Storage battery management device and storage battery management method

Abstract

The SOC of a storage battery is estimated with high precision. A battery management device manages a battery having SOC-OCV characteristics including a flat region in which an OCV change rate, which is an absolute value of an amount of change in OCV with respect 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. A storage battery management device is provided with: an OCV acquisition unit that acquires the OCV of a storage battery; a first SOC estimation unit that estimates a first SOC on the basis of the OCV of the storage battery and SOC-OCV characteristics when the OCV of the storage battery acquired by the OCV acquisition unit is within a change region and the change region is a first change region including SOC 100%; and a second SOC estimation unit that estimates a second SOC on the basis of the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value relating to the deterioration state of the storage battery when the OCV of the storage battery is within a change region other than the first change region.

Description

Technical Field

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

[0002] As a method for estimating the SOC (State of Charge) of a battery, the OCV (Open Circuit Voltage) method is known (for example, refer to Patent Document 1). In the OCV method, the OCV of the battery is obtained, and the SOC is estimated based on the correspondence between the obtained OCV and the SOC-OCV characteristic curve of the battery. In 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 battery can be obtained, or in a battery having an SOC-OCV characteristic including an area where the absolute value of the change in OCV relative to the change in SOC is relatively small (for example, a flat area), it may be impossible to estimate the SOC with high accuracy.

[0003] On the other hand, as another method for estimating the SOC of a battery, a current accumulation method is known. In the current accumulation method, the change in the capacity of the battery since the initial period is determined by accumulating the measurement results of the current flowing through the battery, and the SOC is estimated based on the initial capacity, the determined change in capacity, and the FCC (Full Charge Capacity). In the current accumulation method, unlike OCV, the SOC can be estimated without being limited by the period during which the OCV can be obtained or the influence of the flat area, but it is possible that the SOC cannot be estimated with high accuracy due to the measurement error of the current measuring unit that measures the current flowing through the battery. In contrast, there is a method that uses the current accumulation method and the OCV method at the same time (for example, refer to Patent Document 2). For this method, the following method is known: at each timing when the OCV can be measured, the initial capacity is reset to the SOC estimated by the OCV method, thereby eliminating the accumulation error caused by the measurement error of the current measuring unit.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-81244

[0007] Patent Document 2: Japanese Patent Application Publication No. 2020-60581 Summary of the invention

[0008] Problems to be solved by the invention

[0009] When the SOC of a battery is estimated using a pre-prepared SOC-OCV characteristic, the characteristic may contain an error between the assumed state of the battery and the actual state (hereinafter referred to as "battery state error"). The causes of the battery state error include, for example, individual differences in batteries at the time of shipment and changes in batteries over time. Therefore, the following problem arises: when the SOC-OCV characteristic is used to estimate the SOC of a battery, the SOC cannot be estimated with high accuracy.

[0010] This specification discloses a technology that can solve the above-mentioned problems.

[0011] Means for solving problems

[0012] The technology disclosed in this specification can be implemented as the following aspects, for example.

[0013] (1) A battery management device disclosed in the present specification manages a battery having the following SOC-OCV characteristics, wherein the SOC-OCV characteristics include a flat region in which the amount of change in OCV relative to the absolute value of the amount of change in SOC, i.e., the OCV change rate, is relatively low, and a plurality of change regions in which the OCV change rates are relatively high, wherein the battery management device comprises: an OCV acquisition unit that acquires the OCV of the battery; a first SOC estimation unit that estimates a first SOC based on the OCV of the battery and the SOC-OCV characteristics when the OCV of the battery acquired by the OCV acquisition unit is within a first change region including SOC 100% as the change region; and a second SOC estimation unit that estimates a second SOC based on the OCV of the battery, the SOC-OCV characteristics, and a correlation value related to the degradation state of the battery when the OCV of the battery is within another of the change regions other than the first change region.

[0014] When the OCV of the battery is within the first variation region including SOC 100%, the SOC estimated based on the SOC-OCV characteristic is less affected by the state error of the battery, and therefore the estimation accuracy is high. When the OCV of the battery is within other variation regions, the SOC estimated based on the SOC-OCV characteristic is greatly affected by the state error of the battery, and therefore the estimation accuracy is low. Therefore, in the present battery management device, when the OCV of the battery is within the first variation region, the first SOC is estimated based on the OCV and SOC-OCV characteristics of the battery. On the other hand, when the OCV of the battery is within other variation regions, the second SOC is estimated based on the OCV of the battery, the SOC-OCV characteristics, and the correlation value related to the degradation state of the battery. Therefore, according to the present battery management device, the SOC of the battery can be estimated with high accuracy.

[0015] (2) In the above-mentioned battery management device, the following structure can be adopted, which also includes: a current measuring unit that measures the 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 measuring unit; a first reference SOC setting unit that sets the SOC estimated by the first SOC estimating unit as the 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 based on the condition that the OCV of the battery moves from the first change region to a second change region in which the OCV of the other change regions is less than a specified value, the correlation value correction unit corrects the correlation value based on the SOC estimated by the second SOC estimating unit based on the OCV after moving to the second change region, the SOC at the first reference time, and the amount of change in the capacity of the battery calculated by the coulomb counting processing unit during the period from the first change region to the second change region when the OCV of the battery moves.

[0016] (3) In the above-mentioned battery management device, the following structure can be adopted, which also includes: a current measuring unit that measures the current flowing through the battery device; a coulomb counting processing unit that calculates the capacity of the 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 the SOC at a first reference time when the OCV of the battery is in a second change region in which the OCV is less than a specified value among other change regions; and a correlation value correction unit that corrects the correlation value based on the condition that the OCV of the battery moves from the second change region to the first change region, the correlation value correction unit corrects the correlation value based on the SOC estimated by the first SOC estimating unit based on the OCV after moving to the first change region, the SOC at the first reference time, and the amount of change in the capacity of the battery calculated by the coulomb counting processing unit during the period from the second change region to the first change region when the OCV of the battery moves from the second change region to the first change region.

[0017] (4) In the above-mentioned battery management device, the following structure can be adopted, which also has: a second reference SOC setting unit, which sets the SOC estimated by the first SOC estimation unit or the second SOC estimation unit as the SOC at a second reference time; a cumulative SOC estimation unit, which estimates the cumulative SOC of the battery based on the SOC at the second reference time, the change in the capacity of the battery from the second reference time calculated by the coulomb counting processing unit, and the FCC of the battery; and an FCC correction unit, which corrects the FCC based on the corrected correlation value corrected by the correlation value correction unit.

[0018] (5) The battery management method disclosed in the present specification is a battery management method having the following SOC-OCV characteristics, wherein the SOC-OCV characteristics include a flat region in which the absolute value of the change in OCV relative to the change in SOC, i.e., the OCV change rate, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, wherein the battery management method includes the following steps: obtaining the OCV of the battery; when the obtained OCV of the battery is within a first change region including SOC100% as the change region, estimating a first SOC based on the OCV of the battery and the SOC-OCV characteristics; and when the OCV of the battery is within another of the change regions other than the first change region, estimating a second SOC based on the OCV of the battery, the SOC-OCV characteristics, and a related value related to the degradation state of the battery.

[0019] In addition, the technology disclosed in this specification can be implemented in various forms, such as a battery management device, a battery device including a battery management device and a battery, their management methods, a computer program that implements these methods, a non-volatile recording medium that records the computer program, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is an explanatory diagram schematically showing the structure of the battery device 100 in the embodiment.

[0021] Figure 2 It is an explanatory diagram schematically showing the SOC-OCV characteristics of the battery 12 .

[0022] Figure 3 It is an explanatory diagram showing an example of the SOC-OCV table T1.

[0023] Figure 4 It is an explanatory diagram showing an example of the region division-OCV table T2.

[0024] Figure 5 : is a flowchart showing the OCV acquisition process.

[0025] Figure 6 is a flowchart showing the SOC reset process. DETAILED DESCRIPTION

[0026] A. Implementation method:

[0027] A-1. Structure of the battery device 100:

[0028] Figure 1 1 is an explanatory diagram schematically showing the structure of a battery device 100 in this embodiment. The battery device 100 includes a battery pack 10 and a battery management device 20 .

[0029] The battery pack 10 has a structure in which a plurality of storage batteries 12 are connected in series. In the present embodiment, the battery pack 10 is composed of four storage batteries 12. The battery pack 10 is connected to a load (not shown) and an external power supply via a positive terminal 42 and a negative terminal 44.

[0030] Each storage battery 12 constituting the battery pack 10 is a storage battery having a SOC (State of Charge)-OCV (Open Circuit Voltage) characteristic including a flat region PR. Figure 2 It is an explanatory diagram schematically showing the SOC-OCV of the storage battery 12. As the storage battery 12, for example, an iron phosphate type lithium ion battery and a titanate type lithium ion battery can be cited.

[0031] The SOC-OCV characteristic of the battery 12 has a flat region PR and a variable region CR. The flat region PR is a region where the curve representing the SOC-OCV characteristic is approximately flat. More specifically, it is a region where the OCV change rate (the absolute value of the change in OCV relative to the change in SOC) is less than a specified value (e.g., 2 mV / %). The variable region CR is a region where the OCV change rate exceeds a specified value (non-flat region). Figure 2 In the example shown, three flat regions PR (first flat region PR1, second flat region PR2, third flat region PR3) and four variable regions CR are alternately arranged in the SOC-OCV characteristics of the battery 12. Hereinafter, the variable region including SOC100% is referred to as "upper variable region CR1", the variable region including SOC0% is referred to as "lower variable region CR4", and the other variable regions are referred to as "intermediate variable regions CR2, CR3".

[0032] Figure 2The curve G1 in the figure shows the SOC-OCV characteristics when the battery 12 is new, and the curve G2 shows the SOC-OCV characteristics when the battery 12 deteriorates over time. As can be seen from these graphs G1 and G2, when the battery 12 deteriorates, in the SOC-OCV characteristics, the uppermost change region CR1 hardly changes, but the other change regions CR2 to CR4 move toward the high SOC side (refer to the change regions CR2' to CR4'). The uppermost change region CR1 is an example of the first change region in the claims, and the lowermost change region CR4 is an example of the second change region in the claims.

[0033] The battery management device 20 is a device for managing the battery device 100 including the 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.

[0034] A voltmeter 22 is provided for each storage battery 12. Each voltmeter 22 is connected in parallel with each storage battery 12, measures the voltage of each storage battery 12, and outputs a signal indicating the voltage measurement value to the monitoring unit 28. The ammeter 24 is connected in series with the battery pack 10. The ammeter 24 measures the current flowing in the battery pack 10, and outputs a signal indicating the current measurement value to the monitoring unit 28. The thermometer 26 is arranged 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 temperature measurement value to the monitoring unit 28. The monitoring unit 28 outputs a signal 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 based on the signals received from the voltmeter 22, the ammeter 24, and the thermometer 26. The ammeter 24 and the monitoring unit 28 are an example of a current measuring unit.

[0035] The line switch 40 is provided between the battery pack 10 and the negative terminal 44. The line switch 40 is controlled to be on / off by the control unit 60, thereby opening and closing the connection between the battery pack 10 and the load and the external power supply.

[0036] The control unit 60 is configured using, for example, a CPU, a multi-core CPU, a programmable device (Field Programmable Gate Array (FPGA), Programmable Logic Device (PLD), etc.), 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 each of these units will be described in conjunction with the description of the SOC estimation process described later.

[0037] The recording unit 72 is composed of, for example, a ROM, a RAM, a hard disk drive (HDD), etc., and stores various programs and data, or is used as a work area or a storage area for data when executing various processes. For example, a computer program for executing the SOC estimation described later is stored in the recording unit 72. The computer program is provided in a state of being stored in 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 being installed in the battery device 100.

[0038] In addition, an SOC-OCV table T1 and a region division-OCV table T2 are stored in the recording unit 72. The SOC-OCV table T1 is a table for estimating the SOC of each storage battery 12 based on the OCV method. Figure 3 : is an explanatory diagram showing an example of the SOC-OCV table T1. The SOC-OCV table T1 is a table that associates OCV, battery temperature, and SOC. The relationship specified in the SOC-OCV table T1 is determined in advance through experiments. Figure 3 As shown in FIG. 1 , the SOC-OCV characteristic changes according to the change in battery temperature. By referring to the SOC-OCV table T1, the SOC of the battery 12 can be estimated based on the OCV of each battery 12 and the battery temperature. Figure 3 In the table T1, the OCV is shown as Vn0, Vn1, ... Vn99, Vn100, etc., but in the SOC-OCV table T1, the OCV value is actually specified. Figure 3 , a discharge SOC-OCV table used when the storage battery 12 is discharged and a charge SOC-OCV table used when the storage battery 12 is charged are shown.

[0039] The area division-OCV table T2 recorded in the recording unit 72 ( Figure 1 ) is a table used when determining in which region (flat region PR, changing region CR) the measured OCV is located in the SOC-OCV characteristic (which region it belongs to). Figure 4: is an explanatory diagram showing an example of the region division-OCV table T2. In the present embodiment, the region division-OCV table T2 specifies the relationship between the OCV and each region division of the OCV in the SOC-OCV characteristics and the battery temperature. As described above, the SOC-OCV characteristics change according to the change of the battery temperature, so the region divisions in the SOC-OCV characteristics will change with the change of the SOC-OCV characteristics. Figure 4 In the diagram, OCV is represented as Vo0, Vo1, ..., etc., but in the area division-OCV table T2, the numerical value of OCV is actually specified.

[0040] The history unit 74 is composed of, 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, the history of the processing contents of the SOC processing described later, etc. The interface unit 76 and the like communicate with other devices by wire or wireless. For example, the history recorded in the history unit 74 is updated by the communication with other devices via the interface unit 76.

[0041] A-2.2.SOC estimation process:

[0042] The SOC estimation process performed by the battery management device 20 in the battery device 100 of the present embodiment will be described. In the present embodiment, the SOC estimation process estimates the SOC of each battery 12 constituting the battery pack 10 individually. In the following description, one battery 12 is used as an example for description. The SOC estimation process is started, for example, when the battery management device 20 is started, automatically or in accordance with an instruction from a manager.

[0043] A-2-1. Estimation of cumulative SOC(t) based on current integration method:

[0044] In the battery device 100 of the present embodiment, a process of estimating the SOC (hereinafter referred to as “cumulative SOC(t)”) based on the current integration method is executed. Specifically, the coulomb counting processing unit 64 ( Figure 1 ) calculates the capacity of each battery 12 by integrating the current measured by the ammeter 24 and the monitoring unit 28. Next, the integrated SOC estimation unit 66 of the battery management device 20 estimates the integrated SOC(t) of the battery based on the SOC(0) at the reference time (hereinafter referred to as "integrated reference time SOC(0)"), the change amount Q(t) (charge transfer amount) of the capacity of the battery 12 from the reference time calculated by the coulomb counting processing unit 64, and the FCC of the battery 12. The integrated SOC(t) can be expressed by the following formula (1).

[0045] Cumulative SOC(t) = Cumulative reference time SOC(0) + [Q(t) / FCC]…(1)

[0046] At the beginning of the SOC estimation process, the reference time is, for example, the time of shipment of the battery device 100. Thereafter, the reference time is the execution time of the reference SOC update process in the SOC reset process described later. In addition, the estimation process of the cumulative SOC(t) is continuously executed in the SOC estimation process. The cumulative SOC estimation unit 66 is an example of the third estimation unit in the claims, and the cumulative reference time SOC(0) is an example of the SOC at the second reference time in the claims.

[0047] A-2-2OCV acquisition process:

[0048] Figure 5 1 is a flowchart showing the OCV acquisition process executed in the battery device 100 of the present embodiment. When the current of charging or discharging the storage battery 12 is lower than a predetermined threshold value or the line switch 40 is switched from the closed state to the open state, the control unit 60 determines that the storage battery 12 is in the stopped state, and the OCV acquisition unit 62 ( Figure 1 ) Execute the OCV acquisition process of the battery 12 ( Figure 5 ). Specifically, the OCV acquisition unit 62 determines whether the OCV acquisition timing has arrived, and when it is determined that the OCV acquisition timing has arrived, the OCV acquisition process (S110 to S140) is executed. In the present embodiment, the OCV acquisition timing of the battery 12 is the timing when the polarization of the battery 12 is eliminated to the extent that the OCV of the battery 12 can be obtained, thereby achieving a stable battery voltage state.

[0049] like Figure 5 As shown, the OCV acquisition unit 62 determines again whether the line switch 40 is closed (S110). The line switch 40 being closed means that the battery 12 (battery pack 10) is electrically connected to the load, and the line switch 40 being open means that the battery 12 is not electrically connected to the load (not shown).

[0050] When the OCV acquisition unit 62 determines that the line switch 40 is in the closed state (S110: Yes), it determines whether the stop state in which no current flows through the battery 12 has continued for more than a predetermined time (S120). The control unit 60 always determines whether the current flows through the battery 12 based on the signal input from the monitoring unit 28, and retains the determination result as a history associated with the elapsed time. The OCV acquisition unit 62 can determine whether the stop state of the battery 12 has continued for more than a predetermined time based on the history. In addition, if the current flowing through the battery 12 is less than the reference current value (a value at which the current is substantially regarded as zero), the OCV acquisition unit 62 determines that the current state of the battery 12 is the stop state. The current of the battery 12 is continuously measured in the SOC estimation process.

[0051] When the OCV acquisition unit 62 determines that the stop state of the battery 12 has not continued for more than the prescribed time (S120: No), it returns to S110. On the other hand, when the OCV acquisition unit 62 determines that the stop state of the battery 12 has continued for more than the prescribed time (S120: Yes), it determines whether the rate of change of the battery voltage of the battery 12 within the prescribed time is less than a prescribed reference rate (which can be regarded as a value at which the battery voltage of the battery 12 is substantially stable) based on the signal input from the monitoring unit 28 (S130). In addition, the measurement of the voltage of the battery 12 is continuously performed in the SOC estimation process. In addition, when it is determined that the line switch 40 is in the open state (S110: No), the OCV acquisition unit 62 does not perform the process of 120 and enters S130.

[0052] When the OCV acquisition unit 62 determines that the rate of change of the battery voltage of the battery 12 within the predetermined time is greater than the reference rate (S130: No), the return is made to S110. On the other hand, when the OCV acquisition unit 62 determines that the rate of change of the battery voltage of the battery 12 within the predetermined time is less than the reference rate (S130: Yes), the measured battery voltage of the battery 12 is recorded as the OCV of the battery 12 in the history unit 74 (S140).

[0053] 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 “this time OCV”) is within the change region CR.

[0054] Specifically, the control unit 60 determines the current state (charging state, discharging state) of the battery 12 when the OCV acquisition timing is about to arrive (S150). For example, the signal output from the ammeter 24 is a signal corresponding to the presence or absence of current flowing through the battery 12 and the direction of the current flow (a signal corresponding to the voltage across the detection resistor (not shown) provided in the ammeter 24). The control unit 60 determines the current state (charging state, discharging state) of the battery 12 based on the level of the signal output from the ammeter 24 and the level inversion of the signal.

[0055] When it is determined that the battery 12 is in a discharging state (S150: discharging), the SOC-OCV table for discharging (S160) is referred to, and it is determined whether the current OCV is within the change region CR of the SOC-OCV characteristic for discharging (S180). On the other hand, when it is determined that the battery 12 is in a charging state (S150: charging), the SOC-OCV table for charging (S170) is referred to, and it is determined whether the current OCV is within the change region CR of the SOC-OCV characteristic for charging (S180).

[0056] If it is determined that the current OCV is within the change region CR in the discharge SOC-OCV characteristic or the charge SOC-OCV characteristic (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 does not execute the SOC reset process and returns to S110.

[0057] A-2-3SOC reset processing:

[0058] Figure 6 1 is a flowchart showing the SOC reset process performed in the battery device 100 of the present embodiment. The SOC reset process is a process for estimating the reset SOC (first reset SOC, second reset SOC, third reset SOC) based on the OCV method and resetting (updating) the cumulative SOC (t) estimated by the cumulative SOC estimation unit 66 to the reset SOC.

[0059] In the SOC reset process, the reset SOC used for the SOC reset process differs depending on which change region CR (upper change region CR1, middle change regions CR2, CR3, lower change region CR4) the current OCV is in in the SOC-OCV characteristic.

[0060] A-2-3-1. When the current OCV is in the uppermost change region CR1:

[0061] When it is determined that the current OCV is within the uppermost change region CR1 (S210: CR1), the reset SOC estimation unit 68 estimates the first reset SOC based on the current OCV and SOC-OCV characteristics of the battery 12 (S220). At this time, the reset SOC estimation unit 68 functions as the first SOC estimation unit in the claims. Figure 2 In the example of FIG. 1 , when the current OCV is within the uppermost change region CR1 in the SOC-OCV characteristic, the reset SOC estimation unit 68 refers to the SOC-OCV table T1 and converts the SOC corresponding to the current OCV into Figure 2 The first resetting SOC is estimated as "Sr1" in FIG. 1. In the estimation process of the first resetting SOC, the SOH described later is not used.

[0062] Next, the control unit 60 determines whether the temperature of each 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 refers to, for example, a temperature range (for example, 20° C. or higher and 45° C. or lower) in which the correlation between the degradation state and the SOH (State of Health) of the battery 12 is normally established. When it is determined that the temperature of the battery 12 is within the predetermined temperature range (S230: Yes), the SOH can be normally corrected using the reset SOC estimated by the reset SOC estimating unit 68.

[0063] Therefore, the SOH correction unit 70 corrects the SOH on the condition that the OCV of the battery 12 moves from the lowermost change region CR4 to the uppermost change region CR1 . The SOH is a value (parameter) related to the degradation state of the battery 12 .

[0064] Specifically, the control unit 60 determines whether the SOC set in the previous SOH correction process (hereinafter referred to as "corrected reference time SOC (REF)") is the SOC estimated by the reset SOC estimating unit 68 when the OCV is in the lowest change region CR4 (hereinafter referred to as "second reset SOC" ( Figure 2 When it is determined that the corrected reference time SOC (REF) is the second resetting SOC (S240: YES), it means that the OCV of the battery 12 has moved from the lowermost change region CR4 to the uppermost change region CR1.

[0065] Therefore, the SOH correction unit 70 corrects the SOH based on the value Sr1 of the first resetting SOC, the value Sr2 of the correction reference time SOC (REF) (second resetting SOC), and the amount of change Q1(t) in the capacity of the battery 12 calculated by the coulomb counting processing unit 64 during the period from when the OCV of the battery 12 moves from the lowermost change region CR4 to the uppermost change region CR1 (see S250). Figure 2 For example, the corrected SOH can be calculated by the following equations (2) and (3).

[0066] This time FCC = Q1(t) / [(Sr1)-(Sr2)]…(2)

[0067] Corrected SOH = this FCC / new FCC (3)

[0068] In addition, when the OCV of the battery is within the uppermost change region CR1 or the lowermost change region CR4, the SOC estimated based on the SOC-OCV characteristic is less affected by the state error of the 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) at this time is an example of the SOC at the first reference time in the claims, and the control unit 60 also functions as the first reference SOC setting unit in the claims.

[0069] The FCC correction unit 63 corrects the FCC in the equation (1) used in the above-mentioned cumulative SOC(t) estimation process to the current FCC calculated by the equation (2). This allows the cumulative SOC(t) estimation process to be performed while suppressing the influence of fluctuations due to degradation of the battery 12 .

[0070] On the other hand, when it is determined that the correction reference time SOC (REF) is not the second reset SOC (S240: No), it means that the charging and discharging of the battery 12 is repeated and the cumulative SOC (t) estimation process is continued when the OCV of the battery 12 has not reached the lowest change region CR4. That is, the change amount Q1 (t) of the capacity of the battery 12 from the execution time of the last SOH correction process to the current time is relatively small. Therefore, the control unit 60 does not execute the SOH correction process (S250) and proceeds to S260.

[0071] In addition, when it is determined that the temperature of the battery 12 is outside the prescribed temperature range (S230: No), it is difficult to normally correct the SOH. Therefore, the control unit 60 does not perform the SOH correction process (S250) and proceeds to S290. When the temperature of the battery 12 is outside the prescribed temperature range, the corrected reference time SOC (REF) is not updated. However, as described later, the accumulated reference time SOC (0) is updated.

[0072] In S260, the SOC updating unit 71 ( Figure 1 ) performs a modified reference SOC update process. The modified reference SOC update process is a process of updating the modified reference time SOC (REF) mentioned above to a reset SOC (a first reset SOC, a second reset SOC). When the current OCV is in the uppermost change region CR1, the modified reference time SOC (REF) is updated to the first reset SOC (Sr1). In addition, the change amount Q1(t) and the change amount Q2(t) of the capacity of the battery 12 calculated by the coulomb counting processing unit 64 in the equations (2) and (5) used in the current FCC estimation process are reset to zero.

[0073] Next, the control unit 60 determines whether the current SOH (corrected SOH) is below a specified value (S270). The specified value is, for example, a threshold value for determining whether the battery 12 can be charged and discharged normally. If the SOH is greater than the specified value, it means that the battery 12 is in a state where it can be charged and discharged normally. If the SOH is below the specified value, it means, for example, that the deterioration has worsened and the battery 12 is in a state where it cannot be charged and discharged normally. When it is determined that the SOH is below the specified value (S270: Yes), the control unit 60 performs a notification process (S280). Specifically, the control unit 60 notifies the outside of abnormalities such as degradation of the battery 12 via the interface unit 76. On the other hand, when it is determined that the SOH is greater than the specified value (S270: No), the control unit 60 does not perform the notification process (S280) and proceeds to S290.

[0074] In S290, the SOC updating unit 71 updates the current cumulative SOC(t) and the cumulative reference time SOC(0) estimated in the above-mentioned cumulative SOC(t) estimation process to the reset SOC. When the current OCV is within the uppermost change region CR1, the current cumulative SOC(t) and the cumulative reference time SOC(0) are updated to the first reset SOC(Sr1). In addition, the change amount Q(t) of the capacity of the battery 12 from the reference time calculated by the coulomb counting processing unit 64 in the formula (1) used in the cumulative SOC(t) estimation process is reset to zero. Thereafter, the present SOC reset process ends.

[0075] A-2-3-2. When the OCV is in the lowest change area CR4:

[0076] When it is determined that the current OCV is within the lowermost change region CR4 (S210: CR4), the resetting SOC estimating unit 68 estimates the second resetting SOC (S300) based on the current OCV, SOC-OCV characteristics, and SOH of the battery 12. The SOC when the current OCV is within the other change regions CR (CR2 to CR4) other than the uppermost change region CR1 can be calculated, for example, by the following formula (4).

[0077] SOC=SOCint / SOH···(4)

[0078] Furthermore, SOCint is the SOC corresponding to the current OCV in the SOC-OCV table T1.

[0079] By dividing the SOCint estimated by the OCV method by the SOH, even when the current OCV is in other change regions CR (CR2 to CR4) other than the uppermost change region CR1, the SOC can be estimated while suppressing the influence of the state error of the battery 12. At this time, the reset SOC estimation unit 68 functions as the second SOC estimation unit in the claims. Figure 2 In the example, when the current OCV is within the lowest change region CR4 in the SOC-OCV characteristic, the reset SOC estimation unit 68 refers to the SOC-OCV table T1 and divides the SOCint corresponding to the current OCV by SOH to obtain the SOC ( Figure 2 “Sr2” in FIG. 1 is estimated as the second reset SOC.

[0080] When it is determined that the temperature of the 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 battery 12 has shifted from the uppermost change region CR1 to the lowermost change region CR4 .

[0081] Specifically, the control unit 60 determines whether the correction reference time SOC (REF) set in the previous SOH correction process is the first resetting SOC (Sr1) estimated by the resetting SOC estimating unit 68 when the OCV is in the uppermost change region CR1 (S320). When it is determined that the correction reference time SOC (REF) is the first resetting SOC (S320: Yes), it means that the OCV of the battery 12 has moved from the uppermost change region CR1 to the lowermost change region CR4.

[0082] Therefore, the SOH correction unit 70 performs a correction process for the SOH (S250). Specifically, the SOH correction unit 70 corrects the SOH based on the value Sr2 of the second resetting SOC, the value Sr1 of the correction reference time SOC (REF) (the first resetting SOC), and the change amount Q2(t) of the capacity of the battery 12 calculated by the coulomb counting processing unit 64 during the period from when the OCV of the battery 12 moves from the uppermost change region CR1 to the lowermost change region CR4 (see Figure 2 For example, the corrected SOH can be calculated by the following equations (3) and (5).

[0083] This time FCC = Q2(t) / [(Sr2)-(Sr1)]…(5)

[0084] Corrected SOH = this FCC / new FCC (3)

[0085] Furthermore, the FCC correction unit 63 corrects the FCC in the equation (1) used in the above-mentioned cumulative SOC(t) estimation process to the current FCC calculated by the equation (3). This allows the cumulative SOC(t) estimation process to be performed while suppressing the influence of fluctuations due to degradation of the battery 12 .

[0086] On the other hand, when it is determined that the corrected reference time SOC (REF) is not the first resetting SOC (S320: No), the control unit 60 does not execute the SOH correction process (S250) and proceeds to S260. In addition, when it is determined that the temperature of the battery 12 is outside the prescribed temperature range (S310: No), the control unit 60 does not execute the SOH correction process (S250) and proceeds to S290. When the temperature of the battery 12 is outside the prescribed temperature range, the corrected reference time SOC is not updated, and the accumulated reference time SOC (0) is updated.

[0087] In S260, when the current OCV is within the lowest change region CR4, the corrected reference time SOC (REF) is updated to the second reset SOC (Sr2). In addition, the change amount Q1 (t) and the change amount Q2 (t) of the capacity of the battery 12 calculated by the coulomb counting processing unit 64 in the equations (2) and (5) used in the current FCC estimation process are reset to zero. In addition, in S290, the current cumulative SOC (t) and the cumulative reference time SOC (0) are updated to the second reset SOC (Sr2). In addition, the change amount Q (t) of the capacity of the battery 12 from the reference time calculated by the coulomb counting processing unit 64 in the equation (1) used in the cumulative SOC (t) estimation process is reset to zero.

[0088] A-2-3-3. When the current OCV is in the intermediate change region CR2 or CR3:

[0089] When it is determined that the current OCV is within the intermediate change region CR2, CR3 (S210: CR2, 3), the resetting SOC estimating unit 68 estimates the third resetting SOC ( Figure 2 "Sr3" in (S400). Specifically, similar to the processing of the above-mentioned S300, the third reset SOC can be calculated by the above-mentioned formula (4) used when the current OCV is in the lowest change area CR4. Thereafter, the control unit 60 enters S290. In addition, in S290, the current cumulative SOC (t) and the cumulative reference time SOC (0) are updated to the third reset SOC. As described above, when the OCV of the battery 12 is in the intermediate change area CR2, CR3, the SOC estimated based on the SOC-OCV characteristic is greatly affected by the state error of the battery 12. Therefore, when the OCV of the battery 12 is in the intermediate change area CR2, CR3, the SOH is not corrected, and the correction reference time SOC (REF) is not updated.

[0090] A-3. Effects of implementation methods:

[0091] As described above, when the OCV of the battery 12 is within the uppermost variation region CR1 including SOC 100%, the SOC estimated based on the SOC-OCV characteristic is less affected by the state error of the battery (e.g., individual differences of the battery 12 at the time of shipment, changes in the battery 12 over time), and when the OCV of the battery 12 is within other variation regions CR2 to CR4, the SOC estimated based on the SOC-OCV characteristic is greatly affected by the state error of the battery (see Figure 2 ).

[0092] Therefore, in the battery management device 20 of the present embodiment, when the OCV of the battery 12 is within the uppermost change region CR1 ( Figure 6In the case of S210: CR1, the first SOC (first reset SOC) is estimated based on the OCV and SOC-OCV characteristics of the battery 12 (S220). On the other hand, when the OCV of the battery 12 is in the other change regions CR2 to CR4 (S210: CR2 to CR4), the second SOC (second reset SOC, third reset SOC) is estimated based on the OCV and SOC-OCV characteristics of the battery 12 and the SOH related to the degradation state of the battery 12 (S300, S400). Therefore, according to the present embodiment, the SOC of the battery 12 can be estimated with high accuracy while suppressing the reduction in the estimation accuracy of the SOC caused by the state error of the battery 12.

[0093] B. Modifications:

[0094] The technology disclosed in this specification is not limited to the above-mentioned embodiment, and can be modified into various forms within the scope not departing from the gist thereof. For example, the following modifications are also possible.

[0095] The structure of the battery device 100 in the above embodiment is only an example, and various modifications are possible. For example, in the above embodiments, the number of storage batteries 12 constituting the battery pack 10 can be arbitrarily changed. In addition, in the above embodiments, a thermometer 26 may be provided for each storage battery 12. In addition, the thermometer 26 may be omitted.

[0096] In the above embodiment, an iron phosphate type lithium-ion battery or the like is exemplified as a storage battery, but any storage battery having an SOC-OCV characteristic including a first region where the OCV rate is below a specified value and a variable region where the OCV change rate exceeds a specified value may be any other secondary battery or a primary battery. In addition, the above specified value is not limited to 2mV / %, and can be set arbitrarily. In addition, the number of variable regions CR and flat regions PR can be changed arbitrarily. Furthermore, in the above embodiment, the lowest variable region CR4 is exemplified as the second variable region, but the second variable region may be any variable region as long as the OCV is below a specified value, for example, Figure 2 In the embodiment, the second variation region may include the middle variation region CR3 or a part of the middle variation region CR3 in addition to the lowermost variation region CR4.

[0097] In the above-mentioned embodiments, the contents of the SOC-OCV table T1 and the area division-OCV table T2 are merely examples, and various modifications are possible. In addition, it is not necessary to record at least one of the SOC-OCV table T1 and the area division-OCV table T2 in the recording unit 72. In the above-mentioned embodiments, at least one of the functional units of the control unit 60 may be omitted.

[0098] The content of the SOC estimation process in the above embodiment is only an example, and various modifications are possible. For example, in the above embodiment, the SOC estimation process estimates the SOC of each 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 adopted in which the battery voltage of the battery 12 in a stable state is acquired as the OCV ( Figure 6 However, a known method such as a method of estimating OCV based on changes in the internal resistance of the battery 12, the battery voltage, etc. may be used.

[0099] In the estimation process of the cumulative SOC(t) in the above embodiment, the FCC may be set to a fixed value, and the cumulative SOC(t) may be estimated based on the SOC(0) at the reference time and the amount of change Q(t) in the capacity of the battery 12 from the reference time calculated by the coulomb counting processing unit 64. In the SOC estimation process of the above embodiment, the reference SOC update process (S260) may not be executed. Even in such a configuration, the SOC of the battery 12 can be estimated with high accuracy by correcting the cumulative SOC(t).

[0100] In the above embodiment, SOH is exemplified as the correlation value, but the present invention is not limited thereto and other values ​​(parameters) related to the degradation state of the storage battery 12 (battery pack 10 ) may be used.

[0101] In the above embodiment, the condition for executing the SOH correction process (S250) is that the battery 12 is within a specified temperature range, but it may be other conditions (for example, environmental conditions such as humidity, electrical conditions of the battery 12 (overcurrent, overvoltage, etc.).

[0102] Description of Reference Numerals

[0103] 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: cumulative 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: flat region.

Claims

1. A battery management device for managing a battery having a SOC-OCV characteristic, wherein the SOC-OCV characteristic includes a flat region in which the absolute value of the change in OCV relative to the change in SOC, i.e., the OCV change rate, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, wherein: The battery management device comprises: An OCV acquisition unit that acquires the OCV of the battery; a first SOC estimating unit that estimates a first SOC based on the OCV of the battery and the SOC-OCV characteristic when the OCV of the battery acquired by the OCV acquiring unit is within a first variation region including SOC 100% as the variation region; as well as A second SOC estimating unit estimates a second SOC based on the OCV of the battery, the SOC-OCV characteristic, and a correlation value related to a degradation state of the battery when the OCV of the battery is within the variation region other than the first variation region.

2. The battery management device according to claim 1, wherein: The battery management device also has: a current measuring unit for measuring a current flowing through the battery; a coulomb counting processing unit for calculating 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 estimating unit as the SOC at a first reference time when the OCV of the battery is within the first change region; as well as a correlation value correction unit configured to correct the correlation value on the condition that the OCV of the battery moves from the first change region to a second change region in which the OCV is less than a predetermined value among the other change regions, The correlation value correction unit corrects the correlation value based on the SOC estimated by the second SOC estimation unit according to the OCV after moving to the second change region, the SOC at the first reference time, and the change in capacity of the battery calculated by the coulomb counting processing unit during the period from when the OCV of the battery moves from the first change region to the second change region.

3. The battery management device according to claim 1, wherein: The battery management device also has: a current measuring unit for measuring a current flowing through the battery; a coulomb counting processing unit for calculating 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 the SOC at a first reference time when the OCV of the battery is within a second variation region in which the OCV is less than a predetermined value among the other variation regions; as well as 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, The correlation value correction unit corrects the correlation value based on the SOC estimated by the first SOC estimation unit according to the OCV after moving to the first change region, the SOC at the first reference time, and the change in capacity of the battery calculated by the coulomb counting processing unit during the period from when the OCV of the battery moves from the second change region to the first change region.

4. The battery management device according to claim 2 or 3, wherein: The battery management device also has: a second reference SOC setting unit that sets the SOC estimated by the first SOC estimating unit or the second SOC estimating unit as the SOC at a second reference time; a cumulative SOC estimating unit that estimates a cumulative SOC of the battery based on the SOC at the second reference time, the amount of change in capacity of the battery from the second reference time calculated by the coulomb counting processing unit, and the FCC of the battery; as well as An FCC correction unit corrects the FCC based on the corrected correlation value corrected by the correlation value correction unit.

5. A method for managing a battery, wherein the battery has the following SOC-OCV characteristics, wherein the SOC-OCV characteristics include a flat region where the absolute value of the change in OCV relative to the change in SOC, i.e., the OCV change rate, is relatively low, and a plurality of change regions where the OCV change rate is relatively high, wherein: The battery management method comprises the following steps: Obtaining the OCV of the battery; estimating a first SOC based on the OCV of the battery and the SOC-OCV characteristic when the acquired OCV of the battery is within a first variation region including SOC 100% as the variation region; and When the OCV of the battery is within the variation region other than the first variation region, a second SOC is estimated based on the OCV of the battery, the SOC-OCV characteristic, and a correlation value related to a degradation state of the battery.

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