Battery system control method and control device

Abstract

To improve the accuracy of estimating an SOC and suppress a driver's uneasiness due to a sudden change of the value being calculated on the basis of the estimated value of the SOC.SOLUTION: Provided is a battery system control method that estimates a control SOC that represents a charge rate used for control, on the basis of the integrated value of charge / discharge currents of a secondary battery, estimates a correction SOC that represents a charge rate for correction on the basis of the open-circuit voltage of the secondary battery when at least the ratio of the change amount of the open-circuit voltage of the secondary battery to the change amount of the charge rate lies in a high change rate region greater than or equal to a first threshold, and corrects the control SOC on the basis of the correction SOC when in the high change rate region. When a difference between the control SOC before correction and the control SOC after correction is larger than a second threshold, a display SOC that represents a charge rate displayed to a meter is gradually brought closer to the control SOC after correction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for controlling a battery system. Relates to.

Background Art

[0002] In the control of a battery system having a secondary battery as a battery, it is important to accurately estimate the state of charge of the battery (hereinafter, also referred to as SOC: State of Charge). As methods for estimating the SOC of a battery, the OCV method and the current integration method are known. The OCV method estimates the SOC based on the detected value of the OCV by using the SOC-OCV characteristic indicating the correlation between the SOC and the open circuit voltage (OCV) of the battery. The current integration method integrates the input / output current of the battery, calculates the change amount of the battery capacity based on the integrated value, and estimates the current SOC from the battery capacity at full charge and the change amount of the battery capacity.

[0003] The OCV method has a problem that it cannot accurately estimate the SOC of a battery having a region where the OCV does not change or hardly changes even when the SOC changes on the curve showing the SOC-OCV characteristic. On the other hand, in the current integration method, errors such as detection errors of current sensors accumulate, so there is a problem that the estimation accuracy decreases as the integration period becomes longer.

[0004] Patent Document 1 describes a method for solving these problems. Specifically, when belonging to the SOC region where the change amount of the OCV with respect to the change amount of the SOC is relatively small, the SOC is estimated by the current integration method, and when belonging to the region where the change amount of the OCV with respect to the change amount of the SOC is relatively large, the estimated value by the current integration method is corrected based on the estimated value by the OCV method.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, according to the method described in the above-mentioned literature, if correction is performed while errors from the current integration method have accumulated, the estimated SOC value will change significantly. As a result, the value calculated based on the estimated SOC (for example, the SOC displayed on the meter) will also change significantly, causing discomfort to the driver and potentially undermining the reliability of the value displayed on the meter.

[0007] Therefore, the present invention aims to provide a control method and control device that can improve the estimation accuracy of SOC and suppress the driver's discomfort caused by sudden changes in values ​​calculated based on the estimated SOC. [Means for solving the problem]

[0008] According to one aspect of the present invention, a battery system control method is provided which estimates a control state of charge (SOC), which is the charge rate used for control, based on the integrated value of the charge and discharge currents of the secondary battery; estimates a corrected SOC, which is a corrective charge rate, based on the open-circuit voltage of the secondary battery, when the ratio of the change in the open-circuit voltage of the secondary battery to the change in the charge rate is in a high change rate region of at least a first threshold; and corrects the control SOC based on the corrected SOC when it is in the high change rate region. In this method, If the difference between the control SOC before correction and the control SOC after correction is less than or equal to the second threshold, the displayed SOC is set based on the previously calculated value of the control SOC. On the other hand, If the difference is greater than the second threshold, By multiplying the difference between the corrected control SOC and the displayed SOC from the previous calculation by a coefficient, and subtracting this value from the corrected control SOC in the current calculation, the displayed SOC for the current calculation is obtained. The displayed State of Charge (SOC), which is the charge rate shown on the meter, is gradually brought closer to the corrected control SOC.

[0009] According to another aspect of the present invention, a battery system control device is provided, comprising: a current detection unit for detecting the charge and discharge current of a secondary battery; a first estimation unit for estimating a control SOC, which is the charge rate used for control, based on the integrated value of the charge and discharge currents; a second estimation unit for estimating a corrected SOC, which is a corrective charge rate, based on the open-circuit voltage of the secondary battery, when the ratio of the change in the open-circuit voltage of the secondary battery to the change in the charge rate is in a high change rate region of at least a first threshold; and an SOC correction unit for correcting the control SOC based on the corrected SOC when it is in the high change rate region. The device further comprises a display SOC calculation unit for setting a display SOC, which is the charge rate displayed on a meter, based on the control SOC, wherein the difference between the control SOC before correction and the control SOC after correction is a second threshold. In the following cases, the display SOC calculation unit sets the display SOC based on the previously calculated value of the control SOC, and the difference is the second threshold. If it is greater than, the display SOC calculation unit will By multiplying the difference between the corrected control SOC and the displayed SOC from the previous calculation by a coefficient, and subtracting this value from the corrected control SOC in the current calculation, the displayed SOC for the current calculation is obtained. Set the displayed SOC to a value that gradually approaches the corrected control SOC. [Effects of the Invention]

[0010] According to the above embodiment, it is possible to provide a control method and control device that can improve the estimation accuracy of SOC and suppress the driver's discomfort caused by sudden changes in values ​​calculated based on the estimated SOC. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a system configuration diagram of an electric vehicle. [Figure 2] Figure 2 shows the SOC-OCV characteristics. [Figure 3] Figure 3 is a flowchart showing the SOC estimation routine executed by the first arithmetic unit. [Figure 4] Figure 4 is a flowchart showing the SOC estimation routine executed by the second processing unit. [Figure 5] Figure 5 is a flowchart showing the control SOC calculation routine. [Figure 6] Figure 6 shows the time evolution of the control SOC and display SOC. [Figure 7]FIG. 7 is a flowchart showing a control routine for setting the display SOC. [Figure 8] FIG. 8 is a diagram for explaining the behavior of the display SOC according to the first embodiment. [Figure 9] FIG. 9 is an example of a timing chart of the control SOC and the display SOC when the control of the first embodiment is executed. [Figure 10] FIG. 10 is a flowchart showing a modified example of the control routine for setting the display SOC. [Figure 11] FIG. 11 is a map used when determining the coefficient used in the display SOC calculation. [Figure 12] FIG. 12 is an example of a timing chart of the control SOC and the display SOC when the control according to the modified example of the first embodiment is executed. [Figure 13] [[ID=I8]]FIG. 13 is a flowchart showing an operation routine for the allowable power. [Figure 14] FIG. 14 is a timing chart of the allowable power and the display power when the operation according to the first embodiment is performed. [Figure 15] FIG. 15 is a part of a flowchart showing an operation routine for the allowable power to guarantee the remaining cruising distance before the control SOC correction. [Figure 16] FIG. 16 is the remaining part of a flowchart showing an operation routine for the allowable power to guarantee the remaining cruising distance before the control SOC correction. [Figure 17] FIG. 17 is a diagram for explaining the concept of display SOC correction in the second embodiment. [Figure 18] FIG. 18 is a timing chart showing the change in the distribution ratio of the control SOC. [Figure 19] FIG. 19 is a map used when setting the coefficient α used for setting the distribution ratio of the uncorrected control SOC predicted value and the corrected control SOC. [Figure 20] FIG. 20 is a flowchart showing an operation routine for setting the display SOC. [Figure 21]Figure 21 is a flowchart showing the calculation routine for the allowable power according to the second embodiment. [Figure 22] Figure 22 is a timing chart of the allowable power and display power when the control of the second embodiment is performed. [Figure 23] Figure 23 is a diagram illustrating the behavior of the allowable power and indicated power in the third embodiment. [Figure 24] Figure 24 is a part of a flowchart showing the calculation routine for calculating the allowable power according to the third embodiment. [Figure 25] Figure 25 is the remainder of the flowchart showing the calculation routine for calculating the allowable power according to the third embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the attached drawings.

[0013] [First Embodiment] Figure 1 is a system configuration diagram of an electric vehicle equipped with a battery system.

[0014] The system comprises a battery 100 as the power source for the vehicle, a battery controller 15 that performs various controls on the battery 100, a vehicle controller 200 that is communicatively connected to the battery controller 15, and a motor (not shown) that is powered by the battery 100. The system also comprises a current detection unit 1 that detects the input and output currents of the battery 100, a cell voltage detection unit 4 that detects the cell voltage, a temperature detection unit 8 that detects the temperature of the battery 100, and a meter 300 that informs the driver of vehicle information.

[0015] The current detection unit 1 is a current sensor, the cell voltage detection unit 4 is a voltage sensor, and the temperature detection unit 8 is a temperature sensor.

[0016] Vehicle information includes, for example, the current State of Charge (SOC) of Battery 100 (hereinafter also referred to as the displayed SOC), the power that can be output and is communicated to the driver (hereinafter also referred to as the displayed power), and the distance that can be traveled with the current SOC (hereinafter also referred to as the remaining range).

[0017] The battery controller 15 estimates the control SOC as the current SOC of the battery 100 using a method described later, and calculates the display SOC, display power, remaining range, and the power that the battery 100 can handle (hereinafter also referred to as the allowable power) based on this. In addition to calculating the above vehicle information, the control SOC is also used for various controls of the battery system.

[0018] Battery 100 is a rechargeable battery, for example, a lithium iron phosphate battery.

[0019] Here, we will explain the method for estimating the State of Computing (SOC).

[0020] The current integration method and the OCV method are known methods for estimating SOC. The OCV method is a method that estimates SOC from OCV using the SOC-OCV characteristic.

[0021] Figure 2 shows the SOC-OCV characteristics, where the solid line represents the characteristics of lithium iron phosphate (LFP) lithium-ion batteries, and the dashed line represents the characteristics of nickel manganese chromium (NMC) lithium-ion batteries.

[0022] In the case of NMC systems, OCV changes across the entire SOC range when SOC changes. Therefore, by acquiring and mapping SOC-OCV characteristics in advance, and then searching this map with the detected OCV, the SOC can be estimated with high accuracy.

[0023] In the case of LFP systems, in the high SOC region and the low SOC region (region II in the figure), the change in OCV relative to the change in SOC is relatively large, and SOC can be estimated using the OCV method. However, in the medium SOC region (region I in the figure), the change in OCV relative to the change in SOC is relatively small, and even if SOC changes, OCV does not change, or the change is extremely small. For this reason, it is difficult to estimate SOC using the OCV method in region I. Region I is also called the low rate of change region, and region II is also called the high rate of change region. Whether or not a region is a low rate of change region is determined based on a predetermined threshold (first threshold). For example, if the ratio of the change in OCV to the change in SOC is less than or equal to the first threshold, it is determined to be a low rate of change region. The first threshold may be zero, but is not limited to this. If the change in OCV when SOC changes is very small, SOC cannot be estimated accurately, so it may be set to a value greater than zero, taking into account the detection accuracy of the voltage sensor, etc.

[0024] Therefore, in the case of LFP systems, SOC estimation is performed using the current integration method. However, in the current integration method, detection errors from the current sensor and other factors accumulate, so the longer the integration period, the lower the estimation accuracy becomes.

[0025] Based on the above issues, in this embodiment, the control SOC is estimated by the method described below.

[0026] (Control SOC estimation) The battery controller 15 includes a first calculation unit 16 that estimates the SOC using the current integration method, a second calculation unit 17 that estimates the SOC using the OCV method, an SOC validity determination unit 9 that determines which estimation method is appropriate, and a current integration SOC correction unit 10 that corrects the SOC based on the determination result.

[0027] Figure 3 is a flowchart showing the SOC estimation routine executed by the first arithmetic unit 16. This routine is executed sequentially.

[0028] In step S100, the current flowing to the battery 100 is detected. Specifically, the detected value from the current detection unit 1 is read.

[0029] In step S101, the current full capacity of battery 100 is obtained. The current full capacity is the capacity of battery 100 when fully charged, taking into account factors such as battery temperature and cycle degradation. The current full capacity is calculated by a routine that is executed separately from this routine, and step S101 obtains the result of that calculation.

[0030] In step S102, the current integration calculation unit 2 integrates the current values ​​and calculates the SOC change amount from the current full capacity and the integrated value.

[0031] In step S103, the current SOC calculation unit 3 obtains the previously calculated value of the control SOC.

[0032] In step S104, the current SOC calculation unit 3 calculates the current integrated SOC by adding the amount of SOC change to the control SOC from the previous calculation.

[0033] Figure 4 is a flowchart showing the SOC estimation routine executed by the second arithmetic unit 17. This routine is executed at least in the high rate of change region.

[0034] In step S200, the voltage of each cell of the battery 100 is detected. Specifically, the detected value of the cell voltage detection unit 4 is read.

[0035] In step S201, the current flowing to the battery 100 is detected. Specifically, the detected value from the current detection unit 1 is read.

[0036] In step S202, the temperature inside the battery pack is detected. Specifically, the detected value from the temperature detection unit 8 is read.

[0037] In step S203, the OCV calculation unit 5 calculates the voltage drop due to internal resistance based on the cell voltage, current, and temperature using a known method.

[0038] In step S204, the OCV calculation unit 5 calculates the OCV based on the cell voltage, current, temperature, and voltage drop due to internal resistance.

[0039] In step S205, the OCV-SOC conversion unit 6 calculates a correction SOC from the SOC-OCV map that has been created in advance and stored in the SOC-OCV map unit 7. The correction SOC obtained here is called the map conversion SOC.

[0040] Figure 5 is a flowchart showing the control SOC calculation routine executed by the SOC validity determination unit 9 and the current integration SOC correction unit 10.

[0041] In step S300, the SOC validation unit 9 acquires the map-converted SOC.

[0042] In step S301, the SOC validity determination unit 9 determines whether the map-converted SOC belongs to the low rate of change region. If it does, it executes the process in step S303; otherwise, it executes the process in step S302.

[0043] In step S302, the current integration SOC correction unit 10 updates the control SOC with the map conversion SOC. In other words, it corrects the current integration SOC with the map conversion SOC. Hereinafter, this correction will also be referred to as control SOC correction.

[0044] On the other hand, in step S303, the current integrated SOC correction unit 10 updates the control SOC with the current integrated SOC. In other words, no correction is performed on the current integrated SOC.

[0045] Steps S300 and S301 aim to determine whether the current SOC belongs to the low rate of change region. Therefore, the determination may be made based on the OCV obtained in step S204 of Figure 4 instead of the map-converted SOC.

[0046] Once the control SOC is obtained using the method described above, the display SOC, allowable power, display power, and remaining range are calculated using the control SOC.

[0047] The displayed SOC is the SOC displayed on the meter 300 to inform the driver, and in principle, it is the same value as the control SOC at the time of the previous calculation. Figure 6 is a diagram showing the time change of the control SOC and the displayed SOC when the control SOC and the displayed SOC are set to the same value by estimating the control SOC using the above routine. The period from time t1 to time t2 belongs to region I, and the period from time t2 onward belongs to region II.

[0048] During the period belonging to Region I, as mentioned above, the estimation accuracy of the OCV method is low, and the estimated values ​​obtained by the OCV method have a large variation (dotted line in the figure). For this reason, the control SOC and display SOC are calculated using the current integration method. However, due to the accumulation of the errors mentioned above, the difference from the true SOC (dashed line in the figure) gradually increases.

[0049] Then, when the system enters region II at time t2, control SOC correction is performed, and thereafter the control SOC and displayed SOC become values ​​that align with the true SOC. At this time, if the displayed SOC is set to the same value as the control SOC from the previous calculation, as per the general rule, the displayed SOC will change in a stepwise manner at time t2. In particular, if the control SOC is calculated while the operating time in the low rate of change region is long and the accumulated error is large, the amount of change in the displayed SOC will be large, which will cause discomfort to the driver.

[0050] Therefore, in this embodiment, the displayed SOC is set using the method described below.

[0051] (Display SOC calculation) Figure 7 is a flowchart showing the control routine executed by the display SOC calculation unit 11 to set the display SOC.

[0052] In step S400, the control SOC from the previous calculation is obtained, and in step S401, the display SOC from the previous calculation is obtained.

[0053] In step S402, the difference between the control SOC and the display SOC from the previous calculation is calculated.

[0054] In step S403, it is determined whether the absolute value of the above difference is greater than a predetermined value (second threshold). If it is greater, the process in step S405 is executed; if it is less than or equal to the predetermined value, the process in step S404 is executed. This determination determines whether the driver will feel any discomfort when the displayed SOC changes by the above difference. The predetermined value is a value that can be set arbitrarily and is set by suitability considering the capacity of the battery 100 to which the present invention is applied. For example, in the case of a vehicle with a small total capacity of battery 100, the amount of fluctuation of the control SOC in relation to the consumed power is large, so the predetermined value is set to be small. Conversely, in the case of a vehicle with a large total capacity of battery 100, the amount of fluctuation of the control SOC is small, so the predetermined value is set to be large.

[0055] In step S404, the displayed SOC is updated with the control SOC from the previous calculation. That is, if using the control SOC from the previous calculation as the displayed SOC does not cause any discomfort to the driver, then the control SOC from the previous calculation is used as the displayed SOC.

[0056] Meanwhile, in step S405, A is calculated by multiplying the above difference by a predetermined coefficient. Then, in step S406, the control SOC calculated this time is obtained, in step S407, B is calculated by subtracting A from the control SOC calculated this time, and in step S408, the displayed SOC is updated with B. As a result, the displayed SOC gradually approaches the corrected control SOC. The calculations in steps S405 to S408 to resolve the difference between this control SOC and the displayed SOC are called displayed SOC correction. The coefficient is a value that can be arbitrarily set within the range greater than 0 and less than 1, and is set by adaptation, etc., to a value that allows the displayed SOC to gradually converge to the corrected control SOC without causing any discomfort to the driver, assuming that the displayed SOC will converge to the control SOC by the time the battery is fully charged or depleted.

[0057] Figure 8 illustrates the behavior of the display SOC as it is updated by the above control. In the figure, the black circles represent the control SOC, and the white circles represent the display SOC.

[0058] Prior to time t1, the difference between the control SOC and the display SOC from the previous calculation is less than or equal to a predetermined value. Therefore, the display SOC at time t1 is the value updated with the control SOC from the previous calculation. However, at time t1, a control SOC correction is performed, and the corrected control SOC changes stepwise, causing the difference Diff1 between the control SOC and the display SOC to become larger than the predetermined value. Therefore, in the next calculation at time t1, a display SOC correction is performed, and the display SOC is updated with a value obtained by subtracting the difference Diff2 (diff1 multiplied by a coefficient) from the control SOC at that time. The display SOC correction is repeated thereafter, and when the difference between the control SOC and the display SOC from the previous calculation becomes less than or equal to the predetermined value again, the update returns to the control SOC from the previous calculation (step S404). As a result, even if the control SOC changes significantly due to the control SOC correction, the display SOC does not change abruptly, but gradually approaches the control SOC.

[0059] Figure 9 is an example of a timing chart for the control SOC and display SOC when the above control is executed. In the figure, the dashed line shows the change in true SOC, the solid line C1 shows the corrected control SOC when the cumulative error is negative, the solid line C2 shows the corrected control SOC when the cumulative error is positive, the dashed line M1 shows the corrected display SOC when the cumulative error is negative, and the dashed line M2 shows the corrected display SOC when the cumulative error is positive. Here, the time up to time t1 belongs to region I, and the time from time t1 onward belongs to region II.

[0060] Up to time t1, the displayed SOC matches the controlled SOC because it belongs to region I. When the controlled SOC correction is performed at time t1, the controlled SOC matches the true SOC, and thereafter, it belongs to region II, so it remains in agreement with the true SOC with almost no estimation error.

[0061] When the amount of change in the control SOC due to control SOC correction exceeds a predetermined value, display SOC correction is performed. As a result, the display SOC does not change as abruptly as the control SOC, but gradually approaches the control SOC from time t1 onward.

[0062] (A variation of the displayed SOC calculation) Here, a modified example of the method for setting the display SOC will be described. This modified example also falls within the scope of the present invention, similar to the embodiment described above. In the embodiment described above, the coefficient multiplied by the difference between the control SOC and the display SOC during the previous calculation was constant, but in this modified example, the coefficient is made variable according to the difference.

[0063] Figure 10 is a flowchart showing the control routine executed by the display SOC calculation unit 11 to set the display SOC in this modified example. The difference from Figure 7 is step S505. Steps S500 to S504 and S506 to S509 are the same as steps S400 to S404 and S405 to S408 in Figure 7, respectively, so their explanation is omitted.

[0064] In step S505, the coefficient is determined using a map, for example, as shown in Figure 11, based on the difference between the control SOC and the display SOC from the previous calculation and the current SOC. The coefficient is set based on the following concept. The specific numerical value will be determined by suitability depending on the full capacity of the battery 100, etc.

[0065] When the difference is negative and the current control SOC is small (region E1), there is a concern that the vehicle may run out of power even though it should still be able to run according to the displayed SOC. Therefore, the coefficient for region E1 is set to a coefficient that can cause the displayed SOC to converge to the control SOC early while suppressing any discomfort to the driver.

[0066] If the difference is negative and there is sufficient margin in the current control SOC (region E2), there is ample time before the battery runs out, so a coefficient is set that prioritizes minimizing discomfort for the driver.

[0067] When the difference is positive and the current control SOC is small (region E3), the same concerns as in region E1 do not arise, so a coefficient is set that prioritizes suppressing discomfort for the driver.

[0068] If the difference is positive and there is sufficient margin in the current control SOC (region E4), a coefficient is set that allows the displayed SOC to converge to the control SOC early, while minimizing any discomfort to the driver, in order to synchronize the timing of the full charge determination and the displayed SOC reaching 100%.

[0069] Figure 12 shows an example of a timing chart for the control SOC and display SOC when this modified example is implemented. In the figure, the dashed line represents the true SOC, the solid line C represents the control SOC, and the dashed-dotted line group M represents the display SOC. Note that Figure 12 shows the case where the difference between the control SOC and the display SOC from the previous calculation becomes positive due to the control SOC correction.

[0070] Up to time t1, the behavior is the same as in Figure 9 described in the above embodiment, so the explanation is omitted. After time t1, the displayed SOC can exhibit various behaviors depending on the set coefficients, until it converges to the control SOC, as shown by the dashed-dotted line group M.

[0071] (Allowable power / Display power calculation) Next, we will explain the calculation of allowable power and displayed power. Allowable power is the input / output power that battery 100 can handle, as mentioned above, and is calculated in principle based on the control SOC. If the requested power determined based on the driver's operation exceeds the allowable power, the requested power is limited by the allowable power. Hereinafter, this limitation by allowable power will be referred to as the power limit. Displayed power is the power displayed on meter 300 to inform the driver of the current allowable power.

[0072] Figure 13 is a flowchart showing the allowable power calculation routine executed by the allowable power calculation unit 12.

[0073] In step S600, it is determined whether or not display SOC correction is being performed. If it is being performed, the process in step S602 is executed; otherwise, the process in step S601 is executed.

[0074] In step S601, the allowable power is calculated based on the control SOC.

[0075] In step S602, it is determined whether the absolute value of the difference between the control SOC and the display SOC is greater than a predetermined value. If it is greater, the process in step S603 is executed; otherwise, the process in step S601 is executed. The predetermined value is a value that can be arbitrarily set based on the cumulative value of power calculation errors expected in the control of the battery system. For example, when the allowable power is calculated based on the control SOC, the allowable power may change in steps due to the correction of the control SOC, but if the amount of change is small, it will not cause discomfort to the driver. Therefore, the upper limit of the difference between the control SOC and the display SOC that does not cause discomfort to the driver is set as the predetermined value.

[0076] In step S603, it is determined whether or not a power limit is currently in place. If a limit is in place, the process in step S604 is executed; otherwise, the process in step S601 is executed.

[0077] In step S604, the allowable power is calculated based on the displayed power.

[0078] The display power calculation unit 13 obtains the allowable power as a result of the above calculation and calculates the display power based on this. For example, the allowable power may be used as the display power as is, or a value obtained by adding a margin to the allowable power may be used as the display power.

[0079] Figure 14 is a timing chart of the allowable power and display power when the above calculation is performed. It is assumed that the allowable power and display power are the same value. The dashed line in the figure shows the calculation result when calculated based on the true SOC, the solid line shows the calculation result when calculated based on the controlled SOC, and the dashed-dot line shows the calculation result when calculated based on the display SOC.

[0080] Just before time t1, the allowable power and display power calculated based on the control SOC begin to decrease. This is because the control SOC becomes smaller than the true SOC due to the accumulation of errors in the current integration method. Then, when the control SOC correction is performed at time t1, the allowable power and display power calculated based on the control SOC change stepwise and become the same as the calculation result based on the true SOC. If the amount of change during this stepwise change is large, using the calculation result based on the control SOC as the allowable power and display power will cause discomfort to the driver. However, according to the calculation routine described above, after time t1, the allowable power is calculated based on the display SOC until the absolute value of the difference between the control SOC and the display SOC falls below a predetermined value, so the allowable power and display power remain constant as shown by the dashed line. This suppresses discomfort to the driver.

[0081] (Ensuring remaining cruising range) Next, we will explain how to calculate the allowable power required to ensure the remaining cruising range.

[0082] The remaining range is a value that indicates how far the vehicle can travel, and is calculated using a known method that utilizes the current SOC and predicted future power consumption, and is displayed on the meter 300.

[0083] Incidentally, during driving, the SOC decreases and moves from region I to region II, and as a result of the control SOC correction, the corrected control SOC may become smaller than the control SOC before correction. In this case, the remaining driving range also decreases along with the decrease in control SOC. Furthermore, if the change in remaining driving range due to the control SOC correction is large, it can cause discomfort to the driver. Also, drivers plan their driving based on the displayed remaining driving range, and if the remaining driving range suddenly decreases, it may be difficult to revise the driving plan.

[0084] Therefore, in this embodiment, even if the control SOC decreases due to control SOC correction, the remaining cruising range displayed on the meter 300 is secured by calculating based on the control SOC before correction. Specifically, the amount of power consumed during future driving is reduced by limiting the allowable power.

[0085] Figure 15 is a portion of a flowchart showing the calculation routine for the allowable power required to ensure the remaining range before control SOC correction. Figure 16 is a portion of the same flowchart.

[0086] In step S700, it is determined whether or not display SOC correction is being performed. If it is being performed, the process in step S702 is executed; otherwise, the process in step S701 is executed.

[0087] In step S701, the allowable power is calculated based on the control power, and this routine ends. In other words, no limit is placed on the allowable power. This is because the change in control SOC before and after the control SOC correction is small, and the change in the remaining range calculated based on the control SOC is also small, so there is no need to limit the allowable power.

[0088] In step S702, it is determined whether it is the first calculation after control SOC correction. If it is the first calculation, the process in step S707 in Figure 16 is executed; otherwise, the process in step S703 is executed. This step is performed because, while the power limiting factor described later needs to be set during the first calculation, the already calculated power limiting factor can be used for subsequent calculations.

[0089] In step S703, the product of the allowable power calculated based on the corrected control SOC and the power limiting ratio G set by the processing in steps S708 to S711 described later is calculated and taken as the allowable power value D required to secure the remaining cruising range before the control SOC correction.

[0090] In step S704, it is determined whether or not power calculation based on the displayed SOC is being performed. If it is being performed, the process in step S706 is executed; otherwise, the process in step S705 is executed. This determination is made because, even when display SOC correction is being performed, the allowable power calculation based on the control SOC may also be performed, as shown in step S601 of Figure 13, and it is necessary to differentiate the conditions.

[0091] In step S705, the allowable power value D is set as the allowable power.

[0092] In step S706, the allowable power calculated based on the displayed SOC is compared with the allowable power value D, and the smaller one is set as the allowable power.

[0093] In step S707, it is determined whether the control SOC before correction is greater than or equal to the control SOC after correction. If the control SOC before correction is greater or both are equal, this routine is terminated. If the control SOC before correction is greater, the process in step S708 is executed.

[0094] In step S708, the remaining capacity E of battery 100 is calculated from the control SOC after control SOC correction.

[0095] In step S709, the control SOC immediately before the control SOC correction is obtained, and in step S710, the remaining capacity F is calculated from the control SOC immediately before the control SOC correction.

[0096] In step S711, the value G obtained by dividing the remaining capacity E by the remaining capacity F is stored as the power limiting ratio. After the processing in step S711 is completed, the processing in step S703 in Figure 15 is performed.

[0097] As described above, limiting the allowable power using the power limiting factor G reduces power consumption after the control SOC correction is performed. This ensures that the remaining cruising range, which was calculated based on the control SOC before the correction and the power consumption based on the allowable power before the limiting, is maintained and displayed on the meter 300.

[0098] As described above, this embodiment provides a battery system control method that estimates a control SOC, which is the charge rate used for control, based on the integrated value of the charge and discharge current of the secondary battery. When the ratio of the change in the open-circuit voltage of the battery 100 (secondary battery) to the change in the charge rate is in region II (high change rate region) or higher than the first threshold, a corrected SOC, which is a charge rate for correction, is estimated based on the open-circuit voltage of the battery 100. When the battery is in region II, the control SOC is corrected based on the corrected SOC. In this method, if the difference between the control SOC before correction and the control SOC after correction is greater than a predetermined value (second threshold), the displayed SOC, which is the charge rate displayed on the meter 300, is gradually brought closer to the corrected control SOC. This improves the accuracy of SOC estimation and suppresses the driver's discomfort caused by sudden changes in the value calculated based on the estimated SOC.

[0099] In this embodiment, if the difference between the control SOC before correction and the control SOC after correction is less than or equal to a predetermined value, the displayed SOC is set based on the previously calculated value of the control SOC. If the difference is greater than the predetermined value, the value obtained by multiplying the difference between the corrected control SOC and the displayed SOC at the time of the previous calculation by a coefficient is subtracted from the corrected control SOC at the time of the current calculation to obtain the displayed SOC at the time of the current calculation. This ensures consistency between the actual charge / discharge state changes and the displayed SOC, while smoothly converging the displayed SOC to the control SOC.

[0100] In this embodiment, the above coefficient is determined according to the difference between the corrected control SOC and the displayed SOC in the previous calculation and the corrected control SOC in the current calculation. This allows the process of smoothly converging the displayed SOC to the control SOC described above to be performed more appropriately according to the amount of change in the control SOC due to the correction.

[0101] In this embodiment, when the control SOC is corrected and the input / output power of the battery 100 is limited by the allowable power, which is the limit value, in the most recent calculation, the allowable power and the display power, which is the power displayed on the meter, are calculated based on the display SOC. This makes it possible to suppress sudden fluctuations in the allowable power and display power when the control SOC is corrected.

[0102] In this embodiment, the allowable power is calculated based on the control SOC, and if the corrected control SOC is smaller than the uncorrected control SOC, a power limiting factor is set based on the change in control SOC due to the correction, and this power limiting factor is used to limit the upper limit of the allowable power calculated based on the corrected control SOC. As a result, even if the control SOC decreases due to the control SOC correction, a remaining cruising range close to the remaining cruising range displayed on the meter 300 immediately before the control SOC correction can be secured.

[0103] [Second Embodiment] In this embodiment, the battery system configuration and other aspects are the same as in the first embodiment, but the content of the displayed SOC correction and the calculation method for the allowable power and displayed power differ from the first embodiment. The following will explain these differences in detail.

[0104] (Display SOC calculation) Figure 17 is a diagram illustrating the concept of display SOC correction in this embodiment. In the figure, black circles represent the control SOC, solid white circles represent the display SOC, and dashed white circles represent the predicted value of the control SOC assuming that no control SOC correction is performed (hereinafter also referred to as the uncorrected control SOC predicted value). In addition, the dashed line in the figure is a line that shows the behavior of the control SOC when no control SOC correction is performed, predicted based on the history of the control SOC before control SOC correction (hereinafter also referred to as the uncorrected control SOC prediction line).

[0105] In the first embodiment, the display SOC correction was performed by multiplying the difference between the control SOC and the display SOC by a coefficient and subtracting this from the control SOC to obtain the display SOC. In contrast, in this embodiment, the display SOC for the current calculation is obtained by summing the uncorrected control SOC prediction value, which is predicted based on the control SOC before correction, with the corrected control SOC, multiplied by the allocation ratio. Then, by changing the allocation ratio of each SOC, the display SOC is gradually brought closer to the control SOC. The allocation ratio is determined according to the elapsed time since the start of correction, the corrected control SOC for the current calculation, and the difference between the uncorrected control SOC prediction value and the corrected control SOC for the current calculation.

[0106] In Figure 17, control SOC correction is performed at time t1, causing a significant change in the control SOC. Therefore, the uncorrected control SOC obtained from the uncorrected control SOC prediction line and the corrected control SOC are multiplied by a distribution ratio, and the sum of the results of these multiplications is taken as the displayed SOC at time t1. By repeating this process at times t2, t3, etc., while changing the distribution ratio, the displayed SOC is gradually brought closer to the control SOC.

[0107] Figure 18 shows the change in the control SOC allocation ratio over time from the start of correction. The control SOC allocation ratio curve is represented by a function (for example, equation (1) below) in which the allocation ratio P is zero at the start of correction, gradually increases, and eventually becomes 1. The solid, dashed, and dotted lines in Figure 18 illustrate three allocation ratio curves with different coefficients α in equation (1).

number

[0108] As shown in Figure 18, by changing the allocation ratio as described above, the ratio of the corrected control SOC is low immediately after correction, then gradually increases, and eventually the corrected control SOC becomes the displayed SOC.

[0109] The method for setting the allocation ratio is not limited to the method described above. For example, the allocation ratio may be changed to increase monotonically according to the elapsed time since the start of control SOC correction.

[0110] Figure 20 is a flowchart showing the specific calculation routine for the display SOC setting method described above.

[0111] In step S800, it is determined whether the absolute value of the difference between the control SOC and the display SOC is greater than a predetermined value. If it is greater, the process in step S802 is executed; otherwise, the process in step S801 is executed. The determination in this step is the same as in step S403 in Figure 7.

[0112] In step S801, the display SOC is updated with the current control SOC, and this routine is terminated. This is because the difference between the control SOC and the display SOC is small, and using the control SOC as the display SOC will not cause any discomfort to the driver.

[0113] In step S802, it is determined whether or not this is the first calculation after control SOC correction. If it is the first calculation, the process in step S803 is executed; otherwise, the process in step S806 is executed.

[0114] In step S803, the calculation result of the most recent control SOC is referenced to determine the SOC change rate for each calculation, and the average change rate is calculated based on this. The calculation result is stored in memory. The range of "most recent" can be arbitrarily set, for example, from the start of this operation to the present, or from one hour ago to the present.

[0115] In step S804, the uncorrected control SOC prediction value is calculated using the uncorrected control SOC and the average rate of change, and in step S805, this uncorrected control SOC prediction value is stored in memory. After the processing in step S805 is completed, the process proceeds to step S808, which will be described later.

[0116] In step S806, the average rate of change is read, and the current uncorrected control SOC prediction value is calculated from the average rate of change and the previous uncorrected control SOC prediction value.

[0117] In step S807, the uncorrected control SOC prediction value is updated with the value calculated in step S806.

[0118] In step S808, the difference between the current control SOC and the predicted control SOC value without correction is calculated.

[0119] In step S809, the coefficient α is determined based on the above difference, the current control SOC, and the elapsed time since the start of control SOC correction, and in step S810, the allocation ratio is determined based on the coefficient α. Note that the processing in steps S809 to S810 may also be performed to determine the allocation ratio based only on the elapsed time since the start of control SOC correction, as described above.

[0120] In step S811, the displayed SOC is calculated based on the allocation ratio.

[0121] In step S812, similar to step S800, it is determined whether the absolute value of the difference between the control SOC and the display SOC is greater than a predetermined value. If it is greater, the routine ends; otherwise, the process in step S813 is executed.

[0122] If the absolute value of the difference between the control SOC and the display SOC is less than or equal to a predetermined value, it means that display SOC correction is no longer necessary. Therefore, in step S813, the uncorrected control SOC prediction value and average rate of change, which have been saved, are cleared so that they do not affect the next time display SOC correction is performed.

[0123] Once step S813 is complete, the process proceeds to step S801. In other words, the display SOC is updated by the control SOC.

[0124] Even with the above control, the displayed SOC behaves similarly to that shown in Figure 9, gradually converging to the control SOC.

[0125] (Allowable power / Display power calculation) In the first embodiment, while display SOC correction is being performed, the allowable power and display power are calculated based on the display SOC in principle. However, even while display SOC correction is being performed, while power limiting is being performed, the allowable power and display power are calculated based on the control SOC. In this embodiment, as in the first embodiment, the allowable power and display power are calculated based on the display SOC in principle while display SOC correction is being performed. However, the conditions for switching to calculating the allowable power and display power based on the control SOC during display SOC correction are different.

[0126] Figure 21 is a flowchart showing the calculation routine for the allowable power according to this embodiment. Steps S900-S902 and S904 are the same as steps S600-S602 and S604 in Figure 13, so their explanation is omitted.

[0127] In step S903, which is executed when the absolute value of the difference between the control SOC and the display SOC is greater than a predetermined value, it is determined whether the conditions for which the driver can be considered to be tolerating a change in vehicle behavior caused by a change in permissible power (hereinafter also referred to as the permissible conditions) are met.

[0128] Acceptable conditions are met, for example, when charging, when the actual power fluctuation falls outside a preset range, or when the change in the power reading is extremely small, such as when cruising at a constant speed. When the actual power fluctuation falls outside a preset range, this refers to situations where the driver performs operations that cause large changes in the power reading, such as sudden acceleration and sudden deceleration.

[0129] If the acceptable conditions are met, the allowable power is calculated in step S901 based on the control SOC. This is because even if the allowable power fluctuates significantly due to the control SOC correction, it is unlikely to cause discomfort to the driver. On the other hand, if the acceptable conditions are not met, the allowable power is calculated in step S904 based on the displayed SOC. This suppresses sudden changes in the allowable power and reduces discomfort to the driver.

[0130] Figure 22 is a timing chart of the allowable power and display power when the above control is performed. In the figure, the dashed line shows the calculation based on the true SOC, the solid line shows the calculation based on the control SOC after control SOC correction, and the dashed line shows the case when the control of this embodiment is performed.

[0131] When control SOC correction is performed at time t1, the allowable power and display power calculated based on the control SOC increase. To suppress the unnatural feeling caused by this sudden change in allowable power, from time t1 onwards, the allowable power and display power are calculated based on the display SOC, so the values ​​at time t1 are maintained. Then, when the allowable condition is met at time t2, the calculation is based on the control SOC, and increases stepwise as shown in the figure.

[0132] As described above, in this embodiment, if the difference between the uncorrected control SOC and the corrected control SOC is greater than a predetermined value, the displayed SOC for the current calculation is set by adding the uncorrected control SOC prediction value predicted based on the uncorrected control SOC and the corrected control SOC, multiplied by the allocation ratio. The allocation ratio is determined according to the elapsed time since the start of correction, the corrected control SOC for the current calculation, and the difference between the uncorrected control SOC prediction value and the corrected control SOC for the current calculation, or according to the elapsed time since the start of correction. This ensures consistency between the actual charge / discharge state changes and the displayed SOC, while smoothly converging the displayed SOC to the control SOC in accordance with the amount of change in the control SOC due to correction.

[0133] In this embodiment, when the control SOC is corrected, the allowable power and the display power (power to be displayed on the meter) are calculated based on the control SOC as a general rule. However, as an exception, when charging is in progress or when the actual power fluctuation falls outside a preset range, the allowable power and the display power (power to be displayed on the meter) are calculated based on the control SOC. In other words, in situations where the driver can be considered to be tolerating the change in allowable power, or in other words, in situations where a sudden change in allowable power and display power is unlikely to cause discomfort to the driver, the allowable power and display power are calculated based on the control SOC. This allows for a quick transition to the allowable power and display power corresponding to the corrected control SOC.

[0134] [Third Embodiment] In this embodiment, the battery system configuration and other aspects are the same as in the first embodiment, but the method for calculating the allowable power and display power differs from that of the first embodiment. The differences will be explained below in detail.

[0135] The calculation method for the allowable power and display power according to this embodiment is, in principle, the same as in the second embodiment. However, if it can be determined from the driver's driving history that the driver will not be subject to power limitations based on the allowable power, the allowable power is calculated by subtracting a margin from the allowable power calculated based on the control SOC, and power limitations are imposed if this is exceeded. The margin may be determined, for example, according to the ratio of the allowable power calculated based on the control SOC to the allowable power calculated based on the display SOC, or according to the difference between the allowable power in the past history and the power actually used according to the driver's operation (hereinafter also referred to as actual power).

[0136] Figure 23 is a diagram illustrating the behavior of the allowable power and display power in this embodiment. In the figure, the dashed lines show the allowable power and display power when calculated based on the true SOC, the solid lines show the allowable power and display power when calculated based on the control SOC after control SOC correction, and the dashed-dotted lines show the allowable power and display power when the control of this embodiment is executed. The double-dotted-dotted lines in the figure show the history of the actual power. The allowable power up to time t1 is the same as in Figure 22, so the explanation is omitted.

[0137] When control SOC correction is performed at time t1, the allowable power calculated based on the control SOC increases stepwise as shown by the solid line, and then gradually decreases as the control SOC decreases.

[0138] On the other hand, the allowable power after deducting the margin remains the same as the allowable power immediately before the control SOC correction at time t1, as shown by the dashed line, and gradually decreases from there. If the actual power exceeds the allowable power after deducting the margin, power limiting is performed using that allowable power. In other words, from time t2 onward, regardless of how the allowable power fluctuates within the shaded region DZ in Figure 23 due to the control SOC correction, the allowable power used for power limiting will be the value shown by the dashed line. In other words, region DZ is a region that cannot be used for actual power.

[0139] Figure 24 is a portion of a flowchart showing the specific calculation routine for calculating the allowable power mentioned above. Figure 25 is the remaining portion of the same flowchart.

[0140] In step S1000, it is determined whether or not display SOC correction is being performed. If it is being performed, the process in step S1005 is executed; otherwise, the process in step S1001 is executed.

[0141] In step S1001, the system checks past driving history to determine whether power limitations have ever been imposed, that is, whether the actual power has ever exceeded the allowable power. If power limitations have been imposed, the system executes the process in step S1003; otherwise, the system executes the process in step S1002. The past history checked here is the history from the start of the current trip to the present. However, it is not limited to this; for example, it could be the driving history for the most recent month, or the entire lifetime history.

[0142] In step S1002, the allowable power is calculated based on the control SOC.

[0143] In step S1003, it is determined whether the power limitation is caused by the addition of a margin. If it is, the process in step S1004 is executed; otherwise, the process in step S1002 is executed. A case where the power limitation is caused by the addition of a margin means that the power limitation was imposed because a margin was added, but the power limitation would not have been imposed if the margin had not been added.

[0144] The reason for executing step S1002 when the power limit is not due to margin allocation is that the power limit not caused by margin allocation is due to battery performance constraints, and therefore the allowable power calculation should not be modified.

[0145] In step S1004, the margin applied to the allowable power is removed. This is to eliminate a situation where the actual power is limited due to the application of a margin, even though there is no actual need for power restriction, preventing the driver from driving as intended.

[0146] In step S1005, it is determined whether the difference between the control SOC and the display SOC is greater than a predetermined value. If it is greater than the predetermined value, the process in step S1006 in Figure 25 is executed; if it is less than or equal to the predetermined value, the process in step S1002 is executed. The content of this step is the same as in step S902 in Figure 21. The reason for executing the process in step S1002 when the difference is less than or equal to the predetermined value is that if the difference is sufficiently small, the change in allowable power and display power will also be small, and the possibility of causing discomfort to the driver is low.

[0147] In step S1006, similar to step S1001, it is determined whether or not power limitations have been imposed in the past. If power limitations have been imposed, the process in step S1009 is executed; otherwise, the process in step S1007 is executed.

[0148] In step S1007, the operating history is referenced to obtain the minimum difference between the allowable power and the actual power.

[0149] In step S1008, it is decided to apply the margin based on the difference to the allowable power calculation, and the process proceeds to step S1002. In other words, a margin is added to the result of the allowable power calculation in step S1002. Along with the control SOC correction, the allowable power calculated based on the control SOC also changes, but by adding a margin, this change becomes a change within the unused region of the actual power. Therefore, there is no risk that the driver will feel uncomfortable due to an abrupt power limitation caused by the control SOC correction.

[0150] In step S1009, similar to step S1003, it is determined whether the power limitation received is due to the addition of a margin. If it is due to the addition of a margin, the process in step S1010 is executed; otherwise, the process in step S1011 is executed. In step S1010, the margin is removed, similar to step S1004.

[0151] In step S1011, the allowable power is calculated based on the displayed SOC. If the allowable power calculation continues based on the control SOC, as mentioned above, there is a risk of sudden power limitations causing a step in the driving force. Therefore, in this step, the power calculation is performed based on the displayed SOC, which changes more gradually than the control power.

[0152] As described above, in this embodiment, when the allowable power and displayed power are calculated based on the displayed SOC, if it is determined that the input / output power of the battery 100 is not being limited by the allowable power based on the operating history, the upper limit of the allowable power is limited based on the actual input / output power obtained from the operating history. In other words, a region (margin) that cannot be used as actual power is provided based on the operating history. This prevents situations in which power limitations are suddenly applied and driving force steps occur due to changes in the allowable power accompanying control SOC correction.

[0153] It goes without saying that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the technical idea described in the claims. [Explanation of Symbols]

[0154] 15 Battery controllers, 100 Batteries, 200 Vehicle controllers, 200 Meters

Claims

1. Based on the integrated value of the charge and discharge current of the secondary battery, the control state of charge (SOC), which is the charge rate used for control, is estimated. When the ratio of the change in the open-circuit voltage of the secondary battery to the change in the charge level is in a high-rate-of-change region of at least a first threshold, a corrected SOC, which is a corrected charge level, is estimated based on the open-circuit voltage of the secondary battery. When in the high rate of change region, the control SOC is corrected based on the corrected SOC. In a method for controlling a battery system, If the difference between the control SOC before correction and the control SOC after correction is less than or equal to the second threshold, the display SOC, which is the charge rate displayed on the meter, is set based on the previously calculated value of the control SOC. A battery system control method characterized in that, if the difference is greater than the second threshold, the display SOC is gradually brought closer to the corrected control SOC by subtracting the value obtained by multiplying the difference between the corrected control SOC and the display SOC at the time of the previous calculation by a coefficient from the corrected control SOC at the time of the current calculation, thereby obtaining the display SOC at the time of the current calculation.

2. In the battery system control method described in Claim 1, A battery system control method wherein the coefficient is determined according to the difference between the corrected control SOC and the displayed SOC during the previous calculation and the corrected control SOC during the current calculation.

3. In the battery system control method described in claim 1, If the difference is greater than the second threshold, the displayed SOC for the current calculation is set by summing the uncorrected control SOC prediction value predicted based on the control SOC before correction and the corrected control SOC by the allocation ratio. A battery system control method that determines the distribution ratio according to the elapsed time since the start of correction, the corrected control SOC at the time of the current calculation, and the difference between the predicted value of the uncorrected control SOC and the corrected control SOC at the time of the current calculation, or according to the elapsed time since the start of correction.

4. A method for controlling a battery system according to any one of claims 1 to 3, A battery system control method that, when the control SOC is corrected and the input / output power of the secondary battery is limited by the allowable power which is a limit value in the most recent calculation, calculates the allowable power and the display power which is the power to be displayed on the meter based on the display SOC.

5. In the battery system control method described in Claim 4, When the aforementioned control SOC is corrected, the allowable power and the display power (the power displayed on the meter) are calculated based on the aforementioned control SOC, As an exception, a battery system control method that calculates the allowable power and the display power, which is the power to be displayed on the meter, based on the control SOC, when charging or when the actual power fluctuation falls outside a preset range.

6. In the battery system control method according to claim 4 or 5, A battery system control method in which, when the calculation of the allowable power and the displayed power based on the displayed SOC is being performed, if it is determined that the input / output power of the secondary battery is not being limited by the allowable power based on the operating history, the upper limit of the allowable power is limited based on the actual input / output power obtained from the operating history.

7. In the battery control method according to any one of claims 4 to 6, A battery control method that calculates the allowable power based on the control SOC, and if the corrected control SOC becomes smaller than the uncorrected control SOC, sets a power limiting rate based on the amount of change in the control SOC due to the correction, and uses the power limiting rate to limit the upper limit of the allowable power calculated based on the corrected control SOC.

8. A current detection unit for detecting the charging and discharging current of a secondary battery, A first estimation unit estimates the control state of charge (SOC), which is the charge rate used for control, based on the integrated value of the charge and discharge currents. A second estimation unit estimates a corrected state of charge (SOC), which is a corrected charge rate, based on the open-circuit voltage of the secondary battery, when the ratio of the change in the open-circuit voltage of the secondary battery to the change in the charge rate is in a high change rate region of at least a first threshold, When in the high rate of change region, the SOC correction unit corrects the control SOC based on the corrected SOC, In a control device for a battery system, The system further includes a display SOC calculation unit that sets a display SOC, which is the charge rate displayed on the meter, based on the control SOC. If the difference between the control SOC before correction and the control SOC after correction is less than or equal to the second threshold, the display SOC calculation unit sets the display SOC based on the previously calculated value of the control SOC. A battery system control device characterized in that, if the difference is greater than the second threshold, the display SOC calculation unit subtracts the value obtained by multiplying the difference between the corrected control SOC and the display SOC at the time of the previous calculation by a coefficient from the corrected control SOC at the time of the current calculation, thereby setting the display SOC to a value that gradually approaches the corrected control SOC.

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