Correction device, power storage device, and correction method

Abstract

To correct a measurement value of a current of a power storage cell or a battery pack.SOLUTION: A correction device for correcting a measurement value of a current of a power storage cell or a battery pack calculates a correction value of a measurement value of a current based on a SOC difference that is the difference between a first SOC of the power storage cell or the battery pack estimated based on an integrated value of the measurement value of the current and a second SOC of the power storage cell or the battery pack estimated based on a voltage of the power storage cell or the battery pack and corrects the measurement value of the current based on the calculated correction value.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a technique for correcting a measured value of a current. [Background technology]

[0002] There is known a technique for measuring the current and voltage of a storage cell or a battery pack and estimating the SOC (State of Charge) of the storage cell or the battery pack from the measurement results. Patent Document 1 discloses a technique for improving the accuracy of SOC estimation by combining two or more different estimation means. [Prior art documents] [Patent documents]

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

[0004] The measured value of the current of the power storage cell or the battery pack includes a measurement error caused by the current sensor. The estimated SOC value of the power storage cell or the battery pack, which is estimated based on the integrated value of the measured current, includes an accumulated current measurement error associated with the passage of current through the power storage cell or the battery pack.

[0005] The present invention discloses a technique for calculating a correction value to correct a measured current value. [Means for solving the problem]

[0006] A correction device that corrects a measurement value of a current of a storage cell or a battery pack calculates a correction value for the measurement value of the current based on an SOC difference, which is the difference between a first SOC of the storage cell or the battery pack estimated based on an integrated value of the measurement value of the current and a second SOC of the storage cell or the battery pack estimated based on a voltage of the storage cell or the battery pack, and corrects the measurement value of the current based on the calculated correction value.

[0007] The present invention can be applied to an electricity storage device and an electricity storage device for a vehicle, and can also be applied to a correction method for correcting a measured current value and a program for correcting a measured current value. Effect of the Invention

[0008] According to the above configuration, by focusing on the relationship between the current measurement error and the SOC estimation value and calculating the correction value to correct the current measurement value, the measurement accuracy of the current of the storage cell or the assembled battery can be improved. By improving the current measurement accuracy, the accuracy of the SOC estimation based on the current integration can be improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a vehicle according to a first embodiment; [Diagram 2] Exploded perspective view of the battery [Diagram 3] Plan view of a secondary battery cell [Figure 4] Cross section of line AA in Figure 3 [Diagram 5] Block diagram showing the electrical configuration of a vehicle [Figure 6] Block diagram showing the electrical configuration of the battery [Figure 7] SOC-OCV correlation characteristics of LFP / Gr batteries [Figure 8] FIG. 1 shows a flowchart of SOC estimation (first embodiment). [Figure 9] FIG. 1 shows a flowchart of SOC estimation (second embodiment). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Outline of the correction device and power storage device> A correction device that corrects a measurement value of a current of a storage cell or a battery pack calculates a correction value for the measurement value of the current based on an SOC difference, which is the difference between a first SOC of the storage cell or the battery pack estimated based on an integrated value of the measurement value of the current and a second SOC of the storage cell or the battery pack estimated based on a voltage of the storage cell or the battery pack, and corrects the measurement value of the current based on the calculated correction value.

[0011] Since the second SOC is estimated based on the voltage of the storage cell or the battery pack, the measurement error included in the measured value of the current is not accumulated. Therefore, the SOC difference, which is the difference between the first SOC and the second SOC, is considered to be the accumulated measurement error included in the first SOC. Therefore, the measurement error included in the measured value of the current can be calculated based on this SOC difference. By correcting the measured value of the current using the calculated measurement error as a correction value, the measured value of the current can be brought closer to the true value, thereby improving the current measurement accuracy.

[0012] Current measurement errors include gain error and offset error. Since errors in the SOC estimation value caused by gain error are offset by charging and discharging, it is necessary to reduce the effect of offset error in order to improve the accuracy of SOC estimation. It is generally believed that offset error is difficult to detect unless the storage cell or assembled battery is made to have no current. In the above configuration, the measurement error (offset error) is calculated using the SOC difference without making the storage cell or assembled battery have no current, and the measurement value of the current can be corrected using the measurement error as a correction value.

[0013] The process of estimating the second SOC may be a process (full charge detection method) of charging the storage cell or the battery pack until it is fully charged and estimating the SOC to 100% or a value close to that. The full charge detection method is a process of setting the SOC of the storage cell or the battery pack to a predetermined value when the storage cell or the battery pack reaches a predetermined voltage value. By comparing the first SOC with the second SOC calculated by the full charge detection method, which does not have accumulated measurement errors, the accumulated measurement errors can be calculated with high accuracy and the measured current value can be appropriately corrected.

[0014] The energy storage device includes the correction device, the energy storage cell or the battery pack, a current measurement unit that measures a current of the energy storage cell or the battery pack, and a SOC estimation unit that estimates a first SOC of the energy storage cell or the battery pack based on an integrated value of the measurement value of the current after correction of the energy storage cell or the battery pack.

[0015] In this configuration, the SOC is estimated by integrating the measured values ​​of the corrected current, so that the accumulation of measurement errors is small and the estimation accuracy of the first SOC can be improved. By improving the estimation accuracy of the first SOC, the usable range (SOC range between the lower and upper limits) of the storage cell or assembled battery can be set broadly. When the estimation accuracy of the first SOC is low, the usable range becomes narrower because it is necessary to take the estimation error into account, but when the estimation accuracy is high, the performance of the storage cell or assembled battery can be utilized to the maximum extent.

[0016] The correction device may correct the measured current value when the SOC difference exceeds a threshold value. In this configuration, the correction is performed when the SOC difference increases, so that the increase in the SOC difference can be suppressed and the deterioration of the estimation accuracy of the first SOC can be suppressed. By suppressing the SOC difference to a threshold value or less, it is possible to suppress the storage cell or the assembled battery from being used beyond the usable range. For example, when the storage cell or the assembled battery is for a mobile body, it is possible to ensure the acceptability of regenerative charging.

[0017] The correction device may correct the measured value of the current when a change in the SOC difference per unit time exceeds a threshold value.

[0018] When the change in the SOC difference per unit time is large, the estimation accuracy of the first SOC decreases in a short time, and the difference with the second SOC increases. Since correction is performed when the change in the SOC difference per unit time exceeds the threshold before the SOC difference exceeds the threshold, the measured current value can be corrected early. This makes it possible to suppress the decrease in the estimation accuracy of the first SOC.

[0019] The correction device may correct the measured current value using the correction value calculated based on the amount of change in the SOC difference per unit time. For example, the correction value may be calculated to offset the amount of change in the SOC difference per unit time, and the measured current value may be corrected to suppress a decrease in the estimation accuracy of the first SOC.

[0020] <Embodiment 1> 1. Battery Description FIG. 1 is a side view of automobile 10, and FIG. 2 is an exploded perspective view of battery 50. Automobile 10 is an engine-driven vehicle and is equipped with battery 50. Automobile 10 may be equipped with a power storage device or a fuel cell as a vehicle drive device instead of an engine (internal combustion engine). FIG. 1 shows only automobile 10 and battery 50, and other parts that make up automobile 10 are not shown. Automobile 10 is an example of a "vehicle", and battery 50 is an example of an "power storage device".

[0021] As shown in FIG. 2, the battery 50 includes a battery pack 60, a circuit board unit 65, and a container 71.

[0022] The container 71 includes a main body 73 and a lid 74 made of a synthetic resin material. The main body 73 is cylindrical with a bottom. The main body 73 includes a bottom portion 75 and four side portions 76. An upper opening 77 is formed at the upper end portion by the four side portions 76.

[0023] The container 71 houses the battery pack 60 and the circuit board unit 65. In the embodiment shown in Fig. 2, the battery pack 60 has twelve secondary battery cells 62. The secondary battery cells 62 are an example of a "storage cell".

[0024] The twelve secondary battery cells 62 are connected in a three-parallel configuration and four-series configuration. The circuit board unit 65 is disposed on the upper part of the battery pack 60. In the block diagram of Fig. 6 described later, the three secondary battery cells 62 connected in parallel are represented by one battery symbol.

[0025] The lid 74 shown in Fig. 2 closes an upper opening 77 of the main body 73. An outer peripheral wall 78 is provided around the lid 74. The lid 74 has a protruding portion 79 that is generally T-shaped in plan view. The positive external terminal 52 is fixed to one corner of the front portion of the lid 74 (the front left side in Fig. 2), and the negative external terminal 51 is fixed to the other corner.

[0026] 3 and 4, the secondary battery cell 62 is configured by housing an electrode assembly 83 together with a non-aqueous electrolyte in a rectangular parallelepiped case 82. The secondary battery cell 62 in this embodiment is a lithium ion secondary battery. The case 82 has a case body 84 and a lid 85 that closes the upper opening.

[0027] The secondary battery cell 62 is not limited to the prismatic cell shown in FIG. 3 and FIG. 4, but may be a cylindrical cell or a pouch cell having a laminate film case.

[0028] The electrode body 83 is formed by disposing a separator made of a porous resin film between a negative electrode element in which an active material is applied to a substrate made of, for example, copper foil, and a positive electrode element in which an active material is applied to a substrate made of aluminum foil. Both of these are strip-shaped, and are wound flatly so that they can be housed in the case body 84, with the negative electrode element and the positive electrode element shifted to opposite sides in the width direction relative to the separator.

[0029] The electrode body 83 may be of a laminated type instead of a wound type.

[0030] A positive electrode terminal 87 is connected to the positive electrode element via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode element via a negative electrode current collector 88 (see FIG. 4). The positive electrode current collector 86 and the negative electrode current collector 88 each comprise a flat base portion 90 and legs 91 extending from the base portion 90. A through hole is formed in the base portion 90. The legs 91 are connected to the positive electrode element or the negative electrode element.

[0031] The positive electrode terminal 87 and the negative electrode terminal 89 each comprise a terminal body 92 and a shaft 93 that protrudes downward from the center of the lower surface of the terminal body 92. Of these, the terminal body 92 and shaft 93 of the positive electrode terminal 87 are integrally formed from aluminum (a single material). In the negative electrode terminal 89, the terminal body 92 is made of aluminum, and the shaft 93 is made of copper, and these are assembled together. The terminal body 92 of the positive electrode terminal 87 and the negative electrode terminal 89 are disposed on both ends of the lid 85 via gaskets 94 made of an insulating material, and are exposed to the outside from the gaskets 94.

[0032] The lid 85 has a pressure relief valve 95. As shown in Fig. 3, the pressure relief valve 95 is located between the positive electrode terminal 87 and the negative electrode terminal 89. The pressure relief valve 95 opens to reduce the internal pressure of the case 82 when the internal pressure of the case 82 exceeds a limit value.

[0033] FIG. 5 is a block diagram showing the electrical configuration of the automobile 10, and FIG. 6 is a block diagram showing the electrical configuration of the battery 50. As shown in FIG.

[0034] As shown in FIG. 5, the automobile 10 includes an engine 20 as a drive device, an engine control unit 21, an engine starting device 23, an alternator 25 as a vehicle generator, an electric load 27, a vehicle ECU (Electronic Control Unit) 30, and a battery 50.

[0035] The battery 50 is connected to the power line 37. The engine starting device 23, the alternator 25, and the electric load 27 are connected to the battery 50 via the power line 37.

[0036] The engine starting device 23 includes a starter motor. When the ignition switch 24 is turned on, a cranking current flows from the battery 50 to drive the engine starting device 23. The driving of the engine starting device 23 rotates the crankshaft, and the engine 20 can be started.

[0037] The electric load 27 is an electric load mounted on the automobile 10 other than the engine starting device 23. The electric load 27 has a rated voltage of 12 V, and is an air conditioner, an audio system, a car navigation system, an auxiliary device, or the like.

[0038] The alternator 25 is a vehicle generator that generates electricity using the power of the engine 20. When the amount of electricity generated by the alternator 25 exceeds the amount of electricity consumed by the electrical load of the automobile 10, the battery 50 is charged by the alternator 25. When the amount of electricity generated by the alternator 25 is less than the amount of electricity consumed by the electrical load of the automobile 10, the battery 50 discharges to make up for the shortage of electricity generated.

[0039] The vehicle ECU 30 is communicatively connected to the battery 50 via a communication line L1, and is communicatively connected to the alternator 25 via a communication line L2. The vehicle ECU 30 receives SOC information from the battery 50, and controls the amount of power generation of the alternator 25, thereby controlling the SOC of the battery 50.

[0040] The vehicle ECU 30 is communicatively connected to the engine control unit 21 via the communication line L3. The engine control unit 21 is mounted on the automobile 10, and monitors the operating state of the engine 20. The engine control unit 21 monitors the running state of the automobile 10 from the measurement values ​​of instruments such as a speedometer. The vehicle ECU 30 obtains from the engine control unit 21 information on the on / off state of the ignition switch 24, information on the operating state of the engine 20, and information on the running state of the automobile 10 (driving, stopped, idling stop, etc.).

[0041] 6, the battery 50 includes a current interruption device 53, a battery pack 60, a current measurement unit 54, and a management device 100. The battery 50 is a rated 12V battery.

[0042] The current interruption device 53, the battery pack 60, and the current measurement unit 54 are connected in series via power lines 55P and 55N. The power line 55P connects the positive external terminal 52 and the positive electrode of the battery pack 60. The power line 55N connects the negative external terminal 51 and the negative electrode of the battery pack 60.

[0043] The current interruption device 53 is provided on the positive power line 55P. The current measurement unit 54 is provided on the negative power line 55N.

[0044] A contact switch (mechanical) such as a relay or a semiconductor switch such as an FET can be used as the current interruption device 53. The current interruption device 53 is normally controlled to be in the CLOSE state. If an abnormality occurs in the battery 50, the current interruption device 53 is opened to interrupt the current, thereby protecting the battery 50.

[0045] The current measurement unit 54 measures the current I [A] of the battery pack 60 and outputs the measured current value Im to the control unit 120.

[0046] The management device 100 is provided on the circuit board unit 65 (see FIG. 2). The management device 100 includes a voltage measurement unit 110 and a control unit 120. The control unit 120 is an example of a "correction device" and a "SOC estimation unit."

[0047] The voltage measurement unit 110 is connected to both ends of each secondary battery cell 62 by a signal line, and measures the cell voltage V of each secondary battery cell 62. The voltage measurement unit 110 outputs to the control unit 120 the voltage V of each secondary battery cell 62 and the inter-terminal voltage VB of the assembled battery 60 obtained by summing all of the voltages V.

[0048] The control unit 120 includes a CPU 121 having a calculation function, and a memory 123 which is a storage unit.

[0049] The control unit 120 monitors the current I (current measurement value Im) measured by each measurement unit 54, 110, the voltage V of each secondary battery cell 62, and the voltage VB of the battery pack 60, to monitor the state of the battery 50.

[0050] The memory 123 is a non-volatile storage medium such as a flash memory, an EEPROM, etc. The memory 123 stores a program for monitoring the state of the battery pack 60, a program for executing a decision flow for correcting the measured current value Im and estimating the SOC, and data required for executing each program.

[0051] 2. Characteristics of secondary battery cells (battery packs) and method for estimating SOC The secondary battery cells 62 in this embodiment are LFP / Gr (iron phosphate) type lithium ion secondary battery cells that use lithium iron phosphate (LiFePO4) as the positive electrode active material and graphite as the negative electrode active material. Instead of connecting the twelve secondary battery cells 62 in four series by three parallel connections as shown in FIG. 2, four secondary battery cells 62 may be connected in series to configure one assembled battery 60.

[0052] The same amount of current I flows through each of the secondary battery cells 62 constituting the battery pack 60, and the voltage VB of the battery pack 60 is the sum of the voltages V of the four secondary battery cells 62 connected in series. In the SOC estimation described below, the SOC of the battery pack 60 is estimated.

[0053] The SOC estimation may be performed for a battery pack having a configuration other than the battery pack 60 including four secondary battery cells 62 connected in series. Although not shown, when the battery 50 has a single secondary battery cell 62, the control unit 120 may estimate the SOC of the secondary battery cell 62.

[0054] The SOC is the ratio [%] of the remaining capacity Cr to the fully charged capacity Co of the battery pack 60, and is expressed by the following formula (1): The fully charged capacity Co is the amount of electricity that can be discharged from the fully charged battery pack 60. SOC = (Cr / Co) × 100 (1)

[0055] Methods for estimating the SOC of the battery pack 60 (or the secondary battery cells 62) include an estimation method based on the current of the battery pack 60 (secondary battery cells 62) and an estimation method based on the voltage of the battery pack 60 (secondary battery cells 62).

[0056] A current integration method is a method for estimating the SOC based on the current. In this embodiment, the first SOC is estimated using the current integration method.

[0057] As shown in equation (2), the current integration method estimates the SOC based on the time integral of the current I. The sign of the current I is positive when charging and negative when discharging. SOC=SOCo+100×(∫Idt / Co)···(2) SOCo is the initial value of SOC, I is the current, and t is the integration time.

[0058] An LFP / Gr type lithium-ion secondary battery cell, which uses lithium iron phosphate for the positive electrode and graphite for the negative electrode, has a plateau region in the SOC-OCV correlation characteristics where the change in OCV (Open Circuit Voltage) is small, as shown in Figure 7. Within the plateau region, it is difficult to estimate the SOC using the correlation between SOC and OCV, and so SOC estimation using the current integration method is generally used.

[0059] Since the plateau region occupies the majority of the usable range of LFP / Gr-based lithium-ion secondary battery cells or assembled batteries using them, it is important to maintain the accuracy of SOC estimation using the current integration method.

[0060] A full charge detection method is a method for estimating the SOC based on the terminal voltage VB of the battery pack 60. In this embodiment, the second SOC is estimated by the full charge detection method. The full charge detection method is a method in which, when the control unit 120 detects that the battery pack 60 has been charged to a voltage equivalent to a full charge, the SOC at that time is estimated to be 100% or a predetermined set value close to that.

[0061] In the case of constant voltage charging, whether the battery pack 60 has been fully charged is determined by comparing the charging time and the drooping current value after the voltage VB of the battery pack 60 reaches a predetermined target voltage with a threshold value (full charge completion condition).

[0062] Programs for executing the above-mentioned current integration method and full charge detection method are stored in memory 123 of control unit 120, and when executing the SOC estimation process in the flowchart described later, these programs are appropriately loaded from memory 123 into CPU 121.

[0063] 3. Errors in current measurements and their correction As shown in the following formula (3), a measurement error ε is included in the measurement value Im of the current output by the current measuring unit 54. The measurement error ε is an example of a "correction value" used to correct the measurement value Im of the current, as will be described later. Im = Ic + ε (3) Im is the measured current value before correction, Ic is the current after correction, and ε is the measurement error.

[0064] In SOC estimation using the current integration method, the error in the SOC estimate (SOC estimation error Se, described later) increases due to the accumulation of measurement error ε associated with current flow. The measurement error ε of the current measurement value Im is mainly known to be caused by gain error and offset error. The error in the SOC estimate caused by gain error is offset by charging and discharging, so the offset error is considered to be dominant.

[0065] In this embodiment, the control unit 120 estimates the SOC of the battery pack 60 by two methods, a current integration method and a full charge detection method. From a first SOC calculated by the current integration method and a second SOC calculated by the full charge detection method, an SOC difference Sx, which is the difference between these two SOCs, is calculated.

[0066] The second SOC calculated using the full charge detection method has a smaller error than the first SOC calculated using the current integration method because there is no accumulation of measurement error ε. The SOC difference Sx is considered to be the accumulation of measurement error ε contained in the first SOC. Therefore, the measurement error ε contained in the measured current value Im can be calculated based on the SOC difference Sx. When the integration time t is constant, the larger the SOC difference Sx, the larger the measurement error ε and the lower the estimation accuracy of the first SOC. The smaller the SOC difference Sx, the smaller the measurement error ε and the higher the estimation accuracy of the first SOC.

[0067] The measured current value Im is corrected using the measurement error ε as a correction value according to the following equation (4), which is a modification of equation (3). By executing the current integration method using the corrected current Ic, the effect of the measurement error ε on the first SOC can be suppressed, and the first SOC can be calculated with high accuracy. Ic = Im - ε (4)

[0068] 4. Explanation of SOC estimation process 8 is a flowchart of the SOC estimation process. The SOC estimation process is made up of steps S10 to S19, and is executed at a predetermined calculation period T after the control unit 120 is started. The memory 123 stores an initial value SOCo of the SOC and an empirical value ε0 of the measurement error ε.

[0069] When the SOC estimation process starts, the control unit 120 determines whether the battery pack 60 is fully charged or not based on the voltage VB of the battery pack 60 (S10). If the SOC does not satisfy the above-mentioned full charge completion condition, it is determined that the battery pack 60 is not fully charged.

[0070] When it is determined that the battery is not fully charged (S10: NO), the control unit 120 executes a current integration method to estimate the first SOC of the battery pack 60. Specifically, as shown in formula (2), the control unit 120 integrates the measurement value Im of the current measured by the current measurement unit 54, and adds or subtracts this from the initial SOC value SOCo to estimate the first SOC.

[0071] Next, the control unit 120 calculates the SOC estimation error Se (S12). The SOC estimation error Se is the magnitude of an error estimated to be included in the first SOC. The SOC estimation error Se is calculated by integrating the measurement error ε0 (empirical value) according to the following formula (5). Se = ∫ε0dt / Co × 100 (5)

[0072] Next, the control unit 120 compares the magnitude of the SOC estimation error Se with the threshold value TH1 (S13). The threshold value TH1 is an arbitrary value that can be set according to the estimation accuracy required for the first SOC. If the SOC estimation error Se is smaller than the threshold value TH1 (S13: NO), the process proceeds to S11, and the first SOC is estimated again by the current integration method. The longer the integration time t, the greater the SOC estimation error Se will be due to the accumulated measurement error ε0, and the greater it will eventually be.

[0073] When the control unit 120 determines that the SOC estimation error Se is greater than the threshold value TH1 (S13: YES), it requests the vehicle ECU 30 to charge the battery pack 60 (S14).

[0074] Even while the battery pack 60 is being charged, the control unit 120 continues to estimate the first SOC using the current integration method until the battery pack 60 is fully charged, and stores the results one by one in the memory 123. When the above-mentioned full charge completion condition is met, the control unit 120 determines that the battery pack 60 is fully charged (S10: YES), and estimates the second SOC to be 100% or a value close to it using the full charge detection method (S15).

[0075] Next, the control unit 120 calculates the absolute value of the SOC difference Sx based on the following equation (6) (S16). Sx=|2nd SOC-1st SOC|...(6)

[0076] The SOC difference Sx is the difference between the second SOC and the first SOC at the time when the battery pack 60 is fully charged.

[0077] For example, when the measured current value Im=1 A, the calculation period T=0.1 s, and the full charge capacity Co=60 Ah, the SOC difference Sx is calculated as follows.

[0078] The remaining capacity at the start of the current integration method is 59.5Ah. If a full charge is detected when the calculation cycle T is repeated 1000 times (100 seconds), the remaining capacity at the time of full charge detection is 59.5+1×100 / 3600=59.528Ah. When this remaining capacity is converted to SOC, the first SOC is 59.528 / 60×100=99.21%.

[0079] Therefore, if the second SOC is estimated to be 100% in S15, the SOC difference Sx is 100-99.21=0.79% (S16).

[0080] Next, the control unit 120 corrects the first SOC to a set value of 100% or close to it, and sets the SOC estimation error Se to 0% (S17).

[0081] Next, the control unit 120 determines whether the SOC difference Sx is greater than a threshold value TH2 (S18).

[0082] If the SOC difference Sx is smaller than the threshold value TH2 (S18: NO), the process proceeds to S11, where the control unit 120 integrates the current measurement value Im of the current measurement unit 54 without correcting it, to estimate the first SOC.

[0083] When the SOC difference Sx is greater than the threshold value TH2 (S18: YES), the control unit 120 proceeds to S19 and calculates the measurement error ε included in the measured current value Im (S19).

[0084] The measurement error ε can be calculated from the following formula (7) based on the amount of change Sx1 per unit time of the SOC difference Sx. ε = Sx1 × Co / 100 (7) Sx1 is (second SOC-first SOC) / t, and is the amount of change in the SOC difference Sx per unit time.

[0085] The control unit 120 stores the calculated measurement error ε in the memory 123. After calculating the measurement error ε in S19, the control unit 120 proceeds to S11, where it corrects the current measurement value Im of the current measurement unit 54 based on the calculated measurement error ε using equation (4). Thereafter, the corrected current Ic is used to execute a current integration method, and the first SOC is estimated (S11).

[0086] The calculation and correction of the measurement error ε should not be limited to one time, but should be performed each time the SOC difference Sx exceeds the threshold value TH2. In other words, if the measurement error ε has changed by Δε from the previous correction due to a change in the state of the current measurement unit 54 or a change over time, an error equivalent to the change Δε in the measurement error ε will accumulate even if the first SOC is calculated based on the corrected current Ic.

[0087] Since the accumulated change amount Δε appears as the SOC difference Sx, it is possible to obtain the change amount Δε of the measurement error ε based on the SOC difference Sx. By correcting the measured current value Im at that time with Δε, the effect of the measurement error can be suppressed and the first SOC can be estimated with high accuracy.

[0088] 5.Effects In this configuration, the control unit 120 estimates a first SOC based on an integrated value of a measured value Im of a current flowing through the battery pack 60 (current integration method), and estimates a second SOC based on a terminal voltage VB of the battery pack 60.

[0089] The measurement value Im of the current contains a measurement error ε, and the measurement error ε is accumulated in the first SOC. On the other hand, the measurement error ε is not accumulated in the second SOC. Therefore, the control unit 120 can calculate the measurement error ε contained in the measurement value Im of the current based on the SOC difference Sx, which is the difference between the first SOC and the second SOC.

[0090] By correcting the current measurement value Im using the calculated measurement error ε as a correction value, the current measurement value Im can be brought closer to the true value, thereby improving the current measurement accuracy. The improvement in the current measurement accuracy can improve the estimation accuracy of the first SOC.

[0091] The measurement error ε of the current includes a gain error and an offset error. The error in the SOC estimated value due to the gain error is offset by charging and discharging the battery pack 60. By calculating the measurement error ε included in the measurement value Im of the current using the SOC difference Sx, the measurement value Im of the current can be corrected without directly measuring the gain error and the offset error.

[0092] In this configuration, the control unit 120 estimates the second SOC using a full charge detection method. By comparing the second SOC estimated using the full charge detection method, which does not accumulate measurement error ε, with the first SOC, the measurement error ε included in the SOC difference Sx can be obtained with high accuracy. This allows the current measurement value Im to be appropriately corrected, improving the estimation accuracy of the first SOC.

[0093] The value of the measurement error ε may vary due to changes in the surrounding environment of the current measuring unit 54 or changes over time. Even if the measurement error ε is calculated and the current measurement value Im is corrected, if the measurement error ε varies thereafter, the SOC difference Sx increases and the estimation accuracy of the first SOC decreases.

[0094] In this configuration, when the SOC difference Sx increases and exceeds the threshold value TH2 even after correcting the current measurement value Im, the control unit 120 corrects the current measurement value Im again. This makes it possible to suppress a decrease in the estimation accuracy of the first SOC even if the measurement error ε varies after correction.

[0095] In this configuration, the control unit 120 calculates the measurement error ε based on the amount of change Sx1 per unit time of the SOC difference Sx, and corrects the measured current value Im using the calculated measurement error ε as a correction value. By calculating the measurement error ε so as to offset the amount of change Sx1 per unit time, it is possible to improve the estimation accuracy of the first SOC calculated by integrating the corrected current Ic.

[0096] <Embodiment 2> In the first embodiment, in S18, when the "SOC difference Sx" exceeds the threshold value TH2, the control unit 120 corrects the measured current value Im.

[0097] A flowchart of SOC estimation in the second embodiment is shown in Fig. 9. The flowchart in Fig. 9 differs only in that S18 in the first embodiment (Fig. 8) is changed to S118. In S118, the control unit 120 calculates a change amount Sx1 per unit time from the SOC difference Sx, and compares the calculated change amount Sx1 with a threshold value TH3. If the change amount Sx1 exceeds the threshold value TH3 (S118: YES), the control unit 120 calculates a measurement error ε and corrects the measured current value Im (S19). The threshold value TH3 is set to an arbitrary value as the maximum allowable value of Sx1.

[0098] When the amount of change Sx1 per unit time in the SOC difference Sx is large, the measurement error ε included in the measured current value Im is large. When the measurement error ε is large, the measurement error ε accumulates over time, reducing the estimation accuracy of the first SOC and increasing the SOC difference Sx.

[0099] In the configuration of the second embodiment, an increase in the amount of change Sx1 per unit time can be detected and the measured current value Im can be corrected at an early stage, thereby suppressing a decrease in the estimation accuracy of the first SOC.

[0100] <Other embodiments> The present invention is not limited to the embodiments described above and in the drawings. For example, the following embodiments are also included within the technical scope of the present invention. Furthermore, in addition to the embodiments described below, various modifications can be made without departing from the spirit of the present invention.

[0101] (1) In the above embodiment, the second SOC is estimated by the full charge detection method. Alternatively, the second SOC may be estimated based on the OCV of the battery pack 60 by utilizing the SOC-OCV correlation characteristic shown in FIG.

[0102] (2) In the above embodiment, the measured current value Im is corrected by the formula (4). The correction formula for the measured current value Im is not limited to the formula (4), and may be any other formula using the measurement error ε. For example, as shown in the formula (8), the correction value may be a value obtained by multiplying the measurement error ε by a constant K that is a positive value less than 1. Ic = Im-ε × K (8)

[0103] In this way, even if abnormal values ​​unrelated to the measurement error ε are temporarily measured as the measured current value Im or the measured voltage VB due to external disturbances or the like, the influence of these abnormal values ​​on the corrected current Ic can be reduced.

[0104] (3) The secondary battery cell 62 is not limited to a lithium ion secondary battery, and may be another non-aqueous electrolyte secondary battery. The secondary battery cell 62 is not limited to a case where a plurality of cells are connected in series and parallel, but may be connected in series or may be a single cell. A capacitor may be used instead of the secondary battery cell 62. The capacitor is an example of a storage cell.

[0105] (4) In the above embodiment, the battery 50 is for an automobile, but it may be for a motorcycle. The battery 50 may be used for other moving objects such as ships, AGVs, and aircraft.

[0106] (5) In the above embodiment, the control unit 120 is provided inside the battery 50. The control unit 120 may be provided outside the battery 50. In other words, the control unit 120 provided outside the battery 50 may correct the current measurement value Im. In this case, the control unit 120 may acquire information on the current measurement value Im and the voltage VB from the current measurement unit 54 and the voltage measurement unit 110 provided inside the battery 50 via communication, calculate the measurement error ε, and correct the current measurement value Im.

[0107] (6) In the above embodiment, the configuration (first embodiment) corrects the current measurement value Im when the SOC difference Sx exceeds the threshold value TH2, and the configuration (second embodiment) corrects the current measurement value Im when the change amount Sx1 per unit time of the SOC difference Sx exceeds the threshold value TH3. The control unit 120 may correct the current measurement value Im when the SOC difference Sx exceeds the threshold value TH2 or when the change amount Sx1 per unit time exceeds the threshold value TH3.

[0108] In this way, if the amount of change Sx1 per unit time is small, the measurement error ε accumulates over time, causing the SOC difference Sx to increase, and correction is performed when the SOC difference Sx exceeds the threshold value TH2. If the amount of change Sx1 per unit time is large, correction is performed when Sx1 exceeds the threshold value TH3, even if the accumulated time is short and the SOC difference Sx is small. Therefore, correction can be performed at the appropriate time regardless of the size of Sx1.

[0109] (7) In the above embodiment, the SOC (first SOC, second SOC) of the battery pack 60 is estimated, and the measurement error ε is calculated based on the SOC difference between the first SOC and the second SOC. The remaining capacity (first remaining capacity, second remaining capacity) of the battery pack 60 may be estimated using a method similar to that used for estimating the SOC, and the measurement error ε may be calculated based on the remaining capacity difference between the first remaining capacity and the second remaining capacity.

[0110] The first remaining capacity [Ah] and the first SOC [%] are an example of a “first remaining amount of electricity” of the secondary battery cell 62 or the assembled battery 60. The second remaining capacity [Ah] and the second SOC [%] are an example of a “second remaining amount of electricity” of the secondary battery cell 62 or the assembled battery 60. The remaining capacity difference [Ah] and the SOC difference [%] are an example of a “remaining amount of electricity difference” of the secondary battery cell 62 or the assembled battery 60. [Explanation of symbols]

[0111] 10: Automobile (an example of a "vehicle") 50: Battery (an example of an "energy storage device") 54: Current measurement section 60: Battery pack 62: Secondary battery cell (an example of a "storage cell") 110: Voltage measurement section 120: Control unit (an example of a "correction device" and a "SOC estimation unit") Sx: SOC difference ε: Measurement error (an example of a "correction value") Im: Current measurement

Claims

1. A correction device for correcting a measurement value of a current of a storage cell or a battery pack, a correction device that estimates a first SOC of the storage cell or the assembled battery based on an integrated value of the measured current, estimates a second SOC of the storage cell or the assembled battery based on a voltage of the storage cell or the assembled battery, calculates an SOC difference that is a difference between the first SOC and the second SOC, calculates a correction value for the measured current based on the SOC difference, and corrects the measured current based on the calculated correction value.

2. The correction device according to claim 1 , The process of estimating the second SOC is a process of estimating an SOC by charging the power storage cell or the battery pack until the power storage cell or the battery pack is fully charged.

3. A power storage device, A correction device according to claim 1 or 2; The storage cell or the battery pack; a current measuring unit that measures a current of the storage cell or the assembled battery; an SOC estimating unit that estimates a first SOC of the power storage cell or the battery pack based on an integrated value of the corrected measured current of the power storage cell or the battery pack.

4. The power storage device according to claim 3, The correction device corrects the measured value of the current when the SOC difference exceeds a threshold value.

5. The power storage device according to claim 3 or 4, The correction device corrects the measured value of the current when a change amount of the SOC difference per unit time exceeds a threshold value.

6. The power storage device according to any one of claims 3 to 5, The correction device corrects the measured value of the current using the correction value calculated based on an amount of change per unit time of the SOC difference.

7. The vehicle power storage device according to any one of claims 3 to 6.

8. A correction device for correcting a measurement value of a current of a storage cell or a battery pack, a correction device that estimates a first remaining amount of electricity in the storage cell or the assembled battery based on an integrated value of the measurement values ​​of the current, estimates a second remaining amount of electricity in the storage cell or the assembled battery based on a voltage of the storage cell or the assembled battery, calculates a remaining amount difference that is a difference between the first remaining amount of electricity and the second remaining amount of electricity, calculates a correction value for the measurement value of the current based on the remaining amount difference, and corrects the measurement value of the current based on the calculated correction value.

9. A correction method for correcting a measurement value of a current of a storage cell or a battery pack, comprising: a correction method comprising: estimating a first SOC of the storage cell or the assembled battery based on an integrated value of the measured current values; estimating a second SOC of the storage cell or the assembled battery based on a voltage of the storage cell or the assembled battery; calculating an SOC difference which is a difference between the first SOC and the second SOC; calculating a correction value for the measured current values ​​based on the SOC difference; and correcting the measured current values ​​based on the calculated correction value.

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