GB2030350A

GB2030350A - Lead-acid Batteries

Info

Publication number: GB2030350A
Application number: GB7926668A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1978-09-14
Filing date: 1979-07-31
Publication date: 1980-04-02
Also published as: GB2030350B

Abstract

In a lead-acid battery, in order to connect respective sets of battery plates in adjacent cell compartments through a hole in a partition wall between the compartments, each battery plate spaced from the partition wall is provided with a conductive terminal lug which has been bent to define a first portion 15a extending out of the plane of the grid towards the partition wall and a second portion 15b extending generally parallel with the partition wall. Thus, in each set of plates, the second portions 15b and a terminal lug defined by the battery plate directly adjacent the partition wall extend in face-to-face relationship into registry with the hole and, to complete the intercell connection, are resistance welded through the hole to the correspondingly shaped lugs of the further set of plates. <IMAGE>

Description

SPECIFICATION Lead-acid Batteries This invention relates to lead-acid batteries of the kind including a battery box divided into a plurality of cell compartments by partition walls, and packs of positive and negative battery plates having insulating separators interposed therebetween located in the cell compartments, each battery plate including a conductive grid which supports the active material of the plate and is provided with a projecting, conductive terminal lug, sets of like polarity battery plates in each cell compartment being electrically interconnected by way of said lugs and intercell connections between said sets of battery plates in adjacent cell compartments being made through holes in the partition walls between the compartments.

In conventional lead-acid batteries of the kind specified, the lugs projecting from the grids of each set of like polarity battery plates are interconnected by a lead or lead alloy strap. In addition, the straps are shaped to allow the intercell connections between the sets of plates in adjacent cell compartments to be made by way of the straps. However, production of the straps involves either flame burning or casting molten lead or lead alloy around the lugs, which leads to a problem since each of these techniques is difficult to control and generates toxic fumes.

Moreover, the use of connecting straps adds an extra step in the battery manufacturing process since the straps are necessarily produced separately from the completion of the intercell connections.

In order to avoid the problems of flame burning and casting, it has also been proposed to join each set of lugs to an already-formed connecting strap by resistance welding. However, this proposal suffers from the disadvantage that the cross-sectional area of the join between each lug and its associated strap is necessarily small and hence it is difficult to produce reliable joints in production. In addition producing suitable welding electrodes has been found to be a problem.

An object of the present invention is to overcome or alleviate the above-mentioned disadvantages experienced in the prior art.

In one aspect, the invention resides in a leadacid battery of the kind specified wherein, in each set of battery plates connected through a hole in a respective partition wall to a further set of plates in an adjacent cell compartment, the lug of each grid spaced from the partition wall includes a first portion extending out of the plane of the grid towards said partition wall and a second portion extending generally parallel with the partition wall, and said second portions and the lug of the grid directly adjacent the partition wall extend in face-to-face relationship into registry with the hole in the partition wall and are resistance welded through the hole to correspondingly shaped lugs of the further set of plates.

Conveniently, the lug of said grid directly adjacent said partition wall also includes said first and second portions.

In a further aspect, the invention resides in a method of manufacturing a lead-acid battery of the kind specified comprising the steps of: a) starting with a plurality of positive and negative battery plates, with the grid of each plate including a projecting conductive terminal lug extending substantially in the plane of the grid b) subjecting the lug of each grid to a first deformation operation so that the lug includes a first portion projecting out of the plane of the grid, c) subjecting the first portion of each lug to a second deformation operation so as to produce a second portion extending generally parallel with, but spaced from, the plane of the grid, d) before or after the first or both deformation operations, assembling the plates into packs with insulating separators between the plates and with the lugs of like polarity plates in each pack aligned and spaced from the lugs of the plates of opposite polarity, then e) before or after the first or both deformation operations, introducing each pack into a respective cell compartment of a battery box, the arrangement of the plates in each pack after the first and second deformation operations being such that the second portions of the lugs of each set of like polarity plates extend in face-to-face relationship parallel with and adjacent cell compartment and into registry with a hole in the partition wall, and then f) forming an intercell connection between respective sets of plates in each pair of adjacent cell compartments by deforming the second portions of the lugs in each set of plates into the hole in the partition wall between the compartments so that the second portions make contact through the hole and then resistance welding the deformed second portions together to produce the required intercell connection and seal the hole in the partition wall.

In the battery and method of the invention, resistance welding is used not only to effect the intercell connections but also to interconnect electrically the battery plates of likely polarity in each pack, thereby avoiding the problems involved in using lead casting and flame burning.

Moreover, the shape and disposition of the deformed lugs subjected to the resistance welding operation not only ensures a large joint area between the interconnected lugs, but also allows an intercell connection to be completed between plate packs in a pair of adjacent cell compartments at the same time as the interconnection of the like polarity battery plates in the packs.

Preferably, the deformation and the resistance welding operations of step (f) are performed by a pair of resistance welding electrodes shaped to deform the second portions into the respective holes in the partition walls.

In yet a further aspect, the invention resides in a battery plate grid for use in the method according to said further aspect of the invention, the grid comprising a lattice structure adapted to receive active material and a generally Lshaped terminal lug projecting from one external member of the lattice structure so as to be located substantially in the plane of the lattice structure, the lug being formed of a deformable material and having one relatively short limb extending generally perpendicular to said external member and another relatively long limb extending generally parallel with said member.

In still a further aspect, the invention resides in a battery plate grid comprising a lattice structure adapted to receive active material and a terminal lug which projects fron one external member of the lattice structure and which has been deformed so as to include a first portion projecting out of the plane of the lattice structure and a second portion generally parallel with, but spaced from, the plane of the lattice structure.

In the accompanying drawings, which illustrate a method according to one example of the invention, Figure 1 is a front view of a blanked battery plate grid, Figure 2 is a side view of the grid shown in Figure 1 after deformation thereof, Figures 3 to 5 are sectional views illustrating three stages respectively during the production of an intercell connection in an electric storage battery of the kind specified, and Figure 6 is a front view of a modification of the grid shown in Figure 1.

Referring to Figures 1 to 5, the method of the one example involves initially blanking battery plate grids from a sheet of lead or any lead alloy conventionally used in the battery field provided the alloy is capable of substantial deformation without fracture. The shape of the blanked grids is shown in Figure 1 from which it will be seen that each grid includes a rectangular body portion 11, in the form of a lattice structure (not shown) adapted to receive lead-acid battery paste, and a generally L-shaped terminal lug 12 projecting from one external member 13 of the body portion 1 1.Each lug 12 is located in the plane of its associated portion 11 and includes one relatively short limb 14 which extends perpendicular to the associated member 13 adjacent one end of the member 13, and another relatively long limb 15 which extends generally parallel with the member 13 so as to project from said one end thereof.

The blanked grids are then supplied in conventional manner with lead-acid battery paste and the resultant battery plates are assembled into packs of positive and negative plates having insulating separators interposed therebetween. In each pack, the plates of like polarity are arranged so that their lugs 12 are aligned and are spaced from the lugs of the plates of opposite polarity so that the limbs 15 of opposite polarity plates project from opposite sides respectively of the pack.

Each pack of plates and separators is then inserted into a forming tool which performs a two-fold deformation operation on the aligned lugs in the pack so that, as shown in Figure 2, each limb 15 defines a first portion 1 5a which projects at right angles from the plane of its associated grid and a second portion which extends in parallel spaced relationship with the plane of the grid. The deformation of the lugs in each pack is arranged so that the first portions 1 5a of the lugs of the positive and negative plates extend in opposite directions respectively from their associated plates and the second portions 1 5b of each set of aligned lugs extend in face-toface contact.

After deformation, each pack of battery plates and separators is introduced in a respective cell compartment of a battery box which is divided into a plurality of such compartments by integral partition walls 16 (only one shown in Figures 3 to 5). The arrangement of each pack is such that the second portions 1 Sb of each set of aligned lugs extend parallel with and adjacent the partition wall 16 defined with an adjacent cell compartment and into registry with a hole 17 formed in the partition wall. The holes 17 are provided to enable intercell connections between like polarity plates in adjacent cell compartments to be made through the partition walls between the compartments.

Completion of the intercell connections involves the use of the resistance welding electrodes shown at 18 in Figures 3 and 4. Each electrode 18 includes a generally cylindrical head 19 formed at one axial end with an integral frusto-conicai projection 21 of maximum diameter less than the diameter of the holes 17.

To produce an intercell connection between like polarity plates in a pair of adjacent cell compartments, the electrodes 18 are urged against the portions 1 Sb of the respective sets of plates so that the projections 21 deform the portions 1 5b into the hole 17 in the partition wall 16 between the compartments. The deformation is continued until the portions 1 5b in the two compartments make electrical contact through the hole 17, whereafter an electric current is passed between the electrodes. The resistance at the interface between the deformed portions 1 5b causes heating to occur at the interface so as to produce localised melting of the portions 1 5b.

The molten material fills the hole 17 so that, on cooling, the hole 17 is sealed and a resistance weld is produced between the portions to provide the required intercell connection. This is the situation shown in Figure 5.

The above operation is repeated for each pack of battery plates and separators in the central cell compartments on the box. In each end cell compartment, one set of like polarity plates is connected to a set of plates of the same polarity in the next cell compartment, while the other set of plates is connected by way of the portions 1 5b to a terminal post of the battery. Alternatively, the other set of plates in each end cell compartment could be connected to a terminal post using a conventional casting or flame burning technique, although this would suffer from the disadvantages outlined above.

In one practical embodiment of the method described above, the grids were produced from a lead 3% by weight antimony alloy and had a thickness of 1.01 mm over both the lattice structure 1 1 and the terminal lug 12. Moreover, each limb of the terminal lug had a width of 20.3 mm. The pasted plates were assembled into eleven plate packs and the packs were inserted into a polypropylene battery box divided into cell compartments by 1.5 mm thick polypropylene partition walls formed with holes 17 of the diameter 10.16 mm. The head 19 of each welding electrode 18 had a diameter of 19.5 mm and was formed at one axial end with a 1.01 mm high frusto-conical projection defining an included angle of 900 and having a minimum diameter of 7.62 mm.Deformation of the portions 1 5b in each pair of adjacent cell compartments was effected by applying a force of 4.88 kN between the electrodes 18 for at least 0.1 seconds. Then, when electrical contact between the portions 1 5b was established, a welding current of 12500 amps was past for ten cycles of a 50 cycle second a.c. supply to effect the required resistance welding of the portions 1 Sb, the force of 4.88 kN being maintained between the electrodes 18 during resistance welding.

After completion of the intercell connections, the battery plates are formed before or after a lid is sealed to the box.

Referring now to Figure 6, in the modification shown therein each blanked grid is again initially formed with a generally L-shaped lug 12, but now the limb 1 5 thereof extends away from said one end of the member 13 so as to be wholly defined between the ends of the member. With this arrangement, if the pasted plates were assembled into packs before any deformation of the lugs 12, the limbs 15 of opposite polarity plates would overlap to prevent the required deformation to produce the portions 1 spa. Thus, before the pack assembly operation, the lug 12 of each grid is deformed to produce at least the portion 1 spa, the remainder of the method then proceeding as described above. Similarly, in the method of said one example, part or all of the deformation of each lug could be effected before assembly of the plate packs. Alternatively, at least part of the deformation of each lug could be carried out with its associated plate pack being at least partly received in a respective cell compartment of a battery box.

As a further alternative, each grid could be provided with a generally straight, elongated lug 12 extending perpendicular to the member 13 of the grid, the lug again being deformed to produce the portions 1 spa, 1 sub.

Claims

1. A lead-acid battery of the kind specified, wherein, in each set of battery plates connected through a hole in a respective partition wall to a further set of plates in an adjacent cell compartment, the lug of each grid spaced from the partition wall includes a first portion extending out of the plane of the grid towards said partition wall and a second portion extending generally parallel with the partition wall, and said second portions and the lug of the grid directly adjacent the partition wall extend in face-to-face relationship into registry with the hole in the partition wall and are resistance welded through the hole to correspondingly shaped lugs of the further set of plates.

2. A battery as claimed in Claim 1, wherein the lug of said grid directly adjacent said partition wall also includes said first and second portions.

3. A lead-acid battery of the kind specified comprising the combination and arrangement of parts substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

4. A method of manufacturing a lead-acid battery of the kind specified comprising the steps of: a) starting with a plurality of positive and negative battery plates, with the grid of each plate including a projecting conductive terminal lug extending substantially in the plane of the grid, b) subjecting the lug of each grid to a first deformation operation so that the lugs includes a first portion projecting out of the plane of the grid, c) subjecting the first portion of each lug to a second deformation operation so as to produce a second portion extending generally parallel with, but spaced from, the plane of the grid, d) before or after the first or both deformation operations, assembling the plates into packs with insulating separators between the plates and with the lugs of like polarity plates in each pack aligned and spaced from the lugs of the plates of opposite polarity, then e) before or after the first or both deformation operations, introducing each pack into a respective cell compartment of a battery box, the arrangement of the plates in each pack after the first and second deformation operations being such that the second portions of the lugs of each set of like polarity plates extend in face-to-face relationship parallel with the adjacent cell compartment and into registry with a hole in the partition wall, and then f) forming an intercell connection between respective sets of plates in each pair of adjacent cell compartments by deforming the second portions of the lugs in each set of plates into the hole in the partition wall between the compartments so that the second portions make contact through the hole and then resistance welding the deformed second portions together to produce the required intercell connection and seal the hole in the partition wall.

5. A method as claimed in Claim 4, wherein the deformation and the resistance welding operations of step (f) are performed by a pair of resistance welding electrodes shaped to deform the second portions into the respective holes in the partition walls.

6. A method of manufacturing a lead-acid battery of the kind specified substantially as hereinbefore described with reference to the accompanying drawings.

7. A lead-acid battery of the kind specified manufactured by a method as claimed in any one of Claims 4 to 6.

8. A battery plate grid for use in the method of Claim 4, comprising a lattice structure adapted to receive active material and a generally L-shaped terminal lug projecting from one external member of the lattice structure so as to be located substantially in the plane of the lattice structure, the lug being formed on a deformable material and having one relatively short limb extending generally perpendicular to said external member and another relatively long limb extending generally parallel with said member.

9. A battery plate grid comprising a lattice structure adapted to receive active material and a terminal lug which projects from one external member of the lattice structure and which has been deformed so as to include a first portion projecting out of the plate of the lattice structure and a second portion generally parallel with but spaced from, the plane of the lattice structure.

10. A battery plate grid substantially as hereinbefore described with reference to any one of Figures 1 , 2 and 6.

11. A battery plate including a grid as claimed in any one of Claims 8 to 10 and active material supported by the grid.