CN220856679U - Battery cell, battery pack and energy storage equipment - Google Patents

Abstract

The application provides a battery cell, a battery pack and energy storage equipment. The battery cell comprises a battery cell shell and a battery cell body. The cell shell comprises an outer shell and an inner shell, wherein the inner shell is arranged in the outer shell, and a sealing cavity is formed between the inner shell and the outer shell. The battery cell body is arranged in the inner shell. The sealed cavity is provided with a plurality of first wicks arranged in parallel. A first runner is arranged between two adjacent first liquid suction cores. When the first liquid suction core is applied to the battery core, the first liquid suction core is injected with a liquid cooling working medium and absorbs the liquid cooling working medium. The heat of electric core body passes through the inner shell and transmits in the sealed cavity. The liquid cooling working medium is evaporated at high temperature and forms a high-temperature steam working medium. The high-temperature steam working medium enters the first flow passage and escapes to a low-temperature area of the sealing cavity, and is condensed into liquid cooling working medium in the low-temperature area. The first liquid suction core absorbs the condensed liquid cooling working medium again, so that a heat dissipation function is realized in the process of back flow of the cooling working medium, the heat dissipation performance of the battery cell is improved, and the temperature consistency in the battery cell is realized.

Description

Battery cell, battery pack and energy storage equipment

Technical Field

The embodiment of the application relates to the technical field of batteries, in particular to a battery cell, a battery pack and energy storage equipment.

Background

Most manufacturers reduce cost by increasing the energy density of the energy storage system to increase the competitiveness of the product. With the increase of energy density, the heat dissipation requirement of the energy storage system is gradually increased. The liquid cooling gradually becomes one of the main stream thermal management modes of the energy storage system.

Currently, in some energy storage systems, the energy storage liquid cooling is mainly implemented by arranging cold plates at the bottom and the side surfaces of the battery cell for cooling. However, the existing battery cell has only one or two surfaces attached to the cold plate, so that only the attached area can obtain better heat dissipation, and the heat dissipation effect of other parts of the battery cell is poor. The uneven heat dissipation easily causes poor temperature uniformity in the battery cell.

Disclosure of utility model

The application provides a battery cell, a battery pack and energy storage equipment, which are used for improving the heat dissipation performance of the battery cell and realizing the temperature consistency in the battery cell.

In a first aspect, the present application provides a cell. The battery cell comprises a battery cell shell and a battery cell body. Specifically, the cell housing includes an outer housing and an inner housing. Wherein the inner shell is disposed inside the outer shell, and a sealed cavity is formed between the inner shell and the outer shell. The battery cell body is arranged in the inner shell. The sealed cavity is provided with a plurality of first wicks arranged in parallel. The first liquid suction core is used for adsorbing the liquid cooling working medium and enabling the liquid cooling working medium to flow along the first liquid suction core. A first flow passage is arranged between two adjacent first liquid suction cores, and the first flow is used for gas flow.

In practical application, liquid cooling working medium is injected into the sealed cavity. The plurality of first wicks absorb a liquid cooling medium. When the battery cell works, the battery cell body is used as a heat source to generate heat, and the heat is transferred into the sealing cavity through the inner shell. In the first liquid suction core corresponding to the heat source position, the liquid cooling working medium is evaporated at high temperature and forms a high-temperature steam working medium. The high temperature vapor working fluid then enters the first flow path and escapes along the first flow path to the low temperature region of the sealed cavity where it is condensed into a liquid cooled working fluid. Thus, the first liquid suction core can absorb the condensed liquid cooling working medium again, and the reflux of the cooling working medium is realized. Through evaporation and condensation of the cooling working medium, heat generated by the battery cell body can be brought from a high-temperature area to a low-temperature area for heat dissipation, so that the heat dissipation performance of the battery cell can be improved, and the temperature consistency in the battery cell is realized.

When the first liquid suction cores and the first flow channels are arranged, the first liquid suction cores and the first flow channels are alternately arranged in the sealing cavity, and the size of each first liquid suction core along the thickness direction is equal to that of each first flow channel along the thickness direction, so that the thickness of the sealing cavity is uniform, the thinning of the battery cell shell is facilitated, and the influence on the energy density of the energy storage system is reduced. Wherein the thickness direction is perpendicular to the arrangement of the plurality of first wicks and perpendicular to the extending direction of the first wicks.

In some embodiments, the sealed cavity may further comprise at least one secondary wick. The second wick is in communication with the plurality of first wicks. Wherein the extending direction of the second liquid absorption core is not parallel to the extending direction of the first liquid absorption core. In the technical scheme, the cooling working medium can flow in a first net structure formed by the first liquid absorption core and the second liquid absorption core, so that heat dissipation can be carried out on each high-temperature area in the battery cell shell, and the heat dissipation uniformity of the battery cell shell can be improved.

The specific number of the second wicks described above is not limited. In some embodiments, the at least one secondary wick may comprise a secondary wick. The second wick may be located on one side of the plurality of first wicks, and the extending direction of the second wick is perpendicular to the extending direction of the first wick. In this embodiment, the cell housing may include opposite top and bottom surfaces, and at least one side surface connecting the top and bottom surfaces. The plurality of first liquid absorbing cores can be distributed on the side face of the battery cell shell and are arranged in parallel along the circumferential direction of the battery cell shell. The second wick may be disposed adjacent to the top or bottom surface of the cell housing.

In the above-described cell case, the structure of the first wick may include a sintered powder structure, a foamed metal structure, a sintered wire mesh structure, or a composite structure, and the structure of the second wick may include a sintered powder structure, a foamed metal structure, a sintered wire mesh structure, or a composite structure.

In other embodiments, the sealed cavity may further include at least one second flow channel. The second flow passage communicates with the first flow passage, and an extending direction of the second flow passage is not parallel to an extending direction of the first flow passage. In the technical scheme, the steam cooling working medium can flow in a second net structure formed by the first flow channel and the second flow channel, so that the steam cooling working medium can radiate in each low-temperature area of the shell, and the radiating uniformity of the battery cell shell can be improved.

The specific number of the second flow passages is not limited. In some embodiments, the at least one second flow channel may include a second flow channel. The second flow channels are positioned on one side of the plurality of first liquid absorbing cores, and the extending direction of the second flow channels is perpendicular to the extending direction of the first flow channels. In this embodiment, the cell housing may include opposite top and bottom surfaces, and at least one side surface connecting the top and bottom surfaces. The first flow channel may be disposed on a side surface of the battery cell casing, where the first flow channel may extend in a direction perpendicular to a circumferential direction of the battery cell casing, and the second flow channel may extend in the circumferential direction of the battery cell casing and may be disposed near a top surface or a bottom surface of the battery cell casing.

The cell housing of the present application may comprise a square cell housing or a cylindrical cell housing. In particular, the cell housing may include opposing top and bottom surfaces, and at least one side surface connecting the top and bottom surfaces. The sealing cavity is distributed on at least one surface of the battery cell shell. That is, the plurality of first liquid-absorbing cores may be distributed on the side surface of the cell housing, or may be distributed on the bottom surface and the side surface of the cell housing.

In a second aspect, the present application provides a battery pack. The battery pack may include a battery case and the battery cell of the first aspect described above, the battery cell being disposed in the battery case. The battery core in the battery pack has better heat dissipation and better temperature consistency, thereby improving the overheat phenomenon of the battery pack.

In some technical schemes, a cold plate is arranged in the battery shell, and the cold plate can be used for radiating heat of the battery cell. The electrical core is mounted to the cold plate and the plurality of first wicks within the sealed cavity may be positioned opposite the cold plate. Therefore, the cold plate can directly radiate the high-temperature cooling working medium in the first liquid suction core and the first flow channel, and the radiating efficiency is improved.

In a third aspect, the present application provides an energy storage device. The energy storage device comprises a plurality of battery packs of the second aspect, and the plurality of battery packs are connected in series or in parallel to supply power to the bus bars. In the energy storage device, the temperature consistency of each battery pack is better, and the overheating phenomenon of the battery packs can be improved, so that the reliability of the energy storage device is improved.

Drawings

Fig. 1 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

FIG. 2 is a schematic cross-sectional view of the cell housing of FIG. 1 along the direction B-B;

Fig. 3 is a schematic structural diagram of another battery cell according to an embodiment of the present application;

fig. 4 is a schematic structural view of a battery pack according to an embodiment of the present application;

Fig. 5 is a schematic view of another structure of a battery pack according to an embodiment of the present application.

Reference numerals:

10-an electric core;

11-a cell housing;

12-electrode lugs;

20-battery pack;

21-a battery housing;

22-cold plate;

111-a housing;

112-an inner shell;

113-sealing the cavity;

114-a first wick;

115-a first flow channel;

116-a secondary wick;

117-second flow channel.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings.

It is noted that the terminology used in the following embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the specification of the application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include, for example, "one or more" such forms of expression, unless the context clearly indicates to the contrary.

Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.

In practice, a plurality of cells may be typically included in a battery pack in order to enable the battery pack to store a sufficient amount of electrical energy. In order to reduce the size of the battery pack, the position layout of the plurality of battery cells is compact. During the charge and discharge of the battery cell, heat is generated. In order to avoid the occurrence of an excessively high temperature, a heat dissipation structure may be provided in the battery pack.

The existing heat dissipation structure is generally divided into an air cooling mode and a liquid cooling mode. The heat dissipation structure of the air cooling mode mainly depends on air flow to take away heat on the surface of the battery cell, so that the heat dissipation purpose is achieved. The heat dissipation structure of the liquid cooling mode mainly relies on circulation of cooling working medium (such as water or oil) to take away heat on the surface of the battery cell, so that the purpose of heat dissipation is achieved. The liquid cooling type heat dissipation structure has a higher heat dissipation efficiency and a smaller occupied volume, and is therefore widely used in the industry.

However, the existing liquid cooling mode mainly performs heat dissipation through attaching cold plates to one or two surfaces of the battery cell, so that a better heat dissipation effect can be obtained only in an area attached to the cold plates, and therefore heat dissipation of the battery cell is uneven, and poor temperature consistency in the battery cell is easily caused.

Based on the above, the application provides the battery cell, the battery pack and the energy storage equipment, so that the heat dissipation performance of the battery cell is improved, and the temperature consistency in the battery cell is realized.

Fig. 1 is a schematic structural diagram of a battery cell according to an embodiment of the present application, and fig. 2 is a schematic sectional view of a battery cell casing in a direction B-B in fig. 1. As shown in fig. 1 and 2, the battery cell 10 includes a battery cell body (not shown in the drawings) and a battery cell housing 11, the battery cell body being disposed within the battery cell housing 11. The cell housing 11 may specifically include an outer housing 111 and an inner housing 112. Wherein the inner case 112 is disposed inside the outer case 111, and a sealing cavity 113 is formed between the inner case 112 and the outer case 111. A plurality of first wicks 114 are arranged in parallel in the sealed cavity 113, and a first flow channel 115 is arranged between two adjacent first wicks 114.

In use, the sealed cavity 113 of the cell housing 11 is filled with a liquid cooling medium. The plurality of first wicks 114 are configured to absorb the liquid cooling medium and to flow the liquid cooling medium along the first wicks 114. When the cell 10 is operated, the cell body serves as a heat source to generate heat, and the heat is transferred into the sealed cavity 113 through the inner case 112. In sealed cavity 113, the liquid cooling medium in first wick 114 corresponding to the location of the heat source is evaporated, and a high-temperature vapor medium is formed. Subsequently, the vapor working fluid enters the first flow channel 115 and escapes along the first flow channel 115 to the low temperature region of the sealed cavity 113. The vapor working medium may be condensed into a liquid cooling working medium in the low temperature region. In this way, first wick 114 may reabsorb the condensed liquid cooling medium, effecting reflux of the cooling medium. Through evaporation and condensation of the cooling working medium, heat generated by the battery cell body can be brought from a high-temperature area to a low-temperature area for heat dissipation, so that the heat dissipation performance of the battery cell 10 can be improved, and the temperature consistency in the battery cell 10 is realized.

It should be noted that, the first wick 114 of the present application is strip-shaped and extends in a direction perpendicular to the thickness of the sealed cavity 113 (as indicated by an arrow C in fig. 2). The parallel arrangement of the plurality of first wicks 114 may be understood as the same extending direction of the plurality of first wicks 114. Further, first wick 114 has a cross-section along a direction perpendicular to the direction of extension, as shown in fig. 2. The dimension of this cross section in direction C is equal to the thickness of the sealed cavity 113, so that in direction D perpendicular to direction C, adjacent two first flow channels 115 are isolated from each other.

In actual use, the surface of the cell housing 11 may be bonded with a cold plate for heat dissipation. The area where the housing 111 is bonded to the cold plate may be a low temperature area. Therefore, the heat transferred from the inside of the inner case 112 to the inner case 112 can be concentrated to a low temperature region by the cooling medium and transferred to the cold plate, thereby maintaining the temperature of the cell case 11 uniform and realizing the self-temperature equalizing function.

In practical applications, the shape of the battery cell 10 may include a square or a cylinder, and the shape of the battery cell housing 11 is also a square or a cylinder. The battery cell 10 may include opposite top and bottom surfaces and at least one side surface connected between the top and bottom surfaces, wherein the top surface is provided with a tab 12, and the tab 12 passes through the battery cell housing 11 and is connected with the battery cell body. As shown in fig. 1, the cell 10 may include four sides. When the cell 10 is a cylindrical cell, the cell 10 may include an annular side.

As shown in fig. 1, the sealing cavity 113 may be distributed on at least one surface of the cell housing 11. That is, the sealed cavities 113 may be distributed on at least one side of the cell housing 11, or the plurality of first liquid-absorbing cores 114 may be distributed on the bottom and side of the cell housing 11, which is not particularly limited herein. Taking a square cell as an example, in one embodiment, the sealed cavity 113 may be distributed on one surface of the cell housing 11, where the sealed cavity 113 is a rectangular cavity. In another embodiment, the sealing cavities 113 may be distributed on four sides of the cell housing 11, where the sealing cavities 113 are annular cavities. In another embodiment, the sealing cavities 113 may be distributed on one side and the bottom of the cell housing 11, where the sealing cavities 113 are L-shaped cavities.

In a specific embodiment, the sealed cavities 113 may be distributed on the sides of the cell housing 11. That is, each side of the cell housing 11 may be provided with the plurality of first wicks 114 and the first flow channels 115 described above. Specifically, the plurality of first wicks 114 may be disposed in parallel in the circumferential direction of the cell housing 11 (the direction indicated by arrow a in fig. 1), that is, the first wicks 114 extend in the vertical direction in fig. 1. The bottom surface of the cell housing 11 may be bonded to the cold plate such that the vapor working fluid may converge toward the bottom surface of the cell housing 11 along the first flow path 115 and heat exchange with the cold plate occurs near the bottom surface. Of course, the plurality of first wicks 114 may be disposed in parallel in a circumferential direction perpendicular to the cell housing 11 (i.e., perpendicular to the direction of arrow a), i.e., the first wicks 114 extend in the direction indicated by arrow a in fig. 1.

As shown in fig. 2, when first wicks 114 and first flow channels 115 are provided, since first wicks 114 and first flow channels 115 are alternately arranged in sealed cavity 113, the thickness of each first wick 114 may be set equal to the thickness of first flow channel 115, so that the thickness of sealed cavity 113 is uniform, which is beneficial to realizing the light and thin of cell housing 11, so as to reduce the influence on the energy density of the energy storage system. The thickness of first wick 114 and the thickness of first flow channel 115 refer to dimensions along the thickness direction of sealed cavity 113 (as indicated by arrow C in fig. 2).

Fig. 3 is a schematic structural diagram of another battery cell according to an embodiment of the present application. As shown in fig. 3, in some embodiments, sealed cavity 113 may also include at least one secondary wick 116. The extending direction of the second wick 116 is not parallel to the extending direction of the first wicks 114, and the second wick 116 communicates with the plurality of first wicks 114. In this embodiment, the cooling medium may flow in the first mesh structure formed by the first wick 114 and the second wick 116, so that heat dissipation can be performed on each high-temperature region of the inner casing 112, and further heat dissipation uniformity of the cell casing 11 can be improved. Note that the fact that the extending direction of the second wick 116 is not parallel to the extending direction of the first wick 114 means that the extending direction of the second wick 116 is not parallel to the extending direction of the first wick 114 on the same surface of the battery case 11.

The particular number of secondary wicks 116 described above is not limited. In some embodiments, the at least one secondary wick 116 may comprise one secondary wick 116. The second wick 116 may be disposed on one side of the plurality of first wicks 114, and the extending direction of the second wick 116 is perpendicular to the extending direction of the first wicks 114. In this embodiment, the secondary wick 116 may be annular in shape and may be disposed adjacent to the top or bottom surface of the cell housing 11. In other embodiments, the at least one secondary wick 116 may comprise two secondary wicks 116. In this embodiment, one second wick 116 of the two second wicks 116 may be annular in shape and may be disposed proximate to the top or bottom surface of the cell housing 11; the other secondary wick 116 may be strip-shaped and communicate with only a portion of the plurality of primary wicks 114, respectively.

In the above-described cell housing 11, the structure of the first wick 114 includes a sintered powder structure, a foamed metal structure, a sintered wire mesh structure, or a composite structure, and the structure of the second wick 116 includes a sintered powder structure, a foamed metal structure, a sintered wire mesh structure, or a composite structure, which are not exemplified herein.

As shown in fig. 1 and 3, the sealed cavity 113 may further include at least one second flow passage 117. The second flow passage 117 communicates with the first flow passage 115, and the extending direction of the second flow passage 117 is not parallel to the extending direction of the first flow passage 115. In this embodiment, the steam cooling medium may flow in the second mesh structure formed by the first flow channel 115 and the second flow channel 117, so that the steam cooling medium may dissipate heat in each low temperature region of the casing 111, and further, the heat dissipation uniformity of the cell casing 11 may be improved.

The specific number of the second flow passages 117 is not limited. In some embodiments, the at least one second flow channel 117 may comprise one second flow channel 117. The second flow channel 117 extends in a direction perpendicular to the direction in which the first flow channel 115 extends, and is provided on one side of the plurality of first wicks 114. In this embodiment, the second flow channel 117 may be annular in shape and may be disposed proximate to the top or bottom surface of the cell housing 11. In other embodiments, the at least one second flow channel 117 may include two second flow channels 117. In this embodiment, one second flow channel 117 of the two second flow channels 117 may be annular and may be disposed near the top or bottom surface of the cell housing 11; the other second flow passage 117 may be strip-shaped and communicate with only a portion of the plurality of first flow passages 115, respectively.

In a specific embodiment, as shown in fig. 1, sealed cavities 113 are distributed on four sides of the cell housing 11 and include a plurality of first wicks 114, second wicks 116, and second flow channels 117. The plurality of first wicks 114 are arranged in parallel along the circumferential direction of the cell housing 11. A first flow channel 115 is provided between two adjacent first wicks 114. A second wick 116 is disposed circumferentially of the cell housing 11 and adjacent the top surface of the cell 10, the second wick 116 being in communication with the plurality of first wicks 114. The second flow passage 117 is provided along the circumferential direction of the cell housing 11 and near the bottom surface of the cell 10, and the second flow passage 117 communicates with the first flow passage 115. When cell 10 is radiating heat, liquid cooling medium may flow between first wick 114 and second wick 116, and vapor medium may flow between first flow channel 115 and second flow channel 117.

Based on the same technical concept, the application provides a battery pack. Fig. 4 is a schematic structural view of a battery pack according to an embodiment of the present application, and fig. 5 is a schematic structural view of a battery pack according to an embodiment of the present application. As shown in fig. 4 and 5, the battery pack 20 may include a battery case 21 and the battery cell 10 of any of the above embodiments, and the battery cell 10 is disposed in the battery case 21. The heat dissipation of the battery cell 10 in the battery pack 20 is better, and the temperature uniformity in the battery cell 10 is better, so that the overheating phenomenon of the battery pack 20 can be improved.

In some embodiments, a cold plate 22 is disposed within the battery housing 21, and the cold plate 22 may be used to dissipate heat from the battery cells 10. The battery cell 10 is mounted to a cold plate 22. In this embodiment, as shown in fig. 4, cold plate 22 may be attached to the side of cell 10. Alternatively, as shown in fig. 5, the cold plate 22 may be attached to the bottom surface of the battery cell 10.

Of course, for different cold plate structures, different positions of the first wick 114 and the second wick 116 may be designed to achieve a better heat dissipation effect and reduce the cost. In some embodiments, as shown in fig. 4, in the above-described embodiments, a plurality of first wicks 114 within sealed cavity 113 may be positioned opposite cold plate 22. Therefore, the cooling plate 22 can directly dissipate heat of the cooling medium in the first wick 114 and the first flow channel 115, thereby improving heat dissipation efficiency. In other embodiments, as shown in fig. 5, second wick 116 within sealed cavity 113 may be positioned adjacent cold plate 22, dissipating heat through the cooling medium within second wick 116.

Based on the same technical conception, the application provides energy storage equipment. The energy storage device includes a plurality of battery packs 20 of any of the above embodiments, wherein the plurality of battery packs 20 are connected in series or in parallel to supply power to the bus bars. In the energy storage device, the temperature consistency of each battery pack 20 is better, and the overheating phenomenon of the battery packs 20 can be improved, so that the reliability of the energy storage device is improved.

The terminology used in the above embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the specification of the application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include, for example, "one or more" such forms of expression, unless the context clearly indicates to the contrary.

The foregoing is merely illustrative embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about variations or substitutions within the technical scope of the present application, and the application should be covered. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims (10)

1. The utility model provides a electricity core, its characterized in that includes electric core casing and electric core body, wherein:

The battery cell shell comprises an outer shell and an inner shell, the inner shell is arranged in the outer shell, a sealing cavity is formed between the inner shell and the outer shell, and the battery cell body is arranged in the inner shell;

The sealed cavity is provided with a plurality of first liquid suction cores which are arranged in parallel, and the first liquid suction cores are used for adsorbing liquid cooling working media and enabling the liquid cooling working media to flow along the first liquid suction cores; a first flow passage is arranged between two adjacent first liquid suction cores, and the first flow passage is used for gas flow.

2. The cell of claim 1, wherein each of the first wicks has a dimension in a thickness direction that is equal to a dimension of the first flow channel in a thickness direction that is perpendicular to an alignment direction of the plurality of first wicks and perpendicular to an extension direction of the first wicks.

3. The cell of claim 1 or 2, wherein the sealed cavity further comprises at least one second wick, the second wick being in communication with the plurality of first wicks, and wherein the direction of extension of the second wick is non-parallel to the direction of extension of the first wick.

4. The electrical cell of claim 3, wherein the at least one second wick comprises a second wick, the second wick being located on one side of the plurality of first wicks, and wherein the second wick extends in a direction perpendicular to the direction of extension of the first wick.

5. The cell of any one of claims 1 to 4, wherein the sealed cavity further comprises at least one second flow channel, the second flow channel being in communication with the first flow channel, and wherein the direction of extension of the second flow channel is non-parallel to the direction of extension of the first flow channel.

6. The cell of claim 5, wherein the at least one second flow channel comprises a second flow channel, the second flow channel is located on one side of the plurality of first wicks, and the second flow channel extends in a direction perpendicular to the direction of extension of the first flow channel.

7. The cell of any one of claims 1 to 6, wherein the sealed cavities are distributed on at least one face of the cell housing.

8. A battery pack comprising a battery housing and the cell of any one of claims 1 to 7, the cell being disposed within the battery housing.

9. The battery pack of claim 8, wherein a cold plate is disposed within the battery housing, the electrical cells are mounted to the cold plate, and the plurality of first wicks are positioned opposite the cold plate.

10. An energy storage device comprising a plurality of battery packs according to claim 8 or 9, wherein the plurality of battery packs are connected in series or in parallel to power a bus bar.