Claims:We claim,

1. An assembly of a battery pack (100) comprising of plurality of battery modules (102) stacked together in a compressed assembly, tie rods (110), top pressure plate (114) and bottom pressure plate (116), a battery housing (130) with top and side covers (134,136) and a handle of the battery pack (140),
characterized in that
each said battery module (102) includes a battery cell (104) covered by a battery cell protective frame (106) and a cell holding plate (108) and plurality of the said battery modules (102) are stacked together with the bottom support plate (116) as the bottom most component and the convex top pressure plate (114) as the top most component of the battery pack assembly, all held together by at least four tie rods on the four corners of the battery pack assembly; and
the said cell protective frame (106) has four slots in its four corners that are guides (118) for tie -rods (110) made of durable metal like steel having self-locking tie rod heads (112) at one end and nuts for tightening at the other end and the said tie rod heads (112) can be placed vertically or horizontally at the bottom support plate (116) as the locking means; and
the tie rods (110) locked in the bottom support plate (116),pass through the notches of the cell holding plate (108) and are guided through the guides for tie rods (118) on the protective frame (106), extend to the top pressure plate (114) that ensure that the tie rods (110) are positioned correctly and hold and support the stacked configuration of the battery modules (102) in the battery pack (100); and
the stacked assembly of battery modules (102) with the bottom support plate (116) and the convex top pressure plate (114) is compressed using external pressure of about 150 kgs distributed evenly on the convex top pressure plate (114) and the compression is achieved by tightening the nuts on the tie rods (110) till they are gently snapped onto the top pressure plate (114); after which external pressure is removed and tightened tie rods and the proper alignment of steps (120) of the side folds of the adjacent cell holding plates (108) ensure uniformly distributed pressure on the battery pack throughout the service life; and
the compressed assembly is covered on three sides by a single Aluminium sheet of thickness 1 to 2 mm that is molded into a C shape housing (130), the end of the housing (130) that partially covers the bottom support plate (116) has holes for case mounting screws (132) and the side folds of the cell holding plates (108) are bend such that they fit snapped or snugged to the inner surface of the housing (130) and there is no gap or space between the battery pack (100) and the housing(130); and
the heat generated during the charging and discharging cycles of the battery pack (100) is efficiently transmitted to the external surroundings with the help of the battery pack housing (130) that helps to dissipate the heat and level the temperature on the battery pack due to intimate contact between the cell holding plates (108) and the housing (130) thus providing easy thermal management of the battery pack during its working.

2. The assembly as claimed in claim 1, wherein the battery cell (104) has at least two cell terminals (124) and the battery cells (104) are electrically coupled in series or parallel to one another.

3. The assembly as claimed in claim 1, wherein the said battery cell protective frame (104) is molded from a polymeric material including polypropylene, polystyrene (PS), polyimide (PI) or another suitable polymer or plastic or combination thereof and the battery cell (104) is exactly disposed between the inner surfaces of the frame (106) that has a layer of foam material or any other non-rigid material to protect the battery cell (104) from shocks, vibrations and sudden jerks.

4. The assembly as claimed in claim 1, wherein the frame (106) has molded seats (126)for proper placement of battery cell terminals (124) and provide rigid support for interconnection of adjacent cell terminals and also has a support (128) for mounting cell interconnections PCB of the battery pack (100).

5. The assembly as claimed in claim 1, wherein the cell holding plate (108) is sized and shaped to approximate the profile of the cell (104) and has thickness of 0.7 mm.

6. The assembly as claimed in claim 1, wherein the guides (118) for the tie rods (110) ensure that the tie rods (110) are positioned correctly and hold the stacked configuration of the battery modules (102) in the battery pack (100) and the guides (118) being made of plastic material that is electrically insulating, they electrically isolate the tie rods (110) from each battery module (102).

7. The assembly as claimed in claim 1, wherein the top pressure plate (114) and the bottom support plate (116) are made of Aluminium and have thickness in the range of 5 to 8 mm and the convex top pressure plate (114) has a difference of 2.5 mm thickness in the central curved region.

8. The assembly as claimed in claim 1, wherein for the compressed stacked assembly of the battery pack (100), the bottom support plate (116) with the locked in tie rods (110) on it 4 corners is kept in a vertical position, then plurality of the battery modules (102) are stacked one on top of the other through the tie -rods (110) that are guided by the guides (118) present on the protective frames (106),the front and the back sides of the battery modules are aligned and accordingly stacked on the bottom pressure plate(116) such that the cell terminals of all the battery cells are positioned at the front side of the battery pack and finally the top pressure plate (114) is placed on the top most battery module (102).

9. The assembly as claimed in claim 1, wherein the side of the battery pack (100) with the battery cell terminals and the cell interconnection PCB is covered with a side plastic cover (134) and the top portion of the battery pack (100) with the top pressure plate (114) is covered with a top plastic cover (136).

10. The assembly as claimed in claim 1, wherein the tie rods (110) on the four corners of the battery pack extend beyond top pressure plate (114) and pass through four tie rod guides of the top cover (136) and the top cover fits onto the housing (130) with closed nuts used to secure the top cover (136) in position with the four tie rods (110).

11. The assembly as claimed in claim 1, wherein the top cover (136) has built in handle (140) either molded into the top cover (136) or assembled on the top cover (136) separately such that while lifting the battery pack (100) with the handle (140), the battery pack weight is effectively supported on the four tie rods (110).

12. The assembly as claimed in claim 1, wherein the heat generated during charging and discharging cycles in the battery cells (104) is transferred to the cell holding plates (108) because of their high thermal conductivity and is subsequently conducted to the battery pack housing (130) which is also made of high thermal conductive material which in turn dissipates the heat to the external surroundings.

13. The assembly as claimed in claim, wherein external additional heat extraction mechanisms can be added to the battery pack assembly including appropriate cooling mechanisms such as fan air cooling , natural air cooling, heat sinks, water cooling, cooling fins, cooling snugs depending on the application and requirements.
, Description:FIELD OF INVENTION
The present invention in general relates to battery pack assembly and more particularly it relates to a compressed stacked assembly of battery cells in a battery pack .
BACKGROUND OF THE INVENTION

Recently, batteries capable of charging and discharging have been widely used as an energy source for electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle that are proposed as a solution to air pollution such as gasoline vehicles and diesel vehicles that use fossil fuels. It is also attracting attention as a power source such as (Plug-In HEV). In medium- to large-sized automobiles, due to the necessity of high-power and large-capacity, a medium- to large-sized battery module electrically connected to a plurality of battery cells is used.
From the prior art , it is known that batteries , for example of an electric or hybrid vehicle such as specifically lithium - ion batteries are comprised at least of a battery module or advantageously of a plurality of battery cells . Furthermore , a battery module is moreover preferably comprised of a plurality of individual battery cells , which are mutually interconnected to form a battery module. To this end , the individual battery cells can be mutually electrically interconnected , in series or in parallel .
Since it is preferable that the battery modules are manufactured with a small size and weight as possible, prismatic batteries and pouch type batteries that can be charged with a high degree of integration and have a small weight to capacity are mainly used as battery cells of battery modules. In particular, pouch-type batteries using an aluminum laminate sheet or the like as an exterior member are attracting a lot of attention due to advantages such as low weight, low manufacturing cost, and easy shape transformation.
One particular challenge when developing these types of battery modules is thermal management. For example, the individual battery cells of a battery module tend to heat during charging and/or discharging cycles. As such, the packaging of a battery module typically includes thermal management features, such as cooling plates and/or heat sinks, to dissipate into the external environment the heat produced by the internal battery cells.
Accordingly, it is now recognized that it is desirable to develop a battery module in which the battery cells are in good thermal contact with the thermal management features of the battery module. However, variations in the individual battery cells (e.g., due to manufacturing variability, surface deformities or irregularities, differences in the state of charge of the battery cells) can make it challenging to provide the desired thermal contact between the surfaces of the battery cells and the thermal management features during assembly of the battery module. Further, even when good thermal contact is provided between the battery cells and the thermal management feature at the time of manufacturing, successive expansion and contraction of the battery cells during operation may degrade or interrupt the thermal contact between the battery cells and the thermal management features over the life of the battery module.
In some traditional configurations, the battery cells of a battery module are tightly packed and maintained within the battery housing with an attached clamping mechanism to, for example, maximize energy density of the battery module. Traditional clamping mechanisms often include external features of the battery module (e.g., to facilitate access to the clamping mechanism for manufacture) and are activated after all of the battery cells have been positioned within the battery module. It is now recognized that such clamping mechanisms can add bulk, weight, and some complexity to the battery module and assembly process.
It is further recognized that, in certain systems, differences in the thickness between battery cells as a result of manufacturing variability can prove problematic when positioning the battery cells within the battery housing. Accordingly, it is now recognized that enhancements to such battery module manufacturing processes, battery module reproducibility, and so forth, may be desirable by providing mechanisms for arranging the battery cells within the battery housing that allow greater variability in the dimensions of each battery cell, while still enabling a desired degree of compression/clamping.
Ageing processes associated with charging and discharging cycles in the individual battery cells generate internal forces, as a result of which the individual battery cells do not maintain a constant shape during their service life , but rather these processes , described as distension , generate strain in the housing of the battery cells . These processes thus dictate the adoption of a battery module design which can accommodate the internal forces associated with ageing processes , and can limit the deformation of the housings of the individual battery cells. The loading of the individual battery cells , or the housing thereof , with a force, in the interests of limiting deformation , is generally described as compression.

DEFINITIONS:
The expression “Battery pack” used hereinafter in this specification refers to, but is not limited to a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage and capacity.

OBJECTIVES OF THE INVENTION
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present invention is to provide a compressed stacked assembly of a battery pack with battery cells.
Another object of the present invention is to provide a battery pack assembly that protects the battery cells from handling, impact and vibration damage.
Another object of the present invention is to provide a battery pack assembly that provides thermal management to maintain the ambient operating temperature within the battery pack.
Another object of the present invention is to provide a battery pack assembly that provides compression mechanism as well as ensures variability of the battery cells during manufacturing, uniformity of the compression across the surface of the battery cells and sustainability of the compression force during service life of the battery pack and easy manufacturing.
Another object of the present invention is to provide a compressed battery pack assembly with enhanced performance like cycle life and charge and discharge rates for application usage.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY OF THE INVENTION
Before the present invention is described, it is to be understood that present invention is not limited to particular methodologies and materials described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention.
According to an embodiment of the invention, an assembly of a battery pack comprises of plurality of battery modules stacked together in a compressed assembly with tie rods, top pressure plate and bottom pressure plate, a battery housing with top and side covers and a handle of the battery pack.

According to the embodiment of the invention, each said battery module includes a battery cell covered by a battery cell protective frame and a cell holding plate and plurality of the said battery modules are stacked together with the bottom support plate as the bottom most component and the top pressure plat as the top most component of the battery pack assembly, all held together by at least four tie rods on the four corners of the battery pack assembly.

According to the embodiment of the invention the said cell protective frame has four slots in its four corners that are guides for tie -rods made of durable metal like steel having self-locking tie rod heads at one end and nuts for tightening at the other end and the said tie rod heads can be placed vertically or horizontally at the bottom pressure plate as the locking means and the tie rods locked in the bottom support plate, pass through the notches of the cell holding plate and are guided through the guides for tie rods on the protective frame, extend to the top pressure plate that ensure that the tie rods are positioned correctly and hold and support the stacked configuration of the battery modules in the battery pack securely.

According to the embodiment of the invention, the stacked assembly of battery modules with the bottom support plate and the top pressure plate is compressed using external pressure the tie rods ensure that even and adequate pressure is applied to the battery pack through the top pressure plate and the compression is achieved by tightening the nuts on the tie rods till they are gently snapped onto the top pressure plate.

According to the embodiment of the invention, the compressed assembly is covered on three sides by a single Aluminium sheet of thickness 1 to 2 mm that is molded into a C shape housing, the end of the housing that partially covers the bottom support plate has holes for case mounting screws and the side folds of the cell holding plates are bend such that they fit snapped or snugged to the inner surface of the housing and there is no gap or space between the battery pack and the housing.

According to the embodiment of the invention, the heat generated during the charging and discharging cycles of the battery pack is efficiently transmitted to the external surroundings with the help of the battery pack housing that helps to dissipate the heat and level the temperature on the battery pack due to intimate contact between the cell holding plates and the housing thus providing easy thermal management of the battery pack during its working.

BRIEF DESCRIPTION OF THE DRAWINGS
A complete understanding of the present invention may be made by reference to the following detailed description which is to be taken in conjugation with the accompanying drawing. The accompanying drawing, which is incorporated into and constitutes a part of the specification, illustrates one or more embodiments of the present invention and, together with the detailed description, it serves to explain the principles and implementations of the invention.
FIG.1 is the front perspective isometric view of the compressed stacked battery pack according to an embodiment of the invention;
FIG.2 is the exploded view of a couple of battery modules that are a part of the battery pack as shown in FIG.1 according to the embodiment of the invention;
FIG.3 is the exploded perspective view of the top side of couple of battery modules that are a part of the battery pack as shown in FIG.1 according to the embodiment of the invention;
FIG.4 is the perspective view of the front side of the battery pack as shown in FIG.1 according to the embodiment of the invention;
FIG. 5 is the isometric view of the battery case (housing) having the battery pack of the present invention extended out to demonstrate the configuration of the battery case according to the embodiment of the invention;
FIG 6 is the isometric view of the battery case (housing) and the handle covering the battery pack of the present invention according to the embodiment of the invention; and
FIG. 7 is the isometric exploded view of the different parts of the battery case (housing) having a battery pack of the present invention according to the embodiment of the invention;

DETAILED DESCRIPTION OF THE INVENTION
Before the present invention is described, it is to be understood that this invention is not limited to particular methodologies described, as these may vary as per the person skilled in the art. It is also to be understood that the terminology used in the description is for the purpose of describing the particular embodiments only, and is not intended to limit the scope of the present invention. Throughout this specification, the word “comprises”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

LIST OF REFERENCE NUMERALS:

Sr. No. Description of the part
100 Battery pack
102 Battery module
104 Battery cell
106 Battery cell protective frame
108 Cell holding plate
110 Tie-rods
112 Self- locking tie-rod heads
114 Top pressure plate
116 Bottom support plate
118 Guides for tie rods
120 Step along the length of the side fold of the cell holding plate
122 Notch on the cell holding plate
124 Battery cell terminals
126 Seat on frame for battery cell terminals
128 Support for cell interconnections PCB
130 Battery case/housing
132 Holes for battery case mounting screws
134 Side plastic cover
136 Top plastic cover
138 Top end of the tie-rod
140 Handle of the battery pack

The present invention describes the assembly of a battery pack which consists of battery modules stacked together in a compressed assembly. Referring to FIG. 1 and FIG. 2 of the present invention, a battery pack (100) in accordance with an exemplary embodiment is provided. The battery pack (100) comprises of a plurality of battery modules (102), tie rods (110), top pressure plate (114) and bottom pressure plate (116). Each battery module (102) includes a battery cell (104), a battery cell protective frame (106) and a cell holding plate (108). Plurality of the said battery modules (102) are stacked together with the bottom support plate (116) as the bottom most component and the top pressure plate as the top most component of the assembly, all held together by at least four tie rods on the four corners of the assembly. The battery modules (102) are stacked in one direction in a battery pack (100). The orientation of the stacked battery pack during service life usage is vertical or horizontal according to suitable packaging configurations requirements of the battery pack applications.

In the given embodiment of the present invention, each of the battery cells (104) are pouch type lithium -ion battery cells. The pouch type battery cells have a case typically made with Aluminium foil- laminated plastic film. Other types of battery cells known in the art can also be utilized. A typical pouch type battery cell has at least two cell terminals (124) .The battery cells (104) are electrically coupled in series or parallel to one another. A cell interconnections PCB (not shown in the figures) is positioned for connecting the battery cells to the Battery Management system (BMS) of the battery pack (100).

In the given embodiment of the present invention, the battery cell (104) is supported by a battery cell protective frame (106). The protective frame (106) is a rectangular ring-shaped frame. The frames (106) are molded from a polymeric material such as polypropylene, polystyrene (PS), a polyimide (PI) or another suitable polymer or plastic or combination thereof. The battery cell (104) is exactly disposed between the inner surfaces of the frame (106).The inner surfaces of the frame (106) have a layer of material such as foam or any other non- rigid material to protect the battery cell (104) from shocks, vibrations and sudden jerks. The frame (106) also helps to keep the battery cell (104) in its required position and orientation while stacking in a battery pack. The frame (106) also helps in insulating the battery cell (104) during usage abuse. The frame (106) further has molded seats (126) for proper placement of battery cell terminals (124) and provide rigid support for interconnection of adjacent cell terminals (124) The frame (106) also has a support (128) for mounting cell interconnections PCB of the battery pack (100).

In the given embodiment of the present invention, the cell protective frame (106) has four holes/ or slots in its four corners. These holes/slots are guides (118) for tie -rods (110). Tie rods (110) are rods made of durable metal like steel. Self-locking tie rod heads (112) are present at one end of the tie rods (110). The other end of the tie rods (110) has threading for the nuts for tightening. The tie rod heads (112) can be placed vertically or horizontally at the bottom pressure plate (116) as the locking means for the tie rods (110). The tie rods (110) pass through only the guides (118) in the battery pack (100). The guides (118) ensure that the tie rods (110) are positioned correctly and hold the stacked configuration of the battery modules (102) in the battery pack (100). Further, the guides (118) being made of plastic material that is electrically insulating, the guides (118) also electrically isolate the tie rods (110) from the battery modules (102).

The battery pack (100) includes a plurality of battery modules (102) that further comprises of a plurality of battery cells (104) arranged in a stacked conformation. Interspersed between every other battery cell (104) is a cell holding plate (108). The cell holding plate (108) contacts at least one major surface of each battery cell (104). The plates (108) are made of metal material , preferably Aluminium. The plates (108) have high thermal conductivity and have thickness in the range of 0.5 mm to 1 mm. The desired thickness of each cell holding plate (108) is 0.7 mm.

In the given embodiment, the cell holding plate (108) consists of a top flat surface and at least two side folds. The side folds of the cell holding plate (108) have a step (120) throughout the length of the side fold. The plate (108) also consists of at least two notches (122) at one end on at least two sides of the plate (106).

According to FIG. 1 of the present invention, the stacked arrangement of the plurality of battery modules (102) usually 15-20 in number in one battery pack (100). The top end of the battery pack (100) has top pressure plate (114) and the bottom end of the battery pack (100) has the bottom support plate (116). Further, at least 4 tie rods (110) are present in the battery pack (100) on its four corners to hold and support the battery modules (102) and the battery cells (104) along with the top and bottom support plate (114, 116). The frame (106) and the plate (108) are configured to be coupled together to hold the battery cell (104) therebetween.

In accordance with FIG. 2 of the present invention, the exploded view of a couple of battery modules (102) that are a part of the battery pack (100) as shown in FIG.1 according to the embodiment of the invention is described. The battery cell (104) is configured to be firmly placed in its required position without any loose ends in the frame (106) as well as the plate (108). For a given battery module (102), at least one major flat surface of the battery cell (104) is in contact with the flat surface of the plate (108) on at least one side. The side folds of the plate (108) are in contact with the cell protective frame (106) which covers the side surfaces of the battery cell (104). The frame (106) that protects and covers the outer boundaries of the battery cell (104) provide an extra layer of cushioning and ensure that the battery cell is fixed in the plate (108) and there is no lateral movement of the battery cell (104).

In the given embodiment of the present invention, the tie rods (110) are shown as extended portions for clear representation and understanding. The bottom support plate (116) is made of Aluminium and has thickness in the range of 5 to 8 mm. The ends of the four tie rods (110) have self-locking heads (112) which are placed horizontally or vertically and thus lock the tie rods (110) in the bottom support plate (116). No external hinges, nuts, bolts or locking mechanism is required to fix the tie rods (110) that hold and support the battery cells (104) in the stacked confirmation in the battery pack (100). Further, the tie rods (110) pass through the battery modules (102). The tie rods (110) are specifically guided through guides (118) present as slots on four corners of the cell protective frame (106). Apart from the guides for tie -rods (118) present on the frame (106), the tie rods (110) are simply positioned in the notch (122) of the cell holding plate (108). FIG. 2 clearly demonstrated the arrangement of the tie rods (110) in the battery modules (102) and the bottom support plate (116).

In accordance with FIG. 3 of the present invention, exploded perspective view of the top side of couple of battery modules that are a part of the battery pack as shown in FIG.1 are described. The tie rods (110) that are locked in the bottom support plate (116) pass through the notches of the cell holding plate (108) and are guided through the guides for tie rods (118) on the protective frame (106), extend to the top pressure plate (114). The top pressure plate (114) is convex in shape and is made of Aluminium material and has thickness in the range of 5 to 8 mm. The curve in the center of the top pressure plate (114) has a difference of 2.5 mm thickness. The top pressure plate has a grid like structure and has four holes/slots for making the passage for the tie rods (110).

In accordance with FIG. 4 of the present invention, the compressed stacked assembly of the battery pack (100) is described. First of all, the bottom support plate (116) with the locked in tie rods (110) on it 4 corners is kept in a vertical position. For the next step, the plurality of the battery modules (102) are stacked one on top of the other through the tie -rods (110) that are guided by the guides (118) present on the protective frames (106). The front and the back sides of the battery modules are aligned and accordingly stacked on the bottom pressure plate(116). The cell terminals of all the battery cells are positioned at the front side of the battery pack. Once all the battery modules (102) are stacked, the top pressure plate (114) is placed on the top most battery module (102). The tie rods (110) extend through the top pressure plate (114) to hold the top cover and handle of the battery pack (100).

In the given embodiment of the present invention, once the battery modules are stacked and the top pressure plate (114) is positioned on the top of the battery modules (102) through the tie rods, external pressure of about 150 kgs is applied on the top pressure plate (114) with the help of weights uniformly distributed on the top pressure plate (114). The pressure is predetermined and calibrated based on the number of battery modules present in the battery pack according to the Industry standards. The tie rods (110) ensure that even and adequate pressure is applied to the battery pack through the convex top pressure plate (114). The battery modules are compressed under the pressure of the weights without affecting the integrity, shape and configuration of the battery modules. The battery cells (104) are protected during the pressurizing or compressing process and in pressurized condition during service life by the cell holding plates (108) during compression as well as in the compressed state. The compression is achieved by tightening the nuts on the tie rods (110) till they are gently snapped onto the convex top pressure plate (114). The weights on the top pressure plate (114) are then removed. The gentle snapping by nut tightening on the tie rods (110) and the proper alignment of steps (120) of the side folds of the adjacent cell holding plates (108) ensures that the requisite pressure is maintained even when the weights are removed. No additional internal compression maintenance is required in the battery pack and there is scope of reasonable expansion according to battery usage.

In accordance with FIG. 5 of the present invention, the isometric view of the battery case (housing) having the battery pack of the present invention extended out to demonstrate the configuration of the battery case according to the embodiment of the invention is described. The battery pack is compressed using pressure on the convex top pressure plate (114) and compressed battery pack is obtained. The convex shape of the top pressure plate (114) helps to apply uniform pressure on the battery pack during compression. A battery pack case or housing ( 130) is placed that covers or packages the battery pack from at least 3 sides. The housing (130) is made of a single Aluminium sheet of thickness 1 to 2 mm that is molded into a C shape to cover the battery pack from three sides. The end of the housing (130) that partially covers the bottom support plate (116) has holes for case mounting screws (132). The screws on the bottom support plate (116) are tightened in the holes (132) to mount the battery pack in the housing (130). The side folds of the cell holding plates (108) are bend such that they fit snapped or snugged to the inner surface of the housing (130). There is no gap or space between the battery pack and the housing (130).

In accordance with FIG 6 of the present invention, the isometric view of the battery case (housing) and the handle covering the battery pack of the present invention according to the embodiment of the invention is shown. The side of the battery pack with the battery cell terminals and the cell interconnection PCB is covered with a side plastic cover (134). The top portion of the battery pack with the top pressure plate (114) is covered with a top plastic cover (136). The top plastic cover (136) has the opening for wired connections and a display unit. The top cover (136) also has a handle (140). The tie rods (110) on the four corners of the battery pack extend to the top cover of the battery pack (140). The battery handle is provided on the top cover. The tie rods support the battery top cover securely such that during lifting of the battery pack using the handle, the entire weight of the battery pack is transferred to the tie rods. The top ends of the tie rods (138) are a part of the handle (140) of the battery pack . The tie rods (110) extend beyond top pressure plate (114). The top cover (136) is molded plastic cover with four holes at the four corners which are aligned with the position of the four tie rods (110). The tie rods (110) extending out of the top pressure plate (114) pass through these four tie rod guides of the top cover (136) and the top covers fits onto the housing (130). Closed nuts are used to secure the top cover (136) in position with the four tie rods (110). The closed nuts are dome shaped that provide some leverage for the difference in heights of the tie rods (110) outside the top cover (136) due to assembly variance. The top cover (136) has built in handle (140) either molded into the top cover (136) or assembled on the top cover (136) separately. While lifting the battery pack (100) with the handle (140) , the battery pack weight is effectively supported on the four tie rods (110).
In accordance with FIG. 7 of the present invention, the isometric exploded view of the different parts of the battery case (housing) having a battery pack of the present invention according to the embodiment of the invention is described. The Battery pack housing (130), the side plastic cover (134) and top plastic cover (136) completely encase the battery pack (100). The battery pack (100) is in direct contact with the housing (130)on all the sides of the side folds of the cell holding plate (108). The step on the entire length(120) of the side folds of the cell holding plates (108) are arranged on top of one another in the stacked battery modules (102). The step (120) along the length of the side folds of the cell holding plate (108) holds the protective cover (106) in position, provides necessary allowance in the battery pack (100) assembly for dimensional tolerance to ensure uniform contact between the two adjacent battery cells (104) and also provides guides for perfect alignment of the adjacent cell assemblies. During the charging and discharging of the battery pack in use, heat is generated in the battery cells (104). The heat generated is then transferred to the cell holding plates (108) because of their high thermal conductivity, Once the heat is transferred to the cell holding plates (108), the heat is immediately conducted to the battery pack housing (130) which is also made of high thermal conductive material. The heat generated during the charging and discharging cycles of the battery pack is efficiently transmitted to the external surroundings with the help of the battery pack housing (130) that helps to dissipate the heat and level the temperature on the battery pack due to intimate contact between the cell holding plates (108) and the housing (130). Therefore, the compressed assembly of the battery pack with the housing (130) provides easy thermal management of the battery pack during its working.

In the given embodiment, external additional heat extraction mechanisms can be added to the battery pack assembly. Appropriate cooling mechanisms such as fan air cooling , natural air cooling, heat sinks, water cooling, cooling fins, cooling snugs can be provided depending on the application and requirements.

The compressed battery pack assembly of the present invention provides thermal management of the battery pack during its working without the need of any external cooling components. The assembly further ensures that the battery pack is protected from vibrations , jerks and accidental impacts. The housing provides structural rigidity to the battery pack and also helps in heat dissipation. The battery pack with its unique assembly with the help of tie rods ensures easy servicing, repair and maintenance as the tie rods can be operated using a single tool.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.