DE102017102877A1 - Method and device for controlling a battery system - Google Patents

Abstract

Method and apparatus for controlling a battery system having at least two battery cells, characterized by detecting information about a time course of an incremental capacity on a battery cell of the battery system by detecting a time course of a voltage of the battery cell of the battery system and the detection of the time course of a current of the battery cell the battery system,
Determining information about a time when the time course meets a condition, determining information about a time difference between the times,
Determining information about a charge difference between a charge of the battery cell based on a specified as compensation target battery level, depending on the information about the time, and the time course of the current of the battery cell, regulating the battery system depending on the information about the charge difference.

Description

The invention relates to a method and a device for controlling a battery system, in particular a battery system with a plurality of battery cells in a discharge or a charging process.

In a battery system having a plurality of battery cells, the capacity of different battery cells may differ due to manufacturing tolerances, temperature differences, and other factors, particularly with increasing use or age. The battery cells described below are secondary battery cells, i. Battery cells. If each of the battery cells were charged during charging so that all the battery cell in the battery system reach their end-of-charge voltage, the low-capacity battery cells may become overloaded. This would lead to damage to these battery cells. During the discharge process, a battery cell with a relatively lower charge in the battery system would possibly first reach the discharge end voltage. The discharge of the battery system would then have to be stopped in order to avoid damage to the already completely discharged battery cell, although not yet fully discharged battery cells are available in the battery system. Differences in capacity are not the only relevant mechanism here. Even with multiple battery cells with identical capacity, for example, due to differences in the self-discharge relative shifts of the current charge levels (state-of-charge, short: SoC) can be adjusted. The state-of-charge is the charge in the cell based on its capacity.

By balancing charges between the battery cells, the balancing, the charging state of the individual battery cells is matched to each other, so that the battery cell with the highest capacity in the battery system can be fully charged without other battery cells are damaged by overcharging in contrast, lower capacity , For this purpose, for example, during a charging of the battery system by a corresponding electronic circuit, the battery cell which would first reach the end of charge to discharge other battery cells in the battery system discharged. Charging continues for all battery cells. During the discharge process, a procedure is followed to charge the battery cell with the lowest charge in the battery system by charging it from the battery cell with the highest charge in the battery system.

For example, to estimate how high the charge balance requirement, ie, a balancing demand of the battery system, is, as in DE 10 2012 207 826 A1 and US 7923969 B1 represented voltages of the battery cells measured and compensated the voltages of the battery cells via a charge state equalization circuit with each other.

Out EP 1 685 622 B1 a charging method is known in which the cell voltages of individual battery cells are continuously measured and the battery cells, depending on the respective state of charge of the battery cells are charged differentiated.

In EP 2320242 B1 an estimation means is provided, which determines the voltage of a battery cell by means of a voltage measuring unit, a temperature measuring unit, a memory unit and an estimating unit. A compensation unit balances the charging states of the individual battery cells with each other.

US 8710800 B1 in this regard, discloses a battery equalization current path that allows charging of individual battery cells of the battery system while other battery cells of the battery system are not being charged.

EP 2 592 714 B1 in this regard, discloses the detection of correction voltages needed to balance the charges based on an internal resistance of the battery cell to be equalized.

US 2015/318721 A1 discloses a control unit for balancing the states of charge between individual battery cells of a battery, the balancing requirement being determined by forming a difference between the capacitance of a reference battery cell and the capacities of the individual battery cells.

US 9472977 B1 discloses a method of balancing the states of charge between individual battery cells of a battery, wherein the state of charge of a battery cell is derived by comparing the cell voltage with an average cell voltage, and balancing the battery cells based thereon.

EP 0 998 799 B1 discloses a method of charging serially connected battery cells, wherein the charging current amount is controlled via a balancing circuit.

DE 10 2013 206 885 A1 discloses a method for preparing a charging process of a battery, wherein before the charging process for each battery cell in each case a characteristic characteristic of the aging state is determined, and based on an individual starting voltage is determined, with which the charging operation is started.

Such regulations require consideration of the charging or discharging operation over a long period of time, an ampere-hour meter and / or complex electronic circuits to determine the current balancing demand. The ampere hour counter estimates the charge level of a battery cell, for example, by integrating instantaneous values of the charging current or the discharge current from this battery cell during the entire duration of the charging process or the discharging process. The period for determining the current balancing requirement is thereby long. In addition, the determination of the state of charge due to integration is subject to errors. Furthermore, voltage-controlled balancing due to low dV / dQ gradients in a plateau region is severely faulty, so that such methods can preferably only be used with complete charge and discharge cycles.

The present invention addresses the problem of providing an improved method of controlling the battery system.

According to the invention, this problem is solved by a method and a device according to the independent claims. Advantageous embodiments are the subject of the dependent claims.

Regarding the method, this problem is solved by acquiring information about a first time course of a first incremental capacity at a first battery cell of the battery system by detecting a first time course of a first voltage of the first battery cell of the battery system and detecting the first time course of a first current the first battery cell of the battery system, detecting information about a second time course of a second incremental capacity at a second battery cell of the battery system by detecting a second time course of a second voltage of the second battery cell of the battery system and the detection of the second time course of a second current of the second Battery cell of the battery system, determining information about a first time at which the first time course meets a condition, obtaining information about a second Time at which the second time course satisfies the condition, determining information about a charge difference between a first charge of the first battery cell based on a specified first compensation target charge level of the first battery cell and a second charge of the second battery cell with respect to a predetermined as a second compensation target Charging the second battery cell depending on the information about the time difference, and regulating the battery system depending on the information about the charge difference. For the regulation, the time profile of the incremental capacity is used by means of the ICA curve. For example, the aim of the scheme is to compensate, i. a coincidence of the charge states (SoC) of the battery cells at a time and at a defined state of charge can be achieved. Since the extreme values of the ICA curve occur with characteristic charge levels, it is equally possible to use a match of the ICA curve at one time and at a defined point of the ICA curve as a control target.

The balancing demand, i. An amount of charge which has to flow to compensate for the difference from one battery cell to at least one other battery cell is determined by the evaluation of voltages and currents of individual battery cells. This allows a simple way the control regardless of the way in which the individual battery cells are interconnected in the battery system to form a composite. In addition, this allows an improved charge balance control without faulty integration of a current.

The information about the charge difference between at least two battery cells, which are connected in series, is preferably determined as a function of information about an instantaneous current intensity in the series circuit. By means of the instantaneous current intensity, the difference of the charge with respect to the respective compensation target of the charge level between at least two battery cells which are connected in series can be easily determined.

Preferably, a time course of a voltage fulfills the condition when a derivative of the charge after the voltage has an extreme value. This condition makes it possible to draw conclusions about the state of charge of the relevant battery cell in the ICA curve. The voltage at which these occur is particularly suitable for conclusions since the voltages at which these extreme values occur are identical for batteries of the same cell chemistry at the same temperature and the same aging state. Temperature-related and aging-related changes are not negligible. These effects are compensated for by determining their influence on the ICA curve and then mathematically neutralizing it. Extreme values are therefore particularly well suited to determine information about the charge difference between battery cells.

Preferably, the extreme value is a maximum value. For example, a maximum value is used as a compensation target. That is, exactly one point of both ICA curves is used, which is to be achieved at the same time in both ICA curves. Typical variations of battery charge cell charge have two maximum values for certain voltages. The analysis of the slope of the charge Q over the voltage V during the charging or discharging process and the determination of extremes or maximum values enables the particularly simple detection of suitable times at which reliable information about differences in charges of battery cells with respect to a desired balance target of the charge state are obtained can. This procedure is based on an incremental capacity analysis, ICA. In this case, the ICA curve is determined by a derivation of the temporal voltage curve during a charging process or discharge process with a known constant current or by an OCV estimation and integral formation of the current for a battery cell. The characteristic extreme points of the ICA curve occur at characteristic values of the voltage of identical battery cells. Furthermore, the characteristic extreme points of the ICA curve occur at characteristic values of the charge state. Therefore, the control can be done on the basis of the characteristic extreme points. The incremental capacity is defined as: $$\text{ICA}=\text{dQ}/\text{dV}$$

Preferably, the information about voltages during the duration of a charging process is detected in a voltage interval that is shorter than a voltage range between a first voltage when the battery cell is completely discharged and a second voltage when the battery cell is fully charged. It is sufficient if the detected area contains at least one extreme value or at least one maximum value. For example, in the case of battery cells, their ICA curve has two maximum values, the voltage across the battery cell during the charging process is detected only in a region in which the higher of the maximum values lies. The ICA curve therefore does not have to be checked over the entire voltage range. The real voltage curves in battery cells vary depending on cell chemistry, temperature or aging state. For a specific cell chemistry, the influence of temperature on the stress at which the extreme sites occur is low. Assuming a normal spread of the aging state of the individual battery cells, the influence of the aging state on the voltage level of the extreme points can be neglected. In order to acquire information about the voltages of the battery cells, it is sufficient to detect and evaluate a short portion of the course of the change in the vicinity of extreme points. The entire ICA curve does not need to be known.

With regard to the method, this problem is also solved in particular by acquiring information about a first current to the first battery cell of the battery system, acquiring information about a second current to the second battery cell of the battery system, wherein the first time profile depends on a first integral of the first Current over time is determined, the second time course is determined depending on a second integral of the second current over time. This means that the time profile of the integral Q = I dt is used for an evaluation of the incremental capacitance by means of the ICA curve.

Preferably, the controller is designed to charge or discharge the battery system with a constant current.

With regard to the device, this problem is solved in that a control device, a measuring device, a computing device and a compensation device are provided, wherein the measuring device is formed by the detection of a first time course of a first voltage of a first battery cell of a battery system and the detection of a first temporal History of a first current of a first battery cell of a battery system to detect information about a first time course of a first incremental capacity at a first battery cell of a battery system, and by detecting a second time course of a second voltage of a second battery cell of a battery system and the detection of a second time Course of a second stream of a second battery cell of a battery system information about a second time course of a second incremental capacity on a second battery to detect cell of the battery system, wherein the computing device is adapted to determine information about a first time at which the first time course meets a condition to determine information about a second time at which the second time course meets the condition. The computing device is also designed information about the charge difference between the first charge of the first battery cell based on a specified first compensation target charge level of the first battery cell and the second charge of the second battery cell based on a second balance target predetermined charge level of the second battery cell depending on the information about determine the first time, the information about the second time, and the first time course of the current of a first battery cell and the second time course of the current of a second battery cell. The control device is designed to regulate the compensation device depending on the information about the charge difference.

• 1 schematisch einen Teil eines Batteriesystems,
• 2 schematisch einen Verlauf einer Ableitung einer Ladung einer Batteriezelle nach der Spannung aufgetragen über der Spannung der Batteriezelle,
• 3 schematisch einen Verlauf von zwei Ableitungen von Ladungen zweier verschiedener Batteriezellen nach der Spannung aufgetragen über der Spannung der Batteriezellen,
• 4 schematisch Teile eines Verfahrens zur Regelung eines Batteriesystems.

Other features and advantages of the invention will become apparent from the dependent claims, from the description, and from the drawing. In the drawing shows:

• 1 schematically a part of a battery system,
• 2 schematically a profile of a derivative of a charge of a battery cell after the voltage plotted against the voltage of the battery cell,
• 3 schematically a plot of two derivatives of charges of two different battery cells after the voltage plotted against the voltage of the battery cells,
• 4 schematically parts of a method for controlling a battery system.

In the figures, like reference numerals refer to like, similar or functionally identical components.

1 schematically shows a device 100 for controlling a battery system 102 with at least two battery cells 104 . 106 , ..., 108 , which are connected in series. Several of these series circuits can also be connected in parallel.

A control device 110 and a measuring device 112 are with a computing device 114 connected via data lines. The control device 110 is designed to the battery cells 104 . 106 , ..., 108 with a current I current to load or discharge. The control device 110 also controls the compensation device 116 when charging or discharging the battery system 102 , It is preferably provided to interrupt the charging process during charge equalization. The discharging process is preferably not interrupted.

The measuring device 112 is formed, information about a first time course of a first incremental capacity at a first battery cell 104 a battery system, and information about a second time course of a second incremental capacity at a second battery cell 106 of the battery system.

The measuring device 112 is for example formed during charging or discharging information about voltages V1, ..., Vn to the battery cells 104 . 106 , ..., 108 to capture. For example, corresponding serve parallel to the battery cells 104 . 106 , ..., 108 switched measuring circuits 1121 . 1122 , ..., 112n that with the measuring device 112 are connected. The electrical connections are in 1 shown as dashed lines. Information about the current I, for example, also detected by appropriately switched measuring circuits.

The computing device 114 is configured to determine information about a first time at which the first time course meets a condition and to obtain information about a second time at which the second time course meets the condition.

The computing device 114 For example, it is designed to determine, for each of the battery cells 104, 106,..., 108, depending on the measured voltages V1,..., Vn, information about a time at which a time profile of the incremental capacity fulfills the condition. The condition is met, for example, if the incremental capacity of the battery cell has an extreme value, in particular a maximum value. Further details are described in the following procedure.

The computing device 114 is designed to information about a charge difference between the charges of the battery cells 104 . 106 , ..., 108 Based on a given as compensation target charge level of the battery cells depending on the information about the time difference to determine.

The control device 110 is formed, the compensation device 116 depending on the difference. When battery cells 104 . 106 , ..., 108 have different charges with respect to the charge level of the battery cells specified as a compensation target during the charging process, for example, a battery cell 104 . 106 , ..., 108 with lowest charge based on the specified as compensation target battery level of the battery cells from another battery cell 104 . 106 , ..., 108 with a higher charge, based on the charge level of the battery cells specified as the compensation target, until the charge state of the battery cells is reached 104 . 106 , ..., 108 at a selected balancing point of the ICA curve, which corresponds to the balancing target of the charging state of the battery cells, is approximately equal. For example, this is the midpoint of the two maxima of the ICA curve. The regulation takes place during the unloading process accordingly. As a result, charge flows from a battery cell 104 . 106 , ..., 108 with a larger charge in relation to the charge level of the battery cells in the battery cell specified as a compensation target 104 . 106 , ..., 108 with a lower charge based on the charge level of the battery cells specified as compensation target. The electrical connections are in 1 shown as dash-dotted lines. Alternatively, the excess energy of a battery cell with a larger charge can be dissipated by an ohmic load, based on the charge level of the battery cells specified as a compensation target.

The following is a method for determining the balancing need using the example of lithium-ion battery cells, which in any way to a composite in the form of a battery system 102 or a battery are described. In this case, in the example for determining the balancing requirement, information about the voltages V1, V2,..., Vn of the battery cells is obtained 104 . 106 , ..., 108 used.

The method is based on the incremental capacity analysis, ICA. Incremental capacity analysis represents a slope of the charge over the voltage of a battery cell during a charged current or current I charge or discharge process. An ICA curve can be determined as follows, depending on the derivative of the voltage curve with known current: $$\text{dQ}/\text{dV}=\mathrm{{\rm I}}{\left(\text{dV}/\text{dt}\right)}^{-1},$$

Depending on the aging state of the battery cell, the cell temperature and the cell chemistry, the ICA curve has characteristic extreme points, which are also referred to below as maximum values. Minimum values can also be used. During charging or discharging with constant current I this is also known. An instantaneous current I may also be from the measuring device 112 be recorded. If the instantaneous voltage V and / or the instantaneous current I are known for a battery cell, the ICA curve can be used with differentiation operations, for example statistical counting methods, depending on the time derivative of the voltage curve with known current I during the charging or discharging process. determine. The derivative dQ / dV of the charge Q of a battery cell after the voltage V is determined, for example, without integration of the current for determining the charge. A course of an inverse rupture of the time derivative of the voltage V is proportional to the course of the derivative of the charge Q to the voltage V. Another possibility is to determine the charge Q by integration of the current I and to derive this after the voltage U. For both methods, this is possible at constant current I or non-constant current I. For non-constant current I, an open cell voltage estimation is additionally connected upstream.

A typical ICA curve, ie, a typical course of the derivative dQ / dV, with two significant extremities E1, E2, is in 2 as an example of the voltage V for a battery cell. In 2 VEoDCH denotes the discharge end voltage and VEoCH the end-of-charge voltage. A first arrow 202 indicates the loading direction from VeoDCH to VEoCH. A second arrow 204 indicates in the reverse direction unloading. Starting from the discharge end voltage VEoDCH, the ICA curve rises up to a first extreme point E1, a maximum value, at a first voltage VP2. Then, the ICA curve first drops and increases again up to a second extreme point E2, a second maximum value, at a second voltage VP1. Subsequently, the ICA curve falls to the final charging voltage VEoCH.

Relevant is not the expression, shape or shape of the extreme point E1, E2, i. in the diagram, its value for dQ / dV, but the voltage V, i. in the illustration, the value VP2 or VP1 at which these extreme positions E1, E2 occur. The extreme points E1, E2 are in a voltage interval VI. This is shorter than an entire voltage range which is limited by the voltage VEoDCH at fully discharged battery cell and the voltage VEoCH at fully charged battery cell. Each of the extreme positions E1, E2 lies in different voltage intervals VI1, VI2. A limit of the voltage interval VI or the different voltage intervals VI1, VI2 is preferably determined depending on the slope dQ / dV of the charge over the voltage for the battery cell during charging or discharging with current I, such that the voltage interval VI or the different voltage intervals VI1, VI2 comprises or include at least one extreme point E1, E2 of the voltage curve.

These voltages VP1, VP2 are identical for two battery cells with the same cell chemistry at the same temperature and aging state. Experiments for a specific cell chemistry showed that the influence of temperature on the voltage level of the extremities is low. Likewise, assuming a normal spread of the aging state of the battery cells, its influence can be neglected.

3 schematically shows a course of a comparison of two derivatives dQ / dV of charge Q of two different battery cells after the voltage V. These are two battery cells of different capacity, which were gebalanced on the loading or unloading. The comparison of the derivatives dQ / dV is also possible for other starting situations. The derivatives dQ / dV of two series-connected battery cells is in 3 applied over time t. The course for a first battery cell is shown by a solid line. The course for a second battery cell is shown with a dashed line. It is irrelevant whether the battery cells are charged or discharged. By tstart is meant a first time of the beginning of the charging or discharging process. By tend a second time of the end of the loading or unloading process is designated. As in 3 represented occur two significant extreme points E11, E12 of the first battery cell earlier in time than the two significant extreme points E21, E22 of the second battery cell. The temporal difference of the respective significant extremities is called in 3 denoted by ΔT1 and ΔT2. An evaluation of the time interval of the local minimum is also possible.

Based on the time differences .DELTA.T1 and .DELTA.T2, as well as the information about the known charging or discharging current I during these intervals, it is determined how large the spread of the charge difference between the battery cells with respect to a predefined as balancing target charge level of the battery cells derived from the balancing need.

For the operation of the method, it is not necessary to know the entire ICA curve, but only the area of the extreme point (s), i. at least one of the voltage intervals VI1, VI2. Sufficient is the analysis of only one extreme point, however, the uncertainty can be minimized by looking at other extreme points. Depending on the availability of the ICA curve, compensation for full or partial load and unload operations can be performed. As a result, this is brought into temporal coverage. If a point of the ICA curve, which is not an extreme value, is brought into temporal coincidence, the detection of both extreme values is provided at least at intervals of some charging cycles.

4 schematically shows parts of a method for controlling the battery system.

The method is used to control the battery system 102 with at least two battery cells 104 . 106 , ..., 108 and preferably when charging or discharging the battery system 102 with instantaneous current I applied. The method is explained below with two battery cells 104 . 106 , which are connected in series. The method is also applicable to several battery cells and parallel connection of multiple series, consisting of series-connected battery cells, for individual series strands. Information about a momentary current I in the series circuit is assumed to be known or is provided by the measuring device 112 recorded continuously.

In one step 402 After startup, information about a first time profile of a first incremental capacitance is applied to a first battery cell 104 of the battery system detected. In the example, information about a first voltage V1 is applied to the first battery cell 104 of the battery system 102 detected.

Subsequently, in one step 404 Information about a second time course of a second incremental capacity at a second battery cell 106 of the battery system 102 detected. In the example, information about a second voltage V2 at the second battery cell 106 of the battery system 102 detected.

Subsequently, in one step 406 Information about a first time determined when the first time course meets a condition. In the example, information is determined about the time at which a first time profile of the first voltage V1 fulfills the condition. The condition is fulfilled if a time profile of a derivative dQ1 / dV1 of a first charge Q1 of the first battery cell 104 after the first voltage V1, the condition is fulfilled. This is detected, for example, by differentiation by means of a statistical counting method. Which of the extreme values is reached depends on whether it is a charge or a discharge, and how high the charge was initially. During partial loading and unloading processes, determined extreme values can be identified by defining plausible stress intervals.

Subsequently, in one step 408 Information about a second time determined, to which the second time course meets the condition. In the example, information is determined about the time at which a second time profile of the second voltage V2 fulfills the condition. The condition is satisfied if a time course of a second derivative dQ2 / dV2 of a second charge Q2 of the second battery cell 106 after the second voltage V2 meets the condition. This is recognized, for example, by differentiation by means of the statistical counting method. Which of the extreme values is exceeded depends on whether it is a charge or a discharge, and how high the charge was initially.

Subsequently, in one step 410 Information about a time difference ΔT, ie either ΔT1 or ΔT2, determined between the first time and the second time.

Subsequently, in one step 412 Information about the charge difference between a first charge of the first battery cell 104 in relation to a charge level of the first battery cell specified as the first compensation target 104 and a second charge of the second battery cell 106 based on a charge level of the second battery cell specified as a second compensation target 106 depending on the time difference .DELTA.T and the present during this time interval current current I determined.

Subsequently, in a cut 414 the regulation of the battery system 102 depending on the information about the charge difference. Then the cut 402 executed. In the example, the regulation takes place as a function of the spread of the SoC in order to reduce it to zero by means of charge compensation at a point in time at a defined SoC.

The information about the difference is preferably determined with increasing voltage V or decreasing voltage V for several extreme values, and for the regulation of the battery system 102 used at different times. The extreme values are preferably values at which the course of the derivative of the charge of the battery cell after the voltage has a maximum value.

The information about the voltages V is preferably detected during the duration of a charging process only in the voltage interval VI or the different voltage interval VI1, VI2.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012207826 A1 [0004]
• US 7923969 B1 [0004]
• EP 1685622 B1 [0005]
• EP 2320242 B1 [0006]
• US 8710800 B1 [0007]
• EP 2592714 B1 [0008]
• US 2015318721 A1 [0009]
• US 9472977 B1 [0010]
• EP 0998799 B1 [0011]
• DE 102013206885 A1 [0012]

Claims (11)

A method of controlling a battery system (102) having at least two battery cells (104, 106, ..., 108) characterized by detecting (402) information about a first time history of a first incremental capacitance on a first battery cell (104) of the battery system (102) by detecting a first time course of a first voltage (V1) of the first battery cell (104) of the battery system (102) and detecting the first time profile of a first current of the first battery cell (104) of the battery system (102), detecting ( 404) of information about a second time course of a second incremental capacity at a second battery cell (106) of the battery system (102) by detecting a second time course of a second voltage (V2) of the second battery cell (106) of the battery system (102) and the Detecting a second time course of a second current of the second battery cell (106) of the battery system (1 02), determining (406) information about a first time when the first time course satisfies a condition, determining (408) information about a second time when the second time course satisfies the condition, determining (412) of Information about a charge difference between a first charge of the first battery cell (104) in relation to a charge level of the first battery cell (104) specified as the first compensation target and a second charge of the second battery cell (106) relative to a charge state of the second battery cell specified as a second compensation target ( 106) depending on the information about the first time, the information about the second time and the first time course of the first current of the first battery cell (104) and the second time course of the second current of the second battery cell (106), control (414) of the battery system (102) depending on the information about the charge difference ied. Method according to Claim 1 , characterized in that the information about the charge difference between at least two battery cells (104, 106, ..., 108), which are connected in series, depending on information about a current current strength (I) in the series circuit is determined. Method according to one of Claims 1 or 2 Characterized in that a time profile of a voltage (V1, V2) satisfying the condition, when a time profile of a discharge line (DQ1 / dV1, dQ2 / dV2) a charge (Q1, Q2) to the voltage (V1, V2) a Extreme value (E11, E21, E12, E22). Method according to one of Claims 1 to 3 , characterized in that the information about voltages (V1, V2, ..., Vn) during the duration of a charging process in a voltage interval (VI, VI1, VI2) is detected which is shorter than a voltage range between a first voltage (VEoDCH) with fully discharged battery cell and a second voltage (VEoCH) with fully charged battery cell. Method according to one of Claims 1 to 4 characterized by detecting information about the first current to the first battery cell (104) of the battery system (102), acquiring information about the second current to the second battery cell (106) of the battery system (102), the first time history depending on a first integral of the first current over time is determined, wherein the second time profile is determined depending on a second integral of the second current over time. Method according to one of Claims 1 to 5 , characterized by charging or discharging the battery system with a constant current. Device (100) for controlling a battery system (102) having at least two battery cells (104, 106, 108), characterized by a control device (110), a measuring device (112), a computing device (114) and a compensation device (116), wherein the Measuring device (112) is formed by the detection of a first time course of a first voltage (V1) of a first battery cell (104) of a battery system (102) and the detection of a first time course of a first current of the first battery cell (104) of the battery system ( 102) to detect information about a first time course of a first incremental capacity at the first battery cell (104) of the battery system (102), and by detecting a second time course of a second voltage (V2) of a second battery cell (106) of the battery system ( 102) and the detection of a second time course of a second current of the second battery cell (106) of the Batt eriesystems (102) to detect information about a second time course of a second incremental capacity at the second battery cell (106) of the battery system (102), wherein the computing means (114) is adapted to determine information about a first time at which the first temporal Course meets a condition to determine information about a second time at which the second time course satisfies the condition, and information about a charge difference between a first charge of the first battery cell (104) based on a first compensation target charge state of the first battery cell ( 104) and a second charge of the second battery cell (106) to a charge level of the second battery cell (106) specified as a second compensation target as a function of the information about the first time, the information about the second time and the first time course of the current of the first battery cell (104) and the second time course of the current of the second Battery cell (106) to determine, and wherein the control device (110) is adapted to regulate the compensation device (116) depending on the information about the charge difference. Device (100) according to Claim 7 , characterized in that the measuring device (112) is designed to detect information about the first voltage (V1) at the first battery cell (104) of the battery system, and information about the second voltage (V2) at the second battery cell (106) of the The first time course is a first derivative (dQ1 / dV) of a first charge (Q1) of the first battery cell (104) after the first voltage (V1), and wherein the second time course is a second derivative (dQ2 / dV2) of a second charge (Q2) of the second battery cell (106) after the second voltage (V2). Device after Claim 7 or 8th Characterized in that at least two battery cells (104, 106, ..., 108) are connected in series, with differences between charges of the at least two battery cells (104, 106, ..., 108) depending on information about an instantaneous current (I) is determined in the series connection. Device according to one of Claims 7 to 9 , characterized in that a time profile of a voltage (V1, V2) meets the condition when a time course of a derivative (dQ1 / dV1, dQ2 / dV2) of a charge (Q1, Q2) after the voltage (V1, V2) a Extreme value (E11, E21, E12, E22). Device according to one of Claims 7 to 10 characterized in that the measuring device (112) is adapted to detect information about a first current to the first battery cell (104) of the battery system (102), and information about a second current to the second battery cell (106) of the battery system (102) wherein the first time course is determined as a function of a first integral of the first current over time, wherein the second time profile is determined as a function of a second integral of the second current over time.

Images