JP2009218222A - Lead-acid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent corrosion of an electrode plate lug in the vicinity of a negative electrode strap of a lead-acid battery used at high temperatures. <P>SOLUTION: A gap between the lower surface of a negative electrode strap 6 and the upper end of a separator 5 is made ≥6 mm when a glass mat 4 is jointly used as a constitution element of the separator, and is made ≥4 mm when the glass mat 4 is not jointly used as the constitution element of the separator. By this constitution, corrosion of the negative electrode lug can be prevented, and reliability and safety of the lead-acid battery can be secured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a safe and reliable lead storage battery.

  Lead-acid batteries are used in many fields such as automobiles, stationary machines, and electric cars because of their low cost and high reliability.

  On the other hand, the environment in which lead-acid batteries are used has recently become particularly severe. For example, in automobiles that use lead-acid batteries for automobiles, the amount of heat generated increases due to an increase in the cooler installation rate and higher engine output, while the inflow of cold air is insufficient due to the slant nose and high-density arrangement of various electrical components. It has been observed that lead-acid batteries installed in the hood are easily exposed to high temperatures and rise to nearly 100 ° C in summer.

  Furthermore, the increase in charging current due to the output increase of the alternator causes further increase in the temperature and overcharge of the lead storage battery. In addition, lead-acid batteries tend to be discharged more deeply due to an increase in electric devices such as rear wipers and power windows, an increase in accessories such as audio equipment, and an increase in dark current due to computerization.

  These factors of high temperature, overcharge, and deep discharge shorten the life of the lead-acid battery, and none of them are desirable, but in particular, high temperature is an important problem. This is because, when used at a high temperature for a long time, not only deterioration of the electrode plate is promoted, but also the negative electrode plate ear near the lower surface of the strap may be abnormally corroded in some cases.

  In the present invention, in order to prevent corrosion of the negative electrode plate ear, a number of tests were conducted, and the state of the battery in the test, particularly the state of the negative electrode strap in the electrolyte, was observed inside the specially manufactured lead acid battery with acid resistance. If the separator that does not use the glass mat is used, the distance from the upper end of the separator to the lower surface of the negative strap is 4 mm or more. When a separator with a glass mat as a constituent element is used, the distance from the upper end of the separator to the lower surface of the negative strap is set to 6 mm or more. However, it is clear that it is possible to prevent corrosion of the negative electrode tabs.

  According to the present invention, corrosion of the negative electrode ear can be prevented even under severe use conditions, and the reliability and safety of the lead storage battery can be ensured.

It is the schematic diagram which showed each position of the negative electrode strap cross section of a general lead acid battery for motor vehicles, and a positive electrode plate and a separator. It is the model which expanded the part of FIG.

  The present invention will be described below based on examples.

  FIG. 1 is a schematic diagram showing a cross section of a negative electrode strap and a position of a positive electrode plate / isolator of a general lead-acid battery for automobiles. FIG. 2 is an enlarged view of the portion of FIG.

  Reference numerals 1 and 2 are a negative electrode plate and a positive electrode plate, respectively, and 5 is a separator. As shown in the enlarged view of FIG. 2, the separator 5 includes a paper body 3 (thickness 0.3 mm) and a glass mat 4 (thickness 0.7 mm). The glass mat 4 is attached to the positive electrode plate 2. It is in contact. A paper body made of synthetic fiber and silica was used as the paper body. Ribs are not formed on the paper body. Reference numeral 1a denotes a negative electrode plate ear. The electrode plate pitch (distance between the centers of the same polarity electrode plates in the thickness direction) was set to 5.5 mm.

  Here, a casting grid made of an alloy containing lead-1.7 wt% antimony-0.25 wt% arsenic-0.015 wt% selenium and a small amount of impurities is formed on the positive electrode, and lead-0.065 wt% calcium- Using a grid obtained by expanding a rolled sheet made of 0.5 wt% tin-0.007 wt% aluminum alloy, the strap is lead-2.2 wt% antimony-0.25 wt% arsenic-0.015 wt% selenium. A general lead-acid battery for automobiles formed by a cast-on-strap (COS) method using an alloy consisting of: At this time, the length of the negative electrode plate ear 1a was variously changed, and the distance A from the upper end of the separator to the lower surface of the negative strap was changed to 2, 4, 6, 8, 10 mm. Needless to say, the length of the positive electrode tab also changes in the same manner as the length of the negative electrode plate.

  Next, these batteries were energized continuously in a water tank at a constant voltage of 14.8 V for 8 weeks. In order to accelerate the test, the water bath temperature was set to 80 ° C. and the electrolyte specific gravity was set to 1.40 (20 ° C. conversion). Because of the high-temperature test, water was decomposed and evaporated vigorously. During the test, water was replenished to the upper specified liquid surface line (upper level) once a day. In addition, during the test, the state near the negative electrode strap in the electrolyte was clearly observed with a specially manufactured acid observation device for internal observation of lead acid batteries. After the test, the battery was disassembled, the corrosion state of the negative electrode ear near the lower surface of the negative electrode strap was observed, and a detailed analysis was performed comparing with the state near the negative electrode strap under test.

  The analysis results are shown in Table 1.

  As is clear from Table 1, when the distance A from the upper end of the separator to the lower surface of the negative electrode strap was 4 mm or less, there was a large amount of gas accumulation on the lower surface of the negative electrode strap, and the degree of corrosion of the negative electrode ears was moderate to large. When A is 6 mm, the gas accumulation is reduced and the corrosion of the negative electrode ears is reduced, which is not a practically problematic level. When A was further increased to 8, 10 mm, the gas accumulation was reduced and the corrosion of the negative electrode ear was also reduced.

  It is speculated that the reason why the gas accumulation decreases as A becomes longer is that the oxygen and hydrogen gas generated from the positive and negative electrode plates during charging do not accumulate on the lower surface of the strap, and there are many opportunities to diffuse to other parts. The In addition, the reason why the corrosion of the negative electrode ear is more severe as the gas reservoir is larger is not clear, but is considered as follows. That is, when the gas accumulates, the surface of the negative electrode ear is not covered with a sufficient electrolytic solution, and is covered with a very thin electrolytic solution film. As a result, even during charging, the negative electrode ear surface is not sufficiently polarized to the cathode side, and is placed near the equilibrium potential of lead / lead sulfate. Then, the formed lead sulfate film is unstable and is more easily broken by the generated gas.

  The same test was performed using the same lead storage battery as in Example 1. However, for the positive electrode of the lead-acid battery, a grid obtained by expanding a rolled sheet made of lead-0.065 wt% calcium-1.3 wt% tin-0.01 wt% aluminum alloy is used, and a glass mat is used as the separator. Not used, the surface that contacts the negative electrode plate is relatively low (about 0.25 mm) and a fine rib with a pitch of about 5 mm is provided, and the surface that contacts the positive electrode plate is relatively high (about 0.2 mm). 5 mm) and microporous polyethylene (substrate thickness 0.25 mm) provided with coarse ribs having a pitch of about 10 mm were used. Moreover, this microporous polyethylene was made into a bag shape, and the negative electrode plate was put in it.

  The analysis results are shown in Table 2.

  As in the case of Example 1, there was a tendency that the longer A was, the smaller the gas accumulation at the lower surface of the negative electrode strap and the less the negative electrode ear corrosion, but in this example, A was as short as 4 mm. However, there was little gas accumulation, and it was not at a level that would cause problems in practice.

  Although the tendency is the same, even though A is shorter than in the case of Example 1, it is not clear why the gas accumulation on the lower surface of the negative electrode strap is small. However, the separator of this example does not have a glass mat as a constituent element. Also, because the ribs are provided, the generated oxygen gas or hydrogen gas is presumed to have diffused more quickly than when the electrode plate is pressed with a separator made of glass mat. .

1. Negative electrode plate 1a. 1. Negative electrode plate ear Positive electrode plate Paper body 4. Glass mat 5. Isolator 6. Negative strap

Claims (2)

  A lead-acid battery characterized in that a separator that does not include a glass mat is used, and the distance from the upper end of the separator to the lower surface of the negative strap is 4 mm or more.   A lead-acid battery characterized in that a separator having a glass mat as a constituent element is used, and the distance from the upper end of the separator to the lower surface of the negative strap is 6 mm or more.