Method for testing electric storage device for short circuit, method for manufacturing electric storage device, and method for manufacturing connected device restraint body

Abstract

To provide a method for inspecting a power storage device for a short circuit, capable of appropriately determining whether or not a short circuit exists in the power storage device that has been initially charged and adjusted to a predetermined device voltage, a method for manufacturing the power storage device using the inspection method, and a method for manufacturing a connected device restraining body.SOLUTION: A method for inspecting a battery 10 for a short circuit includes: a voltage adjustment step S4 for adjusting the battery 10 which has been subjected to initial charging and subsequent charging and discharging, to a first device voltage VB1; a pre-leaving voltage measurement step S51, S281 for measuring a pre-leaving device voltage VB2a; a leaving step S52 for leaving for a leaving period IH with terminals in an open state; a post-leaving voltage measurement step S53 for measuring a post-leaving device voltage VB2b; an actual measurement step S54 for obtaining an actual measured voltage drop rate DVB2; a short circuit determination step S57 for determining whether or not the battery is short-circuited; and an estimation step S55 for acquiring an estimated voltage drop rate EDV2 according to elapsed time KT and the leaving period IH prior to the short circuit determination step S57. The short circuit determination step S57 determines whether or not the battery is short-circuited using the actual measured voltage drop rate DVB2 and the estimated voltage drop rate EDV2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for testing an electricity storage device for short circuits, a method for manufacturing an electricity storage device, and a method for manufacturing a connected device restraint body. [Background technology]

[0002] When manufacturing an electric storage device such as a secondary battery, a short circuit inspection is performed. For example, Patent Document 1 shows a method of inspecting a secondary battery for short circuit, which includes an SOC adjustment step of discharging a secondary battery (hereinafter also referred to as a battery) that has been initially charged in an initial activation step to adjust the SOC value, and a self-discharge step of leaving the SOC-adjusted battery, i.e., the battery adjusted to a predetermined battery voltage, to self-discharge, and detects the presence or absence of a short circuit based on the amount of voltage drop of the battery in the self-discharge step. This is because a short-circuited battery generates a larger amount of voltage drop during the same period of the self-discharge step compared to a non-shorted battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-134395 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, if a battery is set to a certain battery voltage after the initial charge and then left to stand, as described above, the battery voltage of a short-circuited battery drops significantly in the same period of time as a non-shorted battery. This is because the charge stored in the battery is discharged through the short-circuited part inside the battery. In this case, assuming that the resistance value of the short-circuited part does not change, the discharge will be at a roughly constant current, and the battery voltage of a short-circuited battery will drop at a roughly constant rate, except for the range in which the battery voltage changes nonlinearly and abruptly with respect to the amount of stored charge, such as when the battery's SOC is low (e.g., when the SOC is 10% or less).

[0005] However, the decrease in battery voltage that occurs when a battery is set to a predetermined battery voltage after the initial charge and then left to stand is not only the decrease in battery voltage due to the short circuit described above. For example, a (non-defective) battery that does not have a short circuit is initially charged. Charging and discharging are performed for a capacity test or the like. If the battery voltage is further adjusted to a predetermined battery voltage by charging and then left to stand, the battery voltage drops relatively significantly immediately after the battery voltage is adjusted. However, thereafter, the voltage drop becomes gentle with the passage of time, and finally the battery voltage behaves to approach a generally constant battery voltage value. This is thought to be because the formation of an SEI film on the particle surface due to the reaction between the active material particles and the electrolyte slows down with time, and the decrease in battery voltage due to such film formation converges. In other words, for a battery that has undergone initial charging and charging and discharging, the amount of decrease in battery voltage that occurs during the short circuit test varies depending on the length of time that has elapsed between the completion of adjustment to a predetermined battery voltage by charging or discharging and the start of the short circuit test. In addition, the amount of decrease in battery voltage also varies depending on the length of the period (left-standing period) from the voltage measurement before leaving to the voltage measurement after leaving.

[0006] Therefore, in a battery that is not short-circuited, the battery voltage drops as described above after adjustment to a predetermined battery voltage is completed. On the other hand, in a battery that is short-circuited, a voltage drop occurs that is the sum of the voltage drop that occurs in a battery that is not short-circuited and the voltage drop due to the short circuit. For this reason, it has been difficult to determine whether a battery (electricity storage device) is short-circuited simply by obtaining the rate of drop in battery voltage that occurs during the short-circuit inspection period.

[0007] The present invention has been made in consideration of the current situation, and provides a short-circuit inspection method for an electricity storage device that can properly determine the presence or absence of a short circuit in an electricity storage device that has been initially charged and adjusted to a predetermined device voltage, a method for manufacturing an electricity storage device using this inspection method, and a method for manufacturing a connected device restraint using this inspection method. [Means for solving the problem]

[0008] (1) One aspect of the present invention for solving the above problem includes a voltage adjustment step of charging or discharging an initially charged power storage device to adjust it to a first device voltage, a pre-left-standing voltage measurement step of measuring a pre-left-standing device voltage of the power storage device, a leaving step of leaving the power storage device whose pre-left-standing device voltage has been measured in an open terminal state for a leaving period, a post-left-standing voltage measurement step of measuring a post-left-standing device voltage of the power storage device after the leaving step, and calculating an actual voltage drop rate between the pre-left-standing device voltage and the post-left-standing device voltage of the power storage device. Dividing the voltage drop from the device voltage before storage to the device voltage after storage by the storage period and a short circuit determination step of determining whether or not a short circuit exists in the power storage device by using the measured voltage drop rate of the power storage device, Using a typical example of a change in the device voltage after the completion of adjustment in the voltage adjustment step, which has been obtained in advance, The method further includes an estimation process for acquiring an estimated voltage drop rate that is estimated to occur in the power storage device based on the elapsed time from the completion of voltage adjustment in the voltage adjustment process to the measurement of the pre-left-standing device voltage in the pre-left-standing voltage measurement process, and the left-standing period, and the short-circuit determination process is a short-circuit inspection method for a power storage device that determines whether or not a short circuit exists in the power storage device using the actual measured voltage drop rate and the estimated voltage drop rate.

[0009] In this method for testing short circuits in an electricity storage device, an actual voltage drop rate is measured for each electricity storage device, while an estimated voltage drop rate based on the elapsed time and the period of time the device has been left unused is obtained, and these two rates are used to determine whether or not the electricity storage device has a short circuit, thereby making it possible to appropriately determine whether or not the electricity storage device has a short circuit.

[0010] In addition, when obtaining an estimated voltage drop rate according to the elapsed time and the unused period in the estimation process, it is preferable to obtain the estimated voltage drop rate by using an actual voltage drop rate according to the elapsed time and the unused period obtained for a preceding energy storage device of the same lot or a different lot of the same product number.

[0011] Examples of the "electricity storage device" include secondary batteries such as lithium ion secondary batteries, and capacitors such as lithium ion capacitors. You can go.

[0012] (2)(1) A short-circuit inspection method for an electricity storage device, further comprising a restraining step, which is performed after the voltage adjustment step and before the pre-left-standing voltage measurement step, of restraining the plurality of electricity storage devices adjusted to the first device voltage with a restraining member while leaving them unconnected from each other to form a device restraint body including a plurality of restrained devices, and the pre-left-standing voltage measurement step, the left-standing step, and the post-left-standing voltage measurement step are performed on the restrained devices restrained by the device restraint body.

[0013] In this method for testing a power storage device for short circuits, it is possible to appropriately determine whether or not a short circuit exists in the restrained device in a state in which the power storage device is restrained.

[0014] The "device restraint" may be any restraint that restrains a plurality of power storage devices in a predetermined direction using restraining members, for example, a device stack such as a battery stack in which a plurality of power storage devices such as secondary batteries are stacked in a row in the stacking direction.

[0015] In constraining the plurality of power storage devices after the voltage adjustment step to the first device voltage to form a device constrained body including a plurality of constrained devices, the power storage devices may be quickly constrained to form a device constrained body after being adjusted to the first device voltage. Alternatively, each power storage device may be left unconstrained or under weaker constraint than that of the device constrained body for an appropriate period of time, and any power storage device determined to be short-circuited in this state may be removed before forming the device constrained body.

[0016] The method for manufacturing an electricity storage device may preferably include a short circuit inspection step of inspecting the electricity storage device for the presence or absence of a short circuit by the short circuit inspection method for an electricity storage device described in (3) or (1), and a discharge step of discharging the electricity storage device determined to be short circuited in the short circuit inspection step.

[0017] In the above-described method for manufacturing an electricity storage device, a short-circuited electricity storage device is discharged, so that a non-short-circuited electricity storage device can be appropriately manufactured.

[0018] It is preferable that the method for manufacturing a connected device restraint body includes a short circuit inspection process for inspecting the presence or absence of a short circuit in each of the restrained devices included in a single device restraint body using the short circuit inspection method for an energy storage device described in (4) or (2), and a connection process for connecting the restrained devices of the device restraint body in which it has been determined that none of the multiple restrained devices included therein is short circuited.

[0019] In this method of manufacturing a connected device restraint body, the presence or absence of a short circuit of each of the restrained devices included in a single device restraint body is inspected in a short circuit inspection step, and for device restraint bodies in which it is determined that none of the multiple restrained devices included in the device restraint body is short circuited, the restrained devices are connected to each other in a connection step. Thus, only device restraint bodies having multiple restrained devices that are determined to be none of the short circuits are connected to each other, making it possible to easily manufacture a connected device restraint body.

[0020] The connection between the restrained devices (electricity storage devices) may be appropriately selected depending on the structure of the connection terminals of the electricity storage devices, and may be made using, for example, a bus bar. The electricity storage devices may be electrically connected in series or in parallel.

[0021] (5) The method for manufacturing a connected device restraint body described in (4) may further include a removal process for removing at least one of the restrained devices determined to have a short circuit in the short circuit inspection process from among the multiple restrained devices included in the same device restraint body, and a re-restraint process for reconfiguring the device restraint body with the remaining multiple restrained devices determined to have no short circuit in the short circuit determination process and a supplementary energy storage device that is included in another device restraint body, determined to have no short circuit in the short circuit inspection process, and prepared in advance.

[0022] In this method for manufacturing a connected device restraint, the power storage device determined to be short-circuited in the removal step is removed, while the device restraint is reconstructed in the re-restraint step with the remaining power storage device that is not short-circuited and a supplemental power storage device that is included in another device restraint and is determined to be not short-circuited. Thus, even if a power storage device that has caused a short circuit is included in the restrained device, the device restraint can be easily reconstructed to manufacture a connected device restraint. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is an explanatory diagram of a battery according to a first embodiment. [Diagram 2] 1 is a flowchart showing the manufacturing process of the batteries according to the first and second embodiments. [Diagram 3] 4 is a graph showing an example of a change in battery voltage after a voltage adjustment process in a battery that is not short-circuited in the first and second embodiments. [Figure 4] FIG. 6 is an explanatory diagram of a battery stack according to a second embodiment. [Diagram 5] FIG. 11 is an explanatory diagram of an unconnected battery stack according to a second embodiment. [Figure 6] 6 is a flowchart showing a manufacturing process of a battery stack according to the second embodiment. [Figure 7] 10 is a flowchart showing the contents of a restraint short-circuit inspection step in the manufacturing process of the battery stack according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] (Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows a vertical cross-sectional view of a battery (electricity storage device) 10 according to this embodiment. The battery 10 is a rectangular sealed lithium ion secondary battery that can be mounted in vehicles such as hybrid cars, plug-in hybrid cars, and electric cars, drones, and various devices.

[0025] This battery 10 has a rectangular parallelepiped case 11 made of aluminum, an electrode body 12 housed inside the case 11, and a positive terminal 14 and a negative terminal 15 that are supported by the case 11 and connected to the electrode body 12 inside the case 11 and protrude outside the case 11 (upward in Figure 1).

[0026] Next, the manufacture of the battery 10 will be described with reference to FIG. 2 and FIG. 3. First, an uncharged battery 10 is manufactured. The manufacture of a sealed battery 10 having a rectangular parallelepiped case 11 is well known, so the description will be omitted. In the initial charging step S1 (see FIG. 2), the uncharged battery 10 is initially charged by CCCV charging at room temperature to an SOC of 60 to 100%. In this embodiment, for example, in an environment of 25°C, CCCV charging is performed with a constant current of 7C, a cut voltage of 3.75V (corresponding to SOC 60%), and a cut current of 0.3C. Next, in the high-temperature aging step S2, each initially charged battery 10 is left in an open state in an environment of 50 to 80°C for 10 to 200 hours to perform high-temperature aging (for example, in this embodiment, in an environment of 70°C for 18 hours). After the battery 10 is cooled, in a capacity inspection process S3, the battery 10 is charged to SOC 100%, and then discharged to SOC 0% to measure the capacity of the battery 10 (discharge capacity in the case of the above-mentioned method).

[0027] Next, in a voltage adjustment step S4, the battery voltage VB of each battery 10 is charged to a first voltage VB1 within the range of SOC 30 to 100% at room temperature. In this embodiment, for example, in an environment of 25° C., CCCV charging is performed with a constant current of 7 C, a cutoff voltage of 3.75 V (corresponding to SOC 60%), and a cutoff current of 0.3 C, which are the same as in the initial charging step S1. That is, the battery voltage VB of each battery 10 is temporarily adjusted to the same first voltage VB1 (VB1=3.75 V in this embodiment).

[0028] Next, in the individual short-circuit inspection step S5, a short-circuit inspection is performed on each battery 10 after the voltage adjustment step S4. Specifically, first, in the pre-discarded voltage measurement step S51, the pre-discarded second voltage VB2a, which is the battery voltage VB of the battery 10, is measured. As described above, the battery voltage VB of the battery 10 is once adjusted to the same first voltage VB1 by CCCV charging. However, immediately after the CCCV charging is completed, the battery voltage VB drops by the voltage drop caused by the charging current due to the battery resistance during CV charging. In addition, even if the battery 10 is not short-circuited, the battery voltage VB gradually drops over time as described later (see FIG. 3). For this reason, prior to the individual discarded step S52 described next, the pre-discarded second voltage VB2a of each battery 10 after it has been charged to the first voltage VB1 is measured.

[0029] As described above, in the voltage adjustment step S4, when the battery voltage VB of the battery 10 is set to the first voltage VB1 by CCCV charging (hereinafter, this timing is referred to as the adjustment completion time Tc), if the battery 10 is not short-circuited after the adjustment completion time Tc, the battery voltage VB of the battery 10 decreases with an increase in the elapsed time KT, as shown in the graph of FIG. 3, for example. That is, when the CCCV charging is terminated, the battery voltage VB quickly decreases by the voltage drop caused by the battery resistance due to the cutoff current (e.g., 1C) flowing through the battery 10 immediately before the end of the CV charging. Furthermore, the battery voltage VB decreases significantly (e.g., 0.003V=3mV in FIG. 6) during the period from immediately after the adjustment completion time Tc until several hours to one day, and then decreases gradually further. However, the decrease in the battery voltage VB gradually becomes gentler, and the battery voltage VB stabilizes after several hundred days. That is, even after several days have passed since the adjustment completion time Tc when the battery voltage VB is set to the first voltage VB1, the battery voltage VB continues to decrease. However, the decrease does not occur linearly. Instead, the decrease in the battery voltage VB becomes more gradual as the elapsed time KT increases, resulting in a graph with a downward convex shape as shown in FIG. 3.

[0030] On the other hand, when the battery 10 is short-circuited, the charge stored in the battery 10 is discharged through a short-circuited portion (not shown) within the battery 10. For this reason, assuming that the short-circuit resistance value of the short-circuited portion does not change, the discharge is a roughly constant current, and the battery voltage VB of the battery 10 drops at a roughly constant rate. In other words, when the battery 10 is short-circuited, the change is the same as the drop in the battery voltage VB when the battery 10 is not short-circuited (see FIG. 3), but is also accompanied by a constant rate drop in the battery voltage VB due to the constant current discharge of the short-circuited portion.

[0031] Next, in an individual leaving step S52, the battery 10 with the positive electrode terminal 14 and the negative electrode terminal 15 in an open state is left unconstrained or slightly constrained in an environment of 25° C. for an individual leaving period IH (in the first embodiment, IH≧5.0 days (IH≧120 hours)). Thereafter, in a post-leaving voltage measurement step S53, a post-leaving second voltage VB2b, which is the battery voltage VB of the battery 10 after being left alone, is measured.

[0032] In the subsequent decrease rate acquisition process S54, the differential voltage (second voltage decrease amount ΔVB2) between the second voltage before leaving VB2a and the second voltage after leaving VB2b is divided by the actual individual leaving period IH to calculate a second voltage decrease rate DVB2, which is the second voltage decrease amount per unit time (for example, per day or per hour).

[0033] The length of the individual leaving period IH may vary depending on whether the individual leaving period IH includes a weekend, whether the post-leave voltage measuring step S53 is delayed, etc., since the timing at which the post-leave voltage measuring step S53 can be performed differs for each lot of the individual leaving step S52. For this reason, in the short-circuit determining step S57 described below, it is easier to compare with the determination criterion by using a drop rate such as the second voltage drop rate DVB2 rather than using the differential voltage (second voltage drop amount ΔVB2) between the pre-leave second voltage VB2a and the post-leave second voltage VB2b.

[0034] In FIG. 3, the elapsed time KT=5.0 day And the individual standby period IH=5.0 day 13 illustrates a case in which the second voltage before being left unused VB2a, the second voltage after being left unused VB2b, the second voltage drop amount ΔVB2, and the second voltage drop rate DVB2 are obtained when it is assumed that VB2a is the second voltage before being left unused VB2b.

[0035] In the subsequent estimated drop rate acquisition step S55, an estimated voltage drop rate EDV2 that is estimated to occur in the battery 10 is acquired. Specifically, a typical change example (see FIG. 3) of the battery voltage VB after the adjustment completion time Tc in the voltage adjustment step S4 of the battery 10, which has been obtained separately from a previous battery 10 of the same lot or a different lot of the same product number, a relational expression obtained using the elapsed time KT from the adjustment completion time Tc in the voltage adjustment step S4 to the measurement of the pre-left-standing second voltage VB2a in the pre-left-standing voltage measurement step S51, and the second voltage drop rate DVB2 actually measured according to the individual left-standing period IH, and a graph or a relational table showing the relational expression are obtained. Using these, an estimated voltage drop rate EDV2 according to the elapsed time KT from the adjustment completion time Tc and the individual left-standing period IH is obtained for the battery 10 tested this time.

[0036] For example, as a typical change example of the battery voltage VB, if a graph shown in FIG. 3 has been obtained in advance, the estimated voltage drop rate EDV2 corresponding to the elapsed time KT and the individual storage period IH can be obtained in the same manner as the above-described second voltage drop rate DVB2 using the graph of FIG. 3. In FIG. 3, the elapsed time KT = 5.0 day and the individual storage period IH = 5.0 day are illustrated as an example of obtaining the estimated voltage drop rate EDV2. That is, the estimated voltage before storage EV2a at the time when the elapsed time KT (KT = 5.0 days in FIG. 3) from the adjustment completion time Tc to the measurement of the second voltage VB2a before storage has elapsed, and further the estimated voltage after storage EV2b at the time when the individual storage period IH has elapsed from this time (KT + IH = 10.0 days in FIG. 3) are obtained, the estimated second voltage drop amount ΔEV2 (= EV2a - EV2b) is calculated, and this is divided by the individual storage period IH to obtain the estimated voltage drop rate EDV2 (= ΔEV2 / IH).

[0037] As can be easily understood, in the first embodiment, for each battery 10, even if the elapsed time KT varies from the adjustment completion time Tc until the individual short-circuit inspection step S5 (voltage measurement step S51 before storage) is performed, or the length of the individual storage period IH varies, the estimated voltage drop rate EDV2 corresponding to the elapsed time KT and the individual storage period IH can be obtained.

[0038] Furthermore, in the threshold drop rate calculation step S56, a tolerance width PW2 determined in advance is added to the obtained estimated voltage drop rate EDV2 to calculate a threshold drop rate THD2 (= EDV2 + PW2). The tolerance width PW2 is determined in consideration of variations that can occur in the estimated voltage drop rate EDV2.

[0039] Then, in the short-circuit determination step S57, the presence or absence of a short circuit in the battery 10 is determined based on the second voltage drop rate DVB2 obtained for the battery 10. Specifically, it is determined whether the second voltage drop rate DVB2 is greater than the threshold drop rate THD2 (DVB2 > THD2). In the case of No, that is, when the second voltage drop rate DVB2 is smaller than the threshold drop rate THD2 (DVB2 < THD2), it is assumed that no short circuit has occurred in the battery 10. Thus, the individual short-circuit inspection step S5 is terminated, and the battery 10 is completed.

[0040] If the individual short-circuit determination step S57 judges that the battery 10 is short-circuited, that is, if the second voltage drop rate DVB2 is greater than the threshold drop rate THD2 (DVB2>THD2), the battery 10 is judged to be short-circuited, and the process proceeds to the battery removal step S6. In the battery removal step S6, the defective battery 10N judged to be short-circuited is removed from the manufacturing process.

[0041] In the method for testing for short circuits and the method for manufacturing a battery 10 according to the first embodiment, the second voltage drop rate DVB2 is actually measured for each battery 10, while an estimated voltage drop rate EDV2 is obtained according to the elapsed time KT and the individual unused period IH. These two rates are then used to determine whether or not the battery 10 is short-circuited, so that it is possible to appropriately determine whether or not the battery 10 is short-circuited. Furthermore, because short-circuited batteries 10 are removed from the manufacturing process, batteries 10 that are not short-circuited can be appropriately manufactured.

[0042] (Embodiment 2) A battery stack 1 according to the second embodiment will be described below with reference to the drawings. FIG. 4 shows a battery stack (connected device restraint) 1 according to the second embodiment. The battery stack 1 is formed by stacking a plurality of rectangular parallelepiped batteries (electricity storage devices) 10 (see FIG. 1) of the first embodiment (for example, 28 batteries in the second embodiment) and restraining them to a fixed size with a restraining member 5. In this battery stack 1, a plurality of batteries 10 are stacked in a stacking direction SH (left-right direction in FIG. 1) with spacers 2 interposed therebetween, and these are pressed in the stacking direction SH by the restraining member 5 to restrain them. Specifically, a plurality of restrained batteries 10P (batteries 10) and spacers 2 are alternately stacked and sandwiched between a pair of restraining plates 51, and each restrained battery 10P is pressed in the stacking direction SH and restrained using a restraining bolt 52 extending in the stacking direction SH and spanning between the restraining plates 51, a nut 53 screwed thereto, and a washer 54. The positive electrode terminal 14 and negative electrode terminal 15 of each of the constrained batteries 10P are connected to each other via the bus bar 3. In the battery stack 1 of the second embodiment, as shown in Fig. 4, the constrained batteries 10P are arranged alternately inverted such that the positive electrode terminals 14 and negative electrode terminals 15 are arranged alternately in a row in the stacking direction SH, and the constrained batteries 10P are connected in series by connecting the bus bar 3. The battery stack 1 is mounted and used in vehicles such as hybrid cars, plug-in hybrid cars, and electric cars.

[0043] Next, the manufacture of the battery stack 1 will be described below with reference to FIGS. 5 to 7. An uncharged battery 10 is manufactured by a known method. Then, as in the first embodiment, initial charging is performed by CCCV charging in an initial charging step S1 (see FIG. 6). Next, high-temperature aging is performed in a high-temperature aging step S2. After cooling the battery 10, the battery 10 is further charged and discharged in a capacity inspection step S3 to measure the capacity of the battery 10. Furthermore, as in the first embodiment, in a voltage adjustment step S4, each battery 10 is charged and the battery voltage VB is temporarily adjusted to a first voltage VB1, specifically, VB1=3.75V. Furthermore, as in the first embodiment, an individual short-circuit inspection step S5 is performed, and in a battery removal step S6, a defective battery 10N is removed from the manufacturing process, while a battery 10 that is not short-circuited is obtained.

[0044] Therefore, at this stage, it is possible to appropriately determine whether or not each battery 10 is short-circuited, similarly to embodiment 1. Then, since short-circuited batteries 10 are removed from the manufacturing process, non-short-circuited batteries 10 can be appropriately manufactured and supplied to the subsequent process.

[0045] In the subsequent restraining step S27 (see FIG. 6), an unconnected battery stack 1M (see FIG. 5) is formed by a known method using each battery 10 that was determined not to be short-circuited in the individual short-circuit inspection step S5 (short-circuit determination step S57) as well as the spacer 2 and restraining member 5. In this unconnected battery stack 1M, each battery 10 is pressed and restrained in the stacking direction SH (left-right direction in the figure) to become a restrained battery 10P. Therefore, in the electrode body 12 of the restrained battery 10P, the positive and negative plates (not shown) are compressed in the thickness direction that coincides with the stacking direction SH via the separator. However, unlike the battery stack 1 (see FIG. 4), the bus bar 3 is not used, and the positive terminals 14 and negative terminals 15 of the restrained batteries 10P are not connected to each other, and each restrained battery 10P is in an open state. In this unconnected battery stack 1M state, a short-circuit inspection is performed on each restrained battery 10P under restraint. After the restraining step S27, a plurality of (for example, 28 in this embodiment) restrained batteries 10P included in a single unconnected battery stack 1M (or battery stack 1) are treated as one group.

[0046] In this embodiment 2, following the restraint process S27, in a restraint short-circuit inspection process S28 (see Figure 7), a short-circuit inspection is performed on each restrained battery 10P under restraint (compression) in the unconnected battery stack 1M state, and the presence or absence of a short circuit is detected for each restrained battery 10P.

[0047] In the pre-discarded voltage measurement step S281 of the restrained short circuit inspection step S28, the pre-discarded third voltage VB3a, which is the battery voltage VB of each of the group of restrained batteries 10P constituting a single unconnected battery stack 1M, is measured. As described above, even if the restrained batteries 10P are not short-circuited, the battery voltage VB gradually decreases over time (see FIG. 3). Therefore, prior to the restrained discarded step S282 described below, the pre-discarded third voltage VB3a of each of the restrained batteries 10P is measured.

[0048] Next, in a constrained leaving step S282, the unconnected battery stack 1M, and therefore each of the group of constrained batteries 10P restrained by the restraining members 5 with the positive terminals 14 and negative terminals 15 in an open state, is left for a constrained leaving period PH (in this embodiment, PH≧5.0 days (≧120 hours)) in an environment of 25° C. Then, in a post-leaving voltage measurement step S283, the post-leaving third voltage VB3b, which is the battery voltage VB, is measured for each of the post-leaving constrained batteries 10P belonging to a single unconnected battery stack 1M.

[0049] In the subsequent voltage drop rate acquisition process S284, a third voltage drop amount ΔVB3 (=VB3a-VB3b), which is the differential voltage between the third voltage VB3a before left unused and the third voltage VB3b after left unused, is calculated for each of a group of constrained batteries 10P belonging to a single unconnected battery stack 1M.

[0050] Furthermore, the third voltage drop amount ΔVB3 of each constrained battery 10P is divided by the actual constrained left-alone period PH to calculate a third voltage drop rate DVB3, which is the third voltage drop amount per unit time (for example, per day or per hour). The length of the constrained left-alone period PH may differ slightly for each unconnected battery stack 1M depending on whether the constrained left-alone period PH includes a weekend, whether there is a delay in the post-alone voltage measurement step S283, etc. For this reason, in the constrained short-circuit determination step S287 described later, it is easier to make a determination using the third voltage drop rate DVB3 rather than using the third voltage drop amount ΔVB3 itself.

[0051] In FIG. 3, the elapsed time KT=20.0 daySo, the pH during the restraint period is 5.0. day 13 illustrates a case in which the third voltage before unused VB3a, the third voltage after unused VB3b, the third voltage drop amount ΔVB3, and the third voltage drop rate DVB3 are obtained when it is assumed that VB3a is a positive voltage.

[0052] In the subsequent estimated drop rate acquisition step S285, an estimated voltage drop rate EDV3 estimated to occur in each constrained battery 10P is acquired. Specifically, a relational expression, a graph or a relational table showing the relational expression is obtained using a typical change example of the battery voltage VB after the adjustment completion time Tc obtained separately from the preceding constrained battery 10P of the same lot or a different lot of the same part number, the elapsed time KT from the adjustment completion time Tc in the voltage adjustment step S4 to the measurement of the third voltage VB3a before leaving in the pre-leaving voltage measurement step S281, and the third voltage drop rate DVB3 actually measured according to the constrained leaving period PH. Using these, an estimated voltage drop rate EDV3 according to the elapsed time KT from the adjustment completion time Tc and the constrained leaving period PH is obtained for each constrained battery 10P tested this time.

[0053] For example, if the graph shown in FIG. 3 is obtained in advance as a typical change example of the battery voltage VB, the graph of FIG. 3 can be used to calculate the elapsed time KT and Constraints Period of suspension P In addition, in FIG. 3, the estimated voltage drop rate EDV3 corresponding to the elapsed time KT=20.0 day So, the pH during the restraint period is 5.0. day In other words, the estimated third voltage before storage EV3a at the time when the elapsed time KT (KT=20.0 days in FIG. 3) from the adjustment completion time Tc to the measurement of the third voltage before storage VB3a and the estimated third voltage after storage EV3b at the time when the restricted storage period PH has elapsed (KT+PH=25.0 days in FIG. 3) are obtained, the estimated third voltage drop ΔEV3 (=EV3a-EV3b) is calculated, and the estimated voltage drop rate EDV3 (=ΔEV3 / IH) is obtained by dividing the estimated third voltage drop ΔEV3 by the restricted storage period PH.

[0054] For easy understanding, in the second embodiment, even if the elapsed time KT until the restraint short-circuit inspection step S28 (open-circuit voltage measurement step S281) is performed after the adjustment completion time Tc is different for each of the group of restrained batteries 10P belonging to a single unconnected battery stack 1M, and even if the length of the restraint storage period PH is different for each unconnected battery stack 1M, the elapsed time KT of each restrained battery 10P and Constraints Storage period P the estimated voltage drop rate EDV3 corresponding to H can be obtained.

[0055] Furthermore, in the threshold drop rate calculation step S286, a predetermined tolerance width PW3 is added to the obtained estimated voltage drop rate EDV3 to calculate the threshold drop rate THD3 (=EDV3 + PW3). The tolerance width PW3 is determined in consideration of variations that can occur in the estimated voltage drop rate EDV3.

[0056] Then, in the restraint short-circuit determination step S287, using the third voltage drop rate DVB3 obtained for each of the group of restrained batteries 10P belonging to a single unconnected battery stack 1M, the presence or absence of a short circuit in each restrained battery 10P belonging to the unconnected battery stack 1M is determined. Specifically, when the third voltage drop rate DVB3 is smaller than the threshold drop rate THD3 (DVB3 < THD3), it is assumed that the restrained battery 10P is not short-circuited. On the other hand, when the third voltage drop rate DVB3 is larger than the threshold drop rate THD3 (DVB3 > THD3), it is assumed that the restrained battery 10P is short-circuited, that is, it is a defective battery 10N.

[0057] Furthermore, in this restraint short-circuit determination step S287, it is determined whether or not a defective battery 10N is included in the group of restrained batteries 10P belonging to a single unconnected battery stack 1M. Here, if Yes, that is, if a defective battery 10N is included in the unconnected battery stack 1M, the unconnected battery stack 1M is transferred to the removal step S2A described later. On the other hand, if No, that is, if a defective battery 10N is not included in the unconnected battery stack 1M, the unconnected battery stack 1M is transferred to the connection step S29.

[0058] Next, in the connection process S29, the bus bar 3 is connected to the positive terminals 14 and negative terminals 15 of the group of constrained batteries 10P that make up the unconnected battery stack 1M, and the constrained batteries 10P are connected to each other to complete the battery stack 1 (see FIG. 4).

[0059] Thus, this method of testing for short circuits in batteries 10 can appropriately determine the presence or absence of a short circuit in a restrained battery 10P in the state in which the battery 10 is restrained. Furthermore, only unconnected battery stacks 1M having multiple restrained batteries 10P that have been determined to have no short circuits can be connected together to easily convert them into connected batteries. Miden Pond Stack 1 It can be manufactured.

[0060] Meanwhile, in the removal process S2A, a defective battery 10N is removed from an unconnected battery stack 1M that includes at least one defective battery 10N. Specifically, the fastening between the restraining bolts 52 and nuts 53 of the restraining members 5 is loosened, the defective battery 10N is removed from the unconnected battery stack 1M, and the stack is discharged from the manufacturing process.

[0061] In the subsequent re-restraint step S2B, the unconnected battery stack 1M from which the defective battery 10N has been removed is replenished with replacement batteries 10H to make up for the shortage, and the group of restrained batteries 10P is restrained again using the restraining member 5 to reconstruct the unconnected battery stack 1M (see FIG. 6). The replacement batteries 10H are batteries 10 that are included in another unconnected battery stack 1M, have already been determined to be free of short-circuits in the restraint short-circuit inspection step S28, and have been prepared in advance for replacement. Thereafter, the restraint short-circuit inspection step S28 is performed again for the reconstructed unconnected battery stack 1M, and replacement batteries 10H are replenished until no defective batteries 10N are generated, and the reconstruction of the unconnected battery stack 1M is repeated. If the reconstructed unconnected battery stack 1M does not contain any defective batteries 10N in the restraint short-circuit determination step S287, the reconstructed unconnected battery stack 1M is transitioned to the connection step S29, as described above.

[0062] Then, in the connection step S29, the bus bar 3 is connected to the positive terminals 14 and negative terminals 15 of the group of constrained batteries 10P constituting the reconstituted unconnected battery stack 1M, and the constrained batteries 10P are connected to each other to form the battery stack 1 (FIG. 4 Thus, even if the unconnected battery stack 1M contains a battery 10 that has developed a short circuit, the unconnected battery stack 1M can be easily reconstructed to manufacture the battery stack 1.

[0063] In the re-restraint step S2B, if there is a low possibility of a defective battery 10N occurring in the unconnected battery stack 1M reconstituted by re-restraining, in the second connection step S2C, as shown by the dashed lines in FIG. 6, the bus bar 3 is connected to the positive terminals 14 and the negative terminals 15 of the group of restrained batteries 10P constituting the reconstituted unconnected battery stack 1M, and the restrained batteries 10P are connected to each other to form the battery stack 1 (FIG. 4 In this way, the unconnected battery stack 1M can be reconstructed to manufacture the battery stack 1 more easily.

[0064] The present invention has been described above with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the battery stack 1 of the second embodiment, the constrained batteries 10P are electrically connected in series with each other via the bus bar 3. However, the constrained batteries 10P may also be electrically connected in parallel to form a device constraint body.

[0065] In the manufacturing process of the battery 10 in the first and second embodiments, the battery 10 is charged to SOC 100% in the capacity inspection step S3, then the battery 10 is discharged to SOC 0% to measure the capacity of the battery 10, and then the battery voltage VB is set to the first voltage VB1 by charging in the voltage adjustment step S4. However, contrary to the embodiments, the battery 10 may be discharged to SOC 0% in the capacity inspection step, then the battery 10 is charged to SOC 100% to measure the charge capacity of the battery 10, and then the battery voltage VB may be set to the first voltage VB1 by discharging in the voltage adjustment step S4. [Explanation of symbols]

[0066] 1 Battery Stack (Connected Device Restraint) 1M Unconnected Battery Stack (Device Restraint) SH Stacking direction 5 Restraining member 10 Batteries (secondary batteries, power storage devices) 10N defective battery 10H refill battery 10P Restrained battery (Restrained device) VB Battery voltage VB1 First voltage (first device voltage) VB2a Second voltage before storage (device voltage before storage) VB2b Second voltage after storage (device voltage after storage) DVB2 2nd voltage drop rate (actual voltage drop rate) EDV2,EDV3 Estimated decline rate PW2, PW3 allowable width THD2, THD3 threshold drop rate VB3a Third voltage before storage (device voltage before storage) VB3a Third voltage after storage (device voltage after storage) ΔVB3 Third voltage drop DVB3 3rd voltage drop rate (actual voltage drop rate) EV3a Estimated third voltage before storage EV3b Estimated third voltage after storage ΔEV3 Estimated third voltage drop When Tc adjustment is completed KT Elapsed Time S1 Initial charging process S4 Voltage adjustment process S5 Individual short circuit inspection process (short circuit inspection process) S51, S281 Voltage measurement process before storage S52 Individual leaving process (leaving process) IH Individual Standing Period S53, S283 Voltage measurement process after storage S54, S284 Decrease amount calculation process (actual measurement process) S55,S285 Estimated decline rate acquisition process (estimation process) S56, S286 Threshold drop rate calculation process S57 Individual short circuit judgment process (short circuit judgment process) S6 Battery discharge process (discharge process) S27 Restraint process S28 Restraint short circuit inspection process (short circuit inspection process) S282 Restraint leaving process (leaving process) PH detention period S287 Restraint short circuit judgment process (short circuit judgment process) S29 Connection process S2A removal process S2B Re-constraint process S2C 2nd connection process

Claims

1. a voltage adjustment step of charging or discharging the power storage device that has been initially charged to adjust the voltage to a first device voltage; a pre-discarded voltage measuring step of measuring a pre-discarded device voltage of the power storage device; a step of leaving the power storage device, the device voltage before being left unattended measured, for a period of time in an open terminal state; a post-standing voltage measurement step of measuring a post-standing device voltage of the power storage device after the post-standing step; a measuring step of obtaining an actual voltage drop rate between the pre-discarded device voltage and the post-discarded device voltage of the power storage device by dividing an amount of voltage drop from the pre-discarded device voltage to the post-discarded device voltage by the storage period; and a short circuit determination step of determining whether or not a short circuit exists in the power storage device by using the actual measured voltage drop rate of the power storage device. A method for testing a short circuit in an electricity storage device, comprising: Prior to the short circuit determination step, Using a typical example of a change in the device voltage after the completion of adjustment in the voltage adjustment step, which has been obtained in advance, According to the elapsed time from the completion of the voltage adjustment in the voltage adjustment step to the measurement of the pre-discarded device voltage in the pre-discarded voltage measurement step and the discontinuous period, An estimation step of acquiring an estimated voltage drop rate estimated to occur in the power storage device, The short circuit determination step includes: The actual voltage drop rate and the estimated voltage drop rate are used to determine whether or not the power storage device is short-circuited. A method for testing an electricity storage device for short circuits.

2. The method for testing a short circuit in an electricity storage device according to claim 1, After the voltage adjustment step and before the pre-existing voltage measurement step, The plurality of power storage devices adjusted to the first device voltage are restrained by a restraining member while being unconnected to each other, A constraining step of forming a device constraining body including a plurality of constrained devices is further included, The pre-discarding voltage measuring step, the leaving step, and the post-discarding voltage measuring step are performed on the constrained device constrained by the device restraint body. A method for testing an electricity storage device for short circuits.

3. a short circuit inspection step of inspecting the electric storage device for the presence or absence of a short circuit by the method for inspecting a short circuit of an electric storage device according to claim 1; and a discharge step of discharging the power storage device determined to be short-circuited in the short-circuit inspection step. A method for manufacturing an electricity storage device.

4. a short circuit inspection step of inspecting whether or not each of the restrained devices included in the single device restraining body is short circuited by the method for inspecting a short circuit of an electric storage device according to claim 2; a connecting step of connecting the restrained devices of the device restraint body in which it has been determined that none of the plurality of restrained devices included therein is short-circuited. A method for making a connected device restraint.

5. 5. A method for manufacturing the connected device restraint of claim 4, comprising the steps of: a removing step of removing at least one of the restrained devices determined to have a short circuit in the short circuit inspection step from among the plurality of restrained devices included in the same device restraining body; and a re-restraining step of reconfiguring the device restraining body using the remaining plurality of restrained devices determined in the short-circuit determination step to be free of a short circuit and a supplementary electric storage device that is included in another of the device restraining bodies, determined in the short-circuit inspection step to be free of a short circuit, and prepared in advance. A method for making a connected device restraint.

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