GB2102621A - An electric storage battery - Google Patents

Abstract

A plate pack for use in producing an electric storage battery, including first and second conductive straps provided at one edge surface of the pack and connected to the positive and negative battery plates respectively, each conductive strap 19, 21 having an intercell connecting portion 19ab, 21ab, which is so disposed relative to an axis of the pack extending perpendicular to, and through the centre of, said one edge surface that, if the pack is turned through an angle of 180 DEG about said axis, the connecting portions of the first and second straps occupy different positions from those originally occupied by the connecting portions of the second and first straps respectively. The invention in a further aspect relates to a battery box for use with such a plate pack. <IMAGE>

Description

SPECIFICATION An electric storage battery This invention relates to an electric storage battery of the kind including a battery box closed by a lid and divided by partition walls into a plurality of cell compartments, packs of positive and negative battery plates housed in the cell compartments and conductive intercell connectors extending between adjacent cell compartments and electrically connecting sets of plates of opposite polarity in said adjacent cell compartments. Particularly, but not exclusively, the invention relates to electric storage batteries of the kind specified for use in powering electrically driven vehicles.

Prior to the advent of synthetic resin battery boxes, the intercell connectors of electric storage batteries of the kind specified were normally produced before the packs were located in the cell compartments, and consisted of generally U-shaped components which located over the free ends of the partition wall and were housed in adhesive-filled recesses in the battery lid.

In the past decade, it has become increasingly common to use synthetic resin battery boxes and to arrange for the intercell connectors to extend through holes in the partition walls so that the top of the box is left free for connection to the lid. The production of through-the-wall connectors requires that the packs are constructed as separate units which are provided with conductive straps which interconnect like polarity plates in the pack.

Each pack is then introduced into its respective cell compartment so that an integral extension of each strap is in registry with a hole in one of the partition walls and with the extension of a strap pack in an adjacent cell compartment. The extensions of each pair aligned through a hole in a respective partition wall are then welded together, conveniently using resistance welding, by means of a conductive slug which may initially be integral with one or both of, or separate from both of, the extensions.

A problem, however, exists in producing through-the-wall connections as described in the preceding paragraph in that plate packs are traditionally designed so that the two conductive straps (one connected to the positive plates and the other connected to the negative plates) are disposed symmetrically about the major axis of the pack. This means that, if a pack of plates is accidentally reversed when located in its respective cell compartment, it is possible to connect each set of plates in the pack to the wrong polarity plates in the adjacent compartment so that, for example the negative plates in one cell may accidentally be connected to the negative plates in the adjacent cell.When the reversed cell is part of a 12 volt S.L.I. battery for a road vehicle, the fault will not normally be detected during manufacture and the battery may give reasonable service before failure.

However, with a high energy battery designed to provide power for an electrically driven vehicle, a reversed cell constitutes a far more serious problem. Thus, in an electric vehicle application, where as many as thirty six 6 volt batteries may be connected in series, large currents flow through each battery so that, if one cell of a battery is reversed, the temperature may rise to such an extent that part of the electrolyte and/or a large quantity of gas will be expelled from the cell. In the former case, if the electrolyte comes into contact with the chassis of the vehicle the chassis may become live with obvious and dangerous consequences, whereas in the latter case the gases could form an explosive mixture. An object of the present invention is therefore to overcome or alleviate the above-mentioned problems.

Accordingly, the invention resides in one aspect in a plate pack for use in producing an electric storage battery of the kind specified wherein the intercell connectors extend through the partition walls, the plate pack including first and second conductive straps provided at one edge surface of the pack and connected to the positive and negative battery plates respectively, each conductive strap having an intercell connecting portion which is so disposed relative to an axis of the pack extending perpendicular to, and through the centre of, said one edge surface that, if the pack is turned through an angle of 1 80 about said axis, the connecting portions of the first and second straps occupy different positions from those originally occupied by the connecton portions of the of the second and first straps respectively.

In a further aspect, the invention resides in a battery box for use with at least one plate pack according to said one aspect of the invention in producing an electric storage battery of the kind specified, wherein the battery box is divided by said partition walls into a pair of end cell compartments and at least one central cell compartment, and the partition walls defining the or each central cell compartment are formed with respective apertures which are located at different distances respectively from the base and/or the external walls of said central compartment so that the intercell connecting portions of said plate pack can only be aligned with the apertures respectively when the plate pack is inserted into said cell compartment in a single predetermined orientation relative to the compartment.

The accompanying drawing is a plan view of a partly-assembled, three cell lead-acid battery including a plate pack according to one example of the present invention.

Referring to the drawing, the battery includes a generally rectangular battery box 11 which is moulded from polypropylene or other suitable thermoplastics material. The box 11 is divided into three cell compartments by a pair of spaced partition walls 12 which extend parallel to the shorter, end walls 1 3 of the box 11. Each of the partition walls 12 has an aperture 14 stamped therein to enable the intercell connections to be made through the partition walls.

Each cell compartment receives a preformed pack 15 of positive and negative battery plates which are arranged alternatively in the pack and are insulated from one another by porous separators. Each battery plate includes a a conductive terminal lug which extends from one edge surface of its associated pack 15, with the terminal lugs of the negative battery plates being aligned and disposed at one side of a plane passing through the centre of, and extending perpendicular to, said one edge surface of the pack. Similarly, the lugs of the positive plates in each pack are aligned, but are disposed on the opposite side of said central plane.

In each of the two packs 15 which are mounted in the end cell compartments respectively of the box 11, the lugs of one set of like polarity plates are interconnected by a lead strap 16 formed with an integral upstanding terminal post 17, while the lugs of the opposite polarity plates are interconnected by a lead strap 18 formed with an integral upstanding extension 1 8a which extends parallel to and adjacent a respective partition wall 1 2.

Each extension 1 8a is formed with a bore 1 8b which is positioned so that, when the respective pack is correctly located in the requisite end compartment of the box 11, the bore 1 8b is aligned with the aperture 14 in the adjacent partition wall 12.

The pack according to said one example of the invention is located in the central cell compartment of the box and has the terminal lugs of its two sets of like polarity plates connected to first and second lead straps 19, 21 respectively. The straps 19, 21 are formed integrally with respective upstanding extensions which are indicated by the suffix a in the drawing and which extend parallel with and adjacent the partition walls defined at opposite sides respectively of the central cell compartment. As in the case of the extensions 1 boa, each of the extensions 1 9 a, 21 a is formed with a bore therein which, when the pack of said one example is correctly located in the central cell compartment of the box, is aligned with the aperture 14 in one of the partition walls 12.The required intercell connections between the packs 15 can then be produced through the partition walls in the manner described below. The bores 1 9b, 21 b are, however, non-symmetrically disposed relative to the plane passing through the centre of, and extending perpendicular to.

said one edge surface of the Dack In oarticular, the bore 21 b is located closer to said plate than the bore 19b. The apertures 14 are necessarily disposed in the same non-symmetrical arrangement and hence, during assembly of the battery, if the central pack 15 is loaded into the central cell compartment in the incor react orientation (i.e. turned through an angle of 1 80' about an axis extending through the centre of, and perpendicular to, said one end surface of the pack). the bores 1 9b. 21 b will not be aligned with the apertures 14 in the partition walls 12. In this situation, it will not be possible to complete the intercell connections to the central pack, thereby avoiding the possibility of the connections to the pack being reversed.In the case of the packs in the end cell compartments, it will be appreciated that reverse insertion of each pack is inherently avoided by the fact that the pack is provided with only a single apertured extension 1 Sa. Moreover, in view of the nonsymmetrical positioning of the apertures 14 relative to said central plane, the bores 1 8b must have the same asymmetric disposition and hence the intercell connections can only be completed if each end pack is located in the correct end cell compartment.

The required intercell connections of the battery are of course formed through the apertures 1 4 between the extensions 1 9 a, 21 a in the central cell compartments and the extension 1 8a in each end cell compartment.

In the example shown in the drawing, these connections are produced by way of conductive slugs (not shown) which are formed separately from the extensions and are inserted through the bores 18b, 1 9b and 18b, 21b and the apertures 14, after the packs 15 are loaded into the box 11. Each pair of adjacent extensions is then joined to the slug extending therethrough by electrical resistance welding.

As an alternative to the arrangement shown in the drawings, one or both of each pair of adjacent extensions could be provided with an integral lug extending into the hole 14 in the associated partition wall 12. The adjacent extensions would then be resistance welded together through the lug(s).

While in the above example the apertures 1 4 are spaced by different distances from their adjacent external box walls it is to be understood that the apertures could alternatively be spaced by different distances from the base of the box 11. As a further alternative the apertures 14 could be spaced by different distances from both the base and the adjacent external walls. In each case the e tensions 1 9 a 21 a will be correspondingly positioned on their respective pack 15.

Claims (7)

1. A plate pack for use in producing an electric storage battery of the kind wherein intercell connectors extend through the Dartition walls of the batterv box. the date nack including first and second conductive straps provided at one edge surface of the pack and connected to positive and negative battery plates respectively, each conductive strap having an intercell connecting portion which is so disposed relative to an axis of the pack extending perpendicular to, and through the centre of, said one edge surface that, if the pack is turned through an angle of 1 80' about said axis, the connecting portions of the first and second straps occupy different positions from those originally occupied by the connecting portions of the of the second and first straps respectively.
2. 2. A battery box for use with at least one plate pack as claimed in claim 1, wherein the battery box is divided by partition walls into a pair of end cell compartments and at least one central cell compartment, and the partition walls defining the or each central cell compartment are formed with respective apertures which are located at different distances respectively from the base and/or the external walls of said central compartment so that the intercell connecting portions of said plate pack can only be aligned with the apertures respectively when the plate pack is inserted into said cell compartment in a single predetermined orientation relative to the compartment.
3. 3. A plate pack substantially as hereinbefore described with reference to the accompanying drawings.
4. 4. A battery box substantially as hereinbefore described with reference to the accompanying drawings.
5. 5. An electrical storage battery utilizing one or more plate packs as claimed in claim 1 of claim 3.
6. 6. An electric storage battery utilizing a battery box as claimed in claim 2 or claim 4.
7. 7. An electrical storage battery as claimed in claim 5, utilizing a battery box as claimed in claim 2 or claim 4.