How to operate the battery

Abstract

The present invention relates to a method for operating a battery comprising at least two battery cells, the method comprising: a balancing process in which the states of charge of the battery cells are continuously or repeatedly balanced; a first measurement process carried out during the balancing process for a first set period of time, in which repeated measurements are carried out and each measurement identifies the battery cell having the lowest open-circuit voltage at each measurement; a determination of whether the same battery cell has always been identified as the battery cell with the lowest open-circuit voltage; and, if so, a test process for interrupting or terminating the balancing process and testing whether the battery cell identified with the lowest open-circuit voltage during the preceding first measurement process is showing an increased charge loss, which may be indicative of a possible defect. The present invention also relates to a battery system comprising a battery and a control unit configured to carry out the method according to the present invention.

Description

[Technical field]

[0001] The present invention relates to a method for operating a battery comprising at least two battery cells, as well as to a battery system comprising a battery and a control unit arranged to control the battery. [Background technology]

[0002] Electric vehicles use batteries that contain many electrochemical cells connected together. On the one hand, it is necessary to ensure that the state of charge of the individual cells matches each other. This is done by cell equalization or balancing. On the other hand, it is necessary to know in time if the cell is losing charge, since this could otherwise lead to an internal short circuit or a thermal event in that cell. The cause of the increased charge loss can be conductive impurities in the cell. These impurities can be pushed into the separator, especially at the end of the charging process, when the pressure inside the cell is highest, and trigger a short circuit between the anode and the cathode. However, cell equalization makes it difficult to determine the increased charge loss in the cells, and therefore to identify defective cells. Summary of the Invention [Problem to be solved by the invention]

[0003] It is therefore an object of the present invention to provide a method for use in batteries having two or more electrochemical cells that can reliably and reliably account for increased charge loss in the cells. [Means for solving the problem]

[0004] This problem is solved by the teaching of claim 1. Various embodiments and developments of the invention are the subject matter of dependent claims 2 to 9.

[0005] It is a further object of the present invention to provide a battery having two or more electrochemical cells which is less susceptible to thermal events.

[0006] This problem is solved by the teaching of claim 10.

[0007] Another object of the present invention is to provide a vehicle equipped with a high-voltage battery with improved safety.

[0008] This problem is solved by the teaching of claim 12.

[0009] A first aspect of the present invention is a method of operating a battery having at least two battery cells, comprising the steps of: an equalization process in which the state of charge of the battery cells is equalized continuously or repeatedly; a first measurement process performed during the equalization process for a first set period of time, the first measurement process performing repeated measurements and identifying, at each measurement, a battery cell among the battery cells having a lowest open circuit voltage at each measurement; determining whether the same battery cell is consistently identified as having the lowest open circuit voltage; and If it is determined that the same battery cell is always identified, interrupting or terminating the equalization process and performing an inspection process to check whether the battery cell identified as having the lowest open circuit voltage consistently during the preceding first measurement process is exhibiting an increase in charge loss, which may be indicative of a possible defect.

[0010] This allows for reliable detection of increased cell charge loss in a battery having two or more electrochemical cells whose states of charge are balanced by a control unit, thereby preventing thermal events in the battery.

[0011] The identification of the battery cell having the lowest open circuit voltage may be performed at the beginning and end of the first set period. It may also be possible to identify several more times within the first set period which battery cell has the lowest open circuit voltage. In particular, the identification of the battery cell having the lowest open circuit voltage may be performed (almost) evenly distributed over the first set period. It may be advantageous if balancing of the state of charge of the battery cells is not performed immediately before identifying the battery cell having the lowest open circuit voltage. The battery cells may be lithium ion cells.

[0012] In the sense of the present invention, the terms "balancing" and "proportioning" are used synonymously. Balancing or proportioning must ensure a uniform charge distribution in all electrochemical cells.

[0013] Preferred embodiments of the all-solid-state battery according to the present invention will be described below. These embodiments can be freely combined with each other, unless expressly excluded or technically impossible, and can also be combined with other aspects of the present invention to be described.

[0014] In a preferred embodiment, the measurement of the first measurement process is performed upon wake-up of a control unit controlling the battery, Waking up the control unit switches the control unit from its sleep mode to its active mode.

[0015] This makes it easy to arrange for the measurements of the first measurement process to be carried out repeatedly.

[0016] Preferably, the wake-up of the control unit is performed periodically. The control unit may be a battery operation management system.

[0017] In a preferred embodiment, after the control unit wakes up, the measurement of the first measurement process is first carried out and only then is the possible equalization of the state of charge of the battery cells carried out.

[0018] This reduces the equalization effect on the charge state of the cells, making it easier to detect cells that have experienced increased charge loss.

[0019] In a preferred embodiment, each measurement execution of the first measurement process includes measuring the open circuit voltages of all battery cells contained in the battery; and determining the lowest open circuit voltage measured among all the battery cells.

[0020] This allows easy determination of the minimum open circuit voltage.

[0021] In a preferred embodiment, after each execution of a measurement of the first measurement process, an identifier representing the battery with the lowest open circuit voltage is written to the history; The history maintains an identification of the battery cell for which the lowest open circuit voltage was identified; Based on the identifier written in the history within the set first period, it is determined whether or not there is a battery cell among the battery cells that consistently has the lowest open circuit voltage during the set first period, and which battery cell this is.

[0022] This makes it possible to efficiently determine the operating cell that always has the lowest open circuit voltage during the first set period.

[0023] In a preferred embodiment, the inspection process comprises: A second measurement process is performed for up to a second set period, in which one or more measurements are performed, and each measurement is performed to determine the smallest open circuit voltage U1 among the open circuit voltages of the battery cells, the battery cell with the smallest open circuit voltage U1, the second smallest open circuit voltage U2 among the open circuit voltages of the battery cells, and an average open circuit voltage U corresponding to the average open circuit voltage of all the battery cells. mand a second measurement process in which For the battery cell that consistently has the lowest open circuit voltage identified during the first measurement process, The smallest open circuit voltage U1 is measured for this battery cell, U S1 and U S2 represent the positive voltage thresholds, and U S1 U S2 As follows, the following relationship |U1-U2| S1 and |U1-U m | S2 , determining an increase in charge loss in the battery cell when At this time, the second set period is continuous with the first set period.

[0024] This makes it possible to determine with a high degree of certainty that the battery cell that always has the lowest open circuit voltage during the first set period will also experience an increased charge loss.

[0025] In a preferred embodiment, each measurement in the second measurement process includes measuring the open circuit voltages of all battery cells contained in the battery; Determination of the lowest open circuit voltage U1 and the second lowest open circuit voltage U2 among the open circuit voltages measured in all the battery cells, and the average open circuit voltage U using the open circuit voltages measured in all the battery cells. m The decision to Identifying the battery cell with the lowest open circuit voltage U1; Includes:

[0026] This results in open circuit voltages U1, U2 and U m can be determined in a simple manner.

[0027] In a preferred embodiment, the equalization process is re-enabled after determining an increase in charge loss or at the latest after the expiration of a second set period of time.

[0028] This can then be arranged for the equalisation of the state of charge of the battery cells to be resumed.​​

[0029] A preferred embodiment further comprises: The method further includes notifying the increased charge loss upon identifying an increased charge loss upon execution of the inspection process.

[0030] This allows the user to be alerted to possible battery cell defects so that the affected battery cells can be replaced early, before a thermal event occurs.

[0031] A second aspect of the present invention relates to a battery system comprising a battery with at least two battery cells and a control unit connected to the battery cells, the control unit being configured to perform the method according to the present invention.

[0032] This allows for the provision of a battery having two or more electrochemical cells in which the occurrence of thermal events is virtually eliminated.

[0033] The battery cells may be lithium ion cells.

[0034] In a preferred embodiment, the control unit includes a ring buffer in which a history is stored that holds the identities of the battery cells that have been identified as having the lowest open circuit voltages.

[0035] This allows automatic erasure of the identifiers of battery cells that are no longer relevant to the method.

[0036] A third aspect of the present invention relates to a vehicle comprising a battery system according to the present invention.

[0037] This makes it possible to provide a vehicle equipped with a high-voltage battery with improved safety.

[0038] In a preferred embodiment, the vehicle is configured to begin the measurement process upon start-up of the vehicle.

[0039] This will further improve the safety of vehicles equipped with high-voltage batteries.

[0040] Further advantages, features and applications of the present invention will become apparent from the following detailed description taken in conjunction with the drawings. [Brief description of the drawings]

[0041] [Figure 1] FIG. 1 is a schematic diagram of a battery system according to the present invention; [Diagram 2] 1 is a flow diagram of a method according to the present invention for operating a battery having at least two battery cells. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] FIG. 1 shows a schematic diagram of a battery system 100 according to the invention, comprising a battery 101 with at least two battery cells 1021 and 1022 and a control unit 104 electrically connected to the battery cells. The control unit is configured to execute the method according to the invention shown in FIG. 2. The battery cells 1021 and 1022 contained in the battery 100 are coupled and connected to each other, so that in a charged state the battery 100 provides a predefined open circuit voltage at its connection terminals 103. The control unit 104 may include a ring buffer, the function of which will be explained further below. The control unit 104 also has a sleep mode and an active mode, and can switch between these two modes. Switching from the sleep mode to the active mode is referred to below as waking up the control unit.

[0043] FIG. 2 shows a flow diagram of a method according to the invention for operating a battery comprising at least two battery cells.

[0044] In step S200 of this method, hereinafter also referred to as the equalization process, the charge states of the battery cells contained in the battery 100 are equalized (or balanced). The battery 100 may contain more than two batteries. Equalization involves equalizing charge among all the battery cells contained in the battery. Battery cell equalization or balancing is well known to those skilled in the art and will not be described further.

[0045] In step S201 of the method, a first measurement process is started, which will be described in more detail below.

[0046] In step S203 belonging to the first measurement process, a measurement is performed to identify the battery cell with the lowest open circuit voltage among the multiple battery cells. The battery cell with the lowest open circuit voltage can be identified by i) measuring the open circuit voltage of each battery cell contained in the battery, ii) determining the lowest open circuit voltage among the open circuit voltages measured in all the battery cells, and iii) identifying the battery cell with the lowest measured open circuit voltage among all the battery cells contained in the battery. The measurements of the open circuit voltage should be performed as simultaneously as possible so that the measured open circuit voltage can represent the current state of the battery.

[0047] After the first measurement process is performed, the identifier of the battery cell with the lowest measured open circuit voltage is written to the history, which can be stored in a ring buffer preferably included in the memory unit 104.

[0048] Advantageously, the measurements of the first measurement process can be performed upon wake-up of the control unit 104. If the battery system 100 is integrated into and connected to a vehicle, the measurements can be performed upon start-up of this vehicle.

[0049] In step S205 belonging to the first measurement process, it is determined whether or not a set first period has elapsed since the start of the first measurement process. If the set first period has elapsed since the start of the first measurement process (the "Yes" branch of step S205), step S207 is executed, and if not, step S203 is executed again (the "No" branch of step S205).

[0050] The balancing process and the first measurement process can proceed independently of each other. Thus, the balancing process S200 and the first measurement process S203 can overlap in time. For example, a first balancing of the balancing process can be performed at time t1; a first measurement of the first measurement process can be performed at a later time t2 to identify the battery cell with the lowest open circuit voltage at time t2; a second balancing of the balancing process can be performed at time t3 (t3>t2); a second measurement of the first measurement process can be performed at time t4 (t4>t3) to identify the battery cell with the lowest open circuit voltage at time t4, and so on. After each measurement of the first measurement process, the history can store the identity of the battery cell with the lowest open circuit voltage and the time it was measured.

[0051] In step S207, it is determined whether the same battery cell is always identified as the battery cell with the lowest open circuit voltage. If it is determined that the same battery cell is always identified, step S209 is executed (the "Yes" branch of S207). If not, step S201 is executed and the first measurement process is started anew (the "No" branch of S207).

[0052] Whether the same battery cell has always been identified as the battery cell with the lowest open circuit voltage during the first measurement process can be determined based on a history, where the history includes at least an identifier of the battery cell with the lowest open circuit voltage identified each time during the last executed first measurement process. If the same identifier is always written in the history for the period of the last executed first measurement process, the battery cell specified by the identifier is indeed the battery cell with the lowest open circuit voltage identified each time during the first measurement process.

[0053] In step S209, the equalization process is disabled and a second measurement process is started. After the equalization process is disabled, the charge states of the battery cells are no longer equalized until the equalization process is re-enabled.

[0054] In step S211 belonging to the second measurement process, i) the open circuit voltage of each battery cell included in the battery is measured, ii) the smallest open circuit voltage U1 and the second smallest open circuit voltage U2 among the open circuit voltages measured in all the battery cells are determined, and iii) an average open circuit voltage U is calculated using the open circuit voltages measured in all the battery cells. m is calculated, and iv) the battery cell with the lowest measured open circuit voltage U1 is identified.

[0055] Following step S211, in step S213 belonging to the second measurement process, i) whether the battery cell whose lowest open circuit voltage is always identified during the first measurement process is the same as the battery cell whose lowest open circuit voltage U1 was measured in the preceding step S211 (of the second measurement process); ii) It is determined whether the following relationship is satisfied: |U1-U2| S1 and |U1-U m | S2 (1) Here, U S1 and U S2 represent the positive voltage thresholds, and U S1 U S2 The following is the result. ​​

[0056] If it is determined that the lowest open-circuit voltage U1 has been measured in the battery cell in which the lowest open-circuit voltage was always identified during the first measurement process (i.e., item i) is determined to be affirmative) and condition (1) is satisfied, step S215 is executed (the "Yes" branch of S213).

[0057] If it is determined in step S211 that the battery cell whose lowest open circuit voltage was identified during the first measurement process does not match the battery cell whose lowest open circuit voltage U1 was measured, or if it is determined that one of the two conditions (1) is not satisfied, step S217 is executed (the "No" branch of S213).

[0058] In step S215, it is notified that the battery cell that was identified as having the lowest open circuit voltage consistently during the first measurement process is experiencing increased charge loss.

[0059] Step S215 is followed by step S219, in which the smoothing process is re-enabled and the second measurement process is terminated. After step S219, step S200 is executed.

[0060] In step S217 belonging to the second measurement process, it is determined whether or not the set second period has elapsed since the disabling of the proportionality process (or the start of the second measurement process). If the set second period has elapsed since the disabling of the proportionality process (or the start of the second measurement process), step S221 is executed (the "Yes" branch of step S217), otherwise step S211 is executed again (the "No" branch of step S217).

[0061] In step S221, the smoothing process is re-enabled and the second measurement process ends. After step S221, step S200 is executed.

[0062] Although at least one exemplary embodiment has been described above, it should be noted that many more variations exist. It should also be noted that the exemplary embodiment described is merely a non-limiting example, and is not intended to limit the scope, applicability, or configuration of the apparatus and methods described herein. On the contrary, while providing a person skilled in the art with a guide for implementing at least one exemplary embodiment, it is apparent that various changes can be made in the structure and functionality of the elements described in the exemplary embodiment without departing from the subject matter identified in the following claims and their legal equivalents. In addition to the invention described in the claims, the disclosure of this application also includes the following: 1. 1. A method of operating a battery having at least two battery cells, comprising: an equalization process in which the state of charge of the battery cells is equalized continuously or repeatedly; a first measurement process performed during the equalization process for a first set period of time, the first measurement process performing repeated measurements and identifying, at each measurement, a battery cell among the battery cells having a lowest open circuit voltage at each measurement; determining whether the same battery cell is consistently identified as having the lowest open circuit voltage; and If it is determined that the same battery cell is always identified, interrupting or terminating the equalization process and performing a test process in which the battery cell identified as having the lowest open circuit voltage consistently during the preceding first measurement process is tested for an increase in charge loss indicative of a possible defect; The method according to claim 1, 2. The method according to claim 1, the measurement of the first measurement process is performed upon wake-up of a control unit controlling the battery; A method in which waking up the control unit switches the control unit from its sleep mode to its active mode. 3. 3. The method according to claim 2, The method, in which, after the wake-up of the control unit, a measurement of a first measurement process is first carried out and only then is the possible equalization of the states of charge of the battery cells carried out. 4. 4. The method according to any one of claims 1 to 3, wherein each measurement run of the first measurement process comprises: Measurement of the open circuit voltage of all battery cells contained in the battery; Determining the lowest open circuit voltage measured among all the battery cells; The method includes: 5. 5. The method according to any one of claims 1 to 4, further comprising the steps of: after each measurement of the first measurement process, writing an identifier indicative of the battery having the lowest open circuit voltage into the history; The history maintains an identification of the battery cell for which the lowest open circuit voltage was identified; A method for determining whether or not there is a battery cell among the battery cells that consistently has the lowest open circuit voltage during a set first period, and which battery cell that is the battery cell, based on an identifier written to the history within a set first period. 6. 6. The method according to any one of claims 1 to 5, wherein the inspection process comprises: A second measurement process is performed for up to a second set period of time, in which one or more measurements are performed, and each measurement is performed to determine the smallest open circuit voltage U among the open circuit voltages of the battery cells. 1 , the smallest open circuit voltage U 1 The second smallest open circuit voltage U among the open circuit voltages of the battery cells identified 2 and the average open circuit voltage U, which corresponds to the average open circuit voltage of all the battery cells m and a second measurement process in which For the battery cell for which the lowest open circuit voltage was always identified during the first measurement process, the smallest open circuit voltage U 1 is measured, and U S1 and U S2 represent the positive voltage thresholds, and U S1 U S2 As follows, the following relationship |U 1 -U 2 |<U S1 and |U 1 -U m |<U S2 , determining an increase in charge loss in the battery cell when The second set period is consecutive to the first set period. method. 7. 6. The method according to claim 6, For each measurement run of the second measurement process, Measurement of the open circuit voltage of all battery cells contained in the battery; The minimum open circuit voltage U among all the battery cells 1 and the second smallest open circuit voltage U 2 Determination of the average open circuit voltage U using the open circuit voltages measured in all battery cells m The decision to Minimum open circuit voltage U 1 Identifying the battery cell that is The method includes: 8. 8. The method according to claim 6 or 7, wherein the equalization process is reactivated after determining an increase in charge loss or at the latest after the end of a second set period of time. 9. 9. A method as claimed in any one of claims 1 to 8, further comprising notifying an increase in charge loss if an increase in charge loss is identified during performance of the inspection process. 10. A battery system comprising a battery having at least two battery cells and a control unit connected to the battery cells, the control unit being configured to execute any one of the methods described in 1 to 8 above. 11. A battery system as described in claim 10, wherein the control unit has a ring buffer, and the ring buffer stores a history of the identifier of the battery cell that has the lowest open circuit voltage identified. 12. 12. A vehicle having the battery system according to claim 10 or 11. 13. 13. A vehicle as claimed in claim 12, configured to initiate the measurement process upon start-up of the vehicle. [Explanation of symbols]

[0063] 100 Battery System 101 Batteries 1021,1022 battery cells 103 Battery connection terminal 104 Control Unit

Claims

1. 1. A method of operating a battery having at least two battery cells, comprising: an equalization process in which the state of charge of the battery cells is equalized continuously or repeatedly; a first measurement process performed during the equalization process for a first set period of time, the first measurement process performing repeated measurements and identifying, at each measurement, a battery cell among the battery cells having a lowest open circuit voltage at each measurement; A determination of whether the same battery cell was always identified as the battery cell with the lowest open circuit voltage, and if so, interrupting or terminating the equalization process and performing a test process in which the battery cell identified as having the lowest open circuit voltage consistently during the preceding first measurement process is tested for an increase in charge loss indicative of a possible defect; having the measurement of the first measurement process is performed upon wake-up of a control unit controlling the battery, A method in which waking up the control unit switches the control unit from its sleep mode to its active mode.

2. 2. The method of claim 1 , A method in which, after wake-up of the control unit, the measurement of the first measurement process is first performed without equalization of the states of charge of the battery cells.

3. 3. The method according to claim 1 or 2, wherein each execution of a measurement of the first measurement process comprises: Measurement of the open circuit voltage of all battery cells contained in the battery; Determining the lowest open circuit voltage measured among all the battery cells; The method includes:

4. 4. A method according to claim 1, further comprising the steps of: after each measurement of the first measurement process, writing in the history an identifier indicative of the battery with the lowest open circuit voltage; The history maintains an identification of the battery cell for which the lowest open circuit voltage was identified; A method for determining whether or not there is a battery cell among the battery cells that consistently has the lowest open circuit voltage during a set first period, and which battery cell that is the battery cell, based on an identifier written to the history within a set first period.

5. 5. The method according to claim 1, wherein the inspection process comprises: A second measurement process is performed for a maximum second set period, in which one or more measurements are performed, and each measurement is performed to determine the smallest open circuit voltage U among the open circuit voltages of the battery cells. １ , the smallest open circuit voltage U １ The second smallest open circuit voltage U among the battery cells with the specified open circuit voltage ２ and an average open circuit voltage U corresponding to the average open circuit voltage of all the battery cells ｍ and a second measurement process in which For the battery cell for which the lowest open circuit voltage was always identified during the first measurement process, the smallest open circuit voltage U １ is measured, and U Ｓ１ and U Ｓ２ represent the positive voltage thresholds, and U Ｓ１ U Ｓ２ As follows, the following relationship |U １ -U ２ |<U Ｓ１ and |U １ -U ｍ |<U Ｓ２ , determining an increase in charge loss in the battery cell when The second set period is consecutive to the first set period. method.

6. 6. The method of claim 5, For each measurement run of the second measurement process, Measurement of the open circuit voltage of all battery cells contained in the battery; The minimum open circuit voltage U among all the battery cells １ and the second smallest open circuit voltage U ２ Determination of the average open circuit voltage U using the open circuit voltages measured in all battery cells ｍ The decision to Minimum open circuit voltage U １ Identifying the battery cell that is The method includes:

7. 7. The method according to claim 5 or 6, wherein the equalization process is reactivated after determining an increase in charge loss or at the latest after expiry of a second set period of time.

8. 8. The method of claim 1, further comprising: notifying an increase in charge loss if an increase in charge loss is identified during execution of the inspection process.

9. A battery system comprising a battery having at least two battery cells and a control unit connected to the battery cells, the control unit being configured to perform a method according to any one of claims 1 to 7.

10. 10. The battery system according to claim 9, wherein the control unit has a ring buffer, and the ring buffer stores a history of identifiers of battery cells that have been identified as having the lowest open circuit voltage.

11. A vehicle comprising the battery system according to claim 9 or 10.

12. 12. The vehicle of claim 11, configured to initiate the first measurement process upon start-up of the vehicle.

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