Method and apparatus for monitoring operating parameters of a battery arrangement with multiple battery cells

Abstract

Method for monitoring a control system for a battery arrangement (2) with multiple battery cells (21), comprising the following steps: - Implementing (S2) a control for operating the battery arrangement (2) such that at least one operating range of the battery cells (21) is maintained; - Monitoring (S4, S5) of an operational variable with respect to a first predefined operational variable range and a second predefined operational variable range; and - Detecting (S4, S8) a first fault if the operating parameter is outside the first operating parameter range and within the second operating parameter range for more than a predetermined period of time, taking into account that operating parameters are maintained within the respective predetermined battery cell-specific operating parameters.

Description

Technical field

[0001] The invention relates to battery arrangements with multiple battery cells and in particular to measures for increasing the service life of the battery cells in the battery arrangement. State of the art

[0002] Battery arrays for battery management systems are primarily designed to consist of a large number of battery cells, especially lithium-ion cells, for use in electric or hybrid vehicles. These battery arrays comprise multiple battery cells connected in series or parallel.

[0003] To prevent damage or destruction and to protect against accelerated aging, each individual battery cell must be operated within specific operating ranges with respect to one or more operating parameters. Operating each battery cell at a voltage below a maximum voltage, known as the charging cut-off voltage, and above a minimum voltage, known as the discharging cut-off voltage, is advantageous, as consistently maintaining these operating conditions guarantees maximum battery cell lifespan. The same applies to the operating temperature of each battery cell, with a specific temperature range, depending on the type of battery cell, ensuring maximum lifespan and protection against damage or destruction.

[0004] German patent application DE 10 2010 040 031 A1 discloses a method for monitoring the voltage of a cell in a battery energy storage system to detect whether it exceeds or falls below a reference voltage. Threshold monitoring determines whether the cell voltage is within a permissible range. If the cell voltage level is outside a predefined voltage window, this is detected by an evaluation unit, and a battery controller can initiate appropriate measures to correct this operating condition so that the voltage level quickly returns to a defined voltage window or range.

[0005] By monitoring the individual cell voltages of different battery cells within a battery array, harmful or faulty operating conditions of the battery energy storage system can be quickly detected. Appropriate measures, such as shutting down the battery energy storage system or a portion thereof, can prevent a complete and damaging discharge of at least part of the battery energy storage system.

[0006] A battery management system for monitoring and controlling a lithium-ion cell is known from publication EP 2 180 574 A2. Sensors determine the cell's voltage, transmit it to the central control unit, and forward it to the data storage device. Using the determined values, the battery management system is able to operate the battery cells with maximum efficiency and maximize their lifespan. Battery cell parameters are recorded, such as cell temperature and electrical parameters like voltage, current, internal resistance, and the like. These parameters are used to optimally control the charging and discharging processes of the battery cells. Furthermore, the battery cells can be operated with maximum efficiency, thereby maximizing their lifespan.

[0007] From German patent application DE 10 2007 038 532 A1, a monitoring device for a battery arrangement with multiple battery cells is known, wherein each battery cell is assigned a monitoring circuit to monitor the function of the battery cell and to provide cell information accordingly. Depending on the cell information, a charging process is terminated or, in the case of a low state of charge, the current draw of a consumer is reduced.

[0008] A charging and discharging monitoring system for battery arrangements is known from German patent application DE 42 25 746 A1. This system comprises a monitoring module for each battery cell, which includes a charging current limiting circuit and a signal generator to indicate the operating status of the charging current limiting circuit. When an undervoltage occurs, the discharge monitoring system either reduces the discharge current or disconnects the load from the battery cells. If an overcurrent occurs during charging, the charger immediately reduces the current in stages until the overcurrent is dissipated.

[0009] In the publication DE 24 14 355 A, a method and a device for monitoring battery voltage are disclosed.

[0010] One disadvantage of the above battery management systems is that the limits of the operating parameters within which optimal operation of the battery cells is ensured are usually fluid, and when a fixed window for the operating parameter is defined, measures that go too far, such as switching off the battery assembly, are often taken, which are usually inappropriate for protecting the individual battery cells and restrict the usability of the battery assembly, e.g. for traction applications.

[0011] The object of the present invention is to provide improved monitoring of a control system for operating battery cells of a battery arrangement, in which a protective measure is only taken when it is necessary to protect the individual battery cells. Disclosure of the invention

[0012] This problem is solved by the method for monitoring a control system for a battery arrangement according to claim 1, as well as by the device for monitoring a control system for a battery arrangement and the computer program product according to the dependent claims.

[0013] Further advantageous embodiments of the present invention are specified in the dependent claims.

[0014] According to a first aspect, a method for monitoring a control system for a battery arrangement with multiple battery cells is provided, comprising the following steps: - Implementing a regulation for the operation of the battery arrangement so that at least one operating range of the battery cells is maintained; - Monitoring an operational parameter with respect to a first predefined operational parameter range and a second predefined operational parameter range; and - Determining a first fault if the operating size is outside the first operating size range and within the second operating size range for more than a predetermined period of time.

[0015] One aspect of the monitoring method described above is to monitor the operation of a controller for a battery array, particularly for charging and discharging. Typically, the controller manages the charging and discharging process, ensuring that cell voltages do not exceed a specified charging cut-off voltage during charging and that cell voltages do not fall below the specified discharge cut-off voltage during discharging. Furthermore, the controller usually regulates the cell current, thus limiting the current. Overall, the controller ensures that operating parameters remain within predefined, cell-specific operating ranges.

[0016] The above method provides for monitoring this control by defining a first operating size window. This window includes a first upper operating size limit greater than an upper limit specified by the control system for an operating size and a first lower operating size limit less than a lower limit specified by the control system for the operating size. The first operating size range defined by the first upper and lower limits represents a safe operating size range. While the battery cells within this first operating size range can be operated without damage or destruction, continuous operation within this range but outside the controlled range would result in an intensification or acceleration of aging effects.

[0017] Furthermore, a second upper and lower operating size limit is defined for a second operating size window. This second limit is greater than the first upper limit and lower limit, respectively, and defines a second operating size range. While the battery cells can still be operated within this second operating size range, even brief operation within the second range but outside the first would intensify or accelerate aging effects. If the operating size remains outside the first range but within the second range for a predetermined period, a first fault is detected, and initial fault handling is initiated.

[0018] While the control system already includes measures to interrupt a charging or discharging process of the battery arrangement if the specified operating range between the charging cut-off voltage and the discharging cut-off voltage, or between an upper temperature limit and a lower temperature limit, or the like, is exceeded, the above method serves to further monitor the function of the control system, thereby preventing inappropriate measures to protect the battery cells.

[0019] Furthermore, in the event of a fault, a circuit can be interrupted by the battery arrangement.

[0020] According to one embodiment, a second fault can be detected as soon as the operating parameter falls outside the second operating parameter range. Thus, if the operating parameter is outside the second operating parameter range, a second fault is detected and a second fault handling procedure is performed. For example, in the second fault handling procedure, the circuit is immediately interrupted.

[0021] The operating parameters may include cell voltage, state of charge and / or cell temperature.

[0022] The regulation for compliance with operating ranges can generate a control variable to keep the operating size within the operating range.

[0023] Furthermore, the operating range can be smaller than the first operating range and the second operating range can be larger than the first operating range. According to one embodiment, the control can be based on several operating parameters, such that an operating range of the battery cells is maintained, wherein the operating parameters are monitored with respect to a respective first predetermined operating range and a respective second predetermined operating range, and wherein a first fault is detected if one of the operating parameters lies outside the respective first operating range and within the respective second operating range for more than a respective predetermined period of time.

[0024] According to another aspect, a device for monitoring a battery arrangement with multiple battery cells is provided, comprising: - a control unit that is trained to • to implement a control or regulation system for operating the battery arrangement, so that at least one operating range of the battery cells is maintained; • to monitor the size of the operation with respect to a first predefined range of operating sizes and a second predefined range of operating sizes; and • to detect a first fault if the operating size is outside the first operating size range and within the second operating size range for more than a predetermined period of time.

[0025] According to another aspect, a computer program product is provided which contains program code stored on a computer-readable data carrier and which, when executed on a data processing device, performs the above procedure. Brief description of the drawings

[0026] Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1. A schematic representation of a battery management system comprising a battery arrangement and a monitoring device for monitoring one or more operating parameters of the battery cells of the battery arrangement; and Fig. 2. A flowchart illustrating a procedure for monitoring operating parameters of a battery arrangement. Description of embodiments

[0027] Fig. Figure 1 shows a battery management system 1 with a battery arrangement 2 and a control unit 3 for controlling charging and discharging processes of the battery arrangement 2.

[0028] The battery arrangement 2 comprises a series of battery cells 21 connected in series. Instead of individual battery cells 21, a parallel connection of battery cells 21 can also be provided, which is connected in series with other parallel connection systems of battery cells 21.

[0029] The battery cells 21 can correspond to lithium-ion cells or other rechargeable battery cells 21, in particular battery cells that can be used as a traction battery to operate an electric or hybrid vehicle.

[0030] A cell voltage measuring unit 4 is provided, which measures the cell voltage of each of the battery cells 21 or of each of the parallel circuits of battery cells 21 and provides corresponding cell voltage information, e.g. as digitized voltage values, to the control unit 3.

[0031] The control unit 3 has a first processing unit 31, which receives the cell voltage data from the cell voltage measuring unit 4 and executes a control algorithm that ensures each of the battery cells 21 does not exceed a predetermined charging voltage during charging and does not exceed a predetermined discharging voltage during discharging. The control algorithm of the first processing unit 31 provides a manipulated variable S, for example, a value indicating a charging or discharging current to be set, to the environment of the battery management system 1. Based on the manipulated variable S, an external system (not shown) is designed to maintain a current drawn from or supplied by the battery arrangement 2, thereby keeping the cell voltages within a voltage operating range (operating range) specified by the control algorithm.

[0032] A disconnect element 5 is provided, which is connected to the control unit 3. The disconnect element 5 can be designed as a contactor, relay or other circuit breaker and is provided between the consumer and / or power generator and the battery arrangement 2 in order to interrupt a circuit through the battery arrangement 2.

[0033] The control algorithm of the first computing unit 31 is designed to guarantee lifetime-optimized operation of the battery cells 21. As long as the control algorithm functions correctly, the first computing unit 31 continues to provide a first signal level (e.g., a logical 1) of a first enable signal FS1, which is supplied to an AND gate 33 of the control unit 3. When operating correctly, the signal level of the first enable signal FS1 indicates that a circuit through the battery arrangement 2 should be closed by means of the shutdown element 5 connected to the control unit 3. If the control algorithm does not operate correctly, the first computing unit 31 provides the AND gate 33 with a second signal level (e.g., a logical 0) of the first enable signal FS1.

[0034] The control unit 3 also includes a second processing unit 32, which monitors the correct functioning of the first processing unit 31. For this purpose, the second processing unit 32 also receives the cell voltage data from the cell voltage measuring unit 4 and determines whether the cell voltage values ​​are above a predefined first upper cell voltage limit (first operating limit) or below a predefined first lower cell voltage limit (first operating limit). The first upper cell voltage limit is above the charging cut-off voltage, and the first lower cell voltage limit is below the discharging cut-off voltage; both define a first cell voltage range (first operating range).Within the first cell voltage range and outside the control range to be maintained by the first computing unit 31, the battery cells 21 can be operated without damage, but continuous operation is not desirable due to increased aging effects.

[0035] The second processing unit 32 is configured to detect when the first cell voltage limit is exceeded or fallen below for more than a predetermined voltage duration. If such a case is detected by the second processing unit 32, the first signal level of a second enable signal FS2, which signals an enable (i.e., closing) of the shutdown element 5, is changed to a second signal level, which signals an opening of the shutdown element 5, in order to remove the enable signal from the shutdown element 5 via the AND gate of the AND gate 33.

[0036] Furthermore, a monitoring unit 6 is provided which, like the cell voltage measuring unit 4, measures the cell voltages of the individual battery cells 21 or of parallel connections of battery cells 21 and provides a corresponding cell voltage reading. This can be done with the cell voltage measuring unit 4 or separately. The cell voltage readings are checked for each of the battery cells 21 with respect to a predefined second cell voltage upper limit (second operating limit) and a predefined second cell voltage lower limit (second operating limit), which define a second cell voltage range (second operating range).

[0037] The second cell voltage upper limit is higher than the first cell voltage upper limit, and the second cell voltage lower limit is lower than the first cell voltage lower limit. The second cell voltage upper limit and the second cell voltage lower limit are chosen such that, outside the first cell voltage range but within the second cell voltage range, they define an extended safe cell voltage range in which the battery cells 21 can be operated, but even brief operation would result in an intensification or acceleration of aging effects.

[0038] The monitoring unit 6 generates a third enable signal FS3, which is also fed to the AND gate 33 and indicates whether the shutdown element 5 should close or open the circuit with the battery assembly 2. If an exceedance or fall below the second cell voltage upper or lower limit is detected, the first signal level of the third enable signal FS3, which signals enable (i.e., closing) the shutdown element 5, is immediately changed to a second signal level, which signals opening the shutdown element 5. Due to the AND gate of the enable signals, the circuit is opened by the battery assembly 2 using the shutdown element 5 as soon as at least one of the enable signals FS1, FS2, or FS3 reaches the second signal level.

[0039] A cell temperature measuring unit 8 is provided, which is connected to first temperature sensors 9 on each of the battery cells 21 to provide cell temperature data to the control unit 3. Based on the cell temperature data, the first processing unit 31 controls the operation of the battery arrangement 2 using the manipulated variable S. The first processing unit 31 thus provides the manipulated variable S such that a predetermined upper cell temperature limit is not exceeded by any of the cell temperature data, or a predetermined lower cell temperature limit is not undercut by any of the cell temperature data, i.e., so that the cell temperature data remains within a predetermined temperature range. If the first processing unit 31 behaves correctly, the first enable signal FS1 is set to the first signal level; otherwise, it is changed to the second signal level.

[0040] Furthermore, the cell temperature reading is provided to the second processing unit 32, which checks whether the cell temperature reading lies within a first temperature range defined by a predefined first upper cell temperature limit and a predefined first cell temperature lower limit. If it is determined that the cell temperature reading for each of the battery cells 21 lies outside the predefined first temperature range for more than a predefined period of time, the second enable signal FS2 is changed from a first signal level to a second signal level in order to interrupt the circuit by the switching element 5.

[0041] The monitoring unit 6 is further coupled to second temperature sensors 7, which are arranged on each of the battery cells 21. Alternatively, the monitoring unit 6 can also be connected to the first temperature sensors 9. The monitoring unit 6 checks the cell temperature in each case and influences the third enable signal FS3, so that if a predefined second cell temperature upper limit is exceeded or if a predefined second cell temperature lower limit is undershot, which together define a second temperature range, the signal level of the third enable signal FS3 changes immediately to the second signal level.

[0042] In Fig. Figure 2 is a flowchart illustrating the procedure for monitoring an operating parameter, such as cell voltage or cell temperature. In step S1, the operating parameter is measured by a suitable measuring unit. Subsequently, a control algorithm is executed by the first processing unit 31 to control a charging or discharging process using a manipulated variable S based on the measured operating parameter (step S2). If the first processing unit 31 determines in step S3 that the control algorithm is working correctly (alternative: Yes), the procedure continues with step S4. Otherwise (alternative: No), the procedure continues with step S7.

[0043] In the second processing unit 32, step S4 checks whether the operating size for each of the battery cells 21 lies within a first operating size range defined between a first upper operating size limit and a first lower operating size limit. If step S4 determines that the operating size for each of the battery cells 21 lies outside the first operating size range (alternative: No), the procedure continues with step S8. Otherwise (alternative: Yes), the procedure continues with step S5.

[0044] In step S8, it is checked whether the operating size for each of the battery cells 21 lies outside the first operating size range for more than a predetermined period of time. If this is the case (alternative: Yes), the procedure continues with step S7. Otherwise (alternative: No), the procedure continues with step S5.

[0045] The monitoring of step S5 includes a check to determine whether the operating parameter BG for each of the battery cells 21 lies within a second operating parameter range, defined by the second upper and lower operating parameter limits. If step S5 determines that the operating parameters lie within the second operating parameter range (alternative: Yes), the shutdown element 5 is activated to close the circuit of the battery arrangement 2, or the circuit with the battery arrangement 2 remains closed (step S6). The process then returns to step S1.

[0046] If, in steps S4 and S8, it is determined that at least one of the measured operating variables lies outside the first operating variable range for a predetermined period of time, or in step S5, it is determined that at least one of the measured operating variables lies outside the second operating variable range, then in step S7 the release to close the circuit is lifted by the switching element 5 and the circuit with the battery arrangement 2 is opened.

[0047] In step S4, it can also be implemented that under certain operating conditions, such as when leaving operating ranges due to several operating parameters, the release signal is withdrawn as soon as an exceedance of a charging cut-off voltage or a fall below a discharging cut-off voltage is detected, without, however, the first upper or lower operating parameter limit having been exceeded or fallen below.

[0048] The one in Fig. The method described in section 2 can be implemented simultaneously for different operating parameters or jointly within a battery management system 1. In particular, the cell voltage, cell temperature, state of charge of the cells, and similar parameters can be checked or monitored as operating parameters.

[0049] The procedural steps relating to Fig. As explained in section 2, in connection with Fig. The battery management system described in section 1 will be implemented.

[0050] Furthermore, the following can be used in conjunction with the battery management system 1 of the Fig. 1 described process steps with reference to Fig. The two explained process steps can be combined. Reference symbol list 1 Battery management system 2 Battery arrangement 3 Control unit 4 cell voltage measuring unit 5 Shutdown element 6 monitoring unit 7 second temperature sensor 8 cell temperature measuring unit 9 first temperature sensor 21 battery cells 31 first computing unit 32 second computing unit 33 AND clause

Claims

Method for monitoring a control system for a battery arrangement (2) with multiple battery cells (21), comprising the following steps: - Performing (S2) a control operation for the battery arrangement (2) such that at least one operating range of the battery cells (21) is maintained; - Monitoring (S4, S5) an operating parameter with respect to a first predetermined operating parameter range and a second predetermined operating parameter range; and - Detecting (S4, S8) a first fault if the operating parameter is outside the first operating parameter range and within the second operating parameter range for more than a predetermined time period, wherein the control system takes into account that operating parameters are maintained within the respective predetermined battery cell-specific operating ranges. Method according to claim 1, wherein, upon detection of the first fault, a circuit is interrupted by the battery arrangement (2). Method according to claim 1 or 2, wherein a second fault is detected as soon as the operating size is outside the respective second operating size range. Method according to any one of claims 1 to 3, wherein the operating parameter comprises a cell voltage, a state of charge and / or a cell temperature. Method according to any one of claims 1 to 4, wherein the control for maintaining the operating range generates a control variable (S) to keep the operating size within the respective operating ranges. Method according to claim 5, wherein the operating range is smaller than the first operating range and the second operating range is larger than the first operating range. Method according to any one of claims 1 to 6, wherein the control is carried out based on several operating parameters so that an operating range of the battery cells (21) is maintained, wherein the operating parameters are monitored with respect to a respective first predetermined operating parameter range and a respective second predetermined operating parameter range, and wherein a first fault is detected if one of the operating parameters lies outside the respective first operating parameter range and within the respective second operating parameter range for more than a respective predetermined period of time. Device for monitoring a control system for a battery arrangement (2) with multiple battery cells (21), comprising: - a control unit (3) configured to: • perform a control for operating the battery arrangement (2) such that at least one operating range of the battery cells (21) is maintained; • monitor an operating parameter with respect to a first predetermined operating parameter range and a second predetermined operating parameter range; and • detect a first fault if the operating parameter lies outside the first operating parameter range and within the respective second operating parameter range for more than a predetermined period of time, wherein the control system takes into account that operating parameters are maintained within the respective predetermined battery cell-specific operating ranges. Battery system comprising a battery arrangement and a device according to claim 8. Computer program product containing program code stored on a computer-readable data carrier which, when executed on a data processing device, performs the method according to any one of claims 1 to 7.

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