Battery management device and battery management method

Abstract

The present invention accurately infers the SOC of a storage battery. A storage battery management device according to the present invention manages a storage battery that has an SOC-OCV characteristic including a plateau region where an OCV change rate, which is the absolute value of the amount of change in an OCV relative to the amount of change in the SOC, is relatively low and a plurality of change regions where the OCV change rate is relatively high. The storage battery management device comprises: an OCV acquisition unit that acquires an OCV of the storage battery; a first SOC inference unit that, when the OCV of the storage battery acquired by the OCV acquisition unit is within a first change region which is a change region and which includes an SOC of 100%, infers a first SOC on the basis of the OCV and the SOC-OCV characteristic of the storage battery; and a second SOC inference unit that, when the OCV of the storage battery is within a change region other than the first change region, infers a second SOC on the basis of the OCV and the SOC-OCV characteristic of the storage battery and on the basis of a correlation value which correlates with a deterioration state of the storage battery.

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a storage battery management device and a storage battery management method. [Background technology]

[0002] The OCV (Open Circuit Voltage) method is known as a method for estimating the SOC (State of Charge) of a storage battery (see, for example, Patent Document 1). In the OCV method, the OCV of the storage battery is acquired, and the SOC is estimated based on the acquired OCV and the correspondence relationship in the SOC-OCV characteristic curve of the storage battery. With the OCV method, for example, the period during which the SOC can be estimated is limited to the period during which the OCV of the storage battery can be acquired, or the SOC may not be accurately estimated for a storage battery having SOC-OCV characteristics that include a region (e.g., a plateau region) in which the absolute value of the change in OCV relative to the change in SOC is relatively small.

[0003] Meanwhile, the current integration method is known as another method for estimating the SOC of a storage battery. In the current integration method, the change in the capacity of the storage battery from its initial state is determined by integrating the measurement results of the current flowing through the storage battery, and the SOC is estimated based on the initial capacity, the change in the determined capacity, and the FCC (Full Charge Capacity). Unlike the OCV method, the current integration method can estimate the SOC without being restricted by the time when the OCV can be obtained or being affected by the plateau region. However, there is a risk that the SOC cannot be accurately estimated due to measurement errors in the current measurement unit that measures the current flowing through the storage battery. In response to this issue, a method that combines the current integration method and the OCV method has been known (see, for example, Patent Document 2). This method eliminates integration errors due to measurement errors in the current measurement unit by resetting the initial capacity to the SOC estimated by the OCV method each time the OCV can be measured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-81244 [Patent Document 2] Japanese Patent Publication No. 2020-60581 Summary of the Invention [Problem to be solved by the invention]

[0005] When the SOC of a storage battery is estimated using a prepared SOC-OCV characteristic, the characteristic may contain an error between the assumed state of the storage battery and the actual state (hereinafter referred to as a "storage battery state error"). Causes of the storage battery state error include, for example, individual differences between storage batteries at the time of shipping and aging of the storage battery. Therefore, when the SOC of a storage battery is estimated using the SOC-OCV characteristic, there is a problem in that the SOC cannot be estimated accurately.

[0006] This specification discloses a technique that can solve the above-mentioned problems. [Means for solving the problem]

[0007] The technology disclosed in this specification can be realized, for example, in the following forms.

[0008] (1) The battery management device disclosed in this specification is a battery management device that manages a battery having an SOC-OCV characteristic including a plateau region where the OCV change rate, which is the absolute value of the amount of change in OCV relative to the amount of change in SOC, is relatively low, and multiple change regions where the OCV change rate is relatively high. The battery management device includes: an OCV acquisition unit that acquires the OCV of the battery; a first SOC estimation unit that, when the OCV of the battery acquired by the OCV acquisition unit is within the change region and a first change region including an SOC of 100%, estimates a first SOC based on the OCV of the battery and the SOC-OCV characteristic; and a second SOC estimation unit that, when the OCV of the battery is within a change region other than the first change region, estimates a second SOC based on the OCV of the battery, the SOC-OCV characteristic, and a correlation value correlating with the deterioration state of the battery.

[0009] When the OCV of the battery is within a first change region including 100% SOC, the SOC estimated based on the SOC-OCV characteristics is highly accurate because it is less affected by errors in the battery's state. When the OCV of the battery is within another change region, the SOC estimated based on the SOC-OCV characteristics is highly affected by errors in the battery's state, so the estimation accuracy is low. Therefore, in this battery management device, when the OCV of the battery is within the first change region, a first SOC is estimated based on the OCV of the battery and the SOC-OCV characteristics. On the other hand, when the OCV of the battery is within another change region, a second SOC is estimated based on the OCV of the battery, the SOC-OCV characteristics, and a correlation value correlating with the deterioration state of the battery. Therefore, this battery management device can accurately estimate the SOC of the battery.

[0010] (2) The battery management device may further include a current measurement unit that measures a current flowing through the battery, a coulomb counting processing unit that calculates the capacity of the battery by integrating the current measured by the current measurement unit, a first reference SOC setting unit that sets the SOC estimated by the first SOC estimation unit as an SOC at a first reference time when the OCV of the battery is within the first change region, and a correlation value correction unit that corrects the correlation value on the condition that the OCV of the battery moves from the first change region to a second change region among the other change regions in which the OCV is equal to or less than a predetermined value, and the correlation value correction unit may be configured to correct the correlation value based on the SOC estimated by the second SOC estimation unit based on the OCV after moving to the second change region, the SOC at the first reference time, and an amount of change in the capacity of the battery calculated by the coulomb counting processing unit during the time when the OCV of the battery moves from the first change region to the second change region. In this battery management device, the correlation value is corrected in accordance with changes in the state of the battery due to degradation, etc. As a result, the battery management device can accurately estimate the SOC of the battery while suppressing the effects of changes in the state of the battery.

[0011] (3) The battery management device may further include a current measurement unit that measures a current flowing through the battery, a coulomb counting processing unit that calculates the capacity of the battery by integrating the current measured by the current measurement unit, a first reference SOC setting unit that sets the SOC estimated by the second SOC estimation unit as an SOC at a first reference time when the OCV of the battery is in a second change region among the other change regions in which the OCV is equal to or less than a predetermined value, and a correlation value correction unit that corrects the correlation value on the condition that the OCV of the battery moves from the second change region to the first change region, and the correlation value correction unit may be configured to correct the correlation value based on the SOC estimated by the first SOC estimation unit based on the OCV after moving to the first change region, the SOC at the first reference time, and an amount of change in the capacity of the battery calculated by the coulomb counting processing unit during the time when the OCV of the battery moves from the second change region to the first change region. In this battery management device, the correlation value is corrected in accordance with changes in the state of the battery due to degradation, etc. As a result, the battery management device can accurately estimate the SOC of the battery while suppressing the effects of changes in the state of the battery.

[0012] (4) The battery management device may further include a second reference SOC setting unit that sets the SOC estimated by the first SOC estimating unit or the second SOC estimating unit as an SOC at a second reference time, an integrated SOC estimating unit that estimates an integrated SOC of the battery based on the SOC at the second reference time, the change in capacity of the battery from the second reference time calculated by the coulomb counting processing unit, and an FCC of the battery, and an FCC correcting unit that corrects the FCC based on the corrected correlation value corrected by the correlation value correcting unit. With this battery management device, the FCC is corrected based on the correlation value that correlates with the degradation state of the battery, making it possible to accurately estimate the SOC based on the current integration method.

[0013] (5) A method for managing a storage battery disclosed herein has an SOC-OCV characteristic including a plateau region where the OCV change rate (the absolute value of the OCV change rate relative to the SOC change rate) is relatively low and multiple change regions where the OCV change rate is relatively high, and includes the steps of: acquiring the OCV of the storage battery; estimating a first SOC based on the OCV of the storage battery and the SOC-OCV characteristic if the acquired OCV of the storage battery is within the change region and a first change region including 100% SOC; and estimating a second SOC based on the OCV of the storage battery, the SOC-OCV characteristic, and a correlation value correlating with the deterioration state of the storage battery if the OCV of the storage battery is within another change region other than the first change region. This battery management method enables accurate estimation of the SOC of the storage battery.

[0014] The technology disclosed in this specification can be realized in various forms, such as a battery management device, a battery device including a battery management device and a battery, a management method thereof, a computer program that realizes the method, and a non-transitory recording medium on which the computer program is recorded. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a battery device 100 according to an embodiment. [Figure 2] FIG. 1 is an explanatory diagram illustrating the SOC-OCV characteristics of a storage battery 12. [Figure 3] FIG. 10 is an explanatory diagram showing an example of an SOC-OCV table T1. [Figure 4] FIG. 10 is an explanatory diagram showing an example of an area division-OCV table T2. [Figure 5] Flowchart showing OCV acquisition processing [Figure 6] Flowchart showing SOC reset processing DETAILED DESCRIPTION OF THE INVENTION

[0016] A. Implementation: A-1. Configuration of battery device 100: 1 is an explanatory diagram showing a schematic configuration of a battery device 100 according to this embodiment. The battery device 100 includes a battery pack 10 and a battery management device 20.

[0017] The battery pack 10 has a configuration in which a plurality of storage batteries 12 are connected in series. In this embodiment, the battery pack 10 is composed of four storage batteries 12. The battery pack 10 is connected to a load and an external power supply (not shown) via a positive terminal 42 and a negative terminal 44.

[0018] Each storage battery 12 constituting the battery pack 10 is a storage battery having an SOC (State of Charge)-OCV (Open Circuit Voltage) characteristic that includes a plateau region PR. Fig. 2 is an explanatory diagram that schematically shows the SOC-OCV of the storage battery 12. Examples of the storage battery 12 include an iron phosphate-based lithium ion battery and a titanate-based lithium ion battery.

[0019] The SOC-OCV characteristics of the storage battery 12 have a plateau region PR and a change region CR. The plateau region PR is a region where the curve representing the SOC-OCV characteristics is approximately flat, and more specifically, a region where the OCV change rate (the absolute value of the amount of change in OCV relative to the amount of change in SOC) is equal to or less than a predetermined value (e.g., 2 mV / %). The change region CR is a region (non-plateau region) where the OCV change rate exceeds a predetermined value. In the example shown in FIG. 2, the SOC-OCV characteristics of the storage battery 12 alternate between three plateau regions PR (a first plateau region PR1, a second plateau region PR2, and a third plateau region PR3) and four change regions CR. Hereinafter, the change region including an SOC of 100% will be referred to as the "top change region CR1," the change region including an SOC of 0% will be referred to as the "bottom change region CR4," and the other change regions will be referred to as "intermediate change regions CR2 and CR3."

[0020] 2, graph G1 shows the SOC-OCV characteristic when the storage battery 12 is new, and graph G2 shows the SOC-OCV characteristic when the storage battery 12 has deteriorated over time. As can be seen from these graphs G1 and G2, when the storage battery 12 deteriorates, the SOC-OCV characteristic shows that the top change region CR1 remains almost unchanged, but the other change regions CR2 to CR4 shift to the higher SOC side (see change regions CR2' to CR4'). The top change region CR1 is an example of a first change region in the claims, and the bottom change region CR4 is an example of a second change region in the claims.

[0021] The battery management device 20 is a device for managing a battery device 100 including a battery pack 10. The battery management device 20 includes a voltmeter 22, an ammeter 24, a thermometer 26, a monitoring unit 28, a line switch 40, a control unit 60, a recording unit 72, a history unit 74, and an interface (I / F) unit 76.

[0022] One voltmeter 22 is provided for each storage battery 12. Each voltmeter 22 is connected in parallel to each storage battery 12, measures the voltage of each storage battery 12, and outputs a signal indicating the measured voltage value to the monitoring unit 28. The ammeter 24 is connected in series to the battery pack 10. The ammeter 24 measures the current flowing through the battery pack 10 and outputs a signal indicating the measured current value to the monitoring unit 28. The thermometer 26 is disposed near the battery pack 10. The thermometer 26 measures the temperature of the battery pack 10 (each storage battery 12) and outputs a signal indicating the measured temperature value to the monitoring unit 28. Based on signals received from the voltmeter 22, ammeter 24, and thermometer 26, the monitoring unit 28 outputs signals indicating the voltage of each storage battery 12, the current flowing through the battery pack 10, and the temperature of the battery pack 10 (each storage battery 12) to the control unit 60. The ammeter 24 and monitoring unit 28 are an example of a current measurement unit.

[0023] The line switch 40 is installed between the battery pack 10 and the negative terminal 44. The line switch 40 is controlled to be turned on and off by the control unit 60, thereby opening and closing the connection between the battery pack 10 and the load and external power source.

[0024] The control unit 60 is configured using, for example, a CPU, a multi-core CPU, or a programmable device (such as a field programmable gate array (FPGA) or a programmable logic device (PLD)), and controls the operation of the battery management device 20. The control unit 60 has functions as an OCV acquisition unit 62, a coulomb counting processing unit 64, an integrated SOC estimation unit 66, a reset SOC estimation unit 68, an SOH correction unit 70, and an SOC update unit 71. The functions of these units will be described in conjunction with the description of the SOC estimation process below.

[0025] The recording unit 72 is configured with, for example, a ROM, a RAM, a hard disk drive (HDD), etc., and is used to store various programs and data, and as a work area and data storage area when executing various processes. For example, the recording unit 72 stores a computer program for executing the SOC estimation described below. The computer program is provided in a state stored on a computer-readable recording medium (not shown), such as a CD-ROM, a DVD-ROM, or a USB memory, and is stored in the recording unit 72 by installing it in the battery device 100.

[0026] The recording unit 72 also stores an SOC-OCV table T1 and a region division-OCV table T2. The SOC-OCV table T1 is a table used to estimate the SOC of each storage battery 12 based on the OCV method. FIG. 3 is an explanatory diagram showing an example of the SOC-OCV table T1. The SOC-OCV table T1 associates the OCV with the battery temperature and the SOC. The relationship defined in the SOC-OCV table T1 is experimentally determined in advance. As shown in FIG. 3, the SOC-OCV characteristics fluctuate with changes in battery temperature. By referring to the SOC-OCV table T1, the SOC of each storage battery 12 can be estimated based on the OCV and battery temperature of the storage battery 12. Note that although FIG. 3 shows OCVs as Vn0, Vn1, . . . Vn99, Vn100, etc., the SOC-OCV table T1 actually defines numerical values ​​for the OCV. FIG. 3 also shows a discharging SOC-OCV table used when discharging the storage battery 12 and a charging SOC-OCV table used when charging the storage battery 12.

[0027] The region division-OCV table T2 (FIG. 1) recorded in the recording unit 72 is a table used to determine which region (plateau region PR, change region CR) of the SOC-OCV characteristic the measured OCV is in (which region it belongs to). FIG. 4 is an explanatory diagram showing an example of the region division-OCV table T2. In this embodiment, the region division-OCV table T2 defines the relationship between the OCV, each region division of the OCV in the SOC-OCV characteristic, and the battery temperature. As described above, the SOC-OCV characteristic fluctuates in response to changes in battery temperature, and therefore each region division in the SOC-OCV characteristic fluctuates in accordance with the fluctuation of the SOC-OCV characteristic. Note that although FIG. 4 shows OCV as Vo0, Vo1, etc., the region division-OCV table T2 actually defines numerical values ​​of the OCV.

[0028] The history unit 74 is configured with, for example, a ROM, a RAM, a hard disk drive (HDD), etc., and records various histories related to the battery device 100. Examples of such histories include the OCV of the storage battery 12 and the processing details of the SOC processing described below. The interface unit 76 and the like communicate with other devices via a wired or wireless connection. For example, the history recorded in the history unit 74 is updated by communication with other devices via the interface unit 76.

[0029] A-2. SOC estimation process: The SOC estimation process executed by the battery management device 20 in the battery device 100 of this embodiment will be described. In this embodiment, the SOC estimation process estimates the SOC of each storage battery 12 that constitutes the battery pack 10 individually. In the following explanation, one storage battery 12 will be described. The SOC estimation process is started automatically when the battery management device 20 is started, or in response to an instruction from an administrator, for example.

[0030] A-2-1. Estimation of integrated SOC(t) based on current integration method: In the battery device 100 of this embodiment, a process is executed to estimate the SOC based on the current integration method (hereinafter referred to as "integrated SOC(t)"). Specifically, the coulomb counting processing unit 64 (FIG. 1) of the storage battery management device 20 calculates the capacity of each storage battery 12 by integrating the current measured by the ammeter 24 and the monitoring unit 28. Next, the integrated SOC estimating unit 66 of the storage battery management device 20 estimates the integrated SOC(t) of the storage battery based on the SOC(0) at the reference time (hereinafter referred to as "integrated reference time SOC(0)"), the amount of change Q(t) (amount of charge transfer) in the capacity of the storage battery 12 from the reference time calculated by the coulomb counting processing unit 64, and the FCC of the storage battery 12. The integrated SOC(t) can be expressed by the following equation (1): Accumulated SOC(t)=Accumulated standard SOC(0)+[Q(t) / FCC]...(1) At the start of the SOC estimation process, the reference time is, for example, the time when the battery device 100 is shipped, and thereafter, the reference time is the time when the reference SOC update process is executed in the SOC reset process described below. Note that the process of estimating the integrated SOC(t) is executed continuously during the SOC estimation process. The integrated SOC estimator 66 is an example of a third estimator in the claims, and the integrated reference time SOC(0) is an example of a second reference time SOC in the claims.

[0031] A-2-2.OCV acquisition process: 5 is a flowchart showing the OCV acquisition process executed in the battery device 100 of this embodiment. When the charge or discharge current to or from the storage battery 12 falls below a predetermined threshold or the line switch 40 transitions from a closed state to an open state, the control unit 60 determines that the storage battery 12 is in a stopped state, and the OCV acquisition unit 62 (FIG. 1) of the storage battery management device 20 executes the OCV acquisition process (FIG. 5) for the storage battery 12. Specifically, the OCV acquisition unit 62 determines whether the OCV acquisition timing has arrived, and if it determines that the OCV acquisition timing has arrived, executes the OCV acquisition process (S110 to S140). In this embodiment, the OCV acquisition timing for the storage battery 12 is the timing at which it is detected that the polarization of the storage battery 12 has been resolved to the extent that the OCV of the storage battery 12 can be acquired and the battery voltage has stabilized.

[0032] 5, the OCV acquisition unit 62 again determines whether the line switch 40 is in the closed state (S110). The line switch 40 being in the closed state means that the storage battery 12 (battery pack 10) is electrically connected to a load, and the line switch 40 being in the open state means that the storage battery 12 is in an unloaded state, that is, not electrically connected to a load (not shown).

[0033] When the OCV acquisition unit 62 determines that the line switch 40 is in the closed state (S110: YES), it determines whether the stopped state in which no current flows through the storage battery 12 has continued for a predetermined time or longer (S120). The control unit 60 constantly determines whether or not a current is flowing through the storage battery 12 based on a signal input from the monitoring unit 28, and stores the determination result as a history associated with the elapsed time. Based on this history, the OCV acquisition unit 62 can determine whether or not the stopped state of the storage battery 12 has continued for a predetermined time or longer. Note that if the current flowing through the storage battery 12 is equal to or less than a reference current value (a value at which the current can be considered to be approximately zero), the OCV acquisition unit 62 determines that the current state of the storage battery 12 is in the stopped state. Measurement of the current through the storage battery 12 is continuously performed during the SOC estimation process.

[0034] If the OCV acquisition unit 62 determines that the stopped state of the storage battery 12 has not continued for a predetermined time or longer (S120: NO), the process returns to S110. On the other hand, if the OCV acquisition unit 62 determines that the stopped state of the storage battery 12 has continued for a predetermined time or longer (S120: YES), the OCV acquisition unit 62 determines whether the rate of change in the battery voltage of the storage battery 12 within the predetermined time is less than a predetermined reference rate (a value at which the battery voltage of the storage battery 12 is considered to be generally stable) based on a signal input from the monitoring unit 28 (S130). Note that measurement of the voltage of the storage battery 12 is continuously performed during the SOC estimation process. Furthermore, if it determines that the line switch 40 is in an open state (S110: NO), the OCV acquisition unit 62 proceeds to S130 without performing the process of S120.

[0035] If the OCV acquisition unit 62 determines that the rate of change in the battery voltage of the storage battery 12 within the predetermined time is equal to or greater than the reference rate (S130: NO), the process returns to S110. On the other hand, if the OCV acquisition unit 62 determines that the rate of change in the battery voltage of the storage battery 12 within the predetermined time is less than the reference rate (S130: YES), the OCV acquisition unit 62 records the measured battery voltage of the storage battery 12 in the history unit 74 as the OCV of the storage battery 12 (S140).

[0036] Next, the control unit 60 determines whether the OCV of the storage battery 12 acquired at the current OCV acquisition timing (hereinafter referred to as "current OCV") is within the change region CR.

[0037] Specifically, the control unit 60 determines the current state (charge state, discharge state) of the storage battery 12 immediately before the OCV acquisition timing (S150). For example, the signal output from the ammeter 24 is a signal corresponding to the presence or absence and direction of current flowing through the storage battery 12 (a signal corresponding to the level of the voltage across a detection resistor (not shown) provided in the ammeter 24). The control unit 60 determines the current state (charge state, discharge state) of the storage battery 12 based on the level of the signal output from the ammeter 24 and an inversion of the level of that signal.

[0038] If it is determined that the storage battery 12 is in a discharging state (S150: discharging), the discharge SOC-OCV table is referenced (S160) to determine whether the current OCV is within the change region CR of the discharge SOC-OCV characteristic (S180). On the other hand, if it is determined that the storage battery 12 is in a charging state (S150: charging), the charge SOC-OCV table is referenced (S170) to determine whether the current OCV is within the change region CR of the charge SOC-OCV characteristic (S180).

[0039] If it is determined that the current OCV is within the change region CR of the SOC-OCV characteristic for discharge or the SOC-OCV characteristic for charge (S180: YES), the control unit 60 proceeds to the SOC reset process (S190). On the other hand, if it is determined that the current OCV is not within the change region CR (S180: NO), the control unit 60 returns to S110 without executing the SOC reset process.

[0040] A-2-3.SOC reset process: 6 is a flowchart showing the SOC reset process executed in the battery device 100 of this embodiment. The SOC reset process is a process for estimating reset SOCs (first reset SOC, second reset SOC, third reset SOC) based on the OCV method and resetting (updating) the integrated SOC(t) estimated by the integrated SOC estimator 66 to the reset SOCs.

[0041] In the SOC reset process, the reset SOC used in the SOC reset process differs depending on which change region CR (top change region CR1, middle change region CR2, CR3, bottom change region CR4) the current OCV is in in the SOC-OCV characteristics.

[0042] A-2-3-1. If the current OCV is within the top change region CR1: If it is determined that the current OCV is within the highest change region CR1 (S210: CR1), the reset SOC estimator 68 estimates a first reset SOC based on the current OCV of the storage battery 12 and the SOC-OCV characteristic (S220). At this time, the reset SOC estimator 68 functions as the first SOC estimator in the claims. In the example of FIG. 2, if the current OCV is within the highest change region CR1 of the SOC-OCV characteristic, the reset SOC estimator 68 references the SOC-OCV table T1 and estimates the SOC corresponding to the current OCV ("Sr1" in FIG. 2) as the first reset SOC. Note that the SOH, which will be described later, is not used in this first reset SOC estimation process.

[0043] Next, the control unit 60 determines whether the temperature of each storage battery 12 is within a predetermined temperature range based on the signal indicating the temperature from the monitoring unit 28 (S230). The predetermined temperature range is, for example, a temperature range (e.g., 20°C or higher and 45°C or lower) in which a correlation between the degradation state of the storage battery 12 and the SOH (State of Health) of the storage battery 12 is normally established. If it is determined that the temperature of the storage battery 12 is within the predetermined temperature range (S230: YES), the reset SOC estimated by the reset SOC estimating unit 68 can be used to normally correct the SOH.

[0044] Therefore, the SOH correction unit 70 corrects the SOH on the condition that the OCV of the storage battery 12 has moved from the lowest change region CR4 to the highest change region CR1. The SOH is a value (parameter) that correlates with the degradation state of the storage battery 12.

[0045] Specifically, the control unit 60 determines whether the SOC set in the previous SOH correction process (hereinafter referred to as the "corrected reference SOC (REF)") is the SOC estimated by the reset SOC estimator 68 when the OCV was in the lowest change region CR4 (hereinafter referred to as the "second reset SOC" ("Sr2" in FIG. 2)) (S240). If the corrected reference SOC (REF) is determined to be the second reset SOC (S240: YES), this means that the OCV of the storage battery 12 has moved from the lowest change region CR4 to the highest change region CR1.

[0046] Therefore, the SOH correction unit 70 corrects the SOH based on the value Sr1 of the first reset SOC, the value Sr2 of the corrected reference time SOC(REF) (second reset SOC), and the amount of change Q1(t) in the capacity of the storage battery 12 calculated by the coulomb counting processing unit 64 while the OCV of the storage battery 12 moves from the lowest change region CR4 to the highest change region CR1 (S250, see arrow P1 in Figure 2). For example, the corrected SOH can be calculated using the following equations (2) and (3). This time, FCC = Q1(t) / [(Sr1)-(Sr2)] (2) Corrected SOH = Current FCC / New FCC (3) When the OCV of the storage battery is within the uppermost change region CR1 or the lowermost change region CR4, the SOC estimated based on the SOC-OCV characteristics is relatively little affected by the state error of the storage battery 12. Therefore, the SOH can be accurately corrected using the first reset SOC and the second reset SOC. The corrected reference-time SOC (REF) in this case is an example of the first reference-time SOC in the claims, and the control unit 60 also functions as a first reference SOC setting unit in the claims.

[0047] The FCC correction unit 63 corrects the FCC in equation (1) used in the above-described process of estimating the integrated SOC(t) to the current FCC calculated by equation (2). This makes it possible to perform the process of estimating the integrated SOC(t) while suppressing the influence of fluctuations due to deterioration of the storage battery 12.

[0048] On the other hand, if it is determined that the corrected reference time SOC(REF) is not the second reset SOC (S240: NO), this means that the storage battery 12 has been repeatedly charged and discharged without the OCV of the storage battery 12 reaching the lowest change region CR4, and the process of estimating the integrated SOC(t) has continued. In other words, the amount of change Q1(t) in the capacity of the storage battery 12 from the time the previous SOH correction process was performed to the present time is relatively small. Therefore, the control unit 60 proceeds to S260 without performing the SOH correction process (S250).

[0049] Furthermore, if it is determined that the temperature of the storage battery 12 is outside the predetermined temperature range (S230: NO), it is difficult to correctly correct the SOH. Therefore, the control unit 60 proceeds to S290 without executing the SOH correction process (S250). If the temperature of the storage battery 12 is outside the predetermined temperature range, the corrected reference time SOC(REF) is not updated. However, as described below, the integrated reference time SOC(0) is updated.

[0050] In S260, the SOC update unit 71 (FIG. 1) of the control unit 60 executes a correction reference SOC update process. The correction reference SOC update process updates the above-described correction reference time SOC (REF) to a reset SOC (first reset SOC, second reset SOC). If the current OCV is within the highest change region CR1, the correction reference time SOC (REF) is updated to the first reset SOC (Sr1). In addition, the change amounts Q1(t) and Q2(t) in the capacity of the storage battery 12 calculated by the coulomb counting processing unit 64 in equations (2) and (5) used in the current FCC estimation process are reset to zero.

[0051] Next, the control unit 60 determines whether the current SOH (the corrected SOH) is equal to or less than a specified value (S270). The specified value is, for example, a threshold value for determining whether the storage battery 12 can be normally charged or discharged. An SOH greater than the specified value indicates that the storage battery 12 can be normally charged or discharged, while an SOH equal to or less than the specified value indicates, for example, that the storage battery 12 has deteriorated and is no longer able to be normally charged or discharged. If it is determined that the SOH is equal to or less than the specified value (S270: YES), the control unit 60 executes a notification process (S280). Specifically, the control unit 60 notifies an external device of an abnormality, such as deterioration of the storage battery 12, via the interface unit 76. On the other hand, if it is determined that the SOH is greater than the specified value (S270: NO), the control unit 60 proceeds to S290 without executing the notification process (S280).

[0052] In S290, the SOC update unit 71 updates the current integrated SOC(t) and the integrated reference SOC(0) estimated in the integrated SOC(t) estimation process described above to a reset SOC. If the current OCV is within the highest change region CR1, the current integrated SOC(t) and the integrated reference SOC(0) are updated to a first reset SOC (Sr1). In addition, the change in capacity Q(t) of the storage battery 12 from the reference time calculated by the coulomb counting processor 64 in equation (1) used in the integrated SOC(t) estimation process is reset to zero. Then, the SOC reset process ends.

[0053] A-2-3-2. If the current OCV is within the lowest change region CR4: If it is determined that the current OCV is within the lowest change region CR4 (S210: CR4), the reset SOC estimator 68 estimates a second reset SOC based on the current OCV, SOC-OCV characteristics, and SOH of the storage battery 12 (S300). If the current OCV is within a change region CR other than the highest change region CR1 (CR2 to CR4), the SOC can be calculated, for example, by the following equation (4). SOC = SOCint / SOH (4) Note that SOCint is the SOC corresponding to the current OCV in the SOC-OCV table T1.

[0054] By dividing the SOCint estimated by the OCV method by the SOH, it is possible to estimate the SOC while suppressing the influence of state errors of the storage battery 12, even if the current OCV is within a change region CR (CR2 to CR4) other than the top change region CR1. In this case, the reset SOC estimator 68 functions as a second SOC estimator in the claims. In the example of FIG. 2, if the current OCV is within the bottom change region CR4 of the SOC-OCV characteristic, the reset SOC estimator 68 refers to the SOC-OCV table T1 and estimates the SOC obtained by dividing the SOCint corresponding to the current OCV by the SOH ("Sr2" in FIG. 2) as the second reset SOC.

[0055] If it is determined that the temperature of the storage battery 12 is within the predetermined temperature range (S310: YES), the SOH correction unit 70 corrects the SOH on the condition that the OCV of the storage battery 12 has moved from the uppermost change region CR1 to the lowermost change region CR4.

[0056] Specifically, the control unit 60 determines whether the corrected reference time SOC (REF) set in the previous SOH correction process is the first reset SOC (Sr1) estimated by the reset SOC estimator 68 when the OCV was within the highest change region CR1 (S320). If the corrected reference time SOC (REF) is determined to be the first reset SOC (Sr1) (S320: YES), this means that the OCV of the storage battery 12 has moved from the highest change region CR1 to the lowest change region CR4.

[0057] Therefore, the SOH correction unit 70 executes a SOH correction process (S250). Specifically, the SOH correction unit 70 corrects the SOH based on the value Sr2 of the second reset SOC, the value Sr1 of the correction reference time SOC(REF) (first reset SOC), and the amount of change Q2(t) in the capacity of the storage battery 12 calculated by the coulomb counting processing unit 64 while the OCV of the storage battery 12 moves from the uppermost change region CR1 to the lowermost change region CR4 (S250, see arrow P2 in FIG. 2). For example, the corrected SOH can be calculated using the following equations (3) and (5): This time, FCC = Q2(t) / [(Sr2)-(Sr1)] (5) Corrected SOH = Current FCC / New FCC (3) The FCC correction unit 63 corrects the FCC in equation (1) used in the above-described process of estimating the integrated SOC(t) to the current FCC calculated by equation (3). This makes it possible to perform the process of estimating the integrated SOC(t) while suppressing the influence of fluctuations due to deterioration of the storage battery 12.

[0058] On the other hand, if it is determined that the corrected reference time SOC(REF) is not the first reset SOC (S320: NO), the control unit 60 proceeds to S260 without executing the SOH correction process (S250). Also, if it is determined that the temperature of the storage battery 12 is outside the predetermined temperature range (S310: NO), the control unit 60 proceeds to S290 without executing the SOH correction process (S250). If the temperature of the storage battery 12 is outside the predetermined temperature range, the corrected reference time SOC is not updated, and the integrated reference time SOC(0) is updated.

[0059] In S260, if the current OCV is within the lowest change region CR4, the corrected reference time SOC(REF) is updated to a second reset SOC(Sr2). Furthermore, the change amounts Q1(t) and Q2(t) in the capacity of the storage battery 12 calculated by the coulomb counting processor 64 in equations (2) and (5) used in the current FCC estimation process are reset to zero. Furthermore, in S290, the current integrated SOC(t) and the integrated reference time SOC(0) are updated to a second reset SOC(Sr2). Furthermore, the change amount Q(t) in the capacity of the storage battery 12 from the reference time calculated by the coulomb counting processor 64 in equation (1) used in the integrated SOC(t) estimation process is reset to zero.

[0060] A-2-3-3. If the OCV is within the intermediate change range CR2 or CR3: If it is determined that the current OCV is within the intermediate change region CR2, CR3 (S210: CR2,3), the reset SOC estimator 68 estimates a third reset SOC ("Sr3" in FIG. 2) based on the current OCV, SOC-OCV characteristic, and SOH of the storage battery 12 (S400). Specifically, the third reset SOC can be calculated using the above-mentioned formula (4) used when the current OCV is within the lowest change region CR4, similar to the process of S300. The control unit 60 then proceeds to S290. Also, in S290, the current integrated SOC(t) and the integrated reference time SOC(0) are updated to the third reset SOC. As described above, when the OCV of the storage battery 12 is within the intermediate change region CR2, CR3, the SOC estimated based on the SOC-OCV characteristic is relatively significantly affected by the state error of the storage battery 12. Therefore, when the OCV of the storage battery 12 is within the intermediate change ranges CR2 and CR3, the SOH is not corrected, and the corrected reference time SOC(REF) is not updated.

[0061] A-3. Effects of the embodiment: As explained above, when the OCV of the storage battery 12 is within the highest change region CR1, which includes an SOC of 100%, the SOC estimated based on the SOC-OCV characteristics is less affected by errors in the state of the storage battery (for example, differences between individual storage batteries 12 at the time of shipment and changes in the storage battery 12 over time), whereas when the OCV of the storage battery 12 is within other change regions CR2 to CR4, the SOC estimated based on the SOC-OCV characteristics is more affected by errors in the state of the storage battery (see FIG. 2).

[0062] Therefore, in the battery management device 20 according to this embodiment, when the OCV of the storage battery 12 is within the highest change region CR1 (S210:CR1 in FIG. 6), a first SOC (first reset SOC) is estimated (S220) based on the OCV of the storage battery 12 and the SOC-OCV characteristics. On the other hand, when the OCV of the storage battery 12 is within another change region CR2 to CR4 (S210:CR2 to CR4), a second SOC (second reset SOC, third reset SOC) is estimated (S300, S400) based on the OCV of the storage battery 12, the SOC-OCV characteristics, and the SOH, which correlates with the degradation state of the storage battery 12. Therefore, according to this embodiment, the SOC of the storage battery 12 can be accurately estimated while suppressing a decrease in the estimation accuracy of the SOC due to an error in the state of the storage battery 12.

[0063] B. Variations: The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into various forms without departing from the spirit thereof, for example, the following modifications are also possible.

[0064] The configuration of the battery device 100 in the above-described embodiment is merely an example and can be modified in various ways. For example, in each of the above-described embodiments, the number of storage batteries 12 constituting the battery pack 10 can be changed as desired. Also, in the above-described embodiments, a thermometer 26 may be provided for each storage battery 12. Note that the thermometer 26 may be omitted.

[0065] In the above embodiment, an iron phosphate lithium-ion battery or the like is exemplified as the storage battery. However, other secondary batteries or primary batteries may be used as long as they have SOC-OCV characteristics including a first region where the OCV rate is equal to or less than a predetermined value and a change region where the OCV change rate exceeds the predetermined value. The predetermined value is not limited to 2 mV / % and can be set arbitrarily. The number of change regions CR and plateau regions PR can be arbitrarily changed. In the above embodiment, the lowest change region CR4 is exemplified as the second change region. However, the second change region may be any change region where the OCV is equal to or less than a predetermined value. For example, in FIG. 2, the second change region may include the intermediate change region CR3 or a portion of the intermediate change region CR3 in addition to the lowest change region CR4.

[0066] In the above embodiments, the contents of the SOC-OCV table T1 and the area division-OCV table T2 are merely examples and can be modified in various ways. It is not necessary for at least one of the SOC-OCV table T1 and the area division-OCV table T2 to be recorded in the recording unit 72. In each of the above embodiments, at least one of the functional units of the control unit 60 may be omitted.

[0067] The SOC estimation process in the above embodiment is merely an example and can be modified in various ways. For example, in the above embodiment, the SOC estimation process estimates the SOC of each storage battery 12 constituting the battery pack 10 individually, but the SOC may be estimated for the entire battery pack 10. In the OCV acquisition process in the above embodiment, a method is used in which the battery voltage of the storage battery 12 in a stable state is acquired as the OCV (S110 to S130 in FIG. 6). However, any known method may be used, such as a method of estimating the OCV based on changes in the internal resistance or battery voltage of the storage battery 12.

[0068] In the process of estimating the accumulated SOC(t) in the above embodiment, the FCC may be a fixed value, and the accumulated SOC(t) may be estimated based on the SOC(0) at the reference time and the change Q(t) in the capacity of the storage battery 12 from the reference time calculated by the coulomb counting processing unit 64. Furthermore, in the SOC estimation process in the above embodiment, the reference SOC update process (S260) does not have to be executed. Even with such a configuration, the SOC of the storage battery 12 can be accurately estimated by correcting the accumulated SOC(t).

[0069] In the above embodiment, the SOH is used as an example of the correlation value, but the correlation value is not limited to this, and other values ​​(parameters) that correlate with the deterioration state of the storage battery 12 (battery pack 10) may be used.

[0070] In the above embodiment, the condition for executing the SOH correction process (S250) is that the storage battery 12 is within a predetermined temperature range, but other conditions (e.g., environmental conditions such as humidity, or electrical conditions of the storage battery 12 (overcurrent, overvoltage, etc.)) may also be used. [Explanation of symbols]

[0071] 10: Battery pack 12: Storage battery 20: Storage battery management device 22: Voltmeter 24: Ammeter 26: Thermometer 28: Monitoring unit 40: Line switch 42: Positive terminal 44: Negative terminal 60: Control unit 62: OCV acquisition unit 63: FCC correction unit 64: Coulomb counting processing unit 66: Integrated SOC estimation unit 68: Reset SOC estimation unit 70: SOH correction unit 71: SOC update unit 72: Recording unit 74: History unit 76: Interface unit 100: Battery device CR: Change region PR: Plateau region

Claims

1. A battery management device that manages a battery having an SOC-OCV characteristic including a plateau region in which an OCV change rate, which is an absolute value of an amount of change in OCV relative to an amount of change in SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, an OCV acquisition unit that acquires an OCV of the storage battery; a first SOC estimation unit that estimates a first SOC based on the OCV of the storage battery and the SOC-OCV characteristics when the OCV of the storage battery acquired by the OCV acquisition unit is within the change region and a first change region including an SOC of 100%; a second SOC estimation unit that, when an OCV of the storage battery is within another change region other than the first change region, estimates a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value that correlates with a degradation state of the storage battery; a current measurement unit that measures a current flowing through the storage battery; a coulomb counting processing unit that calculates the capacity of the storage battery by integrating the current measured by the current measuring unit; a first reference SOC setting unit that sets the SOC estimated by the first SOC estimation unit as an SOC at a first reference time when an OCV of the storage battery is within the first change region; a correlation value correcting unit that corrects the correlation value on the condition that the OCV of the storage battery moves from the first change region to a second change region among the other change regions in which the OCV is equal to or less than a predetermined value, the correlation value correction unit corrects the correlation value based on an SOC estimated by the second SOC estimation unit based on the OCV after the OCV has moved to the second change region, an SOC at the first reference time, and an amount of change in capacity of the storage battery calculated by the coulomb counting processing unit during a period until the OCV of the storage battery moves from the first change region to the second change region. Storage battery management device.

2. A battery management device that manages a battery having SOC-OCV characteristics including a plateau region in which an OCV change rate, which is an absolute value of an amount of change in OCV relative to an amount of change in SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, an OCV acquisition unit that acquires an OCV of the storage battery; a first SOC estimation unit that estimates a first SOC based on the OCV of the storage battery and the SOC-OCV characteristics when the OCV of the storage battery acquired by the OCV acquisition unit is within the change region and a first change region including an SOC of 100%; a second SOC estimation unit that, when an OCV of the storage battery is within another change region other than the first change region, estimates a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value that correlates with a degradation state of the storage battery; a current measurement unit that measures a current flowing through the storage battery; a coulomb counting processing unit that calculates the capacity of the storage battery by integrating the current measured by the current measuring unit; a first reference SOC setting unit that sets the SOC estimated by the second SOC estimating unit as an SOC at a first reference time when the OCV of the storage battery is within a second change region among the other change regions, the second change region being a second change region in which the OCV is equal to or less than a predetermined value; a correlation value corrector that corrects the correlation value on condition that the OCV of the storage battery moves from the second change region to the first change region, the correlation value correction unit corrects the correlation value based on an SOC estimated by the first SOC estimation unit based on the OCV after the OCV has moved to the first change region, an SOC at the first reference time, and an amount of change in capacity of the storage battery calculated by the coulomb counting processing unit during a period until the OCV of the storage battery moves from the second change region to the first change region. Storage battery management device.

3. A battery management device according to claim 1 or claim 2, further comprising: a second reference SOC setting unit that sets the SOC estimated by the first SOC estimation unit or the second SOC estimation unit as an SOC at a second reference time; an integrated SOC estimation unit that estimates an integrated SOC of the storage battery based on the SOC at the second reference time, the amount of change in capacity of the storage battery from the second reference time calculated by the coulomb counting processing unit, and an FCC of the storage battery; an FCC correction unit that corrects the FCC based on the correlation value corrected by the correlation value correction unit, Storage battery management device.

4. A method for managing a storage battery having an SOC-OCV characteristic including a plateau region in which an OCV change rate, which is an absolute value of an amount of change in OCV relative to an amount of change in SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, obtaining an OCV of the storage battery; When the acquired OCV of the storage battery is within the change region and a first change region including an SOC of 100%, estimating a first SOC based on the OCV of the storage battery and the SOC-OCV characteristics; When the OCV of the storage battery is within another change region other than the first change region, estimating a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value correlating with a deterioration state of the storage battery; a current measuring step of measuring a current flowing through the storage battery; a coulomb counting step of calculating the capacity of the storage battery by integrating the current measured in the current measuring step; a first reference SOC setting step of setting the SOC estimated in the first SOC estimating step as a first reference SOC when the OCV of the storage battery is within the first change region; a correlation value correcting step of correcting the correlation value on the condition that the OCV of the storage battery moves from the first change region to a second change region among the other change regions in which the OCV is equal to or less than a predetermined value, In the correlation value correcting step, the correlation value is corrected based on an SOC estimated in a step of estimating the second SOC based on the OCV after the OCV has moved to the second change region, an SOC at the first reference time, and an amount of change in capacity of the storage battery calculated in the coulomb counting step during a period until the OCV of the storage battery moves from the first change region to the second change region. How to manage storage batteries.

5. A management method for a storage battery having SOC-OCV characteristics including a plateau region in which an OCV change rate, which is an absolute value of an amount of change in OCV relative to an amount of change in SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, comprising: obtaining an OCV of the storage battery; When the acquired OCV of the storage battery is within the change region and a first change region including an SOC of 100%, estimating a first SOC based on the OCV of the storage battery and the SOC-OCV characteristics; When the OCV of the storage battery is within another change region other than the first change region, estimating a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value correlating with a deterioration state of the storage battery; a current measuring step of measuring a current flowing through the storage battery; a coulomb counting step of calculating the capacity of the storage battery by integrating the current measured in the current measuring step; a first reference SOC setting step of setting the SOC estimated in the second SOC estimating step as an SOC at a first reference time when the OCV of the storage battery is within a second change region among the other change regions, the second change region being a region in which the OCV is equal to or less than a predetermined value; a correlation value correcting step of correcting the correlation value on condition that the OCV of the storage battery moves from the second change region to the first change region, the correlation value correcting step corrects the correlation value based on an SOC estimated in a step of estimating the first SOC based on the OCV after the OCV has moved to the first change region, an SOC at the first reference time, and an amount of change in capacity of the storage battery calculated in the coulomb counting step during a period until the OCV of the storage battery moves from the second change region to the first change region. How to manage storage batteries.

Images