Battery management device and method

Abstract

The present disclosure provides a battery management device that manages a battery containing a plurality of battery cells each of which has a smaller change in OCV with respect to a change in SOC in a first SOC range than a change in OCV with respect to a change in SOC in a second SOC range, the battery management device configured to calculate the SOC of each battery cell by accumulating the current flowing through the battery cell, configured to control a plurality of battery cell equalization circuits so that, when the calculated SOC stays in the first SOC range for a prescribed period or more, the SOC of a target battery cell selected from the plurality of battery cells is included in the second SOC range, configured to calculate the SOC of the target battery cell based on the relationship between the SOC and the OCV in the second SOC range, and configured to correct the SOC of each battery cell according to a correction amount obtained from the calculated SOC.

Description

TECHNICAL FIELD

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

[0002] As a related art, a hybrid vehicle (HEV, PHEV) having a battery including a plurality of battery cells connected in series and an equalization circuit that reduces a deviation of SOC of each battery cell by selectively discharging a battery cell having a relatively high remaining capacity (for example, refer to Japanese Patent Application Laid-Open No. 2010-283922) and a control device that manages the battery is known. Each battery cell of the hybrid vehicle includes one or more battery cells that are olivine-type lithium-iron ion secondary batteries. In the olivine-type lithium-iron ion secondary battery, a change characteristic of OCV (open circuit voltage) with respect to SOC of the battery has a first region in which a change amount of OCV with respect to a change amount of SOC exceeds a threshold value and a second region (flat region) in which the change amount of OCV with respect to the change amount of SOC does not exceed the threshold value. In addition, in a case where an estimated value of SOC of the battery belongs to the second region, the control device that manages the battery accumulates a current input to / from the battery to estimate the SOC. Further, in a case where a period in which the estimated value of SOC of the battery belongs to the second region exceeds a prescribed period, the control device changes a power consumption amount of a motor and a power generation amount of a generator driven by an engine to temporarily make the SOC of the battery belong to the first region. Also, the control device uses an estimation method based on an internal reaction model to calculate OCV from a battery voltage and derives a SOC corresponding to the OCV. Thus, it is possible to reduce an error of the estimated value of SOC caused by an error of a current sensor that detects a current and make the estimated value close to a value of a true SOC. In addition, the above-described control device temporarily makes the SOC of the battery belong to the first region and estimates the SOC using the estimation method based on the internal reaction model before making the equalization circuit operate to equalize the SOC of the plurality of battery cells. SUMMARY

[0003] In the above-described hybrid vehicle including an engine and a generator, it is possible to forcibly change the SOC (estimated value) of the battery from the second region to the first region by changing the power consumption amount of the motor and the power generation amount of the generator driven by the engine. However, in a case where the power consumption amount of the motor and the power generation amount of the generator are changed in order to change the SOC of the battery, it is possible that the efficiency of the vehicle as a whole is reduced. In addition, in an electric vehicle that does not include the generator driven by the engine, even if the above-described control device is used, it is substantially impossible to forcibly change the SOC of the battery from the second region to the first region. Thus, the application object of the control device of the above-described related art is limited.

[0004] Therefore, this disclosure provides a battery management device and method that, while suppressing efficiency degradation and limiting the application scope, improves the estimated SOC accuracy of a battery containing multiple cells, wherein the change in OCV of the cells is relatively small relative to the change in SOC within a first SOC range, and the change in OCV is relatively large relative to the change in SOC within a second SOC range.

[0005] One aspect of the battery management device disclosed herein is configured to manage a battery containing multiple cells, wherein the change in OCV of a cell within a first SOC range is smaller than the change in SOC within a second SOC range. The battery management device includes: multiple cell balancing circuits configured to charge at least one other cell using discharge power from at least one of the cells; a SOC calculation unit configured to calculate the SOC of each of the multiple cells by accumulating the current flowing through the cells; a cell balancing control unit configured to control the multiple cell balancing circuits such that, when the SOC calculated by the SOC calculation unit remains within the first SOC range for a predetermined period or longer, the SOC of a target cell among the multiple cells is included within the second SOC range; and a SOC correction unit configured to derive the SOC of the target cell based on the relationship between SOC and OCV within the second SOC range, calculate a correction amount based on the derived SOC, and correct the SOC of each of the multiple cells according to the correction amount.

[0006] The battery management device disclosed herein manages a battery containing multiple cells, wherein the change in OCV of each cell is relatively small relative to the change in SOC within a first SOC range, and the change in OCV is relatively large relative to the change in SOC within a second SOC range. Furthermore, the battery management device includes multiple cell balancing circuits that use discharge power from at least one cell to charge at least one of the other cells. In addition, the battery management device calculates the SOC of each cell by accumulating the current flowing through the cells, and controls the multiple cell balancing circuits so that when the calculated SOC remains within the first SOC range for a predetermined period or longer, the SOC of one of the target cells is included within the second SOC range. Moreover, the battery management device derives the SOC of the target cell based on the relationship between SOC and OCV within the second SOC range, calculates a correction amount based on the derived SOC, and corrects the SOC of each of the multiple cells according to this correction amount. Thus, it is possible to significantly reduce energy loss in the battery (multiple cells) while using multiple cell balancing circuits to shift the SOC of the target cell towards the second SOC range. Furthermore, the SOC of the target cell can be derived with high accuracy based on the relationship between SOC and OCV within the second SOC range, and the SOC correction amount for each cell can be correctly calculated based on the SOC of the target cell. Moreover, when converting the SOC of the target cell to the second SOC range, it is not necessary to use power-consuming machinery or power-generating generators. Therefore, it is possible to suppress efficiency degradation in the application scope of the battery management device and expand its application range. As a result, the battery management device according to this disclosure can improve the estimation accuracy of the SOC of a battery containing multiple cells where the change in OCV is small relative to the change in SOC within the first SOC range and large relative to the change in SOC within the second SOC range, while suppressing efficiency degradation and limiting the application scope.

[0007] Furthermore, in the aforementioned battery management device, the cell balancing control unit can also be configured to control the plurality of cell balancing circuits to restore the target cell's SOC to the SOC before it receives / transmits electrical energy with other cells, after the SOC of the target cell is derived by the SOC correction unit based on the relationship between SOC and OCV. This prevents the target cell's SOC from being determined to have reached a separately set upper or lower limit SOC after it has been adjusted to a second SOC range.

[0008] Furthermore, in the aforementioned battery management device, the cell balancing control unit can also be configured to select a cell from among a plurality of cells to become the target cell in a manner that prevents the same cell from consecutively becoming the target cell. This prevents the degradation caused by a specific cell being consistently selected as the target cell.

[0009] Furthermore, in the aforementioned battery management device, the SOC correction unit can also be configured to calculate the correction amount for each of the plurality of cells based on the SOC calculated by the SOC calculation unit during the period when the target cell is charged or discharged by the plurality of cell equalization circuits, and the difference between the SOC calculated and the SOC obtained based on the relationship between the SOC and OCV. This allows for the accurate calculation of the correction amount for each of the plurality of cells.

[0010] Furthermore, in the aforementioned battery management device, the SOC calculation unit can also be configured to assess the SOC of each of the plurality of cells as lower than when the residence time is shorter than the first period, even when the residence time is shorter than the first period, when the residence time is shorter than the first period. Therefore, when the SOC of the target cell is shifted towards a second SOC range that is lower than the first SOC range, the minimum SOC of the plurality of cells decreases significantly before the shift. As a result, even when the SOC of the target cell after shifting to the second SOC range is communicated to the user, the user can be prevented from experiencing a faster-than-expected decrease in the SOC of the battery supplied to them.

[0011] Furthermore, in the aforementioned battery management device, the battery cell can also be a lithium iron phosphate secondary battery. However, the battery cell managed by the battery management device of this disclosure can be any cell that has a smaller change in OCV relative to the change in SOC within the first SOC range and a larger change in OCV relative to the change in SOC within the second SOC range; it can also be a battery other than a lithium iron phosphate secondary battery.

[0012] Furthermore, in the aforementioned battery management device, the battery can also be installed in an electric vehicle that does not include an engine and a generator driven by the engine. That is, the battery management device of this disclosure is very useful for managing batteries installed in electric vehicles because it can improve the estimation accuracy of the battery's State of Charge (SOC) without using electrical devices that consume battery power or a generator that generates power.

[0013] Other battery management methods disclosed herein are configured to manage a battery containing multiple cells using multiple cell balancing circuits that charge at least one other cell using discharge power from at least one of the cells, wherein the change in OCV of a cell within a first SOC range is smaller than the change in OCV within a second SOC range. This battery management method includes: calculating the SOC of each of the multiple cells by summing the current flowing through the cells; controlling the multiple cell balancing circuits such that, when the SOC calculated by summing the current resides within the first SOC range for a predetermined period or longer, the SOC of one of the multiple cells is included within the second SOC range; and deriving the SOC of the target cell based on the relationship between SOC and OCV within the second SOC range, calculating a correction amount based on the derived SOC, and correcting the SOC of each of the multiple cells according to the correction amount.

[0014] According to the method, while suppressing efficiency degradation and limiting the application targets, it is possible to improve the estimation accuracy of the SOC of a battery containing multiple cells in which the change of OCV is small relative to the change of SOC in the first SOC range and the change of OCV is large relative to the change of SOC in the second SOC range.

[0015] Other battery management devices disclosed herein are configured to manage a battery containing multiple cells, wherein the change in OCV of a cell relative to the state of charge (SOC) within a first SOC range is smaller than the change in OCV relative to the SOC within a second SOC range. In this battery management device, the device includes: multiple cell equalization circuits configured to charge at least one of the other battery blocks using discharge power from at least one of the multiple battery blocks, each battery block containing at least one of the cells; and an SOC calculation unit configured to accumulate the current flowing through the battery blocks to calculate the multiple cell equalization circuits. The system comprises: a state of charge (SOC) of each battery cell; a cell balancing control unit configured to control the plurality of cell balancing circuits such that, when the SOC calculated by the SOC calculation unit remains within the first SOC range for a predetermined period or longer, the SOC of one of the plurality of battery cells is included in the second SOC range; and a SOC correction unit configured to derive the SOC of the target battery cell based on the relationship between SOC and OCV within the second SOC range, calculate a correction amount based on the derived SOC, and correct the SOC of each of the plurality of battery cells according to the correction amount.

[0016] According to the battery management device, it is also possible to improve the estimated SOC accuracy of a battery containing multiple cells in which the change in OCV is small relative to the change in SOC in the first SOC range and the change in OCV is large relative to the change in SOC in the second SOC range, while suppressing efficiency degradation and limiting the application targets.

[0017] Other battery management methods disclosed herein are configured to manage a battery containing multiple cells, each of which contains at least one of the cells, using a plurality of cell balancing circuits that charge at least one of the other battery cells with discharge power from at least one of the plurality of battery cells. The cell's change in OCV relative to SOC within a first SOC range is smaller than the change in OCV relative to SOC within a second SOC range. This battery management method includes: calculating the SOC of each of the plurality of battery cells by summing the current flowing through the battery cells; controlling the plurality of cell balancing circuits such that the SOC of a target battery cell is included in the second SOC range when the residence time of the SOC calculated by summing the current within the first SOC range is greater than a predetermined period; and deriving the SOC of the target battery cell based on the relationship between SOC and OCV within 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 according to the correction amount.

[0018] According to the method, it is also possible to improve the estimated SOC accuracy of a battery containing multiple cells with a small change in OCV relative to the change in SOC within a first SOC range and a large change in OCV relative to the change in SOC within a second SOC range, while suppressing efficiency degradation and limiting the application targets. Attached Figure Description

[0019] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, wherein similar reference numerals denote similar elements, and wherein:

[0020] Figure 1 This is a schematic diagram showing the configuration of a vehicle equipped with the battery management device disclosed herein.

[0021] Figure 2 It is a diagram showing the characteristics of the battery cells managed by the battery management device of this disclosure.

[0022] Figure 3 This is a schematic diagram illustrating the configuration of the battery management device disclosed herein.

[0023] Figure 4This is a flowchart illustrating an example of a routine executed by the battery management device of this disclosure to calculate the SOC of multiple battery cells.

[0024] Figure 5 This is a flowchart illustrating an example of a routine executed by the battery management device of this disclosure to correct the SOC of multiple battery cells.

[0025] Figure 6 This is an explanatory diagram illustrating the steps involved in forcibly changing the SOC of a battery cell.

[0026] Figure 7 This is an explanatory diagram illustrating the steps involved in forcibly changing the SOC of a battery cell.

[0027] Figure 8 This is a schematic diagram illustrating the configuration of other battery management devices disclosed herein. Detailed Implementation

[0028] The invention used for carrying out this disclosure will now be described with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic configuration diagram of a vehicle 100 equipped with the battery management device 10 of this disclosure. The vehicle 100 shown is an electric vehicle (BEV) and includes: a battery 1 managed by the battery management device 10; and an electric motor / generator (three-phase AC motor) MG, which is connected to the battery 1 via a power control device (not shown) containing a system main relay, converter, etc., and is capable of accessing and storing power from the battery 1 to output driving power and regenerative braking force. Furthermore, in the vehicle 100, the battery 1 can be charged using power from an external charging device (not shown).

[0030] As shown in the figure, battery 1 is a so-called high-voltage battery containing, for example, multiple battery cells 2 connected in series. The multiple battery cells 2 can be distributed and housed within a module housing of multiple battery modules (not shown), which can be connected in series, for example. The battery cell 2 constituting the battery module is, for example, a lithium iron phosphate battery, containing a positive electrode (LiFePO4 positive electrode) formed of lithium iron phosphate with an olivine-type crystalline structure, and a negative electrode formed of graphite-like carbon materials, etc. The positive and negative electrodes of the battery cell 2, along with separators, organic solvents, and other electrolytes, are housed inside an outer casing.

[0031] Figure 2This is a graph showing the relationship between the SOC (State of Charge) and OCV (Open Circuit Voltage) of cell 2. In this graph, the solid line represents the relationship between SOC and OCV during cell 2 discharge, and the dashed line represents the relationship between SOC and OCV during cell 2 charging. As shown in the figure, in cell 2 with a positive electrode formed of lithium iron phosphate, the change in OCV is very small relative to the change in SOC over a large SOC range. That is, Figure 2 Within ranges r2 and r4 (where the SOC is higher than r2), the change in OCV relative to the change in SOC is approximately zero. Hereinafter, ranges r2 and r4 will be collectively referred to as the "plateau range (first SOC range)". In contrast, within ranges r1 (where the SOC is lower than r2), r3 (where the SOC is higher than r2 but lower than r4, between r2 and r4), and r5 (where the SOC is higher than r4), the change in OCV relative to the change in SOC increases (the slope increases). Hereinafter, ranges r1, r3, and r5 will be collectively referred to as the "non-plateau range (second SOC range)". The change in OCV relative to SOC within the first SOC range of cell 2 is smaller than the change in OCV relative to SOC within the second SOC range.

[0032] like Figure 3 As shown, the battery management device 10 of the vehicle 100 includes a microcomputer (hereinafter referred to as "microcomputer") 11, multiple cell balancing circuits 15 equal to the total number of battery cells 2 in the battery 1, and multiple management ICs 17. The microcomputer 11 includes a CPU, ROM, RAM, etc. Each cell balancing circuit 15 includes a flyback converter Tf, two switching elements SW1 and SW2 such as FETs, and two resistors R1 and R2. One cell balancing circuit 15 is connected to each of the multiple battery cells 2.

[0033] like Figure 3 As shown, the primary winding L1 of each flyback converter Tf is connected in parallel with the corresponding cell 2 via a switching element SW1 and a resistor R1. Additionally, the secondary winding L2 of each flyback converter Tf is connected to a group of multiple cells 2 to form SOC (voltage) equalization. Figure 3 In this example, four cells 2 are connected in parallel. That is, one end of the secondary coil L2 of each flyback converter Tf is connected to one end (e.g., the positive terminal) of the multiple cells 2 via an electric field line. Furthermore, the other end of the secondary coil L2 of each flyback converter Tf is connected to the other end (e.g., the negative terminal) of the multiple cells 2 via a switching element SW2, a resistor R2, and an electric field line.

[0034] Therefore, by controlling the switching elements SW1 and SW2 of multiple cell balancing circuits 15 corresponding to a group, it is possible to charge at least one other cell 2 using the discharge power from at least one cell 2 within that group. For example, when charging the remaining cells 2 using the discharge power from any one cell 2 in a group, the switching element SW1 of the cell balancing circuit 15 corresponding to that cell 2 is turned on. Then, while turning off that switching element SW1, the switching elements SW2 of all cell balancing circuits 15 in that group are turned on. Then, while turning off the switching elements SW2 of all cell balancing circuits 15, the switching elements SW1 of the cell balancing circuits 15 corresponding to a cell 2 other than the aforementioned cell 2 are turned on, and the above process is repeated.

[0035] Furthermore, when charging any one cell 2 in a group using the discharge power of the other cells 2, the switching element SW1 of the cell balancing circuit 15 corresponding to the cell 2 other than that one cell 2 is turned on. Then, while turning off these switching elements SW1, the switching elements SW2 of all cell balancing circuits 15 in that group are turned on. Then, while turning off the switching elements SW2 of all cell balancing circuits 15, the switching element SW1 of the cell balancing circuit 15 corresponding to the aforementioned one cell 2 is turned on, and the above process is repeated.

[0036] Multiple management ICs 17 interact with the microcomputer 11 and control the corresponding cell equalization circuits 15. In this embodiment, one management IC 17 is provided for each group of multiple (4) cells 2 formed by SOC (voltage) equalization. Each management IC 17 controls the switching elements SW1 and SW2 of the corresponding multiple (4) cell equalization circuits 15 to be turned on and off according to the instruction signal from the microcomputer 11. Furthermore, each management IC 17 has multiple (4) voltage sensors (not shown) that detect the voltage of each of the corresponding multiple (4) cells 2, and each voltage sensor detects the voltage of the corresponding cell 2 at a predetermined period, and sends the detection value of each voltage sensor to the microcomputer 11. In addition, each management IC 17 has multiple (4) current sensors (not shown) that detect the current flowing through each of the corresponding multiple (4) cells 2, and each current sensor detects the current flowing through the corresponding cell 2 at a predetermined period, and sends the detection value of each current sensor to the microcomputer 11.

[0037] The microcomputer 11 calculates the State of Charge (SOC) of each battery cell 2 by summing the currents flowing through each battery cell 2 detected by the current sensors of the management IC 17. Furthermore, when the specified execution condition is met, including the case where the SOC of each battery cell 2 is within a non-platform range (i.e., within the aforementioned ranges r1, r3, or r5), the microcomputer 11 calculates the Open Voltage Value (OCV) of each battery cell 2 based on the detection values ​​of the voltage sensors of the management IC 17, and calculates the OCV based on the relationship between SOC and OCV within the non-platform range (see [reference]). Figure 2 The SOC of each cell 2 corresponding to the OCV is derived. Then, the SOC of each cell 2 derived based on the OCV is used to correct the SOC of each cell 2 calculated based on the current. Then, when the predetermined execution conditions of cell equalization control are met, the microcomputer 11 controls multiple cell equalization circuits 15 in coordination with the management IC 17 to equalize the SOC (voltage) of multiple cells 2. In addition, in the vehicle 100, an SOC display unit for displaying the SOC of the battery 1 is provided on the instrument panel (not shown). The display control unit (not shown) of the vehicle 100 causes the SOC display unit to display the minimum value of the SOC of each cell 2 calculated by the microcomputer 11 of the battery management device 10, i.e., the minimum SOC.

[0038] Next, refer to Figures 4 to 6 The steps for calculating the State of Charge (SOC) of each cell 2 performed by the battery management device 10 are explained. Figure 4 The flowchart illustrates an example of the following routine, which is repeatedly executed by the microcomputer 11 (CPU) of the battery management device 10 at predetermined intervals (very short intervals) during the period when the start switch (IG switch) of the vehicle 100 (not shown) is turned on and the vehicle 100 is started by the system, in order to calculate the SOC of each cell 2.

[0039] exist Figure 4 At the start of the routine, the microcomputer 11 acquires the value of flag F1 (step S100) and determines whether the value of flag F1 is 0 (step S110). If the value of flag F1 is determined to be 0 (step S110: Yes), the microcomputer 11 sets the coefficient k used for SOC calculation to "1" (step S120). Conversely, if the value of flag F1 is determined to be "1" (step S110: No), the microcomputer 11 sets the coefficient k used for SOC calculation to a predetermined positive value α less than "1" (step S125). The value α is set to, for example, a value of approximately 0.95-0.99, taking into account the error of the current sensor (approximately 1-5%). After the processing in steps S120 or S125, the microcomputer 11 acquires the current I flowing through each of the plurality of cells 2, detected by the current sensors of each management IC 17. n(Where, “n” represents the serial number of cell 2, and when “N” is taken as the total number of cells 2, n = 1, 2, ..., N-1, N) (Step S130).

[0040] Then, the microcomputer 11 sets the variable n (the serial number of cell 2) to "1" (step S140) and calculates the SOC of the nth cell 2 (step S150). In step S150, the microcomputer 11 combines the coefficient k with the current I of the nth cell 2 obtained in step S130. n The product of these two values ​​divided by the separately calculated full-charge capacity of the nth cell 2 is the same as the value obtained by multiplying them. Figure 4 The SOC (previous value) of the nth cell 2 calculated during the previous execution of the routine is added to calculate the current SOC of the nth cell 2. Furthermore, the full charge capacity of each cell 2 is calculated by correcting the SOC of each cell 2 for values ​​calculated when it falls outside the platform range based on temperature frequency information. Then, the microcomputer 11 increments the variable n (step S160) and determines whether the variable n exceeds the total number N of the aforementioned cells 2 (step S170). If it is determined that the variable n is less than or equal to the total number N (step S170: No), the microcomputer 11 repeats the processing starting from step S150.

[0041] If the SOC is calculated for all (N) cells 2 in step S150, then in step S170, it is determined that variable n exceeds the total number N. If it is determined that variable n exceeds the total number N (step S170: Yes), the microcomputer 11 obtains the maximum and minimum values ​​of the SOC of all cells 2, i.e., the maximum SOC and the minimum SOC (step S180). Then, the microcomputer 11 determines whether the maximum SOC and the minimum SOC are included within the aforementioned platform range, i.e., range r2 or r4 (step S190). If it is determined that neither the maximum SOC nor the minimum SOC is included within the platform range (step S190: No), the microcomputer 11 resets the count value C (step S195) and then... Figure 4 The routine is temporarily terminated. With the counter value C reset and other pre-set execution conditions met, the microcomputer 11 derives the SOC of each cell 2 based on the OCV corresponding to the voltage of each cell 2, and uses the derived SOC obtained based on the OCV to analyze the current I. n The calculated SOC of each cell 2 is then corrected.

[0042] Furthermore, if it is determined that both the maximum SOC and the minimum SOC are within the platform range (step S190: Yes), the microcomputer 11 increments the count value C (step S200) and then determines whether the count value C is greater than or equal to a preset first threshold Cref1 (step S210). In this embodiment, the first threshold Cref1 used in step S210 is determined in the following manner: the first threshold Cref1 is compared with...Figure 4 The product of the execution cycles of the routines is, for example, one week (168 hours). That is, the count value C indicates the dwell time of the SOC of each cell 2 within the platform range (range r2 or r4). If it is determined that the count value C is less than the first threshold Cref1 (step S210: No), the microcomputer 11 temporarily terminates at that moment. Figure 4 The routine.

[0043] On the other hand, if it is determined that the count value C is greater than or equal to the first threshold Cref1 (step S210: Yes), the microcomputer 11 determines whether the count value C is less than the preset second threshold Cref2 (step S220). In this embodiment, the second threshold Cref2 used in step S220 is determined in the following manner: the second threshold Cref2 is compared with... Figure 4 The product of the execution cycles of the routines is, for example, one month (720 hours). If it is determined that the count value C is less than the second threshold Cref2 (step S220: Yes), the microcomputer 11 sets the flag F1 to "1" (step S230). At this point, the process temporarily ends. Figure 4 The routine.

[0044] When the count value C is less than the second threshold Cref2, the SOC of each cell 2 remains within the platform range (range r2 or r4) for more than one week but less than one month. In this case, by setting the flag F1 to "1" in step S230, Figure 4 When the routine is executed, in step S125 the coefficient k is set to a value α less than "1" and in step S150, the SOC of each of the multiple cells 2 is evaluated to be lower than the SOC calculated in step S140.

[0045] Furthermore, if the count value C is determined to be above the second threshold Cref2 (step S220: No), the microcomputer 11 sets flag F1 to 0 and flag F2 to "1" (step S235). The process temporarily ends at this point. Figure 4 The routine is as follows. Here, when the count value C is above the second threshold Cref2, the SOC of each cell 2 remains within the plateau range (range r2 or r4) for more than one month. That is, if the usage mode of the vehicle 100 is, for example, charging the battery 1 using an external charging device at the user's residence, or commuting daily to a workplace relatively close to the residence, the SOC of each cell 2 of the battery 1 may sometimes remain within the plateau range (e.g., range r4) for more than one month. Furthermore, if the SOC of each cell 2 remains within the plateau range for a long time, the current I flowing through each cell 2 is detected by a current sensor. nThe detection error is continuously accumulated, thereby reducing the calculation accuracy of the SOC of each cell 2. The SOC of the battery 1 displayed on the SOC display of the vehicle 100 deviates from the minimum SOC among the multiple cells 2.

[0046] Based on this, the microcomputer 11 of the battery management device 10 sets the flag F2 to "1" in step S235 and ends the process. Figure 4 Following the routine, the SOC of multiple cells 2 is calibrated. Figure 5 The routine. In Figure 5 At the start of the routine, the microcomputer 11 selects one of the multiple battery cells 2 as the SOC to force a change of battery cell 2x (object battery cell, refer to Figure 6 (Step S300). The SOC-forced change cell 2x is a cell 2 that forces the SOC to shift from a plateau range to a non-plateau range. Essentially, it is the SOC that is closest to the maximum or minimum value of the SOC in the non-plateau range adjacent to the plateau range containing multiple cells 2 (refer to...). Figure 2 Cell 2 (marked with a circular symbol in the image).

[0047] Additionally, in step S300, the cell 2 with the SOC closest to the maximum or minimum SOC within the non-platform range is... Figure 5 If cell 2 was selected as the SOC-forced change cell 2x during the previous execution of the routine, it will not be selected as the SOC-forced change cell 2x this time. In this case, for example, cell 2 with a SOC that is closest to the maximum or minimum SOC value outside the platform range will be selected as the SOC-forced change cell 2x. That is, in step S300, the same cell 2 will not be selected as the SOC-forced change cell 2x consecutively.

[0048] After the processing in step S300, the microcomputer 11 and the management IC 17 work together to control the switching elements SW1 and SW2 of the multiple cell balancing circuits 15 corresponding to the group containing the SOC-forced change cell 2x, so that the SOC of the SOC-forced change cell 2x is included in the corresponding non-platform range (see reference). Figure 2 (The triangular mark in the middle), (step S310). For example, as Figure 6 As shown, among the cells 21, 22, 23, and 24 forming a group, cell 22 is selected as the SOC-forced change cell 2x. When the SOC of cell 22 shifts from range r4 to range r5 (a higher SOC range), the switching elements SW1 and SW2 of the multiple cell equalization circuit 15 are controlled to charge cell 22 (the SOC-forced change cell 2x) with discharge power from cells 21, 23, and 24 (other than cell 22). Additionally, for example, as... Figure 7As shown, in the group of cells 21, 22, 23 and 24, cell 22 is selected as the SOC forced change cell 2x, and when the SOC of cell 22 changes from range r4 to range r3, which is lower than SOC, the switching elements SW1 and SW2 of the multiple cell equalization circuit 15 are controlled in such a way that the discharge power from cell 22, which is the SOC forced change cell 2x, charges the cells 21, 23 and 24 other than cell 22.

[0049] During the execution of the process in step S310, the microcomputer 11 and Figure 4 Similarly, in step S150, the SOC of the SOC-forced cell 2x is calculated by accumulating the current flowing through it (step S320). Then, the microcomputer 11 determines whether the SOC calculated in step S320 is included in the non-platform range (step S330). If it is determined that the SOC calculated in step S320 is not included in the non-platform range (step S330: No), the microcomputer 11 again executes the above steps S310-S330.

[0050] If it is determined that the SOC calculated in step S320 is included in the non-platform range (step S330: Yes), the microcomputer 11 calculates the OCV based on the SOC detected by the voltage sensor of the management IC 17, which forces a change in the voltage of cell 2x, and calculates the OCV based on the relationship between SOC and OCV (refer to...). Figure 2 The generated (not shown) mapping map is used to derive the SOC of the corresponding OCV-forced change cell 2x (step S340). Then, the microcomputer 11 calculates the SOC correction amount for each cell 2 based on the difference between the SOC of the forced change cell 2x calculated in step S320 before the processing of step S340 and the SOC of the forced change cell 2x derived in step S340 (step S350). In step S350, the microcomputer 11 calculates the SOC correction amount for each cell 2 by multiplying the difference between the SOC calculated in step S320 and the SOC derived in step S340 by a coefficient obtained based on the ratio of the full charge capacity of the forced change cell 2x to the full charge capacity of each cell 2. Then, the microcomputer 11 uses the SOC correction amount calculated in step S350 to adjust the SOC of the cell 2x before the processing of step S340. Figure 5 Before the routine Figure 4 The SOC of each cell 2 calculated in step S150 is corrected (step S360).

[0051] After the processing in step S360, the microcomputer 11 and the management IC 17 work together to control the switching elements SW1 and SW2 of the multiple cell balancing circuits 15 corresponding to the group containing the SOC forced change cell 2x, so that the SOC of the SOC forced change cell 2x is restored to the SOC before it receives / transmits power between the SOC forced change cell 2x and the corresponding other cells 2 (step S370). Furthermore, during the execution of step S370, the microcomputer 11 and... Figure 4 Similarly to step S150, the SOC of the SOC-forced change cell 2x is calculated by accumulating the current flowing through it (step S380).

[0052] Then, the microcomputer 11 determines whether the SOC calculated in step S380 matches the value of the value calculated in the upcoming execution. Figure 5 The routine before Figure 4 In step S150, the SOC calculated for the forced change of cell 2x is approximately the same as the SOC before the forced change (step S390). If it is determined that the SOC of cell 2x calculated in step S380 is not approximately the same as the SOC before the forced change (step S390: No), the microcomputer 11 executes the above steps S370-S390 again. Furthermore, if it is determined that the SOC of cell 2x calculated in step S380 is approximately the same as the SOC before the forced change (step S390: Yes), the microcomputer 11 sets flag F2 to 0 (step S400), making... Figure 5 The routine has ended.

[0053] As described above, the battery management device 10 of the vehicle 100 manages a battery 1 containing multiple cells 2. Each of these cells 2 exhibits a small change in OCV relative to SOC within a plateau range (first SOC range) and a larger change in OCV relative to SOC within a non-plateau range (second SOC range). Furthermore, the battery management device 10 includes multiple cell balancing circuits 15, which are capable of charging at least one other cell 2 using the discharge power from at least one cell 2 within a corresponding group.

[0054] Furthermore, the microcomputer 11, which serves as the SOC computing unit, will control the current I flowing through the battery cell 2. n The SOC of each of the multiple cells 2 is calculated by summing them up. Figure 4Step S150). Furthermore, the microcomputer 11, acting as the cell balancing control unit, controls multiple corresponding cell balancing circuits to, when the calculated SOC remains in the plateau range (first SOC range) for more than, for example, one month (a predetermined period), forcibly change the SOC of any one of the multiple cells 2 so that the SOC of cell 2x (the target cell) is included in the non-plateau range (second SOC range). Figure 5 Steps S310-S330). Furthermore, the microcomputer 11, acting as the SOC correction unit, derives the SOC of the cell 2x forcibly changing the SOC based on the relationship between SOC and OCV within the non-platform range, calculates the SOC correction amount based on the derived SOC, and corrects the SOC of each of the multiple cells 2 according to this SOC correction amount. Figure 5 Steps S340-S360).

[0055] Therefore, according to the battery management device 10, while significantly reducing energy loss in the battery 1 (multiple cells 2), the SOC of the cells 2x can be forcibly changed to a non-plateau range using multiple cell balancing circuits 15. Furthermore, the SOC of the cells 2x can be derived with high accuracy based on the relationship between the SOC and OCV within the non-plateau range, and the SOC correction amount for each cell 2 can be correctly calculated based on this SOC of the cells 2x. Moreover, when forcibly changing the SOC of the cells 2x to a non-plateau range, it is not necessary to use electric motors such as electric motors / generators (MG) that consume power from the battery 1, or generators that generate power. Therefore, it is possible to suppress efficiency degradation in applications where the battery management device 10 is used, and to expand the application scope of the battery management device 10 to vehicles such as battery electric vehicles (BEVs) that do not contain generators. As a result, according to the battery management device 10, it is possible to suppress the efficiency degradation of a vehicle 100 that does not contain a generator driven by an engine, while improving the estimated SOC accuracy of a battery 1 containing multiple cells 2 with small changes in OCV relative to SOC within a platform range and large changes in OCV relative to SOC outside a platform range.

[0056] Furthermore, in the above embodiment, the microcomputer 11, which serves as the cell balancing control unit, controls the corresponding multiple cell balancing circuits 15 to, after deriving the SOC obtained in step S340 based on the relationship between SOC and OCV within the non-platform range, restore the SOC of the cell 2x that was forcibly changed to the SOC before the cell 2x received / transmitted electrical energy with other cells 2. Figure 5 (Steps S370-S390). Thus, after the SOC of the cell 2x is forcibly changed to a non-platform range, it is possible to prevent the SOC of the cell 2x from being determined to have reached a separately set upper or lower limit SOC.

[0057] Furthermore, the microcomputer 11, which serves as the cell balancing control unit, selects a cell 2 from multiple cells 2 as the SOC-forced cell 2x according to a pre-set constraint (e.g., an order close to the maximum or minimum SOC value in the non-platform range) in a manner that prevents the same cell 2 from consecutively becoming the SOC-forced cell 2x. Figure 5 Step S300). This prevents degradation that occurs when a specific cell 2 is always selected as the SOC-forced cell 2x. Furthermore, in cases where multiple cells 2 include multiple cells that have already been swapped, it is also possible to… Figure 5 In step S300, only SOC-forced change cell 2x is selected from the plurality of cells that have already been swapped. Alternatively, it can also be done in... Figure 5 In step S300, based on the temperature frequency information of multiple cells 2, cells 2 that are likely to deteriorate faster and are at high temperature more frequently are excluded from the selection of cells 2x for forced change of SOC.

[0058] Furthermore, in the above embodiment, the microcomputer 11, which serves as the SOC correction unit, calculates the SOC correction amount for each of the multiple cells 2 based on the difference between the SOC calculated in step S320 and the SOC derived in step S340 based on the relationship between the SOC and OCV during the period when the SOC of the multiple cell equalization circuits 15 is forcibly changed by charging or discharging the cell 2x, and the full charge capacity of each cell 2. Figure 5 (Step S350). Thus, the SOC correction amount of each of the multiple cells 2 can be calculated correctly.

[0059] Furthermore, when the SOC of cell 2 remains in the platform range (range r2 or r4) for a period shorter than one month as a specified period, but more than one week but less than one month as a first period, the microcomputer 11, as the SOC calculation unit, evaluates the SOC of each of the multiple cells 2 to be lower compared to when the residence time is less than one week. Figure 4 Steps S125, S130-S170). Therefore, when the SOC of the cell 2x is forcibly changed to a non-platform range (range r1 or r3) that is lower than the platform range (range r2 or r4), the minimum SOC of the multiple cells 2 decreases significantly before the change. As a result, even if the SOC of the cell 2x after being changed to a non-platform range is notified to the user via the SOC display unit, the user's perception that the SOC of the battery 1 is decreasing faster than expected can be suppressed. Furthermore, by evaluating the SOC of the multiple cells 2 as low when the aforementioned residence time is more than one week but less than one month, it is possible to... Figure 4The SOC calculated in step S150 is close to the non-plateau range (range r1 or r3), suppressing Figure 5 During the processing, the change in SOC of the 2x cell due to forced SOC change is larger.

[0060] Furthermore, the battery management device 10 can be installed in an electric vehicle, i.e., a vehicle 100, that does not contain an engine or a generator driven by the engine. By not using electric motors such as the electric motor / generator (MG) that consume the battery 1's power, and the generator that generates power, the estimated state of charge (SOC) of the battery 1 can be improved. Therefore, the battery management device 10 is very useful in managing the battery 1 installed in the electric vehicle, i.e., the vehicle 100. However, the battery 1 and the battery management device 10 can also, of course, be installed in hybrid electric vehicles (HEVs, PHEVs) that contain an engine and a generator driven by the engine.

[0061] Furthermore, in the above embodiment, each cell 2 of battery 1 is a lithium iron phosphate secondary battery, but it is not limited to this. That is, the cell 2 of battery 1 managed by battery management device 10 can be any cell whose change in OCV relative to SOC is small within the plateau range and whose change in OCV relative to SOC is large outside the plateau range, and can be a battery other than a lithium iron phosphate secondary battery.

[0062] Furthermore, in the battery management device 10, a cell balancing circuit 15 is provided for each of the plurality of battery cells 2 in a one-to-one correspondence, but it is not limited to this. Figure 8 In the battery management device 10B shown, a cell balancing circuit 15 is provided for each of the plurality of battery blocks B, each containing a plurality of cells 2. That is, the battery management device 10B contains the same number (multiple) of cell balancing circuits 15 as the total number of battery blocks B, which is less than the total number of cells 2. In this battery management device 10B, the number of cell balancing circuits 15 can be reduced, thereby suppressing cost increases. Furthermore, in the battery management device 10B, for example, by controlling the switching elements SW1 and SW2 of the four cell balancing circuits 15 corresponding to a group of four battery blocks B, the discharge power from at least one battery block B (multiple cells 2) in that group can be used to charge at least one other battery block B (multiple cells 2).

[0063] In addition, Figure 8In the battery management device 10B, the microcomputer 11, which serves as the SOC calculation unit, calculates the SOC of each of the multiple battery blocks B by accumulating the current flowing through the battery blocks B detected by the current sensor (not shown) of the management IC 17. Furthermore, the microcomputer 11, which serves as the cell balancing control unit, controls, for example, the switching elements SW1 and SW2 of the corresponding multiple cell balancing circuits 15. When the maximum and minimum SOCs of the multiple battery blocks B remain within the plateau range for a specified period (e.g., one month) or more, the SOC of the target battery block (the one whose SOC is being forcibly changed) is included in the non-plateau range. In addition, the microcomputer 11, which serves as the SOC correction unit, derives the SOC of the target battery block based on the relationship between the SOC and OCV in the non-plateau range, calculates a SOC correction amount based on the derived SOC, and corrects the SOC of each of the multiple battery blocks B according to this SOC correction amount. Therefore, according to the battery management device 10B, it is also possible to improve the estimated SOC accuracy of a battery 1B containing multiple cells 2 while suppressing the efficiency degradation of the application and limiting the application.

[0064] Furthermore, in the battery management devices 10 and 10B, the configuration of the cell balancing circuit 15 is not limited to... Figure 3 and Figure 8 The configuration shown is such that the cell balancing circuit 15 can also be, for example, a circuit that includes a bidirectional DC / DC converter.

[0065] Furthermore, the invention disclosed herein is not limited to the above-described embodiments, and various modifications can be made within the scope of this disclosure. In addition, the above-described embodiments are merely one specific embodiment of the invention described in the summary section and are not limited to the elements of the invention described in the summary section.

[0066] The invention disclosed herein can be applied in fields such as the manufacture of battery management devices that manage batteries containing multiple cells.

Claims

1. A battery management device configured to manage a battery containing multiple cells, wherein the change in OCV of each cell relative to the change in SOC is smaller in a first SOC range than the change in OCV relative to the change in SOC in a second SOC range. The battery management device is characterized by including: A multi-cell equalization circuit is configured to charge at least one of the other cells using discharge power from at least one of the cells. The SOC calculation unit is configured to calculate the SOC of each of the plurality of cells by accumulating the current flowing through the cells. A cell balancing control unit is configured to control the plurality of cell balancing circuits such that when the SOC calculated by the SOC calculation unit stays in the first SOC range for a period of time or more, the SOC of one of the plurality of cells is included in the second SOC range. as well as The SOC correction unit is configured to derive the SOC of the target cell based on the relationship between SOC and OCV within the second SOC range, calculate a correction amount based on the derived SOC, and correct the SOC of each of the plurality of cells according to the correction amount. The cell balancing control unit is configured to control the plurality of cell balancing circuits to restore the SOC of the target cell to the SOC before the target cell receives / transmits electrical energy with other cells after the SOC correction unit derives the SOC of the target cell based on the relationship between the SOC and OCV.

2. The battery management device according to claim 1, characterized in that, The cell balancing control unit is configured to select the cell that will become the target cell from among the plurality of cells in such a way that the same cell will not be consecutively selected as the target cell.

3. The battery management device according to claim 1 or 2, characterized in that, The SOC correction unit is configured to calculate the correction amount for each of the plurality of cells based on the SOC calculated by the SOC calculation unit during the period when the target cell is charged or discharged by the plurality of cell equalization circuits, and the difference between the SOC calculated and the SOC obtained according to the relationship between the SOC and OCV.

4. The battery management device according to claim 1 or 2, characterized in that, The SOC calculation unit is configured to evaluate the SOC of each of the plurality of cells to be lower than when the residence time is shorter than the first period, when the residence time is shorter than the first period but longer than the specified period.

5. The battery management device according to claim 1 or 2, characterized in that, The battery cell is a lithium iron phosphate secondary battery.

6. The battery management device according to claim 1 or 2, characterized in that, The battery is mounted on an electric vehicle, which does not include an engine or a generator driven by the engine.

7. A battery management method configured to manage a battery containing multiple cells using a multiple cell balancing circuit that charges at least one other cell using discharge power from at least one cell, wherein the change in OCV of a cell relative to the change in SOC within a first SOC range is smaller than the change in OCV relative to the change in SOC within a second SOC range. The battery management method is characterized by including: The SOC of each of the multiple cells is calculated by summing the currents flowing through the cells; The multiple cell equalization circuits are controlled such that when the SOC calculated by accumulating the current stays in the first SOC range for a period longer than a predetermined period, the SOC of one of the multiple cells is included in the second SOC range. The SOC of the target cell is derived based on the relationship between SOC and OCV within the second SOC range, and a correction amount is calculated based on the derived SOC. The SOC of each of the multiple cells is then corrected according to the correction amount. as well as The multiple cell equalization circuits are controlled to restore the SOC of the target cell to the SOC before it receives / transmits electrical energy with the other cells, after deriving the SOC of the target cell based on the relationship between the SOC and OCV.

8. A battery management device configured to manage a battery containing multiple cells, wherein the change in OCV of each cell relative to the change in SOC is smaller in a first SOC range than the change in OCV relative to the change in SOC in a second SOC range. The battery management device is characterized by including: A multi-cell equalization circuit is configured to charge at least one of the other battery blocks using discharge power from at least one of the multiple battery blocks, each of the battery blocks containing at least one of the battery cells. The SOC calculation unit is configured to calculate the SOC of each of the plurality of battery cells by accumulating the current flowing through the battery cells. A cell balancing control unit is configured to control the plurality of cell balancing circuits so that when the SOC calculated by the SOC calculation unit stays in the first SOC range for a period of time or more, the SOC of one of the plurality of battery blocks is included in the second SOC range. as well as The SOC correction unit is configured to derive the SOC of the target battery cell based on the relationship between SOC and OCV within the second SOC range, calculate a correction amount based on the derived SOC, and correct the SOC of each of the plurality of battery cells according to the correction amount. The cell balancing control unit is configured to control the plurality of cell balancing circuits to restore the SOC of the target battery block to the SOC before the target battery block receives / transmits electrical energy with other battery blocks after the SOC correction unit derives the SOC of the target battery block based on the relationship between the SOC and OCV.

9. A battery management method configured to manage a battery containing multiple cells using a plurality of cell equalization circuits that charge at least one of the other battery cells using discharge power from at least one of a plurality of battery cells, each of the battery cells containing at least one of the cells, wherein the change in OCV of a cell relative to the change in SOC in a first SOC range is smaller than the change in OCV relative to the change in SOC in a second SOC range. The battery management method is characterized by including: The SOC of each of the multiple battery cells is calculated by summing the currents flowing through them. The multiple cell balancing circuits are controlled such that when the SOC calculated by accumulating the current remains in the first SOC range for a period longer than a predetermined period, the SOC of one of the multiple battery blocks is included in the second SOC range. The SOC of the target battery block is derived based on the relationship between SOC and OCV within the second SOC range, and a correction amount is calculated based on the derived SOC. The SOC of each of the multiple battery blocks is then corrected according to the correction amount. as well as The multiple cell equalization circuits are controlled to restore the SOC of the target battery block to the SOC before it receives / transmits power between the target battery block and the other battery blocks, after deriving the SOC of the target battery block based on the relationship between the SOC and OCV.

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