SECONDARY BATTERY DETERIORATION DEGREE DETERMINATION DEVICE

A deterioration degree determination device includes a charging and discharging control unit, a battery characteristic acquisition unit, and a determination unit. The charging and discharging control unit, in a state where multiple secondary batteries are connected to each other to form a battery pack, performs a charging and discharging operation of the battery pack while voltages of the secondary batteries are individually measured. The battery characteristic acquisition unit acquires a battery characteristic related to transition in a battery state over a predetermined voltage section for at least some of the multiple secondary batteries. The determination unit determines a deterioration degree of at least some of the multiple secondary batteries based on the battery characteristic or a battery characteristic relationship value calculated based on the battery characteristic.

TECHNICAL FIELD

The present disclosure relates to a deterioration degree determination device for a secondary battery.

BACKGROUND

It has been known to diagnose the deterioration degree of a secondary battery that deteriorates with use. For example, it has been known a configuration related to deterioration diagnosis of a battery forming a power storage unit mounted on a vehicle. In the configuration, in a service mode for diagnosing deterioration, the rechargeable capacity of a battery is determined by discharging the battery until the remaining capacity of the battery reaches zero and then charging the battery until the battery is fully charged, such that the deterioration diagnosis of the battery is performed.

SUMMARY

The present disclosure describes a secondary battery deterioration degree determination device. According to an aspect of the present disclosure, a secondary battery deterioration degree determination device includes a charging and discharging control unit, a battery characteristic acquisition unit, and a determination unit. The charging and discharging control unit, in a state where a plurality of secondary batteries are connected to each other to form a battery pack, performs a charging and discharging operation of the battery pack while voltages of the secondary batteries are individually measured. The battery characteristic acquisition unit acquires a battery characteristic related to transition in a battery state over a predetermined voltage section for at least some of the plurality of secondary batteries. The determination unit that determines a deterioration degree of the secondary battery of at least some of the plurality of secondary batteries based on the battery characteristic or a battery characteristic relationship value calculated based on the battery characteristic.

DETAILED DESCRIPTION

When a battery is configured with a battery pack including multiple secondary batteries, the deterioration degree of each secondary battery may vary with the use of the battery. Therefore, although the deterioration degree of some of the secondary batteries of the battery exceeds a reference, the deterioration degree of the battery as a whole is high, and determination may be made that the battery cannot be used. Therefore, in the battery determined to be unusable, the deterioration degree of some of the secondary batteries only may exceed the reference, and the deterioration degree of other secondary batteries may be low. Therefore, in order to improve the reuse rate of the secondary battery, the secondary battery having a high deterioration degree may be removed and the battery pack may be reused as a rebuilt product in which the battery pack is reconstructed from the batteries having a low deterioration degree. Therefore, the improvement of the utilization rate of the secondary battery can be attempted by acquiring the deterioration degree of the individual secondary battery forming the battery pack.

In a method in related art, in order to determine the individual deterioration degree of the multiple secondary batteries provided in the battery pack, it is necessary to make determination individually in a state where the individual secondary battery is taken out from the battery pack, such that in determining the deterioration degree of multiple secondary batteries contained in the vehicle-purpose battery, first, the battery is removed from the vehicle, furthermore, the secondary battery is taken out from the battery, and then it is necessary to connect the individual secondary battery to a deterioration degree determination device, an electric load, and the like. Therefore, the work of determining the deterioration degree is complicated, and the workload is high.

The present disclosure provides a secondary battery deterioration degree determination device capable of reducing a load of determination work of a deterioration degree of the secondary battery forming a battery pack.

According to an aspect of the present disclosure, a secondary battery deterioration degree determination device includes: a charging and discharging control unit, in a state where multiple secondary batteries are connected to each other to form a battery pack, that performs a charging and discharging operation of the battery pack while voltages of the secondary batteries are individually measured; a battery characteristic acquisition unit that acquires a battery characteristic related to transition in a battery state over a predetermined voltage section for at least some of the multiple secondary batteries; and a determination unit that determines a deterioration degree of the secondary battery of at least some of the multiple secondary batteries based on the battery characteristic or a battery characteristic relationship value calculated based on the battery characteristic.

In the above-mentioned secondary battery deterioration degree determination device, the charging and discharging operation is performed in a state where multiple secondary batteries are connected to each other to form the battery pack, and for at least some of the secondary batteries, the battery characteristic related to the transition in the battery state over the predetermined voltage section is acquired. The deterioration degree of at least some of the secondary batteries is determined based on the battery characteristic or the battery characteristic relationship value calculated based on the battery characteristic. Accordingly, the deterioration degree of at least some of the secondary batteries can be determined without removing the secondary batteries from the battery pack. When the deterioration degree is determined, the multiple secondary batteries forming the battery pack are already connected to each other, and thus there is no need to take out the secondary battery from the battery pack and wire the individual secondary battery to a deterioration degree determination device. Therefore, workability when the deterioration degree of the secondary battery is determined can be improved.

As described above, according to the above aspect, the secondary battery deterioration degree determination device which is capable of improving workability when the deterioration degree of the secondary batteries forming the battery pack is determined, can be provided.

Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings.

An embodiment of a secondary battery deterioration degree determination device will be described with reference toFIGS.1to7.

The secondary battery deterioration degree determination device1of the present embodiment includes a charging and discharging control unit71, a battery characteristic acquisition unit61, and a determination unit63.

The charging and discharging control unit71charges and discharges a battery pack2while individually measuring the voltages of secondary batteries21to26in a state where multiple secondary batteries21to26are connected to each other to form the battery pack2.

The battery characteristic acquisition unit61acquires a battery characteristic related to the transition of a battery state over a predetermined voltage section for at least some of the multiple secondary batteries21to26.

The determination unit63determines the deterioration degree of at least some of the multiple secondary batteries21to26based on the battery characteristic or a battery characteristic relationship value calculated based on the battery characteristic.

Hereinafter, the deterioration degree determination device1for the secondary battery of the present embodiment will be described in detail.

The deterioration degree determination device1shown inFIG.1can set the secondary batteries21to26forming the battery pack2as a determination target. The “secondary battery” is a rechargeable battery and includes a battery configured with a single cell or multiple cells. The “battery pack” refers to a battery pack in which the multiple the secondary batteries are electrically connected to each other. In the present embodiment, the types of the secondary batteries21to26are not limited, and known secondary batteries such as nickel-metal hydride batteries and lithium ion batteries can be targeted, and may have a single cell or multiple cells. In the present embodiment, as shown in (a) inFIG.2, the secondary batteries21to26form a secondary battery module that is a module that can be individually attachable and detachable. The number of secondary batteries provided in the battery pack2is not particularly limited, and is six in the present embodiment. As shown in (b) inFIG.2, the secondary batteries21to26are connected in series. When the secondary batteries21to26form an individually detachable module and the cells are connected in parallel in the module, the corresponding modules may be connected in parallel.

As shown inFIG.1, the deterioration degree determination device1includes a detection unit3, a storage unit4, a memory unit5, a calculation unit6, and a control unit7.

The detection unit3includes a voltage value detection unit31and a current value detection unit32. The voltage value detection unit31is configured with a predetermined voltmeter, and as shown in (b) inFIG.2, detects the voltage value of the individual secondary batteries21to26in the battery pack2. The current value detection unit32is configured with a predetermined ammeter, is connected to the secondary batteries21to26, and acquires the current value flowing through the secondary batteries21to26. The open circuit voltage of the secondary batteries21to26is configured to be acquired based on the voltage value detected by the voltage value detection unit31.

The storage unit4shown inFIG.1is configured with a rewritable non-volatile memory, and includes a voltage value storage unit41and a current value storage unit42. The voltage value storage unit41stores the voltage value detected by the voltage value detection unit31, and the current value storage unit42stores the current value detected by the current value detection unit32.

A memory unit5shown inFIG.1is configured with a non-volatile memory, and includes a correspondence relationship memory unit51and a reference value memory unit52. The correspondence relationship memory unit51stores the correspondence relationship between the battery characteristic and a total capacity. The form of the corresponding correspondence relationship is not particularly limited, and can be, for example, a calculation formula, a map, a graph, and a table. The corresponding correspondence relationship can be created by machine learning using the measurement-purpose secondary battery, or created based on the actual measurement value obtained by performing an accelerated deterioration test by using the measurement-purpose secondary battery, or created by a calculation formula that logically derives the correspondence relationship between the battery characteristic and the total capacity in a predetermined voltage section by using the model of the secondary battery. The correspondence relationship stored in the correspondence relationship memory unit51is appropriately set according to the battery characteristic acquired by the battery characteristic acquisition unit61described later.

The above-mentioned total capacity can be the capacity from a fully discharged state to a fully charged state in the charging time. Alternatively, the total capacity can be the capacity from the fully charged state to the fully discharged state in the discharging time. The fully discharged state may be an effective fully discharged state defined by a system such as a vehicle on which the battery pack2is mounted, and may be a state in which the lower limit voltage set by the user who uses the deterioration degree determination device1has been reached. The fully charged state may be an effective fully charged state defined by the system such as the vehicle and the like, or may be a state in which the upper limit voltage specified by the user has been reached.

In the reference value memory unit52shown inFIG.1, a reference value for determining the deterioration degree used in the determination unit63described later is stored in advance. The reference value is appropriately set according to the mode of determination by the determination unit63, and in the present embodiment, multiple reference values are set such that the deterioration degree can be divided into five stages and determined.

The control unit7shown inFIG.1includes a charging and discharging control unit71. The charging and discharging control unit71controls charging and discharging to charge and discharge the battery pack2, that is, causes a charging and discharging operation of the battery pack2, while individually measuring the voltages of the secondary batteries21to26by the voltage value detection unit31. Accordingly, the secondary batteries21to26forming the battery pack2are simultaneously charged and discharged in a state of forming the battery pack2. Accordingly, as shown inFIG.3, the deterioration degree of each of the secondary batteries21to26can be determined without taking out the secondary batteries21to26from the battery pack2in a state of being still mounted on the vehicle100. When the deterioration degree is determined in a state of being mounted on the vehicle100, the charging and discharging control unit71can discharge the secondary batteries21to26by using an in-vehicle electrical device101such as an air conditioner and a headlight mounted on the vehicle100as shown inFIG.3or forcibly charges the secondary batteries21to26by regeneration by the engine or an external charging device102connected to the vehicle. The secondary batteries21to26may be charged and discharged by a serviceman driving the vehicle100brought into a service station or by using the chassis dynamometer provided in the service station. In the present disclosure, “charging and discharging” by the charging and discharging control unit71, that is, the charging and discharging operation of the battery pack2by the charging and discharging control unit71includes any of a case of only charging, a case of only discharging, a case of discharging and then charging, and a case of charging and then discharging.

In the present embodiment, the charging and discharging control unit71can perform discharging until any one of the secondary batteries21to26forming the battery pack2reaches a preset discharging target voltage VP or perform charging until a preset charging target voltage is reached. In the present embodiment, as shown inFIG.4, the charging and discharging control unit71continues discharging until the voltage of the first secondary battery21reaches the discharging target voltage VP. In the present embodiment, the discharging target voltage VP is set outside a normal use range Vn, and the charging and discharging control unit71is configured to allow deviation from the normal use range Vn when the secondary batteries21to26are charged and discharged. The normal use range is a voltage range allowed when the secondary batteries21to26are used, and is appropriately set in advance according to the configuration of the secondary batteries21to26, the configuration of the battery pack2, and the like.

When any of the secondary batteries21to26exceeds the discharging target voltage at an early stage and reaches a usage limit lower limit Vmin, any of the other secondary batteries21to26is continuously discharged until the discharging target voltage is reached. For example, as shown inFIG.5, the first secondary battery21exceeds the discharging target voltage VP and reaches the usage limit lower limit Vmin at an early stage, and thus any of the other secondary batteries22to26is continuously discharged until the discharging target voltage is reached. A usable range is a voltage range preset as a range that does not cause over-discharging or over-charging in the secondary batteries21to26. The usage limit lower limit Vmin indicates the lower limit of the usable range set in advance in the secondary batteries21to26.

The calculation unit6shown inFIG.1is configured with a predetermined arithmetic device, and includes the battery characteristic acquisition unit61, a capacity estimation unit62as an estimation unit, and the determination unit63. The battery characteristic acquisition unit61acquires the battery characteristic of the secondary batteries21to26. The battery characteristic of the secondary batteries21to26can be, for example, a characteristic based on the voltage transition and the temperature transition of the secondary batteries21to26in a predetermined voltage section Vs. The battery characteristic acquisition unit61may acquire the absolute value of the acquired value as the battery characteristic. The predetermined voltage section Vs in which the battery characteristic of the secondary batteries21to26is acquired can be set for each of the secondary batteries21to26, or can be appropriately changed.

The battery states of the secondary batteries21to26forming the battery pack2are not always uniform, and the variation in the battery states increases with the use of the battery pack2. Therefore, the voltage transition in the same voltage section also differs according to the deterioration state. The corresponding voltage transition, for example, can be calculated based on at least one of the section capacity of the secondary batteries21to26in the predetermined voltage section, the ratio of the voltage change of the secondary batteries21to26with respect to the capacity change of the secondary batteries21to26in the predetermined voltage section, and the ratio of the voltage change of the secondary batteries21to26with respect to the elapsed time in the predetermined voltage section. The predetermined voltage section can be a voltage section in which the deterioration degree of the secondary batteries21to26and the transition of the battery state show a correlation. Such a voltage section can be set based on the type and configuration of the secondary batteries21to26, or can be derived by machine learning using the secondary battery.

In the present embodiment, as shown inFIG.4, in the multiple secondary batteries21to26forming the battery pack2, the secondary batteries21to23are set with a first voltage section Vs1from a voltage V1ato a voltage V1b,and the secondary batteries24to26are set with a second voltage section Vs2from a voltage V2ato a voltage V2bdifferent from the first voltage section. In the multiple secondary batteries21to26forming the battery pack2, the first secondary battery21, the second secondary battery22and the third secondary battery23are set in the voltage section Vs1common to each other, and the fourth secondary battery24, the fifth secondary battery25, and the sixth secondary battery26are set in the voltage section Vs2common to each other.

In the present embodiment, the discharging voltage characteristic is used as the battery characteristic. The discharging voltage characteristic is calculated based on the voltage transition when the battery pack2is discharged. The voltage transition when the battery pack2is discharged is different for each of the secondary batteries21to26. In the present embodiment, as shown inFIG.4, when the first secondary battery21and the fourth secondary battery24among the secondary batteries21to26are compared, the voltage of the first secondary battery21is lower than the voltage of the fourth secondary battery24at the discharging start time T0, and at the discharging end time Te, the voltage of the first secondary battery21drops to a value close to the usage limit lower limit Vmin. On the other hand, the voltage of the fourth secondary battery24gradually decreases from the discharging start time T0to the discharging end time Te, but is higher than the voltage of the first secondary battery21at any time and maintains a value sufficiently higher than the usage limit lower limit Vmin even at the discharging end time Te.

As shown inFIG.4, the battery characteristic acquisition unit61calculates the first battery characteristic in the first voltage section Vs1from the voltage V1ato the voltage V1bwith respect to the first secondary battery21. On the other hand, in the fourth secondary battery24, the voltage transition of a portion of the first voltage section Vs1is not acquired, and thus the battery characteristic in the first voltage section Vs1cannot be acquired. Therefore, with respect to the fourth secondary battery24, the battery characteristic acquisition unit61selects the voltage section Vs2from the voltage V2ato the voltage V2bas a section in which the battery characteristic can be acquired from the voltage section acquired until the discharging end time Te, and calculates the second battery characteristic in the second voltage section Vs2.

The battery characteristic acquisition unit61acquires the battery characteristic of the other secondary batteries22and23based on the voltage transition in the first voltage section Vs1like the first secondary battery21, and acquires the battery characteristic of the other secondary batteries25and26based on the voltage transition in the second voltage section Vs2like the fourth secondary battery24.

In the present embodiment 1, the capacity estimation unit62shown in FIG.1estimates the total capacity of the secondary batteries21to26based on the battery characteristic acquired by the battery characteristic acquisition unit61. For the estimation of the total capacity, a prediction model such as a regression equation can be used, and for example, linear regression, Lasso regression, Ridge regression, decision tree, and support vector regression can be used.

The determination unit63shown inFIG.1determines the deterioration degree of the secondary batteries21to26based on the battery characteristic or the battery characteristic relationship value. The battery characteristic relationship value is a value calculated based on the battery characteristic, and in the present embodiment 1, the estimation result of the total capacity of the secondary batteries21to26by the capacity estimation unit62is adopted as the battery characteristic relationship value. Therefore, in the present embodiment 1, the determination unit63determines the deterioration degree of the secondary batteries21to26based on the estimation result of the capacity estimation unit62. The determination method can be performed by comparing the estimation result of the capacity estimation unit62with the reference value stored in advance in the reference value memory unit52.

When the voltage falls below the usage limit lower limit Vmin from the discharging start time T0to the discharging end time Te as in the first secondary battery21in a modified embodiment 1 shown inFIG.5, the first secondary battery21cannot be reused, and thus individual parts can be recycled by performing disassembling and the like without determining the deterioration degree without acquiring the battery characteristic.

In the deterioration degree determination device1, for example, as shown inFIG.3, the detection unit3and the storage unit4are configured with an apparatus and a device previously installed in the vehicle on which the battery pack2is mounted, and the memory unit5, the calculation unit6, and the control unit7can be configured with a scan tool110possessed by a service station and the like that inspects or repairs the vehicle100.

A method for determining the deterioration degree by the deterioration degree determination device1of the present embodiment will be described below.

First, in the present embodiment, in a step S1shown inFIG.6, as a preparation process, a vehicle mounted with the battery pack2is brought to the service station, and is connected to the scan tool110forming the memory unit5, the calculation unit6, and the control unit7of the deterioration degree determination device1of the vehicle.

Next, in a step S2shown inFIG.6, discharging is performed until the open circuit voltage of at least one of the secondary batteries21to26reaches the discharging target voltage VP. Accordingly, the remaining capacity of each of the secondary batteries21to26is discharged. In the present embodiment, as shown inFIG.4, the discharging is continued until the first secondary battery21reaches the discharging target voltage. In the present embodiment, the secondary batteries21to26are nickel-metal hydride batteries, and thus a memory effect may occur in the corresponding secondary batteries21to26, but the cancellation of the memory effect is also performed at the same time for one, which is discharged down to the discharging target voltage VP or to a voltage close to the discharging target voltage VP, among the secondary batteries21to26.

Along with discharging of the remaining capacity in the step S2, in a step S3shown inFIG.6, the battery characteristic of each of the secondary batteries21to26is acquired by the battery characteristic acquisition unit61. In the present embodiment, the above-mentioned discharging voltage characteristic is acquired as the battery characteristic.

In the present embodiment, as shown inFIG.4, with respect to the secondary batteries21to26, the battery characteristic acquisition unit61acquires the voltage temporal change that indicates the relationship of the voltage change individually acquired with respect to the passage of time from the discharging start time T0to a discharging end time Te as the voltage transition. The battery characteristic acquisition unit61acquires the discharging voltage characteristic based on the voltage transition in the first voltage section with respect to the secondary batteries21to23, among the secondary batteries21to26forming the battery pack2, for which the voltage transition has been able to be acquired in the entire range of the first voltage section Vs1. On the other hand, with respect to the secondary batteries24to26for which the voltage transition has not been able to be acquired in the entire range of the first voltage section Vs1, the battery characteristic acquisition unit61acquires the discharging voltage characteristic based on the voltage transition in the second voltage section Vs2included in a range in which the voltage transition has been able to be acquired.

In each of the secondary batteries21to23, the differential value at a predetermined voltage in the first voltage section Vs1, that is, the slope of the tangent line at the predetermined voltage in the first voltage section Vs1in the graph of the voltage temporal change shown inFIG.4is calculated, and is used as the discharging voltage characteristic of each of the secondary batteries21to23. As shown inFIG.4, in each of the secondary batteries24to26, the differential value at a predetermined voltage in the second voltage section Vs2, that is, the slope of the tangent line at the predetermined voltage in the second voltage section Vs2in the graph of the voltage temporal change shown inFIG.4is calculated, and is used as the discharging voltage characteristic of each of the secondary batteries24to26.

In the present embodiment, as the discharging voltage characteristic, the voltage temporal change is acquired as the voltage transition to use the differential value in a predetermined voltage within the predetermined voltage sections Vs1and Vs2, but instead of the above-mentioned, the ratio of the voltage change between the two points in the voltage temporal change derived as the voltage transition, that is, the slope of the straight line passing through the corresponding two points in the graph of the voltage temporal change may be calculated and used as the discharging voltage characteristic. For example, as two points in the voltage temporal change of the secondary batteries21to23shown inFIG.4, two points of the start time and the end time of the voltage section Vs1can be adopted, and as two points in the voltage temporal change of the secondary batteries24to26, two points of the start time and the end time of the voltage section Vs2can be adopted.

In the present embodiment, as the discharging voltage characteristic, the voltage temporal change is acquired as the voltage transition to use the differential value in a predetermined voltage within the predetermined voltage section Vs, but instead of the above-mentioned, the voltage-capacity change indicating the relationship of the voltage change with respect to the capacity from a capacity QO at the discharging start time to a capacity QP1at the discharging end time as the voltage transition, may be acquired. The differential value at a predetermined voltage in the voltage sections Vs1and Vs2, that is, the slope of the tangent line at the predetermined voltage in the graph of the voltage-capacity change may be calculated, and may be used as the discharging voltage characteristic of each of the secondary batteries21to26.

Then, in a step S4as shown inFIG.6, the capacity estimation unit62estimates the total capacity of the secondary batteries21to26, that is, the full charging capacity or the full discharging capacity, based on the battery characteristic acquired by the battery characteristic acquisition unit61. In the present embodiment, the capacity estimation unit62estimates the total capacity of the secondary batteries21to26from the discharging voltage characteristic acquired by the battery characteristic acquisition unit61as the battery characteristic, based on the correspondence relationship between the total capacity and the discharging voltage characteristic based on the prediction model stored in the correspondence relationship memory unit51.

In a step S5shown inFIG.6, the determination unit63determines the deterioration degree of the secondary batteries21to26based on the total capacity estimated by the capacity estimation unit62.

In the battery pack2in a state of being mounted on the vehicle, the secondary batteries21to26are appropriately recombined or replaced according to the deterioration degree determined individually, and newly assembled into the battery pack, such that a rebuilt product can be manufactured. In the present embodiment, the rebuilt product can be manufactured as follows.

First, in a step S10shown inFIG.7, the secondary batteries are ranked according to the deterioration degree acquired as described above. In the present embodiment, the absolute value of the deterioration degree is divided into a predetermined range of five stages, and the ranks are A, B, C, D, and E in order from the one with the smallest absolute value of the deterioration degree. Accordingly, the secondary batteries included in the same rank have the same deterioration degree. The ranking criteria can be set as appropriate.

In a step S11shown inFIG.7, the secondary battery is taken out from the battery pack and sorted by rank. Similarly sorted secondary batteries are collected from other battery packs. In a step S12, the secondary batteries are assembled such that the ranks of the secondary batteries are in a desired combination, and the battery pack as a rebuilt product is manufactured. The combination of ranks of the secondary batteries can be set as appropriate. For example, by assembling the battery pack2by combining the secondary batteries of the same rank, the difference in the deterioration degrees of the secondary batteries included in the corresponding battery pack2can be set to a predetermined reference value or less. The present disclosure is not limited thereto, and the battery pack2may be created within a predetermined range of ranks, for example, the battery pack may be created from the secondary batteries included in the A rank and the B rank. The secondary battery ranked at the lowest rank E may be discarded as unusable, or may be disassembled and used for recycling of members. Thereafter, in the present embodiment, in a step S13shown inFIG.7, supplementary charging of the battery pack is performed. Accordingly, the secondary battery can be used as a battery pack.

Next, the operation effect of the deterioration degree determination device1of the present embodiment will be described in detail.

In the deterioration degree determination device1, the charging and discharging operation is performed in a state where the multiple secondary batteries21to26are connected to each other to form the battery pack2, and for at least some of the secondary batteries21to26, the battery characteristic related to transition in a battery state over the predetermined voltage sections Vs1and Vs2is acquired. The deterioration degree of at least some of the secondary batteries21to26is determined based on the battery characteristic or the battery characteristic relationship value calculated based on the battery characteristic. When the deterioration degree is determined, the multiple secondary batteries21to26forming the battery pack2are already connected to each other, and thus there is no need to take out the secondary batteries21to26from the battery pack2and wire the secondary battery to the deterioration degree determination device for individual charging and discharging. Therefore, it is possible to reduce the workload for determining the deterioration degree of the secondary batteries21to26.

In the present embodiment, the multiple secondary batteries21to26forming the battery pack2includes a secondary battery that is set with a predetermined voltage section for acquiring the battery characteristic different from a voltage section of another secondary batteries of the multiple secondary batteries21to26. That is, the first voltage section Vs1is set as the predetermined voltage section for a portion of the multiple secondary batteries21to26, and the second voltage section Vs2is set as the predetermined voltage section for the other portions. Accordingly, for the secondary batteries24to26for which the voltage transition in the first voltage section Vs1has not be able to be acquired, when the voltage transition in the second voltage section Vs2different from the first voltage section Vs1can be acquired, the deterioration degree can be determined based on the above-mentioned, and thus it becomes easy to determine the deterioration degree of the individual secondary batteries21to26without removing the secondary batteries21to26from the battery pack.

In the present embodiment, the multiple secondary batteries21to26forming the battery pack2include the secondary battery set with voltage sections Vs1and Vs2common to each other as the predetermined voltage section for acquiring the battery characteristic. That is, among the multiple secondary batteries21to26, the secondary batteries21to23have the first voltage section Vs1set as the common voltage section, and the secondary batteries24to26have the second voltage section Vs2set as the common voltage section. Accordingly, the management of the voltage section can be easier, the load of calculating the battery characteristic can be reduced.

In the present embodiment, the charging and discharging control unit71is configured to allow the voltage of the secondary batteries21to26to deviate from the preset normal use range when the charging and discharging operation of the battery pack2is performed. Accordingly, a wide voltage section for acquiring the battery characteristic can be secured, and thus the determination accuracy of the deterioration degree can be improved.

In the present embodiment, the charging and discharging control unit71is configured to allow the voltage of the secondary batteries21to26to deviate from the preset usable range when the charging and discharging operation of the battery pack2is performed. Accordingly, in a case where the secondary batteries21to26forming the battery pack2include a secondary battery of which the deterioration has progressed more than others, when the charging and discharging operation is performed in the state of the battery pack2, there is a case where the voltage transition over the entire predetermined voltage section in the other secondary batteries cannot be acquired during the charging and discharging period within the usable range of the secondary battery for which the corresponding deterioration has progressed. Therefore, by allowing some secondary batteries to deviate from the usable range, it is possible to acquire the voltage transition of the entire predetermined voltage section in other secondary batteries, and the determination accuracy of the deterioration degree of the other secondary batteries can be improved. The secondary battery charged and discharged outside the usable range cannot be used as a secondary battery, and thus the secondary battery can be disassembled and the parts and the like can be recycled.

In the present embodiment, the battery pack2is for a vehicle, and the charging and discharging control unit71is configured to charge and discharge the battery pack2in a state of being mounted on the vehicle. Accordingly, it is not necessary to remove the battery pack2from the vehicle when the deterioration degree of the secondary batteries21to26is determined, and thus workability can be improved.

Instead of the charging and discharging operation of the battery pack2in a state of being mounted on the vehicle, the battery pack2may be removed from the vehicle and the charging and discharging operation may be performed by the charging and discharging control unit71in the state of the battery pack2. In this case, the battery pack2may be wired to the deterioration degree determination device1, and thus the labor of wiring work can be reduced as compared with a case where the secondary batteries21to26are taken out from the battery pack2and individually wired to the deterioration degree determination device1, such that the workability can be improved.

In the present embodiment, the charging and discharging control unit71is configured to charge and discharge the secondary battery via the apparatus mounted on the vehicle. Accordingly, it is not necessary to separately prepare a charging device or a discharging device for charging and discharging the secondary batteries21to26, and thus the configuration of the deterioration degree determination device1can be simplified and the manufacturing cost can be reduced.

In the present embodiment, the capacity estimation unit62estimates the total capacity of the secondary batteries21to26from the battery characteristic acquired by the battery characteristic acquisition unit61, and the determination unit63determines the deterioration degree of the secondary batteries21to26based on the corresponding estimation result, but instead of the above-mentioned, the capacity estimation unit62may not estimate the total capacity and the determination unit63may determine the deterioration degree of the secondary batteries21to26based on the battery characteristic acquired by the battery characteristic acquisition unit61. The battery characteristic acquisition unit61may acquire the absolute value of the acquired value as the battery characteristic, and the determination unit63may determine the deterioration degree based on the corresponding absolute value. The determination unit63may determine the deterioration degree of the secondary batteries21to26based on the difference in the battery characteristic acquired by the battery characteristic acquisition unit61.

In the present embodiment, the battery pack2is assembled by classifying the secondary batteries21to26into classes such that the deterioration degree of the secondary batteries21to26is within a predetermined range, but the battery pack2may be assembled by classifying the secondary batteries21to26into classes such that the difference of the deterioration degree of the secondary batteries21to26is within a predetermined range.

In the present embodiment, the battery characteristic is the discharging voltage characteristic based on the voltage transition in the predetermined voltage sections Vs1and Vs2in the secondary batteries21to26. When the secondary batteries21to26are nickel-metal hydride batteries, at the time of reusing the used secondary batteries21to26, the used secondary batteries21to26may be discharged for the purpose of canceling the memory effect, and by acquiring the discharging voltage characteristic during the discharging, the work process for reusing the secondary batteries21to26can be simplified.

In the present embodiment, the discharging voltage characteristic is calculated based on the voltage transition during the discharging of the secondary batteries21to26, but instead of or together with the above-mentioned, the discharging voltage characteristic may be calculated based on the voltage transition during the voltage relaxation in which the voltage of the secondary batteries21to26returns to the open circuit voltage after the discharging is stopped. In the modified embodiment 1 shown inFIG.8, each of the secondary batteries21to26has the voltage relaxation after the discharging end time Te. In the first secondary battery21, based on the voltage transition in the first voltage section Vs1included in the voltage range in which the voltage relaxation occurs, as in the case of the embodiment 1, the discharging voltage characteristic can be acquired by calculating the differential value of the corresponding voltage section. Similarly, in the second secondary battery22and the third secondary battery23, the discharging voltage characteristic can be acquired based on the voltage transition in the second voltage section Vs2, in the fourth secondary battery24, the discharging voltage characteristic can be acquired based on the voltage transition in the third voltage section Vs3, and in the fifth secondary battery25and the sixth secondary battery26, the discharging voltage characteristic can be acquired based on the voltage transition in the fourth voltage section Vs4. Also in this case, the same operation effect as the operation effect of the present embodiment is obtained.

According to the deterioration degree determination device1of the present embodiment, the battery pack includes the multiple secondary batteries having the usage history, and the battery pack can be provided in which the total capacity is estimated by using the discharging voltage characteristic of the multiple secondary batteries and the difference in the deterioration degree of each of the multiple secondary batteries, which is determined based on the corresponding total capacity, is within a predetermined range. In such a battery pack, the variation in the deterioration degree of the secondary battery included in the battery pack becomes smaller, and thus the lifetime of the battery pack as a rebuilt product can be extended and the quality improvement can be attempted.

The battery characteristic acquisition unit61may replace calculating the ratio of the voltage change of the secondary batteries21to26to the elapsed time in the predetermined voltage section Vs as the voltage transition, or in addition to the above-mentioned, may calculate the capacity change amount of each of the secondary batteries21to26in the predetermined voltage section as a section capacity Qp and use the section capacity Qp as the discharging voltage characteristic. For example, in the present embodiment shown inFIG.4, the section capacity Qp of the secondary batteries21to23can be calculated from the current value flowing through the secondary batteries21to23in the voltage section Vs1detected by the current value detection unit32and the time during which the current flows. Similarly, the section capacity Qp of the secondary batteries24to26can be calculated from the current value flowing through the secondary batteries24to25in the voltage section Vs1detected by the current value detection unit32and the time during which the current flows. Each section capacity Qp can be expressed as shown inFIG.9. Also in this case, the deterioration degree of the secondary batteries21to26can be easily and accurately determined based on the corresponding section capacity Qp as the discharging voltage characteristic.

As shown inFIG.4, a total charging and discharging capacity Qt shown inFIG.9may be calculated as the capacity of all sections of discharging time T0to Te in each of the secondary batteries21to26, and the capacity ratio, that is, the ratio of the section capacity Qp to the total charging and discharging capacity Qt, may be calculated and be used as the discharging voltage characteristic. Instead of the total charging and discharging capacity Qt, a specific section capacity Qt′ that is the capacity of the specific voltage section including the voltage section for calculating the battery characteristic may be calculated, and the capacity ratio that is a ratio of the section capacity Qp to the specific section capacity Qt′ may be calculated and used as the discharging voltage characteristic. Also in this case, the deterioration degree of the secondary batteries21to26can be determined with high accuracy and easily based on the discharging voltage characteristic.

As the voltage transition, the ratio of the voltage change of the secondary batteries21to26to the capacity change in the predetermined voltage sections Vs1and Vs2, that is, the differential value of the voltage in the voltage sections Vs1and Vs2in the voltage capacity change may be calculated, and may be used as the discharging voltage characteristic. Also in this case, the same operation effect as the operation effect of the present embodiment is obtained.

As in the modified embodiment 3 shown inFIG.10, as the voltage transition, the ratio of the voltage change of the secondary batteries21to26to the capacity change in the predetermined voltage section, that is, the differential value of the voltage in the voltage section in the voltage capacity change may be calculated, and may be used as the discharging voltage characteristic. In the modified embodiment 3, as the voltage section, the first voltage section Vs1is set in the secondary batteries21to23, and the second voltage section Vs2is set in the secondary batteries24to26. Also in this case, the same operation effect as the operation effect of the present embodiment is obtained.

According to the deterioration degree determination device1of the present embodiment, the battery pack includes the multiple secondary batteries having the usage history, and the battery pack can be provided in which the total capacity is estimated by using the battery characteristic based on the voltage transition calculated based on at least one of the capacity change amount of the secondary battery in the predetermined voltage sections Vs1and Vs2, the ratio of the voltage change of the secondary battery to the capacity change of the secondary battery in the voltage sections Vs1and Vs2, and the ratio of the voltage change of the secondary batteries21to26to the elapsed time in the voltage sections Vs1and Vs2, and the difference in the deterioration degree of each of the multiple secondary batteries, which is determined based on the corresponding total capacity, is within a predetermined range. In such a battery pack, the variation in the deterioration degree of the secondary battery included in the battery pack becomes smaller, and thus the quality improvement of the battery pack as a rebuilt product can be attempted.

In the present embodiment, the battery characteristic acquisition unit61provided in the deterioration degree determination device1calculates the battery characteristic to acquire the battery characteristic, but instead of the above-mentioned, the deterioration degree determination device1may have an external input unit and calculate the battery characteristic by using an externally provided arithmetic device, such that by inputting the corresponding battery characteristic to the battery characteristic acquisition unit61via the external input unit, the battery characteristic acquisition unit61may acquire the battery characteristic.

The memory unit5, the calculation unit6, and the control unit7of the deterioration degree determination device1of the present embodiment are provided in the scan tool110possessed by the vehicle-purpose service station, but instead of the above-mentioned, as shown inFIG.11, a configuration may be provided such that at least one of the memory unit5, the calculation unit6, and the control unit7in the deterioration degree determination devices1is provided in an external server120and the like and the scan tool110having a communication function as a client terminal provided in the service station and the like connects to an external server and the like via a network, or a configuration may be provided by using a cloud service130via the Internet. The deterioration degree determination device1may be configured such that the memory unit5, the calculation unit6, and the control unit7of the deterioration degree determination device1are provided in the external server and the vehicle is provided with a communication function to use the cloud service130to enable communication with the external server. When the deterioration degree determination is performed using the cloud service130, the scan tool110or the vehicle100is provided with display units111and103to be able to display a diagnosis result and the measures to be taken according to the diagnosis result and the like.

In the determination of the deterioration degree by the deterioration degree determination device1of the present embodiment, after the above-mentioned preparation process S1as in a modified embodiment 4 shown inFIG.12, in a step S20, temperature adjustment may be performed to control the temperature of the secondary batteries21to26to a predetermined temperature. The temperature adjustment can allow the vehicle mounted with the battery pack2to control the temperature of the storage room, or control the temperature of the vehicle including the battery pack2by using the air conditioner for a vehicle cabin mounted on the vehicle. By adjusting the above temperature by the temperature adjustment and soaking the secondary batteries21to26, the temperature of the secondary batteries21and2can be set to a preset set temperature. Multiple temperatures may be set as the set temperature.

In the modified embodiment 4, the temperature of the battery pack2can be detected by a temperature sensor (not shown) provided on the battery pack2. When a temperature sensor is provided for each of the secondary batteries21to26, the temperature detected by each temperature sensor may be set as the temperature of the secondary batteries21to26, but when the temperature sensor is not provided for each of the secondary batteries21to26, the temperature of each secondary batteries21to26may be estimated from the temperature detected by the temperature sensor in consideration of the configuration of the battery pack2and the disposition of the secondary batteries21to26. The corresponding temperature estimation can be performed by using an estimation formula that logically derives the temperature of the secondary battery, a map of the detected temperature and the secondary battery temperature created based on the model of the battery pack, and the like. After the step S20shown inFIG.12, the same procedure as in S2to S5ofFIG.6is performed. According to the determination method, the deterioration degree determination can be performed by setting the temperature of the secondary batteries21to26to a preset set temperature, and thus the determination accuracy can be improved.

In the present embodiment, as shown inFIG.4, the initial voltage, which is the voltage at the discharging start time T0, varies in the secondary batteries21to26, but when the secondary batteries21to26are lithium ion batteries, before determining the deterioration degree, equalization may be performed to equalize the initial voltages in the secondary batteries21to26. The equalization can be performed by performing the charging and discharging operation of the battery pack2in a state where any of the secondary batteries21to26is bypassed. By performing the equalization, it becomes easy to detect the voltage transition of the secondary batteries21to26in a common voltage section, and thus the determination accuracy can be improved.

As described above, according to the present aspect, the deterioration degree determination device1for a secondary battery capable of improving workability when the deterioration degree of the secondary batteries21to26forming the battery pack2is determined, can be provided.

In the embodiment 1 described above, the discharging voltage characteristic is adopted as the battery characteristic, but in the embodiment 2, as shown inFIG.13, charging is performed from the charging start time T1to the charging end time Te after discharging is ended. As the battery characteristic, along with the discharging voltage characteristic of the embodiment 1, the charging voltage characteristic is acquired based on the voltage transition when one of the secondary batteries21to26is charged to the predetermined charging target voltage VQ. The charging target voltage VQ is not particularly limited, but in the present embodiment, is set to a value within the normal use range Vn.

As shown inFIG.13, among the multiple secondary batteries21to26, for the secondary batteries21to23, the first voltage section Vs1is set as a predetermined voltage section for acquiring the voltage transition, and based on the above-mentioned, the battery characteristic acquisition unit61acquires the first charging voltage characteristic as the battery characteristic. On the other hand, for the other secondary batteries24to26, the voltage transition of a portion of the first voltage section Vs1has not been acquired, and thus instead of the above-mentioned, the second voltage section Vs2is selected as a section in which the battery characteristic can be acquired from the voltage section acquired from the charging start time T1to the charging end time Te, and based on the above-mentioned, the battery characteristic acquisition unit61acquires the second charging voltage characteristic as the battery characteristic. The charging voltage characteristic as the battery characteristic in the present embodiment can be calculated in the same manner as the discharging voltage characteristic in the embodiment 1 and each modified embodiment. The other configuration elements are the same as in the case of the embodiment 1, and the same reference numerals as those in the embodiment 1 will be used in the present embodiment as well, and the description thereof will be omitted.

The charging voltage characteristic may be the ratio of the voltage change between two points of the start time and the end time of the predetermined voltage sections Vs1and Vs2as in the case of calculating the discharging voltage characteristic in the above-described embodiment 1, may be the section capacity in the voltage sections Vs1and Vs2, or may be the capacity ratio of the section capacity to the total charging and discharging capacity that is the capacity of all sections at the charging time. Instead of the total charging and discharging capacity, a specific section capacity that is the capacity of the specific voltage section including the voltage section for calculating the battery characteristic may be calculated, and the capacity ratio of the section capacity to the specific section capacity may be calculated and used as the charging voltage characteristic.

In the present embodiment 2, the battery characteristic acquisition unit61acquires both the discharging voltage characteristic and the charging voltage characteristic, and the capacity estimation unit62estimates the total capacity of the secondary batteries21to26based on the discharging voltage characteristic and the charging voltage characteristic. Accordingly, the deterioration degree of the secondary batteries21to26can be determined with higher accuracy.

When the battery pack of a rebuilt product is manufactured by using the deterioration degree determination device1of the present embodiment 2, each of the secondary batteries is charged before the battery pack2is assembled, and thus supplementary charging of the battery pack in the step S13inFIG.7becomes unnecessary.

In the present embodiment 2, the battery characteristic acquisition unit61acquires the charging voltage characteristic after acquiring the discharging voltage characteristic by discharging and then charging the secondary batteries21to26but is not limited thereto, and may acquire the discharging voltage characteristic after acquiring the charging voltage characteristic by charging and then discharging the secondary batteries21to26.

In the present embodiment 2, the battery characteristic acquisition unit61acquires both the discharging voltage characteristic and the charging voltage characteristic, but instead of the above-mentioned, may acquire only the charging voltage characteristic. In this case, the determination accuracy may be inferior to the determination accuracy in the case of acquiring both the discharging voltage characteristic and the charging voltage characteristic. On the other hand, when the secondary batteries21to26are nickel-metal hydride batteries, a memory effect may occur, and when only the discharging voltage characteristic is acquired, in the discharging voltage characteristic, variation may occur in the voltage transition due to the influence of the memory effect, such that there is a concern that the improvement of the determination accuracy is restricted. However, when only the charging voltage characteristic is acquired after the remaining capacity is discharged, with respect to one among the secondary batteries21to26, which is discharged to the discharging target voltage VP or a voltage close to the discharging target voltage VP, the charging voltage characteristic is acquired after the cancellation of the memory effect is attempted, and thus the influence of the memory effect is small, such that the determination accuracy can be expected to be improved.

The charging voltage characteristic in the present embodiment 2, as in the case of the discharging voltage characteristic of the embodiment 1, may be calculated based on the voltage transition during the voltage relaxation in which the open circuit voltage is returned after charging is stopped. Also in this case, the same operation effect as the operation effect of the present embodiment is obtained.

Also in the present embodiment 2, as in the modified embodiment in the embodiment 1, the determination unit63may determine the deterioration degree of the secondary batteries21to26based on the battery characteristic acquired by the battery characteristic acquisition unit61without estimating the total capacity by the capacity estimation unit62. The battery characteristic acquisition unit61may acquire the absolute value of the acquired value as the battery characteristic, and the determination unit63may determine the deterioration degree based on the corresponding absolute value. The determination unit63may determine the deterioration degree of the secondary batteries21to26based on the difference in the battery characteristic acquired by the battery characteristic acquisition unit61. The battery pack2may be assembled by classifying the secondary batteries21to26into classes such that the difference between the deterioration degrees of the secondary batteries21to26is within a predetermined range.

In the deterioration degree determination device1of the present embodiment 3, in addition to the configuration of the embodiment 1, the calculation unit6includes an impedance characteristic relationship value acquisition unit64as shown inFIG.14. The impedance characteristic relationship value acquisition unit64acquires the impedance characteristic relationship value of the secondary batteries21to26by DC-IR measurement and low frequency AC-IR measurement based on the detection value of the voltage value detection unit31and the current value detection unit32. Other configurations are the same as those of the embodiment 1, and the same reference numerals are given to the same configurations of the embodiment 1, and the description thereof will be omitted.

In the present embodiment 3, the battery characteristic acquisition unit61acquires the discharging voltage characteristic in the predetermined voltage sections Vs1and Vs2shown inFIG.4, as in the case of the embodiment 1. The impedance characteristic relationship value acquisition unit64acquires the impedance characteristic relationship value of the secondary batteries21to26at the discharging end time Te.

The correspondence relationship memory unit51stores in advance the correspondence relationship between the impedance characteristic relationship value and the total capacity. The corresponding correspondence relationship can be created by machine learning using the measurement-purpose secondary battery, or created based on the actual measurement value obtained by performing an accelerated deterioration test by using the measurement-purpose secondary battery, or created by a calculation formula that logically derives the correspondence relationship between the impedance characteristic relationship value and the total capacity in a predetermined voltage by using the model of the secondary battery.

In the present embodiment 3, the capacity estimation unit62shown inFIG.14estimates the total capacity of the secondary batteries21to26based on the discharging voltage characteristic acquired by the battery characteristic acquisition unit61and the impedance characteristic relationship value acquired by the impedance characteristic relationship value acquisition unit64. The determination unit63determines the deterioration degree of the secondary batteries21to26based on the estimation result of the capacity estimation unit62as in the case of the embodiment 1. According to the present embodiment 3, the total capacity is estimated based on the discharging voltage characteristic and the impedance characteristic relationship value, and thus the determination accuracy can be further improved.

In the present embodiment, the timing at which the impedance characteristic relationship value acquisition unit64acquires the impedance characteristic relationship value is not particularly limited, and for example, may be at the charging end time when the battery characteristic acquisition unit61acquires the charging voltage characteristic as in the embodiment 2.

According to the deterioration degree determination device1of the present embodiment 3, the battery pack includes the multiple secondary batteries having the usage history, and the battery pack can be provided in which the difference in the deterioration degree of each of the multiple secondary batteries, which is determined based on the total capacity estimated by using the battery characteristic and the impedance characteristic relationship value related to the impedance when the secondary battery is charged or discharged, is within a predetermined range. In such a battery pack, the variation in the deterioration degree of the secondary battery included in the battery pack becomes smaller, and thus the lifetime of the battery pack as a rebuilt product can be extended and the quality improvement can be attempted.

In the present embodiment 4, in addition to the configuration of the embodiment 1, an initial voltage acquisition unit65is provided as shown inFIG.15. As shown inFIG.16, the initial voltage acquisition unit65acquires initial voltages VI1to VI6that are the open circuit voltages of the secondary batteries21to26at the discharging start time T0, respectively. The correspondence relationship memory unit51stores in advance the correspondence relationship among the initial voltage value, the battery characteristic, and the total capacity. The correspondence relationship can be created as in the case of the embodiment 1. Other configurations are the same as those of the embodiment 1, and the same reference numerals are given to the same configurations of the embodiment 1, and the description thereof will be omitted.

According to the deterioration degree determination device1of the present embodiment 4, the deterioration degree of the secondary batteries21to26is determined also in consideration of the initial voltage in addition to the battery characteristic, and thus the determination accuracy can be further improved with a simple configuration. Instead of the initial voltage, the initial voltage relationship value calculated based on the initial voltage may be used. As the initial voltage relationship value, for example, an absolute value of the initial voltage or a difference of the initial voltage acquired by the initial voltage acquisition unit65can be used.

According to the deterioration degree determination device1of the present embodiment 4, the battery pack includes the multiple secondary batteries including the usage history, and the battery pack can be provided in which the difference in the deterioration degree of each of the multiple secondary batteries, which is determined based on the total capacity estimated by using the battery characteristic and the initial voltage that is the open circuit voltage of the secondary batteries when the acquisition of the battery characteristic is started, is within a predetermined range. In such a battery pack, the variation in the deterioration degree of the secondary battery included in the battery pack becomes smaller, and thus the lifetime of the battery pack as a rebuilt product can be extended and the quality improvement can be attempted.

Also in the present embodiment 4, as in the modified embodiment in the embodiment 1, the determination unit63may determine the deterioration degree of the secondary batteries21to26based on the battery characteristic acquired by the battery characteristic acquisition unit61without estimating the total capacity by the capacity estimation unit62. The determination unit63may determine the deterioration degree of the secondary batteries21to26based on the battery characteristic acquired by the battery characteristic acquisition unit61and the initial voltage. The battery characteristic acquisition unit61may acquire the absolute value of the acquired value as the battery characteristic, and the determination unit63may determine the deterioration degree based on the corresponding absolute value. The determination unit63may determine the deterioration degree of the secondary batteries21to26based on the difference in the battery characteristic acquired by the battery characteristic acquisition unit61. The battery pack may be assembled by classifying the secondary batteries into classes such that the difference between the deterioration degrees of the secondary batteries is within a predetermined range.

As another modified embodiment 5, as shown inFIG.17, the calculation unit6may have an internal resistance acquisition unit66that acquires the internal resistance of the secondary battery21, and the correspondence relationship memory unit51may store in advance the correspondence relationship among the internal resistance, the battery characteristic, and the total capacity. In the internal resistance acquisition unit66, the internal resistance can be calculated and acquired from the measured voltage, which is the voltage value itself detected by the voltage value detection unit31, the open circuit voltage of the secondary batteries21to26, and the current flowing through the secondary batteries21to26. The open circuit voltage of the secondary batteries21to26can be estimated and acquired for each time by using a map showing the correspondence relationship between the residual discharge amount and the initial voltage of the secondary batteries21to26. The internal resistance can also be estimated and acquired by using an estimation formula that logically derives the internal resistance of the secondary battery. According to the deterioration degree determination device1of the present modified embodiment 5, the deterioration degree of the secondary batteries21to26is determined also in consideration of the internal resistance in addition to the battery characteristic, and thus the determination accuracy can be further improved with a simple configuration.

In the modified embodiment 5, the internal resistance is acquired separately from the battery characteristic to determine the deterioration degree, but instead of the above-mentioned, as the battery characteristic, the change in the internal resistance may be acquired based on the voltage transition in a predetermined voltage section.

As shown inFIG.18, the deterioration degree determination device1of the present embodiment 5 includes a temperature detection unit33in addition to the configuration of the embodiment 1 shown inFIG.1, and the battery pack2includes the secondary batteries21and22. As shown in (a) inFIG.19and (b) inFIG.19, the temperature detection unit33acquires the temperature of the secondary batteries21and22during the charging and discharging operation. In the above-described present embodiment 1, the battery characteristic acquisition unit61is configured to acquire the discharging voltage characteristic based on the voltage transition of the secondary batteries21and22in the predetermined voltage section Vs as the battery characteristic, but in the present embodiment 5, instead of the above-mentioned, the battery characteristic acquisition unit61, as shown in (a) inFIG.19, acquires the temperature characteristic based on the temperature transition of the secondary batteries21and22in predetermined voltage sections VsA and VsB as the battery characteristic. In the present embodiment 5, the voltage section VsA indicates the voltage section from a voltage V1to a voltage V2, and the voltage section VsB indicates the voltage section from a voltage V3to a voltage V4.

In the present embodiment, as shown in (a) inFIG.19and (b) inFIG.19, as the temperature characteristic, a first discharging temperature characteristic TA1corresponding to the voltage section VsA in the first secondary battery21and a first charging temperature characteristic TB1corresponding to the voltage section VsB are set. As the temperature characteristic, a second discharging temperature characteristic TA2corresponding to the voltage section VsA in the second secondary battery22and a second charging temperature characteristic TB2corresponding to the voltage section VsB are set. Other configurations are the same as those of the embodiment 1, and the same reference numerals are given to the same configurations of the embodiment 1, and the description thereof will be omitted. The voltage section VsA is a section in which the difference in the discharging voltage characteristic is remarkable according to the deterioration degree of the secondary batteries21and22, and the voltage section VsB is a section in which the difference in the charging voltage characteristic is remarkable according to the deterioration degree of the secondary batteries21and22.

Although the secondary batteries21and22are incorporated in the same battery pack2, the temperature transition in charging and discharging may show different behaviors depending on the disposition, the temperature environment, and the like of the secondary batteries21and22. In the present embodiment 5, as shown in (b) inFIG.19, the temperature transitions in the first secondary battery21and the second secondary battery22are within a measured room temperature setting range Tn, but show slightly different behaviors from each other. In the present embodiment 5, the battery characteristic acquisition unit61acquires the discharging temperature characteristics TA1and TA2that are the temperature characteristic in discharging and the charging temperature characteristics TB1and TB2that are the temperature characteristic in charging, based on the battery temperature detected by the temperature detection unit33in both the predetermined voltage section VsA in discharging and the predetermined voltage section VsB in charging after discharging. The capacity estimation unit62estimates the total capacity of each of the secondary batteries21and22based on both temperature characteristics, and the determination unit63determines the deterioration degree.

The temperature characteristic acquired by the battery characteristic acquisition unit61can be, as in the case of calculating the discharging voltage characteristic in the case of the embodiment 1 and the case of calculating the charging voltage characteristic in the case of the embodiment 2, the differential value of the temperature change of the predetermined voltage in the predetermined voltage sections VsA and VsB, the ratio of the temperature change between two points in the predetermined voltage sections VsA and VsB, and the ratio of the temperature change of the secondary batteries21and22to the capacity change of the secondary batteries21and22in the voltage sections VsA and VsB.

Also in the present embodiment 5, the same operation effect as in the case of the embodiment 1 can be obtained. In the present embodiment 5, the temperature characteristic is acquired in both discharging and charging but is not limited thereto, and only one of discharging and charging may be used.

According to the deterioration degree determination device1of the present embodiment 5, the battery pack includes the multiple secondary batteries having the usage history, and the battery pack can be provided in which the difference in the deterioration degree of each of the multiple secondary batteries, which is determined based on the total capacity estimated by using the battery characteristic including the temperature characteristic based on the temperature transition of the secondary battery in the predetermined voltage sections VsA and VsB, is within a predetermined range. In such a battery pack, the variation in the deterioration degree of the secondary battery included in the battery pack2becomes smaller, and thus the quality improvement of the battery pack as a rebuilt product can be attempted.

Also in the present embodiment 5, as in the modified embodiment in the embodiment 1, the determination unit63may determine the deterioration degree of the secondary batteries21to22based on the temperature characteristic acquired by the battery characteristic acquisition unit61without estimating the total capacity by the capacity estimation unit62. The battery characteristic acquisition unit61may acquire the absolute value of the acquired value as the temperature characteristic, and the determination unit63may determine the deterioration degree based on the corresponding absolute value. The determination unit63may determine the deterioration degree of the secondary battery based on the difference in the temperature characteristic acquired by the battery characteristic acquisition unit61. The battery pack may be assembled by classifying the secondary batteries into classes such that the difference between the deterioration degrees of the secondary batteries is within a predetermined range.

In the present embodiment 5, as shown in (a) inFIG.19, as the temperature characteristic at the charging time, the temperature characteristic is acquired when the charging target voltage VQ is within the normal use range Vn and the predetermined voltage section VsB is within the normal use range Vn, but instead of the above-mentioned, as in a modified embodiment 6 shown in (a) inFIG.20, as the temperature characteristic at the charging time, the temperature characteristic may be acquired when the charging target voltage VQ exceeds the normal use range Vn and the predetermined voltage section VsB is in an area beyond the normal use range Vn. In this case, as shown in (b) inFIG.20, the temperature of the secondary batteries21and27easily rises, and thus the deterioration degree is easily reflected in the temperature transition. As a result, the determination accuracy can be improved. In the present modified embodiment 6, the secondary batteries21and27are charged to the charging target voltage VQ and then discharged to return the voltage of the secondary batteries21and22to the normal use range Vn.

In the modified embodiment 6, the secondary battery2is discharged, then charged, and then discharged again, but instead of the above-mentioned, as in a modified embodiment 7 shown inFIG.21, the battery may be charged first and then discharged without first discharging. In this case, the battery characteristic acquisition unit61may acquire the charging time temperature characteristic at the charging time and then acquire the discharging time temperature characteristic at the discharging time. Also in this case, the same operation effect as the operation effect of the embodiment 1 is obtained.

In the above-described embodiment 1, the capacity estimation unit62as the estimation unit estimates the total capacity of the secondary battery2based on the battery characteristic acquired by the battery characteristic acquisition unit61, but is not limited thereto, and the capacity estimation unit62may estimate at least one of the positive electrode capacity, the negative electrode capacity, the deviation amount of the relative relationship between the negative electrode SOC and the positive electrode SOC, the total capacity variation among the multiple cells forming the secondary batteries21to26, and the battery resistance, positive electrode resistance, and negative electrode resistance of the secondary batteries21to26. In the embodiment 6, the capacity estimation unit62estimates a positive electrode capacity Qc of each of the secondary batteries21to26. The correspondence relationship memory unit51stores the correspondence relationship between the battery characteristic and the positive electrode capacity Qc. The form of the corresponding correspondence relationship and the method for creating the correspondence relationship are not particularly limited, and can be, for example, a calculation formula, a map, a graph, and a table, as in the case of the embodiment 1. The corresponding correspondence relationship can be created by machine learning using the measurement-purpose secondary battery2, or created based on the actual measurement value obtained by performing an accelerated deterioration test by using the measurement-purpose secondary battery2, or created by a calculation formula that logically derives the correspondence relationship between the battery characteristic and the total capacity in a predetermined voltage section by using the model of the secondary battery2. In the present embodiment, the correspondence relationship memory unit51, for example, stores the correspondence relationship between the battery characteristic and the positive electrode capacity Qc based on the prediction model shown in (a) to (c) inFIG.22. Other configurations are the same as in the case of the embodiment 1, and the same reference numerals as those in the case of the embodiment 1 are assigned and the description thereof will be omitted.

Next, a method for determining the deterioration degree by the deterioration degree determination device1of the present embodiment 6 will be described below. The description of the same steps as in the case of the embodiment 1 shown inFIG.6may be omitted by using the same reference numerals.

First, in the present embodiment 6, the steps S1to S3shown inFIG.23are performed as in the case of the embodiment 1 shown inFIG.6. Accordingly, as shown in (a) inFIG.24, the battery characteristic acquisition unit61acquires a discharging curve as the battery characteristic of each of the secondary batteries21to26in the predetermined voltage section Vs. The predetermined voltage section can be a section corresponding to a specific SOC range.

Next, in a step S40shown inFIG.23, the capacity estimation unit62estimates the positive electrode capacity Qc of the secondary batteries21to26from the discharging curve acquired by the battery characteristic acquisition unit61based on the correspondence relationship between the battery characteristic and the positive electrode capacity Qc based on the prediction model stored in the correspondence relationship memory unit51. Thereafter, in the step S5shown inFIG.23, the determination unit63determines the deterioration degree of the secondary batteries21to26based on the positive electrode capacity Qc estimated by the capacity estimation unit62.

The present embodiment 6 also has the same operation effect as the operation effect of the embodiment 1. In the present embodiment 6, the battery characteristic acquisition unit61acquires the discharging curve shown in (a) inFIG.24, but instead of the above-mentioned, may acquire the charging curve shown in (b) inFIG.24. Also in this case, the same operation effect as the operation effect of the embodiment 1 is obtained.

In the embodiment 6, the capacity estimation unit62estimates the positive electrode capacity Qc, but instead of the above-mentioned, in the embodiment 7, the capacity estimation unit62estimates a negative electrode capacity QA. That is, in the embodiment 7, as shown inFIG.25, in a step S41, based on the prediction model shown in (a) to (c) inFIG.22, the negative electrode capacity QA of the secondary batteries21to26is estimated based on the correspondence relationship between the battery characteristic and the negative electrode capacity QA. The embodiment 7 also has the same operation effect as the operation effect of the embodiment 1.

In the present embodiment 8, the capacity estimation unit62estimates the deviation amount of the relative relationship between the negative electrode SOC and the positive electrode SOC of each of the secondary batteries21to26. The correspondence relationship memory unit51stores the correspondence relationship between the battery characteristic and the deviation amount of in the relative relationship between the negative electrode SOC and the positive electrode SOC. The form of the corresponding correspondence relationship and the method for creating the correspondence relationship are not particularly limited, and can be as in the case of the embodiment 1.

For example, when the secondary batteries21to26are made of nickel-metal hydride batteries, as shown inFIG.26, when hydrogen escapes from the reaction system in the battery container, the relative relationship between the negative electrode SOC and the positive electrode SOC deviates, and the OCV curve of the negative electrode deviates to the right side of the figure. For example, when the secondary batteries21to26are configured with lithium ion batteries, as shown inFIG.26, the lithium in the electrolytic solution is consumed in the formation of the solid electrolyte interface (SEI) film, such that the relative relationship between the negative electrode SOC and the positive electrode SOC deviates, and thus the OCV curve of the negative electrode deviates to the right side of the figure.

In the present embodiment 8, based on the prediction model shown inFIG.26, the correspondence relationship memory unit51stores the correspondence relationship between a deviation amount Qx of the relative relationship between the negative electrode SOC and the positive electrode SOC, and the battery characteristic. Other configurations are the same as in the case of the embodiment 1, and the same reference numerals as those in the case of the embodiment 1 are assigned and the description thereof will be omitted.

A method for determining the deterioration degree by the deterioration degree determination device1of the present embodiment 8 is performed as in the case of the above-mentioned embodiment 6, but as shown inFIG.27, in the step S3, the battery characteristic acquisition unit61acquires, as the battery characteristic, a discharging curve of the predetermined voltage section Vs corresponding to a low SOC range as the battery. Thereafter, in a step S42, the deviation amount Qx of the secondary batteries21to26is estimated based on the correspondence relationship between the battery characteristic calculated from the corresponding discharging curve, and the deviation amount Qx of the relative relationship between the negative electrode SOC and the positive electrode SOC stored in the correspondence relationship memory unit51. Thereafter, in the step S5shown inFIG.27, the determination unit63determines the deterioration degree of the secondary batteries21to26based on the deviation amount Qx estimated by the capacity estimation unit62. The present embodiment also has the same operation effect as in the operation effect of the embodiment 1. In the present embodiment 8, the battery characteristic is acquired from a low SOC range as the battery, but instead of the above-mentioned, may be acquired from a high SOC range. In the present embodiment 8, the discharging curve is acquired as the battery characteristic, but the charging curve may be acquired.

In the present embodiment 9, the correspondence relationship memory unit51stores the correspondence relationship between the battery characteristic, and the amount of change of the discharging capacity in the charging and discharging curve for each of the secondary batteries21to26, the capacity estimation unit62estimates the amount of change of the discharging capacity in the charging and discharging curve in the predetermined voltage section Vs, and the determination unit63detects whether the self-discharge amount of the cell increases based on the estimation result as the deterioration degree. In the present embodiment 9, other configurations are the same as in the case of the embodiment 1, and the same reference numerals as those in the case of the embodiment 1 are assigned and the description thereof will be omitted.

In the present embodiment 9, each of the secondary batteries21to26has six cells. For example, the discharging curve shown in (a) inFIG.28is stored in the correspondence relationship memory unit51as a discharging curve showing an initial state, and the discharging curve shown in (b) inFIG.28is stored in the correspondence relationship memory unit51as a discharging curve indicating that one of the cells has an increasing self-discharge amount. When the discharging curve shown in (a) inFIG.28is estimated by the capacity estimation unit62based on the battery characteristic of the predetermined voltage section Vs, the determination unit63determines that there is no cell having the increasing self-discharge amount. When the discharging curve shown in (b) inFIG.28is estimated by the capacity estimation unit62based on the battery characteristic of the predetermined voltage section Vs, the determination unit63determines that there is a cell having the increasing self-discharge amount. When the discharging curve shown in (b) inFIG.28is estimated, the use lower limit can be set to a second use lower limit Vmin2that is a value higher than a first use lower limit Vmin1that is for a case where there is no cell having an increasing self-discharge amount in the secondary battery module. Accordingly, each cell can be prevented from being excessively discharged.

In the present embodiment 10, each of the secondary batteries21to26includes six cells. The correspondence relationship memory unit51stores the correspondence relationship between the total capacity variation between the cells in one of the secondary batteries21to26and the battery characteristic. The total capacity variation between the cells indicates the degree of variation in the total capacity of each cell in multiple cells included in one of the secondary batteries21to26. In the present embodiment 10, as the total capacity variation between the cells, as shown inFIG.29, a difference Qmax-min obtained by subtracting a minimum Qmin from a maximum Qmax in the total capacity of the multiple cells is adopted. Other configurations are the same as in the case of the embodiment 1, and the same reference numerals as those in the case of the embodiment 1 are assigned and the description thereof will be omitted.

In the present embodiment 10, the capacity estimation unit62estimates the difference Qmax-min from the correspondence relationship stored in the correspondence relationship memory unit51based on the battery characteristic acquired by the battery characteristic acquisition unit61. The determination unit63detects the presence or absence of specific capacity deterioration of the cell based on the estimated difference Qmax-min. For example, when the estimated difference Qmax-min is determined to be equal to or greater than a predetermined value, determination is made that specific capacity deterioration occurs in one of the cells of the corresponding secondary battery module.

As shown inFIG.30, the embodiment 11 has a resistance estimation unit621as an estimation unit. The resistance estimation unit621estimates the internal resistance of the secondary batteries21to26based on the battery characteristic of the secondary batteries21to26. The correspondence relationship memory unit51stores the correspondence relationship between the internal resistance and the battery characteristic of one of the secondary batteries21to26. The battery characteristic acquisition unit61can acquire the battery characteristic by performing a pulse charging and discharging operation in a state of stack in which the secondary batteries21to26are connected to each other. The voltage section for acquiring the battery characteristic can be a predetermined voltage section corresponding to a specific SOC range.

When the temperature and SOC are different between the secondary batteries21to26, the temperature and the voltage change during the charging and discharging operation or the voltage change during the voltage relaxation after the charging and discharging operation are acquired as the battery characteristic, and the resistance value can be estimated when the temperature and SOC are the same conditions. In this case, the correspondence relationship memory unit51stores the correspondence relationship between the internal resistance, the temperature, and the battery characteristic of one of the secondary batteries21to26. The secondary batteries21to26may be individually charged and discharged to acquire the battery characteristic. In this case, it is not necessary to adjust the temperature and SOC to the same conditions, and the determination time can be shortened.

Next, a method for determining the deterioration degree by the deterioration degree determination device1of the present embodiment 11 will be described below. First, in the present embodiment 6, the steps S1to S3shown inFIG.31are performed as in the case of the embodiment 1 shown inFIG.11. Next, in a step S43shown inFIG.31, the resistance estimation unit621acquires the internal resistance of the secondary batteries21to26from the battery characteristic acquired by the battery characteristic acquisition unit61, based on the correspondence relationship between the battery characteristic and the internal resistance of the secondary batteries21to26stored in the correspondence relationship memory unit51. Thereafter, in the step S5shown inFIG.31, the determination unit63determines the deterioration degree of the secondary batteries21to26based on the internal resistance estimated by the resistance estimation unit621. The present embodiment 11 also has the same operation effect as the operation effect of the embodiment 1.

In the deterioration degree determination device1of the embodiment 12, the resistance estimation unit621estimates the negative electrode resistance of the secondary batteries21to26, and the determination unit63determines the deterioration degree of the secondary batteries21to26.

From the frequency characteristic in the voltage curve of the secondary batteries21to26, the resistance value of the positive electrode, the negative electrode, and other battery elements in the secondary batteries21to26can be calculated. In nickel-metal hydride batteries and lithium ion batteries, the negative electrode resistance is remarkably reflected in the high frequency region in the voltage curve, and the positive electrode resistance is remarkably reflected in the low frequency region. In the present embodiment 12, nickel-metal hydride batteries are used as the secondary batteries21to26, and the battery characteristic acquisition unit61acquires a voltage curve in a predetermined voltage section in a high frequency region as the battery characteristic. The correspondence relationship memory unit51stores in advance the correspondence relationship between the voltage curve in the high frequency region as the battery characteristic and the negative electrode resistance. The other configuration elements are the same as in the case of the embodiment 11, and the same reference numerals are given and the description thereof will be omitted.

In the internal resistance having a correlation with the deterioration degree of the secondary batteries21to26, the dominant resistance element differs depending on the deterioration mode. First, the internal resistance of the secondary battery is determined by the relationship among the three resistance components of electronic resistance, reaction resistance, and the resistance of internal material transfer, and the secondary battery can be considered to be a series equivalent circuit of the three resistance components. In general, the electronic resistance is a resistance component mainly generated in the time region immediately after a constant current is applied to a battery. The reaction resistance is a resistance component mainly generated in the time region after the time region in which the electronic resistance is generated. The internal material transfer resistance is generated when a constant current is applied for a long time, and is a resistance component mainly generated in the time region after the time region of the reaction resistance. The negative electrode reaction resistance dominant area is a temporal area in which the ratio of the reaction resistance of the negative electrode in a discharging period among the above three resistance components is the largest. In the corresponding negative electrode reaction resistance dominant area, the reaction resistance of the negative electrode predominantly determines the internal resistance of the secondary battery2. In the present embodiment 12, the determination unit63determines the deterioration degree of the secondary batteries21to26based on the negative electrode resistance estimated by the resistance estimation unit621in the corresponding negative electrode reaction resistance dominant area.

In a method for determining the deterioration degree by the deterioration degree determination device1of the present embodiment 12, the steps S1to S3shown inFIG.31are performed as in the case of the embodiment 11. In the step S43, the resistance estimation unit621estimates the negative electrode resistance of the secondary batteries21to26based on the voltage curve acquired by the battery characteristic acquisition unit61and the correspondence relationship stored in the correspondence relationship memory unit51. The determination unit63determines the deterioration degree of the secondary batteries21to26from the estimated negative electrode resistance. The present embodiment 12 also has the same operation effect as the operation effect of the embodiment 1.

In the deterioration degree determination device1of the embodiment 13, the resistance estimation unit621estimates the positive electrode resistance of the secondary batteries21to26, and the determination unit63determines the deterioration degree of the secondary batteries21to26. In the present embodiment 13, nickel-metal hydride batteries are used as the secondary batteries21to26, and the battery characteristic acquisition unit61acquires a voltage curve in a predetermined voltage section in a low frequency region as the battery characteristic. The correspondence relationship memory unit51stores in advance the correspondence relationship between the voltage curve as the battery characteristic and the positive electrode resistance. The determination unit63determines the deterioration degree of the secondary batteries21to26based on the positive electrode resistance estimated by the resistance estimation unit621in the positive electrode reaction resistance dominant area. The other configuration elements are the same as in the case of the embodiment 12, and the same reference numerals are given and the description thereof will be omitted.

In a method for determining the deterioration degree by the deterioration degree determination device1of the present embodiment 13, the steps S1to S3shown inFIG.31are performed as in the case of the embodiment 12. In the step S43, the resistance estimation unit621estimates the positive electrode resistance of the secondary batteries21to26based on the voltage curve acquired by the battery characteristic acquisition unit61and the correspondence relationship stored in the correspondence relationship memory unit51. The determination unit63determines the deterioration degree of the secondary batteries21to26from the estimated positive electrode resistance. The present embodiment 13 also has the same operation effect as the operation effect of the embodiment 1.

The present disclosure is not limited to each of the above embodiments, and can be applied to various embodiments without departing from the gist thereof.

Although the present disclosure has been described in accordance with the embodiments, it is understood that the present disclosure is not limited to such embodiments or structures. The present disclosure also includes various modified embodiments and a modification within an equivalent scope. Various combinations or forms as well as other combinations or forms including only one element, one or more elements, or one or fewer elements, fall within the scope or the spirit of the present disclosure.

The deterioration degree determination device1and the method described in the present disclosure may be implemented by a special purpose computer, which includes a memory and a processor programmed to execute one or more special functions implemented by computer programs of the memory. Alternatively, the deterioration degree determination device1and the method described in the present disclosure may be implemented by a dedicated computer configured as a processor with one or more dedicated hardware logic circuits. Alternatively, the deterioration degree determination device1and the method thereof described in the present disclosure may be implemented by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or multiple functions and a processor configured by one or more hardware logic circuits. The computer program may also be stored in a computer readable non-transitory tangible storage medium as computer executable instructions. The deterioration degree determination device1and the method thereof described in the present disclosure do not necessarily need to include software, and all the functions may be implemented using one or more hardware circuits.

Multiple functions of one configuration element in the above embodiments may be implemented by multiple configuration elements, or a single function of one configuration element may be implemented by multiple configuration elements. Multiple functions of multiple configuration elements in the above embodiments may be implemented by one configuration element, or one function implemented by multiple configuration elements may be implemented by one configuration element. A part of the configurations of the above embodiments may be omitted as appropriate. At least a part of the configuration in one embodiment may be added to or substituted for the configuration of another embodiment.

In addition to the above deterioration degree determination device1, the present disclosure can also be implemented in various forms, such as a system including the deterioration degree determination device1as an element, a program that controls a computer to function as deterioration degree determination device1, a non-transitory tangible storage medium, such as a semiconductor memory in which the above-described program is recorded, and a deterioration degree determination method.