Battery diagnosis device and battery diagnosis method

Abstract

The purpose of the present invention is to provide a technique capable of quickly and detailedly determining the state of a battery. This battery diagnostic device determines whether or not a battery is in a first state on the basis of a first difference in battery voltage within 4 milliseconds from an end time point at which charging or discharging of the battery has ended, and determines whether or not the battery is in a second state on the basis of a second difference in battery voltage following the first difference.

Description

Technical Field

[0001] The present invention relates to a technique for diagnosing the state of a battery. Background Art

[0002] As a method for determining the deterioration state of a storage battery, there is a technique described in Patent Document 1. This document describes the problem of "accurately determining the deterioration state", and "setting the inter-terminal voltage of the secondary battery at the end of charging or at the stop of charging or at the end of discharging or at the stop of discharging as the first voltage value, and after a predetermined time has elapsed since the measurement of the first voltage value, setting the inter-terminal voltage of the secondary battery measured as the second voltage value, calculating the difference between the first voltage value and the second voltage value as the change amount ΔV, and comparing the change amount ΔV with a predetermined reference change amount to determine the deterioration state" such a technique (see the abstract). This document also describes that when the ohmic loss resistance R1 is greater than the reference battery resistance value within 0.01 seconds after the end of charging or discharging, it is determined that the battery is deteriorated (see Figure 9 、0058 - 0059、0063、0070).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011 - 054413 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Patent Document 1 uses the voltage change amount after charge and discharge to calculate the battery resistance R, and compares it with the reference battery resistance value to determine whether there is deterioration. On the other hand, at the actual site of storage battery evaluation, it is necessary to judge whether to replace the battery or whether it can continue to be used. Therefore, it is necessary to determine the state of the storage battery in detail. For example, consider judging detailed states such as (a) a failure state, (b) a state where the SoH (State of health) rapidly decreases, etc. Although the prior art such as Patent Document 1 judges whether the battery is deteriorated, it is difficult to judge the detailed state of the battery. And it is also required to diagnose the state of the battery at high speed.

[0008] The present invention has been completed in view of the above problems, and its object is to provide a technique capable of judging the state of a battery at high speed and in detail.

[0009] Means for Solving the Problems

[0010] The battery diagnosis device of the present invention determines whether the battery is in a first state based on a first difference in battery voltage within 4 msec from the end moment when the battery ends charging or discharging, and determines whether the battery is in a second state based on a second difference in battery voltage thereafter.

[0011] Advantages of the Invention

[0012] According to the battery diagnosis device of the present invention, the state of the battery can be determined at high speed and in detail. Through the following description of the embodiments, other problems, structures, advantages, etc. of the present invention will become clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a block diagram of the battery diagnosis device 100 according to Embodiment 1.

[0014] Figure 2 It is an example of the screen of UI130.

[0015] Figure 3 It is a flowchart showing the sequence of the arithmetic unit 120 diagnosing the battery 200.

[0016] Figure 4 It is a graph showing the change over time of the current and voltage output by the battery 200 after discharge.

[0017] Figure 5 It is an example of the phase frequency characteristic obtained in S301.

[0018] Figure 6 It is a Cole-Cole curve made by performing Fourier transform on the voltage change amount with respect to time from the first measurement point to obtain the amplitude frequency characteristic and using the amplitude.

[0019] Figure 7 It is a graph showing the change over time of the battery voltage during the rest period after charging.

[0020] Figure 8 It is a flowchart explaining the sequence of the battery diagnosis device 100 diagnosing the battery 200 according to Embodiment 2.

[0021] Figure 9 It shows a state where the phase on the phase frequency characteristic changes significantly with respect to the reference value in the frequency domain below f3.

[0022] Figure 10 It is a flowchart explaining the sequence of the battery diagnosis device 100 diagnosing the battery 200 according to Embodiment 3.

[0023] Figure 11 It shows an example of the combination of the positive electrode material and the negative electrode material.

[0024] Figure 12Examples of temperature regions.

[0025] Figure 13 Are examples of amplitude - frequency characteristics used in S702 and S704.

[0026] Figure 14 Is a flowchart illustrating the order of determining the temperature region in S705.

[0027] Figure 15 Represents another structural example of the battery diagnostic device 100. Detailed implementation

[0028] <Embodiment 1>

[0029] Figure 1 Is a block diagram of the battery diagnostic device 100 according to Embodiment 1 of the present invention. The battery diagnostic device 100 includes a detection unit 110, an arithmetic unit 120, and a UI (User Interface) 130. The battery diagnostic device 100 is connected to the battery 200 when diagnosing the battery 200, and can charge or discharge the battery 200, or instruct the charge - discharge device to start and stop charge - discharge. The battery 200 can be a storage battery module or a battery pack composed of multiple batteries, etc.

[0030] The detection unit 110 obtains the detection value V of the voltage output by the battery 200, the detection value I of the current, and the time t. The arithmetic unit 120 uses the detection values obtained by the detection unit 110 to diagnose the state of the battery 200. The diagnosis order will be described later. The UI 130 can perform input of the battery type as information required for diagnosis, indication of the start of diagnosis, output of the diagnosis result, etc.

[0031] Figure 2 Is an example of the screen of the UI 130. An operator can input instructions for the battery diagnostic device 100 via the UI 130 and confirm the diagnosis result of the battery diagnostic device 100 at the diagnosis site, etc.

[0032] Figure 3 Is a flowchart showing the order in which the arithmetic unit 120 diagnoses the battery 200. The arithmetic unit 120 starts this flowchart at an appropriate timing, such as when there is an instruction from the UI 130, when the SoC (State Of Charge) of the battery 200 reaches a predetermined value, or at each predetermined cycle. According to this flowchart, the arithmetic unit 120 determines the state of the battery 200 as one of grade A, grade B, and grade C. The definition of the grade will be described later.

[0033] ( Figure 3 : Step S301)

[0034] The arithmetic unit 120 performs a Fourier transform on the change in the battery voltage after the battery current is cut off, based on the input values from the detection unit 110, namely the voltage V, current I, and time t, to obtain the phase frequency characteristics and amplitude frequency characteristics. Moreover, using this result, it calculates dV0 / dt0, dV1 / dt1, and dV2 / dt2, which will be described later.

[0035] ( Figure 3 : Step S302)

[0036] When dV0 / dt0 (the first time change rate of the first difference) is higher than a pre-determined reference value, the arithmetic unit 120 determines that the state of the battery 200 is grade C (the first state). If it is not determined to be grade C, the process proceeds to step S303.

[0037] ( Figure 3 : Step S303)

[0038] The arithmetic unit 120 obtains multiple measurement results of the voltage V and calculates dV2 / dt2 (the second time change rate of the second difference) for each of them. The arithmetic unit 120 determines that the state of the battery is grade B (the second state) if either (a) dV2 / dt2 has changed by more than the reference value during multiple measurements, or (b) among the voltage change amounts per unit time measured after charging and after discharging respectively, the voltage change amount after charging exceeds the voltage change amount after discharging (for normal products, due to the influence of hysteresis, the voltage change amount after charging is less than the voltage change amount after discharging). If it is not determined to be grade B, it is determined to be grade A.

[0039] (Definition of the state of a single battery)

[0040] Grade A, grade B, and grade C are defined as follows:

[0041] · Grade A: A state where it can be used normally

[0042] · Grade B: A state where deterioration acceleration is observed and the SoH decreases rapidly, or the state immediately preceding it

[0043] · Grade C: A state indicating abnormal voltage and abnormal resistance, a state where charging and discharging are not possible, or the state immediately preceding it.

[0044] If the resistance of a grade C battery is measured, a state where the internal resistance, negative electrode resistance, positive electrode resistance, and diffusion resistance are all high resistance values can be observed. At the stable state after the current is cut off, a sharp voltage rise is sometimes observed. In S302, this situation is used to diagnose whether it is grade C.

[0045] When measuring the resistance of a Grade B battery, it is mainly possible to confirm an increase in the internal resistance, an increase in the positive electrode resistance, and deviations in multiple measurements. The positive electrode resistance of a Grade B battery depends on the charge capacity, and when the charge capacity is low, the deviation of the positive electrode resistance becomes significant. In S303, this situation is used to diagnose whether it is Grade B.

[0046] Regarding the battery 200 determined to be Grade B or Grade C, it is recommended to replace it or reuse it considering safety. The operation unit 120 can also output a message or the like to this effect on the UI130. As the factors for these grades, there are various factors represented by physical damage, foreign matter intrusion, lithium metal precipitation, and accumulation of by-products.

[0047] (As the definition of a battery pack)

[0048] The operation unit 120 can also perform performance evaluation of the battery pack and prediction of the incidence rate of each grade, etc., by statistically processing the incidence rate of each grade and the measurement results of SoH in multiple batteries.

[0049] The relationship between the incidence rate of grades in the Grade C group and the Grade B group and the cumulative usage time of the battery can be described as statistical data. This data, for example, has a region where the incidence rate decreases with time, a region that is constant regardless of time, and a region that increases with time. By using the cumulative usage time of the battery and referring to this curve, the incidence rate of each grade and whether it can continue to be used can be determined. Or, by using the Weibull distribution or the like to define the relationship between the incidence rate and the cumulative usage time in each region, it is possible to determine whether each battery pack can continue to be used, predict the incidence rate of each grade, etc. For example, if the m value of the Weibull distribution is above the threshold, it can be determined that it cannot continue to be used. The battery diagnostic device 100 only needs to store the pre-generated statistical data.

[0050] When measuring the SoH of a battery pack determined to be in the Grade B group, in the same battery pack under the same usage conditions, it is possible to assume that the relationship between the SoH and the number of batteries having that SoH follows a normal distribution. The quality of the battery pack can be quantified based on the standard deviation and SoH of this distribution, and the reliability of different battery packs can be compared. For example, as the cumulative usage time increases, various battery individuals such as batteries with accelerated degradation and those without accelerated degradation are generated, so the variance of the distribution increases. On the contrary, the variance is small during the period of small cumulative usage time. Therefore, the quality of the battery pack can be quantified using the standard deviation. Or, the process capability index or a value similar thereto can also be used as the quality index of the battery pack. Other appropriate statistical indicators can also be used.

[0051] Figure 4It is a graph showing the change over time of the current and voltage output by the battery 200 after discharge. The arithmetic unit 120 performs a Fourier transform on the voltage change amount with respect to time from the first measurement point after the current is cut off, and obtains the phase frequency characteristic and the amplitude frequency characteristic. The arithmetic unit 120 can use the phase frequency characteristic ( Figure 5 ) thus obtained to determine Figures 4 - 5 t1, t2, and t3 in

[0052] t1 is the start time point for measuring dV1 / dt1. t2 is the end time point for measuring dV2 / dt2. t0 is the start time of the rest period (however, depending on the sampling frequency, it may not be possible to strictly obtain the value of the start time of the rest period, so for example, it can also be the sampling point immediately after it). It is possible to measure dV0 / dt0 with t0 as the start time point and before t1 as the end time point. The end time point of dV1 / dt1 is between t1 and t2. The start time point of dV2 / dt2 can be the same as the end time point of dV1 / dt1 or after it. t3 will be described later. The time regions of dt0 to dt2 can partially overlap or there can be an interval between the regions.

[0053] Figure 5 is an example of the phase frequency characteristic obtained in S301. In Figure 5 , f1 to f2 is the frequency domain where the influence of the reaction of the negative electrode is significant, f2 to f3 is the frequency domain where the influence of the reaction of the positive electrode is significant, and below f3 is the frequency domain where the influence of the diffusion reaction is significant.

[0054] For example, in the phase frequency characteristic of Figure 5 , t1 can be obtained based on the time when the change amount of the phase gradually approaches 0 on the high-frequency side. More simply, it is also possible to obtain the first inflection point (the inflection point that appears first during the rest period) when the time axis is set to logarithmic display in the relationship between the voltage change amount and time shown in Figure 4 as t1. The range from f1 to f2 is the interval corresponding to the time constant of the negative electrode included in the equivalent circuit of the battery 200 (the interval including the front and back of the reciprocal of the time constant).

[0055] For example, in the phase frequency characteristic of Figure 5 , t2 can be obtained based on the value corresponding to the time constant of the positive electrode included in the equivalent circuit of the battery 200. More simply, it is also possible to obtain the second inflection point (the inflection point that appears second during the rest period) when the time axis is set to logarithmic display in the relationship between the voltage change amount and time shown in Figure 4 as t2. That is, dt2 is within the interval divided by the 2 inflection points on the logarithmic time axis.

[0056] For example, in Figure 5In the phase-frequency characteristic, t3 can be obtained based on the frequency at which the change amount of the phase with respect to the frequency gradually approaches 0 on the low-frequency side.

[0057] (Calculation order of dV0 / dt0, dV1 / dt1, dV2 / dt2)

[0058] dV0 / dt0 is Figure 4 the voltage change amount per unit time from the first measurement point (t0) to after passing dt0 after the current is cut off in. In this method, the measurement start time (t1) of dV1 / dt1 is mostly set around 4 msec after the current is cut off, so the time length of dt0 is set to be within 4 msec. However, within 2 msec is a time period when the influence of voltage abnormality or resistance abnormality is particularly significant, and the sampling period in this method needs to be set to be less than 1 / 2 of 4 msec, which is the measurement start time (t1) of dV1 / dt1. Therefore, dt0 is preferably set to be within 2 msec. The present inventor has found that dV0 / dt0 obtained as above has a high correlation with the generation of abnormal voltage and abnormal resistance of the storage battery. Use this situation to implement the determination in step S302.

[0059] Figure 6 obtained by performing a Fourier transform on the voltage change amount with respect to time starting from the first measurement point to obtain an amplitude-frequency characteristic, and using this amplitude to make a Cole-Cole curve graph. dV1 / dt1 corresponds to Figure 6 the voltage change amount per unit time in range (1) in. This region is a region where the influence of the internal resistance appears significantly. For example, dV1 / dt1 is obtained as the voltage change amount per unit time when dt1 is set to be within 4 msec from t1. However, when setting range (1), it is set in an appropriate interval in view of the sampling period, resolution, etc. of the measurement. The present inventor has found that dV1 / dt1 obtained as above has a high correlation with the internal resistance of the storage battery. Use this situation to implement the determination in step S705 described later.

[0060] dV2 / dt2 is obtained as the voltage change amount per unit time within any range from t2 to t1. Specifically, it corresponds to Figure 6 the voltage change amount per unit time in range (2) in. This region is a region where the influence of the negative electrode appears significantly. When determining dt2, it can be appropriately set within the interval from t1 to t2 according to the type of battery, device, use, measurement accuracy, etc. The present inventor has found that dV2 / dt2 obtained as above has a high correlation with the deterioration state of the negative electrode of the storage battery. In the first embodiment, use this situation to implement the determination in step S303.

[0061] It is not necessarily possible to obtain a Cole-Cole diagram for all frequencies, as Figure 6As shown by the dashed line portion, sometimes a part is missing. When the dashed line portion needs to be used, it can be used after compensating for the value by any interpolation operation.

[0062] Figure 7 Represents the change over time of the battery voltage during the rest period after charging. dV0 / dt0, dV1 / dt1, and dV2 / dt2 can be obtained in the same manner as the method described in Figures 4 - 6 This is also the case in the following embodiments.

[0063] <Embodiment 1: Summary>

[0064] The battery diagnostic device 100 of this Embodiment 1 uses dV0 / dt0 during the rest period after charging or discharging to determine whether the battery 200 is of grade C, and uses dV2 / dt2 to determine whether it is of grade B. These diagnoses can be implemented from the start of the rest period, for example, on the order of about several tens of milliseconds. Therefore, the detailed state of the battery 200 can be diagnosed at high speed.

[0065] In the prior art, for example, the SoH is sometimes determined based on the internal resistance of the battery. However, in recent years, lead-acid batteries with low internal resistance have become mainstream, so it is difficult to determine the deterioration state and the detailed state of the SoH only based on the difference in internal resistance. The diagnostic procedure of this embodiment is useful in that it can diagnose the detailed state even for lead-acid batteries with an internal resistance of 1 mΩ or less.

[0066] <Embodiment 2>

[0067] Figure 8 This is a flowchart showing the procedure by which the battery diagnostic device 100 of Embodiment 2 of the present invention diagnoses the battery 200. In the second embodiment, if it is not determined to be grade B in step S303, step S601 is further implemented. Other configurations are the same as those in Embodiment 1.

[0068] ( Figure 8 : Step S601)

[0069] The arithmetic unit 120 determines whether dendrites are generated on the electrodes of the battery 200 by using the phase frequency characteristics of the voltage change amount obtained in step S301. For example, in Figure 5 the frequency domain below f3, when the phase in the phase frequency characteristics decreases by a threshold or more relative to the reference value, it is determined that dendrites are generated. If these conditions are not met, it is determined to be grade A.

[0070] ( Figure 8 : Step S601: Supplement)

[0071] The present inventor has found that the phase in the frequency region below f3 is affected by the reaction of the diffusion resistance of the battery 200 and becomes an index for dendrite generation. This step uses this situation to determine the presence or absence of dendrites. A battery with dendrites may catch fire due to a short circuit or the like, so it is necessary to consider safety to determine whether it can continue to be used. For example, the arithmetic unit 120 can determine the risk caused by dendrites based on the degree of decrease of the phase from the reference value and prompt this meaning on the UI 130.

[0072] Figure 9 It represents a state where the phase in the frequency domain below f3 changes significantly with respect to the reference value in the phase-frequency characteristic. When the phase drops by more than the threshold value from the reference value (solid line) as shown by the dotted line in Figure 9 , it can be determined that dendrites have been generated. The reference value shown by the solid line can be obtained, for example, by pre-measuring a normal battery.

[0073] <Embodiment 3>

[0074] In Embodiment 3 of the present invention, a temperature region determination is performed on the battery 200 that has not been determined to be Grade C or Grade B in Embodiment 1. The temperature region refers to the temperature environment that is most dominant for the deterioration of the battery 200, such as the longest temperature region in the past usage environment of the battery 200, and the temperature region that has promoted the deterioration of the storage battery even instantaneously.

[0075] Figure 10 It is a flowchart showing the procedure for the battery diagnostic device 100 of the present invention to diagnose the battery 200. In Embodiment 3, when it is not determined to be Grade B in S303, S701 to S705 are further performed. S601 may or may not be performed. Other configurations are the same as those in Embodiments 1 to 2.

[0076] ( Figure 10 : Step S701)

[0077] The arithmetic unit 120 classifies the battery based on the positive electrode material and the negative electrode material of the battery 200. Examples of the classification will be described later. Here, the battery 200 is classified into one of types 1 to 4.

[0078] ( Figure 10 : Steps S702 to S705)

[0079] The arithmetic unit 120 performs a temperature region determination corresponding to the classification result of S701. S702 is performed for type 1, S703 is performed for type 2, S704 is performed for type 3, and S705 is performed for type 4. Different temperature region determination processes can be performed for each type of the battery 200, or the same determination process can be performed for any type. The detailed content of each step will be described later.

[0080] Figure 11 Represents an example of the combination of the positive electrode material and the negative electrode material. For example, the following combinations can be considered. Battery type 1: Positive electrode material A (lithium manganate) and negative electrode material E (graphite), Battery type 2: Positive electrode material B (lithium nickel manganese cobalt oxide) and negative electrode material E, Battery type 3: Positive electrode material C (lithium iron phosphate) and negative electrode material E, Battery type 4: Positive electrode material D (lithium manganate) and negative electrode material F (lithium titanate). According to the combination of various electrode materials, batteries other than these 4 types can also be classified.

[0081] Figure 12 Represents an example of the temperature region. The temperature region has different definitions according to the battery type. Regarding type 1 and type 2, the temperature region and the C-rate have Figure 12 the relationship as described in the upper paragraph. Regarding type 3, the temperature region and the C-rate have Figure 12 the relationship as described in the middle paragraph. Regarding type 4, the temperature region, the internal resistance, and dV1 / dt1 have Figure 12 the relationship as described in the lower paragraph. In S702 to S705, the temperature region is determined according to these relationships.

[0082] In S702, on the amplitude frequency characteristic calculated in S301, when the amplitude on the low-frequency side increases relative to the reference value, it is determined that the temperature region of the battery 200 is temperature region B. When there is no increase in amplitude, it is determined to be temperature range A. An example of the amplitude frequency characteristic in this step is described later.

[0083] In S703, the temperature region of the type 2 battery is not discriminated. This is because whether the type 2 battery is in temperature region A or B, it has a tendency to deteriorate with the same activation energy. Therefore, it is not necessary to distinguish the temperature region when applying the acceleration coefficient described later. In addition, the relationship between dV2 / dt2 and SoH can be obtained regardless of the temperature region. Therefore, SoH can be estimated as described later using this situation. Type 2 also does not need to distinguish the temperature region in this regard.

[0084] In S704, on the amplitude frequency characteristic calculated in S301, when the amplitude on the low-frequency side increases relative to the reference value, it is determined that the temperature region of the battery 200 is temperature region E. When there is no increase in amplitude, it is determined to be temperature region D. An example of the amplitude frequency characteristic in this step is common to the example in S702.

[0085] Figure 13This is an example of the amplitude-frequency characteristics used in S702 and S704. When the battery 200 deteriorates mainly due to the use of the battery 200 in the temperature region B or E, the influence appears in the reaction of the positive electrode and the diffusion resistance. Therefore, when the amplitude on the low-frequency side below f2 increases above the threshold with respect to the reference value as shown by the dashed line in Figure 13 it can be determined that the battery 200 has been used in the temperature region B or E. Regarding the reference value (solid line), it can be obtained by actual measurement in advance, for example.

[0086] Figure 14 This is a flowchart illustrating the order of determining the temperature region in S705. The arithmetic unit 120 pre-obtains the first data describing the relationship between dV0 / dt0 and the internal resistance, and the second data describing the relationship between dV1 / dt1 (the third time change rate of the third difference) and the internal resistance in each temperature region (in the example of Figure 12 it is F to H). For example, this data can be pre-stored in the storage device provided in the battery diagnosis device 100.

[0087] The arithmetic unit 120 estimates the internal resistance of the battery 200 by using dV0 / dt0 and referring to the first data. Then, by using dV1 / dt1 and the estimated internal resistance and referring to the second data, the temperature region of the battery 200 is estimated. Regarding the second data, interpolation can also be performed for the missing part. For example, when obtaining dV1 / dt1 and the internal resistance corresponding to the region between temperature regions G and H, the temperature region between temperature regions G and H can be appropriately obtained through interpolation calculation.

[0088] In addition to the above, the arithmetic unit 120 can also estimate the C-rate used in the past in the battery 200 according to the relationship in Figure 12 . Specifically, by using the temperature region estimated through the above procedure and referring to the data (temperature region data) describing the relationship in Figure 12 , the C-rate used for this battery in the past can be estimated. For example, when the estimated temperature region of the battery of type 3 is D, it can be estimated that the C-rate used for this battery in the past is approximately constant. When it is estimated to be the temperature region C or E, at least it can be estimated that there is a possibility that the C-rate is not constant.

[0089] In addition to the above, the arithmetic unit 120 can also obtain the data describing the correlation between dV2 / dt2 and SoH in each temperature region, use dV2 / dt2 and refer to this data to estimate SoH for the batteries classified into each temperature region. And by applying the acceleration coefficient corresponding to each temperature region, the remaining life of the battery 200 can also be predicted. The acceleration coefficient is set by using a pre-made Eyering plot, etc.

[0090] <Embodiment 4>

[0091] Figure 15 Shows another structural example of the battery diagnostic device 100. The detection unit 110 can communicate with the arithmetic unit 120 via the communication unit 140 and via a network. In addition, the arithmetic unit 120 can also learn the measurement results of multiple batteries to update each determination criterion. Other structures are the same as those in Embodiments 1 to 3.

[0092] <Regarding the modification examples of the present invention>

[0093] The present invention is not limited to the above embodiments and includes various modification examples. For example, the above embodiments are the embodiments described in detail for easy understanding of the present invention and are not limited to having all the structures described. In addition, a part of the structure of a certain embodiment can be replaced with the structure of another embodiment, and in addition, the structure of another embodiment can be added to the structure of a certain embodiment. In addition, regarding a part of the structure of each embodiment, addition, deletion, and replacement of other structures can be performed.

[0094] In the above embodiments, the detection unit 110 and the arithmetic unit 120 can be constituted by hardware such as a circuit device installed with their functions, or can be constituted by a computing device such as a CPU (Central Processing Unit) executing software installed with their functions.

[0095] In the above embodiments, it is preferable that t2 is, for example, within several seconds at the latest from the start time of the rest period. The specific value of t2 varies widely depending on the individual battery and the type of battery, so it can be appropriately determined according to them.

[0096] Explanation of reference numerals

[0097] 100: Battery diagnostic device

[0098] 110: Detection unit

[0099] 120: Arithmetic unit

[0100] 130: UI

[0101] 200: Battery.

Claims

1. A battery diagnosis device that diagnoses the state of a battery, characterized in that, the battery diagnosis device includes: a detection unit that obtains a detection value of the voltage output by the battery; and an arithmetic unit that estimates the state of the battery using a difference representing the change over time of the voltage, the arithmetic unit determines whether the battery is in a first state based on a first difference that is the difference between the voltage at a first starting time point after an end time point when the battery has finished charging or discharging and the voltage at a first time point within a first period of 4 milliseconds or less from the end time point, the arithmetic unit uses a second difference that is the difference between the voltage at a second starting time point after the first starting time point and the voltage at a second time point within a second period from the second starting time point to determine whether the battery is in a second state.

2. The battery diagnosis device according to claim 1, characterized in that, when the first time change rate of the first difference is equal to or greater than a first threshold, the arithmetic unit determines that the battery is in the first state, the arithmetic unit measures the second time change rate of the second difference multiple times, when the deviation between the respective second time change rates is equal to or greater than a second threshold, or when the charging voltage of the battery exceeds the discharging voltage, the arithmetic unit determines that the battery is in the second state.

3. The battery diagnosis device according to claim 1, characterized in that, the second period is an interval between the frequency of an inflection point where the slope of the phase changes from negative to positive in the phase frequency characteristic obtained by performing a Fourier transform on the change over time of the voltage after the end time point and the frequency corresponding to the time constant of the negative electrode of the battery, or the second period is within a range of an interval divided by an inflection point when representing the change over time of the voltage after the end time point on a logarithmic time axis.

4. The battery diagnosis device according to claim 1, characterized in that, when the arithmetic unit determines that the battery is in the first state, it outputs a judgment result indicating that the battery is in a state where an abnormal voltage or abnormal resistance makes it non - chargeable or dischargeable, or a state immediately preceding it, when the arithmetic unit determines that the battery is in the second state, it outputs a judgment result indicating that the battery is in a state where the deterioration has accelerated and a sharp decrease in SoH is observed, or a state immediately preceding it.

5. The battery diagnosis device according to claim 1, characterized in that, when the arithmetic unit determines that the battery is not in either the first state or the second state, it outputs a judgment result indicating that the battery is in a state where it can be used normally, when the arithmetic unit determines that the battery is in the first state or the second state, even if the cumulative usage time of the battery has not reached a predetermined usable time, it outputs a notification recommending battery replacement.

6. The battery diagnosis device according to claim 1, wherein, the operation unit defines the relationship between the occurrence rate of each of the first state and the second state and the cumulative usage time of the battery through a region where the occurrence rate of each of the first state and the second state decreases together with the cumulative usage time, a region where the occurrence rate is constant regardless of the cumulative usage time, and a region where the occurrence rate increases together with the cumulative usage time, and the operation unit determines, according to the definition, at least any one of the occurrence rates of each of the first state and the second state and whether the battery can be used continuously.

7. The battery diagnosis device according to claim 1, wherein, the operation unit estimates the relationship between the value of SoH and the number of the batteries having the value according to a normal distribution for a plurality of the batteries determined to be in the second state, and the operation unit quantifies the quality of the battery using the standard deviation of the normal distribution.

8. The battery diagnosis device according to claim 1, wherein, the operation unit obtains a phase frequency characteristic obtained by performing a Fourier transform on a measurement result of the temporal change of the voltage after the end time point, and in the phase frequency characteristic, when the phase in a region corresponding to the diffusion resistance of the battery decreases by more than a threshold with respect to a reference value, the operation unit determines that dendrites are generated inside the battery.

9. The battery diagnosis device according to claim 1, wherein, the operation unit determines which one of the first type, the second type, the third type, and the fourth type the battery belongs to according to the material of the electrode of the battery, the operation unit estimates a temperature region that is most dominant for the deterioration of the battery for each type of the battery, when the battery is of the first type, in an amplitude frequency characteristic obtained by performing a Fourier transform on the temporal change of the voltage after the end time point, when the amplitude in a region corresponding to the positive electrode of the battery increases by more than a threshold with respect to a reference value, it is estimated that the temperature region is the first temperature region, and when it does not increase, it is estimated that the temperature region is less than the first temperature region, when the battery is of the second type, the operation unit does not estimate the temperature region, when the battery is of the third type, in an amplitude frequency characteristic obtained by performing a Fourier transform on the temporal change of the voltage after the end time point, when the amplitude in a region corresponding to the positive electrode of the battery increases by more than a threshold with respect to a reference value, it is estimated that the temperature region is the second temperature region, and when it does not increase, it is estimated that the temperature region is less than the second temperature region, when the battery is of the fourth type, the operation unit estimates the internal resistance of the battery according to the first difference, and uses the estimated internal resistance to estimate the temperature region.

10. The battery diagnosis device according to claim 9, Characterized in that, The arithmetic unit obtains a third time change rate of a third difference in voltage during a period between the first difference and the second difference; The arithmetic unit obtains a correspondence relationship among the internal resistance of the battery, the third time change rate, and the temperature region; The arithmetic unit uses the deduced internal resistance and the third time change rate and refers to the correspondence relationship to deduce the temperature region.

11. The battery diagnosis device according to claim 9, Characterized in that, The battery of the first type is composed of a first positive electrode material and a first negative electrode material; The battery of the second type is composed of a second positive electrode material and the first negative electrode material; The battery of the third type is composed of a third positive electrode material and the first negative electrode material; The battery of the fourth type is composed of a fourth positive electrode material and a second negative electrode material.

12. The battery diagnosis device according to claim 9, Characterized in that, The arithmetic unit respectively obtains temperature region data describing a relationship between the temperature region and the C-rate to be used in the temperature region for the first type, the second type, and the third type; The temperature region data describes that the C-rate during charge and discharge is constant regardless of the temperature region for the batteries of the first type and the second type; The temperature region data describes that for the battery of the third type, the C-rate during charge and discharge decreases as the temperature rises in the second temperature region, the C-rate during charge and discharge is constant in a third temperature region lower than the second temperature region, and the C-rate during charge and discharge decreases as the temperature decreases in a fourth temperature region lower than the third temperature region; The arithmetic unit uses the deduced temperature region and refers to the temperature region data to deduce the C-rate used for the battery in the past.

13. The battery diagnosis device according to claim 9, Characterized in that, The arithmetic unit deduces the remaining life of the battery by applying an acceleration constant corresponding to the deduced temperature region.

14. A battery diagnosis method for diagnosing the state of a battery, Characterized in that, It has: A step of obtaining a detected value of the voltage output by the battery; and A step of using a difference representing the change over time of the voltage to deduce the state of the battery, In the step of making the deduction, based on a first difference as the difference, it is judged whether the battery is in a first state, where the first difference is a difference between the voltage at a first starting time point after an end time point when the battery has ended charging or discharging and the voltage at a first time point within a first period of 4 milliseconds or less from the end time point; In the step of making the deduction, a second difference as the difference is used to judge whether the battery is in a second state, where the second difference is a difference between the voltage at a second starting time point after the first starting time point and the voltage at a second time point within a second period from the second starting time point.

15. The battery diagnosis method according to claim 14, characterized in that, the diagnosis is performed on the battery with an internal resistance of 1 mΩ or less.

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