Estimation device, power storage device, estimation method, and computer program

Abstract

The estimation device is provided with a control unit that estimates the full charge capacity or the degree of degradation of the power storage element. The control unit discharges the power storage element at a constant voltage until a necessary SOC is reached, charges the power storage element to a fully charged state thereof, and controls the power storage element to be charged on the basis of an integrated value of a charging current until the necessary SOC reaches the fully charged state or an integrated value of a discharging current until the necessary SOC reaches the fully charged state from the fully charged state. The full charge capacity or the degree of degradation of the power storage element is estimated.

Description

Technical Field

[0001] The present invention relates to an estimation device, a power storage device, an estimation method, and a computer program. Background Art

[0002] In recent years, the electrification of devices such as brakes and power steering in mobile bodies has been promoted to achieve autonomous driving. In the power supply from a storage device such as a 12V battery to those electric devices (also called auxiliary machines), higher stability is required. Therefore, the demand for monitoring / estimating the power supply capacity of the 12V battery, the so-called state of function (SOF), is increasing.

[0003] The storage battery deteriorates with the passage of time and with the passage of power (charging and / or discharging), and its full charge capacity decreases. In order to stably supply power from the storage battery to auxiliary machines, it is necessary to grasp the full charge capacity that has decreased in this way.

[0004] Patent Document 1 discloses a technology for setting the state of charge (SOC) of a battery to a predetermined SOC with high accuracy and performing a battery degradation determination.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-236381 Summary of the invention

[0008] Problems to be solved by the invention

[0009] There is a method that estimates the full charge capacity of a battery based on the cumulative value of the charging current from the low SOC to the full charge state after discharging the battery to a low SOC (e.g., SOC near 0%). Research on applying this method to a storage cell (cell) for a purpose such as a battery for a mobile body that is required to provide a specified power supply capacity whenever the mobile body is started, or a storage device including a plurality of storage cells, has not been fully conducted. Hereinafter, storage cells and storage devices are collectively referred to as "storage elements".

[0010] One aspect of the present invention provides an estimation device, a power storage device, an estimation method, and a computer program capable of estimating the full charge capacity or the degree of degradation of a power storage element while ensuring power supply capability.

[0011] Means for solving problems

[0012] An estimation device according to one embodiment of the present invention comprises: a control unit for estimating the full charge capacity or the degree of degradation of an electric storage element. The control unit estimates the full charge capacity or the degree of degradation of the electric storage element based on the cumulative value of the charging current from the required SOC to the fully charged state when the electric storage element is discharged at a constant voltage (CV discharge) until the required SOC is reached and the electric storage element is charged to its fully charged state, or the cumulative value of the discharging current from the fully charged state to the required SOC.

[0013] Effects of the Invention

[0014] According to the above aspect, it is possible to estimate the full charge capacity or the degree of degradation of the power storage element while ensuring the power supply capability (required SOC). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a perspective view showing a configuration example of a power storage device on which the estimation device according to the embodiment is mounted.

[0016] Figure 2 It is an exploded perspective view showing a configuration example of the power storage device.

[0017] Figure 3 It is a block diagram showing a configuration example of a power storage device.

[0018] Figure 4 This is a diagram for explaining a method of estimating the power supply capacity of the power storage device.

[0019] Figure 5 This is a circuit diagram showing an example of a power storage device model.

[0020] Figure 6 It is a graph showing a part of a SOC-open circuit voltage (OCV) profile.

[0021] Figure 7 This is a diagram for explaining a method of determining the required SOC.

[0022] Figure 8 It is a diagram for explaining the voltage behavior of the power storage cell when CV discharge is performed.

[0023] Fig. 9 It is a diagram for explaining the voltage behavior of the power storage cell when constant current discharge (CC discharge) is performed.

[0024] Fig.10 It is a diagram for explaining the voltage behavior of the power storage cell when charging from the required SOC to the fully charged state. DETAILED DESCRIPTION

[0025] The following is a description of an outline of the embodiments.

[0026] (1) The estimation device includes a control unit for estimating the full charge capacity or the degree of degradation of the storage element. The control unit estimates the full charge capacity or the degree of degradation of the storage element based on the cumulative value of the charging current from the required SOC to the fully charged state when the storage element is discharged at a constant voltage (CV discharge) until the required SOC is reached and the storage element is charged to its fully charged state, or the cumulative value of the discharging current from the fully charged state to the required SOC.

[0027] Here, the "required SOC" means the SOC near the discharge end point determined so that the storage element can supply a predetermined amount of power to an electric load connected thereto. In a storage element mounted on a moving object, the required SOC may be the SOC required to supply a predetermined amount of power for starting the moving object when it is stopped.

[0028] The “degree of deterioration” may be the capacity retention rate of the power storage element or the state of health (SOH).

[0029] CV discharge may also be terminated when the discharge current becomes less than a threshold value (e.g., less than 1 ampere). The storage element may perform CV discharge in the entire region of the discharge process for estimating the full charge capacity or the degree of degradation, or may perform CV discharge near the discharge termination point after performing CC discharge (i.e., CCCV discharge may also be performed).

[0030] According to the above-described estimation device, the full charge capacity or the degree of degradation of the power storage element can be estimated with high accuracy based on the required SOC reached by using CV discharge.

[0031] In CC discharge, in which discharge is stopped based on the detected voltage of the storage element, it is difficult to reach the target SOC due to the influence of polarization characteristics that change according to the operating conditions of the storage element (temperature, current, degree of degradation of the storage element, etc.). Therefore, if the full charge capacity or degree of degradation of the storage element is estimated based on the necessary SOC to be reached by CC discharge, the estimation accuracy is unstable.

[0032] In contrast, in the above-described estimation device, the required SOC to be reliably reached by discharging power storage element CV is used to estimate the full charge capacity or the degree of degradation, and therefore the estimation accuracy is stable.

[0033] (2) In the estimation device described in (1) above, the required SOC may be determined as a non-flat region included in a SOC-open circuit voltage (OCV) curve of the power storage element.

[0034] The positive electrode active material includes lithium iron phosphate (LiFePO 4 The SOC-OCV curve of a lithium-ion battery (so-called LFP battery) includes a "flat region" where the voltage change accompanying charge and discharge hardly occurs. The "non-flat region" means an SOC region near the discharge end point where the SOC-OCV curve has a slope greater than a specified value (a slope at which OCV can be reset). Storage elements other than LFP batteries also have an SOC region with a large slope of the SOC-OCV curve near the discharge end point. This SOC region with a large slope is called a "non-flat region."

[0035] According to the above structure, by discharging the storage element to the necessary SOC, an SOC value closer to the true value (i.e., the SOC value after OCV is reset) is obtained based on the detected voltage of the storage element after polarization is eliminated, and the SOC value is added to the accumulated value of the charging current, thereby being able to estimate the full charge capacity or degree of degradation of the storage element with high accuracy.

[0036] (3) In the estimation device described in (1) or (2) above, the required SOC may be determined using a storage element model that simulates voltage behavior of the storage element associated with discharge.

[0037] The storage element model may be an equivalent circuit model, but is not limited thereto. The equivalent circuit model may simulate the voltage behavior of a single storage cell (battery unit) or the voltage behavior of a storage device including a plurality of storage cells.

[0038] Alternatively, the storage element model may be a lookup table in which the internal resistance and temperature are stored in correspondence with the required SOC.

[0039] According to the above configuration, the required SOC is derived from the power storage element model in consideration of the influence of the polarization characteristics that vary according to the operating conditions of the power storage element (temperature, degree of deterioration of the power storage element, etc.).

[0040] (4) In the estimation device described in (3) above, the power storage element model may be a power storage device model that simulates the operation of a power storage device having a plurality of power storage cells and a conductive member.

[0041] Here, "conductive member" means a member other than a storage element that constitutes a conductive path (power line) in a storage device. The conductive member may also include a wiring member (e.g., wiring, bus bar, etc.), a connection portion of the wiring member (e.g., a welding portion, a connection portion based on a screw, etc.), and a circuit breaker (e.g., a semiconductor switch).

[0042] According to the above configuration, by using the power storage device model, it is possible to determine the required SOC with high accuracy, and estimate the full charge capacity or the degree of degradation of the power storage element with high accuracy.

[0043] (5) The estimation device described in (4) above may provide the electrical storage device model with a resistance component of the conductive member.

[0044] The resistance component of the conductive member may be obtained by adding up the resistance values ​​of each conductive member, or one or more resistance values ​​may be experimentally obtained using a test circuit. A plurality of resistance components of the conductive member may be prepared depending on the temperature.

[0045] According to the above structure, by considering the resistance component of the conductive member (hereinafter also referred to as the structural resistance), the required SOC can be determined with high accuracy, and the full charge capacity or the degree of degradation of the storage element can be estimated with high accuracy. For example, as in a low-voltage battery (12V battery, 48V battery, etc.), when the total number of storage cells is relatively small and the internal resistance (e.g., 10mΩ) of the storage cell is of the same order as the structural resistance (e.g., 2mΩ) and the structural resistance cannot be ignored, an appropriate estimation can be made.

[0046] (6) In the estimation device described in any one of (1) to (5) above, the control unit may start searching for the required SOC in a predetermined order starting from any one of a plurality of SOC values ​​included in the non-flat region.

[0047] Here, the "prescribed order" may also be the order of the direction of increasing SOC value or decreasing SOC value from the low SOC value or the high SOC value included in the non-flat area, but is not limited thereto. The "low SOC value" may also be the lowest SOC value in the non-flat area, and the "high SOC value" may also be the highest SOC value in the non-flat area, but is not limited thereto. The "low SOC value" may also be set to an SOC value lower than the "high SOC value".

[0048] The control unit may be configured to be able to select at which of the low SOC value and the high SOC value included in the non-flat region the search for the necessary SOC should be started.

[0049] According to the above configuration, it is possible to select whether to prioritize the accuracy of the estimation of the full charge capacity or the degree of degradation of the storage element or to prioritize the estimation in a short time. It is also possible to determine whether to start the search for the necessary SOC from a low SOC value or a high SOC value based on instructions from a host device or the operating status of the storage element.

[0050] (7) A power storage device includes the estimation device described in any one of (1) to (6) above, and a plurality of power storage cells.

[0051] (8) A method for estimating the full charge capacity or the degree of degradation of a storage element, wherein the storage element is discharged at a constant voltage until a required SOC is reached, and the storage element is charged to its fully charged state, and the full charge capacity or the degree of degradation of the storage element is estimated based on an accumulated value of a charging current from the required SOC to the fully charged state, or an accumulated value of a discharging current from the fully charged state to the required SOC.

[0052] (9) A computer program that causes a computer for estimating the full charge capacity or degree of degradation of an electric storage element to execute the following processing: estimating the full charge capacity or degree of degradation of the electric storage element based on the cumulative value of the charging current from the necessary SOC to the full charge state when the electric storage element is discharged at a constant voltage until the required SOC (state of charge) is reached, and the cumulative value of the discharging current from the full charge state to the required SOC when the electric storage element is charged to its full charge state.

[0053] The following is a detailed description with reference to the accompanying drawings showing the embodiments.

[0054] Figure 1 is a perspective view showing a configuration example of a power storage device 1 equipped with an estimation device according to the embodiment, Figure 2 1 is an exploded perspective view showing a configuration example of the power storage device 1. The power storage device 1 is, for example, a 12V battery (low voltage battery) preferably mounted on an engine vehicle, an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV). The power storage device 1 may also be mounted on other mobile objects such as an aircraft, a railway train, and a ship.

[0055] The power storage device 1 includes an estimation device 2, a plurality of power storage cells 3, and a rectangular parallelepiped housing case 40 for housing them. The power storage cells 3 may be battery cells such as lithium-ion secondary batteries or electrochemical cells (battery cells) such as capacitors. The estimation device 2 is, for example, a battery management system (BMS).

[0056] The battery pack 30 is composed of four storage cells 3 connected in series. Alternatively, some of the storage cells 3 may be connected in parallel. For example, the battery pack 30 may include 12 storage cells 3 connected in parallel (three in parallel) and in series (four in series).

[0057] The housing case 40 is made of synthetic resin. The housing case 40 includes a housing body 41, a cover 42 for closing the opening of the housing body 41, a housing portion 43 provided on the cover 42, a cover 44 for covering the housing portion 43, an intermediate cover (bus bar frame) 45, and a separator 46. The intermediate cover 45 and the separator 46 may not be provided. The storage cell 3 is inserted between the separators 46 of the housing body 41.

[0058] A plurality of metal bus bars 61 are placed on the middle cover 45. The middle cover 45 is arranged near the terminal surface where the cell terminals 32 of the storage cells 3 are provided, and the adjacent cell terminals 32 of the adjacent storage cells 3 are connected by the bus bars 61, so that the storage cells 3 are connected in series. The bus bars 61 are an example of a conductive member.

[0059] The housing portion 43 is box-shaped and has a protrusion 43a protruding outward in the center of one long side when viewed from above. A pair of external terminals 62, 62 made of metal such as lead alloy and having different polarities are provided on both sides of the protrusion 43a in the cover portion 42. The estimation device 2 is accommodated in the housing portion 43. The estimation device 2 is connected to the storage cell 3 via a wiring member and a bus bar 61 not shown. Instead of being accommodated in the housing portion 43, the estimation device 2 may be arranged, for example, adjacent to the top or side of the battery pack 30.

[0060] The storage cell 3 includes a hollow rectangular parallelepiped case 31 and a pair of cell terminals 32, 32 of different polarities provided on one side surface (terminal surface, upper surface) of the case 31. The case 31 accommodates an electrode body 33 formed by stacking a positive electrode, a separator, and a negative electrode, and an electrolyte (electrolyte solution) not shown.

[0061] Although the electrode body 33 is not shown in detail, it is formed by overlapping a positive electrode and a negative electrode in the form of a sheet through two thin sheet-like separators and winding them (vertically or horizontally). The separator is formed of a porous resin film. As the porous resin film, a porous resin film composed of a resin such as polyethylene (PE) or polypropylene (PP) can be used.

[0062] The positive electrode is an electrode plate having a positive electrode active material layer formed on the surface of a long strip-shaped positive electrode substrate made of, for example, aluminum or an aluminum alloy. The positive electrode active material layer includes a positive electrode active material. As the positive electrode active material used in the positive electrode active material layer, a material capable of absorbing and releasing lithium ions can be used. As the positive electrode active material, for example, LiFePO 4 The positive electrode active material layer may further include a conductive additive, a binder, and the like.

[0063] The negative electrode is an electrode plate formed by forming a negative electrode active material layer on the surface of a long strip-shaped negative electrode substrate composed of, for example, copper or a copper alloy. The negative electrode active material layer includes a negative electrode active material. The negative electrode active material can use a material that can absorb and release lithium ions. Examples of the negative electrode active material include graphite, hard carbon, soft carbon, etc. The negative electrode active material layer may further include a binder, a thickener, etc.

[0064] The electrolyte contained in the housing 40 together with the electrode body 33 can be the same as that of the conventional lithium-ion secondary battery. For example, an electrolyte containing a supporting salt in an organic solvent can be used as the electrolyte. For example, a non-protonic solvent such as carbonate, ester, or ether can be used as the organic solvent. As the supporting salt, it is preferred to use, for example, LiPF 6 , LiBF 4 、LiClO 4 The electrolyte may contain various additives such as a gas generating agent, a coating film forming agent, a dispersant, and a thickening agent.

[0065] Figure 2 A square lithium-ion battery having a wound electrode body 33 is shown as an example of the storage cell 3. Alternatively, the storage cell 3 may be a cylindrical lithium-ion battery or a laminated (pouch) lithium-ion battery. The storage cell 3 may also be a lithium-ion battery having a laminated electrode body. The storage cell 3 may also be an all-solid lithium-ion battery using a solid electrolyte.

[0066] Figure 3 2 is a block diagram showing a configuration example of the power storage device 1 . The power storage device 1 includes an estimation device 2 , a battery pack 30 , a circuit breaker 53 , a current sensor 54 , a voltage sensor 55 , and a temperature sensor 56 .

[0067] In the power storage device 1, a vehicle ECU (Electronic Control Unit) 150, a DC-DC converter 160 for converting power from a high voltage battery, and an on-vehicle electric load 170 (auxiliary machines) are electrically connected via external terminals 62, 62. In an engine vehicle, an AC generator is used as a generator for generating electric power using the power of the engine instead of the converter 160.

[0068] The vehicle ECU 150 is a vehicle control unit, and controls the converter 160 and the electric load 170. The vehicle ECU 150 controls the converter 160 and the electric load 170 based on the estimation result related to the charge and discharge performance (power supply capacity) received from the estimation device 2, thereby controlling the charging voltage and the allowed charge and discharge amount of the power storage device 1. The vehicle ECU 150 is an example of a "host device".

[0069] The estimation device 2 is a flat circuit substrate that estimates the state of each storage cell 3 at a predetermined timing and estimates the charge and discharge performance of the storage device 1. The shape of the estimation device 2 is not limited to a flat plate. The estimation device 2 may also be configured as a circuit substrate unit in which a circuit breaker 53, a current sensor 54, a voltage sensor 55, etc. are mounted on a circuit substrate. The estimation device 2 includes a control unit 21, a storage unit 22, an input / output unit 23, etc.

[0070] The control unit 21 is a computing circuit including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. The CPU included in the control unit 21 executes various computer programs stored in the ROM and the storage unit 22, and controls the operation of each of the above-mentioned hardware components, thereby making the entire device function as an estimation device. The control unit 21 may also include a timer for measuring the elapsed time from providing a measurement start instruction to providing a measurement end instruction, a counter for counting the number, a clock for outputting date and time information, and the like.

[0071] The storage unit 22 is a non-volatile storage device such as a flash memory. The storage unit 22 stores programs and data referenced by the control unit 21. The computer programs stored in the storage unit 22 include a program 221 for estimating information related to whether the charging or discharging of the power storage device 1 can be performed. The data stored in the storage unit 22 include estimation data 222 for the program 221 and a power storage device model of the power storage device 1 used in the simulation. The power storage device model is expressed by structural information representing the circuit structure, and the values ​​of each component constituting the power storage device model. In the storage unit 22, structural information representing the circuit structure of such a power storage device model, and the values ​​of each component constituting the power storage device model are stored.

[0072] The computer program (computer program product) stored in the storage unit 22 can also be provided via a non-temporary recording medium M that can read and record the computer program. The recording medium M is a portable memory such as a CD-ROM, a USB memory, or an SD (Secure Digital) card. The control unit 21 uses a reading device not shown in the figure to read the desired computer program from the recording medium M and stores the read computer program in the storage unit 22. Alternatively, the above-mentioned computer program can also be provided through communication. The program 221 is configured on a single computer or a site, or can be distributed across multiple sites and deployed on multiple computers connected to each other through a communication network so as to be executed.

[0073] The input / output unit 23 includes an input / output interface for connecting to an external device. The vehicle ECU 150 , the circuit breaker 53 , the current sensor 54 , the voltage sensor 55 , the temperature sensor 56 , and the like are connected to the input / output unit 23 .

[0074] The circuit breaker 53 includes, for example, a semiconductor switch such as FET or a relay having mechanical contacts, etc. The circuit breaker 53 switches between an ON state and an OFF state according to a control signal output from the control unit 21 , thereby interrupting the current of the battery pack 30 .

[0075] The current sensor 54 is connected in series with the battery pack 30. The current sensor 54 may also be a shunt resistor. The current sensor 54 measures the current flowing through the storage cell 3 in a time series based on the voltage across the resistor element. Discharging and charging can be distinguished according to the polarity (positive or negative) of the voltage across the terminals. Alternatively, the current sensor 54 may also be a magnetic sensor. The control unit 21 obtains the data of the current measured by the current sensor 54 at any time through the input / output unit 23.

[0076] The voltage sensor 55 is connected in parallel to each storage cell 3. The voltage sensor 55 is connected to both ends of each storage cell 3, respectively, and measures the terminal voltage of each storage cell 3 in a time series. The control unit 21 obtains data on the voltage of each storage cell 3 and the total voltage of the battery pack 30 measured by the voltage sensor 55 at any time through the input / output unit 23.

[0077] The temperature sensor 56 is provided near the storage cell 3 and detects the temperature related to the storage device 1. The temperature sensor 56 may also be a thermocouple, a thermistor, etc. The temperature related to the storage device 1 may also be the temperature of the storage cell 3 or the surroundings of the storage device 1. The control unit 21 obtains the temperature data measured by the temperature sensor 56 at any time through the input / output unit 23.

[0078] When the estimation result of whether or not power storage device 1 can be energized is obtained, control unit 21 outputs information based on the estimation result to vehicle ECU from input / output unit 23. Vehicle ECU executes various processes based on the information acquired from estimation device 2.

[0079] The input / output unit 23 may also include an interface for connecting a display device. An example of a display device is a liquid crystal display device. When an estimation result of whether or not power can be supplied to the power storage device 1 is obtained, the control unit 21 outputs information based on the estimation result from the input / output unit 23 to the display device. The display device displays the estimation result based on the information output from the input / output unit 23.

[0080] The input / output unit 23 may also include a communication interface for communicating with an external device. The external device connected to the input / output unit 23 in a communicable manner is a terminal device such as a personal computer or a smart phone used by a user, an administrator, etc. When an estimation result of whether the power storage device 1 can be powered on is obtained, the control unit 21 sends information based on the estimation result from the input / output unit 23 to the terminal device. The terminal device receives the information sent by the input / output unit 23 and displays the estimation result on the display of the device based on the received information. The estimation device 2 may also include a notification unit such as an LED lamp and a buzzer to notify the user of the estimation result of whether the power storage device 1 can be powered on.

[0081] Figure 4 1 is a diagram for explaining a method of estimating the discharge performance (power supply capability) when the power supply mode notified from the vehicle ECU 150 (host device) is discharge. Figure 4 In FIG. 1 , the upper left graph shows the time change of the voltage value of the power storage device 1 accompanying the energization, and the lower left graph shows the time change of the current value of the power storage device 1 accompanying the energization. Figure 4 In FIG. 1 , the upper right graph shows the time change of the voltage value of the storage cell 3 accompanying the energization, and the lower right graph shows the time change of the current value of the storage cell 3 accompanying the energization.

[0082] Assume that, based on the estimated time, a predetermined discharge current value is supplied to the power storage device 1 for a predetermined time (t seconds). Figure 4 As shown, if the discharge current value is set to be constant, the voltage value of the power storage device 1 decreases with the discharge. The voltage value of each power storage cell 3 also decreases with the discharge. When the estimated voltage after t seconds is greater than the preset lower limit voltage of the power storage device 1, it can be determined that power can be supplied. When the estimated voltage after t seconds is less than the preset lower limit voltage of the power storage device 1, it can be determined that power cannot be supplied.

[0083] Similarly, it can be determined whether power can be supplied to power storage device 1 when a predetermined charging current value is supplied to power storage device 1 for a predetermined time based on the estimated time. If the estimated voltage after t seconds is greater than the upper limit voltage of power storage device 1, it can be determined that power supply is not possible.

[0084] Figure 5 1 is a circuit diagram showing an example of a power storage device model that simulates the operation of the power storage device 1 . Figure 5 The power storage device model shown is an equivalent circuit model, which combines a voltage source of the power storage device 1 including a plurality of power storage cells 3 and circuit elements such as resistors and capacitors to simulate the charging and discharging operation of the power storage device 1 .

[0085] Figure 5 The equivalent circuit model shown includes n storage cells 3 connected in series between a positive external terminal and a negative external terminal, and a structural resistor. Each storage cell 3 includes a constant voltage power supply, a DC resistor simulating a DC resistance component, and an RC parallel circuit for simulating transient polarization characteristics.

[0086] The structural resistor simulates the resistance component (structural resistance) of the conductive member in the power storage device 1, and includes a resistance element R struct . Resistor element R struct For example, it represents the resistance component of each of the multiple components including the busbar 61 and the circuit breaker 53. struct It may also be given as a value that varies according to temperature.

[0087] In each storage cell 3, the constant voltage power source is a voltage source (electromotive force) that outputs a DC voltage. The voltage output by the constant voltage power source is the OCV of the storage cell 3, which is recorded as V OCV . V OCV The value is given as a value that changes according to the SOC of the storage cell 3 , for example, as a function of the SOC.

[0088] In each storage cell 3, the DC resistor is used to simulate the DC resistance component (DC impedance) of the storage device 1, and includes a resistance element R 0 . Resistor element R 0 It is given as a value that changes according to the current, voltage, SOC, temperature, etc. If the impedance of the DC resistor is determined, the voltage generated in the DC resistor when the current I flows in the equivalent circuit model can be calculated. The voltage generated in the DC resistor is recorded as the DC resistance voltage R 0 I.

[0089] In each storage cell 3, the RC parallel circuit is composed of resistance elements R connected in parallel. 1 And the capacitor element C 1 Composition. Resistor element R1 And the capacitor element C 1 The value is given as a value that changes according to SOC, temperature, etc. 1 And the capacitor element C 1 , determine the impedance of the RC parallel circuit. If the impedance of the RC parallel circuit is determined, it is possible to calculate the voltage generated in the RC parallel circuit when the current I flows through the equivalent circuit model. The voltage generated in the RC parallel circuit is recorded as the polarization voltage V R1C1 .

[0090] Resistor element R struct , R 0 , R 1 And the capacitor element C 1 (hereinafter also referred to as circuit parameters) can be obtained by a known method. The circuit parameters can be set based on the actual measurement data of the battery test, for example, taking into account the relationship between temperature and SOC, etc. The estimation device 2 associates the obtained circuit parameters with the temperature and SOC, etc. and stores them as estimation data 222. The circuit parameters can also be determined using the inspection results when the product is launched, the measurement values ​​of the sensor after the product is installed, and can also be appropriately corrected (calibrated) based on the usage history after the product is installed.

[0091] According to the voltage sum rule, the polarization voltage V of each storage cell 3 when the estimated time is set to t=0 is R1C1 The cell voltage V of the storage cell 3 generated during discharge can be used separately. cell 、V OCV , I, and R 0 And it is estimated by the following formula (1).

[0092] [Mathematical formula 1]

[0093] V R1C1 (0) = V cell (0)-V ocv (0)-R 0 I(0)...(1)

[0094] For the cell voltage V cell and I, the current sensor 54 and the voltage sensor 55 (see Figure 3 ) is a measured value. The current value I is a positive value in the case of charging, for example, and a negative value in the case of discharging. V OCV For example, the SOC-OCV table can be used to obtain the SOC at the estimated time. The SOC can also be calculated by the current accumulation method. The SOC-OCV table can be set for each temperature, or a common table can be used. For the temperature, the measured value of the temperature sensor 56 can be used. The polarization voltage V R1C1For example, it can also be obtained by a method such as the successive least squares method or the Kalman filter.

[0095] Assume that the discharge current I is supplied for a predetermined time period t seconds from the estimated time (supply according to the pre-announced supply pattern). Figure 5 As shown, the voltage V of the power storage device 1 bat The cell voltage V in each of the n storage cells 3 can be cell Using the power storage device model, the voltage V of the power storage device 1 at the time t seconds later is bat Ability to use V OCV ,I,R 0 , R 1 , C 1 , and R struct And it is estimated by the following formula (2).

[0096] [Mathematical formula 2]

[0097]

[0098] The predetermined time t can be the power-on time given by the host device. OCV (t) can also be obtained by taking into account the change in SOC.

[0099] In addition, the voltage of each storage cell 3 at a time t seconds later can be estimated using a storage cell model that simulates the operation of each storage cell 3. The voltage V of each storage cell 3 at a time t seconds later is cell Can use V OCV ,I,R 0 , R 1 and C 1 And it is estimated by the following formula (3).

[0100] [Mathematical formula 3]

[0101]

[0102] The following describes how to determine the “required SOC”.

[0103] The power storage device 1 mounted on the mobile body is required to exert a predetermined power supply capability for the electric load connected thereto whenever the mobile body is started (discharge is required). The 12V battery mounted on the vehicle is required to maintain a voltage above a threshold value (e.g., 9V) even if the discharge current specified by the host device is discharged over a predetermined time (t seconds) according to the power consumption of the on-board electric load 170.

[0104] In the process of discharging the battery to a low SOC and then charging it to a fully charged state, and estimating the full charge capacity from the integrated value of the charging current until the fully charged state is reached, the power supply capacity of the battery needs to be not less than a threshold value.

[0105] The power supply capacity of the battery is not always fixed, but changes according to the operating conditions of the battery (temperature, current, degree of degradation of the storage cell 3, etc.). Therefore, the "necessary SOC" corresponding to the operating conditions is determined using the storage device model of formula (2) or the storage cell model of formula (3).

[0106] Figure 6 This is a diagram showing a portion of the SOC-OCV curve of an LFP battery (storage cell 3). The SOC-OCV curve of an LFP battery has a flat region (substantially horizontal) in which there is almost no voltage change associated with charge and discharge, and a non-flat region in which there is a voltage change associated with charge and discharge and has a slope greater than a specified value. Figure 6 In the example, there is a first non-flat region across a predetermined range from SOC 0%, and a second non-flat region slightly away from the first non-flat region. The region between the first non-flat region and the second non-flat region and the region beyond the second non-flat region become a flat region where the voltage hardly changes.

[0107] In the present embodiment, the required SOC is determined using equation (2) so that the required SOC is included in the first non-flat region or the second non-flat region.

[0108] As shown in Table 1 Figure 6 The relationship between SOC and OCV in the first non-flat region of the SOC-OCV curve shown in FIG. 1 and the relationship between SOC and OCV in the second non-flat region are shown in Table 2.

[0109] [Table 1]

[0110] SOC(%) OCV(V) Priority 1 2.90 1 3 3.00 2 5 3.05 3 7 3.10 4 9 3.15 5

[0111] [Table 2]

[0112] SOC(%) OCV(V) Priority 20 3.22 6 25 3.24 7 30 3.26 8

[0113] From SOC 10% to SOC 19%, there is a flat region where the OCV is substantially the same (about 3.2 V).

[0114] In the present embodiment, the search for the required SOC starts from the lowest SOC value of the storage cells 3 . Figure 7 The simplified flowchart is shown in FIG. As the estimated power supply capacity, V at time t=0 OCV(0), the OCV corresponding to SOC 1% in Table 1, 2.90 V, is applied to formula (2) ( Figure 7 , step 1).

[0115] By V OCV (SOC1% - I × t / full charge capacity × 100) is used to calculate: the OCV of the single storage cell 3 in the formula (2), that is, V, which is reached when the discharge current I specified by the host device is discharged over a specified time (a period of t seconds) OCV (t). In addition, the remaining voltage drop due to the resistance in equation (2) is calculated. In this way, the voltage V after the power supply in the pre-notification power supply mode is performed in the power storage device 1 at the estimated time t=0 and the SOC of each power storage cell 3 is 1% is obtained. bat .

[0116] If the V bat If the value is 9V or above, it is judged that the power supply capacity after power-on can be ensured ( Figure 7 , Step 2: Yes), SOC 1% is determined as the required SOC of each storage cell 3. If the V bat The value is lower than 9V ( Figure 7 , Step 2: No), Next, the OCV corresponding to SOC 3% in Table 1, 3.00V, is applied to equation (2) ( Figure 7 , step 3), based on the obtained reaching voltage V bat , determine whether the power supply capacity can be ensured ( Figure 7 , step 2). This process is repeated until a SOC that can ensure power supply capability is determined.

[0117] The power storage device 3 is subjected to CV discharge (with the required SOC of each power storage cell 3 determined in this way as the target (with the SOC of the power storage device 1 at which each power storage cell 3 reaches the required SOC as the target). Figure 7 , step 4).

[0118] In this way, by ensuring the power supply capacity and determining the lowest possible SOC value as the required SOC of each storage cell 3, the OCV can be reset at the position with a large slope of the SOC-OCV curve after polarization is eliminated. Therefore, the accuracy of estimating the full charge capacity or the degree of degradation of the storage element can be improved.

[0119] On the contrary, V at time t = 0, which is the estimated power supply capacity OCV(0), the OCV corresponding to the highest SOC value in Table 2 (second non-flat region), 3.26V, can be applied to equation (2) to start searching for the required SOC of each storage cell 3 from the highest SOC value. In this way, the required SOC can be determined in a short time, shortening the time required for estimation.

[0120] Alternatively, the required SOC may be searched from the OCV corresponding to the highest SOC value in Table 1 (first non-flat region), 3.15V, toward the low SOC. The required SOC may also be searched from the OCV corresponding to the lowest SOC value in Table 2 (second non-flat region), 3.22V, toward the high SOC.

[0121] exist Figure 8 In FIG. 1 , the voltage behavior of the storage cell 3 when CV discharge is performed from the discharge start SOC (the SOC estimated at time t=0) until the required SOC is reached is indicated by a single-dot chain line. CV discharge may also be terminated when the discharge current becomes less than a threshold value (for example, less than 1A). Figure 8 In the embodiment, the storage element is subjected to CV discharge in the entire region of the discharge process for estimating the full charge capacity or the degree of degradation of the storage element. Alternatively, the storage element may be subjected to CCCV discharge.

[0122] One side reference Fig. 9 The advantages of performing CV discharge on the power storage element will be described while referring to the case of CC discharge shown in FIG.

[0123] In CC discharge, based on the voltage sensor 55 (refer to Figure 3 ) to stop the discharge. The cell voltage detected by the voltage sensor 55 reflects the internal resistance (polarization). Fig. 9 The difference between the solid line (real OCV curve) and the dashed line (cell voltage behavior with CC discharge) in the graph represents polarization. This polarization varies depending on the operating conditions of the storage element (temperature, current, degree of degradation of the storage element, etc.). Figure 7 ) when CC discharge is performed based on the required SOC determined by the battery, it is difficult to appropriately set the cell voltage for determining the end of discharge.

[0124] By the above method, the required SOC is determined to be included in the non-flat area of ​​the SOC-OCV curve, but when the discharge end cell voltage is set to Fig. 9In the case of V1 in , the discharge is stopped at a point where the necessary SOC deviates toward the high SOC. In this case, since each storage cell 3 included in the storage device 1 has not left the flat area, the OCV reset of the SOC cannot be properly performed after the polarization is eliminated. Therefore, even if charging is performed from there toward full charge, the full charge capacity of the storage element or the degree of degradation cannot be estimated with high accuracy. The process is a failure.

[0125] When the discharge end cell voltage is set to Fig. 9 In the case of V2 in the above diagram, the discharge stops near the required SOC after the flat region is removed. Therefore, by resetting the OCV of the SOC after the polarization is eliminated and charging toward full charge from there, the full charge capacity or the degree of degradation of the storage element can be estimated with high accuracy. The process is successful.

[0126] When the discharge end cell voltage is set to Fig. 9 In the case of V3 in the above example, the discharge stops at a point where the SOC is lower than the required SOC. In this state, although the battery has left the flat area, it cannot exert the specified power supply capacity. The process is a failure.

[0127] Although the requirement Fig. 9 V2 in FIG. 1 , that is, a voltage value corresponding to the required SOC is set as the discharge end voltage. However, as described above, since polarization differs depending on the operating conditions of the power storage element, it is difficult to stably perform such setting.

[0128] In contrast, Figure 8 As shown, by making the storage element perform CV discharge toward the required SOC, the determined required SOC can be stably reached. The storage element can also be made to perform CV discharge at the voltage at the point where the determined required SOC intersects with the SOC-OCV curve. Alternatively, the storage element can also be made to perform CCCV discharge to reach the required SOC in a short time.

[0129] After reaching the required SOC through CV discharge, the storage element is left without charging or discharging, and after polarization is eliminated, the voltage of the storage cell 3 is detected by the voltage sensor 55 to obtain the OCV (or the value regarded as the OCV), and the SOC is reset by the OCV. This process is preferably performed when the moving body is stopped (for example, when the vehicle is parked). Since the required SOC is calculated and ensured, the storage element can exert the specified power supply capacity whenever the moving body is started.

[0130] exist Fig.10In this case, a dotted line is used to indicate the voltage operation of the storage battery cell 3 when charging from the necessary SOC to the full charge state. By adding the cumulative value of the charging current during the period from the necessary SOC to the full charge state to the SOC after OCV reset, it is possible to accurately estimate the full charge capacity or the degree of deterioration of the energy storage element.

[0131] The present invention is not limited to the above-described embodiments and can be appropriately changed. The disclosed power storage device 1, estimation device 2, estimation method, and computer program can also be applied to uses other than for moving bodies. The power storage device can also be a high-voltage storage battery.

[0132] The energy storage element can also be first charged to the full charge state and then subjected to CV discharge (or CCCV discharge) to the necessary SOC, and the full charge capacity or the degree of deterioration can be estimated based on the cumulative value of the discharge current.

[0133] The estimation device 2 can also be provided away from the energy storage element. The estimation method and the computer program can also be executed by a computer (for example, an ECU, a remote monitoring computer) located at a position away from the energy storage element.

[0134] The present invention can also be implemented as follows.

[0135] (Modification Example 1)

[0136] An estimation device includes: a control unit that estimates the full charge capacity or the degree of deterioration of an energy storage element,

[0137] The control unit estimates the full charge capacity or the degree of deterioration of the energy storage element based on the cumulative value of the charging current from the necessary SOC to the full charge state or the cumulative value of the discharge current from the full charge state to the necessary SOC in a case where the energy storage element is discharged until it reaches the necessary SOC and then charged to its full charge state, wherein the necessary SOC is determined to be one of a plurality of non-flat regions included in the SOC-OCV curve of the energy storage element.

[0138] (Modification Example 2)

[0139] An estimation device includes: a control unit that estimates the full charge capacity or the degree of deterioration of an energy storage element,

[0140] The control unit estimates the full charge capacity or degree of degradation of the storage element based on an integrated value of a charging current from the required SOC to the full charge state, or an integrated value of a discharging current from the full charge state to the required SOC, when the storage element is discharged until the required SOC is reached and the storage element is charged to its full charge state, wherein the required SOC is searched in a prescribed order from SOC values ​​in a non-flat region in an SOC-OCV curve of the storage element.

[0141] (Variant 3)

[0142] An estimation device comprises: a control unit for estimating a full charge capacity or a degree of degradation of a storage element;

[0143] The control unit estimates the full charge capacity or degree of degradation of the storage element based on an integrated value of a charging current from the required SOC to the fully charged state, or an integrated value of a discharging current from the fully charged state to the required SOC, when the storage element is discharged until the required SOC is reached and the storage element is charged to its fully charged state, wherein the required SOC is determined using a storage element model for simulating a voltage action of the storage element accompanying discharge.

[0144] The electricity storage element model may be an electricity storage device model for simulating the operation of an electricity storage device including a plurality of electricity storage cells and a conductive member.

[0145] The estimation device may provide the power storage device model with a resistance component of the conductive member.

[0146] Description of Reference Numerals

[0147] 1 power storage device, 2 estimation device, 21 control unit, 22 storage unit, 23 input / output unit, 221 program, 222 estimation data, M recording medium, 3 power storage cell.

Claims

1. An estimation device comprising: The control unit estimates the full charge capacity or the degree of degradation of the storage element. The control unit estimates the full charge capacity or degree of deterioration of the storage element based on an integrated value of a charging current from a required SOC to a fully charged state, or an integrated value of a discharging current from a fully charged state to the required SOC, when the storage element is discharged at a constant voltage until the required charge state, i.e., a required SOC, is reached and the storage element is charged to its fully charged state.

2. The estimation device according to claim 1, in, The required SOC is determined to be included in a non-flat region of a SOC-open circuit voltage curve, ie, a SOC-OCV curve, of the power storage element.

3. The estimation device according to claim 1 or 2, in, The required SOC is determined using an electric storage element model for simulating voltage behavior of the electric storage element associated with discharge.

4. The estimation device according to claim 3, in, The power storage element model is a power storage device model for simulating the operation of a power storage device including a plurality of power storage cells and a conductive member.

5. The estimation device according to claim 4, in, The resistance component of the conductive member is provided to the power storage device model.

6. The estimation device according to claim 1 or 2, in, The control unit starts searching the required SOC in a predetermined order starting from one of a plurality of SOC values ​​included in the non-flat region.

7. An electric storage device comprising: The estimation device as claimed in claim 1 or 2; and Multiple battery cells.

8. A method for estimating a full charge capacity or a degree of degradation of a power storage element, in, The power storage element is discharged at a constant voltage until a required state of charge, i.e., a required SOC, is reached. charging the storage element to its fully charged state, The full charge capacity or the degree of degradation of the power storage element is estimated based on an integrated value of the charging current from the required SOC to the fully charged state or an integrated value of the discharging current from the fully charged state to the required SOC.

9. A computer program for causing a computer for estimating the full charge capacity or the degree of degradation of a power storage element to execute the following processing: The full charge capacity or the degree of degradation of the storage element is estimated based on the cumulative value of the charging current from the necessary SOC to the full charge state when the storage element is discharged at a constant voltage until the necessary charge state, i.e., the necessary SOC, is reached and the storage element is charged to its full charge state, or the cumulative value of the discharging current from the full charge state to the necessary SOC.

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