Energy storage system

Abstract

The embodiment of the utility model relates to the field of energy storage, and provides an energy storage system, which comprises a liquid cooling unit provided with a liquid inlet and a liquid outlet; the battery packs are arranged in the first direction, each battery pack is communicated with the liquid inlet through a liquid inlet pipe, cooling liquid output by the liquid inlet of the liquid cooling unit flows into the battery packs through the liquid inlet pipe, and each battery pack is communicated with the liquid outlet through a liquid outlet pipe; cooling liquid in the battery pack flows to the liquid outlet through the liquid outlet pipe, so that the cooling liquid flows back to the liquid cooling unit; and the balancing device is provided with an opening, the battery pack is communicated with the opening through the connecting pipe, and the balancing device is used for receiving part of the cooling liquid flowing in from the battery pack through the opening when the temperature of the battery pack rises, so that the pressure in the energy storage system can be balanced.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the field of energy storage, and in particular, to an energy storage system. BACKGROUND

[0002] The energy storage system is provided with battery cells. Heat is generated during the charging and discharging of the battery cells, which causes the temperature of the battery cells to rise. If the temperature of the battery cells is not controlled, the efficiency and service life of the battery cells may be reduced or the battery cells may be out of control. The natural heat dissipation of the battery cells cannot maintain the temperature within the working range, and therefore an external cooling system is required.

[0003] Immersion liquid cooling is a cooling system applied to an energy storage device. The battery pack is filled with an insulated immersion cooling medium, and the immersion cooling medium directly contacts the battery cells for heat exchange. In the energy storage system, there is a liquid cooling unit and a liquid cooling pipeline. The immersion cooling medium flows in the pipeline and is cooled by the liquid cooling unit to control the temperature of the battery cells. Immersion liquid cooling has good temperature control effect and safety, can reduce the temperature difference between the battery cells, and reduce the risk of thermal runaway. It is a promising liquid cooling technology for energy storage devices.

[0004] It is necessary to improve the reliability of the energy storage system. CONTENT OF THE INVENTION

[0005] The present disclosure provides an energy storage system, which can at least balance the pressure in the energy storage system.

[0006] According to some embodiments of the present disclosure, an energy storage system is provided. The energy storage system comprises a liquid cooling unit having an inlet and an outlet; a plurality of battery packs arranged along a first direction, each battery pack being in communication with the inlet via an inlet pipe, and the cooling liquid output by the inlet of the liquid cooling unit flowing into the battery pack via the inlet pipe, each battery pack being in communication with the outlet via an outlet pipe, and the cooling liquid in the battery pack flowing to the outlet via the outlet pipe to return to the liquid cooling unit; and a balancing device having an opening, the battery pack being in communication with the opening via a connecting pipe, the balancing device being configured to receive part of the cooling liquid flowing into the opening from the battery pack when the temperature of the battery pack rises.

[0007] In some embodiments, the balancing device comprises a housing having an accommodation space therein; and an air bag arranged in the accommodation space, the air bag being in communication with the opening, and the cooling liquid in the battery pack flowing into the air bag via the opening.

[0008] In some embodiments, the air bag is filled with a reserved cooling liquid before the cooling liquid is absorbed, and the ratio of the volume of the reserved cooling liquid to the volume of the air bag is 1 / 5 to 1 / 3.

[0009] In some embodiments, the balancing device is located between adjacent battery packs and communicates with two adjacent battery packs.

[0010] In some embodiments, the energy storage system further comprises thermal insulation cotton located on the top surface of the topmost battery pack arranged in the first direction.

[0011] In some embodiments, the battery pack comprises a plurality of battery cells, the cooling liquid in the battery pack immerses the surface of the battery cells, and the liquid level of the cooling liquid is higher than the top surface of the connecting pipe.

[0012] In some embodiments, the energy storage system further comprises a temperature measuring device for measuring the temperature of the cooling liquid in the battery pack.

[0013] In some embodiments, the energy storage system further comprises a valve arranged on the connecting pipe and configured to be opened when the temperature of the cooling liquid in the battery pack exceeds a first preset temperature or when the temperature of the cooling liquid in the battery pack is lower than a second preset temperature.

[0014] In some embodiments, the energy storage system further comprises a clamping device fixed to the top surface of the topmost battery pack arranged in the first direction.

[0015] In some embodiments, the clamping device comprises a bearing portion extending in a second direction, a bending portion located on opposite sides of the bearing portion in the second direction and connected to the bearing portion and extending away from the battery pack, and a limiting portion located on the top surface of the bending portion and connected to the bending portion and extending in the second direction.

[0016] The technical scheme provided by the embodiment of the present disclosure has at least the following advantages: the liquid cooling unit is used to transmit cooling liquid to the battery pack, the cooling liquid is used for heat exchange with the battery pack, so as to complete the temperature reduction of the battery pack, and then the cooling liquid with the temperature increased after the heat exchange is recovered to the liquid cooling unit, and the cooling liquid is cooled again to complete the recycling of the cooling liquid. However, when the external environment temperature of the energy storage system is low, the cooling liquid in the energy storage system is affected by the external environment, so that the initial temperature is reduced. With the operation of the energy storage system, the temperature of the cooling liquid gradually increases, so that the cooling liquid is expanded by heat. At this time, the pressure in the battery pack increases, which has a potential safety hazard. The present disclosure further provides a balancing device to receive the cooling liquid from the battery pack when the cooling liquid is expanded by heat, so as to maintain the pressure balance in the battery pack. When the external temperature of the energy storage system is high, the initial temperature of the cooling liquid is high. With the operation of the energy storage system, the temperature in the energy storage system decreases, so that the cooling liquid is contracted by cold. The pressure in the battery pack decreases, which also has a potential safety hazard. The balancing device can also flow the cooling liquid in the balancing device to the battery pack, so as to maintain the pressure balance in the battery pack, thereby improving the reliability of the energy storage system. BRIEF DESCRIPTION OF DRAWINGS

[0017] One or more embodiments are illustrated by way of example in the drawings that are for illustrative purposes only, and not for the purposes of limiting the embodiments, unless otherwise specifically stated in the description. None of the drawings, except for any flow charts, is necessarily to scale; apparent deviations in the sizes of objects and distances in the drawings are intentional to provide a clearer presentation of the embodiments; and, unless otherwise indicated, the drawings are meant to be explanatory only. As will be realized, the application is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present application. Accordingly, the drawings are to be regarded as illustrative in nature, and explanations in the specification are similarly treated.

[0018] Fig. 1 A structural schematic diagram of an energy storage system provided by the embodiment of the present disclosure is provided.

[0019] Fig. 2 A partial enlarged structural schematic diagram of an energy storage system provided by the embodiment of the present disclosure is provided.

[0020] Fig. 3 Another partial enlarged structural schematic diagram of an energy storage system provided by the embodiment of the present disclosure is provided. DETAILED DESCRIPTION

[0021] As known from the background, it is necessary to provide an energy storage system to improve the reliability of the energy storage system.

[0022] The present disclosure utilizes a liquid cooling unit to transmit cooling liquid to the battery pack, the cooling liquid is used for heat exchange with the battery pack, so as to complete the cooling of the battery pack, and then the cooling liquid with the temperature increased after the heat exchange is recovered into the liquid cooling unit, and the cooling liquid with the temperature increased is cooled again to complete the recycling of the cooling liquid. However, when the external environment temperature of the energy storage system is low, the cooling liquid in the energy storage system is affected by the external environment, so that the initial temperature is reduced. With the operation of the energy storage system, the temperature of the cooling liquid gradually increases, so that the cooling liquid is expanded by heat. At this time, the pressure in the battery pack increases, which has a potential safety hazard. The present disclosure also provides a balancing device to receive the cooling liquid from the battery pack when the cooling liquid is expanded by heat, so as to maintain the pressure balance in the battery pack. When the external temperature of the energy storage system is high, the initial temperature of the cooling liquid is high. With the operation of the energy storage system, the temperature in the energy storage system decreases, so that the cooling liquid is contracted by cold. The pressure in the battery pack decreases, which also has a potential safety hazard. The balancing device can also flow the cooling liquid in the balancing device into the battery pack, so as to maintain the pressure balance in the battery pack, thereby improving the reliability of the energy storage system.

[0023] In the description of the embodiments of the present disclosure, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present disclosure, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0024] In this document, the term "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present disclosure. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it independent or alternative to other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments of the present disclosure, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases of A, A and B, and B. In addition, the character " / " in this document generally represents a "or" relationship between the front and rear associated objects.

[0026] In the description of the embodiments of the present disclosure, the term "a plurality of" means two or more (including two), and similarly, "a plurality of groups" means two or more groups (including two groups), and "a plurality of pieces" means two or more pieces (including two pieces).

[0027] In the description of the embodiments of the present disclosure, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present disclosure.

[0028] In the description of the embodiments of the present disclosure, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium, or can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present disclosure can be understood according to the specific circumstances.

[0029] In the corresponding drawings of the embodiments of the present disclosure, in order to better understand and facilitate the description, the thickness and area of the layer are enlarged. When describing that a component (such as a layer, a film, a region or a substrate) is on or on the surface of another component, the component can be "directly" on the surface of the other component, or there can be a third component between the two components. On the contrary, when describing that a component is on the surface of another component or that a component surface is formed or provided with another component, it means that there is no third component between the two components. In addition, when describing that a component is "formed substantially" on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on the edge of the entire surface.

[0030] In the description of the embodiments of the present disclosure, when a certain component "includes" another component, unless otherwise stated, other components are not excluded and other components can also be further included. In addition, when a layer, film, region or plate and the like component is referred to as "on / over" another component, it can be "directly on" another component (i.e. between the surface of another component and another component without other components), or another component can exist therebetween. In addition, when a layer, film, region, plate and the like component is "directly on" another component, or when a layer, film, region, plate and the like component is on the surface of another component, it means that no other component is located therebetween.

[0031] The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments of the disclosure and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "or" as used herein refers to a non-exclusive "or," unless otherwise indicated.

[0032] The embodiments of the present disclosure will be described in detail with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present disclosure, many technical details are presented in order to make the reader better understand the present disclosure. However, the technical solutions claimed by the present disclosure can be implemented even without these technical details and based on various changes and modifications of the following embodiments.

[0033] Reference Figs. 1 to 3 wherein, Fig. 1 A structural schematic diagram of an energy storage system provided by an embodiment of the present disclosure, Fig. 2 A partial enlarged structural schematic diagram of an energy storage system provided by an embodiment of the present disclosure, Fig. 3 Another partial enlarged structural schematic diagram of an energy storage system provided by an embodiment of the present disclosure.

[0034] In some embodiments, the energy storage system can include a liquid cooling unit 100 having a liquid inlet and a liquid outlet.

[0035] The energy storage system can further include a plurality of battery packs 101 arranged along a first direction, each battery pack 101 being in communication with the liquid inlet via a liquid inlet pipe, the cooling liquid output by the liquid inlet of the liquid cooling unit 100 flowing into the battery pack 101 via the liquid inlet pipe, each battery pack 101 being in communication with the liquid outlet via a liquid outlet pipe, the cooling liquid in the battery pack 101 flowing to the liquid outlet via the liquid outlet pipe to return to the liquid cooling unit 100.

[0036] The energy storage system can further include a balancing device 102 having an opening, the battery pack 101 being in communication with the opening via a connecting pipe 103, the balancing device 102 being configured to receive part of the cooling liquid flowing from the battery pack 101 into the opening when the temperature of the battery pack 101 rises.

[0037] The present disclosure utilizes the liquid cooling unit 100 to transmit cooling liquid to the battery pack 101, the cooling liquid is used for heat exchange with the battery pack 101, so as to complete the cooling of the battery pack 101, and then the cooling liquid with the temperature increased after completing the heat exchange is recovered into the liquid cooling unit 100, and the cooling liquid is cooled again to complete the recycling of the cooling liquid. However, when the external environment temperature of the energy storage system is low, the cooling liquid in the energy storage system is affected by the external environment, so that the initial temperature is reduced. With the operation of the energy storage system, the temperature of the cooling liquid will gradually increase, causing the cooling liquid to expand in volume. At this time, the pressure in the battery pack 101 will increase, which exists a safety hazard. The present disclosure also provides a balancing device 102 to receive the cooling liquid from the battery pack 101 when the cooling liquid is heated and expanded, so as to maintain the pressure balance in the battery pack 101. When the external temperature of the energy storage system is high, the initial temperature of the cooling liquid is high, and with the operation of the energy storage system, the temperature in the energy storage system is reduced, causing the cooling liquid to shrink due to cooling, causing the pressure in the battery pack 101 to decrease, which also exists a safety hazard. The balancing device 102 can also flow the cooling liquid in the balancing device 102 into the battery pack 101, so as to maintain the pressure balance in the battery pack 101, thereby improving the reliability of the energy storage system.

[0038] In some embodiments, the liquid cooling unit 100 can include a refrigerator and a compressor.

[0039] In some embodiments, the battery pack 101 includes a plurality of battery cells, the cooling liquid in the battery pack 101 immerses the surface of the battery cells, and the liquid level of the cooling liquid is higher than the top surface of the connecting pipe 103. By immersing the surface of the battery cells in the cooling liquid, the cooling liquid directly exchanges heat with the battery cells, thereby facilitating the control of the temperature of the battery cells. In addition, the liquid level of the cooling liquid is higher than the top surface of the connecting pipe 103, so that when the cooling liquid is heated and expands in volume, the cooling liquid is transmitted through the connecting pipe 103, ensuring that the cooling liquid, not the gas in the battery pack 101, enters the balancing device 102 through the connecting pipe 103, thereby improving the reliability of the battery pack 101.

[0040] For the balancing device 102, in some embodiments, the balancing device 102 can include a housing, the housing having an accommodation space; and an air bag, the air bag being arranged in the accommodation space and being in communication with an opening, the cooling liquid in the battery pack 101 flowing into the air bag through the opening. The housing is used to protect the air bag, and the housing can also be used to fix the balancing device 102 in the energy storage system. The air bag is used to receive the cooling liquid from the battery pack 101, so as to provide an accommodation space for the heated and expanded cooling liquid, thereby balancing the pressure of the entire battery pack 101 and improving the reliability of the energy storage system.

[0041] In some embodiments, the air bag is internally provided with a reserved cooling liquid before the cooling liquid is absorbed, and the ratio of the volume of the reserved cooling liquid to the volume of the air bag is 1 / 5 to 1 / 3. For the air bag, the air bag needs to reserve a certain space to carry the cooling liquid from the battery pack 101, therefore, the ratio of the volume of the reserved cooling liquid to the volume of the air bag is set to be less than 1 / 3 to avoid excessive impact on the accommodation capacity of the cooling liquid of the balancing device 102, on the other hand, when the ambient temperature is high, the initial temperature of the cooling liquid in the energy storage system is also high, and the reserved cooling liquid in the air bag is also needed to balance the pressure of the battery pack 101, therefore, the ratio of the volume of the reserved cooling liquid to the volume of the air bag is greater than 1 / 5, by setting the ratio of the volume of the reserved cooling liquid to the volume of the air bag to be 1 / 5 to 1 / 3, the versatility of the balancing device 102 can be improved under different ambient temperatures.

[0042] In some embodiments, the ratio of the volume of the reserved cooling liquid to the volume of the air bag is set to be 1 / 5 to 1 / 3, and the structure of the air bag and the shell can also play a role in heat preservation for the battery pack 101.

[0043] The reserved cooling liquid can be the same kind of liquid as the cooling liquid, to avoid abnormal reactions between different cooling liquids, or mutual contamination problems, thereby improving the reliability of the energy storage system.

[0044] In some embodiments, the balancing device 102 is located between adjacent battery packs 101 and communicates with the two adjacent battery packs 101, by setting the balancing device 102 between the two adjacent battery packs 101, the length of the connecting pipe 103 between the battery pack 101 and the balancing device 102 can be shortened, the path length of the cooling liquid from the battery pack 101 into the balancing device 102 can be reduced, thereby reducing the amount of substances that retain the cooling liquid in the connecting pipe 103.

[0045] For example, the battery pack 101 located above the balancing device 102 is defined as the top battery pack, and the battery pack 101 located below the balancing device 102 is defined as the bottom battery pack, the flow direction of the cooling liquid of the bottom battery pack is from bottom to top, if the connecting pipe 103 between the bottom battery pack and the balancing device 102 is too long, a large amount of cooling liquid will be retained in the connecting pipe 103, rather than entering the balancing device 102, if the cooling liquid is to be controlled to flow into the balancing device 102, the bottom battery pack 101 needs to have a larger pressure, and a larger pressure in the battery pack 101 will affect the reliability of the energy storage system, therefore, by setting the balancing device 102 between the adjacent battery packs 101, the pressure problem of the battery pack 101 under different ambient temperatures can be further alleviated, and the reliability of the energy storage system can be further improved.

[0046] In some embodiments, the balancing device 102 can also be arranged on the top surface of the topmost battery pack 101 arranged in the first direction. Arranging the balancing device 102 on the top surface of the topmost battery pack 101 arranged in the first direction can use the balancing device 102 as a heat preservation device, thereby reducing the number of heat preservation devices.

[0047] For the present disclosure, whether the balancing device 102 is arranged between the battery packs 101 or on the top surface of the battery packs 101, the air pressure balance in the battery packs 101 can be maintained without occupying additional space of the energy storage system, thereby improving the energy density of the energy storage system while improving the reliability of the energy storage system.

[0048] In some embodiments, the balancing device 102 is arranged between the adjacent battery packs 101, and the energy storage system can further include heat preservation cotton (not shown) arranged on the top surface of the topmost battery pack 101 arranged in the first direction. Arranging the heat preservation cotton on the top surface of the topmost battery pack 101 can also serve as a heat preservation function, thereby improving the reliability of the energy storage system.

[0049] In some embodiments, the energy storage system can further include a temperature measuring device (not shown) for measuring the temperature of the cooling liquid in the battery pack 101. The temperature measuring device can facilitate the detection of temperature changes in the battery pack 101 and facilitate the adjustment of the energy storage system.

[0050] In some embodiments, the energy storage system further includes a valve 104 arranged on the connecting pipe 103 and configured to be opened when the temperature of the cooling liquid in the battery pack 101 exceeds a first preset temperature or when the temperature of the cooling liquid in the battery pack 101 is lower than a second preset temperature. When the temperature of the cooling liquid in the battery pack 101 exceeds the first preset temperature, it indicates that the cooling liquid is likely to expand due to heat, and it indicates that part of the cooling liquid needs to be introduced into the balancing device 102 to balance the pressure in the battery pack 101. At this time, the valve 104 can be opened to connect the passage between the battery pack 101 and the balancing device 102. Similarly, when the temperature of the cooling liquid in the battery pack 101 is lower than the second preset temperature, it indicates that the volume of the cooling liquid is likely to decrease, and the passage between the balancing device 102 and the battery pack 101 needs to be connected to balance the pressure in the battery pack 101.

[0051] In some embodiments, the energy storage system can further include a pressure measuring device (not shown) for measuring the pressure in the battery pack 101, thereby allowing different control measurements to be selected according to the pressure in the battery pack 101.

[0052] In some embodiments, the opening and closing of the valve 104 can be controlled by the battery management system.

[0053] For example, when the temperature of the cooling liquid in the battery pack 101 is detected to be higher than a first preset temperature, or the temperature of the cooling liquid is detected to be lower than a second preset temperature, or the pressure in the battery pack 101 is detected to be higher than a third preset value, or the pressure in the battery pack 101 is detected to be lower than a fourth preset value, the valve 104 can be controlled to open by the battery management system to communicate the battery pack 101 with the balancing device 102, so as to control the pressure in the battery pack 101.

[0054] In some embodiments, the energy storage system can further comprise a clamping device 105 fixed to the top surface of the topmost battery pack 101 arranged in the first direction. The clamping device 105 can be used to fix the balancing device 102 or other structures such as thermal insulation cotton, to provide a mounting clamping position, so as to avoid the structures mounted on the top surface of the battery pack 101 from sliding or falling off.

[0055] In some embodiments, the clamping device 105 comprises a bearing part 115 extending in a second direction, a bending part 125 located on opposite sides of the bearing part 115 in the second direction, connected with the bearing part 115 and extending away from the battery pack 101, and a limiting part 135 located on the top surface of the bending part 125, connected with the bending part 125 and extending in the second direction. The bearing part 115 is used to bear the structures mounted on the top of the battery pack 101, and the bending part 125 and the limiting part 135 are used to clamp the structures mounted on the top of the battery pack 101, so as to avoid the structures mounted on the top of the battery pack 101 from displacing in the energy storage system, thereby improving the reliability of the energy storage system.

[0056] In some embodiments, the second direction can be perpendicular to the first direction.

[0057] The present disclosure utilizes the liquid cooling unit 100 to transmit cooling liquid to the battery pack 101, the cooling liquid is used for heat exchange with the battery pack 101, so as to complete the cooling of the battery pack 101, and then the cooling liquid with the temperature increased after completing the heat exchange is recovered into the liquid cooling unit 100, and the cooling liquid with the temperature increased is cooled again to complete the recycling of the cooling liquid, however, when the external environment temperature of the energy storage system is low, the cooling liquid in the energy storage system is affected by the external environment, so that the initial temperature is reduced, and with the operation of the energy storage system, the temperature of the cooling liquid will gradually increase, so that the cooling liquid is expanded by heat, at this time, the pressure in the battery pack 101 will increase, and there is a safety hazard, the present disclosure also provides a balancing device 102, so as to receive the cooling liquid from the battery pack 101 when the cooling liquid is expanded by heat, and maintain the pressure balance in the battery pack 101; when the external temperature of the energy storage system is high, the initial temperature of the cooling liquid is high, and with the operation of the energy storage system, the temperature in the energy storage system is reduced, so that the cooling liquid is contracted by cold, so that the pressure in the battery pack 101 is reduced, and there is also a safety hazard, and the balancing device 102 can also flow the cooling liquid in the balancing device 102 into the battery pack 101, so as to maintain the pressure balance in the battery pack 101, so as to improve the reliability of the energy storage system.

[0058] Those skilled in the art can understand that the above-mentioned embodiments are specific embodiments for realizing the present application, and in actual application, various changes can be made in form and details without departing from the spirit and scope of the embodiments of the present application. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the embodiments of the present application, therefore, the protection scope of the embodiments of the present application should be limited by the scope defined in the claims.

Claims

1. An energy storage system, characterized by, The energy storage system comprises: a liquid cooling unit having an inlet and an outlet; a plurality of battery packs arranged along a first direction, each of the battery packs being in communication with the inlet via an inlet pipe, and the cooling liquid outputted from the inlet of the liquid cooling unit flowing into the battery packs via the inlet pipe, each of the battery packs being in communication with the outlet via an outlet pipe, and the cooling liquid in the battery packs flowing to the outlet via the outlet pipe to return to the liquid cooling unit; a balancing device having an opening, the battery packs being in communication with the opening via a connecting pipe, and the balancing device being used to receive part of the cooling liquid flowing into the opening from the battery packs when the temperature of the battery packs rises.

2. The energy storage system of claim 1, wherein, The balancing device comprises: a housing having a containing space; an air bag arranged in the containing space, the air bag being in communication with the opening, and the cooling liquid in the battery packs flowing into the air bag via the opening.

3. The energy storage system according to claim 2, wherein: the air bag contains a reserved cooling liquid before absorbing the cooling liquid, and the ratio of the volume of the reserved cooling liquid to the volume of the air bag is 1 / 5-1 / 3.

4. The energy storage system of claim 1, wherein, The balancing device is located between adjacent battery packs and is in communication with the two adjacent battery packs.

5. The energy storage system of claim 4, wherein, The energy storage system further comprises: thermal insulation cotton located on the top surface of the topmost battery pack arranged along the first direction.

6. The energy storage system of claim 1, wherein, The battery pack comprises a plurality of battery cells, the cooling liquid in the battery pack immersing the surface of the battery cells, and the liquid level of the cooling liquid being higher than the top surface of the connecting pipe.

7. The energy storage system of claim 1, wherein, The energy storage system further comprises: a temperature measuring device used to detect the temperature of the cooling liquid in the battery pack.

8. The energy storage system of claim 1 or 7, wherein, The energy storage system further comprises: a valve arranged on the connecting pipe and used to be opened when the temperature of the cooling liquid in the battery pack exceeds a first preset temperature, or to be opened when the temperature of the cooling liquid in the battery pack is lower than a second preset temperature.

9. The energy storage system of claim 1, wherein, The energy storage system further comprises: a clamping device fixed on the top surface of the topmost battery pack arranged along the first direction.

10. The energy storage system of claim 9, wherein, The clamping device comprises: a bearing portion extending along a second direction; a bending portion located on the opposite sides of the bearing portion along the second direction, connected with the bearing portion, and extending away from the battery pack; a limiting portion located on the top surface of the bending portion, connected with the bending portion, and extending along the second direction.

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