Method for operating a battery

Abstract

The invention relates to a method for operating a battery having at least two battery cells, the method comprising: a balancing process, in which the state of charge of the battery cells is continuously or repeatedly balanced; a first measurement process during the balancing process, in which measurements are repeatedly carried out, in each measurement determining the battery cell having the lowest stable voltage in the respective measurement; determining whether the same battery cell is always determined as the battery cell having the lowest stable voltage during the first measurement process; and if this is the case: carrying out a test process, in which the balancing process is interrupted or ended and a test is carried out as to whether the battery cell, for which the lowest stable voltage has always been determined during the previous first measurement process, has an elevated charge loss. The invention also relates to a battery system having a battery and a control unit, which is configured for carrying out the method according to the invention.

Description

Technical Field

[0001] The present invention relates to a method for operating a battery having at least two battery cells, and a battery system having a battery and a control unit configured to control the battery. Background Technology

[0002] Electric vehicles use batteries comprising a large number of interconnected electrochemical cells. To achieve this, it is essential to ensure the state of charge (SOC) of each cell is coordinated. This is achieved through cell balancing or equalization. On the other hand, it is crucial to promptly identify cells with elevated charge losses, as this could lead to internal short circuits or even thermal events within the cell. Elevated charge losses can be caused by conductive contaminants within the cell, which are primarily forced into the separator at the end of the charging process (when pressure within the cell is at its maximum) and trigger a short circuit between the anode and cathode. However, balancing the cells hinders the determination of elevated charge losses within the cells, and therefore also hinders the identification of faulty cells. Summary of the Invention

[0003] Therefore, the object of the present invention is to provide a method for safely and reliably identifying increased charge loss in a cell within a battery having two or more electrochemical cells.

[0004] The objective is achieved by a method according to the present invention for operating a battery having at least two battery cells.

[0005] Furthermore, the object of the present invention is to provide a battery having two or more electrochemical cells, in which thermal events are minimized.

[0006] The objective is achieved by a battery system according to the present invention.

[0007] Furthermore, the object of the present invention is to provide a vehicle with a high-voltage memory, which provides improved safety.

[0008] The objective is achieved by a vehicle according to the invention.

[0009] A first aspect of the present invention relates to a method for operating a battery having at least two individual cells, the method comprising:

[0010] The balancing process, in which the state of charge of individual battery cells is continuously or repeatedly balanced;

[0011] A first measurement process is performed during the balancing process for a predetermined first duration, and the measurement is repeatedly performed during the first measurement process, wherein in each measurement of the measurement, the battery cell is determined to have the lowest stable voltage among the battery cells in the corresponding measurement;

[0012] Determine whether the same battery cell is consistently identified as having the lowest stable voltage throughout the first measurement process; and if so:

[0013] The testing process is carried out, during which the balancing process is interrupted or terminated and the following test is performed: whether the battery cell has increased charge loss indicating a possible fault, for which the minimum stable voltage was always determined during the previous first measurement process.

[0014] This allows for the safe and reliable identification of increased charge loss in individual cells within the battery, and thus prevents thermal events from occurring in the battery, which has two or more electrochemical cells and whose state of charge is balanced by a control unit.

[0015] The battery cell with the lowest stable voltage can be determined at the beginning or end of a predetermined first duration. Alternatively, the determination of which battery cell has the lowest stable voltage can be performed multiple times within the predetermined first duration. In particular, the determination of the battery cell with the lowest stable voltage can be performed (substantially) uniformly over the predetermined first duration. Advantageously, the balancing of the state of charge of the battery cell is not performed directly before determining the battery cell with the lowest stable voltage. The battery cell may be a lithium-ion cell.

[0016] In the context of this invention, the terms "equilibrium" and "balance" are used synonymously. Equilibrium or balance should ensure a uniform charge distribution among all electrochemical cells within the battery.

[0017] The following describes preferred embodiments of the solid-state battery according to the present invention. These embodiments can be arbitrarily combined with each other and with other aspects of the invention further described herein, provided that this is not explicitly excluded or technically impractical.

[0018] In a preferred embodiment, the measurement of the first measurement process is performed when the control unit controlling the battery is woken up, and the control unit switches from its sleep mode to its active mode by waking up the control unit.

[0019] This allows for the repeated implementation of the first measurement process in a simple manner.

[0020] Preferably, the control unit is woken up cyclically. The control unit may be a battery operation management system.

[0021] In a preferred embodiment, after waking up the control unit, a first measurement process is first performed, and then a possible balancing of the state of charge of the battery cells is carried out.

[0022] This reduces the impact of equilibrium on the charge state of individual cells and makes it easier to detect cells with increased charge loss.

[0023] In a preferred embodiment, each measurement of the first measurement process includes: measuring the stable voltage of all battery cells contained in the battery; and identifying the lowest stable voltage among the stable voltages measured on all battery cells.

[0024] This allows for the determination of the minimum stable voltage in a simple way.

[0025] In a preferred embodiment, after each measurement of the first measurement process, the identifier representing the battery with the lowest stable voltage is registered in the history.

[0026] The history includes the identification of the following battery cells, for which the lowest stable voltage was determined, and

[0027] Based on the identifiers registered in the history during a predetermined first duration, it is determined whether there is a battery cell among the battery cells that consistently has the lowest stable voltage during the predetermined first duration, and which battery cell it is.

[0028] This allows for the efficient identification of the operating cell that consistently maintains the lowest stable voltage during the predetermined first duration.

[0029] In a preferred embodiment, the testing process includes: a second measurement process performed for at most a predetermined second duration, wherein one or more measurements are performed during the second measurement process, wherein in each of the measurements, the following are determined: a minimum stable voltage U1 among the stable voltages of each battery cell; a battery cell to which the minimum stable voltage U1 is determined; a second minimum stable voltage U2 among the stable voltages of each battery cell; and an average stable voltage U corresponding to the average of the stable voltages of all battery cells. m ;and

[0030] Determine the increased charge loss on the following battery cells, for which the lowest stable voltage is consistently determined during the first measurement process, if a minimum stable voltage U1 is measured on the battery cell and the following relationship applies:

[0031] |U1 - U2| < U S1 And |U1 - U m | < U S2 ,

[0032] Among them, U S1 and U S2 These represent positive voltage thresholds, and U... S1 Less than or equal to U S2 ;and

[0033] The predetermined second duration is connected to the predetermined first duration.

[0034] Therefore, it can be determined with a high probability that the battery cell that consistently has the lowest stable voltage during the predetermined first duration also has increased power loss.

[0035] In a preferred embodiment, each measurement performed during the second measurement process includes: measuring the stable voltage of all battery cells contained in the battery; and

[0036] Identify the lowest stable voltage U1 and the second lowest stable voltage U2 among the stable voltages measured on all battery cells, and identify the average stable voltage U using the stable voltages measured on all battery cells. m ;and

[0037] Identify the battery cell with the lowest stable voltage U1.

[0038] This allows for the simple implementation of stable voltages U1, U2, and U... m The investigation has been completed.

[0039] In a preferred embodiment, the balancing process is reactivated after the increased charge loss is determined or at the latest after a predetermined second duration.

[0040] This enables the rebalancing of the state of charge of individual battery cells.

[0041] A preferred embodiment further includes:

[0042] If increased charge loss is determined during the testing process, the increased charge loss should be reported.

[0043] This allows the system to indicate potential faults in individual battery cells to users, enabling them to replace the affected cells earlier, or even before a thermal event occurs.

[0044] A second aspect of the invention relates to a battery system having: a battery having at least two battery cells, and a control unit coupled to the battery cells, wherein the control unit is configured to implement the method according to the invention.

[0045] This enables the provision of a battery having two or more electrochemical cells in which thermal events are minimized.

[0046] The battery cell can be a lithium-ion cell.

[0047] In a preferred embodiment, the control unit has a ring memory, and a history of identifiers of battery cells, determined to the lowest stable voltage for each battery cell, is stored in the ring memory.

[0048] Therefore, the identifiers of battery cells that are no longer relevant to the method can be automatically deleted.

[0049] A third aspect of the invention relates to a vehicle having a battery system according to the invention.

[0050] This provides a vehicle with a high-voltage memory, which has improved safety.

[0051] In a preferred embodiment, the vehicle is configured to trigger the measurement process when the vehicle is started.

[0052] This can further improve the safety of vehicles containing high-voltage memory. Attached Figure Description

[0053] Other advantages, features, and applicable solutions of the present invention are given in the following detailed description in conjunction with the accompanying drawings. In the drawings:

[0054] Figure 1 A battery system according to the invention is illustrated schematically; and

[0055] Figure 2 A flowchart is shown for a method according to the present invention for operating a battery having at least two battery cells. Detailed Implementation

[0056] Figure 1 A battery system 100 according to the invention is schematically shown, the battery system comprising: a battery 101 having 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 implement in Figure 2The method according to the invention is shown in the figure. Battery cells 1021 and 1022 contained in battery 100 are connected to each other such that battery 100, in a charged state, can provide a predetermined open-circuit voltage at its connection terminal 103. Control unit 104 may include a ring memory, the function of which will be further described below. Furthermore, control unit 104 may have a sleep mode and an active mode, and the control unit is capable of switching between these two modes. The switching from sleep mode to active mode will hereinafter be referred to as waking up the control unit.

[0057] Figure 2 A flowchart is shown for a method according to the present invention for operating a battery having at least two battery cells.

[0058] In step S200 of the method (hereinafter also referred to as the balancing process), the state of charge of the battery cells contained in the battery 100 is balanced (or equalized). The battery 100 may contain more than two batteries. During balancing, a uniform charge distribution occurs in all the battery cells contained in the battery. The balancing or equalization of battery cells is known to those skilled in the art and will not be discussed further here.

[0059] In step S201 of the method, the first measurement process begins. This process will be described in more detail below.

[0060] In step S203, which belongs to the first measurement process, a measurement is performed to determine a battery cell that has the lowest stable voltage among all battery cells. The battery cell with the lowest stable voltage can be determined by: i) measuring the stable voltage of each battery cell contained in the battery; ii) determining the lowest stable voltage among the stable voltages measured on all battery cells; and iii) determining, among all battery cells contained in the battery, a battery cell for which the lowest stable voltage was measured. The measurements of the stable voltage should be performed as simultaneously as possible so that the measured stable voltage can represent the instantaneous state of the battery cell.

[0061] After the first measurement process is performed, the identifiers of the battery cells characterized by the lowest stable voltage measured for those cells can be registered in the history. This history can be stored in a ring memory, preferably contained in storage unit 104.

[0062] Advantageously, the measurement of the first measurement process is performed when the control unit 104 is woken up. If the battery system 100 is included in and coupled to the vehicle, the measurement can also be performed when the vehicle is started.

[0063] In step S205, which belongs to the first measurement process, it is determined whether a predetermined first duration has elapsed since the start of the first measurement process. If the predetermined first duration has elapsed since the start of the first measurement process (the "yes" branch of step S205), then step S207 is executed; otherwise, step S203 is re-executed (the "no" branch of step S205).

[0064] The balancing process and the first measurement process can be performed independently of each other. Therefore, the balancing process S200 and the first measurement process S203 may overlap in time. For example, it is possible that: the first balancing of the balancing process occurs at time point t1; the first measurement of the first measurement process is performed at a later time point t2, and the first measurement determines the battery cell with the lowest stable voltage at time point t2; the second balancing of the balancing process occurs at time point t3 (t3>t2); the second measurement of the first measurement process is performed at time point t4 (t4>t3), and the second measurement determines the battery cell with the lowest stable voltage at time point t4, and so on. After each measurement in the first measurement process, the identifier of the battery cell with the lowest stable voltage and the time point at which the lowest stable voltage was measured can be stored in the history.

[0065] In step S207, it is determined whether the same battery cell is consistently identified as the battery cell with the lowest stable voltage throughout the first measurement process. If so, step S209 is executed (the "yes" branch of S207). If not, step S201 is executed and a new first measurement process begins (the "no" branch of S207).

[0066] The history can be used to determine whether the same battery cell was consistently identified as having the lowest stable voltage during the first measurement process. The history includes at least the identifiers of battery cells for which the lowest stable voltage was determined in the previous first measurement process. If, for the duration of the previous first measurement process, the same identifier is consistently registered in the history, then the battery cell identified by that identifier is the one for which the lowest stable voltage was consistently determined in the first measurement process.

[0067] In step S209, the balancing process is deactivated and the second measurement process begins. From the time the balancing process is deactivated until it is reactivated, no further balancing of the state of charge of the battery cells occurs.

[0068] In step S211, which belongs to the second measurement process: i) the stable voltage of each battery cell contained in the battery is measured; ii) the lowest stable voltage U1 and the second lowest stable voltage U2 among the stable voltages measured on all battery cells are determined; iii) the average stable voltage U is calculated using the stable voltages measured on all battery cells. m ; and iv) determine the following battery cells on which the lowest stable voltage U1 is measured.

[0069] In step S213 (which follows step S211 and belongs to the second measurement process), it is determined whether: i) the battery cell whose lowest stable voltage is consistently determined during the first measurement process is consistent with the battery cell whose lowest stable voltage U1 is measured on it in the earlier step S211 (of the second measurement process); and ii) whether the following relationships apply:

[0070] |U1 - U2| < U S1 And |U1 - U m | < U S2 , (1)

[0071] Among them, U S1 and U S2 These represent positive voltage thresholds, and U... S1 Less than or equal to U S2 .

[0072] If it is determined that the lowest stable voltage U1 is measured on the following battery cell, and the lowest stable voltage is always determined for the battery cell during the first measurement process (i.e., the i-th point is determined to be positive) and condition (1) is met, then step S215 (the "yes" branch of S213) is performed.

[0073] If it is determined that the cell whose lowest stable voltage is consistently determined during the first measurement process is inconsistent with the cell whose lowest stable voltage U1 is measured on it in step S211, or one of the two conditions (1) is not met, then step S217 (the "No" branch of S213) is performed.

[0074] In step S215, it is reported that the battery cell that consistently reaches the lowest stable voltage during the first measurement process has increased charge loss.

[0075] In step S219, following step S215, the balancing process is reactivated and the second measurement process ends. Step S200 is then performed after step S219.

[0076] In step S217, which belongs to the second measurement process, it is determined whether a predetermined second duration has elapsed since the balancing process was stopped (or the second measurement process was started). If the predetermined second duration has elapsed since the balancing process was stopped (or the second measurement process was started), step S221 (the "yes" branch of step S217) is executed; otherwise, step S211 (the "no" branch of step S217) is re-executed.

[0077] In step S221, the balancing process is reactivated and the second measurement process ends. Step S200 is then performed after step S221.

[0078] While at least one exemplary embodiment has been described above, it should be noted that numerous variations exist. It should also be noted that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description is intended to provide guidance to those skilled in the art for implementing at least one exemplary embodiment, wherein it should be understood that the elements described in one exemplary embodiment can be varied in their operating principles and arrangement without departing from the subject matter correspondingly defined in the appended claims and their legal equivalents.

[0079] List of reference numerals

[0080] 100 Battery System

[0081] 101 Battery

[0082] 1021 and 1022 battery cells

[0083] 103 Battery connection terminal

[0084] 104 Control Unit

Claims

1. A method for operating a battery having at least two battery cells, the method comprising: a balancing process in which the state of charge of the battery cells is continuously or repeatedly balanced; a first measuring process which is carried out over a predetermined first duration during the balancing process, in which measuring process measurements are repeatedly carried out, wherein in each of the measurements a battery cell is respectively determined which has the lowest stable voltage among the battery cells in the respective measurement; a determination of whether the same battery cell is always determined as the battery cell having the lowest stable voltage during the first measuring process; and if this is the case: a test process is carried out in which the balancing process is interrupted or ended and a test is carried out as to whether the battery cell which is always determined to the lowest stable voltage during the previous first measuring process has an elevated charge loss which is indicative of a possible malfunction, wherein the test process has: a second measurement process performed over a predetermined second duration, in which one or more measurements are carried out, in each of which measurements a minimum stable voltage U1 in the stable voltages of the individual battery cells is determined, a battery cell over which the minimum stable voltage U1 is determined, a second smallest stable voltage U2 in the stable voltages of the individual battery cells, and an average stable voltage U m ; and a determination of an elevated charge loss on the battery cell which is always determined to the lowest stable voltage during the first measuring process, if a minimum stable voltage U1 is measured on the battery cell and the following relationship applies: | U1 - U2| < U S1 and |U1 - U m | < U S2 , where U S1 and U S2 represent positive voltage thresholds, respectively, and U S1 is less than or equal to U S2 ; and wherein a predetermined second duration is concatenated to the predetermined first duration.

2. The method of claim 1, wherein, the measurements of the first measuring process are carried out when waking up a control unit which controls the battery, and the control unit is switched from its sleep mode to an active mode by waking up the control unit.

3. The method of claim 2, wherein, after waking up the control unit, the measurements of the first measuring process are carried out first and only then is a possible balancing of the state of charge of the battery cells carried out.

4. The method according to one of claims 1 to 3, wherein each time the measurements of the first measuring process are carried out, this comprises: measuring the stable voltage of all battery cells contained in the battery; and 5. The method according to one of claims 1 to 3, wherein finding the lowest stable voltage among the stable voltages measured on all battery cells. after each time the measurements of the first measuring process are carried out, an identification of the battery cell having the lowest stable voltage is registered in a history, the history contains the identifications of the battery cells for which the determination to the lowest stable voltage was made, and 6. The method according to one of claims 1 to 3, wherein based on the identifications registered in the history over a predetermined first duration, it is determined whether there is a battery cell among the battery cells which always had the lowest stable voltage during the predetermined first duration and which it is, and identifying the lowest stable voltage U1 and the second lowest stable voltage U2 among the stable voltages measured on all battery cells, and identifying the average stable voltage U using the stable voltages measured on all battery cells m ; and each time the measurements of the second measuring process are carried out, this comprises:

7. The method according to one of claims 1 to 3, wherein measuring the stable voltage of all battery cells contained in the battery; 8. The method according to one of claims 1 to 3, further comprising: determining the battery cell having the lowest stable voltage U1.

9. A battery system having a battery with at least two battery cells and a control unit coupled with the battery cells, wherein, after the determination of the elevated charge loss or at the latest after the predetermined second duration has elapsed, the balancing process is activated again.

10. The battery system of claim 9, wherein, if an elevated charge loss is determined when carrying out the test process, the elevated charge loss is reported. the control unit is configured for carrying out a method according to one of claims 1 to 8. the control unit has a ring memory in which a history containing the identifications of the battery cells for which the determination to the lowest stable voltage was made is stored. the control unit is configured for carrying out a method according to one of claims 1 to 8. the control unit has a ring memory in which a history containing the identifications of the battery cells for which the determination to the lowest stable voltage was made is stored.

11. A vehicle having a battery system according to claim 9 or 10.

12. The vehicle of claim 11, wherein, The vehicle is configured to trigger the measurement procedure upon start of the vehicle. The vehicle is configured to trigger the measurement procedure upon start of the vehicle.

Images