VEHICLE BATTERY MANAGEMENT SYSTEM FOR PRESSURE DETERMINATION OF LITHIUM-BASED BATTERIES

Abstract

Some of the embodiments disclosed herein relate to battery management systems for vehicles for determining the pressure of lithium-based batteries. Some embodiments may include generating a pressure measurement for a lithium-based battery based on a normalized pressure and an initial pressure value assigned to the lithium-based battery, and setting or maintaining a compression level applied to the lithium-based battery based on the generated pressure measurement. Other embodiments may be disclosed or claimed.

Description

INITIATIONThe present disclosure relates to lithium-based batteries. More particularly, embodiments of the present disclosure relate to battery management systems for vehicles for pressure determination of lithium-based batteries.Increasingly, vehicles are being manufactured with propulsion systems that utilize an electric motor powered by a lithium-based battery system, such as lithium metal batteries (LMB). Such battery systems may include multiple battery modules that are under pressure. The pressure of a lithium-based battery may vary widely during charging and discharging and may significantly degrade the performance of the battery. Some aspects of the operation of such systems relate to monitoring and maintaining the pressure of lithium-based batteries to optimize the performance of the battery. Among other things, embodiments of the present disclosure provide improved systems for determining the pressure of lithium-based batteries in real-time or near real-time.SUMMARYIn an exemplary embodiment, a battery management system is provided. The battery management system includes a processor and a memory coupled to the processor. The memory stores instructions that, when executed by the processor, cause the battery management system to receive measurement signals from a lithium-based battery, the measurement signals including a voltage measurement, a current measurement, and a temperature measurement. The memory further stores instructions for determining, based on the received measurement signals, a normalized pressure of the lithium-based battery and generating a pressure measurement for the lithium-based battery based on the normalized pressure and an initial pressure value associated with the lithium-based battery. The memory further stores instructions for adjusting or maintaining a compression level applied to the lithium-based battery based on the generated pressure measurement.In addition to one or more of the features described herein, determining the normalized pressure of the lithium-based battery is performed without a pressure measurement for the lithium-based battery from a pressure sensor.In addition to one or more of the features described herein, determining the normalized pressure for the lithium-based battery is further based on a state of charge (SOC) measurement and a lithium density measurement.In addition to one or more of the features described herein, the lithium density measurement is associated with a lithium surface density at an anode of the lithium-based battery.In addition to one or more of the features described herein, the SOC measurement is associated with a change in an estimated pressure of the lithium-based battery over a predetermined period of time.In addition to one or more of the features described herein, the measurement signals are received from a plurality of sensors coupled to the lithium-based battery.In addition to one or more of the features described herein, the measurement signals reflect measurements for the lithium-based battery taken in real-time or near real-time.In addition to one or more of the features described herein, generating the pressure measurement for the lithium-based battery is based on the normalized pressure, and the initial pressure value associated with the lithium-based battery is further based on one or more of: a maximum pressure of the lithium-based battery, a minimum pressure of the lithium-based battery, and a pressure of the lithium-based battery associated with a particular SOC value.In an exemplary embodiment, a propulsion system for a vehicle is provided. The propulsion system includes an electric motor, a lithium-based battery coupled to the electric motor, and a battery management system coupled to the lithium-based battery. The battery management system includes a processor and memory coupled to the processor storing instructions that, when executed by the processor, cause the battery management system to receive measurement signals from a lithium-based battery, the measurement signals including a voltage measurement, a current measurement, and a temperature measurement. The memory further stores instructions to cause the battery management system to determine, based on the received measurement signals, a normalized pressure of the lithium-based battery and generate a pressure measurement for the lithium-based battery based on the normalized pressure and an initial pressure value associated with the lithium-based battery. The memory further stores instructions that cause the battery management system to adjust or maintain a compression level applied to the lithium-based battery based on the generated pressure measurement.In addition to one or more of the features described herein, determining the normalized pressure of the lithium-based battery is performed without a pressure measurement for the lithium-based battery from a pressure sensor.In addition to one or more of the features described herein, determining the normalized pressure for the lithium-based battery is further based on a state of charge (SOC) measurement and a lithium density measurement.In addition to one or more of the features described herein, the lithium density measurement is associated with a lithium surface density at an anode of the lithium-based battery.In addition to one or more of the features described herein, the SOC measurement is associated with a change in an estimated pressure of the lithium-based battery over a predetermined period of time.In addition to one or more of the features described herein, the measurement signals include one or more of measurements received from a plurality of sensors coupled to the lithium-based battery and measurements for the lithium-based battery taken in real-time or near real-time.In addition to one or more of the features described herein, generating the pressure measurement for the lithium-based battery is based on the normalized pressure, and the initial pressure value associated with the lithium-based battery is further based on one or more of: a maximum pressure of the lithium-based battery, a minimum pressure of the lithium-based battery, and a pressure of the lithium-based battery associated with a particular SOC value.In an exemplary embodiment, a vehicle is provided. The vehicle includes a lithium-based battery and a battery management system coupled to the lithium-based battery. The battery management system includes a processor and a memory coupled to the processor. The memory stores instructions that, when executed by the processor, cause the battery management system to receive measurement signals from a lithium-based battery, the measurement signals including a voltage measurement, a current measurement, and a temperature measurement. The memory further stores instructions for determining, based on the received measurement signals, a normalized pressure of the lithium-based battery and generating a pressure measurement for the lithium-based battery based on the normalized pressure and an initial pressure value associated with the lithium-based battery. The memory further stores instructions for adjusting or maintaining a compression level applied to the lithium-based battery based on the generated pressure measurement.In addition to one or more of the features described herein, determining the normalized pressure of the lithium-based battery is performed without a pressure measurement for the lithium-based battery from a pressure sensor.In addition to one or more of the features described herein, determining the normalized pressure for the lithium-based battery is further based on a state of charge (SOC) measurement associated with a change in an estimated pressure of the lithium-based battery over a predetermined period of time and a lithium density measurement associated with a lithium surface density at an anode of the lithium-based battery.In addition to one or more of the features described herein, the measurement signals include one or more of measurements received from a plurality of sensors coupled to the lithium-based battery and measurements for the lithium-based battery taken in real-time or near real-time.In addition to one or more of the features described herein, generating the pressure measurement for the lithium-based battery is based on the normalized pressure, and the initial pressure value associated with the lithium-based battery is further based on one or more of: a maximum pressure of the lithium-based battery, a minimum pressure of the lithium-based battery, and a pressure of the lithium-based battery associated with a particular SOC value.The above features and advantages, as well as other features and advantages of the disclosure, will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSOther features, advantages and details are set forth, by way of example only, in the following detailed description, wherein: FIG. 1 is a schematic diagram of a vehicle for use in connection with one or more embodiments of the present disclosure; FIG. 2 is a functional block diagram illustrating aspects of a battery management system, in accordance with embodiments of the present disclosure; FIGS. 3A and 3B are functional block diagrams illustrating methods for determining the pressure of a lithium-based battery, in accordance with embodiments of the present disclosure; FIG. 3C illustrates examples of graphs for calibrating normalized pressure of a lithium-based battery, according to various embodiments of the present disclosure; and FIG. 4 is a flow diagram illustrating a method according to various aspects, in accordance with the present disclosure.DETAILED DESCRIPTIONThe following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or its use. It should be understood that throughout the drawings, corresponding reference numerals designate like or corresponding parts and features.According to an exemplary embodiment, a battery management system for an electric motor is provided. The battery management system may determine a pressure measurement for a lithium-based battery based on measurement signals of the battery such as voltage, current, and temperature. In this way, embodiments of the present disclosure may accurately determine a pressure measurement for a lithium-based battery in real-time or near real-time without requiring special pressure sensors.Referring now to FIG. 1, a schematic diagram of a vehicle 100 for use in connection with one or more embodiments of the present disclosure is shown. The vehicle 100 includes a charge port 102, a battery 104, and an electric motor 106. In one embodiment, the vehicle 100 is a hybrid vehicle that uses both an internal combustion engine and an electric motor. In another embodiment, the vehicle 100 is an electric vehicle that uses only electric motors. In example embodiments, the vehicle 100 is configured to be connected via the charging port 102 to a high voltage power source (i.e., a voltage source of at least 200 volts (V)) used to charge the battery 104. The electric motor 106 is configured to receive power from the battery 104 to provide propulsion to the vehicle 100. In example embodiments, the battery 104 is configured to supply direct current (DC) to an inverter (not shown) that converts the direct current to three-phase alternating current (AC). The three-phase alternating current is supplied to the electric motor 106 for propulsion for the vehicle 100.FIG. 2 is an example of a functional block diagram illustrating aspects of a battery management system, in accordance with embodiments of the present disclosure. In this example, the battery 104 includes a plurality of lithium-based battery modules 210, 220, 230. Each individual battery module is coupled to the respective battery monitoring unit 215, 225, 235. The battery monitoring units 215, 225, 235 are coupled to a battery management system (BMS) 250.In the example illustrated in FIG. 2, three battery modules are illustrated as an example, however, a practical system may include any number of battery modules. In some embodiments, a single battery monitoring unit may be coupled to a plurality of battery modules. Additionally or alternatively, the BMS 250 may be directly coupled to some or all of the battery modules 210, 220, 230 to perform the functions of the battery monitoring units 215, 225, 235.In some example embodiments, the BMS 250 includes at least one processor, such as a general processor, a central processing unit, an application specific integrated circuit (ASIC), a digital signal processor, a field programmable gate array (FPGA), a digital circuit, an analog circuit, or combinations thereof. In some embodiments, the BMS 250 includes a memory that communicates with the processor to store data and instructions executable by the processor to retrieve measurements from the battery 104 and control functions of the battery 104.For example, in some embodiments, the BMS 250 manages the charging of the vehicle battery 104 (a lithium ion battery in this example) and monitors and controls the battery 104 when it discharges during operation of the vehicle 100. The BMS receives measurement signals from the battery modules 210, 220, 230 (in this example, via battery monitoring units 215, 225, 235) from sensors coupled to the battery modules. The measurement signals may include one or more voltage measurements, a current measurement, and a temperature measurement. The BMS 250 may determine other measurements based on the received measurement signals, such as a state of charge (SOC) measurement and a lithium density measurement. The BMS 250 may receive any other suitable measurements from the battery 104.FIGS. 3A and 3B are functional block diagrams illustrating methods for determining the pressure of a lithium-based battery, according to embodiments of the present disclosure. The functions of plots 300 and 350 may be performed by any suitable system or combination of systems, such as BMS 250 in FIG. 2. FIG. 3A, the BMS 250 receives measurement signals from the battery 104 including a voltage measurement 302 and a current measurement 304. The BMS 250 further determines a state of charge (SOC) measurement 306 and a lithium density measurement 308.At block 310, the BMS 250 processes the measurement signals (e.g., current, voltage, and temperature) and the determined values for the SOC measurement 306 and the lithium density measurement 308 using a data controlled model in a recurrent neural network (RNN) to generate a normalized pressure value 312 for the battery 104. At 315, the BMS 250 generates a pressure measurement 316 for the lithium-based battery 104 based on the normalized pressure 312 and an initial pressure value 314 associated with the lithium-based battery.FIG. 3B illustrates an example of a process for generating the normalized pressure 312 using the RNN. In this example, the battery management system 250 receives the measurements 302, 304, 306, 308 in block 352, which may be collectively referred to below as inputs x, where x1=voltage, x2=current, x3= SOC, and x4=Li density. At 354, the BMS 250 assigns a first weight U to each discrete measurement (e.g., U 1 for voltage, U 2 for current, etc.). In block 356, the BMS 250 performs a first activation function process h, which is based on a recurrent connection V in 358. At 360, each discrete measurement is assigned a second weight (e.g., W1 for voltage, W2 for current, etc.). The normalized pressure output 312 is determined based on a second activation function o. The activation processes h and o may be carried out according to:Where b y and b h are bias values.As illustrated in FIGS. 3A and 3B, the BMS 250 generates a normalized pressure 312 of the battery 104 in real-time or near real-time based on the measurements 302, 304, 306, 308. An actual pressure for the battery 316 is then determined by multiplying the normalized pressure 312 by the initial pressure of the battery 316. In this example, the initial pressure 316 for the battery 104 (or each individual battery module 210, 220, 230 of the battery 104) may be determined during manufacture of the battery 104 or during installation in the vehicle 100.In some embodiments, the model used by the BMS 250 for the RNN may be calibrated using a target pressure value from a pressure sensor, whereupon the BMS 250 may perform a cycle test and measure voltage, current, temperature, and pressure from a battery or battery module. Either during or after testing, the system may calculate the normalized pressure by dividing the pressure values by the output pressure, the maximum pressure, the minimum pressure, or the pressure relative to a particular SOC value. After calibration, a dedicated pressure sensor is no longer required for the BMS 250 to determine the pressure of the battery 104, thereby reducing the cost and complexity of the BMS 250 and the vehicle 100.FIG. 3C illustrates examples of graphs for calibrating normalized pressure of a lithium-based battery, in accordance with various embodiments of the present disclosure. In this example, the graph 370 represents the actual pressure Pr(k) measured by a pressure sensor during calibration. Plot 375 depicts determination of normalized pressure based on output pressure according to:Plot 380 depicts determining the normalized pressure based on a minimum pressure of the battery according to:Plot 385 depicts determining the normalized pressure based on the maximum pressure of the battery according to:FIG. 4 illustrates an example of a process that may be performed according to various embodiments. The method 400 of FIG. 4 may be performed by any suitable device or combination of devices, for example, a processor of the battery management system 250 executing computer readable instructions stored in a memory of the battery management system 250.In this example, the process 400 includes receiving measurement signals for a lithium-based battery at 410. In some embodiments, the measurement signals may include one or more of: a voltage measurement, a current measurement, and a temperature measurement. The system 250 may further determine or estimate a state of charge (SOC) measurement and a lithium density measurement.The process 400 further includes, at 420, determining a normalized pressure of the lithium-based battery based on the received and determined measurements. The process 400 further includes, at 430, generating a pressure measurement for the lithium-based battery. In some embodiments, the pressure measurement is generated based on the normalized pressure and an initial pressure value associated with the lithium-based battery. In alternative embodiments, as illustrated above in FIG. 3C, the pressure measurement may be generated based on the normalized pressure, in conjunction with one or more of: a maximum pressure of the lithium-based battery, a minimum pressure of the lithium-based battery, and a pressure of the lithium-based battery associated with a particular SOC value.The process 400 further includes, at 440, adjusting or maintaining a compression level applied to the lithium-based battery based on the generated pressure measurement. In some embodiments, the BMS 250 may generate and communicate a warning to a user of the vehicle 100 or other device if the generated pressure measurement is above a predetermined threshold.The terms "a" and "an" do not mean a quantity limitation, but rather denote the presence of at least one of the stated objects. The term "or" means "and / or" unless the context clearly indicates otherwise. Throughout the specification, when "an aspect" is mentioned, it means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the aspect is included in at least one of the aspects 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 may be directly on the other element or intervening elements may also be present. In contrast, there are no intervening elements when an element is referred to as being "directly on" another element.Unless otherwise specified herein, all testing standards are the latest standard in effect on the filing date of this application or, if a priority is claimed, the filing date of the earliest priority application in which the testing standard appears.Unless otherwise defined, the 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 pertains.Although the foregoing disclosure has been described with reference to exemplary embodiments, it will be known to those skilled in the art that various changes may be made and equivalent elements may be substituted without departing from the scope thereof. In addition, many changes may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, the present disclosure is not intended to be limited to the particular embodiments disclosed, but to include all embodiments falling within its scope.

Claims

A battery management system, comprising: a processor; and memory coupled to the processor and storing instructions that, when executed by the processor, cause the battery management system to: receive measurement signals from a lithium-based battery, the measurement signals comprising: a voltage measurement, a current measurement, and a temperature measurement; determine, based on the received measurement signals, a normalized pressure of the lithium-based battery; generate a pressure measurement for the lithium-based battery based on the normalized pressure and an initial pressure value associated with the lithium-based battery; and adjust or maintain a compression level applied to the lithium-based battery based on the generated pressure measurement.The battery management system of claim 1, wherein the determining of the normalized pressure of the lithium-based battery is performed without a pressure measurement for the lithium-based battery from a pressure sensor.The battery management system of claim 1, wherein determining the normalized pressure for the lithium-based battery is further based on a state of charge (SOC) measurement and a lithium density measurement.The battery management system of claim 3, wherein the lithium density measurement is associated with a lithium surface density at an anode of the lithium-based battery.The battery management system of claim 3, wherein the SOC measurement is associated with a change in an estimated pressure of the lithium-based battery over a predetermined period of time.The battery management system of claim 1, wherein the measurement signals are received from a plurality of sensors coupled to the lithium-based battery.The battery management system of claim 1, wherein the measurement signals reflect measurements for the lithium-based battery taken in real-time or near real-time.The battery management system of claim 1, wherein generating the pressure measurement for the lithium-based battery is based on the normalized pressure and the initial pressure value associated with the lithium-based battery, further based on one or more of: a maximum pressure of the lithium-based battery, a minimum pressure of the lithium-based battery, and a pressure of the lithium-based battery associated with a particular SOC value.A propulsion system for a vehicle, comprising: an electric motor; a lithium-based battery coupled to the electric motor; and a battery management system coupled to the lithium-based battery, and comprising: a processor; and memory coupled to the processor and storing instructions that, when executed by the processor, cause the battery management system to: receive measurement signals from a lithium-based battery, the measurement signals comprising: a voltage measurement, a current measurement, and a temperature measurement; determine, based on the received measurement signals, a normalized pressure of the lithium-based battery; generate a pressure measurement for the lithium-based battery based on the normalized pressure and an initial pressure value associated with the lithium-based battery; adjusting or maintaining a compression level applied to the lithium-based battery based on the generated pressure measurement.The propulsion system of claim 9, wherein the determining of the normalized pressure of the lithium-based battery is performed without a pressure measurement for the lithium-based battery from a pressure sensor.

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