Sealed lead-acid cells and batteries having internal and external restraint for accommodating plate growth
Inactive Publication Date: 2002-07-23
EXIDE TECHNOLOGIES LLC
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Benefits of technology
Other preferred aspects of the present invention include a cell design highly amenable to reliable production and assembly. Indeed, in accordance with the preferred embodiments of this invention, alignment of the cell element when inserted into the container is facilitated. Other preferred design features allow both heat sealing of the cover to the terminals and to the container, as well as minimizing the requisite accuracy of alignment of the terminal and cover for the heat seal step.
Still other features of the present invention provide a sealed cell design amenable to the reliable production of cells of relatively large capacity, cell sizes up to 2,000 to 3,000 Ampere Hours and even larger can thus be provided. Such cells are likewise configured to provide a desired configuration in use.
Problems solved by technology
Such uninterruptible power supplies concern, for example, systems which back-up computers and communication networks.
Such an uninterruptible power source will also accommodate short, or intermittent, losses in power.
In the event of a power interruption, the uninterruptible power source is subject to a rapid, and sometimes deep, discharge.
A common problem encountered by such VRLA cells and batteries is the integrity of the seals over time as a result of grid growth which occurs in service.
As has been especially common at the positive terminal, grid growth occurs as a battery grid corrodes over time, hence causing the battery terminal to move outwardly relative to the battery cover.
As the container and cover are commonly made of plastic, each was known to fail in various ways, such as by fracturing, cracking at welds, and so forth.
Failures such as these have resulted in the leakage of electrolyte from the cells and batteries and has also resulted in failure of the cell to operate properly.
This well-known problem is particularly acute in sealed lead-acid cells and batteries because relatively high internal temperatures in service can be reached.
Such relatively high temperatures lead to an increase in the rate of grid corrosion which can result in significant grid growth.
Further, what can occur in service is deflection of the positive terminal post which can result in a possible loss of connection to the adjacent stationary terminal post.
Indeed, such grid growth can result in the buckling of a positive plate resulting in loss of capacity as well as possible shorting and the like.
There are several other issues and concerns which complicate the design of sealed lead-acid cells.
This design approach can be relatively expensive, and amenability to automatic production, while achieving satisfactory quality control, can be difficult.
These design issues and considerations often can be exacerbated as the size of the individual cells required for the particular application is increased.
Indeed, relatively large capacity cells raise additional design issues, such as insuring that satisfactorily reliable electrical connections between the plates and the respective terminals are retained.
Yet another design issue concerns satisfactory alignment of the cell element in the jar or container during assembly.
Considerable difficulty in achieving commercial production with acceptable quality control is encountered when designing cells of such relatively large capacities.
Method used
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FIG. 1 shows a sealed, VRLA cell, shown generally 10 having a container 12 (often termed a "jar") and a cover 14. Any material useful for lead-acid cells and batteries can be used for the container and cover, and the many useful materials are known. Typically, conventionally used plastics materials include ethylene-propylene copolymers. Polycarbonates or other plastics materials suitable for withstanding higher thermal conditions are also known. Such containers and covers can be made by any technique desired, such as, for example, injection molding. For the containers, and particularly for containers of relatively large size, it is desirable to eliminate, or at least essentially minimize any draft from the bottom to the top of the container so that the internal container size does not vary significantly from the top to the bottom, thereby allowing more uniform compression of the cell element, as will be discussed hereinafter.
Valve 16, a conventional safety valve, maintains the inter...
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Sealed lead-acid cells are disclosed which include an internal cell restraint contacting the interior surface of the cover and positioned between the positive plates and the cover, the internal cell restraint cooperates with an external cell restraint, such as a coated metal face plate, to direct positive plate growth which occurs in service away from the cover, the features disclosed allowing plastic-to-plastic terminal post-cover seals to be used and allow cells of capacities of up to 2,000 Ampere Hours or more to be provided.
Description
FIELD OF THE INVENTIONThe present invention relates to lead-acid cells and batteries, and more particularly to such cells and batteries capable of accommodating the positive grid growth which occurs in service while providing desirable performance.BACKGROUND OF THE INVENTIONSealed lead-acid cells and batteries, for many applications, have significant advantages in comparison to the use of conventional, flooded lead-acid cells and batteries. Such cells and batteries, sometimes termed "VRLA" cells and batteries (i.e., valve-regulated, lead-acid), utilize a safety valve (e.g., a Bunsen valve) to maintain the desired internal pressure for an efficient oxygen recombination cycle.Some applications where such sealed cells and batteries are used are termed stationary battery applications. In such applications, such cells and batteries are maintained at a full state-of-charge and in a ready-to-use condition, typically by floating at a constant preset voltage. Stationary cells and battery app...
Claims
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Login to View More IPC IPC(8): H01M10/16H01M2/04H01M2/10H01M2/06H01M2/02H01M10/06H01M10/12H01M2/30H01M10/04H02J7/00H01M50/103H01M50/121H01M50/171H01M50/176H01M50/209H01M50/253H01M50/466H01M50/541H01M50/55H01M50/553H01M50/562
CPCH01M10/0413H01M10/045H01M10/0459H01M10/0463H01M10/12H01M10/16Y02E60/10Y02P70/50H01M50/562H01M50/171H01M50/466H01M50/253H01M50/209H01M50/103H01M50/55H01M50/553H01M50/121H01M50/176
InventorMATTAN, EDWARD M.
OwnerEXIDE TECHNOLOGIES LLC