GB2069747A

GB2069747A - Lead-acid batteries

Info

Publication number: GB2069747A
Application number: GB8004592A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1980-02-12
Filing date: 1980-02-12
Publication date: 1981-08-26

Abstract

A device 27 is described for use in the production of a charged lead-acid battery capable of activation by the addition of electrolyte thereto. The device 27 includes a trough-shaped body 28, a resilient sealing member 29 extending around the open end of the body 28, and a plurality of longitudinally spaced legs 31 supported by the base of the body 28 and extending generally perpendicular to the longitudinal axis of the body. Each leg 31 is adapted at its free end to receive a vent plug 21 for insertion in a respective vent aperture 16 in a container 13, 15 of a battery. The device 27 also includes means 34 for connecting the interior of the body 28 to a vacuum pump to allow air pressure within the body to be reduced. <IMAGE>

Description

SPECIFICATION Lead-acid batteries This invention relates to lead-acid batteries.

For some years, lead-acid batteries of the dry charged type have found increasing use in the battery replacement market. This type of battery is charged by the manufacturer but is transported to the supplier without its electrolyte so that the batter must be activated with aqueous sulphuric acid solution before being put into service. In this way, it is possible to alleviate some of the disadvantages associated with the transportation and storage of fully-charged wet batteries. In particular, wet batteries tend to discharge if stored for any appreciable length of time and, in view of the weight and corrosive nature of the electrolyte, transportation is hazardous and more costly than with dry, charged batteries.

However, the production of dry, charged lead-acid batteries involves removal of all the electrolyte used in forming the battery plates, followed by washing and drying the plates before assembly and sealing of the battery. This creates a problem since washing and drying the formed plates are relatively difficult and expensive operations, but nevertheless must be performed rigorously if performance of the battery is not to deteriorate during storage. Moreover, when activating a dry, charged battery, it is necessary to allow sufficient time for the activation electrolyte to saturate the plates before the battery is ready for service.

Recently, an alternative type of lead-acid battery, referred to herein as a drain, charged battery, has been developed in order to overcome the problems associated with dry, charged batteries. A drain, charged battery, is similar to its dry, charged counterpart in that it requires activation with electrolyte before it can be put into service but, unlike a dry battery, it is stored with part of the forming electrolyte being retained by the plates. There is therefore no requirement for initial washing and drying of the plates, although it is of course necessary to remove sufficient of the forming electrolyte, normally by merely draining the battery, to prevent adjacent plates being electrically connected through the electrolyte during storage. Drain, charged batteries can also be put into service immediately upon addition of the required activation electrolyte.

One problem experienced with drain, charged batteries is that in order to ensure a prolonged storage life, it is necessary not only to remove the majority of the forming electrolyte, but also to isolate the readily oxidizable negative plates from atmosphere. This is normally effected by inserting plugs in the apertures provided in the battery lid to enable filling and venting during service. However, although the plugs seal the battery against ingress of air, there is nevertheless some oxidation of the negative plates as a result of the air trapped in the battery when the plugs are inserted.

A further problem experienced with drain, charged lead-acid batteries arises as a result of the fact that there is inherently some gas evolution during storage because of reaction between the negative plates and the retained acid. Thus, to avoid an undesirable pressure build-up in the battery, the plugs used to prevent air ingress are normally arranged to allow evolved gas to vent to atmosphere when the internal pressure exceeds a predetermined value, typically 0.7 p.s.i. It will, however, be apparent that the plugs can only achieve their desired function of preventing air ingress while allowing evolved gases to escape provided they are correctly seated in their respective apertures. In practice, however, it is found that when the plugs are fitted by hand they do not always seat directly so that, for example, a cell may become discharged as a result of air ingress.

An object of the present invention is to alleviate or overcome the above-mentioned problems experienced with drain, charged lead-acid batteries.

Accordingly, the invention resides in its broadest aspect in a device for use in the production of a charged lead-acid battery capable of activation by the addition of electrolyte thereto, the device including means for introducing vent plugs into vent apertures in a container of the battery and for simultaneously introducing a suitable atmosphere into the battery to reduce oxidation of the negative plates during storage.

In a further aspect, the invention resides in a device for use in the production of a charged lead-acid battery capable of activation by the addition of electrolyte thereto, the device including a trough-shaped body, a resilient sealing member extending around the open end of the body, a plurality of longitudinally spaced legs supported by the base of the body and extending generally perpendicular to the longitudinal axis of the body so that the free end of each leg projects from the open end of the body, each leg being adapted at its free end to receive a vent plug for insertion in a vent aperture in a container of the battery, and means for connecting the interior of the body to a vacuum pump to allow air pressure within the body to be reduced.

The device described in the preceding paragraphs is used in the production of a lead-acid battery after the battery plates have been formed and charged in the battery container and the forming electrolyte has been drained from the container. Considering the device of said further aspect, the vent plugs for insertion in the apertures in the container are engaged with the free ends of the legs respectively and, with the legs aligned with the apertures in the container, the open end of the body is urged against the container. The distance by which the legs project from the open end of the body is such that the vent plugs are accurately located in their respective apertures when the sealing member is resiliently deformed against the container to provide a seal between the body and the container.By connecting the body to a vacuum pump and operating the pump, not only can the body be urged against the container to effect location of the vent plugs but also the air pressure in the interior of the body can then be reduced so that, by virtue of the resulting pressure differential across the vent plugs, the plugs will allow air trapped in the battery container to vent to the body for withdrawal by the pump. In this way, the amount of oxygen available in the battery container, the vacuum pump is de-energised and the air pressire in the body is allowed to return to atmospheric pressure, whereupon the plugs will cease to vent. The device can then be removed from the battery, the arrangement being such that this operation withdraws the legs from the plugs without disengaging the plugs from their respective apertures in the battery container.

Preferably, the sealing member is formed of a porous material such that air can flow through the member to return the body to atmospheric pressure after operation of the vacuum pump. If required, the body can be provided with a relief valve to assist in returning the body to atmospheric pressure.

Preferably, the device includes means for connecting the interior of the body to a gas source, most preferably an inert gas source. In this way, as air is withdrawn from the interior of the container, it can be replaced by the gas.

In a further aspect, the invention resides in a method of producing a charged lead-acid battery capable of activation by the addition of electrolyte thereto, the method comprising the steps of: (a) forming and charging battery plates immersed in aqueous sulphuric acid solution contained in cell compartments of a battery container, the container being formed with apertures communicating with the cell compartments respectively, then (b) draining sufficient of the acid solution from the container to prevent the remaining acid electrically connecting the charged plates during storage, then (c) engaging plugs with the legs respectively of a device according to said one aspect of the invention and, with said legs aligned with the apertures respectively in the container, urging said open end of the body against the container so that said sealing member engages the container and the plugs are inserted in their respective apertures, each plug serving to seal its associated aperture against ingress of air but allowing gas to escape from the battery container, then (d) reducing the air pressure within the body so as to withdraw trapped air from the battery container past said plugs, and then (e) allowing the pressure within the body to return to atmospheric pressure and then removing the body from the container and the legs from the plugs without withdrawing the plugs from their respective apertures.

Preferably, the battery container includes a box closed at an open end by a lid with said aperture being provided in the lid.

In the accompanying drawings, Figure 1 is a sectional view of a lead-acid battery during one stage of manufacture by a method according to one example of the invention, Figure2 is a sectional view along the line 2-2 in Figure 1, and Figure 3 is a sectional view to an enlarged scale, of a vent plug used in the method shown in Figure 1.

Referring to the drawings, the method shown is for producing a drain, charged lead-acid battery and initially involves assembling pasted battery plate grids and separators into packs 11. In each pack 11, each pair of adjacent grids carries the paste required to produce a negative battery plate and a positive battery plate respectively with a separtor being interposed between the grids. The packs 11 are then positioned in cell compartments 12 defined within a thermoplastic battery box 13 and the required intercell connections are completed through partition walls 14 dividing the box into the cell compartments 12. The cell compartments 12 are then filled with an aqueous solution of sulphuric acid having a specific gravity between 1.16 and 1.30, preferably between 1.21 and 1.30 and most preferably between 1.22 and 1.25.Before or after introduction of the sulphuric acid electrolyte, a thermoplastic battery lid 15 is welded to an open end of the box. The lid 15 is welded to an open end of the box. The lid 15 is formed in conventional manner with filling and venting apertures 16 which communicate with the cell compartments to one or more manifolds 17 defined by short upstanding walls 18 integral with the lid 15.

An electric current is then passed between the grids in the battery box 13 so as to convert the paste on the grids into the required active material of the plates and subsequently charge the plates. Preferably, the passage of the electric current is performed in two stages separated by a period of standing of at least 30 minutes, the first stage being terminated when the charge of the plates is at least 50%, or more preferably at least 90%, of the required final value.During the forming operation, the temperature and specific gravity of the sulphuric acid electrolyte rise, the magnitude of the current passed between the grids preferably being arranged so that the temperature of the electrolyte increases to a value in excess of 65 C but not normally greater than 99 C. When the initial specific gravity of the electrolyte is within the preferred range of 1.16 to 1.30, the final specific gravity is normally between 1.26 and 1.35.

On completion of the forming operation, the battery box is inverted to allow the forming acid to drain through the filling and venting apertures 16.

After drainage, some of the forming acid is necessarily retained in the box, mainly being absorbed in the separators and the active material of the plates. In some cases, however, some of the retained acid can be free in the bottom of the box provided it is of insufficient depth to connect the plates electrically when the battery is stored in its normal upright condition. Preferably, the draining operation is arranged so that each positive plate retains at least 0.1 c.c. of the forming acid per gram of the positive plate active material.

After drainage of the forming acid, the box is sealed aganst ingress of air inserting vent plugs 21 into the apertures 16 respectively. Each vent plug 21 is formed of a resiliently deformable material, such as rubber, and, as shown best in Figure 3, includes a general cup-shaped body 22 formed at its base with an integral spigot 23. The spigot 23 extends through the body beyong the open end thereof and defines an annular space 19 with the upstanding walls of the body. Extending around the open end of the body is a curved, outwardly projecting flange 24 beneath which the body is formed with four equi-angularly spaced tags 25.As shown in Figure 1, when each plug 21 is correctly located in its associated aperture 16, the tags 25 engage the internal surface of the lid 15 and urge the flange 24 into sealing contact with the external surfaceofthe lid 15 so asto prevent ingress of air past the flange. Aligned with the tags 25 and extending between the tags and the flange 24 are respective ribs 26 (only one shown) which, in use, ensure that spaces are defined between the body 22 and the wall of the associated aperture 16.

Thus, when the plugs 21 are in position in the 'apertures 16, gases generated in the compartments 12 can vent to atmosphere when the gas pressure is sufficient to lift the flanges 24 out of sealing contact with the lid 16.

In order to insert the plugs 21 within the apertures 16, the device indicated generally at 27 in Figure 1 is employed. The device 27 includes a trough-shaped body 28 which is shaped to fit over the upstanding walls 18 and which carries at its open end a porous sealing ring 29, conveniently formed of foamed neoprene rubber. Supported by the base of the body 28 are a plurality of longitudinally spaced legs 31 which extend generally perpendicular to the longitudinal axis of the body so that the free end of each leg 31 projects from the open end of the body. As shown in Figure 2, the free end of each leg 31 is formed with a blind bore 32 and is stepped inwardly to define a hollow bush 33 which is engageable in the annular space 19 of a respective vent plug 21.The diameter of the bore 32 in each bush 33 is such that the spigot 23 of the associated vent plug 21 is received as a tight fit in the bore so that the plug 21 is releasably retained by the bush 33. However, the force required to disengage each vent plug 21 from its associated bush 33 is arranged to be less than that required to remove the vent plug from its associated aperture 16.

Connected to one end of the body 28 is a conduit 34 which, serves to connect the interior of the body to a vacuum pump (not shown). As its other end, the body 28 is provided with a further conduit 35 which, in use, is connected to an inert gas source (not shown). In addition, the base of the body 28 may be provided with a relief valve 36 th rough which the interior of the body can be returned to atmospheric pressure after operation of the vacuum pump.

To insert the vent plugs 21 within the apertures 16, each plug is initially engaged with a respective leg 31 of the device 27 and then the open end of the body 28 is located over the walls 18. The arrangement of the legs 31 is such that the plus 21 are then accurately aligned with the apertures 16 respectively. The body 28 is then pressed by hand against the lid 15 and the vacuum pump is energised so as to draw the body towards the lid so as to trap and deform the ring 29 into sealing engagement with the lid. The distance by which the legs 31 project from the free end of the body is such that the plugs are then accurately located in the apertures 16 respectively.Further operation of the vacuum pump then serves to reduce pressure within the body 28 until the resultant pressure differential across the plugs 21 is sufficient to lift the flanges 24 out of sealing contact with the lid 15. The vacuum pump then withdraws the air remaining in the battery box 13 after drainage of the forming acid so that the amount of oxygen availble to oxidize the negative plates during subsequent storage of the battery is reduced.

When sufficient air has been withdrawn from the battery box, the vacuum pump is de-energised and the interior of the body 28 returns to atmospheric pressure by flow of air through the porous ring 29 and, if required, by opening the relief value 36. As the pressure in the body 28 returns to atmospheric pressure, the plugs 21 cease to vent and when the pressures have been equalised, the device 27 can be removed from the lid 15. This operation withdraws the legs 31 from the plugs 21 without disengaging the plugs 21 from their respective apertures 16.

If desired, an inert gas can be supplied to the body 28 through the conduit 35 during operation of the vacuum pump. The inert gas will then flow past the lifted flanges 24 to replace the air withdrawn from the battery by the pump.

Claims

1. A device for use in the production of a charged lead-acid battery capable of activation by the addition of electrolyte thereto, the device including means for introducing vent plugs into vent apertures in a container of the battery and for simultaneously introducing a suitable atmosphere into the battery to reduce oxidation of the negative plates during storage.

2. A device for use in the production of a charged lead-acid battery capable of activation by the addition of electrolyte thereto, the device including a trough-shaped body, a resilient sealing member extending around the open end of the body, a plurality of longitudinally spaced legs supported by the base of the body and extending generally perpendicular to the longitudinal axis of the body so that the free end of each leg projects from the open end of the body, each leg being adapted at its free end to receive a vent plug for insertion in a vent aperture in a container of the battery, and means for connecting the interior of the body to a vacuum pump to allow air pressure within the body to be reduced.

3. A device as claimed in Claim 2, wherein the sealing member is formed of a porous material such that air can flow through the member to return the body to atmospheric pressure after operation of the vacuum body.

4. A device as claimed in Claim 2 or Claim 3, wherein the body is provided with a relief valve to assist in returning the body to atmospheric pressure.

5. A device as claimed in any one of Claims 2 to 4 and including means for connecting the interior of the body to a gas source.

6. A device as claimed in Claim 1 or Claim 2, for use in the production of a charged lead-acid battery capable of activation by the addition of electrolyte thereto comprising the combination and arrange ment of parts substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

7. A method of producing a charged lead-acid battery capable of activation by the addition of electrolyte thereto, the method comprising the steps of: (a) forming and charging battery plates immersed in aqueous sulphuric acid solution contained in cell compartments of a battery container, the container being formed with apertures communicating with the cell compartments respectively, then (b) draining sufficient of the acid solution from the container to prevent the remaining acid electrically connecting the charged plates during storage, then (c) engaging plugs with the legs respectively of a device as claimed in Claim 2, and, with said legs aligned with the apertures respectively in the container, urging said open end of the body against the container so that said sealing member engages the container and the plugs are inserted in their respective apertures, each plug serving to seal its associated aperture against ingress of air but allowing gas to escape from the battery container, then (d) reducing the air pressure within the body so as to withdraw trapped air from the battery container past said plugs, and then (e) allowing the pressure within the body to return to atmospheric pressure and then removing the body from the container and the legs from the plugs without withdrawing the plugs from their respective apertures.

8. A method as claimed in Claim 7, wherein the battery container includes a box closed at an open end by a lid with said aperture being provided in the lid.

9. A method as claimed in Claim 7 of producing a lead-acid battery capable of activation by the addition of electrolyte thereto substantially as hereinbefore described.

10. A lead-acid battery capable of activation by the addition of electrolyte thereto produced by a method as claimed in any one of Claims 7 to 9.