Description:TECHNICAL FIELD
[0001] The present subject matter relates, generally to, secondary
batteries, and particularly to thermal management and structural designs of
rechargeable lithium-ion battery cells.
5
BACKGROUND
[0002] Rechargeable lithium-ion battery cells are essential for modern
energy storage applications. Battery cells are increasingly employed in
various high-performance applications, including but not limited to electric
vehicles (EVs), grid-scale energy storage systems, 10 and portable electronics.
However, during operation, battery cells generate heat due to internal
electrochemical reactions and resistive losses. This may degrade battery
performance and lifespan, highlighting the critical need for effective heat
management strategies in battery design and operation.
15
BRIEF DESCRIPTION OF FIGURES
[0003] Systems and/or methods, in accordance with examples of the
present subject matter are not described and with reference to the
accompanying figures, in which:
20 [0004] FIG. 1 illustrates a perspective view of a battery pack, in
accordance with an example of the present subject matter;
[0005] FIG. 2 (A) illustrates a perspective view of a casing of a prismatic
cell, in accordance with an example of the present subject matter;
[0006] FIG. 2 (B) illustrates another perspective view of the casing of the
25 prismatic cell, in accordance with an example of the present subject matter;
and
[0007] FIG. 3 illustrates a schematic of an assemble view of fins of
adjacent prismatic cells in a battery pack, in accordance with an example of
the present subject matter.
30 It may be noted that throughout the drawings, identical reference numbers
designate similar, but not necessarily identical, elements. The figures are
2
not necessarily to scale, and the size of some parts may be exaggerated to
more clearly illustrate the example shown. Moreover, the drawings provide
examples and/or implementations consistent with the description; however,
the description is not limited to the examples and/or implementations
5 provided in the drawings.
DETAILED DESCRIPTION
[0008] During operation, rechargeable battery cells are subject to
electrochemical reactions that generate heat. Over time, as the battery
10 undergoes numerous charge and discharge cycles, internal resistance
within the cell tends to increase. This internal resistance buildup may be
attributed to the degradation of electrodes, decomposition of the electrolyte,
growth of solid-electrolyte interphase (SEI) layers, and other
physicochemical changes. The elevated internal resistance leads to
15 localized thermal accumulation within the cell, particularly during highcurrent
or fast-charging events.
[0009] Effective heat management is essential for maintaining
performance and safety of battery cells. If heat generated during operation
is not effectively dissipated, the accumulated heat may lead to reduced
20 charge acceptance, accelerated degradation of internal components, such
as electrodes and separator. Moreover, the accumulated heat may further
promote side reactions that further increase resistance and gas generation.
Collectively, these effects diminish the operational efficiency, capacity
retention, and overall lifespan of the battery cell.
25 [0010] These thermal management challenges are more pronounced in
prismatic cells, which are characterized by their dense packaging and
limited surface area available for cooling. In such configurations, the risk of
localized heat buildup is aggravated, increasing the likelihood of severe
thermal stress. Moreover, under extreme thermal stress, the prismatic cells
30 are susceptible to thermal runaway- a hazardous condition wherein selfsustaining
exothermic reactions cause a rapid and uncontrollable rise in
3
temperature. Thermal runaway not only compromises the individual cell but
can also propagate to adjacent cells, resulting in catastrophic failure of the
entire battery module pack, potentially accompanied by fire, smoke, or
explosion.
[0011] Given these risks, various thermal management 5 strategies have
been proposed to mitigate heat-related issues in the prismatic cells. Such
techniques include the incorporation of external or internal cooling systems
(e.g., liquid or air-cooled channels), the application of thermal interface
materials (TIMs), the use of heat spreaders, and the integration of phase
10 change materials (PCMs) to absorb excess thermal energy. Despite these
developments, there remains a critical need for improved methods and
systems that effectively manage heat generation and dissipation within
prismatic cells, particularly under high-demand or extreme environmental
conditions.
15 [0012] Example designs for a casing for a prismatic cell and a battery
pack for accommodating prismatic cells are described. The present subject
matter relates to a casing for a prismatic cell. The case includes a first wall,
and a second wall disposed opposite the first wall for enclosing the prismatic
cell. A first set of fins, having a first curved profile, is positioned on an outer
20 surface of the first wall. Further, a second set of fins, having a second curved
profile complementary to the first curved profile, is positioned on an outer
surface of the second wall. Continuing further, upon stacking the plurality of
casings, the first set of fins are configured to interleave with the second set
of fins without contact to define a continuous airflow path between adjacent
25 casings.
[0013] In another aspect, the present subject matter relates to a battery
pack comprising at least two prismatic cells having respective casings,
arranged adjacent to one another in the battery pack. Each casing includes
a first wall and second wall with a first and second set of fins, respectively.
30 The fins are positioned on an outer surface of the respective walls of the
casing of the first and second prismatic cell. The first and second sets of
4
fins have a first curved profile and a second curved profile complementary
to the first curved profile, respectively, defining an airflow path between the
casings. Upon stacking a plurality of casings, the integration of the first and
second sets of fins generates turbulent airflow across the wall of the casing.
[0014] For example, battery pack may include at 5 least a first and a second
prismatic cell positioned adjacent to one other. Each of the first and second
prismatic cell includes a casing having at least a first wall and a second wall
disposed opposite the first wall for enclosing the prismatic cells. The casing
may further comprise a first set of fins positioned on an outer surface of the
10 first wall and a second set of fins positioned on an outer surface of the
second wall. In an example, the first set of fins has a first curved profile, and
the second set of fins has a second curved profile complementary to the
first curved profile. Upon stacking a plurality of casings, the first set of fins
are configured to interleave with the second set of fins without contact, to
15 define a continuous airflow path between adjacent casings.
[0015] Accordingly, the airflow path defined between the first set of fins
and the second set of fins provides a path to direct the airflow across the
cell surface, ensuring more uniform cooling and effectively reducing the
temperature of the cell. Further, the curved shape profile of the fins induces
20 turbulence in airflow, hence ensuring optimal heat dissipation. Additionally,
the alignment of the first set of fins with the second set of fins allows an
optimal spatial arrangement maximizing the space utilization by ensuring
that the first set of fins integrate seamlessly with the second set of fins.
[0016] The above aspects are further described in conjunction with the
25 figures, and in the associated description below. It should be noted that the
description and figures merely illustrate principles of the present subject
matter. Therefore, various assemblies that encompass the principles of the
present subject matter, although not explicitly described or shown herein,
may be devised from the description, and are included within its scope.
30 [0017] FIG. 1 illustrates a perspective view of a battery pack 100, in
accordance with an example of the present subject matter. The battery pack
5
100 may include a housing 102 to accommodate and to provide structural
support and protection to a plurality of internal components. In an example,
the housing 102 may be manufactured from a lightweight material, such as
aluminum alloys, high-strength polymers, or carbon fiber composites. In
some implementations, the housing 102 may 5 incorporate reinforced corners
or impact-resistant zones to enhance durability.
[0018] In an example, the battery pack 100 may feature internal partitions
or cell holders to securely position and isolate individual prismatic cells. For
example, the battery pack 100 may include a plurality of prismatic cells 104-
10 1, 104-2, 104-3, …, 104-N (collectively referred to as cells 104) arranged
adjacent to one another. Although FIG. 1 illustrates a side-by-side
configuration of the cells 104, it may be understood that in other
implementations, the cells 104 may be arranged in multiple rows or a matrix
formation. The number of cells 104 in the battery pack 100 may vary
15 depending on the desired capacity and application requirements. In some
cases, the battery pack 100 may incorporate different sizes or capacities of
prismatic cells 104 within the same assembly.
[0019] The battery pack 100 may be designed with various form factors
to suit different applications. In some cases, the battery pack 100 may have
20 a flat, low-profile configuration for integration into vehicle floors. In other
example, the battery pack 100 may feature a more compact, cube-like
structure for stationary energy storage applications.
[0020] Each prismatic cell 104 may have a casing 106 with at least two
opposite walls. A first set of fins 108 may be positioned on an outer surface
25 of one wall, and a second set of fins 110 may be positioned on an outer
surface of the opposite wall. The first set of fins 108 and the second set of
fins 110 have respective curved profiles. In some examples, a number of
columns of the first set of fins 108 may be different than a number of
columns of the second set of fins 110. Further, the first set of fins 108 and
30 the second set of fins 110 are arranged at pre-defined locations of the
6
respective walls of the cells 104. Details pertaining to the casing of the
prismatic cell 104 are explained in conjunction with FIG. 2(A) and FIG. 2(B).
[0021] In an example, the first and second set of fins may be
manufactured using various materials and methods. In one example, the
fins may be made from the same material as 5 that of the casing 106.
Alternatively, the fins may be constructed from a material that has a higher
thermal conductivity than that of the casing 106.
[0022] The integration of the first set of fins 108 and the second set of fins
110 with the prismatic cells may be achieved through different
10 manufacturing approaches known in the art. In some aspects, the fins may
be integrated directly with the casing during the manufacturing process of
the prismatic cells. In other examples, the fins may be fabricated separately
and then attached or placed onto the cell casing after the cells have been
manufactured.
15 [0023] Referring back to FIG. 1, when the cells 104 are arranged side-byside
in an adjacent configuration, a first wall of one cell 104 is positioned
adjacent to a second wall of another cell 104. As a result, the curved fins
formed on the opposing walls of the respective prismatic cells may
interleave with one another without coming into direct contact. The
20 interleaving arrangement of the curved fins may define a continuous an
airflow path between adjacent prismatic cells. The airflow path may facilitate
airflow through inter-cell gaps, thereby enhancing thermal management by
allowing heat to be dissipated more effectively from surfaces of the prismatic
cells.
25 [0024] FIGS. 2 (A) and 2(B) illustrate different perspective views of a
casing 200 of a prismatic cell (not shown), in accordance with an example
of the present subject matter. The casing 200 may serve as an enclosure
for the prismatic cell. For example, the casing 200 may house a plurality of
internal electrochemical components, such as electrodes, separator, and
30 electrolyte materials, of the prismatic cell. In an example, the casing 200
7
may be fabricated from a durable material, such as metal or rigid plastic to
withstand the internal pressures and temperatures generated during cell
operation.
[0025] In an example, the casing 200 may have at least a first wall 202
and a second wall 204 disposed opposite 5 to the first wall 202. These two
opposing walls define primary lateral surfaces of the casing 200 and
collectively contribute to the external geometry of the prismatic cell. The first
wall 202 and the second wall 204 may be generally planar, flat surfaces that
extend in parallel to each other. Each of these walls may have a
10 substantially rectangular profile, thereby contributing to the box-like,
cuboidal form factor that is characteristic of the prismatic cell. As may be
understood, the casing 200 may include additional structural elements, such
as side walls, a top surface, and a bottom surface to fully enclose the
prismatic cell. The casing 200 may also incorporate features for electrical
15 connections and thermal management.
[0026] As depicted in FIG. 2(A), the first wall 202 includes a first set of
fins 206 arranged on an outer surface 208 of the first wall 202. The first set
of fins 206 may be arranged in matrix of M rows and N columns, where M
and N are integers greater than 1. In an example, the first set of fins 206
20 may be arranged in a M X N arrangement depending on the cell size and
cooling requirements of the cell. Further, the first set of fins 206 have a first
curved profile. In an implementation, in the M X N arrangement, all columns
of fins, except a first column, from the first set of fins 206 may have a
concave profile.
25 [0027] Further, each fin in the first column of the first set of fins 206 may
include a half curved and half straight profile. In an example, the first column
of fins may be positioned at an air inlet of the airflow path. The hybrid design
of the fins in the Nth column may serve a dual purpose. For example, the
half-curved profile may help to guide and direct the incoming airflow
30 efficiently into the battery pack, while the half straight profile may ensure a
8
smooth transition of air into the subsequent fin arrangement. The length of
the straight profile and the point of transition to the curved profile may be
optimized based on computational fluid dynamics simulations and
experimental testing to achieve the best balance of airflow characteristics.
[0028] In an example, the number and spacing 5 of the first set of fins 206
on the first wall 202 of the casing 200 may be calculated using keeping into
account the cell dimensions and desired fin parameters. For example,
equation (1) may be followed for calculating the dimensions and quantity of
fins 206 on the first wall 202:
10 NAx + (NA-1)y = cell length - 1 … (1)
where, NA is the number of fins on the first wall 202;
x is the length of each fin on the first wall 202; and
y is the gap between two adjacent fins in the horizontal direction (H).
[0029] The value "1" in the equation (1) may represent a small offset that
15 may be incorporated in the design of the casing 200 to account for
manufacturing or handling considerations. For example, when calculating
the total available length along the first wall 202 for fin placement, 1 mm is
subtracted from the overall cell length. This subtraction reserves 0.5 mm
clearance on each side of the cell (i.e., at both lateral edges of the first wall
20 202). This offset helps to ensure that the fins 206 are not positioned too
close to the edges of the first wall 202, where they might be susceptible to
damage during assembly, handling, or transport.
[0030] Referring now to FIG. 2(B), the second wall 204 includes a second
set of fins 210 arranged on an outer surface 212 of the second wall 204.
25 The second set of fins 210 may be arranged in matrix of M rows and N
columns. M and N are integers greater than 1. In an example, the second
set of fins 210 have a second curved profile complementary to the first
curved profile of the first set of fins 206. For example, when the first set of
fins 206 has a concave profile, the second set of fins 210 are configured to
30 have a convex profile, and vice versa. In the present implementation, the
9
second set of fins 210 may be arranged in a M X N arrangement. In an
example, the number of rows of the first set of fins 206, depicted in FIG. 2
(A) may be more than the number of rows of the second set of fins 210. In
another example, the number of columns of the first set of fins 206 may be
more than the number of columns 5 of the second set of fins 210.
[0031] In an example, for calculating the dimension and number of fins
on the second wall 204, the equation (2) may be followed. The equation (2)
provides the optimal number of fins and the dimension of fins, based on the
cell length.
10 NBa + (NB-1)b = cell length - 0.85a … (2)
where, NB is the number of fins on the second wall 204;
a is the length of each fin on the second wall 204; and
b is the gap between two adjacent fins in the horizontal direction (H).
[0032] If the coefficient of ‘a’ on the right-hand side (RHS) of the
15 expression (0.85) is changed, then the number of fins may no longer fit
evenly (as whole numbers) into the given cell length. In an example, the
0.85a term may represent a non-usable margin or boundary adjustment, at
an edge of the second wall 204. Therefore, any change in the 0.85a may
change the usable length available on the outer surface 212 for placing the
20 fins and gaps. That, in turn, affects how many fins can fit exactly on the
second wall 204.
[0033] In an implementation, the first set of fins 206 and the second set
of fins 210 may be manufactured from the same material as that of the
casing 200. For example, the fins and the casing 200 may be made of
25 aluminum or a thermally conductive polymer. Alternatively, the first set of
fins 206 and the second set of fins 210 may be made from a material having
higher thermal conductivity than that of the casing 200. For example, the
fins may be made of materials, like copper or a specialized heat-dissipating
alloy.
10
[0034] Further, the first set of fins 206 and the second set of fins 210 may
be integrally formed with the casing 200 during a molding or extrusion
process. Alternatively, the first set of fins 206 and the second set of fins 210
may be separately fabricated and then attached to the outer surfaces of the
respective walls 202 and 204, through welding, 5 adhesive bonding, or
mechanical fastening.
[0035] Further, each fin from the first set of fins 206 and the second set
of fins 210, may form an arc angle θ between an axis A drawn from a base
of the curved fin and passing through a tip of the curved fin, and a horizontal
10 axis B extending laterally from the base of the curved fin. In an example, the
arc angle θ may vary between about 20 degrees to about 50 degrees.
Further, each fin of the first set of fins 206 and the second set of fins 210
may have a thickness of approximately 2 millimeters (mm) at a center
region.
15 [0036] In an example, a relation between fin length and gap between two
adjacent fins from the first set of fins 206 and the second set of fins 210 may
be given by x/y = 1.5, where x is length of one fin and y is the gap between
two adjacent fins in the horizontal direction. For instance, the first set of fins
206 and the second set of fins 210 may be arranged on the respective walls
20 such that a ratio of fin length to a gap between adjacent fins along a
horizontal direction (depicted by arrow H) may be approximately 20:13. In
other words, for every 33 units of horizontal distance along the first wall 202
or the second wall 204, about 20 units may be occupied by the fin, while the
remaining 13 units define the gap between fins. As an illustrative example,
25 if the total length of one fin-gap unit along the horizontal direction is 33 mm,
then the fin may be approximately 20 mm long and the gap between that fin
and the next fin may be 13 mm. This repeating pattern (20 mm fin, 13 mm
gap) continues along the horizontal surface of the first wall 202 and the
second wall 204, thereby maintaining the 20:13 ratio for consistent spacing
30 and thermal performance.
11
[0037] Further, the first set of fins 206 and the second set of fins 210 may
be configured with specific dimensional ratios in both horizontal and vertical
directions to optimize spatial arrangement and functional performance. For
example, a ratio of the length of each fin to the distance between two
adjacent fins in the horizontal direction (H) may range 5 from about 1.2:1 to
about 2:1. The ratio may ensure an effective balance between structural
density and spacing for airflow or other functional considerations. For
instance, if the fin length is 12 mm, two adjacent fins may be positioned at
a gap or spacing of about 6 mm to about 10 mm.
10 [0038] In the vertical direction (as depicted by arrow V), the relation
between fin height and gap between two adjacent fins on the first wall 202
or on the second wall 204 may be given by u/v = 0.4, where u is the height
of one fin and v is the gap between two adjacent fins in the vertical direction.
For instance, a ratio of fin height to vertical gap between fins on the first wall
15 202 and the second wall 204 may be approximately 5:13. This indicates that
for every 18 units of vertical distance, about 5 units may be occupied by the
fin, and the remaining 13 units may comprise the gap between adjacent
vertical fins. For instance, if the total vertical distance is 18 mm, each fin
may be approximately 5 mm tall with a 13 mm gap separating the fins from
20 the next fin above or below it.
[0039] In an implementation, the number and spacing of fins, in the
vertical direction, on the first wall 202 and the second wall 204 may be
calculated by taking into account the cell dimensions and desired fin
parameters. For example, equation (3) below may be followed for
25 calculating the dimensions and quantity of fins on the first wall 202 and the
second wall 204:
NAu + (NA-1)v = cell height – 0.5 … (3)
where, NA is the number of fins on the first wall 202 or the second wall 206;
u is the height of each fin on the first wall 202 or the second wall 206; and
30 v is the gap between two adjacent fins in the vertical direction (V).
12
[0040] In the aforementioned relationships, the specific values for NA, x,
y, u, and v, may vary depending on factors such as the overall dimensions
of the prismatic cell, the desired heat dissipation capacity, manufacturing
constraints, and the intended interleaving pattern with adjacent cells in the
5 battery pack.
[0041] The value "0.5" in the above equation represents a deliberate
offset, for instance 0.5 mm, which may be provided at a lower edge of the
first wall 202 and the second wall 204. The offset is subtracted from the
overall length of the casing 200 to ensure that the fins 206 or 210 do not
10 extend all the way to the bottom edge of the first wall 202 or the second wall
204, respectively. Instead, the fins 206 or 210 are positioned to begin
slightly above the bottom edge, specifically, 0.5 mm higher. By avoiding
placement of the fins 206 or 210 at the very bottom edge of the first wall 202
or the second wall 204, the present subject matter accommodates
15 tolerances and reduces the risk of mechanical interference or deformation
of the fins during assembly and operation.
[0042] In another aspect, in the vertical direction, the ratio of fin height to
gap between fins may fall within a range of approximately 0.35:1 to 0.7:1.
This range is selected to optimize airflow between the fins for effective
20 thermal management. If the ratio falls below 0.35:1, the height of each fin
may become too short relative to the gap, resulting in a configuration where
the fins and gaps are nearly equal in size. In such a case, airflow tends to
pass straight through the gaps without effectively interacting with the
surfaces of adjacent fins, thereby reducing thermal transfer efficiency.
25 [0043] Conversely, if the ratio exceeds 0.7:1, the fins may become
comparatively too tall and the gaps too narrow. This may restrict airflow and
prevent air from entering the gap between fins at a suitable angle of attack,
which may disrupt the intended flow dynamics and further reduce cooling
performance. Accordingly, maintaining the fin height-to-gap ratio within the
30 specified range promotes a balance between sufficient airflow penetration
13
and effective surface contact, thereby enhancing overall thermal
dissipation.
[0044] These dimensional ratios may also be influenced by
manufacturing considerations. The chosen ranges may allow for efficient
production processes while maintaining tight 5 tolerances necessary for
proper fin interleaving between adjacent cells. The dimensional
relationships may be designed to create channels that allow for efficient
airflow while maximizing heat transfer surface area. The ratios may enable
the fins from adjacent cells to interleave without contact, potentially creating
10 turbulent airflow patterns that enhance heat dissipation. Furthermore, these
dimensions may balance the need for sufficient fin surface area for heat
transfer with adequate spacing for airflow.
[0045] By utilizing the mathematical relationships as described in the
above equations, the fin arrangement may be precisely tailored to maximize
15 cooling efficiency while maintaining compact form factor of the prismatic
cells within the battery pack. These calculations may also facilitate
consistent and repeatable manufacturing of the finned cell casings across
different production batches.
[0046] Although the present subject matter has been described in
20 conjunction with a standard-sized prismatic cell, the dimensions and
quantity of fins may vary according to the size of the prismatic cell. The
spacing and dimensions of the curved fins may be optimized to balance heat
transfer performance with pressure drop considerations. In some aspects,
the fin thickness, curvature radius, and gap between two adjacent fins may
25 be adjusted to achieve desired thermal management characteristics while
minimizing airflow resistance through the battery pack.
[0047] FIG. 3 illustrates a schematic of an assembled view 300 of fins of
adjacent prismatic cells in a battery pack (not shown), in accordance with
an example of the present subject matter. Upon being arranged adjacent to
30 each other, the first wall of a first prismatic cell may face the second wall of
14
a second prismatic cell. For example, the first prismatic cell and the second
prismatic cell may be the same as the first prismatic cell 102-1 and the
second prismatic cell 102-2 depicted in FIG. 1.
[0048] The first wall of the first prismatic cell may have a first set of fins
302 and the second wall of the second prismatic 5 cell may have a second
set of fins 304. As may be understood, the first set of fins 302 and the
second set of fins 304 may be the same as the first set of fins and the second
set of fins described in conjunction with FIG. 2 (A) and 2 (B), respectively.
Therefore, the aspects with respect to the first set of fins 302 and the second
10 set of fins 304 have not been described again to maintain brevity.
[0049] In an example, the number of columns of the first set of fins 302 is
more than the number of columns of the second set of fins 304. In an
example, the fins in a column positioned at an edge of the first wall have a
half curved and half straight profile. The curved portion of the fins maintains
15 continuity with the overall curved design of the fins, while the straight portion
provides a different airflow characteristic at the inlet of the airflow.
Continuing further, the first set of fins 302 and the second set of fins 304
have complementary curved profiles. For example, the first set of fins 302
may have a concave profile, and the second set of fins 304 may have a
20 convex profile.
[0050] In one example, when multiple prismatic cells are stacked together
within the battery pack, the first set of fins 302 on a wall of the first prismatic
cell are arranged to face the second set of fins 304 formed on an opposite
and adjacent wall of the second prismatic cell. Specifically, the first set of
25 fins 302 interleave with the second set of fins 304 in an alternating manner,
without coming in contact with each other. It is to be noted that even though
the fins from both cells extend into the same space between them, they are
sized and positioned so that they do not actually touch each other. Such
interleaving arrangement facilitates thermal management by increasing the
30 surface area for heat dissipation and promoting airflow between the fins,
15
while also preventing direct contact that could lead to mechanical wear or
electrical conduction between adjacent cells.
[0051] In an example, arrangement of curved fins in both the first set of
fins 302 and the second set of fins 304 may create a network of channels
between adjacent prismatic cells. The channels may 5 define an airflow path
306 that extends horizontally across the surface of neighboring prismatic
cells. For example, the airflow path 306 may be defined between a first row
of fins from the first set of fins 302 and a corresponding first row of the
second set of fins 304. This pattern continues throughout the entire
10 interleaved arrangement, such that each pair of interleaving rows from the
two sets of fins defines a separate airflow path. These airflow channels
enhance ventilation and heat dissipation between the prismatic cells,
contributing to improved thermal management of the battery pack.
[0052] During operation, both the first and second prismatic cells may
15 generate heat as a result of charging and/or discharging cycles. To manage
this heat, the prismatic cells may be subjected to air cooling via a blower or
other air-cooling methods known in the art. In this configuration, is directed
around and between the prismatic cells. The incoming air enters the airflow
path 306 created between the interleaving rows of the first set of fins 302
20 and the second set of fins 304 via inlet fins. The inlet fins have half straight
profile that may serve to guide and direct the incoming airflow from the
blower, directing it into the channels between adjacent cells.
[0053] The transition in the fins from straight to curved profile may assist
in managing air pressure at the inlet, thereby reducing pressure drop and
25 promoting even distribution of airflow across entire fin array. Furthermore,
the geometry change from straight to curved may introduce mild turbulence
in the airflow at the inlet, which may enhance heat transfer by disrupting
boundary layers and increasing air-to-surface contact, specifically at the
leading edge of each cell.
16
[0054] As the cooling air flows through the channels formed by the
interleaving fins, the air travels along the contoured surfaces of the fins.
When the air moves across the concave surface of one fin and then
encounters the convex surface of a neighboring fin, the air may undergo
rapid changes in direction and velocity. These 5 abrupt changes may lead to
the formation of secondary flows and localized vortices within the main
airstream. The airflow path 306 may be designed to guide the air across the
outer surfaces of both the first prismatic cell and the second prismatic cell.
Due to interleaving, the airflow follows a serpentine path instead of a straight
10 line. The serpentine path may be characterized by alternating expanding
and contracting passages as the air weaves between the curved fins of
adjacent cells.
[0055] As the air moves through these dynamically shaped passages, the
air may experience repeated acceleration and deceleration. For example,
15 the spacing between the fins may create alternating narrow and wide
sections within the airflow channels. In the narrower sections of the
channels, the airflow is constricted, leading to an increase in velocity. Such
acceleration may enhance convective heat transfer by facilitating the
contact between the air and the surfaces of the fins and cells. In wider
20 sections of the channels, the air may decelerate, which may promote mixing
and help to maintain turbulent flow characteristics. These fluctuations in
airflow velocity may further enhance turbulence and mixing, thereby
enhancing heat transfer between the air and the cell surfaces.
[0056] In some examples, the airflow may not be uniform across the
25 entire fin structure. Regions near the center of the cell may experience
different flow characteristics compared to those near the edges. The flow
patterns may also vary along the length of the fins, with potentially higher
velocities and more intense turbulence at the leading edges where the air
first encounters the fins. As the air exits the fins, the air may carry thermal
30 energy absorbed from the cell surfaces. The turbulent nature of the flow at
17
this point may help to mix the heated air with cooler air from adjacent
channels, improving the overall heat distribution within the battery pack.
[0057] These complex airflow patterns, characterized by turbulence,
vortex formation, and variable velocities, may enhance the convective heat
transfer from the cell surfaces to the cooling 5 air. By promoting thorough
mixing and disrupting thermal boundary layers, this flow regime may
contribute to more efficient and uniform cooling of the prismatic cells,
potentially improving the overall thermal management and performance of
the battery pack.
10 [0058] Accordingly, the casing and the battery pack of the present subject
matter may provide improved heat dissipation. The complementary profiles
of the fins on opposite sides of the casing may create airflow paths that
promote more effective heat transfer from prismatic cells to the surrounding
air. The interleaving design of the curved fins may allow for efficient space
15 utilization within the battery pack. This arrangement may enable compact
packaging of multiple prismatic cells while still maintaining adequate cooling
channels between them. In some implementations, the space-efficient
design may result in higher energy density for the overall battery pack.
[0059] Moreover, the turbulence induced in the airflow due to the curved
20 geometry of the cooling fins and the interleaved channels created by the
curved fins enhance the convective heat transfer coefficient between the
cell surfaces and the cooling air and also promote even air distribution
throughout the battery pack, potentially reducing hot spots and temperature
gradients between cells. As a result, the thermal management system
25 achieves uniform cooling across the prismatic cells. The improved thermal
management provided by the curved fin arrangement may contribute to
enhanced overall performance of the battery pack Improving the
charge/discharge efficiency, increased cycle life, and more consistent
performance of the battery pack over time.
18
[0060] Although aspects and other examples have been described in a
language specific to structural features and/or methods, the present subject
matter is not necessarily limited to such specific features or elements as
described. Rather, the specific features are disclosed as examples and
should not be construed to limit the scope of 5 the present subject matter.
19
I/We Claim:
1. A casing (106. 200) for a prismatic cell (104), the casing (106. 200)
comprising:
a first wall (202);
a second wall (204) disposed 5 opposite the first wall (202) for
enclosing the prismatic cell (104);
a first set of fins (108, 206, 302) positioned on an outer surface (208)
of the first wall (202), wherein the first set of fins (108, 206, 302) has a first
curved profile; and
10 a second set of fins (110, 210, 304) positioned on an outer surface
(212) of the second wall (204), wherein the second set of fins (110, 210,
304) has a second curved profile complementary to the first curved profile,
and
wherein upon stacking a plurality of casings, the first set of fins (108,
15 206, 302) are configured to interleave with the second set of fins (110, 210,
304) without contact to define a continuous airflow path (306) between
adjacent casings.
2. The casing (106. 200) as claimed in claim 1, wherein each fin of the first
set of fins (108, 206, 302) and second set of fins (110, 210, 304) has an arc
20 angle of about 20 degrees to about 50 degrees relative to a horizontal axis
(A).
3. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and the second set of fins (110, 210, 304) have a thickness
of approximately 2 millimeters (mm).
25 4. The casing (106. 200) as claimed in claim 1, wherein a ratio of a length
of each fin and a distance between two fins is in a range of 1.2:1 to 2:1.
5. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and the second set of fins (110, 210, 304) are made from a
20
material having higher thermal conductivity than that of the casing (106,
200).
6. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and second set of fins (110, 210, 304) and the casing (106,
200) 5 are made from a same material.
7. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and the second set of fins (110, 210, 304) are arranged in
matrix of M rows and N columns, where M and N are integers greater than
1.
10 8. The casing (106. 200) as claimed in claim 7, wherein the first set of fins
(108, 206, 302) is arranged in as M rows and N-1 columns and have a
concave profile.
9. The casing (106. 200) as claimed in claim 8, wherein the fins in an Nth
column of the first set of fins (108, 206, 302), positioned at an air inlet of the
15 airflow path (306), include a half curved and half straight profile.
10. The casing (106. 200) as claimed in claim 7, wherein the second set of
fins (110, 210, 304) is arranged in the M rows and N columns have a convex
profile.
11. The casing (106. 200) as claimed in claim 7, wherein the number of
20 columns of the first set of fins (108, 206, 302) is more than the number of
columns of the second set of fins (110, 210, 304).
12. A battery pack (100) comprising:
at least a first prismatic cell (104-1) and a second prismatic cell (104-
2) positioned adjacent to one other, each of the first prismatic cell (104-1)
25 and the second prismatic cell (104-2) includes a casing (106. 200) having
at least a first wall (202) and a second wall (204) disposed opposite to the
first wall (202) for enclosing the prismatic cells;
21
a second wall (204) disposed opposite the first wall (202) for
enclosing the prismatic cell;
a first set of fins (108, 206, 302) positioned on an outer surface (208)
of the first wall (202), wherein the first set of fins (108, 206, 302) has a first
5 curved profile; and
a second set of fins (110, 210, 304) positioned on an outer surface
(212) of the second wall (204), wherein the second set of fins (110, 210,
304) has a second curved profile complementary to the first curved profile,
and
10 wherein upon stacking a plurality of casings, the first set of fins (108,
206, 302) are configured to interleave with the second set of fins (110, 210,
304) without contact to define a continuous airflow path (306) between
adjacent casings
13. The battery pack (100) as claimed in claim 12, wherein each fin of the
15 first set of fins (108, 206, 302) and second set of fins (110, 210, 304) has
an arc angle of about 20 degrees to about 50 degrees relative to a horizontal
axis.
14. The battery pack (100) as claimed in claim 12, wherein the first set of
fins (108, 206, 302) and the second set of fins (110, 210, 304) have a
20 thickness of approximately 2 millimeters (mm).
15. The battery pack (100) as claimed in claim 12, wherein a ratio of a length
of each fin and a distance between two fins is in a range of 1.2:1 to 2:1. .
16. The battery pack (100) as claimed in claim 12, wherein the first set of
fins (108, 206, 302) and second set of fins (110, 210, 304) are manufactured
25 from a material having higher thermal conductivity than the casing (106,
200).
17. The battery pack (100) as claimed in claim 16, wherein the first set of
fins (108, 206, 302) and second set of fins (110, 210, 304) and the casing
22
(106, 200) are made from a same material.
18. The battery pack (100) as claimed in claim 12, wherein the first set of
fins (108, 206, 302) and the second set of fins (110, 210, 304) are arranged
in matrix of M rows and N columns, where M and N are integers greater
5 than 1.
19. The battery pack (100) as claimed in claim 18, wherein the first set of
fins (108, 206, 302) arranged in the M rows and N-1 columns have a
concave profile.
20. The battery pack (100) as claimed in claim 19, wherein a column of the
10 first set of fins (108, 206, 302), positioned at an air inlet of the airflow path
(306), has a half curved and half straight profile.
21. The battery pack (100) as claimed in claim 18, wherein the second set
of fins (110, 210, 304) arranged in the M rows and N columns have a convex
profile.
15 22. The battery pack (100) as claimed in claim 18, wherein the number of
columns of the first set of fins (108, 206, 302) is more than the number of
columns of the second set of fins (110, 210, 304).
23
ABSTRACT
THERMAL MANAGEMENT IN PRISMATIC CELLS
The present subject matter discloses a casing 5 (106, 200) having at least a
first wall (202) and a second wall (204) disposed opposite to the first wall
(202) for enclosing prismatic cells. A first set of fins (108, 206, 302) having
a first curved profile and a second set of fins (110, 210, 304) having a
complementary curved profile are disposed on an outer surface of the first
10 wall and the second wall. Upon stacking a plurality of casings, the first set
of fins are configured to interleave with the second set of fins without contact
to define a continuous airflow path between adjacent casings.
To be published with Fig. 3
15
24 , Claims:I/We Claim:
1. A casing (106. 200) for a prismatic cell (104), the casing (106. 200)
comprising:
a first wall (202);
a second wall (204) disposed 5 opposite the first wall (202) for
enclosing the prismatic cell (104);
a first set of fins (108, 206, 302) positioned on an outer surface (208)
of the first wall (202), wherein the first set of fins (108, 206, 302) has a first
curved profile; and
10 a second set of fins (110, 210, 304) positioned on an outer surface
(212) of the second wall (204), wherein the second set of fins (110, 210,
304) has a second curved profile complementary to the first curved profile,
and
wherein upon stacking a plurality of casings, the first set of fins (108,
15 206, 302) are configured to interleave with the second set of fins (110, 210,
304) without contact to define a continuous airflow path (306) between
adjacent casings.
2. The casing (106. 200) as claimed in claim 1, wherein each fin of the first
set of fins (108, 206, 302) and second set of fins (110, 210, 304) has an arc
20 angle of about 20 degrees to about 50 degrees relative to a horizontal axis
(A).
3. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and the second set of fins (110, 210, 304) have a thickness
of approximately 2 millimeters (mm).
25 4. The casing (106. 200) as claimed in claim 1, wherein a ratio of a length
of each fin and a distance between two fins is in a range of 1.2:1 to 2:1.
5. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and the second set of fins (110, 210, 304) are made from a
20
material having higher thermal conductivity than that of the casing (106,
200).
6. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and second set of fins (110, 210, 304) and the casing (106,
200) 5 are made from a same material.
7. The casing (106. 200) as claimed in claim 1, wherein the first set of fins
(108, 206, 302) and the second set of fins (110, 210, 304) are arranged in
matrix of M rows and N columns, where M and N are integers greater than
1.
10 8. The casing (106. 200) as claimed in claim 7, wherein the first set of fins
(108, 206, 302) is arranged in as M rows and N-1 columns and have a
concave profile.
9. The casing (106. 200) as claimed in claim 8, wherein the fins in an Nth
column of the first set of fins (108, 206, 302), positioned at an air inlet of the
15 airflow path (306), include a half curved and half straight profile.
10. The casing (106. 200) as claimed in claim 7, wherein the second set of
fins (110, 210, 304) is arranged in the M rows and N columns have a convex
profile.
11. The casing (106. 200) as claimed in claim 7, wherein the number of
20 columns of the first set of fins (108, 206, 302) is more than the number of
columns of the second set of fins (110, 210, 304).
12. A battery pack (100) comprising:
at least a first prismatic cell (104-1) and a second prismatic cell (104-
2) positioned adjacent to one other, each of the first prismatic cell (104-1)
25 and the second prismatic cell (104-2) includes a casing (106. 200) having
at least a first wall (202) and a second wall (204) disposed opposite to the
first wall (202) for enclosing the prismatic cells;
21
a second wall (204) disposed opposite the first wall (202) for
enclosing the prismatic cell;
a first set of fins (108, 206, 302) positioned on an outer surface (208)
of the first wall (202), wherein the first set of fins (108, 206, 302) has a first
5 curved profile; and
a second set of fins (110, 210, 304) positioned on an outer surface
(212) of the second wall (204), wherein the second set of fins (110, 210,
304) has a second curved profile complementary to the first curved profile,
and
10 wherein upon stacking a plurality of casings, the first set of fins (108,
206, 302) are configured to interleave with the second set of fins (110, 210,
304) without contact to define a continuous airflow path (306) between
adjacent casings
13. The battery pack (100) as claimed in claim 12, wherein each fin of the
15 first set of fins (108, 206, 302) and second set of fins (110, 210, 304) has
an arc angle of about 20 degrees to about 50 degrees relative to a horizontal
axis.
14. The battery pack (100) as claimed in claim 12, wherein the first set of
fins (108, 206, 302) and the second set of fins (110, 210, 304) have a
20 thickness of approximately 2 millimeters (mm).
15. The battery pack (100) as claimed in claim 12, wherein a ratio of a length
of each fin and a distance between two fins is in a range of 1.2:1 to 2:1. .
16. The battery pack (100) as claimed in claim 12, wherein the first set of
fins (108, 206, 302) and second set of fins (110, 210, 304) are manufactured
25 from a material having higher thermal conductivity than the casing (106,
200).
17. The battery pack (100) as claimed in claim 16, wherein the first set of
fins (108, 206, 302) and second set of fins (110, 210, 304) and the casing
22
(106, 200) are made from a same material.
18. The battery pack (100) as claimed in claim 12, wherein the first set of
fins (108, 206, 302) and the second set of fins (110, 210, 304) are arranged
in matrix of M rows and N columns, where M and N are integers greater
5 than 1.
19. The battery pack (100) as claimed in claim 18, wherein the first set of
fins (108, 206, 302) arranged in the M rows and N-1 columns have a
concave profile.
20. The battery pack (100) as claimed in claim 19, wherein a column of the
10 first set of fins (108, 206, 302), positioned at an air inlet of the airflow path
(306), has a half curved and half straight profile.
21. The battery pack (100) as claimed in claim 18, wherein the second set
of fins (110, 210, 304) arranged in the M rows and N columns have a convex
profile.
15 22. The battery pack (100) as claimed in claim 18, wherein the number of
columns of the first set of fins (108, 206, 302) is more than the number of
columns of the second set of fins (110, 210, 304).