Method and vehicle for internal short circuit detection

Abstract

A method includes operating a device with a rechargeable energy storage system (RESS) including parallel groups of cells with overcurrent protection elements by passing a current through the cells based on instructions provided by a processor; obtaining sensor data via sensors; determining, via the processor, whether a group of cells has a decreasing rate of change of resistance; if the group of cells has a decreasing rate of change of resistance, determining, via the processor, whether the group of cells has a sufficient voltage deviation to indicate an internal short circuit condition; if the group of cells does not, determining, via the processor, whether the group of cells has a voltage rate of change that is unrelated to current;and if the cell group has a voltage change rate that is unrelated to the current, inferring, via the processor, that an internal short circuit exists and modifying the operation of the device to prevent damage to the RESS;

Description

[0001] The technical field relates generally to rechargeable energy storage systems (RESS) and, more specifically, to methods and systems for detecting internal short circuits in cells within rechargeable energy storage systems.

[0002] Rechargeable energy storage systems, including lithium-ion and related batteries, are increasingly being used in various fields to generate, store, and distribute electrical energy more efficiently. In the automotive industry, rechargeable energy storage systems are used to complement conventional internal combustion engines in hybrid electric vehicles (HEVs) or to replace them in pure electric vehicles (EVs), i.e., battery electric vehicles (BEVs). The ability to passively store energy from stationary and portable sources, as well as from the kinetic energy recovered by the vehicle and its components, makes batteries an ideal component of a propulsion system for cars, trucks, buses, motorcycles, and similar vehicle platforms.In the present context, a cell is a single electrochemical unit, whereas a battery consists of one or more cells connected in series, parallel, or both, depending on the desired output voltage and capacity.

[0003] Temperature is one of the most important factors affecting both the performance and lifespan of a battery. Ambient temperatures (e.g., prolonged inactivity in cold or hot environments, or prolonged operation with associated heat generation on hot days) or abuse conditions (e.g., rapid charging / discharging or internal / external short circuits caused by physical deformation, cell penetration, or manufacturing defects) can negatively impact the battery's ability to operate properly, and in severe cases, the battery may be completely destroyed. Side effects of prolonged exposure to high temperatures include premature aging and accelerated capacity loss, both of which are undesirable.

[0004] Excess heat can be generated by an internal short circuit in a battery cell. An onset temperature is the temperature at which an exothermic reaction occurs. The heat required to sustain such an exothermic reaction is referred to as the latent heat of reaction, while a heat source that exceeds the initial temperature and maintains the latent heat of reaction represents a thermal event. Such thermal events, if left uncontrolled, can lead to accelerated heat generation, referred to herein as thermal runaway—a condition in which the cooling mechanism is no longer capable of bringing one or more battery components to a safe operating temperature (once initiated).In the present context, thermal runaway is a function of the self-heating rate of the exothermic reaction and the temperature, and the duration of the reaction is a function of the degradation rate and the mass of the active components participating in such a reaction. Of particular concern is the potential for excessive heating and consequent damage to a battery cell, group, pack, or related component used as a propulsion energy source.

[0005] US 2022 / 0 352 737 A1 describes a vehicle, a system, and a method for monitoring the occurrence of thermal runaway in a battery pack of the vehicle. The system includes a plurality of voltage sensors and a processor. The plurality of voltage sensors receive a plurality of voltage measurements at each of the plurality of battery cells of the battery pack. The processor is configured to determine an average based on the plurality of voltage measurements, compare a voltage measurement obtained from a selected battery cell to the average, and generate a notification signal when a difference between the voltage measurement from the selected battery cell and the average is greater than or equal to a predictive threshold.

[0006] DE 10 2023 110 299 A1 describes a vehicle comprising a system that performs a method for operating a battery pack of the vehicle. The system comprises one or more sensors and a processor. The one or more sensors determine a measured value of a battery parameter of the battery pack. The processor is configured to calculate an expected value of the battery parameter from a model of the battery pack, compare the measured value with the expected value to determine a blown fuse state of the battery pack, determine an available current from the battery pack based on the blown fuse state, and control an operating state of the vehicle based on the available current.

[0007] WO 2020 / 189 919 A1 describes a battery state estimation device according to an embodiment of the present invention, comprising: a voltage measuring unit that measures a voltage of a battery cell and measures an open-circuit voltage of the battery cell each time the measured voltage reaches a reference charging voltage; and a control unit configured to receive the open-circuit voltage measured by the voltage measuring unit, compare the received open-circuit voltage with a pre-stored reference voltage to calculate a voltage regulation, determine a voltage increase / decrease pattern based on the calculated voltage regulation and the pre-stored voltage regulation data, and determine a degree of deterioration acceleration of the battery cell according to the determined voltage increase / decrease pattern.

[0008] Accordingly, it is the object of the present invention to provide methods and systems with which internal short circuits in a cell group can be diagnosed as early as possible in order to provide mitigation before excess heat leads to thermal runaway.

[0009] The problem is solved by the subject matter of the independent claims.

[0010] Furthermore, other desirable features and characteristics of the present description will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing introduction.

[0011] According to the invention, a method comprises operating a device with a rechargeable energy storage system (RESS) that includes cells arranged in parallel in cell groups, each cell being provided with an overcurrent protection element by passing a current through the cells based on instructions provided by a processor; obtaining sensor data via one or more sensors of the device; determining, via the processor, whether a cell group has a decreasing rate of change in resistance; if the cell group has a decreasing rate of change in resistance, determining, via the processor, whether the cell group has a sufficient voltage deviation to indicate an internal short circuit condition;If the cell group does not exhibit a sufficient voltage variation to indicate an internal short-circuit condition, determining, via the processor, whether the cell group exhibits a voltage change rate that is unrelated to the current; and if the cell group exhibits a voltage change rate that is unrelated to the current, concluding, via the processor, that an internal short circuit exists and modifying the operation of the device to prevent damage to the RESS.

[0012] In certain embodiments, the method further comprises inferring, via the processor, that an internal short circuit exists and altering the operation of the device to prevent damage to the RESS when the cell group has a sufficient voltage deviation indicative of an internal short circuit condition.

[0013] In certain embodiments of the method, changing the operation of the device to prevent damage to the RESS includes cooling the RESS and / or discharging the RESS.

[0014] In certain embodiments, the method further comprises determining, via the processor, whether an overcurrent protection element in the cell group has opened if the cell group does not have a current-independent voltage change rate, and inferring, via the processor, that the overcurrent protection element has opened due to fatigue if an overcurrent protection element in the cell group has opened.

[0015] In certain embodiments, the method further comprises determining, via the processor, whether the cell group has an increasing rate of change of resistance if the cell group does not have a decreasing rate of change of resistance; determining, via the processor, whether an overcurrent protection element in the cell group has opened if the cell group has an increasing rate of change of resistance; and inferring, via the processor, that the overcurrent protection element has opened due to fatigue, and altering operation of the device if an overcurrent protection element in the cell group has opened.

[0016] In certain embodiments of the method, changing the operation of the device includes revising the RESS charge and discharge limits to prevent damage to the cell array and revising the RESS power estimates based on a reduced storage capability of the cell array.

[0017] In certain embodiments of the method, the device is a battery electric vehicle (BEV).

[0018] In certain embodiments of the method, the device is a hybrid electric vehicle (HEV).

[0019] Furthermore, a vehicle according to the invention comprises a rechargeable energy storage system (RESS) including cells arranged in parallel in cell groups, each cell being provided with an overcurrent protection element; sensors configured to receive sensor data regarding voltage, resistance, and / or capacitance of each cell group; a processor coupled to the sensors and configured to instruct the RESS to pass a current through the cells to power the vehicle; receive the sensor data from the sensors; perform an initial diagnosis of the sensor data to determine whether an internal short-circuit condition exists; and perform a secondary diagnosis of the sensor data to determine whether an internal short-circuit condition exists, wherein the secondary diagnosis takes into account sensor data behavior representative of an open overcurrent protection element.

[0020] In certain embodiments of the vehicle, the initial diagnosis includes determining whether the voltage of an affected cell group has a voltage drop greater than a threshold representative of the internal short circuit condition.

[0021] In certain embodiments of the vehicle, the secondary diagnosis includes determining whether the voltage of the affected cell group has an initial voltage drop representative of the internal short circuit condition before the voltage of the affected cell has a voltage increase indicative of the open overcurrent protection element.

[0022] In certain embodiments of the vehicle, the secondary diagnosis includes determining whether the voltage change rate of the affected cell group is unrelated to the current.

[0023] In certain embodiments of the vehicle, the processor is configured to perform a tertiary diagnosis of the sensor data to determine if an overcurrent protection element has opened; the tertiary diagnosis includes monitoring the capacitance of each cell group and determining that the capacitance of the cell group of the affected cell has decreased; and / or monitoring the resistance of each cell group and determining that the resistance of the cell group of the affected cell has increased; and the processor is configured to change limits and calculations for controlling operation of the vehicle to compensate for the RESS limited by the affected cell group with a decreased capacity if the tertiary diagnosis concludes that an overcurrent protection element has opened.

[0024] The present specification will now be described in conjunction with the following drawings, in which like numerals refer to like elements: Fig. 1 is a functional block diagram of a vehicle including a RESS and a control system for controlling it, among various other components, according to example implementations; Fig. Figure 2 is a schematic representation of the battery cells in cell groups in a part of the RESS of Fig. 1; Fig. Figure 3 is a graph showing a general voltage response for a cell group after a battery cell circuit opens in an application involving repeated discharging and charging of the RESS. Fig. Figure 4 is a graph showing a general voltage response for a cell group after a battery cell circuit opens in a constant charge RESS application. Fig. Figure 5 is a flowchart illustrating a method for controlling the operation of a RESS to determine whether an internal short circuit exists when an overcurrent protection element opens. Fig. Figure 6 is a graph showing the voltage change over time for a cell group with a cell that has an internal short circuit and an overcurrent protection element that has opened, compared to normally operating cell groups. Fig. Figure 7 is a flowchart illustrating a method for controlling the operation of a RESS to determine whether an internal short circuit exists when an overcurrent protection element opens. Fig. 8 is a flowchart illustrating a method for determining whether an overcurrent protection element in a RESS has opened based on cell group capacity. Fig. 9 is a flowchart illustrating a method for determining whether an overcurrent protection element in a RESS has opened based on cell group resistance. Fig. Figure 10 is a graph showing the general resistance response per increment for a cell group after opening a battery cell circuit.

[0025] Fig. 1 illustrates a vehicle 100 according to an exemplary implementation. As described in more detail below, the vehicle 100 includes, among other components, a rechargeable energy storage system (RESS) 101 and a control system 102. In various embodiments, the RESS 101 includes a plurality of cell groups 170, such as those described in Fig. 2 and are described in more detail below in connection therewith. In various embodiments, control system 102 controls RESS 101.

[0026] As in Fig. 1, the RESS 101 and the control system 102 are depicted as part of the vehicle 100 in accordance with example implementations. In various embodiments, the vehicle 100 comprises an automobile, such as any number of different types of automobiles, such as a sedan, a station wagon, a truck, a sport utility vehicle (SUV), or the like. In certain embodiments, the vehicle 100 may also comprise a motorcycle or other vehicle, such as an aircraft, a spacecraft, a watercraft, etc., and / or one or more other types of mobile platforms (e.g., a robot and / or other mobile platform). In other embodiments, the RESS 101 and the control system 102 may instead be part of and / or coupled to any number of other types of platforms and / or other systems that are moving or not moving, such asa building, an infrastructure, a secondary use, a domestic power generator, a non-car and / or other platforms and / or other systems.

[0027] In the illustrated embodiment, the vehicle 100 includes a body 104 disposed upon a chassis 116. The body 104 substantially encloses other components of the vehicle 100. The body 104 and the chassis 116 may together form a frame. The vehicle 100 also includes a plurality of wheels 112. The wheels 112 are each pivotally connected to the chassis 116 near a corner of the body 104 to facilitate movement of the vehicle 100. In one embodiment, the vehicle 100 includes four wheels 112, although this may vary in other embodiments (e.g., for trucks, motorcycles, and certain other vehicles).

[0028] Mounted on the chassis 116 is a drive system 110 that drives the wheels 112, for example, via axles 114. In certain embodiments, the drive system 110 includes a drive system with an electric motor 113. In various embodiments, the drive system 110, including the motor 113, receives high voltage from the RESS 101.

[0029] In various embodiments, the RESS 101 not only supplies the high voltage to the motor 113, but also low voltage to one or more low-voltage systems 111 of the vehicle 100. In various embodiments, the low-voltage systems 111 may include, for example, one or more climate control systems, radio systems, seat heating systems, etc.

[0030] As in Fig. 1, in various embodiments, the vehicle also includes a braking system 106 and a steering system 108. In example implementations, the braking system 106 controls braking of the vehicle 100 using braking components controlled via driver inputs (e.g., via a brake pedal) and / or automatically via a control system (such as the control system 102 and / or one or more other control systems). Also in example implementations, the steering system 108 controls the steering of the vehicle 100 via steering components controlled via driver inputs (e.g., via a steering wheel) and / or automatically via a control system (such as the control system 102 and / or one or more other control systems).

[0031] In the Fig. In the implementation illustrated in Figure 1, the control system 102 is coupled to the RESS 101, receives inputs from it, and controls its functionality. Furthermore, in certain implementations, the control system 102 is coupled to one or more of the braking systems 106, the steering system 108, the propulsion system 110, and / or the low-voltage systems 111, and in certain implementations, may also receive inputs from and / or control these additional systems.

[0032] As also in Fig. 1, the control system 102, in various embodiments, includes a sensor assembly 120 and a control module 140 (or control unit), as described in more detail below.

[0033] In various implementations, sensor array 120 includes various sensors that receive sensor data from vehicle 100 for use in controlling RESS 101 (among other functions). In the illustrated implementation, sensor array 120 includes one or more voltage sensors 130, current sensors 132, temperature sensors 134, state-of-charge sensors 136, brake sensors 137, and steering sensors 138.

[0034] In certain embodiments, voltage sensors 130 measure the voltage of the RESS 101, including the various cell groups 170. In certain embodiments, current sensors 132 measure the electrical current of the RESS 101, including the cell groups 170. In various implementations, temperature sensors 134 measure the temperature of the RESS 101, including the cell groups 170. In various embodiments, state of charge sensors 136 measure the state of charge of the RESS 101, including the cell groups 170. Additionally, in various implementations, brake sensors 137 measure one or more parameters of the brake system 106 (e.g., brake inputs, brake force, or the like), while steering sensors 138 measure one or more parameters of the steering system 108 (e.g., steering inputs, steering angle, or the like).

[0035] In various implementations, the control module 140 is coupled to the sensor assembly 120 and receives sensor data therefrom. In various embodiments, the control module 140 is also coupled to the RESS 101. Furthermore, in certain embodiments, the control module 140 may also be coupled to one or more other systems of the vehicle 100, such as the braking system 106, the steering system 108, the propulsion system 110, and / or low-voltage systems, for example, to receive inputs therefrom and / or to control them.

[0036] As in Fig. 1, in various embodiments, the control module 140 comprises a computer system and includes a processor 142, a memory 144, an interface 146, a storage device 148, and a computer bus 150.

[0037] Processor 142 performs the computation and control functions of control module 140 and may comprise any type of processor or multiple processors, individual integrated circuits such as a microprocessor, or any number of integrated devices and / or circuit boards that cooperate to perform the functions of a processing unit. During operation, processor 142 executes one or more programs 152 contained in memory 144 and, as such, controls the overall operation of control module 140 and the computer system of control module 140, generally in performing the processes described herein.

[0038] Memory 144 may be any suitable storage, including various types of non-transferable computer-readable storage media. In certain examples, memory 144 is located on and / or disposed on the same computer chip as processor 142. In the illustrated implementation, memory 144 stores the aforementioned program 152 along with stored values ​​157 (e.g., lookup tables, thresholds, and / or other values ​​related to controlling RESS 101).

[0039] The interface 146 enables communication with the computer system of the control module 140, e.g., from a system driver and / or another computer system, and can be implemented using any suitable method and device. In one implementation, the interface 146 receives the various data from the sensor assembly 120, among other possible data sources. The interface 146 can include one or more network interfaces for communicating with other systems or components. The interface 146 can also include one or more network interfaces for communicating with technicians and / or one or more storage interfaces for connecting to storage devices, such as the device 148.

[0040] The storage device 148 may be any suitable type of storage device, including various types of random access memory and / or other storage devices. In an exemplary implementation, the device 148 includes a program product from which the memory 144 may receive a program 152 that performs one or more implementations of one or more methods of the present description, such as the steps of the method 500 of Fig. 5, which is described further below in connection therewith. In another exemplary implementation, the program product may be stored and / or otherwise accessed directly in memory 144 and / or a disk (e.g., disk 156), as described below.

[0041] Bus 150 is used to transfer programs, data, status, and other information or signals between the various components of the computer system of control module 140. Bus 150 may be any suitable physical or logical means for connecting computer systems and components. These include, but are not limited to, direct, hard-wired connections, fiber optic, infrared, and wireless bus technologies. During operation, program 152 is stored in memory 144 and executed by processor 142.

[0042] While this example implementation is described in the context of a fully functional computer system, those skilled in the art will recognize that the mechanisms of the present description may be distributed as a program product having one or more types of non-transitory, computer-readable, signal-bearing media used to store the program and its instructions and to carry out its distribution, such as a non-transitory, computer-readable medium carrying the program and having computer instructions stored therein for causing a computer processor (such as processor 142) to execute and execute the program.

[0043] Fig. 2 is a functional diagram of a part of the RESS 101 of Fig. 1, comprising a plurality of cell groups 170 according to example implementations.

[0044] As in Fig. 2, in various embodiments, the RESS 101 includes a number of cell groups 170, such as the illustrated first cell group 170 and the second cell group 170B, etc., up to an "nth" cell group. In certain embodiments, the cell groups 170 are connected in series via a power bus 180. The cell groups may be electrically connected in series and / or parallel as illustrated. It will be appreciated that the number and configuration of the cell groups 170 may vary in different implementations, and the subject matter described herein is not limited to any particular number, type, or configuration of cell groups 170.

[0045] In certain embodiments, each cell group 170 may include one or more battery cells 200 or other energy storage elements electrically connected in parallel, as shown, to provide a desired DC voltage level and / or DC output current. While each cell group 170 is shown as five battery cells 200, the number of battery cells 200 per cell group 170 may be any suitable number desired.

[0046] As illustrated, each battery cell 200 is equipped with an overcurrent protection element 220. For example, each battery cell 200 may be provided with an internal overcurrent protection element 220. Alternatively, each battery cell 200 may be provided with an external overcurrent protection element 220. In various embodiments, the RESS 101 may include overcurrent protection elements 220 in the form of internal fuses, external fuses, fuse links or fusible links, fuse busbars, or other fuse cell interconnections. In certain embodiments, each battery cell 200 is equipped with its own overcurrent protection element 220.

[0047] The structure of the cell groups 170 and the battery cells 200 of Fig. 2, the opening of a circuit through a selected battery cell 201 by an overcurrent protection element 220 results in the known changes in electrical performance. For example, if a circuit of an individual battery cell 201 in cell group 171 is opened by the overcurrent protection element 220, the capacity of the affected cell group 171 decreases by 20% compared to normally operating cell groups 170. If a circuit of an individual battery cell 201 in cell group 171 is opened by the overcurrent protection element 220, the resistance of the affected cell group 171 increases by 25% compared to normally operating cell groups 170.

[0048] Fig. Figure 3 is a diagram showing a general voltage response for an affected cell group 171 after a circuit of a selected battery cell 201 has been opened by the overcurrent protection element 220. In Fig. 3, the voltage is plotted on the Y-axis and the time on the X-axis. In Fig. 3, the RESS 101 is repeatedly discharged and charged, as in typical hybrid electric vehicle (HEV) usage. As shown, the voltage 320 increases from low voltage troughs 322 to high voltage peaks 321 when charging the cell group 170, and decreases from high voltage peaks 321 to low voltage troughs 322 when discharging the cell group 170.

[0049] In Fig. 3, the overcurrent protection element 220 of a single battery cell 201 in the cell group 171 opens at time 330, reducing the cell group 171 to four operable battery cells 201. Thereafter, the voltage 340 fluctuates between higher voltage peaks 341 and lower voltage troughs 342 compared to a cell group 170 with five operable battery cells 201.

[0050] Fig. Figure 4 is another diagram showing a general voltage response for a cell group 171 after a circuit of a selected battery cell 201 has been opened by the overcurrent protection element 220. In Fig. 4, the voltage is plotted on the Y-axis and the time on the X-axis. In Fig. 4, the RESS 101 is continuously charged, such as during typical use by a battery electric vehicle (BEV). As shown, the voltage 420 increases at a constant rate as the cell group 171 is charged when the cell group 171 has five operable battery cells 200.

[0051] In Fig. 4, the overcurrent protection element 220 of a single battery cell 201 in the cell group 171 opens at time 330, reducing the cell group 171 to four operable battery cells 201. Thereafter, the voltage 440 increases more rapidly compared to a cell group 170 with five operable battery cells 201.

[0052] A cross-reference to the Fig. Figure 2-4 shows that when an internal short circuit occurs in a selected battery cell 201, the current to the parallel cells 200 in cell group 170 is drawn to the shorted cell 201, and the voltage of cell group 170 drops. Then, the overcurrent protection element 220 opens the circuit to the shorted cell 201 to prevent the internal short circuit from raising the temperature enough to cause thermal runaway.

[0053] When the overcurrent protection element 220 opens, the current for the cell group 171 intended for use with five battery cells 200 is now directed to the four remaining operable battery cells 200. As a result, the RESS 101 may experience control issues. For example, because the remaining operable battery cells 200 receive more current than planned, the probability of failure of the remaining operable battery cells 200 is greater, e.g., due to a cascade failure. If the circuit of a battery cell 201 opens, the affected cell group 171 may also be the performance-limiting factor of the RESS 101. Even if the remaining functional battery cells 200 in the affected cell group 170 do not fail, the affected cell group 171 will charge the fastest of the cell groups 170 in the RESS 101, as shown in Fig. 3 and Fig. 4, and the fastest of the cell groups 170 in the RESS 101 discharged, as shown in Fig. 3 and Fig. 4. Additionally, the battery cells 200 in the affected cell group 171 reach the upper and lower voltage limits most frequently and most quickly compared to the other cell groups 170 in the RESS 101. Such behavior may cause the control system 102 to attempt to protect the affected cell group 171. As a result, the device may exhibit poor performance. For example, a vehicle with a RESS 101 with an affected cell group 171 may experience poor drivability, receive poor range or remaining charge estimates, and / or receive poor charging time estimates.

[0054] The present embodiments protect the RESS 101 from damage while improving the performance of the RESS, e.g., after opening an overcurrent protection element 220.

[0055] A method 500 for operating a RESS, such as RESS 101, is described in Fig. 5. As shown, the method 500 may begin with start-up process 501. The method 500 includes, at process 510, diagnosing whether an overcurrent protection element in a cell group in the RESS has opened. Specifically, at query 511, the method 500 determines whether a cell group (CG) capacitance delta, i.e., a change in capacitance, exists. If there is a cell group capacitance change, then an overcurrent protection element has opened, and the method may continue with query 520. If there is no cell group capacitance change, process 510 continues with query 512, which determines whether a cell group (CG) capacitance delta, i.e., a change in cell group resistance, exists. If there is a change in cell group resistance, then an overcurrent protection element has opened, and the method may continue with query 520.If there is no change in cell group resistance, method 500 may restart with operation 501.

[0056] At query 520, method 500 determines whether an internal short circuit (ISC) has been diagnosed. For example, a voltage drop in a cell group can be detected and used to diagnose an internal short circuit condition. Query 520 can determine whether the voltage drop has reached the threshold.

[0057] In Fig. Figure 6 shows a general voltage diagram, with voltage on the Y-axis and time on the X-axis. Note that the voltage for each cell group may be relatively equal, but for clarity, they are shown at a certain distance from each other on the Y-axis. The diagram shows the voltage 610 of a selected cell group and the voltages 620 of the other cell groups. In the selected cell group, an internal short circuit occurs in one battery cell, after which an overcurrent protection element opens to protect the cell group. Specifically, the internal short circuit occurs at time 630, and the overcurrent protection element opens at time 640. As shown, starting at time 630, the voltage 610 decreases. At the same time, the voltages 620 do not decrease.Then, at time 640, the voltage 610 of the selected cell group rises rapidly to return to the previous level and then exhibits an increasing increase compared to the voltages 620. This behavior indicates an initial internal short circuit, indicated by the voltage drop between time 630 and time 640, as well as the opening of an overcurrent protection element, indicated by the increase in voltage after time 640.

[0058] As in Fig. 6, all voltages 620 of the other cell groups follow essentially the same contour. However, voltage 610 exhibits a dip, indicating an internal short circuit. Specifically, the internal short circuit pulls voltage 610 downward, and when the overcurrent protection element opens, the cell group voltage rises again. For a cell group with an open overcurrent protection element caused by fatigue or severe stress, the dip from time 630 to time 640 is not present. Rather, the cell group will exhibit a rising voltage relative to the other voltages 620, e.g., after time 650.

[0059] Back to Fig. 5: If an internal short circuit (ISC) condition is diagnosed at query 520, the method 500 may proceed to operation 530 and conclude that an internal short circuit has occurred. After determining that an internal short circuit has occurred, the method 500 may proceed to operation 540 by performing thermal runaway mitigation processes, for example, to prevent an increase in heat within the RESS. For example, operation 540 may include preventing the RESS from charging, discharging energy from the RESS, cooling the RESS, issuing appropriate warnings to an operator of the RESS, or a combination thereof.

[0060] If no internal short circuit (ISC) condition is diagnosed at query 520, e.g., because no cell group has sufficient voltage drop, method 500 may continue at query 550.

[0061] At query 550, method 500 determines whether internal short circuit (ISC) indications were present but insufficient to be diagnosed at query 520. For example, an initial voltage drop may have occurred briefly before being stopped by the opening of an overcurrent protection element. In certain embodiments, the method identifies certain behavioral patterns as indications of an internal short circuit.

[0062] For example, the method may look for an irregular cell voltage, i.e., a cell voltage that does not evolve like the other cell voltages. In certain cases, the irregular cell voltage may drop faster than other cell voltages or rise faster than other cell voltages. In other words, the method monitors for unexpected deviations from the behavior of the other cells. In certain embodiments, a monitoring device may be tuned to an erratic cell voltage as a deviation from the behavior of other cells. Furthermore, the method may look for the magnitude of the deviation of a cell voltage compared to other cell voltages. For example, a monitor may monitor the value of the deviation of the irregular cell voltage.The two monitoring devices in combination can evaluate not only the absolute amount of the monitored preload, but also the irregular movement of this preload within the absolute preload threshold.

[0063] If query 550 determines that internal short circuit (ISC) indications were present, the method 500 proceeds to query 560 to determine whether independent internal short circuit (ISC) indications are present. For example, query 560 may determine whether the internal short circuit indications are decaying in a profile consistent with the opening of an overcurrent protection element. Generally, query 550 looks for non-cell voltage-related indications. For example, temperature sensors may indicate that the local temperature near a particular cell has increased more rapidly than temperatures measured farther away from that cell. Such a temperature increase, by itself, does not necessarily indicate an internal short circuit, but a temperature increase may be used to confirm other indications of an internal short circuit.

[0064] If query 560 determines that independent internal short circuit (ISC) indications are present, method 500 concludes that an internal short circuit exists at operation 530 and performs thermal runaway mitigation processes at operation 540.

[0065] If query 560 determines that there are no internal short circuit (ISC) indications, the method 500 concludes in operation 570 that the overcurrent protection element opened due to fatigue or severe stress and not due to an internal short circuit. The method 500 then proceeds to control the operation of the RESS to compensate for the cell group failure in operation 580. For example, operation 580 may include changing limits and calculations for controlling RESS operation.

[0066] Fig. 7 is a flowchart illustrating a method for operating a RESS, such as RESS 101. As shown, method 700 may begin with startup procedure 701. Method 700 includes determining, at query 710, whether a decreasing cell group (CG) resistance change rate is detected for any cell group. If query 710 determines that a decreasing cell group (CG) resistance change rate is detected, method 700 proceeds to query 720.

[0067] Query 720 determines whether a sufficient voltage deviation has been detected for the affected cell group. For example, query 720 may determine whether a voltage drop of the affected cell group has reached a threshold indicating an internal short circuit.

[0068] If query 720 determines that a sufficient voltage deviation has been detected, method 700 proceeds to operation 730 by inferring that an internal short circuit exists in the affected cell group. Then, method 700 proceeds to operation 740 by performing thermal runaway mitigation processes, for example, to prevent an increase in heat within the RESS. For example, operation 740 may include preventing charging of the RESS, discharging energy from the RESS, cooling the RESS, issuing appropriate warnings to an operator of the RESS, or a combination thereof.

[0069] If query 720 determines that insufficient voltage variation is detected, method 700 proceeds to query 750. At query 750, method 700 determines whether the voltage change rate of the affected cell group is unrelated to the cell group's current.

[0070] If query 750 determines that the voltage change rate of the affected cell group is unrelated to the cell group's current, method 700 concludes that an internal short circuit exists in the affected cell group. Then, in operation 740, method 700 proceeds to perform processes to mitigate the thermal runaway.

[0071] If query 750 determines that the voltage change rate of the affected cell group is not independent of the cell group's current, method 700 proceeds to query 770. At query 770, method 700 determines whether the fuse monitoring detection is open, meaning that a fuse has opened. In other words, if the voltage movement is not related to current changes, an internal short circuit is diagnosed. If the voltage change is not independent of the current change, meaning that the voltage readings are related to the current, then a fuse has opened.

[0072] If query 770 determines that the fuse monitoring determination is open, method 700 proceeds to operation 780. In operation 780, it is determined that the overcurrent protection element opened due to fatigue or severe stress, rather than due to an internal short circuit. Method 700 then proceeds to control the operation of the RESS to compensate for the failure of a cell group in operation 790. For example, operation 790 may include changing limits and calculations to control RESS operation.

[0073] If query 770 determines that the backup monitoring determination is not open, method 700 proceeds to and ends at end operation 799.

[0074] If query 710 determines that a decreasing cell group (CG) resistance change rate is not detected, method 700 proceeds to query 760. At query 760, method 700 determines whether an increasing cell group (CG) resistance change rate is detected.

[0075] If query 760 determines that an increasing cell group (CG) resistance change rate is detected, the method proceeds to query 770 as described above. If query 760 determines that an increasing cell group (CG) resistance change rate is not detected, the method may restart with start-up process 701.

[0076] Fig. 8 is a flowchart illustrating a method 800 for determining whether an overcurrent protection element in a RESS 101 has opened based on cell group capacity. In general, the method 800 calculates the capacity, monitors the capacity of each cell group, and detects if a cell group suddenly behaves as if it has a lower capacity than the other cell groups.

[0077] As illustrated, method 800 may begin with startup operation 801. Method 800 includes measuring the voltage and current of each cell group at operation 810. Method 800 proceeds to query 820 to determine whether sufficient charge or discharge exists. For example, a minimum value of measurable ampere-hours is required for calculations. When a cell group is charged at a certain current for a certain time, the cell group is expected to rise to a certain voltage based on its capacity. When a higher voltage is reached, the capacity has decreased. Query 820 may be performed for the duration of an event or over a time window. For example, for every ten minutes of direct current fast charging (DCFC).

[0078] If query 820 determines that there is insufficient charge or discharge, method 800 may restart with startup process 801.

[0079] If query 820 determines that sufficient charging or discharging has occurred, method 800 proceeds to operation 830. In operation 830, method 800 calculates the capacities of the array of cell groups. For example, in operation 830, the equation may be used that states that capacity equals the ampere-hours transferred divided by the voltage-based state of change (SOC).

[0080] The method 800 then proceeds to query 840. At query 840, the method 800 determines whether the capacity of each cell group is substantially equal to the previously calculated capacity.

[0081] For example, the method 800 determines for each cell group whether the current capacity C N≈ the previous capacity C N-1 If query 840 determines that the currently calculated capacity of each cell group is equal to the previously calculated capacity of each cell group, method 800 proceeds to operation 850. In operation 850, method 800 determines that no overcurrent protection element has opened. Method 800 may then proceed to restart with startup operation 801.

[0082] If query 840 determines that the current calculated capacity of a cell group does not match the previously calculated capacity of that cell group, method 800 proceeds to query 860. At query 860, method 800 determines whether the calculated capacity of the affected cell group is substantially equal to 80% of the previously calculated capacity of the affected cell group. For example, method 800 determines whether the current capacity C N ≈ (0.8) of the previous capacity C N-1for the affected cell group.

[0083] If query 860 determines that the calculated capacity of the affected cell group does not substantially equal 80% of the previously calculated capacity of the affected cell group, method 800 proceeds to operation 850. In operation 850, method 800 determines that no overcurrent protection element has opened. Method 800 may then proceed to restart with start operation 801.

[0084] If query 860 determines that the calculated capacity of the affected cell group is substantially equal to 80% of the previously calculated capacity of the affected cell group, method 800 may proceed to operation 870. At operation 870, method 800 determines that the overcurrent protection element in the affected cell group has opened. Method 800 then proceeds to operation 880 to control the operation of the RESS to compensate for the cell group failure. For example, operation 880 may include modifying limits and calculations for controlling RESS operation.

[0085] Fig. 9 is a flowchart illustrating a method 900 for determining whether an overcurrent protection element in a RESS 101 has opened based on cell group resistance. In general, method 900 calculates the resistance, monitors the resistance of each cell group, and detects if a cell group suddenly behaves as if it has a greater resistance than the other cell groups.

[0086] As illustrated, method 900 may begin with startup operation 901. Method 900 includes measuring the synchronized current and voltage of each cell group at operation 910. Method 800 proceeds to query 920 to determine whether sufficient current is present to perform calculations to determine resistance.

[0087] If query 920 determines that there is insufficient power to perform calculations to determine the resistance, method 800 may restart with startup process 901.

[0088] If query 920 determines that sufficient current is available to perform calculations to determine resistance, method 800 may proceed to analyze the resistance of each cell group at operation 930. Specifically, method 900 calculates the current cell group resistance for each cell group at operation 931. Method 900 proceeds to filter the data obtained at operation 931 at operation 932, e.g., by using the equation R1 = (R0 - Ravg) / Ravg (resistance average, Ravg).

[0089] At operation 933, the method 900 continues to calculate the subsequent cell group resistances for each cell group. At operation 934, the method 900 plots the resistance per increment for each cell group and calculates the step delta, the rate of change (RoC).

[0090] The method 900 then proceeds to query 940. At query 940, the method 900 determines whether the step delta is substantially equal to + 25%.

[0091] In Fig. For example, Figure 10 shows a graph of resistance per step. As shown, resistance 1010 at 1020 has a step change of approximately +25%.

[0092] Back to Fig. 9: If query 940 determines that the step delta is substantially equal to +25%, method 900 proceeds to operation 950. In operation 950, method 900 determines that the overcurrent protection element in the affected cell group has opened. Method 900 then proceeds to operation 960 by controlling the operation of the RESS to compensate for the cell group failure. For example, operation 960 may include modifying limits and calculations for controlling RESS operation.

[0093] If query 940 determines that the step delta is not substantially equal to +25%, method 900 proceeds to query 970. At query 970, method 900 determines whether the rate of change is outside the range of values ​​for a non-defective part. In certain embodiments, method 900 may determine whether the overcurrent protection element has tripped slowly.

[0094] If query 970 determines that the rate of change is greater than a worst performing acceptable (WPA) value, method 900 may proceed to operation 950 by inferring that an overcurrent protection element has opened and proceed to operation 960 to modify RESS operation.

[0095] If query 970 determines that the rate of change is not greater than the minimum acceptable value (WPA), method 900 may proceed to operation 980, where method 900 concludes that no overcurrent protection element has opened.

[0096] The tax system 102 of Fig.1 may perform any of methods 500, 700, 800, and 900, including combinations of such methods. In certain embodiments, control system 102 changes the RESS performance by reducing the current limits based on the reduced number of cells of the cell group that have an open overcurrent protection element. Control system 102 may use the changed cell group resistance in the current and power limits to ensure that the voltage limits are not exceeded. Furthermore, control system 102 may use the reduced capacity of the cell group to adjust the device calculations, i.e., vehicle range and RESS charging time.

[0097] Certain embodiments herein derive cell group resistance under RESS high load conditions to monitor an expected delta caused by the opening of an individual cell circuit.

[0098] In certain embodiments, the current correlation with the cell group resistance rate of change is used to distinguish a fuse opening caused by an internal short circuit from a fuse fatigue.

[0099] Certain embodiments utilize the cell group resistance rate of change, particularly at high loads, to infer that a fuse has partially opened but an arc or slow burn-through effect prevents a step change for diagnostics.

[0100] In certain embodiments, the capacity of the cell group is calculated under predictable conditions to monitor an expected delta caused by the opening of a single cell circuit.

[0101] In certain embodiments, the fuse monitor status is used as an affirmative thermal runaway trip condition.

[0102] Certain embodiments herein use the fuse monitoring status and the capacity of the faulty cell group as input to RESS controls for power, current, and / or voltage limits to protect the RESS from additional damage that may lead to safety concerns.

[0103] In certain embodiments, the backup monitor status is used as input to the RESS controller to estimate range and charging time to ensure maximum benefit from the RESS.

[0104] For example, based on the behavior of the cell group voltage under defined conditions, parameters can be calculated that indicate a sudden change in behavior that correlates with the shutdown of a cell (~20% drop in capacity, ~25% increase in resistance). By calculating the rate of change of the cell group voltage under known loads and monitoring a change in the rate of change that corresponds to a 25% increase in resistance, it can be determined that a fuse has blown. By calculating the individual cell group capacity per discharge or charge process and monitoring for a change in capacity that corresponds to a cell disconnection (e.g., 20%), it can be determined that a fuse has blown. By calculating the internal short-circuit voltage and the rate of change of the cell group resistance, a step can be distinguished that indicates a fuse opening due to an internal short circuit.

[0105] Certain embodiments detect a cell group experiencing a cell fuse opening via the cell group delta capacitance. Certain embodiments exploit the effects of capacitance on cell voltage behavior.

[0106] Certain embodiments detect a cell group experiencing a cell fuse opening via the cell group delta resistance. Certain embodiments exploit the effects of the resistance on cell voltage behavior.

[0107] Certain embodiments distinguish a cell group with a voltage drop (internal short-circuit effect) that leads to the opening of the fuse from a normally operating cell group that experiences a load-dependent voltage change after the fuse opens (ISC vs. RESS high-current responses).

[0108] Certain embodiments use the detection of a cell group opening a cell fuse due to an internal short circuit as an indication of thermal runaway.

[0109] Certain embodiments detect a blown fuse in a cell group and use the detection as part of RESS control to enable continued use of a RESS at reduced power.

[0110] Certain embodiments can prevent cascade failures of other fuses in the cell group and resulting power loss.

[0111] Certain embodiments recognize and mitigate the fact that a cell group missing a cell is prone to over- and undervoltages in dynamic applications, resulting in a combination of cell damage and undesirable driving behavior due to voltage limit violations.

[0112] Certain embodiments detect the opening of a cell fuse under certain thermal runaway conditions and use the detection as a triggering condition for implementing a thermal runaway protocol to mediate RESS conditions.

[0113] Certain embodiments enable the diagnosis of RESS power losses. Certain embodiments ensure accurate propulsion range estimates based on the weakest cell group. Certain embodiments enable accurate calculation of charging times based on the weakest cell group. Certain embodiments enable the isolation of a cell group identified as burned out at a location within the battery pack (e.g., for service purposes, propagation monitoring, battery pack shutdown).

Claims

[1] Method (500, 700), comprising: Operating a device with a rechargeable energy storage system (RESS) (101) comprising cells (200, 201) arranged in parallel in cell groups (170, 171), each cell being provided with an overcurrent protection element (220), by passing a current through the cells (200) based on instructions (152) provided by a processor (142); Obtaining (510) sensor data via one or more sensors (120) of the device; Determining (710), via the processor (142), whether a cell group (170; 171) has a decreasing resistance change rate; if the cell group (170, 171) has a decreasing rate of change in resistance, determining (520, 720), via the processor (142), whether the cell group (170, 171) has a sufficient voltage deviation to indicate an internal short circuit condition; if the cell group (170, 171) does not have a sufficient voltage deviation to indicate an internal short-circuit condition, determining (750), via the processor (142), whether the cell group (170, 171) has a voltage change rate that is not related to the current; and if the cell group (170, 171) has a voltage change rate that is not related to the current, inferring (530, 730), via the processor (142), that an internal short circuit exists, and altering (540, 740) the operation of the device to prevent damage to the RESS (101). [2] The method of claim 1, further comprising: if the cell group (170, 171) has a sufficient voltage deviation to indicate an internal short circuit condition, inferring (530, 730), via the processor (142), that an internal short circuit exists, and altering (540, 740) the operation of the device to prevent damage to the RESS (101). [3] The method of claim 2, wherein changing the operation of the device to prevent damage to the RESS (101) comprises cooling the RESS (101) and / or discharging the RESS (101). [4] The method of claim 2, further comprising: if the cell group (170, 171) does not have a voltage change rate that is unrelated to the current, determining (770), via the processor (142), whether an overcurrent protection element (220) in the cell group (170, 171) has opened; and if an overcurrent protection element (220) in the cell group (170) has opened, inferring, via the processor (142), that the overcurrent protection element (220) has opened due to fatigue. [5] The method of claim 4, further comprising: if the cell group (170, 171) does not have a decreasing resistance change rate, determining, via the processor (142), whether the cell group (170, 171) has an increasing resistance change rate; if the cell group (170, 171) has an increasing resistance change rate, determining, via the processor (142), whether an overcurrent protection element (220) in the cell group (170, 171) has opened; and if an overcurrent protection element (220) in the cell group (170, 171) has opened, inferring (780), via the processor (142), that the overcurrent protection element (220) has opened due to fatigue and changing (790) the operation of the device. [6] The method of claim 4, wherein changing the operation of the device comprises: Revising the charge and discharge limits of the RESS (101) to prevent damage to the cell group (170, 171); and Revise RESS performance estimates based on reduced cell group storage capacity (170, 171). [7] The method of claim 1, wherein the device is a battery electric vehicle (BEV). [8] The method of claim 1, wherein the device is a hybrid electric vehicle (HEV). [9] Vehicle (100), comprising: a rechargeable energy storage system (RESS) (101) having cells (200, 201) arranged in parallel in cell groups (170, 171), each cell (200, 201) being provided with an overcurrent protection element (220); Sensors (120) configured to receive sensor data on voltage (320, 340, 420, 440), resistance (1010) and / or capacitance (CN) of each cell group (170, 171); a processor (142) connected to the sensors (120) and configured to: instructing the RESS (101) to pass a current through the cells (200, 201) to power the vehicle (10); receives the sensor data from the sensors (120); performs an initial diagnosis of the sensor data to determine whether an internal short-circuit condition exists; and performs a secondary diagnosis of the sensor data to determine whether an internal short circuit condition exists, wherein the secondary diagnosis takes into account the sensor data behavior representative of an open overcurrent protection element (220). [10] Vehicle (100) according to claim 9, wherein: the initial diagnosis comprises determining whether a voltage of an affected cell group (170, 171) has a voltage drop of a magnitude greater than a threshold value representative of the internal short-circuit condition; and the secondary diagnosis has: Determining whether the voltage (320, 340, 420, 440) of the affected cell group (170, 171) has an initial voltage drop representative of the internal short-circuit condition before the voltage (320, 340, 420, 440) of the affected cell (200, 201) has a rising voltage (320, 340, 420, 440) indicative of the opened overcurrent protection element (220); and Determine whether the voltage change rate of the affected cell group (170, 171) is unrelated to the current.

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