JP2023029091A - State-of-charge estimation device of power storage element, and state-of-charge estimation method thereof - Google Patents

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

The present invention relates to a charging rate estimation device and a charging rate estimation method for a power storage element in which a flat region and a large change region of open circuit voltage change appear with respect to changes in the charging rate.

Conventionally, as this kind of charging rate estimation device and charging rate estimation method, for example, there is a state estimation device and a state estimation method disclosed in Patent Document 1.

The state estimation device and the state estimation method disclosed in the same document are for estimating the charging rate of a lithium iron phosphate secondary battery (LFP), and the SOC-OCV characteristics of the LFP shown in FIG. 2 of the same document. take advantage of This SOC-OCV characteristic is expressed with the horizontal axis as SOC (charge rate) and the vertical axis as OCV (open circuit voltage), and the OCV change with respect to the SOC change 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 OCV change with respect to the SOC change is relatively small and a large change region.

In the state estimation device and the state estimation method disclosed in the document, attention is paid to the fact that applying correction using a battery model and a Kalman filter to the LFP may reduce the accuracy of SOC estimation. 6, in a change region where the OCV change with respect to the SOC change is large, the SOC estimated by the current integration method is corrected using the Kalman filter. In a flat region where the OCV change with respect 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.

Japanese Patent No. 6657967

In this document, based on the SOC estimated by the current integration method, the SOC-OCV characteristic is referenced to determine whether the SOC estimated by the LFP is in a flat area or in a changing area. Then, based on the result of the region determination, it is determined whether or not to perform Kalman filter correction for the SOC. However, the SOC estimated by the current integration method accumulates errors each time the current integration is performed. Therefore, as the discharge of the LFP progresses, the estimation error increases, and the accuracy of region determination is significantly reduced. This is especially pronounced in LFPs that have plateau regions with relatively small OCV changes with SOC changes.

In view of this point, SOC estimation accuracy is improved by accurately determining whether the SOC is in a flat region or a changing region based on information different from the SOC estimated by the current integration method. It is desirable to

For this reason, the present invention
a current measuring unit for measuring the current flowing through the storage element having an open circuit voltage characteristic in which a relatively small flat area and a large open circuit voltage change area appear with respect to changes in the charging rate;
a temperature measuring unit that measures the temperature of the storage element;
a charging rate estimating unit for estimating the charging rate of the storage element;
a charging rate correcting unit that corrects the charging rate of the storage element estimated by the charging rate estimating unit;
a temperature rise value calculation unit that calculates a temperature rise value of the storage element measured by the temperature measurement unit;
When the current measured by the current measurement unit is the 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 the flat region. and a charging rate correcting unit that sets the charging rate estimated by the charging rate estimating unit to the charging rate of the storage element.

In addition, the present invention
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 area and a large open circuit voltage change area appear with respect to changes in the charging rate;
a temperature measurement step of measuring the temperature of the storage element;
a charging rate estimation step of estimating the 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 the current measured in the current measurement step is the discharge current of the storage element;
a temperature rise value calculation step of calculating a temperature rise value of the storage element measured in the temperature measurement step when the discharge current determination step determines that the current measured by the current measurement unit is the discharge current of the storage element; ,
If the temperature rise value of the storage element calculated by the temperature rise value calculating step is equal to or less than the predetermined value defining the flat region, the charging rate estimated by the charging rate estimating step is set as the charging rate of the storage element. and a charging rate correcting step.

According to these configurations, when the temperature rise value of the power storage element calculated by the temperature rise value calculating unit or the temperature rise value calculating step is a temperature rise value equal to or lower than the predetermined value that defines the flat region, the power storage element is charged. It is determined that the open circuit voltage to rate characteristic lies in a plateau region of small open circuit voltage variation. Moreover, the temperature of the storage element can be measured without increasing the error, unlike the SOC estimated by the current integration method, even if the discharge of the storage element progresses.

Therefore, according to these configurations, it is possible to accurately determine whether the SOC of the storage element is in the flat area or in the changing area based on the temperature information of the storage element that is different from the SOC estimated by the current integration method. can be done. As a result, it becomes possible to appropriately correct the SOC according to the result of the area determination, and it is possible to improve the estimation accuracy of the SOC.

In addition, the predetermined value is a charging rate at which the change rate of the average temperature rise value change of the storage element with respect to the charging rate change turns negative, and the change rate of the average temperature rise value change of the storage element with respect to the charging rate change. is characterized by demarcating the temperature rise value of the storage element in the range between the charging rate at which the value turns positive and the flat region.

The present invention is based on the measurement results shown in FIG. 3, in which the temperature rise value is lower in the plateau region than in the change region with respect to a predetermined threshold value y that defines the plateau region. can be seen. Although the reason for this is not clear, for example, the power storage element is a lithium iron phosphate secondary battery (LFP), lithium iron phosphate is adopted as the positive electrode active material, graphite is adopted as the negative electrode active material, and at the time of discharge When the discharge current value is within a certain range, heat generation due to Joule heat proportional to the square of the current is dominant when the SOC of the storage element is in the variable region, and entropy absorption proportional to the current is dominant when the SOC is in the flat region. This is thought to be due to being dominant.

A power storage element whose SOC is in the variable region generates Joule heat or heat of reaction inside, and the temperature rises. In addition, the endothermic reaction inside the electric storage element whose SOC is in the flat region is large, and the rise in temperature is suppressed. Therefore, when the SOC transitions from the variable region to the flat region, the temperature of the storage element, which tends to increase due to Joule heat and reaction heat inside the storage element, tends to decrease due to the endothermic reaction inside the storage element. In addition, when the SOC transitions from the flat region to the variable region, the temperature of the storage element tends to decrease due to the endothermic reaction inside the storage element, but the temperature tends to rise due to Joule heat and reaction heat inside the storage element. Therefore, according to this configuration, in the relationship between the charging rate of the storage element and the temperature, the range between the charging rate at which the tendency of the rate of change in the temperature rise value of the storage element turns negative and the charging rate at which it turns positive. By defining the temperature rise value of the storage element at , by a predetermined temperature rise value and comparing it with the measured temperature rise value of the storage element, the flat region of the SOC can be accurately determined.

In addition, the present invention
A plurality of power storage elements are connected in series and arranged in close proximity to form an assembled battery,
the temperature measurement unit measures the temperature of at least one of the power storage elements connected in series;
A temperature rise value calculation unit calculates a temperature rise value of one power storage element measured by the temperature measurement unit or an average temperature rise value of a plurality of predetermined power storage elements measured by the temperature measurement unit. death,
The state of charge correction unit corrects the temperature below a predetermined value at which the temperature rise value of one power storage element calculated by the temperature rise value calculation unit or the average temperature rise value of a plurality of predetermined power storage elements defines a flat region. In the case of a rising value, the charging rate estimated by the charging rate estimating unit is used as the charging rate of each power storage element.

According to this configuration, when a plurality of storage elements are arranged close to form an assembled battery, the assembled battery can be configured without calculating the temperature rise values of all the storage elements that form the assembled battery. A temperature rise value of one power storage element or an average temperature rise value of a plurality of predetermined power storage elements constituting an assembled battery is calculated. If the temperature rise value is less than or equal to the value, the charging rate estimated by the charging rate estimating unit can be used as the charging rate of each power storage element. Therefore, when a plurality of storage elements are arranged close to each other to form an assembled battery, the temperature measurement process and the temperature rise value calculation process need only be performed for some of the storage elements that make up the assembled battery. is simplified. Therefore, the estimation of the SOC of each power storage element that constitutes the assembled battery can be performed with high accuracy and speed.

In addition, the present invention
The charging rate estimating unit estimates the charging rate of the storage element by the current integration method,
The charging rate corrector corrects the charging rate estimated by the charging rate estimator using a Kalman filter.

According to this configuration, the charge rate correction unit corrects the charge rate by correcting the charge rate of the storage element estimated by the current integration method by the charge rate estimation unit using the Kalman filter.

According to the present invention, there is provided a charging rate estimating device and a charging rate estimating method for a power storage element that can accurately determine whether the SOC is in a flat region or in a changing region and improve the accuracy of SOC estimation. can provide.

1 is a block diagram showing a schematic configuration of a battery pack including a device for estimating a state of charge of a power storage element according to an embodiment of the present invention; FIG. 5 is a graph showing the SOC-OCV characteristics of a secondary battery that is subject to charging rate estimation by the device and method for estimating charging rate of a power storage element according to an embodiment; The temperature with respect to the SOC change of the secondary battery from which the temperature rise value of the secondary battery of the predetermined value defining the flat region is derived, which is referred to in the charging rate estimation device and charging rate estimation method of the storage element according to one embodiment. It is a graph which shows a rise value change. 4 is a flow chart showing an outline of processing in a method for estimating a charging rate of an electric storage element according to an embodiment of the present invention;

Next, an apparatus for estimating a charging rate of a power storage element and a method for estimating a charging rate according to an embodiment of the present invention will be described.

FIG. 1 is a block diagram showing a schematic configuration of a battery pack 2 including a device 1 for estimating a state of charge of a power storage element according to one embodiment.

The battery pack 2 supplies electric power to a power source that operates on electric energy, for example, in an electric vehicle, a small boat, or the like. The battery pack 2 has an assembled battery 3 , a current sensor 4 , and a battery management unit (BMU) 5 that manages the assembled battery 3 . These current sensor 4 and BMU 5 constitute the charging rate estimating device 1 .

The assembled battery 3 is configured by stacking a plurality of laminate cells each composed of a secondary battery 31 and connecting them in series, and each secondary battery 31 is used as a power storage element. In this embodiment, each secondary battery 31 is an olivine-based (iron phosphate) lithium ion secondary battery (LFP), and the change in open circuit voltage (OCV) with respect to the change in state of charge (SOC) is shown in the graph of FIG. 4 shows the SOC-OCV characteristics shown. The horizontal axis of the graph is SOC [%], the vertical axis is OCV [mV], and the graph shows an SOC-OCV curve. Each secondary battery 31 exhibits an open circuit voltage characteristic having a flat region L where the OCV change with respect to the SOC change is relatively small and a large change region H, as shown in this SOC-OCV characteristic. The flat region L is set to a region where the OCV change with respect to the SOC change is, for example, 0.5 [mV/%] or less.

The charging rate is the ratio [%] of the remaining capacity to the full charge 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 is flowing through the secondary battery 31, and is called OCV (Open Circuit Voltage).

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

The current sensor 4 constitutes a current measuring section 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 value to the control unit 51 in the BMU 5 . The BMU 5 includes a controller 51 and a module monitoring unit (MMU) 52 including a voltage detection circuit and a temperature detection circuit.

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

The temperature detection circuit of the MMU 52 constitutes a temperature measurement section that measures the temperature of at least one of the secondary batteries 31 connected in series, and responds to an instruction from the control section 51 to detect the corresponding two The temperature T [° C.] of the secondary battery 31 is measured by contact or non-contact. That is, the temperature detection circuit detects the temperature of each secondary battery 31 that constitutes the assembled battery 3, or detects the temperature of one secondary battery 31, for example, the temperature of each secondary battery 31 that constitutes the assembled battery 3. The temperature of only the secondary battery 31 located in the center is detected, or the temperature of a predetermined plurality of secondary batteries 31, for example, the odd-numbered or even-numbered secondary batteries 31 in the row constituting the assembled battery 3 is detected. Detect temperature. Although the MMU 52 is included inside the BMU 51 in this embodiment, it may be integrated with the assembled battery 3 .

A memory 51b in the control unit 51 stores in advance a computer program for executing the method for estimating the state of charge of the storage element according to the present embodiment, and data necessary for executing the program. Various functional blocks are configured in the control unit 51 by controlling each circuit unit of the CPU 51a according to the computer program. This functional block includes a charging rate estimator 51d, a charging rate correcting section 51e, a temperature rise value calculating section 51f, and a charging rate correcting section 51g.

The charging rate estimator 51 d functions to estimate the charging rate of each secondary battery 31 . Also, the charging rate correction unit 51e functions to correct the charging rate of each secondary battery 31 estimated by the charging rate estimation unit 51d. In this embodiment, the charging rate estimator 51d estimates the charging rate of the secondary battery 31 by the current integration method. The charging rate correction unit 51e uses a Kalman filter to correct the charging rate of the secondary battery 31 estimated by the charging rate estimation unit 51d. In this case, the product of the "Kalman gain" and the "prediction error of the terminal voltage" in the charging rate correction unit 51e is obtained by applying the Kalman filter is added to correct the "prior estimate of SOC".

The temperature rise value calculation unit 51f calculates the temperature rise value of any one secondary battery 31 measured by the temperature detection circuit of the MMU 52, or the temperature rise value of a plurality of predetermined secondary batteries 31 measured by the temperature detection circuit. It performs the function of calculating the average rise value of each temperature. The charging rate correction unit 51g determines that the current measured by the current sensor 4 is the discharge current of each secondary battery 31, and that the temperature rise value of each secondary battery 31 calculated by the temperature rise value calculation unit 51f is As will be described later, when the temperature rise value is equal to or less than a predetermined value y that defines the flat region L, the charging rate estimated by the charging rate estimating unit 51 d is used as the charging rate of each secondary battery 31 .

The memory 51b also includes an estimated charging rate storage unit that stores the charging rate estimated by the charging rate estimating unit 51d, a corrected charging rate storage unit that stores the charging rate corrected by the charging rate correcting unit 51e, and temperature detection of the MMU 52. A temperature storage section for storing the temperature of each secondary battery 31 detected by the circuit and a predetermined value storage section for storing a predetermined value y defining the flat region L are configured. Also, the memory 51b constitutes an open circuit voltage characteristic storage unit that stores the open circuit voltage characteristic shown in FIG.

The graph shown in FIG. 3 shows changes in the temperature rise value with respect to changes in the SOC during discharging of the secondary battery 31, along with changes in the cell temperature of the secondary battery 31, changes in the inter-terminal voltage, and changes in the ambient temperature. In the graph, the horizontal axis is SOC [%], the left vertical axis is temperature [°C], and the right vertical axis is temperature rise value [°C/min] and voltage [V]. A change in the temperature rise value of the secondary battery 31 is represented by a characteristic line A drawn by a short dashed line corresponding to the temperature rise value [°C/min] indicated on the vertical axis on the right side. A change in cell temperature of the secondary battery 31 is represented by a characteristic line B drawn as a solid line corresponding to the temperature [° C.] indicated on the left vertical axis. A change in voltage between terminals of the secondary battery 31 is represented by a characteristic line C drawn by a long dashed line corresponding to the voltage [V] shown on the vertical axis on the right side. Ambient temperature change of the secondary battery 31 is represented by a characteristic line D drawn by a dashed dotted line corresponding to the temperature [° C.] indicated on the left vertical axis.

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 variable region H is determined based on the characteristic line A representing the temperature rise value change with respect to the SOC change of the secondary battery 31 . That is, 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 falls within the flat region L. The SOC determined to be present and estimated by the charging rate estimating unit 51 d is used as the charging rate of the secondary battery 31 .

The predetermined value y is the rate of change of the average temperature rise value change of the secondary battery 31 with respect to the SOC change, that is, the SOC value at which the slope of the characteristic line A′ representing the tendency of the slope of the characteristic line A turns negative. A flat region L is defined as a temperature rise value of the secondary battery 31 in a range between 70[%] and about 39[%], which is the SOC value at which the slope of the characteristic line A' turns positive.

The secondary battery 31 whose SOC is in the change region H generates Joule heat and heat of reaction inside, and the temperature rises. Further, in the secondary battery 31 whose SOC is in the flat region L, the endothermic reaction inside becomes large, and the rise in temperature is suppressed. Therefore, when the SOC transitions from the variable region H to the flat region L at about 70[%], the secondary battery 31 tends to increase in temperature due to Joule heat and reaction heat inside the secondary battery 31. The temperature tends to drop due to the endothermic reaction inside 31 . Further, when the SOC transitions from the flat region L to the variable region H at about 39[%], the temperature of the secondary battery 31 tends to drop due to the endothermic reaction inside the secondary battery 31. The temperature tends to rise due to Joule heat and reaction heat.

Therefore, in the relationship between the SOC of the secondary battery 31 and the temperature, the secondary battery 31 is in the range between the SOC at which the tendency of the change rate 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 the predetermined value y, and compared with the measured temperature rise value of the secondary battery 31, the flat region L of the SOC can be accurately determined.

When the SOC is slightly less than 100[%], the temperature rise value of the secondary battery 31 becomes a temperature rise value equal to or less than the predetermined value y. Excluded because it is not an SOC in the range between the SOC and the SOC that goes positive.

FIG. 4 is a flow chart showing an outline of the processing of the method for estimating the state of charge of the storage element according to the present embodiment.

First, the current SOC value of each secondary battery 31 is acquired by the CPU 51a (see step 101). Next, the SOC of each secondary battery 31 is estimated by the charging rate estimator 51d by the 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 or not the current flowing through each secondary battery 31 is a discharge current (see step 103). The CPU 51a determines whether or not the current measured by the current sensor 4 is the current flowing from the assembled battery 3 to the load 7, thereby determining whether or not it is the discharge current.

If it is determined that the current flowing through each secondary battery 31 is not the discharging current and the determination result in step S103 becomes No, the determination in step S103 continues until it is determined that the current flowing through the secondary battery 31 is the discharging current. The process is repeated. Further, when it is determined that the current flowing through each secondary battery 31 is a discharge current and the determination result in step S103 becomes Yes, next, the temperature rise value calculation unit 51f measures the temperature of the temperature detection circuit of the MMU 52. Temperature rise value of any one secondary battery 31, or average temperature rise value of a plurality of predetermined secondary batteries 31 measured by a temperature detection circuit, or all secondary batteries 31 is calculated (see step S104).

When the temperature rise value is calculated for a plurality of secondary batteries 31, the temperature rise value of each secondary battery 31 is calculated first, and the average of the calculated temperature rise values is calculated afterwards. Alternatively, the average temperature of each secondary battery 31 may be calculated first, and then calculated from the difference between the calculated average temperature value and the previously calculated average temperature value.

Next, the charging rate correction unit 51g determines whether any temperature rise value calculated in step S104 is a temperature rise value equal to or less than the predetermined value y stored in the predetermined value storage unit ( See step S105). When 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 becomes Yes, the SOC of the secondary battery 31 is brought to the flat region L by the state of charge correction unit 51. The charging rate estimated by the charging rate estimating unit 51d, that is, the SOC estimated by the current integration method is set as the charging rate of the secondary battery 31 (see step S106).

On the other hand, when 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 becomes No, the SOC of the secondary battery 31 is set in the change range by the state of charge correction unit 51. The charging rate that is determined to be H and is estimated by the charging rate estimating section 51d is corrected by the charging rate correcting section 51e using a Kalman filter. Then, the charging rate correction unit 51 sets the SOC corrected by the charging rate correction unit 51e as the charging rate of the secondary battery 31 (see step S107).

According to the charging rate estimating device and charging rate estimating method of the storage element according to the present embodiment, 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 a temperature rise value equal to or less than the predetermined value y that defines the flat region L, the secondary battery 31 is in the state of the flat region L where the OCV (open circuit voltage) characteristic with respect to the SOC is small in OCV change, be judged. Also, the temperature of the secondary battery 31 can be measured without increasing the error, unlike the SOC estimated by the current integration method, even if the discharge of the secondary battery 31 progresses.

Therefore, according to the device for estimating the state of charge of the storage element and the method for estimating the state of charge of the storage element according to the present embodiment, the temperature of the secondary battery 31 is determined based on the temperature information of the secondary battery 31, which is different from the SOC estimated by the current integration method. Whether the SOC is in the flat region L or in the changing region H can be accurately determined. As a result, it becomes possible to appropriately correct the SOC according to the result of the area determination, and it is possible to improve the estimation accuracy of the SOC.

In the prior art that determines the region based on the SOC estimated by the current integration method, for example, the secondary battery 31 is determined to be in the change region H when it should be determined to be in the flat region L. Therefore, there is a possibility that the accuracy of SOC estimation may decrease due to the correction of the charging rate by the Kalman filter. However, according to the present embodiment, focusing on the relationship between the SOC of the secondary battery 31 and the temperature rise value, instead of the SOC that is estimated by the current integration method and has a large error, it is measured without a large error. By performing the region determination based on the temperature rise value obtained, the determination accuracy of the flat region L can be improved, so that the possibility of deterioration in the SOC estimation accuracy can be reduced.

In addition, in the prior art, as the discharge progressed, it was determined to be in the change region H instead of being in the flat region L. Therefore, the charging rate was corrected by the Kalman filter. , there is a possibility that each secondary battery 31 is estimated to have an SOC higher than the actual one. Therefore, as a result of proceeding with operation with an erroneous understanding that each secondary battery 31 has a sufficient battery capacity, there is a possibility that a sudden system failure may occur. However, according to the present embodiment, the flat region L can be accurately determined, and the possibility of erroneously estimating the SOC can be reduced, so that the possibility of a sudden system failure can be reduced.

Further, according to the device for estimating the state of charge of an electric storage element and the method for estimating the state of charge of an electric storage element according to the present embodiment, the plurality of secondary batteries 31 are arranged in close proximity to form the assembled battery 3. Even if the temperature rise value of the secondary battery 31 is not calculated, the temperature rise value of one secondary battery 31 constituting the assembled battery 3, or a predetermined plurality of secondary batteries constituting the assembled battery 3 31 is calculated, and if any of these temperature rise values is a temperature rise value equal to or less than a predetermined value y that defines the flat region L, the SOC estimated by the charging rate estimating unit 51d can be taken as the charging rate of each secondary battery 31 . Therefore, when the assembled battery 3 is configured by stacking a plurality of secondary batteries 31 as laminated cells and arranged close to each other as in the present embodiment, the temperature measurement process and the temperature rise value calculation process are performed on the assembled battery 3. Each of these processes is simplified because it is sufficient to perform only a part of the constituent secondary batteries 31 . Therefore, the estimation of the SOC of each secondary battery 31 constituting the assembled battery 3 can be performed with high accuracy and speed.

The device for estimating the state of charge of the storage element and the method for estimating the state of charge of the storage element according to the above-described embodiment have been described for 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. can be similarly applied to other storage elements having Also in this case, the same effects as those of the device for estimating the charging rate and the method for estimating the charging rate of the storage element according to the above-described embodiments can be obtained.

1: Charging rate estimation device 2: Battery pack 3: Battery assembly 31: Secondary battery (storage element)
4: Current sensor (current measurement part)
5: Battery Management Unit (BMU)
51: Control unit 51a: CPU
51b: memory 51d: charging rate estimator 51e: charging rate corrector 51f: temperature rise calculator 52: module monitoring unit (MMU)

Claims (5)

a current measuring unit for measuring the current flowing through the storage element having an open circuit voltage characteristic in which a relatively small flat area and a large open circuit voltage change area appear with respect to changes in the charging rate;
a temperature measuring unit that measures the temperature of the storage element;
a charging rate estimating unit for estimating the charging rate of the storage element;
a charging rate correcting unit that corrects the charging rate of the storage element estimated by the charging rate estimating unit;
a temperature rise value calculation unit that calculates a temperature rise value of the storage element measured by the temperature measurement unit;
The current measured by the current measurement unit is the 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 equal to or lower than a predetermined value defining the flat region. and a charging rate correction unit that sets the charging rate estimated by the charging rate estimating unit to the charging rate of the storage element when the value is a rising value. The predetermined value includes a charging rate at which a rate of change in the average temperature rise value of the storage element with respect to the change in the charging rate turns negative, and a rate of change in the average temperature rise value of the storage element with respect to the change in the charging rate. 2. The device for estimating a charging rate of an accumulating element according to claim 1, wherein a temperature rise value of the accumulating element in a range between a positive charging rate and a charging rate is defined in the flat region. a plurality of the storage elements are connected in series and arranged in close proximity to form an assembled battery;
the temperature measuring unit measures the temperature of at least one of the power storage elements connected in series;
The temperature rise value calculation unit calculates a temperature rise value of one storage element measured by the temperature measurement unit, or an average temperature of a plurality of predetermined storage elements measured by the temperature measurement unit. Calculate the increase value of
The charging rate correcting unit defines the flat region based on the temperature rise value of one storage element calculated by the temperature rise value calculation unit or an average temperature rise value of a predetermined plurality of storage elements. 3. The storage element according to claim 1, wherein when the temperature rise value is equal to or less than the predetermined value, the charging rate estimated by the charging rate estimating unit is set as the charging rate of each storage element. charging rate estimator. The charging rate estimating unit estimates the charging rate of the storage element by a current integration method,
The charging rate of the storage element according to any one of claims 1 to 3, wherein the charging rate correcting section corrects the charging rate estimated by the charging rate estimating section using a Kalman filter. estimation device. 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 area and a large open circuit voltage change area appear with respect to changes in the charging rate;
a temperature measurement step of measuring the temperature of the storage element;
a charging rate estimation step of estimating the 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 the current measured in the current measurement step is the discharge current of the storage element;
When the discharge current determination step determines that the current measured by the current measuring unit is the discharge current of the storage element, the temperature for calculating the temperature rise value of the storage element measured by the temperature measurement step. an increase value calculation step;
When the temperature rise value of the storage element calculated by the temperature rise value calculation step is a temperature rise value equal to or lower than a predetermined value defining the flat region, the charging rate estimated by the charging rate estimation step is and a charging rate correction step of setting the charging rate to .

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