JP2020153881A - Rechargeable battery degradation estimation device, and rechargeable battery degradation estimation method - Google Patents

Abstract

To accurately estimate the degradation of a rechargeable battery even when unusual usage is performed.SOLUTION: A rechargeable battery degradation estimation device includes: calculation means (CPU10a) for calculating values of elements constituting an equivalent circuit of a rechargeable battery; detection means (I/F 10e) for detecting the usage aspect of the rechargeable battery; storage means (RAM 10c) for storing the relational expression showing the relation between at least one element constituting the equivalent circuit and an SOH showing the degradation of the rechargeable battery, for the usage aspect of the rechargeable battery; and estimation means (CPU 10a) for estimating the SOH of the rechargeable battery by acquiring the relational expression corresponding to the usage aspect detected by the detection means from the storage means and applying the value of the element calculated by the calculation means to the relational expression.SELECTED DRAWING: Figure 1

Description

The present invention relates to a rechargeable battery deterioration estimation device and a rechargeable battery deterioration estimation method.

Conventionally, a technique for estimating the deterioration state of a rechargeable battery has been proposed. For example, in the technique disclosed in Patent Document 1, the degree of deterioration of a rechargeable battery is estimated from the usage history information of the rechargeable battery in consideration of the influence of temperature and SOC.

Japanese Unexamined Patent Publication No. 2014-105995

By the way, the method of estimating the deterioration state based on the history information disclosed in Patent Document 1 can detect the deterioration state with relatively good accuracy under the condition that the target rechargeable battery is completely fixed. .. However, when rechargeable batteries from multiple manufacturers or rechargeable batteries of different sizes are used in various ways, such as lead-acid batteries for automobiles, the usage history is the same depending on each manufacturer or size. However, since the deterioration state is completely different, there is a problem that it is difficult to detect the deterioration with high accuracy.

In addition, the capacity of the rechargeable battery is determined by the most deteriorated cell among the 6 cells connected in series, but the equivalent circuit model is measured by the average value of 6 cells, so if there is variation in deterioration between cells. There is also a problem that the estimation accuracy is lowered.

As a method for improving these problems, a method has been proposed in which the deterioration variation between cells is weighted to the equivalent circuit model using historical information to correct the variation between cells. However, while this method can be used in various ways, there is a problem that the weighting of the equivalent circuit model change rate cannot be followed when the usage is different from the usual one, and the estimation accuracy is lowered. There is.

The present invention has been made in view of the above circumstances, and is a rechargeable battery deterioration estimation device capable of accurately estimating deterioration of a rechargeable battery even when it is used differently than usual. An object of the present invention is to provide a method for estimating deterioration of a rechargeable battery.

In order to solve the above problems, the present invention provides a calculation means for calculating the value of an element constituting the equivalent circuit of the rechargeable battery in the rechargeable battery deterioration estimation device for estimating the deterioration of the rechargeable battery, and the charging. A relational expression showing the relationship between the detection means for detecting the usage mode of the rechargeable battery, at least one element constituting the equivalent circuit, and the SOH indicating the deterioration of the rechargeable battery is expressed for each usage mode of the rechargeable battery. By acquiring the storage means to be stored and the relational expression corresponding to the usage mode detected by the detection means from the storage means and applying the value of the element calculated by the calculation means to the relational expression. It is characterized by having an estimation means for estimating the SOH of the rechargeable battery.
According to such a configuration, it is possible to accurately estimate the deterioration of the rechargeable battery even if it is used differently than usual.

Further, in the present invention, the storage means stores a plurality of the relational expressions corresponding to the usage mode, and the estimation means corresponds to the usage mode detected by the detection means from the plurality of the relational expressions. It is characterized in that the SOH of the rechargeable battery is estimated by acquiring the relational expression of 1 and applying the value of the element calculated by the calculation means to the relational expression.
According to such a configuration, the SOH of the rechargeable battery can be estimated accurately by selecting the relational expression according to the usage mode.

Further, in the present invention, the storage means stores the coefficients constituting the relational expression for each usage mode, and the estimation means corresponds to the usage mode detected by the detection means from the plurality of relational expressions. It is characterized in that the SOH of the rechargeable battery is estimated by acquiring the coefficient to be used and applying the value of the element calculated by the calculation means to the relational expression having the coefficient.
According to such a configuration, the SOH of the rechargeable battery can be estimated accurately by selecting the coefficient according to the usage mode.

Further, in the present invention, in the relational expression, the difference value between the initial value and the current value of at least one element constituting the equivalent circuit of the rechargeable battery is multiplied by the coefficient corresponding to the usage mode. Then, the SOH is estimated by applying the obtained value to the relational expression.
According to such a configuration, SOH can be estimated accurately based on the difference value.

Further, in the present invention, the usage mode includes a history of the temperature of the rechargeable battery, a history of the depth of discharge, a history of the amount of electricity charged and discharged, a history of the frequency of falling below a certain charge rate, and a constant charge rate. It is characterized in that the determination is made based on at least one of the history of the frequency as described above, the history of the duration for each charging rate, and the elapsed time from the start of use.
According to such a configuration, the usage mode can be specified from various histories.

Further, the present invention is characterized in that the history is measured stratified by any one of SOC, voltage, current, and temperature of the rechargeable battery.
According to such a configuration, the usage mode can be further embodied by grouping the history according to the desired characteristics.

Further, in the present invention, the equivalent circuit includes a conductor element inside the rechargeable battery and a resistance component corresponding to the electrolyte resistance, a resistance component corresponding to the reaction resistance of the active material reaction of the electrode of the rechargeable battery, and a resistance component. It is characterized by having at least one capacitive component corresponding to the electric double layer at the interface between the electrode and the electrolytic solution.
According to such a configuration, the deterioration of the rechargeable battery can be estimated accurately based on the element reflecting the state of deterioration.

Further, the present invention is characterized in that the calculation means corrects the values of the elements constituting the equivalent circuit to the values of the elements at the reference temperature and the reference SOC.
With such a configuration, the deterioration of the rechargeable battery can be estimated accurately regardless of the temperature and the SOC state.

Further, the present invention is characterized in that the rechargeable battery is mounted on a vehicle and the vehicle is controlled based on the SOH estimated by the estimation means.
According to such a configuration, the fuel efficiency of the vehicle can be improved by optimally controlling the state of the rechargeable battery.

Further, the present invention provides a calculation step for calculating the value of an element constituting the equivalent circuit of the rechargeable battery and a usage mode of the rechargeable battery in the rechargeable battery deterioration estimation method for estimating the deterioration of the rechargeable battery. Storage in which a relational expression showing the relationship between the detection step to be detected and at least one element constituting the equivalent circuit and SOH indicating deterioration of the rechargeable battery is stored in the storage means for each usage mode of the rechargeable battery. The charging is possible by acquiring the step and the relational expression corresponding to the usage mode detected in the detection step from the storage means and applying the value of the element calculated in the calculation step to the relational expression. It is characterized by having an estimation step for estimating the SOH of the battery.
According to such a method, it is possible to accurately estimate the deterioration of the rechargeable battery even if it is used differently than usual.

According to the present invention, it is possible to provide a rechargeable battery deterioration estimation device and a rechargeable battery deterioration estimation method capable of accurately estimating the deterioration of a rechargeable battery even when it is used differently from the usual one. Become.

It is a figure which shows the structural example of the rechargeable battery deterioration estimation apparatus which concerns on embodiment of this invention. It is a block diagram which shows the detailed configuration example of the control part of FIG. It is a figure which shows an example of the equivalent circuit of the rechargeable battery shown in FIG. It is a figure which shows the relationship between the usage mode which causes the capacity decrease of a rechargeable battery, and the affected part. It is a figure which shows typically an example of the mode of use of a rechargeable battery. It is a figure which shows the relationship between the estimated value of the health degree by the prior art, and the measured value. It is a figure which shows the correction coefficient for every use mode. It is a figure which shows the relationship between the estimated value of health degree and the measured value by this embodiment. It is a figure which shows the classification example of the usage mode in this embodiment. This is an example of a flowchart for explaining the flow of processing executed when the rechargeable battery is mounted in the embodiment shown in FIG. This is an example of a flowchart for explaining the flow of the equivalent circuit learning process executed in the embodiment shown in FIG. This is an example of a flowchart for explaining a flow of a process for specifying a usage mode executed in the embodiment shown in FIG. This is an example of a flowchart for explaining the flow of the process of estimating the SOH executed in the embodiment shown in FIG. It is a figure which shows another example of the equivalent circuit of the rechargeable battery shown in FIG.

Next, an embodiment of the present invention will be described.

(A) Explanation of Configuration of Embodiment of the Present Invention FIG. 1 is a diagram showing a power supply system of a vehicle having a rechargeable battery deterioration estimation device according to the embodiment of the present invention. In this figure, the rechargeable battery deterioration estimation device 1 has a control unit 10, a voltage sensor 11, a current sensor 12, a temperature sensor 13, and a discharge circuit 15 as main components, and determines the state of charge of the rechargeable battery 14. Control. The control unit 10, the voltage sensor 11, the current sensor 12, the temperature sensor 13, and the discharge circuit 15 may not be configured separately, but may be partially or all of them. Further, at least one of the voltage sensor 11, the current sensor 12, the temperature sensor 13, and the discharge circuit 15 may be configured independently of the rechargeable battery deterioration estimation device 1.

Here, the control unit 10 refers to the outputs from the voltage sensor 11, the current sensor 12, and the temperature sensor 13, detects the state of the rechargeable battery 14, and charges by controlling the generated voltage of the alternator 16. Controls the charging state of the possible battery 14. The voltage sensor 11 detects the terminal voltage of the rechargeable battery 14 and notifies the control unit 10. The control unit 10 does not control the charging state of the rechargeable battery 14 by controlling the generated voltage of the alternator 16, but for example, an ECU (Electric Control Unit) (not shown) is based on the information from the control unit 10. The charging state may be controlled.

The current sensor 12 detects the current flowing through the rechargeable battery 14 and notifies the control unit 10. The temperature sensor 13 detects the rechargeable battery 14 itself or the ambient temperature, and notifies the control unit 10. The discharge circuit 15 is composed of, for example, a semiconductor switch and a resistance element connected in series, and the rechargeable battery 14 is intermittently discharged by controlling the semiconductor switch on / off by the control unit 10.

The rechargeable battery 14 is composed of, for example, a lead storage battery, a nickel cadmium battery, a nickel hydrogen battery, a lithium ion battery, or the like, is charged by the alternator 16, drives the starter motor 18, starts the engine, and loads 19. Power to. The alternator 16 is driven by the engine 17, generates AC power, converts it into DC power by a rectifier circuit, and charges the rechargeable battery 14. The alternator 16 is controlled by the control unit 10 so that the generated voltage can be adjusted.

The engine 17 is composed of, for example, a reciprocating engine such as a gasoline engine and a diesel engine, a rotary engine, or the like, is started by a starter motor 18, drives drive wheels via a transmission, gives propulsion to a vehicle, and is an alternator 16. To generate power. The starter motor 18 is composed of, for example, a DC motor, and generates a rotational force by the electric power supplied from the rechargeable battery 14 to start the engine 17. The load 19 is composed of, for example, an electric steering motor, a defogger, a seat heater, an ignition coil, a car audio, a car navigation system, and the like, and is operated by electric power from the rechargeable battery 14.

FIG. 2 is a diagram showing a detailed configuration example of the control unit 10 shown in FIG. As shown in this figure, the control unit 10 includes a CPU (Central Processing Unit) 10a as a processor, a ROM (Read Only Memory) 10b, a RAM (Random Access Memory) 10c, a communication unit 10d, and an I / F (Interface) 10e. have. Here, the CPU 10a controls each unit based on the program 10ba stored in the ROM 10b. The program 10ba has an instruction group that can be executed by the CPU 10a, and by executing these instruction groups, the processing described later is realized. The ROM 10b is composed of a semiconductor memory or the like and stores the program 10ba or the like. The RAM 10c is composed of a semiconductor memory or the like, and stores data generated when the program 10ba is executed, mathematical formulas and coefficients described later, and parameters 10ca such as a table. The communication unit 10d communicates with an ECU or the like which is a higher-level device, and notifies the higher-level device of the detected information or control information. The I / F 10e converts the signals supplied from the voltage sensor 11, the current sensor 12, and the temperature sensor 13 into digital signals and captures them, and transfers the drive current to the discharge circuit 15, the alternator 16, the starter motor 18, and the like. Supply and control these.

In the example of FIG. 2, one CPU 10a is provided, but the distributed processing may be executed by a plurality of CPUs. Further, instead of the CPU 10a, it may be configured by a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like. Alternatively, the processing may be performed on the computer on the server by a general-purpose processor or cloud computing that executes a function by loading a software program. Further, in FIG. 2, the ROM 10b and the RAM 10c are provided, but for example, a storage device other than these (for example, an HDD (Hard Disk Drive) which is a magnetic storage device) may be used.

(B) Description of Operation of Embodiment of the Present Invention Next, the operation of the embodiment of the present invention will be described. In the following, after explaining the operating principle of the embodiment of the present invention, detailed operation will be described.

First, the operating principle of this embodiment will be described. In the present embodiment, the equivalent circuit of the rechargeable battery 14 shown in FIG. 3 is calculated by learning processing or fitting processing, and the components of the equivalent circuit are obtained. In the example of FIG. 3, the equivalent circuit consists of Rohm, which is a resistance component corresponding to the conductor element and electrolyte resistance inside the rechargeable battery 14, and Rct1 which is a resistance component corresponding to the reaction resistance of the active material reaction of the electrode. , Rct2 and C1 and C2 which are capacitive components corresponding to the electric double layer at the interface between the electrode and the electrolytic solution. As the rechargeable battery 14 deteriorates, the value of the resistance component increases and the value of the capacitance component decreases. Therefore, by substituting the equivalent circuit component thus obtained into the equation (1) shown below, the SOH (State of Health) of the rechargeable battery 14 is calculated and the deteriorated state is estimated.

SOH = f (Rohm, Rct1, Rct2, C1, C2) ... (1)

As described above, the method using the components constituting the equivalent circuit has a feature that deterioration can be accurately estimated regardless of the type of the rechargeable battery.

However, on the other hand, in the deterioration estimation by such a method, the deterioration estimation accuracy may decrease depending on the usage mode of the rechargeable battery 14.

FIG. 4 is a diagram showing the relationship between the usage mode of the rechargeable battery 14, the deterioration phenomenon, and the affected portion. As shown in FIG. 4, for example, in the case of insufficient charging, sulfation occurs as a deterioration phenomenon and the negative electrode active material is affected (in the equivalent circuit of FIG. 3, Rct1 and C1 are affected). Further, in the case of overcharging, corrosion occurs as a deterioration phenomenon, and the lattice / electrolytic solution is affected (Rohm is affected in the equivalent circuit of FIG. 3). Further, in the case of repeated deep charging and discharging, the active material is softened and dropped off, and the positive electrode active material is affected (Rct2 and C2 are affected in the equivalent circuit of FIG. 3).

As described above, the type of deterioration that occurs differs depending on the mode of use, and the affected part also differs.

FIG. 5 is a diagram schematically showing an example of various usage modes. In FIG. 5, the horizontal axis indicates the time, the arrow indicates the timing at which the engine 17 is started, the hatched rectangle indicates the period during which the engine 17 operates, and the broken line indicates the SOC of the rechargeable battery 14. It shows the change of State of Charge). In FIG. 5, in order to simplify the drawing, the timing at which the engine 17 is started and the period during which the engine 17 is operated are fixed, but they are actually different depending on the user.

Here, FIG. 5A shows a usage mode in which the vehicle is left unattended for a long period of time. More specifically, the example of FIG. 5A shows a state in which the engine 17 is left unstarted for 6 months, and the rechargeable battery 14 self-discharges and the vehicle darkens over time. The SOC is gradually reduced by the current (current flowing through the load 19 when the engine 17 is stopped). In the following, the usage mode of FIG. 5 (A) will be referred to as usage mode A.

FIG. 5B shows a usage mode B in which the vehicle is used for commuting, for example. In the usage mode B, the engine 17 is operated for 5 days on weekdays and is not operated for 2 days on holidays. In the usage mode B, since the rechargeable battery 14 is charged on weekdays, the SOC is maintained in a high state.

FIG. 5C shows, for example, a usage mode C in which the vehicle is not used for 5 days on weekdays and the vehicle is operated for 2 days on holidays. In the usage mode C, since the battery is not charged on weekdays, the SOC of the rechargeable battery 14 becomes low, and the SOC returns to the high state by the operation on holidays.

FIG. 5 (D) shows, for example, in a vehicle such as a taxi, the engine 17 is operated every day and the SOC is basically maintained at a high state, but when waiting for a customer, the discharge due to the load 19 of the vehicle is discharged. It shows the usage mode D which is present and temporarily becomes low.

FIG. 5 (E) shows, for example, a usage mode E in which a state close to full charge (SOC = 100%) is maintained in a state where a current does not substantially flow through the load 19 of the vehicle.

FIG. 6 is a diagram showing the relationship between the results of estimating the health of the rechargeable batteries 14 of the above-mentioned usage modes A to E by the prior art and the measured values. The degree of health is a deterioration index of the rechargeable battery 14 represented by the following formula (1), which is 1 when the battery is new and decreases with deterioration.

Health = current capacity of rechargeable battery / capacity of rechargeable battery when new ... (2)

In the example of FIG. 6 according to the prior art, in the case of usage mode B (used only on weekdays), which is a standard usage mode, it is located on a broken line segment in which the estimated health level and the measured health level match. However, the usage mode C (used only on two days off), the usage mode D (daily operation and temporary over-discharging use), the usage mode E (use of overcharging), and the usage mode A (use for a long period of time). In order, the estimated value and the measured value deviate from each other.

In the prior art, the usage history function corrects the estimated state of the rechargeable battery 14, but the function itself is fixed. Therefore, there is a problem that the correction does not function properly depending on the usage mode, and the estimated value and the actually measured value deviate from each other.

Therefore, in the present embodiment, a plurality of functions of the correction coefficient optimized for each usage mode of the vehicle are prepared, the usage mode is determined for each arbitrary period, and the history correction coefficient according to the usage mode is determined. By selecting and applying the function, high estimation accuracy can be maintained regardless of the usage mode.

More specifically, in the present embodiment, for example, when the rechargeable battery 14 is mounted in the vehicle manufacturing process, or when the user replaces the rechargeable battery 14 with a new one, the CPU 10a of the control unit 10 is charged. The rechargeable battery 14 is pulse-discharged by the discharge circuit 15 to learn the values of the elements (Rohm, Rct1, Rct2, C1, C2) constituting the equivalent circuit of the rechargeable battery 14 (for example, the equivalent circuit shown in FIG. 3). Then, the obtained element values are stored in the parameter 10ca of the RAM 10c as initial values Rohmi, Rct1i, Rct2i, C1i, and C2i.

Next, the CPU 10a periodically measures the SOC when the engine 17 is started and the SOC when the engine 17 is stopped, and measures the start frequency (or operation frequency) of the engine 17 to input the parameter 10ca to the RAM 10c. Remember as.

Next, the CPU 10a executes the SOH estimation process at an arbitrary timing. More specifically, the CPU 10a calculates and acquires the element values Rohm, Rct1, Rct2, C1 and C2 of the equivalent circuit at that time by the learning process. Further, the CPU 10a acquires the initial values Rohmi, Rct1i, Rct2i, C1i, and C2i of the element values of the equivalent circuit stored in the RAM 10c as the parameter 10ca, and the difference values ΔRohm, ΔRct1 between the element values and the initial values at that time. , ΔRct2, ΔC1, ΔC2 are calculated based on the following equations (3) to (7).

ΔRohm = Rohm-Rohmi ・ ・ ・ (3)
ΔRct1 = Rct1-Rct1i ... (4)
ΔRct2 = Rct2-Rct2i ... (5)
ΔC1 = C1-C1i ... (6)
ΔC2 = C2-C2i ... (7)

Next, the CPU 10a acquires information on the starting frequency of the engine 17 from the parameter 10ca of the RAM 10c, and classifies the usage mode of the vehicle into usage modes A to E based on this information. If the same usage mode does not exist, it is classified into a closer usage mode. For example, when it is used four times a week and not three times a week, it is classified into the usage mode D because the usage mode D is the closest.

Next, the CPU 10a acquires a correction coefficient according to the usage mode from the parameter 10ca of the RAM 10c. FIG. 7 is a diagram showing an example of a correction coefficient according to a usage mode, which is stored in the parameter 10ca of the RAM 10c. In this example, the correction coefficients f_Rohm_A, f_Rct1_A, f_Rct2_A, f_C1_A, and f_C2_A are stored for the usage mode A. Similar correction coefficients are stored for usage B to E. The CPU 10a acquires a correction coefficient from the RAM 10c according to the usage mode of the user. For example, the correction coefficient corresponding to the usage mode A is acquired from the RAM 10c.

Next, the CPU 10a calculates Δα_Rohm, Δα_Rct1, Δα_Rct2, Δα_C1, and Δα_C2 based on the following equations (8) to (12). In the case of usage mode B to usage mode E, the second term on the right side of the equations (8) to (12) changes.

Δα_Rohm = ΔRohm × f_Rohm_A ... (8)
Δα_Rct1 = ΔRct1 × f_Rct1_A ... (9)
Δα_Rct2 = ΔRct2 × f_Rct2_A ... (10)
Δα_C1 = ΔC1-C1i × f_C1_A ... (11)
Δα_C2 = ΔC2-C2i × f_C2_A ... (12)

Next, the CPU 10a calculates the SOH indicating the deteriorated state of the rechargeable battery 14 based on the following formula (13). Note that f () is a predetermined function with Δα_Rohm, Δα_Rct1, Δα_Rct2, Δα_C1, and Δα_C2 as variables. The function can be obtained, for example, by actual measurement.

SOH = f (Δα_Rohm, Δα_Rct1, Δα_Rct2, Δα_C1, Δα_C2) ... (13)

By the above processing, highly accurate SOH can be obtained according to the usage mode. Based on the SOH obtained in this way, for example, when the SOH becomes less than a predetermined threshold value, the CPU 10a notifies the user that the rechargeable battery 14 has deteriorated and warns the user. be able to. Further, by controlling the charge / discharge of the rechargeable battery 14 according to the SOH, the optimum control according to the deterioration can be performed.

FIG. 8 is a diagram showing the relationship between the estimated value and the measured value of the health of each of the rechargeable batteries 14 of the usage modes A to E when the present embodiment is used. Compared with the case where the prior art shown in FIG. 6 is used, the estimated value is closer to the measured value in the cases of the usage mode A, the usage mode D, and the usage mode E. From this, according to the present embodiment, it is possible to accurately estimate the deterioration of the rechargeable battery 14 regardless of the usage mode.

In the above embodiment, as shown in FIG. 7, correction coefficients are prepared for all of the usage modes A to E, but the deviation from the ideal value shown in FIG. 6 is relatively small. The usage mode B, the usage mode C, and the usage mode D may be corrected by using a common correction coefficient, and only the usage mode A and the usage mode E may be corrected by using individual correction coefficients.

More specifically, as shown in FIG. 9, the usage mode may be divided into three regions, region X to region Z, and a correction coefficient may be prepared for each region. The horizontal axis of FIG. 9 shows the charge / discharge amount when the charge / discharge amount actually measured in a predetermined period is standardized to one year, and the vertical axis shows DoD (Depth of Discharge) which is the discharge depth. ing. DoD indicates the ratio of the amount of discharge to the rechargeable capacity of the rechargeable battery 14. For example, when a rechargeable battery 14 having a capacity of 100 Ah is discharged by 30 Ah, DoD = 30% (= 30 Ah / 100 Ah). Become. The rechargeable battery 14 is generally characterized in that the larger the DoD, the more easily the deterioration progresses even with the same charge / discharge amount. In the example of FIG. 9, one common correction coefficient is used for the usage mode B, the usage mode C, and the usage mode D belonging to the region X, and an individual correction coefficient is used for the usage mode A belonging to the region Y. However, individual correction coefficients can be used for the usage mode E belonging to the region Z. As a result, the required storage area of the RAM 10c can be reduced by reducing the number of correction coefficients.

Next, the detailed operation of the embodiment of the present invention will be described with reference to the flowchart. FIG. 10 is a flowchart for explaining an example of processing executed when the rechargeable battery 14 is mounted. When the flowchart of FIG. 10 is started, the following steps are executed.

In step S10, the CPU 10a of the control unit 10 determines whether or not a new rechargeable battery 14 is installed (or is replaced with a new rechargeable battery 14), and the new rechargeable battery 14 is installed. If it is determined that the process has been performed (step S10: Y), the process proceeds to step S11, and in other cases (step S10: N), the process ends. For example, when a new rechargeable battery 14 is mounted in the vehicle assembly process, it is determined to be Y and the process proceeds to step S11.

In step S11, the CPU 10a executes a learning process of the equivalent circuit of the rechargeable battery 14 shown in FIG. The details of the learning process of the equivalent circuit will be described later with reference to FIG.

In step S12, the CPU 10a acquires the values of the elements Rohm, Rct1, Rct2, C1, and C2 constituting the equivalent circuit obtained by the learning process of step S11.

In step S13, the CPU 10a stores the values of the elements Rohm, Rct1, Rct2, C1, and C2 acquired in step S12 as initial values Rohmi, Rct1i, Rct2i, C1i, and C2i in the parameter 10ca of the RAM 10c.

Next, the details of the equivalent circuit learning process shown in step S11 of FIG. 10 will be described with reference to FIG. When the flowchart of FIG. 11 is started, the following steps are executed.

In step S30, the CPU 10a starts discharging the rechargeable battery 14. For example, the CPU 10a discharges the rechargeable battery 14 (for example, pulse discharge) by switching and controlling the discharge circuit 15. The opportunity of discharge by the starter motor 18 or the load 19 may be used instead of the discharge circuit 15.

In step S31, the CPU 10a measures the terminal voltage of the rechargeable battery 14 with reference to the signal output from the voltage sensor 11.

In step S32, the CPU 10a measures the current flowing through the rechargeable battery 14 with reference to the signal output from the current sensor 12.

In step S33, the CPU 10a determines whether or not the discharge is completed, and if it is determined that the discharge is completed (step S33: Y), the process proceeds to step S34, and in other cases (step S33: N). Returning to S31, the same process as described above is repeated.

In step S34, the CPU 10a optimizes each component of the equivalent circuit. As an optimization method, for example, as described in Japanese Patent No. 4532416, the optimum state vector X is estimated by the extended Kalman filter operation, and the adjustment parameter (component) of the equivalent circuit is obtained from the estimated state vector X. Update to the optimal one. Specifically, based on an equivalent circuit using the adjustment parameter obtained from the state vector X in a certain state, the voltage drop ΔV when the rechargeable battery is discharged with a predetermined current pattern is calculated, and this approaches the measured value. The state vector X is updated as follows. Then, the optimum adjustment parameter is calculated from the state vector X optimized by the update. Alternatively, as described in WO2014 / 136593, when the rechargeable battery 14 is pulsed discharged, a temporal change in the voltage value is acquired, and the obtained voltage value change is fitted by a predetermined function with the time as a variable. By doing so, the parameters of the predetermined function can be calculated, and the components of the equivalent circuit of the rechargeable battery 14 can be obtained based on the calculated parameters of the predetermined function. Of course, methods other than these may be used.

In step S35, the CPU 10a measures the temperature. More specifically, the CPU 10a measures the temperature of the rechargeable battery 14 itself or its surroundings with reference to the signal output from the temperature sensor 13.

In step S36, the CPU 10a corrects each component of the equivalent circuit optimized in step S34 to the value at the standard temperature. For example, when the standard temperature is 25 ° C., it is corrected to the value at the standard temperature by, for example, multiplying the current temperature measured in step S35 by a correction coefficient corresponding to the difference value of 25 ° C. Of course, the standard temperature may be other than 25 ° C.

In step S37, the CPU 10a calculates the SOC of the rechargeable battery 14. For example, the SOC is calculated based on the OCV (Open Circuit Voltage) of the rechargeable battery 14.

In step S38, the CPU 10a corrects each component of the equivalent circuit optimized in step S34 to the value in the standard SOC. For example, when the standard SOC is 100%, it is corrected to the value in the standard SOC by, for example, multiplying the current SOC calculated in step S37 by the correction coefficient corresponding to the difference value of 100%. Of course, the standard SOC may be other than 100%.

Next, with reference to FIG. 12, a flowchart executed when acquiring information on the usage mode of the rechargeable battery 14 will be described. When the processing of the flowchart shown in FIG. 12 is started, the following steps are executed.

In step S50, the CPU 10a executes a process of calculating SOC periodically (for example, every 1 to several hours) based on the process shown in FIG.

In step S51, the CPU 10a stores the SOC calculated in step S50 in the parameter 10ca of the RAM 10c as information indicating the usage mode. As a method for obtaining the SOC, for example, the OCV can be measured and calculated based on the relational expression between the OCV and the SOC.

In step S52, the CPU 10a determines whether or not the engine 17 has been started, and if it is determined that the engine 17 has been started (step S52: Y), the process proceeds to step S53, and in other cases (step S52: N). The process returns to step S50 and the same process as described above is repeated.

In step S53, the CPU 10a specifies the starting frequency of the engine 17 calculated in step S52. For example, use five times a week is specified.

In step S54, the CPU 10a stores the information indicating the usage mode specified in step S53 in the parameter 10ca of the RAM 10c. For example, information such as use five times a week is stored in the parameter 10ca of the RAM 10c.

In step S55, the CPU 10a executes a process of calculating the SOC periodically (for example, every one to several hours) based on the process shown in FIG. As a method for obtaining the SOC, the charge / discharge current detected by the current sensor 12 can be cumulatively added to the SOC when the engine 17 is stopped, which is obtained in step S50.

In step S56, the CPU 10a stores the SOC calculated in step S55 in the parameter 10ca of the RAM 10c as information indicating the usage mode.

In step S57, the CPU 10a determines whether or not the engine 17 has been stopped, and if it determines that the engine 17 has been stopped, the process proceeds to step S58 (step S57: Y), and in other cases (step S57: N). The process returns to step S55 and the same process as described above is repeated.

In step S58, the CPU 10a determines whether or not to repeat the process, and if it is determined to repeat the process (step S58: Y), the CPU 10a returns to step S50 and repeats the same process as described above, and other than that. In the case (step S58: N), the process ends.

Next, a process of estimating the SOH of the rechargeable battery 14 will be described with reference to FIG. When the processing of the flowchart shown in FIG. 13 is started, the following steps are executed.

In step S70, the CPU 10a calculates Rohm, Rct1, Rct2, C1, and C2 at that time based on the process shown in FIG. 11, and acquires the calculated result.

In step S71, the CPU 10a acquires the initial values Rohmi, Rct1i, Rct2i, C1i, and C2i of the elements stored in the parameter 10ca of the RAM 10c by the process of step S13 of FIG.

In step S72, the CPU 10a converts the difference values ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2 between the element value acquired in step S70 at that time and the initial value acquired in step S71 into equations (3) to (7). Calculate based on.

In step S73, the CPU 10a acquires the history information indicating the usage mode stored in the parameter 10ca of the RAM 10c by the process shown in FIG. As a result, historical information regarding the engine start frequency and SOC is obtained.

In step S74, the CPU 10a classifies the vehicle into any of the usage modes A to E based on the history information acquired in step S73. For example, if it is used 5 days a week on weekdays and not 2 days a week on holidays, it is classified into usage mode B.

In step S75, the CPU 10a acquires the correction coefficients corresponding to the usage modes A to E from the parameter 10ca of the RAM 10c. For example, in the case of usage mode B, f_Rohm_B, f_Rct1_B, f_Rct2_B, f_C1_B, f_C2_B shown in FIG. 7 are acquired.

In step S76, the CPU 10a corrects the difference values ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2 by applying the correction coefficient acquired in step S75 to the above-mentioned equations (8) to (12), and Δα_Rohm, Calculate Δα_Rct1, Δα_Rct2, Δα_C1, and Δα_C2.

In step S77, Δα_Rohm, Δα_Rct1, Δα_Rct2, Δα_C1, and Δα_C2 calculated in step S76 are applied to the equation (13) to calculate SOH.

In step S78, the CPU 10a compares the SOH calculated in step S77 with a predetermined threshold value Th, determines whether or not SOH <Th, and if SOH <Th is satisfied (step S78: Y), proceeds to step S79. In other cases (step S78: N), the process proceeds to step S80.

In step S79, the CPU 10a executes a warning process of notifying and warning the user that the rechargeable battery 14 has deteriorated via the upper ECU.

In step S80, the CPU 10a determines whether or not to repeat the process, and if it is determined to repeat the process (step S80: Y), the CPU 10a returns to step S70 and repeats the same process as described above, and other than that. In the case (step S80: N), the process ends.

As described above, according to the processing of the flowchart shown in FIGS. 10 to 13, the operation of the above-described embodiment can be realized.

(C) Description of Modified Embodiment The above embodiment is an example, and it goes without saying that the present invention is not limited to the cases described above. For example, in the above embodiment, the SOH is obtained by multiplying the correction coefficient according to the usage mode. For example, the following equation (14) can be used. Note that g () is a function having a value such that the relationship between the estimated case normality and the measured normality shown in FIG. 6 approaches a broken line. For example, the usage mode A has a value close to g () = 1, the usage mode C has a value slightly larger than 1, and the usage mode D, the usage mode E, and the usage mode A have smaller values in this order. It is a function having (<1).

SOH = f (ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2) × g (one or more variables depending on the usage mode) ... (14)

Moreover, you may change the formula itself according to the mode of use. For example, in the case of usage mode A, SOH is calculated using fA (ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2), and in the case of usage mode B, fB (ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2) is used. Similarly, in the case of usage mode C to usage mode E, fC (ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2), fD (ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2), and fE ( ΔRohm, ΔRct1, ΔRct2, ΔC1, ΔC2) can be used, respectively.

Further, in the above embodiment, the formula for calculating SOH or the like is changed based on the history information indicating the frequency of use of the vehicle, but for example, the environmental temperature may be used as the history information. Specifically, in the example of FIG. 9, the regions are divided based on the charge / discharge amount equivalent to one year and DoD, and the usage mode is defined for each region. However, the usage mode is added by adding the environmental temperature. May be divided. As an example, the usage mode is defined by dividing a three-dimensional space in which the X-axis is the charge / discharge amount equivalent to one year, the Y-axis is DoD, the Z-axis is the ambient temperature, and the origin of the Z-axis is 25 ° C. You may do so.

In addition, the temperature history of the rechargeable battery 14, the history of the discharge depth, the history of the amount of electricity charged and discharged, the history of the frequency of falling below a certain charging rate, the history of the frequency of exceeding a certain charging rate, and the charging. The usage mode may be determined based on the history of the duration for each rate and at least one of the elapsed time since the start of use.

Further, the above-mentioned history may be measured layered according to any one of the SOC, voltage, current, and temperature of the rechargeable battery.

Further, in the above embodiment, the equivalent circuit shown in FIG. 3 is used, but other equivalent circuits may be used. For example, as shown in FIG. 14A, an equivalent circuit including Rohm and Rct1 and C1 may be used. Alternatively, as shown in FIG. 14 (B), an equivalent circuit consisting of only Rohm and Rct1 may be used. Alternatively, at least one element of the equivalent circuit shown in FIG. 3 or 14 may be used. Further, it is desirable to change the above-mentioned equations (1) to (14) according to the equivalent circuit.

Further, in the equation (13) used in the above embodiment, all of Δα_Rohm, Δα_Rct1, Δα_Rct2, Δα_C1, and Δα_C2 are used as the variables of the function on the right side, but some of them are used. May be good. For example, as shown in FIG. 4, in the case of insufficient charging, the negative electrode active material is affected, so correction is performed centering on Rct1 and C1, and in the case of overcharging, the lattice / electrolytic solution is affected, so Rohm. Since the positive electrode active material is affected in the case of repeated deep charging and discharging, the correction may be performed centering on Rct2 and C2.

Further, in the above embodiment, the correction by the correction coefficient is executed at a predetermined timing, but for example, when the usage time exceeds a predetermined time, or the value of the function f () is a predetermined threshold value. When the following occurs, the correction by the correction coefficient may be executed.

Further, in the above embodiment, as the processing when the estimated SOH becomes less than a predetermined threshold value, (1) a processing for issuing a warning and (2) a processing for changing the control of the vehicle are executed. You may try to do it.

More specifically, with respect to (1), when the SOH becomes less than a predetermined threshold value, the CPU 10a of the control unit 10 outputs information indicating that the SOH has decreased to an ECU (not shown) via the communication unit 10d. Then, the ECU may display information indicating that the SOH has decreased on a display device (not shown), and in some cases, display information indicating that the rechargeable battery 14 needs to be replaced. In addition, a voice warning may be issued at the same time.

Regarding (2), when the CPU 10a of the control unit 10 outputs information indicating that the SOH has decreased to an ECU (not shown) via the communication unit 10d, the ECU controls the control corresponding to the low SOH (for example,). The control to keep the SOC high) may be executed.

Further, it goes without saying that the flowcharts shown in FIGS. 10 to 13 are examples, and the present invention is not limited to these flowcharts.

1 Rechargeable battery deterioration estimation device 10 Control unit 10a CPU
10b ROM
10c RAM
10d communication unit 10e I / F
11 Voltage sensor 12 Current sensor 13 Temperature sensor 14 Rechargeable battery 15 Discharge circuit 16 Alternator 17 Engine 18 Starter motor 19 Load

Claims (10)

In the rechargeable battery deterioration estimation device that estimates the deterioration of the rechargeable battery,
A calculation means for calculating the values of the elements constituting the equivalent circuit of the rechargeable battery, and
A detection means for detecting the usage mode of the rechargeable battery and
A storage means for storing a relational expression showing the relationship between at least one element constituting the equivalent circuit and SOH indicating deterioration of the rechargeable battery for each usage mode of the rechargeable battery.
By acquiring the relational expression corresponding to the usage mode detected by the detection means from the storage means and applying the value of the element calculated by the calculation means to the relational expression, the rechargeable battery can be described. Estimating means for estimating SOH and
A rechargeable battery deterioration estimator characterized by having. The storage means stores a plurality of the relational expressions corresponding to the usage mode, and stores the relational expression.
The estimation means acquires one of the relational expressions corresponding to the usage mode detected by the detection means from the plurality of relational expressions, and applies the value of the element calculated by the calculation means to the relational expression. By doing so, the SOH of the rechargeable battery is estimated.
The rechargeable battery deterioration estimation device according to claim 1. The storage means stores the coefficients constituting the relational expression for each of the usage modes.
The estimation means acquires the coefficient corresponding to the usage mode detected by the detection means from the plurality of relational expressions, and the value of the element calculated by the calculation means is converted into the relational expression having the coefficient. By applying, the SOH of the rechargeable battery is estimated.
The rechargeable battery deterioration estimation device according to claim 1. The relational expression is a value obtained by multiplying the difference value between the initial value and the current value of at least one element constituting the equivalent circuit of the rechargeable battery by the coefficient corresponding to the usage mode. The rechargeable battery deterioration estimation device according to claim 3, wherein the SOH is estimated by applying the above to the relational expression. The usage modes include a history of the temperature of the rechargeable battery, a history of the depth of discharge, a history of the amount of electricity charged and discharged, a history of the frequency of falling below a certain charge rate, and a history of the frequency of exceeding a certain charge rate. The charge according to any one of claims 1 to 4, wherein the determination is made based on at least one of the history, the history of the duration for each charge rate, and the elapsed time since the start of use. Possible battery deterioration estimation device. The rechargeable battery deterioration estimation device according to claim 5, wherein the history is stratified and measured according to any one of the SOC, voltage, current, and temperature of the rechargeable battery. The equivalent circuit comprises a conductor element inside the rechargeable battery and a resistance component corresponding to the electrolyte resistance, a resistance component corresponding to the reaction resistance of the active material reaction of the electrode of the rechargeable battery, and the electrode and the electrolyte. The rechargeable battery deterioration estimation device according to any one of claims 1 to 6, wherein the rechargeable battery deterioration estimation device has at least one capacitance component corresponding to the electric double layer at the interface. The rechargeable battery deterioration estimation device according to claim 7, wherein the calculation means corrects the values of the elements constituting the equivalent circuit to the values of the elements at the reference temperature and the reference SOC. The rechargeable battery is mounted on the vehicle and
The vehicle is controlled based on the SOH estimated by the estimation means.
The rechargeable battery deterioration estimation device according to any one of claims 1 to 8, characterized in that. In the rechargeable battery deterioration estimation method for estimating the deterioration of the rechargeable battery,
A calculation step for calculating the values of the elements constituting the equivalent circuit of the rechargeable battery, and
A detection step for detecting the usage mode of the rechargeable battery and
A storage step of storing a relational expression showing a relationship between at least one element constituting the equivalent circuit and SOH indicating deterioration of the rechargeable battery in a storage means for each usage mode of the rechargeable battery.
By acquiring the relational expression corresponding to the usage mode detected in the detection step from the storage means and applying the value of the element calculated in the calculation step to the relational expression, the rechargeable battery can be described. Estimating steps to estimate SOH and
A rechargeable battery deterioration estimation method characterized by having.