Lead storage battery

Abstract

A lead storage battery 10 includes: a battery case 20 having a plurality of cell chambers 24 partitioned by a partition wall 23; a plurality of electrode plate groups 30 respectively housed in the plurality of cell chambers 24; and an electrolyte injected into the plurality of cell chambers 24. Each electrode plate group 30 includes: a plurality of positive electrode plates 30P and a plurality of negative electrode plates 30N alternately laminated via separators SP; a positive electrode strap 32P connected to an ear part 31P provided to each positive electrode plate 30P; a negative electrode strap 32N connected to an ear part 31N provided to each negative electrode plate 30N; a positive-electrode intermediate electrode column 34P extending along the partition wall 23 from the positive electrode strap 32P; and a negative-electrode intermediate electrode column 34N extending along the partition wall 23 from the negative electrode strap 32N. The positive-electrode intermediate electrode column 34P and the negative-electrode intermediate electrode column 34N are connected by an inter-cell connection part 36 penetrating the partition wall 23. The liquid level of the electrolyte is disposed below the lower end of the inter-cell connection part 36. In a case such that the direction in which the positive electrode plates 30P and the negative electrode plates 30N are arranged in each cell chamber 24 is defined as a first direction, the relational expression (L1 2 + T1 2)1 / 2 ≥ W is established, if L1 is the length of the positive electrode strap 32P in the first direction, W is the interval between the partition walls 23 in the first direction, and T1 is the thickness of the positive electrode strap 32P.

Description

lead acid battery

[0001] The present disclosure relates to lead-acid batteries.

[0002] Conventionally, a lead-acid battery described in Japanese Patent Laid-Open No. 2014-63579 (Patent Document 1 below) is known. Patent Document 1 proposes a lead-acid battery comprising: a battery case whose interior is divided into a plurality of cell chambers by partitions; electrode groups housed in each of the cell chambers; and a lid welded to a side wall and the partition of the battery case; a connecting strap pair, which is a pair of straps of opposite polarities connected to each other via the partition between the electrode group housed in one adjacent cell chamber and the electrode group housed in the other adjacent cell chamber; and an unconnecting strap pair, which is a pair of straps of opposite polarities that are not connected to each other; a portion of the partition that is sandwiched between the unconnecting strap pair is a first step portion that has a first inclined side that is formed above an upper end of the side wall of the battery case and has an upward slope; a portion of the partition that is sandwiched between the connecting strap pair is a second step portion that is continuous with the first step portion and has a second inclined side that is formed above an upper end of the first step portion and has an upward slope; a partition through-hole is formed in the second step portion for connecting the connecting strap pair; and the inclination angle of the first inclined side of the first step portion is smaller than the inclination angle of the second inclined side of the second step portion.

[0003] The electrode group has a plurality of negative and positive electrode plates stacked alternately with separators sandwiched between them. The connection strap pair includes a positive electrode strap connecting the plurality of positive electrode plates and a negative electrode strap connecting the plurality of negative electrode plates. An inter-cell connection piece extends from each of the negative electrode strap and the positive electrode strap. The inter-cell connection piece located in one of two adjacent cell chambers is connected to the inter-cell connection piece located in the other of the two adjacent cell chambers through a partition wall through-hole.

[0004] JP 2014-63579 A

[0005] In recent years, efforts have been made to increase design flexibility by reducing the amount of electrolyte compared to conventional lead-acid batteries. Repeated charge / discharge cycles in lead-acid batteries can cause expansion (hereinafter also referred to as growth) of the positive electrode plate. This can lead to warping of the positive electrode strap and inter-cell connectors, which can cause cracks in the connections connecting the inter-cell connectors (corresponding to the inter-cell connectors in the present disclosure). When these cracks occur in lead-acid batteries with a low amount of electrolyte, oxygen and sulfuric acid can penetrate the cracks, causing corrosion of the connections of the inter-cell connectors. Progressive corrosion of the connections of the inter-cell connectors can impair the airtightness of the cell chambers, resulting in gas leaks. As a result, as charge / discharge cycles are repeated, the state of charge of the electrode groups (corresponding to the electrode group in the present disclosure) in each cell chamber varies greatly, resulting in a decrease in the capacity of the lead-acid battery. This, in turn, shortens the life of the lead-acid battery.

[0006] The lead-acid battery of the present disclosure includes a battery case having a plurality of cell chambers separated by partition walls, a plurality of electrode plate groups housed in each of the plurality of cell chambers, and an electrolyte injected into the plurality of cell chambers, wherein each of the electrode plate groups includes a plurality of positive and negative electrode plates alternately stacked with separators interposed therebetween, a positive electrode strap connected to a lug provided on each of the positive electrode plates, a negative electrode strap connected to a lug provided on each of the negative electrode plates, a positive electrode intermediate pole extending from the positive electrode strap along the partition wall, and a negative electrode intermediate pole extending from the negative electrode strap along the partition wall, wherein the positive electrode intermediate pole and the negative electrode intermediate pole are connected by an inter-cell connector penetrating the partition wall, and a liquid level of the electrolyte is located below a lower end of the inter-cell connector, and when a direction in which the positive electrode plates and the negative electrode plates are arranged in each of the cell chambers is defined as a first direction, the length of the positive electrode strap in the first direction is L １ the spacing between the partition walls in the first direction is W, and the thickness of the positive electrode strap is T １ In this case, (L １ ２ +T １ ２ ) １／２ ≧W.

[0007] According to the present disclosure, a lead-acid battery with a long life can be provided.

[0008] 1 is a perspective view of a lead-acid battery according to a first embodiment; 2 is a plan view of a battery case; 3 is a plan view of a battery case, and a positive electrode strap, a negative electrode strap, an end positive electrode strap, and an end negative electrode strap arranged in the battery case; 4 is a cross-sectional view taken along the line A-A of FIG. 1; 5 is a schematic view of a portion of the cross-section B-B of FIG. 4, including a positive electrode strap, a negative electrode strap, and an inter-cell connection; 6 is a schematic view of a portion of the cross-section C-C of FIG. 4, including an end positive electrode strap and an end negative electrode strap; 7 is an explanatory view illustrating deformation of a positive electrode strap of a conventional lead-acid battery in a cross-section corresponding to FIG. 5; 8 is an explanatory view illustrating dimensions of a positive electrode strap and a negative electrode strap in a cross-section corresponding to FIG. 5; 9 is an explanatory view illustrating a state in which deformation of a positive electrode strap is suppressed in a cross-section corresponding to FIG. 5; 10 is an explanatory view illustrating dimensions of a positive electrode strap according to a modified example of the first embodiment in a cross-section corresponding to FIG. 5; 11 is a plan view of a battery case according to a second embodiment, and a positive electrode strap, a negative electrode strap, an end positive electrode strap, and an end negative electrode strap arranged in the battery case; 12 is a diagram illustrating a support portion in a cross-section corresponding to FIG. 5. 6 is a cross-sectional view corresponding to FIG. 5 showing a support portion according to a third embodiment. FIG.

[0009] (Summary of the present embodiment) (1) A lead-acid battery according to the present disclosure includes a battery case having a plurality of cell chambers separated by partition walls, a plurality of electrode plate groups housed in each of the cell chambers, and an electrolyte injected into the cell chambers. Each of the electrode plate groups includes a plurality of positive and negative electrode plates alternately stacked with separators interposed therebetween, a positive electrode strap connected to a lug provided on each of the positive electrode plates, a negative electrode strap connected to a lug provided on each of the negative electrode plates, a positive electrode intermediate pole extending from the positive electrode strap along the partition wall, and a negative electrode intermediate pole extending from the negative electrode strap along the partition wall. The positive electrode intermediate pole and the negative electrode intermediate pole are connected by an inter-cell connector penetrating the partition wall. A liquid level of the electrolyte is located below a lower end of the inter-cell connector. When a direction in which the positive electrode plates and the negative electrode plates are arranged in each of the cell chambers is defined as a first direction, a length of the positive electrode strap in the first direction is L. １ the spacing between the partition walls in the first direction is W, and the thickness of the positive electrode strap is T １ In this case, (L １ ２ +T １ ２ ) １／２ The relational expression ≧W holds true.

[0010] With this configuration, when the positive plate elongates and stress is applied to the positive strap, the end of the positive strap opposite the positive intermediate electrode post comes into contact with the partition wall, thereby suppressing warping of the positive strap. This prevents stress from being applied from the positive strap to the inter-cell connection via the positive intermediate electrode post. This prevents cracks from forming in the inter-cell connection, which would allow electrolyte and oxygen to enter the cracks and corrode the inter-cell connection. This prevents gas leaks caused by loss of airtightness in the cell chamber and shortens the life of the lead-acid battery.

[0011] In lead-acid batteries, where the electrolyte level is lower than the bottom of the inter-cell connections, cracks in the inter-cell connections caused by the stress of grid expansion in the positive plates are exposed to the gas phase. When oxygen penetrates the cracks, the lead in the inter-cell connections converts to lead oxide, and the electrolyte then penetrates, producing lead sulfate. The lead oxide in the inter-cell connections then converts to lead sulfate and expands, pushing the gap between the inter-cell connections and the positive intermediate pole, further corroding the inter-cell connections. This results in a gas leak, which compromises the airtightness of adjacent cell chambers. In contrast, in conventional flooded lead-acid batteries, the electrolyte level is higher than the bottom of the inter-cell connections, making it difficult for oxygen to penetrate the cracks in the inter-cell connections, preventing the formation of lead oxide. In other words, even in conventional flooded lead-acid batteries, cracks in the inter-cell connections do not progress to the above-mentioned mechanism, and no gas leaks occur.

[0012] Examples of lead-acid batteries in which the electrolyte level is lower than the bottom of the inter-cell connections include flooded lead-acid batteries where the electrolyte level is lower than the bottom of the positive strap (the inter-cell connections and positive strap are exposed to the gas phase) and lead-acid batteries in which the electrolyte is impregnated in a glass mat (the top of the impregnated glass mat is considered the electrolyte level). Even in these lead-acid batteries, electrolyte can travel down the partition wall to the inter-cell connections and penetrate cracks in the inter-cell connections, causing lead oxide to convert to lead sulfate and expand, resulting in corrosion of the inter-cell connections. This can lead to gas leaks, which compromise the seal between adjacent cell chambers. Here, the electrolyte level in a flooded lead-acid battery refers to the electrolyte level when the battery case is filled to the upper level indicated on the battery case. If the upper level is not indicated on the battery case, the upper level refers to the electrolyte level of an unused lead-acid battery. An unused lead-acid battery is one that has never been used by a user (general consumer). Lead-acid batteries that have undergone quality inspection testing or recharged during manufacturing, or that have been recharged at a retail store, are also considered unused lead-acid batteries.

[0013] Considering the tendency of corrosion at the cell-cell connection, the configuration of the present disclosure is more preferably applied to a lead-acid battery in which the cell-cell connection and the positive electrode strap are exposed to a gas phase. When a crack occurs at the cell-cell connection, a coating layer of lead sulfate is formed at the crack due to the gas absorption reaction shown in the following formula 1. At this time, the sulfuric acid concentration decreases partially near the cell-cell connection, and the decrease in sulfuric acid concentration increases the solubility of lead sulfate, making it more likely for lead sulfate to dissolve.

[0014] (Formula 1) Pb+1 / 2O ２ +SO ４ ２－ +2H ＋ →PbSO ４ +H ２ O

[0015] In a lead-acid battery where the electrolyte level is at or above the bottom end of the positive strap, the positive strap and the electrolyte come into contact, and the electrolyte easily travels down the positive strap to the cell-to-cell connection, or the electrolyte level is close to the bottom end of the cell-to-cell connection, so the sulfuric acid concentration at the lowered cell-to-cell connection is likely to increase.

[0016] On the other hand, in a lead-acid battery in which the inter-cell connection and the positive electrode strap are exposed to the gas phase (the electrolyte level is lower than the bottom end of the positive electrode strap), the distance between the inter-cell connection and the electrolyte level is long, making it more difficult for the electrolyte to be supplied to the inter-cell connection compared to when the electrolyte level is higher than the bottom end of the positive electrode strap. As a result, it takes a relatively long time for the reduced sulfuric acid concentration to increase. As the sulfuric acid concentration decreases, the solubility of lead sulfate increases, making lead sulfate more likely to dissolve, dissolving part of the coating layer and exposing the lead underneath. In the exposed lead portion, the reaction represented by Equation 1 occurs again, forming a new lead sulfate layer. This reaction is repeated in cracks that occur in the inter-cell connection, further promoting corrosion of the inter-cell connection. Therefore, in a configuration in which the inter-cell connection and the positive electrode strap are exposed to the gas phase, gas leaks that compromise the airtightness between adjacent cell chambers are likely to occur, and therefore, the configuration disclosed herein is preferably applied.

[0017] Considering the ease of suppressing corrosion at the cell-cell connections, the separator preferably includes a glass mat impregnated with an electrolyte in the configuration of the present disclosure. With this configuration, oxygen generated from the positive electrode plate is consumed in a reaction at the negative electrode plate, making it difficult for oxygen to be supplied to the vicinity of the cell-cell connections. This further suppresses corrosion at the cell-cell connections.

[0018] (2) In the lead-acid battery described in (1), the length of the negative electrode strap in the first direction is L ２ When 2W-(L １ ２ +T １ ２ ) １／２ ≦L ２ It is preferable that the following relational expression holds true.

[0019] When growth of the positive electrode plate causes the positive electrode strap to warp and the end of the positive electrode strap opposite the positive electrode intermediate post comes into contact with the partition wall, stress through the positive electrode strap can deform the partition wall where the positive electrode intermediate post of the positive electrode strap is located or the partition wall in contact with the end of the positive electrode strap, potentially preventing the positive electrode strap from being properly secured. However, with the above configuration, the partition wall deforms, causing the end of the negative electrode strap to come into contact with the partition wall, eliminating any room for further partition wall deformation, making it easier to secure the positive electrode strap. This can further reduce gas leakage between adjacent cell chambers.

[0020] (3) In the lead-acid battery of (1) or (2), each of the plate groups comprises an end positive electrode strap having a positive electrode end pole connected to an external positive electrode terminal of the lead-acid battery, and an end negative electrode strap having a negative electrode end pole connected to an external negative electrode terminal of the lead-acid battery, and the length of the end positive electrode strap in the first direction is L ３ If W=L ３ It is preferable that the following relational expression holds true.

[0021] With this configuration, the end positive electrode straps come into contact with the partition walls, eliminating any room for deformation of the partition walls, making it easier to fix the positive electrode straps.

[0022] (4) In the lead-acid battery of (3), the length of the end negative electrode strap in the first direction is L ４ If W=L ４ It is preferable that the following relational expression holds true.

[0023] With this configuration, the end negative electrode strap comes into contact with the partition wall, eliminating any room for deformation of the partition wall, making it easier to fix the positive electrode strap.

[0024] (5) In any one of the lead-acid batteries (1) to (4), W=L １ It is preferable that the following relational expression holds true.

[0025] With this configuration, both ends of the positive electrode strap are fixed by two adjacent partition walls, which makes it even easier to suppress warping of the positive electrode strap.

[0026] (6) A lead-acid battery according to the present disclosure includes a battery case having a plurality of cell chambers separated by partition walls, a plurality of electrode plate groups housed in each of the cell chambers, and an electrolyte injected into the cell chambers. Each electrode plate group includes a plurality of positive and negative electrode plates alternately stacked with separators interposed therebetween, a positive electrode strap connected to an ear provided on each of the positive electrode plates, a negative electrode strap connected to an ear provided on each of the negative electrode plates, a positive electrode intermediate electrode post extending from the positive electrode strap along the partition wall, and a negative electrode intermediate electrode post extending from the negative electrode strap along the partition wall. The intermediate electrode post and the negative electrode intermediate electrode post are connected by an inter-cell connection part that penetrates the partition wall, the liquid level of the electrolyte is located below a lower end of the inter-cell connection part, and when a direction in which the positive electrode plates and the negative electrode plates are arranged in each cell chamber is defined as a first direction, the partition wall includes a support part that is located at a position overlapping an end of the positive electrode strap opposite the positive electrode intermediate electrode post when viewed from above, the support part is formed to be recessed or protrude from a wall surface of the partition wall in the first direction, and the support part may be in contact with the end of the positive electrode strap opposite the positive electrode intermediate electrode post. The support part may be a support part that contacts the end of the positive electrode strap opposite the positive electrode intermediate electrode post to suppress warping of the positive electrode strap.

[0027] With this configuration, when the positive electrode plate elongates and stress is applied to the positive electrode strap, the end of the positive electrode strap opposite the positive electrode intermediate post comes into contact with the support, thereby suppressing warping of the positive electrode strap. This prevents stress from being applied from the positive electrode strap to the inter-cell connection via the positive electrode intermediate post. This prevents cracks from forming in the inter-cell connection, which would allow electrolyte and oxygen to enter the cracks and corrode the inter-cell connection. This prevents gas leaks that compromise the airtightness between adjacent cell chambers.

[0028] (7) In the lead-acid battery of (6) above, it is preferable that the support portion contacts an end of the positive electrode strap opposite to the positive electrode intermediate electrode post when the lead-acid battery is in an unused state.

[0029] If there is a gap between the support part and the end of the positive strap opposite the positive intermediate electrode post when the lead-acid battery is unused, the positive strap may warp before the support part comes into contact with the end of the positive strap opposite the positive intermediate electrode post, which may cause cracks in the inter-cell connection. However, with the above configuration, the support part is in contact with the end of the positive strap opposite the positive intermediate electrode post when the lead-acid battery is unused, which further reduces the possibility of cracks in the inter-cell connection.

[0030] (8) In the lead-acid battery according to any one of (1) to (6) above, the positive electrode strap may be made of a Pb—Sn alloy that does not contain Sb.

[0031] (9) In the lead-acid battery according to any one of (1) to (8) above, the battery case may be made of polypropylene resin.

[0032] Because polypropylene resin has lower water vapor permeability than ABS resin, polypropylene resin is often used as a battery case material for batteries used in high-temperature environments where electrolyte loss (depletion of water) is likely to occur. Furthermore, low water vapor permeability increases the airtightness of the battery case, making the interior of a battery made of polypropylene resin prone to high temperatures. In other words, batteries made of polypropylene resin are likely to undergo repeated charging and discharging in high-temperature environments due to their intended use and material characteristics, which can promote grid elongation of the positive electrode plate. To prevent such issues, it is preferable to apply the configuration of the present disclosure when the battery case is made of polypropylene resin.

[0033] First Embodiment A first embodiment of the present disclosure will be described with reference to Fig. 1 to Fig. 12. In the following description, the front-rear direction, left-right direction, and up-down direction are based on the front-rear direction, left-right direction, and up-down direction shown in Fig. 1. In this embodiment, the front-rear direction is an example of a first direction.

[0034] 1-1. Battery Configuration A lead-acid battery 10 is mounted on a vehicle such as a four-wheeled vehicle or a two-wheeled vehicle. As shown in FIG. 1, the lead-acid battery 10 includes a battery case 20 and a cover member 50 having an external positive terminal 60P and an external negative terminal 60N. The battery case 20 is made of synthetic resin. The synthetic resin may be, for example, polypropylene (PP) or polyacrylonitrile butadiene styrene (ABS). As shown in FIG. 2, the battery case 20 has four outer walls 21A-21D and a bottom wall 22, forming a box shape with an open top. The interior of the battery case 20 is divided into multiple cell chambers 24 by partition walls 23. Six cell chambers 24 are arranged in a longitudinal direction. Each cell chamber 24 contains a plate assembly 30 (see FIG. 4) along with a flowable electrolyte.

[0035] 1, the lid member 50 is made of synthetic resin and seals the top surface of the battery case 20. An external negative electrode terminal 60N and an external positive electrode terminal 60P are provided at the front and rear ends of the lid member 50, respectively.

[0036] As shown in Figures 4 to 6, the electrode plate pack 30 includes a plurality of positive electrode plates 30P, a plurality of negative electrode plates 30N, and a separator SP separating the adjacent electrode plates 30P, 30N. In each cell chamber 24, the positive electrode plates 30P and the negative electrode plates 30N are aligned in the front-to-rear direction. Each electrode plate 30P, 30N is formed by filling a grid with an active material. The active material of the positive electrode plates 30P is mainly composed of lead dioxide, and the active material of the negative electrode plates 30N is mainly composed of lead. The separator SP may include a glass mat impregnated with an electrolyte.

[0037] 4 to 6, ears 31P, 31N are provided on the top of each electrode plate 30P, 30N. The ears 31P of the multiple positive electrode plates 30P are connected by positive electrode straps 32P or end positive electrode straps 33P. The ears 31N of the multiple negative electrode plates 30N are connected by negative electrode straps 32N or end negative electrode straps 33N.

[0038] Each of the straps 32P, 32N, 33P, and 33N has, for example, a plate shape that is long in the front-rear direction. Each of the straps 32P, 32N, 33P, and 33N is made of, for example, a Pb—Sn alloy. As shown in FIG. 3 , one cell chamber 24 disposed at one end (the front end in this embodiment) of the plurality of cell chambers 24 accommodates one positive electrode strap 32P and one end negative electrode strap 33N. One cell chamber 24 disposed at the other end (the rear end in this embodiment) of the plurality of cell chambers 24 accommodates one end positive electrode strap 33P and one negative electrode strap 32N. One cell chamber 24 disposed at a location other than both ends of the plurality of cell chambers 24 accommodates one positive electrode strap 32P and one negative electrode strap 32N.

[0039] As shown in Fig. 4, the end negative electrode strap 33N arranged in the front cell chamber 24 is connected to the external negative electrode terminal 60N via the negative electrode end pole 35N. The negative electrode end pole 35N is formed integrally with the end negative electrode strap 33N and extends upward from the end negative electrode strap 33N. Similarly, the end positive electrode strap 33P arranged in the rear cell chamber 24 is connected to the external positive electrode terminal 60P via the positive electrode end pole 35P (see Figs. 3 and 6).

[0040] As shown in FIGS. 4 and 5 , the positive strap 32P is provided with a positive intermediate electrode post 34P extending upward from the front or rear end of the positive strap 32P. As shown in FIG. 5 , the negative strap 32N is provided with a negative intermediate electrode post 34N extending upward from the front or rear end of the negative strap 32N. Each intermediate electrode post 34P, 34N extends along the partition wall 23. The positive intermediate electrode post 34P and the negative intermediate electrode post 34N, which are arranged adjacent to each other in the front-rear direction with the partition wall 23 interposed therebetween, are connected by an inter-cell connection 36. The inter-cell connection 36 penetrates the partition wall 23. In the lead-acid battery 10 of this embodiment, the liquid level of the electrolyte is located below the lower end of the inter-cell connection 36. The inter-cell connection 36 is exposed from the liquid level of the electrolyte and is located in the gas phase. Alternatively, the liquid level of the electrolyte may be located below the lower end of the positive strap 32P and the lower end of the negative strap 32N. At this time, the positive electrode strap 32P, the negative electrode strap 32N, the end positive electrode strap 33P, the end negative electrode strap 33N, and the inter-cell connector 36 are exposed above the liquid surface of the electrolyte and are disposed in the gas phase.

[0041] FIG. 7 is a cross-sectional view showing a conventional lead-acid battery 1000 not included in the present disclosure. This lead-acid battery 1000 has a positive electrode strap 1032P instead of the positive electrode strap 32P of the first embodiment. The configuration other than the positive electrode strap 1032P is the same as that of the lead-acid battery 10. It is known that repeated charge and discharge of the lead-acid battery 1000 causes growth in the positive electrode plate 30P, causing the positive electrode plate 30P to elongate in the vertical direction. This causes the positive electrode strap 1032P connecting multiple positive electrode plates 30P to be pushed upward. Meanwhile, the positive electrode intermediate post 34P extending from the positive electrode strap 1032P is fixed by an inter-cell connector 36 penetrating the partition wall 23. As a result, the portion of the positive strap 1032P away from the positive intermediate post 34P is pushed upward, causing the positive strap 1032P to warp and deform, generating stress at the connection between the positive intermediate post 34P and the inter-cell connection 36 that causes the positive intermediate post 34P to peel off from the inter-cell connection 36. This causes cracks in the inter-cell connection 36, allowing oxygen and sulfuric acid to penetrate into the cracks, corroding the inter-cell connection 36. As corrosion of the inter-cell connection 36 progresses, the airtightness of the cell chamber 24 is compromised, causing gas leakage to the adjacent cell chamber 24. During the charge cycle, oxygen is generated in the positive plate 30P that is already fully charged. If this oxygen migrates to the adjacent cell chamber 24 through the corroded portion of the inter-cell connection 36, a negative electrode absorption reaction that consumes oxygen occurs in the negative plate 30N. As a result, the negative electrode plate 30N that is not yet fully charged is not charged, and variations in the state of charge occur among the electrode plate groups 30 arranged in each cell chamber 24. As charge / discharge cycles are repeated, such variations in the state of charge increase, resulting in a decrease in the capacity of the lead-acid battery 1000 and a shortened lifespan of the lead-acid battery 1000. In particular, when deep charge / discharge cycles are repeated, variations in the state of charge among the electrode plate groups 30 arranged in each cell chamber 24 are likely to increase.

[0042] In this embodiment, in order to suppress gas leakage between adjacent cell chambers 24 due to damage to the inter-cell connection portion 36 as described above, a configuration is considered in which warping of the positive electrode strap 32P is suppressed when positive electrode growth occurs.

[0043] 1-2. Configuration of the Positive Electrode Strap Figure 8 shows the positive electrode strap 32P, the negative electrode strap 32N, and the cell chamber 24 in a state before positive electrode growth occurs. The distance between the partition walls 23 in the front-to-rear direction is W. The length of the positive electrode strap 32P in the front-to-rear direction is L. １ The thickness (vertical dimension) of the positive electrode strap 32P is T １ In this embodiment, the length of the diagonal of the cross section of the positive electrode strap 32P in FIG. 8 is set to be larger than the distance between the partition walls 23 in the front-rear direction. That is, in this embodiment, the following relational expression (hereinafter referred to as Relational Expression 1) holds true.

[0044] (L １ ２ +T １ ２ ) １／２ ≧W

[0045] In this embodiment, when the end 32P1 of the positive electrode strap 32P opposite the positive electrode intermediate post 34P in the front-rear direction is about to displace upward due to positive electrode growth, Relational Formula 1 holds, and therefore, as shown in Fig. 9, the end 32P1 of the positive electrode strap 32P comes into contact with the partition wall 23. Therefore, further upward warping of the positive electrode strap 32P can be suppressed.

[0046] As long as Relational Expression 1 is satisfied, a gap may exist between the end 32P1 of the positive electrode strap 32P and the partition wall 23 (see FIG. 8). In other words, the length of the positive electrode strap 32P in the front-rear direction may be smaller than the distance between the partition walls 23 (i.e., L １ <W). In such a case, the end 32P1 of the positive electrode strap 32P comes into contact with the partition wall 23 during the positive electrode growth process.

[0047] More preferably, as shown in FIG. 10 , the end 32P1 of the positive electrode strap 32P may be in contact with the partition wall 23 before positive electrode growth occurs. In other words, when the positive electrode strap 32P is housed in the cell chamber 24, the length of the positive electrode strap 32P in the front-rear direction is preferably equal to the distance between the partition walls 23 (i.e., L １=W). In such a case, the end 32P1 of the positive electrode strap 32P is in contact with the partition wall 23 before the positive electrode growth occurs, so that the warping of the positive electrode strap 32P can be further suppressed.

[0048] The positive electrode strap 32P of this embodiment may be made of a Pb—Sn alloy that does not contain Sb. Here, a Pb—Sn alloy that does not contain Sb is defined as an alloy that contains 2.0% or more Sn and 0.002% or less Sb. A Pb—Sn alloy that does not contain Sb has lower strength than a Pb—Sn alloy that contains Sb. Therefore, when the positive electrode strap 32P is made of a Pb—Sn alloy that does not contain Sb, it is considered that the positive electrode strap 32P is particularly susceptible to deformation due to positive electrode growth. However, by adopting a configuration in which the positive electrode strap 32P contacts the partition wall 23 during or before positive electrode growth occurs, as in this embodiment, upward warping of the positive electrode strap 32P can be suppressed.

[0049] 1-3. Structure of the negative electrode strap As shown in FIG. 8, the length of the negative electrode strap 32N in the front-rear direction is L ２ In this embodiment, it is preferable that the following relational expression (hereinafter referred to as relational expression 2) further holds true.

[0050] 2W-(L １ ２ +T １ ２ ) １／２ ≦L ２

[0051] 9 , if positive electrode growth continues while end 32P1 of positive electrode strap 32P is in contact with partition wall 23, it is conceivable that partition wall 23 in contact with end 32P1 of positive electrode strap 32P and partition wall 23 in contact with positive electrode intermediate pole 34P will deform so as to move away from each other in the front-to-rear direction. In FIG. 9 , partition wall 23 in contact with positive electrode intermediate pole 34P attempts to deform rearward (toward the left in the figure).

[0052] When Relational Expression 2 is satisfied, when the partition wall 23 in contact with the positive intermediate electrode post 34P tries to deform backward, the end 32N1 of the negative electrode strap 32N on the opposite side of the negative electrode intermediate electrode post 34N in the front-to-rear direction comes into contact with the partition wall 23. This prevents further deformation of the partition wall 23 in contact with the positive intermediate electrode post 34P, so that the end 32P1 of the positive electrode strap 32P can be maintained in contact with the partition wall 23. This prevents the positive electrode strap 32P from warping upward.

[0053] 1-4. Configuration of End Negative Electrode Strap As shown in FIG. 6, the length of the end negative electrode strap 33N in the front-rear direction is L ４ The length of the end negative electrode strap 33N in the front-rear direction is preferably equal to the distance between the partition walls 23 (i.e., L ４ =W). In other words, it is preferable that both front and rear ends of the end negative electrode strap 33N are in contact with the partition wall 23. As shown in FIG. 3 , the positive electrode strap 32P is arranged behind the end negative electrode strap 33N, with the partition wall 23 sandwiched between them. Therefore, by having both front and rear ends of the end negative electrode strap 33N in contact with the partition wall 23, deformation of the partition wall 23 in contact with the end 32P1 of the positive electrode strap 32P due to positive electrode growth can be suppressed. Therefore, upward warping of the positive electrode strap 32P can be suppressed.

[0054] 1-5. Configuration of the End Positive Electrode Strap As shown in FIG. 6, the length of the end positive electrode strap 33P in the front-rear direction is L ３ The length of the end positive electrode strap 33P in the front-rear direction is preferably equal to the distance between the partition walls 23 (i.e., L ３=W). In other words, it is preferable that both front and rear ends of the end positive electrode strap 33P contact the partition wall 23. As shown in FIG. 3 , the positive electrode strap 32P is disposed to the left and front of the end negative electrode strap 33P. Furthermore, the positive electrode strap 32P is disposed in front of the end negative electrode strap 33P, with the negative electrode strap 32N and the partition wall 23 sandwiched between them. Therefore, by having both front and rear ends of the end positive electrode strap 33P in contact with the partition wall 23, deformation of the partition wall 23 in contact with the end 32P1 of the positive electrode strap 32P due to positive electrode growth can be more easily suppressed. It is therefore thought that upward warping of the positive electrode strap 32P can be suppressed.

[0055] 1-6. Experiments and Considerations To investigate the effects of the above-described positive electrode strap configuration, the inventors conducted the following verification experiments. Note that in "1-6. Experiments and Considerations" of this specification, components not included in this disclosure will be described, and therefore will not be labeled with reference numerals.

[0056] In the verification experiment, three lead-acid batteries were fabricated: a lead-acid battery (Sample S1) in which the positive electrode strap contacts the partition wall as the positive electrode growth occurs, a lead-acid battery (Sample S2) in which the positive electrode strap contacts the partition wall before the positive electrode growth occurs, and a lead-acid battery (Sample S3) in which the positive electrode strap does not contact the partition wall even when the positive electrode growth occurs. Sample S1 corresponds to the configuration shown in FIG. 8. That is, in Sample S1, Relational Expression 1 and L １ <W. In detail, L １ = 60.3 mm, T １ = 5.0 mm, W = 60.4 mm. Sample S2 corresponds to the configuration shown in FIG. 10. That is, in sample S2, W = L １ The sample S3 corresponds to the conventional configuration shown in FIG. 7 and is not included in this disclosure.

[0057] The inventors conducted charge-discharge cycle tests for samples S1, S2, and S3 under the same conditions. The charge-discharge cycle tests were conducted in a 60°C environment. In the charge-discharge cycle tests, discharging was performed at a discharge current of 20 A until the discharge capacity reached 36 Ah. Charging was performed using a five-stage constant current charging method. Specifically, charging was performed using the following method. First, constant current charging was performed at 12 A, and when the charging voltage reached a switching voltage, the charging current was reduced to 6 A. The reduced charging current reduced the charging voltage, and when the charging voltage again reached the switching voltage, the charging current was reduced to 3 A. When the charging voltage again reached the switching voltage, the charging current was reduced to 1.5 A. When the charging voltage again reached the switching voltage, the charging current was maintained at 1.5 A, and charging continued until the charge capacity reached 42.48 Ah. In this manner, five-stage charging was performed. The switching voltage was 13.35 V.

[0058] A capacity confirmation test (3-hour rate capacity test) was conducted at 25°C every 50 cycles, and when the confirmed capacity was less than 43 Ah, the number of cycles was defined as the cycle life. Table 1 shows the cycle lives of samples S1, S2, and S3.

[0059]

[0060] In Table 1, the cycle life of sample S3 having the conventional configuration is set to 100%. In other words, if the cycle life is greater than 100%, it can be determined that good results have been obtained.

[0061] Table 1 shows that samples S1 and S2 according to this embodiment have a longer cycle life than sample S3 with a conventional configuration. It can also be seen that sample S2, in which the positive electrode strap contacts the partition wall before positive electrode growth occurs, has a longer cycle life than sample S1, in which the positive electrode strap contacts the partition wall during positive electrode growth. These results suggest that the positive electrode strap configuration according to this embodiment is effective in extending the life of lead-acid batteries.

[0062] 1-7. Effects As described above, the lead-acid battery 10 according to the first embodiment includes a battery case 20 having a plurality of cell chambers 24 separated by partition walls 23, a plurality of electrode plate groups 30 housed in each of the cell chambers 24, and an electrolyte injected into the cell chambers 24. Each electrode plate group 30 includes a plurality of positive electrode plates 30P and negative electrode plates 30N stacked alternately with separators SP interposed therebetween, a positive electrode strap 32P connected to an ear 31P provided on each positive electrode plate 30P, and a negative electrode strap 32P connected to an ear 31N provided on each negative electrode plate 30N. 2N, a positive electrode intermediate pole 34P extending from the positive electrode strap 32P along the partition wall 23, and a negative electrode intermediate pole 34N extending from the negative electrode strap 32N along the partition wall 23, the positive electrode intermediate pole 34P and the negative electrode intermediate pole 34N are connected by an inter-cell connection part 36 penetrating the partition wall 23, the liquid level of the electrolyte is located below the lower end of the inter-cell connection part 36, and when the direction in which the positive electrode plate 30P and the negative electrode plate 30N are arranged in each cell chamber 24 is defined as a first direction (front-rear direction), the length of the positive electrode strap 32P in the first direction is L １ The spacing between the partition walls 23 in the first direction is W, and the thickness of the positive electrode strap 32P is T １ In this case, (L １ ２ +T １ ２ ) １／２ The relational expression ≧W holds true.

[0063] With this configuration, when the positive plate 30P elongates and stress is applied to the positive strap 32P, the end 32P1 of the positive strap 32P opposite the positive intermediate electrode post 34P comes into contact with the partition wall 23, thereby suppressing warping of the positive strap 32P. This prevents stress from being applied from the positive strap 32P to the inter-cell connection 36 via the positive intermediate electrode post 34P. This prevents cracks from forming in the inter-cell connection 36, which would allow electrolyte and oxygen to enter the cracks and corrode the inter-cell connection 36. This prevents gas leaks that would compromise the airtightness between adjacent cell chambers 24.

[0064] In the first embodiment, the length of the negative electrode strap 32N in the first direction is L ２ In this case, 2W-(L１ ２ +T １ ２ ) １／２ ≦L ２ It is preferable that the following relational expression holds true.

[0065] When growth of the positive plate 30P causes warping of the positive strap 32P and the end 32P1 of the positive strap 32P opposite the positive intermediate electrode post 34P comes into contact with the partition wall 23, stress through the positive strap 32P may deform the partition wall 23 where the positive intermediate electrode post 34P of the positive strap 32P is provided or the partition wall 23 in contact with the end 32P1 of the positive strap 32P, potentially making it impossible to properly secure the positive strap 32P. However, with the above configuration, deformation of the partition wall 23 causes the end of the negative strap 32N to come into contact with the partition wall 23, eliminating room for deformation of the partition wall 23, making it easier to secure the positive strap 32P. This makes it easier to suppress gas leakage between adjacent cell chambers 24.

[0066] In the lead-acid battery 10 of the first embodiment, each plate pack 30 includes an end positive electrode strap 33P having a positive electrode end pole 35P connected to an external positive electrode terminal 60P of the lead-acid battery 10, and an end negative electrode strap 33N having a negative electrode end pole 35N connected to an external negative electrode terminal 60N of the lead-acid battery 10, and the length of the end positive electrode strap 33P in the first direction is L ３ If W=L ３ It is preferable that the following relational expression holds true.

[0067] With this configuration, the end positive electrode straps 33P come into contact with the partition walls 23, eliminating any room for deformation of the partition walls 23, and therefore the positive electrode straps 32P are more easily fixed.

[0068] In the first embodiment, the length of the end negative electrode strap 33N in the first direction is L ４ If W=L ４ It is preferable that the following relational expression holds true.

[0069] With this configuration, the end negative electrode strap 33N comes into contact with the partition wall 23, eliminating any room for deformation of the partition wall 23, and therefore the positive electrode strap 32P can be more easily fixed.

[0070] In the first embodiment, W=L １ It is preferable that the following relational expression holds true.

[0071] With this configuration, both ends of the positive electrode strap 32P are fixed by two adjacent partition walls 23, which makes it even easier to suppress warping of the positive electrode strap 32P.

[0072] In the first embodiment, the positive electrode strap 32P may be made of a Pb—Sn alloy that does not contain Sb.

[0073] In the first embodiment, the separator SP preferably comprises a glass mat impregnated with an electrolyte solution.

[0074] With this configuration, oxygen generated from the positive electrode plate 30P is consumed in a reaction in the negative electrode plate 30N, making it difficult for oxygen to be supplied to the vicinity of the inter-cell connection portion 36. Therefore, corrosion of the inter-cell connection portion 36 is further suppressed.

[0075] <Embodiment 2> Embodiment 2 of the present disclosure will be described with reference to Figs. 11 and 12. Unlike in Embodiment 1, the battery case 120 of the lead-acid battery 110 of Embodiment 2 includes a support portion 125. The configuration of the lead-acid battery 110 of Embodiment 2 is substantially the same as that of Embodiment 1 except for the support portion 125. Hereinafter, the same members as in Embodiment 1 will be assigned the same reference numerals, and descriptions that overlap with Embodiment 1 may be omitted. Note that in Embodiment 2, the dimensions (L １ , L ２ , L ３ , L ４ , T １ The relation between the distance (W) between the partition walls 23 in the front-rear direction and the distance (W) between the partition walls 23 in the front-rear direction does not necessarily have to be established.

[0076] 2-1. Support Configuration As shown in FIG. 11 , the battery case 120 includes a support 125 that protrudes forward or backward from the wall surface of the partition wall 23. The support 125 is disposed within the cell chamber 24 that houses the positive electrode strap 32P. As shown in FIG. 12 , the support 125 is disposed in each cell chamber 24 above the end 32P1 of the positive electrode strap 32P on the side opposite the positive electrode intermediate post 34 in the front-to-rear direction. The support 125 has a contact surface 125A that contacts the end 32P1 of the positive electrode strap 32P from above. With this configuration, contact between the contact surface 125A and the end 32P1 of the positive electrode strap 32P can prevent the positive electrode strap 32P from warping upward when positive electrode growth occurs.

[0077] In this embodiment, the end 32P1 of the positive electrode strap 32P and the contact surface 125A are in contact before positive electrode growth occurs (i.e., when the lead-acid battery 110 is unused). With this configuration, warping of the positive electrode strap 32P can be further suppressed compared to, for example, a configuration in which the end 32P1 of the positive electrode strap 32P and the contact surface 125A come into contact during the process of positive electrode growth.

[0078] The support portion 125 preferably has an inclined portion 125B that is inclined so that the protrusion dimension from the wall surface of the partition wall 23 increases downward. With this configuration, when the positive electrode strap 32P is accommodated in the cell chamber 24, the end portion 32P1 of the positive electrode strap 32P is brought into sliding contact with the inclined portion 125B, thereby deforming the partition wall 23 and guiding the end portion 32P1 of the positive electrode strap 32P to be disposed downward over the support portion 125.

[0079] 2-2. Effects The lead-acid battery 110 of the second embodiment includes a battery case 120 having a plurality of cell chambers 24 separated by partition walls 23, a plurality of electrode plate groups 30 housed in each of the cell chambers 24, and an electrolyte injected into the plurality of cell chambers 24. Each electrode plate group 30 includes a plurality of positive electrode plates 30P and negative electrode plates 30N stacked alternately with separators SP interposed therebetween, a positive electrode strap 32P connected to an ear 31P provided on each positive electrode plate 30P, a negative electrode strap 32N connected to an ear 31N provided on each negative electrode plate 30N, a positive electrode intermediate electrode post 34P extending from the positive electrode strap 32P along the partition wall 23, and a negative electrode intermediate electrode post 34N extending from the negative electrode strap 32N along the partition wall 23. The intermediate electrode column 34P and the negative intermediate electrode column 34N are connected by an inter-cell connection portion 36 that penetrates the partition wall 23. The liquid level of the electrolyte is located below the lower end of the inter-cell connection portion 36. When the direction in which the positive electrode plates 30P and the negative electrode plates 30N are arranged in each cell chamber 24 is defined as a first direction (front-to-back direction), the partition wall 23 includes a support portion 125 that is located at a position overlapping with an end portion 32P1 of the positive electrode strap 32P opposite to the positive electrode intermediate electrode column 34P when viewed from above. The support portion 125 is formed to protrude from the wall surface of the partition wall 23 in the first direction. The support portion 125 comes into contact with the end portion 32P1 of the positive electrode strap 32P opposite to the positive electrode intermediate electrode column 34P, thereby suppressing warping of the positive electrode strap 32P.

[0080] With this configuration, when the positive plate 30P elongates and stress is applied to the positive strap 32P, the end 32P1 of the positive strap 32P opposite the positive intermediate electrode post 34P comes into contact with the support portion 125, thereby suppressing warping of the positive strap 32P. This prevents stress from being applied from the positive strap 32P to the inter-cell connection 36 via the positive intermediate electrode post 34P. This prevents cracks from forming in the inter-cell connection 36, which would allow electrolyte and oxygen to enter the cracks and corrode the inter-cell connection 36. This prevents gas leaks that would compromise the airtightness between adjacent cell chambers 24.

[0081] In the second embodiment, the support portion 125 contacts the end portion 32P1 of the positive electrode strap 32P opposite to the positive electrode intermediate pole 34P when the lead-acid battery 110 is in an unused state.

[0082] According to this configuration, when the lead-acid battery 110 is not in use, the support portion 125 is in contact with the end portion 32P1 of the positive electrode strap 32P opposite the positive electrode intermediate electrode post 34P, which further reduces the possibility of cracks occurring in the inter-cell connection portion 36.

[0083] <Embodiment 3> Embodiment 3 of the present disclosure will be described with reference to Fig. 13 . Unlike in Embodiment 1, the battery case 220 of the lead-acid battery 210 of Embodiment 3 includes a support portion 225. The configuration of the lead-acid battery 210 of Embodiment 3 is substantially the same as that of Embodiment 1 except for the support portion 225. Hereinafter, the same members as in Embodiment 1 will be assigned the same reference numerals, and descriptions that overlap with Embodiment 1 may be omitted. Note that in Embodiment 3, the dimensions (L １ , L ２ , L ３ , L ４ , T １ The relation between the distance (W) between the partition walls 23 in the front-rear direction and the distance (W) between the partition walls 23 in the front-rear direction does not necessarily have to be established.

[0084] 3-1. Support Configuration As shown in FIG. 13 , the battery case 220 includes a support 225 recessed forward or backward from the wall surface of the partition wall 23. The support 225 is disposed within the cell chamber 24 that houses the positive electrode strap 32P. In each cell chamber 24, the support 225 houses the end 32P1 of the positive electrode strap 32P on the side opposite the positive electrode intermediate post 34 in the front-to-rear direction. Before positive electrode growth occurs, the support 225 has a contact surface 225A that contacts the end 32P1 of the positive electrode strap 32P from above. With this configuration, the contact between the contact surface 225A and the end 32P1 of the positive electrode strap 32P can prevent the positive electrode strap 32P from warping upward when positive electrode growth occurs.

[0085] 3-2. Effects The lead-acid battery 210 of the third embodiment includes a battery case 220 having a plurality of cell chambers 24 separated by partition walls 23, a plurality of electrode plate groups 30 housed in each of the cell chambers 24, and an electrolyte injected into the plurality of cell chambers 24. Each electrode plate group 30 includes a plurality of positive electrode plates 30P and negative electrode plates 30N stacked alternately with separators SP interposed therebetween, a positive electrode strap 32P connected to an ear 31P provided on each positive electrode plate 30P, a negative electrode strap 32N connected to an ear 31N provided on each negative electrode plate 30N, a positive electrode intermediate electrode post 34P extending from the positive electrode strap 32P along the partition wall 23, and a negative electrode intermediate electrode post 34N extending from the negative electrode strap 32N along the partition wall 23. The intermediate electrode column 34P and the negative intermediate electrode column 34N are connected by an inter-cell connection portion 36 that penetrates the partition wall 23. The liquid level of the electrolyte is located below the lower end of the inter-cell connection portion 36. When the direction in which the positive electrode plates 30P and the negative electrode plates 30N are arranged in each cell chamber 24 is defined as a first direction (front-to-back direction), the partition wall 23 includes a support portion 225 that is located at a position overlapping with an end portion 32P1 of the positive electrode strap 32P opposite the positive electrode intermediate electrode column 34P when viewed from above. The support portion 225 is recessed from the wall surface of the partition wall 23 in the first direction. The support portion 225 comes into contact with the end portion 32P1 of the positive electrode strap 32P opposite the positive electrode intermediate electrode column 34P, thereby suppressing warping of the positive electrode strap 32P.

[0086] With this configuration, when the positive plate 30P elongates and stress is applied to the positive strap 32P, the end 32P1 of the positive strap 32P opposite the positive intermediate electrode post 34P comes into contact with the support portion 225, thereby suppressing warping of the positive strap 32P. This prevents stress from being applied from the positive strap 32P to the inter-cell connection 36 via the positive intermediate electrode post 34P. This prevents cracks from forming in the inter-cell connection 36, which would allow electrolyte and oxygen to enter the cracks and corrode the inter-cell connection 36. This prevents gas leaks that would compromise the airtightness between adjacent cell chambers 24.

[0087] In the third embodiment, the support portion 225 contacts the end portion 32P1 of the positive electrode strap 32P opposite to the positive electrode intermediate pole 34P when the lead-acid battery 210 is in an unused state.

[0088] According to this configuration, when the lead-acid battery 210 is not in use, the support portion 225 is in contact with the end portion 32P1 of the positive electrode strap 32P opposite the positive electrode intermediate electrode post 34P, which further reduces the possibility of cracks occurring in the inter-cell connection portion 36.

[0089] <Other Embodiments> The present disclosure is not limited to the embodiments described above and illustrated in the drawings, but is intended to include all modifications within the meaning and scope of the claims as defined by the claims. The technical scope of the present disclosure also includes, for example, the following embodiments.

[0090] The support portion of the present disclosure may have a shape different from the support portions 125 and 225 described above, as long as it has a contact surface that comes into contact from above with the end portion of the positive electrode strap opposite the intermediate positive electrode post.

[0091] The support part of the present disclosure may be arranged so that the contact surface is not in contact with the end of the positive strap opposite the positive intermediate electrode post when the lead-acid battery is not in use, and so that the contact surface comes into contact with the end of the positive strap opposite the positive intermediate electrode post as positive electrode growth occurs during the process of using the lead-acid battery.

[0092] The shape of the positive electrode strap of the present disclosure may be different from that of the above embodiment. For example, the shape of the positive electrode strap in plan view does not have to be rectangular.

[0093] 10, 110, 210: Lead-acid battery 20, 120, 220: Battery case 23: Partition wall 24: Cell chamber 30: Plate group 30N: Negative electrode plate 30P: Positive electrode plate 31N: Ear portion of negative electrode plate 30N 31P: Ear portion of positive electrode plate 30P 32N: Negative electrode strap 32P: Positive electrode strap 33N: End negative electrode strap 33P: End positive electrode strap 34N: Negative electrode intermediate electrode post 34P: Positive electrode intermediate electrode post 35N: Negative electrode end electrode post 35P: Positive electrode end electrode post 36: Inter-cell connection portion 50: Lid member 60N: External negative electrode terminal 60P: External positive electrode terminal 125: Support portion 225: Support portion SP: Separator

Claims

1. A battery comprising: a battery case having a plurality of cell chambers separated by partition walls; a plurality of electrode plate groups housed in each of the plurality of cell chambers; and an electrolyte injected into the plurality of cell chambers, wherein each of the electrode plate groups comprises a plurality of positive and negative electrode plates alternately stacked with separators interposed therebetween; a positive electrode strap connected to a lug provided on each of the positive electrode plates; a negative electrode strap connected to a lug provided on each of the negative electrode plates; a positive electrode intermediate pole extending from the positive electrode strap along the partition wall; and a negative electrode intermediate pole extending from the negative electrode strap along the partition wall, wherein the positive electrode intermediate pole and the negative electrode intermediate pole are connected by an inter-cell connector penetrating the partition wall, wherein the liquid level of the electrolyte is located below a lower end of the inter-cell connector, and wherein, when the direction in which the positive electrode plates and the negative electrode plates are arranged in each of the cell chambers is defined as a first direction, the length of the positive electrode strap in the first direction is L １ the spacing between the partition walls in the first direction is W, and the thickness of the positive electrode strap is T １ In this case, (L １ ２ +T １ ２ ) １／２ ≧W is a relational expression for lead-acid batteries.

2. The length of the negative electrode strap in the first direction is L ２ When 2W-(L １ ２ +T １ ２ ) １／２ ≦L ２ The lead-acid battery according to claim 1, wherein the following relationship holds:

3. Each of the electrode plate groups comprises an end positive electrode strap having a positive end pole connected to the external positive terminal of the lead-acid battery, and an end negative electrode strap having a negative end pole connected to the external negative terminal of the lead-acid battery, and the length of the end positive electrode strap in the first direction is L ３ When W=L ３ The lead-acid battery according to claim 1, wherein the following relationship holds:

4. The length of the end negative electrode strap in the first direction is L ４ When W=L ４ The lead-acid battery according to claim 3, wherein the following relationship holds:

5. W=L １ The lead-acid battery according to claim 1, wherein the following relationship holds:

6. A battery container having a plurality of cell chambers separated by partition walls; a plurality of electrode plate groups housed in each of the plurality of cell chambers; and an electrolyte injected into the plurality of cell chambers, wherein each of the electrode plate groups comprises a plurality of positive and negative electrode plates alternately stacked with separators interposed therebetween, a positive electrode strap connected to an ear provided on each of the positive electrode plates, a negative electrode strap connected to an ear provided on each of the negative electrode plates, a positive electrode intermediate pole extending from the positive electrode strap along the partition wall, and a negative electrode intermediate pole extending from the negative electrode strap along the partition wall, wherein the positive electrode intermediate pole and the negative electrode intermediate pole are connected by an inter-cell connector penetrating the partition wall, and the liquid level of the electrolyte is located below a lower end of the inter-cell connector, and when the direction in which the positive electrode plates and the negative electrode plates are arranged in each of the cell chambers is defined as a first direction, a lead-acid battery, wherein the partition wall includes a support portion disposed at a position overlapping an end of the positive strap opposite the positive intermediate electrode post when viewed from above, the support portion being recessed or protruding from a wall surface of the partition wall in the first direction, and the support portion being in contact with the end of the positive strap opposite the positive intermediate electrode post.

7. The lead-acid battery according to claim 6, wherein the support portion is in contact with the end of the positive electrode strap opposite the positive electrode intermediate pole when the lead-acid battery is not in use.

8. The lead-acid battery according to claim 1 or claim 6, wherein the positive electrode strap is made of a Pb-Sn alloy that does not contain Sb.

9. The lead-acid battery according to claim 1 or 6, wherein the battery case is made of polypropylene resin.

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