Patent Application
20240367551
The subject disclosure relates to operation of battery cells in a battery pack of an electric vehicle and, in particular, to a system and method of heating the battery cells by sharing electrical energy between the cells.
Electric vehicles include electric motors that run off electric power provided by electrical power sources such as a battery pack. A battery pack includes multiple battery cells, many of which can have different compositions and have different power characteristics. Each battery cell includes an optimal temperature range for operation. Operating a battery cell at a temperature below the optimal operating temperature range can decrease the life of the battery. Unfortunately, the temperature of the battery tends to reach equilibrium with the ambient temperature, which can be less than the optimal temperature range, especially on cold days. Accordingly, it is desirable to provide a system and method for heating a battery cell.
In one exemplary embodiment, a method of heating a battery of a vehicle is disclosed. A first cell of the battery is connected to a first side of a direct current converter (DC/DC converter). A second cell of the battery is connected to a second side of the DC/DC converter. A first current is flowed between the first cell and the second cell through the DC/DC converter to heat the first cell and the second cell during a first heating phase. A second current is flowed between the second cell and the DC/DC converter to heat the second cell during a second heating phase.
In addition to one or more of the features described herein, the DC/DC converter generates an alternating current to heat the first cell and the second cell. A first heating rate of the first cell is greater than a second heating rate of the second cell. The method further includes selecting a magnitude of the first current based on the first heating rate. The method further includes switching from the first heating phase to the second heating phase when a first temperature of the first cell rises to a target temperature. The method further includes operating the vehicle in one of a propulsion mode and a heating mode, wherein the DC/DC converter connects the second cell to a motor of the vehicle in the propulsion mode and connects the second cell to the first cell in the heating mode. The method further includes operating the motor off of the first cell in both the propulsion mode and the heating mode.
In another exemplary embodiment, a system for heating a battery of a vehicle is disclosed. The system includes a first cell having a first cell type, a second cell having a second cell type, a direct current converter (DC/DC converter) having a first side coupled to the first cell and a second side coupled to the second cell, and a processor. The processor is configured to control flow of a first current between the first cell and the second cell through the DC/DC converter to heat the first cell and the second cell during a first heating phase and control flow of a second current between the second cell and the DC/DC converter to heat the second cell during a second heating phase.
In addition to one or more of the features described herein, the DC/DC converter generates an alternating current to heat the first cell and the second cell. A first heating rate of the first cell is greater than a second heating rate of the second cell. The processor is further configured to select a magnitude of the first current based on the first heating rate. The processor is further configured to switch from the first heating phase to the second heating phase when a first temperature of the first cell rises to a target temperature. The processor is further configured to operate the vehicle in one of a propulsion mode and a heating mode, wherein the DC/DC converter couples the second cell to a motor of the vehicle in the propulsion mode and couples the second cell to the first cell in the heating mode. The processor is further configured to operate the motor off of the first cell in both the propulsion mode and the heating mode.
In another exemplary embodiment, a vehicle is disclosed. The vehicle includes a battery having a first cell having a first cell type and a second cell having a second cell type, a direct current converter (DC/DC converter) having a first side coupled to the first cell and a second side coupled to the second cell, and a processor. The processor is configured to control flow of a first current between the first cell and the second cell through the DC/DC converter to heat the first cell and the second cell during a first heating phase and control flow of a second current between the second cell and the DC/DC converter to heat the second cell during a second heating phase.
In addition to one or more of the features described herein, the DC/DC converter generates an alternating current to heat the first cell and the second cell. A first heating rate of the first cell is greater than a second heating rate of the second cell. The processor is further configured to select a magnitude of the first current based on the first heating rate. The processor is further configured to switch from the first heating phase to the second heating phase when a first temperature of the first cell rises to a target temperature. The processor is further configured to operate the vehicle in one of a propulsion mode and a heating mode, wherein the DC/DC converter couples the second cell to a motor of the vehicle in the propulsion mode and couples the second cell to the first cell in the heating mode.
The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which:
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 numerals indicate like or corresponding parts and features.
In accordance with an exemplary embodiment,
The vehicle 10 may be an electrically powered vehicle (EV), a hybrid vehicle or any other vehicle. In an embodiment, the vehicle 10 is an electric vehicle that includes multiple motors and/or drive systems. Any number of drive units may be included, such as one or more drive units for applying torque to front wheels (not shown) and/or to rear wheels (not shown). The drive units are controllable to operate the vehicle 10 in various operating modes, such as a normal mode, a high-performance mode (in which additional torque is applied), all-wheel drive (“AWD”), front-wheel drive (“FWD”), rear-wheel drive (“RWD”) and others.
For example, the propulsion system 16 is a multi-drive system that includes a front drive unit 20 for driving front wheels, and rear drive units for driving rear wheels. The front drive unit 20 includes a front electric motor 22 and a front inverter 24 (e.g., front power inverter module or FPIM), as well as other components such as a cooling system. A left rear drive unit 30L includes an electric motor 32L and an inverter 34L. A right rear drive unit 30R includes an electric motor 32R and an inverter 34R. The inverters 24, 34L and 34R (e.g., power inverter units or PIMs) each convert DC power from a high voltage (HV) battery system 40 to poly-phase (e.g., two-phase, three-phase, six-phase, etc.) alternating current (AC) power to drive the front electric motor 22 and rear electric motors 32L and 32R.
As shown in
As also shown in
In the propulsion system 16, the front drive unit 20, left rear drive unit 30L and right rear drive unit 30R are electrically connected to the battery system 40. The battery system 40 may also be electrically connected to other electrical components (also referred to as “electrical loads”), such as vehicle electronics (e.g., via an auxiliary power module or APM 42), heaters, cooling systems and others. The battery system 40 may be configured as a rechargeable energy storage system (RESS).
In an embodiment, the battery system 40 includes a plurality of separate battery assemblies, in which each battery assembly can be independently charged and can be used to independently supply power to a drive system or systems.
For example, the battery system 40 includes a first battery assembly such as a first battery sub-pack 44 connected to the front inverter 24, and a second battery sub-pack 46. The first battery sub-pack 44 includes a plurality of battery modules 48, and the second battery sub-pack 46 includes a plurality of battery modules 50. Each battery module 48, 50 includes a number of individual cells (not shown). In various embodiments, one or more of the battery packs can include a MODACS (Multiple Output Dynamically Adjustable Capacity) battery, as described herein with respect to
Each of the front electric motor 22 and the rear electric motors 32L and 32R is a three-phase motor having three phase motor windings. However, embodiments described herein are not so limited. For example, the motors may be any poly-phase machines supplied by poly-phase inverters, and the drive units can be realized using a single machine having independent sets of windings.
The battery system 40 and/or the propulsion system 16 includes a switching system having various switching devices for controlling operation of the battery packs 44 and 46, and selectively connecting the battery packs 44 and 46 to the front drive unit 20, left rear drive unit 30L and right rear drive unit 30R. The switching devices may also be operated to selectively connect the first battery sub-pack 44 and the second battery sub-pack 46 to a charging system. The charging system can be used to charge the first battery sub-pack 44 and the second battery sub-pack 46, and/or to supply power from the first battery sub-pack 44 and/or the second battery sub-pack 46 to charge another energy storage system (e.g., vehicle-to-vehicle (V2V) and/or vehicle-to-everything (V2X) charging). The charging system includes one or more charging modules. For example, a first onboard charging module (OBCM) 52 is electrically connected to a charge port 54 for charging to and from an AC system or device, such as a utility AC power supply. A second OBCM 53 may be included for DC charging (e.g., DC fast charging or DCFC).
In an embodiment, the switching system includes a first switching device 60 that selectively connects the first battery sub-pack 44 to the inverters 24, 34L and 34R, and a second switching device 62 that selectively connects the second battery sub-pack 46 to the inverters 24, 34L and 34R. The switching system also includes a third switching device 64 (also referred to as a “battery switching device”) for selectively connecting the first battery sub-pack 44 to the second battery sub-pack 46 in series.
Any of various controllers can be used to control functions of the battery system 40, the switching system and the drive units. A controller includes any suitable processing device or unit and may use an existing controller such as a drive system controller, an RESS controller, and/or controllers in the drive system. For example, a controller 65 may be included for controlling switching and drive control operations as discussed herein.
The controller 65 may include processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. The controller 65 may include a non-transitory computer-readable medium that stores instructions which, when processed by one or more processors of the controller 65, implement a method of heating a battery pack, according to one or more embodiments detailed herein.
The vehicle 10 also includes a computer system 55 that includes one or more processing devices 56 and a user interface 58. The computer system 55 may communicate with the charging system controller, for example, to provide commands thereto in response to a user input. The various processing devices, modules and units may communicate with one another via a communication device or system, such as a controller area network (CAN) or transmission control protocol (TCP) bus.
An energy balance at the DC/DC converter 302 is shown in Eq. (1).
where V1 and I1 are the voltage and current of the first cell 202, respectively and V2 and I2 are the voltage and current of the second cell 204, respectively. A heating rate for each cell is dependent on the amount of current, the resistance of the cell, the mass of the cell and the specific heat of the cell. For the first cell, the first heating rate is shown in Eq. (2):
where I1 is the root mean squared (RMS) current through the first cell, R1 is the resistance of the first cell, m1 is the mass of the first cell and Cp1 is the specific heat of the first cell. Similarly, the second heating rate for the second cell is given in Eq. (3):
where I2 is the RMS current through the second cell, R2 is the resistance of the second cell, m2 is the mass of the second cell and Cp2 is the specific heat of the second cell. Combining Eqs. (1), (2) and (3) gives a relation between the heating rates of the first cell and second cell based on their physical properties, as shown in Eq. (4):
From Eq. (4), the heating rates of the first cell and the second cell are generally different from each other. (e.g.,
During the first heating phase 402, both cells are heated. A first line 406 represents a first temperature T1 of the first cell during the first heating phase 402, and a second line 408 represents a second temperature T2 of the second cell 204 during the second heating phase 404. For illustrative purposes, the heating rate T1 of the first cell (i.e., the slope of first line 406) is greater than the heating rate T2 of the second cell (i.e., the slope of the second line 408). A desired first heating rate for the first cell can be determined and an AC current can be selected using the Eq. (2) that produces the desired heating rate. The first heating phase 402 is ended once a temperature T1 of the first cell 202 reaches or rises to a target temperature Ttarget. The target temperature can be selected by a user or processor prior to commencing the heating process.
The second heating phase 404 commences at the end of the first heating phase 402. At the end of the first heating phase 402, the remaining battery (e.g., the second cell 204) is not yet at the target temperature. The second heating phase 404 involves having the remaining battery heat itself. Line 410 represents the second temperature T2 of the second battery during the second phase 404. The heating rate
In box 508, the heating is performed using the mutual heating of the first phase. In box 510, the temperature T1 of the first cell is monitored and compared to the target temperature. While the temperature T1 has not reached the target temperature (i.e., while T1 is less than then target temperature), the method returns to box 508. Once the temperature T1 reaches the target temperature, the method proceeds to box 512.
In box 512, a second heating current is determined for the second cell for a second heating phase. The second heating current I2′ can be determined by selecting a second heating rate and using Eq. (3). In box 514, heating is performed using the individual heating of the second phase. In box 516, the temperature T2 of the second cell is monitored and compared to the target temperature. While the temperature T2 has not reached the target temperature (i.e., T2 is less than then target temperature), the method returns to box 514. Once the temperature T2 reaches the target temperature, the method proceeds to box 518. At box 518, the process ends.
During the second heating phase 404, the switches of the DC/DC converter can be configured to circulate only through one cell (e.g., the first cell). As illustrated in
The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term “or” means “and/or” unless clearly indicated otherwise by context. Reference throughout the specification to “an aspect”, means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various aspects.
When an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.
Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this disclosure belongs.
While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof.
