Method for carrying out a charging process in a battery system

Abstract

Method (100) for carrying out a charging process (L) in a battery system (1), characterized by the following steps: a) Initiating the charging process (L) at the battery system (1), b) Acquiring at least one charge state information (110) that is specific to a charge state of the battery system (1), c) Initiating an interruption phase (U) depending on the detected state of charge information (110), so that the charging process (L) is interrupted during the interruption phase (U), d) Acquiring at least one balancing current information (120) which is specific for at least one balancing current in the battery system (1) during the interruption phase (U), e) Determining an adapted charging end (E) depending on the balancing current information (120), f) Continuing the charging process (L) taking into account the adjusted charging end (E).

Description

[0001] The present invention relates to a method for carrying out a charging process in a battery system according to the independent method claim. Furthermore, the invention relates to a system and a charging device according to the independent device claims. State of the art

[0002] It is known from the prior art that battery cells (e.g., lithium-ion battery cells) can be connected in series and / or parallel. This serves in particular to provide the required power and energy capacity, for example, for electric traction batteries. Such a connection can be achieved, for example, by connecting cells, modules, or strings in parallel to form a battery pack.

[0003] Various charging strategies can be used to charge such battery packs, such as CC-CV (Constant Current-Constant Voltage) or pulse charging. Disclosure of the invention

[0004] The invention relates to a method with all the features of the independent method claim, a system with the features of claim 11, and a charging device with all the features of claim 12. Further features and details of the invention will become apparent from the respective dependent claims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the system and the charging device according to the invention, and vice versa, so that the disclosure of the individual aspects of the invention always makes, or can make, reciprocal references.

[0005] In particular, the invention provides a method for carrying out a charging process in a (rechargeable) battery system, preferably a lithium-ion battery system.

[0006] Preferably, the battery system is designed as a battery pack and / or comprises at least one battery pack, in particular a rechargeable battery, preferably as a parallel connection of battery units, in particular battery cells (hereinafter referred to as cells) or battery modules (hereinafter referred to as modules) or battery strings (hereinafter referred to as strings).

[0007] For example, with such a parallel connection of battery units, different charge levels may occur due to operational inhomogeneities. For example, at least one of the following inhomogeneities may occur in the battery system: - an inhomogeneous temperature distribution, - an inhomogeneous state of aging, - an inhomogeneous capacitance and / or internal resistance distribution due to manufacturing tolerances, - an inhomogeneous connection of the parallel battery units.

[0008] In particular, such inhomogeneities can lead to an inhomogeneous distribution of capacity and internal resistance in the individual cells, which can result in an inhomogeneous load on the parallel battery units during charging and discharging. Specifically, due to the resulting different states of charge at the end of a load phase (i.e., charging and / or discharging and / or interruption of charging) and during periods without a load (e.g., during a balancing phase), this leads to balancing currents between the parallel-connected battery units.

[0009] For example, equalizing currents can lead to overcharging. If, for instance, one of the cells in the battery system (e.g., in a parallel string) is already charged to 100% SOC (state of charge) after the charging phase, an equalizing current may flow into this cell (from another parallel string), and the cell may be overcharged by this equalizing current (i.e., SOC > 100%). The cell voltage may then exceed a maximum permissible cell voltage. The maximum permissible cell voltage is, for example, 4.2 V.

[0010] The inventive method is therefore preferably used to prevent and / or reduce overcharging in the battery system, particularly in the cells, preferably without actively interrupting the balancing currents, and especially preferably without the use of additional switching elements to interrupt (i.e., also to reduce) the balancing currents. In particular, the charging process is adapted according to the inventive method so that the end of charging (e.g., the maximum state of charge) is flexibly adjusted, thus preferably preventing at least one of the cells of the battery system from being overcharged by balancing currents. This has the particular advantage that no overcharging occurs due to balancing currents and / or the usable capacity can be increased by flexibly adjusting the end of charging.

[0011] Advantageously, in the method according to the invention at least the following steps can be carried out, in particular one after the other or in any order, whereby individual steps can also be repeated if necessary: a) Initiating the charging process in the battery system, b) Acquiring at least one charge state information that is specific to a charge state of the battery system (e.g., proportional to it), in particular during the charging process and / or outside of an interruption phase, preferably repeatedly and / or cyclically during the charging process, c) Initiating an interruption phase depending on the recorded state of charge information, so that the charging process is interrupted (paused) during the interruption phase, d) Recording at least one balancing current information that is specific for at least one balancing current in the battery system during the interruption phase, e.g., proportional to it, in particular cyclical and / or repeated, e) Determining an adapted charging end depending on the balancing current information, f) Continue the charging process taking into account the adjusted charging end time.

[0012] Preferably, according to step f), the charging process continues at most until the adjusted charging end (and is then, if necessary, completely terminated), so that after the adjusted charging end, overcharging, e.g., of cells in the battery system, is prevented by the balancing current. This has the advantage that an adjusted charging end can be determined reliably and quickly, thus preventing overcharging. In particular, the adjusted charging end can still provide (at least approximately) the maximum possible and / or useful charge.

[0013] For example, in steps b) and / or c), a state of charge (SOC) is determined based on the state of charge information, with the initiation of the interruption phase preferably occurring when the state of charge exceeds a predefined minimum value. This minimum value is, for example, in the range of 60% to 90%, preferably 80% to 85%. For example, the initiation of the interruption phase only occurs if the state of charge is less than 90%. The balancing currents flowing during this interruption phase (i.e., a charging interruption) can then be detected or measured, for example, according to step d), and / or determined based on the balancing current information. Preferably, a charge quantity transferred by the balancing currents and / or a calculated charge quantity can be determined based on the balancing current information. The calculated charge quantity is, for example, a charge quantity that approximately corresponds to a charge quantity transferred during a balancing phase.

[0014] Preferably, the duration of the interruption phase is a maximum of 0.5 min, 1 min, or 2 min, so that after this duration is exceeded, the charging process resumes (according to step f). In particular, this makes it impossible to determine the total amount of charge transferred by the balancing currents during a typical balancing phase, since the balancing current might continue to flow after this duration if the interruption persists (e.g., for more than 10 minutes). Therefore, preferably, to determine the calculated charge quantity relevant for the adjusted charging end, the balancing current information is evaluated, in particular by extrapolation and / or based on stored characteristic curves.The advantage here is that the short interruption during the interruption phase, which is shorter than a theoretical complete equalization phase, does not significantly lengthen the actual charging process.

[0015] Preferably, the adjusted loading end is determined based on the following calculation, e.g. by calculating a processing device: SOC_ln=SOC_la−ΔQ_a / (C_n*SOH_c) This includes: SOC_In is the new adjusted charging end (taking into account balancing currents) in %, SOC_Ia the old charging end (without considering balancing currents) in %, ΔQ_a is a calculated amount of charge dissipated by the balancing current in Ah (ampere-hours). C_n is the nominal capacity of the battery cell in Ah, SOH_c is the aging state (capacity) of the cell in %.

[0016] The charging end point can be adjusted, for example, from an old charging end point with a state of charge of 100% to an adjusted charging end point with a state of charge below 100% (e.g., 99.4%). In other words, according to step f), the charging process then continues until a state of charge below 100% is reached, which corresponds to the adjusted charging end point (e.g., 99.4%).

[0017] In particular, the timing of the initiation of the interruption phase according to step c) depends on an evaluation of the recorded state-of-charge information. This evaluation can be performed electronically, for example, by a processing device such as a microprocessor or the like.

[0018] For example, the state-of-charge information is a battery voltage or another parameter that is particularly proportional to and / or correlated with the battery's state of charge. Preferably, the balancing current information is a charge quantity or the like that correlated with a balancing current and / or a charge quantity that is transferred, particularly during the interruption phase, between battery units of the battery system (e.g., battery cells, battery modules, or battery strings).

[0019] According to an advantageous embodiment of the invention, it can be provided that, according to step e), the adapted charging end is determined as a reduction of a predetermined charging end (old charging end), so that overcharging of the battery system by a further balancing current after completion of the charging process is avoided, wherein preferably the adapted charging end is calculated on the basis of the predetermined charging end and / or the balancing current information and / or at least one nominal capacity of the battery system and / or at least one aging state of the battery system.

[0020] Furthermore, it may be possible to determine a (possibly calculated) charge quantity based on the balancing current information, which is specific to a charge quantity transferred by the balancing current during the interruption or balancing phase. In particular, the (calculated) charge quantity is specific to a charge quantity in the balancing phase, which preferably lasts longer than the interruption phase. For example, the entire possible balancing current would flow during the balancing phase, which may not be the case during the interruption phase due to a predefined maximum duration. Limiting the interruption phase to a maximum duration has the advantage that the charging process does not have to be interrupted unnecessarily long.

[0021] Advantageously, the invention may provide that (particularly according to step e) for determining the adjusted charging end) a ratio is determined between a charge quantity specific to the balancing current, in particular a charge quantity transferred and / or calculated during the interruption phase, and a further parameter, wherein the further parameter preferably comprises at least one capacity-dependent and / or one age-dependent parameter of the battery system. The capacity-dependent parameter is, for example, a nominal capacity of the battery cell and / or the age-dependent parameter is, for example, an aging state of the cell. For example, the ratio is determined by a calculation of a processing device, so that a reliable and rapid determination of the adjusted charging end is possible.

[0022] It can be advantageous if, within the scope of the invention, the balancing current is determined, and in particular measured, as a balancing current between parallel-connected cells and / or modules and / or strings of the battery system, based on the balancing current information. In particular, a module comprises several cells and / or a string comprises several modules in series, with the strings optionally being connected in parallel. This has the advantage that an increased energy content can be provided.

[0023] A further advantage of the invention can be achieved if a (calculated) charge quantity is determined by an estimation method, in particular by extrapolation, based on the balancing current information. This has the advantage that the interruption phase can be of short duration, so that the charging process does not have to be interrupted for a significantly long time. Furthermore, the extrapolation, which is carried out, for example, by a processing device, allows for a particularly reliable estimation of the charge quantity.

[0024] It is also advantageous if a (calculated) charge quantity is determined by comparing the balancing current information with a target value, particularly with predefined characteristic curves. This has the advantage that the interruption phase can be of short duration, so that the charging process does not have to be significantly interrupted. Nevertheless, a (calculated) charge quantity can be determined that corresponds approximately to a charge quantity in an uninterrupted balancing phase.

[0025] In another possibility, the charging process can be carried out with a charging current, particularly a constant one, whereby the charging current is preferably reduced predominantly or substantially to 0 A (amperes) during the interruption phase, so that a balancing current can flow. Preferably, the balancing current is lower than the charging current and / or operating current of the battery system. This allows the balancing current to be reliably determined.

[0026] It is also conceivable that, according to step f), the charging process continues until a predetermined charging end (e.g., until a state of charge (SOC) of 100%) if the balancing current information indicates essentially no balancing current (i.e., a charge amount of essentially 0 Ah), and otherwise the charging process continues until the adjusted charging end, where preferably the adjusted charging end is lower than the predetermined charging end. This has the advantage that overcharging can be avoided after the adjusted charging end, since the state of charge of the cells then potentially has a certain "reserve".

[0027] Furthermore, within the scope of the invention, it is conceivable that (according to step e) ) the adapted charging end is determined depending on a predetermined charging end, wherein, in particular, the predetermined charging end is specified without taking the balancing currents into account. In particular, the predetermined charging end is 100% SOC (of the battery system or the battery) to ensure a complete charge.

[0028] The invention also relates to a system comprising: - at least one control unit, which is preferably designed to carry out a method according to the invention, - at least one sensor element for detecting at least one balancing current information in a battery system.

[0029] In particular, it is intended that the sensor element is connected to the control unit electrically or wirelessly.

[0030] The system according to the invention thus offers the same advantages as those described in detail with reference to a method according to the invention.

[0031] The invention also relates to a charging device for a battery system. In particular, the charging device includes a control unit designed to carry out a method according to the invention. The charging device according to the invention thus offers the same advantages as those described in detail with reference to a method and / or a system according to the invention.

[0032] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination. The drawings show: Fig. 1 a schematic representation of a battery system, Fig. 2 another schematic representation of a battery system, Fig. 3. An example diagram with measured equalizing current information. Fig. 4 a schematic representation for visualizing a method according to the invention, Fig. 5 a further schematic representation for visualizing a method and system according to the invention and a charging device according to the invention.

[0033] In the following figures, identical reference numerals are used for the same technical features even for different embodiments.

[0034] In Fig. Figure 1 schematically depicts a battery system 1 according to the invention. It is shown that the battery system 1 can be configured as a battery pack and / or may include a battery pack, wherein the battery pack can be configured as a parallel connection of battery units. In particular, the battery units can comprise, for example, cells 2, modules 3 and / or strings 4.

[0035] Examples include: Fig. 1. A first strand 4.1 and a second strand 4.2 are connected in parallel, each comprising modules 3, namely a first module 3.1, a second module 3.2, a third module 3.3, and a fourth module 3.4. Each strand can also contain 1 to n modules, where n can be any number and is 2 here. In another example, in Fig. 2. A first module 3.1 and a second module 3.2 are connected in parallel, each comprising 2 cells, namely a first cell 2.1, a second cell 2.2, a third cell 2.3, and a fourth cell 2.4. Each module can also have 1 to m cells, where m can be any number and here is 2.

[0036] In Fig. Figure 3 illustrates a measurement result as an example of a balancing current information 120. A measured balancing current information 130, which was recorded, for example, by a current measurement, is represented by a continuous line with a current value I over time t. Based on this measured information, it is possible to determine a calculated balancing current information 140 (represented as a dashed line). For this purpose, for example, an extrapolation of the measured values ​​can be performed. It is also possible to determine a calculated charge quantity using this method.

[0037] In Fig. Figure 4 schematically visualizes a method 100 according to the invention. It shows that a charging process L is initially carried out, which is then interrupted in an interruption phase U. After a measurement of balancing current information 120, the charging process L is resumed until a (adapted) charging end E is reached. The charging end E indicates, for example, a state of charge at which the charging process L is to be terminated. The indicated state of charge of the adapted charging end E is lower than the state of charge of the predetermined charging end VE, the latter being, for example, 100% SOC.

[0038] In Fig.Figure 5 shows a further illustration for visualizing a method 100 and a system according to the invention. It can be seen that a charging device 10 according to the invention can be provided, which includes at least one control unit 11. The control unit 11 uses, for example, at least one sensor element 20 to detect at least one balancing current information 120 in a battery system 1. The sensor element 20 can be part of the charging device 10 or be designed separately from it. This detection of the at least one balancing current information 120 takes place, for example, during an interruption phase U, which is initiated, in particular, depending on a detected state-of-charge information 110, for example, by the control unit 11. Based on the balancing current information 120, an adapted charging end E can be determined. The adapted charging end E is, in particular, earlier than a predetermined charging end VE.The predefined charging end VE is, for example, identical to the adjusted charging end if, based on the balancing current information 120, it is determined that no balancing current is flowing. The charging process can then be resumed. For example, the control unit 11 then interrupts the charging process when the adjusted charging end E is reached.

[0039] The preceding explanation of the embodiments describes the present invention exclusively by way of examples.

[0040] Of course, individual features of the embodiments can be freely combined with one another, provided this is technically feasible, without leaving the scope of the present invention.

Claims

[1] Method (100) for carrying out a charging process (L) in a battery system (1), characterized by the following steps: a) Initiating the charging process (L) at the battery system (1), b) Acquiring at least one charge state information (110) that is specific to a charge state of the battery system (1), c) Initiating an interruption phase (U) depending on the detected state of charge information (110), so that the charging process (L) is interrupted during the interruption phase (U), d) Acquiring at least one balancing current information (120) which is specific for at least one balancing current in the battery system (1) during the interruption phase (U), e) Determining an adapted charging end (E) depending on the balancing current information (120), f) Continuing the charging process (L) taking into account the adjusted charging end (E). [2] Method (100) according to claim 1, characterized by , that according to step e) the adapted charging end (E) is determined as a reduction of a predetermined charging end (VE) so that an overcharging of the battery system (1) by a further balancing current after completion of the charging process (L) is avoided, wherein preferably the adapted charging end (E) is calculated on the basis of the predetermined charging end (VE) and / or the balancing current information (120) and / or at least one nominal capacity of the battery system (1) and / or at least one aging state of the battery system (1). [3] Method (100) according to claim 1 or 2, characterized by , that based on the balancing current information (120) a charge quantity is determined which is specific for a charge quantity transferred by the balancing current in the interruption phase (U). [4] Method (100) according to any one of the preceding claims, characterized by, that according to step e) to determine the adapted charging end (E) a ratio of a charge quantity specific for the balancing current and a further parameter to each other is determined, wherein preferably the further parameter comprises at least one capacity-dependent and / or one aging-dependent parameter of the battery system (1). [5] Method (100) according to any one of the preceding claims, characterized by , that the balancing current is determined, in particular measured, based on the balancing current information (120) as a balancing current between parallel connected cells (2) and / or modules (3) and / or strings (4) of the battery system (1). [6] Method (100) according to any one of the preceding claims, characterized by , that a charge quantity is determined by an estimation procedure, in particular by extrapolation, based on the balancing current information (120). [7] Method (100) according to any one of the preceding claims, characterized by , that a charge quantity is determined by comparing the balancing current information (120) with a specification, in particular with predefined characteristic maps. [8] Method (100) according to any one of the preceding claims, characterized by , that the charging process (L) is carried out with a, in particular constant, charging current, wherein the charging current is predominantly or substantially reduced to 0 A during the interruption phase (U). [9] Method (100) according to any one of the preceding claims, characterized by , that according to step f) the charging process (L) continues to a predetermined charging end (VE) if the balancing current information (120) substantially indicates no balancing current, and otherwise the charging process (L) continues to the adapted charging end (E), wherein the adapted charging end (E) is less than the predetermined charging end (VE). [10] Method (100) according to any one of the preceding claims, characterized by, that according to step e) the adapted charging end (E) is determined as a function of a given charging end (VE), whereby the given charging end (VE) is specified without taking into account the balancing current. [11] System, having: - at least one control unit (11) configured to perform a method (100) according to any of the preceding claims, - at least one sensor element (20) for detecting at least one balancing current information (120) in a battery system (1), wherein the sensor element (20) is electrically or wirelessly connected to the control unit (11). [12] Charging device (10) for a battery system (1), characterized by that the charging device (10) comprises a control unit (11) which is configured to perform a method (100) according to one of the preceding claims.

Images