HEATING AND COOLING A PARALLEL-CONNECTED BATTERY PACK WITH MIXED CHEMICAL COMPOSITION

Abstract

A method for operating a vehicle comprises drawing operating power from a first set of battery cells and providing heating or cooling to the first set of battery cells, but not to a second set, to maintain the first set of battery cells within an operating temperature window in a first operating mode. In response to a power support request, the method switches to a second operating mode and draws operating power from both the first and second sets of battery cells, providing heating or cooling to maintain both sets within the operating temperature window during the second operating mode.

Description

INTRODUCTION

[0001] The present disclosure relates to heating and cooling systems for parallel-connected battery packs containing battery cells having a plurality of different chemical compositions.

[0002] Vehicles, including electric and hybrid-electric vehicles, have battery storage systems for purposes such as powering electric motors, electronics, and other vehicle subsystems. Batteries for the battery storage system typically contain several different battery cells, each of which stores energy and is highly capable of dissipating power. The battery cells are electrically connected to provide a power output. Operating the battery cells at temperatures outside a specific temperature range known as the operating window can result in reduced battery life and reduced charge capacity.

[0003] Furthermore, in some examples, some of the battery cells cannot be used for startup or short-distance driving, so heating or cooling all battery cells results in unnecessary power consumption.

[0004] Accordingly, it is desirable to provide a flexible battery heating and cooling system. SUMMARY

[0005] According to an exemplary embodiment, an energy storage system for a vehicle includes a battery system having a first set of battery cells and a second set of battery cells electrically connected in parallel with the first set of battery cells, a coolant loop having a first portion passing through the first set of battery cells, a second portion passing through the second set of battery cells, and a flow control device, and a controller configured to cause the flow control device to confine the coolant to the first portion according to a first mode of operation and configured to cause the flow control device to allow the coolant to pass through the first portion and the second portion according to a second mode of operation.

[0006] In addition to one or more of the features described herein, the coolant loop further includes a third mode in which the flow control device is configured to allow the coolant to pass through the second section rather than the first section.

[0007] In addition to one or more of the features described herein, the first set of battery cells consists of a first cell type and the second set of battery cells consists of a second cell type that is different from the first cell type.

[0008] In addition to one or more of the features described herein, the first set of cells is connected to a power distribution bus and the second set of battery cells is connected to the first set of battery cells via a direct current (DC / DC) converter.

[0009] In addition to one or more of the features described herein, the DC / DC converter is actively controlled by the controller, wherein the controller includes a memory including instructions for operating the DC / DC converter in AC heating mode.

[0010] In addition to one or more of the features described herein, the memory stores instructions that cause the controller to control the DC / DC converter in AC heating mode and heat the first set of battery cells, while causing the flow control device to direct the coolant through the second section rather than the first section.

[0011] In addition to one or more of the features described herein, a thermal barrier is disposed between the first set of battery cells and the second set of battery cells.

[0012] In addition to one or more of the features described herein, the first set of battery cells has a higher charge rate and a lower power density than the second set of battery cells, wherein the first mode of operation is a mode in which power is drawn exclusively from the first set of battery cells.

[0013] In addition to one or more of the features described herein, the second mode of operation is a mode in which power is drawn from the first set of battery cells and the second set of battery cells.

[0014] According to another exemplary embodiment, a method for operating a vehicle comprises drawing operating power from a first set of battery cells and providing heating or cooling to the first set of battery cells, wherein the heating or cooling is limited to the first set of battery cells to maintain the first set of battery cells within an operating temperature window in a first operating mode; in response to a power assist request, switching to a second operating mode and drawing operating power from the first set of battery cells and a second set of battery cells, and providing heating or cooling to maintain the first set of battery cells and the second set of battery cells within the operating temperature window during the second operating mode.

[0015] In addition to one or more of the features described herein, switching to the second mode of operation includes changing a mode of a flow control device such that a coolant is directed through both a first coolant sub-loop passing through the first set of battery cells and a second coolant sub-loop passing through the second set of battery cells.

[0016] In addition to one or more of the features described herein, the coolant is evenly distributed between the first coolant sub-loop and the second coolant sub-loop.

[0017] In addition to one or more of the features described herein, the coolant is unevenly distributed between the first coolant sub-loop and the second coolant sub-loop.

[0018] In addition to one or more of the features described herein, some examples include switching to a third mode of operation, wherein the third mode of operation includes operating a direct current (DC / DC) converter connecting the first set of battery cells to the second set of battery cells as an alternating current (AC) heater.

[0019] In addition to one or more of the features described herein, the third mode of operation further comprises heating one of the first set of battery cells and the second set of battery cells using the DC / DC converter operating as an AC heating device, and cooling the other of the first set of battery cells and the second set of battery cells, respectively, by passing coolant through a corresponding coolant sub-loop using a flow control device.

[0020] In addition to one or more of the features described herein, the first set of battery cells and the second set of battery cells are thermally separated by a thermal barrier.

[0021] According to yet another exemplary embodiment, a vehicle includes a propulsion system having at least one electric motor connected to a power distribution bus, an energy storage system having a first set of battery cells connected to the power distribution bus, a second set of battery cells connected to the first set of battery cells via a direct current (DC / DC) converter, the energy storage system further comprising a coolant system including a coolant loop, the coolant loop including a first coolant sub-loop passing through the first set of battery cells and a second coolant sub-loop passing through the second set of battery cells, and a controller configured to cause the at least one electric motor to draw operating power from the first set of battery cells and the energy storage system to provide heating and cooling.provide cooling to the first set of battery cells and not to the second set of battery cells to maintain the first set of battery cells within an operating temperature window in a first operating mode that switches to a second operating mode in response to a power assist request, and draw operating power from a first set of battery cells and a second set of battery cells and provide heating or cooling to maintain the first set of battery cells and the second set of battery cells within the operating temperature window during the second operating mode.

[0022] In addition to one or more of the features described herein, the controller is further configured to cooperate with a direct current (DC / DC) converter connecting the first set of battery cells to the second set of battery cells as an alternating current (AC) heater in a third mode of operation.

[0023] In addition to one or more of the features described herein, the controller is configured to cause the DC / DC converter to heat one of the first set of battery cells and the second set of battery cells by operating as an AC heater, and to cool the other of the first set of battery cells and the second set of battery cells, respectively, by directing the coolant through a corresponding coolant sub-loop using a flow control device.

[0024] In addition to one or more of the features described herein, switching to the second mode of operation includes changing a mode of a flow control device such that a coolant is directed through both a first coolant sub-loop passing through the first set of battery cells and a second coolant sub-loop passing through the second set of battery cells.

[0025] The above-described features and advantages and other features and advantages of the disclosure will become apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further features, advantages and details appear only as examples in the following detailed description, which refers to the drawings; they show: Fig. 1 a vehicle containing a battery-based energy storage system; Fig. 2A illustrates an exemplary battery pack according to one embodiment; Fig. 2B shows a circuit diagram of the exemplary battery pack of the Fig. 2A; Fig. 3A illustrates an exemplary coolant scheme for a heating / cooling system of a battery pack according to an exemplary embodiment in a first operating mode; and Fig. 3B illustrates an exemplary coolant schematic for a heating / cooling system of a battery pack according to an exemplary embodiment in a second operating mode. DETAILED DESCRIPTION

[0027] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference characters indicate similar or corresponding portions and features.

[0028] As used herein, the term module refers to a processing circuit arrangement that may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) with memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality.

[0029] As used herein, the term coolant refers to a material, typically a fluid or gas, configured to change the temperature of a neighboring object based on a difference between the temperature of the object and the temperature of the coolant. The term coolant does not imply or have a cooling operation and can be used in a cooling system, a heating system, and / or a combined cooling and heating system.

[0030] According to an exemplary embodiment, a vehicle energy storage system includes a battery pack having a first set of battery cells and a second set of battery cells, the battery cells arranged in parallel. The first set of battery cells and the second set of battery cells are constructed from different power cell chemistries, the first power cell type being low energy storage density fast charging battery cells and the second power cell type being high energy density slow charging battery cells. A heating and cooling loop is included in the battery pack. The heating and cooling loop is configured in one mode to independently cool and / or heat the first set of battery cells without cooling or heating the second set of battery cells, and is configured in a second mode to simultaneously cool or heat both sets of battery cells.

[0031] With continued reference to the general system described above, Fig. 1 illustrates an embodiment of a motor vehicle 10 including a battery system controller 24 configured to control a battery system. The vehicle 10 includes a vehicle body 12 that at least partially defines a passenger compartment 14. The vehicle body 12 also supports various vehicle subsystems, including a propulsion system 16, a battery system 22, other subsystems to support functions of the propulsion system 16, and other vehicle components such as a braking subsystem, a suspension system, a steering subsystem, a fuel injection subsystem, an exhaust subsystem, and others.

[0032] The vehicle 10 may be an internal combustion engine vehicle, an electric vehicle (EV), or a hybrid vehicle. In one embodiment, the vehicle 10 is a hybrid vehicle that includes an internal combustion engine system 18 and at least one electric motor assembly. For example, the propulsion system 16 includes a first electric motor 20 and a second electric motor 21. The motors 20 and 21 may be configured to drive wheels 23 on opposite sides of the vehicle 10. Any number of motors positioned at various additional locations within the vehicle 10 may be used to impart mechanical rotation to corresponding systems and subsystems.

[0033] The battery system 22 may be electrically connected to the motors 20 and 21 and / or other components such as vehicle electronics. The battery system 22 may be configured as a rechargeable energy storage system (RESS) and includes a plurality of battery cells divided into sections. A battery system controller 24 is included in the battery system 22 and controls the charging and discharging functions of the batteries in the battery system 22. In alternative configurations, the battery system controller 24 may be a general vehicle controller remote from the battery system 22 and configured to control multiple systems and / or subsystems. The general vehicle controller may be located at any location within the vehicle 10.In still further alternatives, the battery system controller 24 may be a distributed control system that includes multiple coordinating controllers throughout the vehicle 10, including controllers in the battery system 22 and controllers remote from the battery system 22.

[0034] According to one embodiment, the battery system 22 includes one or more battery packs 28. The battery packs 28 include a plurality of different battery cells connected in parallel and connected to a power distribution bus 29 to provide power to one or more systems. In the exemplary system of Fig. 1, the power distribution bus 29 is shown in simplified form and provides power to the propulsion systems 16 via an inverter 26.

[0035] With continued reference to Fig. 1 shows Fig. 2A schematically shows a single battery pack 28 and Fig. 2B shows an exemplary circuit diagram for implementing the schematic battery pack 28 of the Fig. 2A. The battery pack 28 shown includes a first power cell 210 and a second power cell 230 connected in parallel with the first power cell 210 via a direct current (DC / DC) converter 220. Although each is shown as a single power cell for ease of illustration, it is recognized that each power cell 210 and 230 will in practice be implemented by multiple battery cells of the same type arranged in a group according to known principles and practices, without changing the schematic arrangements of the Fig. 2A and Fig. 2B and without changing the modes of operation described herein. Consequently, the first battery cell 210 and the second battery cell 230 are alternatively referred to as a set of battery cells.

[0036] The first set of battery cells 210 and the second set of battery cells 230 are constructed with different chemistries (e.g., NCM-based battery cells, LFP-based battery cells, Na-ion-based battery cells, Si-anode-based battery cells), and as a result, the first set of battery cells 210 and the second set of battery cells 230 have different performance characteristics. In general, the first set of battery cells 210 has a lower energy density and a higher charge rate relative to the second set of battery cells 230. The use of mixed chemistries allows a designer to balance the conflicting needs of fast charging, which can be achieved using the higher charge rate, lower energy density battery cells, and the need for high-energy-density power storage for longer-range applications.The different combined chemical composition types are generally referred to herein as a mixed configuration battery pack.

[0037] In the parallel circuit, which is in the Fig. 2A and Fig. 2B, the sets of battery cells 210 and 230 are connected to each other via a bidirectional DC / DC buck converter or DC / DC boost converter 220. In this arrangement, the voltage of one of the sets of battery cells 210 or 230 is always kept higher or lower than the voltage of one of the other sets of battery cells 210 or 230. In the example shown, the Fig. 2A and Fig. 2B, the one or more power cells are maintained at a higher voltage level in the voltage of the battery cells with the higher power density and the lower charging rate (second set of battery cells 230) of the second set of battery cells 230.

[0038] Battery cells, such as those used in both the first set of battery cells 210 and the second set of battery cells 230, exhibit a relatively steady voltage decrease once a state of charge decreases to a dip point, after which the power cell voltage decreases at a rapid rate. The state of charge at which the dip point is reached depends on the temperature of the power cells 210 and 230, with a low temperature leading to a dip point at a significantly higher state of charge than when the power cells 210 and 230 are warm. This is the result of low temperatures increasing the internal resistance of the sets of battery cells 210 and 230.When both sets of battery cells 210 and 230 experience a low temperature, the output power of the battery pack 28 is typically limited to avoid violating the voltage constraints, which requires that the first set of battery cells 210 have a lower voltage than the second set of battery cells 230.

[0039] A disadvantage of mixed-configuration battery packs, such as battery pack 28, is that high and low ambient temperatures can accelerate the degradation of sets of battery cells 210 and 230, and operating sets of battery cells 210 and 230 outside of a temperature window (e.g., when the battery cells are either too hot or too cold) contributes to the degradation. Additionally, a low temperature can cause an early reliance on the high-power density battery cells (the second set of battery cells 230) instead of the faster-charging, low-power density battery cells (the second set of battery cells 210).

[0040] To mitigate this disadvantage, the battery pack 28 includes a heating or cooling system configured to heat or cool the sets of battery cells 210 and 230 of the battery pack 28, ensuring that the battery pack 28 remains within a desired operating temperature window. The cooling loop is configured to independently heat or cool the low-power density battery cells of the first set of battery cells 210 in some modes, and is configured, in another configuration, to simultaneously heat or cool the first set of battery cells 210 and the slower-charging, high-power density battery cells (the second set of battery cells 230).

[0041] During operation, the one or more low-power-density fast-charging power cells 210 are used to provide power to the propulsion system 16 and are referred to as traction battery cells. During the initial portions of vehicle operation, only power from the traction battery cells 210 is provided to the propulsion system 16. Power from the second set of battery cells 230, which has a higher power density but a lower charge rate, is only expended after a power assist request is made due to the first set of battery cells 210 approaching a low state of charge.

[0042] Since only the first set of battery cells 210 is used for the initial operating phases or, in the case of a short trip, for the entire operation, simultaneous heating or cooling of both the first set of battery cells 210 and the second set of battery cells 230 within the operating window is not necessary and increases the time required for the battery cells 210 of the first set of battery cells 210 to reach the optimal operating temperatures.

[0043] The Fig. 3A and Fig. 3B illustrate a cooling system 300 that can direct all heating or cooling power to the first set of battery cells 210 for the initial portions of vehicle operation and switch to a balanced heating / cooling power supply between the two sets of battery cells 210 and 230 once a power assist request has been made (i.e., once the power of the first set of battery cells 210 alone is insufficient to sustain operation). The switch is accomplished using a valve 310 or other flow control device disposed at an upstream end of a portion 314 of the cooling system 300 that passes through the second set of battery cells 230.

[0044] Fig. 3A shows an example in which the valve 310 is closed (e.g., at the beginning of vehicle operation) and all of the coolant 301 is directed through a portion 312 of the cooling system 300 that passes through the first set of battery cells 210 and is then returned to a beginning of the coolant system. Fig. Figure 3B shows the identical cooling system 300, with the valve 310 opened, allowing the coolant 301 to pass through both the first set of battery cells 210 and the second set of battery cells 230 simultaneously. In the example of Fig. 3A, 100% of the heating or cooling power is directed to the first set of battery cells 210, which ensures a rapid temperature change of the first set of battery cells 210 without wasting any heating or cooling power. In the example of Fig. 3B, both sets of battery cells 210 and 230 are used, with the heating or cooling power being divided between the sets of battery cells 210 and 230.

[0045] In some examples, the valve 310 may be metered to allow both sections 312 and 314 to receive coolant 301 while providing a different flow rate of coolant 301 to each of the sections 312 and 314, thereby allowing one of the sections 312 and 314 to receive more heating or cooling from the passing coolant than the other of the sections 312 and 314. In this example, the heating or cooling power is unevenly split, and the section 312 or 314 with the higher flow rate receives more heating or cooling power, resulting in a faster temperature change.

[0046] In yet further examples, the valve 310 may be configured to completely divert the coolant flow from the first section 312, allowing coolant flow through the second section 314. Examples in this configuration may be used when the first section 312 is within a desired temperature window and the second section 314 is outside or departing from the desired temperature window and / or when another heating or cooling source is available to control a temperature of the first section 312.

[0047] The ability to provide cooling or heating to one of sections 312 and 314 without providing cooling or heating to the other of sections 312 and 314 and to provide different amounts of cooling or heating to sections 312 and 314 is referred to herein as independent cooling or heating of sections 312 and 314, and the configuration with multiple sections 312 and 314 may be referred to as dual-loop or multi-loop.

[0048] In some examples, a thermal barrier 330 is present between the battery cells 210 and 230. The thermal barrier 330 may be a physical barrier having a low heat transfer rate, an air gap, or any physical configuration that prevents heat transfer from the first set of battery cells 210 to the second set of battery cells 230, or vice versa. Alternatively, the thermal barrier may be achieved by physically disposing the first set of battery cells 210 and the second set of battery cells 230 at different locations within the vehicle 10. Regardless of the form the thermal barrier 330 takes, a fundamental feature of the thermal barrier 330 is that temperatures from each of the sets of battery cells 210 and 230 are prevented from affecting the temperature of the other sets of battery cells 210 and 230.

[0049] In yet further examples, the DC / DC converter 220 (in the Fig. 2A and Fig. 2B) may be disposed adjacent to one of the sets of battery cells 210 and 230 and include an electric heating mode of operation. In the electric heating mode of operation, the DC / DC converter 220 is operated in a manner that converts electrical energy into "waste heat" without conducting the electrical energy to another component. The electric heating operation may be effected by using a controller that switches the DC / DC converter 220 according to any known electric heating mode. In such a case, the coolant may be provided to one of the sets of battery cells 210 and 230, and the DC / DC converter 220 may provide direct heating to the other of the sets of battery cells 210 and 230, whereby one of the sets of battery cells 210 and 230 may be heated while the other of the sets of battery cells 210 and 230 is cooled.

[0050] With joint reference to the figures, an exemplary use case of the dual-loop heating and cooling system disclosed herein provides rapid heating or cooling of the first set of battery cells 210. In the first use case, the first set of battery cells 210 provides power to the propulsion system 16, with initially all heating or cooling power being directed to the section 312 passing through the first set of battery cells 210. This heating or cooling power distribution is maintained until the power demand of the propulsion system exceeds the maximum power output of the first set of battery cells 210 and power assistance from the second set of battery cells 230 is required. At this time, the heating or cooling power is divided between the two sets of battery cells 210 and 230, and power is drawn from both sets of battery cells.

[0051] Another exemplary use case of the dual-loop heating and cooling system 300 disclosed herein provides heating or cooling of the second set of battery cells 230 at vehicle startup when the first set of battery cells is already within the target temperature window.

[0052] The terms "a" and "an" do not imply a limitation of number, but rather denote the presence of at least one of the referenced elements. The term "or" means "and / or" unless clearly indicated otherwise by context. A reference throughout the application text to "an aspect" means that a particular element (e.g., a feature, structure, step, or property) described in connection with the aspect is included in at least one aspect described herein and may or may not be present in further aspects. In addition, it is to be understood that the described elements in the various aspects may be combined in any suitable manner.

[0053] Unless otherwise specified herein, schematic representations do not uniquely correspond to physical structures, and the relative positioning, size, orientation, and other configuration of components in the schematic representation is not limiting.

[0054] When an element, such as a layer, film, region, or substrate, is referred to as "on" another element, it may be directly adjacent to the other element or may also have intervening elements present. In contrast, when an element is referred to as "directly adjacent" to another element, no intervening elements are present.

[0055] Unless otherwise specified herein, all examination standards shall be the most recent standard in force as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0056] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0057] While the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalents may be substituted for elements without departing from the scope thereof. Additionally, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within its scope.

Claims

[1] Energy storage system for a vehicle, comprising: a battery system having a first set of battery cells and a second set of battery cells connected in parallel with the first set of battery cells; a coolant loop having a first portion passing through the first set of battery cells, a second portion passing through the second set of battery cells, and a flow control device; and a controller configured to cause the flow control device to confine coolant to the first section in a first mode of operation and configured to cause the flow control device to allow the coolant to pass through the first section and the second section in a second mode of operation. [2] The energy storage system of claim 1, wherein the coolant loop further comprises a third mode in which the flow control device is configured to allow the coolant to pass through the second section and not through the first section. [3] The energy storage system of claim 1, wherein the first set of battery cells is a first cell type and the second set of battery cells is a second cell type different from the first cell type. [4] The energy storage system of claim 1, wherein the first set of battery cells is connected to a power distribution bus and the second set of battery cells is connected to the first set of battery cells via a direct current (DC / DC) converter, the DC / DC converter being actively controlled by the controller; and wherein the controller includes memory containing instructions for operating the DC / DC converter in an AC heating mode and instructions to cause the controller to control the DC / DC converter in the AC heating mode and to heat the first set of battery cells while causing the flow control device to direct the coolant through the second section rather than the first section. [5] The energy storage system of claim 1, further comprising a thermal barrier disposed between the first set of battery cells and the second set of battery cells. [6] The energy storage system of claim 1, wherein the first set of battery cells has a higher charge rate and a lower power density than the second set of battery cells, and wherein the first operating mode is a mode in which power is drawn exclusively from the first set of battery cells. [7] The energy storage system of claim 6, wherein the second operating mode is a mode in which power is drawn from the first set of battery cells and the second set of battery cells. [8] A method of operating a vehicle comprising: Drawing operating power from a first set of battery cells and providing heating or cooling, wherein the heating or cooling is limited to the first set of battery cells to keep the first set of battery cells within an operating temperature window in a first operating mode; Switching to a second operating mode in response to a power assistance request; and during the second operating mode, drawing operating power from the first set of battery cells and a second set of battery cells and providing heating or cooling to keep the first set of battery cells and the second set of battery cells within the operating temperature window. [9] The method of claim 8, wherein switching to the second operating mode comprises changing an operating mode of a flow control device such that a coolant is directed to both a first coolant sub-loop passing through the first set of battery cells and a second coolant sub-loop passing through the second set of battery cells. [10] The method of claim 8, further comprising switching to a third operating mode, the third operating mode comprising operating a direct current (DC / DC) converter connecting the first set of battery cells to the second set of battery cells as an alternating current (AC) heater, the third operating mode further comprising heating one of the first set of battery cells and the second set of battery cells using the DC / DC converter operating as an AC heater, and cooling the other of the first set of battery cells and the second set of battery cells, respectively, by directing the coolant through a corresponding coolant sub-loop using a flow control device.

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