JP2012129029A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of visually recognizing a condition of a binding force applied to a power storage element.SOLUTION: A power storage device (100) has a plurality of power storage elements (10) aligned in a predetermined direction (X-direction), a pair of end plates (40) nipping the plural power storage elements in a predetermined direction, and a plurality of coupling members (50) extending in a predetermined direction, coupling a pair of the end plates, and providing a binding force to the plural power storage elements via the pair of the end plates. Among the plural coupling members, at least one coupling member has marks (S, 62), and a shape of the mark is varied by deformation together with variation of the binding force.

Description

  The present invention relates to a power storage device having a structure that applies a binding force to a plurality of power storage elements.

  When a plurality of unit cells (so-called rectangular unit cells) are arranged in one direction to form an assembled battery, a binding force may be applied to the plurality of unit cells. The binding force is a force acting in the arrangement direction of the plurality of unit cells, and is a force for sandwiching each unit cell in the arrangement direction.

  Specifically, by arranging a pair of end plates at positions sandwiching the plurality of unit cells, and connecting the pair of end plates by a restraining band extending in the arrangement direction of the plurality of unit cells, a plurality of unit cells are obtained. A restraining force can be applied to the. If the restraining force is too high or too low, there is a risk that a malfunction may occur, and therefore it is preferably within a predetermined range.

JP 2009-076265 A JP 2006-024445 A JP 2009-238606 A JP 10-503079 gazette

  Even if the binding force for a plurality of single cells is set at the stage of assembling the assembled battery, the binding force after starting to use the assembled battery cannot be confirmed. Here, in patent document 1 etc., the pressure sensor is arrange | positioned inside an assembled battery and the constraint force which acts on an assembled battery is monitored based on the output of a pressure sensor. In the configuration using the pressure sensor, it is necessary to calculate the binding force by processing the output signal of the pressure sensor.

  The objective of this invention is providing the electrical storage apparatus which can confirm the state of the binding force which acts on an electrical storage element visually.

  A power storage device according to a first invention of the present application includes a plurality of power storage elements arranged side by side in a predetermined direction, a pair of end plates sandwiching the plurality of power storage elements in the predetermined direction, and a pair of end plates extending in a predetermined direction And a plurality of connecting members for applying a binding force to the plurality of power storage elements via the pair of end plates. Here, at least one of the plurality of connecting members has a mark, and the shape of the mark is changed by deformation associated with a change in restraining force.

  The connecting member has a first region where the mark is formed and a second region where the mark is not formed, and the size of the first region can be made smaller than the size of the second region. . As a result, when the restraining force changes, stress can be concentrated in the first region, and the first region can be positively deformed. In addition, the shape of the mark formed in the first region can be easily changed.

  As the mark, a scale formed along the longitudinal direction of the connecting member can be used. Here, the interval between the scales can be changed by the deformation of the connecting member accompanying the change in the restraining force. By confirming the change in the interval between the scales, the state of the binding force can be confirmed.

  The connecting member may be provided with an arm branched from the area where the scale is formed. The arm can be formed with an index provided at a position adjacent to the scale. In this configuration, the state of the restraining force can be confirmed based on the positional relationship between the scale and the index.

  A power storage device according to a second invention of the present application includes a plurality of power storage elements arranged side by side in a predetermined direction, a pair of end plates sandwiching the plurality of power storage elements in the predetermined direction, and a pair of end plates extending in a predetermined direction And a plurality of connecting members for applying a binding force to the plurality of power storage elements via the pair of end plates. Among the plurality of connecting members, at least one connecting member includes a first connecting member having a scale formed along a longitudinal direction of the connecting member, a second connecting member separated from the first connecting member, And a spring connected to the first connecting member and the second connecting member and provided with an index indicating the scale.

  According to the second invention of the present application, the spring expands or contracts according to the state of the restraining force, and the positional relationship between the scale and the index changes due to the deformation of the spring. Therefore, if the positional relationship between the scale and the index is confirmed, the state of the binding force acting on the power storage element can be confirmed.

  The connecting member described above can be disposed on the upper surface of the power storage element. Thereby, the mark and scale provided on the connecting member can be easily confirmed from above the power storage device. On the other hand, a partition member can be disposed between two power storage elements adjacent in a predetermined direction. The partition member can be used to form a space on the surface of the power storage element for moving a gas used for temperature adjustment of the power storage element.

  According to the present invention, it is possible to confirm the state of the binding force acting on the power storage element only by looking at the shape of the mark formed on the connecting member.

1 is an external view of a battery stack in Example 1. FIG. 1 is a cross-sectional view of a battery pack that is Example 1. FIG. In Example 1, it is a figure which shows a part of restraint band when it exists in a natural state. In Example 1, it is a figure which shows a part of restraint band when it exists in a restraint state. FIG. 6 is a diagram illustrating a part of a restraint band in a modification of the first embodiment. It is a figure which shows a part of restraint band in Example 2. FIG. In the modification of Example 2, it is the schematic of a restraint band and a pack case. It is a figure which shows a part of restraint band in the other modification of Example 2. FIG. It is a figure which shows a part of restraint band in Example 3. FIG.

  Examples of the present invention will be described below.

  A battery pack (corresponding to a power storage device) that is Embodiment 1 of the present invention will be described. FIG. 1 is an external view of the battery stack, and FIG. 2 is a cross-sectional view of the battery pack. 1 and 2, an X axis, a Y axis, and a Z axis are orthogonal to each other. In this embodiment, an axis corresponding to the vertical direction is a Z axis.

  The battery pack of the present embodiment can be mounted on a vehicle, for example. By using the output of the battery pack, kinetic energy for driving the vehicle can be generated. Further, the kinetic energy generated during braking of the vehicle can be stored in the battery pack as regenerative power.

  As shown in FIG. 2, the battery pack 100 includes a battery stack 1 and a pack case 110 that houses the battery stack 1. The pack case 110 includes an upper case 111 and a lower case 112. The upper case 111 and the lower case 112 can be made of metal, for example.

  The battery stack 1 includes a plurality of single cells (corresponding to power storage elements) 10 arranged side by side in the X direction (predetermined direction). The unit cell 10 is a so-called rectangular unit cell, and the outer surface of the unit cell 10 includes a plane (YZ plane) orthogonal to the arrangement direction (X direction) of the plurality of unit cells 10. As the unit cell 10, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery. The number of unit cells 10 constituting the battery stack 1 can be appropriately set based on the required output of the battery stack 1 (battery pack 100).

  In the present embodiment, the plurality of single cells 10 are arranged in the X direction, but the present invention is not limited to this. Specifically, a single battery module (corresponding to a power storage element) can be configured by a plurality of single cells, and the plurality of battery modules can be arranged in the X direction.

  A positive electrode terminal 11 and a negative electrode terminal 12 are provided on the upper surface of the unit cell 10. The power generation element is accommodated inside the unit cell 10, and the power generation element includes, for example, a positive electrode element, a negative electrode element, and a separator (including an electrolytic solution) disposed between the positive electrode element and the negative electrode element. Can be configured. In the positive electrode element, a layer containing a positive electrode active material or the like is formed on the surface of the current collector plate. In the negative electrode element, a layer containing a negative electrode active material or the like is formed on the surface of the current collector plate. The positive electrode terminal 11 is electrically connected to the positive electrode element of the power generation element, and the negative electrode terminal 12 is electrically connected to the negative electrode element of the power generation element.

  The plurality of single cells 10 constituting the battery stack 1 are electrically connected in series by a bus bar module 20. The bus bar module 20 includes a plurality of bus bars and a holding plate that holds these bus bars. The bus bar is a conductive member, and is connected to the positive electrode terminal 11 of one unit cell 10 and the negative electrode terminal 12 of the other unit cell 10 out of two unit cells 10 adjacent in the X direction. The holding plate is made of an insulating material such as resin.

  In this embodiment, all the unit cells 10 are electrically connected in series, but a plurality of unit cells 10 electrically connected in parallel may be included. Moreover, although the positive electrode terminal 11 and the negative electrode terminal 12 are provided in the upper surface of the cell 10, it does not restrict to this. For example, the positive electrode terminal 11 and the negative electrode terminal 12 can be provided on both end faces of the unit cell 10 in the Y direction.

  A partition plate (corresponding to a partition member) 30 is disposed between two unit cells 10 adjacent in the X direction, and the partition plate 30 can be formed of resin, for example. In addition, the shape of the partition plate 30 can be set as appropriate. For example, a structure that can hold the unit cell 10 can be provided in the partition plate 30.

  The partition plate 30 has a rib (not shown) protruding in the X direction on the surface facing the unit cell 10. A space is formed between the unit cell 10 and the partition plate 30 when the rib contacts the unit cell 10. This space becomes a passage through which a gas used for temperature adjustment of the unit cell 10 moves.

  When the unit cell 10 is generating heat, the temperature rise of the unit cell 10 can be suppressed by using a cooling gas. When the unit cell 10 is excessively cooled, the temperature drop of the unit cell 10 can be suppressed by using a gas for heating. When the battery pack 100 is mounted on a vehicle, the air in the vehicle compartment can be supplied to the battery pack 100 by driving the blower. The passenger compartment is a space where passengers get in, and the air in the passenger compartment may be set to a temperature suitable for temperature adjustment of the unit cell 10 by an air conditioner or the like.

  A pair of end plates 40 are disposed at both ends of the battery stack 1 in the X direction. A restraining band (corresponding to a connecting member) 50 extending in the X direction is connected to the pair of end plates 40. Both ends of the restraining band 50 are bent along the outer surface of the end plate 40 and are fixed to the end plate 40 using bolts or rivets.

  By connecting the pair of end plates 40 using the binding band 50, a binding force can be applied to the plurality of unit cells 10 sandwiched between the pair of end plates 40. The restraining force is a force that sandwiches the unit cell 10 in the X direction. By imparting a binding force to the unit cell 10, expansion of the unit cell 10 can be suppressed, and deterioration of input / output characteristics of the unit cell 10 can be suppressed.

  The structure for fixing the restraining band 50 to the end plate 40 can be designed as appropriate. Moreover, the shape of the restraint band 50 can also be set suitably. In the present embodiment, the cross section orthogonal to the longitudinal direction of the restraining band 50 is formed in a rectangular shape, but may be formed in another shape, for example, a circle.

  Two restraining bands 50 are disposed on the upper surface of the battery stack 1, and two restraining bands 50 are disposed on the lower surface of the battery stack 1. The restraining band 50 disposed on the upper surface of the battery stack 1 is disposed at a position avoiding the positive electrode terminal 11 and the negative electrode terminal 12.

  In this embodiment, the restraining bands 50 are disposed on the upper and lower surfaces of the battery stack 1, but the present invention is not limited to this. That is, it is only necessary that a binding force can be applied to the plurality of unit cells 10 sandwiched between the pair of end plates 40 by connecting the pair of end plates 40. For example, the restraining bands 50 can be disposed on both side surfaces of the battery stack 1 in the Y direction.

  Next, the configuration of the restraining band 50 will be described. Of the four restraining bands 50, at least one restraining band 50 has the structure shown in FIG. FIG. 3 is a front view showing a part of the restraining band 50. It is preferable that the restraint band 50 having the structure shown in FIG. 3 can be easily confirmed from the outside. For example, the restraint band 50 arranged on the upper surface of the battery stack 1 can have the structure shown in FIG. .

  The restraint band 50 has a scale region R in which the scale S is formed, and the width (length in the Y direction) W1 of the scale region R is larger than the width (length in the Y direction) W2 of other regions. narrow. The scale region R has a length L1 in the X direction. An arm 51 extending in the X direction is provided at a position adjacent to the scale region R in the Y direction, and an index 51 a is provided at the tip of the arm 51.

  The proximal end portion of the arm 51 is connected to one region having the width W2, and the distal end portion of the arm 51 is separated from the other region having the width W2. In the Y direction, a space is formed between the arm 51 and the scale region R. In other words, the arm 51 branches off from the scale region R. The arm 51 has a length L2 in the X direction, and the length L2 is shorter than the length L1. The width (length in the Y direction) W3 of the arm 51 is narrower than the width W2. The width W3 may be the same as the width W1, or may be different from each other.

  FIG. 3 is a view when the restraint band 50 is in a natural state. The natural state is a state in which the restraining band 50 is not attached to the pair of end plates 40, in other words, a state in which the restraining band 50 does not receive the force that the plurality of single cells 10 try to spread in the X direction. .

  When a restraining force is applied to the plurality of unit cells 10, the restraint band 50 receives a load indicated by an arrow F in FIG. 4 from the plurality of unit cells 10. The load F is a force that the plurality of single cells 10 tries to spread in the X direction. When the restraining band 50 receives the load F, the restraining band 50 extends and deforms in the X direction. In the restraint band 50 in the natural state, the width W1 of the scale region R is narrower than the width W2. Therefore, when the restraint band 50 receives the load F, the scale region R is easily deformed. In FIG. 4, when the scale region R is deformed, the width of the scale region R changes from W1 to W4 (<W1), and the length of the scale region R changes from L1 to L3 (> L1).

  When the scale region R extends in the X direction, the interval between the scales S formed in the scale region R also changes. Specifically, the interval between the scales S in the state shown in FIG. 4 is wider than the interval between the scales S in the state shown in FIG. On the other hand, the arm 51 is branched from the scale region R, and the arm 51 is not deformed even when the load F acts on the restraining band 50. For this reason, the relative positional relationship between the index 51a of the arm 51 and the scale S formed in the scale region R changes.

  By visually observing the relative positional relationship between the index 51a and the scale S, the state of the binding force acting on the plurality of single cells 10 can be grasped. For example, immediately after the binding force is applied to the plurality of single cells 10, in other words, immediately after the battery stack 1 is assembled, the position of the scale S facing the index 51a is set as the reference position. And if the restraint band 50 (scale area | region R) is extended by the change of restraint force, the relationship between the position of the parameter | index 51a and a reference | standard position will change. By confirming this change, the state of the binding force can be grasped.

  A modification of this embodiment will be described with reference to FIG. FIG. 5 is a view showing a part of the restraining band in the present modification, and corresponds to FIGS. 3 and 4. In this modification, the same reference numerals are used for members having the same functions as those described in the present embodiment.

  In this modification, the scale S is formed along the outer edge of the region having the width W2. Further, the index 51a of the arm 51 is disposed at a position adjacent to the scale S in the Y direction. Also in this modification, the region having the width W1 is more easily deformed than the region having the width W2.

  The state shown in FIG. 5 shows the state of the restraint band 50 immediately after the restraint force is applied to the plurality of single cells 10, in other words, immediately after the battery stack 1 is assembled. When the binding force changes from the state shown in FIG. 5, the position of the index 51a with respect to the scale S changes. Specifically, when the restraint band 50 (the region of the width W1) extends from the state illustrated in FIG. 5, the index 51a moves with respect to the scale S in the direction of the arrow D1. On the other hand, when the restraint band 50 (region of width W1) is contracted as compared with the state shown in FIG.

  In this modified example, “MAX” and “MIN” are provided at both ends of the scale S. “MAX” indicates that the binding force is the maximum value in the allowable range, and “MIN” indicates that the binding force is the minimum value in the allowable range. The range between “MAX” and “MIN” can be set based on the deformation characteristics of the restraining band 50.

  When the index 51a is not located in the region between “MAX” and “MIN”, it can be determined that there is a problem in the restraint state of the unit cell 10. When constraining a plurality of unit cells 10, it is preferable to constrain the unit cells 10 in a desired constrained state, and by using the scale S of this modification, it is confirmed whether the desired constrained state is maintained. be able to.

  When the unit cell 10 undergoes thermal expansion or the like, the restraint band 50 extends in the X direction, whereby the index 51a moves in a direction approaching “MAX”. Here, when the index 51a is positioned in the direction of the arrow D1 rather than the position of “MAX”, it can be determined that an excessive binding force is generated. On the other hand, when a creep phenomenon occurs in the partition plate 30 or the like, the restraint band 50 contracts in the X direction, so that the index 51a moves in a direction approaching “MIN”. Here, when the index 51a is positioned in the direction of the arrow D2 relative to the position of “MIN”, it can be determined that the binding force is insufficient.

  In this modification, since the index 51a moves with respect to the scale S, the state of the binding force can be confirmed by looking at the position of the index 51a with respect to the scale S.

  A battery pack that is Embodiment 2 of the present invention will be described. Here, the same members as those described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In this embodiment, the structure of the restraint band is changed with respect to the first embodiment. Hereinafter, differences from the first embodiment will be mainly described.

  FIG. 6 is a view showing a part of a restraining band (corresponding to a connecting member) 60 in the present embodiment, and corresponds to FIGS. 3 and 4 described in the first embodiment. Two recesses 61 are formed at the edge of the restraining band 60. The recess 61 has a curvature, and the two recesses 61 are provided side by side in the Y direction. The position where the two concave portions 61 are provided can be set as appropriate. A plurality of scales 62 are formed in a region located between the two recesses 61. The plurality of scales 62 are formed along the X direction and the Y direction, respectively.

  FIG. 6 is a view when the restraint band 60 is in a natural state. When the restraint band 60 is in a natural state, the intervals of all the scales 62 are set to M1 in the X direction. Further, with respect to the Y direction, the intervals between all the scales 62 are set to M2. Here, the intervals M1 and M2 may be equal or different from each other.

  When the battery stack 1 is assembled, a restraining force is applied to the plurality of single cells 10, and the restraining band 60 extends in the X direction by receiving a force from the end plate 40. Since the constraining band 60 is provided with the concave portion 61, the stress can be concentrated on the region located between the two concave portions 61, and this region can be most easily deformed. In other words, the region located between the two recesses 61 is easily stretched in the X direction.

  Immediately after assembling the battery stack 1, the interval M1 of the scale 62 is maintained at a predetermined value (referred to as a reference value). And if the restraint force of the cell 10 changes, the space | interval M1 of the scale 62 will change by the restraint band 60 expanding or contracting. Specifically, if the restraining force acting on the unit cell 10 is increased, the interval M1 between the scales 62 is larger than the reference value, and if the restraining force is reduced, the interval D1 between the scales 62 is smaller than the reference value. Therefore, the state of the binding force acting on the unit cell 10 can be confirmed by comparing the interval M1 after the change with the reference value.

  When the interval M1 after the change is compared with the reference value, for example, if a ruler indicating the reference value is prepared, the comparison with the reference value can be easily performed. On the other hand, a scale indicating a reference value can be provided at a position adjacent to the restraining band 60. Specifically, as shown in FIG. 7, a scale S indicating the reference value Dref can be provided in a region adjacent to the concave portion 61 of the restraining band 60 in the pack case 110. Even in the configuration shown in FIG. 7, the state of the restraining force can be confirmed by comparing the reference value Dref and the interval M <b> 1 of the scale 62.

  In the configuration shown in FIG. 7, the reference value Dref can be set as appropriate. If the reference value Dref is the interval M1 of the scale 62 immediately after the battery stack 1 is assembled, the scale S formed on the pack case 110 and the scale 62 formed on the restraining band 60 can be matched. On the other hand, when the reference value Dref is a value different from the interval M1 of the scale 62 immediately after the battery stack 1 is assembled, the state of the binding force can be confirmed by considering these differences.

  In the configuration shown in FIG. 7, the scale S indicating the reference value Dref is provided in the pack case 110, but is not limited thereto. That is, the scale S indicating the reference value Dref may be provided on a member different from the restraining band 60, and may be provided on the unit cell 10, for example.

  In the present embodiment, the scales 62 are formed along the X direction and the Y direction, respectively, but the present invention is not limited to this. Specifically, only the scale 62 along the Y direction can be formed on the restraining band 60 in order to confirm the scale interval M1.

  In this embodiment, the recess 61 has a curvature, but the present invention is not limited to this. That is, it is only necessary that the width of the area forming the scale 62 is narrower than the width of other areas. For example, a restraining band shown in FIG. 8 can be used. In the configuration shown in FIG. 8, the recess 61 includes a surface extending in the X direction and a surface extending in the Y direction.

  A battery pack that is Embodiment 3 of the present invention will be described. About the same member as the member demonstrated in Example 1, 2, the same code | symbol is used and detailed description is abbreviate | omitted. In the present embodiment, the structure of the restraint band is changed with respect to the first and second embodiments. Hereinafter, differences from the first and second embodiments will be mainly described.

  FIG. 9 is a view showing a part of a restraining band (corresponding to a connecting member) in the present embodiment, and corresponds to FIGS. 3 and 4 described in the first embodiment. The restraining band 70 has a first band (corresponding to a first connecting member) 71 and a second band (corresponding to a second connecting member) 72 that are separated from each other, and the first band 71 and the second band 72 are Are connected by a spring 73.

  As described in the first embodiment, one end (not shown) of the first band 71 is fixed to the end plate 40, and one end 73 a of a spring 73 is fixed to the other end of the first band 71. Yes. As a method of fixing the first band 71 and the spring 73, for example, a hook is provided at one end 73a of the spring 73, and this hook can be hooked on an opening formed in the first band 71.

  As described in the first embodiment, one end (not shown) of the second band 72 is fixed to the end plate 40, and the other end 73 b of the spring 73 is fixed to the other end of the second band 72. ing. The fixing method of the second band 72 and the spring 73 can be the same as the fixing method of the first band 71 and the spring 73.

  An arm 71 a extending in the X direction is formed at the other end of the first band 71, and the arm 71 a is arranged side by side with the spring 73 in the Y direction. The tip of the arm 71a is separated from the second band 72, and a scale S is formed on the arm 71a. The spring 73 is provided with an index 74, and the index 74 indicates the scale S.

  In the present embodiment, when the binding force acting on the unit cell 10 changes, the interval between the first band 71 and the second band 72 changes. Specifically, when the restraining force increases, the distance between the first band 71 and the second band 72 increases and the spring 73 extends. On the other hand, when the restraining force is reduced, the distance between the first band 71 and the second band 72 is narrowed, and the spring 73 is contracted.

  When the spring 73 is extended or contracted, the position of the index 74 with respect to the scale S changes. Here, immediately after the battery stack 1 is assembled, if the position of the scale S relative to the index 74 is determined as the reference position, the state of the binding force can be confirmed by looking at the deviation of the index 74 from the reference position. Can do.

  In Examples 1 to 3 described above, the scale is formed on the restraining band, but this is not a limitation. Specifically, a mark can be formed on the outer surface of the restraining band, and the shape of the mark can be changed by deformation of the restraining band accompanying a change in restraining force. In such a configuration, the state of the restraining force can be confirmed by confirming a change in the shape of the mark.

  As the mark described above, for example, a circle can be used. The direction of deformation of the circle is different when the restraint band is extended and when the restraint band is contracted. That is, when the restraint band is extended or contracted, the circle changes to an ellipse. Here, when the restraint band extends, the major axis of the ellipse becomes an axis along the longitudinal direction of the restraint band. When the restraint band contracts, the major axis of the ellipse becomes an axis along the direction orthogonal to the longitudinal direction of the restraint band.

1: Battery stack 10: Single battery (storage element)
11: Positive terminal 12: Negative terminal 20: Bus bar module 30: Partition plate (partition member)
40: End plate 50: Restraint band (connection member)
51: Arm 51a: Index 100: Battery pack (power storage device) 110: Pack case 111: Upper case 112: Lower case

Claims (7)

A plurality of power storage elements arranged side by side in a predetermined direction;
A pair of end plates sandwiching the plurality of power storage elements in the predetermined direction;
A plurality of connecting members extending in the predetermined direction to connect the pair of end plates and applying a binding force to the plurality of power storage elements via the pair of end plates;
Among the plurality of connecting members, at least one of the connecting members has a mark, and the shape of the mark is changed by deformation associated with the change in the binding force. The at least one connecting member has a first region where the mark is formed and a second region where the mark is not formed,
The power storage device according to claim 1, wherein a size of the first region is smaller than a size of the second region. The mark is a scale formed along the longitudinal direction of the connecting member,
The power storage device according to claim 1, wherein the connecting member changes the interval of the scales by deformation accompanying the change of the restraining force. The connecting member has an arm branched from the area where the scale is formed,
The power storage device according to claim 3, wherein the arm has an index provided at a position adjacent to the scale. A plurality of power storage elements arranged side by side in a predetermined direction;
A pair of end plates sandwiching the plurality of power storage elements in the predetermined direction;
A plurality of connecting members extending in the predetermined direction to connect the pair of end plates and applying a binding force to the plurality of power storage elements via the pair of end plates;
Of the plurality of connecting members, at least one of the connecting members is:
A first connecting member having a scale formed along the longitudinal direction of the connecting member;
A second connecting member separated from the first connecting member;
A spring connected to the first connecting member and the second connecting member and provided with an index indicating the scale;
A power storage device comprising:   The power storage device according to claim 1, wherein the at least one connecting member is disposed on an upper surface of the power storage element. The power storage device according to any one of claims 1 to 6, further comprising a partition member disposed between the two power storage elements adjacent in the predetermined direction.

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