JP2018056027A - Lead battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead battery capable of efficiently suppressing corrosion in a bonding part of a strap and an ear part.SOLUTION: A positive electrode of a lead battery, includes: a plurality of positive electrode plates P each having an ear part 2b; a strap Ps in which one part of the ear part 2b is embedded; a first lead-tin alloy layer 2 Lthat is formed so as to cover a part of a surface of the ear part 2b to be exposed without being embedded to the strap Ps; a second lead-tin alloy layer 2 Lthat is formed between the part and the strap Ps so as to cover the part of the surface of the ear part 2b to be embedded in the strap Ps; and a fillet 2F made from lead-tin alloy formed in a root part of the ear part 2b to the strap Ps. A negative electrode of the lead battery has a similar construction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a lead acid battery.

  As one mode of a lead storage battery, a battery including a plurality of electrode plates each having an ear part and a strap in which a part of each ear part is embedded is known (see Patent Document 1). In Patent Document 1, in order to suppress abnormal corrosion of the negative electrode strap of the lead-acid battery, a fillet is provided at the base of the ear portion with respect to the negative electrode strap, and a lead-tin alloy layer is formed at a part of the joint interface between the negative electrode strap and the ear portion. Disclose the non-existing alloy uncoated portion. In addition, the electrode plate (a positive electrode plate and a negative electrode plate) of a lead storage battery is generally configured by a lattice body (current collector plate) having ears and an active material filled in the lattice body.

JP 11-329399 A

  Lead acid batteries are secondary batteries excellent in cost, safety, and reliability, and are used in various applications. One of the uses of the lead storage battery is an auxiliary battery for a hybrid vehicle (HV) or an electric vehicle (EV). A lead storage battery used as an auxiliary battery (hereinafter referred to as “auxiliary lead storage battery”) supplies electricity to motors and engine control computers and general electrical components of the above-mentioned vehicle types.

  The auxiliary lead-acid battery for HV or EV has a technical problem that the ears of the lattice body are easily cut from the base of the strap. This is thought to be due to the progress of corrosion from the gap at the base of the ear with respect to the strap, and the reason why the corrosion is likely to proceed is that the grain boundaries generated by recrystallization of the ear remaining in the strap are caused by corrosion. Inferred to be sensitive. As a countermeasure, it is conceivable to provide a fillet resistant to corrosion at the base of the ear portion with respect to the strap (Patent Document 1). Thereby, it can suppress that the crystal grain boundary produced by recrystallization is exposed to electrolyte solution, As a result, progress of corrosion of both junction parts can be suppressed.

  As described in Patent Document 1, it can be said that providing a fillet at the base of the ear is an effective means to some extent. However, this measure can stably form a fillet that is effective against corrosion, maintain high mechanical strength of the ears, and suppress the ear thinning when welding the ears and straps It was difficult to overcome technical problems such as to do, and there was still room for improvement. In particular, in the invention described in Patent Document 1, a fillet made of a lead-tin alloy is provided at the base of the ear part, but there is no lead-tin alloy layer at the interface between the strap and the ear part. It is considered that crystal grain boundaries are formed in the ear, and the mechanical strength of the ears is anxious.

  This invention is made | formed in view of the said situation, and it aims at providing the lead storage battery which can fully suppress the corrosion in the junction part of a strap and an ear | edge part.

  The lead storage battery according to the present invention includes a plurality of electrode plates each having an ear part, a strap in which a part of the ear part is embedded, and a part of the surface of the ear part that is exposed without being embedded in the strap. A first lead-tin alloy layer formed so as to cover the surface and a second lead formed between the portion and the strap so as to cover a portion of the surface of the ear portion embedded in the strap A tin alloy layer and a fillet formed at the base of the ear with respect to the strap;

  For example, an auxiliary lead-acid battery mounted on an HV or EV is supplied with electricity from a driving battery (for example, a nickel metal hydride battery) to maintain high charge / discharge, so that the lattice body (particularly the ear portion of the lattice body) Battery deterioration progresses due to corrosion. As described above, in the lead storage battery according to the present invention, in addition to the first lead-tin alloy layer and the fillet, the second lead-tin alloy layer is provided between the portion embedded in the strap in the ear portion and the strap. Since it is formed, corrosion caused by the formation of crystal grain boundaries at these interfaces can be sufficiently suppressed. Thereby, the high mechanical strength of the ear can be maintained for a sufficiently long period. Currently, in lead-acid batteries for HV or EV, auxiliary lead-acid batteries using lead-antimony alloy for the grid of the positive plate and lead-calcium alloy for the grid of the negative plate are mainly used. Yes. By forming the second lead-tin alloy layer when the ears of the lattice body made of these alloys and the strap are welded, the strength of these joints can be increased.

  The strap in the lead storage battery according to the present invention is preferably made of a lead-calcium alloy from the viewpoint of achieving further excellent corrosion resistance.

  It is preferable that the lead acid battery which concerns on this invention is a control valve type lead acid battery (VRLA: Valve Regulated Lead Acid). Since HV or EV has a limited space in the engine room, an auxiliary lead-acid battery may be mounted in a compartment other than the engine room (for example, in a vehicle compartment such as a trunk room or under a rear seat). Since the gas generated from the lead storage battery becomes a problem when the mounting location is in the vehicle interior, it is preferable to employ the control valve type lead storage battery as the auxiliary battery as described above.

  ADVANTAGE OF THE INVENTION According to this invention, the lead acid battery which can fully suppress the corrosion in the junction part of a strap and an ear | edge part is provided.

FIG. 1 is a perspective view showing an embodiment of a lead storage battery according to the present invention. FIG. 2A is a plan view showing an example of the positive electrode lattice body, and FIG. 2B is a plan view showing an example of the negative electrode lattice body. FIG. 3A is a cross-sectional view schematically showing the structure of the junction between the strap and the plurality of ears in the positive electrode, and FIG. 3B schematically shows the structure of the junction between the strap and the plurality of ears in the negative electrode. FIG.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. For example, in the following embodiment, a lead storage battery used as an auxiliary battery mounted on HV or EV is illustrated, but the present invention is not limited to this. The materials exemplified below may be used alone or in combination of two or more unless otherwise specified. The content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. The numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present specification, the upper limit value or lower limit value of a numerical range of a certain step may be replaced with the upper limit value or lower limit value of the numerical range of another step. In the numerical range described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples.

<Lead battery>
A lead storage battery 1 shown in FIG. 1 includes a plurality of positive plates P, a plurality of negative plates N, a plurality of separators 4 provided between the positive plates P and the negative plates N, a battery case 5, and a lid 6. With. An electrode group in which positive plates P, separators 4 and negative plates N are alternately stacked is housed in a battery case 5. The lead storage battery 1 is manufactured by accommodating a plate group in a battery case 5 and closing it with a lid 6, and then injecting a predetermined amount of electrolyte to perform battery case formation.

  The lead storage battery 1 is used as an auxiliary battery mounted on an HV or EV. When the fully charged state is 100%, the charged state (typically 95 to 100% (preferably 98 to 100%)) ( SOC). The lead storage battery 1 is preferably a control valve type lead storage battery from the viewpoint of sealing. The control valve type lead-acid battery has the advantage that there is no flowing free electrolyte inside the battery and the electrolyte does not spill even when the battery is placed sideways. In addition, even when an electrolysis reaction of water occurs during charging, the generation of hydrogen gas is suppressed, and the generated oxygen gas is also reduced to the original water by a chemical reaction on the surface of the negative electrode plate N and returned to the electrolyte. In addition, there is an advantage that moisture is not easily lost, and checking of the amount of liquid and rehydration are unnecessary. Of the oxygen gas generated in the positive electrode plate P during charging, excess gas that could not be absorbed by the gas absorption reaction in the negative electrode plate N is discharged from the control valve 7 to the outside of the battery case 5.

  The battery case 5 may be divided into a plurality of cell chambers. In this case, electrode plate groups are accommodated in each cell chamber, and straps having opposite polarities to the electrode plate groups accommodated in the adjacent cell chambers are mutually connected. By connecting to, a lead storage battery having a predetermined rated voltage and rated capacity is configured. On the other hand, in the case of a single cell battery case, a battery having a predetermined voltage or capacity can be configured by connecting terminals of a plurality of lead storage batteries in parallel or in series using a conductive plate.

(Positive electrode plate)
The positive electrode plate P includes a positive electrode lattice body 2 shown in FIG. 2A and a positive electrode active material filled between the lattices of the positive electrode lattice body 2. The positive electrode grid body 2 is not particularly limited, but is made of, for example, a lead alloy containing lead as a main component, and may contain one or more elements selected from antimony, tin, calcium, and aluminum as components other than lead. . The lead alloy may further contain, for example, bismuth and / or silver. The antimony concentration of the lead alloy constituting the positive electrode grid 2 is, for example, 0.5 to 5.0% by mass based on the total mass of the lead alloy. The positive grid 2 may be obtained by casting the lead alloy, or an expanded grid made of the lead alloy.

  The positive electrode grid body 2 includes a grid body 2a and ears 2b provided so as to protrude outward from the grid body 2a. A positive electrode plate P is obtained by filling a paste-like active material between the grids of the positive electrode grid 2 and then performing an aging step and a drying step. The active material used for manufacturing the positive electrode plate P is not particularly limited, but is a paste-like active material obtained by mixing lead powder and red lead, dilute sulfuric acid, water and additives. It's okay. The additive is added, for example, for the purpose of increasing the strength of the active material, and may be PET (polyethylene terephthalate), acrylic fiber, or the like. In the aging step, for example, aging is performed for 4 to 40 hours in an environment at a temperature of 75 to 85 ° C. and a relative humidity of 95 to 98%, and then aging is performed for 20 hours or more in an environment of 50 to 65 ° C. and a relative humidity of 50% or more. . In the drying step, for example, drying is performed for 20 to 40 hours in an environment at a temperature of 40 to 65 ° C.

By connecting the ears 2b of each positive electrode grid body 2 via the straps Ps, the plurality of positive electrode plates P are electrically connected to each other. The strap Ps has a shelf portion Pt that is a portion where a plurality of ear portions 2b are joined. A positive pole 8 a for connecting the positive plate P to the positive terminal 8 is provided on the positive strap Ps. As shown in FIG. 3A, a part on the upper end side of the ear portion 2b is embedded in the shelf portion Pt. Of the surface of the ear portion 2b, the first lead so as to cover the portion exposed without being embedded in the ledge Pt strap Ps - tin alloy layer 2L ₁ is formed. The first lead - the thickness of the tin alloy layer 2L ₁ is preferably 6～15Myuemu, more preferably from 8 to 12 .mu.m, more preferably about 10 [mu] m. The first lead - lead constituting the tin alloy layer 2L ₁ - tin concentrations of tin alloy is preferably 20 to 70 wt%, more preferably from 58 to 62 wt%.

Of the surface of the ear portion 2b, a second lead between said portion and the ledge Pt to cover the portion that is embedded in the ledge Pt strap Ps - tin alloy layer 2L ₂ are formed. The second lead - the thickness of the tin alloy layer 2L ₂ is preferably 6～15Myuemu, more preferably from 8 to 12 .mu.m, more preferably about 10 [mu] m. The second lead - lead constituting the tin alloy layer 2L ₂ - Tin concentration of the tin alloy is preferably 20 to 70 wt%, more preferably from 58 to 62 wt%.

  A fillet 2F is formed at the base of the ear 2b with respect to the shelf Pt of the strap Ps. The tin concentration of the lead-tin alloy constituting the fillet 2F is preferably 20 to 70% by mass, more preferably 58 to 62% by mass.

By adopting these structures (first and second lead-tin alloy layers 2L ₁ and 2L _{2 and} fillet 2F), corrosion caused by generation of crystal grain boundaries at the interface between the ear portion 2b and the shelf portion Pt. Can be sufficiently suppressed. From the viewpoint of further reliably suppressing corrosion at the interface, the first lead-tin alloy layer 2L ₂ covers the entire portion of the surface of the ear portion 2b embedded in the shelf portion Pt. preferable. In order to realize this, prior to joining the ear portion 2b and the shelf portion Pt by welding, the above lead-tin alloy melt may be applied to the surface of the ear portion 2b. What is necessary is just to immerse the ear | edge part 2b in a melt. The dipping time (application time) is preferably 6 to 14 seconds, more preferably 8 to 12 seconds. The temperature of the melt to be soaked is preferably 215 to 245 ° C, more preferably 220 to 240 ° C.

  The welding of the ear portion 2b to the strap Ps (shelf portion Pt) may be performed by, for example, the Caston method or the burning method, and is preferably performed by the Caston method from the viewpoint of easy temperature control. In the caston method, the ear part 2b is arranged on the upper part of the mold, and the molten lead alloy is poured into the mold and then solidified to form the shelf part Pt, and the ear part 2b with respect to the strap Ps (shelf part Pt). Embed the upper end of the. Although depending on the composition of the lead alloy constituting the shelf Pt, the temperature of the mold in the Caston method is preferably 220 to 250 ° C, more preferably 230 to 240 ° C, and the temperature of the pouring poured into the mold is Preferably it is 390-470 degreeC, More preferably, it is 400-460 degreeC.

  As a lead alloy constituting the strap Ps (particularly, the shelf portion Pt), it is preferable to employ a lead-calcium alloy. The calcium concentration of the lead-calcium alloy is preferably 0.5 to 5.0% by mass.

(Negative electrode plate)
The negative electrode plate N includes the negative electrode lattice body 3 shown in FIG. 2B and a negative electrode active material filled between the lattices of the negative electrode lattice body 3. The negative electrode lattice body 3 is not particularly limited, but is made of, for example, a lead alloy containing lead as a main component, and may contain one or more elements selected from calcium, tin and / or bismuth as components other than lead. Good. The calcium concentration of the lead alloy constituting the negative electrode grid 3 is, for example, 0.06 to 0.10% by mass based on the total mass of the lead alloy. The negative electrode lattice body 3 may be obtained by casting the lead alloy, or an expanded lattice made of the lead alloy.

The negative electrode lattice body 3 includes a lattice body portion 3a and ear portions 3b provided so as to protrude outward from the lattice body portion 3a. A negative electrode plate N is obtained by filling a paste-like active material between the grids of the negative electrode grid 3 and then performing an aging step and a drying step. The active material used for manufacturing the negative electrode plate N is not particularly limited, but may be a paste-like active material obtained by mixing lead powder, dilute sulfuric acid, water, and additives. . Additives include barium sulfate (BaSO ₄ ) that functions as a nucleus of lead sulfate (PbSO ₄ ) generated during discharge, organic compounds such as lignin that suppress crystal growth of negative electrode active material particles, carbon materials that impart conductivity, etc. It may be. Similar to the positive electrode plate P, the additive may be PET, acrylic fiber, or the like. In the aging step, for example, aging is performed for about 24 hours in an environment having a temperature of 37 to 43 ° C. and a relative humidity of 92 to 98%, and then, for example, 16 hours or more in an environment having a temperature of 37 to 43 ° C. and a relative humidity of 50% or more. Mature. In the drying step, for example, drying is performed for 12 to 40 hours in an environment at a temperature of 35 to 45 ° C.

The plurality of negative electrode plates N are electrically connected to each other by connecting the ear portions 3b of the negative electrode lattice bodies 3 via the straps Ns. The strap Ns has a shelf portion Nt that is a portion where a plurality of ear portions 3b are joined. The negative strap Ns is provided with a negative pole 9 a for connecting the negative plate N to the negative terminal 9. As shown in FIG. 3B, a part on the upper end side of the ear portion 3b is embedded in the shelf portion Nt. Of the surface of the ear portion 3b, the first lead so as to cover the portion exposed without being embedded in the ledge Nt strap Ns - tin alloy layer 3L ₁ is formed. The first lead - the thickness of the tin alloy layer 3L ₁ is preferably 6～15Myuemu, more preferably from 8 to 12 .mu.m, more preferably about 10 [mu] m. The first lead - lead constituting the tin alloy layer 3L ₁ - tin concentrations of tin alloy is preferably 20 to 70 wt%, more preferably from 58 to 62 wt%.

Of the surface of the ear portion 3b, a second lead between said portion and the ledge Nt to cover the portion that is embedded in the ledge Nt strap Ns - tin alloy layer 3L ₂ is formed. The second lead - the thickness of the tin alloy layer 3L ₂ is preferably 6～15Myuemu, more preferably from 8 to 12 .mu.m, more preferably about 10 [mu] m. The second lead - lead constituting the tin alloy layer 3L ₂ - Tin concentration of the tin alloy is preferably 20 to 70 wt%, more preferably from 58 to 62 wt%.

  A fillet 3F is formed at the base of the ear 3b with respect to the shelf Nt of the strap Ns. The tin concentration of the lead-tin alloy constituting the fillet 3F is preferably 20 to 70% by mass, more preferably 58 to 62% by mass.

By adopting these structures (first and second lead-tin alloy layers 3L ₁ and 3L _{2 and} fillet 3F), corrosion caused by generation of crystal grain boundaries at the interface between the ear 3b and the shelf Nt Can be sufficiently suppressed. Corrosion more terms more reliably suppress in the interface, the first lead - that tin alloy layer 3L ₂ covers the entire portion which is embedded in the shelf portion Nt of the surfaces of the ear portion 3b preferable. In order to realize this, prior to joining the ear portion 3b and the shelf portion Nt by welding, the above lead-tin alloy melt may be applied to the surface of the ear portion 3b, more specifically, What is necessary is just to immerse the ear | edge part 3b in a melt. The dipping time (application time) is preferably 6 to 14 seconds, more preferably 8 to 12 seconds. The temperature of the melt to be soaked is preferably 215 to 245 ° C, more preferably 220 to 240 ° C.

  The welding of the ear portion 3b to the strap Ns (shelf Nt) may be performed by, for example, the Caston method or the burning method, and is preferably performed by the Caston method from the viewpoint of easy temperature control. In the caston method, the ear portion 3b is arranged on the upper portion of the mold, and the molten lead alloy is poured into the mold and then solidified to form the shelf portion Nt, and the ear portion 3b with respect to the strap Ns (shelf portion Nt). Embed the upper end of the. Although it depends on the composition of the lead alloy constituting the shelf Nt, the temperature of the mold in the Caston method is preferably 220 to 250 ° C, more preferably 230 to 240 ° C, and the temperature of the pouring poured into the mold is Preferably it is 390-470 degreeC, More preferably, it is 400-460 degreeC.

  As a lead alloy constituting the strap Ns (especially the shelf Nt), it is preferable to employ a lead-calcium alloy. The calcium concentration of the lead-calcium alloy is preferably 0.5 to 5.0% by mass.

(Separator)
The separator 4 is, for example, an electrolytic solution holder (retainer) that holds an electrolytic solution such as dilute sulfuric acid. The separator 4 may have a plate shape as shown in FIG. 1, and may have a bag shape that can wrap the positive electrode plate P in other embodiments, for example. The separator 4 is not particularly limited as long as it prevents the electrical contact between the positive electrode plate P and the negative electrode plate N while holding the electrolytic solution and allowing sulfate ions and hydrogen ions (protons) to pass therethrough. It is not a thing. The separator 4 is preferably an AGM (Absorbed Glass Mat) made from fine glass fibers (cotton). Although the thickness per separator 4 is arbitrarily set, it may be, for example, 1 to 3 mm.

(Other)
The battery case 5 is not particularly limited as long as it can accommodate an electrode plate group including the positive electrode plate P, the negative electrode plate N, and the separator 4 and has resistance to an electrolytic solution such as dilute sulfuric acid. The battery case 5 is made of PP (polypropylene), PE (polyethylene), ABS resin, or the like. In one embodiment, the inside of the battery case may be divided into a plurality of cell chambers. In this case, an electrode plate group is accommodated in each cell chamber. Then, the electrode plate group accommodated in one cell chamber and the electrode plate group accommodated in the cell chamber adjacent thereto are connected to each other so that the straps of opposite polarities are connected to each other. A lead-acid battery having a rated voltage or a rated capacity is configured.

  The lid 6 is formed of the same material as the battery case 5, for example, so that the battery case 5 can be sealed. The lid 6 is attached to the battery case 5 by, for example, heat sealing or bonding using an adhesive.

  The electrolyte solution of the lead storage battery 1 is dilute sulfuric acid, for example. The electrolytic solution preferably contains aluminum ions. The aluminum ion concentration of the electrolytic solution is preferably 0.002 to 0.2 mol / L, based on the total amount of the electrolytic solution, from the viewpoint of further improving charge acceptance and cycle characteristics, and 0.003 to 0.1 mol / L. Is more preferable, and 0.005-0.08 mol / L is still more preferable. The concentration of aluminum ions in the electrolytic solution can also be measured by, for example, ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy). The electrolytic solution is contained not only in the separator 4 but also in the positive electrode plate and the negative electrode plate.

  A casting grid made of a lead-antimony alloy (antimony concentration: in the range of 0.5 to 5.0% by mass) is used as the positive electrode lattice body, and a lead-calcium alloy (calcium concentration: 0.06- A cast grid consisting of 0.10% by mass) was used. Paste materials were used as active materials for the positive electrode and the negative electrode, respectively, and kneaded onto the positive electrode lattice and the negative electrode lattice, respectively. A plurality of these electrode plates were arranged via separators, and a plurality of ears and straps were joined to each electrode plate group by strap welding by the Caston method.

  Prior to the strap welding, the surface of the ears of the positive electrode plate and the negative electrode plate is subjected to scratching treatment with a blade so that the welding state is good, and then a paste-like flux is applied, and then the lead-tin alloy The melt was applied. Application of the lead-tin alloy melt was performed by immersing the electrode plate ears in the melt. As shown in Table 1, the tin concentration of the lead-tin alloy to be applied to the ear, the temperature and the immersion time, and the temperature of the soot pouring the lead-tin alloy into the mold (salt temperature) and the mold temperature were changed, Ear and strap joints were obtained by welding, respectively.

  The cross section of the joint between the ear part and the strap is confirmed with a microscope, and a lead-tin alloy layer (first and second lead-tin alloy layers) is formed so as to cover the entire ear part, and the root of the ear part is formed. The test example in which the fillet was formed in this part was taken as an example (Examples 1 to 5). When the temperature of the lead-tin alloy melt was too high, the ears melted out, resulting in the occurrence of ear thinning (Comparative Examples 1 and 2). In addition, it is guessed that when the wrinkle temperature or the mold temperature is too high, the thickness of the lead-tin alloy layer at the interface between the ear portion and the strap increases and the ear wrinkle occurs. Also, if the soot temperature is too high, the strap side will be burned, and if the mold temperature is too high, the weld will be hard to solidify. When various temperatures were too low, fillets were not formed, welding was not performed, or tearing occurred by hand (Comparative Example 3).

<Production of control valve type lead acid battery>
Three positive electrode plates and four negative electrode plates were alternately laminated via a glass nonwoven fabric to prepare an electrode plate group. The prepared electrode plate group was inserted into the battery case, and after the positive electrode terminal and the negative electrode terminal were welded to the electrode plate group, the battery case was sealed. After injecting an electrolytic solution containing dilute sulfuric acid as a main component through the exhaust plug opening, a battery case was formed. Thereby, the control valve type lead acid battery was obtained. The battery tank formation conditions were as follows: water temperature: 40 ° C., amount of electricity applied: 250% of the theoretical amount of electricity generated by the positive electrode active material, and time: 60 hours.

(Life test)
A high pack LHM-38-12 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was used as a lead storage battery, and a high temperature accelerated life test was carried out by charging and discharging under conditions of a temperature of 65 ° C. and a humidity of 30%. Tables 1 and 2 show the results (5HR discharge time equivalent to 14 years).

1 ... lead storage battery, 2b, 3b ... ear, Ps, Ns ... straps, _2L 1, 3L 1 _... first lead - tin alloy layer, _2L 2, 3L 2 _... second lead - tin alloy layer, 2F, 3F ... fillet, 7 ... control valve, P ... positive electrode plate, N ... negative electrode plate.

Claims (3)

A plurality of electrode plates each having an ear;
A strap in which a part of the ear is embedded;
A first lead-tin alloy layer formed to cover a portion of the surface of the ear portion that is exposed without being embedded in the strap;
A second lead-tin alloy layer formed between the portion of the surface of the ear portion and the strap so as to cover the portion embedded in the strap;
A fillet formed at the base of the ear with respect to the strap;
A lead acid battery.   The lead acid battery according to claim 1, wherein the strap is made of a lead-calcium alloy.   The lead acid battery of Claim 1 or 2 which is a control valve type lead acid battery.

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