Apparatus and method for estimating charging rate of storage element

Abstract

To provide a state-of-charge estimation device and state-of-charge estimation method of a power storage element that highly accurately perform a region determination of whether an SOC is in a flat region or in a change region, and can improve estimation accuracy of the SOC.SOLUTION: A Module Monitoring Unit (MMU) 52 is configured to measure a temperature of at least one secondary battery 31 of secondary batteries 31 connected in series. A state-of-charge estimation unit 51d is configured to estimate a state of charge of each secondary battery 31. A state-of-charge correction unit 51e is configured to correct the estimated state of charge of each secondary battery 31. A temperature rising value calculation unit 51f is configured to calculate a rising value of a temperature of the secondary battery 31 measured by the MMU 52. A state-of-charge correction unit 51g is configured to, when an electric current to be measured by an electric current sensor 4 is a discharge electric current of each secondary battery 31, and a temperature rising value of each secondary battery 31 to be calculated is equal to or less than a prescribed value y defining a flat region L, determine the state of charge estimated by the state-of-charge estimation unit 51d as the state of charge of each secondary battery 31.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for estimating a state of charge of an electric storage element in which a flat region with small open circuit voltage changes and a region with large changes appear with respect to changes in the state of charge. [Background technology]

[0002] Conventionally, as this type of state of charge estimation device and state of charge estimation method, for example, there is a state estimation device and a state estimation method disclosed in Patent Document 1.

[0003] The state estimation device and state estimation method disclosed in the document estimate the charging rate of a lithium iron phosphate secondary battery (LFP), and utilize the SOC-OCV characteristics of the LFP shown in Figure 2 of the document. This SOC-OCV characteristic is expressed with the horizontal axis representing SOC (charging rate) and the vertical axis representing OCV (open circuit voltage), and the change in OCV relative to the change in SOC is expressed as the open circuit voltage characteristic of the LFP. As shown in this SOC-OCV characteristic, the LFP has a flat region where the change in OCV relative to the change in SOC is relatively small, and a region where the change is large.

[0004] In the state estimation device and state estimation method disclosed in the document, focusing on the fact that applying correction using a battery model and a Kalman filter to the LFP may reduce the accuracy of SOC estimation, the SOC estimated by the current integration method is corrected using a Kalman filter in a change region where the OCV change relative to the SOC change is large, as shown in Figure 6 of the document. Also, in a flat region where the OCV change relative to the SOC change is small, the SOC estimated by the current integration method is not corrected, and the SOC estimated by the current integration method is used as the SOC at that time. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6657967 Summary of the Invention [Problem to be solved by the invention]

[0006] In this document, the SOC-OCV characteristics are referenced based on the SOC estimated by the current integration method, and a region judgment is made as to whether the SOC estimated by the LFP is in a plateau region or a change region. Then, depending on the result of the region judgment, it is decided whether or not to perform Kalman filter correction for the SOC. However, since the SOC estimated by the current integration method accumulates errors with each current integration, the estimation error increases as the LFP discharge progresses, and the accuracy of the region judgment is significantly reduced. This is particularly noticeable in LFPs that have a plateau region where the OCV change relative to the SOC change is relatively small.

[0007] In view of this, it is desirable to improve the accuracy of SOC estimation by accurately determining whether the SOC is in a plateau region or a variable region based on information other than the SOC estimated by the current integration method. [Means for solving the problem]

[0008] For this purpose, the present invention provides a current measuring unit for measuring a current flowing through an energy storage element having an open circuit voltage characteristic in which a relatively small flat region and a relatively large change region of the open circuit voltage appear with respect to a change in the charging rate; A temperature measuring unit for measuring the temperature of the storage element; A charging rate estimating unit that estimates a charging rate of the storage element; a charging rate correction unit that corrects the charging rate of the storage element estimated by the charging rate estimation unit; a temperature rise value calculation unit that calculates a rise value of the temperature of the energy storage element measured by the temperature measurement unit; a charging rate correction unit that sets the charging rate estimated by the charging rate estimation unit as the charging rate of the storage element when the current measured by the current measurement unit is a discharge current of the storage element and the temperature rise value of the storage element calculated by the temperature rise value calculation unit is a temperature rise value equal to or less than a predetermined value that defines a flat region; The above-mentioned components are included in the device for estimating the state of charge of a storage element.

[0009] The present invention also provides a method for producing a semiconductor device comprising the steps of: a current measuring step of measuring a current flowing through a storage element having an open circuit voltage characteristic in which a relatively small flat region and a relatively large change region of the open circuit voltage appear with respect to a change in the charging rate; a temperature measuring step of measuring a temperature of the storage element; A charging rate estimating step of estimating a charging rate of the storage element; a charging rate correction step of correcting the charging rate of the storage element estimated in the charging rate estimation step; a discharge current determination step of determining whether or not the current measured in the current measurement step is a discharge current of the storage element; Discharge current measurement by discharge current judgment step Steps a temperature rise value calculation step of calculating a rise value of the temperature of the storage element measured in the temperature measurement step when it is determined that the current measured in the temperature measurement step is a discharge current of the storage element; a charging rate correcting step in which the charging rate of the storage element is set to the charging rate estimated in the charging rate estimating step when the temperature rise value of the storage element calculated in the temperature rise value calculating step is equal to or less than a predetermined value that defines a flat region; The above-mentioned features constitute a method for estimating the charging rate of a storage element.

[0010] According to these configurations, when the temperature rise value of the storage element calculated by the temperature rise value calculation unit or the temperature rise value calculation step is equal to or less than a predetermined value that defines the flat region, the storage element is determined to be in a flat region where the open circuit voltage characteristic with respect to the charging rate is small. Furthermore, even if the storage element is discharged, the temperature of the storage element is measured without large errors, unlike the SOC estimated by the current integration method.

[0011] Therefore, these configurations make it possible to accurately determine whether the SOC of the storage element is in a flat region or a variable region based on information about the temperature of the storage element, which is different from the SOC estimated by the current integration method. As a result, the SOC can be appropriately corrected according to the result of the region determination, and the accuracy of the SOC estimation can be improved.

[0012] The present invention is also characterized in that the specified value defines a flat region for the temperature rise value of the storage element in a range between the charging rate at which the rate of change of the average temperature rise value of the storage element with respect to the change in charging rate turns negative and the charging rate at which the rate of change of the average temperature rise value of the storage element with respect to the change in charging rate turns positive.

[0013] The present invention is based on the measurement results shown in Fig. 3, and in these measurement results, a phenomenon is observed in which the temperature rise value is lower in the flat region than in the change region at the boundary of a certain threshold y that defines the flat region. The reason for this is unclear, but it is thought that when the storage element is a lithium iron phosphate secondary battery (LFP), lithium iron phosphate is used as the positive electrode active material, graphite is used as the negative electrode active material, and the discharge current value is within a certain range during discharge, when the SOC of the storage element is in the change region, heat generation due to Joule heat proportional to the square of the current becomes dominant, and when it is in the flat region, entropy heat absorption proportional to the current becomes dominant.

[0014] An electric storage element whose SOC is in the change region generates Joule heat and reaction heat inside, causing the temperature to rise. Meanwhile, an electric storage element whose SOC is in the plateau region experiences a large endothermic reaction inside, suppressing the rise in temperature. Therefore, when the SOC transitions from the change region to the plateau region, an electric storage element whose temperature tends to rise due to Joule heat and reaction heat inside the electric storage element will tend to have its temperature decrease due to the endothermic reaction inside the electric storage element. Meanwhile, when the SOC transitions from the plateau region to the change region, an electric storage element whose temperature tends to decrease due to the endothermic reaction inside the electric storage element will tend to have its temperature increase due to Joule heat and reaction heat inside the electric storage element. Therefore, according to this configuration, the temperature rise value of the storage element in the range between the charging rate at which the rate of change of the temperature rise value of the storage element turns negative and the charging rate at which it turns positive in the relationship between the charging rate and temperature of the storage element is defined by a predetermined temperature rise value, and by comparing it with the measured temperature rise value of the storage element, the plateau region of the SOC can be accurately determined.

[0015] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: A plurality of storage elements are connected in series and arranged in close proximity to each other to form a battery pack; The temperature measurement unit measures the temperature of at least one of the storage elements connected in series; a temperature rise value calculation unit that calculates a temperature rise value of one storage element measured by the temperature measurement unit, or an average rise value of each temperature of a predetermined number of storage elements measured by the temperature measurement unit; When the temperature rise value of one storage element calculated by the temperature rise value calculation unit or the average temperature rise value for a predetermined number of storage elements is equal to or less than a predetermined value that defines a flat region, the charging rate correction unit sets the charging rate estimated by the charging rate estimation unit as the charging rate of each storage element. It is characterized by:

[0016] According to this configuration, when a battery pack is formed by arranging a plurality of storage elements closely to each other, the temperature rise value of one storage element constituting the battery pack or the average rise value of each temperature of a predetermined plurality of storage elements constituting the battery pack is calculated without calculating the temperature rise value of all the storage elements constituting the battery pack, and if any of these temperature rise values ​​is equal to or less than a predetermined value that defines a flat region, the charging rate estimated by the charging rate estimation unit can be set as the charging rate of each storage element. Therefore, when a battery pack is formed by arranging a plurality of storage elements closely to each other, it is sufficient to perform the temperature measurement process and the temperature rise value calculation process for only some of the storage elements constituting the battery pack, and these processes are simplified. Therefore, the SOC of each storage element constituting the battery pack can be estimated quickly and accurately.

[0017] The present invention also provides a method for producing a semiconductor device comprising the steps of: A charging rate estimation unit estimates a charging rate of the storage element by a current integration method, The charging rate correction unit corrects the charging rate estimated by the charging rate estimation unit using a Kalman filter.

[0018] According to this configuration, the charging rate correction unit corrects the charging rate by using a Kalman filter to correct the charging rate of the power storage element estimated by the charging rate estimation unit using the current integration method. Effect of the Invention

[0019] According to the present invention, it is possible to provide a storage element state of charge estimation device and a state of charge estimation method that can accurately determine whether the SOC is in a plateau region or a variable region, thereby improving the estimation accuracy of the SOC. [Brief description of the drawings]

[0020] [Figure 1] 1 is a block diagram showing a schematic configuration of a battery pack including a storage element state of charge estimation device according to an embodiment of the present invention; [Diagram 2]1 is a graph showing the SOC-OCV characteristics of a secondary battery that is a subject of charge estimation by a charging rate estimation device and a charging rate estimation method for a storage element according to an embodiment. [Diagram 3] 1 is a graph showing the change in temperature rise value of a secondary battery relative to the change in SOC, in which a predetermined value of the temperature rise value of the secondary battery that defines a flat region is derived and is referred to in a storage element charging rate estimation device and charging rate estimation method according to one embodiment. [Figure 4] 4 is a flowchart showing an outline of a process in a method for estimating a charging rate of a storage element according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Next, a storage element state of charge estimation device and a storage element state of charge estimation method according to an embodiment of the present invention will be described.

[0022] FIG. 1 is a block diagram showing a schematic configuration of a battery pack 2 including a storage element state estimation device 1 according to an embodiment.

[0023] The battery pack 2 supplies power to a power source that operates on electrical energy, for example, in an electric vehicle, a small boat, etc. The battery pack 2 has a battery pack 3, a current sensor 4, and a battery management unit (BMU) 5 that manages the battery pack 3. The current sensor 4 and the BMU 5 constitute the state of charge estimation device 1.

[0024] The battery pack 3 is configured by stacking a plurality of laminated cells, each of which is made up of a secondary battery 31, and connecting them in series, and each secondary battery 31 serves as a power storage element. In this embodiment, each secondary battery 31 is an olivine (iron phosphate) lithium ion secondary battery (LFP), and the change in open circuit voltage (OCV) relative to the change in state of charge (SOC) shows the SOC-OCV characteristics shown in the graph of FIG. 2. The horizontal axis of the graph is SOC [%], the vertical axis is OCV [mV], and the graph shows an SOC-OCV curve. As shown in the SOC-OCV characteristics, each secondary battery 31 shows open circuit voltage characteristics having a flat region L where the change in OCV relative to the change in SOC is relatively small, and a large change region H. The flat region L is set in a region where the change in OCV relative to the change in SOC is, for example, 0.5 [mV / %] or less.

[0025] The charging rate is the ratio [%] of the remaining capacity to the fully charged capacity of the secondary battery 31, and is called SOC (State Of Charge). The open circuit voltage is the voltage between the terminals of the secondary battery 31 when no current flows through the secondary battery 31, and is called OCV (Open Circuit Voltage).

[0026] Each secondary battery 31 and current sensor 4 are connected in series via wiring 6, and are connected to a load 7, such as a charger 7 mounted on an electric vehicle or the like, or a power source provided inside an electric vehicle, etc. The charger 7 charges the battery pack 3, and the load 7 receives power from the battery pack 3 and consumes it.

[0027] The current sensor 4 constitutes a current measurement unit that measures the current flowing through each secondary battery 31. The current sensor 4 measures the current value of each secondary battery 31 at regular intervals and transmits data of the measured current measurement value to a control unit 51 in the BMU 5. The BMU 5 includes the control unit 51 and a module monitoring unit (MMU) 52 that includes a voltage detection circuit and a temperature detection circuit.

[0028] The control unit 51 includes a central processing unit (CPU) 51a, a memory 51b, and a communication unit 51c. The communication unit 51c communicates with an ECU (Electronic Control Unit) 8 mounted on an electric vehicle, a small boat, or the like, and transmits information related to the secondary batteries 31 to the ECU 8. The voltage detection circuits of the MMU 52 are connected to both ends of each secondary battery 31 via detection lines, and measure the inter-terminal voltage of each secondary battery 31 in response to an instruction from the control unit 51.

[0029] The temperature detection circuit of the MMU 52 constitutes a temperature measurement unit that measures the temperature of at least one of the secondary batteries 31 connected in series, and measures the temperature T [°C] of the corresponding secondary battery 31 in a contact or non-contact manner in response to an instruction from the control unit 51. That is, the temperature detection circuit detects the temperature of each of the secondary batteries 31 constituting the battery pack 3, or detects the temperature of only one secondary battery 31, for example, the secondary battery 31 located in the center of the secondary batteries 31 constituting the battery pack 3, or detects the temperatures of a predetermined number of secondary batteries 31, for example, each odd-numbered or even-numbered secondary battery 31 in a column constituting the battery pack 3. In this embodiment, the MMU 52 is configured to be included inside the BMU 51, but may be configured to be integrated with the battery pack 3.

[0030] A computer program for executing the method for estimating the state of charge of an energy storage element according to this embodiment and data required to execute the program are stored in advance in the memory 51b in the control unit 51. Various functional blocks are configured in the control unit 51 by the CPU 51a controlling each part of the circuit in accordance with the computer program. These functional blocks include a state of charge estimation unit 51d, a state of charge correction unit 51e, a temperature rise value calculation unit 51f, and a state of charge correction unit 51g.

[0031] The charging rate estimating unit 51d serves to estimate the charging rate of each secondary battery 31. The charging rate correcting unit 51e serves to correct the charging rate of each secondary battery 31 estimated by the charging rate estimating unit 51d. In this embodiment, the charging rate estimating unit 51d estimates the charging rate of the secondary battery 31 by a current integration method. The charging rate correcting unit 51e corrects the charging rate of the secondary battery 31 estimated by the charging rate estimating unit 51d using a Kalman filter. In this case, the charging rate correcting unit 51e adds the product of a "Kalman gain" and a "terminal voltage prediction error" to the "pre-estimated SOC value", which is the charging rate estimated by the charging rate estimating unit 51d, by the Kalman filter, thereby correcting the "pre-estimated SOC value".

[0032] The temperature rise value calculation unit 51f has a function of calculating the temperature rise value of any one of the secondary batteries 31 measured by the temperature detection circuit of the MMU 52, or the average rise value of each temperature measured by the temperature detection circuit for a predetermined number of secondary batteries 31. The charging rate correction unit 51g has a function of setting the charging rate estimated by the charging rate estimation unit 51d as the charging rate of each secondary battery 31 when the current measured by the current sensor 4 is the discharge current of each secondary battery 31 and the temperature rise value of each secondary battery 31 calculated by the temperature rise value calculation unit 51f is a temperature rise value equal to or less than a predetermined value y that defines a flat region L as described later.

[0033] The memory 51b also constitutes an estimated charging rate storage unit that stores the charging rate estimated by the charging rate estimator 51d, a corrected charging rate storage unit that stores the charging rate corrected by the charging rate corrector 51e, a temperature storage unit that stores the temperature of each secondary battery 31 detected by the temperature detection circuit of the MMU 52, and a predetermined value storage unit that stores a predetermined value y that defines the flat region L. The memory 51b also constitutes an open circuit voltage characteristic storage unit that stores the open circuit voltage characteristic shown in FIG.

[0034] In the graph shown in FIG. 3, the change in the temperature rise value of the secondary battery 31 with respect to the change in SOC during discharge is shown together with the cell temperature change, terminal voltage change, and ambient temperature change of the secondary battery 31. The horizontal axis of the graph is SOC [%], the left vertical axis is temperature [°C], and the right vertical axis is temperature rise value [°C / min] and voltage [V]. The change in the temperature rise value of the secondary battery 31 is shown by characteristic line A drawn with a short dashed line corresponding to the temperature rise value [°C / min] shown on the right vertical axis. The change in the cell temperature of the secondary battery 31 is shown by characteristic line B drawn with a solid line corresponding to the temperature [°C] shown on the left vertical axis. The change in the terminal voltage of the secondary battery 31 is shown by characteristic line C drawn with a long dashed line corresponding to the voltage [V] shown on the right vertical axis. The change in the ambient temperature of the secondary battery 31 is shown by characteristic line D drawn with a dashed line corresponding to the temperature [°C] shown on the left vertical axis.

[0035] The temperature rise value y [°C / min] written on the right vertical axis indicates a predetermined value that defines the flat region L (see FIG. 2). In this embodiment, whether the SOC of the secondary battery 31 is in the flat region L or in the change region H is determined based on the characteristic line A that indicates the change in temperature rise value relative to the change in SOC of the secondary battery 31. In other words, when the temperature rise value of the secondary battery 31 calculated by the temperature rise value calculation unit 51f is equal to or less than the predetermined value y, the SOC estimated by the charging rate estimation unit 51d is determined to be in the flat region L, and the SOC estimated by the charging rate estimation unit 51d is set as the charging rate of the secondary battery 31.

[0036] The specified value y defines the rate of change of the average temperature rise value of the secondary battery 31 in response to changes in SOC, that is, the temperature rise value of the secondary battery 31 in the range between approximately 70% which is the SOC value at which the slope of characteristic line A', which represents the tendency of the slope of characteristic line A, turns negative, and approximately 39% which is the SOC value at which the slope of characteristic line A' turns positive, as a flat region L.

[0037] In the secondary battery 31 whose SOC is in the change region H, Joule heat and reaction heat are generated therein, causing the temperature to rise. In the secondary battery 31 whose SOC is in the plateau region L, the endothermic reaction is increased therein, suppressing the rise in temperature. Therefore, when the SOC transitions from the change region H to the plateau region L at approximately 70% the secondary battery 31, whose temperature tends to rise due to Joule heat and reaction heat in the secondary battery 31, tends to have its temperature fall due to the endothermic reaction in the secondary battery 31. In addition, when the SOC transitions from the plateau region L to the change region H at approximately 39% the secondary battery 31, whose temperature tends to fall due to the endothermic reaction in the secondary battery 31, tends to have its temperature rise due to Joule heat and reaction heat in the secondary battery 31.

[0038] Therefore, in the relationship between the SOC and temperature of the secondary battery 31, the temperature rise value of the secondary battery 31 in the range between the SOC at which the rate of change of the temperature rise value of the secondary battery 31 turns negative and the SOC at which it turns positive is defined by the temperature rise value of a predetermined value y, and by comparing it with the measured temperature rise value of the secondary battery 31, the flat region L of the SOC can be accurately determined.

[0039] It should be noted that even when the SOC is just under 100%, the temperature rise value of the secondary battery 31 will be below the predetermined value y, but this is excluded because it is not an SOC in the range between the SOC at which the rate of change in the temperature rise value turns negative and the SOC at which the rate of change in the temperature rise value turns positive.

[0040] FIG. 4 is a flow chart showing an outline of the process of the method for estimating the state of charge of an energy storage element according to this embodiment.

[0041] First, the CPU 51a acquires the current SOC value of each secondary battery 31 (see step 101). Next, the charging rate estimation unit 51d estimates the SOC of each secondary battery 31 by a current integration method (see step 102). The charging rate estimated in the charging rate estimation step of step 102 is stored in the estimated charging rate storage unit. Next, the current value flowing through each secondary battery 31 is measured by the current sensor 4, and it is determined whether the current flowing through each secondary battery 31 is a discharging current (see step 103). The CPU 51a determines whether the current measured by the current sensor 4 is a current flowing from the battery pack 3 to the load 7, thereby determining whether the current is a discharging current.

[0042] When it is determined that the current flowing through each secondary battery 31 is not a discharge current and the determination result in step S103 is No, the determination process in step S103 is repeated until it is determined that the current flowing through the secondary battery 31 is a discharge current. When it is determined that the current flowing through each secondary battery 31 is a discharge current and the determination result in step S103 is Yes, the temperature rise value calculation unit 51f then calculates the temperature rise value of any one secondary battery 31 measured by the temperature detection circuit of the MMU 52, or the average rise value of each temperature for a predetermined number of secondary batteries 31 measured by the temperature detection circuit, or the average rise value of each temperature for all secondary batteries 31 (see step S104).

[0043] When the temperature rise values ​​are calculated for multiple secondary batteries 31, the temperature rise values ​​of each secondary battery 31 may be calculated first, and the average of the calculated temperature rise values ​​may be calculated later, or the average temperature value of each secondary battery 31 may be calculated first, and the average temperature value may be calculated from the difference between the calculated average temperature value and the previously calculated average temperature value.

[0044] Next, the charging rate corrector 51g determines whether any of the temperature rise values ​​calculated in step S104 is equal to or less than the predetermined value y stored in the predetermined value storage unit (see step S105). If it is determined that the calculated temperature rise value is equal to or less than the predetermined value y, and the determination result in step S105 is Yes, the charging rate corrector 51 determines that the SOC of the secondary battery 31 is in the flat region L, and sets the charging rate estimated by the charging rate estimator 51d, i.e., the SOC estimated by the current integration method, as the charging rate of the secondary battery 31 (see step S106).

[0045] On the other hand, if it is determined that the calculated temperature rise value is not equal to or less than the predetermined value y, and the determination result in step S105 is No, the charging rate correction unit 51 determines that the SOC of the secondary battery 31 is in the change region H, and the charging rate estimated by the charging rate estimation unit 51d is corrected by the charging rate correction unit 51e using a Kalman filter. Then, the charging rate correction unit 51 determines the SOC corrected by the charging rate correction unit 51e as the charging rate of the secondary battery 31 (see step S107).

[0046] According to the storage element state of charge estimation device and state of charge estimation method of this embodiment, when the temperature rise value of the secondary battery 31 calculated by the temperature rise value calculation unit 51f and the temperature rise value calculation step of step S104 is equal to or less than the predetermined value y that defines the flat region L, the secondary battery 31 is determined to be in a state of the flat region L where the OCV (open circuit voltage) characteristic with respect to the SOC has small OCV changes. Moreover, even if the discharge of the secondary battery 31 progresses, the temperature of the secondary battery 31 is measured without large errors, unlike the SOC estimated by the current integration method.

[0047] Therefore, according to the storage element state of charge estimation device and state of charge estimation method of this embodiment, it is possible to accurately determine whether the SOC of the secondary battery 31 is in the flat region L or the variable region H, based on information on the temperature of the secondary battery 31, which is different from the SOC estimated by the current integration method. As a result, it becomes possible to appropriately correct the SOC according to the result of the region determination, and it becomes possible to improve the estimation accuracy of the SOC.

[0048] In the conventional technology in which the region is determined based on the SOC estimated by the current integration method, for example, the secondary battery 31 should be determined to be in the flat region L, but is determined to be in the change region H, and the charging rate is corrected by the Kalman filter, which may reduce the accuracy of the SOC estimation. However, according to the present embodiment, by focusing on the relationship between the SOC of the secondary battery 31 and the temperature rise value, the region is determined based on the temperature rise value measured without a large error, instead of the SOC estimated by the current integration method, which has a large error, and the accuracy of the determination of the flat region L can be improved, thereby reducing the risk of a decrease in the accuracy of the SOC estimation.

[0049] Furthermore, in the conventional technology, as the discharge progresses, the SOC of each secondary battery 31 is determined to be in the change region H when it should have been determined to be in the flat region L, and as a result of the correction of the charging rate by the Kalman filter, there is a possibility that each secondary battery 31 is estimated to have a higher SOC than the actual SOC. Therefore, the operation of each secondary battery 31 may be carried out under the mistaken belief that it has sufficient battery capacity, which may result in a sudden system failure. However, according to the present embodiment, the flat region L can be accurately determined, and the risk of erroneously estimating the SOC can be reduced, thereby reducing the possibility of a sudden system failure.

[0050] In addition, according to the storage element charging rate estimation device and charging rate estimation method of the present embodiment, since the battery pack 3 is constituted by a plurality of secondary batteries 31 arranged in close proximity, the temperature rise value of one secondary battery 31 constituting the battery pack 3 or the average rise value of each temperature for a predetermined plurality of secondary batteries 31 constituting the battery pack 3 is calculated without calculating the temperature rise value of all the secondary batteries 31 constituting the battery pack 3, and if any of these temperature rise values ​​is equal to or less than the predetermined value y that defines the flat region L, the SOC estimated by the charging rate estimation unit 51d can be used as the charging rate of each secondary battery 31. Therefore, when the battery pack 3 is constituted by stacking a plurality of secondary batteries 31 as laminate cells and arranged in close proximity as in the present embodiment, the temperature measurement process and the temperature rise value calculation process are performed only for some of the secondary batteries 31 constituting the battery pack 3, and therefore these processes are simplified. Therefore, the SOC of each secondary battery 31 constituting the battery pack 3 can be estimated quickly and accurately. [Industrial Applicability]

[0051] The above embodiment of the state of charge estimation device and state of charge estimation method for a storage element has been described with reference to the case where the secondary battery 31 is an LFP. However, the present invention is not limited to the case where the secondary battery 31 is an LFP, and can be similarly applied to other storage elements having open circuit voltage characteristics in which a relatively small flat region and a large change region of the open circuit voltage change appear with respect to the state of charge. Even in such cases, the same effects as those of the above embodiment of the state of charge estimation device and state of charge estimation method for a storage element can be achieved. [Explanation of symbols]

[0052] 1: Charging rate estimation device 2: Battery pack 3: Battery pack 31: Secondary battery (energy storage element) 4: Current sensor (current measurement section) 5: Battery Management Unit (BMU) 51: Control unit 51a: CPU 51b:Memory 51d: Charging rate estimation section 51e: Charging rate correction section 51f: Temperature rise calculation section 52: Module Monitoring Unit (MMU)

Claims

1. a current measuring unit for measuring a current flowing through an energy storage element having an open circuit voltage characteristic in which a relatively small flat region and a relatively large change region of the open circuit voltage appear with respect to a change in the charging rate; A temperature measurement unit that measures the temperature of the energy storage element; A charging rate estimation unit that estimates a charging rate of the storage element; a charging rate correction unit that corrects the charging rate of the storage element estimated by the charging rate estimation unit; a temperature rise value calculation unit that calculates a rise value of the temperature of the energy storage element measured by the temperature measurement unit; a charging rate correcting unit that sets the charging rate estimated by the charging rate estimating unit as the charging rate of the storage element when the current measured by the current measuring unit is a discharge current of the storage element and the temperature rise value of the storage element calculated by the temperature rise value calculating unit is a temperature rise value equal to or less than a predetermined value that defines the flat region; and A storage element charging rate estimating device comprising:

2. The device for estimating the charging rate of a storage element as described in claim 1, characterized in that the specified value defines the flat region as a temperature rise value of the storage element in a range between the charging rate at which a rate of change of the average temperature rise value of the storage element relative to the change in the charging rate turns negative and the charging rate at which a rate of change of the average temperature rise value of the storage element relative to the change in the charging rate turns positive.

3. A plurality of the storage elements are connected in series and arranged adjacent to each other to form a battery pack, the temperature measurement unit measures a temperature of at least one of the storage elements connected in series; the temperature rise value calculation unit calculates a temperature rise value of one of the storage elements measured by the temperature measurement unit, or an average rise value of each temperature of a predetermined number of the storage elements measured by the temperature measurement unit; When the temperature rise value of one of the storage elements calculated by the temperature rise value calculation unit or the average temperature rise value for a predetermined number of the storage elements is equal to or less than the predetermined value that defines the flat region, the charging rate correction unit sets the charging rate estimated by the charging rate estimation unit as the charging rate of each of the storage elements.

3. The device for estimating a state of charge of a storage element according to claim 1 or 2.

4. The charging rate estimation unit estimates the charging rate of the storage element by a current integration method, 4. The storage element state of charge estimating device according to claim 1, wherein the state of charge correction unit corrects the state of charge estimated by the state of charge estimation unit using a Kalman filter.

5. a current measuring step of measuring a current flowing through a storage element having an open circuit voltage characteristic in which a relatively small flat region and a relatively large change region of the open circuit voltage appear with respect to a change in the charging rate; a temperature measuring step of measuring a temperature of the energy storage element; a charging rate estimating step of estimating a charging rate of the storage element; a charging rate correction step of correcting the charging rate of the storage element estimated in the charging rate estimation step; a discharge current determination step of determining whether or not the current measured in the current measurement step is a discharge current of the storage element; a temperature rise value calculation step of calculating a rise value of the temperature of the storage element measured in the temperature measurement step when the current measured in the current measurement step is determined to be a discharge current of the storage element by the discharge current determination step; a charging rate correcting step of setting the charging rate of the storage element to the charging rate estimated in the charging rate estimating step when the temperature rise value of the storage element calculated in the temperature rise value calculating step is equal to or less than a predetermined value that defines the flat region; A method for estimating a charging rate of a storage element comprising:

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