Storage battery management device and method for managing a storage battery

Abstract

To estimate the SOC of the storage battery with high accuracy, the storage battery management device manages a storage battery with SOC-OCV characteristics including a plateau region and a plurality of change regions where an OCV change rate is relatively high. The storage battery management device includes: an OCV acquisition unit that acquires the 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 is within a first change range; and a second SOC estimation unit that estimates a second SOC based on the OCV, the SOC-OCV characteristics, and a correlation value correlated with the degradation state of the storage battery when the OCV of the storage battery is within the other change regions except the first change range.

Description

TECHNICAL FIELDThe technology disclosed herein relates to a storage battery management device and a method for managing a storage battery.BACKGROUND OF THE INVENTIONThe open-circuit voltage (OCV) method is known as a method for estimating the state of charge (SOC) of storage batteries (see, e.g., Patent Literature 1). The OCV method detects the OCV of a storage battery to estimate the SOC based on the correspondence between the detected OCV and the SOC-OCV characteristic of the storage battery. In the OCV method, the period for estimating the SOC may be limited to the period in which the OCV of the storage battery is available, and the SOC of the storage battery may not be accurately estimated for storage batteries having SOC-OCV characteristics including a range in which the absolute value of a change amount of the OCV relative to the change amount of the SOC is relatively small (e.g., plateau range).The current integration method is another well-known method for estimating the SOC of storage batteries. In the current integration method, the amount of change in capacity of the storage battery from the initial state is calculated by integrating the measurement results of the current flowing through the storage battery, and the SOC is estimated based on the output capacity, the calculated change in capacity, and the full charge capacity (FCC). Unlike the OCV method, the current integration method may estimate the SOC without being affected by the limitation of the period in which the OCV is available or by the plateau region; however, the SOC may not be accurately estimated due to measurement errors in the current measurement unit that measures the current flowing through the storage battery. In this regard, a method combining the current integration method and the OCV method is known (see, e.g., Patent Literature 2). In this method, the initial capacitance is reset to the SOC estimated by the OCV method every time the OCV can be measured, thereby eliminating the integration error caused by the measurement error of the current measurement unit.REFERENCE LISTPATENT LITERATUREPatent Literature 1: JP 2021-081244 APatent Literature 2: JP 2020-060581 ASUMMARY OF THE INVENTIONTECHNICAL PROBLEMWhen estimating the SOC of a storage battery using SOC-OCV characteristics prepared in advance, the characteristics may include an error between the assumed state and the actual state of the storage battery (hereinafter, referred to as "storage battery state error"). Factors that may cause the failure of the storage battery state include individual differences of the storage battery at the time of shipping and aging. Therefore, when the SOC of a storage battery is estimated using the SOC-OCV characteristics, the SOC cannot be accurately estimated.Herein, a technology capable of solving the above-mentioned problems is disclosed.SOLUTION TO PROBLEMThe technology disclosed herein may be implemented in the following aspects.(1) A storage battery management device disclosed herein is a device for managing a storage battery having SOC-OCV characteristics, including a plateau region in which an OCV change rate, which is the absolute value of the change amount of the OCV relative to the change amount of the SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, the storage battery management device including: an OCV detection unit that detects the OCV of the storage battery; a first SOC estimating 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 detected by the OCV detecting unit is within a first change range that is the change range including 100% SOC; and a second SOC estimating unit that estimates a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value that correlates with the degradation state of the storage battery when the OCV of the storage battery is within the change ranges other than the first change range.When the OCV of the storage battery is within the first change range including 100% SOC, the SOC estimated based on the SOC-OCV characteristics is highly accurate because the effect of the failure of the storage battery is small. When the OCV of the storage battery is within the other variation ranges, the SOC estimated based on the SOC-OCV characteristics is less accurate because the effect of the failure of the storage battery is large. Therefore, in this storage battery management device, when the OCV of the storage battery is in the first change range, the first SOC is estimated based on the OCV of the storage battery and the SOC-OCV characteristics. On the other hand, when the OCV of the storage battery is within the other variation ranges, the second SOC is estimated based on the OCV of the storage battery, the SOC-OCV characteristics, and the correlation value correlated with the degradation state of the storage battery. Therefore, this storage battery management device can accurately estimate the SOC of the storage battery.(2) The above storage battery management device may be configured to further include: a current measurement unit that measures the current flowing through the storage battery; a coulomb count processing unit that calculates the capacity of the storage 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 the SOC at the first reference timing when the OCV of the storage battery is within the first change range; A correlation value correction unit that corrects the correlation value on the condition that the OCV of the storage battery moves from the first change range to a second change range in which the OCV is equal to or less than a predetermined value among the other change ranges, wherein the correlation value correction unit may be configured to correct the correlation value on the basis of the SOC estimated by the second SOC estimation unit on the basis of the OCV after the movement into the second change range, the SOC at the first reference time, and the change amount of the capacity of the storage battery calculated by the coulomb count processing unit during the period in which the OCV of the storage battery moves from the first change range into the second change range. This storage battery management device corrects the correlation value according to changes in the state of the storage battery due to deterioration or the like. As a result, this storage battery management device can accurately estimate the SOC of the storage battery while suppressing the effects of changes in the state of the storage battery.(3) The above storage battery management device may be configured to further include: a current measurement unit that measures the current flowing through the storage battery; a coulomb count processing unit that calculates the capacity of the storage 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 the SOC at the first reference timing when the OCV of the storage battery is within a second change range in which the OCV is equal to or less than a predetermined value among the other change ranges; A correlation value correction unit that corrects the correlation value on the condition that the OCV of the storage battery moves from the second change range to the first change range, wherein 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 the movement to the first change range, correct the SOC at the first reference timing, and the change amount of the capacity of the storage battery calculated by the coulomb count processing unit during the time period in which the OCV of the storage battery moves from the second change range to the first change range. This storage battery management device corrects the correlation value according to changes in the state of the storage battery due to deterioration or the like. As a result, this storage battery management device can accurately estimate the SOC of the storage battery while suppressing the effects of changes in the state of the storage battery.(4) The above storage battery management device may be configured to 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 the SOC at the second reference time; an integrated SOC estimating unit that estimates the 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 count processing unit, and the FCC of the storage battery; and an FCC correcting unit that corrects the FCC based on the correlation value corrected by the correlation value correcting unit. This storage battery management device can accurately estimate the SOC based on the current integration method because the FCC is corrected based on the correlation value correlated with the degradation state of the storage battery.(5) A method disclosed herein is a method for managing a storage battery having SOC-OCV characteristics including a plateau region in which an OCV change rate, which is the absolute value of the change amount of the OCV relative to the change amount of the SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, the method including: a step of detecting the OCV of the storage battery; and a step of estimating the first SOC based on the OCV of the storage battery and the SOC-OCV characteristics when the detected OCV of the storage battery is within a first change region, which is the change region including 100% SOC; and a step of estimating a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value correlated with the degradation state of the storage battery when the OCV of the storage battery is within the variation ranges other than the first variation range. This storage battery management method can accurately estimate the SOC of the storage battery.The technology disclosed herein may be implemented in various aspects, such as a storage battery management device, a battery device equipped with a storage battery management device and a storage battery, a method for managing these devices, a computer program implementing these methods, and a non-temporary recording medium recording this computer program, and others.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is an explanatory view schematically showing a configuration of a battery device 100 in an embodiment. FIG. 2 is an explanatory view schematically showing the SOC-OCV characteristic of a storage battery 12. FIG. 3 is an explanatory view showing an example of an SOC-OCV table T 1. FIG. 4 is an explanatory view showing an example of a region classification OCV table T 2. FIG. 5 is a flowchart showing an OCV detection process. FIG. 6 is a flowchart showing an SOC reset process.DESCRIPTION OF EMBODIMENTSA. EMBODIMENT:A-1. CONFIGURATION OF BATTERY DEVICE 100:FIG. 1 is an explanatory view schematically showing a configuration of a battery device 100 in an embodiment. The battery device 100 includes a battery assembly 10 and a storage battery management device 20.The battery assembly 10 has a configuration in which a plurality of storage batteries 12 are connected in series. In this embodiment, the battery assembly 10 is composed of four storage batteries 12, and the battery assembly 10 is connected to a load and an external power source, not shown, via a positive pole 42 and a negative pole 44.Each of the storage batteries 12 constituting the battery array 10 is a storage battery having SOC (state of charge) OCV (open circuit voltage) characteristics including a plateau region PR. FIG. 2 is an explanatory view schematically showing the SOC-OCV characteristics of the storage battery 12. Examples of the storage battery 12 may include iron phosphate lithium ion batteries and titanic acid lithium ion batteries.The SOC-OCV characteristics of the storage battery 12 include a plateau region PR and a change region CR. The plateau region PR is a region in which the curve representing the SOC-OCV characteristic is nearly flat, or more specifically, in which the OCV change rate (absolute value of the OCV change amount relative to the SOC change amount) is equal to or less than a predetermined value (e.g., 2 mV / %). The change range CR is the range in which the OCV change rate exceeds the predetermined value (non-plateau range). In the example shown in FIG. 2, three plateau regions PR (first plateau region PR 1, second plateau region PR 2, and third plateau region PR 3) and four change regions CR alternately appear in the SOC-OCV characteristics of the storage battery 12.Graph G 1 in FIG. 2 shows the SOC-OCV characteristics when the storage battery 12 is new, and graph G 2 shows the SOC-OCV characteristics when the storage battery 12 has deteriorated over time. As can be seen from these graphs G1 and G2, in the SOC-OCV characteristics, the uppermost change range CR1 remains almost unchanged when the storage battery 12 has deteriorated, but the other change ranges CR2 to CR4 shift to the high SOC side (see change ranges CR2' to CR4'). The uppermost change range CR 1 is an example of the first change range in the claims, and the lowermost change range CR 4 is an example of the second change range in the claims.The storage battery management device 20 is a device for managing a battery device 100 including a battery assembly 10. the storage 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 unit 76 (I / F).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 measured voltage to the monitoring unit 28. Ammeter 24 is connected in series with battery assembly 10. The ammeter 24 measures the current flowing through the battery assembly 10 and outputs a signal indicating the measured current to the monitoring unit 28. The thermometer 26 is located near the battery assembly 10, and the thermometer 26 measures the temperature of the battery assembly 10 (each storage battery 12), and outputs a signal indicating the measured temperature to the monitoring unit 28. Based on the signals received from the voltmeter 22, the ammeter 24, and the thermometer 26, the monitoring unit 28 outputs signals indicating the voltage of each storage battery 12, the current flowing through the battery assembly 10, and the temperature of the battery assembly 10 (each storage battery 12) to the control unit 60. The combination of the ammeter 24 and the monitoring unit 28 is an example of a current measurement unit.The line switch 40 is provided between the battery assembly 10 and the negative terminal 44. The line switch 40 is turned on and off by the control unit 60 to open and close the connection between the battery assembly 10 and the load / external power source.The control unit 60 is configured to use, for example, a CPU, a multi-core CPU, or a programmable device (such as a field programmable gate array (FPGA), a programmable logic device (PLD)) to control the operation of the storage battery management device 20. The control unit 60 has functions such as an OCV acquisition unit 62, a coulomb count processing unit 64, an SOC integrated estimation unit 66, a reset SOC estimation unit 68, an SOH correction unit 70, and an SOC update unit 71.The recording unit 72 is made of, for example, ROM, RAM, or a hard disk drive (HDD), and is used for storing various programs and data or as a work area or data storage area when various processes are executed. For example, the recording unit 72 stores a computer program for executing the SOC estimation process described below. The computer program is provided in the form of, for example, a computer readable recording medium (not illustrated) such as a CD-ROM, DVD-ROM, and a USB memory, and is stored in the recording unit 72 by being installed in the battery device 100.The recording unit 72 also stores an SOC OCV table T 1 and an area classification OCV table T 2. The SOC-OCV table T 1 is a table used for SOC estimation based on the OCV method for each of the storage batteries 12. FIG. 3 is an explanatory view showing an example of the SOC-OCV table T 1. The SOC-OCV table T 1 is a table that associates the OCV, the battery temperature, and the SOC with each other. The relationship indicated in the SOC-OCV table T 1 is experimentally determined in advance. As shown in FIG. 3, the SOC-OCV characteristics vary with changes in battery temperature. Referring to the SOC-OCV table T 1, the SOC of each storage battery 12 may be estimated based on the OCV of each storage battery 12 and the battery temperature. In FIG. 3, OCV is represented as Vn0, Vn1,... Vn99, Vn100, but the actual SOC-OCV table T1 defines the numerical value of the OCV. Moreover, FIG. 3 shows the SOC-OCV table for discharge used in discharging the storage battery 12 and the SOC-OCV table for charge used in charging the storage battery 12.The area classification OCV table T 2 (FIG. 1 ) recorded in the recording unit 72 is used to determine in which area (plateau area PR, change area CR) the measured OCV is in the SOC-OCV characteristics (which area belongs to). FIG. 4 is an explanatory view showing an example of a region classification OCV table T 2. In this embodiment, the area classification OCV table T 2 defines the relationship between the OCV, each area classification in the SOC-OCV characteristics, and the battery temperature. As mentioned above, since the SOC-OCV characteristics vary depending on changes in the battery temperature, each range classification in the SOC-OCV characteristics varies depending on the variation in the SOC-OCV characteristics. In FIG. 4, the OCV is indicated as Vo0, Vo1,..., but the actual area classification OCV table T2 defines the numerical value of the OCV.The history unit 74 is composed of, for example, ROM, RAM, and a hard disk drive (HDD), and records various history with respect to the battery device 100. Such a history includes, for example, the history of the OCV of the storage battery 12 and the SOC process described below. The interface unit 76 communicates with other devices by wired or wireless means. For example, the history recorded in the history unit 74 is updated by communication with other devices via the interface unit 76.A-2. SOC ESTIMATION PROCESS:The process of SOC estimation performed by the storage 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 individually for each of the storage batteries 12 constituting the battery array 10. The following description focuses on a storage battery 12.A-2-1. ESTIMATION PROCESS OF INTEGRATED SOC (T) BASED ON CURRENT INTEGRATION METHODS:The battery device 100 of this embodiment performs a process for estimating the SOC based on the current integration method (hereinafter referred to as "integrated SOC(t)"). Specifically, the coulomb count processing unit 64 (FIG. 1 ) of the storage battery management device 20 calculates the capacity of each storage battery 12 by integrating the currents measured by the ammeter 24 and the monitoring unit 28. Next, the integrated SOC estimation unit 66 of the storage battery management device 20 estimates the integrated SOC(t) of the storage batteries on the basis of the SOC(0) at the reference time point (hereinafter referred to as "reference integrated time point SOC(0)"), the amount of change in the capacity Q(t) (charge transfer) of the storage batteries 12 from the reference time point calculated by the coulomb count processing unit 64, and the FCC of the storage batteries 12.At the beginning of the SOC estimation process, the reference time point is the time point at which the battery device 100 is delivered, and thereafter, the reference time point is the time point at which the reference SOC update process is performed in the reset SOC process described below. The integrated SOC (t) estimation process is continuously executed during the SOC estimation process. The integrated SOC estimation unit 66 is an example of the third estimation unit in the claims, and the reference integrated time SOC( 0) is an example of the SOC at the second reference time in the claims.A-2-2. OCV ACQUISITION PROCESS:FIG. 5 is a flowchart showing an OCV detection process performed in the battery device 100. When the charging or discharging current to / from the storage battery 12 falls below a predetermined threshold or when the line switch 40 changes from the closed state to the open state, the control unit 60 determines that the storage battery 12 is in a stopped state, and the OCV detection unit 62 (FIG. 1 ) of the storage battery management device 20 executes the OCV detection process (FIG. 5 ) for the storage battery 12. Specifically, the OCV detection unit 62 determines whether or not the OCV detection timing has arrived, and when it determines that the OCV detection timing has arrived, the OCV detection unit 62 performs the OCV detection process (S 110 to S 140). In this system, the OCV detection timing for the storage battery 12 is the timing at which it is determined that the polarization of the storage battery 12 has resolved to stabilize the battery voltage to such an extent that the OCV of the storage battery 12 can be detected.As shown in FIG. 5, the OCV detection unit 62 again determines whether the line switch 40 is in the closed state (S 110). When the line switch 40 is in the closed state, it means that the storage battery 12 (battery assembly 10) is electrically connected to a load, and when the line switch 40 is in the open state, it means that the storage battery 12 is in the open state and is not electrically connected to a load (not shown).When the OCV detection unit 62 determines that the line switch 40 is in the closed state (S 110: YES), the OCV detection unit 62 determines whether the stopped state in which no current flows to the storage battery 12 has continued for a predetermined time or longer (S 120). The control unit 60 always determines the presence or absence of current flowing through the storage battery 12 based on the signals input from the monitoring unit 28, and stores the results of the determination as a history associated with the elapsed time, and the OCV detection unit 62 may determine whether the stopped state of the storage battery 12 has stopped for a predetermined time or longer based on this history. The OCV detection unit 62 determines that the current state of the storage battery 12 is in the stopped state when the current flowing through the storage battery 12 is a reference current value (a value at which the current can be regarded as approximately zero) or less. The measurement of the current in the storage battery 12 is continuously performed during the SOC estimation process.When the OCV detection unit 62 determines that the stopped state of the storage battery 12 does not continue for a predetermined time or longer (S 120: NO), the process returns to S 110. On the other hand, when the OCV detection unit 62 determines that the stopped state of the storage battery 12 has continued for a predetermined time or longer (S 120: YES), the OCV detection unit 62 determines whether the rate of change of the battery voltage of the storage battery 12 during 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 approximately stable) based on the signal input from the monitoring unit 28 (S 130). The measurement of the voltage of the storage battery 12 is continuously performed during the SOC estimation process. When it is determined that the line switch 40 is in the open state (S 110: NO), the OCV detection unit 62 proceeds to S 130 without performing the process in S 120.When the OCV detection unit 62 determines that the rate of change of the battery voltage of the storage battery 12 during the predetermined time is the reference rate or higher (S 130: NO), the process returns to S 110. On the other hand, when the OCV detection unit 62 determines that the rate of change of the battery voltage of the storage battery 12 during the predetermined time is less than the reference rate (S 130: YES), the OCV detection 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 (S 140).Next, the control unit 60 determines whether the OCV of the storage battery 12 (hereinafter, referred to as "the current OCV") detected at the current OCV detection timing is within the change range CR.Specifically, the control unit 60 determines the current state (state of charge or discharge state) of the storage battery 12 immediately before the OCV detection timing (S 150). For example, the signal output from the ammeter 24 corresponds to the presence / absence and the direction of the current flowing through the storage battery 12 (a signal corresponding to the high and low voltages at both ends of the detection resistor (not shown) provided in the ammeter 24). The control unit 60 determines the current state (charge or discharge state) of the storage battery 12 based on the level of the signal output from the ammeter 24 and the level inversion of this signal.When it is determined that the storage battery 12 is in the discharged state (S 150: discharging), the control unit 60 refers to the SOC-OCV table for discharging (S 160) to determine whether the current OCV is within the change range CR in the SOC-OCV characteristics for discharging (S 180). On the other hand, when it is determined that the storage battery 12 is in the state of charge (S 150: charging), the control unit 60 refers to the SOC-OCV table for charging (S 170) to determine whether the current OCV is within the change range CR in the SOC-OCV characteristics for charging (S 180).When it is determined that the current OCV is within the change range CR in the SOC-OCV characteristics for discharge or the SOC-OCV characteristics for charge (S 180: YES), the control unit 60 proceeds to the SOC reset process (S 190). On the other hand, when it is determined that the current OCV is not within the change range CR (S 180: NO), the control unit 60 returns to S 110 without performing the SOC reset process.A-2-3. SOC-RESET PROCESS:FIG. 6 is a flowchart showing the SOC reset process executed in the battery device 100. The SOC reset process is a process for estimating the reset SOC (first reset SOC, second reset SOC, and third reset SOC) based on the OCV method and resetting (updating) the integrated SOC (t) estimated by the integrated SOC estimation unit 66 to the reset SOC.In the SOC reset process, the reset SOC used in the SOC reset process differs depending on which change range CR (uppermost change range CR 1, intermediate change ranges CR 2 and CR 3, and lowermost change range CR 4) the current OCV is in the SOC-OCV characteristics.A-2-3-1. IF CURRENT OCV is within the uppermost change range cr1:When it is determined that the current OCV is within the uppermost change range CR 1 (S 210: CR 1), the reset SOC estimation unit 68 estimates the first reset SOC based on the current OCV of the storage battery 12 and the SOC-OCV characteristics (S 220). In this case, the reset SOC estimation unit 68 functions as the first SOC estimation unit in the claims. In the example in FIG. 2, when the current OCV is within the uppermost change range CR 1 in the SOC-OCV characteristics, the reset SOC estimating unit 68 refers to the SOC-OCV table T 1 to estimate the SOC corresponding to the current OCV ("Sr 1" in FIG. 2 ) as the first reset SOC. In this estimation process for the first reset SOC, the SOH described below is not used.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 (S 230). The predetermined temperature range is, for example, a temperature range within which the correlation between the degradation state and the health state (SOH) of the storage battery 12 is normally established (e.g., 20° C. or higher and 45° C. or lower). When it is determined that the temperature of the storage battery 12 is within the predetermined temperature range (S 230: YES), the SOH can be corrected appropriately by using the reset SOC estimated by the reset SOC estimation unit 68.Therefore, the SOH correction unit 70 corrects the SOH on the condition that the OCV of the storage battery 12 has moved from the lowermost change range CR 4 to the uppermost change range CR 1. The SOH is a value (parameter) correlated with the degradation state of the storage battery 12.Specifically, the control unit 60 determines whether the SOC set in the previous SOH correction process (hereinafter referred to as "correction reference time SOC (REF)") is the SOC estimated by the reset SOC estimation unit 68 when the OCV is within the lowermost change range CR 4 (hereinafter referred to as "second reset SOC" (Sr 2 in FIG. 2 )) (S 240). The fact that it is determined that the correction reference time SOC (REF) is the second reset SOC (S 240: YES) means that the OCV of the storage battery 12 has moved from the lowermost change range CR 4 to the uppermost change range CR 1.Therefore, the SOH correction unit 70 corrects the SOH based on the value Sr 1 of the first reset SOC, the value Sr 2 of the correction reference time SOC (REF) (second reset SOC), and the change amount Q 1( t) of capacity of the storage battery 12 calculated by the coulomb count processing unit 64 during the period in which the OCV of the storage battery 12 has moved from the lowermost change range CR 4 to the uppermost change range CR 1 (S 250, see arrow P 1 in FIG. 2 ). For example, the corrected SOH may be calculated by the following equations (2) and (3).When the OCV of the storage battery is within the uppermost change range CR 1 or the lowermost change range CR 4, the SOC estimated based on the SOC-OCV characteristics is relatively little affected by the state error of the storage battery 12. Therefore, the first reset SOC and the second reset SOC can be used to accurately correct the SOH. The correction reference time SOC (REF) in this case 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.The FCC correction unit 63 corrects the FCC in Equation (1) used in the above-mentioned integrated SOC estimation process (t) to the current FCC calculated by Equation (2). In this way, the estimation process of the integrated SOC (t) can be performed while suppressing the effects of variations due to degradation of the storage battery 12.On the other hand, the fact that it is determined that the correction reference timing SOC (REF) is not the second reset SOC (S 240: NO) means that the estimation process of the integrated SOC (t) has been continued by repeatedly charging and discharging the storage battery 12 without the OCV of the storage battery 12 reaching the lowermost change range CR 4. In other words, the amount of change Q 1( t) in the capacity of the storage battery 12 from the time point at which the previous SOH correction process was executed to the present time point is relatively small. Therefore, the control unit 60 proceeds to S 260 without executing the SOH correction process (S 250).When it is determined that the temperature of the storage battery 12 is outside the predetermined temperature range (S 230: NO), it is difficult to properly correct the SOH. Therefore, the control unit 60 proceeds to S 290 without executing the SOH correction process (S 250). When the temperature of the storage battery 12 is outside the predetermined temperature range, the correction reference time SOC (REF) is not updated. However, as described below, the reference integrated time SOC( 0) is updated.In S 260, the SOC update unit 71 (FIG. 1 ) of the control unit 60 performs the correction reference time SOC update process. The correction reference time SOC update process is a process for updating the above-described correction reference time SOC (REF) to the reset SOC (the first reset SOC and the second reset SOC). When the current OCV is within the uppermost change range CR 1, the correction reference time SOC (REF) is updated to the first reset SOC (Sr 1). Moreover, the change amount Q 1( t) and the change amount Q 2( t) of the capacity of the storage battery 12 calculated by the coulomb count processing unit 64 in Equations (2) and (5) and used in this FCC estimation method are reset to zero.Next, the control unit 60 determines whether the current SOH (corrected SOH) is less than or equal to a predetermined value (S 270). The predetermined value is, for example, a threshold for determining whether the storage battery 12 can be normally charged and discharged, and the fact that the SOH is larger than the predetermined value means that the storage battery 12 can be normally charged and discharged, and the fact that the SOH is equal to or smaller than the predetermined value means, for example, that the storage battery 12 has deteriorated and cannot be normally charged and discharged. When it is determined that the SOH is equal to or less than the predetermined value (S 270: YES), the control unit 60 executes a notification process (S 280). Specifically, the control unit 60 informs the outside world of an abnormality, such as deterioration of the storage battery 12, via the interface unit 76. On the other hand, when it is determined that the SOH value is greater than the predetermined value (S 270: NO), the control unit 60 proceeds to S 290 without executing the notification process (S 280).In S 290, the SOC update unit 71 updates the current integrated SOC (t) estimated in the above-mentioned integrated SOC (t) estimation process and the reference time integrated SOC (0) to the reset SOC. When the current OCV is within the uppermost change range CR 1, the current integrated SOC(t) and the reference integrated time SOC(0) are updated to the first reset SOC (Sr 1). In addition, the change amount Q(t) of the capacity of the storage battery 12 from the reference time point calculated by the coulomb counting processing unit 64 in Equation (1) and used in the integrated SOC(t) estimation process is reset to zero. Thus, the SOC reset process is completed.A-2-3-2. IF CURRENT OCV WITHIN THE LOWESTCHANGE RANGE CR4When it is determined that the current OCV is within the lowermost change range CR 4 (S 210: CR 4), the reset SOC estimation unit 68 estimates the second reset SOC based on the current OCV of the storage battery 12, the SOC-OCV characteristics, and the SOH (S 300). The SOC when the current OCV is within the other change ranges CR (CR 2 to CR 4) except the uppermost change range CR 1 may be calculated by, for example, the following equation (4).SOCint is the SOC corresponding to the current OCV in the SOC-OCV table T 1.By dividing the SOCint estimated by the OCV method by SOH, the SOC can be estimated even when the current OCV is within the change ranges CR (CR 2 to CR 4) other than the uppermost change range CR 1, suppressing the effects of the failure of the storage battery 12. In this case, the reset SOC estimation unit 68 functions as the second SOC estimation unit in the claims. In the example in FIG. 2, when the current OCV is within the lowermost change range CR 4 in the SOC-OCV characteristics, the reset SOC estimating unit 68 refers to the SOC-OCV table T 1 to estimate the SOC obtained by dividing the SOCint corresponding to the current OCV by the SOH ("Sr 2" in FIG. 2 ) as the second reset SOC.When it is determined that the temperature of the storage battery 12 is within the predetermined temperature range (S 310: YES), the SOH correction unit 70 corrects the SOH on condition that the OCV of the storage battery 12 has moved from the uppermost change range CR 1 to the lowermost change range CR 4.Specifically, the control unit 60 determines whether the correction reference time SOC (REF) set in the previous SOH correction process is the first reset SOC (Sr 1) estimated by the reset SOC estimation unit 68 when the OCV was within the uppermost change range CR 1 (S 320). The fact that it is determined that the correction reference time point SOC (REF) is the first reset SOC (S 320: YES) means that the OCV of the storage battery 12 has moved from the uppermost change range CR 1 to the lowermost change range CR 4.Therefore, the SOH correction unit 70 executes the SOH correction process (S 250). Specifically, the SOH correction unit 70 corrects the SOH based on the value Sr 2 of the second reset SOC, the value Sr 1 of the correction reference time SOC (REF) (first reset SOC), and the change amount Q 2( t) of the storage battery 12 calculated by the coulomb count processing unit 64 during the period in which the OCV of the storage battery 12 has moved from the uppermost change range CR 1 to the lowermost change range CR 4 (S 250, see arrow P 2 in FIG. 2 ). The corrected SOH may be calculated using the following equations (3) and (5), for example.The FCC correction unit 63 corrects the FCC in Formula (1) used in the above-mentioned integrated SOC estimation process (t) to the current FCC calculated by Equation (3). In this way, the estimation process of the integrated SOC (t) can be performed while suppressing the effects of variations due to degradation of the storage battery 12.On the other hand, when it is determined that the correction reference timing SOC (REF) is not the first reset SOC (S 320: NO), the control unit 60 proceeds to S 260 without executing the SOH correction process (S 250). When it is determined that the temperature of the storage battery 12 is outside the predetermined temperature range (S 310: NO), the control unit 60 proceeds to S 290 without executing the correction process (S 250) for SOH. When the temperature of the storage battery 12 is outside the predetermined temperature range, the correction reference time SOC is not updated and the reference integrated time SOC( 0) is updated.In S 260, when the current OCV is within the lowermost change range CR 4, the correction reference time SOC (REF) is updated to the second reset SOC (Sr 2). Moreover, the change amount Q 1( t) and the change amount Q 2( t) of the capacity of the storage battery 12 calculated by the coulomb count processing unit 64 in Equations (2) and (5) and used in this FCC estimation method are reset to zero. In addition, in S 290, the current integrated SOC (t) and the reference time integrated SOC (0) are updated to the second reset SOC (Sr 2). In addition, the change amount Q(t) of the capacity of the storage battery 12 from the reference time point calculated by the coulomb counting processing unit 64 in Equation (1) and used in the integrated SOC(t) estimation process is reset to zero.A-2-3-3. IF CURRENT OCV IS WITHIN INTERMEDIATE CHANGE RANGE CR2, CR3:When it is determined that the current OCV is within the middle change range CR 2 or CR 3 (S 210: CR 2, CR 3), the reset SOC estimating unit 68 estimates the third reset SOC ("Sr 3" in FIG. 2 ) based on the current OCV of the storage battery 12, the SOC OCV characteristics, and the SOH (S 400). Specifically, the third reset SOC may be calculated by the above equation (4) used when the current OCV is within the lowermost change range CR 4 as in the above process of S 300. The control unit 60 then proceeds to S 290. In S 290, the current integrated SOC (t) and the reference integrated time SOC (0) are updated to the third reset SOC. As described above, the effect of the state error of the storage battery 12 on the SOC estimated based on the SOC-OCV characteristics is relatively large when the OCV of the storage battery 12 is within the average change range CR 2 or CR 3. Therefore, when the OCV of the storage battery 12 is within the middle change range CR 2 or CR 3, the SOH is not corrected and the correction reference time SOC (REF) is not updated.A-3. EFFECTS OF THE EMBODIMENT:As explained above, when the OCV of the storage battery 12 is within the uppermost change range CR 1 including 100% SOC, the effect of the failure state of the storage battery (e.g., individual differences in the storage batteries 12 at the time of shipping and aging of the storage battery 12) on the SOC estimated based on the SOC-OCV characteristics is small, and when the OCV of the storage battery 12 is within the other change ranges CR 2 to CR 4, the effect of the failure state of the storage battery on the SOC estimated based on the SOC-OCV characteristics is large (see FIG. 2 ).Therefore, in the storage battery management device 20 of this embodiment, when the OCV of the storage battery 12 is within the uppermost change range CR 1 (S 210: CR 1 in FIG. 6 ), the first SOC (first reset SOC) is estimated based on the OCV of the storage battery 12 and the SOC-OCV characteristics (S 220). On the other hand, when the OCV of the storage battery 12 is within the other change ranges CR 2 to CR 4 (S 210: CR 2 to CR 4), the second SOC (second reset SOC) is estimated based on the OCV of the storage battery 12, the SOC-OCV characteristics, and the SOH correlated with the degradation state of the storage battery 12 (S 300, S 400). As a result, this embodiment can accurately estimate the SOC of the storage battery 12 while suppressing the decrease in estimation accuracy of the SOC caused by the state error of the storage battery 12.B. MODIFICATIONS:The technology disclosed herein is not limited to the above-described embodiments, but may be modified in various forms without departing from the spirit of the present invention. For example, the following changes are possible.The configuration of the battery device 100 in the above embodiments is only an example and may be modified in various ways. For example, in each of the above embodiments, the number of the storage batteries 12 constituting the battery assembly 10 may be changed as desired. In the above embodiments, a thermometer 26 may be provided for each of the storage batteries 12. The thermometer 26 may be omitted.In the above embodiment, the storage battery is exemplified as an iron phosphate lithium ion battery, but any other secondary or primary battery may be used as long as the storage battery has SOC-OCV characteristics including a first range in which the OCV change rate is a predetermined value or less and a second range in which the OCV change rate exceeds the predetermined value. The predetermined value is not limited to 2 mV / %, but may be freely selected. In the above embodiment, the second change range is illustrated by the lowermost change range CR 4, but the second change range may be any change range in which the OCV is below a predetermined value, for example, in FIG. 2, it may include the middle change range CR 3 or a part of the middle change range CR 3 in addition to the lowermost change range CR 4.In the above embodiment, the contents of the SOC OCV table T 1 and the area classification OCV table T 2 are only examples and can be changed in various ways. It is not necessary that at least one of the SOC OCV table T 1 or the area classification OCV table T 2 is recorded in the recording unit 72. Also, in each of the above embodiments, at least one of the functional parts of the control unit 60 may be omitted.The content of the SOC estimation method in the above embodiments is only an example and can be changed in various ways. In the above embodiment, for example, the SOC estimation process is to individually estimate the SOC for each of the storage batteries 12 constituting the battery array 10, but the SOC may also be estimated for the entire battery array 10. In the OCV detection process in the above embodiment, the method for detecting the battery voltage of the storage batteries 12 in a stable state has been adopted as the OCV (S 110 to S 130 in FIG. 6 ), but a known method such as a method for estimating the OCV based on changes in the internal resistance and the battery voltage of the storage batteries 12 may also be adopted.In the estimation process of the integrated SOC(t) in the above embodiment, the FCC may be set as a fixed value, and the integrated SOC(t) may be estimated based on the SOC(0) at the reference time point and the change amount Q(t) of the capacity of the storage battery 12 from the reference time point calculated by the coulomb count processing unit 64. In the SOC estimation process in the above embodiment, the reference SOC update process (S 260) may not be executed. Even in such a configuration, the SOC of the storage battery 12 can be accurately estimated by correcting the integrated SOC (t).In the above embodiment, the correlation value is exemplified by the SOH, but it is not limited thereto, and other values (parameters) correlated with the degradation state of the storage battery 12 (the battery array 10) may also be used.In the above embodiment, the condition for executing the SOH correction process (S 250) 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 (over-current, over-voltage, and the like) of the storage battery 12) may be used.LIST OF REFERENCE CHARACTERS10: Battery Assembly, 12: Storage Battery, 20: Storage Battery Management Device, 22: Voltmeter, 24: Ammeter, 26: Thermometer, 28: Monitoring Unit, 40: Circuit Switch, 42: Positive Pole, 44: Negative Pole, 60: Control Unit, 62: OCV Detection 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 Equipment, CR: Change range, PR: Plateau rangeReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2021-081244 A

[0003] JP 2020-060581 A

[0003]

Claims

A storage battery management device for managing a storage battery having SOC-OCV characteristics including a plateau region in which an OCV change rate, which is the absolute value of the change amount of the OCV relative to the change amount of the SOC, is relatively low, and a plurality of change regions in which the OCV change rate is relatively high, the storage battery management device comprising: an OCV detection unit that detects the OCV of the storage battery; a first SOC estimating 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 detected by the OCV detecting unit is within a first change range that is the change range including 100% SOC; and a second SOC estimating unit that estimates a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value that correlates with the degradation state of the storage battery when the OCV of the storage battery is within the change ranges other than the first change range.The storage battery management device according to claim 1, further comprising: an ammeter that measures the current flowing through the storage battery; a coulomb count processing unit that calculates the capacity of the storage 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 the SOC at the first reference timing when the OCV of the storage battery is within the first change range; A correlation value correction unit that corrects the correlation value on the condition that the OCV of the storage battery moves from the first change range to a second change range in which the OCV is equal to or less than a predetermined value among the other change ranges, wherein the correlation value correction unit corrects the correlation value based on the SOC estimated by the second SOC estimation unit based on the OCV after the transition to the second change range, the SOC at the first reference time, and the change amount of the capacity of the storage battery calculated by the coulomb count processing unit during the period in which the OCV of the storage battery moves from the first change range to the second change range.The storage battery management device according to claim 1, further comprising: an ammeter that measures the current flowing through the storage battery; a coulomb count processing unit that calculates the capacity of the storage 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 the SOC at the first reference timing when the OCV of the storage battery is within a second change range in which the OCV is equal to or less than a predetermined value among the other change ranges; A correlation value correction unit that corrects the correlation value on the condition that the OCV of the storage battery moves from the second change range to the first change range, wherein the correlation value correction unit corrects the correlation value based on the SOC estimated by the first SOC estimation unit based on the OCV after moving to the first change range, the SOC at the first reference time, and the change amount of the capacity of the storage battery calculated by the coulomb count processing unit during the period in which the OCV of the storage battery moves from the second change range to the first change range.The storage battery management device according to claim 2 or claim 3, further comprising: 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 the second reference time; an integrated SOC estimating unit that estimates the 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 count processing unit, and the FCC of the storage battery; and an FCC correcting unit that corrects the FCC based on the correlation value corrected by the correlation value correcting unit.A method for managing a storage battery having SOC-OCV characteristics including a plateau region in which an OCV change rate, which is the absolute value of the change amount of the OCV relative to the change amount of the SOC, is relatively low, and includes a plurality of change regions in which the OCV change rate is relatively high, the method comprising: a step of detecting the OCV of the storage battery; and a step of estimating the first SOC based on the OCV of the storage battery and the SOC-OCV characteristics when the detected OCV of the storage battery is within a first change region, which is the change region including 100% SOC; and a step of estimating a second SOC based on the OCV of the storage battery, the SOC-OCV characteristics, and a correlation value correlated with the degradation state of the storage battery when the OCV of the storage battery is within the variation ranges other than the first variation range.

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