Capacity measuring device

Abstract

To provide a capacity measuring device that accurately measures the capacity of a secondary battery 2 so as to accurately detect the presence or absence of an abnormal change in the capacity, thereby investigating the cause of the abnormal change in the capacity.SOLUTION: A capacity measuring device comprises: a charge / discharge amount acquisition unit that acquires the amount of charge / discharge of a secondary battery multiple times at a predetermined timing in each of a plurality of charge / discharge conditions including at least self-discharge; an operation unit that calculates the battery capacity of the secondary battery on the basis of the acquired charge / discharge amounts; and a storage unit that stores the charge / discharge amounts and the battery capacity.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a capacity measurement device that measures the capacity of a secondary battery. [Background technology]

[0002] BACKGROUND ART Conventionally, a method is known in which the battery capacity and remaining capacity of a secondary battery are measured by integrating the current flowing through the secondary battery (see, for example, Patent Document 1).

[0003] On the other hand, secondary batteries discharge due to self-discharge even when left unused for a long period of time. Therefore, for example, when the battery capacity is measured using the discharge current after being left unused for several hours, the battery capacity may decrease due to self-discharge, which is called "blow-in" (hereinafter referred to as "abnormal change in capacity"). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-315430 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the discharge current during self-discharge is too small to be measured by a current sensor. Therefore, the normal capacity measurement process described in Patent Document 1 cannot measure the discharge amount due to self-discharge. Therefore, the conventional battery capacity measurement process has a problem in that it is difficult to investigate the cause of the abnormal change in capacity.

[0006] An object of the present disclosure is to provide a capacity measurement device that accurately measures the capacity of a secondary battery 2 so as to accurately detect the presence or absence of an abnormal change in capacity and to investigate the cause of the abnormal change in capacity. [Means for solving the problem]

[0007] The capacitance measurement device according to the present disclosure comprises: a charge / discharge amount acquisition unit that acquires charge / discharge amounts of the secondary battery multiple times at predetermined timings under each of a plurality of charge / discharge conditions including at least self-discharge; a calculation unit that calculates the battery capacity of the secondary battery based on the acquired charge / discharge amounts; a storage unit that stores the charge / discharge amount and the battery capacity; Equipped with. [Effects of the Invention]

[0008] According to the present disclosure, the capacity of the secondary battery 2 can be accurately measured so that the presence or absence of an abnormal change in capacity can be detected with high accuracy and the cause of the abnormal change in capacity can be investigated. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit diagram showing an example of the configuration of a capacitance measuring device according to this embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of the microcomputer of FIG. [Figure 3] FIG. 3 is a flowchart showing an example of the flow of a capacitance measurement process performed by the capacitance measurement device according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure. Furthermore, the present disclosure includes all combinations of possible configurations among the configurations shown in the following embodiments. Furthermore, in each drawing, components with the same reference numerals are the same or equivalent, and this is common throughout the entire specification.

[0011] [Configuration of capacitance measurement device 1] 1 is a circuit diagram showing an example of the configuration of a capacity measurement device 1 according to this embodiment. To the capacity measurement device 1, a secondary battery 2, a load 3, and a charger 4 are connected.

[0012] The secondary battery 2 is composed of one or more secondary battery cells. When the secondary battery 2 is composed of multiple secondary battery cells, the secondary battery 2 is composed, for example, of the secondary battery cells connected in series or in parallel. The secondary battery cells are, for example, nickel-metal hydride secondary batteries. Note that the type of secondary battery cell is not limited to this example, and secondary battery cells other than nickel-metal hydride secondary batteries, such as lithium-ion secondary batteries, may also be used.

[0013] A load 3 and a charger 4 are connected to the secondary battery 2 via the capacity measurement device 1. As a result, a discharge path is formed between the secondary battery 2 and the load 3, through which a discharge current flows from the secondary battery 2 to the load 3, and a charge path is formed between the secondary battery 2 and the charger 4, through which a charge current flows from the charger 4 to the secondary battery 2.

[0014] The load 3 is a device or the like that operates when power is supplied from the secondary battery 2.

[0015] The charger 4 is provided to charge the secondary battery 2. The charger 4 converts power received from an external power supply (not shown) into power suitable for charging the secondary battery 2. The charger 4 then supplies the converted power to the secondary battery 2 via the capacity measurement device 1.

[0016] Furthermore, in this embodiment, a charger having a refresh function for discharging the secondary battery 2 is used as the charger 4. The refresh function is a function for forcibly discharging the connected secondary battery 2.

[0017] The capacity measurement device 1 is a device for measuring the battery capacity of a secondary battery 2. As shown in Fig. 1, the capacity measurement device 1 includes a charge switch 11, a discharge switch 12, a detection unit 13, a microcomputer (hereinafter referred to as "microcomputer") 14, and a memory unit 15.

[0018] The charging switch 11 is disposed on a charging path through which current flows when charging the secondary battery 2. The charging switch 11 switches between connecting and disconnecting the charging path under the control of the microcomputer 14. This switches between charging and stopping the charging of the secondary battery 2.

[0019] The discharge switch 12 is disposed on the discharge path. The discharge switch 12 switches between connecting and disconnecting the discharge path under the control of the microcomputer 14. This switches between discharging and stopping discharging of the secondary battery 2.

[0020] The detection unit 13 is, for example, a sensor group made up of various sensors. The detection unit 13 detects various state quantities related to the secondary battery 2 and supplies the detection results to the microcomputer 14. The detection unit 13 is, for example, a current sensor and / or a voltage sensor.

[0021] When the detection unit 13 is a current sensor, the detection unit 13 detects the charging current or discharging current (hereinafter sometimes referred to as the “charging / discharging current”) of the secondary battery 2. The detection unit 13 supplies the detected charging / discharging current value to the microcomputer 14.

[0022] The microcomputer 14 controls the entire capacity measurement device 1. In particular, in this embodiment, the microcomputer 14 controls charging and discharging of the secondary battery 2 by the capacity measurement device 1, and performs a capacity measurement process that measures the capacity of the secondary battery 2. Details of the capacity measurement process will be described later.

[0023] The microcomputer 14 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (none of which are shown). The CPU reads a program corresponding to the processing content from the ROM, loads it into the RAM, and centrally controls the operation of the capacitance measurement device 1 in cooperation with the loaded program.

[0024] The storage unit 15 is, for example, a nonvolatile memory, and stores various types of information used by the microcomputer 14. For example, in this embodiment, the storage unit 15 stores the discharge amount and battery capacity history of the secondary battery 2 obtained by the capacity measurement process, as well as arithmetic expressions used in various calculations performed by the microcomputer 14.

[0025] Fig. 2 is a block diagram showing an example of the configuration of the microcomputer 14 in Fig. 1. Fig. 2 shows only a processing unit for functions related to capacity measurement processing among the functions provided in the microcomputer 14. As shown in Fig. 2, the microcomputer 14 has an A / D conversion unit 141, a condition setting unit 142, a charge / discharge control unit 143, and a calculation unit 144.

[0026] The A / D conversion unit 141 acquires the value of the charge / discharge current detected by the detection unit 13. Here, the charge / discharge current value detected by the detection unit 13 is analog data. Therefore, the A / D conversion unit 141 converts the charge / discharge current value of the analog data into the charge / discharge current value of digital data.

[0027] The condition setting unit 142 sets charge / discharge conditions related to charging / discharging of the secondary battery 2. The charge / discharge conditions are conditions that are defined when charging or discharging the secondary battery 2. The charge / discharge conditions include, for example, the value of the current when charging or discharging, and the time for which the current flows. Specific charge / discharge conditions will be described later.

[0028] The charge / discharge control unit 143 controls each unit including the charge switch 11 and the discharge switch 12 so as to charge or discharge the secondary battery 2 according to the conditions set by the condition setting unit 142. For example, when charging the secondary battery 2, the charge / discharge control unit 143 generates and outputs a charge control signal for connecting a charge path to the charge switch 11. Furthermore, for example, when discharging the secondary battery 2, the charge / discharge control unit 143 generates and outputs a discharge control signal for connecting a discharge path to the discharge switch 12.

[0029] The calculation unit 144 calculates the charge / discharge amount and the like of the secondary battery 2 under the charge / discharge conditions set by the condition setting unit 142 based on the charge / discharge current values ​​of the digital data converted by the A / D conversion unit 141. The calculation unit 144 also calculates the battery capacity of the secondary battery 2 based on the charge / discharge amount under each charge / discharge condition. Various values ​​obtained by the calculations are stored in the storage unit 15. The A / D conversion unit 141 and the calculation unit 144 described above correspond to the "charge / discharge amount acquisition unit" of the present disclosure.

[0030] [Capacity measurement processing] A description will now be given of the capacity measurement process performed by the capacity measurement device 1 having the above configuration. Conventionally, the battery capacity of a secondary battery can be obtained by measuring the discharge current value of the secondary battery during discharge and integrating the measured discharge current value.

[0031] On the other hand, secondary batteries discharge due to self-discharge even when left unused for a long period of time. Therefore, for example, when the battery capacity is measured using the discharge current after being left unused for several hours, the battery capacity may decrease due to self-discharge, and an abnormal change in capacity called "jump" may occur.

[0032] The discharge current during self-discharge is too low to be measured by a current sensor, so a normal capacity measurement process cannot measure the amount of discharge due to self-discharge, making it difficult to investigate the cause of the abnormal change in capacity using conventional battery capacity measurement processes.

[0033] Therefore, the capacity measurement device 1 according to this embodiment performs a capacity measurement process to accurately measure the capacity of the secondary battery 2 so that the presence or absence of an abnormal change in capacity can be accurately detected and the cause of the abnormal change in capacity can be investigated.

[0034] First, in the capacity measurement process, the charge / discharge conditions under which the secondary battery 2 is charged / discharged are classified into a plurality of charge / discharge conditions, and the discharge amount of the secondary battery 2 under each classified charge / discharge condition is calculated. At this time, the charge / discharge conditions are set to, for example, the following first to fifth charge / discharge conditions, taking into consideration the circumstances that arise during use and storage of the secondary battery 2.

[0035] The first charge / discharge condition is discharge at a current equal to or greater than a predetermined value. The second charge / discharge condition is discharge at a current less than a predetermined value. Discharge under the first or second charge / discharge condition is performed with a load 3 connected to the secondary battery 2. The predetermined value of the current set during discharge is, for example, 300 mA, and is set based on the nominal capacity of the secondary battery 2 to be measured.

[0036] The third charge / discharge condition is charging using the charger 4. Charging under the third charge / discharge condition is performed with the charger 4 connected to the secondary battery 2. Note that the third charge / discharge condition may also include charging other than normal charging, such as regenerative charging with the load 3 connected to the secondary battery 2.

[0037] The fourth charge / discharge condition is discharging using the refresh function of the charger 4. Discharging under the fourth charge / discharge condition is performed using the refresh function of the charger 4 while the charger 4 is connected to the secondary battery 2.

[0038] The fifth charge / discharge condition is self-discharge. Self-discharge is discharge that occurs when the secondary battery 2 is not connected to the load 3. Self-discharge can be simulated by discharging the secondary battery 2 with a minute current, for example. In other words, the fifth charge / discharge condition is discharge with a minute current.

[0039] The condition setting unit 142 of the microcomputer 14 sets the charge / discharge condition for the secondary battery 2 to any one of the first to fifth charge / discharge conditions described above. Once the charge / discharge condition is set, the charge / discharge control unit 143 controls each unit including the charge switch 11 and the discharge switch 12 according to the set charge / discharge condition.

[0040] For example, when any one of the first, second, fourth, and fifth charge / discharge conditions is set as the charge / discharge condition and the secondary battery 2 is to be discharged, the charge / discharge control unit 143 generates a discharge control signal for connecting a discharge path and outputs it to the discharge switch 12. In this case, the discharge switch 12 connects the discharge path, so that a discharge current from the secondary battery 2 flows to the load 3 or the charger 4, and the secondary battery 2 is discharged.

[0041] Furthermore, for example, when a third charge / discharge condition is set as the charge / discharge condition and the secondary battery 2 is charged, the charge / discharge control unit 143 generates a charge control signal for connecting the charge path and outputs it to the charge switch 11. In this case, the charge switch 11 connects the charge path, causing a charge current from the charger 4 to flow to the secondary battery 2, and the secondary battery 2 is charged.

[0042] Next, the calculation unit 144 calculates the charge / discharge amount of the secondary battery 2 based on the value of the charge / discharge current during charging / discharging under the current charge / discharge conditions measured by the detection unit 13. In this case, the calculation unit 144 calculates the charge / discharge amount of the secondary battery 2, for example, by multiplying the measured charge / discharge current value by the charge / discharge time required for charging / discharging.

[0043] In this way, when the charge / discharge amount of the secondary battery 2 under one charge / discharge condition is calculated, the condition setting unit 142 switches the charge / discharge condition to the next charge / discharge condition and sets it. Then, the calculation unit 144 calculates the charge / discharge amount under the set charge / discharge condition as described above. Thereafter, when the charge / discharge amount of the secondary battery 2 is calculated, the charge / discharge conditions are set sequentially, and the calculation unit 144 calculates the charge / discharge amount of the secondary battery 2 under all the charge / discharge conditions.

[0044] The charge / discharge conditions are set in the order of, for example, the first to fifth charge / discharge conditions, but are not limited to this and may be set in any order.

[0045] Next, after calculating the charge and discharge amounts under all charge and discharge conditions, the calculation unit 144 calculates the battery capacity of the secondary battery 2 based on these charge and discharge amounts. Specifically, the calculation unit 144 adds up the charge and discharge amounts under each charge and discharge condition to obtain the battery capacity of the secondary battery 2. At this time, the calculation unit 144 adds up the charge and discharge amounts, with the discharge amount being a positive value and the charge amount being a negative value.

[0046] Here, an error may occur between the battery capacity of the secondary battery 2 calculated based on the discharge amount obtained by classifying the charge / discharge conditions into a plurality of conditions as described above and the actual battery capacity of the secondary battery 2. Therefore, the calculation unit 144 multiplies the calculated battery capacity by a correction coefficient for suppressing an error occurring in the calculated battery capacity to calculate a corrected battery capacity. The correction coefficient is determined in advance by an experiment or the like and stored in the storage unit 15 in advance.

[0047] Next, charging and discharging of the secondary battery 2 under the first to fifth charge and discharge conditions is repeated a predetermined number of times at a predetermined timing. Then, if the calculated corrected battery capacity satisfies a predetermined storage condition, the microcomputer 14 stores it as history in the storage unit 15. The microcomputer 14 also stores the charge and discharge amounts corresponding to each of the acquired various charge and discharge conditions in the storage unit 15.

[0048] The results of multiple measurements under each charge / discharge condition stored in the memory unit 15 can be used to determine whether there is an abnormal change in capacity and to determine the charge / discharge conditions that are thought to be the cause of the abnormal change in capacity. Specifically, for example, the microcomputer 14 compares the results of multiple measurements, and if a difference of a predetermined value or more is found in the values, it determines that an abnormal change in capacity occurred during charging / discharging under the charge / discharge condition under which the difference was found.

[0049] FIG. 3 is a flowchart showing an example of the flow of a capacitance measurement process performed by the capacitance measurement device 1 according to this embodiment.

[0050] In step S1, the condition setting unit 142 of the microcomputer 14 sets charge / discharge conditions for the secondary battery 2 for carrying out this capacity measurement process. As a result, charging / discharging of the secondary battery 2 is carried out under the set charge / discharge conditions. Note that when a series of processes under one charge / discharge condition is completed, the next charge / discharge condition is set.

[0051] In step S2, the A / D conversion unit 141 acquires the charge / discharge current value of the secondary battery 2 under the set charge / discharge conditions from the detection unit 13. Then, the A / D conversion unit 141 converts the acquired analog data charge / discharge current value into digital data charge / discharge current value. In step S3, the calculation unit 144 calculates the charge / discharge amount resulting from charging / discharging the secondary battery 2 under the charge / discharge conditions based on the converted charge / discharge current value.

[0052] In step S4, the microcomputer 14 determines whether the charge / discharge amounts have been calculated for all the charge / discharge conditions. If the charge / discharge amounts have not been calculated for all the charge / discharge conditions (step S4: No), the process returns to step S1, and the next charge / discharge condition is set. Then, the process from step S1 to step S3 is repeated until the charge / discharge amounts for all the charge / discharge conditions have been calculated.

[0053] On the other hand, if the charge / discharge amounts have been calculated for all charge / discharge conditions (step S4: Yes), the process proceeds to step S5. In step S5, the calculation unit 144 adds up the charge / discharge amounts for each charge / discharge condition to calculate the battery capacity of the secondary battery 2. The calculation unit 144 also multiplies the calculated battery capacity by a correction coefficient to calculate a corrected battery capacity.

[0054] In step S6, microcomputer 14 determines whether the calculated corrected battery capacity satisfies a predetermined storage condition. If the corrected battery capacity satisfies the storage condition (step S6: Yes), microcomputer 14 stores the measured charge / discharge amounts under each charge / discharge condition and the calculated corrected battery capacity in memory unit 15 in step S7. Then, the process proceeds to step S8.

[0055] On the other hand, if the corrected battery capacity does not satisfy the storage condition (step S6: No), the charge / discharge amount and the corrected battery capacity are not stored in the storage unit 15, and the process proceeds to step S8.

[0056] In step S8, the microcomputer 14 determines whether the charge / discharge amount and the corrected battery capacity have been stored a predetermined number of times. If the charge / discharge amount and the corrected battery capacity have been stored a predetermined number of times (step S8: Yes), the series of processes ends.

[0057] On the other hand, if the charge / discharge amount and corrected battery capacity have not been stored the predetermined number of times (step S8: No), the process returns to step S1, and steps S1 to S7 are repeated until they have been executed the predetermined number of times.

[0058] 3 is completed, the microcomputer 14 can determine whether or not an abnormal change in capacity has occurred based on the stored history of charge and discharge amounts corresponding to each charge and discharge condition. For example, if a difference of a predetermined value or more is found in the charge and discharge amounts under a certain charge and discharge condition, the microcomputer 14 can determine that an abnormal change in capacity has occurred during charge and discharge under that charge and discharge condition.

[0059] As described above, the capacity measurement device 1 according to this embodiment acquires the charge / discharge amounts of the secondary battery 2 under each of a plurality of charge / discharge conditions, and calculates the battery capacity of the secondary battery 2 based on the acquired charge / discharge amounts. This allows the charge / discharge amounts under various conditions that occur in the secondary battery 2 to be acquired, thereby enabling the capacity of the secondary battery 2 to be measured accurately.

[0060] In this embodiment, the acquired charge / discharge amount and the calculated battery capacity are stored as history in the storage unit 15. This allows the presence or absence of an abnormal change in capacity to be detected, making it possible to investigate the cause of the abnormal change in capacity. [Explanation of symbols]

[0061] 1. Capacity measuring device 2 Secondary battery 3. Load 4 charger 11 Charging switch 12 Discharge switch 13 Detector 14 Microcomputer 15 Storage section 141 A / D conversion section 142 Condition setting section 143 Charge / discharge control unit 144 Arithmetic section

Claims

1. a charge / discharge amount acquisition unit that acquires charge / discharge amounts of the secondary battery multiple times at predetermined timings under each of a plurality of charge / discharge conditions including at least self-discharge; a calculation unit that calculates the battery capacity of the secondary battery based on the acquired charge / discharge amounts; a storage unit that stores the charge / discharge amount and the battery capacity; A capacitance measuring device comprising:

2. The calculation unit calculating the battery capacity by adding up the charge / discharge amounts corresponding to each of the plurality of charge / discharge conditions; The capacitance measuring device according to claim 1 .

3. The calculation unit The battery capacity is calculated by multiplying the total amount of charge and discharge by a correction coefficient. The capacitance measuring device according to claim 2 .

4. the plurality of charge / discharge conditions are set in consideration of situations occurring in the secondary battery; The capacitance measuring device according to claim 1 .

5. The plurality of charge / discharge conditions include: a first charge / discharge condition for discharging the secondary battery at a current equal to or greater than a predetermined value; a second charge / discharge condition for discharging the secondary battery at a current less than the predetermined value; a third charge / discharge condition for charging the secondary battery; a fourth charge / discharge condition for forcibly discharging the secondary battery; At least one of the following is included: The capacitance measuring device according to claim 1 .

6. comparing the charge / discharge amounts stored in the storage unit for a plurality of times under any charge / discharge conditions; Based on the comparison result, it is determined whether or not there is an abnormal change in the battery capacity of the secondary battery. The capacitance measuring device according to claim 1 .

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