PRESSURE AND HEAT RESILIENT BATTERY CONTAINER Technical field The present invention relates to a container for a Valve Regulated Lead-Acid Battery, and more specifically to a container that provides high resilience to internal pressure and external heat during operation of the battery.

Background of the invention

A VRLA battery contains electrolyte cells. Unlike in flooded lead-acid batteries, the hydrogen and oxygen produced in the cells of a Valve Regulated Lead Acid (VRLA) battery is largely recombined back into water. In order to function properly, the interior of the battery cells needs to be pressurized. Containers for VRLA batteries typically contain a valve regulated degassing system that allows a surplus of gas to be evacuated from the interior of the container.

The electrolyte inside the cells of a VRLA battery may be in the form of a liquid or a gel substance. Use of a gelified electrolyte, which presents a higher inertia to movement than liquid, allows the installation of the battery in a multitude of positions, without risking spillage of the electrolyte. In Absorbed Glass Mat (AGM) VRLA batteries, the liquid electrolyte inside a battery cell is contained in a mat of fine glass fibres. This allows for the design of batteries which may be put at tilted angles without spilling the liquid electrolyte.

VRLA batteries, and in particular AGM batteries, are used for a wide range of applications, such as for example starter batteries for cars, or power supplies on boats.

An AGM battery is typically housed in a polypropylene (PP) moulded box, which is formed by a container having six equally large compartments, and a lid or cover, which is typically welded to the container. Each compartment in the container box contains a battery cell. Starter batteries are put to use in a multitude of environments, for example on a boat, or near the motor block of an automobile, where they are exposed to a multitude of external conditions. A main drawback of known PP moulded VRLA battery container boxes is that they could present important and permanent deformations when they are exposed to temperatures of 90 'Ό or higher. The outer walls, which are parallel to the internal baffles separating the compartments, tend to curve towards the outside, or bulge with increasing heat. Depending on the positioning of a starter battery beneath the hood of an automobile, it may well be exposed to temperatures higher than 90 °C if the heat generating motor block is nearby. In such a configuration, the temperatures could put the battery container to structural damage and decrease the battery's lifespan. A standard battery container that is moulded integrally from PP, when exposed to a temperature of 90 'Ό and an internal pressure of 200 mbar, shows important deformations in the center of its side wall faces. Due to the high temperatures, PP softens and permanent deformations are likely to ensue. VRLA containers moulded integrally from PP with talc could be an alternative solution to reduce bulging at higher temperatures, but this advantage is annihilated due to new disadvantages. As this material is more fragile, material breaks may arise at lower temperatures, and it could be problematic to heat-seal a lid to a container made of PP and talc during production.

The dimensions of battery container boxes should conform to the European Standard EN 50342-2. As a result of applying the standard, which dictates the end-to-end dimensions of a container box, the typical resulting outer wall thickness of VRLA container boxes is of about 5 mm. Increasing the thickness of the outer walls significantly will either increase the end-to-end dimensions of the box, which would no longer comply with the standard, or it would decrease the size of the battery compartments inside the container.

A known container, described in EP 1 041 655 B1 , presents ribbings on the outer surfaces of two lateral walls of the container, which aim to increase the structural rigidity of the walls, in order decrease their tendency to bulge. The document does not disclose moulding techniques for such a design. However, such a design will inevitably discard some of the benefits inherent to the VRLA and AGM technologies. Indeed, such batteries have the benefit of being mountable at tilted angles, which is not the case with flooded lead-acid batteries. The suggested ribbings form a series of pockets on two of the container's lateral walls. If such a battery container is mounted at a tilted angle, substances such as oil, which may be spilled on the battery during its normal operation, may become trapped in these pockets. The pockets do not allow the spilled substances to be evacuated by flowing along the outside surfaces of the container. Moreover, the pockets formed by the suggested outer ribbings may gather dust and dirt. Such externally ribbed container boxes therefore present some drawbacks for their use as VRLA/ AGM battery housing containers, which is why the automotive industry does in general not accept externally ribbed containers for use in cars.

Technical problem to be solved It is an objective of the present invention to provide a container for VRLA and AGM batteries, which overcomes at least some of the disadvantages of the prior art. Summary of the invention

According to a first aspect of the present invention, a battery container having four sidewalls and a floor is provided. The battery container further comprises at least one separating wall for separating battery compartments. The separating wall is arranged parallel to two opposing sidewalls of the container. At least one of these two sidewalls is strengthened by a panel part arranged parallel to said sidewall, and the panel part comprises a base plate. The surface area of the panel part substantially matches the surface area of the sidewall. The panel part may preferably be provided inside said reinforced sidewall.

The panel part may be provided centrally inside the sidewall, so that the distance between a first face of the base plate to the interior face of the sidewall equals the distance between a second face of the base plate and the exterior face of the sidewall.

The panel part may be positioned relative to the sidewall so that it is located over a central region of the sidewall.

A periphery of the sidewall may be spaced from the periphery of the base plate to form a spacing. The spacing may be located at any one or a combination of: a side of the sidewall, on two sides of the sidewall, on a top of the sidewall, or a bottom of the sidewall.

The linear dimensions of the base plate may be less than the linear dimensions of the sidewall. At least one of the faces of the base plate may comprise a ribbing pattern.

Preferably, both of the faces of the base plate may comprise a ribbing pattern.

The profile of the ribbing pattern may preferably such that the ribs extend from the first face of the base plate to the interior face of the sidewall, and from the second face of the base plate to the exterior face of the sidewall.

The sidewall of the container may preferably have a thickness of 5 mm, wherein the base plate may have a thickness of 2.5 mm, and wherein the ribbing pattern may have a profile depth of 1 .25 mm on both sides of the base plate. The ribbing pattern may comprise a pattern composed of parallel lines.

Furthermore, the panel part may be made of a material having reinforcing and/or isolating properties. The material may preferably polypropylene with a filler, which may preferably be talc.

According to a second aspect according to the present invention, there is provided method of moulding a battery container according to the first aspect of the invention. The method comprises the steps of

- releasably fastening said panel to a moulding core,

- injecting the moulding material into a moulding form, which comprises said moulding core including said panel,

- ejecting the moulded battery container, which comprises said panel, from the moulding form. The moulding core may preferably comprise air-suction means for releasably fastening said panel.

More preferably, the moulding core may comprise a bedding that is adapted to receive said panel.

According to a third aspect of the present invention, a battery container comprising a containing part, which comprises four sidewalls and a floor, is provided. The containing part is moulded from polypropylene, and comprises at least one battery compartment. The container further includes at least one panel part, wherein the panel part is arranged in parallel to, and in contact with, the interior face of a first sidewall of the containing part.

Furthermore, the panel part may be made of a material having reinforcing and/or isolating properties. The material may preferably polypropylene with a filler, which may preferably be talc.

Preferably, the panel part may comprise at least one substantially smooth surface. Even more preferably, the panel part may comprise ribbings on at least one of its faces.

Most preferably, a further panel part may be arranged in parallel to and in contact with the interior face of a second sidewall, wherein the second sidewall opposes said first sidewall of said containing part. The containing part may comprise at least six battery compartments.

The thickness of said sidewalls of the containing part may preferably equal 2.5 mm.

The thickness off the panels may preferably be substantially equal to 2.5 mm.

Preferably, the total thickness of the container walls, including said panels, may substantially equal 5 mm.

According to the present invention, a method of moulding the battery container according to the third aspect of the present invention is provided. The method comprises the steps of

- releasably fastening a panel to a moulding core,

- injecting a moulding material into a moulding form, which comprises said moulding core including said panel,

- ejecting the moulded battery container, which comprises said panel, from the moulding form

The moulding core may preferably comprise air-suction means for releasably fastening said panel. The moulding core may comprise a bedding that is adapted to receive said panel.

A battery container according to the present invention presents smooth outside surfaces, yet it incorporates structural reinforcements of the container's sidewalls, without increasing the battery dimensions.

The container according to the present invention increases the longevity of the battery box, as it is less prone to bulging when it is exposed to high temperatures. This allows it to be used in a number of new applications, wherein high temperatures prevail. Brief description of the drawings

Several embodiments of the present invention are illustrated by way of figures, which do not limit the scope of the invention, wherein: Fig. 1 shows an isometric view of an embodiment of a device according to the present invention. Fig. 2 shows an isometric view of an embodiment of a device according to the present invention.

Fig. 3 shows a blown-up view of schematic cross-section of a panel part and container sidewall according to the present invention.

Fig. 4 shows a blown-up view of schematic cross-section of a panel part and container sidewall according to the present invention. Fig. 5 shows a schematic cross section of a battery compartment of a container according to the present invention, including a moulding core, wherein the container is turned upside-down.

Fig. 6 shows an embodiment of a panel part according to the present invention. Fig.7 show isometric view of a further embodiment of a device according to the present invention.

Fig. 8 is a schematic diagram showing the position of a base plate relative to a sidewall according to various embodiments of the invention.

Detailed description of the invention

This section describes the invention in further detail based on embodiments and on the figures. As shown in Fig 1 , the battery container 001 according to the present invention comprises four outside walls. The container further comprises at least one but preferably six battery compartments 015 that are separated by separation walls or baffles 014. The baffles are substantially parallel to two of the container's sidewalls 010, 013. The sidewall 010 has an external face 01 1 oriented toward the outside of the container, and an internal face 012 oriented toward the interior of the container. The container is preferably moulded from polypropylene (PP).

At least one of the sidewalls 010, 013 is structurally strengthened by a panel part 020, which is arranged parallel to the sidewall 010 and to the baffles 014. The surface area of the reinforcing panel part 020 is substantially equal to the surface area of the sidewall 010. The panel part may be made of any material. It is advantageous to use a material with thermal insulation, acoustic insulation, and structurally strengthening properties. In an embodiment, the panel is made of PP with a filler such as talc or glass fibres. A first embodiment 101 of the present invention is illustrated in Fig 2. A panel part 120 is provided inside each reinforced sidewall 1 10, 1 13. The panel part 120 is further depicted in Figs 3 and 4, which illustrate longitudinal and lateral cuts of the reinforced sidewall 1 10. The panel part 120 comprises a base plate 121 and a profiled ribbing pattern 123, which cannot be seen on Fig 3, but which is shown in Fig 4. Advantageously, the panel part is provided centrally inside the sidewall of the container. The distance between a first face 125 of the base plate 121 to the interior face 1 12 of the sidewall 1 10 equals the distance between a second face 122 of the base plate and the exterior face 1 1 1 of the sidewall. The sidewall comprises a sandwiched structure, wherein the base plate 121 of the panel part is surrounded by a layer of moulded PP on both sides.

It is further advantageous that the edges of the base plate are surrounded by PP.

As shown in Fig 4, a ribbing pattern extends from the base plate 121 , preferably on both faces 122, 125. The ribbing pattern is advantageously provided as a series of parallel linear ribs 123, 126 extending from the top to the bottom of the panel part. The profile of the ribs is such that the ribs 123, 126 extend on both sides 122, 125 of the panel part's base plate 121 to reach both the exterior 1 1 1 and interior 1 12 faces of the container's sidewall. Therefore, the ribbing pattern 123 on the first side 122 of the panel's base plate 121 is provided flush with the exterior side face of 1 1 1 the container's sidewall, while the ribbing pattern 126 on the second side 125 of the panel part's base plate 121 is provided flush with the interior face 1 12 of the container's sidewall. The ribbing pattern thereby creates an alternating series of ribs 123, 126 and gaps 124, 127 on both sides of the panel's base plate 121 .

Preferably the base plate of the panel part has a thickness of 2.5 mm, while the ribbing on both sides of the base plate has a profile depth of 1 .25 mm. The total thickness of the panel part, and of the reinforced container wall, is therefore of 5 mm.

While any other panel thickness may be used in accordance with the present invention, the above example leads to a container wall thickness that is comparable with the thickness of a standard container sidewall, while the stiffness of the container according to the present invention is increased. Tests have shown that a container according to an embodiment of the present invention, comprising overmoulded panels made from a polypropylene base compound comprising 20% of talc, allow to increase the stiffness of the shorter side walls as compared to similar containers made of PP. At the same time, the advantages of standard PP containers are maintained and it remains possible to heat-seal a lid to the container box. The reinforcements can be further strengthened. For example, a container according to the present invention comprising overmoulded panels with a talc ratio of 40% presents up to 36% higher resistance to bulging when it is exposed to an exterior temperature of 90 'Ό and an internal pressure of 200 mbar, as compared to a known battery container moulded integrally from polypropylene and having identical dimensions.

A possible method of moulding a container according to an embodiment of the present invention is described herein, with reference to Fig 5, without limiting the scope of protection of the container itself to products resulting from the use of this method. Indeed, the described container may be moulded for example by bi-injection, if a corresponding moulding core is provided.

In a method of producing the container 101 according to an embodiment of the present invention, the described panel parts 120 are moulded from a polypropylene base compound including talc as a filler. Any other material presenting a high structural and resistance may be used.

As shown in Fig 5, a moulding core 150 is provided in order to mould the battery compartment 1 15, which is adjacent to the sidewall 1 10. The dimensions of the moulding core 150 mirror the dimensions of the battery compartment. A bedding 151 is provided at one of the faces of the moulding core 150. The bedding has a shape that complements and receives the shape of the panel part 120.

The bedding contacts the ribs 126 on the internal face of the panel part 120, thereby creating interstices between the bedding and the base plate of the panel part corresponding to the gaps 127 between ribs 126.

The moulding core 150 provides air-suction means 140, which provide at least one air inlet 141 on the surface of the bedding 151 . The air-suction means 140 further provide air outlets 142, to which a non-depicted vacuum pump may be connected. Using this arrangement, the panel part 120 may be safely received on the bedding 151 of the moulding core 150. By creating a vacuum through the use of the suction means 140, the panel part 120 is pressed and fastened onto the bedding 151 .

Advantageously, as illustrated in Fig 6, at least one area 128 of the internal face 125 of the panel part is devoid of ribs, so that the air inlets 141 can contact the base plate of the panel part in this area, in order to fasten the panel safely to the moulding core. Furthermore, at least one retaining means is provided on the surface of the bedding, which complements at least one corresponding engaging means 129 on the panel part. The retaining means helps to keep the panel part centered on the bedding during the moulding process.

The resulting assembly, including the panel part 120, is used as a moulding core element. The container is injection moulded around the core element that comprises the panel part.

During the moulding process of the container, the polypropylene fills the interstices 124, 127 that are provided by the ribbing profile on both faces 122, 125 of the panel part 120. Once the moulding process is completed, the panel part 120 is released from the moulding core 150 as air is allowed to flow back into the air-suction means 140. The moulding core 150 may then be retracted from the finished battery compartment by means of a simple translational movement 160.

A second embodiment according to the present invention is shown in Fig 7.

The panel part 220 is arranged parallel to, and in contact with, the interior face of the sidewall 213. The panel 220 may be made of a polypropylene base compound with a filler, such as for example talc or glass fibres.

The panel comprises a first smooth face, which is oriented towards the interior of the adjacent battery compartment, whereas a second face contacts the interior face of the sidewall 213 of the container 201 . The second face of the panel may either be smooth, or may comprise a ribbing pattern, which may provide ribbing pockets. Said pattern may be in the form of circular pockets or any geometrical arrangement. In an embodiment the ribbing pattern is formed by a square grid. One of the edges of the panel 220, which is oriented towards the opening of the adjacent battery compartment has a tapered shape.

During production of the container 201 , the panel part is arranged so that one of its faces contacts the interior face of a sidewall 213 of the container. In a further embodiment, a similar arrangement comprising a second panel is provided at an opposing sidewall 210. Figure 8 illustrates the sidewall 1 10 of Figure 2. As illustrated in this Figure, the sidewall 1 10 has a central region 154 located in the middle of the sidewall 1 10. The base plate 121 is sandwiched in the sidewall 1 10 in the manner described so that it is located over the central region 154. The base plate 121 helps to avoid buckling and bulging of the sidewall 1 10 and since the central region 154 illustrated in Figure 8 is the most prone to such deformation, the reinforcing provided by the base plate in this region is advantageous.

As illustrated in Figure 8, the precise location of the base plate 121 relative to the sidewall is not essential. The aforementioned advantages are present when the size and location of the base plate relative to the sidewall is varied. Dashed lines 156 and 154 represent, in a schematic manner, minimum and maximum sizes of the base plate according to a set of embodiments, although it is to be realised that the invention is not so limited and other shapes and relative sizes and positioning are also possible.

In certain embodiments, the base plate extends to the bottom 158 of the sidewall 1 10 so that, when the base plate 121 is installed in the sidewall 1 10, the bottom 158 of the sidewall 1 10 coincides with a bottom of the base plate 121 . In further embodiments, the bottom of the base plate 121 is spaced from the bottom 158 of the sidewall 1 10 when the base plate has been installed.

In embodiments of the invention, at least one of the sides of the base plate is spaced from sides of the sidewall when the base plate has been inserted. As illustrated in Figure 8, the periphery or side 162 of the sidewall 1 10 is spaced from the periphery or side 164 of the base plate. In certain embodiments, it is the top and sides where this spacing is found, but in further embodiments (corresponding to position 154), the spacing is to be found at the bottom too.

As illustrated in Figure 8, the sidewall 1 10 has a height H and a length L. The base plate 121 has a height H' and length L'. In different embodiments, the differences between L and L', and that between H and H' will vary. However, it has been found that it is advantageous if the length L' of the base plate 121 is less than the length L of the sidewall 1 10. Alternatively, or in addition, it has also been found that it is advantageous if the height H' of the base plate 121 is less than the height H of the sidewall 1 10.

In an embodiment, H' is between 0.95 H and 0.55 H. H' may be between 0.9 H and 0.7 H. H' may also be between 0.9 H and 0.85 H. In a further embodiment, H may be 145 mm and H' may be 165 mm. In an embodiment, L' is between 0.95 L and 0.55 L. L' may be between 0.9 L and 0.7 L. L' may also be between 0.95 L and 0.9 L. In a further embodiment, L may be 165 mm and L' may be 150 mm. In certain embodiments, the surface area of the base plate substantially matches the surface area of the sidewall. In certain of such embodiments, the base pate has a set of integrally formed ribs 123, 126 (Figure 4). The sidewall, on the other hand, has a smooth interior face 1 12 and exterior side face 1 1 1 . Therefore, the increase in surface area dictated by the ribs will correspond to a decrease in the linear dimensions of the base plate in comparison to the sidewall.

This difference in the linear dimensions between the base plate and the sidewall are advantageous in that this arrangement provides a balance between ease of manufacture of the base plates which can be cast or moulded in a single operation and ease of manufacture of the resulting battery container whereby the base plate can be easily located and moulded into the sidewall.

As mentioned, the ribs provide for a convenient manner of locating the base plate relative to the sidewall in the manufacturing method previously described. In an embodiment, the panel part 120 is provided centrally inside said sidewall, so that the distance between a first face of the base plate 121 to the interior face of the sidewall equals the distance between a second face of the base plate and the exterior face of the sidewall. In a further embodiment, it is not necessary for the distance between the first face of the base plate to the interior face of the sidewall to equal the distance between the second face of the base plate and the exterior face of the sidewall; it is sufficient that the base plate is sandwiched by the sidewall.

In an embodiment, the sidewall is formed to enclose the base plate. The ribbing is integrally formed on the base plate and conveniently serves to locate the base plate relative to the sidewall during the manufacturing process. Therefore, additional spacers and supports are not needed during the manufacturing process to place the base plate relative to the sidewall.

As noted, the base plate 121 is embedded in the sidewall 1 10. According to embodiments of the invention, the reinforcing provided by the base plate is restricted to the sidewalls of the battery container. This allows the container to adhere to standardised dimensions while still providing the required reinforcing. As illustrated in Figure 6, the base plate is, in these embodiments, formed as a contiguous integral part which ensures that it is easier to manufacture and install in the sidewall when compared to reinforcing which comprises multiple parts.

It should be understood that the detailed description of specific embodiments is given by way of illustration only, since various changes and modifications within the scope of the invention will be apparent to the skilled man. The scope of protection is defined by the following set of claims.