

[0014] The battery management method disclosed herein is a battery management method for managing a battery including a plurality of battery cells in which the amount of change in OCV relative to the amount of change in SOC is small in a first SOC range and the amount of change in OCV relative to the amount of change in SOC is large in a second SOC range, and a plurality of cell balancing circuits that charge at least one of the battery cells with discharge power from at least one of the battery cells, the method comprising: integrating a current flowing through the battery cells to calculate an SOC of each of the plurality of battery cells; controlling the plurality of cell balancing circuits so that an SOC of a target battery cell, which is one of the plurality of battery cells, falls within the second SOC range when the SOC calculated by integrating the current remains in the first SOC range for a predetermined period of time or longer; deriving an SOC of the target battery cell based on a relationship between SOC and OCV in the second SOC range; calculating a correction amount based on the derived SOC; and correcting the SOC of each of the plurality of battery cells using the correction amount.

[0015] According to this method, it is possible to improve the estimation accuracy of the SOC of a battery including multiple battery cells in which the amount of change in OCV relative to the amount of change in SOC is small in a first SOC range and the amount of change in OCV relative to the amount of change in SOC is large in a second SOC range, while suppressing deterioration in efficiency and limiting the scope of application.

[0016] Another battery management device of the present disclosure is a battery management device that manages a battery including a plurality of battery cells in which a change in OCV relative to a change in SOC becomes small in a first SOC range and a change in OCV relative to a change in SOC becomes large in a second SOC range, and includes a plurality of cell balancing circuits that charge at least one of a plurality of battery blocks, each of which includes at least one of the battery cells, with discharge power from another of the plurality of battery blocks; a SOC calculation unit that calculates the SOC of each of the plurality of battery blocks by integrating a current flowing through the battery blocks; a cell balancing control unit that controls the plurality of cell balancing circuits so that the SOC of a target battery block, which is one of the plurality of battery blocks, falls within the second SOC range when the residence time of the SOC calculated by the SOC calculation unit in the first SOC range becomes equal to or longer than a predetermined period of time; and a SOC correction unit that derives the SOC of the target battery block based on a relationship between SOC and OCV in the second SOC range, calculates a correction amount based on the derived SOC, and corrects the SOC of each of the plurality of battery blocks using the correction amount.

[0017] Such a battery management device can also improve the accuracy of estimating the SOC of a battery including multiple battery cells in which the amount of change in OCV relative to the amount of change in SOC is small in a first SOC range and the amount of change in OCV relative to the amount of change in SOC is large in a second SOC range, while suppressing deterioration in efficiency and limitation of application.

[0018] Another battery management method disclosed herein is a battery management method for managing a battery including a plurality of battery cells in which the amount of change in OCV relative to the amount of change in SOC is small in a first SOC range and the amount of change in OCV relative to the amount of change in SOC is large in a second SOC range, and a plurality of cell balancing circuits that charge at least one of a plurality of battery blocks, each of which includes at least one of the battery cells, with discharge power from at least one of the other battery blocks, the method comprising: integrating a current flowing through the battery blocks to calculate an SOC of each of the plurality of battery blocks; controlling the plurality of cell balancing circuits so that an SOC of a target battery block, which is one of the plurality of battery blocks, falls within the second SOC range when the SOC calculated by integrating the current remains in the first SOC range for a predetermined period of time or longer; deriving an SOC of the target battery block based on a relationship between SOC and OCV in the second SOC range; calculating a correction amount based on the derived SOC; and correcting the SOC of each of the plurality of battery blocks using the correction amount.

[0019] With this method, it is possible to improve the accuracy of estimating the SOC of a battery including multiple battery cells in which the amount of change in OCV relative to the amount of change in SOC is small in a first SOC range and the amount of change in OCV relative to the amount of change in SOC is large in a second SOC range, while suppressing deterioration in efficiency and limiting the scope of application. [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic configuration diagram showing a vehicle equipped with a battery management device according to the present disclosure. [Diagram 2] 4 is a table showing characteristics of battery cells of a battery managed by the battery management device of the present disclosure. [Diagram 3] 1 is a schematic configuration diagram showing a battery management device according to the present disclosure; [Figure 4] 5 is a flowchart showing an example of a routine executed by a battery management device of the present disclosure to calculate the SOC of a plurality of battery cells. [Diagram 5] 5 is a flowchart showing an example of a routine executed by a battery management device of the present disclosure to correct the SOC of a plurality of battery cells. [Figure 6] FIG. 11 is an explanatory diagram for explaining a procedure for changing the SOC of a SOC forced variation cell. [Figure 7] FIG. 11 is an explanatory diagram for explaining a procedure for changing the SOC of a SOC forced variation cell. [Figure 8] FIG. 13 is a schematic configuration diagram showing another battery management device of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Next, an embodiment of the present disclosure will be described with reference to the drawings.

[0022] 1 is a schematic diagram showing a vehicle 100 equipped with a battery management device 10 of the present disclosure. The vehicle 100 shown in the figure is an electric vehicle (BEV) including a battery 1 managed by the battery management device 10, and a motor generator (three-phase AC motor) MG that is connected to the battery 1 via a power control device (none of which are shown) including a system main relay, an inverter, and the like, and that can output driving power and regenerative braking power by exchanging power with the battery 1. In the vehicle 100, the battery 1 can be charged with power from an external charging device (not shown).

[0023] As shown in the figure, the battery 1 is a so-called high-voltage battery including a plurality of battery cells 2 connected in series, for example. The plurality of battery cells 2 may be dispersed and housed in module cases of a plurality of battery modules (not shown), and the plurality of battery modules may be connected in series, for example. The battery cells 2 constituting the battery module are lithium iron phosphate ion batteries including a positive electrode (LiFePO positive electrode) formed of lithium iron phosphate having an olivine crystal structure, for example LiFePO4, and a negative electrode formed of a graphite-based carbon material or the like. The positive electrode and the negative electrode of the battery cell 2 are housed inside an exterior body together with a separator and an electrolyte solution, such as an organic solvent.

[0024] FIG. 2 is a diagram showing the relationship between the SOC (charging rate) and the OCV (open circuit voltage) of the battery cell 2. In the figure, the solid line shows the relationship between the SOC and the OCV when the battery cell 2 is discharged, and the dashed line shows the relationship between the SOC and the OCV when the battery cell 2 is charged. As shown in the figure, in the battery cell 2 having a positive electrode formed of lithium iron phosphate, the amount of change in OCV relative to the amount of change in SOC is very small over a wide SOC range. That is, in the range r2 in FIG. 2 and in the range r4 on the higher SOC side, the amount of change in OCV relative to the amount of change in SOC is approximately zero. Hereinafter, the ranges r2 and r4 are collectively referred to as the "plateau range (first SOC range)." In contrast, in range r1 on the low SOC side of range r2, range r3 on the high SOC side of range r2 and the low SOC side of range r4 (between ranges r2 and r4), and range r5 on the high SOC side of range r4, the amount of change in OCV relative to the amount of change in SOC becomes large (the slope becomes steeper). Hereinafter, ranges r1, r3, and r5 are collectively referred to as the "non-plateau ranges (second SOC ranges)."

[0025] 3, the battery management device 10 of the vehicle 100 includes a microcomputer (hereinafter referred to as "microcomputer") 11 including a CPU, ROM, RAM, etc., the same number (plurality) of cell balancing circuits 15 as the total number of battery cells 2 of the battery 1, and multiple management ICs 17. Each cell balancing circuit 15 includes one flyback transformer Tf, two switching elements SW1 and SW2 such as FETs, and two resistors R1 and R2, and one cell balancing circuit 15 is connected to each of the multiple battery cells 2.

[0026] As shown in Fig. 3, the primary coil L1 of each flyback transformer Tf is connected in parallel to the corresponding battery cell 2 via a switching element SW1 and a resistor R1. The secondary coil L2 of each flyback transformer Tf is connected in parallel to a plurality of battery cells 2 (four in the example of Fig. 3) that form one group in which the SOC (voltage) is equalized. That is, one end of the secondary coil L2 of each flyback transformer Tf is connected to one end (e.g., positive electrode) of the plurality of battery cells 2 via a power line. The other end of the secondary coil L2 of each flyback transformer Tf is connected to the other end (e.g., negative electrode) of the plurality of battery cells 2 via a switching element SW2, a resistor R2, and a power line.

[0027] As a result, by controlling the on / off of the switching elements SW1 and SW2 of the cell balancing circuits 15 corresponding to one group, it becomes possible to charge at least any one of the battery cells 2 in the group with the discharge power from at least any one of the other battery cells 2. For example, when the remaining battery cells 2 in one group are charged with the discharge power from any one of the battery cells 2, the switching element SW1 of the cell balancing circuit 15 corresponding to that one of the battery cells 2 is turned on. Next, the switching element SW1 is turned off and the switching elements SW2 of all the cell balancing circuits 15 in the group are turned on. Furthermore, the switching elements SW2 of all the cell balancing circuits 15 are turned off and the switching elements SW1 of the cell balancing circuits 15 corresponding to the battery cells 2 other than the one of the battery cells 2 are turned on, and these processes are repeated thereafter.

[0028] Furthermore, when any one battery cell 2 in one group is charged using the discharge power of the remaining battery cells 2, the switching elements SW1 of the cell balancing circuits 15 corresponding to the battery cells 2 other than that one battery cell 2 are turned on. Next, these switching elements SW1 are turned off and the switching elements SW2 of all the cell balancing circuits 15 in that group are turned on. Furthermore, the switching elements SW2 of all the cell balancing circuits 15 are turned off and the switching element SW1 of the cell balancing circuit 15 corresponding to that one battery cell 2 is turned on, and thereafter, these processes are repeatedly executed.

[0029] Each of the management ICs 17 exchanges information with the microcomputer 11 and controls the corresponding cell balance circuit 15. In this embodiment, one management IC 17 is provided for one group formed by a plurality (four) of battery cells 2 whose SOC (voltage) is equalized. Each management IC 17 controls the on / off of the switching elements SW1, SW2 of the corresponding plurality (four) of cell balance circuits 15 according to a command signal from the microcomputer 11. Furthermore, each management IC 17 has a plurality (four) of voltage sensors (not shown) that detect the voltage of each of the corresponding plurality (four) of battery cells 2, causes each voltage sensor to detect the voltage of the corresponding battery cell 2 at a predetermined cycle, and transmits the detection value of each voltage sensor to the microcomputer 11. Furthermore, each management IC 17 has a plurality (four) of current sensors (not shown) that detect the current flowing through each of the corresponding plurality (four) of battery cells 2, causes each current sensor to detect the current flowing through the corresponding battery cell 2 at a predetermined cycle, and transmits the detection value of each current sensor to the microcomputer 11.

[0030] The microcomputer 11 calculates the SOC of each battery cell 2 by integrating the current flowing through each battery cell 2 detected by each current sensor of the management IC 17. When a predetermined execution condition is met, including that the SOC of each battery cell 2 is in the non-plateau range, i.e., the above-mentioned range r1, r3, or r5, the microcomputer 11 calculates the OCV of each battery cell 2 based on the detection value of each voltage sensor of the management IC 17, and derives the SOC of each battery cell 2 corresponding to the OCV from the relationship between the SOC and OCV in the non-plateau range (see FIG. 2). Then, the microcomputer 11 corrects the SOC of each battery cell 2 calculated based on the current using the SOC of each battery cell 2 derived based on the OCV. Furthermore, when a predetermined execution condition for cell balance control is met, the microcomputer 11 controls the multiple cell balance circuits 15 in cooperation with the management IC 17 so as to equalize the SOC (voltage) of the multiple battery cells 2. In addition, the vehicle 100 is provided with an SOC display unit that displays the SOC of the battery 1 on an instrument panel (not shown), and a display control unit (not shown) of the vehicle 100 displays the minimum SOC, which is the minimum value of the SOCs of each battery cell 2 calculated by the microcomputer 11 of the battery management device 10, on the SOC display unit.

[0031] Next, a procedure for calculating the SOC of each battery cell 2 by the battery management unit 10 will be described with reference to Fig. 4 to Fig. 6. Fig. 4 is a flowchart showing an example of a routine that is repeatedly executed at predetermined time intervals (very short time intervals) by the microcomputer 11 (CPU) of the battery management unit 10 to calculate the SOC of each battery cell 2 while a start switch (IG switch) of the vehicle 100 (not shown) is turned on and the system of the vehicle 100 is started up.

[0032] At the start of the routine of FIG. 4, the microcomputer 11 acquires the value of the flag F1 (step S100) and judges whether the value of the flag F1 is zero or not (step S110). If it is judged that the value of the flag F1 is zero (step S110: YES), the microcomputer 11 sets the coefficient k used in the calculation of the SOC to "1" (step S120). On the other hand, if it is judged that the value of the flag F1 is "1" (step S110: NO), the microcomputer 11 sets a predetermined positive value α smaller than "1" to the coefficient k used in the calculation of the SOC (step S125). The value α is set to a value of, for example, about 0.95-0.99, taking into account the error (about 1 to 5%) of the current sensor. After the process of step S120 or S125, the microcomputer 11 calculates the current I flowing through each of the multiple battery cells 2 detected by each current sensor of each management IC 17. n (where "n" indicates the battery cell 2 number, and where "N" is the total number of battery cells 2, n=1, 2, . . . , N-1, N) is acquired (step S130).

[0033] Next, the microcomputer 11 sets the variable n (the number of the battery cell 2) to "1" (step S140), and calculates the SOC of the n-th battery cell 2 (step S150). In step S150, the microcomputer 11 calculates the SOC of the n-th battery cell 2 based on the coefficient k and the current I n The product of these values ​​is divided by the full charge capacity of the n-th battery cell 2, which is calculated separately, and the result is added to the SOC (previous value) of the n-th battery cell 2, which was calculated the previous time the routine of Fig. 4 was executed, to calculate the current SOC of the n-th battery cell 2. The full charge capacity of each battery cell 2 is calculated by correcting the value calculated when the SOC of each battery cell 2 is included in the non-plateau range, based on the temperature frequency information. Furthermore, the microcomputer 11 increments the variable n (step S160), and determines whether the variable n is greater than the total number N of the battery cells 2 described above (step S170). If it is determined that the variable n is equal to or less than the total number N (step S170: NO), the microcomputer 11 repeatedly executes the processes from step S150 onwards described above.

[0034] When the SOCs of all (N) battery cells 2 are calculated in step S150, it is determined in step S170 that the variable n exceeds the total number N. When the microcomputer 11 determines that the variable n exceeds the total number N (step S170: YES), it acquires the maximum SOC and the minimum SOC, which are the maximum values ​​among the SOCs of all the battery cells 2 (step S180). Furthermore, the microcomputer 11 determines whether or not both the maximum SOC and the minimum SOC are included in the above-mentioned plateau range, i.e., range r2 or r4 (step S190). When it is determined that both the maximum SOC and the minimum SOC are not included in the plateau range (step S190: NO), the microcomputer 11 resets the counter C (step S195) and then temporarily ends the routine of FIG. 4. When the counter C is reset and other predetermined execution conditions are satisfied, the microcomputer 11 derives the SOC of each battery cell 2 based on the OCV corresponding to the voltage of each battery cell 2, and calculates the current I n The SOC of each battery cell 2 calculated based on the above is corrected.

[0035] Furthermore, when it is determined that both the maximum SOC and the minimum SOC are included in the plateau range (step S190: YES), the microcomputer 11 increments the counter C (step S200) and then determines whether the counter C is equal to or greater than a first threshold Cref1 that is determined in advance (step S210). In this embodiment, the first threshold Cref1 used in step S210 is determined so that the product of the first threshold Cref1 and the execution period of the routine in FIG. 4 is, for example, one week (168 hours). That is, the counter C indicates the time that the SOC of each battery cell 2 remains in the plateau range (range r2 or r4). When it is determined that the counter C is less than the first threshold Cref1 (step S210: NO), the microcomputer 11 temporarily ends the routine in FIG. 4 at that point in time.

[0036] On the other hand, when it is determined that the counter C is equal to or greater than the first threshold Cref1 (step S210: YES), the microcomputer 11 determines whether the counter C is less than a predetermined second threshold Cref2 (step S220). In this embodiment, the second threshold Cref2 used in step S220 is determined so that the product of the second threshold Cref2 and the execution period of the routine in FIG. 4 is, for example, one month (720 hours). When it is determined that the counter C is less than the second threshold Cref2 (step S220: YES), the microcomputer 11 sets the flag F1 to "1" (step S230). At that point, the routine in FIG. 4 is temporarily terminated.

[0037] When the counter C is less than the second threshold value Cref2, the time that the SOC of each battery cell 2 has remained in the plateau range (range r2 or r4) is one week or more and less than one month. In this case, by setting the flag F1 to "1" in step S230, a value α smaller than "1" is set to the coefficient k in step S125 when the routine of Fig. 4 is executed, and in step S150, the SOC of each of the multiple battery cells 2 is estimated lower than when the SOC was calculated in step S140.

[0038] Also, when it is determined that the counter C is equal to or greater than the second threshold Cref2 (step S220: NO), the microcomputer 11 sets the flag F1 to zero and sets the flag F2 to "1" (step S235). At that point, the routine in FIG. 4 is temporarily terminated. Here, when the counter C is equal to or greater than the second threshold Cref2, the SOC of each battery cell 2 has been in the plateau range (range r2 or r4) for one month or more. That is, when the usage pattern of the vehicle 100 is, for example, a repeat of charging the battery 1 at the user's home using an external charging device and commuting to a workplace relatively close to the home every day, the SOC of each battery cell 2 of the battery 1 may remain in the plateau range (for example, range r4) for one month or more. When the SOC of each battery cell 2 remains in the plateau range for a long period of time, the current I flowing through each battery cell 2 detected by the current sensor may become too long. nAs the detection errors continue to accumulate, the accuracy of calculating the SOC of each battery cell 2 decreases, and the SOC of the battery 1 displayed on the SOC display unit of the vehicle 100 differs from the minimum SOC of the multiple battery cells 2.

[0039] In light of this, the microcomputer 11 of the battery management unit 10 sets the flag F2 to "1" in step S235 and ends the routine of Fig. 4, and then executes the routine of Fig. 5 to correct the SOC of the multiple battery cells 2. When starting the routine of Fig. 5, the microcomputer 11 selects one of the multiple battery cells 2 as a SOC forcibly changed cell 2x (target battery cell, see Fig. 6) (step S300). The SOC forcibly changed cell 2x is a battery cell 2 whose SOC is to be forcibly shifted from the plateau range to the non-plateau range, and is basically a battery cell 2 having an SOC (see the circle in Fig. 2) closest to the maximum or minimum value of the SOC in the non-plateau range adjacent to the plateau range in which the SOC of the multiple battery cells 2 is included.

[0040] Furthermore, in step S300, if a battery cell 2 having an SOC closest to the maximum or minimum SOC value in the non-plateau range was selected as the SOC forcibly changed cell 2x in the previous execution of the routine in Fig. 5, the battery cell 2 is not selected as the current SOC forcibly changed cell 2x. In this case, for example, a battery cell 2 having an SOC that is second closest to the maximum or minimum SOC value in the non-plateau range is selected as the SOC forcibly changed cell 2x. In other words, in step S300, the same battery cell 2 is not consecutively selected as the SOC forcibly changed cell 2x.

[0041] After the process of step S300, the microcomputer 11 cooperates with the management IC 17 to control the switching elements SW1 and SW2 of the multiple cell balancing circuits 15 corresponding to the group including the SOC forcibly changed cell 2x so that the SOC of the SOC forcibly changed cell 2x falls within the corresponding non-plateau range (see the triangle mark in FIG. 2) (step S310). For example, as shown in FIG. 6, when the battery cell 22 of the battery cells 21, 22, 23, and 24 forming one group is selected as the SOC forcibly changed cell 2x and the SOC of the battery cell 22 is shifted from the range r4 to the range r5 on the high SOC side, the switching elements SW1 and SW2 of the multiple cell balancing circuits 15 are controlled so that the battery cell 23, which is the SOC forcibly changed cell 2x, is charged by the discharge power from the battery cells 21, 23, and 24 other than the battery cell 22. Also, for example, as shown in FIG. 7, when battery cell 22 of battery cells 21, 22, 23, and 24 forming one group is selected as SOC forcibly changed cell 2x and the SOC of battery cell 22 is shifted from range r4 to range r3 on the low SOC side, switching elements SW1, SW2 of multiple cell balancing circuits 15 are controlled so that battery cells 21, 23, and 24 other than battery cell 22 are charged with discharge power from battery cell 22, which is SOC forcibly changed cell 2x.

[0042] While the process of step S310 is being performed, the microcomputer 11 integrates the current flowing through the SOC forcibly changed cell 2x to calculate the SOC of the SOC forcibly changed cell 2x (step S320), in the same manner as step S150 in Fig. 4. Furthermore, the microcomputer 11 determines whether the SOC calculated in step S320 is within the non-plateau range (step S330). If the microcomputer 11 determines that the SOC calculated in step S320 is not within the non-plateau range (step S330: NO), it executes the processes of steps S310-S330 again.

[0043] When it is determined that the SOC calculated in step S320 is included in the non-plateau range (step S330: YES), the microcomputer 11 calculates the OCV based on the voltage of the SOC forcibly changed cell 2x detected by the voltage sensor of the management IC 17, and derives the SOC of the SOC forcibly changed cell 2x corresponding to the OCV from a map (not shown) created based on the relationship between the SOC and OCV (see FIG. 2) (step S340). Next, the microcomputer 11 calculates the SOC correction amount for each battery cell 2 based on the difference between the SOC of the SOC forcibly changed cell 2x calculated in step S320 immediately before the processing of step S340 and the SOC of the SOC forcibly changed cell 2x derived in step S340 (step S350). In step S350, the microcomputer 11 calculates the SOC correction amount for each battery cell 2 by multiplying the difference between the SOC calculated in step S320 and the SOC derived in step S340 by a coefficient based on the ratio between the full charge capacity of the SOC forcibly change cell 2x and the full charge capacity of each battery cell 2. Then, the microcomputer 11 corrects the SOC of each battery cell 2 calculated in step S150 in Fig. 4 immediately before executing the routine in Fig. 5 with the SOC correction amount calculated in step S350 (step S360).

[0044] After the process of step S360, the microcomputer 11 cooperates with the management IC 17 to control the switching elements SW1, SW2 of the cell balancing circuits 15 corresponding to the group including the SOC forcibly changed cell 2x so as to restore the electric energy exchanged between the SOC forcibly changed cell 2x and the other corresponding battery cells 2 (step S370). During the process of step S370, the microcomputer 11 also integrates the current flowing through the SOC forcibly changed cell 2x to calculate the SOC of the SOC forcibly changed cell 2x in the same manner as in step S150 of FIG. 4 (step S380).

[0045] Furthermore, the microcomputer 11 determines whether the SOC calculated in step S380 generally matches the SOC of the SOC forcibly changed cell 2x calculated in step S150 in Fig. 4 immediately before executing the routine of Fig. 5 (step S390). If the microcomputer 11 determines that the SOC of the SOC forcibly changed cell 2x calculated in step S380 does not generally match the SOC before the forcibly changed (step S390: NO), it executes the processes of steps S370-S390 again. If the microcomputer 11 determines that the SOC of the SOC forcibly changed cell 2x calculated in step S380 generally matches the SOC before the forcibly changed (step S390: YES), it sets flag F2 to zero (step S400) and ends the routine of Fig. 5.

[0046] As described above, the battery management unit 10 of the vehicle 100 manages the battery 1 including a plurality of battery cells 2 in which the amount of change in OCV relative to the amount of change in SOC is small in a plateau range (first SOC range) and the amount of change in OCV relative to the amount of change in SOC is large in a non-plateau range (second SOC range). The battery management unit 10 also includes a plurality of cell balancing circuits 15, and each of the plurality of cell balancing circuits 15 is capable of charging at least one of the battery cells 2 in a corresponding group with discharge power from at least one of the other battery cells 2.

[0047] Furthermore, the microcomputer 11 as the SOC calculation unit calculates the current I nand calculates the SOC of each of the battery cells 2 (step S150 in FIG. 4). When the calculated SOC remains in the plateau range (first SOC range) for a period of time equal to or longer than one month (predetermined period), the microcomputer 11 as a cell balance control unit controls the corresponding cell balance circuits 15 so that the SOC of the SOC forcibly changed cell 2x (target battery cell) that is one of the battery cells 2 falls within the non-plateau range (second SOC range) (steps S310-S330 in FIG. 5). The microcomputer 11 as a SOC correction unit derives the SOC of the SOC forcibly changed cell 2x based on the relationship between the SOC and OCV in the non-plateau range, calculates an SOC correction amount based on the derived SOC, and corrects the SOC of each of the battery cells 2 using the SOC correction amount (steps S340-S360 in FIG. 5).

[0048] As a result, the battery management device 10 can shift the SOC of the SOC forcibly changed cell 2x to the non-plateau range using the multiple cell balance circuits 15 while significantly reducing the loss of electric energy in the battery 1 (multiple battery cells 2). In addition, it is possible to accurately derive the SOC of the SOC forcibly changed cell 2x based on the relationship between the SOC and OCV in the non-plateau range, and to properly calculate the SOC correction amount of each battery cell 2 from the SOC of the SOC forcibly changed cell 2x. Furthermore, it is not necessary to use a power device such as a motor generator MG that consumes the power of the battery 1 and a generator that generates power in order to shift the SOC of the SOC forcibly changed cell 2x to the non-plateau range. Therefore, it is possible to suppress the deterioration of efficiency in the application target of the battery management device 10, and to expand the application range of the battery management device 10 to include those that do not include generators such as electric vehicles (BEVs). As a result, the battery management device 10 makes it possible to improve the estimation accuracy of the SOC of the battery 1 including multiple battery cells 2 in which the amount of change in OCV relative to the amount of change in SOC is small in the plateau range and large in the non-plateau range, while suppressing deterioration in the efficiency of the vehicle 100 that does not include a generator driven by an engine.

[0049] In the above embodiment, the microcomputer 11 as a cell balancing control unit controls the corresponding cell balancing circuits 15 to restore the electric energy exchanged between the SOC forcibly changed cell 2x and the other battery cells 2 after the SOC based on the relationship between the SOC and the OCV in the non-plateau range is derived in step S340 (steps S370-S390 in FIG. 5). This makes it possible to prevent the SOC of the SOC forcibly changed cell 2x from being determined to have reached a separately set upper limit SOC or lower limit SOC after the SOC of the SOC forcibly changed cell 2x is shifted to the non-plateau range.

[0050] Furthermore, the microcomputer 11 as the cell balance control unit selects a battery cell 2 to be a SOC forcibly changed cell 2x from among the multiple battery cells 2 according to a predetermined constraint (for example, in order of proximity to the maximum or minimum value of SOC in the non-plateau range) so that the same battery cell 2 does not become a SOC forcibly changed cell 2x consecutively (step S300 in FIG. 5). This makes it possible to prevent a specific battery cell 2 from being constantly selected as a SOC forcibly changed cell 2x and thus causing deterioration. If the multiple battery cells 2 include multiple replaced battery cells, in step S300 in FIG. 5, the SOC forcibly changed cell 2x may be selected only from among the multiple replaced battery cells. Furthermore, in step S300 in FIG. 5, a battery cell 2 that is frequently on the high temperature side and may be deteriorating may be excluded from the selection of the SOC forcibly changed cell 2x based on the temperature frequency information of the multiple battery cells 2.

[0051] In the above embodiment, while the SOC forcibly changed cell 2x is being charged or discharged by the cell balance circuits 15, the microcomputer 11 as the SOC corrector calculates the SOC correction amount for each of the battery cells 2 based on the difference between the SOC calculated in step S320 and the SOC based on the relationship between the SOC and the OCV derived in step S340, and the full charge capacity of each battery cell 2 (step S350 in FIG. 5). This makes it possible to properly calculate the SOC correction amount for each of the battery cells 2.

[0052] Furthermore, when the time during which the SOC of the battery cell 2 remains in the plateau range (range r2 or r4) is equal to or longer than one week and shorter than one month as a first period shorter than one month as a predetermined period, the microcomputer 11 as an SOC calculation unit estimates the SOC of each of the battery cells 2 lower than when the time during which the SOC remains in the plateau range (range r2 or r4) is shorter than one week (steps S125, S130-S170 in FIG. 4). As a result, when the SOC of the SOC forcibly changed cell 2x is shifted to a non-plateau range (range r1 or r3) on the lower SOC side than the plateau range (range r2 or r4), the minimum SOC of the battery cells 2 appears to have decreased to a certain degree immediately before the shift. As a result, even if the SOC of the SOC forcibly changed cell 2x shifted to the non-plateau range is notified to the user via the SOC display unit, it is possible to prevent the user from feeling uncomfortable that the SOC of the battery 1 has decreased more rapidly than expected. In addition, by underestimating the SOC of the multiple battery cells 2 when the residence time is greater than or equal to one week and less than one month, the SOC calculated in step S150 of FIG. 4 can be brought closer to the non-plateau range (range r1 or r3), thereby preventing the amount of change in SOC of the SOC forcibly changed cell 2x in the processing of FIG. 5 from becoming too large.

[0053] Moreover, the battery management device 10 is mounted on the vehicle 100, which is an electric vehicle that does not include an engine and a generator driven by the engine, and can improve the estimation accuracy of the SOC of the battery 1 without using power equipment such as a motor generator MG that consumes the power of the battery 1 and a generator that generates the power. Therefore, the battery management device 10 is extremely useful for managing the battery 1 mounted on the vehicle 100, which is an electric vehicle. However, it goes without saying that the battery 1 and the battery management device 10 may be mounted on a hybrid vehicle (HEV, PHEV) that includes an engine and a generator driven by the engine.

[0054] In the above embodiment, each battery cell 2 of the battery 1 is a lithium iron phosphate secondary battery, but is not limited to this. That is, the battery cells 2 of the battery 1 managed by the battery management device 10 may be batteries other than lithium iron phosphate secondary batteries as long as the change in OCV relative to the change in SOC is small in the plateau range and the change in OCV relative to the change in SOC is large in the non-plateau range.

[0055] In the battery management unit 10, one cell balance circuit 15 is provided for each of the battery cells 2, but the present invention is not limited to this. In the battery management unit 10B shown in FIG. 8, one cell balance circuit 15 is provided for each of the battery blocks B, each of which includes a plurality of battery cells 2. That is, the battery management unit 10B includes the same number (multiple) of cell balance circuits 15 as the total number of battery blocks B, which is less than the total number of battery cells 2, and the battery management unit 10B can reduce the number of cell balance circuits 15 and suppress an increase in costs. In the battery management unit 10B, for example, by controlling on / off of the switching elements SW1 and SW2 of the four cell balance circuits 15 corresponding to one group formed by four battery blocks B, it is possible to charge at least one of the battery blocks B (a plurality of battery cells 2) of the group with the discharge power from at least one of the other battery blocks B (a plurality of battery cells 2).

[0056] 8, the microcomputer 11 as an SOC calculation unit calculates the SOC of each of the battery blocks B by integrating the current flowing through the battery block B detected by a current sensor (not shown) of the management IC 17. The microcomputer 11 as a cell balance control unit controls the switching elements SW1 and SW2 of the corresponding cell balance circuits 15 so that the SOC of one of the battery blocks B, an SOC forced change battery block (target battery block), falls within the non-plateau range when the maximum and minimum SOCs of the battery blocks B remain in the plateau range for a predetermined period (e.g., one month) or more. The microcomputer 11 as an SOC correction unit derives the SOC of the SOC forced change battery block based on the relationship between the SOC and OCV in the non-plateau range, calculates an SOC correction amount based on the derived SOC, and corrects the SOC of each of the battery blocks B using the SOC correction amount. As a result, the battery management unit 10B can also improve the accuracy of estimating the SOC of the battery 1B including a plurality of battery cells 2 while suppressing deterioration in efficiency of the target of application and limiting the target of application.

[0057] Furthermore, in the battery management units 10 and 10B, the configuration of the cell balancing circuit 15 is not limited to that shown in Fig. 3. That is, the cell balancing circuit 15 may include, for example, a bidirectional DC / DC converter.

[0058] The present disclosure is not limited to the above embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0059] The invention of the present disclosure can be used in fields such as the manufacturing of battery management devices that manage batteries including a plurality of battery cells. [Explanation of symbols]

[0060] 1,1B battery, 2,21,22,23,24 battery cells, 2x SOC forced change cells, 10,10B battery management device, 11 microcontroller, 15 cell balance circuit, 17 management IC, 100 vehicle, B battery block, L1 primary coil, L2 secondary coil, R1,R2 resistor, r1,r2,r3,r4,r5 range, SW1,SW1 switching element, Tf flyback transformer.

Claims

1. A battery management device that manages a battery including a plurality of battery cells in which an amount of change in OCV relative to an amount of change in SOC becomes small in a first SOC range and an amount of change in OCV relative to an amount of change in SOC becomes large in a second SOC range, a plurality of cell balance circuits each configured to charge at least one of the battery cells with discharge power from at least one of the battery cells; an SOC calculation unit that calculates an SOC of each of the plurality of battery cells by integrating a current flowing through the battery cell; a cell balancing control unit that controls the plurality of cell balancing circuits so that an SOC of a target battery cell that is any one of the plurality of battery cells is included in the second SOC range when a residence time of the SOC calculated by the SOC calculation unit in the first SOC range becomes equal to or longer than a predetermined period of time; an SOC correction unit that derives an SOC of the target battery cell based on a relationship between an SOC and an OCV in the second SOC range, calculates a correction amount based on the derived SOC, and corrects the SOC of each of the plurality of battery cells using the correction amount; A battery management device comprising:

2. 2. The battery management device according to claim 1, The cell balancing control unit is a battery management device that controls the multiple cell balancing circuits to restore electrical energy exchanged between the target battery cell and the other battery cells after the SOC of the target battery cell based on the relationship between the SOC and OCV is derived by the SOC correction unit.

3. 3. The battery management device according to claim 1, The cell balance control unit is a battery management device that selects the battery cell to be the target battery cell from among the plurality of battery cells such that the same battery cell is not consecutively selected as the target battery cell.

4. The battery management device according to any one of claims 1 to 3, The SOC correction unit calculates the correction amount for each of the plurality of battery cells based on a difference between an SOC calculated by the SOC calculation unit while the target battery cell is being charged or discharged by the plurality of cell balancing circuits and an SOC based on a relationship between the SOC and an OCV.

5. The battery management device according to any one of claims 1 to 4, The SOC calculation unit estimates the SOC of each of the plurality of battery cells lower when the residence time is equal to or longer than a first period that is shorter than the predetermined period and is shorter than the predetermined period, compared to when the residence time is shorter than the first period.

6. 6. The battery management device according to claim 1, wherein the battery cells are lithium-ion iron phosphate secondary batteries.

7. The battery management device according to any one of claims 1 to 6, The battery management device is installed in an electric vehicle, the battery not including an engine and a generator driven by the engine.

8. A battery management method for managing a battery including a plurality of battery cells in which an amount of change in OCV relative to an amount of change in SOC becomes small in a first SOC range and an amount of change in OCV relative to an amount of change in SOC becomes large in a second SOC range, and a plurality of cell balance circuits that charge at least one of the battery cells with discharge power from at least one of the battery cells, integrating currents flowing through the battery cells to calculate an SOC of each of the battery cells; when a residence time of the SOC calculated by integrating the current in the first SOC range becomes equal to or longer than a predetermined period, the plurality of cell balancing circuits are controlled so that an SOC of a target battery cell, which is any one of the plurality of battery cells, is included in the second SOC range; deriving an SOC of the target battery cell based on a relationship between an SOC and an OCV in the second SOC range, calculating a correction amount based on the derived SOC, and correcting the SOC of each of the plurality of battery cells using the correction amount; Battery management methods.

9. A battery management method for managing a battery including a plurality of battery cells in which an amount of change in OCV relative to an amount of change in SOC is small in a first SOC range and an amount of change in OCV relative to an amount of change in SOC is large in a second SOC range, comprising: a plurality of cell balance circuits each configured to charge at least one of a plurality of battery blocks, each including at least one of the battery cells, with discharge power from at least one of the battery blocks; an SOC calculation unit that calculates an SOC of each of the plurality of battery blocks by integrating currents flowing through the battery blocks; a cell balance control unit that controls the plurality of cell balance circuits so that an SOC of a target battery block that is any one of the plurality of battery blocks falls within the second SOC range when a residence time of the SOC calculated by the SOC calculation unit in the first SOC range becomes equal to or longer than a predetermined period of time; an SOC correction unit that derives an SOC of the target battery block based on a relationship between an SOC and an OCV in the second SOC range, calculates a correction amount based on the derived SOC, and corrects the SOC of each of the plurality of battery blocks using the correction amount; A battery management method comprising:

10. A battery management method for managing a battery including a plurality of battery cells in which an amount of change in OCV relative to an amount of change in SOC becomes small in a first SOC range and an amount of change in OCV relative to an amount of change in SOC becomes large in a second SOC range, and a plurality of cell balance circuits each of which charges at least one of a plurality of battery blocks, each of which includes at least one of the battery cells, with discharge power from at least one of the other battery blocks, the method comprising: integrating currents flowing through the battery blocks to calculate an SOC for each of the battery blocks; when a time during which the SOC calculated by integrating the current remains in the first SOC range becomes equal to or longer than a predetermined period, the plurality of cell balance circuits are controlled so that an SOC of a target battery block, which is any one of the plurality of battery blocks, falls within the second SOC range; deriving an SOC of the target battery block based on a relationship between an SOC and an OCV in the second SOC range, calculating a correction amount based on the derived SOC, and correcting the SOC of each of the plurality of battery blocks using the correction amount; Battery management methods.

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