GB2041632A

GB2041632A - Electric storage batteries

Info

Publication number: GB2041632A
Application number: GB7943162A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1979-01-17
Filing date: 1979-12-14
Publication date: 1980-09-10
Also published as: GB2041632B

Abstract

An electric storage battery includes a plurality of packs 11 of positive and negative battery plates having insulating separators therebetween, with conductive bars 13 supporting the packs 11 in spaced relationship and electrically interconnecting opposite polarity plates in adjacent packs 11. A plurality of cell casings 15 enclose the plate packs 11 to define cell compartments for receiving electrolyte in use, each cell casing 15 being formed in at least two interengaging parts shaped to receive therebetween the or each conductive bar 13 connecting the associated plate pack 11 to an adjacent pack 11. An outer container 16 composed of a foamed material is moulded around said cell casings 15 to surround the cell casings 15 and seal the casings against electrolyte escape in use. The portion of the outer container 16 located uppermost in use is formed with a plurality of apertures which communicate with respective holes in the cell casings 15 respective, and means is provided for sealing the apertures in the outer container 16 against ingress of atmosphere while allowing escape of gases generated in the battery in use. Positive and negative terminals are exposed at the external surface of the outer container 16 and are electrically connected to respective battery plates in the end cell compartments.

Description

SPECIFICATION Electric storage batteries This invention relates to electric storage batteries and more particularly to lead-acid batteries.

At the present time, production of a lead-acid battery normally involves assembly of packs of battery plates and separators into respective cell compartments of an already-formed, open-topped battery box which is often moulded in a thermoplastic material such as polypropylene, and which is divided into the cell compartments by integral partition walls. The intercell connections between battery plates in adjacent cell compartments are completed individually after assembly of the plate packs in the cell compartments by conductive slugs which normally extend through the partition walls defined between respective adjacent pairs of cell compartments. The conductive slugs are joined, conveniently by resistance welding, to extensions of conductive straps which are connected, normally by a lead casting operation, to respective sets of plates in the packs.After completion of the intercell connections, the box is sealed by a separate lid which is welded, or adhesively secured, to the open top of the box.

Batteries of the kind described above are widely used throughout the world, particularly as S L I batteries for cars, vans, lorries and the like. However, although these batteries perform well in service, their construction is such that manufacture is a time consuming and expensive procedure. An object of the present invention is therefore to alleviate this problem.

Accordingly, the invention resides in one aspect in an electric storage battery including a plurality of packs of positive and negative battery plates having insulating separators therebetween, conductive bars supporting the packs in spaced relationship and electrically interconnecting opposite polarity plates in adjacent packs, a plurality of cell casings enclosing the plate packs to define cell compartments for receiving electrolyte in use, each cell casing being formed in at least two interengaging parts shaped to receive therebetween the or each conductive bar connecting the associated plate pack to an adjacent pack, an outer container composed of a foamed material moulded around said cell casings to surround the cell casings and seal the casings against electrolyte escape in use, the portion of the outer container located uppermost in use being formed with a plurality of apertures which communicate with respective holes in the cell casings respectively, means for sealing the apertures in the outer container against ingress of atmosphere while allowing escape of gases generated in the battery in use, and positive and negative terminals exposed at the external surface of the outer container and electrically connected to respective battery plates in the end cell compartments.

Using the construction described in the preceding paragraph above simplifies battery production since not only are the electrical connections between the plates in adjacent packs effected before the packs are enclosed in cell compartments, but also all the connections can readily be completed in a single operation. Moreover, the conductive bars used to provide the intercell connections allow the length of the connections to be reduced to a minimum which not only lowers the internal resistance of the battery but also reduces the amount of material required to effect the interconnections.In addition the use of a moulded, foamed material to produce the outer container of the battery allows the container to be formed in situ in a single moulding operation whereas, as previously stated, existing batteries require the production of separate pre-formed battery boxes and lids which are difficult to mould and must be sealingly joined to provide the required battery container. On the other hand, of course, the battery described in the preceding paragraph requires the provision of individual cell casings separate from the outer container of the battery. However, this is not a serious disadvantage, since the cell casings can be very simple structures and there is no necessity for the interengaging parts of the cell casings to seal around the conductive bars since moulding of the outer container provides the required sealing of the cell compartments.

In a further aspect, the invention resides in a method of manufacturing an electric storage battery comprising the steps of: a) producing packs of positive and negative battery plates having insulating separatorstherebe- tween, b) with said packs located in parallel, spaced relationship joining sets of plates in adjacent packs to respective conductive bars such that the bars provide electrical connections between the sets of plates in the adjacent packs, c) enclosing each plate pack in a respective cell casing formed in at least two parts which engage one another to receive therebetween the or each conductive bar connecting the plate pack to an adjacent pack, each cell casing defining a cell compartment for receiving battery electrolyte and being formed with a hole in the portion thereof located uppermost in use, d) locating said plate packs enclosed within their respective cell casings in a mould and performing a foam moulding process to produce a foamed outer container surrounding the cell casings and sealing the casings against electrolyte escape, the outer container being formed with apertures communicating with the holes respectively in the cell casings, and e) sealing the apertures in the outer container against ingress of atmosphere, the sealing permitting escape of gases generated in the battery in use.

Preferably, step (b) is performed by casting the conductive bars around projecting lugs provided on the battery plates.

Preferably, the conductive bars are provided with a coating to which the material of the oute#r container sealingly bonds during moulding.

Preferably, the outer casing is composed of a foamed synthetic resin or a foamed rubber material.

The accompanying drawing is a perspective view, partly cut away, of a lead-acid battery according to one example of the invention.

Referring to the drawing, the battery includes a plurality of packs 11 of positive and negative battery plates having insulating separators therebetween.

The battery plates in each pack are entirely conventional and hence each plate includes an eiectrochemically active paste supported by a grid formed of lead a lead alloy or a synthetic resin material coated with lead or a lead alloy. Projecting from each plate is a terminal lug 12 which is also formed of lead or a lead alloy and which is located adjacent one side edge of the plate. The plates in each pack 11 are arranged so that the terminal lugs 12 projecting from the positive plates are aligned adjacent one side of the pack, while the terminal lugs of the negative plates are aligned adjacent the other side of the pack.

It will be appreciated that to provide a standard 12 volt car battery six plate packs 11 would be employed.

Cast around the terminal lugs 12 of respective sets of plates in the packs 11 are conductive bars 13 which serve to provide the required electrical connections within and between the packs and which support the packs so that they extend in parallel, spaced relationship in a row such that the peripheral edges of all the plates are substantially aligned. The electrical connections provided by the conductive bars 13 are such that like polarity plates in each pack are interconnected, whereas in adjacent packs plates of one polarity are connected to plates of the opposite polarity so that the packs are connected in series. Moreover, in each of the packs at the two ends of the row of packs, the conductive bar 13 interconnecting one set of like polarity plates is provided with an upstanding electrode post 14 which, in use, defines a terminal of the battery.

Surrounding each of the conductive bars 13 connecting adjacent packs 11 is a coating of a synthetic resin material which, as is described in detail below, is sealingly bonded to the external container of the battery.

Each plate pack 11 and its associated conductive bars 13 is enclosed within an individual, generally rectangular cell casing 15 which is formed as a two-part synthetic resin moulding. The two parts of each casing 15 are arranged so that their mating edges define grooves shaped accurately to receive therebetween the or each conductive bar connecting the associated plate pack to an adjacent pack.

However, the walls of the grooves in the casing parts do not form a seal around the conductive bars. The mating edges of each pair of casing parts are also provided with mechanical locking means, such as a projection on one part and a complementary recess in the other part, so as to retain the parts in interengagement. There is, however, no necessity to produce a weld or adhesive bond between the casing parts.

Provided on the wall of each cell casing 15 which is positioned lowermost in use, are a plurality of internal, upstanding walls (not shown) on which the associated plate pack 11 is supported. These walls ensure that there is a space at the base of each cell casing below the plate pack so that any sediment from the plate pack can collect in the space without shorting out the plates in the pack. Moreover, the wall of each cell casing located uppermost in use is formed with at least one vent hole, while the upper wall of each end cell casing is formed with a further hole for receiving the associated electrode post 14. It will be appreciated that the cell casings 15 define cell compartments of the battery and in use receive battery electrolyte.

Moulded around and between the assembly of cell casings 15 iS an external battery container 16 which is formed of a foamed, synthetic resin or rubber material, such as polyurethane. The material of the container 16 is chosen so that, during moulding, it becomes bonded to the synthetic resin coating on the conductive bars 13 and thereby seals the cell casings 15 against escape of electrolyte. Conveniently, a similar synthetic resin coating is provided on at least part of each electrode post 14 so that a seal is also produced between the container and the electrode posts, the latter projecting from the container to define the required battery terminals. Moulding of the container 16 is arranged so that the top surface of the container is formed with apertures (not shown) aligned with the holes respectively in the cell casings 15.In the finished battery, the holes and apertures are closed by vent plugs or a single-piece vent cover to prevent ingress of foreign material into the battery, while at the same time allowing escape of gases generated in the battery in use.

To produce the battery described above, the plate packs 11 are assembled and are then arranged in the required orientation in a suitable jig. One or more moulds defining the shape of the required conductive bars 13 are then located around the rows of terminal lugs 12 and molten lead or lead alloy is poured into the or each mould so as to cast the bars 13 and simultaneously join the bars to the terminal 1 lugs. The casting process may also be arranged to produce the upstanding electrode posts 14. After the casting process, and while the conductive bars 13 are still hot, the synthetic resin coating is applied to each of the bars 13 defining an inter-pack connection so that the coating fuses and bonds to the bars. A similar coating may also be applied to the electrode posts 14.The cell casings 15 are then located around the interconnected packs 11, whereafter the entire assembly is placed in a mould having the outline of the required battery container 16. The mould is also provided with pins which engage in the holes in the cell casings 15 to locate the cell assembly in position in the mould. The foamed container 16 is then produced around the cell assembly, the foaming process being effected at a low pressure so as to ensure that the material of the container fills the spaces between adjacent casings 15. During moulding, the material of the container 16 bonds to the synthetic resin coating on the conductive bars and, if present, to the synthetic resin coating on the electrode posts. Moreover, by virtue of the locating pins provided on the mould, the moulding process also produces the required apertures in the cell container.

After removal from the mould, electrolyte is introduced into each cell casing 15 through the associated aperture and vent hole, whereafter the battery is sealed by the vent plugs or vent cover.

If required, the containers 16 and cell casings 15 may be provided with further openings for receiving probes to monitor the electrolyte level in the battery in use. Moreover, forming of the active material of the battery plates can be effected in the assembled battery.

Claims

1. An electric storage battery including a plurality of packs of positive and negative battery plates having insulating separators therebetween, conductive bars supporting the packs in spaced relationship and electrically interconnecting opposite polarity plates in adjacent packs, a plurality of cell casings enclosing the plate packs to define cell compartments for receiving electrolyte in use, each cell casing being formed in at least two interengaging parts shaped to receive therebetween the or each conductive bar connecting the associated plate pack to an adjacent pack, an outer container composed of a foamed material moulded around said cell casings to surround the cell casings and seal the casings against electrolyte escape in use, the portion of the outer container located uppermost in use being formed with a plurality of apertures which communicate with respective holes in the cell casings respectively, means for sealing the apertures in the outer container against ingress of atmosphere while allowing escape of gases generated in the battery in use, and positive and negative terminals exposed at the external surface of the outer container and electrically connected to respective battery plates in the end cell compartments.

2. A battery as claimed in Claim 1, wherein the conductive bars are provided with a coating to which the material of the outer container sealingly bonds during moulding.

3. A battery as claimed in Claim 1 or Claim 2, wherein the outer casing is composed of a foamed synthetic resin or a foamed rubber material.

4. A method of manufacturing an electric storage battery comprising the steps of: a) producing packs of positive and negative battery plates having insulating separators therebetween, b) with said packs located in parallel, spaced relationship joining sets of plates in adjacent packs to respective conductive bars such that the bars provide electrical connections between the set of plates in the adjacent packs, c) enclosing each plate pack in a respective cell casing formed in at least two parts which engage one another to receive therebetween the or each conductive bar connecting the plate pack to an adjacent pack, each cell casing defining a cell compartment for receiving battery electrolyte and being formed with a hole in the portion thereof located uppermost in use, d) locating said plate packs enclosed within their respective cell casings in a mould and performing a foam moulding process to produce a foamed outer container surrounding the cell casings and sealing the casings against electrolyte escape, the outer container being formed with apertures communicating with holes respectively in the cell casings, and e) sealing the apertures in the outer container against ingress of atmosphere, the sealing permitting escape of gases generated in the battery in use.

5. A method as claimed in Claim 4, wherein step (b) is performed by casting the conductive bars around projecting lugs provided on the battery plates.

6. A method as claimed in Claim 4 or Claim 5, wherein the conductive bars are provided with a coating to which the material of the outer container sealingly bonds during moulding.

7. A method as claimed in any one of Claims 4 to 6, wherein the outer casing is composed of a foamed synthetic resin or a foamed rubber material.

8. A method as claimed in any one of Claims 4 to 7 of manufacturing a lead-acid battery wherein, after step (d) and before step (e), electrolyte is introduced into each cell casing and battery paste carried by each plate is formed into the required active material of the plate by passing an electric current through the paste.

9. A method as claimed in Claim 4, of manufacturing an electric storage battery substantially as hereinbefore described.

10. An electric storage battery manufactured by a method as claimed in any one of Claims 4 to 9.

11. An electric storage battery as claimed in Claim 1, comprising the combination and arrangement of parts substantially as hereinbefore described with reference to and as shown in the accompanying drawing.