Early detection of battery cell performance degradation

Abstract

Aspects of the present disclosure include detecting battery cell degradation. An exemplary battery management system may include a memory, computer readable instructions, and one or more processors to perform operations including: in response to determining that a state of charge has been completed, measuring a first cell voltage of a cell of a battery pack; in response to the first cell voltage exceeding the reference voltage, measuring a second cell voltage of a cell of the battery pack; in response to a second cell voltage being equal to the reference voltage, measuring a cell pressure of a cell of the battery pack at the reference voltage; determining a difference between the cell pressure and a previous cell pressure at the reference voltage; and in response to a difference between the cell pressure and a previous cell pressure exceeding a threshold, identifying the cell of the battery pack as a degraded cell.

Description

Technical Field

[0001] The subject disclosure relates to battery cell technology, and in particular to early detection of battery cell performance degradation. Background Art

[0002] High voltage electrical systems are increasingly used to power onboard functions of mobile and stationary systems. For example, in motor vehicles, the need to increase fuel economy and reduce emissions has led to the development of advanced electric vehicles (EVs). EVs rely on a rechargeable energy storage system (RESS), which typically includes one or more high voltage battery packs and an electric drive train for delivering power from the batteries to the wheels. The battery pack may include any number of interconnected battery modules, depending on the power requirements of a given application. Each battery module includes a collection of conductively coupled electrochemical cells. The battery pack is configured to provide a direct current (DC) output voltage at a level suitable for powering a coupled electrical and / or mechanical load (e.g., an electric motor).

[0003] The capacity of a battery pack can be increased by increasing the number of modules and / or cells in the battery pack, and by increasing the number of parallel core-rolls, the number of electrode layers, and the electrode surface area within each cell of the battery pack. The cell chemistry also affects the total capacity. Two common battery chemistries are nickel-cobalt-manganese (NCM) batteries and lithium iron phosphate (LFP) batteries. Summary of the invention

[0004] In an exemplary embodiment, a vehicle includes an electric motor, a battery pack electrically coupled to the electric motor, and a battery management system coupled to the battery pack. The battery management system includes a memory, computer-readable instructions, and one or more processors for executing the computer-readable instructions. The computer-readable instructions control the one or more processors to perform operations. The operations include detecting a state of charge of the battery pack, and in response to determining that the state of charge has been completed, measuring a first cell voltage of a battery cell of the battery pack. The operations also include measuring a second cell voltage of a battery cell of the battery pack in response to the first cell voltage exceeding a reference voltage, and measuring a cell pressure of a battery cell of the battery pack at a reference voltage in response to the second cell voltage being equal to the reference voltage. Determine a difference between the cell pressure and a previous cell pressure at a reference voltage, and in response to the difference between the cell pressure and the previous cell pressure exceeding a threshold, identify a battery cell of the battery pack as a degraded cell.

[0005]

[0013] In addition to one or more of the features described herein, in some embodiments, in response to determining that the charging state has been completed, a charging counter is incremented.

[0006] In some embodiments, a cell degradation warning is issued in response to identifying a cell of the battery pack as a degraded cell.

[0007] In some embodiments, in response to identifying a battery cell of the battery pack as a degraded battery cell, cell balancing is performed to equalize a state of charge among the plurality of battery cells of the battery pack.

[0008] In some embodiments, in response to identifying a battery cell of a battery pack as a degraded battery cell, current entering or leaving the battery cell is limited during a charging or discharging process.

[0009] In some embodiments, in response to identifying a battery cell of a battery pack as a degraded battery cell, a charge or discharge current is adjusted to maintain a target temperature condition in the battery cell.

[0010] In some embodiments, the battery cell is isolated by electrically disconnecting the battery cell from the battery pack in response to identifying the battery cell of the battery pack as a degraded battery cell.

[0011] In another exemplary embodiment, a battery management system may include a memory, computer-readable instructions, and one or more processors for executing the computer-readable instructions. The computer-readable instructions control the one or more processors to perform operations. The operations include detecting a state of charge of a battery pack, and in response to determining that the state of charge has been completed, measuring a first cell voltage of a battery cell of the battery pack. The operations also include measuring a second cell voltage of a battery cell of the battery pack in response to the first cell voltage exceeding a reference voltage, and measuring a cell pressure of a battery cell of the battery pack at a reference voltage in response to the second cell voltage being equal to the reference voltage. Determine a difference between a cell pressure and a previous cell pressure at a reference voltage, and in response to the difference between the cell pressure and the previous cell pressure exceeding a threshold, identify a cell of the battery pack as a degraded cell.

[0012] In yet another exemplary embodiment, a method for detecting battery cell degradation may include detecting a state of charge of a battery pack, and in response to determining that the state of charge has been completed, measuring a first battery cell voltage of a battery cell of the battery pack, measuring a second battery cell voltage of a battery cell of the battery pack in response to the first battery cell voltage exceeding a reference voltage, and measuring a battery cell pressure of the battery cell of the battery pack at a reference voltage in response to the second battery cell voltage being equal to the reference voltage, determining a difference between the battery cell pressure and a previous battery cell pressure at the reference voltage, and identifying a battery cell of the battery pack as a degraded battery cell in response to the difference between the battery cell pressure and the previous battery cell pressure exceeding a threshold.

[0013] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features, advantages and details appear, by way of example only, in the following detailed description, which refers to the accompanying drawings, in which:

[0015] Figure 1 is a vehicle configured according to one or more embodiments;

[0016] Figure 2 is a graph depicting a relationship between battery cell pressure and battery cell voltage across a plurality of charge-discharge cycles according to one or more embodiments;

[0017] Figure 3 is a graph depicting an exemplary battery cell pressure-cycle curve and an exemplary capacity-cycle curve according to one or more embodiments;

[0018] Figure 4 is a graph depicting an example delta battery cell pressure-cycle curve over the progression of a charge-discharge cycle according to one or more embodiments;

[0019] Figure 5 is a process workflow for detecting battery cell degradation according to one or more embodiments;

[0020] Figure 6 is a computer system according to one or more embodiments; and

[0021] Figure 7 is a flow chart according to one or more embodiments. DETAILED DESCRIPTION

[0022] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or use. It should be understood that throughout the drawings, corresponding reference numerals represent identical or corresponding components and features. As used herein, the term module refers to a processing circuit, which may include an application specific integrated circuit (ASIC), an electronic circuit, a (shared, dedicated or group) processor 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.

[0023] As mentioned earlier, two common battery chemistries are nickel-cobalt-manganese (NCM) batteries and lithium iron phosphate (LFP) batteries. While NCM and LFP batteries offer reasonable energy density and charge / discharge profiles, other battery chemistries, including lithium metal batteries (LMBs), are being pursued as next-generation battery solutions.

[0024] The main difference between lithium metal batteries and lithium ion batteries (e.g., LFP batteries) lies in the composition and behavior of their respective anodes (negative electrodes). Lithium metal batteries use metallic lithium as the anode material. During charging, lithium ions from the cathode (positive electrode) are deposited onto the lithium metal anode, forming a metallic lithium layer. This deposition process is known as lithium plating. During discharge, lithium ions are released from the anode and travel through the electrolyte to the cathode, thereby generating an electric current.

[0025] Lithium metal batteries offer several advantages over NCM and LFP batteries. For example, lithium metal batteries have the potential for relatively higher energy density than NCM and LFP batteries because the use of metallic lithium as the anode material allows for a higher theoretical specific capacity. In short, more energy can be stored per unit weight or volume in a lithium metal battery. Another advantage is the lower self-discharge rate. This means that lithium metal batteries can hold their charge for longer durations when not in use, making them more suitable for applications that require long-term storage. Yet another advantage is the potential for faster charging capabilities. The deposition of metallic lithium during charging can occur at a high speed, enabling fast charging rates and reduced charging times compared to NCM and LFP batteries.

[0026] Lithium metal batteries experience significant volume changes (including swelling and shrinkage) during charge and discharge due to the hostless deposition and dissolution of lithium. During the charging process, lithium ions are deposited as lithium metal on the anode, causing the electrode to swell. This reversible expansion is a natural part of the operation of lithium metal batteries and is known as the lithium plating process. During discharge, lithium dissolves back into the electrolyte, causing the electrodes to shrink. These volume changes can cause mechanical stresses within the battery cell, which can lead to electrode damage, loss of electrical connectivity, and ultimately a reduction in overall battery cell performance.

[0027] In addition to reversible expansion / contraction, lithium metal batteries also experience an irreversible cell swelling component as they age. Over time, repeated cycles of lithium deposition and dissolution can lead to electrode degradation, resulting in the formation of a solid electrolyte interface (SEI) layer and other irreversible structural changes. These irreversible swelling phenomena are mainly caused by the gradual accumulation of side reactions, permanent dendrite formation, and the growth of lithium metal deposits in non-uniform patterns.

[0028] The reversible swelling and shrinkage and irreversible expansion of lithium metal batteries present several challenges in battery pack design. For example, the design should be able to accommodate the increased volume of lithium metal batteries within the limited space of the battery pack. In addition, the growth of lithium metal deposits during cycling can lead to the formation of dendrites, needle-like structures that can penetrate the separator between electrodes and cause short circuits within the battery cell. These short circuits can lead to thermal runaway, in which the battery generates excessive heat, resulting in the release of electrolyte and gas.

[0029] The present disclosure introduces a battery management system that utilizes cell pressure progression as an indicator of cell degradation. Cell pressure progression can be a good indicator of battery degradation in lithium-based batteries and other batteries that require high pressure (e.g., greater than 1,000 kPa) for normal operation, because it has been found that cell pressure progression exhibits two continuous behaviors in these batteries. Initially, the cell pressure increases linearly while the coulombic efficiency and cell capacity remain constant. This "linear" regime persists during the initial life of the battery (i.e., from the first cycle to the nth cycle), after which the cell pressure behavior transitions to an "exponential" regime. During the exponential regime, the cell pressure increases exponentially between cycles, and the coulombic efficiency drops significantly. Without wishing to be bound by theory, it should be understood that when lithium-based or other high-voltage batteries degrade beyond a certain level, particularly after a threshold level of delta-irreversibility, a transition from linear to exponential behavior occurs. In some embodiments, the battery management system detects the transition from linear behavior to exponential behavior by monitoring the point at which the cell pressure at a given voltage begins to deviate from a linear relationship. In some embodiments, battery degradation is inferred when the difference between the battery cell pressures measured between consecutive cycles begins to increase significantly (ie, exceeds the norm of the previous cycle).

[0030] Detecting cell degradation in accordance with one or more embodiments provides several technical advantages over other battery management systems. Notably, a rapid increase in the difference between cell pressures measured at the same cell voltage in consecutive cycles serves as an early indicator of cell degradation, typically operating several cycles before Coulombic efficiency degradation. Thus, the battery management system described herein can utilize cell pressure progression to identify and mitigate faulty cells in a more responsive manner than existing platforms alone.

[0031] According to an exemplary embodiment, the vehicle Figure 11. The vehicle 100 is shown generally at 100. The vehicle 100 is shown in the form of an automobile having a body 102. The body 102 includes a passenger compartment 104, within which a steering wheel, front seats, and rear passenger seats (not shown separately) are arranged. A plurality of components are arranged within the body 102, including, for example, an electric motor 106 (shown by a protrusion under the front hood). The electric motor 106 is shown only for ease of illustration and discussion. It should be understood that the configuration, location, size, arrangement, etc. of the electric motor 106 are not meant to be particularly limited, and all such configurations (including multi-motor configurations) are within the intended scope of the present disclosure.

[0032] The electric motor 106 is powered via a battery pack 108 (shown by a protrusion near the rear of the vehicle 100). The battery pack 108 is shown for ease of illustration and discussion only. It should be understood that the configuration, location, size, arrangement, etc. of the battery pack 108 is not meant to be particularly limited, and all such configurations (including separate configurations) are within the intended scope of the present disclosure. In addition, while the present disclosure is primarily discussed in the context of a battery pack 108 configured for an electric motor 106 of the vehicle 100, the aspects described herein may be similarly incorporated within any system (vehicle, building, or other) having an energy storage system (e.g., one or more battery packs), and all such configurations and applications are within the intended scope of the present disclosure.

[0033] As will be described in detail herein, the battery pack 108 is monitored and controlled via a battery management system 110 (shown by a protrusion near the battery pack 108). Although the battery management system 110 may be included in, for example, a battery pack of an electric vehicle (e.g., the battery pack 108 of the vehicle 100), other energy storage applications (for vehicles, structures, or otherwise) are within the contemplated scope of the present disclosure.

[0034] In some embodiments, the battery management system 110 is configured to operate over multiple charge-discharge cycles (see Figure 2 ) monitors the battery cell pressure as a function of the battery cell voltage. The battery cell pressure may be measured using, for example, (one or more) pressure sensors (not shown separately) of the battery management system 110. Alternatively, the battery cell pressure may be measured using an upstream system, for example, using an onboard electronic control unit (ECU, not shown separately) configured to provide battery cell pressure measurements to the battery management system 110. In other embodiments, the battery cell pressure may be estimated. For example, a physics-based or data-driven empirical model may be used to estimate the battery cell pressure, but other techniques for battery cell pressure estimation are also within the intended scope of the present disclosure.

[0035] Figure 2A graph 200 depicting the relationship between battery cell pressure and battery cell voltage across a plurality of charge-discharge cycles 202 is shown in accordance with one or more embodiments. Figure 2 As shown, the cell pressure (here, measured in kPa) increases relatively slowly while progressing from an initial cell voltage of approximately 2.5 volts to an intermediate cell voltage of approximately 3.4 volts. This relatively stable region is sometimes referred to as a high hysteresis region 204 .

[0036] like Figure 2 As further shown in , further increases in the battery cell voltage beyond the high hysteresis region 204 result in a faster battery cell pressure response. It is observed that between about 3.7 and about 3.9 volts, the battery cell pressure increases rapidly, but slightly linearly. This region may be referred to as the measurement region 206. In some embodiments, the battery management system 110 is configured to measure, poll, or otherwise receive battery cell pressure measurements within the measurement region 206. In some embodiments, the battery management system 110 is configured to measure, poll, or otherwise receive battery cell pressure measurements at the same reference voltage across multiple charge-discharge cycles 202. In some embodiments, the reference voltage is 3.7, 3.8, or 3.9 volts, but other reference voltages (including reference voltages outside the measurement region 206) are also within the intended scope of the present disclosure.

[0037] In some embodiments, the battery management system 110 is configured to perform cell pressure measurements at a single (e.g., 3.7 volt) reference voltage across multiple charge-discharge cycles 202. In some embodiments, the battery management system 110 is configured to perform cell pressure measurements at two or more reference voltages (e.g., 2.9 volts and 3.9 volts) across multiple charge-discharge cycles 202. In some embodiments, the battery management system 110 is configured to perform cell pressure measurements at (one or more) reference voltages when charging during one or more charge-discharge cycles 202. For example, a cell pressure measurement may be performed when the cell voltage increases (due to charging) to 3.7 volts. In some embodiments, the battery management system 110 is configured to perform cell pressure measurements at (one or more) reference voltages when discharging during one or more charge-discharge cycles 202. For example, a cell pressure measurement may be performed when the cell voltage decreases (due to driving) to 3.7 volts.

[0038] The charge-discharge cycles 202 may include a first (initial) cycle 208 and a last (most recent) cycle 210. It is observed that the battery cell pressure obtained at the same (reference) voltage increases along the progression between the first cycle 208 and the last cycle 210. For example, the battery cell pressure at 3.7 volts for the first cycle 208 is approximately 1425 kPa, while the battery cell pressure at 3.7 volts for the last cycle 210 is approximately 1810 kPa. This relationship holds true both within the high hysteresis region 204 and the measurement region 206. It is further observed that the gap (Δ) in the battery cell pressure obtained at the same voltage between consecutive cycles is relatively small over the initial group of charge-discharge cycles 202, but increases rapidly as the charge-discharge cycles 202 approach the last cycle 210. About Figure 3 and Figure 4 This behavior in the gap (Δ) in the cell pressure progression is discussed in more detail.

[0039] Figure 3 A graph 300 depicting an example battery cell pressure-cycle curve 302 and an example capacity-cycle curve 304 according to one or more embodiments is shown. In some embodiments, the battery cell pressure-cycle curve 302 is constructed by taking a battery cell pressure measurement at each cycle at the same reference voltage (reference voltage). Figure 2 ). Similarly, in some embodiments, the capacity-cycle curve 304 is constructed by measuring the coulombic efficiency (capacity) of each cycle at the same reference voltage. In some embodiments, the reference voltage is 3.7 volts. The battery cell pressure-cycle curve 302 and the capacity-cycle curve 304 are merely illustrative and will vary for a given application.

[0040] like Figure 3 As shown in the battery cell pressure-cycle curve 302, during 20 charge-discharge cycles, the battery cell pressure increases linearly from an initial battery cell pressure of approximately 1425 kPa to an intermediate battery cell pressure of approximately 1625 kPa. In some embodiments, the battery management system 110 fits a linear regression 306 to the battery cell pressure data. In some embodiments, an upper threshold 308 and a lower threshold 310 can be constructed from the linear regression 306. For example, the upper threshold 308 and the lower threshold 310 can represent a percentage deviation from the linear regression 306 of ±5, 10, 20, 25, 50, 100, etc. Equation (1) describes the relatively constant linear cycle-to-cycle increase in battery cell pressure due to irreversible expansion (i.e., the linear regression 306):

[0041] Δ CP =K ± ε (1)

[0042] where Δ CPis the change in cell pressure between two cycles, K is a constant (e.g., the slope of the linear increase), and ε represents the noise (e.g., the random deviation of the cell pressure measurements between cycles). The noise ε represents the limit of the equipment and measurement accuracy and can vary, for example, between 0.1% and 5%. Observe that in Figure 3 In the example, K is 10.6, although K will vary with the application.

[0043] The change in cell pressure (Δ CP , also called "CP"):

[0044]

[0045] where Pr(.) is the pressure measured at a reference voltage, and N>M (i.e., N is the current cycle and M is the previous cycle).

[0046] In some embodiments, the battery management system 110 compares the measured cell pressure at each cycle to the upper threshold 308, the lower threshold 310, and / or the linear regression 306. In some embodiments, the battery management system 110 identifies a cell pressure transition cycle 312 (here, the 21st cycle) where the cell pressure exceeds the upper threshold 308. In some embodiments, the battery management system 110 identifies a transition from a linear cell pressure progression to an exponential cell pressure progression at the cell pressure transition cycle 312. In some embodiments, the battery management system 110 identifies a cell degradation condition at the cell pressure transition cycle 312. In some embodiments, the battery management system 110 identifies a fault condition where the cell pressure drops below the lower threshold 310 (indicating, for example, a punctured cell and / or pressure release).

[0047] like Figure 3 As shown in the capacity cycle curve 304, (for example, Figure 1 The battery capacity of the battery pack 108 is relatively stable (within 5%) until the capacity transition cycle 314 (here, the 22nd cycle). It is observed that the capacity transition cycle 314 occurs after the battery cell pressure transition cycle 312.

[0048] Figure 4 Graph 400 depicting an exemplary ΔCP cycle curve 402 over the progression of a charge-discharge cycle 202 is shown according to one or more embodiments. Figure 4 As shown, the change in battery cell pressure (Cp) between cycles remains below a critical battery cell pressure threshold of about 25 kPa. The critical battery cell pressure threshold may be referred to as a critical ΔCP (or, as shown, Δ C), and may vary depending on the application. In some embodiments, Δ C .

[0049] In some embodiments, the battery management system 110 compares the change (Δ) in the battery cell pressure data between cycles with Δ C In some embodiments, when the change (Δ) of the battery cell pressure data exceeds Δ C When the battery management system 110 identifies the battery cell degradation condition. For example, the battery management system 110 may identify the battery cell degradation condition at cycle 21.

[0050] Figure 5 A process workflow 500 for detecting battery cell degradation according to one or more embodiments is shown. The workflow 500 may be performed using, for example, the battery management system 110 of the vehicle 100 (see FIG. Figure 1 ) is executed. The workflow 500 begins at step 502, where battery cell pressure monitoring is initialized (eg, cycle N=1) and various thresholds are set, including, for example, Δ CP , Δ C and the reference battery cell voltage (V REF , also known as V MONITOR ).

[0051] At step 504 , the battery management system 110 determines whether the vehicle 100 is being charged. If the vehicle 100 is being charged (ie, yes), the battery management system 110 proceeds to step 506 . If the vehicle 100 is not being charged (ie, no), the battery management system 110 proceeds to step 508 .

[0052] At step 506, the battery management system 110 determines whether charging is complete after a predetermined delay. If the vehicle 100 is still charging (ie, no), the battery management system 110 returns to step 504 and rechecks the charging conditions after a predetermined delay. If the vehicle 100 is no longer charging (ie, yes), the battery management system 110 proceeds to step 510.

[0053] At step 510 , the charge counter is incremented (eg, N=N+1), and the battery management system 110 proceeds to step 508 .

[0054] At step 508, the battery management system 110 generates (or receives) a battery cell voltage measurement value V CURRENT (Also known as V DISCHARGING ).

[0055] At step 512, the battery management system 110 checks whether V CURRENT ≥V REF If VCURRENT <V REF (ie, no), the battery management system 110 may indicate that the battery cell voltage was not raised above V during the last charging cycle. REF This may indicate, for example, an incomplete and / or partial recharging operation. In some embodiments, the process may return to step 504 and the battery management system 110 may resume monitoring the charging state. CURRENT ≥V REF (ie, yes), the battery management system 110 may instruct to keep the battery cell voltage above V during the last charging cycle. REF , and the process can proceed to step 514.

[0056] At step 514, the battery management system 110 periodically checks whether V CURRENT =V REF If V CURRENT >V REF (ie, no), the battery management system 110 may indicate that the battery has not been sufficiently discharged to make a battery cell pressure measurement. In some embodiments, the process may return to step 512 and the battery management system 110 may resume monitoring the battery cell voltage. If V CURRENT =V REF (ie, yes), the battery management system 110 may proceed to step 516 .

[0057] At step 516, the battery management system 110 measures and / or otherwise records a snapshot of the battery cell pressure for the current cycle N (ie, Pr(V REF )N). In some embodiments, the battery management system 110 proceeds to step 518 after making, retrieving and / or recording the battery cell pressure measurements.

[0058] In step 518, the battery cell pressure (Δ CP )| N In some embodiments, the battery management system 110 proceeds to step 520 after calculating the change in battery cell pressure.

[0059] At step 520 , the battery management system 110 checks whether Δ CP >Δ C If Δ CP <Δ C (ie, no), the battery management system 110 may indicate that the change in cell pressure between cycles remains below the critical cell pressure threshold, and the process may return to step 504. CP >Δ C(ie, yes), the battery management system 110 may indicate that the change in cell pressure between cycles has exceeded the critical cell pressure threshold, and the process may proceed to step 522 .

[0060] In some embodiments, at block 522, the battery management system 110 indicates that the corresponding battery cell has degraded. In some embodiments, upon detecting battery cell degradation in one or more battery cells of the battery pack, the battery management system 110 may take one or more of a number of actions to mitigate the problem and ensure safe and optimal operation of the battery pack.

[0061] Warnings / Alarms: In some embodiments, the battery management system 110 issues battery cell degradation warnings to a user of the vehicle and / or to an internal system (eg, ECU) of the vehicle.

[0062] Cell Balancing: In some embodiments, the battery management system 110 can initiate cell balancing to equalize the state of charge (SOC) between the battery cells in the battery pack. Cell balancing can minimize cell-to-cell performance variations and can mitigate the effects of cell degradation in individual battery cells. In some embodiments, cell balancing involves redistributing energy and / or charge between the battery cells in the battery pack to achieve a more uniform SOC.

[0063] Current Limiting: In some embodiments, if a particular battery cell is showing signs of degradation, the battery management system 110 can limit the current entering or leaving the corresponding battery cell during the charging and / or discharging process. The current can be limited, for example, between an upper threshold and a lower threshold (i.e., between 15% and 85%, etc.). By limiting the current, the battery management system 110 can reduce the stress on the degraded battery cell and can minimize the rate of further battery cell degradation.

[0064] Temperature Management: In some embodiments, the battery management system 110 can actively monitor and / or control the temperature of the battery pack. In some embodiments, the battery management system 110 can adjust the charge and / or discharge current and / or can activate a passive or active cooling system to maintain target temperature conditions in the corresponding battery cells.

[0065] Fault Isolation and Battery Replacement: In some embodiments, the battery management system 110 can isolate a faulty battery cell by electrically disconnecting the battery cell from the system and / or battery pack. In some embodiments, the battery management system 110 can initiate a battery cell replacement process by identifying a degraded battery cell for replacement and / or by replacing the battery cell with a new (spare) battery cell.

[0066] System Shutdown: In some embodiments, the battery management system 110 may initiate an automatic shutdown and / or limit the operation of the battery pack in response to identification of battery cell degradation. In some embodiments, the battery management system 110 may request another system (e.g., an ECU) to initiate an automatic shutdown in response to identification of battery cell degradation.

[0067] Figure 6 600 that can perform various aspects of the embodiments described herein. In some embodiments, the computer system 600 can be used as a system (e.g., Figure 1 The battery management system 110 of the embodiment is incorporated into the battery pack (e.g., Figure 1 108) within or with a battery pack (e.g., Figure 1 In some embodiments, the computer system 600 may be configured to receive signals (eg, battery cell pressure signals, battery cell voltage signals, charge status signals, temperature signals, etc.) from one or more battery cells of the battery pack.

[0068] The computer system 600 includes at least one processing device 602, which typically includes one or more processors for performing various functions, such as controlling an electric motor (e.g., Figure 1 The electric motor 106 of the vehicle (e.g., vehicle 100) controls the power delivery of one or more batteries (e.g., Figure 1 The computer system 600 may also include the logic required to detect battery cell degradation and take appropriate action based on this data (see Figure 5 ).

[0069] Components of computer system 600 include a processing device 602 (such as one or more processors or processing units), a system memory 604, and a bus 606 that couples various system components including system memory 604 to processing device 602. System memory 604 may include various computer system readable media. Such media may be any available media that can be accessed by processing device 602, and includes both volatile and nonvolatile media and removable and non-removable media.

[0070] For example, system memory 604 includes non-volatile memory 608, such as a hard drive, and may also include volatile memory 610, such as random access memory (RAM) and / or cache memory. Computer system 600 may also include other removable / non-removable, volatile / non-volatile computer system storage media.

[0071] The system memory 604 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments described herein. For example, the system memory 604 stores various program modules that generally perform the functions and / or methods of the embodiments described herein. One or more modules 612, 614 may be included to perform functions related to the monitoring and / or control of the battery pack 108, for example, determining one or more current battery cell temperatures, the current state of charge of the battery pack 108 and / or any battery cell of the battery pack 108, the charging duration, the charging current and / or voltage, etc. The computer system 600 is not limited thereto, as other modules may be included depending on the desired functionality of the vehicle 100. As used herein, the term "module" refers to a processing circuit, which may include an application specific integrated circuit (ASIC), an electronic circuit, a (shared, dedicated or group) processor 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. For example, a module may be configured to stop charging and / or otherwise isolate one or more battery cells of the battery pack of the vehicle 100 via software, hardware, and / or firmware.

[0072] The processing device 602 may also be configured to communicate with one or more external devices 616, such as a keyboard, pointing device, and / or any device that enables the processing device 602 to communicate with one or more other computing devices (e.g., a network card, a modem, a vehicle ECU, etc.). Communication with various devices may occur via input / output (I / O) interfaces 618 and 620.

[0073] The processing device 602 may also communicate with one or more networks 622, such as a local area network (LAN), a general wide area network (WAN), a bus network, and / or a public network (e.g., the Internet) via a network adapter 624. In some embodiments, the network adapter 624 is or includes an optical network adapter for communicating over an optical network. It should be understood that, although not shown, other hardware and / or software components may be used in conjunction with the computer system 600. Examples include, but are not limited to, microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, and data archival storage systems, among others.

[0074] Reference now Figure 7 , generally shows a flowchart 700 for detecting battery cell degradation according to an embodiment. Figures 1 to 6 Flowchart 700 is described and may include Figure 7 Although depicted in a particular order, Figure 7 The blocks depicted in the drawings may be rearranged, subdivided, and / or combined.

[0075] At block 702, a charge state of a battery pack is detected. In some embodiments, the charge state indicates whether the battery pack is charging, at rest, or discharging.

[0076] At block 704, a first cell voltage of a battery cell of the battery pack is measured in response to determining that the state of charge has been completed. In some embodiments, in response to determining that the state of charge has been completed, a charge counter is incremented.

[0077] At block 706 , a second cell voltage of a battery cell of the battery pack is measured in response to the first cell voltage exceeding the reference voltage.

[0078] At block 708 , in response to the second cell voltage being equal to the reference voltage, a cell pressure of a battery cell of the battery pack is measured at the reference voltage.

[0079] At block 710 , a difference between a cell pressure and a previous cell pressure at a reference voltage is determined.

[0080] At block 712 , in response to a difference between the cell pressure and a previous cell pressure exceeding a threshold, a cell of the battery pack is identified as a degraded cell.

[0081] In some embodiments, in response to identifying a battery cell of the battery pack as a degraded battery cell, a battery cell degradation warning is issued.

[0082] In some embodiments, in response to identifying a battery cell of the battery pack as a degraded battery cell, cell balancing is performed to equalize the state of charge among the plurality of battery cells of the battery pack.

[0083] In some embodiments, in response to identifying a cell of a battery pack as a degraded cell, current entering and / or leaving the cell is limited during a charging and / or discharging process.

[0084] In some embodiments, in response to identifying a battery cell of the battery pack as a degraded battery cell, charging and / or discharging current is adjusted to maintain target temperature conditions in the battery cell and / or the battery pack.

[0085] In some embodiments, in response to identifying a battery cell of the battery pack as a degraded battery cell, the battery cell is isolated by electrically disconnecting the battery cell from the battery pack.

[0086] The terms "a" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced item. Unless the context clearly indicates otherwise, the term "or" means "and / or". References to "aspects" throughout the specification mean that a particular element (e.g., a feature, structure, step, or characteristic) described in conjunction with that aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it should be understood that the described elements may be combined in any suitable manner in the various aspects.

[0087] 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.

[0088] Unless stated to the contrary herein, all test standards are the most current standards 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 standards appear.

[0089] Unless defined otherwise, 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.

[0090] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A vehicle comprising: Electric motor; a battery pack electrically coupled to the electric motor; as well as A battery management system coupled to the battery pack, the battery management system comprising a memory, computer readable instructions, and one or more processors for executing the computer readable instructions, the computer readable instructions controlling the one or more processors to perform operations comprising: detecting a charging state of the battery pack; In response to determining that the charging state has been completed, measuring a first cell voltage of a battery cell of the battery pack; measuring a second battery cell voltage of a battery cell of the battery pack in response to the first battery cell voltage exceeding a reference voltage; In response to the second battery cell voltage being equal to the reference voltage, measuring a battery cell pressure of a battery cell of the battery pack at the reference voltage; determining a difference between the cell pressure and a previous cell pressure at the reference voltage; and In response to a difference between the cell pressure and the previous cell pressure exceeding a threshold, a cell of the battery pack is identified as a degraded cell. 2 . The vehicle of claim 1 , further comprising incrementing a charge counter in response to determining that the charging state has been completed. 3 . The vehicle of claim 1 , further comprising issuing a battery cell degradation warning in response to identifying a battery cell of the battery pack as a degraded battery cell. 4 . The vehicle of claim 1 , further comprising, in response to identifying a battery cell of the battery pack as a degraded battery cell, performing cell balancing to equalize states of charge among a plurality of battery cells of the battery pack. 5 . The vehicle of claim 1 , further comprising limiting current entering or leaving a battery cell of the battery pack during a charging or discharging process in response to identifying the battery cell as a degraded battery cell. 6 . The vehicle of claim 1 , further comprising, in response to identifying a battery cell of the battery pack as a degraded battery cell, adjusting a charge or discharge current to maintain a target temperature condition in the battery cell. 7 . The vehicle of claim 1 , further comprising isolating the battery cell of the battery pack by electrically disconnecting the battery cell from the battery pack in response to identifying the battery cell of the battery pack as a degraded battery cell.

8. A battery management system comprising a memory, computer readable instructions, and one or more processors for executing the computer readable instructions, wherein the computer readable instructions control the one or more processors to perform operations, the operations comprising: Detect the charging status of the battery pack; In response to determining that the charging state has been completed, measuring a first cell voltage of a battery cell of the battery pack; measuring a second battery cell voltage of a battery cell of the battery pack in response to the first battery cell voltage exceeding a reference voltage; In response to the second battery cell voltage being equal to the reference voltage, measuring a battery cell pressure of a battery cell of the battery pack at the reference voltage; determining a difference between the cell pressure and a previous cell pressure at the reference voltage; as well as In response to a difference between the cell pressure and the previous cell pressure exceeding a threshold, a cell of the battery pack is identified as a degraded cell.

9. The battery management system of claim 8, wherein the one or more processors perform operations further comprising: In response to determining that the charging state has been completed, a charging counter is incremented.

10. The battery management system of claim 8, wherein the one or more processors perform operations further comprising: In response to identifying a battery cell of the battery pack as a degraded battery cell, a battery cell degradation warning is issued.

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