Battery and method for operating the same

Abstract

The invention relates to a method for operating a battery having a series circuit with energy storage units, each of the energy storage units being removable from the series circuit, the voltage and the maximum current thereof being determined for each of the energy storage units, a first maximum power of all the energy storage cells connected in series is determined by means of the voltages of the energy storage cells and by means of the maximum currents thereof, the energy storage cell having the minimum maximum current being determined, a second maximum power for the series circuit of the energy storage cells is determined by means of the voltage of the energy storage cells and by means of the maximum current thereof without an energy storage cell having a minimum maximum current, and wherein the second maximum power is greater than the first maximum power if the second maximum power is greater than the first maximum power. If yes, the energy storage unit with the minimum maximum current is cut off from the series circuit. The invention further relates to such a battery and to a motor vehicle having such a battery.

Description

Technical Field

[0001] This invention relates to a method for operating a battery having a series circuit with an energy storage unit. Furthermore, this invention relates to a battery operable according to the method and a motor vehicle having such a battery. Background Technology

[0002] Electrically driven motor vehicles typically have a traction battery (high-voltage, HV battery) that supplies energy to the electric motor used to drive the vehicle. Here, electrically driven motor vehicles should be understood in particular as electric vehicles that store the energy necessary for propulsion solely in a traction battery (BEV), range-extended electric vehicles (REEV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and / or fuel cell electric vehicles (FCEV), which temporarily store electrical energy generated by a fuel cell in a traction battery.

[0003] This type of traction battery typically comprises multiple battery cells, especially lithium-ion battery cells, which are interconnected in a pre-defined manner.

[0004] Typically, in partially discharged batteries, at least two cells in a traction battery cell have different states of charge (SOCs). That is, they have different values ​​for the SOC. This is due, for example, to non-uniformity of the cell material (especially its electrodes), tolerances in the manufacture of the cell, and / or operation of the cell at different temperatures.

[0005] Here, the maximum current that can be provided by a given battery cell depends on its state of charge (SOC). This correlation is independent for each cell, for example, due to the aforementioned tolerances and / or non-uniformities. Typically, a relatively low SOC is accompanied by a relatively small maximum current that can be provided by the battery cell. Consequently, the electrical power that can be provided by the entire battery also depends on the SOC of the individual battery cells.

[0006] Here and below, the state of charge, also referred to as State-of-Charge (SOC), should be understood in particular as the ratio between the current available capacity of the battery cell (i.e., the charge that can currently be provided by the battery cell) and the nominal value of the capacity (i.e., the maximum amount of charge that can be stored in the battery).

[0007] Methods for cell balancing (cell compensation) are known. For example, WO 2022 / 199771 A1 discloses a battery management method for a battery having cells that can be connected in series with each other. A health state is determined for each cell of the battery, and these values ​​are compared with each other. At least one cell with a worse health state than other cells is determined. Furthermore, at least one cell with a better health state than other cells is determined. During a charging cycle, when a threshold for the maximum state of charge for that cell is reached, the at least one cell with the better health state is selectively disconnected, and / or during a discharging cycle, when a threshold for the minimum state of charge for that cell is reached, the at least one cell with the worse health state is disconnected. Summary of the Invention

[0008] This invention is based on the objective of describing a particularly suitable method for operating a battery. Specifically, it should be possible for the battery to provide and / or feed as much electrical power as possible, especially even if at least two battery cells have different states of charge. Furthermore, a suitable battery and a motor vehicle having such a battery should be described.

[0009] In view of this method, the task is solved according to the invention by means of a method for operating a battery. In view of this battery, the task is solved according to the invention using a battery, and in view of this motor vehicle, the task is solved according to the invention using an electrically driven motor vehicle with a battery. Advantageous designs and improvements are the subject of each embodiment. Here, embodiments associated with this method are also applicable, by their meaning, to the battery and / or the motor vehicle, and vice versa.

[0010] This method is used to operate a battery. Suitably, the battery is a traction battery, preferably for electrically driven motor vehicles. The battery has a (first) series circuit with energy storage units (ESUs). In other words, the battery comprises energy storage units connected in series, i.e., in rows. Each energy storage unit is or separately comprises a (unique) battery cell, or alternatively comprises at least two battery cells connected in series and / or in parallel with each other. For example, one energy storage unit or each energy storage unit comprises (exactly) two battery cells connected in parallel with each other. Such an energy storage unit is also referred to as a cell tuple.

[0011] In particular, the battery is a lithium-ion battery, therefore the battery cell is a lithium-ion battery cell.

[0012] Each energy storage unit in the energy storage unit can be disconnected from the series circuit by one or more switches (especially individually). For this purpose, for example, each energy storage unit in the energy storage unit can be bypassed independently.

[0013] In summary, the battery includes energy storage units that can be connected in series and / or disconnected from each other. In other words, each energy storage unit in the energy storage unit can be connected in series with at least one energy storage unit in other energy storage units, and / or, each energy storage unit in the energy storage unit can be disconnected from a series circuit having at least one other energy storage unit.

[0014] According to this method, the (electrical) voltage of each energy storage unit in the energy storage unit is determined, and in particular, its electrical voltage is measured. Specifically, the voltage supplied by the respective energy storage unit is detected, for example, using a voltage sensor.

[0015] Furthermore, a maximum (electrical) current is determined for each energy storage unit in the energy storage unit. Here, the maximum current is preferably determined as the current that can be provided by the corresponding energy storage unit to the maximum extent, in other words, its maximum discharge current. Additionally or alternatively, the maximum charging current is determined as the maximum current.

[0016] The maximum current (i.e., maximum discharge current and / or maximum discharge current) of the corresponding energy storage unit is appropriately determined by its voltage, and is calculated in particular. For example, the state of charge (SOC) of each energy storage unit is first calculated by its voltage, and additionally or alternatively by its current temperature and / or by the previous time curve of the current flowing through that energy storage unit. For this purpose, predefined characteristic curves, predefined characteristic fields, predefined tables, and / or predefined (mathematical) functions are used. Subsequently, the maximum current is associated with the state of charge, for example by a predefined table, a predefined characteristic curve, or a predefined characteristic field, or the maximum current is calculated based on the state of charge using a predefined function.

[0017] Appropriately, the maximum current of each energy storage unit in the energy storage unit is determined, and in particular, calculated, based on its voltage, in an appropriate manner.

[0018] Furthermore, the energy storage cell with the smallest maximum current (especially given its magnitude) is determined. For this purpose, the maximum currents determined for these energy storage cells are appropriately compared with each other. Alternatively, as the energy storage cell with the smallest maximum current (especially given its magnitude), the energy storage cell with the smallest state of charge (for the battery discharge process) and / or the energy storage cell with the largest state of charge (for the battery discharge process) is determined.

[0019] According to this method, the first maximum (electrical) power of all energy storage units connected in series is determined by the (pre-determined) voltage of the energy storage unit and the (pre-determined) maximum current of the energy storage unit. In other words, the maximum power for a series circuit with all energy storage units is determined, and here in particular calculated.

[0020] Here, the first maximum power is the product of the sum of the voltages of the series-connected energy storage units and the maximum current flowing through these energy storage units. Here, the current is limited to the maximum current with the minimum magnitude due to the series circuit. That is, the energy storage unit with the minimum maximum current in terms of magnitude acts as the power limiter.

[0021] If the maximum discharge current is used as the maximum current, then the first maximum power is the maximum (discharge) power that can be provided by the battery. If the maximum charging current is used as the maximum current, then the first maximum power is the maximum (charging) power that can be fed into the battery.

[0022] Furthermore, according to this method, the second maximum (electrical) power for a series circuit of energy storage units is determined, and in particular, calculated in the absence of any energy storage units with a minimum maximum current, based on the voltage of the energy storage units and the maximum current of the energy storage units. That is, the maximum power is determined for a series circuit that includes all energy storage units except those with a minimum maximum current. Specifically, the series circuit does not include any energy storage units with a minimum maximum current.

[0023] In particular, the energy storage unit with the minimum maximum current has not been or has not yet been disconnected. Therefore, suitablely, only this second maximum power is calculated first.

[0024] The current flowing through this series circuit (i.e., a series circuit containing all energy storage units except the one with the minimum maximum current) is no longer limited by the energy storage unit with the minimum maximum current. Therefore, the maximum current flowing through this series circuit is increased. Depending on the voltage of the energy storage unit with the minimum maximum current, the maximum power of this series circuit is correspondingly greater than, less than, or equal to the maximum power of the series circuit containing all energy storage units.

[0025] If the second maximum power is greater than the first maximum power, then the energy storage unit with the minimum maximum current (and preferably only that energy storage unit) is subsequently removed from the series circuit. Suitablely, this energy storage unit is bypassed for this purpose.

[0026] In summary, the circuitry advantageously implements an energy storage unit in which the battery can provide maximum power or in which maximum power can be fed to the battery. If necessary, one of the energy storage units can be disconnected for this purpose.

[0027] According to a preferred design of the method, in order to determine the energy storage unit with the minimum maximum current, the maximum current of all energy storage units and / or the state of charge of all energy storage units are compared with each other.

[0028] Therefore, all energy storage units and / or their properties are considered in this determination. Thus, no pre-selection of the sub-number of energy storage units is performed, whereby only the energy storage unit with the minimum maximum current is determined from that sub-number.

[0029] For example, the determination and / or removal of energy storage units with minimum and maximum current is based on another criterion. This other criterion is, for example, that the charging state and / or health state of the energy storage unit with minimum and maximum current exceeds a preset threshold.

[0030] Alternatively, the energy storage unit with the minimum maximum current may be determined from all energy storage units solely by its previously determined maximum current and / or its previously determined state of charge. In particular, this determination is therefore not based on the health status of the energy storage unit. For example, additionally or alternatively, in determining the energy storage unit with the minimum maximum current, it is suitable not to use a threshold, but rather, for example, to simply compare the properties of all energy storage units with each other.

[0031] In summary, this approach advantageously avoids situations where, for example, due to pre-selection and / or due to thresholds, battery cells with the minimum maximum current are not identified, are not removed from the series circuit accordingly, and thus the battery power is not increased.

[0032] According to a suitable design scheme, energy storage units with minimum maximum current are cut off based on the power requirements of the battery (except when the second maximum power is greater than the first maximum power requirement).

[0033] This power requirement is, for example, a target power for an electrical appliance (e.g., a traction drive) powered by a battery. For instance, an energy storage unit with a minimum maximum current is disconnected only to increase battery power when the power requirement exceeds a predefined threshold. Thus, for example, in the operation of a motor vehicle equipped with this battery, to accelerate (especially during overtaking), if the corresponding power requirement exceeds the threshold (and if a determined second maximum power is greater than a determined first maximum power), the power supplied by the battery is increased.

[0034] According to a suitable design of this method, if a preset time has elapsed after the disconnection, the disconnected energy storage unit (i.e., the energy storage unit with the minimum maximum current) is reconnected in series (i.e., connected) to other energy storage units. Additionally or alternatively, if the power requirement has decreased by a preset amount and / or the power requirement is below a preset threshold, the energy storage unit with the minimum maximum current is reconnected in series to other energy storage units. Additionally or alternatively, if the state of charge of at least one energy storage unit has changed by a preset amount, the energy storage unit with the minimum maximum current is reconnected in series to other energy storage units.

[0035] Another aspect of the invention relates to a battery that is operable and / or operated according to the method in one of the variations shown above. In particular, the battery is configured as a traction battery for an electrically driven motor vehicle. Additionally or alternatively, the battery is a lithium-ion battery.

[0036] Here, the battery (as shown in the associated method) comprises a series circuit with energy storage units, wherein each energy storage unit can be disconnected from the series circuit (particularly by means of a switch). Each energy storage unit is preferably configured as a (unique) battery cell. Alternatively, the corresponding energy storage unit comprises at least two battery cells connected in series and / or in parallel with each other.

[0037] Furthermore, the battery includes (e.g., configured as a controller) a control device for performing the method in one of the variations shown above. In particular, the control device is therefore configured and set to determine the voltage and maximum current of each energy storage cell in the energy storage unit, and / or to receive a voltage-corresponding measurement (suitably from a corresponding sensor) for each energy storage cell in the energy storage unit, thereby determining, in particular, calculating, the corresponding maximum current.

[0038] Furthermore, the control device is suitably configured and set to determine the first maximum power of all energy storage units connected in series (in other words, the series circuit consisting of all energy storage units) by means of the voltage of the energy storage unit and the maximum current of the energy storage unit.

[0039] Furthermore, the control device is suitably configured and set to determine the energy storage unit with the minimum maximum current, and to determine, in particular calculate, the second maximum power of the series circuit consisting of the other energy storage units.

[0040] Furthermore, the control device is suitably configured and set to operate the energy storage unit switch such that if the second maximum power is greater than the first maximum power, the energy storage unit with the minimum maximum current is disconnected from the series circuit.

[0041] Another aspect of the invention relates to a motor vehicle. It includes a battery operable and / or operated according to a method in one of the variations shown above, and / or a battery constructed according to the battery shown above.

[0042] In particular, the vehicle is an electrically driven vehicle, wherein the battery is preferably a traction battery for the vehicle. Therefore, the traction battery provides electrical energy to the traction drive unit used to move the vehicle. Suitably, the battery is electrically connected to the traction motor (electric travel motor, electric drive motor) for this purpose, particularly by means of an inverter. Attached Figure Description

[0043] The embodiments of the present invention will be explained in more detail below with reference to the accompanying drawings. Wherein: Figure 1 An electrically driven motor vehicle is schematically shown, having a battery with energy storage units in series and / or series-connectable, and Figure 2 The flowchart illustrates the method flow for operating the battery. Detailed Implementation

[0044] In all the drawings, corresponding parts and parameters are always given the same reference numerals.

[0045] exist Figure 1 The diagram schematically illustrates an electrically driven motor vehicle 2. It has a battery 4, which, according to the example shown here, is a traction battery. An electrical appliance 6, in particular an inverter and / or a (traction) motor, is connected to the battery 4, so that the electrical appliance 6 is powered by and / or can be powered by the battery 4.

[0046] The battery includes energy storage units 8. According to the embodiment shown here, each energy storage unit 8 is a unique battery cell. For clarity, only four battery cells are shown here. This is indicated by three points: the battery 4 includes additional energy storage units 8. These energy storage units 8 can be connected in series with each other via a switch. Furthermore, each energy storage unit 8 can be independently disconnected from the series circuit. In other words, each energy storage unit 8 can be connected in series with at least one other energy storage unit 8, and / or, each energy storage unit 8 can be disconnected from a series circuit having at least one other energy storage unit 8.

[0047] Therefore, according to the embodiment shown here, each energy storage unit in the energy storage unit 8 is associated with two switches 10a, 10b. One of the switches 10a (the first switch) is connected in series with the corresponding energy storage unit 8, while the other switch 10b (the second switch) is connected in parallel to the series circuit formed by the first switch 10a and the energy storage unit 8. The switches 10a, 10b are suitably configured as semiconductor switches.

[0048] According to alternatives not further shown, the corresponding energy storage unit is configured as a series circuit and / or parallel circuit consisting of at least two battery cells, suitably having fewer than 20, especially fewer than 10, and preferably fewer than 5 battery cells.

[0049] Furthermore, battery 4 has a control unit 12. It is connected to switches 10a and 10b via signal and / or data transmission technology. Switches 10a and 10b are controlled by and / or controlled by 12. In particular, the state of each switch 10a and 10b can therefore be set to an open (current blocking) state and / or a closed (current conducting) state.

[0050] The control device 12 is further connected to the appliance 6 via signal and / or data transmission technology and / or, according to an alternative not further shown, to another control unit at the next higher level of the appliance 6. Therefore, the appliance 6 can transmit the power demand P to the battery 4. soll It is specifically configured to represent the value of power required to operate appliance 6.

[0051] The control device 12 is configured to perform... Figure 2 The method shown.

[0052] exist Figure 2 The flowchart illustrates the process for running according to... Figure 1 The battery 4 and / or the method for operating the motor vehicle 2 having the battery 4.

[0053] First, all energy storage units 8 and 8' are connected in series. In other words, all energy storage units 8 and 8' form a series circuit, so that electrical energy (especially for appliance 6) can be provided and / or supplied by all energy storage units 8 and 8'.

[0054] In the first step I, the received power requirement P soll The control device 12, which outputs power from the electrical appliance 6 to the battery 4, is appropriately configured.

[0055] In the second step II, the voltage U supplied by each of the series-connected energy storage units 8 is determined. n In particular, the voltage U of each energy storage unit 8 is measured using a corresponding voltage sensor (not shown further). n And feed it to the control device 12 (control unit 12). Furthermore, in step II, the maximum current I is determined, and in particular calculated, for each energy storage unit in energy storage units 8 and 8'. max,n This determination is appropriately made by means of control device 12.

[0056] For example, for each energy storage unit in energy storage units 8 and 8', by virtue of its voltage U n Determine its State of Charge (SOC) n (State of Charge), and based on this charging state SOC n Determine the maximum current I max,n Therefore, it is appropriate to store the corresponding characteristic curves, characteristic fields, and / or functions in the memory (not shown further) of the control device 12. For example, consider the current temperature of the corresponding energy storage unit 8, wherein the temperature is appropriately determined by a corresponding temperature sensor and the measurement data is transmitted to the control device 12. In summary, for each energy storage unit in the energy storage units 8, 8', its voltage U is determined, and in particular measured. n And determine, in particular calculate, its maximum current I. max,n .

[0057] Here, step II can be executed sequentially from step I in time, simultaneously with step I, or before step I in time, as shown in the figure.

[0058] In step III, the energy storage cell with the minimum maximum current is determined. For better differentiation, it is designated as reference numeral 8', and the other energy storage cells are also designated as reference numeral 8'. To this end, the maximum current I of all energy storage cells 8 and 8' is determined. max,n and / or the State of Charge (SOC) of all energy storage units 8, 8' n Compare with each other.

[0059] In the fourth step, the first maximum power P for the series circuit of all (current) energy storage units 8, 8' (i.e., including the energy storage unit 8' with the minimum maximum current) is determined, and in particular calculated. max,1 .

[0060] First maximum power P max,1 The conclusion here is: Here, N is the total number of energy storage units 8 and 8' in the series circuit, and I min Equal to the maximum current I max,n The smallest value in terms of quantity.

[0061] In the fourth step, it is further determined, and in particular calculated, in the absence of a minimum maximum current I. max In the case of energy storage unit 8', the second maximum power P for the (unimplemented or not yet implemented) series circuit of all energy storage units 8. max,2 Therefore, determine the second maximum power P for (another) series circuit. max,2 In this series circuit, the circuit with the minimum and maximum current I is cut off. max The energy storage unit 8' is connected in series with other (especially all other) energy storage units 8.

[0062] Second maximum power P max,2 This leads to the conclusion that Here, N is the total number of energy storage units 8 and 8' in the series circuit, where the Nth energy storage unit has the minimum and maximum current I. max,n That energy storage unit, and I min 'Equal to the maximum current I of the other energy storage unit 8 in the series circuit' max,n The minimum value in terms of magnitude, that is, the minimum value in terms of magnitude of the maximum current of energy storage unit 8 without the Nth energy storage unit 8'.

[0063] In step V, the second maximum power P is first... max,2 With the first maximum power P max,1 A comparison is then made. Subsequently, if the second maximum power P... max,2 Greater than the first maximum power P max,1 And if the power requirement P soll If the preset threshold S is exceeded, the energy storage unit 8' with the minimum maximum current will be cut off.

[0064] If these criteria are not met, the energy storage unit 8' is not disconnected. In particular, the battery 4 continues to operate using all energy storage units 8 and 8' in the same series circuit.

[0065] exist Figure 1 In the diagram, the battery cell at the bottom of the drawing plane is shown in an exemplary cut-off state. Here, the first switch 10a associated with this energy storage cell 8' is switched to block current, while the second switch 10b is switched to conduct current.

[0066] If the energy storage unit 8' with the minimum maximum current has been disconnected in step V, then in step VI, if a preset time has elapsed after disconnecting the energy storage unit 8' with the minimum maximum current, and if the power requirement P... soll The preset amount has been reduced and / or is below a preset threshold, and / or if the state of charge (SOC) of at least one energy storage unit in energy storage unit 8 is... n If the preset value has been changed, the energy storage unit 8' will be reconnected to other energy storage units 8.

[0067] Therefore, it is appropriate to switch the first switch 10a associated with the energy storage unit 8' having the minimum maximum current to conduct current, and switch the second switch 10b associated with the energy storage unit 8' to block current.

[0068] The following is a calculation example used to illustrate the method. For clarity, it is simplified to assume that the battery comprises 96 battery cells as energy storage units, wherein 95 of these battery cells have a voltage U of 3712 mV. n 650A maximum current and / or 55% SOC n Another battery cell (i.e., the cell not included in these 95 battery cells) 8' has a voltage U of 3704 mV. n The maximum current I is 621.4 A. max,n and / or 54% SOC ,N .

[0069] Therefore, Pmax,1 is derived as follows: and Therefore, when the battery cell with the minimum maximum current is removed, the power of battery 4 is increased.

[0070] This invention is not limited to the embodiments described above. Rather, those skilled in the art can derive other variations of the invention within the scope of the claims without departing from the subject matter. In particular, all related embodiments and / or individual features described in the claims can be combined with each other in other ways without departing from the subject matter.

[0071] List of reference numerals in the attached diagram: 2 Motor vehicles 4 batteries 6 Electrical Appliances 8, 8' Energy Storage Unit Switches 10a and 10b 12 Control devices I max,n Maximum current of energy storage unit U n Voltage of energy storage unit P max,1 First maximum power P max,2 Second maximum power SOC n State of charge of energy storage unit I. Receive power requirements II. Determine the voltage and maximum current for the energy storage unit. III. Determine the energy storage unit with the minimum and maximum current. IV. Determine the first and second maximum power. V cuts off the energy storage unit with the minimum maximum current. VI. Connect to the disconnected energy storage unit.

Claims

1. A method for operating a battery (4) having a series circuit with energy storage units (8, 8'), wherein each of the energy storage units (8, 8') is able to be decoupled from the series circuit, - wherein for each of the energy storage units (8, 8') its voltage (U n ) and its maximum current (I max,n ) are determined, - wherein a first maximum power (P max,1 ) of all series-connected energy storage units (8, 8') is determined by means of the voltage (U n ) of the energy storage unit (8, 8') and by means of the maximum current of the energy storage unit (8, 8'), - wherein the energy storage unit (8') having the smallest maximum current (I max,n ) is determined, - wherein a second maximum power (P max,2 ) for the series circuit of the energy storage units (8) without the energy storage unit (8') having the minimum maximum current (I max,n ) is determined by means of the voltage (U n ) of the energy storage units (8) and by means of the maximum current (I max,n ) of the energy storage units (8), - wherein, if the second maximum power (P max,2 ) is greater than the first maximum power (P max,1 ), the energy storage unit (8') having the smallest maximum current (I max,n ) is cut out of the series circuit.

2. The method according to claim 1, characterized in that In order to determine the energy storage unit (8') having the smallest maximum current, the maximum currents (I max,n ) of all energy storage units (8, 8') and / or the state of charge (SOC n ) of all energy storage units (8, 8') are compared with each other.

3. The method according to claim 1 or 2, characterized in that The cut-out of the energy storage unit (8') with the smallest maximum current (I max,n ) is performed in accordance with the power requirement (P soll ) of the battery (4).

4. The method according to any one of claims 1 to 3, characterized in that the decoupled energy storage unit (8') is re-coupled in series to the other energy storage units (8), - if a preset time period has elapsed after the decoupling, - if the power requirement has decreased by a preset magnitude and / or is below a preset threshold value, and / or - if the state of charge (SOC n ) of at least one of the energy storage units (8) has changed by a preset amount.

5. A battery (4), in particular traction battery for an electrically driven motor vehicle (2), - having a series circuit with an energy storage unit (8, 8'), wherein each of the energy storage units (8, 8') is able to be decoupled from the series circuit, and - a control device (12) for carrying out the method according to any one of claims 1 to 4.

6. An electrically driven motor vehicle (2) having a battery (4), which is constructed according to claim 5 and / or is operated and / or operable according to the method according to any one of claims 1 to 4.

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