Battery diagnostic equipment

Abstract

A battery diagnosing device (12) according to the present invention comprises a current source (40) for applying a pulse current to a battery (10), a voltage sensor (42) for detecting a voltage between terminals of the battery (10), and a control device (54), the control device (54) including one or a plurality of processors (60) and one or a plurality of memories (62) connected to the processors (60), wherein the processors (60) execute processing including: acquiring a voltage response obtained by causing one of the pulse currents to be applied to the battery (10) from the current source (40); deriving, on the basis of the voltage response, an index indicating a comparison between an ON ATRF, which is an apparent transient response resistance function of the battery (10) when the pulse current is turned on, and an OFF ATRF, which is the apparent transient response resistance function of the battery (10) when the pulse current is turned off; and determining a degree of lithium precipitation in the battery (10) on the basis of the derived index.

Description

[Technical Field]

[0001] The present invention relates to a battery diagnostic device for diagnosing the state of a battery. [Background technology]

[0002] For example, Patent Document 1 discloses a battery diagnostic device that determines the degree of battery degradation. This battery diagnostic device obtains a resistance value from the current and voltage when a pulse current is applied to the battery, and determines the degree of battery degradation based on the resistance value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6991616 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in lithium-ion batteries, a phenomenon occurs in which lithium gradually deposits on the negative electrode. This deposit of lithium accelerates deterioration and, in some cases, may cause thermal runaway of the battery. Detecting this lithium deposition requires disassembling the battery and visually inspecting it. This requires a great deal of time, effort, and expense to determine the degree of deterioration, such as lithium deposition.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a battery diagnostic device that can easily diagnose battery degradation. [Means for solving the problem]

[0006] In order to solve the above problem, a battery diagnostic device according to one embodiment of the present invention comprises: A battery diagnostic device for diagnosing the state of a battery, a current source capable of applying a pulsed current to the battery; a voltage sensor for detecting a voltage between the terminals of the battery; a control device; Equipped with The control device one or more processors; one or more memories coupled to said processor; and The processor: applying one of the pulse currents from the current source to the battery and obtaining a voltage response; Deriving an index indicating a comparison between an on-ATRF, which is an apparent transient response resistance function of the battery when the pulse current is turned on, and an off-ATRF, which is an apparent transient response resistance function of the battery when the pulse current is turned off, based on the voltage response; determining the degree of lithium deposition in the battery based on the derived index; Execute the process including. [Effects of the Invention]

[0007] According to the present invention, it is possible to easily diagnose the deterioration of a battery. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a battery diagnostic system according to this embodiment. [Figure 2] FIG. 2 is a diagram showing an example of pulse current and voltage response when there is almost no lithium deposition. [Figure 3] FIG. 3 is a diagram showing an example of the relationship between the specific time and the on-ATRF and an example of the relationship between the specific time and the off-ATRF in the case where there is almost no lithium deposition. [Figure 4] FIG. 4 is a diagram showing an example of pulse current and voltage response when there is a large amount of lithium deposition. [Figure 5]FIG. 5 is a diagram showing an example of the relationship between the specific time and on-ATRF, and an example of the relationship between the specific time and off-ATRF, when lithium deposition is large. [Figure 6] FIG. 6 is a diagram illustrating an example of the determination criteria table. [Figure 7] FIG. 7 is a flowchart illustrating the flow of operations of the battery diagnostic device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0010] 1 is a schematic diagram showing the configuration of a battery diagnostic system 1 according to this embodiment. The battery diagnostic system 1 includes a battery 10 and a battery diagnostic device 12.

[0011] The battery 10 is, for example, a lithium-ion battery. The battery 10 is, for example, one that is mounted on and used in an electric vehicle or a hybrid electric vehicle, but is not limited to this example and may be one that is used in any electrical device or the like.

[0012] The battery 10 has two current terminals 20 and two voltage terminals 21. A first current terminal of the two current terminals 20 and a first voltage terminal of the two voltage terminals 21 of the battery 10 are connected to the positive electrode of the battery 10. A second current terminal of the two current terminals 20 and a second voltage terminal of the two voltage terminals 21 of the battery 10 are connected to the negative electrode of the battery 10.

[0013] Here, if lithium precipitates in the negative electrode of a lithium-ion battery, the precipitated lithium prevents lithium ions in the solution from migrating into the graphite layer of the negative electrode and induces side reactions on the surface of the graphite layer, thereby degrading the performance of the lithium-ion battery. In other words, the more lithium precipitates, the more the deterioration of the battery 10 progresses.

[0014] The battery diagnostic device 12 is a device that diagnoses the state of the battery 10, such as the degree of deterioration. More specifically, the battery diagnostic device 12 diagnoses the degree of lithium deposition. The battery diagnostic device 12 is not mounted on the vehicle in which the battery 10 is mounted, for example, but is managed by a company that repairs or inspects the vehicle. Note that the battery diagnostic device 12 may also be mounted on the vehicle in which the battery 10 is mounted.

[0015] The battery diagnostic device 12 includes two external current terminals 30, two external voltage terminals 31, two current cables 32, and two voltage cables 33. A first current cable of the two current cables 32 is connected to a first external current terminal of the two external current terminals 30. An end of the first current cable opposite the first external current terminal is electrically connectable to a first current terminal of the two current terminals 20 of the battery 10. A second current cable of the two current cables 32 is connected to a second external current terminal of the two external current terminals 30. An end of the second current cable opposite the second external current terminal is electrically connectable to a second current terminal of the two current terminals 20 of the battery 10. A first voltage cable of the two voltage cables 33 is connected to a first external voltage terminal of the two external voltage terminals 31. The end of the first voltage cable opposite the first external voltage terminal is electrically connectable to a first voltage terminal of two voltage terminals 21 of battery 10. A second voltage cable of two voltage cables 33 is connected to a second external voltage terminal of two external voltage terminals 31. The end of the second voltage cable opposite the second external voltage terminal is electrically connectable to a second voltage terminal of two voltage terminals 21 of battery 10. Note that in the case of a battery 10 that does not have a voltage terminal 21, the voltage terminal 21 may be connected to the same terminal as the current terminal 20. In this embodiment, by connecting the voltage terminal 21 to a position closer to battery 10 than the current terminal 20, it is possible to achieve measurement accuracy comparable to that of a battery 10 that has both a current terminal 20 and a voltage terminal 21.

[0016] The battery diagnostic device 12 includes a current source 40, a voltage sensor 42, a temperature sensor 44, and an SOC adjustment device 46. The SOC (State Of Charge) is a ratio of the battery 10 to the fully charged capacity. Indicates the current charge capacity expressed as a percentage.

[0017] The current source 40 is electrically connected to each of the two external current terminals 30. The current source 40 is configured to be capable of generating a pulse current, which is a pulsed current. The current source 40 is also configured to be capable of changing the current value of the pulse current that it generates.

[0018] With the external current terminal 30 electrically connected to the current terminal 20 of the battery 10 through the current cable 32 , the current source 40 is capable of applying a pulsed current to the battery 10 .

[0019] The voltage sensor 42 is electrically connected to each of the two external voltage terminals 31. The voltage sensor 42 detects the voltage between the two external voltage terminals 31. That is, when the external voltage terminal 31 is electrically connected to the voltage terminal 21 of the battery 10 via the voltage cable 33, the voltage sensor 42 detects the voltage between the voltage terminals 21 of the battery 10. Hereinafter, for ease of explanation, the electrical connection of the external current terminal 30 to the current terminal 20 of the battery 10 via the current cable 32, and the electrical connection of the external voltage terminal 31 to the voltage terminal 21 of the battery 10 via the voltage cable 33 may be referred to as the battery diagnostic device 12 being connected to the battery 10.

[0020] The temperature sensor 44 detects the temperature of the battery 10. In order to appropriately detect the temperature of the battery 10, the temperature sensor 44 may be in contact with the battery 10 or may be disposed in the vicinity of the battery 10, for example.

[0021] The SOC adjusting device 46 is electrically connected between the two external current terminals 30. The SOC adjusting device 46 is configured to receive power output from the battery 10 when the battery diagnostic device 12 is connected to the battery 10. The SOC adjusting device 46 is also configured to supply power to the battery 10 when the battery diagnostic device 12 is connected to the battery 10.

[0022] That is, the SOC adjusting device 46 is capable of intentionally lowering the SOC by discharging the battery 10, and is also capable of intentionally raising the SOC by charging the battery 10. The SOC adjusting device 46 may be any electrical device capable of charging and discharging the battery 10, such as a motor generator or a battery separate from the battery 10. Note that the SOC adjusting device 46 may be configured, for example, by combining an electrical device capable of discharging the battery 10 with an electrical device capable of charging the battery 10.

[0023] The battery diagnostic device 12 includes an input / output device 50, a storage device 52, and a control device 54. The input / output device 50 has an input device, such as a keyboard, a mouse, or a touch panel, that accepts input operations from a user. The input / output device 50 also has an output device, such as a display device that displays diagnostic results, that presents various types of information to the user.

[0024] The storage device 52 is configured with a non-volatile storage element such as a hard disk drive or a flash memory, etc. The storage device 52 may store diagnostic results and the like.

[0025] The control device 54 includes one or more processors 60 and one or more memories 62 connected to the processors 60. The memories 62 include a ROM in which programs and the like are stored and a RAM as a work area. The processor 60 cooperates with the programs stored in the memory 62 to control the entire battery diagnostic device 12.

[0026] By executing the program, the processor 60 also functions as a voltage response acquisition unit 70, an index derivation unit 72, a determination unit 74, a determination criterion setting unit 76, and an SOC adjustment unit 78. The following description will be given assuming that the battery diagnostic device 12 is connected to the battery 10.

[0027] The voltage response acquisition unit 70 applies one pulse current from the current source 40 to the battery 10. When the pulse current is applied to the battery 10, a voltage is generated between the voltage terminals 21 of the battery 10. The voltage sensor 42 detects the voltage between the voltage terminals 21 of the battery 10. Hereinafter, the voltage obtained by applying such a pulse current may be referred to as a voltage response. The voltage response acquisition unit 70 acquires the voltage response detected by the voltage sensor 42.

[0028] Figure 2 shows an example of pulse current and voltage response when there is almost no lithium deposition. In Figure 2, the time "τ" of the pulse width "W" is set to, for example, 10 seconds, but may be set to any time. "Ip" indicates the current value of the pulse current.

[0029] "TBon" indicates the timing when the pulse current starts to rise, i.e., the timing of the rising edge of the pulse current. "TBoff" indicates the timing when the pulse current starts to fall, i.e., the timing of the falling edge of the pulse current. Time "τ" indicates the application time of the pulse current when the rising start timing "TBon" of the pulse current is set to 0. Time "t" indicates an arbitrary time when the rising start timing "TBon" of the pulse current is set to 0.

[0030] When there is almost no lithium deposition, the time it takes for the voltage to drop in response to turning off the pulse current is approximately the same as the time it takes for the voltage to rise in response to turning on the pulse current.

[0031] "Ton" indicates the timing when a specific time "Ts" has elapsed since the timing "TBon" of the rising edge of the pulse current. "Toff" indicates the timing when a specific time "Ts" has elapsed since the timing "TBoff" of the falling edge of the pulse current. In other words, "Toff" is the timing obtained by adding the specific time "Ts" to the time "τ" based on "TBon." Note that the specific time "Ts" between "TBon" and "Ton" is substantially the same as the specific time "Ts" between "TBoff" and "Toff."

[0032] When the timing when an arbitrary time "t" has passed since "TBon" is "Ton", the specific time "Ts" between "TBon" and "Ton" is the same as the time "t". Also, when the timing when an arbitrary time "t" has passed since "TBon" is "Toff", the specific time "Ts" between "TBoff" and "Toff" is the same as the time "t-τ".

[0033] "V0" indicates the open-circuit voltage value of the battery 10. Here, it is assumed that the voltage value at the timing "TBon" when the pulse current starts to rise is "V0". "Von" indicates the voltage value detected by the voltage sensor 42 at "Ton". "Vτ" indicates the voltage value detected by the voltage sensor 42 at the timing "TBoff" when the pulse current starts to fall. "Voff" indicates the voltage value detected by the voltage sensor 42 at "Toff".

[0034] Here, an apparent transient resistance function (ATRF) can be calculated based on the current value of the pulse current and the voltage response obtained by applying the pulse current. The ATRF is a function that indicates the time change in the apparent transient resistance value in response to the on / off of the pulse current.

[0035] "von", which indicates the voltage response when a pulse current is turned on, can be defined as shown in the following equation (1). von=Von-V0 (1)

[0036] That is, "von" is the voltage value at the timing when an arbitrary time "t" has elapsed since "TBon", for example, the voltage value "Von" at the timing "Ton" when a specific time "Ts" has elapsed, minus the open circuit voltage value "V0" at "TBon". "von" differs depending on the arbitrary time "t" from "TBon" or the specific time "Ts".

[0037] ATRF based on the voltage response when a pulse current is turned on is sometimes called on-ATRF, and is sometimes abbreviated as "ATRFon(t)."

[0038] The on-ATRF "ATRFon(t)" is calculated by dividing the voltage response "von" when the pulse current is turned on by the current value "Ip" of the pulse current, as shown in the following equation (2). ATRFon(t)=von / Ip (2)

[0039] As described above, "von" differs depending on the arbitrary time "t" from "TBon", and therefore ATRFon(t) differs depending on the time "t" and is a function with time "t" as a variable. Note that, since the specific time "Ts" between "TBon" and "Ton" corresponds to time "t", ATRFon(t) can also be said to be a function with the specific time "Ts" between "TBon" and "Ton" as a variable.

[0040] "voff", which indicates the voltage response when the pulse current is turned off, can be defined as shown in the following equation (3). voff=-(Vτ-Voff) (3)

[0041] As described above, the specific time "Ts" between "TBoff" and "Toff" can be expressed as "t-τ" using an arbitrary time "t" and the pulse current application time "τ." "Vτ-Voff" is the difference value obtained by subtracting the voltage value at "t-τ," for example, "Voff," from the voltage value "Vτ" at "TBoff." In other words, "voff" is the voltage value minus the difference value. "voff" varies depending on the arbitrary time "t" from "TBon" or the specific time "Ts."

[0042] ATRF based on the voltage response when the pulse current is turned off is sometimes called off-ATRF, and is sometimes expressed as "ATRFoff(t-τ)".

[0043] The off ATRF, "ATRFoff(t-τ)," is calculated by dividing the voltage response, "voff," when the pulse current is turned off by the current value, "Ip," of the pulse current, as shown in the following equation (4). ATRFoff(t-τ)=voff / Ip ···(4)

[0044] As described above, since "voff" differs depending on the arbitrary time "t" from "TBon", ATRFoff(t-τ) differs depending on the arbitrary time "t" from "TBon", more specifically, the time "t-τ", and is a function with the time "t" or the time "t-τ" as a variable. Note that since the specific time "Ts" between "TBoff" and "Toff" corresponds to the time "t-τ", ATRFoff(t-τ) can also be said to be a function with the specific time "Ts" between "TBoff" and "Toff" as a variable.

[0045] FIG. 3 shows an example of the relationship between the specific time and on-ATRF, and an example of the relationship between the specific time and off-ATRF, when there is almost no lithium deposition. In FIG. 3, the horizontal axis is time "t" for the solid line 100, and time "t-τ" for the dashed line 102, i.e., the specific time "Ts", and is shown in logarithm. The vertical axis is on-ATRF or off-ATRF. The solid line 100 shows the relationship between the specific time and on-ATRF. The dashed line 102 shows the relationship between the specific time and off-ATRF.

[0046] As shown in FIG. 3, when there is little lithium deposition, the on-ATRF and off-ATRF at a common specific time are roughly consistent.

[0047] FIG. 4 is a diagram showing an example of pulse current and voltage response when there is a large amount of lithium deposition.

[0048] As shown in Figure 4, when there is a lot of lithium deposition, the time it takes for the voltage to drop when the pulse current is turned off is longer than the time it takes for the voltage to rise when the pulse current is turned on, compared to Figure 2.

[0049] 5 shows an example of the relationship between the specific time and ON ATRF and an example of the relationship between the specific time and OFF ATRF when lithium deposition is large. A solid line 110 shows the relationship between the specific time and ON ATRF. A dashed line 112 shows the relationship between the specific time and OFF ATRF.

[0050] As shown in FIG. 5, when there is a large amount of lithium deposition, the ON ATRF and OFF ATRF at a common specific time are different from each other compared to FIG.

[0051] Therefore, the index derivation unit 72 shown in FIG. 1 derives an index indicating a comparison between ON ATRF and OFF ATRF based on the voltage response.

[0052] The above-mentioned index is assumed to be, for example, the resistance function ratio "RR(Ts)" which indicates the ratio of the off ATRF "ATRFoff(t-τ)" to the on ATRF "ATFRon(t)", as shown in the following equation (5). The specific time "Ts" of "ATRFoff(t-τ)" used to derive the resistance function ratio "RR(Ts)" is assumed to be the same as the specific time "Ts" of "ATRFon(t)". RR(Ts)=ATRFoff(t) / ATRFon(t-τ) ···(5)

[0053] The index derivation unit 72 derives multiple indices, e.g., multiple resistance function ratios, for different specific times. For example, the index derivation unit 72 derives resistance function ratios "RR(0.05)," "RR(0.089)," "RR(0.16)," "RR(0.28)," and "RR(0.5)" when the specific time "Ts" is "0.05 sec," "0.089 sec," "0.16 sec," "0.28 sec," and "0.5 sec," respectively. Note that the specific time is not limited to the exemplified time and may be set to any time within a range that does not exceed the pulse width of the pulse current. Furthermore, the number of resistance function ratios is not limited to the exemplified five and may be any number.

[0054] The determination unit 74 determines the degree of lithium deposition, which indicates the degree of deterioration of the battery 10, based on the average value of multiple indicators, for example, the average value of multiple resistance function ratios. Hereinafter, the average value of multiple resistance function ratios may be referred to as the average resistance function ratio.

[0055] Here, the memory 62 stores in advance a criterion table indicating criteria for determining the degree of lithium deposition in the battery 10. The determination unit 74 determines the degree of lithium deposition in the battery 10 based on the criterion table and the average resistance function ratio.

[0056] 6 is a diagram showing an example of the criterion table, in which the range of the average resistance function ratio is associated with the State of Li Deposition Tendency (SLDT). Here, SLDT refers to the state of tendency for lithium precipitation and is an index for determining the ease of lithium precipitation. SLDT, for example, classifies the degree of lithium precipitation in battery 10 into multiple stages. The larger the SLDT value, the greater the amount of lithium precipitation, i.e., the higher the proportion of the charging current used for the lithium precipitation reaction. An SLDT value of "0" means that application of a certain magnitude of charging pulse current value can be considered to result in substantially no lithium precipitation.

[0057] 6, the criterion table associates the range of the average resistance function ratio with the SLDT so that the smaller the average resistance function ratio, the larger the SLDT value. For example, when the average resistance function ratio is "0.68", the determining unit 74 determines the SLDT to be "3" from the criterion table.

[0058] The voltage response acquisition unit 70 applies a plurality of pulse currents with different current values ​​to the battery 10 in stages, thereby acquiring a voltage response for each current value. For example, the voltage response acquisition unit 70 increases the current value of the pulse current in stages in the order of "0.1 C," "0.3 C," "0.5 C," and "1 C." The C rate "C" indicates the ratio of the charge / discharge current value to the battery capacity (charge / discharge current value (A) / battery capacity (Ah)).

[0059] The index derivation unit 72 derives an index for each current value based on the voltage response for each current value. For example, the index derivation unit 72 derives an average resistance function ratio for "0.1 C", an average resistance function ratio for "0.3 C", an average resistance function ratio for "0.5 C", and an average resistance function ratio for "1 C".

[0060] The determination unit 74 determines the degree of lithium deposition in the battery 10 based on multiple indicators for each current value. For example, the determination unit 74 determines an SLDT corresponding to the average resistance function ratio of "0.1 C," an SLDT corresponding to the average resistance function ratio of "0.3 C," an SLDT corresponding to the average resistance function ratio of "0.5 C," and an SLDT corresponding to the average resistance function ratio of "1 C." Hereinafter, for ease of explanation, such an SLDT for each current value may be referred to as an SLDT for each current value.

[0061] The determination unit 74 combines the determined SLDTs for each current value to determine the SLDT that is the final determination result of the degree of lithium deposition in the battery. Hereinafter, for convenience of explanation, this SLDT of the final determination result may be referred to as the total SLDT. For example, the determination unit 74 may determine the average value of the SLDTs for each current value as the total SLDT. Alternatively, the determination unit 74 may determine the median value of the SLDTs for each current value as the total SLDT.

[0062] In the battery diagnostic device 12 of this embodiment, the degree of lithium deposition in the battery is determined based on an index that indicates a comparison between ON ATRF and OFF ATRF, which allows the degree of lithium deposition to be easily recognized.

[0063] Furthermore, the resistance function ratio derived based on the voltage response depends on the temperature of the battery 10. For example, when the temperature of the battery 10 is relatively low, the resistance function ratio decreases compared to when the temperature of the battery 10 is relatively high.

[0064] 1 acquires the temperature of the battery 10 using the temperature sensor 44 before applying a pulse current to the battery 10. The judgment criterion setting unit 76 determines the judgment criterion for determining the degree of lithium deposition in the battery 10 based on the acquired temperature of the battery 10.

[0065] For example, the memory 62 stores in advance a criterion table for each temperature of the battery 10. The criterion setting unit 76 selects a criterion table corresponding to the acquired temperature of the battery 10 from among the multiple criterion tables.

[0066] The determination unit 74 determines the degree of lithium deposition in the battery by comparing the determined determination criterion with the index indicating a comparison between ON ATRF and OFF ATRF. For example, the determination unit 74 determines the SLDT based on the determination criterion table selected by the determination criterion setting unit 76 and the average resistance function ratio derived by the index derivation unit 72.

[0067] In the battery diagnostic device 12, an appropriate determination criterion is determined based on the temperature of the battery 10, so that the degree of lithium deposition can be determined more accurately.

[0068] Furthermore, the resistance function ratio derived based on the voltage response varies depending on the battery SOC, so the battery SOC is set to be approximately the same each time a diagnosis is performed.

[0069] More specifically, if the SOC of the battery 10 is outside a predetermined range before the pulse current is applied to the battery 10, the SOC adjustment unit 78 causes the SOC adjustment device 46 to adjust the SOC of the battery 10 so that the SOC of the battery 10 falls within the predetermined range. The predetermined range is, for example, a predetermined error range including an SOC of 50%, but is not limited to this example and may be any range.

[0070] For example, when the SOC of the battery 10 is higher than the upper limit of a predetermined range, the SOC adjusting unit 78 causes the SOC adjusting device 46 to function as a load and transfers the power of the battery 10 to the SOC adjusting device 46, thereby lowering the SOC of the battery 10. Furthermore, when the SOC of the battery 10 is lower than the lower limit of the predetermined range, the SOC adjusting unit 78 causes the SOC adjusting device 46 to function as a power source and transfers the power of the SOC adjusting device 46 to the battery 10, thereby raising the SOC of the battery 10.

[0071] In the battery diagnostic device 12, the SOC of the battery 10 is intentionally adjusted before the diagnosis is performed, so that the degree of lithium deposition can be determined more accurately.

[0072] Fig. 7 is a flowchart illustrating the flow of operations of the battery diagnostic device 12. When the battery diagnostic device 12 is connected to the battery 10 and receives an input operation to instruct the start of diagnosis, a series of processes shown in Fig. 12 starts.

[0073] First, the SOC adjusting unit 78 derives the current SOC of the battery 10 (S10). For example, the SOC adjusting unit 78 acquires the current voltage from the voltage sensor 42, and estimates the current SOC of the battery 10 based on the acquired current voltage.

[0074] Next, the SOC adjustment unit 78 determines whether the current SOC is within a predetermined range (S11). If the current SOC is outside the predetermined range (NO in S11), the SOC adjustment unit 78 intentionally adjusts the SOC using the SOC adjustment device 46 so that the battery SOC is within the predetermined range (S12), and proceeds to the processing of step S13. If the current SOC is within the predetermined range (YES in S11), the SOC adjustment device 46 proceeds to the processing of step S13.

[0075] In step S13, the determination criterion setting unit 76 acquires the temperature of the battery 10 by the temperature sensor 44 (S13). The determination criterion setting unit 76 sets the determination criterion based on the acquired battery temperature (S14).

[0076] Next, the voltage response acquisition unit 70 determines the current value of the pulse current to be applied from among the candidate current values ​​(S15). The voltage response acquisition unit 70 applies the pulse current of the determined voltage value from the current source 40 to the battery (S16). In parallel with the application of the pulse current, the voltage response acquisition unit 70 acquires the voltage response detected by the voltage sensor 42 (S17). The voltage response acquisition unit 70 may store the acquired voltage response in the memory 62 or the storage device 52.

[0077] Next, the index derivation unit 72 derives the on ATRF based on the voltage response when the pulse current is turned on (S18). The index derivation unit 72 derives the off ATRF based on the voltage response when the pulse current is turned off (S19). At this time, the index derivation unit 72 may check whether the on ATRF and the off ATRF are clearly abnormal values. If it is determined that the on ATRF or the off ATRF is an abnormal value, the derivation of the resistance function ratio and the determination of the SLDT by current value may be omitted, and the on ATRF and off ATRF that are abnormal values ​​may be excluded from the derivation of the overall SLDT.

[0078] Next, the index derivation unit 72 divides the off ATRF by the on ATRF to derive a resistance function ratio (S20). At this time, the index derivation unit 72 derives the resistance function ratio at the specific time using the off ATRF and on ATRF that have a common specific time. Furthermore, the index derivation unit 72 derives resistance function ratios for multiple specific times to derive multiple resistance function ratios. Next, the index derivation unit 72 averages the multiple resistance function ratios by the number of resistance function ratios to derive an average resistance function ratio (S21).

[0079] Next, the determination unit 74 determines the SLDT for each current value for the current value determined in step S15 based on the determination criterion set in step S14 and the average resistance function ratio derived in step S21 (S22). Note that the determination unit 74 may store the determination result of the SLDT for each current value in the memory 62 or the storage device 52.

[0080] Next, the determination unit 74 determines whether the measurement completion condition is met (S23). For example, the determination unit 74 determines that the measurement completion condition is met when the determination of the SLDT by current value is completed for all candidate current values. Note that the measurement completion condition is not limited to this example, and any condition may be set.

[0081] If the measurement completion condition is not met (NO in S23), the determination unit 74 returns to step S15 and determines an arbitrary current value from among the current value candidates for which the current-value-specific SLDT determination has not yet been performed (S15). Then, the battery diagnostic device 12 executes the processes from step S16 onwards again.

[0082] If the measurement completion condition is met (YES in S23), the determination unit 74 combines the SLDTs for each current value determined for each current value to determine the total SLDT (S24). The determination unit 74 notifies the user of the total SLDT as the diagnosis result (S25), and ends the series of processes. For example, the determination unit 74 displays the total SLDT as the diagnosis result on the display device of the input / output device. Note that the notification method is not limited to this example, and any method that allows the user to appropriately recognize the diagnosis result may be used.

[0083] As described above, the battery diagnostic device 12 of this embodiment determines the degree of lithium precipitation in the battery 10 based on an index that indicates a comparison between the on-ATRF when the pulse current is turned on and the off-ATRF when the pulse current is turned off. As a result, the battery diagnostic device 12 of this embodiment does not require disassembly of the battery 10, and can easily diagnose lithium precipitation, which indicates deterioration of the battery 10.

[0084] Furthermore, the index showing the comparison between ON ATRF and OFF ATRF changes depending on the degree of lithium precipitation in the lithium ion battery. The battery diagnostic device 12 of this embodiment performs diagnosis using an index related to lithium precipitation, and therefore can clearly indicate the degree of lithium precipitation.

[0085] Furthermore, the battery diagnostic device 12 of this embodiment can non-destructively diagnose the battery 10, thereby reducing the labor and costs involved in dismantling the battery 10. Furthermore, the battery diagnostic device 12 of this embodiment can easily reuse a battery 10 with a small degree of lithium deposition, for example.

[0086] Furthermore, in the battery diagnostic device 12 of this embodiment, the time required to turn the pulse current on and off is short, so the time required to diagnose the battery 10 is short, and diagnostic results can be obtained quickly.

[0087] Furthermore, the battery diagnostic device 12 of this embodiment uses a resistance function ratio indicating the ratio of OFF ATRF to ON ATRF as an index for comparing ON ATRF and OFF ATRF. This allows the battery diagnostic device 12 of this embodiment to easily and accurately diagnose lithium precipitation in the battery 10.

[0088] Furthermore, the indicator in the battery diagnostic device 12 of this embodiment indicates a comparison between the on-ATRF at a timing when a specific time has elapsed since the timing of the rising edge of the voltage corresponding to the on-state of the pulse current and the off-ATRF at a timing when a specific time has elapsed since the timing of the falling edge of the voltage corresponding to the off-state of the pulse current. That is, the battery diagnostic device 12 of this embodiment compares the on-ATRF and off-ATRF at timings when the specific time required for the on-ATRF and the specific time required for the off-ATRF are substantially the same. This allows the battery diagnostic device 12 of this embodiment to accurately determine the degree of lithium precipitation in the battery 10.

[0089] Furthermore, the battery diagnostic device 12 of this embodiment determines the degree of lithium deposition in the battery 10 based on the average value of multiple indexes with different specific times. This allows the battery diagnostic device 12 of this embodiment to reduce errors in the indexes and more accurately determine the degree of lithium deposition in the battery 10.

[0090] Furthermore, the battery diagnostic device 12 of this embodiment determines the degree of lithium deposition in the battery 10 based on multiple indexes for each current value of the pulse current. This allows the battery diagnostic device 12 of this embodiment to more accurately determine the degree of lithium deposition in the battery 10.

[0091] Furthermore, in the battery diagnostic device 12 of this embodiment, the SOC is adjusted so that it falls within a predetermined range before applying a pulse current, which allows the battery diagnostic device 12 of this embodiment to more accurately determine the degree of lithium deposition in the battery 10.

[0092] Furthermore, in the battery diagnostic device 12 of this embodiment, the judgment criterion is determined based on the temperature of the battery before the pulse current is applied, which allows the battery diagnostic device 12 of this embodiment to more accurately judge the degree of lithium deposition in the battery 10.

[0093] In the above embodiment, the resistance function ratio, which is the ratio of off ATRF to on ATRF, was used as an index for comparing on ATRF and off ATRF. However, the index is not limited to the resistance function ratio. For example, Equation (2) and Equation (4) in the above embodiment have in common the division by the pulse current Ip. Taking this into consideration, the degree of lithium deposition in the battery 10 may be determined based on the voltage ratio, which is the ratio of the voltage response "voff" when the pulse current is off to the voltage response "von" when the pulse current is on, instead of the resistance function ratio.

[0094] Furthermore, as explained using FIG. 5, when there is a large amount of lithium deposition, there is a deviation between the ON ATRF and the OFF ATRF. This deviation may be expressed by the absolute value of the difference between the ON ATRF and the OFF ATRF, instead of the resistance function ratio. In other words, the index showing the comparison between the ON ATRF and the OFF ATRF may be the absolute value of the difference between the ON ATRF and the OFF ATRF at a common specific time.

[0095] However, when the absolute value of the difference between the ON ATRF and OFF ATRF is used as an index, there is a risk that the error due to fluctuations in the ON ATRF or OFF ATRF will be larger than when the resistance function ratio is used. In other words, an embodiment using the resistance function ratio allows for more accurate determination than an embodiment using the absolute value of the difference.

[0096] In the above embodiment, the average resistance function ratio is derived by averaging multiple resistance function ratios for one current value. However, the index derivation unit 72 may derive at least one resistance function ratio for one current value, and may omit the derivation of the average resistance function ratio. In this case, the index derivation unit 72 may determine the SLDT for each current value from one resistance function ratio and the judgment criterion table.

[0097] In the above embodiment, the average resistance function ratio is derived for a plurality of current values. However, the index derivation unit 72 may derive the average resistance function ratio or the resistance function ratio for only one current value.

[0098] In the above embodiment, the SOC of the battery 10 is adjusted before the pulse current is applied. However, by preparing a criterion table corresponding to each of a plurality of SOCs, the SOC adjustment may be omitted.

[0099] While the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Explanation of symbols]

[0100] 10 batteries 12 Battery diagnostic device 40 current source 42 Voltage sensor 46 SOC adjustment device 54 Control device 60 processors 62 memory 70 Voltage response acquisition unit 72 Indicator derivation part 74 Judgment section 76 Judgment criteria setting section 78 SOC adjustment section

Claims

1. A battery diagnostic device for diagnosing the state of a battery, a current source capable of applying a pulsed current to the battery; a voltage sensor for detecting a voltage between the terminals of the battery; a control device; Equipped with The control device one or more processors; one or more memories coupled to the processor; and The processor: applying one of the pulse currents from the current source to the battery and obtaining a voltage response; Deriving an index indicating a comparison between an on-ATRF, which is an apparent transient response resistance function of the battery when the pulse current is turned on, and an off-ATRF, which is an apparent transient response resistance function of the battery when the pulse current is turned off, based on the voltage response; determining the degree of lithium deposition in the battery based on the derived index; A battery diagnostic device that performs a process including the steps of:

2. The battery diagnostic device according to claim 1 , wherein the index is a resistance function ratio indicating a ratio of the off ATRF to the on ATRF.

3. 3. The battery diagnostic device according to claim 1, wherein the index indicates a comparison between the on ATRF at a timing when a specific time has elapsed since the timing of a rising edge of a voltage corresponding to the on-state of the pulse current and the off ATRF at a timing when the specific time has elapsed since the timing of a falling edge of a voltage corresponding to the off-state of the pulse current.

4. The processor: In the process of deriving the index, a process is performed including deriving a plurality of the indexes having different specific times; the process of determining the degree of lithium deposition in the battery determines the degree of lithium deposition in the battery based on an average value of the plurality of indicators; The battery diagnostic device according to claim 3 , which executes a process including:

5. The processor: In the process of acquiring the voltage response, a plurality of pulse currents having different current values ​​are applied to the battery in a stepwise manner, and the voltage response is acquired for each of the current values; Perform a process including deriving the index for each current value based on the voltage response for each current value; Perform a process including In the process of determining the degree of lithium deposition in the battery, the degree of lithium deposition in the battery is determined based on the plurality of indicators for each of the current values; The battery diagnostic device according to claim 1 or 2, which executes a process including:

6. Further provided is an SOC adjustment device capable of adjusting the SOC of the battery, The processor: If the SOC of the battery is outside a predetermined range set before the pulse current is applied to the battery, adjusting the SOC of the battery by the SOC adjustment device so that the SOC of the battery falls within the predetermined range. The battery diagnostic device according to claim 1 or 2, which executes a process including:

7. The processor: determining a criterion for determining the degree of lithium deposition in the battery based on the temperature of the battery before the pulse current is applied to the battery; Perform a process including the step of determining the degree of lithium deposition in the battery includes determining the degree of lithium deposition in the battery by comparing the determined determination criterion with the index; The battery diagnostic device according to claim 1 or 2, which executes a process including:

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