METHOD OF ASSEMBLING MULTICELL ELECTRIC STORAGE BATTERIES

METHOD OF ASSEMBLING MULTICELL ELECTRIC STORAGE BATTERIES The present invention relates to a method of assembling multicell electric storage batteries, particularly of the type containing substantially no mobile electrolyte, e.g. batteries in which the 5. electrolyte is in gel form or recombination batteries in which substantially all the electrolyte is absorbed in the plates and separators. The invention is concerned in particular with such batteries of lead acid type. Recombination batteries are those which 10. contain a reduced amount of electrolyte such that substantially all the electrolyte is absorbed in the plates and separators and in which the gas evolved within them during operation or charging is not normally vented to the atmosphere but is induced to 15. recombine Within the battery.

Conventional lead acid batteries include a plurality of cells containing alternating positive and negative plates each of which has an upstanding plate lug. The cells are electrically connected 20. but electrolytically isolated by intercell partitions which are integral with the container and which are sealed to the lid and the plates of each polarity in each cell are connected together by a respective plate strap and plate straps of opposite polarity 25. in adjacent cells are connected together by an intercell connector. The steps of forming the plate straps and forming the intercell connectors are frequently combined, but nevertheless this is a time consuming and thus expensive operation which 30. requires a substantial amount of lead or lead alloy. The electrical paths through the plate straps -iì I 1SO88 o and intercell connectors are relatively long with the result that the battery has an appreciable internal resistance. Furthermore the grids which act as carriers for the active material of the plates and 5. thus the plates themselves are made relatively thick so as to exhibit the rigidity which is essential if the plates are to withstand the forces to which they are subject duringthe assembly of the battery. This thickness of the plates results in their including more i0. lead than is necessary as regards electrochemical requirements and a utilisation of the active material which is substantially less than the theoretical maximum.

It is highly desirable to minimise the amount 15. of lead or lead alloy used in the plates and in the plate straps and intercell connectors and, if possible, to eliminate the steps of forming the plate straps and intercell connectors all together.

It is also desirable that the intercell current 20. paths should be as short as possible thereby reducing the internal resistance of the battery and thus increasing its maximum output current and thus its cranking power in the case of an automotive battery.

British Patent Specification No. 2070844 of the present 25. applicants discloses a multicell electric storage battery of recombination type in which every alternate electrode in the two end cells is a unipolar plate whilst all the remaining electrodes are one half of a bipolar plate which is connected to its other half 30. in an adjacent cell by a bridge piece which passes 1219O38 o around one side of the intercell partitions separating the two cells. Each electrode is therefore integrally connected to an electrode of the opposite polarity in an adjacent cell by a bridge piece and there is thus 5. no need to form separate plate straps or intercell connectors.

In addition, the intercell current paths are of minimum length and the battery thus has a very low internal resistance.

10. Whilst the battery disclosed in this prior specification is very advantageous as regards its low internal resistance and the elimination of the steps of forming plate straps and intercell connectors, it is somewhat complex to assemble since the assembly 15. is a manual operation in which the electrodes are inserted successively into the container.

Accordingly it is an object of the present invention to provide a method of assembling a multicell electric storage battery, particularly of the type 20. containing substantially no mobile electrolyte, which requires a reduced amount of laboured particular handling of the plates, and in which the necessity of separately forming plate straps and intercell connectors is eliminated.

25. According to a first aspect of the present invention there is provided a method of assembling a multicell electric storage battery of the type comprising a plurality of cells electrically connected in series with each plate in each cell being 30. substantially coplanar with one plate in every other 1 19038 4o cell comprising forming a laminated structure from a plurality of superposed substantially planar plate arrays, each array comprising both positive and negative plates and each plate being connected to at 5. least one further plate in the same array by at least one link, the arrays being superposed in the laminated structure so that the plates of each array are in registry with those of the or each adjacent array and superposed plates of adjacent arrays are of opposite I0. polarity and separated by separator material, and forming one or more cuts to sever selected links thereby forming a plurality of stacks of plates of alternating polarity, which stacks constitute the individual cells in the finished battery, with each 15. plate, with the exception of every other plate in the two electrical end stacks of plates, electrically connected by one or more integral links to only a plate of opposite polarity in the same array, which unsevered links constitute the intercell connectors 20. in the finished battery, but with every alternate plate in the two electrical end stacks of plates connected to no other plate.

Thus in the method of the present invention it is not necessary to handle the plates individually 25. but instead they are handled in the form of plate arrays, each of which provides a single plate for each cell of the battery. The plates of each array are interconnected by a combination of temporary links which are subsequently severed in the laminated 30. structure and integral links or bridge pieces which 1 19C38 remain intact and serve as intercell connectors in the finished battery, thereby obviating the necessity of forming separate plate straps and intercell connectors.

5. It will be appreciated that the cells of the finished battery and thus the plates of the individual arrays may be disposed in any configuration. It is, however, preferred as regards the shape and layout of the finishedbattery and also manufacturing 10. convenience that the plates of each array are arranged in two lines.

Thus in accordance with a further aspect of the present invention there is provided a method of assembling an electric storage battery including 15. providing a plurality of elongate plate arrays each having two rows of battery plates extending side by side, the plates of each row being connected and certain plates being electrically connected by regularly spaced bridge pieces to a plate in the 20. other row, forming a laminated structure by superposing the plate arrays interleaved with sheets of separator material in such a manner that each plate of each plate array is adjacent to a plate of opposite polarity on the adjacent plate 25. array or arrays and the bridge pieces of adjacent plate members are offset in the direction of the length of the rows and are thus situated in a plurality of stacks spaced apart in the direction of the length of the laminated structure, forming a 30. plurality of cuts in each side of the laminated 12190,.3B structure, the cuts on the two sides being offset in the direction of the length of the laminated structure thereby forming two lines of stacks of plates of alternating polarity of which certain 5. plates in each line are connected to a plate of opposite polarity in the other line by a respective bridge piece and severing the laminated structure into a plurality of battery elements.

Thus in accordance with this aspect of the 10. present invention an elongate laminated structure is formed, either in a batch process or continuously, and the laminated structure is then cut up into individual battery elements by severing adjacent plates in the two rows and also selected stacks of 15. bridge pieces, if necessary. The battery elements may have two or more cells in which case the resultant battery will be a multicell battery or every plate may be separated from the or each adjacent plate and every stack of bridge pieces 20. severed in which case the resulting battery elements will comprise a single cell and the term "battery" as used herein is to be interpreted accordingly.

According to a further aspect of the present 25. invention a method of assembling a multicell electric storage battery comprises providing a plurality oÆ elongate plate arrays each having two rows of battery plates extending side by side, the plates of each row being connected and certain 30. plates being electrically connected by regularly 12190 7.

spaced bridge pieces to a plate in the other row, forming a laminated structure by superposing the plate arrays interleaved with sheets of separator material in such a manner that each plate of each plate array is adjacent 5. to a plate of opposite polarity of the adjacent plate array or arrays and the bridge pieces of adjacent plate arrays are offset in the direction of the length of the rows and are thus situated in a plurality of stacks spaced apart in the direction of the length 10. of the laminated structure, forming a plurality of cuts in each side of the laminated structure, the cuts on the two sides being offset in the direction of the length of the laminated structure thereby forming a battery element comprising two lines of stacks of 15. plates of alternating polarity of which certain plates in each line are connected to a plate of opposite polarity in the other line by a respective bridge piece.

Thus according to this further aspect of the 20. present invention the plate arrays may be formed or cut to the desired length prior to forming the laminated structure and the laminated structure is not cut up to separate it into individual battery elements since the laminated structure 25. itself constitutes a battery element after the cuts have been formed in it to separate adjacent plates from one anõther.

Thus the battery is assembled by a method in which it is not necessary to form individual 30. plates and then to assemble them into individual plate packs as is conventional but instead plate arrays, e.g. elongate arrays comprising two lines of plates are superposed and appropriate cuts are then made to divide them into individual cell packs and selected 5. bridge pieces are then severed, if necessary, to provide battery elements comprising the requisite number of cells for subsequent insertion into a container as a single unit. The plate arrays may include cast grids or expanded grids formed by 10. expanding a metallic strip leaving a central unexpanded land from which portions are subsequently removed leaving only spaced portions connecting the two expanded areas which portions constitute the bridge pieces. The grids of the arrays are then pasted with 15. positive and negative active electrode material respectively or alternatively they are pasted with the same universal active material which is capable of subsequently being formed into either positive or negative active material. Alternatively, a metallic 20. strip may be expanded over its entire area and portions subsequently removed from its central area leaving spaced expanded portions connecting the two active areas. The two halves of the expanded strip are then pasted with active electrode material, as described 25. above, and it will be appreciated that since the spaced portions connecting the two active areas are of expanded metal rather than solid metal it is desirable that these should be somewhat longer than in the case in which they are of solid metal so as 30. to ensure that they provide the requisite conductivity.

It will be appreciated that various steps in the method can be carried out at different points in the method. Thus the plurality of cuts in each side of the laminated structure may be formed either 5. before or after selected stacks of bridge pieces are severed and electrolyte may be added either before or after the battery elements are inserted into a container.

In one embodiment the battery element includes i0. four or more cells and the method includes placing it in a container which is of substantially rectangular section with one or more intercell partitions integral with each side wall, the intercell partitions extending substantially only to the centre of the container 15. and being offset from the intercell partitions on the other side of the container. In this case no positive step is required to ensure that adjacent stacks of plates, which constitute cells in the finished battery, are electrically separated from one 20. another but if no such integral partitions are present each stack of plates may be placed in a plastics bag prior to placing it in a container.

The cuts in the laminated structure may be formed by any appropriate method, but care must 25. be taken to ensure that the method does not burr the edge of one plate sufficiently far that it contacts an adjacent plate since this would constitute an internal short circuit in the finished battery. It is found that these cuts may be 30. reliably formed by a high speed band saw. The cut 10.

edges of each cell pack may be sharp and relatively unstable and it may therefore be desirable to place a stabilising member, eogo a strip of the same separator material, in contact with each cut surface, 5. i.e. two such members per cell pack, which then engage both the cut edges and the intercell partitions and ensures the mechanical integrity of the former and provides a barrier to lead growths thereby protecting the battery from internal short circuits.

10. As referred to above, the plate arrays may include an expanded metal gr±d, e.g. of lead or lead alloy in the case of a lead acid battery, and it will be appreciated that in this event the individual plates in each line or row of plates are 15. not identifiable as such until the cuts have been formed to separate adjacent plates from one another.

Similarly the temporary links, that is to say the positions where the cuts are to be formed in the plate arrays may not be identifiable as such prior 20. to the formation of the cuts. Preferably however each plate array includes cast grids, preferably produced by continuous casting, and in this case the individual plates may be individually identifiable prior to their being separated. In this event, the 25. individual plates may be connected prior to their separation by identifiable temporary links constituting one or more integrally cast bars. These bars of each plate array are preferably so disposed that when a laminated structure is built up from 30. superposed plate arrays the bars of adjacent plate 1 19035 11.

arrays are not directly superposed but are offset from one another which results in a reduced risk of these bars being pressed into contact with one another when the cuts are formed in the laminated structure 5. which would otherwise lead to internal short circuits within the finished battery.

The battery may be of flooded electrolyte type, in which case the separator may be of conventional type, i.e. micorporous PVC. It is necessary to take i0. great care in this construction to ensure that the cells are electrolytically sealed from one another.

Adjacent cells which are not directly connected by the bridge pieces may be separated by providing intercell partitions, preferably integral with the 15. bottom and two side walls of the container. These preferably extend approximately half way across the width of the container in the case in which the bridge pieces all extend between two lines of cells, the partitions on the two sides of the 20. container being of necessity offset from one another, e.g. by substantially half a pitch and sealed to the battery lid. Those cells which are not directly connected, e.g. the two lines of cells, may be sealed from each other by moulding a 25. partition to form a seal with the bridge pieces in situ in the container by pouring in a settable material, such as epoxy resin. Alternatively, an integral intercell partition may be provided with slots to accommodate the integral bridges which are subsequently 30. sealed by e,g. epoxy resin or hot melt adhesive.

I 13038 12.

In both cases the intercell partitions must also be sealed to the battery lid.

The present invention is however more applicable to batteries of the type containing substantially no 5. mobile electrolyte, e.g. of recombination type. In this latter event, the electrolyte is present in the cells in a reduced amount, that is to say an amount such that there is substantially no free unabsorbed electrolyte, and the separator material is i0. compressible fibrous and absorbent, preferably microfine glass fibre material. In this event, it is still highly desirable that cells which are adjacent but not directly connected be separated by an intercell partition since otherwise the 15. separator material of one cell might contact that of an adjacent cell thus providing an intercell ionic leakage path. These intercell partitions need not be fixed within the container and may thus be constituted by the material of plastics bags 20. within which each cell is accommodated or alternatively by in situ moulded partitions, e.g. of hot melt adhesive. In any event, it is not essential in this construction that the cells be completely sealed from each other and thus the intercell 25. partitions need not be sealed to the lid since in batteries of this type with substantially no mobile electrolyte there is believed to be no, or at least a substantially diminished, risk of intercell ionic leakage currents occurring.

1 19088 13.

Further features and details of the present invention will be apparent from the following description of certain specific embodiments which is given by way of example only with reference to 5. the accompanying drawings, in which:- Figure 1 is a perspective view of a 12 volt lead acid automotive battery of recombination type from which the lid has been omitted for the sake of clarity; I0. Figure 2 is a plan view of the battery of Figure 1 showing only the top layer of plates; Figure 3 is a view similar to Figure 2 showing only the layer of plates below the top layer; Figure 4 is a plan view of a single expanded 15. electrode member for use in the assembly of a battery in accordance with the invention; Figure 5 illustrates diagrammatically the formation of the laminated structure of electrode members and separator material; 20. Figure 6 shows the laminated structure after the cuts have been made in the two sides; Figure 7 is a plan view of a single cast electrode member or grid array for use in the assembly of an alternative construction of 25. battery in accordance with the invention; Figure 8 is a view similar to Figure 2 showing a battery assembled from cast plate arrays; Figures 8 and 10 are views similar to Figure 7 showing modified constructions of cast grid array.

30. Figures Ii and 12 are views similar to Figures 2 and 3 respectively of an alternative embodiment; and 12t9038 14.

Figures 13 and 14 are further views similar to Figures 2 and 3 respectively of a further alternative embodiment.

Referring first to Figures 1 to 3, the 5. battery includes a rectangular section container 2 of polypropylene or like material integral with each of whose two longer sides are three intercell partitions 4. Each partition 4 extends substantially only to the longitudinal centre line of the container I0. and the partitions on ones side of the container are offset from those on the other side by a distance substantially equal to one half of the distance between adjacent partitions. The partitions divide the interior of the container into two lines 15. of three equally sized compartments at one end of which is an empty space 6 and at the other end of the other of which is a similar empty space.

Each compartment defined by the intercell partitions contains a stack of planar horizontal 20. alternating positive and negative plates interleaved with compressible fibrous absorbent separator 15.

material, which in this case comprises a sheet of microfine glass fibres. Every alternate plate in the two endcells, that is to say the left hand cell in the upper line and the right hand 5. cell in the lower line as seen in Figures 2 and 3, constitutes a unipolar plate having a lug 8 projecting therefrom. The lugs 8 are thus disposed in two vertical stacks which are connected to respective positive and negative terminal pillars i0 i0. which are situated in the spaces 6 and which project through the battery lid. The remáining plates in the two end cells and all the plates in the other cells each constitute one half of a bipolar pair of plates whihc is connected to its other half in 15, a cell in the other line of cells by an integral bridge piece 12 which extends perpendicular to the direction of the length of the lines of cells Each cell contains an amount of electrolyte which is insufficient to saturate the electrodes 20. and separator material and if gas is evolved during charging of the battery this is induced to recombine within the battery. The container is sealed by a lid (not shown) which is provided with a single safety vent with which each cell communicates and 25. through which gas may be vented if it is evolved at a rate in excess of that at which it can be recombined. The lid, or pads (not shown) on the underside of the lid engage the tops of the cell elements thereby restraining them against vibration 30. and minimising the volume of the space in which a lZ1903B 16.

potentially explosive gas mixture may accumulate.

As may be seen in Figure 2, there is an appreciable gap between each cell and the adjacent side wall of the container to permit the ready introduction of the 5. electrolyte into the battery and/or to accommodate excess electrolyte at the time when the battery is subjected to its initial formation.

In a modified construction, which is not illustrated, the bridge pieces 12 extend at an acute i0. angle to the direction in which the lines of cells extend. This permits the empty spaces 6 to be reduced in volume but does not permit these to be dispensed with altogether when the container is of rectangular section.

15. The battery is manufactured by a method which will now be described with reference to Figures 4 to 6. A plurality of elongate or continuous electrode members or grid arrays 20, of which one is shown in Figure 4, are formed comprising two continuous spaced 20. grids 22 and 24 of lead or lead alloy each having a respective selvedge 26. Each grid array is substantially symmetrical about a median line 40. The selvedges are integrally connected at spaced intervals by bridge pieces 28. The grid arrays may be cast in a 25. conventional casting machine but in this embodiment a strip of lead or lead alloy is continuously expanded in an expander machine leaving an unexpanded central land from which rectangular portions are subsequently removed to form apertures separated by 121903S 17.

the bridge pieces 28. The grids 22 and 24 are then pasted withpositive and negative active material respectively or alternatively they are both pasted with the same universal active material, that is 5. to say an active material which can be electrolytically formed into either positive or negative active material.

The grid structure of the positive grid 22 is preferably smaller than that of the negative grid 24 since positive active material may require more 10. physical suppose than negative active material, The meshes of the grids are preferably of decreasing ç crossoEection with increasing distance away from the bridge pieces 28 to optimise the electrical performance of the battery per unit weight of lead 15. utilised. A plurality of pasted grid arrays, which may now be regarded as plate arrays, are then overlaid to form a composite laminated structure, shown diagrammatically in Figure 5, with an elongate strip of microfine glass fibre separator 20. material 30 interleaved between eaÇhoadjacent pair of elongate grids 22, 24. The plate arrays are superposed such that each active area of each plate array is adjacent toan active area of opposite polarity on the or each adjacent plate 25. array. In addition, adjacent plate arrays are offset longitudinally by half a pitch with the result that the bridge pieces of each plate array are adjacent to the centres of the apertures defined by the bridge pieces of the or each adjacent 30. plate array.

12190,38 18.

10.

After formation of the laminated structure a plurality of cuts 32 is made in each side of it extending over its full height andlinto the central spaces defined by the bridge pieces 28. The cuts on 5. each side of the laminated structure are spaced apart by a distance equal to the spacing of the bridge pieces of the plate arrays and the cuts on the two sides are offset longitudinally by half a pitch.

The laminated structure is thereby separated into two continuous spaced lines of stacks of separate plates of alternating polarity of which every plate is connected to a plate of opposite polarity in a stack of plates in the other line by an integral bridge piece and thus constitutes one half of a 15. bipolar pair of plates. he cuts may be formed in any suitable manner which does notdeform the cut edges of the plates sufficiently far that they contact an adjacent plate in the same stack and it is found that this may be conveniently performed 20. by means of a high speed band saw.

The two lines of stacks of plates are interconnected by the bridge pieces which are disposed in a plurality of stacks, the bridge pieces in each stack alternately connecting a positive 25. plate in one stack in one line to a negative plate in a stack'in the other line and a negative plate in the one line to a positive plate in the other line.

Selected stacks of bridge pieces are then severed at their central point, for instance by means of the high 30. speed band saw, to separate the laminated structure 19.

into battery elements. It will be appreciated that the stacks of bridge pieces to be severed are selected in accordance with the number of cells to be possessed by the finished battery, and in the 5. case of a six cel! 12 volt battery every sixth stack of bridge pieces is severed. Each battery element thus has a stack of severed bridge pieces at each end and it will be appreciated that in the finished battery these are connected to the battery i0. terminals. This latter operation may be performed in any convenient manner but in this embodiment the laminated structure is placed in a clamp for the severing operation and the bridge pieces of each of the two stacks of severed bridge pieces are « 15. connected together by forming a mould cavity around them whilst still in the clamp, for instance by means of a two part comb mould or by dipping them into a mould cavity into which molten lead or lead alloy is introduced. Each battery element is 20. then placed into a battery container with integral intercell partitions as illustrated in Figures 1 to 3, for instance by lowering a battery container onto the battery element whilst it is supported on the bottom plate of the open clamp, 25. or alternatively each stack of plates is placed, within a respective plastics bag and the battery element then placed into a battery container having no fixed intercell partitions. It will be appreciated that in the assembled battery each 30. stack of plates constitutes one cell and that each 1í 190,3S 20.

plate in the two end cells, that is to say the cells at the electrical end of the series-connected cells, whose bridge piece has been severed constitutes a unìpolar plate and is connected to a terminal of the 5. battery whilst all the remaining plates constitute one half of a bipolar pair of plates whose other half is in the other line of cells.

Electrolyte is added to the cells in any convenient manner either before or after the insertion i0. of the battery element into the battery container in an amount insufficient tosaturate the electrodes and separator material and after the sealing of a lid to the battery container the battery is then complete. The lid, or pads on the lid, exert a 15. compressive force on all the cells thereby pressing the plates nd separators into intimate contact which is believed to be necessary for efficient recombination operation. The formation of plate straps and intercell connectors is not required 20. since each plate which constitutes one hall er a bipolar pair of plates is connected to its other half by a bridge piece which constitutes an intercell connector and thus only terminal pillars need to be formed to connect together the two stacks of 25. severed bridge pieceswhich pillars may extend through the lid or be subsequentlyconnected to respective terminals projecting up from the battery lid.

In the method described above the battery is 30. assembled from electrode members comprising two elongate expanded grids connected by spaced solid I I 038 21.

bridge pieces. Such electrode members are most conveniently made by expanding a metallic strip to leave an unexpanded central land from which portions are subsequently removed. This method is very 5. wasteful of material and thus in an alternative method of assembly, which is not illustrated, each electrode member comprises an elongate metallic strip expanded over its entire area. The central pòrtions removed from these strips are much shorter than in the case i0. in which there is a central unexpanded land and the remaining bridge pieces preferably have a length of between % and ½ of the pitch of the bridge pieces.

The bridge pieces are thus themselves of expanded grid form but are found to perform their electrical 15. function perfectly adequately. It wil! be appreciated that the wastage in this method is substantially reduced firstly because the removed portions are much smaller and secondly because the removed portions are expanded and not solid metal.

20. In the embodiments described above the electrode members or grid arrays and the plates of the finished battery comprise expandedmetal and it will be appreciated that in this case the grids are not identifiable as such in the electrode 25. members and after pasting but prior to cutting the individual plates also are not identifiable and only become identifiable once the cuts have been made and the pasted electrode members separated into individual stacks of plates. However, in a further 30. embodiment, which will be described with reference lí 190, '18 22.

to Figures 7 mnd 8, the plates are cut from a cast array of pasted interconnected grids comprising two lines of separately identifiable plates, the plates in each line being integrally connected by 5. means of temporary links.

Referring now to Figure 7, the battery grid array comprises a planar elongate strip of lead or lead alloy mesh which is continually cast on a casting machine generally of the type described in 10. U.S. Patent Specification No. 4349067, a short length of which cast mesh is shown in Figure 7. The casting is in the form of an array of grids arranged in two spaced parallel lines disposed on opposite sides of what may be termed a median line or line 15. of symmetry 40. The grids Ii of one line are adapted to be formed into negative plates and are offset by half a pitch from the grids 14 of the other line which are adapted to be formed into positive plates. The two lines are separated by a gap 13 but 20. each negative grid is integrally connected to a positive grid by a bridge piece or lug 28 which crosses the gap. The pitch of the lugs 28 is thus equal to the pitch of the grids in the two lines.

The grids of each line are spaced apart but inter25. connected by integral temporary links 15 which give the cast elongate strip some stability but which are severed during assembly of the battery. Each grid is formed with bars 17 extending parallel to the length of the array which are closer spaced in the 30. positive grids than in the negative grids. The 121 3S 23.

negative grids also include bars 18 extending transverse to the length of the array whilst the positive grids include bars 19 generally radiating from the lugs 28. The grid frames are broadened 5. adjacent their point of connection to the lugs 28, as indicated at 21. In general, the bars in the positive grids are wider than those in the negative grids and the thickness of the grids for a typica! automotive battery is about one millimetre, or less.

10. After casting, the strip is pasted, that is to say active material is applied to the grids. Thus positive and negative active material is applied to the lines of positive and negative grids respectively in any conventional manner.

15. Batteries are assembled from such pasted grid arrays, i.e. from plate arrays, by forming a laminated structure and then forming cuts in a manner similar to that described above. However, in this embodiment, the laminated structure is not continuous 20. but each grid array is cut to the desired length prior to forming the laminated structure thereby avoiding the necessity of severing stacks of bridge pieces.

In one specific method of battery assembly a 25. strip comprising 144 interconnecting grids of the form shown in Figure 7 is cast, the two lines of grids are pasted with positive and negative active material respectively and a strip of separator material is then laid on each row of pasted grids, 30. that is to say plates, and optionally lightly 24.

secured thereto. The strip is then severed into 24 arrays of 6 plates each by severing appropriate links 15 and bridge pieces 28 and the separator material overlying the links to be severed. A 24 5. layer laminated structure is then built up and it will be appreciated that this will necessitate the turning of every alternate plate array through 180° to permit the desired registry of plates of alternating polarity to be achieved.

i0. When the laminated structure is separated into individual cell packs a total of four cuts is all that is required, each severing a temporary link 15 in each of the 24 layers. It will be appreciated that the unipolar plates in the two end cells, that is to 15. say the cell at one end of one row and the other end of the other row, has a bridge piece which was severed prior to the formation of the laminated structure and thus terminates short of the other row.

The resultant laminated structure is similar to 20. that shown diagrammatically in the right hand half of Figure 6. As in the previous embodiments the laminated structure may be many layers thick and the precise number of layers will be related to the desired current capacity of the battery. In the first, third, 25. fifth, etc. layers of the laminated structure the negative plates are on one side and in the second, fourth, etc. layers the negative plates are on the other side of the laminated structure.

As may be seen in Figure 7, each bridge piece 28 30. is separated into two by a central gap 46 extending parallel to its length, i.e. transverse to the length 1219O38 25.

of the rows. When the continuously cast strip is separated into individual grid arrays every sixth bridge piece is severed also and this is done by forming two cuts 47 which communicate with the gap 5. 46 to leave two full length but half width terminal connectors, designated 48 in Figure After the laminated structure has been built up from individua! plate arrays it is clamped, as before, to facilitate its separation into individual i0. cell packs by severing the links 15. The connectors 48 are disposed in_two vertical stacks and a tapered terminal pillar 57 is then formed around each such stack, preferably by pouring molten lead into a mould placed around the stack. The cross section of 15. the terminal posts 57 increases such that at their take-off end the cross-section is equa! to the aggregate cross-section of each of the stacks of bridge pieces 28, which of course constitute the intercell connectors in the finished battery. The 20. terminal pillars are positioned as close as possible to the inner faces of the grids to minimise the internal resistance of the battery.

The severed structure is then placed as a unit into an outer container 2, seen in Figure 8, of 25. similar construction to that shown in Figure 2. The battery is then filled with electrolyte and either before or after the addition of the electrolyte side terminal connectors 59 on the container are connected to the terminal posts 57 by resistance 30. welding or the like. The battery is then 26.

electxolytical!y formed and the container sealed by a lid.

In the method referred to above, it is necessary to sever certain of the bridge pieces 28 to leave half 5. connectors 48 to which terminal posts are connected.

This is avoided in the modified construction of grid array shown in Figure 9 in which those bridge pieces, which in the construction of Figure 7 are severed, are cast integral with one grid but terminating i0. short of the other row of grids and thus do not require to be severed. These bridge pieces or connectors are designated 48 and may be of simple rectangular shape. Alternatively, the end of these connectors may be inclined to the length of 15. the connectors, either over their whole width, as shown in the right hand connector 48 in Figure 9, or over only a proportion of their width as shown in the left hand connector 48 in Figure 9. Such shaping of the connectors 48 is found to facilitate 20. the formation of the terminal pillars, the reason for which is believed to be that the molten metal can more readily flow around the connectors 48 and reliably key to them.

In the grid arrays of Figures 7 and 9 the 25. temporary links 15 are differently positioned in the two lines of grids such that when the laminated structure is built up the links in each layer are offset from those in the or each adjacent layer thereby substantially obviating the risk that the 30. links of adjacent layers are "smeared" together lí 1 38 27.

when the cuts are formed which would lead to internal short-circuits in the finished battery.

In a further modified construction of grid array shown in Figure i0, the casting machine is 5. modified so that each row of grids contains grids of positive type and of negative type which are associated with grids of opposite polarity type in the other row. In this case, each row includes groups of threepositive plates alternating with 10. three negative plates and it will be appreciated that this number is appropriate for a six cell battery and will be varied if the battery is to have a number of cells other than six. Certain bridge pieces are again discontinuous and have 15. inclined ends, as described in connection with Figure 9.

The advantage of this construction is that after separation of the cast strip into individual grid arrays, a laminated structure may be formed without 20. the necessity of having to rotate every alternate array through 180°. In this construction the links between the positive grids in each line are offset from those between the negative grids in the same line so that as in the previous constructions the 25. links in adjacent layers in the laminated structure are laterally offset from one another. However manufacturing considerations may require that, if the pasting is to be effected in a rapid single pasting operation, the grids of each row are pasted 30. with the identica! active material and since both tí 19038 28.

rows contain grids of both polarities, both rows are pasted with a universal active paste, that is to say active material paste which may be electrolytically formed into either positive or negative material.

5. Alternatively, each grid may be pasted with an active material specific to the polarity which it is to adopt in the finished battery and this may be effected in any suitable manner, e.g. by manual pasting of the separate grids individually.

10. In the modified construction of 12 volt automotive battery illustrated diagrammatically in Figures ii and 12 only one intercell connector, constituted by a stack of bridge pieces 12, extends between the two lines of cells and the other four such connectors 15. extend in the direction of the length of lines, two being situated in each line. This avoids the necessity of offsetting the two lines of cells and the six cells thus have together a substantially rectangular shape in plan. In addition, the 20. polarity of the plates in each line in each planar plate array is not the same, as is the case in the previous embodiments, but alternates in each line.

Those pairs of cells which are directly connected by an intercell connector are maintained spaced apart 25. only by the bridge pieces constituting the intercell connector whilst those cells which are adjacent but not directly connected, namely the left hand two cells in the upper and lower lines of cells as seen in Figures 9 and 10, are separated by an intercell 30. partition 4 integral with the container 2.

1 19038 29.

Such a battery is assembled by casting a plurality of two types of grid array shown in Figures ii and 12 respectively in which the grids are connected by integral bridge pieces and also by integral temporary 5. links 15, which are shown in dotted lines. The types of array may be cast continuously in a single strip with the two types of array alternating in the strip and connected by temporary links which are severed prior to the formation of the laminated structure. The i0. grid arrays are then all pasted with a universal active material or alternatively each grid is individually pasted with an active material which is specific to the polarity which it is to adopt in the finished battery. A laminated structure is then 15. built up with the two types of plate array alternating and with each plate separated from the or each adjacent plate with which it is in registry by a strip of separator material. A total of six cuts are then made in the laminated structure to sever the 20. temporary links 15 whilst leaving the bridge pieces 12. The battery is then completed as described above in connection with the previous embodiments.

In the still further construction of battery illustrated diagrammatically in Figures 13 and 14, 25. the cells are not disposed in two rows but are assymmetrically disposed. The top layer of plates, and every alternate layer beneath it, comprises three bipolar pairs of plates ii, 14 of opposite polarity connected by a respective integral bridge 30. piece 12 and the layer below the top layer and every 1 ,1903S 30.

alternate layer beneath that comprises two bipolar pairs of plates integrally connected by a bridge piece and two unipolar grids connected to respective terminal posts i0. Each cell comprises a stack of 5. pasted grids of alternating polarity separated by a respective strip of separator material and each cell is maintained spaced apart from the or each cell to which it is directly connected by an intercell connector constituted by a stack of bridge pieces 12 I0. by the said intercell connector only. Each cell is separated from the or each adjacent cell to which it is not directly connected by an intercell connector by an intercell partition 4 integral with the container 2.

15. Such a battery is assembled by forming a laminated structure of two alternating constructions of grid array having the grid configuration shown in Figures 13 and 14 respectively. The grids of each array are interconnected by the integral 20. bridge pieces 12 and additionally by sufficient integral temporary links 15, which are shown in dotted lines, to impart adequate structural stability.

A total of six cuts is then made to sever the links whilst leaving the bridge pieces 12 and the 25. battery is then completed as described above.

The term "batteries of the type containing substantially no mobile electrolyte" does not exclude the possibility that a small amount of free electrolyte may be present, at least at certain times.

30. Thus after electrolytic formation there may be a 1 190 S 31.

small amount of free electrolyte present in a recombination battery but this will simply be electrolysed off once the battery is put into service thereby brining the battery into a full recombination 5. mode. Similarly, when a recombination battery is very deeply discharged a small amount of free water may be produced but this is reabsorbed when the battery is charged again.

The battery makes very economical use of lead i0. because all the lead used during casting is included in the finished battery except for the small amount of lead forming the temporary interconnecting links.

In view of the fact that the plates in the 15. finished battery are "horizontal" and may be retained horizontal at all times during assembly of the battery the plates may be designed primarily for electrochemical efficiency since mechanical strength and in particular bending rigidity is not 20. an important requirement. This enables the plates to be substantially thinner than in a conventional battery which results in a more efficient utilisation of active material and the need for less metallic lead in the battery. This fact coupled with the 25. fact that the intercell connections are integral and necessarily of the minimum theoretical length results in the peak current which the battery may produce being very high, which capability may result in the case of an automotive battery in the battery 30. having a reduced weight and thus reserve capacity for a given cranking power which is a functionof the peak current.

lí 1903 32.