CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/186,977 filed on June 30, 2015. This application is related to U.S. Patent Application Serial No. 14/841,617 filed on August 31, 2015. The subject matter of the

aforementioned applications is incorporated herein by reference for all purposes.

FIELD

[0002] The present application relates generally to heat transfer, and more specifically to heat transfer for vehicle energy-storage systems.

BACKGROUND

[0003] It should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.

[0004] Electric-drive vehicles offer a solution for reducing the impact of fossil- fuel engines on the environment and transforming automotive mobility into a sustainable mode of transportation. Energy -storage systems are essential for electric- drive vehicles, such as hybrid electric vehicles, plug-in hybrid electric vehicles, and all- electric vehicles. However, present energy-storage systems have disadvantages including large size, inefficiency, and poor safety, to name a few. Similar to many sophisticated electrical systems, heat in automotive energy-storage systems should be carefully managed. Current thermal management schemes consume an inordinate amount of space. Present energy-storage systems also suffer from inefficiencies arising variously from imbalance among battery cells and resistance in various electrical connections. In addition, current energy-storage systems are not adequately protected from forces such as crash forces encountered during a collision.

SUMMARY

[0005] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0006] According to various embodiments, the present disclosure may be directed to cooling subsystem for a vehicle comprising: a heat exchanger disposed between two battery modules, the heat exchanger being thermally coupled to each of a plurality of cells of the battery modules at an end of each cell, the heat exchanger being fluidly coupled to a coolant system, the heat exchanger transferring heat from the plurality of cells.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.

[0008] FIG. 1 illustrates an example environment in which an energy-storage system can be used.

[0009] FIG. 2A shows an orientation of battery modules in an energy-storage system, according to various embodiments of the present disclosure.

[0010] FIG. 2B depicts a bottom part of an enclosure of a partial battery pack such as shown in FIG. 2A.

[0011] FIG. 3 is a simplified diagram illustrating coolant flows, according to example embodiments.

[0012] FIG. 4 is a simplified diagram of a battery module, according to various embodiments of the present disclosure.

[0013] FIG. 5 illustrates a half module, in accordance with various embodiments.

[0014] FIGS. 6A and 6B show a current carrier, according to various

embodiments.

[0015] FIG. 7 depicts an example battery cell.

[0016] FIGS. 8A and 8B illustrate further embodiments of a battery module.

DETAILED DESCRIPTION

[0017] While this disclosure is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the disclosure and is not intended to limit the disclosure to the embodiments illustrated. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that like or analogous elements and/or components, referred to herein, may be identified throughout the drawings with like reference characters. It will be further understood that several of the figures are merely schematic representations of the present disclosure. As such, some of the components may have been distorted from their actual scale for pictorial clarity.

[0018] Some embodiments of the present invention can be deployed in a wheeled, self -powered motor vehicle used for transportation, such as hybrid electric vehicles, plug-in hybrid electric vehicles, and all-electric vehicles. For example, FIG. 1 illustrates electric car 100. Electric car 100 can be an automobile propelled by one or more electric motors 110. Electric motor 110 can be coupled to one or more wheels 120 through a drivetrain (not shown in FIG. 1). Electric car 100 can include frame 130 (also known as an underbody or chassis). Frame 130 can be a supporting structure of electric car 100 to which other components can be attached/mounted, such as, for example, a battery pack 140a. Battery pack 140a can supply electricity to power one or more electric motors 110, for example, through an inverter. The inverter can change direct current (DC) from battery pack 140a to alternating current (AC), as can be required for electric motors 110, according to some embodiments.

[0019] As depicted in FIG. 1, battery pack 140a may have a compact "footprint" and be at least partially enclosed by frame 130 and disposed to provide a predefined separation, for example, from structural rails 150 of an upper body that couples to frame 130. Accordingly, at least one of rear crumple zone 160, front crumple zone 170, and lateral crumple zone 180 can be formed around battery pack 140a. Both the frame 130 and structural rails 150 may protect battery pack 140a from forces or impacts exerted from outside of electric car 100, for example, in a collision. In contrast, other battery packs which extend past at least one of structural rails 150, rear crumple zone 160, and front crumple zone 170 remain vulnerable to damage and may even explode in an impact.

[0020] Battery pack 140a may have a compact "footprint" such that it may be flexibly used in and disposed on frame 130 having different dimensions. Battery pack 140a can also be disposed in frame 130 to help improve directional stability (e.g., yaw acceleration). For example, battery pack 140a can be disposed in frame 130 such that a center of gravity of electric car 100 is in front of the center of the wheelbase (e.g., bounded by a plurality of wheels 120).

[0021] FIG. 2A shows battery pack 140b with imaginary x-, y-, and z-axis superimposed, according to various embodiments. Battery pack 140b can include a plurality of battery modules 210. In a non-limiting example, battery pack 140b can be approximately 1000mm wide (along x-axis), 1798mm long (along y-axis), and 152 mm high (along z-axis), and can include thirty-six of battery modules 210. [0022] FIG. 2B illustrates exemplary enclosure 200 for battery pack 140b having a cover removed for illustrative purposes. Enclosure 200 includes a tray 260 and a plurality of battery modules 210. Tray 260 may include positive bus bar 220 and negative bus bar 230. Positive bus bar 220 can be electrically coupled to a positive (+) portion of a power connector of each battery module 210. Negative bus bar 230 can be electrically coupled to a negative (-) portion of a power connector of each battery module 210. Positive bus bar 220 can be electrically coupled to positive terminal 240 of enclosure 200. Negative bus bar 230 can be electrically coupled to negative terminal 250 of enclosure 200. As described above with reference to FIG. 1, because bus bars 220 and 230 can be within structural rails 150, they can be protected from collision damage.

[0023] According to some embodiments, negative bus bar 230 and positive bus bar 220 can be disposed along opposite edges of tray 260 to provide a predefined separation between negative bus bar 230 and positive bus bar 220. Such separation between negative bus bar 230 and positive bus bar 220 can prevent or at least reduce the possibility of a short circuit (e.g., of battery pack 140b) due to a deformity caused by an impact.

[0024] As will be described further in more detail with reference to FIG. 5, battery module 210 can include at least one battery cell (details not shown in FIG. 2A, see FIG. 7). The at least one battery cell can include an anode terminal, a cathode terminal, and a cylindrical body. The battery cell can be disposed in each of battery module 210 such that a surface of the anode terminal and a surface of the cathode terminal are normal to the imaginary x-axis referenced in FIG. 2A (e.g., the cylindrical body of the battery cell is parallel to the imaginary x-axis). This can be referred to as an x-axis cell orientation.

[0025] In the event of fire and/or explosion in one or more of battery modules 210, the battery cells can be vented along the x-axis, advantageously minimizing a danger and/or a harm to a driver, passenger, cargo, and the like, which may be disposed in electric car 100 above battery pack 140b (e.g., along the z-axis), in various embodiments.

[0026] The x-axis cell orientation of battery modules 210 in battery pack 140b shown in FIGS. 2A and 2B can be advantageous for efficient electrical and fluidic routing to each of battery module 210 in battery pack 140b. For example, at least some of battery modules 210 can be electrically connected in a series (forming string 212), and two or more of string 212 can be electrically connected in parallel. This way, in the event one of string 212 fails, others of string 212 may not be affected, according to various embodiments.

[0027] FIG. 3 illustrates coolant flows and operation of a coolant system and a coolant sub-system according to various embodiments. As shown in FIG. 3, the x-axis cell orientation can be advantageous for routing coolant (cooling fluid) in parallel to each of battery modules 210 in battery pack 140b. Coolant can be pumped into battery pack 140b at ingress 310 and pumped out of battery pack 140b at egress 320. A resulting pressure gradient within battery pack 140b can provide sufficient circulation of coolant to minimize a temperature gradient within battery pack 140b (e.g., a temperature gradient within one of battery modules 210, a temperature gradient between battery modules 210, and/or a temperature gradient between two or more of strings 212 shown in FIG. 2A).

[0028] Within battery pack 140b, the coolant system may circulate the coolant, for example, to battery modules 210 (e.g., the circulation is indicated by reference numeral 330). One or more additional pumps (not shown in FIG. 3) can be used to maintain a roughly constant pressure between multiple battery modules 210 connected in series (e.g., in string 212 in FIG. 2A) and between two or more of string 212. Within each battery module 210, the coolant sub-system may circulate the coolant, for example, between and within two half modules 410 and 420 shown in FIG. 4 (e.g., the circulation indicated by reference numeral 340). [0029] In some embodiments, the coolant can enter each battery module 210 through interface 350 between two half modules 410 and 420, in a direction (e.g., along the y- or z- axis) perpendicular to the cylindrical body of each battery cell, and flow to each cell. Driven by pressure within the coolant system, the coolant then can flow along the cylindrical body of each battery (e.g., along the x-axis) and may be collected at two (opposite) side surfaces 360A and 360B of the module that can be normal to the x-axis. In this way, heat can be efficiently managed/dissipated and thermal gradients minimized among all battery cells in battery pack 140b, such that a temperature may be maintained at an approximately uniform level.

[0030] In some embodiments, parallel cooling, as illustrated in FIG. 3, can maintain temperature among battery cells in battery pack 140b at an approximately uniform level such that a direct current internal resistance (DCIR) of each battery cell can be maintained at an substantially predefined resistance. The DCIR can vary with a temperature, therefore, keeping each battery cell in battery pack 140b at a substantially uniform and predefined temperature can result in each battery cell having substantially the same DCIR. Since a voltage across each battery cell can be reduced as a function of its respective DCIR, each battery cell in battery pack 140b may experience substantially the same loss in voltage. In this way, each battery cell in battery pack 140b can be maintained at approximately the same capacity and imbalances between battery cells in battery pack 140b can be minimized, improving battery efficiency.

[0031] In some embodiments, when compared to techniques using metal tubes to circulate coolant, parallel cooling can enable higher battery cell density within battery module 210 and higher battery module density in battery pack 140b. In some

embodiments, coolant or cooling fluid may be at least one of the following: synthetic oil, for example, poly-alpha-olefin (or poly- -olefin, also abbreviated as PAO) oil, ethylene glycol and water, liquid dielectric cooling based on phase change, and the like. [0032] FIG. 4 illustrates battery module 210 according to various embodiments. Main power connector 460 can provide power from battery cells 450 to outside of battery module 210. Coolant can be provided to battery module 210 at main coolant input port 480, receive/transfer heat from battery module 210, and be received at main coolant output port 470. In some embodiments, battery module 210 can include two half modules 410 and 420, each having respective enclosure 430 . Enclosure 430 may be made using one or more plastics having sufficiently low thermal conductivities.

Respective enclosures 430 of each of two half modules 410 and 420 may be coupled with each other to form the housing for battery module 210.

[0033] FIG. 4 includes view 440 of enclosure 430 (e.g., with a cover removed). For each of half modules 410, 420 there is shown a plurality of battery cells 450 oriented (mounted) horizontally (see also FIGS. 5 and 8). By way of non-limiting example, each half module can include one hundred four of battery cells 450. By way of further non- limiting example, eight of battery cells 450 can be electrically connected in a series (e.g., the staggered column of eight battery cells 450 shown in FIG. 4), with a total of thirteen of such groups of eight battery cells 450 electrically connected in series. By way of additional non-limiting example, the thirteen groups (e.g., staggered columns of eight battery cells 450 electrically coupled in series) can be electrically connected in parallel. This example configuration may be referred to as "8S13P" (8 series, 13 parallel). In some embodiments, the 8S13P electrical connectivity can be provided by current carrier 510, described further below in relation to FIGS. 5 and 6. Other combinations and permutations of battery cells 450 electrically coupled in series and/or parallel may be used.

[0034] FIG. 5 depicts a view of half modules 410, 420 without enclosure 430 in accordance with various embodiments. Half modules 410 and 420 need not be the same, for example, they may be mirror images of each other in some embodiments. Half modules 410 and 420 can include a plurality of battery cells 450. The plurality of battery cells 450 can be disposed between current carrier 510 and blast plate 520 such that an exterior side of each of battery cells 450 is not in contact with the exterior sides of other (e.g., adjacent) battery cells 450. In this way, coolant can circulate among and between battery cells 450 to provide submerged, evenly distributed cooling. In addition, to save the weight associated with coolant in areas where cooling is not needed, air pockets can be formed using channels craftily designed in space 530 between current carrier 510 and blast plate 520 not occupied by battery cells 450.

[0035] Coolant can enter half modules 410, 420 through coolant intake 540, be optionally directed by one or more flow channels, circulate among and between the plurality of battery cells 450, and exits through coolant outtake 550. In some

embodiments, coolant intake 540 and coolant outtake 550 can each be male or female fluid fittings. In some embodiments, coolant or cooling fluid is at least one of: synthetic oil such as poly-alpha-olefin (or poly- -olefin, abbreviated as PAO) oil, ethylene glycol and water, liquid dielectric cooling based on phase change, and the like. Compared to techniques using metal tubes to circulate coolant, submerged cooling improves a packing density of battery cells 450 (e.g., inside battery module 210 and half modules 410, 420) by 15%, in various embodiments.

[0036] FIGS. 6A and 6B depict current carrier 510, 510A according to various embodiments. Current carrier 510, 510A can be generally flat (or planar) and can comprise one or more layers (not shown in FIGS. 6A and 6B), such as a base layer, a positive power plane, a negative power plane, and signal plane sandwiched in-between dielectric isolation layers (e.g., made of polyimide). In some embodiments, the signal plane can include signal traces and be used to provide battery module telemetry (e.g., battery cell voltage, current, state of charge, and temperature from optional sensors on current carrier 510) to outside of battery module 210.

[0037] As depicted in FIG. 6B, current carrier 510A can be a magnified view of a portion of current carrier 510, for illustrative purposes. Current carrier 510A can be communicatively coupled to each of battery cells 450, for example, at separate (fused) positive (+)portion 630 and separate negative (-)portion 640 which may be electrically coupled to the positive power plane and negative power plane (respectively) of current carrier 510A, and to each cathode and anode (respectively) of battery cell 450. In some embodiments, positive (+)portion 630 can be laser welded to a cathode terminal of battery cell 450, and negative (-)portion 640 can be laser welded to an anode terminal of battery cell 450. In some embodiments, the laser-welded connection can have on the order of 5 milli-Ohms resistance. In contrast, electrically coupling the elements using ultrasonic bonding of aluminum bond wires can have on the order of 10 milli-Ohms resistance. Laser welding advantageously can have lower resistance for greater power efficiency and take less time to perform than ultrasonic wire bonding, which can contribute to greater performance and manufacturing efficiency.

[0038] Current carrier 510A can include fuse 650 formed from part of a metal layer (e.g., copper, aluminum, etc.) of current carrier 510A, such as in the positive power plane. In some embodiments, fuse 650 can be formed (e.g., laser etched) in a metal layer (e.g., positive power plane) to dimensions corresponding to a type of low- resistance resistor and acts as a sacrificial device to provide overcurrent protection. For example, in the event of thermal runaway of one of battery cell 450 (e.g., due to an internal short circuit), the fuse may "blow," breaking the electrical connection to battery cell 450 and electrically isolating battery cell 450 from current carrier 510A. Although an example of a fuse formed in the positive power plane was provided, a fuse may additionally or alternatively be a part of the negative power plane.

[0039] Additional thermal runaway control can be provided in various embodiments by scoring on end 740 (identified in FIG. 7) of battery cell 450. The scoring can promote rupturing to effect venting in the event of over pressure. In various embodiments, all battery cells 450 may be oriented to allow venting into blast plate 520 for both half modules. [0040] In some embodiments, current carrier 510 can be comprised of a printed circuit board and a flexible printed circuit. For example, the printed circuit board may variously comprise at least one of copper, FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (non-woven glass and epoxy), CEM-4 (woven glass and epoxy), and CEM-5 (woven glass and polyester). By way of further non-limiting example, the flexible printed circuit may comprise at least one of copper foil and a flexible polymer film, such as polyester (PET), polyimide (PI), polyethylene naphthalate (PEN), polyetherimide (PEI), along with various fluoropolymers (FEP), and copolymers.

[0041] In addition to electrically coupling battery cells 450 to each other (e.g., in series and/or parallel), current carrier 510 can provide electrical connectivity to outside of battery module 210, for example, through main power connector 460 (FIG. 4).

Current carrier 510 may also include electrical interface 560 (FIGS. 5, 6A) which transports signals from the signal plane. Electrical interface 560 can include an electrical connector (not shown in FIG. 5, 6a).

[0042] FIG. 7 shows battery cell 450 according to some embodiments. In some embodiments, battery cell 450 can be a lithium ion (li-ion) battery. For example, battery cell 450 may be an 18650 type li-ion battery having a cylindrical shape with an approximate diameter of 18.6 mm and approximate length of 65.2 mm. Other rechargeable battery form factors and chemistries can additionally or alternatively be used. In various embodiments, battery cell 450 may include can 720 (e.g., the

cylindrical body), anode terminal 770, and cathode terminal 780. For example, anode terminal 770 can be a negative terminal of battery cell 450 and cathode terminal 780 can be a positive terminal of battery cell 450. Anode terminal 770 and cathode terminal 780 can be electrically isolated from each other by an insulator or dielectric. [0043] FIG. 8A illustrates an apparatus for heat exchange in battery module 210a, according to various embodiments. Battery module 210a can comprise two half modules 410 and 420, and heat exchanger 810 disposed between two half modules 410 and 420. Each of two half modules 410, 420 can comprise battery cells 450, as described in relation to FIG. 4. Main power connector 460 (as described in relation to FIG. 4) can be represented by male main power connector 460M, optional main power connector openings 460P (e.g., associated with half module 410, half module 420 (not depicted in FIG. 8A), and heat exchanger 810), and female main power connector 460F. In some embodiments, optional main power connector opening 460P (e.g., of heat exchanger 810) can be an electrical connector coupled to at least one electrical connector of half modules 410 and 420 (e.g., an associated main power connector opening 460P). Main coolant input port 480 (as described in relation to FIG. 4) can be represented by female main coolant input port 480F; male main coolant input port (e.g., associated with half modules 410) and main coolant intakes (e.g., associated with heat exchanger 810) are not depicted in FIG. 8A. Main coolant output port 470 (as described in relation to FIG. 4) can be represented by male main coolant output port 470M, main coolant outtakes 470o, and female main coolant output port 470F. Each of female main power connector 460F, female main cooling input 480F, and female main cooling output 470F can include an (rubber) o-ring or other seal. Other combinations and permutations of male and female connectors— such as a mix of male and female connectors on each side, and female connectors on the right side and male connectors on the left side— may be used. In some embodiments, battery module 210a does not include blast plate 420 (FIG. 4).

[0044] Half modules 410 and 420 may include a plurality of battery cells 450 which may be oriented (mounted) horizontally. By way of non-limiting example, each half module can include one hundred four of battery cells 450. By way of further non- limiting example, eight of battery cells 450 can be electrically connected in a series (e.g., the staggered column of eight battery cells 450), with a total of thirteen of such groups of eight battery cells 450 electrically connected in series. By way of additional non- limiting example, the thirteen groups (e.g., staggered columns of eight battery cells 450 electrically coupled in series) may be electrically connected in parallel. This example configuration may be referred to as "8S13P" (8 series, 13 parallel). Other combinations and permutations of battery cells 450 electrically coupled in series and/or parallel may be used. For example, more or less than one hundred and four of battery cells may be included in each half module, depending on the power, capacity, and size of the battery cells. As another example, more or less than thirteen groups of battery cells may be electrically connected in parallel.

[0045] According to some embodiments, battery module 210a can include heat exchanger 810. Heat exchanger 810 can comprise two side surfaces 820 which can be thermally coupled to battery cells 450 (of at least one of two half modules 410 and 420), for example, at end 740 (FIG. 7). In various embodiments, side surfaces 820 can (also) be mechanically coupled to end 740 of battery cells 450 (of at least one of two half modules 410 and 420), for example, using a thermal adhesive or glue (e.g., thermally conductive two-part epoxy resin). In some embodiments, heat exchanger 810 can be thermally coupled and electrically isolated from battery cells 450 (of at least one of two half modules 410 and 420) using dielectric separation having (extremely) low electrical conductivity. For example, an exterior surface of heat exchanger 810 (including side surfaces 420) can comprise at least one of: aluminum oxide, diamond powder based materials, boron nitride, and the like.

[0046] Heat exchanger 810 can comprise at least one of aluminum, copper, an alloy of aluminum and copper, and the like. In some embodiments, heat exchanger 810 may comprise aluminum. Heat exchanger 810 can transfer heat from battery cells 450 (of at least one of two half modules 410 and 420). In operation, heat exchanger 810 may receive heat from battery cells 450 and transfer the heat to another medium, such as coolant or cooling fluid. For example, the coolant can enter heat exchanger 810 (e.g., from the coolant system and/or sub-system) through a main coolant intake (not shown in FIG. 8A) and exit heat exchanger 810 (e.g., to the coolant system and/or sub-system) from main coolant outtake 470o. An interior of heat exchanger 810 (not shown in FIG. 8A) may comprise a plurality of channels to circulate the coolant inside heat exchanger 810 to efficiently transfer heat from battery cells 450 (of at least one of two half modules 410 and 420) to the coolant. For example, the plurality of channels can direct the coolant from the main coolant intake, circulate the coolant inside heat exchanger 810, and direct the coolant to main coolant outtake 470o.

[0047] The coolant may be at least one of the following: synthetic oil, water and ethylene glycol (WEG), poly-alpha-olefin (or poly- -olefin, also abbreviated as PAO) oil, liquid dielectric cooling based on phase change, and the like. In various

embodiments, the coolant can comprise WEG. By way of further non-limiting example, the coolant may be at least one of: perfluorohexane (Flutec PP1),

perfluoromethylcyclohexane (Flutec PP2), Perfluoro-l,3-dimethylcyclohexane (Flutec PP3), perfluorodecalin (Flutec PP6), perfluoromethyldecalin (Flutec PP9),

trichlorofluoromethane (Freon 11), trichlorotrifluoroethane (Freon 113), methanol (methyl alcohol 283-403K), ethanol (ethyl alcohol 273-403K), and the like.

[0048] As described in relation to FIG. 3, the coolant system may evenly circulate coolant through each heat exchanger 810 in a plurality of battery modules 210/210a.

[0049] FIG. 8B shows some example constituent components— half module 410, heat exchanger 810, and half module 420— assembled into battery module 210a, according to various embodiments. In some embodiments, half modules 410 and 420 can each have width 890 within a range of 70 mm - 100 mm, and heat exchanger 810 has width 880 within a range of 2 mm - 30 mm. In various embodiments, half modules 410 and 420 and heat exchanger 810 can have length 885 in a range of 250 mm - 400 mm.

[0050] As would be readily appreciated by one of ordinary skill in the art, various embodiments described herein may be used in additional applications, such as in energy-storage systems for wind and solar power generation. Other applications are also possible.

[0051] The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Exemplary embodiments were chosen and described in order to best explain the principles of the present disclosure and its practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.