JP2009014489A - Water wetting determination structure and cell pack having it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water wetting determination structure that well determines the presence of water wetting, and a cell pack having the water wetting determining structure to well determine the presence of the internal penetration of water. <P>SOLUTION: The cell pack 1 is equipped with: a unit cell 2; the protective circuit board 4 arranged to the side surface of the unit cell 2; and a first trim frame 10 and a second trim frame 11 both of which cover four side surfaces of the elementary cell 2. A water wetting determining seal 9 having an almost rectangular shape is pasted on one end part of the protective circuit board 4 and recording parts 92 and 92 printed in a strip form using water-soluble ink are provided to both end parts in the longitudinal direction of the surface of the base material of the water wetting determining seal 9. The first trim frame 10 is equipped with the board covering part 10a for covering the protective circuit board 4, and a determination window 10e to which the water wetting determining seal 9 is arranged in the state where the central part of the water wetting determining seal 9 is exposed and the recording parts 92 and 92 are not visually confirmed, is provided in the board covering part 10a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a water wetness determination structure in which a water wetness determination seal is disposed to face a window portion of an exterior body, and a water wetness determination object such as a battery is determined to be wet with water, and the water wetness determination structure The present invention relates to a battery pack having

  In recent years, as a power source for portable electronic devices such as video cameras, mobile computers, and mobile phones, which are rapidly spreading, a chargeable / dischargeable rectangular parallelepiped nonaqueous electrolyte secondary battery such as a lithium ion secondary battery is mainly used. It has been. A lithium ion secondary battery (unit cell) is made of aluminum or an aluminum alloy and includes a power generation element in which a positive electrode and a negative electrode are wound via a separator, and is housed in a rectangular parallelepiped case.

On one side of this unit cell, a protection circuit for controlling the battery voltage to prevent overcharge and overdischarge, and a protection circuit having an output terminal for taking out power from the unit cell to the outside or taking in power from outside The battery core is configured by arranging the substrate. The protective circuit board and the unit cell are electrically connected by a connecting lead plate.
Cover the side surface of the battery core with an insulating frame made of, for example, a synthetic resin, or store the battery core in an outer case made of, for example, a synthetic resin, and further label the flat surface of the unit cell and the outer frame or the outer case. The battery pack is obtained by covering with, and this battery pack is attached to the portable electronic device.

  By the way, the mobile phone may get wet or submerged by carelessness of the user, and the water gets into the battery pack used as the power source of the mobile phone due to the wetness. There is. When the battery pack is used in a state in which water has entered the exterior body such as the above-described exterior frame, there is a problem that a short circuit occurs due to this water, resulting in failure or performance degradation.

  Battery packs that have failed or deteriorated performance due to submergence in this way are unlikely to leave traces of water immersion if they are completely dried. Is often very difficult to investigate. For this reason, in order to make it easy to determine whether or not water has entered the inside of the battery pack, a battery pack having a water wetness determination seal has been developed.

  The water wetness determination seal has water-soluble ink attached to one surface of a water-absorbing base material so as to form, for example, characters, figures, and patterns (for example, polka dots), and is provided inside the outer package of the battery pack. The one surface faces the determination window.

  By providing the water wetness determination seal, when water penetrates into the exterior body, the infiltrated water penetrates into the water wetness determination seal and soaks water-soluble ink. The polka dot pattern is blurred and blurred. Even when the battery pack that has been immersed in the exterior body is completely dried, the polka dot pattern on the substrate is dried in a blurred state. By visually recognizing, it can be determined whether water has entered the inside of the battery pack.

  Patent Document 1 discloses an invention of a water wetness determination seal that allows water-soluble ink to appear on the other surface (determination window side) when water-soluble ink is attached to one surface and gets wet with water. . In this water wetness determination seal, since the one surface is not a determination surface, water management when water-soluble ink is attached is simple.

In Patent Document 2, a submerged confirmation mark by water-soluble ink and character / graphic information by water-insoluble ink are formed on the surface of a base made of water-absorbent paper, and the surface is formed by a translucent laminate film. An invention of a small electronic device in which a nameplate formed by coating is attached to the outer surface of a device casing in a state where the back surface of the base is directed to the device casing and the submersion confirmation mark is matched with an opening formed in the device casing. It is disclosed.
JP 2005-189117 A JP 2001-177268 A

  In conventional battery packs such as the battery pack described in Patent Document 2, patterns, characters, figures, and the like recorded on the water wetness determination seal are always visible from the determination window of the exterior body of the battery pack (or electronic device). As described above, when water enters the inside of the battery pack and the water-soluble ink is dissolved in water, the pattern or the like bleeds or discolors, so the presence or absence of water has been determined. .

However, according to this configuration, even if the battery pack is not wet with water, the water-soluble ink may bleed and discolor in a high-temperature and high-humidity environment, and it may be erroneously determined that the battery has been submerged.
In the battery pack of Patent Document 1, the pattern, characters, figures, etc. recorded on the water wetness determination seal are not visually recognized before being wetted, and when the water is immersed inside the exterior body, The applied water-soluble ink is soaked up to the surface side so that a pattern or the like appears. However, in the same way as above, the water-soluble ink penetrates to the surface side and bleeds, resulting in water immersion. There was a risk of misjudgment.
In addition, due to the recent thinning of battery packs, the judgment window has also become smaller, making it difficult to see the pattern recorded on the water wetting judgment sticker. was there.

  The present invention has been made in view of such circumstances, and by forming the recording portion of the water wetness determination seal in a portion other than the portion corresponding to the window portion of the exterior body, the recording portion is Is not visible, it is visible for the first time when water-soluble ink dissolves in water and spreads in the surface direction of the base material and oozes out into the window, so it is visible whether water is wet or not. It is an object of the present invention to provide a water wetness determination structure that can be determined in a simple manner.

  In addition, the present invention forms a recording portion in a strip shape, so that when water is immersed in the exterior body, the water-soluble ink dissolves in water and the recording portion spreads in a strip shape, which is more reliably visible and is wet. An object of the present invention is to provide a water wetting determination structure in which the presence or absence is determined better.

  And this invention forms a recording part in the state which separated from the part corresponding to the edge part of a window part the space | interval wider than the increase amount of the width dimension of the recording part measured by the test supposing a hot and humid environment. Accordingly, it is an object of the present invention to provide a water wetness determination structure in which it is suppressed that a recording portion oozes out to a window portion and is erroneously determined to have been submerged in a hot and humid environment.

  Furthermore, an object of the present invention is to provide a water wetness determination structure in which erroneous determination is further sufficiently suppressed by forming the recording portion so as to be separated from the edge by 0.4 mm or more.

  Another object of the present invention is to provide a battery pack that has the above-described water-wetting determination structure, and that can be satisfactorily determined whether or not there is a fact of water immersion inside.

  The water wetness determination structure according to the first invention includes a water wetness determination object, and a water wetness determination seal in which a recording portion using a water-soluble ink is formed in a portion near one end of one surface of a water-absorbing substrate. The water wetness judgment seal is disposed, the portion near the center of the one surface is exposed, and the recording unit is shielded at a predetermined interval from the edge of the window. And an exterior body covering the wet determination target body.

  In the present invention, since the recording part on which characters, figures, or patterns are recorded with water-soluble ink is formed in a part other than the part corresponding to the window part, the recording part is not visually recognized before being wet. It is first recognized when it is immersed in the exterior body, the water-soluble ink dissolves in water, spreads in the surface direction of the substrate, and oozes out into the window.

  The water wetting determination structure according to a second invention is characterized in that, in the first invention, the recording portion is formed in a band shape.

  In the present invention, when water is immersed in the exterior body, the water-soluble ink dissolves in water and spreads in a band shape, so that the recording portion can be visually recognized more reliably.

  The water wetting determination structure according to a third aspect of the present invention is the first or second aspect of the invention, wherein the interval between the recording portion and the edge of the window portion is left for 72 hours in an environment where the temperature is 50 ° C. or higher and 70 ° C. or lower and the humidity is 90% In this case, it is set to be longer than the amount of increase in the width dimension of the recording portion.

  In the present invention, the recording part is formed in a state in which the gap wider than the increase in the width dimension of the recording part measured in a test assuming a high temperature and humidity environment is separated from the part corresponding to the edge of the window part. Therefore, the recording part does not ooze out from the edge of the window with the amount of water in a high-temperature and high-humidity environment.

  According to a fourth aspect of the present invention, in the third aspect of the invention, the recording portion is formed so as to be separated from the edge by 0.4 mm or more.

  In the present invention, since the recording portion is formed to be sufficiently separated from the edge portion of the window portion, it is more sufficiently suppressed that the recording portion exudes from the edge portion of the window portion in a high temperature and high humidity environment. ing.

  A battery pack according to a fifth aspect of the invention is a battery pack having the water wetting determination structure according to any one of the first to fourth aspects, wherein the water wetness determination object has a rectangular parallelepiped shape having two planes and four side surfaces. It is a unit cell, The said exterior body is comprised so that at least four side surfaces of the said unit cell may be covered, and has a label which covers a part or all of the said unit cell and an exterior body, It is characterized by the above-mentioned.

In the present invention, the recording part is not visually recognized from the window part before being wetted with water, but is first recognized when the water-soluble ink is dissolved in the water and oozes out into the window part by being immersed inside the exterior body. .
Therefore, the presence or absence of the fact of flooding is determined well and can be taken into account when seeking the cause of the failure of the battery pack.

  According to the first invention, the recording part on which characters, figures or patterns are recorded with the water-soluble ink is formed in a part other than the part corresponding to the window part, and the recording part is visually recognized before wetting. First, when the water-soluble ink is immersed in the exterior body and the water-soluble ink dissolves in the water and oozes out to the window portion, it can be visually recognized for the first time.

  According to the second invention, since the recording portion is formed in a band shape, when the water is immersed in the exterior body, the water-soluble ink is dissolved in water and the recording portion is band-shaped toward the center of the water wetness determination seal. Since it spreads and is reliably recognized from the window part of an exterior body, the determination of the presence or absence of water wetting becomes easier.

  According to the third aspect of the present invention, the recording portion is formed in a state in which the gap wider than the increase in the width dimension of the recording portion measured in the test assuming a high-temperature and high-humidity environment is separated from the portion corresponding to the edge portion of the window portion. Therefore, even if the recording part bleeds in a high-temperature and high-humidity environment, it is not visually recognized from the window part.

  According to the fourth aspect of the invention, since the recording part is formed to be separated from the edge part of the window part by 0.4 mm or more, erroneous determination is more sufficiently suppressed.

According to the fifth aspect of the present invention, since the water wetting determination structure according to any one of the first to fourth aspects of the present invention is used, the recording unit is not visually recognized from the window before wetting, but is immersed inside the exterior body, When the water-soluble ink is dissolved and oozes out into the window portion, it is visually recognized for the first time, and the presence or absence of water can be determined well.
In this way, since the presence or absence of flooding is accurately determined, the user can ask the dealer to replace the battery pack, repair the electronic device, etc. in consideration of the above facts. Manufacturers can also respond appropriately.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
Embodiment 1 FIG.
1 is an exploded perspective view showing a battery pack 1 according to Embodiment 1 of the present invention, FIG. 2 is an exploded perspective view showing a water wetness determination seal 9, and FIG. 3 is a partial front view showing the battery pack 1. is there.
The battery pack 1 of the present embodiment is used as a power source for a mobile phone.
The unit cell 2 as a wetted object of the battery pack 1 has a rectangular flat plate shape, for example, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, and the positive electrode and the negative electrode are wound through a separator. The electrode group and the nonaqueous electrolyte are housed in a case made of aluminum or aluminum alloy. A negative electrode terminal 2a is provided on the first side surface 21 of the unit cell 2 via an insulating plate (not shown), and a lead mounting plate (not shown) is provided on the second side surface 22 parallel thereto. ing. The entire unit cell 2 other than the portion where the negative electrode terminal 2a is provided is the positive electrode (terminal).

A protective circuit board 4 is disposed on a third side surface 23 adjacent to the first side surface 21 where the negative electrode terminal 2 a of the unit cell 2 is provided via an insulating spacer 3. The spacer 3 is provided with a terminal window 3a for exposing the negative electrode terminal 2a.
The protection circuit board 4 has a substantially rectangular shape in plan view, and a protection circuit for preventing overcharge or overdischarge of the unit cell 2 is mounted on the back surface, and the protection circuit is covered with an insulating synthetic resin. The protection circuit mounting part 41 is provided. Further, near the one end from the center of the surface of the protection circuit board 4, the power is taken out to the outside of the unit cell 2, and conversely, the positive and negative electrodes for taking in the power from the outside for charging, and the output that is the temperature terminal Terminals 42, 42, 42 are juxtaposed by gold plating.

A water wetness determination seal 9 is attached to the other end of the protection circuit board 4.
The base material 91 of the water wetness determination seal 9 has a substantially rectangular shape and is made of high-quality paper having water absorption. At both ends in the longitudinal direction of the surface of the base material 91, recording portions 92 and 92 are formed by printing in a strip shape using water-soluble ink. The recording units 92 and 92 and the substrate 91 are covered with a transparent resin layer 95 made of, for example, PP (polypropylene) via an adhesive 94 made of acrylic resin or the like. The transparent resin layer 95 prevents the surface of the water wetness determination seal 9 from being scratched, prevents the recording portions 92 and 92 from being peeled off when the battery pack 1 is assembled, and the like. To prevent getting wet. An example of the quality paper is “55K” manufactured by Lintec Corporation, and an example of water-soluble ink is “ADS Color: Red” manufactured by Okubo Ink Co., Ltd.
Adhesives 93, 93 made of acrylic resin or the like are applied to both ends in the short direction of the back surface of the base material 91, and the water wetness determination seal 9 of the protection circuit board 4 is formed by the adhesives 93, 93. Affixed to the surface.

The protection circuit board 4 has a pad (not shown) formed at one end thereof connected to an electrode on the back side of a PTC (Positive Temperature Coefficient) element 6 via a first lead 5, and the surface side of the PTC element 6. The electrode is connected to the negative terminal 2a exposed from the terminal window 3a through the second lead 7.
A pad (not shown) formed on the other end of the protection circuit board 4 is connected to the second side surface 22 of the unit cell 2 via the third lead plate 8 and the lead mounting plate.

The first exterior frame 10 made of synthetic resin includes a substrate covering portion 10 a that covers the protection circuit substrate 4 and side surface covering portions 10 b and 10 c that respectively cover the first side surface 21 and the second side surface 22 of the unit cell 2. Window portions 10d, 10d, 10d for exposing the output terminals 42, 42, 42 of the protection circuit board 4 are provided closer to one end than the central portion of the substrate covering portion 10a. At the other end of the substrate covering portion 10a, a determination window 10e for exposing the central portion of the water wetness determination seal 9 attached to the protective circuit board 4 and determining the presence or absence of water wettability is provided. The determination window 10e has a substantially rectangular shape.
Locking recesses 10f and 10g are provided at the longitudinal ends of the side surface covering portions 10b and 10c, respectively.

  The second exterior frame 11 includes a side surface covering portion 11 a that covers the fourth side surface 24 of the unit cell 2, and side surface covering portions 11 b and 11 c that cover end portions of the first side surface 21 and the second side surface 22. Locking convex portions 11d and 11e are provided at the longitudinal ends of the side surface covering portions 11b and 11c, respectively.

The first exterior frame 10 is fitted to the unit cell 2 so as to cover the protection circuit board 4, the second exterior frame 11 is fitted so as to cover the fourth side surface 24 of the unit cell 2, and the locking recesses 10f, 10g. The first outer frame 10 and the second outer frame 11 are integrated by locking the locking projections 11d and 11e.
Then, a synthetic resin label 13 is attached to both the flat surfaces of the unit cell 2 and the first side surface 21 and the second side surface 22 covered by the first outer frame 10 and the second outer frame 11, and the battery pack 1. Is configured.

In the battery pack 1 according to the present embodiment configured as described above, the fact that the unit cell 2 is wet is determined by the water wetness determination seal 9. As shown in the partial front view of FIG. 3, the water wetness determination seal 9 is disposed on the determination window 10e in a state where the inner ends of the recording portions 92 and 92 are separated from the edge of the determination window 10e by L (mm). ing. In this embodiment, the thickness of the battery pack 1 is 5.6 mm, the size of the water wetness determination seal 9 is about 4 mm × 4 mm, the width of the recording portions 92 and 92 is about 1.4 mm, and L is 0.2 mm. 4 mm.
Therefore, the recording portions 92 are not visually recognized before the battery pack 1 is wet.

FIG. 4 is a partial front view showing a state in which the water-soluble ink is immersed in the first exterior frame 10 and the recording portions 92 and 92 extend beyond the edge of the determination window 10e. .
As shown in FIG. 4, the recording portions 92 and 92 appear only when the water is soaked inside the first exterior frame 10 and the water-soluble ink is dissolved in water and oozes out into the determination window 10e. Then, L is set to an interval at which the recording units 92 and 92 do not ooze into the determination window 10e when the amount of moisture is in a high temperature and high humidity environment. There is no misjudgment that it spreads and flooding occurs.

In the present embodiment, in order to obtain the preferable range of L, the following test was performed in advance.
First, using high-quality paper ("55K" manufactured by Lintec Corporation) and water-soluble ink ("ADS Color: Crimson" manufactured by Okubo Ink Co., Ltd.) in a strip shape having a width of about 1.4 to 1.5 mm. A plurality of samples in which a part was formed were produced. The sample was allowed to stand for 24 hours or 72 hours in a high-temperature and high-humidity environment at a temperature of 60 ° C. and a humidity of 90%, and the amount of increase in the width dimension of the recording portion was measured. The results are shown in Table 1 below.

According to Table 1, when left for 24 hours in a high temperature and high humidity environment with a temperature of 60 ° C. and a humidity of 90%, the average value of the increase in the width dimension of the recording area is 0.221 mm. It can be seen that the average value of the increase amount is 0.334 mm, and the maximum value of the increase amount is 0.372 mm.
In the present embodiment, the L is set to 0.4 mm so that erroneous determination is reliably prevented.
Therefore, in the present embodiment, the recording units 92 and 92 are expanded and visually recognized from the determination window 10e with the amount of water in a high-temperature and high-humidity environment. It can be determined well.
Therefore, the presence or absence of flooding can be reliably determined and taken into account when seeking the cause of the failure of the battery pack. In this way, since the presence or absence of flooding is accurately determined, the user can ask the dealer to replace or repair the battery pack in consideration of the fact, and the dealer, manufacturer, etc. Can also respond appropriately.

Note that if L is set to 0.4 mm or more, erroneous determination in a high-temperature and high-humidity environment can be prevented with certainty. However, the present invention is not limited to this, and erroneous determination is sufficiently prevented in a high-temperature and high-humidity environment. Any interval may be used. The upper limit of L is determined by the amount of water-soluble ink used for forming the recording portions 92 and 92, the thickness of the battery pack 1, and the like.
In the present embodiment, the case where the water wetness determination seal 9 is attached to the protective circuit board 4 has been described. However, the present invention is not limited to this, and the water wetness determination seal 9 is attached to the first exterior frame 10. You may comprise so that it may stick to the outer edge part of the determination window 10e.
Furthermore, in this Embodiment, although the 1st exterior frame 10 and the 2nd exterior frame 11 which are exterior bodies are frame shapes, a package shape etc. may be sufficient as an exterior body.

The recording units 92 and 92 are described as being formed in a band shape, but the present invention is not limited to this, and recording may be performed so as to form other figures, characters, or patterns. Further, the recording units 92 and 92 are not limited to the case where they are formed on the surface of the base material 91 by printing, but may be formed by coating or the like.
Furthermore, although the case where the determination window 10e has a substantially rectangular shape has been described, the present invention is not limited to this, and the determination window 10e may have a shape such as a substantially elliptical shape. When the determination window 10e has a substantially elliptical shape, the recording portions 92 and 92 can be formed in a U shape with a distance of approximately 0.4 mm from the upper and lower edges, for example.

Embodiment 2. FIG.
FIG. 5 is a perspective view showing a water wetness determination seal 96 provided in the battery pack according to Embodiment 2 of the present invention. In the figure, the same parts as those in FIG.
In the battery pack of the present embodiment, the adhesive 97 is applied over the entire back surface of the base material 91 of the water wetness determination seal 96, and the fact that the transparent resin layer 95 is not present is related to the first embodiment. Different from battery pack 1.

In the present embodiment, similarly to the water wetness determination seal 9 according to the first embodiment, the recording units 92 and 92 are configured to be arranged at a predetermined interval from the edge of the determination window 10e. Therefore, it is possible to prevent erroneous determination under a high temperature and humidity environment, and it is possible to satisfactorily determine the presence or absence of water.
Since it is configured as described above, even if the transparent resin layer 95 is omitted, there is no possibility of erroneous determination, and the number of members and the number of processes can be reduced.

Embodiment 3 FIG.
FIG. 6 is a perspective view showing a water wetness determination seal 98 provided in the battery pack according to Embodiment 3 of the present invention. In the figure, the same parts as those in FIG.
In the battery pack of the present embodiment, the adhesive 97 is applied to the entire back surface of the base material 91 of the water wetness determination seal 98, and the recording units 92 and 92 and the base material are used instead of the transparent resin layer 95. It is different from the battery pack 1 according to Embodiment 1 that 91 is covered with a transparent mat varnish layer 99.

In the present embodiment, similarly to the water wetness determination seal 9 according to the first embodiment, the recording units 92 and 92 are configured to be arranged at a predetermined interval from the edge of the determination window 10e. Therefore, it is possible to prevent erroneous determination under a high-temperature and high-humidity environment, and it is possible to satisfactorily determine the presence or absence of water.
Since the printed recording portions 92 and 92 are protected by the mat varnish layer 99, it is possible to prevent the surface of the water wetness determination seal 98 from being damaged or dirty at low cost.

In the first to third embodiments, the case where the unit cell 2 is a lithium ion secondary battery has been described. However, the present invention is not limited to this.
In Embodiments 1 to 3, the case where the battery pack is used as the power source of the mobile phone is described. However, the present invention is not limited to this, and the present invention can be applied to a video camera, a mobile computer, a PDA ( It can also be applied to battery packs used as power sources for other portable electronic devices such as Personal Digital Assistants) and MP3 players.
Since the configuration of the present invention is suitable for a small electronic device, in the first to third embodiments, the water wetness determination structure of the present invention is replaced with a unit cell 2 as a water wetness determination object. Although the case where it applies to the battery pack which has is demonstrated, it is not limited to this, It is possible to apply also to a confectionery packaging container etc.

It is a disassembled perspective view which shows the battery pack which concerns on Embodiment 1 of this invention. It is a disassembled perspective view which shows a water wetness determination seal | sticker. It is a partial front view which shows a battery pack. FIG. 6 is a partial front view showing a state in which the water-soluble ink is immersed in water inside the first exterior frame and the recording unit spreads beyond the edge of the determination window. It is a perspective view which shows the water wet determination seal | sticker with which the battery pack which concerns on Embodiment 2 of this invention is equipped. It is a perspective view which shows the water wetness determination seal | sticker with which the battery pack which concerns on Embodiment 3 of this invention is equipped.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Unit cell 2a Negative electrode terminal 21 1st side surface 22 2nd side surface 23 3rd side surface 24 4th side surface 3 Spacer 4 Protection circuit board 41 Protection circuit mounting part 42 Output terminal 5 1st lead 6 PTC element 7 2nd lead 8 Third lead 9, 96, 98 Water wetness determination seal 91 Base material 92 Recording part 93, 94, 97 Adhesive 95 Transparent resin layer 99 Matt varnish layer 10 First exterior frame 11 Second exterior frame 13 Label

Claims (5)

A wet subject
A water wetness determination seal in which a recording portion formed by using water-soluble ink is formed in a portion near one end of one surface of a water-absorbing substrate;
The water wettability determination seal has a window portion, the portion near the center of the one surface is exposed, and the recording portion is shielded at a predetermined interval from an edge of the window portion, and the water wettability is sealed. A water wetness determination structure comprising: an exterior body that covers a determination target body.   The water wetness determination structure according to claim 1, wherein the recording portion is formed in a strip shape.   The interval between the recording portion and the edge of the window portion is set to be longer than the increase in the width of the recording portion when left for 72 hours in an environment of a temperature of 50 ° C. to 70 ° C. and a humidity of 90%. The water wetting determination structure according to claim 1 or 2.   The water wetness determination structure according to claim 3, wherein the recording portion is formed to be separated from the edge portion by 0.4 mm or more. A battery pack having the water wetting determination structure according to claim 1,
The water wetness determination object is a unit cell having a rectangular parallelepiped shape having two planes and four side surfaces,
The exterior body is configured to cover at least four side surfaces of the unit cell,
A battery pack comprising a label covering part or all of the unit cell and the outer package.

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