DE3139352A1 - SEALED, MAINTENANCE-FREE LEAD / ACID BATTERY FOR BUFFER APPLICATIONS - Google Patents

Description

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GOULD INC., October 2, 1981

Gould Center, GD-54

Rolling Meadows, Illinois 6008,
United States

Sealed, maintenance-free lead / acid battery for buffer applications

Description:

This invention relates to lead-acid batteries, and more particularly, the invention relates to sealed, maintenance-free lead-acid batteries for buffer applications. Typically for buffer applications (so-called "float applications") the removal is quite strong Currents during limited periods of time, such as when used as a starter, lighting and ignition battery for automobiles.

For numerous applications, the trend in lead / acid technology is to provide maintenance-free batteries, ie, such a battery type _; the in the course

the recommended life expectancy without the addition of water the electrolyte can be operated. The lifespan of such batteries is limited by the combined water losses occur with gas evolution and its discharge; for this reason it must be excess from time to time Electrolyte can be added to compensate for the water loss that occurs in order to ensure a satisfactory service life to ensure.

The water loss in such batteries is typically due to the use of grid alloys with a high hydrogen overvoltage has been reduced to a minimum. They are solid, self-supporting and, in some cases, structurally reinforced Grids have been used which are made of various types, either antinome-free or containing a small amount of antimony Lead alloys exist. Examples of such grid alloy systems include calcium-lead, calcium-tin-lead, Cadmium-antimony-lead and selenium-antimony-tin-lead alloys, which may additionally contain various optional alloy components, such as silver and arsenic? combinations of these alloys are also possible.

Lead / acid batteries are also known in which the electrolyte has been made immobile in the form of a gel is. Such batteries can not only be maintenance-free, but also leak-proof? i.e. the battery can be used in any

any position or position can be used without Electrolyte would leak. On the other hand, it should be borne in mind that certain cracks appear in the gel in the course of the loading process are formed and are necessary for the oxygen transport, create conditions that the desired performance adversely affect the battery. In addition, such batteries necessarily have a higher one Internal resistance and therefore such batteries cannot be used where high discharge currents are required such as starter, lighting and ignition batteries in motor vehicles.

In order to provide a sealed construction and yet eliminate the potential difficulties associated with gel-shaped Electrolytes occur, sealed systems have already been used, in which the electrolyte has been immobilized and absorbed in special separators. The separators are not fully saturated; therefore, the gas formed in the overcharged state or at other times can rapidly escape diffuse from one electrode to the other. In this way If the right conditions are observed, the oxygen developed at the positive electrode can become negative Diffuse electrode where it will react quickly with active lead will. As a result, this reaction partially discharges the negative electrode, thereby preventing the negative electrode Electrode assumes its fully charged state in order to reduce the evolution of hydrogen to a minimum.

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to add. This sequence of reactions results in a procedure that has also been referred to as the "oxygen cycle", Since the oxygen recombination rate is greater than the rate of oxygen evolution at the positive electrode, there should be minimal water loss and pressure build-up.

At the present time, sealed lead / acid systems of this type are only low ampere hourly commercially available. The application is therefore generally limited to standby applications, such as such as emergency lighting, alarm systems and limited power sources Lifespan in portable devices such as televisions, lanterns and lights, and in garden tools.

U.S. Patent 3,862,861 (McClelland and Devitt) describes an example of an oxygen recombination cell design that operates at relatively high internal pressures. It is said that under these increased pressures the cell exhibits a higher rate of oxygen recombination » For this reason, a relief valve is provided, which should be biased so that there is gas at releases the highest possible pressures. A Bunsen-type relief valve is disclosed which has an internal pressure of at least 10 to 15 pounds. should withstand. This cell type can be used in buffer applications where relative high peak currents drawn for limited periods of time

("float applications") as well as deep discharge cycles in which a limited service life is accepted.

Furthermore, in Progress in Batteries & Solar Cells , Vol. 2, pp. 167-170 (1979), a cell with a prismatic container is described, obviously a type of cell which is operated at a relatively low internal pressure. This type of cell is also mainly intended for drawing relatively high peak currents for relatively limited periods of time.

Another type of battery is reported in the International Symposium on Batteries , October 21-23, 1958. The batteries described there in general information consist of a stack of plates and flat, soft separators, which stack is inserted into a suitable container after compression. In this stack or block of plates and separators, the active material of the plates is completely held by the separators. Once densified, the block must have a sufficiently high porosity that the block can absorb and hold all of the electrolyte required to operate efficiently and economically. The separators are made of diatomaceous earth. Batteries are described which can be used as starter, lighting and ignition batteries for motor vehicles, the stated advantages relating to vibration resistance, security against leakage and increased performance values at normal and low temperatures.

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Although this report states that the broad Inclusion in the market for commercial considerations rather than shortages in terms of performance or quality, it is assumed that the performance values are those currently required Do not meet values for such applications. Regardless of this, this type of battery described has not yet had any found widespread application and has so far not proven to be commercially successful.

Furthermore, it has already been proposed to increase the dimensions of a sealed lead / acid system in order to achieve greater ampere-hour outputs than is the case with the batteries commercially available up to now ( Engineering, October 1978, "The Age of the Sealed Battery ", pp. 1020-22). There is also indicated in the fact that the characteristic properties of such a sealed _Ä battery system would be advantageous partly for use as a starter, lighting and ignition battery of motor vehicles.

In addition to this application, there are a number of other applications in which the so-called "buffer mode" ("float-pulse" application) occurs, i.e. a mode of operation of the systems in which a relatively high peak current is provided for short periods of time in the case of very high discharge values; The design would also be for such backup batteries desirable as a closed system. Batteries

for motorcycles, starter batteries for outboard motors and Emergency power generators for computers are further examples that fall into this category. Continue to occur at those Applications where a relatively stable direct current is required have similar requirements. Batteries for such Use cases should have a capacity of at least 15 ampere-hours, or even 25 ampere-hours, or even have significantly higher performance values.

For whatever reason, however, self-contained systems with such high performance values are not worth mentioning Extent has become commercially available. This can simply be due to the fact that the necessary performance and characteristic values could not be reached. One can therefore assume that it caused difficulties, at least the performance and to ensure the required service life for such applications. Furthermore, one can assume that a stronger, more stable battery container is required to withstand the high internal pressures that are needed be considered to have a satisfactory oxygen recombination to ensure and that this problem is particularly acute in batteries with relatively high power or capacity values. The use of such stronger or stronger battery containers would of course also lead to a higher total weight of the battery. This would be particularly disadvantageous for use in the automotive sector, as there is the current one The trend is aimed at reducing the weight of battery systems

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Based on this, the main object of the present invention is to provide a sealed, maintenance-free lead / Provide acid battery that has the performance and characteristic values required for use in buffer mode guaranteed to deliver a relatively high peak current with very high discharge values for limited periods of time able.

A further and still further specified object of the present invention is to provide a sealed lead / acid battery which provides the same or higher performance and characteristic values than are required for starter, lighting and ignition batteries of motor vehicles.

Another object of the present invention is to provide a sealed lead / acid battery which has improved volumetric and gravimetric energy density values.

Another object of the present invention is to provide a sealed lead / acid battery which can be designed in different orders of magnitude, ranging from small to extremely high performance or capacity values.

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Yet another object of the present invention is to provide a sealed lead / acid battery that which can be produced using standard equipment such as are used for the production of conventional backup batteries.

Another object of the present invention is to provide a sealed lead / acid battery / which can do with the usual thin-walled plastic containers, which are often used in backup batteries.

Finally, it is another object of this invention to provide a sealed lead / acid battery that which works at an extremely low internal pressure and still remains maintenance-free over its entire service life.

Other objects, objects and advantages of the present invention result from the following description and the drawings, which show:

Fig. 1 is a perspective view of a battery according to the invention, partially cut, to show the internal structure;

2 shows the arrangement of the plates and separators in an exploded, cut-away side view a battery according to the invention;

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3 shows a cross-sectional view of the section along the line 3-3 from FIG. 1, around the internal structure to explain the battery in more detail;

4 shows the dependency in the form of a graphic representation the voltage from the discharge time to the improved cold starting behavior of a sealed lead / acid battery according to the invention to show in comparison to a standard maintenance-free battery; and

Figure 5 graphically shows the performance of a sealed lead / acid battery according to the invention in an industrial endurance test with a large number of charge-discharge cycles.

Although the present invention is capable of various modifications and alternative embodiments is, preferred embodiments of the invention are explained in the drawings and the following description. However, this should in no way restrict the invention to these particular, described embodiments will. On the contrary, it is intended to cover all such modifications and alternative embodiments as which fall under the essential spirit and scope of the present invention as it does with the foregoing Claims and their equivalents is reproduced.

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That is, among other things, although the present invention are essentially explained with reference to a starter, lighting and ignition battery for motor vehicles It should be noted that the present invention is also useful in many other applications where the so-called buffer operation occurs. Furthermore, the present invention is naturally in the same way in the form of a battery or a single cell. Although the present invention is used in conjunction with batteries with greater power or capacity. Capacitance values will be explained, is the invention can be used in the same way for batteries with low power values. In the same way, although with it all Advantages of this invention are not achievable, a more stable or solid container possible than that in operation occurring internal pressures is required; in the case of the batteries according to the invention, such a battery can therefore also be used if required more solid container can be provided.

The present invention is essentially based on the observation that a sealed, maintenance-free lead / acid battery that is suitable for various buffer applications, for example, can be provided as a starter, lighting and ignition battery of motor vehicles by the Electrolyte is immobilized in highly absorbent separators and still operates at extremely low levels Internal pressing is carried out, which allows the use of the usual, thin-walled battery container. The inventive

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Correct battery ensures a higher peak current with relatively high discharge values compared to the commonly used batteries with freely movable batteries Electrolytes; furthermore, the battery according to the invention is also satisfactory with regard to all the other necessary Performance and characteristic values.

The invention is described below, particularly with reference on Figures 1 and 2 explained in detail. This invention Battery 10 has a container 12 which is divided into individual cells by internal partitions 14 is. In each individual cell, a number of positive electrodes 16 are separated from the cells by absorbent separators 20 negative electrodes 18 separated.

The required electrical connections can be made on any of several known techniques can be created. The special, applied technique does not constitute one Part of the present invention. As shown, conductive tapes 22 connect the electrodes to one another, and the connections between the individual cells are of the type shown in FIG Cells are connected to the external connections 24 by means of conventional devices.

As can be seen from FIGS. 1 and 3, a pressure relief through manifold 26 to low-pressure self-relieving relief

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relief valves provided, such as Bunsen valves 28. Although a pressure relief by a Pipe manifold is shown, each individual cell could also be equipped with a relief valve, provided that this is strived for. On the other hand, a single manifold could also be used for the six cells shown could be provided, or more than the two manifolds illustrated could be provided.

The electrodes 16 and 18 and the separators 20 are intended to be tightly arranged within the cells, i.e. the electrodes and separators should retain their position even when the container is turned over. the Electrodes can therefore have almost the same dimensions as the internal dimensions of the cells. About the possibility of short circuits exclude, however, it is desirable to provide such dimensions for the separators that their Edges protrude at least slightly beyond all edges of the electrodes, as shown in FIG. 2. A possibility To achieve this at the bottom edge of the electrodes, is to make the separators U-shaped around the electrodes to fold, as shown in Fig. 2.

A highly effective use of the container interior is guaranteed in this way. On the other hand, spacers such as intermediate layers or spacers can also be used if necessary provided in the event that the cells used are too large for any reason.

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The grid of the positive and negative electrodes of the battery according to the invention can consist of any known grid alloys, such as those used for conventional maintenance-free batteries. According to an example, it is approximately possible to use a calcium-tin-lead alloy, the calcium content of about 0.06 to 0.20% ranges and their tin content of 0.1 to 0.5% (preferably from 0.2 up to 0.3%), based in each case on the total weight of the alloy. The alloys used should be suitable for producing self-supporting grids. The grids can be produced by any known method, for example cast directly in the desired shape or produced from expanded metal.

Ensuring a satisfactory internal structure a sealed system is faced with various difficulties. One of these difficulties results from the need to provide the system with absorbency to hold a required amount of electrolyte in order to achieve the desired performance or capacity will. To some extent this can be achieved by using thicker separators than this is required for freely movable electrolyte systems. In most cases, however, this proposal is not a complete one Solution, since the internal resistance increases when the plate spacing is increased. This necessarily results in ::; one practical limit up to which tradeoffs or compromises are possible with the performance values. Some improvements can

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nen be achieved by using an electrolyte with a slightly higher specific weight than the usual free moving systems; but again there is a practical upper limit based on various factors such as the decreasing conductivity. Another possibility is to determine the density of the pasty, Reduce active material. There is a moss formation of the negative active material and a fall of the positive one Active material prevented by the tight fit of the electrodes within the absorbent separators or at least on should be reduced to a minimum, the reduction in the density of the pasty active materials comes at least possibly into consideration. But here, too, there are limitations, caused by the manufacturing difficulties, if Materials with such a reduced density can be processed with the usual paste application machines as they for example in the manufacture of motor vehicle batteries.

Another difficulty is due to the shrinkage that occurs on negative active material occurs when such batteries are exposed to buffer operation, as is known in the art is. This can be a major cause of failure, which significantly extends the life of such a battery to decrease. For this reason, battery manufacturers are known to have used various expanding materials to provide the desired porosity and the desired surface area

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of the negative material on the negative plates. This difficulty has been found to be particularly acute in sealed systems for buffer applications is.

In order to achieve all the advantages of the present invention, it is preferably provided to use active material pastes ⁸ ^ which have an increased absorption capacity and which can nevertheless be processed by means of conventional equipment and result in a system with a satisfactory service life and satisfactory characteristic and performance data. For this purpose, the paste density values of the positive active material are lower than the paste density values in conventional lead / acid batteries with freely moving electrolytes, in which such long-life lead oxide materials are used, such as those obtained in Barton crucibles. In this regard, it has been found useful to have plate densities in the range of about 2.9 to 4.1 g / cm for the cured, non-formed positive active material

3 to be provided. A density value range of 3.0 to 4.2 g / cm for the cured and forinated positive active material is acceptable.

In order to achieve the desired electrolyte retention properties, is preferably provided in the paste an electrolyte-retaining To incorporate agents such as colloidal silica. The incorporation of colloidal silicon dioxide

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in an amount of about 0.05 to 1.0% based on the Total weight of the non-formed, positive active material, has proven to be satisfactory. They are other electrolyte-retaining ones Materials are known and can be used in the same way as substitutes for the silicon dioxide can partially or completely replace. Expediently, the electrolyte-retaining agent should also be used at the same time Swelling agents work, namely increase the consistency of the moist paste and improve its manageability. Colloidal Silica is also satisfactory in this regard.

In accordance with a further and preferred aspect of the present invention, the properties of the negative active material, not only to increase its absorption capacity, but also to reduce the effects to compensate for shallower cycles to achieve a satisfactory service life and to ensure satisfactory performance and characteristic values. For this purpose, the negative active paste preferably a combination of the commonly used paste additives added in a greater proportion than this usually happens. As a component, a common organic expanding agent is preferably in one portion from about 0.3 to about 1.0 percent based on the weight of the dry, unformed paste. Different Lignosulfonates such as, for example, sodium lignosulfonate, are known for this purpose and are suitable here. Additionally it is preferable to use an additive to physically strengthen the

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Ending lead sulfate crystals to larger crystals and possibly to a substantially solid layer with minimal porosity as this minimizes the Failure of the battery would result. For this purpose, cellulose flakes are suitable, in a proportion of approximately 0.3 to about 1.0% by weight can be used.

There is evidence that maximum benefits will not be achieved using only one type of dilator is used because their modes of action are likely to be different. In some achievements the organic affects Expands the morphology of the lead sulfate structure to counteract loss of porosity. the Additives that counteract solidification presumably act as physically acting spacers as a result.

The paste additives used should preferably act as swelling agents for the paste at the same time. Cellulose flakes and sodium lignosulfate both act in this direction.

A mixture of 0.75% sodium lignosulfate is preferred and 0.6% cellulose flakes, each based on the weight of the dried, unformed paste. Use this mixture seems to guarantee the desired service life with the envisaged number of cycles.

The density values of the cured, but not formed Paste of the negative active material should expediently be in the range from approximately 3.5 to 4.4 g / cm. A range of density values from about 3.2 to 4.1 g / cm for the cured and formed negative active material is satisfactory. Although the above-described additives to the negative paste counteract a loss of porosity and therefore Maintaining the absorption capacity is preferably provided, also in the negative paste, an electrolyte-retentive To incorporate agents such as colloidal silica. Proportions in the range of about 0.05 to 1.0% by weight by weight of the dried, unformed paste are suitable for this purpose.

Typically, it has been considered essential in the professional world (see, for example, US Pat. No. 3,862,861), to provide an excess of negative active material compared to the positive active material in a sealed system, so that the required oxygen cycle is assured remain. In accordance with one aspect of the present invention, it has been found that a satisfactory Oxygen cycle is still guaranteed even if the amount of negative active material is smaller than that of positive active material. It is therefore preferably provided that a weight ratio of negative Active material to positive active material of approximately 0.75

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to about 0.92 or the like. to 1 to be provided. This does not only for a reduction in weight but also at a lower cost with no adverse effect on performance the battery.

The material used for the separators 20 is said to be in sulfuric acid electrolytes be resistant, be resistant to oxidation by lead dioxide (PbO ,,), and should not contain any materials in the electrolyte, which could adversely affect the cell performance. In addition, the material should be highly porous, at least a porosity of 70 to 75% and desirably up to about 90% or the like. exhibit; furthermore, the separator material should be sufficiently compressible that it is at least substantially the Changes in shape of the electrodes can follow in the course of assembly and battery operation. Furthermore, the The mean pore diameter must be sufficiently small to prevent dendrite migration from the negative plate and the falling of the active material from the positive plate will. On the other hand, the mean pore diameter should be sufficiently large so that the separator material from Electrolyte is easily wetted and still not so small, that an excessively high internal resistance results. Furthermore, the separator material must be able to absorb the electrolyte forward over the entire desired height of the separator away like a wick. Finally, and importantly, must the separator material in use is preferably an essentially

union uniform void volume within the separator guarantee. The separator must therefore preferably have a sufficient void volume to the To ensure the speed of oxygen transport, which is necessary to maintain the desired internal cell pressure. It is believed that this Void volume is provided by some of the pores, the walls of which are covered with an electrolyte film, whose central pore section, however, is electrolyte-free. A satisfactory oxygen recombination will do for some Applications achieved even if the separator is carefully wetted with electrolytes. In this regard, can the usefulness can be determined by determining the weight loss (water) that occurs over the course of the charge-discharge cycles occurs. With a suitable material, there must be no excessive loss of water.

The thickness of the separator is generally determined by the cell performance and the expected operating speed for a particular application. In this respect it differs The separator layer thickness does not differ significantly from those separator layer thicknesses that are different for others Types of lead / acid cells have proven suitable for particular uses.

The use of a borosilicate glass material has proven to be suitable proven to be made of glass microfiber and chopped up

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Strands has been formed. Materials of this type are commercially available and have recently been used for sealed lead / acid cells. Such a material (sold by CH Dexter Division, The Dexter Corporation, Windsor Locks, Connecticut, unit designation "225B".) Has been found to be particularly satisfactory and has the following characteristic properties: ⁰ ^ nominal thickness 300 microns

Air permeability (according to ASTMD 737-75) 15.1 l / min / 100 cm ² at 12.7 mm water vapor pressure Δ P (determined with the Frazier Permeometer),

mean pore size 12.6 pm and

a porosity (determined by the mercury penetration

driving) of 1.2 m / g.

Provision is preferably made for at least one layer of this borosilicate glass material to be arranged adjacent to the electrodes. In addition, additional layers of other materials can be provided, for example to reinforce to improve handleability in the course of the manufacturing process. In this regard, for example Commercially available sheets, sheets or thin plates made of fleece-like material made of polyethylene, polypropylene and polyester can be used. Such materials have the desired electrolyte retention capacity and are also inexpensive and ensure increased strength

speed. Such a laminar separator system can be provided to ensure the required strength, to be relatively easy and safe to fold pocket-shaped or U-shaped Separators by means of the commonly used,

High-speed assembly technology to produce backup batteries.

For a specific application, the specific Easily calculate the weight of the electrolyte when fully charged. Typical specific weights when fully charged are in the range from 1.255 to 1.320 g / cm, with satisfactory results, with a range of from 1.285 to 1.320 g / cm being preferred will. Special applications may make it necessary to use an acid with a slightly higher or lower specific Insert weight.

The formation of the electrodes provided with paste can be done according to known procedures. This means that it is possible to form the electrodes using the usual tank formation, before they are assembled in the battery case. If this method is used, the formed electrodes should dried to remove residual electrolyte.

However, the aim is to introduce the non-formed electrodes and the separators into the container, the necessary

digen electrical connections to produce the battery cover to be attached close to the container, to introduce the required electrolyte into the container through an opening provided for the attachment of the relief valve in the lid and then to bring the relief valve into its operating position. The formation will then appear under Conditions carried out as for the usual one-step lead / acid battery formation are suitable. However, it can be useful in the final stages of the formation process provide less severe conditions than is usually the case. Furthermore, it can be desirable be to cool the forming electrolyte a little at first.

In the same way it should be noted that if an in-situ formation is used, the formation is within is started about 30 to 60 minutes or so after the electrolyte is added. Longer delays can create conditions that eventually lead to internal short circuits.

The amount of electrolyte added should preferably not be sufficient for the absorbing materials of the battery to fully saturate; i.e. the battery should remain in a condition with insufficient electrolyte filling. Even though the battery is self-regulating in use, full saturation could lead to excessive gas evolution.

development in the course of the initial stages of charging in cyclical operation. If you continue to use reaches a state of equilibrium where an efficient oxygen recombination cycle is ensured. The one in the course The slightly higher gas evolution that occurs in the initial stages can largely be eliminated by applying this for a effective oxygen recombination required special Void volume is adjusted. Overall, it turned out to be Proven to be useful to add a sufficient amount of electrolyte to the absorption capacity of the system up to one Saturate value of about 90%.

Care must be taken to avoid free electrolytes in the system. Notable amounts of free Electrolytes (i.e., not immobilized in the electrolyte and separators) can increase the performance of these batteries adversely affect.

In accordance with one aspect of the present invention, there is provided a self-closing dosing relief valve, which already carries out the pressure equalization at an extremely low internal pressure. For this purpose there is a valve

2 provided that at internal pressures of approximately 0.35 to 2.1 N / cm Positive pressure (0.5 to 3.0 psig) opens. Indeed, internal working pressures are preferably provided during operation

2 of no more than about 0.7 or perhaps 1.4 N / cm Overpressure (1 or 2 psig) so that the usual

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Wisely used, thin-walled plastic containers can be applied.

The following examples serve to further illustrate the invention without restricting it. Unless otherwise specified absent, all percentages relate to weight.

Example 1;

This example illustrates the performance of a sealed, lead / acid battery according to the invention compared to a conventional, maintenance-free battery with freely movable Electrolytes.

Batteries rated at approximately 71 amp hours were assembled in a hard rubber container. Each battery contained 17 plates per cell. A calcium-tin-lead alloy with a composition of 0.09% calcium, 0.3% tin, the remainder lead, was used as the alloy for the grids of both batteries. The density of the positive paste was 4.0 g / cm and that of the negative paste was 4.4 g / cm, based in each case on the weight of the dried, non-formed paste. The pastes were ^{cured at 60 °} C. for about 16 hours at a relative humidity of 100%, and then kept at 60 ° C. for a period of about 48 hours or the like in an environment with Q% relative humidity. Each electrode of the

The battery according to the invention was made with a 2-layer Separator wrapped around a 0.33 mm thick inner layer made of the above borosilicate glass material and a 0.33 mm thick outer layer made of a point-wise bonded polypropylene nonwoven material. This separator was Folded in a U-shape around the electrode, as shown in FIG. 2. For the usual, maintenance-free battery, a standard one became Polyvinyl chloride separator with a layer thickness of 0.94 mm with a 0.30 mm thick backing fabric is used.

Further structural details can be found in the following table 1:

Table 1

parameter

sealed battery

usual battery

Layer thickness of the positive grid (mm)

Layer thickness of the negative grid (mm)

Weight of dry, positive paste per plate (g)

Weight of dry, negative paste per plate (g)

Weight ratio of positive frame / grid (g: g)

Negative paste / grid weight ratio (g: g)

1.04 0.99 110
101
70/40 62.5 / 38.5

spec. Electrolyte weight (g / cm) 1.285

Distance between neighboring

Plates (mm) 0.56

04 5 / 38.5 O, 99 285 110 10.1 70/40 62, 1,

0.94

Further details of the respective batteries can be found from Table 2 below.

Table 2

3 356 3 375 1 919 2 077 10 , 73 6th , 94

Parameters sealed usual

Battery battery

Total positive paste weight (g) 3,356 Total negative paste weight (g) 3,375 Total weight of positive grids (g) l 919 Total weight of negative grids (g) 2,077

Total lead weight within the

Element (kg) 10.73

Total Electrolyte Weight "(kg) 2.61

The plates and separators were arranged inside the container, the necessary electrical connections were made and the forming acid with a specific weight of 1,200 g / cm ^{3 was} cooled to -18 ° C. A charge sequence of 7 A for 16.5 h, then 4 A for 3 h and then 2 A for 2 h was carried out. The container covers were then attached. The sealed battery had a standard Bunsen relief valve that opened when the internal pressure was 0.35 N / cm gauge (0.5 psig).

The batteries were then tested, with those listed below Results listed in Table 3 were obtained.

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Table 3

Examined property sealed usual

Battery battery

Cold start at -18 ° C, voltage after

30 seconds at a current of 550 A 8.05 7.60 Relative electrical resistance

at -18 ° C 9.9 11.2

Power reserve for a discharge

current of 25 A (min) "■ 78 124

It can be seen that the inventive, sealed Battery guarantees better cold start energy than the usual, maintenance-free battery. Fig. 4 shows this better performance for the 60 second discharge of each battery, curve "1" being the sealed according to the invention System relates, while curve "2" relates to the usual, maintenance-free battery.

However, as can be seen from Table 3, the power reserve of the sealed battery according to the invention was clear smaller than that of the usual, maintenance-free battery. It should be noted here, however, that the active material pastes were not modified as described above, from which the need for suitable modification can be seen is to evaluate all of the benefits of the present invention.

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The sealed battery of the present invention was a usual SLI test (12 minute cycle, J-240 sequence) unterzoyon and failed after approx. 4,500 cycles, which is evident is less than the typical performance of a commercially available, maintenance-free battery. the However, the nature of the failure suggested that the The cause was to be found in a design flaw in the particular positive grid.

Example 2;

This example explains the lifespan that a sealed battery according to the invention can be achieved.

A test battery rated approximately 67 amp-hours, the 13 plates, was assembled contained per cell. The alloys used had the composition given in Example 1. The concentration the hardened, non-formed paste of the negative Active material was about 4.4 g / cm and that of the

3 positive active material approximately 3.9 g / cm. The negative paste was made from a material that essentially contained 1200 g of black lead (lead (II) oxide), 50 g of usual Dilatation mixture and approximately 0.3% colloidal silicon dioxide, based on the weight of the dry, non-formed paste.

The pastes were cured as described in Example 1 is. The positive plates were wrapped with 2 layers of the borosilicate glass material described above; the negative plates were wrapped with a single layer of this borosilicate glass material.

The plates and separators were placed in a standard thin-walled plastic container (for SLI applications), as he does for standard, maintenance-free batteries is used, which however had been modified to the height of the brackets at the bottom of the container to decrease significantly. The assembly and formation were done in essentially the same way as that is described in Example 1, the special sequence with charging processes of 7 A for 18 h, followed for the formation of 4 A for 6 h and finally of 2 A for 2 h became.

Further structural details can be found in Table 4 below, which also provides corresponding information for a standard, maintenance-free battery for comparison are.

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Table 4

parameters sealed
battery

usual battery

Positive Grid Thickness (mm) Negative Grid Thickness (mm)

Weight of dry positive plate (g)

Weight of dry negative plate (g)

Weight ratio of the positive paste to the grid (g: g)

Weight ratio of negative paste to grid (g: g)

spec. Weight of the electrolyte (g / cm ³ )

1.90 , 2 . 1.62 1.29 1.19 148 149 104 107 89.8: 58 87:62 63.5:40 66:41 1.290 1.265

In Table 5 below are details of the assembled Battery listed, including information on the comparison battery.

Table 5

Parameters sealed common battery battery

Total weight Total weight Total weight Total weight

Total weight Total weight Total weight

the positive paste (g) the negative paste (g) the positive grid (g) the negative grid (g)

within d. Elements (kg) of electrolytes (kg) approx. d. Battery (kg)

3 229 3 129 2 613 2,771 2 458 2 231 1 692 1 715 10 , 04 9.84 3 , 13 about 5.26 14th , 60 17.15

The sealed battery according to the invention was examined and the results obtained are shown in Table 6 below, along with information on the usual comparison battery.

Table 6

Property examined

sealed conventional battery battery

Cold start at -18 C, voltage (V) after 30 seconds with a discharge current of 500 A.

Power reserve at a discharge current of 25 A (min)

7.84

91

7.2

102

From Table 6 it can be seen that the inventive, sealed Battery ensures the same improvement in cold start as the battery according to example 1. Although this are not the same as with the usual battery, the modifications have the negative grid along with the increased spacing between adjacent panels for an improvement compared to the battery according to Example 1 out. A further improvement in this regard can be made by another Modification of the active material pastes can be achieved, as described above. The life test given in Example 1 was carried out on the sealed battery (J-240 test) which gave a life of approximately 8000 cycles. In the course of this investigation episode

* a β

- 39 -

the battery was discharged at 500 A and the 5 sec voltage and 30 sec voltage were recorded. The corresponding results are shown graphically in FIG. 5, with curve "3" representing the 5-sec tension and curve "4" representing the 30-sec tension. The failure was due to corrosion of the positive grid, which was apparently due to a design flaw in these ⁵ ^ grids.

As a clear result it can be stated that this invention, sealed battery only approximately 68.0 grams of water throughout the J-240 life test (with a measurement accuracy of + 22.6 g) has lost, which is about an order of magnitude less than for conventional, maintenance-free Batteries is to be expected.

It has thus been demonstrated that the battery according to the invention ensures all the advantages of a sealed system and in particular an improved peak current at relative high discharge values for short periods of time, as can occur in a variety of so-called buffer applications. When used as a starter, lighting and ignition battery in motor vehicles, the present invention ensures a significantly increased cold start energy. This performance is maintained while maintaining the other performance and characteristic data achieved. Ensuring an effective oxygen recombining

- 40 -

nation, even with extremely low values for the internal pressure, allows superior properties with regard to the Maintenance-free. Working with the low internal pressures continues to allow the use of conventional, thin-walled plastic containers, which turns out to be a special proves valuable point of view for application in motor vehicles, where the weight reduction is more and more is gaining in importance. In fact, the relatively high volumetric energy density that can be achieved according to the invention is to be exploited to provide containers with even smaller dimensions, without the performance of the Affect the battery.

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Claims (15)

• · Patent attorneys: * Γ °: 'i _m "TISCHER ^; * KERN & BRE Albert Rosshaupter-Strasse 65 · D 8000 Munich 70 ■ Telephone (089) 7605520 ■ Telex 05-212284 patsd · T elo programs core patent Munich GOULD INC. 2nd October 1981 Gould Center, GD-54 Rolling Meadows, Illinois 60008,
United States Sealed, maintenance-free lead / acid battery for buffer applications Patent claims: Maintenance-free lead / acid battery with properties suitable for buffer applications,
marked by a sealed container (12), the inner sub-part ment (14) is divided into a number of cells? a number of positive plates (16) in each cell are present and a self-supporting grid and a positive, paste-like, applied to the grid Have active material; a number of negative plates (18) in each cell are present and a self-supporting grid and negative - 2 "· tive, paste-like active material applied to the grid exhibit; at least one layer of a separator material (20) which absorbs and retains the electrolyte in intimate contact with the positive and negative plates (16 and 18, respectively) while separating them from one another; a sulfuric acid electrolyte absorbed in these plates (16, 18) and separators (20), these plates (16,18) and separators (20) are sufficiently porous to hold back enough electrolyte to allow performance is assured of at least about 25 amp hours; and this container has at least one, under normal conditions, closed relief valve (28), which is able to release gas from the interior of the container into the surrounding atmosphere when the pressure within the container is in a range of unge
psig). 2 range from approximately 0.35 to 2.1 N / cm overpressure (0.5 to 3.0 2. Battery according to claim 1,
characterized in that at least one of the positive and negative grids is made of a calcium-tin-lead alloy. 3. Battery according to claim 1 or 2,
characterized in that θ β ί tf (J β _fc O. Ö A ** ft κο α α ό ο θ C the positive active material has a density of about 3.0 to 4.2 g / cm. 4. Battery according to one of claims 1 to 3, characterized in that the positive active material contains approximately 0.05 to 1.0% by weight of an electrolyte-retaining agent. 5. Battery according to claim 4, characterized in that the electrolyte-retaining agent is colloidal silicon dioxide. 6. Battery according to one of claims 1 to 5, characterized in that the negative active material has a density of approximately 3.2 to 4.1 g / cm. 7. Battery according to one of claims 1 to 6, characterized in that the negative active material contains approximately 0.05 to 1.0% by weight of an electrolyte-retaining agent. 8. Battery according to claim 7, characterized in that the electrolyte-retaining agent is colloidal silicon dioxide. 9. Battery according to one of claims 1 to 8, characterized in that the negative active material contains an organic expanding agent in a proportion of approximately 0.3 to 1.0% by weight. 10. Battery according to one of claims 1 to 9, characterized in that the negative active material contains an additive which reduces the solidification of the lead sulfate crystals in the course of the charge-discharge cycles to a minimum, which additive in a proportion of approximately 0.3 to 1% by weight is present. 11. Battery according to one of claims 1 to 10, characterized in that the weight ratio of negative active material to positive active material has a value less than 1.0. 12. Battery according to claim 11, characterized in that the value of this ratio is in the range of about 0.75 to 0.92: 1. 13. Battery according to one of claims 1 to 12, characterized in that the separator material which retains and absorbs the electrolyte is a borosilicate glass material. βοο 14. Battery according to claim 13 _f
characterized in that The separator retains at least two layers of electrolyte and absorbent material, wherein the layer adjacent to the plates is made of the borosilicate glass material consists. 15. Battery according to one of claims 1 to 14, characterized in that a common manifold connects a number of these cells to a pressure relief valve.