JP6627401B2 - Secondary battery deterioration detection device and method - Google Patents

Description

  The present invention relates to a secondary battery deterioration detection device and method for detecting deterioration of a secondary battery including a graphite-based active material in a negative electrode.

  The capacity maintenance ratio of the secondary battery, that is, the ratio C / Cf of the current full charge capacity C to the full charge capacity Cf in a non-degraded state (hereinafter, (Cf-C) / Cf is referred to as a deterioration degree) is detected. As a deterioration detecting device, there is known a deterioration detecting device that detects a change in a voltage of a secondary battery and an SOC (State of Charge) with respect to a charge current integrated value.

JP 2011-215125 A

  In a conventional secondary battery deterioration detecting device, a terminal voltage of a secondary battery is detected, and a capacity retention ratio or a degree of deterioration is calculated based on the detected terminal voltage. However, the voltage of the battery during charging / discharging differs from the open-circuit voltage and fluctuates depending on the environment such as the temperature.

  An object of the present invention is to provide a device and a method for detecting deterioration of a secondary battery that can accurately detect deterioration of the secondary battery.

  The present invention detects an increasing point of the frequency of generation of an acoustic emission signal generated from a secondary battery, and detects deterioration of the secondary battery based on a current integrated value of a charging current from this time to a full charge time. Solves the above problem.

  The present inventors have found that even when the secondary batteries have different degrees of deterioration, the point at which the frequency of occurrence of the acoustic emission signal increases during charging / discharging (the battery capacity point) does not change, and the secondary battery is fully charged from this increased point. It has been found that the integrated current values up to are correlated with the degree of deterioration. Based on this knowledge, comparing the current integrated value from the increase point with the charging capacity of the non-deteriorated product, it is possible to accurately determine the deterioration of the secondary battery even during charging / discharging and without using open-circuit voltage. It can be detected well.

FIG. 1 is a block diagram showing a battery control system including an embodiment of a secondary battery deterioration detection device according to the present invention. FIG. 2 is a flowchart illustrating an example of a process performed by the deterioration detector of FIG. FIG. 3 is a flowchart illustrating another example of the process performed by the deterioration detector of FIG. FIG. 4 is a flowchart showing still another example of the processing executed by the deterioration detector of FIG. FIG. 5A is a graph showing charge / discharge characteristics of a secondary battery having a zero degree of deterioration. FIG. 5B is a graph showing the charge / discharge characteristics of a secondary battery having a degree of deterioration of 13%. FIG. 5C is a graph showing the charge / discharge characteristics of a secondary battery having a degree of deterioration of 33%. FIG. 5D is a graph showing the charge / discharge characteristics of a secondary battery having a degree of deterioration of 75%. FIG. 6 is a graph showing the relationship between the negative electrode potential of a secondary battery using a graphite-based active material as a negative electrode active material and the frequency of generation of an acoustic emission signal. FIG. 7 is a diagram showing an example of a control map stored in the storage device of FIG. FIG. 8A is a graph showing a charging curve when charging a secondary battery having a high degree of deterioration is started. FIG. 8B is a graph showing a charging curve when charging is started for a secondary battery having a small degree of deterioration.

  FIG. 1 is a block diagram showing a battery control system including an embodiment of a secondary battery deterioration detection device according to the present invention. As shown in FIG. 1, the battery control system according to the present embodiment is a system for mainly charging a secondary battery 3, and includes a charging device 2 and a deterioration detection device 1. Note that the deterioration detection device 1 may be included in the charging device 2, or conversely, the charging device 2 may be included in the deterioration detection device 1.

  The secondary battery 3 whose degree of deterioration can be detected using the principle of the present embodiment is, for example, a lithium ion secondary battery. A secondary battery 3 of this type uses an active material having a plurality of charge / discharge regions in which the charge / discharge potential changes stepwise as lithium ions are inserted or removed as a negative electrode active material. Can be. As such an active material having a plurality of charge / discharge regions in which the charge / discharge potential changes stepwise as lithium ions are inserted / desorbed, a graphite-based active material having a graphite structure is suitable. Therefore, in the embodiments described below, the present invention will be described by exemplifying a lithium ion secondary battery using a graphite-based active material. However, the active material having a plurality of charge / discharge regions in which the charge / discharge potential changes stepwise with the insertion / desorption of lithium ions is not particularly limited to a graphite-based active material. The positive electrode active material is not particularly limited, and a known positive electrode active material for a lithium ion secondary battery such as a lithium-transition metal composite oxide can be used.

  The charging device 2 is a device for charging a secondary battery 3 mounted on an electric vehicle or a hybrid vehicle, for example. The charging of the secondary battery 3 mounted on the vehicle is performed by removing the charging cable of the charging device 2, attaching the charging gun at the tip of the charging cable to the connector of the charging port of the vehicle, and then operating the charging start switch. The charging circuit 21 converts a commercial AC current into a DC current having a predetermined voltage, and supplies the DC current to the secondary battery. The current integrator 12 and the full charge detector 13 included in the charging device 2 are shared with the deterioration detecting device 1.

  The current integrator 12 is an integrating circuit that measures a current value flowing from the charging circuit 21 to the secondary battery 3 and integrates the value over time. When the current integrator 12 is used for the charging device 2, for example, a current integrated value from the start of charging to the completion of charging is calculated and used for billing and the like. The current integrator 12 of the present embodiment also functions as a constituent unit of the deterioration detection device 1 in addition to the case where the current integrator 12 is used for the charging device 2. That is, the current integrator 12 receives the start signal and the end signal from the deterioration detector 11, which will be described later, measures the value of the current flowing from the charging circuit 21 to the secondary battery 3 during this time, and integrates this over time. I do. The current integrated value calculated by the current integrator 12 is output to the deterioration detector 11.

  The full charge detector 13 detects a full charge state of the secondary battery 3 and can be specifically configured by a voltmeter or the like that measures a voltage between terminals of the secondary battery 3. May be provided. When the full-charge detector 13 is used for the charging device 2, for example, the timing at which charging is completed after the start of charging is detected, and this is used to complete charging. The full charge detector 13 of the present embodiment also functions as a constituent unit of the deterioration detection device 1 other than when used for the charging device 2. That is, when the full charge detector 13 detects the fully charged state of the secondary battery 3 based on the voltage between terminals and the like, it outputs the fact to the deterioration detector 11 described later.

  Incidentally, the current integrator 12 and the full charge detector 13 described above are configured so that the unit provided in the charging device 2 is shared by the deterioration detecting device 1, but these are used as dedicated units of the deterioration detecting device 1. Each may be provided.

  The deterioration detection device 1 of the present embodiment includes a deterioration detector 11, an AE detector 14, a storage device 15, and a vehicle type identification device 16 in addition to the above-described current integrator 12 and full charge detector 13.

  The AE detector 14 is a sensor for detecting an acoustic emission signal (hereinafter, also referred to as an AE signal) generated from the inside of the secondary battery 3. As shown in FIG. Installed in contact. The AE detector 14 is not particularly limited, and may be any sensor that can detect a frequency band corresponding to a signal (elastic wave signal) generated due to a structural change of a component inside the secondary battery 3.

FIG. 6 shows the charge / discharge profile of the negative electrode and the generation from inside the secondary battery 3 when a graphite-based active material having a graphite structure is used as the negative electrode active material constituting the negative electrode of the lithium ion secondary battery 3. 6 is a graph showing a relationship between the frequency of occurrence of the AE signal and the frequency of the AE signal. In FIG. 6 , the charge / discharge profile of the negative electrode is shown by a solid line graph, and the frequency of occurrence of the AE signal is shown by a bar graph. In FIG. 6, the vertical axis on the left indicates the electrode potential of the negative electrode (relative potential with respect to the positive electrode) with respect to the charging / discharging time, and the vertical axis on the right indicates the frequency of occurrence of the AE signal (frequency of occurrence per hour). . Note that the direction in which the electrode potential of the negative electrode with respect to the positive electrode decreases is “charging”, and the direction in which the electrode potential of the negative electrode with respect to the positive electrode increases is discharge. That is, in FIG. 6, when the charge / discharge time axis advances to the right, it means charging, and when it advances to the left, it means discharge.

  As shown by the solid line graph in FIG. 6, the charge / discharge characteristics of a secondary battery using a graphite-based active material as the negative electrode active material include a plurality of charge / discharge regions having different voltage change rates with respect to the charge / discharge capacity. It is known that the negative electrode potential changes stepwise as the secondary battery is charged and discharged. More specifically, as shown by a mark in FIG. 5A, at point P1 near the negative electrode potential 0.21V, transition from the first region RC1 to the second region RC2 occurs, and at point P2 near the negative electrode potential 0.13V. It is known that the transition from the second region RC2 to the third region RC3, and further, at the point P3 near the negative electrode potential 0.08 V, the transition from the third region RC3 to the fourth region RCf. Then, as shown in FIG. 5A, in a secondary battery using a graphite-based active material as such a negative electrode active material, as shown in points P1 to P3 in FIG. And an inflection point of the charge / discharge curve (a point at which the voltage change rate with respect to the charge / discharge capacity changes significantly) is observed. Note that the decrease in the negative electrode potential may slightly change depending on the charge / discharge rate, the type of electrolyte used, and the like. As can be seen from FIG. 6, the AE signal generated from the inside of the secondary battery 3 is an inflection due to the transition of the charge / discharge region of such a graphite-based active material, as shown by a broken line in FIG. At each of the points P1 to P3, there is a characteristic that the occurrence frequency increases. It is inferred that the change in the charge / discharge region at the inflection points P1 to P3 causes some structural change inside the graphite-based active material, such as a change in the stage structure of the graphite-based active material, which is the cause of this characteristic. You.

  Now, in a secondary battery including a graphite-based active material as a negative electrode active material, as described above, there is a characteristic that the frequency of occurrence of the AE signal increases at each of the inflection points P1 to P3 where the charge / discharge region transitions. The present inventors have found that the point at which the frequency of occurrence of the AE signal increases does not change regardless of the degree of deterioration of the secondary battery 3.

  FIG. 5A to FIG. 5D are graphs obtained by measuring the charge / discharge characteristics of secondary batteries having different degrees of deterioration using the secondary batteries 3 having the same structure. That is, a new (non-deteriorated) secondary battery 3 is subjected to an accelerated deterioration test, and the charge / discharge characteristics are measured at a plurality of points before and during the test. 5A is a secondary battery having a zero deterioration degree, FIG. 5B is a secondary battery having a 13% deterioration degree, FIG. 5C is a secondary battery having a 33% deterioration degree, and FIG. 5D is a secondary battery having a 75% deterioration degree. Shows the charge / discharge characteristics of the sample. The degree of deterioration is a physical property value represented by (Cf−C) / Cf or a percentage thereof, where Cf is the non-degraded full charge capacity and C is the current full charge capacity.

  From these results, the profile of the negative electrode potential (relative potential with respect to the positive electrode potential) with respect to the battery capacity is the same regardless of the degree of deterioration of the secondary battery 3, and the only difference is the battery capacity in the fully charged state. Then, it was found that only the right end point of the charge / discharge curve was shortened. Further, it has been found that the point at which the frequency of occurrence of the AE signal increases is the same regardless of the degree of deterioration of the secondary battery 3. The deterioration detection device 1 of the present embodiment calculates the degree of deterioration of the secondary battery 3 based on this knowledge, that is, at least one of the capacity maintenance ratio, the degree of deterioration, and the current full charge capacity. For example, the smaller the current integrated value started from the point where the frequency of occurrence of the AE signal increases (the shorter the right end point of the charge / discharge curves shown in FIGS. 5A to 5D), the greater the degree of deterioration. Details will be described later. Incidentally, the detection of deterioration in the present invention means not only the calculation of the capacity retention ratio or the degree of deterioration but also the calculation of the current full charge capacity.

  The deterioration detector 11 includes a ROM (Read Only Memory) in which a program for detecting deterioration of the secondary battery 3 is stored, a CPU (Central Processing Unit) as an operation circuit for executing the program stored in the ROM, A random access memory (RAM) functioning as an accessible storage device. Note that, as the operation circuit, instead of or together with the CPU, an MPU (Micro Processing Unit), a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like can be used. .

  The deterioration detector 11 reads out the signal from the AE detector 14 at predetermined time intervals, and determines whether or not the frequency of occurrence of the AE signal has increased. Outputting an operation command to the full charge detector 13, receiving a notification from the full charge detector 13 that the secondary battery 3 is fully charged, and detecting a full charge state after an increase in the frequency of occurrence of the AE signal is detected. And a step of detecting the deterioration of the secondary battery based on the current integrated value. These processing procedures will be described later.

The storage unit 15 is a storage medium such as a hard disk, and determines the difference between the remaining capacity and the full charge capacity of the secondary battery at the time when the frequency of occurrence of the AE signal increases in the secondary battery having a zero degree of deterioration. The related information, in other words, the control map is stored. FIG. 7 is a diagram illustrating an example of the control map stored in the storage device 15. The horizontal axis of the control map shown in the figure is the capacity (Ah, or Ah / cm 2) of the secondary battery 3 that scales from zero to the full charge capacity of the secondary battery at the time of non-deterioration, and the vertical axis is relative to the positive electrode potential. It is a relative negative electrode potential (V), and each capacitance value of four charge / discharge regions RC1 to RCf bounded by points P1 to P3 at which the occurrence frequency of the AE signal increases is recorded as information. For example, the capacity of the first area RC1 of the four charge / discharge areas RC1 to RCf is recorded as C1, the capacity of the second area RC2 is C2, the capacity of the third area RC3 is C3, and the capacity of the fourth area RCf is Cf. Have been. In the secondary battery 3 of the present embodiment, the capacity Cf of the fourth area RCf is smaller than the capacity C3 of the third area RC3 (C3> Cf). FIG. 7 shows the charge / discharge curve of the secondary battery 3 and the frequency of occurrence of the AE signal, which is shown for convenience to facilitate understanding of the invention, and this information is stored. It does not have to be. Further, the control map shown in FIG.

  The vehicle type specifying unit 16 is a unit for specifying the specification of the vehicle equipped with the secondary battery 3 to be charged from the charging device 2 and thereby specifying the specification of the secondary battery 3. The camera includes a camera and a database, analyzes an image of the vehicle captured by the camera, specifies a vehicle type from the database, and finally specifies specifications of the secondary battery 3. Information on the specified specifications of the secondary battery 3 is output to the deterioration detector 11 until charging is completed. Note that the vehicle type specifying device 16 is not limited to the camera and the database, but may be a manual input by a user or an analysis of the specification of the secondary battery 3 using the charging circuit 21 of the charging device 2.

<< First control example >>
FIG. 2 is a flowchart illustrating an example of a process performed by the deterioration detector 11 of FIG. In step S <b> 1, when the deterioration detector 11 receives the charge start signal from the charging device 2, the vehicle type specifying device 16 analyzes the vehicle type to be charged and specifies the specification of the secondary battery 3 as necessary. Further, the detection signal from the AE detector 14 is read out at predetermined time intervals, and the frequency of occurrence of the AE signal per unit time is calculated.

  In step S2, the deterioration detector 11 determines whether the frequency of occurrence of the AE signal calculated in step S1 has increased. The increase in the occurrence frequency is compared with the previous value and the present value, and when the difference is equal to or more than a predetermined threshold value, it can be determined that the occurrence frequency has increased. If the difference between the next numerical value and the present numerical value is equal to or greater than the predetermined threshold value after determining the increase in the frequency of occurrence of the AE signal in this way, it is assumed that the above determination is correct. If the difference between the current value and the current numerical value is less than the predetermined threshold, the determination may be canceled because the previous determination is incorrect.

In step S 3, the deterioration detector 11, when detecting an increase in the frequency of AE signal in step S2, and outputs a signal of the integration start with respect to the current integrator 12, thereby a current integrator 12, the charging device The current supplied from the second charging circuit 21 to the secondary battery 3 is measured, and time integration is started. This integration is continued until the fully charged state of the secondary battery 3 is detected in step S5.

As shown in FIG. 5A to FIG. 5D and FIG. 7, the number of times the frequency of occurrence of the AE signal increases differs depending on the SOC of the secondary battery 3 during charging. For example, when the battery capacity of the secondary battery 3 is in the fourth region RCf and the SOC of the secondary battery 3 at the time of charging is in the first region RC1, the AE signal is generated in each of P1, P2, and P3. An increase in frequency is detected. Conversely, when the SOC of the secondary battery 3 at the time of charging is in the third region RC3, an increase in the frequency of occurrence of the AE signal is detected only at P3. Therefore, it is determined whether or not the frequency of occurrence of the AE signal has further increased in step S4, and the number of times N of the increase is counted. This increase number N is used when calculating the current integrated value C in step S6 described later.

  In step S5, the deterioration detector 11 determines whether or not a signal indicating that the secondary battery 3 has reached full charge has been received from the full charge detector 13, and if not received, the steps S3 and S4 until the signal is received. repeat. When the full charge detector 13 detects that the secondary battery 3 has reached a fully charged state, it outputs a signal to that effect to the deterioration detector 11, but when the deterioration detector 11 receives this signal, it proceeds to step S6. move on. In step S6, the deterioration detector 11 outputs an integration end signal to the current integrator 12, and reads the calculated current integrated value C. Further, the number of times N in which the frequency of occurrence of the AE signal is increased, which is counted in step S4, is read.

  Here, when the number of increases is N = 1, it can be determined that charging is started from a state where the SOC of the secondary battery 3 is in the third region RC3, and that an increase in the occurrence frequency of the AE signal at the point P3 has been detected. Then, the read current integrated value C is used as it is in steps S7 and S8. That is, the capacity Cn of the secondary battery 3 is Cn = C1 + C2 + C3 + C. On the other hand, when the number of increases is N = 2, charging is started from a state where the SOC of the secondary battery 3 is in the second region RC2, and an increase in the frequency of occurrence of the AE signal at the points P2 and P3 is detected. Since it can be determined that the reading has been performed, a value obtained by subtracting the capacitance C3 from the read current integrated value C is used in steps S7 and S8. That is, the capacity Cn of the secondary battery 3 is Cn = C1 + C2 + C. When the number of increases is N = 3, the SOC of the secondary battery 3 starts to be charged from the first region RC1, and an increase in the frequency of occurrence of the AE signal at the points P1, P2, and P3 is detected. Since it can be determined, a value obtained by subtracting the capacitance C2 + C3 from the read current integrated value C is used in steps S7 and S8. That is, the capacity Cn of the secondary battery 3 is Cn = C1 + C. Hereinafter, C is the current integrated value calculated in step S6.

  In step S7, the deterioration detector 11 compares the current integrated value C calculated in step S6 with the capacity Cf of the fourth region RCf having a small degree of deterioration. Here, the reason why the calculated current integrated value C is compared with the capacity Cf of the fourth area RCf is that the degree of deterioration of the secondary battery 3 mounted on the vehicle is empirically deteriorated in the fourth area RCf. This is because most of them are rarely deteriorated to the third region or less. An embodiment that considers the case where the deterioration has occurred to the third region or less will be described later.

  In step S7, as described above, the battery capacity of the secondary battery 3 according to the present embodiment has a relationship of C3> Cf. Therefore, if C> Cf is not satisfied, that is, if C ≦ Cf, the degree of deterioration is the fourth. It is determined that it is not in the area RCf, the process proceeds to step S9, and the process ends without executing the evaluation regarding the deterioration such as the calculation of the degree of deterioration. On the other hand, when C> Cf, it is determined that the degree of deterioration is in the fourth region RCf, and the process proceeds to step S8.

  In step S8, the current charge capacity Cn of the secondary battery 3 is obtained by adding the capacity C1 of the first area, the capacity C2 of the second area, and the capacity C3 of the third area to the current integrated value C (Cn = C + C1 + C2 + C3). That is, in the example shown in FIG. 5B, the current integrated value C is added to the capacitance (C1 + C2 + C3) up to the point P3. The capacity retention ratio is calculated as Cn / Cf, and the degree of deterioration is calculated as (Cf-Cn) / Cf. As described above, the deterioration of the secondary battery 3 is detected, and the degree of the deterioration may be expressed by the current battery capacity itself Cn, or may be expressed by calculating the capacity maintenance rate or the degree of deterioration.

<< Second control example >>
FIG. 3 is a flowchart illustrating another example of the process performed by the deterioration detector 11 of FIG. In the processing example illustrated in FIG. 2, when the current battery capacity of the secondary battery 3 is in the fourth region RCf, the deterioration is detected, and other than that, the evaluation is not performed. The deterioration is detected including the case where the battery capacity of the battery 3 is in the third region RC3 or the second region RC2. Steps S11 to S18 shown in FIG. 3 are the same as steps S1 to S8 in FIG.

  If C> Cf is not satisfied in step S17, that is, if C ≦ Cf, it is determined that the degree of deterioration is not in the fourth region RCf, and the process proceeds to step S19. In step S19, the deterioration detector 11 calculates a current integrated value Cr from the start of charging until the current value decreases based on the current value read from the current integrator 12 and the current integrated value. When the secondary battery 3 has deteriorated to the second area RC2 or the first area RC1, as shown in FIG. 8A, the current value after the start of charging rapidly decreases. On the other hand, if the secondary battery 3 has deteriorated to some extent in the third region RC3, as shown in FIG. 8B, the current value is maintained for a predetermined time after the start of charging, and thereafter, the current value decreases. . For this reason, in step S20, it is determined whether or not the current integrated value Cr from the start of charging until the current value decreases exceeds 20% of the current integrated value C calculated in step S16. If the current integrated value Cr is equal to or less than 20% of the current integrated value C, it is determined that the degree of deterioration of the secondary battery 3 has progressed to the second region RC2 or less, and the process proceeds to step S22, where the deterioration is determined. The processing is ended without performing the evaluation regarding the deterioration such as the calculation of the degree.

On the other hand, if the current integrated value Cr exceeds 20 % of the current integrated value C, it is determined that the degree of deterioration of the secondary battery 3 is in the third region RC3, and the process proceeds to step S21. In step S21, the current charging capacity Cn of the secondary battery 3 is obtained by adding the capacity C1 of the first area and the capacity C2 of the second area to the current integrated value C (Cn = C + C1 + C2). That is, in the example shown in FIG. 5C, the current integrated value C is added to the capacity (C1 + C2) up to the point P2. The capacity retention ratio is calculated as Cn / Cf, and the degree of deterioration is calculated as (Cf-Cn) / Cf. As described above, the deterioration of the secondary battery 3 is detected, and the degree of the deterioration may be expressed by the current battery capacity itself Cn, or may be expressed by calculating the capacity maintenance rate or the degree of deterioration.

<< Third control example >>
FIG. 4 is a flowchart showing still another example of the processing executed by the deterioration detector 11 of FIG. When an increase in the frequency of occurrence of the AE signal is detected twice, the integrated current value during that time is calculated, so that it can be specified which of the first to third regions RC1 to RC3. In the present embodiment, the deterioration of the secondary battery 3 is detected after specifying the regions RC1 to RC3 using this.

  In step S <b> 31, when the deterioration detector 11 receives the charge start signal from the charging device 2, the vehicle type specifying device 16 analyzes the vehicle type to be charged and specifies the specification of the secondary battery 3 as necessary. Further, the detection signal from the AE detector 14 is read out at predetermined time intervals, and the frequency of occurrence of the AE signal per unit time is calculated.

  In step S32, the deterioration detector 11 determines whether the frequency of occurrence of the AE signal calculated in step S31 has increased. The increase in the occurrence frequency is compared with the previous value and the present value, and when the difference is equal to or more than a predetermined threshold value, it can be determined that the occurrence frequency has increased. In step 33, when the deterioration detector 11 detects an increase in the frequency of occurrence of the AE signal in step S32 (time T1), the deterioration detector 11 outputs a signal of the first integration start to the current integrator 12, whereby The current integrator 12 measures the current supplied from the charging circuit 21 of the charging device 2 to the secondary battery 3 and starts temporal integration.

  In step S34, the deterioration detector 11 determines whether the frequency of occurrence of the AE signal calculated in step S31 has increased. The increase in the occurrence frequency is compared with the previous value and the present value, and when the difference is equal to or more than a predetermined threshold value, it can be determined that the occurrence frequency has increased. In step S34, if the increase in the frequency of occurrence of the AE signal is not detected, the process proceeds to step S36. However, if the increase in the frequency of occurrence of the AE signal is detected (time T2), the current integrator 12 is given a second signal. A signal for starting integration is output, whereby the current integrator 12 measures the current supplied from the charging circuit 21 of the charging device 2 to the secondary battery 3 and starts temporal integration. The current integration processes in steps S33 and S35 are executed in parallel.

  In step S36, the deterioration detector 11 determines whether a signal indicating that the secondary battery 3 has reached full charge has been received from the full charge detector 13, and if not received, the steps S35 and S36 until the signal is received. repeat. When the full-charge detector 13 detects that the secondary battery 3 is fully charged (time T3), the full-charge detector 13 outputs a signal to that effect to the deterioration detector 11, and the deterioration detector 11 Upon receiving the signal, the process proceeds to step S37. In step S37, the deterioration detector 11 outputs an integration end signal to the current integrator 12, and reads the calculated integrated current value. In the case of the present embodiment, the current integrated value from time T1 to T2 is C, and the current integrated value from time T2 to T3 is C '.

  In step S38, it is determined whether or not the current integrated value C during the time T1 to T2 is equal to the capacity C2 of the second area. In this case, a slight margin may be set for the capacitor C2 in consideration of the calculation error of the current integrated value C. If the current integrated value C is equal to the capacity C2 of the second area, the points of increase in the frequency of occurrence of the two detected AE signals can be determined to be the points P1 and P2. Is a value obtained by adding the capacity C1 of the first area and the capacity C2 of the second area to the integrated current value C ′ during the time T2 to T3 (Cn = C ′ + C1 + C2). That is, in the example shown in FIG. 5C, the current integrated value C ′ between times T2 and T3 is added to the capacity (C1 + C2) up to the point P2. The capacity retention ratio is calculated as Cn / Cf, and the degree of deterioration is calculated as (Cf-Cn) / Cf.

  In step S38, if the current integrated value C during the time T1 to T2 is not equal to the capacity C2 of the second area, the process proceeds to step S40, and the current integrated value C during the time T1 to T2 is changed to the capacity of the third area. It is determined whether it is equal to C3. Alternatively, it may be determined whether or not the current integrated value C during the time T1 to T2 is equal to the capacity C1 of the first area. In these cases, a slight margin may be set for the capacitors C3 and C1 in consideration of the calculation error of the current integrated value C.

  In step S40, if the current integrated value C is equal to the capacitance C3 in the third area, the points of increase in the frequency of occurrence of the two detected AE signals can be determined to be points P2 and P3. The charge capacity Cn of the secondary battery 3 is obtained by adding the capacity C1 of the first area, the capacity C2 of the second area, and the capacity C3 of the third area to the current integrated value C ′ during the time T2 to T3. (Cn = C '+ C1 + C2 + C3). That is, in the example shown in FIG. 5B, the current integrated value C ′ between times T2 and T3 is added to the capacity (C1 + C2 + C3) up to the point P3. The capacity retention ratio is calculated as Cn / Cf, and the degree of deterioration is calculated as (Cf-Cn) / Cf. In step S40, if the current integrated value C is not equal to the capacity C3 of the third area, the process proceeds to step S42, and the process ends without executing the evaluation regarding the deterioration such as the calculation of the degree of deterioration. As described above, the deterioration of the secondary battery 3 is detected, and the degree of the deterioration may be expressed by the current battery capacity itself Cn, or may be expressed by calculating the capacity maintenance rate or the degree of deterioration.

  As described above, according to the secondary battery deterioration detection device 1 of the present embodiment, it is only necessary to detect an increase point of the occurrence frequency of the AE signal from outside the secondary battery 3 and calculate the current integrated value therefrom. Even during charging / discharging, deterioration of the secondary battery can be accurately detected without using an open circuit voltage. The detection of the deterioration of the secondary battery may be any of the capacity maintenance rate, the degree of deterioration, and the current full charge capacity.

  In particular, according to the deterioration detection device 1 of the present embodiment, even when the secondary batteries 3 have different degrees of deterioration, the point at which the frequency of occurrence of the AE signal increases during charging and discharging (the battery capacity point) does not change. In addition, since the knowledge that the integrated current value from this increase point to the full charge correlates with the degree of deterioration is used, the smaller the integrated current value is, the larger the degree of deterioration is detected, and the deterioration of the secondary battery is reduced. Accurate detection is possible.

  According to the secondary battery deterioration detection device 1 of the present embodiment, not only when the battery capacity of the secondary battery 3 is in the fourth region RCf, but also when the battery capacity is in the third region RC3 and the second region RC2. Since deterioration can be detected, data on deterioration can be widely collected. Conversely, if the degree of deterioration of the secondary battery 3 is extremely large, no deterioration is detected, so that only valid data can be collected.

  Further, according to the secondary battery deterioration detection device 1 of the present embodiment, the specification of the secondary battery 3 is specified by the vehicle type specifying device 16 from the vehicle type on which the secondary battery 3 to be deteriorated is mounted, and Since the control map suitable for the battery 3 is selected, the deterioration of the secondary battery 3 can be detected with higher accuracy.

DESCRIPTION OF SYMBOLS 1 ... Deterioration detection apparatus 11 ... Deterioration detector 12 ... Current accumulator 13 ... Full charge detector 14 ... AE detector 15 ... Storage device 16 ... Car type identification device 2 ... Charging device 21 ... Charging circuit 3 ... Secondary battery

Claims (8)

Look containing graphite-based active material in the negative electrode, the deterioration, a deterioration detecting device for a secondary battery and a profile of the negative electrode potential with respect to battery capacity, an increase point in the frequency of acoustic emission signal for the profile, is not changed ,
An integrator for calculating a current integrated value of the charging current of the secondary battery,
And AE detector for detecting the acoustic emission signal generated from the secondary battery,
A full charge detector that detects that the secondary battery is in a fully charged state,
A deterioration detector that detects deterioration of the secondary battery based on the current integrated value from when an increase in the frequency of occurrence of the acoustic emission signal is detected to when the full charge state is detected. Deterioration detection device for secondary batteries.   2. The secondary battery deterioration detection device according to claim 1, wherein the deterioration detector detects the deterioration of the secondary battery by calculating at least one of a capacity maintenance ratio, a deterioration degree, and a current full charge capacity. 3. .   The deterioration detection device for a secondary battery according to claim 1, wherein the deterioration detector detects a degree of deterioration as the current integrated value decreases. In a secondary battery having a degree of deterioration of zero, a storage device for storing relationship information of a capacity difference between the remaining capacity and the full charge capacity of the secondary battery at the time when the frequency of occurrence of the acoustic emission signal increases,
The deterioration detector compares the current integrated value with the capacitance difference, and detects a degree of deterioration as the current integrated value is smaller with respect to the capacitance difference. 2. The deterioration detection device for a secondary battery according to claim 1. The deterioration detector,
The integrator detects an integrated current value from the first time point at which the frequency of occurrence of the acoustic emission signal first increases after the start of charging to the second time point at which the frequency of occurrence of the acoustic emission signal subsequently increases. Comparing the obtained current integrated value with the capacity difference to specify the charging capacity at the first time point and / or the second time point;
5. The secondary battery according to claim 4, wherein deterioration of the secondary battery is detected based on the specified charging capacity and an integrated current value from the second time point to the detection of the full charge state. 6. Deterioration detection device.   The said deterioration detector does not detect the deterioration of the said secondary battery, when the integrated current value from the said 1st time to the said 2nd time is less than the said specified charging capacity. Secondary battery deterioration detection device. A vehicle type specifying device that specifies a vehicle type of a vehicle equipped with the secondary battery,
The deterioration detection device for a secondary battery according to claim 4, wherein the deterioration detector selects information on a capacity difference according to the identified vehicle type. Look containing graphite-based active material in the negative electrode, the deterioration, and profile of the negative electrode potential with respect to battery capacity, an increase point in the frequency of acoustic emission signal for the profile, is a deterioration detecting method for a secondary battery that does not vary ,
Detecting an increase in the frequency of the acoustic emission signal generated from the secondary battery,
When the increase in the occurrence frequency is detected, the calculation of the integrated current value of the charging current of the secondary battery is started,
Detecting that the secondary battery is fully charged,
Calculating the current integrated value from when the increase in the frequency of occurrence of the acoustic emission signal is detected until the full charge state is detected,
A secondary battery deterioration detection method for detecting the deterioration of the secondary battery based on the integrated current value.

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