JP6982783B2 - How to inspect the battery stack - Google Patents

Description

The present invention relates to a method for inspecting a battery stack.

Japanese Patent Application Laid-Open No. 2017-117636 measures the restraining load of the stack when reusing the assembled battery in which a plurality of cells are stacked. Then, when the restraint load is higher than the reference value, the mitigation promotion process for promoting the mitigation of the salt concentration unevenness while being stacked is performed. It is disclosed that when the restraint load is equal to or less than the reference value, the relaxation promotion treatment is performed after disassembling into each cell.
Here, the relaxation promotion process is a process for promoting the relaxation (elimination) of the bias in the salt concentration distribution of the electrolytic solution in the electrode body of each cell, which is caused by repeated charging and discharging of the battery. Here, this bias in the salt concentration distribution is also referred to as "salt concentration unevenness".
In the same publication, as a mitigation promotion process, it is disclosed that an overcharge or an overdischarge is determined by referring to a history of charging or discharging. Then, in the case of overcharging, it is proposed to perform a process for eliminating the salt concentration unevenness caused by the overcharged, and in the case of overdischarged, perform a process for eliminating the salt concentration unevenness caused by the overdischarged. Has been done.
Here, when the charge is excessive, it is said that the process of repeating charging / discharging is performed in a state where the discharge current is larger than the charge current. When the discharge is excessive, it is said that the process of repeating charging and discharging is performed in a state where the current is larger than the discharge current. By performing such a treatment, it is said that the density unevenness can be alleviated and the internal resistance can be reduced.

Japanese Unexamined Patent Publication No. 2017-117636

By the way, according to the knowledge of the present inventor, the factors that deteriorate the performance of the battery stack include the case where some cells among the plurality of cells constituting the battery stack are deteriorated and the battery stack. In some cases, the restraint pressure has decreased. In this case, when the restraining pressure of the battery stack is lowered, the distance between the positive electrode active material and the negative electrode active material in the electrode body becomes large, and the internal resistance may be increased accordingly. Creep over time due to the resin component inside the battery body being subjected to the restraining pressure may cause the restraining pressure of the battery stack to decrease. When the confining pressure of the battery stack is low, the performance of the battery stack may be restored without disassembling the battery stack for each cell. On the other hand, when the battery stack is reused, if all the battery stacks are disassembled for each cell, the number of processes up to reuse such as determination of non-defective products for each cell and reconstruction of the stack increases.

The battery stack inspection method proposed here includes a step of preparing a used battery stack, a first determination step, a step of acquiring a restraint load Pb of the battery stack, a first adjustment step, and a second adjustment. It includes a step and a second determination step.

Here, in the step of preparing a used battery stack, a used battery stack including a plurality of cells constrained under a constrained load is prepared.
In the first determination step, it is determined whether or not the battery stack has a predetermined predetermined performance.
In the step of acquiring the constraint load Pb of the battery stack, the constraint load Pb of the battery stack is acquired in the first determination step when it does not have a predetermined predetermined performance.
In the first adjustment step, when the restraint load Pb is lower than the predetermined second load P2, the restraint load Pb is adjusted so as to be the predetermined predetermined load Pr.
In the second adjustment step, when the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1, the restraint load Pb is first loosened. After that, the load is increased to a load Pra higher than the predetermined predetermined load Pr. After that, the load is unloaded, and the restraint load Pb is adjusted so as to have a predetermined predetermined load Pr.
In the second determination step, it is determined whether or not the battery stack has predetermined predetermined performance after the first adjustment step or after the second adjustment step.

According to such a battery stack inspection method, the battery stack is efficiently reused.

FIG. 1 is a perspective view showing one form of a battery stack. FIG. 2 is a side view showing a configuration example of the restraint mechanisms 71 to 74. FIG. 3 is a graph showing the relationship between the restraint load of the cell 3 and the internal resistance. FIG. 4 is a flowchart showing an example of the procedure of the battery stack inspection method proposed here. FIG. 5 is a plan view schematically showing an example of a measuring device 8 that acquires a restraint load Pb. FIG. 6 is a graph showing the transition of the restraint load in the step of adjusting the restraint load Pb (S15b).

Hereinafter, an embodiment of the battery stack inspection method proposed here will be described. The embodiments described herein are, of course, not intended to specifically limit the invention. The invention is not limited to the embodiments described herein, unless otherwise noted.

FIG. 1 is a perspective view showing one form of a battery stack.
Here, as shown in FIG. 1, the battery stack 2 is a so-called assembled battery including a plurality of cells 3 constrained in a state where a load is applied by a restraining mechanism. For example, in an in-vehicle battery, such battery stacks are further combined to form a battery pack. In FIG. 1, some of the plurality of cells 3 constrained in the battery stack 2 are not shown.

The battery stack 2 shown in FIG. 1 includes a plurality of cells 3, a plurality of cooling plates 4, a pair of end plates 51 and 52, a restraint mechanism 60, and a plurality of bus bars 7.

The plurality of cells 3 are sealed square cells having a substantially rectangular parallelepiped battery case 30 having wide surfaces facing each other. The battery case 30 includes a case body 31 having one side opening and a lid 32 attached to the opening of the case body 31. The case body 31 and the lid 32 are joined by full-circle welding. The lid 32 is provided with a safety valve 33, a positive electrode terminal 36A, a negative electrode terminal 36B, and the like. The safety valve 33 is configured to be opened when the inside of the battery case 30 becomes higher than a predetermined pressure. Although not shown, the battery case 30 contains an electrode body and an electrolytic solution. In the electrode body, a sheet-shaped positive electrode and a sheet-shaped negative electrode face each other with a separator interposed therebetween. The structure of the electrode body is as exemplified in Patent Document 1, for example. Here, detailed description will be omitted.

In the battery stack 2 shown in FIG. 1, the plurality of cells 3 are arranged with the lid 32 facing in the same direction and with the wide surfaces facing each other. A cooling plate 4 is sandwiched between the cells 3. The cooling plate 4 is formed with, for example, an air passage for cooling. The plurality of cells 3 and the plurality of cooling plates 4 are stacked with the cooling plates 4 sandwiched between the cells 3 as described above. End plates 51 and 52 are arranged at both ends of the plurality of cells 3 and the plurality of cooling plates 4 stacked in this way.

The restraint mechanism 60 is a mechanism for applying a restraint load to a plurality of cells 3 stacked as described above. In the embodiment shown in FIG. 1, the restraint mechanism 60 includes a restraint band 61 to 64 and a restraint mechanism 71 to 74.
The restraint bands 61 to 64 are members for connecting the end plates 51 and 52 stacked on the plurality of cells 3 and the plurality of cooling plates 4 as described above. The restraint mechanism 71 to 74 is a mechanism for adjusting the restraint load for restraining the plurality of cells 3. FIG. 2 is a side view showing a configuration example of the restraint mechanisms 71 to 74.

The restraint bands 61 to 64 extend to positions of the end plates 51 and 52 facing the outer surface of the end plates 51 and 52 opposite to the side stacked on the plurality of cells 3 and the plurality of cooling plates 4, respectively. A bolt insertion hole is formed in a portion facing the end plate 51, and nuts 61a to 64a are welded so as to communicate with the bolt insertion hole.

The restraint mechanisms 71 to 74 include nuts 61a to 64a provided on the restraint bands 61 to 64, bolts 71a to 74a, and fixing nuts 71b to 74b.
The bolts 71a to 74a to which the set nuts 71b to 74b are mounted are inserted into the nuts 61a to 64a provided in the restraint bands 61 to 64. Further, for example, a spring washer 71c (see FIG. 2) is mounted between the bolts 71a to 74a and the set nuts 71b to 74b. The spring washer 71c may be mounted between the bolts 71a to 74a and the set nuts 71b to 74b, respectively. Note that the spring washer 71c is not shown in FIGS. 1 and 5. A predetermined reaction force acts between the bolts 71a to 74a and the set nuts 71b to 74b by the spring washer 71c. When the bolts 71a to 74a inserted through the nuts 61a to 64a are screwed into the restraint mechanisms 71 to 74, the end plate 51 is pushed and the restraint load for restraining the plurality of cells 3 and the plurality of cooling plates 4 becomes high. When the bolts 71a to 74a are loosened, the restraining load that restrains the plurality of cells 3 and the plurality of cooling plates 4 is loosened.

In this embodiment, the positive electrode terminal 36A and the negative electrode terminal 36B of the adjacent cells 3 are connected by a bus bar 7, and the battery stack 2 is configured to function as one assembled battery. Note that FIG. 1 shows an example of a battery stack, and the structure of the battery stack is not limited to the form shown in FIG. For example, the structure and the restraining mechanism for restraining the plurality of cells 3 while applying the restraining load are not limited to the above-mentioned forms, and various configurations can be adopted.

In the battery pack mounted on the vehicle, a large capacity and a large output are realized by further combining a plurality of battery stacks 2. Further, the battery pack incorporates an air cooling mechanism that sends cooling air to each cell 3 of each battery stack 2. Further, each battery stack 2 is connected to an ECU (Electronic Control Unit) or the like to manage charging or discharging. In the ECU, not only charging or discharging is managed, but also charging and discharging histories are recorded for each battery stack 2 and even for each cell 3. Further, when the restraint by the restraint bands 61 to 64 is released, the cell 3 is taken out from the battery stack 2.

By the way, the battery pack mounted on the vehicle is charged at a high rate or discharged at a high rate during use in the vehicle. For example, when accelerating a vehicle in EV driving, discharge at a high rate is required. In addition, in order to efficiently recover the regenerative energy generated during braking, charging at a high rate is required. In addition, in order to extend the cruising range in EV driving, it has the required capacity and the amount of electricity (energy density) that can be stored per unit volume is high. Therefore, the performance of the battery pack mounted on the vehicle is higher than that of the battery used for consumer products in other fields. Therefore, the used battery pack collected from the hybrid vehicle or the electric vehicle can be reused as a used battery pack for vehicle use or for batteries of other consumer products. Batteries for consumer products may be used, for example, as storage batteries for solar power generation and small household generators. It is also possible to reuse the battery stack 2 taken out from the battery pack. It is also possible to reuse each of the cells 3 taken out from the battery stack 2.

In the recovered battery pack, the performance of the cell 3 may be deteriorated. For example, a battery pack mounted on a vehicle is repeatedly discharged and charged at a high rate. When discharging and charging at a high rate are repeated, an event in which the electrolyte is biased occurs in the cell 3. Further, when charging or discharging is performed at a higher rate in a state where the electrolyte is biased in the cell 3, the electrolyte is deposited. If the electrolyte is biased in the cell 3, the internal resistance of the cell 3 increases by that amount, which causes the output performance of the cell 3 to deteriorate. Further, even when the electrolyte is deposited, the battery capacity is reduced, which causes deterioration of the performance of the cell 3.

When reusing the battery pack or the battery stack 2, it is necessary to confirm the performance of the battery pack or the battery stack 2 and reuse the battery pack or the battery stack 2. When the on-board battery pack is collected after use and reused, for example, it is disassembled for each cell 3 to inspect whether it has the required performance, and then good products are selected and the battery stack is again. 2 is assembled. This ensures the performance of the reusable battery stack 2.

Further, even if the performance of the cell 3 is deteriorated in the non-defective product inspection of the cell 3, for example, when the electrolyte is biased in the cell 3, if the bias of the electrolyte is eliminated or alleviated, the cell 3 is increased by that amount. The internal resistance may decrease and the performance of the cell 3 may be restored. On the other hand, when the electrolyte is precipitated, it is difficult to recover the performance of the deteriorated cell 3.

Further, in the battery stack 2, a predetermined restraint load is applied to the cell 3. Here, the predetermined restraint load applied to the cell 3 is referred to as a predetermined load Pr.
FIG. 3 is a graph showing the relationship between the restraint load of the cell 3 and the internal resistance. As shown in FIG. 3, the cell 3 has a high internal resistance when the restraining load is low. This is because the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode in the cell 3 is wide, so that the resistance generated between the sheet-shaped positive electrode and the sheet-shaped negative electrode is large. The higher the restraint load, the lower the internal resistance. When the restraining load becomes high to some extent, the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode in the cell 3 is maintained at an appropriate distance, and the internal resistance becomes low. However, the restraint load can be increased to the extent that the battery case does not collapse. The specified load Pr may be set in a range H from a load P1 that keeps the internal resistance of the cell 3 low to an upper limit load P3 that does not crush the battery case. That is, the range H in FIG. 3 is a range in which the specified load Pr can be set. The load P1 is the lower limit of the range H in which the specified load Pr can be set. Here, it is defined by the lower limit of the restraint load that keeps the internal resistance of the cell 3 low. The load P3 is an upper limit value of the range H in which the specified load Pr can be set. Here, the upper limit of the restraint load to the extent that the battery case is not crushed is specified.

The restraining load continuously acts on the cell 3 in the battery stack 2. A resin member such as a separator or an insulating film is arranged in the cell 3. Creep may occur if these resin members are subject to continuous restraining loads. That is, the separator, the insulating film, and the like are deformed by receiving a restraining load. When creep occurs in the separator or the insulating film, the restraining load becomes low. Therefore, even in the battery stack 2 in which the restraint load Pb is initially set to the specified load Pr, the restraint load Pb may gradually decrease and the restraint load Pb may become lower than the specified load Pr. When the restraining load Pb becomes too low, the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode in the cell 3 becomes wide. Therefore, the internal resistance may increase. In such a case, if a specified load Pr is applied to the cell 3, the performance of the cell 3 may be restored, and the performance of the battery stack 2 as a whole may be restored.

According to the knowledge of the present inventor, there are various causes for the performance deterioration of the battery stack 2. Based on such findings, the present inventor proposes an inspection method for efficiently performing an inspection when reusing the battery stack 2. FIG. 4 is a flowchart showing an example of the procedure of the battery stack inspection method proposed here. In the flowchart of FIG. 4, the battery stack is described as "stack".

In the battery stack inspection method proposed here, a step (S11) of preparing a used battery stack 2 (see FIG. 1), a first determination step (S12), and a restraint load Pb of the battery stack 2 are acquired. A step (S13), a first adjustment step (S14), a second adjustment step (S15), a second determination step (S16), and a cell inspection step (S17) are included. As for the structure of the battery stack 2, FIGS. 1 and 2 may be referred to as appropriate.

The step (S11) of preparing the used battery stack 2 is a step of preparing the used battery stack 2 including the plurality of cells 3 constrained with the restraint load applied. In the step of preparing the used battery stack 2, the battery stack 2 taken out from the collected battery pack as described above is prepared. As shown in the flowchart of FIG. 4, the step of preparing the used battery stack 2 (S11) is, for example, a step of collecting the battery pack (S11a) and a step of disassembling the battery pack into the battery stack 2. (S11b) is provided.

The first determination step (S12) is a step of determining whether or not the battery stack 2 has predetermined predetermined performance. In this step, as shown in the flowchart of FIG. 4, the step of measuring the battery performance A1 of the battery stack 2 (S12a) and the measured battery performance A1 of the battery stack 2 are predetermined performances. It includes a step (S12b) of determining whether the value is A0 or higher.

Here, in the flowchart of FIG. 4, in the determination step (S12b), A1 ≧ A0. “A1 ≧ A0” indicates that the measured battery performance A1 of the battery stack 2 is better than the predetermined predetermined performance A0 from the viewpoint of battery performance. For example, the battery performance A1 of the battery stack 2 may be the internal resistance value of the battery stack 2. From the viewpoint of the performance of the battery stack 2, it can be said that the lower the internal resistance value of the battery stack 2, the better. In this case, the measured battery performance A1 of the battery stack 2 is equal to or higher than the predetermined predetermined performance A0, and the resistance value of the internal resistance of the battery stack 2 is equal to or less than the predetermined specified resistance value. Is determined as. In this way, when the resistance value is used for evaluation, the numerical values are simply compared and the judgment is not made. That is, A1 ≧ A0 may be determined by comparing the superiority and inferiority from the viewpoint of the quality of the battery performance. In the determination step (S12b), from this point of view, it is determined that the measured battery performance A1 of the battery stack 2 is equal to or higher than the predetermined predetermined performance A0.

In the first determination step (S12), when the battery stack 2 has a predetermined predetermined performance A0 (Yes), the battery stack 2 is forwarded to the reused step (S30).
Here, the predetermined performance A0 may be set to, for example, about 80% of the initial performance of the battery stack 2. For example, in the evaluation based on the battery capacity of the battery stack 2, it may be determined whether or not the battery capacity is maintained at about 80% or more of the initial capacity. Further, in the evaluation based on the output value of the battery stack 2, for example, the output performance of the battery stack 2 is evaluated under predetermined conditions, and whether or not the evaluation value is maintained at about 80% or more of the initial state is determined. It is good to judge.

In the first determination step (S12), when the predetermined performance A0 is not provided (No), the battery stack 2 is forwarded to the step (S13) of acquiring the restraint load Pb of the battery stack. FIG. 5 is a plan view schematically showing an example of a measuring device 8 that acquires a restraint load Pb.

In the example shown in FIG. 5, the measuring device 8 for acquiring the restraint load Pb is a pair of measuring plates 81, 82 and a measuring device 83 for detecting the reaction force received by the measuring plates 81, 82 from the end plates 51, 52. And have. The spacing between the pair of measuring plates 81, 82 can be adjusted according to the spacing between the end plates 51, 52 on both sides of the battery stack 2. The measuring plates 81 and 82 are attached to the outside of the end plates 51 and 52 so as to sandwich the end plates 51 and 52 on both sides of the battery stack 2. The distance between the measuring plates 81 and 82 is fixed. In this state, the restraint mechanisms 71 to 74 are operated to completely loosen the restraint by the four restraint bands 61 to 64. The restraint by the four restraint bands 61 to 64 may be released. As a result, the reaction force corresponding to the restraining load acting on the plurality of cells 3 of the battery stack 2 acts on the measuring plates 81 and 82. The reaction force corresponding to the restraining load acting on the plurality of cells 3 is measured by the measuring instrument 83. In FIG. 5, the measuring instrument 83 is schematically drawn, but may be provided, for example, on a support member that supports the measuring plates 81 and 82.

The first adjustment step (S14) is a step of adjusting the restraint load Pb so that the restraint load Pb becomes a predetermined predetermined load Pr when the restraint load Pb is lower than the predetermined second load P2.
In the flowchart of FIG. 4, the first adjustment step (S14) is a step (S14a) of determining whether or not the restraint load Pb is lower than the predetermined second load P2 (Pb <P2), and the restraint load Pb. (S14b) is provided. In the step of adjusting the restraint load Pb (S14b), the restraint load Pb may be adjusted by operating the restraint mechanisms 71 to 74. Further, the restraint load Pb may be adjusted while being measured by the measuring device 8, for example, as shown in FIG.

Here, the second load P2 is set to a load measured in a state where the resin member in the cell 3 receives a restraining load and is almost completely creeped. When the restraint load Pb is lower than the second load P2, the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode of the cell 3 constituting the battery stack 2 may be wider than specified. be. In this case, when the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode of the cell 3 is wide, the electrolyte is in a state of being easily diffused, so that the uneven salt concentration can be easily eliminated. Therefore, the deterioration in the performance of the battery stack 2 due to the uneven salt concentration can be easily eliminated. On the other hand, if the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode of the cell 3 constituting the battery stack 2 is wider than specified, the internal resistance between the positive electrode and the negative electrode increases accordingly. This may be the cause of the performance deterioration of the battery stack 2.

Therefore, as shown in FIG. 4, when the restraint load Pb is lower than such a second load P2, the restraint load Pb may be tightened up to the specified load Pr. That is, by the step (S14) of adjusting the restraint load Pb so as to have a predetermined predetermined load Pr, the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode of the cell 3 constituting the battery stack 2 is appropriately narrowed. Become. By this process, the performance of each cell 3 constituting the battery stack 2 and the performance of the battery stack 2 may be restored.

The second adjustment step (S15) is a step of adjusting the restraint load Pb when the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1. In the flowchart of FIG. 4, in the second adjustment step (S15), whether or not the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1 (P2 ≦ Pb). It includes a step of determining <P1) (S15a) and a step of adjusting the restraint load Pb (S15b).

Here, the first load P1 is a lower limit value in a range in which the specified load Pr can be set, as shown in FIG. It is a load that can be detected even when creep in the cell 3 is hardly generated. When the restraint load Pb is P2 ≦ Pb <P1, that is, the inside of the cell 3 is not always completely creeped, and there may be a state where almost no creep occurs in the cell 3. In this case, the deterioration of the battery stack 2 is caused by uneven salt concentration, and the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode of the cell 3 constituting the battery stack 2 is wider than specified. It is also possible that the internal resistance is high.

When the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1 (P2 ≦ Pb <P1), in the step of adjusting the restraint load Pb (S15b), first Loosen the restraint load Pb, then increase the load to make the load Pra higher than the predetermined specified load Pr, and then unload it to make the restraint load Pb so that it becomes the predetermined specified load Pr. adjust. In the step of adjusting the restraint load Pb (S15b), the restraint load Pb may be adjusted by operating the restraint mechanisms 71 to 74. Further, the restraint load Pb may be adjusted while being measured by the measuring device 8, for example, as shown in FIG.

FIG. 6 is a graph showing the transition of the restraint load in the step of adjusting the restraint load Pb (S15b).
In the step of adjusting the restraint load Pb (S15b), as shown in FIG. 6, the restraint load Pb is first loosened (L1). When the restraining load Pb is loosened, the distance between the sheet-shaped positive electrode and the sheet-shaped negative electrode of the cell 3 constituting the battery stack 2 becomes wider than specified. Then, the uneven salt concentration can be easily eliminated. In the state where the restraining load Pb is loosened (L1), the battery stack 2 may be left for a predetermined time. As a result, the uneven salt concentration in the cell 3 is moderately eliminated.

Here, when the electrode body used in the cell 3 is, for example, a so-called wound electrode body in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are wound with a sheet-shaped separator interposed therebetween, for example, It is preferable that the restraining load Pb is loosened so as to be about half of the specified load Pr. In the wound electrode body, if the restraint load Pb is loosened too much, the winding is loosened inside, and when the restraint is further tightened, it may cause wrinkles in the wound electrode body.
In the case where the wound electrode body is a so-called laminated electrode body in which a plurality of sheet-shaped positive electrodes and a plurality of sheet-shaped negative electrodes are laminated with a plurality of separators interposed therebetween. The restraint may be further loosened. By further loosening the restraint, uneven salt concentration can be eliminated at an early stage.

Further, when the restraint load Pb is lower than the predetermined second load P2 (Pb <P2), there is a possibility that creep has completely occurred in the cell 3. In this case, the restraint load is likely to act on the sheet-shaped positive electrode and the sheet-shaped negative electrode, and the restraint load Pb should not be higher than the specified load Pr. Here, the constraint is tightened when the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1 (P2 ≦ Pb <P1). .. In the determination step (S15a), when the restraint load Pb is lower than the predetermined second load P2 (Pb <P2), it is excluded from the target for tightening the restraint.

In the determination step (S15a), when the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1 (P2 ≦ Pb <P1) (Yes), the cell 3 It is possible that there is almost no creep inside. In the step of adjusting the restraint load Pb (S15b), as shown in FIG. 6, after loosening the restraint for a predetermined time (after L1) and before adjusting the restraint load Pb to the specified load Pr (after L1). Before L3), the restraint load Pb is adjusted to a load Pra higher than the predetermined predetermined load Pr by increasing the load (L2). Here, the load Pra is set higher than the specified load Pr, but lower than the limit value P3 (see FIG. 3) of the restraint load Pb at which the battery case is crushed.

By increasing the load and adjusting the restraining load Pb to a load Pra higher than the predetermined predetermined load Pr, the resin material in the cell 3 is in a tightened state. After that, by adjusting the restraining load Pb to the specified load Pr, it is possible to prevent the load from coming off due to creep on the resin material in the cell 3. In addition, when assembling the battery stack 2 in the cell 3 in the initial state, it is advisable to once set the load Pra to be higher than the predetermined specified load Pr and then adjust the restraint load Pb to the specified load Pr for the same reason. ..

The second determination step (S16) determines whether or not the battery stack 2 has predetermined predetermined performance after the first adjustment step (S14) or after the second adjustment step (S15) described above. It is a process. Here, the battery performance A1 of the battery stack 2 after the first adjustment step (S14) or after the second adjustment step (S15) is acquired (S16a) as in the first determination step (S12). Then, it is determined whether the acquired battery performance A1 of the battery stack 2 has a predetermined predetermined performance A0 (A1 ≧ A0) (S16b).

In the second determination step (S16), when the battery stack 2 has a predetermined predetermined performance A0 (Yes), the battery stack 2 is forwarded to the reused step (S30).

As described above, the inspection method of the battery stack 2 includes a step of preparing the used battery stack 2 (S11), a first determination step (S12), and a step of acquiring the restraint load Pb of the battery stack 2 (S13). It is preferable that the first adjusting step (S14), the second adjusting step (S15), and the second determination step (S16) are included.

The steps (S11) to (S16) can be performed while the battery stack 2 is maintained as described above. That is, in the first determination step (S12), even when the battery stack 2 does not have the specified performance A0 (No), the battery stack 2 is used in the first adjustment step (S14) and the second adjustment step (S15). The restraint is loosened while maintaining the. Therefore, when the performance of the battery stack 2 is deteriorated due to the bias of the salt concentration of the cell 3, the bias of the salt concentration of the cell 3 may be eliminated and the performance of the battery stack 2 may be recovered. .. Then, in the first determination step (S12) or the second determination step (S16), when the battery stack 2 has the specified performance A0 (Yes), the battery stack 2 is forwarded to the reused step (S30). To. Therefore, the battery stack 2 can be reused without releasing the constraint of the cell 3. Here, the battery stack 2 is reconstructed without releasing the constraint on the battery stack 2 that is forwarded to the reused step (S30) and without being inspected for each cell 3. The trouble of being done is saved. Therefore, a method for inspecting the battery stack 2 including the above steps (S11) to (S16) before the cell inspection step (S17) for releasing the constraint of the battery stack 2 and inspecting each cell 3 is available. By doing so, the battery stack 2 can be efficiently reused.

If the battery stack 2 does not have a predetermined performance (No) in the second determination step (S16), the battery stack 2 is forwarded to the cell inspection step (S17).
If both the step (S14a) for determining (Pb <P2) and the step (S15a) for determining (P2 ≦ Pb <P1) are determined to be “No”, the cell inspection step (S17). ). That is, when the restraint load Pb is a load P1 or more (P1 ≦ Pb) which is a lower limit value in the range in which the specified load Pr can be set, the battery stack 2 is forwarded to the cell inspection step (S17). That is, here, since the restraint load Pb is equal to or higher than the load P1 which is the lower limit value of the range in which the specified load Pr can be set, the restraint load Pb is within the range of the optimum value, and the restraint load is not loosened. It is forwarded to the cell inspection step (S17).

The cell inspection step (S17) is a step of releasing the constraint of the battery stack 2 and inspecting each of the cells 3 constituting the battery stack 2. As shown in the flowchart of FIG. 4, the cell inspection step (S17) includes, for example, a step of disassembling the battery stack 2 for each cell 3 (S17a), a step of separating the cell 3 into non-defective products (S17b), and the like. It includes a step (S17c) of reconstructing the battery stack 2 with a good cell 3. Then, the battery stack 2 reconstructed by the good cell 3 is forwarded to the step (S30) in which the battery stack 2 is reused. Here, for the non-defective product classification of the cell 3, for example, it may be determined whether the cell 3 maintains the performance of about 80% of the initial performance.

By inspecting each cell 3 by the cell inspection step (S17), the reusable cell 3 can be appropriately sorted. As a result, the reusable cell 3 is reused without being discarded.

In the above, various methods for inspecting the battery stack proposed here have been described. Unless otherwise specified, the embodiments of the battery stack inspection method mentioned here do not limit the present invention.

2 Battery stack 3 Cell 4 Cooling plate 7 Bus bar 8 Measuring device 30 Battery case 31 Case body 32 Lid 33 Safety valve 36A Positive electrode terminal 36B Negative electrode terminal 51, 52 End plate 60 Restraint mechanism 61-64 Restraint band 61a-64a Nuts 71-74 Restraint mechanism 71a to 74a Bolts 71b to 74b Stop nut 71c Spring washer 81,82 Measuring plate 83 Measuring instrument

Claims (1)

The process of preparing a used battery stack with multiple cells constrained under a constrained load, and
A first determination step of determining whether or not the battery stack has predetermined predetermined performance for at least one of the internal resistance and the battery capacity.
In the first determination step, when no said predetermined specified performance, a step of acquiring the constraint force Pb of the cell stack,
When the restraint load Pb is lower than the predetermined second load P2, the first adjustment step of adjusting the restraint load Pb so as to be the predetermined predetermined load Pr, and the first adjustment step.
When the restraint load Pb is equal to or higher than the predetermined second load P2 and lower than the predetermined first load P1, the restraint load Pb is loosened and then the load is increased to be predetermined. A second adjustment step of adjusting the restraint load Pb so that the load Pra is higher than the load Pr, and then the load is unloaded so as to have a predetermined predetermined load Pr.
A second determination step of determining whether or not the battery stack has the predetermined predetermined performance after the first adjustment step or after the second adjustment step is included.
How to inspect the battery stack.

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