Self-discharge inspection method for electricity storage device and method for manufacturing electricity storage device

Abstract

A method for self-discharge inspection of a power storage device and a method for manufacturing a power storage device. In the method for self-discharge inspection of a power storage device, the power storage device has the following characteristics: if the load is reduced from the first load in a state where it is pressed by the first load and charged to the first device voltage, the device voltage decreases. The method for self-discharge inspection of a power storage device includes: a voltage detection step of detecting the first device voltage of the power storage device that is pressed by the first load and charged; a voltage continuous application step of continuously applying a power supply voltage equal to the first device voltage from an external power supply; a current detection step of detecting the power supply current flowing into the power storage device; a determination step of determining the self-discharge state of the power storage device based on the detected power supply current; and a load reduction step of reducing the load applied to the power storage device by a load reduction amount from the first load after the voltage continuous application step starts and before the power supply current stabilizes.

Description

Technical Field

[0001] The present invention relates to a method for inspecting self-discharge of a power storage device for determining a self-discharge state of the power storage device, and a method for manufacturing a power storage device including the self-discharge inspection method. Background Art

[0002] When manufacturing a power storage device such as a lithium-ion secondary battery, there are cases where metal foreign matters such as iron and copper are mixed into the inside of an electrode body or the like, and sometimes self-discharge caused by an internal short circuit occurs in the power storage device due to the mixed metal foreign matters. Therefore, during the manufacturing process of the power storage device, there are cases where it is desired to determine the state of self-discharge such as the presence or absence of an internal short circuit and the magnitude of the self-discharge current in the power storage device.

[0003] As a method for inspecting self-discharge of the power storage device, for example, the following method is known. That is, the pre-charged power storage device's pre-inspection device voltage is measured, and a power supply voltage equal to the pre-inspection device voltage is continuously applied to the power storage device from an external power supply. Then, the power supply current flowing from the external power supply to the power storage device gradually increases from zero and becomes equal to the magnitude of the self-discharge current of the power storage device and stabilizes. Therefore, the power supply current is detected, and based on the detected power supply current, the magnitude of the self-discharge current of the power storage device is determined. In addition, as a related prior art, Patent Document 1 (refer to the claims of Patent Document 1, etc.) can be cited.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-16558

[0005] However, in the above self-discharge inspection method, it is troublesome to determine pass or fail. For example, it takes time for the magnitude of the power supply current to increase to almost stable, and the magnitude of the power supply current at stability is compared with the limit current value to determine whether the battery passes or fails.

[0006] However, the inventors have found that for a charged and loaded battery, there is a case where if the applied load is reduced, the battery voltage (open-circuit voltage) slightly decreases. Summary of the Invention

[0007] The present invention has been completed in view of this finding, and an object thereof is to provide an improved method for inspecting self-discharge of a power storage device and a method for manufacturing a power storage device including the self-discharge inspection method.

[0008] (1) One aspect of the present invention for solving the above problems is a method for inspecting self-discharge of a power storage device, and the power storage device has the following characteristics: if, in a state where it is pressed with a first load and the device voltage is charged to a first device voltage, the load is reduced from the first load, then the device voltage is lower than the first device voltage. The method for inspecting self-discharge of the power storage device includes: a voltage detection step of detecting the first device voltage of the power storage device that is pressed with the first load and charged to the first device voltage; a voltage continuous application step of continuously applying a power supply voltage equal in magnitude to the first device voltage from an external power supply; a current detection step of detecting a power supply current flowing from the external power supply to the power storage device; a determination step of determining the self-discharge state of the power storage device based on the detected power supply current; and a load reduction step of reducing the load applied to the power storage device by a load reduction amount from the first load after the voltage continuous application step starts and before the power supply current stabilizes.

[0009] As described above, the power storage device inspected by the above inspection method has the following characteristics: if the load applied to the power storage device is reduced, the device voltage (open-circuit voltage) decreases.

[0010] Moreover, in the above inspection method, the following are performed: a voltage detection step of detecting the first device voltage of the power storage device, a voltage continuous application step of continuously applying a power supply voltage equal in magnitude to the first device voltage, a current detection step, and a determination step. In addition, a load reduction step is provided, that is, after the voltage continuous application step starts and before the power supply current stabilizes, the load applied to the power storage device is reduced by a load reduction amount from the first load.

[0011] When the power supply voltage is continuously applied through the voltage continuous application step without changing the load, due to the self-discharge of the power storage device, the device voltage gradually decreases and finally stabilizes.

[0012] In addition, in the above inspection method, the load is reduced through the load reduction step, so the device voltage can also be reduced by this reduction in load. That is, the decrease in the device voltage can be accelerated, so an improved new inspection method can be provided that can make the power supply current stabilize earlier than before by appropriately setting the load reduction amount, and can easily determine whether the power storage device is qualified or not based on the state of change of the power supply current.

[0013] As will be described later, the above method for inspecting self-discharge of a power storage device can be performed not only during the manufacturing process of the power storage device, but also for power storage devices that have been mounted on an automobile or the like or sold separately and are in use or at the end of use.

[0014] In addition, examples of the "power storage device" include secondary batteries such as lithium-ion secondary batteries, electric double layer capacitors, and capacitors such as lithium-ion capacitors.

[0015] The first device voltage is the open-circuit voltage generated between the terminals of the power storage device when the current flowing from the outside to the power storage device is zero, and it is not necessary to cut off (open-circuit) the terminals of the power storage device from the circuit for measurement.

[0016] In the determination process, the self-discharge state is determined based on the power supply current. Specifically, examples include a method of determining using the stable power supply current flowing at the time when the power supply current has stabilized, and a method of determining the self-discharge state using the temporal change of the power supply current from the start until it reaches the stable power supply current. As a method of determining the self-discharge state using the stable power supply current, for example, first, for the power storage device under inspection, the value of the stable power supply current is obtained. On this basis, examples of determination methods include a method of determining whether the self-discharge state is qualified (qualified / unqualified) based on the magnitude relationship between the value of the stable power supply current and a reference limit current value, and a method of classifying into multiple grades such as A / B / C... corresponding to the magnitude of the stable power supply current.

[0017] On the other hand, as a method of determining the self-discharge state based on the temporal change of the power supply current from the start until it reaches the stable power supply current, for example, first, the value of the stable power supply current is estimated based on the temporal change of the power supply current from the start until it reaches the stable power supply current. On this basis, examples of determination methods include a method of determining whether the self-discharge state is qualified (qualified / unqualified) based on the magnitude relationship between the estimated value of the stable power supply current and the limit current value, and a method of classifying into multiple grades such as A / B / C... corresponding to the magnitude of the estimated stable power supply current. In addition, examples of determination methods also include directly determining whether the self-discharge state of the power storage device is qualified or classifying it based on the change amount per unit time of the power supply current and changes such as whether it has changed from increasing to decreasing.

[0018] In addition, the detected temporal change of the power supply current refers to the temporal change of the power supply current generated during the period from the start of the voltage application process until the value of the power supply current flowing through the power storage device stabilizes. For example, it can be represented by the increase amount of the power supply current generated within a predetermined period, the slope of the increase, etc. In addition, at the time point when sufficient time has passed in the voltage application process, a stable power supply current corresponding to the magnitude of the self-discharge current flowing through the power storage device flows. This stable power supply current is set as the stable power supply current.

[0019] (2) The self-discharge inspection method of the electricity storage device according to (1) may be configured such that the load reduction process is a process of reducing the load applied to the electricity storage device after a predetermined first time has elapsed since the start of the voltage application process. The load reduction amount is a qualified load reduction amount that satisfies the following conditions: (i) the electricity storage device is a qualified device with good self-discharge, and (ii) for the qualified device, when the load is reduced by the load reduction amount from the first load after the first time has elapsed since the start of the voltage application process, the power supply current rapidly increases due to the decrease in the device voltage accompanying the load reduction and then quickly stabilizes.

[0020] In this inspection method, in advance, for a qualified device with good self-discharge, that is, a qualified device whose self-discharge current is smaller than the limit current value, a qualified load reduction amount is obtained. Specifically, for the qualified device, the following load reduction amount is obtained and set as the qualified load reduction amount, that is, when the load is reduced by the load reduction amount from the first load after the first time has elapsed since the start of the voltage application process, the power supply current rapidly increases due to the decrease in the device voltage accompanying the load reduction and then quickly stabilizes.

[0021] Moreover, in this inspection method, in the load reduction process, after the first time has elapsed since the start of the voltage application process, the load is reduced from the first load by the qualified load reduction amount.

[0022] Therefore, when the electricity storage device under inspection is a qualified device, the power supply current quickly stabilizes. On the other hand, when the electricity storage device under inspection is a device with a self-discharge current larger than that of a qualified device (for example, a limit device or a non-qualified device described later), due to the decrease in the device voltage accompanying the load reduction, the power supply current rapidly increases, and then, after a period of slow increase, it finally stabilizes.

[0023] Therefore, according to this inspection method, regardless of whether the electricity storage device under inspection is a qualified device or not, compared with the existing inspection method in which the power supply current slowly increases due to the absence of a load reduction process, it is possible to determine the qualification of the electricity storage device in advance.

[0024] In addition, it is preferable that the first time when the load reduction process starts after the start of the voltage application process is set to be at most within 1 / 2 of the stabilization arrival time required for the power supply current to stabilize when the voltage application process is performed on the qualified device without performing the load reduction process after the start of the voltage application process. This is because if the first time exceeds 1 / 2 of the stabilization arrival time, the effect of shortening the stabilization arrival time caused by performing the load reduction process becomes smaller. As the first time, it is preferably immediately after the start of the voltage application process (for example, within 30 seconds).

[0025] (3) The self-discharge inspection method of the electricity storage device according to (1) may be configured such that the load reduction process is a process of reducing the load applied to the electricity storage device after a predetermined second time has elapsed since the start of the voltage application process. The load reduction amount is a limit load reduction amount that satisfies the following conditions: (iii) the electricity storage device is a limit device with a self-discharge current equal to the limit current value, and (iv) for the limit device, when the load is reduced by the load reduction amount from the first load after the second time has elapsed since the start of the voltage application process, the power supply current rapidly increases due to the decrease in the device voltage accompanying the load reduction and then quickly stabilizes.

[0026] In this inspection method, in advance, for a limit device with a self-discharge current equal to the limit current value, a limit load reduction amount is obtained. Specifically, for the limit device, the following load reduction amount is obtained and set as the limit load reduction amount, that is, when the load is reduced by the load reduction amount from the first load after the second time has elapsed since the start of the voltage application process, the power supply current rapidly increases due to the decrease in the device voltage accompanying the load reduction and then quickly stabilizes.

[0027] In this inspection method, in the load reduction process, after the second time has elapsed since the start of the voltage application process, the load is reduced from the first load by the limit load reduction amount.

[0028] Therefore, when the electricity storage device under inspection is a limit device, the power supply current quickly stabilizes. On the other hand, when the electricity storage device under inspection is a non-conforming device with a self-discharge current larger than that of the limit device, due to the decrease in the device voltage accompanying the load reduction, the power supply current rapidly increases, and then, after a period of slow increase, it finally stabilizes. On the other hand, when the electricity storage device under inspection is a conforming device with a self-discharge current smaller than that of the limit device, due to the decrease in the device voltage accompanying the load reduction, the power supply current rapidly increases, then reverses and quickly decreases to stabilize.

[0029] That is, depending on whether the electricity storage device under inspection is a limit device, a conforming device, or a non-conforming device, the change in the power supply current becomes different. Therefore, even if the power supply current is unstable, in the determination process, it is possible to easily determine whether the electricity storage device is qualified based on the detected power supply current.

[0030] In particular, in the determination process, a device under inspection whose power supply current rapidly increases, then reverses and quickly decreases is determined as a conforming device, and other devices under inspection are determined as non-conforming devices, so that it is possible to determine whether it is qualified earlier than before.

[0031] In addition, the "boundary current value" refers to a reference current value used to determine the pass or fail of the power storage device by comparing it with the self-discharge current of the power storage device charged to the voltage of the first device, or a reference current value used to determine whether it belongs to any one of multiple reference current values of multiple levels.

[0032] In addition, preferably, the second time when the load reduction process starts after the start of the voltage holding process is set at the latest within 1 / 2 of the stabilization arrival time required for the power supply current to stabilize when the voltage holding process is performed without performing the load reduction process on the qualified device after the start of the voltage holding process. This is because if the second time exceeds 1 / 2 of the stabilization arrival time, the effect of shortening the stabilization arrival time caused by performing the load reduction process becomes smaller. As the second time, it is preferably set immediately after the start of the voltage holding process (for example, within 30 seconds).

[0033] (4) Another solution is a manufacturing method of a power storage device, comprising: a primary charging process of performing primary charging on the assembled uncharged power storage device until a predetermined charging state to make it a pre-charged power storage device; and an inspection process of inspecting the self-discharge state of the power storage device that has completed the primary charging by using the self-discharge inspection method of the power storage device described in any one of the above (1) to (3).

[0034] In the manufacturing method of the power storage device described above, after the primary charging process, an inspection process using the above self-discharge inspection method is performed. Therefore, it is possible to manufacture a power storage device by inspecting the presence or absence and degree of short circuit in the initial stage of the power storage device with an improved new inspection method.

[0035] In addition, it is further preferable to provide a high-temperature aging process of placing the power storage device in an open-circuit state at a high temperature and a subsequent cooling process between the primary charging process and the inspection process, because the voltage of the power storage device is likely to become stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a longitudinal sectional view of the battery according to Embodiments 1 and 2 and Modification 1.

[0037] Figure 2 is a flowchart of the manufacturing process of the battery including the inspection process of the self-discharge of the battery according to Embodiments 1 and 2 and Modification 1.

[0038] Figure 3 is an explanatory view showing a state in which the battery according to Embodiments 1 and 2 and Modification 1 is mounted on a jig capable of increasing and decreasing the load.

[0039] Figure 4It is a circuit diagram in a state where an external power supply is connected to a battery, related to the self-discharge inspection method of the batteries according to Embodiment 1, Embodiment 2, and Modification 1.

[0040] Figure 5 It is a graph schematically showing the time changes of the power supply voltage, load, and power supply current with respect to the voltage application time for each of the qualified and unqualified batteries according to Embodiment 1 and the reference embodiment.

[0041] Figure 6 It is a graph schematically showing the time changes of the power supply voltage, load, and power supply current with respect to the voltage application time for each of the qualified and unqualified batteries according to Modification 1 and the reference embodiment.

[0042] Figure 7 It is a graph schematically showing the time changes of the power supply voltage, load, and power supply current with respect to the voltage application time for each of the qualified, unqualified, and boundary batteries according to Embodiment 2 and the reference embodiment.

[0043] Description of reference numerals

[0044] 1... (charged) battery (power storage device); S2... load application process; KJ... restraint jig; S3... initial charging process; S6... placement process; S7... initial battery voltage measurement process (voltage detection process, inspection process); S8... voltage continuous external processing process (inspection process); S9... current detection process (inspection process); S10... continuous judgment process (inspection process); t... voltage application time; t1... first time; t2... second time; S11... determination process (inspection process); S12... load reduction process (inspection process); BL... (load applied to the battery); BL1... first load; BL2... second load; BL3... third load; BL4... fourth load; ΔBL... load reduction amount; ΔBLg2, ΔBLg3... qualified load reduction amount; ΔBLth... limit load reduction amount; TB... battery temperature (equipment temperature); TB1... first battery temperature (first equipment temperature); VB... battery voltage (equipment voltage); VB1... first battery voltage (first equipment voltage); EP... external power supply; VP... (power supply voltage of the external power supply); VPc... continuous power supply voltage; IP... power supply current; IP0... initial current value; IP(n)... (acquired) power supply current value; IPs... stable power supply current; IPth... (limit current value of the power supply current); 1B... battery component; VBB... (battery component voltage generated in the battery component); Rs... (DC resistance of the battery); Rp... (short-circuit resistance of the battery); ID... self-discharge current; IDth... (limit current value of the self-discharge current) Detailed implementation mode

[0045] (Embodiment 1)

[0046] Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings. Figure 1 FIG. shows a longitudinal sectional view of a lithium-ion secondary battery (hereinafter simply referred to as "battery") 1 according to Embodiment 1. The battery 1 is composed of a battery case 10 in the shape of a rectangular parallelepiped box, a flat wound electrode body 20 and an electrolyte 15 housed therein, a positive terminal component 30 and a negative terminal component 40 supported by the battery case 10, etc. In Embodiment 1, as the positive electrode active material, a lithium transition metal composite oxide is used, specifically, lithium nickel cobalt manganese oxide is used, and as the negative electrode active material, a carbon material is used, specifically, graphite is used. In addition, the battery 1 in the deformation mode 1, Embodiment 2, and the reference mode described later is also the same.

[0047] Next, a self-discharge inspection method for determining the insulation inside the battery 1 and a manufacturing method of the battery 1 including the self-discharge inspection method will be described (see Figure 2 ). First, in the "assembly process" S1, an uncharged battery 1X is assembled (see Figure 1 ). The subsequent initial battery voltage measurement process S7 to determination process S11 and load reduction process S12 also correspond to the inspection processes in the manufacturing method of the battery 1.

[0048] Next, in the "load application process" S2, as the load BL, a predetermined first load BL1 (in the present Embodiment 1, for example, BL1 = 918 kgf = 9 kN) is applied to the assembled battery 1X (the subsequent battery 1). Specifically, as Figure 3 shown, using the restraint jig KJ, the battery 1 (battery 1X) is restrained in an elastically compressed state in the battery thickness direction (the direction perpendicular to the paper surface in Figure 1 ) with the first load BL1. More specifically, for the two fixed plates KJP1 and KJP2 whose intervals are fixed by the support columns KJC and fixing nuts KJN of the restraint jig KJ, the battery 1 (battery 1X) is sandwiched between the lower fixed plate KJP1 and the pressing plate KJMP in the figure below, and using its male thread portion KJMCs, the pressing nut KJMN, and the compression spring KJMS held between two washers KJMW, the columnar pressing member KJMC is elastically pressed in, thereby applying the load BL to the battery 1 (battery 1X).

[0049] In addition, in advance, instead of the battery 1, a pressure measuring element (not shown) is sandwiched between the fixed plate KJP1 and the pressing plate KJMP, and the pressing nut KJMN is tightened to obtain the relationship between the length LL of the compression spring KJMS (the interval between the two washers KJMW on both sides of the compression spring KJMS) and the load applied to the pressure measuring element. Thus, as long as the length LL of the compression spring KJMS is measured, the magnitude of the load BL applied to the battery 1 by the restraint jig KJ can be detected.

[0050] In this way, while keeping the first load BL1 applied to the battery 1 (battery 1X) unchanged, the battery 1 is subjected to the initial charging process S3 to the subsequent continuous determination process S10 and load reduction process S12. In each process, the ambient temperature TK around the battery 1 is detected using a temperature detection device KTS having a temperature sensor KT composed of a thermistor. In addition, the battery temperature TB of the battery 1 is detected using a temperature detection device STS having a temperature sensor ST composed of a thermistor that contacts a specified position of the battery case 10 (see Figure 4 ).

[0051] Next, in the "initial charging process" S3, the uncharged battery 1X is initially charged to become the battery 1. At the initial charging temperature FT (FT = 20°C), the charging and discharging device (not shown) is connected to the two terminal components 30 and 40 of the battery 1X constrained by the used restraint jig KJ, and the battery 1 is initially charged by constant current constant voltage (CCCV) charging until the battery voltage VB of the battery 1X becomes a predetermined value (in this embodiment, VB = 4.0V).

[0052] Next, in the "high-temperature aging process" S4, the battery 1 that has completed the initial charging is aged at the aging temperature ET (ET = 63°C) for the aging period EK (EK = 20 hours) with the two terminal components 30 and 40 open, for high-temperature aging. If this high-temperature aging is performed, the battery voltage VB of the battery 1 decreases and becomes a battery voltage corresponding to about 80% of the SOC.

[0053] Next, in the "cooling process" S5, the battery 1 is placed in the cooling chamber CR at the cooling temperature CT (CT = 20°C) for 20 minutes and forced-cooled with a fan so that the battery temperature TB becomes approximately 20°C (TB ≈ 20°C) (refer to Figure 2 ).

[0054] And, in the "placement process" S6, the battery 1 is transferred to the first chamber KR1 where the ambient temperature TK is set to the first ambient temperature TK1 (TK1 = 20.0°C) and placed for the placement period HP (for example, HP = 30 minutes) so that the battery temperature TB of the battery 1 becomes the same first battery temperature TB1 (TB1 = 20.0°C) as the first ambient temperature TK1 (refer to Figure 2 ). Moreover, after the placement process S6, in the subsequent initial battery voltage measurement process S7 to the continuous determination process S10, it is also performed under the condition that the battery temperature TB of the battery 1 is the first battery temperature TB1.

[0055] In the "initial battery voltage measurement process" S7, the open-circuit voltage of the battery 1, that is, the first battery voltage VB1, at the first ambient temperature TK1 and becoming the first battery temperature TB1 (TB1 = 20.0°C) is measured. Specifically, as Figure 4 shown, a pair of probes P1 and P2 of the external power supply EP are brought into contact with the positive terminal component 30 and the negative terminal component 40 of the battery 1 respectively, the external power supply EP is connected to the battery 1, the power supply current IP flowing from the external power supply EP to the battery 1 is made zero (IP = 0: the state where the DC voltage source EPE is cut off), and the first battery voltage VB1 of the battery 1 is measured with the voltmeter EPV.

[0056] In Figure 4The external power supply EP used in the present Embodiments 1 and 2 and Modification 1 shown is a precision DC power supply that can change and can precisely control the power supply voltage VP generated by the DC voltage source EPE, that is, a variable constant voltage power supply. In addition to the voltmeter EPV that can precisely measure the power supply voltage VP applied to the battery 1, the external power supply EP also has an ammeter EPI that can precisely measure the power supply current IP flowing from the external power supply EP to the battery 1.

[0057] In Figure 4 , the wiring resistance Rw represents the wiring resistance distributed within the external power supply EP and from the external power supply EP to the probes P1 and P2. In addition, the contact resistance R12 represents the sum of the contact resistance generated between one probe P1 of the external power supply EP and the positive terminal component 30 of the battery 1 and the contact resistance generated between the other probe P2 of the external power supply EP and the negative terminal component 40 of the battery 1.

[0058] In addition, Figure 4 also shows the equivalent circuit of the battery 1 (qualified battery 1G, unqualified battery 1N, limit battery 1TH) including the battery component 1B, the DC resistance Rs, and the short-circuit resistance Rp. Among them, the battery component 1B is the capacity component formed by the battery 1 and generates the battery component voltage VBB. The DC resistance Rs is a battery resistance that can be regarded as existing in series with the battery component 1B between the two terminal components 30 and 40 of the battery 1. On the other hand, the short-circuit resistance Rp is a resistance representing the magnitude of the self-discharge generated due to the internal short circuit of the battery 1. The self-discharge current ID shown by the dotted arrow represents the current of the self-discharge flowing from the battery component 1B to the short-circuit resistance Rp.

[0059] The battery component voltage VBB is consistent with the battery voltage VB when the power supply current IP is zero (IP = 0). In the initial battery voltage measurement step S7, only the first battery voltage VB1 was measured. Therefore, at the beginning of the subsequent "voltage continuously applied step" S8 (when the voltage application time t = 0), the battery component voltage VBB generated by the battery component 1B is equal to the first battery voltage VB1 (VBB = VB1, t = 0).

[0060] In addition, (without reconnecting the pair of probes P1 and P2 to the terminal components 30 and 40), maintaining the connection state of the probe P1 with the positive terminal component 30 and the contact state of the probe P2 with the negative terminal component 40, proceeding from this initial battery voltage measurement step S7 to the subsequent continuous determination step S10 (the same in Modification 1 and Embodiment 2). This is to avoid changes in the contact state of the probes P1 and P2 with respect to the terminal components 30 and 40 during each contact, and fluctuations in the magnitude of the contact resistance R12 generated between the probe P1 and the positive terminal component 30 and between the probe P2 and the negative terminal component 40.

[0061] In Embodiments 1 and 2 and Modification 1, the changes in the plurality of batteries 1 (qualified battery 1G, unqualified battery 1N, boundary battery 1TH) are examined. To facilitate the examination, in each battery 1, the only differences are the short-circuit resistance Rp and the magnitude of the self-discharge current ID flowing therethrough, and the capacity of the battery component 1B, the magnitude of the DC resistance Rs, etc. are the same (equal to each other). In addition, the wiring resistance Rw and the contact resistance R12 are also equal. Further, for each battery 1, the initial battery voltage measurement step S7 and the first battery voltage VB1 at the beginning (voltage application time t = 0) of the voltage continuous application step S8, that is, the battery component voltage VBB of the battery component 1B, are also equal to each other.

[0062] Next, in the "voltage continuous application step" S8, at the first ambient temperature TK1, when the first battery temperature TB1 becomes equal to the first ambient temperature TK1, the DC voltage source EPE of the external power supply EP generates a continuous power supply voltage VPc equal to the first battery voltage VB1 obtained in the above-described initial battery voltage measurement step S7 (VPc = VB1), and starts to apply it to the battery 1 (voltage application time t = 0). Thereafter, the continuous power supply voltage VPc is continuously applied. That is, the continuous power supply voltage VPc generated by the external power supply EP is maintained at a magnitude equal to the initially obtained first battery voltage VB1 without change. Since VPc = VB1, similar to Patent Document 1, at the beginning of this voltage continuous application step S8, the power supply current IP does not flow into the battery 1. In addition, as Figure 2 shown, a load reduction step S12 described later is performed in parallel with this voltage continuous application step S8.

[0063] In the "current detection step" S9, the power supply current IP is detected by the ammeter EPI. That is, every predetermined time (in this embodiment, every 10 seconds), the power supply current value IP(n) (n is an integer of 0 or more indicating the acquisition order) of the power supply current IP flowing from the external power supply EP to the battery 1 is obtained. In addition, as described above, the power supply current value IP(0) of the power supply current IP at the beginning (voltage application time t = 0) when the continuous power supply voltage VPc is applied is zero (IP(0) = 0). Moreover, as the voltage application time t elapses, the power supply current IP (power supply current value IP(n)) slowly increases in a manner approaching the magnitude of the inherent self-discharge current ID that varies depending on the different batteries 1 (refer to the reference mode). However, in this Embodiment 1, the load BL applied to the battery 1 is reduced by the load reduction step S12 described later. Therefore, as the load BL is reduced, the power supply current IP (power supply current value IP(n)) rapidly increases, and then changes again toward the magnitude of the self-discharge current ID of the battery 1 and finally stabilizes.

[0064] In the "continuous determination process" S10, it is determined whether the voltage continuous application process S8 and the current detection process S9 are repeated again. In the present Embodiment 1, it is determined whether the power supply current IP (specifically, the power supply current value IP(n)) has stabilized after starting to apply the continuous power supply voltage VPc to the battery 1. Here, when the answer is no, that is, when the power supply current IP has not stabilized, the process returns to the voltage continuous application process S8, and the continuous power supply voltage VPc is continuously applied to the battery 1 (S8), and the power supply current IP is detected again (S9). On the other hand, when the answer is yes, that is, when the power supply current IP has stabilized, the process proceeds to the "determination process" S11 described later.

[0065] In this continuous determination process S10, as a method for determining whether the power supply current IP has stabilized, for example, the following method can be cited. That is, in the continuous determination process S10, the moving average value of the power supply current value IP(n) is calculated in sequence (for example, the moving average value of the 7 power supply current values IP(n - 6) to IP(n) obtained in the most recent 60 seconds), and based on the change of this moving average value (for example, the difference value of the moving average value, the magnitude of the differential value), it is determined whether the power supply current value IP(n) has stabilized.

[0066] The "load reduction process" S12 that is performed in parallel with the voltage continuous application process S8 reduces the load BL applied to the battery 1 by the load reduction amount ΔBL from the first load BL1 after a predetermined first time t1 (t = t1) has elapsed from the start (t = 0) during the period before the power supply current IP stabilizes after the voltage continuous application process S8 starts (the voltage application time t > 0). In the present Embodiment 1, the first time t1 is set to 5.0 minutes (= 300 seconds), and the load reduction amount ΔBL is set to the qualified load reduction amount ΔBLg2. Hereinafter, how the power supply current value IP(n) of the power supply current IP flowing from the external power supply EP to the battery 1 changes in this case will be studied.

[0067] (Reference mode)

[0068] Here, first, as a reference mode, refer to Figure 4 , Figure 5 , and study the method described in Patent Document 1, that is, as shown by the thick solid line in the middle layer of Figure 5 , after the voltage application starts (t = 0), the change of the power supply current IP in the case where the continuous power supply voltage VPc equal to the first battery voltage VB1 is continuously applied from the external power supply EP to the battery 1. In addition, as shown by the thin solid line in the upper layer of Figure 5 , the load BL applied to the battery 1 is constantly the first load BL1.

[0069] If a first battery voltage VB1 is continuously externally applied to the battery 1 from an external power source EP, then as the voltage application time t elapses, the battery component voltage VBB of the battery component 1B gradually decreases from the first battery voltage VB1 at the start of the voltage continuous application process S8 (t = 0). This is because the charge accumulated in the battery component 1B discharges slowly through the short - circuit resistance Rp due to the self - discharge current ID.

[0070] Therefore, at the beginning of the application of the first battery voltage VB1 (voltage application time t = 0), the power supply current IP does not flow (IP(0)=0), but if the battery component voltage VBB generated in the battery component 1B becomes smaller, then as can be easily understood, a potential difference (VB1 - VBB) is generated across the series resistance of the DC resistance Rs, the contact resistance R12, and the wiring resistance Rw, and the corresponding power supply current IP flows through the path shown by the double - dotted arrow to the battery 1 (VB1 = VBB+(Rs + R12+Rw)·IP). Figure 4 Moreover, as shown by the thin solid line and thin dotted line in the lower layer of

[0071] and as shown in Figure 5 the magnitude of the power supply current IP of this reference method gradually increases as the battery component voltage VBB of the battery component 1B decreases. However, as can be understood from Figure 4 if the power supply current IP increases as the battery component voltage VBB decreases, and the back - electromotive force Vp (Vp = Rp·IP) generated in the short - circuit resistance Rp becomes equal to the battery component voltage VBB generated in the battery component 1B, then the self - discharge current ID no longer flows out of the battery component 1B. Thus, the decrease in the battery component voltage VBB in the battery component 1B also stops, and the power supply current IP becomes a stable power supply current Ips of the same magnitude as the self - discharge current ID and stabilizes.

[0072] Therefore, in the case where the battery under test 1 is a qualified battery (a battery with a large short - circuit resistance Rp and a self - discharge current ID smaller than the limit current value IDth) 1G, the battery component voltage VBB of the battery component 1B decreases slowly, and the power supply current IP also increases slowly (refer to the thin solid line in the lower layer of Figure 5 ). In addition, the stable power supply current value IPsg of this qualified battery 1G is small (for example, assuming IPsg = 15 μA as a typical value of the qualified battery 1G).

[0073] In contrast, in the case where the battery under test 1 is a non - qualified battery (a battery with a smaller short - circuit resistance Rp and a self - discharge current ID larger than the limit current value IDth compared to the qualified battery 1G) 1N, compared with the qualified battery 1G, the battery component voltage VBB of the battery component 1B decreases relatively significantly, and the power supply current IP also increases relatively significantly (refer to Figure 5(the thin dashed line in the lower layer). The steady-state power supply current value IPsn of the defective battery 1N is also larger than the steady-state power supply current value IPsg of the non-defective battery 1G (for example, assuming IPsn = 27 μA > IPsg as a typical value of the defective battery 1N).

[0074] Therefore, based on the value of the steady-state power supply current IPs (IPsg, IPsn), or the value and changing state of the increasing speed of the power supply current IP (the change of the power supply current IP over time), it is possible to determine whether the inspected battery 1 is qualified (refer to Patent Document 1). For example, in Figure 5 the lower-layer curve graph, as Figure 5 shown by the thin solid line in, the limit current value IPth of the power supply current IP (equal to the limit current value IDth of the self-discharge current ID) is determined as the intermediate value between the steady-state power supply current value IPsg of the non-defective battery 1G and the steady-state power supply current value IPsn of the defective battery 1N (for example, set IPth = 20 μA). Thus, by comparing the obtained value of the steady-state power supply current IPs (IPsg, IPsn) with the limit current value IPth, it is possible to determine whether the battery 1 is qualified.

[0075] However, in the method of this reference mode, it takes time from the start of continuously applying the power supply voltage VPc to the battery 1 (t = 0) until it is possible to determine whether the battery 1 is qualified. In the case of obtaining the value of the steady-state power supply current IPs for determination, for example, in Figure 5 the above example shown by the thin solid line and the dashed line in the lower-layer curve graph, it can be seen that in order to obtain the value of the steady-state power supply current IPs (IPsg, IPsn), it is necessary to wait for the voltage application time t to pass more than 55 minutes.

[0076] In this way, in the prior art, it takes time until it is possible to determine whether the battery 1 is qualified because the battery component voltage VBB can only be slowly reduced.

[0077] Therefore, in the first embodiment, as Figure 5 shown by the thick solid line in the middle-layer curve graph, after the start of the voltage continuous application process S8 (voltage application time t = 0), the continuous power supply voltage VPc is continuously applied to the inspected battery 1. Moreover, as Figure 5 shown by the thick solid line in the upper-layer curve graph, at the time point after the first time t1 (t1 = 5.0 minutes in this embodiment) has passed, the load BL applied to the battery 1 is rapidly reduced (within 1 minute in the first embodiment, for example, within 10 seconds) from the first load BL1 to the second load BL2. In addition, the load reduction amount ΔBL (= BL1 - BL2) is set as the qualified load reduction amount ΔBLg2 determined by the following method.

[0078] That is, for the qualified battery 1G, at the time point when the first time t1 (= 5.0 minutes) has elapsed since the start of the voltage continuous external processing step S8, the load BL is reduced from the first load BL1 by the load reduction amounts ΔBL of various magnitudes. Moreover, after obtaining a sharp increase in the power supply current due to the reduction of the load BL and then a rapid stabilization of the load reduction amount ΔBL, the load reduction amount ΔBL is set as the qualified load reduction amount ΔBLg2. Specifically, the load reduction amount ΔBL at which the power supply current IP does not increase slowly or conversely decrease after a sharp increase, but rather the power supply current IP stabilizes most rapidly, is set as the qualified load reduction amount ΔBLg2. This qualified load reduction amount ΔBLg2 is substantially equivalent to the magnitude of the load reduction amount ΔBL that causes the following voltage drop in the battery 1. This voltage drop is equivalent to the product (ΔIP·(Rs + R12 + Rw)) of the differential current ΔIP (= IPsg - IP(t1)) between the power supply current IP(t1) flowing through the qualified battery 1G at the first time t1 before the load change and the stable power supply current value IPsg of the qualified battery 1G in the reference method without load reduction, and the series resistance (Rs + R12 + Rw) of the DC resistance Rs, the contact resistance R12, and the wiring resistance Rw.

[0079] Here, consider the case where the battery 1 under inspection is a qualified battery 1G. In this case, as Figure 5 shown by the thick solid line in the lower graph, from the start of the voltage continuous external processing step S8 until the first time t1 has elapsed (until the start of the load reduction step S12), the power supply current IP increases slowly, the same as the qualified battery 1G in the reference method shown by the thin solid line. On the other hand, if the first time t1 has elapsed, due to the reduction of the battery component voltage VBB caused by reducing the load BL applied to the battery 1 by the qualified load reduction amount ΔBLg2, the power supply current IP increases sharply. Moreover, when the load BL is reduced to the second load BL2, the power supply current IP quickly converges to the stable power supply current value IPsg2 of the qualified battery 1G under the new load (the second load BL2), and then maintains this stable power supply current value IPsg2. Here, by comparing with the case of the reference method shown by the thin solid line, it can be seen that if compared among the qualified batteries 1G, according to the method of the first embodiment 1, the time taken for the power supply current IP to stabilize can be significantly shortened compared to the method of the reference method.

[0080] Next, consider the case where the battery 1 under inspection is a non - qualified battery 1N. In this case, as Figure 5As shown by the thick dashed line in the lower-layer curve graph, from the start of the voltage application continuation process S8 until the first time t1 has elapsed (until the start of the load reduction process S12), the power supply current IP increases slowly in the same manner as the defective battery 1N of the reference method shown by the thin dashed line. On the other hand, if the first time t1 has elapsed, due to the decrease in the battery component voltage VBB caused by reducing the load BL applied to the battery 1 by the qualified load reduction amount ΔBLg2, the power supply current IP increases sharply. However, different from the case of the above-mentioned qualified battery 1G, after the load BL becomes the second load BL2, the power supply current IP passes through a period of slow increase and finally stabilizes. That is, it slowly increases toward the stable power supply current value IPsn2 of the defective battery 1N under the new load (the second load BL2), and then reaches this stable power supply current value IPsn2 and becomes stable. Here, by comparing with the case of the reference method shown by the thin dashed line, it can be seen that even when comparing defective batteries 1N with each other, according to the method of the first embodiment 1, compared with the method of the reference method, the time taken for the power supply current IP to reach stability can be significantly shortened.

[0081] Therefore, it can be seen that in the first embodiment 1, regardless of whether the battery 1 is a qualified battery 1G or a defective battery 1N, compared with the method of the reference method, the determination of the self-discharge state of the battery 1 in the determination process S11 can be performed earlier.

[0082] In addition, if the same qualified battery 1G is observed, the stable power supply current value IPsg2 under the second load BL2 of the first embodiment 1 is a slightly smaller value compared with the stable power supply current value IPsg under the reference method, that is, under the first load BL1. When the same defective battery 1N is observed, the stable power supply current value IPsn2 under the second load BL2 of the first embodiment 1 is also a slightly smaller value compared with the stable power supply current value IPsn under the reference method, that is, under the first load BL1. This is because the smaller the load BL, the smaller the self-discharge current ID.

[0083] Then, in the "determination process" S11, based on the obtained power supply current IP, specifically, using the column of power supply current values IP(0), IP(1), …, IP(n) obtained after the start of the voltage application continuation process S8 (voltage application time t = 0), the self-discharge state of the battery 1 is determined.

[0084] In Embodiment 1, specifically, among a series of power supply current values IP(0), IP(1), …, IP(n) obtained at regular time intervals (in this embodiment, every 10 seconds), 7 power supply current values IP(n-6) to IP(n) obtained at the end of the voltage application continuation process S8 (in this embodiment, during the last 60 seconds) are averaged to calculate the average end-period power supply current value IPE (IPE = (IP(n-6) + … + IP(n)) / 7). The average end-period power supply current value IPE represents the value of the stable power supply current IPs obtained at the end of the voltage application continuation process S8. This is compared with the threshold current value IPth, and the battery 1 for which the average end-period power supply current value IPE is smaller than the threshold current value IPth (IPE < IPth) is determined to be a qualified battery 1G. Therefore, it is possible to manufacture the charged battery 1 (qualified battery 1G) and inspect its self-discharge state.

[0085] On the other hand, the battery 1 for which the average end-period power supply current value IPE is greater than or equal to the threshold current value IPth (IPE ≥ IPth) is determined to be a non-qualified battery 1N. The battery 1 that has been determined to be a non-qualified battery 1N is removed and discarded. Or it may be disassembled, etc. and then reused.

[0086] In the above-described Embodiment 1, in the determination process S11, a plurality of power supply current values IP(n), etc. obtained at the end are averaged to calculate the average end-period power supply current value IPE corresponding to the value of the stable power supply current IPs, and this is compared with the threshold current value IPth to determine the qualification of the battery 1.

[0087] However, it is also possible to use the last obtained moving average value MIP(n) among the moving average values MIP(n) of a plurality (for example, 7) of the most recently obtained power supply current values IP(n-6) to IP(n) obtained in the continuous determination process S10 as the above-described average end-period power supply current value IPE, and determine the self-discharge state of the battery 1 in the determination process S11. That is, in the determination process S11, it is also possible to compare the last obtained moving average value MIP(n) in the continuous determination process S10 with the threshold current value IPth to determine the qualification of the battery 1.

[0088] As described above, in the method of the first embodiment 1, it is possible to provide an improved new inspection method by performing self-discharge inspection through the initial battery voltage measurement step S7 to the determination step S11 and the load reduction step S12. In addition, in the manufacturing method of the battery 1 of the first embodiment 1, after the initial charging step S3, an inspection step including the initial battery voltage measurement step S7 to the determination step S11 and the load reduction step S12 is performed. Therefore, it is possible to inspect the presence or absence and degree of short circuit in the initial stage of the battery 1 using the improved new inspection method to manufacture the battery 1.

[0089] In addition, in the inspection method of the first embodiment 1, after the first time has elapsed since the start of the voltage application step, the load BL applied to the battery 1 to be inspected is reduced by the qualified load reduction amount ΔBLg2. Therefore, regardless of whether the battery 1 to be inspected is a qualified battery 1G, it is possible to determine the pass or fail of the power storage device earlier than in the conventional inspection method.

[0090] (Variant 1)

[0091] In the above-described first embodiment 1 (refer to Figure 5 ), through the load reduction step S12, after the first time t1 (specifically, t1 = 5.0 minutes) has elapsed since the start of the voltage application step S8, the load BL of the battery 1 is reduced by the qualified load reduction amount ΔBLg2. However, the load reduction step S12 can also be performed at any time after the start of the voltage application step S8 and before the power supply current IP stabilizes. Among them, for ease of understanding, it is most preferably performed immediately after the start of the voltage application step S8.

[0092] Therefore, in this variant 1, immediately after the start of the voltage application step S8, specifically, setting it as the first time t1 (t1 ≤ 30 seconds), the load reduction step S12 is performed (refer to Figure 2 , Figure 6 ).

[0093] In addition, this variant 1 and the above-described first embodiment 1 only differ in the timing of performing the load reduction step S12, and the others are the same. Therefore, the description will be centered on the different parts, and the same parts will be omitted or simplified.

[0094] The battery 1 used in this variant 1 (refer to Figure 1 ) is the same as the battery 1 used in the first embodiment 1 and the like, so the description is omitted. In addition, the assembly step S1 to the determination step S11 in the manufacturing method of the battery 1 (refer to Figure 2 ) are also the same as those in the first embodiment 1, so the description is omitted.

[0095] As described above, in the first modification 1, the first time t1 = 30 seconds. In addition, the load reduction amount ΔBL is set to the pass load reduction amount ΔBLg3 different from that in the first embodiment.

[0096] In addition, the pass load reduction amount ΔBLg3 is the same as the pass load reduction amount ΔBLg2 obtained in the first embodiment. For the pass battery 1G, at the time point after the first time t1 (= 30 seconds) from the start of the voltage application continuation process S8, the load BL is reduced from the first load BL1 by the load reduction amounts ΔBL of various magnitudes. Then, the load reduction amount ΔBL at which the power supply current IP stabilizes most rapidly after the reduction of the load BL is set as the pass load reduction amount ΔBLg3. This pass load reduction amount ΔBLg3 is larger than the pass load reduction amount ΔBLg2 used in the first embodiment (ΔBLg3 > ΔBLg2). Compared with the first embodiment in which the load reduction process S12 is performed after 5.0 minutes from the start of the voltage application continuation process S8, the increase amount of the power supply current IP in the first modification 1 is small because the decrease of the battery component voltage VBB is small. Therefore, it is necessary to decrease the battery component voltage VBB more greatly by reducing the load BL.

[0097] In the first modification 1, as shown by the thick solid line in the Figure 6 middle layer, after the start of the voltage application continuation process S8 (voltage application time t = 0), the continuous power supply voltage VPc is continuously applied. And, as shown by the thick solid line in the Figure 6 graph in the upper layer, at the time point after the first time t1 (t1 = 30 seconds in the first modification 1), the load BL of the battery 1 is rapidly (also within 1 minute, for example, within 10 seconds in the first modification 1) reduced from the first load BL1 to the third load BL3, reducing the above-mentioned pass load reduction amount ΔBLg3 (= BL1 - BL3).

[0098] Use the Figure 6 graph in the lower layer to explain how the power supply current value IP(n) of the power supply current IP flowing from the external power supply EP to the battery 1 changes in this case.

[0099] Here, in the case where the battery 1 under inspection is a pass battery 1G, as in Figure 6As shown by the thick solid line in the lower-layer curve graph, immediately after the start of the voltage application continuation step S8 (precisely, after the lapse of the first time t1 = 30 seconds), due to the reduction in the battery component voltage VBB caused by reducing the load BL applied to the battery 1 by the qualified load reduction amount ΔBLg3, the power supply current IP increases sharply. Moreover, when the load BL is reduced to the third load BL3, the power supply current IP rapidly converges to the stable power supply current value IPsg3 of the qualified battery 1G under the new load (the third load BL3), and then maintains this stable power supply current value IPsg3. Here, by comparing with the case of the reference method shown by the thin solid line, when comparing between the qualified batteries 1G, according to the method of this modified embodiment 1, compared with the method of the reference method (and also compared with the method of Embodiment 1 (refer to Figure 5 ))), the time taken for the power supply current IP to reach stability can be significantly shortened.

[0100] On the other hand, in the case where the battery 1 under inspection is a non-qualified battery 1N, as Figure 6 shown by the thick dashed line in the lower-layer curve graph, immediately after the start of the voltage application continuation step S8, due to the reduction in the battery component voltage VBB caused by reducing the load BL applied to the battery 1 by the qualified load reduction amount ΔBLg3, the power supply current IP increases sharply. However, different from the case of the above-mentioned qualified battery 1G, after the load BL becomes the third load BL3, the power supply current IP increases slowly. That is, it slowly increases towards the stable power supply current value IPsn3 of the non-qualified battery 1N under the new load (the third load BL3), and then reaches this stable power supply current value IPsn3 and becomes stable. Here, by comparing with the case of the reference method shown by the thin dashed line, even when comparing between the non-qualified batteries 1N, according to the method of this modified embodiment 1, compared with the method of the reference method (and also compared with the method of Embodiment 1 (refer to Figure 5 ))), the time taken for the power supply current IP to reach stability can also be significantly shortened.

[0101] Therefore, it can be seen that in this modified embodiment 1, regardless of whether the battery 1 is a qualified battery 1G or a non-qualified battery 1N, compared with the method of the reference method, and also compared with the method of Embodiment 1 (refer to Figure 5 ), the determination of the self-discharge state of the battery 1 in the determination step S11 can be carried out earlier.

[0102] (Embodiment 2)

[0103] In the above-mentioned Embodiment 1 and Modified Embodiment 1 (refer to Figures 1 to 6)In [the above], in the load reduction process S12, as the load reduction amount ΔBL reduced from the first load BL1, the load BL applied to the battery 1 is reduced by the qualified load reduction amounts ΔBLg2 and ΔBLg3 obtained for the qualified battery 1G.

[0104] In contrast, in the second embodiment 2 (refer to Figures 1 to 4 , Figure 7 ), the difference is that in the load reduction process S12, the limit load reduction amount ΔBLth obtained for the limit battery 1TH is used as the load reduction amount ΔBL, and the load BL applied to the battery 1 is reduced from the first load BL1 by the limit load reduction amount ΔBLth. In addition, the second time t2 is set to t2 = 30 seconds in the same manner as the first time t1 in the first modified embodiment. Therefore, the description will be centered on the different parts, and the description of the same parts will be omitted or simplified.

[0105] The battery 1 used in the second embodiment 2 is the same as the battery 1 used in the first embodiment and the like, so the description is omitted. In addition, the assembly process S1 to the determination process S11 in the manufacturing method of the battery 1 (refer to Figure 2 ) are also the same as those in the first embodiment, so the description is omitted.

[0106] As described above, in the second embodiment 2, the second time t2 is set to t2 = 30 seconds. In addition, the load reduction amount ΔBL is set to a different limit load reduction amount ΔBLth from that in the first embodiment and the like.

[0107] In addition, for the limit load reduction amount ΔBLth, for the limit battery 1TH in which the magnitude of the self-discharge current ID under the first load BL1 is equal to the limit current value IPth, at the time point after the elapse of the second time t2 (= 30 seconds) from the start of the voltage application continuation process S8, the load BL is reduced from the first load BL1 by the load reduction amounts ΔBL of various magnitudes. Moreover, the load reduction amount ΔBL having the magnitude at which the power supply current IP stabilizes most rapidly after the reduction of the load BL is set as the limit load reduction amount ΔBLth. This limit load reduction amount ΔBLth is larger than the qualified load reduction amounts ΔBLg2 and ΔBLg3 used in the first embodiment and the first modified embodiment (ΔBLth > ΔBLg3 > ΔBLg2). As can be easily understood from Figure 7 , this is because when performing the load reduction process S12, it is necessary to reduce the battery component voltage VBB more greatly by reducing the load BL.

[0108] In the second embodiment 2, in the same manner as the above-described first modified embodiment, as shown by the thick solid line in the middle layer in Figure 7 , after the start of the voltage application continuation process S8 (voltage application time t = 0), the continuous power supply voltage VPc is continuously applied. And, as inFigure 7 As shown by the thick solid line in the upper graph, at the time point after the second time t2 (= 30 seconds), the load BL of the battery 1 is rapidly reduced (also within 1 minute, for example, within 10 seconds in the present Embodiment 2) from the first load BL1 to the fourth load BL4, and the reduction of the above-mentioned limit is represented by the load reduction amount ΔBLth (= BL1 - BL4).

[0109] Use Figure 7 the lower graph to explain how the power supply current value IP(n) of the power supply current IP flowing from the external power supply EP to the battery 1 changes in this case.

[0110] Here, when the battery 1 under inspection is the limit battery 1TH, as shown by the thick dotted line in the Figure 7 lower graph, immediately after the start of the voltage application continuation process S8 (precisely, after the second time t2 = 30 seconds has elapsed), due to the decrease in the battery component voltage VBB caused by reducing the load BL applied to the battery 1 by the load reduction amount ΔBLth for the limit, the power supply current IP increases sharply. Moreover, when the load BL is reduced to the fourth load BL4, the power supply current IP quickly converges to the stable power supply current value IPsth4 of the limit battery 1TH under the new load (the fourth load BL4), and then maintains this stable power supply current value IPsth4. This change becomes the determination criterion for the pass / fail of the battery 1.

[0111] On the other hand, when the battery 1 under inspection is a non - compliant battery 1N, as Figure 7 shown by the thick dashed line in the lower graph, immediately after the start of the voltage application continuation process S8, due to the decrease in the battery component voltage VBB caused by reducing the load BL applied to the battery 1 by the load reduction amount ΔBLth for the limit, the power supply current IP increases sharply. However, different from the case of the above - mentioned limit battery 1TH, after the load BL becomes the fourth load BL4, the power supply current IP increases gradually. That is, it gradually increases towards the stable power supply current value IPsn4 of the non - compliant battery 1N under the new load (the fourth load BL4), and then reaches this stable power supply current value IPsn4 and becomes stable. Here, by comparing with the case of the reference method shown by the thin dashed line, even when comparing non - compliant batteries 1N with each other, according to the method of the present Embodiment 2, compared with the method of the reference method (and also compared with the method of Embodiment 1 (refer to Figure 5 ), it is possible to significantly shorten the time taken for the power supply current IP to reach stability.

[0112] On the other hand, when the battery 1 under inspection is a compliant battery 1G, as in Figure 7As shown by the thick solid line in the lower-layer curve graph, immediately after the start of the voltage application continuation process S8, similar to the boundary cell 1TH, due to the decrease in the battery component voltage VBB, the power supply current IP increases sharply. However, thereafter, if the load BL decreases to the fourth load BL4, the power supply current IP rapidly decreases towards the stable power supply current value IPsg4 of the qualified cell 1G under the new load (the fourth load BL4) and stabilizes. Here, by comparing with the case of the reference method shown by the thin solid line, if the qualified cells 1G are compared with each other, according to the method of the second embodiment 2, compared with the method of the reference method (and also compared with the method of the first embodiment (refer to Figure 5 ), the time taken for the power supply current IP to reach stability can be significantly shortened.

[0113] Therefore, in the second embodiment 2 as well, the self-discharge state of the battery 1 can be determined in the determination process S11 using the power supply current value IP(n) obtained after the start (t = 0) of the voltage application continuation process S8 by the same method as in the modified method 1. Therefore, according to the method of the second embodiment 2, compared with the existing method, the pass or fail of the battery 1 can be determined extremely early.

[0114] In the determination process S11, other determination methods can also be adopted. For example, in the determination process S11, using the power supply current value IP(n), a battery 1 with a negative slope of the change in the power supply current value IP(n) within a specified period (for example, a period of t = 6 to 7 minutes) of the voltage application time t is determined as a qualified cell 1G. On the other hand, a battery 1 that is not determined as a qualified cell 1G can be determined as a non-qualified cell 1N. In this case, compared with the first embodiment, the pass or fail of the battery 1 can also be determined extremely early.

[0115] In the inspection method of the second embodiment 2, it is also possible to provide an improved new inspection method by means of the self-discharge inspection performed through the initial battery voltage measurement process S7 to the determination process S11 and the load reduction process S12. In addition, in the manufacturing method of the battery 1 of the second embodiment 2, after the initial charging process S3, an inspection process composed of the initial battery voltage measurement process S7 to the determination process S11 and the load reduction process S12 is performed. Therefore, the presence or absence and the degree of short circuit in the initial stage of the battery 1 can be inspected by the improved new inspection method to manufacture the battery 1.

[0116] In the inspection method of the second embodiment, after a first period of time has elapsed since the start of the voltage application process, the load reduction amount ΔBLth of the load applied to the battery 1 under inspection is reduced. Therefore, depending on whether the battery 1 is a qualified battery 1G or a non-qualified battery 1N, the change in the power supply current IP is different. Thus, even without waiting for the power supply current IP to stabilize, after the load reduction process S12 is performed (after t = t2), by detecting whether the power supply current IP has decreased or increased from the threshold current value IPth, or whether it is in a decreasing trend or an increasing trend, it is possible to easily distinguish whether the battery 1 under inspection is a qualified battery 1G or a non-qualified battery 1N, so that the discrimination can be made earlier.

[0117] As described above, the present invention has been described in conjunction with the first and second embodiments and the first modification, but the present invention is not limited to the above-described embodiments and the like, and can of course be appropriately modified and applied without departing from its gist.

[0118] For example, in the first and second embodiments and the first modification, during the manufacturing process of the battery 1, an inspection process for self-discharge inspection of the battery 1 shown in the initial battery voltage measurement process S7 to the load reduction process S12 is performed. In contrast, for the used-up battery 1 that has been put on the market and used, these inspection processes can also be applied in the self-discharge inspection.

[0119] In addition, in the first and second embodiments and the first and second modifications, the threshold current value IPth is used to determine whether the battery 1 is qualified or not. However, multiple different threshold current values can also be used to classify the battery 1 into three or more grades.

[0120] In addition, an example in which the first time t1 is set to t1 = 5.0 minutes is shown in the first embodiment. However, in Figure 5 in the case where the load reduction process S12 is not performed on the qualified battery 1G but the voltage application process S8 is performed (that is, in the case of the reference method shown by the thin solid line in the lower graph of Figure 5 ), it took about 55 minutes for the power supply current IP to reach stability (the stable arrival time is about 55 minutes). From this, if the first time t1 is set to t1 = 27 minutes or less, which is half of the stable arrival time of the reference method, the effect of shortening the stable arrival time can be obtained to a certain extent.

Claims

1. A method for checking self-discharge of a power storage device, which is used to check the self-discharge of the power storage device, characterized in that, the power storage device has the following characteristics, that is, if it is pressed with a first load and the device voltage is charged to a first device voltage, and then the load is reduced from the first load, the device voltage is lower than the first device voltage, the method for checking self-discharge of the power storage device includes: a voltage detection step of detecting the first device voltage of the power storage device that is pressed with the first load and charged to the first device voltage; a voltage continuous application step of continuously applying a power supply voltage equal to the first device voltage to the power storage device from an external power supply; a current detection step of detecting the power supply current flowing from the external power supply to the power storage device; a determination step of determining the self-discharge state of the power storage device based on the detected power supply current; and a load reduction step of reducing the load applied to the power storage device by a load reduction amount from the first load after the voltage continuous application step starts and before the power supply current stabilizes.

2. The method for checking self-discharge of a power storage device according to claim 1, characterized in that, the load reduction step is a step of reducing the load applied to the power storage device after a predetermined first time after the voltage continuous application step starts, the load reduction amount is a qualified load reduction amount that satisfies the following conditions, (i) the power storage device is a qualified device with good self-discharge, and, (ii) for the qualified device, when the load is reduced by the load reduction amount from the first load after the first time has elapsed since the voltage continuous application step started, the power supply current increases sharply due to the decrease in the device voltage accompanying the load reduction and then quickly stabilizes.

3. The method for checking self-discharge of a power storage device according to claim 1, characterized in that, the load reduction step is a step of reducing the load applied to the power storage device after a predetermined second time after the voltage continuous application step starts, the load reduction amount is a limit load reduction amount that satisfies the following conditions, (iii) the power storage device is a limit device with a self-discharge current of the magnitude of the limit current value, and, (iv) for the limit device, when the load is reduced by the load reduction amount from the first load after the second time has elapsed since the voltage continuous application step started, the power supply current increases sharply due to the decrease in the device voltage accompanying the load reduction and then quickly stabilizes.

4. A manufacturing method of a power storage device, characterized in that, it includes: a primary charging step of performing primary charging on the assembled uncharged power storage device until a predetermined charging state is reached to make it a pre-charged power storage device; and an inspection step of inspecting the self-discharge state of the power storage device that has completed primary charging by using the method for checking self-discharge of a power storage device according to any one of claims 1 to 3.

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