Description:FIELD OF THE INVENTION
[001] The present invention generally relates to a battery pack and particularly relates to a system and a method to regulate a temperature of the battery pack.

BACKGROUND OF THE INVENTION
[002] A battery pack includes a plurality of battery cells interconnected to each other. The battery pack achieves desired voltage by connecting several battery cells in series, such that each battery cell adds its voltage potential to derive the total terminal voltage. Similarly, the battery pack achieves desired current by connecting several battery cells in parallel. The use of battery packs as an energy source is becoming prevalent in all parts of the world because of the advantages offered by stored electrical energy when compared to especially energy generated via fossil fuel powered internal combustion engines. Thus, battery packs are being used to power a variety of electrical and electronic devices including for power intensive applications like powering automobiles, work machines and power tools.
[003] A battery pack is the energy source of an electric vehicle which provides the required electrical energy to propel the vehicle and power its auxiliary components. During charging and discharging cycles of the battery pack, it releases a significant amount of heat which makes the battery cells of the battery pack to heat up as well. Higher temperatures are detrimental to the health of the battery cells as battery cell heating leads to faster capacity degradation and is likely to cause thermal runaway. Capacity degradation of the battery cells reduces performance and longevity of the battery pack. Thermal runaway of the battery cells further poses a huge safety risk as it could lead to fire and explosion of the battery pack. Ideally the battery cells need to be maintained between 25 degrees Celsius and 45 degrees Celsius for optimum performance, longevity and safety, regardless of ambient thermal conditions. To ensure safe operation of cells and optimum battery life, it is important to maintain uniform temperature across cells and optimum thermal condition in the battery pack overall.
[004] Generally, two types of cooling systems are employed for cooling the battery pack, i.e., active cooling and passive cooling. Small capacity battery packs generally require only passive cooling to maintain its temperature below the upper threshold limit. However, larger capacity battery packs would generate more heat and employs active cooling means to maintain its temperature below the upper threshold limit. Conventional passive cooling systems employ regular conduction-convection cooling to dissipate heat generated inside the battery pack to an ambient. Phase Change Material (PCM) may also be employed to absorb heat generated and dissipate this heat gradually to the ambient. Active cooling systems conventionally employ forced air cooling where air flow is continuously maintained over the battery pack surface to carry heat away or uses liquid cooling where a coolant is circulated to the battery pack to absorb heat from the battery cells and dissipate it away outside the battery pack. The passive cooling means are not very effective in cooling the battery pack since cooling efficiency decreases with increase in temperature of the battery pack. In case of PCM, once all of the PCM is melted due to absorption of heat, phase change stops and heat absorption drastically drops. These effects lead to very high battery temperature due to reduced cooling efficiency as the temperature of the battery pack progressively increases.
[005] Additionally, both the active and passive cooling systems known in the art fails to effectively cool the battery pack in high temperature ambient conditions since they work by dissipating heat to the ambient. For e.g., when forced air cooling is used, the source of air for cooling is ambient air. If temperature of the air itself is high, effective cooling of the battery pack cannot be facilitated. Similar problem occurs with liquid coolant as the liquid coolant exchanges heat absorbed from the battery cells with the ambient to cool down before it is pumped back again into the battery pack. Thus, when temperature of the ambient becomes close to temperature of the battery pack, the active and passive cooling systems elucidated above fail to maintain cell temperature below the upper threshold limit. Thus, current thermal management systems fail to uniformly cool the battery cells of the battery pack.
[006] Furthermore, the cooling means discussed above cannot heat the battery cells of the battery pack in extremely cold climatic conditions. The battery cells experience a drop in efficiency and may fail to function when the ambient conditions drop below a lower threshold temperature. As already mentioned, the battery pack would have the best performance, longevity, and safety when the battery cells are maintained between 25 degrees Celsius and 45 degrees Celsius.
[007] Thus, there is a need in the art for a battery pack encompassing a system and a method to regulate a temperature of the battery pack capable of maintaining the battery pack within a prescribed temperature range, which addresses at least the aforementioned problems and limitations.

SUMMARY OF THE INVENTION
[008] In one aspect, the present invention is directed to a battery pack. The battery pack includes a casing, a plurality of battery cells arranged in one or more cell stacks inside the casing, and at least one thermoelectric module. The casing has a plurality of wall members, and the plurality of wall members are thermally conductive. The at least one thermoelectric module has a first surface and a second surface and is disposed between the one or more cell stacks and at least one of the plurality of wall members. The first surface of the thermoelectric module is in thermal communication with one or more of the plurality of battery cells of at least one cell stack and the second surface of the thermoelectric module is in thermal communication with one or more of the plurality of wall members.
[009] In an embodiment, the first surface of the at least one thermoelectric module is opposite the second surface of the at least one thermoelectric module. Further, the at least one thermoelectric module is operable to actively transfer heat between the first surface and the second surface when an electric current is passed through the thermoelectric module.
[010] In an embodiment, the at least one thermoelectric module is adapted to actively transfer heat from the first surface to the second surface when an electric current of a first polarity is passed through the thermoelectric module. The first surface receives heat from the plurality of battery cells and the second surface dissipates heat to the one or more wall members to cool the plurality of battery cells.
[011] In another embodiment, the at least one thermoelectric module is adapted to actively transfer heat from the second surface to the first surface when an electric current of a second polarity is passed through the thermoelectric module. The first surface dissipates heat to the plurality of battery cells and the second surface receives heat from the one or more wall members to warm the plurality of battery cells.
[012] In an embodiment, the battery pack includes a holder to securely mount the at least one thermoelectric module. The holder is disposed inside the casing and the holder has one or more slits to accommodate the at least one thermoelectric module.
[013] In an embodiment, the battery pack includes a heat spreader disposed between the one or more cell stacks and the at least one thermoelectric module. The heat spreader distributes heat flux from the plurality of battery cells and the at least one thermoelectric module to enable optimum heat dissipation between the plurality of battery cells and the at least one thermoelectric module.
[014] In another embodiment, the battery pack includes a fire-retardant sheet disposed between the at least one thermoelectric module and the one or more wall members. The fire-retardant sheet restricts any fire from propagating from the plurality of battery cells to the one or more wall members.
[015] In an embodiment, the one or more wall members in thermal communication with the thermoelectric module is adapted for heat transfer with an ambient. The one or more wall members comprises a plurality of fins at an exterior portion of the one or more wall members, and the plurality of fins effectively transfer heat between the one or more wall members and the ambient.
[016] In an embodiment, the battery pack includes a gap filler disposed between the one or more cell stacks and the heat spreader. The gap filler is adapted to achieve optimum heat conduction between the one or more of the plurality of battery cells of the one or more cell stacks and the at least one thermoelectric module for effective heat transfer. The gap filler also acts as an electrical insulator between the one or more wall members and the plurality of battery cells.
[017] In another aspect, the present invention is directed to a battery pack. The battery pack includes a casing, a plurality of battery cells arranged in one or more cell stacks inside the casing, and at least one thermoelectric module. The casing has a plurality of wall members, and the plurality of wall members are thermally conductive. One or more of the plurality of battery cells of at least one cell stack is in thermal communication with one or more of the plurality of wall members. The at least one thermoelectric module has a first surface and a second surface and is disposed between the one or more wall members which are in thermal communication with the battery cells and an ambient. The first surface of the thermoelectric module is in thermal communication with the one or more wall members and the second surface of the thermoelectric module is in thermal communication with the ambient.
[018] In an embodiment, the first surface of the at least one thermoelectric module is opposite the second surface of the at least one thermoelectric module. Further, the at least one thermoelectric module is operable to actively transfer heat between the first surface and the second surface when an electric current is passed through the thermoelectric module.
[019] In an embodiment, the at least one thermoelectric module is adapted to actively transfer heat from the first surface to the second surface when an electric current of a first polarity is passed through the thermoelectric module. The first surface receives heat from the one or more wall members which are in thermal communication with the plurality of battery cells and the second surface dissipates heat to the ambient to cool the plurality of battery cells.
[020] In another embodiment, the at least one thermoelectric module is adapted to actively transfer heat from the second surface to the first surface when an electric current of a second polarity is passed through the thermoelectric module. The first surface dissipates heat to the plurality of battery cells and the second surface receives heat from the ambient to warm the plurality of battery cells.
[021] In an embodiment, the battery pack includes a holder to securely mount the at least one thermoelectric module. The holder is disposed outside the casing and the holder has one or more slits to accommodate the at least one thermoelectric module.
[022] In another embodiment, the battery pack includes a gap filler disposed between the one or more cell stacks and the one or more wall members. The gap filler is adapted to achieve optimum heat conduction between the one or more of the plurality of battery cells of the cell stack and the one or more wall members for effective heat transfer. The gap filler also acts as an electrical insulator between the one or more wall members and the plurality of battery cells.
[023] In an embodiment, the battery pack includes a cover member disposed over the second surface of the at least one thermoelectric module. The cover member is thermally conductive and in thermal communication with the thermoelectric module to enable heat transfer between the thermoelectric module and the ambient through the cover member.
[024] In another embodiment, the cover member is adapted for heat transfer with the ambient, and the cover member includes a plurality of fins disposed on an exterior surface of the cover member. The plurality of fins effectively transfer heat between the cover member and the ambient.
[025] In an embodiment, the battery pack includes a fire-retardant sheet disposed between the at least one thermoelectric module and the cover member, and the fire-retardant sheet restricts fire from propagating from the thermoelectric module to the cover member.
[026] In another aspect, the present invention is directed to a method to regulate temperature of a battery pack. The battery pack includes a casing, a plurality of battery cells arranged in one or more cell stacks inside the casing, and at least one thermoelectric module. The casing has a plurality of wall members, and the plurality of wall members are thermally conductive. The at least one thermoelectric module has a first surface and a second surface, and the thermoelectric module is operable to actively transfer heat between the first surface and the second surface when an electric current is passed through the thermoelectric module. The first surface of the thermoelectric module is adapted to exchange heat with one or more of the plurality of battery cells of at least one cell stack and the second surface of the thermoelectric module is adapted to exchange heat with an ambient. The method includes the steps of monitoring a temperature of the battery pack by a Battery Management System (BMS), and passing the electric current of a first polarity by the BMS, through the thermoelectric module to actively transfer heat from the first surface to the second surface to cool the plurality of battery cells if the temperature of the battery pack is greater than a predefined upper threshold limit. The method further includes the step of passing the electric current of a second polarity by the BMS, through the thermoelectric module to actively transfer heat from the second surface to the first surface to warm the plurality of battery cells if the temperature of the battery pack is lesser than a predefined lower threshold limit.
[027] In an embodiment, the method includes the step of passing the electric current of the first polarity by the BMS, through the thermoelectric module to actively transfer heat from the first surface to the second surface to cool the plurality of battery cells and maintain the temperature of the battery pack within a predefined temperature range, if the temperature of the battery pack is greater than an upper limit of the predefined temperature range. The method further includes the step of passing the electric current of the second polarity by the BMS, through the thermoelectric module to actively transfer heat from the second surface to the first surface to warm the plurality of battery cells and maintain the temperature of the battery pack within the predefined temperature range, if the temperature of the battery pack is lesser than a lower limit of the predefined temperature range.

BRIEF DESCRIPTION OF THE DRAWINGS
[028] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates an isometric perspective view of an exemplary battery pack, in accordance with an embodiment of the present invention.
Figure 2 illustrates a partial exploded view of the battery pack of Figure 1, in accordance with an embodiment of the present invention.
Figure 3 illustrates an isometric perspective view of the battery pack, in accordance with an embodiment of the present invention.
Figure 4 illustrates a partial isometric exploded view of the battery pack, in accordance with an embodiment of the present invention.
Figure 5 illustrates an orthographic side view of the battery pack, in accordance with an embodiment of the present invention.
Figure 6 illustrates a top isometric partial exploded view of an exemplary battery pack, in accordance with an embodiment of the present invention.
Figure 7 illustrates an orthographic side view of the battery pack, in accordance with an embodiment of the present invention.
Figure 8 illustrates an exemplary method to regulate a temperature of the battery pack, in accordance with an embodiment of the present invention.
Figure 9 illustrates the method to regulate a temperature of the battery pack, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[029] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the battery pack is illustrated as being constituted of battery cell stacks. However, it is contemplated that the disclosure in the present invention may be applied to any type of battery module, group of battery modules or packs capable of accommodating the present subject matter without defeating the scope of the present invention.
[030] The present invention generally relates to a battery pack and particularly relates to a system and a method to regulate a temperature of the battery pack.
[031] Figure 1 illustrates an isometric perspective view of an exemplary battery pack 10, in accordance with an embodiment of the present subject matter. The battery pack 10 includes a casing 20. The casing 20 is formed by a plurality of wall members 22. In an embodiment, the casing 20 is formed by a base wall member, a top wall member, and two C-shaped side wall members (shown in Figures 4 and 5) joined together to form a sealed casing 20. In another embodiment, the casing 20 is formed by a base wall member, a top wall member and four plate shaped side wall members. The casing 20 may be formed by any number of wall members 22 according to design requirements using any process known in the art. The plurality of wall members 22 are thermally conductive and allows for uninhibited transmission of heat from one face of the wall member 22 to the other, i.e., from the inner face to the outer face and vice versa. In the illustrated embodiment, one or more wall members 22 include a plurality of fins 122 at an exterior portion of the one or more wall members 22. The plurality of fins 122 are adapted to effectively transfer heat between the one or more wall members 22 and the ambient.
[032] Figure 2 illustrates a partial exploded view of the battery pack 10, in accordance with an embodiment of the present subject matter. The battery pack 10 includes a plurality of battery cells 12, and the plurality of battery cells 12 are arranged in one or more cell stacks 14 inside the casing 20. The battery pack 10 further includes at least one thermoelectric module 30 disposed between the one or more cell stacks 14 and at least one of the plurality of wall members 22. In the illustrated embodiment, the at least one thermoelectric module 30 is disposed between the cell stacks 14 at an extremity of the battery pack and the C-shaped side wall members. In an embodiment, the thermoelectric module 30 is a Peltier module, operating according to Peltier effect. Peltier effect creates a temperature difference by transferring heat between two electrical junctions of the Peltier module when a voltage is applied across joined conductors of the Peltier module to create an electric current. When the electric current flows through the junctions of the two conductors, heat is removed at one junction causing cooling and heat is deposited at the other junction. In an embodiment, each thermoelectric module 30 features an array of alternating n-type and p-type semiconductors. The semiconductors of different type have complementary Peltier coefficients. The array of n-type and p-type semiconductors are soldered between two ceramic plates, electrically in series and thermally in parallel. Solid solutions of bismuth telluride, antimony telluride, and bismuth selenide are the preferred materials for Peltier effect devices because they provide the best performance from 180 to 400 K and can be made both n-type and p-type semiconductors. The cooling effect of any device or unit using thermoelectric modules 30 is proportional to the number of thermoelectric modules 30 used. Typically, multiple thermoelectric modules 30 are connected side by side to achieve the desired temperature regulation. Cooling occurs when an electric current passes through one or more pairs of n-type and p-type semiconductor elements. This causes a decrease in temperature at the junction, resulting in absorption of heat from an environment. The heat is carried along the n-type and p-type semiconductor elements by electron transport and released on the opposite junction as the electrons move from a high to low energy state. Thus, the thermoelectric module 30 acts as a solid-state heat pump.
[033] The thermoelectric module 30 employed is a small square shaped structure and a few thermoelectric modules 30 are arranged in rows or columns for heat transfer. The square shape of the thermoelectric modules 30 effectively covers a peripheral area of the battery cell 12. However, the shape and size of the thermoelectric module 30 varies based on a type and design of the battery pack 10 and the plurality of battery cells 12. In the illustrated embodiment, three sets of four thermoelectric modules 30, i.e., twelve thermoelectric modules 30 are employed on one side of the battery pack 10. Each of the thermoelectric modules 30 has a first surface 32 and a second surface 34. The first surface 32 of the thermoelectric module 30 is opposite to the second surface 34. The first surface 32 of the thermoelectric module 30 is in thermal communication with one or more of the plurality of battery cells 12 of at least one cell stack 14 and the second surface 34 of the thermoelectric module 30 is in thermal communication with one or more of the plurality of wall members 22. The thermoelectric module 30 is operable to actively transfer heat between the first surface 32 and the second surface 34 when an electric current is passed through the thermoelectric module 30. Thus, the thermoelectric module 30 is an active cooling means for the battery pack 10 which pumps heat between the first surface 32 and the second surface 34.
[034] In an embodiment, the thermoelectric module 30 actively transfers heat from the first surface 32 to the second surface 34, when an electric current of a first polarity is passed through the thermoelectric module 30. The first surface 32 being in thermal communication with one or more of the plurality of battery cells 12 of at least one cell stack 14, receives heat from the plurality of battery cells 12 and cools the plurality of battery cells 12. The one or more of the plurality of battery cells 12 which are in thermal communication with the first surface 32 drops in temperature and the other plurality of battery cells 12 dissipate their heat to the plurality of battery cells 12 which are in thermal communication with the first surface 32, and thus all the battery cells 12 of the battery pack 20 are cooled. The second surface 34 being in thermal communication with one or more of the plurality of wall members 22 is adapted to dissipate heat to the one or more wall members 22. Heat from the plurality of wall members 22 is gradually dissipated to the ambient environment via any passive or active heat dissipation means known in the art. In an embodiment, the heat transmitted to the plurality of wall members 22 from the thermoelectric modules 30 is dissipated to the environment via the plurality of fins 122. In another embodiment, the thermoelectric module 30 actively transfers heat from the second surface 34 to the first surface 32, when an electric current of a second polarity is passed through the thermoelectric module 30. In an embodiment, the electric current of the second polarity is obtained by reversing the polarity of the electric current of the first polarity. The first surface 32 being in thermal communication with one or more of the plurality of battery cells 12 of at least one cell stack 14 dissipates heat to the plurality of battery cells 12 to warm the plurality of battery cells. The second surface 34 is adapted to receive heat from the plurality of wall members 22, and heat from the ambient environment is gradually absorbed by the plurality of wall members 22 to attain thermal equilibrium between its inner and outer portions. The plurality of fins 122 aid in this heat absorption. Similarly, other heat generating components of the battery pack like a module for Battery Management System (BMS) can also be thermally coupled to the thermoelectric modules 30 for temperature regulation.
[035] The battery pack 10 further includes a holder 40 which is adapted to securely mount the at least one thermoelectric module 30. In the illustrated embodiment, the holder 40 is disposed inside the casing 20, to provide the thermoelectric module 30 inside the casing 20. The holder 40 has one or more slits 42 to accommodate the at least one thermoelectric module 30. In the illustrated embodiment, the holder 40 has twelve slits to house the twelve thermoelectric modules 30. The holder 40 secures the thermoelectric modules 30 in position and restricts their relative motion with respect to the battery pack 10. Further, the holder 40 also acts as an insulator as well as a structural member. In an embodiment, the battery pack 10 includes a heat spreader 50 disposed between the one or more cell stacks 14 and the thermoelectric module 30. The heat spreader 50 distributes heat flux from the plurality of battery cells 12 and the thermoelectric modules 30 to enable optimum heat dissipation between the plurality of battery cells 12 and the thermoelectric modules 30. The heat spreader 50 allows for uniform heat transfer aiding in uniform warming and cooling of the plurality of battery cells 12 by the thermoelectric modules 30. In an embodiment, graphene sheets are used as heat spreader 50. Employing the heat spreader 50 enables to use limited number of thermoelectric modules 30 to achieve the desired cooling or warming effects. As illustrated in Figures 2 and 3, the thermoelectric modules 30 are not provided on the entire surface of the heat spreader 50. Instead, the thermoelectric modules 30 are equitably separated for optimum heat transfer by radial conduction between the one or more battery cells 12 in thermal contact with the heat spreader 50 and the thermoelectric modules 30. By employing the heat spreader 50 and reducing the number of thermoelectric modules 30 being used, overall cost of the battery pack 10 can be reduced. Further, employing more thermoelectric modules 30 would require more power to be drawn from the plurality of battery cells 12 to operate them and reduce overall efficiency of the battery pack. However, in an alternate embodiment, if a higher rate of temperature control is required, the thermoelectric modules 30 can be adapted to cover a larger surface area over the cell stacks 14, or even cover all the cell stacks 14 so as to provide more contact area for the battery cells 12 to exchange heat with them. In this scenario, the heat spreader 50 is not required.
[036] The battery pack 10 further includes a fire-retardant sheet 60 disposed between the thermoelectric module 30 and the plurality of wall members 22. The fire-retardant sheet 60 is adapted to restrict propagation of fire from the plurality of battery cells 12 to the one or more wall members 22. Thus, extreme heat and fire if caused within the battery pack 10, is restrained to the battery pack 10 and prevented from escaping outside the casing 20 and causing injury and damage to people and property in its surroundings. This makes the battery pack 10 safe even in the case of thermal runaway conditions. In an embodiment, fire-retardant sheet 60 is disposed on the side of the battery pack 10 where the Current Interrupt Device (CID) is provided, such that any fire or flame would trigger the CID to cut off electrical circuits to prevent further risk. In another embodiment, the battery pack 10 includes a gap filler (not shown) disposed between the one or more cell stacks 14 and the heat spreader 50. The gap filler is adapted to maintain optimum thermal contact and achieve optimum heat conduction between the one or more of the plurality of battery cells 12 of the one or more cell stacks 14 which are adjacent to the thermoelectric module 30 and the thermoelectric module 30 for effective heat transfer. In an embodiment, when the heat spreader 50 is employed in the battery pack 10, the gap filler is adapted to maintain optimum thermal contact and achieve optimum heat conduction between the heat spreader 50 and the plurality of battery cells 12 of the one or more cell stacks 14.
[037] Figure 4 illustrates a partial isometric exploded view of the battery pack 10, in accordance with an embodiment of the present subject matter. Figure 5 illustrates an orthographic side view of the battery pack 10, in accordance with an embodiment of the present subject matter. Referring to Figures 4 and 5, the one or more wall members 22 in thermal communication with the thermoelectric module 30 are adapted for heat transfer with the ambient. The one or more wall members 22 in thermal communication with the thermoelectric module 30 also have the plurality of fins 122 at the exterior portion of the one or more wall members 22 to effectively transfer heat between the one or more wall members 22 and the ambient environment.
[038] Figure 6 illustrates a top isometric partial exploded view of an exemplary battery pack 10, in accordance with an embodiment of the present subject matter. In the alternate embodiment illustrated in Figure 6, the at least one thermoelectric module 30 is disposed outside the casing 20 for easier serviceability of the thermoelectric module 30. Even though placement of the thermoelectric module 30 outside the casing enhances ease of replacement of the thermoelectric module 30 in case it becomes faulty, this arrangement reduces the efficiency of thermal management as the thermoelectric module 30 is farther away from the plurality of battery calls 12 and heat would have to pass through other components. In the illustrated alternate embodiment, one or more of the plurality of battery cells 12 of at least one cell stack 14 are in thermal communication with one or more of the plurality of wall members 22. The at least one thermoelectric module 30 is disposed between the one or more wall members 22 which are in thermal communication with the battery cells 12 and the ambient environment. Further, the first surface 32 of the thermoelectric module 30 is in thermal communication with the one or more wall members 22 and the second surface 34 of the thermoelectric module 30 is in thermal communication with the ambient environment. The first surface 32 of the thermoelectric module 30 is opposite the second surface 34, and the thermoelectric module 30 is operable to actively transfer heat between the first surface 32 and the second surface 34 when an electric current is passed through the thermoelectric module 30.
[039] In an embodiment, the thermoelectric module 30 is actively transfers heat from the first surface 32 to the second surface 34 when the electric current of the first polarity is passed through the thermoelectric module 30. The first surface 32 being in thermal communication with the one or more wall members 22 which are in thermal communication with the plurality of battery cells 12, receives heat from the one or more wall members 22 to cool the plurality of battery cells. The second surface 34 dissipates heat to the ambient and in turn cools the one or more wall members 22 which are in thermal communication with the plurality of battery cells 12. In another embodiment, the thermoelectric module 30 actively transfers heat from the second surface 34 to the first surface 32 when the electric current of the second polarity is passed through the thermoelectric module 30. The first surface 32 is adapted to dissipate heat to the plurality of battery cells 12 and the second surface 34 is adapted to receive heat from the ambient to warm the plurality of battery cells 12.
[040] The holder 40 adapted to securely mount the at least one thermoelectric module 30 is disposed outside the casing 20. In another embodiment, the battery pack 10 has the gap filler 70 disposed between the one or more cell stacks 14 and the one or more wall members 22. The gap filler 70 is adapted to achieve optimum heat conduction between one or more of the plurality of battery cells 12 of the cell stack 14 and the one or more wall members 22 for effective heat transfer. The gap filler 70 also acts as an electrical insulator between the plurality of wall members 22 and the plurality of battery cells 12.
[041] Figure 7 illustrates an orthographic side view of the battery pack 10, in accordance with an embodiment of the present subject matter. Referring to Figures 6 and 7, the battery pack 10 includes a cover member 80. The cover member 80 is disposed over the second surface 34 of the thermoelectric modules 30. Further, the cover member 80 is thermally conductive and in thermal communication with the thermoelectric module 30 to enable heat transfer between the thermoelectric module 30 and the ambient environment. Thus, heat is transmitted between the thermoelectric module 30 and the ambient through the cover member 80. In yet another embodiment, the cover member 80 includes a plurality of fins 182 disposed on an exterior surface of the cover member 80. The plurality of fins 182 enable effective transfer of heat between the cover member 80 and the ambient environment. The fins may have any design known in the art to maximise heat transfer. In the embodiment illustrated in Figure 6, the fire-retardant sheet 60 is disposed between the thermoelectric modules 30 and the cover member 80. The fire-retardant sheet 60 is adapted to restrict propagation of fire from the thermoelectric module 30 to the cover member 80 in case there is a short circuit or thermal runaway condition in the battery pack 10.
[042] Figure 8 illustrates an exemplary method 800 to regulate a temperature of the battery pack 10, in accordance with an embodiment of the present subject matter. At a step 804, a Battery Management System (BMS) monitors a temperature of the battery pack 10. At a step 806, the BMS compares the temperature of the battery pack 10 with a predefined upper threshold limit temperature. If the temperature of the battery pack 10 is lesser than the predefined upper threshold limit, the BMS returns to monitoring 804 the temperature of the battery pack 10. If the temperature of the battery pack 10 is greater than the predefined upper threshold limit, at a step 808, the BMS passes the electric current of the first polarity through the thermoelectric module 30 to actively transfer heat from the first surface 32 to the second surface 34 to cool the plurality of battery cells 12. The BMS then returns to monitoring 804 the temperature of the battery pack 10. At a step 810, the BMS compares the temperature of the battery pack 10 with a predefined lower threshold limit temperature. If the temperature of the battery pack 10 is greater than the predefined lower threshold limit, the BMS returns to monitoring 804 the temperature of the battery pack 10. If the temperature of the battery pack 10 is lesser than the predefined lower threshold limit, at a step 812, the BMS passes the electric current of the second polarity through the thermoelectric module 30 to actively transfer heat from the second surface 34 to the first surface 32 to warm the plurality of battery cells 12. The BMS then returns to monitoring 804 the temperature of the battery pack 10.
[043] Figure 9 illustrates the method 800 to regulate a temperature of the battery pack 10, in accordance with an embodiment of the present subject matter. In the alternate embodiment of the method 800 illustrated in figure 9, at a step 804, the BMS monitors a temperature of the battery pack 10. At a step 814, the BMS compares the temperature of the battery pack 10 with an upper limit temperature of a predefined temperature range. If the temperature of the battery pack 10 is lesser than the upper limit of the predefined temperature range, the BMS returns to monitoring 804 the temperature of the battery pack 10. If the temperature of the battery pack 10 is greater than an upper limit of the predefined temperature range, at a step 816, the BMS passes the electric current of the first polarity through the thermoelectric module 30 to actively transfer heat from the first surface 32 to the second surface 34 to cool the plurality of battery cells 12 and maintain 822 the temperature of the battery pack 10 within the predefined temperature range. The BMS then returns to monitoring 804 the temperature of the battery pack 10. In another embodiment, at a step 818, the BMS compares the temperature of the battery pack 10 with a lower limit temperature of the predefined temperature range. If the temperature of the battery pack 10 is greater than the lower limit of the predefined temperature range, the BMS returns to monitoring 804 the temperature of the battery pack 10. If the temperature of the battery pack 10 is lesser than the lower limit of the predefined temperature range, at a step 820, the BMS passes the electric current of the second polarity through the thermoelectric module 30 to actively transfer heat from the second surface 34 to the first surface 32 to warm the plurality of battery cells 12 and maintain 822 the temperature of the battery pack 10 within the predefined temperature range. The BMS then returns to monitoring 804 the temperature of the battery pack 10.
[044] Advantageously, the present claimed invention provides a battery pack encompassing a system and a method to regulate a temperature of the battery pack. The claimed configurations of the battery pack and the method to regulate the temperature of the battery pack as discussed above are not routine, conventional, or well understood in the art, as the claimed configurations of the battery pack and the method enable the following solutions to the existing problems in conventional technologies. The active cooling of the battery cells and the battery pack by the thermoelectric module enables efficient heat dissipation to ensure that the battery pack operates within intended operating temperatures, thus improving product life and performance. The use of the thermoelectric modules in conjunction with the heat spreader ensures that relatively low power is consumed as compared to the temperature regulation achieved and provide controlled cooling regardless of ambient temperature conditions. The disclosed invention can be employed to cool the battery pack in hotter geographical regions and warm up the battery pack in colder geographical regions to ensure that the battery pack operates in its optimum temperature range at all times. Further, since the active cooling system of the battery pack employs small thermoelectric modules, the whole package of the battery pack is compact, lightweight, and easy to handle when compared to battery packs employing conventional cooling systems. This would improve ease of handling of the battery pack and reduce assembling costs. Furthermore, since the battery pack can be maintained within a predefined optimum temperature range, the battery pack can be moved from a discharging cycle to a charging cycle without any delay to cool the battery pack down. Also, the battery pack can be moved to a charging cycle from a non-active state without delay for warming the battery pack up in very cold ambient conditions.
[045] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

List of Reference Numerals
10 - battery pack
12 - battery cells
14 - cell stacks
20 - casing
22 - wall members
122 - plurality of fins
30 - thermoelectric module
32 - first surface of the thermoelectric module
34 - second surface of the thermoelectric module
40 - holder
42 - slits of the holder
50 - heat spreader
60 - fire-retardant sheet
70 - gap filler
80 - cover member
182 - plurality of fins
, Claims:1. A battery pack (10) comprising:
a casing (20) having a plurality of wall members (22), the plurality of wall members (22) configured to be thermally conductive;
a plurality of battery cells (12) arranged in one or more cell stacks (14) inside the casing (20); and
at least one thermoelectric module (30), the at least one thermoelectric module (30) having a first surface (32) and a second surface (34), the at least one thermoelectric module (30) being disposed between the one or more cell stacks (14) and at least one of the plurality of wall members (22),
wherein the first surface (32) of the thermoelectric module (30) being in thermal communication with one or more of the plurality of battery cells (12) of at least one cell stack (14) and the second surface (34) of the thermoelectric module (30) being in thermal communication with one or more of the plurality of wall members (22).

2. The battery pack (10) as claimed in claim 1, wherein the first surface (32) of the at least one thermoelectric module (30) being opposite to the second surface (34) of the at least one thermoelectric module (30), and the at least one thermoelectric module (30) being operable to actively transfer heat between the first surface (32) and the second surface (34), when an electric current is passed through the thermoelectric module (30).

3. The battery pack (10) as claimed in claim 1, wherein the at least one thermoelectric module (30) is configured to actively transfer heat from the first surface (32) to the second surface (34), when an electric current of a first polarity being passed through the thermoelectric module (30), the first surface (32) configured to receive heat from the plurality of battery cells (12) and the second surface (34) configured to dissipate heat to the one or more wall members (22) to cool the plurality of battery cells (12).

4. The battery pack (10) as claimed in claim 1, wherein the at least one thermoelectric module (30) being configured to actively transfer heat from the second surface (34) to the first surface (32) when an electric current of a second polarity being passed through the thermoelectric module (30), the first surface (32) configured to dissipate heat to the plurality of battery cells (12) and the second surface (34) configured to receive heat from the one or more wall members (22) to warm the plurality of battery cells (12).

5. The battery pack (10) as claimed in claim 1 comprising a holder (40) configured to securely mount the at least one thermoelectric module (30), the holder (40) being disposed inside the casing (20) and the holder (40) having one or more slits (42) to accommodate the at least one thermoelectric module (30).
6. The battery pack (10) as claimed in claim 1 comprising a heat spreader (50) being disposed between the one or more cell stacks (14) and the at least one thermoelectric module (30), the heat spreader (50) being configured to distribute heat flux from the plurality of battery cells (12) and the at least one thermoelectric module (30) to enable optimum heat dissipation between the plurality of battery cells (12) and the at least one thermoelectric module (30).

7. The battery pack (10) as claimed in claim 1 comprising a fire-retardant sheet (60) disposed between the at least one thermoelectric module (30) and the one or more wall members (22), the fire-retardant sheet (60) being configured to restrict fire to propagate from the plurality of battery cells (12) to the one or more wall members (22).

8. The battery pack (10) as claimed in claim 1, wherein the one or more wall members (22) in thermal communication with the thermoelectric module (30) being configured for heat transfer with an ambient, and wherein the one or more wall members (22) comprises a plurality of fins (122) at an exterior portion of the one or more wall members (22), the plurality of fins (122) being configured to effectively transfer heat between the one or more wall members (22) and the ambient.

9. The battery pack (10) as claimed in claim 6, wherein the battery pack (10) comprising a gap filler (70), the gap filler (70) being disposed between the one or more cell stacks (14) and the heat spreader (50), the gap filler (70) being configured to achieve optimum heat conduction between the one or more of the plurality of battery cells (12) of the one or more cell stacks (14) and the at least one thermoelectric module (30) for effective heat transfer.

10. A battery pack (10) comprising:
a casing (20) having a plurality of wall members (22), the plurality of wall members (22) configured to be thermally conductive;
a plurality of battery cells (12) arranged in one or more cell stacks (14) inside the casing (20), one or more of the plurality of battery cells (12) of at least one cell stack (14) being in thermal communication with one or more of the plurality of wall members (22); and
at least one thermoelectric module (30) having a first surface (32) and a second surface (34), the at least one thermoelectric module (30) being disposed between the one or more wall members (22) in thermal communication with the battery cells (12) and an ambient,
wherein the first surface (32) of the at least one thermoelectric module (30) being in thermal communication with the one or more wall members (22) and the second surface (34) of the at least one thermoelectric module (30) being in thermal communication with the ambient.

11. The battery pack (10) as claimed in claim 10, wherein the first surface (32) of the at least one thermoelectric module (30) being opposite the second surface (34) of the at least one thermoelectric module (30), and the at least one thermoelectric module (30) being operable to actively transfer heat between the first surface (32) and the second surface (34) when an electric current being passed through the thermoelectric module (30).

12. The battery pack (10) as claimed in claim 10, wherein the at least one thermoelectric module (30) being configured to actively transfer heat from the first surface (32) to the second surface (34) when an electric current of a first polarity being passed through the thermoelectric module (30), the first surface (32) configured to receive heat from the one or more wall members (22) in thermal communication with the plurality of battery cells (12) and the second surface (34) configured to dissipate heat to the ambient to cool the plurality of battery cells (12).

13. The battery pack (10) as claimed in claim 10, wherein the at least one thermoelectric module (30) being configured to actively transfer heat from the second surface (34) to the first surface (32) when an electric current of a second polarity being passed through the thermoelectric module (30), the first surface (32) configured to dissipate heat to the plurality of battery cells (12) and the second surface (34) configured to receive heat from the ambient to warm the plurality of battery cells (12).

14. The battery pack (10) as claimed in claim 10, wherein the battery pack (10) comprising a holder (40) configured to securely mount the at least one thermoelectric module (30), the holder (40) being disposed outside the casing (20) and the holder (40) having one or more slits (42) to accommodate the at least one thermoelectric module (30).

15. The battery pack (10) as claimed in claim 10 comprising a gap filler (70) disposed between the one or more cell stacks (14) and the one or more wall members (22), the gap filler (70) being configured to achieve optimum heat conduction between the one or more of the plurality of battery cells (12) of the cell stack (14) and the one or more wall members (22) for effective heat transfer and the gap filler (70) acting as an electrical insulator between the one or more wall members (22) and the plurality of battery cells (12).

16. The battery pack (10) as claimed in claim 10 comprising a cover member (80) disposed over the second surface (34) of the at least one thermoelectric module (30), the cover member (80) being thermally conductive and in thermal communication with the thermoelectric module (30) to enable heat transfer between the at least one thermoelectric module (30) and the ambient through the cover member (80).

17. The battery pack (10) as claimed in claim 16, wherein the cover member (80) being configured for heat transfer with the ambient, the cover member (80) comprising a plurality of fins (182) disposed on an exterior surface of the cover member (80), the plurality of fins (182) being configured to effectively transfer heat between the cover member (80) and the ambient.

18. The battery pack (10) as claimed in claim 16 comprising a fire-retardant sheet (60) disposed between the at least one thermoelectric module (30) and the cover member (80), the fire-retardant sheet (60) being configured to restrict fire to propagate from the thermoelectric module (30) to the cover member (80).

19. A method (800) to regulate temperature of a battery pack (10), the battery pack (10) comprising a casing (20), a plurality of battery cells (12) arranged in one or more cell stacks (14) inside the casing (20), at least one thermoelectric module (30) having a first surface (32) and a second surface (34), the thermoelectric module (30) operable to actively transfer heat between the first surface (32) and the second surface (34) when an electric current being passed through the thermoelectric module (30), wherein the first surface (32) of the thermoelectric module (30) being configured to exchange heat with one or more of the plurality of battery cells (12) of at least one cell stack (14) and the second surface (34) of the thermoelectric module (30) being configured to exchange heat with an ambient, the method (800) comprising the steps of:
monitoring (804), by a Battery Management System (BMS), a temperature of the battery pack (10);
passing (808) the electric current of a first polarity, by the BMS, through the thermoelectric module (30) to actively transfer heat from the first surface (32) to the second surface (34) to cool the plurality of battery cells (12) if the temperature of the battery pack (10) being greater than a predefined upper threshold limit; and
passing (812) the electric current of a second polarity, by the BMS, through the thermoelectric module (30) to actively transfer heat from the second surface (34) to the first surface (32) to warm the plurality of battery cells (12) if the temperature of the battery pack (10) being lesser than a predefined lower threshold limit.

20. The method (800) as claimed in claim 19 comprising the steps of:
passing (816) the electric current of the first polarity, by the BMS, through the thermoelectric module (30) to actively transfer heat from the first surface (32) to the second surface (34) to cool the plurality of battery cells (12) and maintain (822) the temperature of the battery pack (10) within a predefined temperature range, if the temperature of the battery pack (10) being greater than an upper limit of the predefined temperature range; and
passing (820) the electric current of the second polarity, by the BMS, through the thermoelectric module (30) to actively transfer heat from the second surface (34) to the first surface (32) to warm the plurality of battery cells (12) and maintain (822) the temperature of the battery pack (10) within the predefined temperature range, if the temperature of the battery pack (10) being lesser than a lower limit of the predefined temperature range.