Charger with data acquisition function for OCV degradation analysis, and method for acquiring OCV data.

Abstract

In the present invention, in a first mode, a secondary battery (90) is charged at a prescribed current value for a first time and a terminal voltage value (α) of the secondary battery (90) is measured immediately after the elapse of the first time. In a second mode, charging is paused for a second time after the first mode has been carried out and an OCV value (β) of the secondary battery (90) is measured immediately after the elapse of the second time. A determination unit (24) compares the terminal voltage value (αA) for a current instance as measured during the first mode and the terminal voltage value (αB) for the preceding instance as measured during the immediately preceding first mode. Where the first time is a (minutes) and the prescribed current value is I (C), the determination unit (24) determines that the mode should not shift to the second mode if αA / αB < (a×I / 250)+1 (0.5 ≤ a ≤ 3, 0.4 ≤ I ≤ 2.4, 0.6 ≤ a×I ≤ 1.2). The determination unit (24) determines that the mode should shift to the second mode if αA / αB ≥ (a×I / 250)+1 (0.5 ≤ a ≤ 3, 0.4 ≤ I ≤ 2.4, 0.6 ≤ a×I ≤ 1.2). A measurement unit (22) measures the OCV value (β) during the second mode.

Description

Technical Field

[0001] The present invention relates to a technique for shortening the acquisition time of OCV data for OCV degradation analysis, which is one of the secondary battery degradation analysis methods.

Background Art

[0002] Conventionally, as shown in Patent Document 1, various analysis methods of the state of charge using SOC and OCV have been considered.

[0003] In order to obtain OCV data (OCV value group) for the SOC-OCV characteristics (SOC-OCV curve) used in such analysis, it has generally been common to perform intermittent charging while setting a sufficient relaxation time (rest time).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the above relaxation time depends on the structure of the secondary battery, it takes 20 to 30 minutes. Therefore, when trying to measure the OCV voltage at short intervals between SOC 0% and 100%, it took an enormous amount of time. For example, when SOC 0% to 100% is divided into 60 parts, intermittent charging is performed with a 1-minute charge at a 1C rate and a 20-minute rest, it takes as long as 21 hours.

[0006] However, Patent Document 1 does not describe a method for shortening the time for measuring the OCV voltage to generate the SOC-OCV characteristics.

[0007] Furthermore, simply reducing the number of measurement divisions or omitting relaxation time in certain periods can lead to a significant difference in fitting accuracy (degree of match) between the SOC-OCV curve obtained from the measured values ​​and the reference SOC-OCV curve.

[0008] Therefore, the objective of the present invention is to shorten the acquisition time of OCV data while suppressing the increase in analytical errors in OCV degradation analysis. [Means for solving the problem]

[0009] The charger of the present invention comprises a measurement unit, a storage unit, a determination unit, a charge control unit, and an output unit. The measurement unit measures a terminal voltage value α and an OCV value β for mode selection from a lithium-ion secondary battery. The storage unit stores the measured terminal voltage value α and OCV value β for mode selection. The determination unit determines the selection between a first mode and a second mode based on the terminal voltage value α for mode selection. The charge control unit controls the charging of the lithium-ion secondary battery in either the first mode or the second mode based on the determination result. The output unit outputs at least one OCV value β measured during the charging process as OCV data.

[0010] The first mode involves charging a lithium-ion secondary battery with a predetermined current value for a first time, and measuring the terminal voltage value α of the lithium-ion secondary battery immediately after the first time has elapsed. The second mode involves performing the first mode, then pausing charging for a second time, and measuring the OCV value β of the lithium-ion secondary battery immediately after the second time has elapsed.

[0011] The determination unit compares the current terminal voltage value αA, measured by the first mode, with the previous terminal voltage value αB, measured by the immediately preceding first mode.

[0012] The determination unit, when the first time is a (minutes) and the predetermined current value is I (C), αA / αB < (a × I / 250) + 1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, determine that you will not transition to the second mode. αA / αB≧(a×I / 250)+1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined to transition to the second mode.

[0013] The measurement unit measures the OCV value β in the second mode.

[0014] In this configuration, the measurement of the OCV value β is omitted when the rate of change of the terminal voltage value used for mode selection is smaller than a threshold set based on the charging time and charging current value. High-precision measurement of the OCV value β requires the execution of a second mode, i.e., a second relaxation time (charging pause time) relative to the charging time. Therefore, reducing the number of OCV value β measurements shortens the time required to acquire OCV data.

[0015] Furthermore, when the rate of change of the terminal voltage value used for mode selection is small, the change in the OCV value β is small in relation to the change in SOC. Therefore, when the rate of change of the terminal voltage value used for mode selection is small, the measurement of the OCV value β can be omitted, and the error in the OCV degradation analysis can be kept small. [Effects of the Invention]

[0016] According to this invention, the acquisition time for OCV data can be shortened while suppressing the increase in analysis errors in OCV degradation analysis. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a diagram showing the configuration of a charging system that includes a charger and a secondary battery according to a first embodiment of the present invention, and is capable of acquiring OCV data. [Figure 2] Figure 2 is a graph showing an example of the relationship between SOC and charging voltage. [Figure 3] Figure 3 is a graph showing an example of the relationship between SOC and the rate of change of voltage. [Figure 4] FIG. 4 is a graph showing the relationship between the voltage change rate, the shortening rate of the OCV data acquisition time, and the maximum error of the parameter calculated by performing degradation analysis using the acquired OCV data. [Figure 5] FIG. 5 is a flowchart showing an example of a method for acquiring OCV data according to the first embodiment of the present invention. [Figure 6] FIG. 6(A) is a graph showing an example of the voltage change rate with respect to the SOC of the positive electrode active material of the secondary battery according to the second embodiment of the present invention, and FIG. 6(B) is a graph showing an example of the voltage change rate with respect to the SOC of the negative electrode active material of the secondary battery according to the second embodiment of the present invention. [Figure 7] FIGS. 7(A), 7(C), and 7(D) are tables showing the relationship between the combination of the SOC ranges in which the second mode is performed and the time shortening rate, and FIG. 7(B) is a table showing the relationship between the combination of the SOC ranges in which the second mode is performed and the maximum error of the parameter calculated by performing degradation analysis using the acquired OCV data. [Figure 8] FIG. 8(A) is a table showing the relationship between the combination of the lowest SOC and the highest SOC in the low SOC range in which the second mode is performed and the time shortening rate, and FIG. 8(B) is a table showing the relationship between the combination of the lowest SOC and the highest SOC in the low SOC range in which the second mode is performed and the maximum error of the parameter calculated by performing degradation analysis using the acquired OCV data. MODE FOR CARRYING OUT THE INVENTION

[0018] [First Embodiment] The charger and the method for acquiring OCV data according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a charging system including a charger and a secondary battery according to the first embodiment of the present invention and capable of acquiring OCV data.

[0019] As shown in FIG. 1, the charger 20 includes a charge control unit 21, a measurement unit 22, a storage unit 23, a determination unit 24, an output unit 25, and a charging terminal 290. Although not shown, the charger 20 is supplied with power from a commercial power supply or the like.

[0020] The secondary battery 90 is, for example, a lithium-ion secondary battery. The secondary battery 90 is charged by connecting it to the charging terminal 290.

[0021] The charging control unit 21 charges the secondary battery 90 connected to the charging terminal 290. In this process, the charging control unit 21 controls the charging according to the mode determined by the determination unit 24. There are two modes: a first mode and a second mode.

[0022] The measurement unit 22 measures the terminal voltage value of the secondary battery 90. More specifically, the measurement unit 22 measures the terminal voltage value α for mode selection and the OCV value β as the terminal voltage values ​​of the secondary battery 90. The measurement unit 22 measures the terminal voltage value α for mode selection in the first mode and measures the OCV value β in the second mode.

[0023] The measurement unit 22 outputs the measured terminal voltage value α and OCV value β for mode selection to the storage unit 23.

[0024] The memory unit 23 includes a mode selection voltage value memory unit 231 and an OCV value memory unit 232. The mode selection voltage value memory unit 231 stores the terminal voltage value α for mode selection. The OCV value memory unit 232 stores the OCV value β.

[0025] The determination unit 24 determines the selection between the first mode and the second mode based on the terminal voltage value α for mode selection. The determination unit 24 outputs the determined mode to the charge control unit 21.

[0026] The output unit 25 acquires at least one OCV value β measured during the pause process after charging from the OCV value storage unit 232 as OCV data and outputs it.

[0027] (Overview of Mode 1) The first mode involves charging the secondary battery 90 with a predetermined current value for a first time, and measuring the terminal voltage value α of the secondary battery 90 immediately after the first time has elapsed.

[0028] (Processing and control in the first mode) The charge control unit 21 charges the secondary battery 90 with a predetermined current value for a first time period (for example, 1 minute). The measurement unit 22 measures the terminal voltage value of the secondary battery 90 immediately after the first time period has elapsed as the terminal voltage value α for mode selection. The measurement unit 22 outputs the measured terminal voltage value α for mode selection to the storage unit 23. The mode selection voltage value storage unit 231 of the storage unit 23 stores the terminal voltage value α for mode selection.

[0029] (Overview of the second mode) The second mode involves performing the first mode, then pausing charging for a second period of time, and measuring the OCV value β of the secondary battery 90 immediately after the second period has elapsed.

[0030] (Processing and control in the second mode) After performing charging control according to the first mode described above, the charging control unit 21 pauses charging for a second period of time (for example, 10 minutes, 20 minutes, or 30 minutes). This second period corresponds to the so-called relaxation time or pause time.

[0031] The measurement unit 22 measures the terminal voltage value of the secondary battery 90 immediately after the charge control unit 21 has performed charge control in the first mode, and uses this as the terminal voltage value α for mode selection. Subsequently, the measurement unit 22 further measures the terminal voltage value of the secondary battery 90 immediately after the second time period has elapsed, and uses this as the OCV value β. The measurement unit 22 outputs the measured terminal voltage value α and OCV value β for mode selection to the storage unit 23. The mode selection voltage value storage unit 231 of the storage unit 23 stores the terminal voltage value α for mode selection, and the OCV value storage unit 232 stores the OCV value β.

[0032] (Specific method of determination) Specifically, the determination unit 24 determines the selection of the first mode and the second mode in the following manner.

[0033] The determination unit 24 reads the current terminal voltage value αA and the previous terminal voltage value αB (the terminal voltage value of the previous measurement) measured by the previous first mode from the mode selection voltage value storage unit 231. The determination unit 24 calculates the ratio (αA / αB) of the current terminal voltage value αA and the terminal voltage value αB of the previous measurement.

[0034] The determination unit 24 calculates (a × I / 250) + 1, where a is the first time (minutes) and I is a predetermined current value (C).

[0035] The determination unit 24 is, αA / αB < (a × I / 250) + 1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined that the system will not transition to the second mode.

[0036] The determination unit 24 is, αA / αB≧(a×I / 250)+1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined to transition to the second mode.

[0037] (Reasons for introducing the judgment formula) The OCV (Optical Voltage Value) of the electrode active materials constituting the secondary battery 90 changes with changes in crystal structure and lithium ion content. OCV analysis is an analytical method that uses the OCV curves of the positive and negative electrode active materials as reference data, and by fitting the acquired battery's OCV curve to the reference data, it is possible to estimate the degradation state and combination state of the positive and negative electrode materials.

[0038] Therefore, the OCV values ​​required for analysis are those within the range that involve characteristic structural changes (changes in OCV voltage) of the positive / negative electrode active materials, while OCV values ​​within the range that do not involve significant structural changes (voltage changes) are not as important for the analysis.

[0039] Therefore, if OCV values ​​can be measured within the range accompanied by characteristic structural changes (OCV voltage changes) in the positive / negative electrode active materials, high-precision fitting is possible, enabling high-precision OCV analysis. On the other hand, by omitting the measurement of OCV values ​​in the range that does not involve significant structural changes (voltage changes), the number of OCV data points to be acquired can be reduced while suppressing a decrease in analysis accuracy.

[0040] Furthermore, overvoltage occurs during charging depending on the internal resistance of the secondary battery 90. When the charging current is stopped, the voltage of the secondary battery 90 gradually decreases by the amount of the overvoltage and settles at a certain voltage value. This voltage value corresponds to the OCV value β. Therefore, when measuring the OCV value β, it is necessary to repeatedly pause charging and pause charging until the voltage settles at the OCV value β. This pause time (relaxation time, pause time) varies depending on the design of the secondary battery 90 and the materials used, and can take a long time of 10 minutes or more. Therefore, if many OCV values ​​β are measured between 0% and 100% SOC, an enormous amount of measurement time will be required. Thus, as mentioned above, by omitting the measurement of OCV values ​​in the range that does not involve much structural change (voltage change), the total time for acquiring OCV data can be shortened.

[0041] Based on this introductory concept, the above-mentioned formula for determination is set as follows.

[0042] A realistic number of divisions for performing OCV analysis with the required accuracy is considered to be "50 to 100". If the number of divisions is too small, the analysis accuracy will decrease, and if it is too large, the acquisition time of OCV data will increase.

[0043] The total time required to acquire OCV data for obtaining SOC-OCV characteristics is, when the second time (rest time) is b (minutes), 60 × (a + b) / (a ​​× I) [minutes], which converts to time, The time is (a+b) / (a×I).

[0044] Considering the delay in the operation of the charging control unit 21, the fact that the secondary battery 90 is prone to degradation when charged with high current, and the fact that the power supply circuit becomes larger as the current increases, a maximum of around 2C is reasonable, and a charging time of 30 seconds or more is required per cycle. On the other hand, charging with a low current for a long time will increase the time required to acquire OCV data, so it is reasonable to limit the charging time to 3 minutes per cycle.

[0045] Furthermore, if the charging current I becomes too high, the rest time b must be lengthened. Therefore, calculated using the division point formula mentioned above, a range of 0.4C to 2.4C is appropriate.

[0046] Thus, if a is between 30 seconds and 3 minutes (0.5 ≤ a ≤ 3.0) and I is between 0.4C and 2.4C (0.4 ≤ I ≤ 2.4), that is, if the relationship 0.6 ≤ a × I ≤ 1.2 is satisfied, the measurement can be set to be completed within one night (8 hours) while suppressing a decrease in measurement accuracy.

[0047] Using the above concept, the determination unit 24 sets a reference value for the rate of change ((a×I / 250)+1) by multiplying the set a×I by a predetermined correction coefficient (for example, 1 / 250 in the above formula) and adding 1. This reference value takes into account the number of measurements and the measurement time, and is based on the ratio (αA / αB) of the current terminal voltage value αA to the terminal voltage value αB of the previous measurement, and is a reference value for how much larger (voltage changed) the current terminal voltage value αA is compared to the terminal voltage value αB of the previous measurement.

[0048] Then, by using the reference value set in this way, the determination unit 24 can determine that the voltage change is in a large range if the ratio (αA / αB) is greater than or equal to the reference value ((a×I / 250)+1). On the other hand, the determination unit 24 can determine that the voltage change is in a small range if the ratio (αA / αB) is less than the reference value ((a×I / 250)+1).

[0049] As described above, the charger 20 can shorten the OCV data acquisition time while suppressing the increase in analysis errors by performing the above-described configuration and processing.

[0050] (A specific example) Figure 2 is a graph showing an example of the relationship between SOC and the charging voltage value. Figure 3 is a graph showing an example of the relationship between SOC and the rate of change of voltage. Figure 3 is based on Figure 2. This rate of change of voltage corresponds to the ratio (αA / αB) mentioned above.

[0051] Figure 4 is a graph showing the relationship between the voltage change rate, the time reduction rate, and the maximum error. In Figure 4, the solid line shows the time reduction rate, and the dashed line shows the maximum error. Figure 4 shows the time reduction rate and the maximum error of the OCV analysis when the measurement of the OCV value is omitted when the voltage change rate is below a standard. The horizontal axis corresponds to the standard voltage change rate, and the vertical axis shows the time reduction rate and the maximum error of the OCV analysis when the voltage change rate shown on the horizontal axis is used as a reference, with the measurement of the OCV value omitted in the range where the voltage change rate is less than the standard, and measured in the range where the voltage change rate is above the standard. The time reduction rate is set to 0% when the measurement of the OCV value is not omitted, and to 100% when the measurement of the OCV value is completely omitted, and shows the percentage of time reduction achieved. In other words, the larger the time reduction rate shown in Figure 4, the greater the time reduction effect.

[0052] As shown in Figures 2 and 3, the rate of voltage change differs depending on the State of Charge (SOC). That is, between SOC 0% and 100%, there are ranges where the rate of voltage change is large and ranges where it is small.

[0053] As shown in Figure 4, changing the reference rate of voltage change alters both the time reduction effect and the maximum error. Increasing the reference rate of voltage change improves the time reduction effect, but increases the maximum error. Conversely, lowering the reference rate of voltage change reduces the maximum error, but suppresses the time reduction effect.

[0054] Therefore, based on the above formula, if we set the voltage change rate to 1.004, for example, OCV data can be acquired in 60% of the time compared to performing the second mode at all division points, and the maximum error can be kept below 2%.

[0055] Furthermore, it is preferable that the charger 20 is equipped with an electronic load that can be connected to the charging terminal 290.

[0056] The charging control unit 21 discharges the secondary battery 90 to a predetermined voltage value using an electronic load, and then starts charging control in the first mode.

[0057] If the secondary battery 90 is not used until it is completely empty (the minimum charge level at which it can be discharged or approximately 0% SOC), and some capacity remains, the OCV value β on the low SOC side used for OCV analysis cannot be obtained. However, by first discharging the battery with an electronic load, the charger 20 can measure the OCV value β on the low SOC side necessary for accurate analysis and obtain OCV data including this value.

[0058] (How to obtain OCV data) Figure 5 is a flowchart showing an example of a method for acquiring OCV data according to the first embodiment of the present invention. Note that a detailed explanation of each process in the flowchart shown in Figure 5 is provided in the above-mentioned description of the configuration; therefore, detailed explanations are omitted here except where necessary. Furthermore, the following description will focus on the charger 20, but each process is performed by the respective functional units constituting the charger 20, as described above.

[0059] The charger 20 charges the secondary battery 90 in a first mode (first time a (minutes), predetermined current value I (C)), and immediately after charging measures the terminal voltage value α for mode selection (S11). The charger 20 stores the terminal voltage value α (S12).

[0060] The charger 20 compares the current terminal voltage value αA with the previous terminal voltage value αB (S13). The previous terminal voltage value αB is the terminal voltage value from one charging cycle ago (when charging in the previous first mode).

[0061] If the comparison result satisfies the conditions for omitting the second mode (S14: YES), the charger 20 does not transition to the second mode and continues to perform the first mode (S11).

[0062] If the comparison result does not satisfy the conditions for omitting the second mode (S14: NO), the charger 20 will switch to the second mode. Specifically, the charger 20 will pause charging for a second period of time and measure the OCV value β immediately after the second period has elapsed (S15).

[0063] The charger 20 completes the measurement when it has measured all OCV values ​​β within the SOC range used for OCV analysis. If the measurement is not complete (S16:NO), the charger 20 returns to the first mode and continues charging and measuring.

[0064] Once the measurement is complete (S16:YES), the charger 20 acquires the multiple OCV values ​​β measured during the charging process as OCV data (S17).

[0065] [Second Embodiment] A charger and OCV data acquisition method according to a second embodiment of the present invention will be described with reference to the figures. The charger and OCV data acquisition method according to the second embodiment of the present invention differ from the charger and OCV data acquisition method according to the first embodiment in that it determines the range of OCV value measurement to be omitted using the voltage change rate of the positive electrode active material and the voltage change rate of the negative electrode active material that form the secondary battery. Other parts of the charger and OCV data acquisition method according to the second embodiment are the same as those of the charger and OCV data acquisition method according to the first embodiment, and the explanation of the similar parts will be omitted.

[0066] Figure 6(A) is a graph showing an example of the voltage change rate with respect to SOC of the positive electrode active material in a secondary battery according to a second embodiment of the present invention. Figure 6(A) is an example in which layered rock salt type positive electrode active material (Li(NiMnCo)O2) is used as the positive electrode active material. Figure 6(B) is a graph showing an example of the voltage change rate with respect to SOC of the negative electrode active material in a secondary battery according to a second embodiment of the present invention. Figure 6(B) is an example in which graphite is used as the negative electrode active material.

[0067] As shown in Figures 6(A) and 6(B), when a layered rock salt type positive electrode active material (Li(NiMnCo)O2) is used as the positive electrode active material and graphite is used as the negative electrode active material, the characteristic curve of the rate of change of voltage with respect to SOC shows maximum points of the rate of change of voltage at SOC from 10% to 30%, from 50% to 60%, and from 80% to 100%.

[0068] The charge control unit 21 and the measurement unit 22 switch from the first mode to the second mode and perform OCV value β measurement when the SOC is in the range of 10% to 30%, 50% to 60%, and 80% to 100%. In other ranges, the charge control unit 21 and the measurement unit 22 do not switch to the second mode and continue to perform the first mode.

[0069] Within a predetermined SOC range that includes the maximum point of voltage change, the voltage change rate is large. Therefore, from the viewpoint of error suppression, measurement of the OCV value β using the second mode is necessary. On the other hand, outside the predetermined SOC range that includes the maximum point, the voltage change rate is small. Therefore, from the viewpoint of error suppression, measurement of the OCV value β using the second mode is not necessary. Furthermore, by not measuring the OCV value β, a time reduction effect can be obtained.

[0070] By performing this processing, the charger according to the second embodiment can reduce the OCV data acquisition time while suppressing the increase in errors in the OCV data.

[0071] Furthermore, in the charger according to the second embodiment, the execution of the second mode can be omitted even when the SOC is in the range of 50% to 60%.

[0072] The charger according to the second embodiment may perform the measurement of the OCV value β in the second mode only in two ranges: a low SOC range (e.g., an SOC range of 0% to 20%) and a high SOC range (e.g., an SOC range of 80% to 100%).

[0073] Figures 7(A), 7(C), and 7(D) are tables showing the relationship between the combination of SOC ranges used for the second mode and the time reduction rate, while Figure 7(B) is a table showing the relationship between the combination of SOC ranges used for the second mode and the maximum error. Figure 7(A) shows the case where the relaxation time (pause time) is 20 minutes, Figure 7(C) shows the case where the relaxation time (pause time) is 10 minutes, and Figure 7(D) shows the case where the relaxation time (pause time) is 30 minutes.

[0074] As shown in Figure 7(B), even when measuring the OCV value β using the second mode in only two ranges—a low SOC range (for example, SOC from 0% to 20%) and a high SOC range (SOC from 80% to 100%)—the maximum error can be suppressed to about 1%, and the time reduction rate can be reduced to about 70%. Note that the SOC range in which the second mode is performed is not limited to these ranges and can be set appropriately based on the acceptable maximum error and the desired time reduction rate.

[0075] Furthermore, in the charger according to the second embodiment, the high SOC range may be excluded from the execution of the second mode, and the second mode may be executed only at SOC 100%. That is, the charger according to the second embodiment executes the second mode only in the low SOC range and at SOC 100%.

[0076] Even with this processing, as shown in the time reduction rates in Figures 7(A), 7(C), and 7(D), and the maximum error in Figure 7(B), it is possible to further reduce the acquisition time of OCV data while suppressing an increase in the error of the OCV data.

[0077] [Third Embodiment] A charger and OCV data acquisition method according to a third embodiment of the present invention will be described with reference to the figures. Note that the charger and OCV data acquisition method according to the third embodiment of the present invention differ from the charger and OCV data acquisition method according to the second embodiment in the setting of the low SOC range. Other parts of the charger and OCV data acquisition method according to the third embodiment of the present invention are the same as those of the charger and OCV data acquisition method according to the second embodiment, and similar parts will be omitted from the description.

[0078] As shown in Figure 6(B) above, the voltage change of the negative electrode active material. rate The SOC is very large in the range of 0% to 5%. Therefore, if the method of the first embodiment described above is simply adopted, the OCV value β in the second mode is measured when the rate of voltage change is large above the reference value, so this interval becomes the target interval for the second mode, and the frequency of measuring the OCV value β increases. As a result, the time-saving effect may decrease. Therefore, the charger according to the third embodiment performs the following processing.

[0079] Figure 8(A) is a table showing the relationship between the combination of minimum and maximum SOC in the low SOC range where the second mode is performed and the time reduction rate, and Figure 8(B) is a table showing the relationship between the combination of minimum and maximum SOC in the low SOC range where the second mode is performed and the maximum error.

[0080] As shown in Figures 8(A) and 8(B), by not measuring the OCV value β using the second mode in the range of 0% to 5% of the SOC, it is possible to achieve a time reduction effect of more than 80% while achieving an error of approximately 0%.

[0081] Therefore, the charger according to the third embodiment can further shorten the OCV data acquisition time while suppressing an increase in the error of the OCV data by setting the minimum SOC in the low SOC range to 5%.

[0082] As shown in Figures 8(A) and 8(B), in the first setting configuration, where the low SOC range is set to the range of 10% to 25% of SOC, and the second setting configuration, where the low SOC range is set to the range of 15% to 25% of SOC, the second setting configuration has fewer measurement points for the OCV value β, but the error is smaller. This is thought to be because, as shown in Figure 6(B), the negative electrode active material has four maximum points in the range of 10% to 30% of SOC. In this characteristic, it is thought that the maximum point on the lowest SOC side was mistakenly fitted as the maximum point around 5% of SOC.

[0083] Thus, for positive and negative electrode active materials that have many maximum points in the SOC range of 10% to 30%, such misfitting can be suppressed by including the range with a relatively small voltage change rate around 30% SOC in the low SOC range.

[0084] Therefore, the charger according to the third embodiment can further suppress errors by setting the SOC range for executing the second mode to include the maximum point of voltage change between the positive electrode active material and the negative electrode active material, and by deliberately setting a range with a relatively small voltage change rate.

[0085] <1> A measurement unit that measures the terminal voltage value α and OCV value β for mode selection for a lithium-ion secondary battery, A storage unit that stores the measured terminal voltage value α for mode selection and the OCV value β, A determination unit that determines the selection between a first mode and a second mode based on the terminal voltage value α for mode selection, Based on the result of the determination, a charge control unit performs charging control of the lithium-ion secondary battery in the first mode or the second mode, An output unit that outputs at least one OCV value β measured during the charging process as OCV data, A charger equipped with, The first mode involves charging the lithium-ion secondary battery with a predetermined current value for a first time, and measuring the terminal voltage value α of the lithium-ion secondary battery immediately after the first time has elapsed. It is a mode, The second mode is a mode in which, after performing the first mode, charging is paused for a second time, and the OCV value β of the lithium-ion secondary battery is measured immediately after the second time has elapsed. The determination unit, The current terminal voltage value αA measured by the first mode is compared with the previous terminal voltage value αB measured by the first mode immediately preceding the first mode. When the first time is a (minutes) and the predetermined current value is I (C), αA / αB < (a × I / 250) + 1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined that the mode will not be changed to the second mode described above. αA / αB≧(a×I / 250)+1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined to transition to the second mode described above. The measurement unit is a charger that measures the OCV value β in the second mode.

[0086] <2> The lithium-ion secondary battery is equipped with an electronic load that can be connected to the aforementioned lithium-ion secondary battery, The charging control unit, After discharging the lithium-ion secondary battery to a predetermined voltage value using the aforementioned electronic load, the charging control according to the first mode is started. <1> A charger.

[0087] <3> The charging control unit and the measuring unit are, A characteristic curve of the voltage change rate with respect to SOC based on the ratio of the terminal voltage value αA and the terminal voltage value αB is obtained. In a predetermined SOC range that includes a plurality of maximum points in the characteristic curve, the measurement of the OCV value β using the second mode is performed. <1> or <2> A charger.

[0088] <4> The charging control unit and the measuring unit are, A predetermined SOC range including at least one maximum point in the characteristic curve, and the measurement of the OCV value β by the second mode at SOC 100%, <3> A charger.

[0089] <5> If it is known that the lithium-ion secondary battery connected to the charger is a secondary battery in which the positive electrode material is a layered rock salt type material and the negative electrode material is a graphite-based material, The charging control unit and the measuring unit perform the measurement of the OCV value β in the second mode in the SOC range of 5% to 20% and at SOC 100%. <3> A charger.

[0090] <6> A measurement step for a lithium-ion secondary battery, which involves measuring the terminal voltage value α and OCV value β for mode selection, A storage step of storing the measured terminal voltage value α for mode selection and the OCV value β, A determination step of determining the selection between a first mode and a second mode based on the terminal voltage value α for mode selection, A charge control step in which the charging control of the lithium-ion secondary battery is performed in the first mode or the second mode based on the result of the determination, An output step that outputs at least one OCV value β measured during the charging process as OCV data, A method for acquiring OCV data having, The first mode is a mode in which the lithium-ion secondary battery is charged with a predetermined current value for a first time, and the terminal voltage value α of the lithium-ion secondary battery is measured immediately after the first time has elapsed. The second mode is a mode in which, after performing the first mode, charging is paused for a second time, and the OCV value β of the lithium-ion secondary battery is measured immediately after the second time has elapsed. The aforementioned determination step is, The current terminal voltage value αA measured by the first mode is compared with the previous terminal voltage value αB measured by the first mode immediately preceding the first mode. When the first time is a (minutes) and the predetermined current value is I (C), αA / αB < (a × I / 250) + 1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined that the mode will not be changed to the second mode described above. αA / αB≧(a×I / 250)+1 (0.5≦a≦3, 0.4≦I≦2.4, 0.6≦a×I≦1.2) If this is the case, it is determined to transition to the second mode described above. The measurement step involves measuring the OCV value β in the second mode, A method for acquiring OCV data, which outputs at least one measured OCV value β as OCV data. [Explanation of Symbols]

[0091] 20: Charger 21: Charging Control Unit 22: Measuring part 23: Storage section 24: Judgment section 25: Output section 90: Secondary battery 231: Mode selection voltage value storage unit 232: OCV value storage unit 290: Charging terminal

Claims

1. A measurement unit that measures the terminal voltage value α and OCV value β for mode selection for a lithium-ion secondary battery, A storage unit that stores the measured terminal voltage value α and OCV value β for mode selection, A determination unit that determines the selection between a first mode and a second mode based on the terminal voltage value α for mode selection, Based on the result of the determination, a charge control unit performs charging control of the lithium-ion secondary battery in the first mode or the second mode, An output unit that outputs at least one OCV value β measured during the charging process as OCV data, A charger equipped with, The first mode involves charging the lithium-ion secondary battery with a predetermined current value for a first time, and measuring the terminal voltage value α of the lithium-ion secondary battery immediately after the first time has elapsed. It is a mode, The second mode is a mode in which, after performing the first mode, charging is paused for a second time, and the OCV value β of the lithium-ion secondary battery is measured immediately after the second time has elapsed. The determination unit, The current terminal voltage value αA measured by the first mode is compared with the previous terminal voltage value αB measured by the immediately preceding first mode. When the first time is a (minutes) and the predetermined current value is I (C), αA / αB<(a×I / 250)+1 (0.5 ≤ a ≤ 3, 0.4 ≤ I ≤ 2.4, 0.6 ≤ a × I ≤ 1.2) If this is the case, it is determined that the transition to the second mode will not occur. αA / αB≧(a×I / 250)+1 (0.5 ≤ a ≤ 3, 0.4 ≤ I ≤ 2.4, 0.6 ≤ a × I ≤ 1.2) If this is the case, it is determined to transition to the second mode described above. The measuring unit measures the OCV value β in the second mode. charger.

2. The lithium-ion secondary battery is equipped with an electronic load that can be connected to the aforementioned lithium-ion secondary battery, The charging control unit, After discharging the lithium-ion secondary battery to a predetermined voltage value using the electronic load, the charging control according to the first mode is started. The charger according to claim 1.

3. The charging control unit and the measuring unit are, A characteristic curve of the voltage change rate with respect to the SOC is obtained based on the ratio of the terminal voltage value αA and the terminal voltage value αB. In a predetermined SOC range that includes a plurality of maximum points in the characteristic curve, the measurement of the OCV value β using the second mode is performed. The charger according to claim 1 or claim 2.

4. The charging control unit and the measuring unit are, The measurement of the OCV value β by the second mode is performed in a predetermined SOC range that includes at least one maximum point in the characteristic curve, and at SOC 100%. The charger according to claim 3.

5. If it is known that the lithium-ion secondary battery connected to the charger is a secondary battery in which the positive electrode material is a layered rock salt type material and the negative electrode material is a graphite-based material, The charging control unit and the measuring unit perform the measurement of the OCV value β in the second mode in the SOC range of 5% to 20% and at SOC 100%. The charger according to claim 3.

6. A measurement step for a lithium-ion secondary battery, which involves measuring the terminal voltage value α and OCV value β for mode selection, A storage step in which the measured terminal voltage value α for mode selection and the OCV value β are stored, A determination step of determining the selection between a first mode and a second mode based on the terminal voltage value α for mode selection, A charge control step in which the charging control of the lithium-ion secondary battery is performed in the first mode or the second mode based on the result of the determination, An output step that outputs at least one OCV value β measured during the charging process as OCV data, A method for acquiring OCV data having, The first mode is a mode in which the lithium-ion secondary battery is charged with a predetermined current value for a first time, and the terminal voltage value α of the lithium-ion secondary battery is measured immediately after the first time has elapsed. The second mode is a mode in which, after performing the first mode, charging is paused for a second time, and the OCV value β of the lithium-ion secondary battery is measured immediately after the second time has elapsed. The aforementioned determination step is, The current terminal voltage value αA measured by the first mode is compared with the previous terminal voltage value αB measured by the immediately preceding first mode. When the first time is a (minutes) and the predetermined current value is I (C), αA / αB<(a×I / 250)+1 (0.5 ≤ a ≤ 3, 0.4 ≤ I ≤ 2.4, 0.6 ≤ a × I ≤ 1.2) If this is the case, it is determined that the transition to the second mode will not occur. αA / αB≧(a×I / 250)+1 (0.5 ≤ a ≤ 3, 0.4 ≤ I ≤ 2.4, 0.6 ≤ a × I ≤ 1.2) If this is the case, it is determined to transition to the second mode described above. The measurement step involves measuring the OCV value β in the second mode, Output the measured OCV value β as OCV data. How to obtain OCV data.

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