LIQUID COOLED BATTERY PACK DESIGNS FOR ELECTRIFIED VEHICLES

A battery pack includes a heat exchanger plate assembly that includes a plate body, a retention cradle protruding outwardly from the plate body, and a coolant conduit secured to the plate body by the retention device. The coolant conduit may snap into the retention cradle to secure the coolant conduit to the plate body.

TECHNICAL FIELD

This disclosure relates to electrified vehicle battery packs, and more particularly to liquid cooled battery pack designs that utilize heat exchanger plates for thermally managing the battery packs.

BACKGROUND

The desire to reduce automotive fuel consumption and emissions is well documented. Therefore, vehicles are being developed that reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles because they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to propel the vehicle.

A high voltage battery pack typically powers the electric machines and other electrical loads of the electrified vehicle. The battery pack includes a plurality of battery cells that store energy for powering these electrical loads. The battery cells generate heat as they are charged and discharged. This heat should be dissipated in order to achieve a desired level of performance.

SUMMARY

A battery pack according to an exemplary aspect of the present disclosure includes, among other things, a heat exchanger plate assembly including a plate body, a retention cradle protruding outwardly from the plate body, and a coolant conduit secured to the plate body by the retention device.

In a further non-limiting embodiment of the foregoing battery pack, the plate body is an extruded, aluminum plate body.

In a further non-limiting embodiment of either of the foregoing battery packs, the coolant conduit is a flexible tube.

In a further non-limiting embodiment of any of the foregoing battery packs, the heat exchanger plate assembly is a base of a battery assembly of the battery pack.

In a further non-limiting embodiment of any of the foregoing battery packs, the heat exchanger plate assembly is a side wall of a battery assembly of the battery pack.

In a further non-limiting embodiment of any of the foregoing battery packs, the heat exchanger plate assembly establishes a tray of an enclosure assembly of the battery pack.

In a further non-limiting embodiment of any of the foregoing battery packs, the retention cradle includes flexible arms that extend from an exterior surface of the plate body.

In a further non-limiting embodiment of any of the foregoing battery packs, the flexible arms establish a channel of the retention cradle.

In a further non-limiting embodiment of any of the foregoing battery packs, the coolant conduit is received in the channel in an interference fit.

In a further non-limiting embodiment of any of the foregoing battery packs, the plate body excludes any internal cooling circuit.

A battery pack according to another exemplary aspect of the present disclosure includes, among other thing, an enclosure assembly, a battery assembly housed within the enclosure assembly, and a heat exchanger plate assembly positioned proximate the battery assembly. The heat exchanger plate assembly includes a plate body and a coolant conduit secured at an exterior surface of the plate body.

In a further non-limiting embodiment of the foregoing battery pack, the battery assembly includes a first grouping of battery cells, and a second battery assembly is laterally spaced from the battery assembly and includes a second grouping of battery cells.

In a further non-limiting embodiment of either of the foregoing battery packs, the battery assembly and the second grouping of battery cells are both received over the heat exchanger plate assembly.

In a further non-limiting embodiment of any of the foregoing battery packs, the heat exchanger plate assembly establishes a tray of the enclosure assembly, and the coolant conduit is outside of an interior of the enclosure assembly.

In a further non-limiting embodiment of any of the foregoing battery packs, the coolant conduit is secured to the plate body using at least one retention cradle.

In a further non-limiting embodiment of any of the foregoing battery packs, the coolant conduit extends along a meandering path inside the enclosure assembly.

In a further non-limiting embodiment of any of the foregoing battery packs, the meandering path is figure eight shaped.

In a further non-limiting embodiment of any of the foregoing battery packs, the coolant conduit includes sections that extend beneath the battery assembly and a second battery assembly.

In a further non-limiting embodiment of any of the foregoing battery packs, the coolant conduit is secured to the plate body and a second plate body of the battery assembly, and is further secured to a third plate body and a fourth plate body of a second battery assembly.

In a further non-limiting embodiment of any of the foregoing battery packs, a thermal interface material is disposed between the battery assembly and the plate body of the heat exchanger plate assembly.

DETAILED DESCRIPTION

This disclosure details exemplary battery pack designs for use in electrified vehicles. A heat exchanger plate assembly is utilized to thermally manage heat generated by battery cells of a battery pack. In some embodiments, the heat exchanger plate assembly includes a plate body having a snap-fit retention device for retaining a flexible coolant conduit to the plate body. These and other features are discussed in greater detail in the following paragraphs of this detailed description.

FIG. 1schematically illustrates a powertrain10for an electrified vehicle12. Although depicted as a hybrid electric vehicle (HEV), it should be understood that the concepts described herein are not limited to HEVs and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEV's), battery electric vehicles (BEVs), fuel cell vehicles, etc.

In an embodiment, the powertrain10is a power-split powertrain system that employs first and second drive systems. The first drive system includes a combination of an engine14and a generator18(i.e., a first electric machine). The second drive system includes at least a motor22(i.e., a second electric machine), the generator18, and a battery pack24. In this example, the second drive system is considered an electric drive system of the powertrain10. The first and second drive systems are each capable of generating torque to drive one or more sets of vehicle drive wheels28of the electrified vehicle12. Although a power-split configuration is depicted inFIG. 1, this disclosure extends to any hybrid or electric vehicle including full hybrids, parallel hybrids, series hybrids, mild hybrids or micro hybrids.

The engine14, which may be an internal combustion engine, and the generator18may be connected through a power transfer unit30, such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, may be used to connect the engine14to the generator18. In a non-limiting embodiment, the power transfer unit30is a planetary gear set that includes a ring gear32, a sun gear34, and a carrier assembly36.

The generator18can be driven by the engine14through the power transfer unit30to convert kinetic energy to electrical energy. The generator18can alternatively function as a motor to convert electrical energy into kinetic energy, thereby outputting torque to a shaft38connected to the power transfer unit30. Because the generator18is operatively connected to the engine14, the speed of the engine14can be controlled by the generator18.

The ring gear32of the power transfer unit30may be connected to a shaft40, which is connected to vehicle drive wheels28through a second power transfer unit44. The second power transfer unit44may include a gear set having a plurality of gears46. Other power transfer units may also be suitable. The gears46transfer torque from the engine14to a differential48to ultimately provide traction to the vehicle drive wheels28. The differential48may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels28. In a non-limiting embodiment, the second power transfer unit44is mechanically coupled to an axle50through the differential48to distribute torque to the vehicle drive wheels28.

The motor22can also be employed to drive the vehicle drive wheels28by outputting torque to a shaft52that is also connected to the second power transfer unit44. In a non-limiting embodiment, the motor22and the generator18cooperate as part of a regenerative braking system in which both the motor22and the generator18can be employed as motors to output torque. For example, the motor22and the generator18can each output electrical power to the battery pack24.

The battery pack24is an exemplary electrified vehicle battery. The battery pack24may be a high voltage traction battery that includes a plurality of battery assemblies25(i.e., battery arrays or groupings of battery cells) capable of outputting electrical power to operate the motor22, the generator18, and/or other electrical loads of the electrified vehicle12. Other types of energy storage devices and/or output devices could also be used to electrically power the electrified vehicle12.

In an embodiment, the electrified vehicle12has two basic operating modes. The electrified vehicle12may operate in an Electric Vehicle (EV) mode where the motor22is used (generally without assistance from the engine14) for vehicle propulsion, thereby depleting the battery pack24state of charge up to its maximum allowable discharging rate under certain driving patterns/cycles. The EV mode is an example of a charge depleting mode of operation for the electrified vehicle12. During EV mode, the state of charge of the battery pack24may increase in some circumstances, for example due to a period of regenerative braking. The engine14is generally OFF under a default EV mode but could be operated as necessary based on a vehicle system state or as permitted by the operator.

The electrified vehicle12may additionally operate in a Hybrid (HEV) mode in which the engine14and the motor22are both used for vehicle propulsion. The HEV mode is an example of a charge sustaining mode of operation for the electrified vehicle12. During the HEV mode, the electrified vehicle12may reduce the motor22propulsion usage in order to maintain the state of charge of the battery pack24at a constant or approximately constant level by increasing the engine14propulsion. The electrified vehicle12may be operated in other operating modes in addition to the EV and HEV modes within the scope of this disclosure.

FIG. 2schematically illustrates a battery pack24that can be employed within an electrified vehicle. For example, the battery pack24could be part of the powertrain10of the electrified vehicle12ofFIG. 1.FIG. 2is a perspective view of the battery pack24, and some external components (e.g., an enclosure assembly58) are shown in phantom to better illustrate the internal components of the battery pack24.

The battery pack24houses a plurality of battery cells56, also shown in phantom, that store energy for powering various electrical loads of the electrified vehicle12. The battery pack24could employ any number of battery cells within the scope of this disclosure. Thus, this disclosure is not limited to the exact configuration shown inFIG. 2.

The battery cells56may be stacked side-by-side to construct a grouping of battery cells56, sometimes referred to as a “cell stack” or “cell array.” In an embodiment, the battery cells56are prismatic, lithium-ion cells. However, battery cells having other geometries (cylindrical, pouch, etc.), other chemistries (nickel-metal hydride, lead-acid, etc.), or both could alternatively be utilized within the scope of this disclosure.

The battery cells56, along with any support structures (e.g., array frames, spacers, rails, walls, plates, bindings, etc.), may collectively be referred to as a battery assembly. The battery pack24depicted inFIG. 2includes a first battery assembly25A and a second battery assembly25B that is side-by-side with the first battery assembly25A. Although the battery pack24ofFIG. 2is depicted as having a two battery assemblies, the battery pack24could include a greater or fewer number of battery assemblies within the scope of this disclosure.

The battery cells56of the first battery assembly25A are distributed along a first longitudinal axis A1, and the battery cells56of the second battery assembly25B are distributed along a second longitudinal axis A2. In an embodiment, the first longitudinal axis A1is laterally spaced from the second longitudinal axis A2. The first and second battery assemblies25A,25B are therefore positioned side-by-side relative to one another in this embodiment.

An enclosure assembly58houses each battery assembly25A,25B of the battery pack24. In an embodiment, the enclosure assembly58is a sealed enclosure that includes a tray60and a cover62that is secured to the tray60to enclose and seal each battery assembly25A,25B of the battery pack24. In an embodiment, the first and second battery assemblies25A,25B are both positioned over the tray60of the enclosure assembly58, and the cover62may be received over the first and second battery assemblies25A,25B. The enclosure assembly58may include any size, shape, and configuration within the scope of this disclosure.

Each battery assembly25A,25B of the battery pack24may be positioned relative to one or more heat exchanger plate assemblies64such that the battery cells56are either in direct contact with or in close proximity to at least one heat exchanger plate assembly64. In an embodiment, the battery assemblies25A,25B share a common heat exchanger plate assembly64(see, e.g.,FIG. 2). Alternatively, each battery assembly25A,25B could be positioned relative to its own heat exchanger plate assembly64(see, e.g.,FIG. 3).

As schematically shown inFIG. 2, a thermal interface material (TIM)66may optionally be positioned between the battery assemblies25A,25B and the heat exchanger plate assembly64such that exposed surfaces of the battery cells56are in direct contact with the TIM66. The TIM66maintains thermal contact between the battery cells56and the heat exchanger plate assembly64and increases the thermal conductivity between these neighboring components during heat transfer events. The TIM66may be made of any known thermally conductive material.

In a first embodiment, the heat exchanger plate assembly64acts as a base plate of the battery assemblies25A,25B (see, e.g.,FIG. 4). In a second embodiment, the heat exchanger plate assembly64acts as a sidewall of the battery assemblies25A,25B, with one heat exchanger plate assembly64disposed along each side of the battery assemblies25A,25B (see, e.g.,FIG. 5). In a third embodiment, the heat exchanger plate assembly64acts as the tray of the enclosure assembly58of the battery pack24(see, e.g.,FIG. 6). In such an embodiment, the heat exchanger plate assembly64includes at least one exterior surface68exposed to an exterior environment70(i.e., the environment that surrounds the outside of the battery pack24).

The heat exchanger plate assembly64is configured for thermally managing the battery cells56of each battery assembly25A,25B. For example, heat may be generated and released by the battery cells56during charging operations, discharging operations, extreme ambient conditions, or other conditions. It may be desirable to remove the heat from the battery pack24to improve capacity and life of the battery cells56. The heat exchanger plate assembly64is configured to conduct the heat out of the battery cells56. In other words, the heat exchanger plate assembly64acts as a heat sync to remove heat from the heat sources (i.e., the battery cells56). The heat exchanger plate assembly64could alternatively be employed to heat the battery cells56, such as during extremely cold ambient conditions. Exemplary heat exchanger plate assembly designs for thermally managing the battery cells56of the battery pack24are further detailed below.

FIG. 7illustrates a heat exchanger plate assembly64according to an embodiment of this disclosure. The heat exchanger plate assembly64includes a plate body72and a coolant conduit74secured relative to the plate body72by a retention cradle76. Although a single coolant conduit74and retention cradle76are illustrated inFIG. 7, the heat exchanger plate assembly64could employ a greater number of conduits and retention devices depending on the cooling requirements of a particular battery pack.

The coolant conduit74may be snapped into the retention cradle76to assemble the heat exchanger plate assembly64. In an embodiment, the coolant conduit74and the retention cradle76are received together to establish an interference fit. Once received in the retention cradle76, the coolant conduit74is in contact with an exterior surface78of the plate body72.

The plate body72of the heat exchanger plate assembly64may be an extruded part. Other manufacturing techniques are also contemplated within the scope of this disclosure. In another embodiment, the plate body72is made of aluminum. Other materials are also suitable for constructing the plate body72.

The coolant conduit74may be a tube, hose, or any other type of conduit and can be made of any sufficiently conductive material. In an embodiment, the coolant conduit74is a flexible conduit that can be easily bent and/or manipulated for simple installation within a battery pack. A coolant C may be selectively circulated through a passageway80of the coolant conduit74to thermally condition the battery cells56of the battery pack24. In an embodiment, the coolant C is a conventional type of coolant mixture such as water mixed with ethylene glycol. However, other coolants, including gases, are also contemplated within the scope of this disclosure. In use, heat from the battery cells56is conducted into the plate body72and then into the coolant C as the coolant C is communicated through the coolant conduit74.

Referring now toFIG. 8, the retention cradle76may be integrally formed with the plate body72. Alternatively, the retention cradle76could be a separate component that is secured (e.g., welded) to the plate body72. The retention cradle76may extend across an entire length of the plate body72or across only a discrete portion of the plate body72.

In an embodiment, the retention cradle76includes flexible arms82that protrude outwardly from the exterior surface78of the plate body72. The flexible arms82establish a channel84for receiving the coolant conduit74. In an embodiment, the channel84is C-shaped.

During assembly of the heat exchanger plate assembly64, the flexible arms82are configured to flex away from one another as the coolant conduit74is pushed into contact with curved flanges85of the flexible arms82. As the coolant conduit74is moved further into the channel84, the flexible arms82flex back toward one another until they contact the coolant conduit74to establish the snap fit or interference fit connection between the two components. The mounting location of the coolant conduit74/retention cradle76is design specific and can be specifically tuned to address the thermal requirements of a given battery pack. For example, the retention cradle76can be positioned at the axial location of the plate body72that contacts the areas of the battery cells56most susceptible to high heat loads.

FIG. 9, with continued reference toFIGS. 2-8, illustrates a first exemplary routing configuration R1of a coolant conduit74of a heat exchanger plate assembly64. In this embodiment, the coolant conduit74is a single, flexible tube that is routed along the plate body72of the heat exchanger plate assembly64for thermally managing first and second battery assemblies25A,25B of a battery pack24. Although not shown inFIG. 9for simplification, one or more retention cradles76can be secured to the plate body72for affixing the coolant conduit74to the plate body72.

In an embodiment, the coolant conduit74includes an inlet86for receiving the coolant C, a first linear section88connected to the plate body72and extending beneath the first battery assembly25A, a first curved section90that connects between the first linear section88and a second linear section92that is connected to the plate body72and extends beneath the second battery assembly25B, a second curved section94that connects between the second linear section92and a third linear section96that is connected to the plate body72and extends beneath the second battery assembly25B, a third curved section98that connects between the third linear section96and a fourth linear section100that is connected to the plate body72and extends beneath the first battery assembly25A, and an outlet102for the coolant C to exit the coolant conduit74. In use, the coolant C enters the inlet86and then circulates along a meandering path through the first linear section88, the first curved section90, the second linear section92, the second curved section94, the third linear section96, the third curved section98, and the fourth linear section100before exiting the outlet102in order to dissipate heat that has been conducted into the plate body from battery cells56of the first and second battery assemblies25A,25B. The coolant C exiting through the outlet102is warmer than the coolant C entering the inlet86.

FIG. 10, with continued reference toFIGS. 2-8, illustrates a second exemplary routing configuration R2of a coolant conduit74of a heat exchanger plate assembly64. In this embodiment, the coolant conduit74is a single, flexible tube that is routed along multiple plate bodies72A-72D for thermally managing first and second battery assemblies25A,25B of a battery pack24. Each battery assembly25A,25B of this embodiment includes two plate bodies72that double as side plates of the battery assemblies25A,25B. Although not shown inFIG. 10for simplification, one or more retention cradles76can be secured to each plate body72for affixing the coolant conduit74to the plate bodies72.

In an embodiment, the coolant conduit74includes an inlet104for receiving the coolant C, a first linear section106connected to the plate body72A of the first battery assembly25A, a first curved section108that connects between the first linear section106and a second linear section110that is connected to the plate body72C of the second battery assembly25B, a second curved section112that connects between the second linear section110and a third linear section114that is connected to the plate body72D of the second battery assembly25B, a third curved section116that connects between the third linear section114and a fourth linear section118that is connected to the plate body72B of the first battery assembly25A, and an outlet120for the coolant C to exit from the coolant conduit74.

In use, the coolant C enters the inlet104and then circulates along a meandering, “figure eight” shaped path through the first linear section106, the first curved section108, the second linear section110, the second curved section112, the third linear section114, the third curved section116, and the fourth linear section118before exiting the outlet120in order to dissipate heat that has been conducted into the plate bodies72A-72D from battery cells56of the first and second battery assemblies25A,25B.

The heat exchanger plate assemblies of this disclosure include snap-fitting, flexible coolant conduits that eliminate the need to form internal coolant cavities inside the plate bodies of the heat exchanger plate assemblies. The concepts presented in this disclosure offer a low-cost alternative with a much simpler design as compared to existing cold plates. The exemplary heat exchanger assemblies may be integrated into the array and/or pack structure to potentially provide cell retention, compression, support, and enclosure functions in addition to cooling. This multifunction potential can reduce cost and weight of the battery pack.