Semi-through type packaging structure of flow battery

Abstract

The invention discloses a flow battery semi-through type packaging structure, which comprises a battery lamination module, a first end plate, a second end plate, a screw rod and a spring, the second end plate comprises a spring pressing plate, a plurality of rectangular pipes and a rectangular pipe fixing plate, and the rectangular pipes are arranged between the spring pressing plate and the rectangular pipe fixing plate at intervals; the spring pressing plate is connected with the rectangular pipe fixing plate through a bolt and clamps the rectangular pipe between the spring pressing plate and the rectangular pipe fixing plate, a plurality of springs are arranged between the rear end of the battery lamination module and the rectangular pipe at intervals, and a plurality of limiting grooves are formed in the first end plate; a screw rod sequentially penetrates through the limiting groove and the second through hole and is in threaded connection with a nut; by adopting the invention, the flow battery can be conveniently mounted, the production efficiency is improved, the production cost is saved, and the light weight and compactness of the flow battery are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical energy storage, and in particular relates to a semi-penetrating packaging structure of a liquid flow battery. Background Art

[0002] Generally speaking, a flow battery stack is composed of dozens to hundreds of stacked single cell components. The two ends of the stack are clamped by front and rear end plates, and the two end plates are fastened by screws or straps to apply pressure to the single cell components in the middle to achieve sealing between layers of the flowing electrolyte in the battery. In order to ensure good sealing, the end plate needs to have strong structural rigidity to achieve uniform distribution of pressure on the entire sealing surface; with the continuous expansion of energy storage scale, the assembly complexity of the stack, as well as the structural complexity caused by volume and weight will lead to a significant increase in system costs, how to achieve lightweight and compact design of the stack is particularly important. Therefore, when designing the stack structure, the primary goal should be to achieve lightweight, compact, high packaging efficiency and uniform packaging pressure.

[0003] In traditional flow batteries, the stack packaging is mainly fastened by screws and nuts or tie rods. There are two main types of fastener installation methods: through-type and non-through-type. The positioning method is mostly a combination of internal and external positioning. The elastic elements include disc springs and helical springs. The end plates, insulation plates and frame plates are mostly rectangular in design, and the screws are evenly arranged around the end plates. In summary, the current flow battery stack design has the following problems:

[0004] a). When the through-type screw and nut are used for fastening, the screw will penetrate the front and rear end plates from top to bottom, and some even pass through the frame plate. In the case of limited assembly space, such a design will invisibly increase the assembly difficulty of the workers, thus affecting the overall production efficiency;

[0005] b). When non-through tie rod fastening is used, the tie rod is too long, the end thread is difficult to process, or the end fastening structure is complicated, and its production cost is much higher than that of traditional screw fastening;

[0006] c). In order to make the pressure at the center of the battery stack as uniform as possible, elastic elements are arranged on the end plate on one side of the flow battery. At the same time, the end plate must be made of a relatively thick metal plate, which is not conducive to the lightweight design of the battery stack. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a semi-penetrating packaging structure for a liquid flow battery, which can effectively solve the problems of the prior art such as great assembly difficulty, low production efficiency and high production cost.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] A semi-through packaging structure of a liquid flow battery, comprising a battery stack module, a first end plate, a second end plate, a screw and a spring, wherein the first end plate is located at one end of the battery stack module, the second end plate is located at the other end of the battery stack module, a plurality of the screws are provided and are arranged at intervals on the outer periphery of the battery stack module, the second end plate comprises a spring pressure plate, a rectangular tube and a rectangular tube fixing plate, the spring pressure plate and the rectangular tube fixing plate are arranged at intervals, a plurality of the rectangular tubes are provided and are arranged at intervals between the spring pressure plate and the rectangular tube fixing plate, the spring pressure plate is connected to the rectangular tube fixing plate by bolts and the rectangular tube is clamped between the spring pressure plate and the rectangular tube fixing plate, The top of the rectangular tube is fixedly connected to the spring pressure plate, and the bottom of the rectangular tube is fixedly connected to the rectangular tube fixing plate. The multiple rectangular tubes are opposite to the multiple springs one by one. The springs are provided in plurality and are arranged at intervals between the battery stack module and the rectangular tube. The rectangular tube and the rectangular tube fixing plate are provided with a plurality of first through holes. One end of the spring is against the battery stack module, and the other end of the spring passes through the first through hole and is against the rectangular tube. The rectangular tube, the rectangular tube fixing plate and the spring pressure plate are all provided with a plurality of second through holes. The first end plate is provided with a plurality of limiting grooves, and the screw rod passes through the limiting groove and the second through hole in sequence and is threadedly connected with the nut.

[0010] As a preferred solution of the present invention, a positioning pin is provided on the rectangular tube fixing plate, and a positioning hole cooperating with the positioning pin is provided on the rectangular tube.

[0011] As a preferred solution of the present invention, the second end plate also includes a reinforcement block, two of which are arranged on both sides between the spring pressure plate and the rectangular tube fixing plate, and the reinforcement block is provided with a plurality of first U-shaped grooves that cooperate with the screw rod.

[0012] As a preferred embodiment of the present invention, a semi-through packaging structure of a liquid flow battery also includes a first gear bar and a second gear bar for limiting the screw, the first gear bar is provided with two and respectively arranged on the upper and lower sides of the battery stack module, the first gear bar is provided with a plurality of second U-shaped grooves that cooperate with the screw, the second gear bar is provided with two and respectively arranged on the left and right sides of the battery stack module, and the second gear bar is provided with a plurality of third U-shaped grooves that cooperate with the screw.

[0013] As a preferred embodiment of the present invention, a semi-through packaging structure of a liquid flow battery also includes a first stop bar and a second stop bar for limiting the screw rod, wherein two first stop bars are provided and are respectively arranged on the upper and lower sides of the first end plate, the first stop bar located on the upper side is fixedly connected to the upper side of the first end plate by bolts, and the first stop bar located on the lower side is fixedly connected to the lower side of the first end plate by bolts, and the second stop bar is provided and is respectively arranged on the left and right sides of the first end plate, the first stop bar located on the left side is fixedly connected to the left side of the first end plate by bolts, and the first stop bar located on the right side is fixedly connected to the right side of the first end plate by bolts.

[0014] As a preferred embodiment of the present invention, the upper and lower sides of the first end plate are provided with first installation grooves for installing the first bar, and the outer side surface of the first bar does not exceed the outer side surface of the first end plate. The left and right sides of the first end plate are provided with second installation grooves for installing the second bar, and the outer side surface of the second bar does not exceed the outer side surface of the first end plate.

[0015] As a preferred solution of the present invention, the depth of the limiting groove is greater than or equal to the diameter of the screw.

[0016] As a preferred embodiment of the present invention, the battery stack module comprises at least two battery stack assemblies and at least three liquid inlet plates, the battery stack assemblies and the liquid inlet plates are stacked, and the liquid inlet plates are provided with a liquid inlet and a liquid outlet.

[0017] As a preferred solution of the present invention, the battery stack assembly, the liquid inlet plate, the rectangular tube fixing plate and the spring pressure plate are all provided with notches for assembly and positioning at four corners.

[0018] As a preferred embodiment of the present invention, the battery stack assembly is composed of 1 to 200 layers of single battery stacks.

[0019] The semi-penetrating packaging structure of a flow battery provided by the present invention has the following beneficial effects compared with the prior art:

[0020] When assembling the battery stack module, after the battery stack module is stacked and pressed to a suitable height, one end of the screw is slid into the limit groove from the side and close to the battery stack module, and then the screw is pushed upward to pass through the second end plate, and finally the nut is locked. This packaging method does not need to penetrate the front and rear end plates from top to bottom, and can achieve semi-through packaging, saving the assembly space of the liquid flow battery and improving production efficiency; and the standard screw is used instead of the pull rod in this scheme, which saves material costs to a certain extent; in addition, a rectangular tube is provided between the spring pressure plate and the rectangular tube fixing plate, and a plurality of first through holes for the spring to pass through are provided on the rectangular tube, which can effectively reduce the weight of the second end plate while ensuring the stiffness of the second end plate, not only can the uniform transmission of pressure be achieved, but also the space of the liquid flow battery is saved, and the purpose of lightweight and compact design of the liquid flow battery is achieved; the present invention can facilitate the installation of the liquid flow battery, improve production efficiency, save production costs, and achieve lightweight and compact liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.

[0022] Figure 1 This is a schematic structural diagram of a semi-penetrating packaging structure of a flow battery provided in Embodiment 1 of the present invention;

[0023] Figure 2 This is a structural schematic diagram of another view of a semi-penetrating packaging structure of a flow battery provided by the first embodiment of the present invention;

[0024] Figure 3 is a schematic structural diagram of a first end plate;

[0025] Figure 4 It is a schematic diagram of the structure of a rectangular tube;

[0026] Figure 5 It is a structural schematic diagram of a rectangular tube fixing plate;

[0027] Figure 6 It is a structural schematic diagram of the reinforcement block;

[0028] Figure 7 It is a structural schematic diagram of a semi-penetrating packaging structure of a flow battery provided in Example 2 of the present invention.

[0029] Markings in the figure:

[0030] Battery stack module 100; battery stack assembly 101; liquid inlet plate 102; liquid inlet port 103; liquid outlet port 104; first end plate 200; limiting groove 201; second end plate 300; spring pressure plate 301; rectangular tube 302; positioning hole 3021; ​​rectangular tube fixing plate 303; positioning pin 3031; reinforcement block 304; first through hole 305; second through hole 306; first U-shaped groove 307; screw 400; spring 500; first gear bar 600; second U-shaped groove 601; first mounting groove 602; second gear bar 700; third U-shaped groove 701; second mounting groove 702; missing corner 800. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0032] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. It should be understood that the terms "first", "second", etc. are used in the present invention to describe various information, but such information should not be limited to these terms, which are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, "first" information may also be referred to as "second" information, and similarly, "second" information may also be referred to as "first" information.

[0033] like Figures 1 to 5As shown, a preferred embodiment of the present invention provides a semi-through packaging structure of a flow battery, which includes a battery stack module 100, a first end plate 200, a second end plate 300, a screw 400 and a spring 500, wherein the first end plate 200 is located at one end of the battery stack module 100, the second end plate 300 is located at the other end of the battery stack module 100, the screw 400 is provided with a plurality of screws and is arranged at intervals on the periphery of the battery stack module 100, the second end plate 300 includes a spring pressure plate 300, and the second end plate 300 includes a spring pressure plate 300. 01, a rectangular tube 302 and a rectangular tube fixing plate 303, the spring pressure plate 301 and the rectangular tube fixing plate 303 are arranged at intervals, the rectangular tube 302 is provided with a plurality of spring pressure plates 301 and arranged at intervals between the rectangular tube fixing plate 303, one end of the rectangular tube 302 is fixedly connected to the spring pressure plate 301, and the other end of the rectangular tube 302 is fixedly connected to the rectangular tube fixing plate 303, the plurality of rectangular tubes 302 are opposite to the plurality of springs 500 one by one, the spring The spring 500 is provided with a plurality of springs 500 and is arranged at intervals between the battery stack module 100 and the rectangular tube 302. The spring pressure plate 301 is connected to the rectangular tube fixing plate 303 by bolts and the rectangular tube 302 is clamped between the spring pressure plate 301 and the rectangular tube fixing plate 303. The bolts are provided with four bolts, which are respectively arranged at the four corners of the spring pressure plate 301 or the rectangular tube fixing plate 303. The rectangular tube 302 and the rectangular tube fixing plate 303 are provided with a plurality of springs 500. The first through hole 305, one end of the spring 500 is fixedly connected to the rectangular tube 302, the other end of the spring 500 passes through the first through hole 305 and is fixedly connected to the spring pressure plate 301, the rectangular tube 302, the rectangular tube fixing plate 303 and the spring pressure plate 301 are each provided with a plurality of second through holes 306, the first end plate 200 is provided with a plurality of limiting grooves 201, the screw rod 400 passes through the limiting grooves 201 and the second through hole 306 in sequence and is threadedly connected to the nut.

[0034] It should also be noted that in order to facilitate the assembly of the screw 400, the limiting groove 201 in this embodiment is configured as a U-shaped groove with an opening on the side wall, so that the screw 400 can be directly pressed into the groove during the installation process, without the need for multiple hole operations, thereby facilitating installation.

[0035] It is understandable that, in a specific implementation, the battery stack module 100 and the rectangular tube fixing plate 303 can be arranged at intervals, and when the pressing force of the battery is large enough, the spring 500 can be completely squeezed, so that the battery stack module 100 and the rectangular tube fixing plate 303 fit each other.

[0036] When assembling the battery stack module 100, after the battery stack module 100 is stacked and pressed to a suitable height, one end of the screw rod 400 is slid into the limiting groove 201 from the side and is close to the battery stack module 100, and then the screw rod 400 is pushed upward to pass through the second end plate 300, and finally the nut is locked. This packaging method does not require penetrating the front and rear end plates from top to bottom, and can achieve semi-through packaging, saving assembly space for the flow battery and improving production efficiency; and in this solution, a standard screw rod 400 is used instead of a pull rod, which saves material costs to a certain extent; In addition, a rectangular tube 302 is provided between the spring pressure plate 301 and the rectangular tube fixing plate 303, and a plurality of first through holes are provided on the rectangular tube 302 for the spring 500 to pass through. While ensuring the rigidity of the second end plate 300, the weight of the second end plate 300 can be effectively reduced, which not only realizes the uniform transmission of pressure, but also saves the space of the liquid flow battery, thereby achieving the purpose of lightweight and compact design of the liquid flow battery. The present invention can facilitate the installation of the liquid flow battery, improve production efficiency, save production costs, and achieve lightweight and compact design of the liquid flow battery.

[0037] Exemplarily, a positioning pin 3031 is provided on the rectangular tube fixing plate 303, and a positioning hole 3021 cooperating with the positioning pin 3031 is provided on the rectangular tube 302. It should also be noted that, in this embodiment, the height of the positioning pin 3031 is at least 1 / 2 of the depth of the positioning hole 3021.

[0038] For example, Figure 6 As shown, the second end plate 300 also includes a reinforcing block 304, and two of the reinforcing blocks 304 are provided. The two reinforcing blocks 304 are arranged on both sides between the spring pressure plate 301 and the rectangular tube fixing plate 303. The reinforcing block 304 is provided with a plurality of first U-shaped grooves 307 that cooperate with the screw 400. Through the arrangement of the reinforcing blocks 304 on both sides, when the screw 400 located on the side of the battery stack module 100 is locked, the bending deformation of the ends of the spring pressure plate 301 and the rectangular tube fixing plate 303 can be effectively reduced, thereby ensuring the strength of the spring pressure plate 301 and the rectangular tube fixing plate 303. In this embodiment, in order to facilitate assembly and positioning, the upper and lower sides of the reinforcing block 304 are provided with missing corners 800.

[0039] It should also be noted that during the specific installation process, the spring pressure plate 301 is bolted through the through hole on the reinforcement block 304 and is threadedly connected to the rectangular tube fixing plate 303, so the reinforcement block 304 can also be clamped between the spring pressure plate 301 and the rectangular tube fixing plate 303.

[0040] For example, Figure 1 and Figure 2As shown, a semi-through packaging structure of a liquid flow battery also includes a first gear bar 600 and a second gear bar 700 for limiting the screw 400, the first gear bar 600 is provided with two and is respectively arranged on the upper and lower sides of the battery stack module 100, the first gear bar 600 is provided with a plurality of second U-shaped grooves 601 cooperating with the screw 400, the second gear bar 700 is provided with two and is respectively arranged on the left and right sides of the battery stack module 100, and the second gear bar 700 is provided with a plurality of third U-shaped grooves 701 cooperating with the screw 400, thereby, the screw 400 can be limited by the first gear bar 600 and the second gear bar 700, so as to prevent the screw 400 from sliding out from the side when the battery is placed on its side and the stress is relaxed, thereby ensuring the stability of the battery structure.

[0041] For example, Figure 7 As shown, in another embodiment, a semi-through packaging structure of a liquid flow battery also includes a first stop bar 600 and a second stop bar 700 for limiting the screw 400, and the first stop bar 600 is provided with two and is respectively arranged on the upper and lower sides of the first end plate 200, the first stop bar located on the upper side is fixedly connected to the upper side of the first end plate 200 by bolts, and the first stop bar located on the lower side is fixedly connected to the lower side of the first end plate 200 by bolts, and the second stop bar 700 is provided with two and is respectively arranged on the left and right sides of the first end plate 200, the first stop bar located on the left side is fixedly connected to the left side of the first end plate 200 by bolts, and the first stop bar located on the right side is fixedly connected to the right side of the first end plate 200 by bolts. Thus, the first stop bar 600 and the second stop bar 700 can be used to limit the screw 400, prevent the screw 400 from sliding out from the side when the battery is placed on its side and stress is relaxed, and ensure the stability of the battery structure.

[0042] It should also be noted that, in the specific installation process, in order to avoid battery short circuit, a certain safety distance is set between the screw and the battery stack module, and the safety distance is ≥ 0.5 mm. In the present embodiment, it is preferably 1.5 mm.

[0043] For example, Figure 7As shown, both upper and lower sides of the first end plate 200 are provided with first mounting grooves 602 for mounting the first bar 600, and the outer side surface of the first bar 600 does not extend beyond the outer side surface of the first end plate 200. Both left and right sides of the first end plate 200 are provided with second mounting grooves 702 for mounting the second bar 700, and the outer side surface of the second bar 700 does not extend beyond the outer side surface of the first end plate 200, thereby preventing the first bar 600 and the second bar 700 from extending beyond the outer side surface of the first end plate 200. The structure is compact, and the screw 400 is also pressed tightly against the surface of the battery stack module 100, thereby limiting the displacement of the screw 400.

[0044] Exemplarily, the depth of the limiting groove 201 is greater than or equal to the diameter of the screw 400 .

[0045] Exemplarily, the depth of the first mounting groove 602 and the second mounting groove 702 is less than or equal to the depth of the limiting groove 201 .

[0046] Exemplarily, the battery stack module 100 includes at least two battery stack assemblies 101 and at least three liquid inlet plates 102 . The battery stack assemblies 101 and the liquid inlet plates 102 are stacked, and the liquid inlet plates 102 are each provided with a liquid inlet 103 and a liquid outlet 104 .

[0047] Exemplarily, the four corners of the battery stack assembly 101 , the liquid inlet plate 102 , the rectangular tube fixing plate 303 and the spring pressure plate 301 are all provided with notched corners 800 for assembly.

[0048] Exemplarily, the battery stack assembly 101 is composed of 1 to 200 layers of single battery stacks, and the stack height of the battery stack module 100 is 5 mm to 1000 mm. In the present application, the battery stack assembly 101 is composed of 20 layers of single batteries, with a height of 200 mm.

[0049] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A semi-penetrating packaging structure of a flow battery, characterized in that: The battery stack module comprises a first end plate, a second end plate, a screw and a spring, wherein the first end plate is located at one end of the battery stack module, the second end plate is located at the other end of the battery stack module, a plurality of screws are provided and are arranged at intervals on the outer periphery of the battery stack modules, the second end plate comprises a spring pressure plate, a rectangular tube and a rectangular tube fixing plate, the spring pressure plate and the rectangular tube fixing plate are arranged at intervals, a plurality of rectangular tubes are provided and are arranged at intervals between the spring pressure plate and the rectangular tube fixing plate, the spring pressure plate is connected to the rectangular tube fixing plate by bolts and the rectangular tube is clamped between the spring pressure plate and the rectangular tube fixing plate, the top of the rectangular tube The top of the rectangular tube is fixedly connected to the spring pressure plate, the bottom of the rectangular tube is fixedly connected to the rectangular tube fixing plate, the multiple rectangular tubes are opposite to the multiple springs one by one, the springs are provided in plurality and are arranged at intervals between the battery stack module and the rectangular tube, the rectangular tube and the rectangular tube fixing plate are provided with a plurality of first through holes, one end of the spring is against the battery stack module, the other end of the spring passes through the first through hole and against the rectangular tube, the rectangular tube, the rectangular tube fixing plate and the spring pressure plate are all provided with a plurality of second through holes, the first end plate is provided with a plurality of limiting grooves, the screw passes through the limiting grooves and the second through holes in sequence and is threadedly connected with the nut.

2. A semi-penetrating packaging structure for a flow battery according to claim 1, characterized in that: The rectangular tube fixing plate is provided with a positioning pin, and the rectangular tube is provided with a positioning hole matched with the positioning pin.

3. A semi-penetrating packaging structure for a flow battery according to claim 1, characterized in that: The second end plate also includes a reinforcing block, two of which are arranged on both sides between the spring pressure plate and the rectangular tube fixing plate, and a plurality of first U-shaped grooves cooperating with the screw rod are provided on the reinforcing block.

4. A semi-penetrating packaging structure for a flow battery according to claim 1, characterized in that: It also includes a first gear bar and a second gear bar for limiting the screw rod, wherein two first gear bars are provided and are respectively arranged on the upper and lower sides of the battery stack module, and the first gear bar is provided with a plurality of second U-shaped grooves cooperating with the screw rod, and two second gear bars are provided and are respectively arranged on the left and right sides of the battery stack module, and the second gear bar is provided with a plurality of third U-shaped grooves cooperating with the screw rod.

5. The semi-penetrating packaging structure of a flow battery according to claim 1, characterized in that: It also includes a first stop bar and a second stop bar for limiting the screw rod, wherein two first stop bars are provided and are respectively arranged on the upper and lower sides of the first end plate, the first stop bar located on the upper side is fixedly connected to the upper side of the first end plate by bolts, and the first stop bar located on the lower side is fixedly connected to the lower side of the first end plate by bolts, and the second stop bar is provided with two and are respectively arranged on the left and right sides of the first end plate, the first stop bar located on the left side is fixedly connected to the left side of the first end plate by bolts, and the first stop bar located on the right side is fixedly connected to the right side of the first end plate by bolts.

6. A semi-penetrating packaging structure for a flow battery according to claim 5, characterized in that: The first end plate has first mounting grooves on both the upper and lower sides for mounting the first bar, and the outer side surface of the first bar does not extend beyond the outer side surface of the first end plate. The first end plate has second mounting grooves on both the left and right sides for mounting the second bar, and the outer side surface of the second bar does not extend beyond the outer side surface of the first end plate.

7. A semi-penetrating packaging structure for a flow battery according to claim 1, characterized in that: The depth of the limiting groove is greater than or equal to the diameter of the screw.

8. The semi-penetrating packaging structure of a flow battery according to claim 1, characterized in that: The battery stack module comprises at least two battery stack assemblies and at least three liquid inlet plates. The battery stack assemblies and the liquid inlet plates are stacked, and the liquid inlet plates are provided with a liquid inlet and a liquid outlet.

9. A semi-penetrating packaging structure for a flow battery according to claim 8, characterized in that: The four corners of the battery stack assembly, the liquid inlet plate, the rectangular tube fixing plate and the spring pressure plate are all provided with notches for assembly and positioning.

10. A semi-penetrating packaging structure for a flow battery according to claim 8, characterized in that: The battery stack assembly is composed of 1 to 200 layers of single battery stacks.

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