JP6278220B2 - Control valve type lead acid battery - Google Patents

Description

  The present invention relates to the quality of a negative electrode weld of a control valve type lead-acid battery.

For lead-acid batteries, the electrolyte is held in an open-type liquid battery that is made by injecting an electrolyte into a battery case in which an electrode plate group is inserted, and a fine glass mat separator (retainer mat). In other words, there is a control valve type battery using a so-called oxygen cycle, in which oxygen gas generated in the above is reduced to water on the negative electrode active material.

  The liquid battery has a problem that maintenance of the liquid battery is troublesome because it is necessary to replenish purified water as appropriate because water in the electrolyte is lost due to electrolysis of water and natural evaporation that occur during charging. On the other hand, the control valve type lead-acid storage battery stores a plate group in which a retainer mat is interposed between a positive electrode plate and a negative electrode plate in a battery case, and holds an electrolyte solution in the electrode plate group. Therefore, its use is progressing in recent years.

  In the control valve type lead-acid battery, since the ear part of the negative electrode plate and the welded part of the strap are exposed from the electrolyte, the lead-acid battery is placed in a noble state from the equilibrium potential of lead even during charging. For this reason, there is a problem that the corrosion of the ear and the strap progresses due to the sulfuric acid that scoops up the ear and the strap and the oxygen generated from the positive electrode and breaks at the weld interface. Alloy compositions are being studied.

  Patent Document 1 describes that the ears of a negative electrode plate lattice made of a Pb—Ca—Sn alloy are welded to each other with a strap made of a Pb—Sn alloy added with 10 to 200 ppm of Se. Describes the mechanism that can suppress the stress corrosion cracking that occurs along the crystal grain boundary portion of the strap shelf, because the nuclei become the core of the crystal of the lead alloy particles during welding and promote the refinement of the crystal grains.

Patent Document 2 includes an electrode plate group having the same number of positive and negative electrode plates, and a ratio S / V between the total surface area (S) of the positive electrode plate and the volume value (V) of the electrode plate group is 2 In a lead-acid battery whose life characteristics are improved by setting it to 2 cm ⁻¹ or more, a negative electrode using a Pb—Sn alloy instead of a Pb—Sb alloy generally used in a liquid battery for the purpose of improving corrosion resistance It describes that a strap and a negative electrode plate using a Pb—Ca—Sn alloy are joined. In addition, although the Sn amount of the negative electrode strap alloy that can obtain the effect is 0.1% by mass or more, only the strap alloy containing 2.5% by mass of Sn is shown in the examples, There is no data showing the relationship between the corrosion resistance of the joint and the Sn content.

  Patent Document 3 uses a Pb—Ca—Sn alloy negative electrode grid and pure lead or a Pb—Sn alloy having a Sn content of 1.3 mass% or less for the negative electrode strap 6. It is described that the corrosion resistance of the welded portion of the strap and the strap body is improved, and the Ca content in the negative electrode lattice alloy is preferably 0.065% by mass or less because the corrosion resistance of the welded portion with the strap decreases. Has been.

JP-A-8-339794 JP 2009-104914 A JP 2002-175798 A

  In a control valve type lead-acid battery, the surface of the electrode plate is strongly pressed by applying moderate pressure to the electrode plate group, reducing the contact resistance of the electrode plate group, and suppressing the growth caused by corrosion of the positive electrode grid. By doing so, the battery life is extended. FIG. 1 shows the relationship between the pressure after formation and the float life. After forming, the tight pressure is measured in the airtight state after measuring the outer dimensions of the battery case in the electrode plate stacking direction. The battery is disassembled and the electrode plate group is taken out. It can be determined by measuring the pressure when the electrode plate group is pressed down to (dimension-battery thickness).

  When the tension pressure is 20 kPa or more, a float life of 10 years or more is obtained on average, and when the pressure is 20 kPa or less, the life becomes remarkably short. When the tension pressure exceeds 60 kPa, problems such as manufacturing defects and battery swelling occur. Therefore, practical tension is 20 kPa or more and 60 kPa or less.

By the way, even in the case of the control valve type lead-acid battery to which the tight pressure in the above range is applied, the life characteristics often vary. In a battery having a short life, it was observed that the welded portion between the negative electrode tab and the negative electrode strap was broken in a short period of time even though corrosion did not progress so much.
The present invention is intended to solve the above problem, and an object of the present invention is to suppress breakage of a welded portion in a control valve type lead-acid battery.

The present invention employs the following means in order to solve the above problems.
(1) In a control valve type lead storage battery in which an electrode plate group in which a retainer mat is interposed between a positive electrode plate and a negative electrode plate is housed in a battery case and an electrolyte is held in the electrode plate group, the ratio of (d) and a negative electrode plate ear length of (l) (d / l) is Ri 0.07 ≦ (d / l) ≦ 0.14 der, the alloy composition of the negative electrode plate ears , Pb—Ca—Sn alloy containing 0.06 to 0.13 mass% of Ca and 0.9 mass% or less of Sn, or Pb—Ca alloy, and welded to the negative electrode plate ear. alloy composition of the negative electrode strap, pure lead, or a valve-regulated lead-acid battery, characterized in Pb-Sn alloy der Rukoto containing 0.4 wt% of Sn.
(2) The alloy composition of the negative electrode tab is a Pb—Ca—Sn alloy or a Pb—Ca alloy containing 0.07 to 0.12 mass% of Ca and 0.75 mass% or less of Sn. And the control valve type lead acid battery of said (1) whose alloy composition of the said negative electrode strap is Pb-Sn type alloy which contains 0.3 mass% or less of pure lead or Sn.
(3) The ratio (d / l) between the ear thickness (d) of the negative electrode plate and the ear length (l) of the negative electrode plate is 0.09 ≦ (d / l) ≦ 0.13 ( The control valve type lead acid battery of 1) or (2).
(4) The alloy composition of the said negative electrode plate ear | edge part is Pb-Ca-Sn type alloy or Pb-Ca type alloy of Ca: 0.09-0.12 mass%, Sn: 0.75 mass% or less. The control valve type lead-acid battery according to any one of (1) to (3).
(5) After performing the test under the condition of performing 18 cycles of charging at a float voltage of 50 ° C. and 2.23 V for 27 days and then leaving at 25 ° C. for 3 days as one cycle, The valve-regulated lead-acid battery according to any one of (1) to (4), wherein no breakage occurs in the welded part.
(6) The valve-regulated lead-acid battery according to any one of (1) to (5) , wherein the current collector of the negative electrode plate of the electrode plate group is a cast current collector.

  ADVANTAGE OF THE INVENTION According to this invention, the battery in which a negative electrode welding part does not fracture | rupture in a control valve type lead acid battery can be provided.

Graph showing the relationship between tension and float life years Photomicrograph showing fracture of negative electrode ear due to intergranular cracking The figure which shows the thickness (d) and length (l) of an ear | edge part Graph showing the relationship between ear length (l) and ear corrosion amount The graph which shows the relationship between the ratio (d / l) of the ear thickness (d) and the ear length (l) and the stress generated in the welded portion Graph showing the relationship between Ca concentration and corrosion resistance in Pb-Ca alloys Graph showing the relationship between Sn concentration and corrosion resistance at different Ca concentrations in Pb-Ca-Sn alloys The graph which shows the relationship between Sn density | concentration and tensile strength in a Pb-Sn alloy Graph showing the relationship between Ca concentration and tensile strength at different Sn concentrations in Pb-Ca-Sn alloys

  As a result of investigating the cause of the breakage of the welded portion in the control valve type lead-acid battery, the present inventors usually have a float charge, the internal pressure of the battery is slightly higher than the external pressure due to gas generation, When the battery internal pressure becomes lower than the external air pressure due to charging suspension or discharge, a dent is generated in the battery case and the pressure on the electrode plate group becomes stronger, so stress is applied to the weld between the negative electrode strap and the negative electrode plate ear. It was estimated that cracks occurred at the grain boundaries and led to fracture even though corrosion was concentrated and corrosion did not progress much. Furthermore, as a result of earnest investigation, it has been found that the thickness and length of the negative electrode tab have an effect on the rate of progress of corrosion and the generation of stress in the weld.

  FIG. 3 shows the ear thickness (d) and the ear length (l) of the negative electrode plate. The negative electrode plate ear length is the distance from the lower end of the negative electrode strap to the lower frame of the upper plate frame of the negative electrode plate and the R portion below the ear.

When the ratio (d / l) between the ear thickness (d) and the ear length (l) of the negative electrode plate is small, the ear thickness is thin with respect to the ear length, so that breakage due to corrosion tends to occur. Further, since the ear length (l) is longer than the ear thickness, the exposed portion of the negative electrode ear increases and corrosion tends to proceed. FIG. 4 shows the relationship between the ear length and the ear corrosion amount with respect to the ear thickness (d) of 2.1 mm for two types of negative electrode lattice alloys in Examples to be described later. In addition, if the ear length (l) is long, the space between the strap and the electrode plate group increases, so that there is a problem that the volume energy density decreases.
The lower limit of (d / l) considering the corrosion resistance is 0.07, preferably 0.09.

On the other hand, when (d / l) is large, the thickness of the ear becomes thicker than the length of the ear, which is advantageous in terms of corrosion resistance. However, the mechanical strength of the negative electrode ear is increased, and high tension is applied to the electrode plate group. When stress is applied, stress is not relieved at the negative electrode ears, stress concentrates on the negative electrode plate ear-strap welded portion, and intergranular cracking is likely to occur. In addition, since the ear part is short with respect to the ear thickness, the distance between the negative electrode plate ear-strap welded part and the electrode plate group is shortened, and when the electrode plate group is subjected to high tension pressure, the negative electrode ear part In this case, the stress is not dispersed, so that intergranular cracking is likely to occur in the weld. FIG. 5 shows the relationship between (d / l) and the stress generated in the weld obtained by CAE analysis. When (d / l) exceeds 0.14, the stress curve rises. Yes.
Therefore, the upper limit of (d / l) is 0.14, preferably 0.13.

Regarding the alloy composition of the negative electrode plate ear and the strap, a combination that is excellent in corrosion resistance and that can relieve stress generated in the negative electrode plate ear-strap weld due to the high pressure of the electrode plate group is preferable.
As a result of examining combinations of various alloy compositions, the use of an alloy with excellent corrosion resistance for the negative electrode grid and the use of an alloy with low mechanical strength and easy absorption of stress for the negative electrode strap suppresses negative electrode ear corrosion and It was found that the stress applied to the strap-lattice ear welds can be relaxed to suppress grain boundary cracking.

FIG. 6 shows the relationship between Ca concentration and corrosion resistance in the Pb—Ca alloy, and FIG. 7 shows the relationship between Sn concentration and corrosion resistance at different Ca concentrations in the Pb—Ca—Sn alloy. The corrosion resistance test was performed under the following conditions.
75 ° C constant potential energization test (+40 mV vs Pb / PbSO ₄ )
Test electrode: Various lead alloy pieces (thickness 2.1mm)
Counter electrode: Pure lead Reference electrode: Pb / PbSO ₄ electrode Electrolyte: Specific gravity 1.28 Sulfuric acid The cross section of the test piece was observed after the test, and the thickness of the uncorroded portion was determined as follows: Ca: 0.09%, Sn: 0. The result was expressed as a relative value with the result of 3% as 100.

From FIG. 6 and FIG. 7, Pb—Ca—Sn alloy or Pb—Ca alloy containing 0.07 to 0.12% by mass of Ca and 0.75% by mass or less of Sn has high corrosion resistance. I understand that. This is because an alloy having this composition range forms fine crystal grains and suppresses intergranular cracking due to corrosion. Therefore, this composition range is preferable as the alloy of the negative electrode tab portion.

  FIG. 8 shows the relationship between the Sn concentration and the tensile strength in the Pb—Sn alloy. FIG. 9 shows the relationship between the Ca concentration and the tensile strength at different Sn concentrations in the Pb—Ca—Sn alloy. The tensile strength was measured as follows. After casting test pieces with different Ca and Sn concentrations and aging at room temperature for one month, a tensile strength test piece was manufactured by punching into a test piece shape of JIS13B, and the tensile strength was 10 mm / min. Measurements were made.

  According to FIG. 8, it can be seen that when Sn is added to pure lead in an amount exceeding 0.3 mass%, the tensile strength is remarkably increased. According to FIG. 9, Ca is added to pure lead or Pb—Sn alloy. However, it can be seen that an increase in tensile strength occurs. Therefore, preferable for the negative electrode strap is pure lead or a Pb—Sn alloy containing 0.3 mass% or less of Sn.

  Since the alloy composition is mixed in the negative electrode strap-lattice ear weld, the alloy composition of the negative electrode plate ear in the present invention is the composition of the lower portion of the negative electrode ear, and the alloy composition of the negative electrode strap is opposite to the weld surface. The alloy composition of the upper side strap.

  Hereinafter, an optimum embodiment of the present invention will be described. In carrying out the present invention, the embodiments can be appropriately changed in accordance with common sense of those skilled in the art and disclosure of prior art.

(Preparation of positive electrode plate)
A positive electrode current collector is prepared by casting a positive electrode grid having a thickness of 3.8 mm containing 0.06% by mass of Ca, 1.5% by mass of Sn, and 0.02% by mass of Al, and the balance being Pb and inevitable impurities. The body. It should be noted that the alloy composition, dimensions, design, and manufacturing method of casting, rolling sheet punching, etc. are arbitrary.
As an unformed positive electrode active material, 99.9% by mass of lead powder by ball milling and 0.1% by mass of synthetic resin fiber are pasted with sulfuric acid having a specific gravity of 1.16 at 25 ° C. and filled into a positive electrode grid. Aged and dried. The composition and density of the positive electrode active material are arbitrary.

(Preparation of negative electrode plate)
Pb-Ca- containing 0.06 to 0.13 mass% of Ca and 0 to 0.9 mass% of Sn, and additionally containing 0.02 mass% or less of Al with the balance being Pb and inevitable impurities A negative electrode grid having a thickness of 1.8 mm, 1.9 mm, and 2.1 mm was cast from a Sn-based alloy or a Pb—Ca-based alloy to obtain a negative electrode current collector. The dimensions and design of the negative electrode grid are arbitrary.
As a negative electrode active material, 98.3% by mass of lead powder of ball mill method, 0.1% by mass of synthetic resin fiber, 0.1% by mass of carbon black, 1.4% by mass of BaSO ₄ , and 0.1% by mass of lignin The paste was made into a paste with sulfuric acid having a specific gravity of 1.14 at 25 ° C., filled in a negative electrode lattice, and aged and dried. The composition and density of the negative electrode active material are arbitrary.

(Battery assembly)
A fine glass mat separator (retainer mat) was disposed between the positive electrode plate and the negative electrode plate to form an electrode plate group.
The electrode plate ears were cut to a predetermined size so that the ratio (d / l) of the ear thickness (d) of the negative electrode plate to the ear length (l) after welding was 0.06 to 0.15. The ears of the positive electrode plate were also cut to a predetermined size so that the height from the foot of the negative electrode group to the lower surface of the strap was the same as the height from the foot of the positive electrode group after welding to the lower surface of the strap.
The ear thickness and the ear length of the negative electrode plate can be appropriately changed depending on the battery capacity, the battery case size, and the like.
A positive electrode strap is formed by using pure lead as the additional lead for the positive electrode plate, and a Pb—Sn alloy containing pure lead and 0.1 to 0.4 mass% of Sn in the additional lead, or Ca. A negative electrode strap was formed using a Pb—Ca alloy containing 0.01% by mass.
Pressure is applied until the length of the electrode plate group reaches the inside dimension of the battery case, and the battery is accommodated in the battery case. Sulfuric acid is added as the electrolyte, and the battery case is formed. A lead-acid battery was used.

(Evaluation of lead-acid battery)
About the lead storage battery of No. 1-149 produced as mentioned above, the acceleration test was done on condition of the following.
Test conditions: After charging for 27 days at a float voltage of 50 ° C. and 2.23 V, left for 3 days at 25 ° C. for 18 cycles (equivalent to 7.5 years in terms of 25 ° C.)
A cross section of the welded portion of the negative electrode strap and ear part cut out from the battery after the test was observed with a metal microscope for intergranular cracking of the negative electrode welded part and corrosion amount of the negative electrode ear part.
The degree of progress of intergranular cracking was evaluated in the following four stages, and 4 was rejected.
1: No intergranular cracking 2: Progression of intergranular cracking is less than 30% of ear thickness 3: Progression of intergranular cracking is 30% or more of ear thickness (but not broken)
4: Breakage The amount of negative electrode ear corrosion was determined by the following equation.
Negative electrode ear corrosion amount (%) = (initial ear thickness−ear thickness after test) / initial ear thickness × 100

(Evaluation results)
(Ratio of ear thickness (d) and ear length (l) of negative electrode plate (d / l))
Table 1 shows the results of evaluating the ratio (d / l) of the ear thickness (d) and the ear length (l) of the negative electrode plate.

No. In Nos. 1 to 10, the strap is made of pure lead with low mechanical strength, and the negative electrode plate ear is made of an alloy of Ca: 0.09% by mass and Sn: 0.3% by mass with excellent corrosion resistance. However, the ratio of the negative electrode ear thickness to the ear length (d / l) is as small as 0.06. No. 1 is considered that since the negative electrode ear was long with respect to the thickness, the exposed portion increased, and corrosion and intergranular cracking progressed.
No. (d / l) as large as 0.15 In No. 10, since the negative electrode ear is short with respect to the thickness, the stress caused by the high pressure is not dispersed in the negative electrode ear, so that although the corrosion has not progressed, it is considered that the intergranular cracking of the weld has progressed.
On the other hand, No. whose (d / l) is 0.07 to 0.14. 2 to 9 do not cause such a problem.

  No. The batteries of Nos. 11 to 20 use a Pb—Ca—Sn alloy of Ca: 0.01 mass% and Sn: 0.1 mass% for the strap, and use an alloy having a slightly high mechanical strength by adding Ca. (See FIG. 9), the stress caused by the high pressure is less likely to be relaxed, and intergranular cracking is more likely to occur in the weld than the No. 1-10 batteries whose strap is pure lead. However, the batteries No. 12 to 19 having (d / l) of 0.07 to 0.14 have not been broken. No. 11 is No. As in 1, the ratio of negative electrode ear thickness to ear length (d / l) is as small as 0.06, and the ear length is long with respect to the ear thickness, so the exposed part increases and corrosion and intergranular cracking progress. It is thought that it broke. No. 20 has a large (d / l) of 0.15, and the stress is not easily dispersed. Therefore, coupled with the alloy composition of the strap, in which the stress is not easily relaxed, the amount of corrosion is small, but the fracture due to intergranular cracking has been reached. Conceivable.

  No. Nos. 21 to 30 are No. 1 except that Ca: 0.06 mass% and Sn: 0.3 mass% of Pb—Ca—Sn based alloys having low corrosion resistance were used for the negative electrode tab (negative electrode lattice). 10 to the same battery. In these batteries, since the corrosion resistance of the negative electrode tab portion is low (see FIG. 7), the amount of ear corrosion is larger than those of Nos. 1-10. However, the ratio of the negative electrode ear thickness to the ear length (d / l) is small and the exposed portion is long. No. 21 battery, No. 21 with large (d / l) and insufficient stress dispersion. With the exception of 30 batteries, no breakage occurred in the batteries Nos. 22 to 29 having (d / l) of 0.07 to 0.14.

  Table 2 shows the evaluation results for (d / l) in a battery having a negative electrode plate with an ear thickness of 1.9 mm.

  Even when the ear thickness is 1.9 mm, the battery of No. 31 to 38 with (d / l) in the range of 0.07 or more and 0.14 or less has a small amount of corrosion and breakage due to intergranular cracking. It was confirmed that it does not cause.

(Alloy composition of strap)
Table 3 shows the evaluation results of the alloy composition of the strap.
No. 40-44, no. 45-49, no. Nos. 50 to 54 are No. 1 in Table 1 except that the alloy composition of the strap was changed. 2, No. 5, no. 9 is the same battery.

No. 41-43, No. 46-48, No. 51-53 which is a Pb—Sn alloy containing 0.3% by mass or less of Sn (see FIG. 8) and has a strap having an alloy composition with low mechanical strength. The batteries of No. 2, No. 5, and No. 9 have almost the same degree of corrosion resistance and the intergranular cracking is suppressed.
In No. 40, No. 45, No. 50 with 0.01% Ca added to the strap, and No. 44, No. 49, No. 54 with 0.4% by mass Sn added, Since the mechanical strength of the strap is high (see FIG. 8 and FIG. 9), the stress caused by high pressure is less likely to be relaxed, and intergranular cracking is more likely to occur than in No.2, No.5, and No.9. This is because (d / l) is an appropriate ratio.
From the above results, the strap alloy is preferably pure lead or a Pb—Sn alloy containing 0.3 mass% or less of Sn.

(Alloy composition of negative electrode tab)
Tables 4 to 6 show that the ratio (d / l) of the thickness and length of the negative electrode plate ears is 0.07, 0.10, and 0.14, respectively, and the alloy composition of the strap is pure lead or Sn In the case of a 0.3% by mass Pb—Sn alloy, a battery was evaluated in which the amounts of Ca and Sn added in the alloy composition of the negative electrode tab portion were varied.

  In the alloy composition of the negative electrode plate lug (negative electrode lattice), No. 1 in which Ca is 0.06% by mass. 55, no. 56, no. 70-72, no. 87-89, no. 103-105, no. 119, no. 120, no. 134-136, and Ca No. which is 0.13 mass%. 68, No. 69, No. 85, No. 86, No. 101, No. 102, No. 117, No. 118, No. 86 132, no. 133, no. 148, no. Since 149 is a composition in which the crystal grains of the alloy are coarse, corrosion is likely to proceed (see FIG. 6), and intergranular cracking is likely to occur. However, since (d / l) is appropriate at 0.07 to 0.14, it does not break.

  No. in which Sn in the alloy composition of the negative electrode tab portion is 0.9% by mass. 60, no. 63, no. 67, no. 76, no. 80, no. 84, no. 93, no. 96, no. 100, no. 109, no. 112, no. 116, no. 124, no. 127, no. 131, no. 140, no. 143, no. No. 147, even if Ca in the composition is 0.07 to 0.12% by mass, because the crystal grains of the alloy are large, corrosion tends to proceed and intergranular cracking is likely to occur (see FIG. 7). However, since (d / l) is appropriate at 0.07 to 0.14, it does not break.

  For these batteries, No. in which the Ca in the alloy composition of the negative electrode tab portion is 0.07 to 0.12% by mass and Sn is 0.75% by mass or less. 57-59, no. 61, no. 62, no. 64-66, no. 73-75, no. 77-79, no. 81-83, no. 90-92, no. 94, no. 95, no. 97-99, no. 106-108, no. 110, no. 111, no. 113-115, no. 121-123, no. 125, no. 126, no. 128-130, no. 137-139, no. 141, no. 142, no. In 144 to 146, since the corrosion resistance of the ear part alloy is high, the amount of corrosion is particularly suppressed, and the progress of intergranular cracking is also suppressed in combination with the effect of (d / l).

  Therefore, the alloy composition of the negative electrode tab is Ca: 0.07 to 0.12% by mass, Sn: 0.75% by mass or less of Pb—Ca—Sn alloy or Pb—Ca alloy. Preferably, it is more preferably a Pb—Ca—Sn based alloy or a Pb—Ca based alloy of Ca: 0.09 to 0.12 mass% and Sn: 0.75 mass% or less.

From the above results, the negative electrode welded portion was fractured by setting the ratio (d / l) of the thickness and length of the negative electrode plate edge to 0.07 to 0.14, preferably 0.09 to 0.13. It has been found that a battery that is prevented and has a long life can be provided.
Further, it was found that when the strap composition and the alloy composition of the negative electrode plate ear were optimized, the negative electrode welded portion was more difficult to break and a long-life battery could be obtained.
In addition, it was confirmed that even in lead storage batteries with capacities other than 200 A · h, the same tendency is exhibited if the range of (d / l) is the above range. The same tendency was found for the strap composition and the alloy composition of the negative electrode tab.

The present invention can provide a long-life control valve type lead-acid battery by preventing breakage of the negative electrode weld, and thus is useful as a VRLA battery for stationary use and cycle use. Moreover, you may use for the VRLA battery for motor vehicles.

Claims (5)

In the control valve type lead-acid storage battery in which the electrode plate group in which the retainer mat is interposed between the positive electrode plate and the negative electrode plate is stored in the battery case, and the electrolyte solution is held in the electrode plate group ,
The ratio (d / l) between the thickness (d) of the negative electrode tab and the length (l) of the negative electrode tab is:
0.07 ≦ (d / l) ≦ 0.14,
The alloy composition of the negative electrode tab is a Pb—Ca—Sn alloy or a Pb—Ca alloy containing 0.06 to 0.13 mass% of Ca and 0.9 mass% or less of Sn,
And the alloy composition of the negative electrode strap welded to the said negative electrode plate ear | edge part is a Pb-Sn type alloy containing 0.4 mass% or less of pure lead or Sn, The control valve type lead acid battery characterized by the above-mentioned. The alloy composition of the negative electrode tab is a Pb—Ca—Sn alloy or a Pb—Ca alloy containing 0.07 to 0.12% by mass of Ca and 0.75% by mass or less of Sn,
2. The control valve according to claim 1, wherein the alloy composition of the negative electrode strap welded to the negative electrode tab is pure lead or a Pb—Sn alloy containing 0.3 mass% or less of Sn. Lead acid battery.   The ratio (d / l) between the thickness (d) of the negative electrode tab and the length (l) of the negative electrode tab is 0.09 ≦ d / l ≦ 0.13. The control valve type lead-acid battery according to claim 1 or 2. After the test was conducted under the conditions of 18 cycles of charging at 50 ° C. and a float voltage of 2.23 V for 27 days and then leaving at 25 ° C. for 3 days as a cycle, the welded portion between the negative electrode tab and the negative strap The control valve type lead-acid battery according to any one of claims 1 to 3, wherein the battery is not broken .   The control valve type lead acid battery according to any one of claims 1 to 4, wherein the current collector of the negative electrode plate of the electrode plate group is a cast current collector.