Method for electrically connecting sets of battery packs in parallel, electronic control unit, computer program, computer-readable storage medium, battery system and vehicle

Abstract

The present invention relates to a method of electrically connecting sets (6) of battery packs in parallel to reduce a balancing current (13) due to non-uniform battery packs (6). In order to keep the balancing current (13) to a minimum, a first battery pack (9) having the highest (U grp,max ) or lowest (U grp,min ) measured voltage value is selected and connected to the output (8) of the battery system (4). A maximum allowable deviation threshold (ΔU lim ) is determined by a decision matrix (18) based on the selection of input parameters (17) to select a second battery pack (10) from the remaining battery packs (6). The second battery pack (10) is connected to the output (8) such that the difference between the measured voltage value (U k ) of the second battery pack (10) and the measured voltage values (U grp,max , U grp,mln ) of the first battery pack (9) is below the deviation threshold (ΔU lim ).

Description

Technical Field

[0001] The present invention relates to a method for electrically connecting sets of battery packs in parallel, an electronic control unit, a computer program, a computer-readable storage medium, a battery system, and a vehicle.

Background Art

[0002] It is known to provide a high-voltage battery system for an electric vehicle that includes at least two battery packs, each battery pack including one battery module or a group of battery modules, each battery module including a group of battery cells. The battery packs together form a battery system and provide electrical energy to an electric drive device or other auxiliary components of the vehicle. The battery packs are typically arranged in various locations of the vehicle.

[0003] For example, at startup, in order to safely electrically connect multiple battery packs, the battery packs should have the same operating parameters such as voltage, temperature, and state of charge (SOC). Otherwise, an imbalance related to one parameter will generate a large balancing current between the connected battery packs, shortening the lifespan and causing damage to the contacts and battery cells within the battery pack.

[0004] In particular, connecting multiple battery packs leads to the generation of a large balancing current. This can result in a rapid capacity degradation of the battery cells, especially lithium-ion battery cells, due to differences in temperature, state of charge, and voltage between each battery pack. When non-uniform battery packs are connected, the energy capacity of each battery pack remains unused, leading to an overall reduction in the energy throughput of the battery system. In extreme cases, a large current imbalance can lead to the destruction of high-voltage components within the battery system, such as contacts or pre-charge resistors.

[0005] EP 3 078 073 B1 describes a method for equalizing a battery consisting of a plurality of battery cells. In this method, a first group of battery cells that are charged until they reach a fully charged state (SOC), and a second group of battery cells that are charged to a certain extent until they reach a preferred charge state lower than the fully charged state, are selected from a randomly selected group of battery cells to be equalized. To provide equalization, the battery cells of the first group are bypassed, and the battery cells of the second group are charged until both groups of battery cells reach the preferred charge state. The selected battery cells within the battery can be rearranged to evenly distribute the charge state across all the battery cells of the battery. Since only a single battery cell is equalized, there is no problem of a high equalization current that could damage the contacts of the battery system.

[0006] DE 10 2009 000 055 A1 shows a battery consisting of a plurality of battery cells, and the battery cells are equalized by an energy conversion circuit. A first group of battery cells having a higher charge state that exceeds the average threshold charge state is selected, and this first group of battery cells transfers its excess electrical energy via the energy conversion circuit to a second group of battery cells whose charge state is below the average threshold charge state until the battery cells of the first group and the second group reach the average threshold charge state.

[0007] DE 10 2018 000 581 A1 describes a method for equalizing a battery consisting of a plurality of battery cells. In this method, each battery cell is adjusted by the electronic control unit to a charge state within the range of the average charge state of all the battery cells by individually charging or discharging each battery cell by the electronic control unit. Further, diagnostic information regarding the soundness of each battery cell is considered, and defective battery cells are fully discharged. SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide a method for keeping the balancing current low in a battery system comprising a set of battery packs electrically connected in parallel.

[0009] The present invention relates to a method, preferably for a vehicle, of electrically connecting a set of battery packs to an output by means of a switching configuration to form a battery system, each battery pack comprising a plurality of battery cells, and the voltage value of each battery pack being measured by a sensor configuration. The method comprises selecting a first battery pack from the set of battery packs, the first battery pack having the highest measured voltage value or the lowest measured voltage value; connecting the first battery pack to the output; setting a maximum allowable deviation threshold for connecting a second battery pack from the set of battery packs; selecting a second battery pack from the set of battery packs such that the difference between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack is below the deviation threshold; connecting the second battery pack to the output and comprises.

[0010] In other words, the battery system may comprise a set of battery packs connected to the output of the battery system by means of a switching configuration for supplying electrical energy to high-voltage components of the vehicle via the output or for receiving electrical energy from a charging device such as an on-board charger of the vehicle. Receiving electrical energy via the output may be a charging operation of the battery system, and transferring electrical energy to high-voltage components via the output may be a discharging operation of the battery system.

[0011] The battery packs may be arranged in various locations within the vehicle.

[0012] The battery cells within the battery pack may be organized into battery modules within the battery pack. The battery modules may include a plurality of battery cells connected in series or in parallel within the battery module to provide a desired voltage and / or capacity.

[0013] The battery modules within the battery pack may be connected in series, in parallel, or a combination thereof to provide a desired voltage and / or capacity of the battery pack, such as a 400V or 800V configuration.

[0014] The battery pack may include a housing for receiving the battery cells and / or battery modules. The housing preferably provides a sealed enclosure so that the battery pack can be safely placed within a vehicle.

[0015] The vehicle's battery pack may preferably be connected in parallel to achieve the desired total capacity of the battery system, but may also be connected in series if the desired output voltage of the battery system is achieved by a combination.

[0016] It is known to provide a high-voltage battery system for an electric vehicle that includes at least two battery packs, each including one battery module or a group of battery modules, and each battery module includes a group of battery cells. The battery packs together form a battery system and provide electrical energy to an electric drive device or other auxiliary components of the vehicle. The battery packs are typically placed in various locations of the vehicle.

[0017] The battery pack or battery module may include, for example, lithium-ion or lithium-polymer battery cells. The battery pack may also include at least one battery module, and each battery module includes a group of battery cells.

[0018] The battery packs may be connected in parallel to the output via a switching configuration, and each battery pack may comprise a group of battery modules and / or battery cells connected in series and / or in parallel.

[0019] The battery system may further comprise a sensor configuration, in particular measurement probes connected to an electronic control unit and adapted to measure the voltage values of each battery pack and / or each battery module and / or each battery cell within each respective battery pack. The electronic control unit may measure the voltage values of each battery pack and / or each battery module and / or each battery cell within each respective battery pack by means of the sensor configuration. For example, the electronic control unit may calculate the voltage value of a battery pack by summing the measured voltage values of each battery cell or each battery module within the respective battery pack. The voltage values of each battery pack and / or each battery module and / or each battery cell may preferably be measured in each cycle, in particular before the first battery pack is selected.

[0020] In addition, the electronic control unit may measure the voltage of each battery pack before selecting the first battery pack if the number of battery packs already connected to the output is zero. If the number of battery packs already connected to the output is greater than zero, the electronic control unit may skip the step of connecting the first battery pack to the output within each connection cycle.

[0021] If the number of battery packs already connected to the output is zero, the first battery pack is selected from the set of all battery packs of the battery system having the highest measured voltage value or the lowest measured voltage value and connected to the output. The maximum allowable deviation threshold is for limiting the balancing current between the battery packs, comprising the first battery pack already connected to the output and the second battery pack most recently connected. The deviation threshold may be a fixed voltage value, such as a voltage value of 10 V or less, for example.

[0022] To limit the balancing current, the second battery pack or a group of second battery packs can be selected such that the deviation amount between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack is equal to or less than the deviation threshold value. This can be expressed by the following formula when selecting the first battery pack having the highest measured voltage value.

[0023]

Number

[0024] On the other hand, when selecting the first battery pack having the lowest measured voltage value, it can be expressed by the following formula.

[0025]

Number

[0026] Here, U grp,max is the highest voltage of the first battery pack including a group of battery cells connected in series and / or in parallel, and U grp,min indicates the lowest voltage. The battery system can include a total of k battery packs, where the voltage value U k of battery pack k can be measured by an electronic control unit for each battery pack of the battery system by a sensor configuration. This can be expressed by the relationship of U grp,max ∈U k and U grp,min ∈U k The highest measured voltage value or the lowest measured voltage value can thus be as follows.

[0027]

Number

[0028]

Number

[0029] For example, the battery system may comprise ten different battery packs that are not yet connected to the output, and thus k ∈ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}. Each battery pack k may comprise n battery cells, which may be connected in series, where the voltage of each battery cell n within battery pack k is U k,n and may be indicated by. The measured voltage value U k of each battery pack can thus be calculated by the electronic control unit as follows.

[0030] [Number]

[0031] If the number of battery packs k that are not yet connected to the output is zero, or if the number of battery packs connected to the output is equal to k, the cycle may end. The method described above minimizes the flow of the equalizing current while a plurality of battery packs in different voltage and / or temperature and / or charge level states are connected to the output of the battery system.

[0032] The battery system may be a 400V or 800V battery system that may be adapted for use in a vehicle.

[0033] This has the advantage that the equalization current of a battery system comprising several battery packs, in particular a set of battery packs connected in parallel, is reduced compared to the case where all battery packs are connected simultaneously. This prevents the destruction of high-voltage components such as contacts due to the high equalization current that can occur after the connection of the battery packs. It also prevents the rapid capacity degradation of the battery system, in particular the aging process of the battery cells due to the high equalization current after connecting non-uniform battery packs. Furthermore, the energy throughput of the connected battery packs of the battery system can be improved. The battery system described above also has the advantage that it can be used for charging or discharging operations even if not all battery packs have exactly the same state of charge or voltage. Furthermore, the disconnected battery packs of the battery system in a vehicle can be connected to the output of the battery system during vehicle operation or charging when the connection tolerance level is reached.

[0034] Normally, the battery packs already connected to the output share the same voltage value. This shared voltage can be used as a reference for the maximum voltage value U grp,max or the minimum voltage value U grp,min

[0035] In one particular embodiment, the first battery pack is selected from the set of battery packs already connected to the output if at least one battery pack from the set of battery packs is already connected to the output. In other words, the charging or discharging operation performed on the battery packs already connected to the output can change the voltage values of the battery packs described above. In particular, the voltage value of each of the above-described battery packs connected to the output can change at different speeds. Therefore, if the number of battery packs already connected to the output is greater than zero and / or if a charging or discharging operation is detected, the first battery pack having the highest or lowest measured voltage value can be selected from among the battery packs already connected to the output from the beginning. If the number of battery packs already connected to the output is greater than zero and / or if a charging or discharging operation is detected, the electronic control unit can measure the voltage value of each battery pack already connected to the output and / or can skip the step of connecting the first battery pack to the output in each cycle. This is advantageous because the voltage values of the battery packs already connected to the output can change at particularly different speeds due to the charging or discharging operation of the battery system, while the voltage values of the battery packs disconnected from the output can in principle remain constant until a certain period of time has elapsed.

[0036] This has the advantage that it can take into account the change in the energy level of the battery packs connected to the output due to the charging or discharging operation. The charging operation of the battery pack can supply electrical energy to the high-voltage components of the vehicle, such as an electric motor. The charging operation may receive electrical energy from the on-vehicle charger of the vehicle via the output. Furthermore, this has the advantage that it can connect the disconnected battery packs of the battery system in the vehicle to the output of the battery system while the vehicle is running or charging when the allowable level of connection is reached.

[0037] In one embodiment, the second battery pack is selected such that the difference between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack is minimized among all pairs of the first and second battery packs. In other words, the measured voltage value U k and the measured voltage value U grp,max or U grp,min One second battery pack having the smallest difference from is selected from a group of second battery packs in which the amount of difference from the measured voltage value U k and the measured voltage value U grp,max or U grp,min of the first battery pack is less than or equal to the deviation threshold. This condition is expressed as follows. For all k,

[0038]

Number

[0039]

Number

[0040] In one embodiment, the deviation threshold is determined by a decision matrix that registers each deviation threshold based on the number and / or voltage of the battery packs already connected to the output, and / or the average state of charge and / or average temperature of the battery system, and / or the amount of current flowing into / out of the battery system. In other words, the decision matrix calculates the deviation threshold ΔU limIt may be a look-up table or a database comprising a list of. The parameters are the number N of battery packs connected to the output, the average state of charge SOC avg , the average temperature T avg , the current amount |I| flowing into / out of the battery system, and further the voltage U of the battery packs connected to the output N . Each deviation threshold ΔU lim can be accessed in a decision matrix, particularly in a database, by the respective values of the respective parameters based on the sensor readings of the sensor configuration. Preferably, the sensor readings of each parameter such as the number N of battery packs, the average state of charge SOC avg , the average temperature T avg , and the current amount |I| are used in the decision matrix.

[0041] For example, the deviation threshold ΔU lim can be calculated by a function based on the following four parameters.

[0042]

Equation

[0043] The first boundary condition of the differential voltage value is as follows.

Equation

[0044] Here, N indicates the number of battery packs for the decision matrix connected to the output.

[0045] The second boundary condition of the differential voltage value ΔU lim is as follows.

[0046]

Equation

[0047] When the number of battery packs connected to the output is zero, i.e., N = 0, the differential voltage value can be set to zero.

[0048] One parameter of the function in Equation (6) is the average state of charge SOC of a battery system comprising N battery packs already connected to the battery system avg and can be. The above-mentioned parameter can be calculated as follows.

[0049]

Number

[0050] Here, SOC avg,grpN represents the average state of charge of a group of battery cells within each of the battery packs N already connected to the output. For example, each battery pack may comprise a group of n battery cells connected in series. Thus, the state of charge of each battery pack may correspond to the lowest state of charge of the battery cells within each battery pack. This can be expressed by the following equation.

[0051]

Number

[0052] Here, SOC N,n represents the state of charge of each battery cell n within the battery pack N.

[0053] One parameter of the function in Equation (6) may be the average temperature T of the battery packs connected to the output avg and can be. The average temperature can be determined by the following equation.

[0054]

Number

[0055] Here, T avg,grpNindicates the average temperature of the group of battery cells in each battery pack already connected to the output. Therefore, the average temperature T of each battery pack N avg,grpN is the highest temperature T within each battery pack N max(N,1) of the first battery cell having and the lowest temperature T min(N,2) of the second battery cell having, and can be the average value between them.

[0056]

Number

[0057] Here, T N,n indicates the temperature in each battery cell n within the battery pack N.

[0058] One parameter of the function of Equation (6) may be the current amount |I| flowing into / out of the battery system to / from the output. For example, the current can flow out of the battery system through the output during the discharge operation and can flow into the battery system through the output during the charging operation. The direction of the current I is considered with respect to the selection of the first battery pack connected to the output. For example, in the case of the charging operation, the first battery pack is the battery pack having the lowest measured voltage value U grp,min and in the case of the discharge operation, the first battery pack can be the battery pack having the highest measured voltage value U grp,max .

[0059] One parameter of the function of Equation (6) may be the number N of battery packs connected to the output of the battery system. For example, the battery system may include k battery packs, and each battery pack may include n battery cells. For example, the battery pack may include a number of battery cells from 1 to 10, and thus, n ∈ {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}.

[0060] When the total number of battery packs in the battery system is k, for a decision matrix including values for connecting one more battery pack to the output, the maximum value of N indicating the number of battery packs already connected to the output can be from 0 to N = k - 1. Thus, when k = 10, N ∈ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}. On the other hand, when the number of battery packs already connected to the output is k, i.e., when N = k, since all battery packs are already connected, the cycle may end.

[0061] Also, the voltage U of the battery pack already connected to the output N can be regarded as a parameter of the deviation threshold ΔU lim . This can be advantageous in the case where the voltage values of each battery pack connected to the output can change due to charging or discharging operations. For example, the voltage U N can be the highest voltage, the lowest voltage, or the average voltage of the battery packs connected to the output. Each battery pack connected to the output can be charged or discharged at different speeds due to the charging or discharging operations performed in the battery system. This can be due to different life cycles or the aging degradation of the battery cells of each battery pack. Thus, the highest measured voltage value U grp,max or the lowest measured voltage value U grp,min of the battery pack, preferably the battery pack already connected to the output, may be newly measured in each cycle when a charging or discharging operation is detected by the electronic control unit.

[0062] This provides a technical effect that the maximum allowable deviation threshold conforms to each operation mode of the battery system and keeps the equalization current low in each operation mode based on the selection of each operation parameter of the battery system. In particular, the use of a decision matrix as a database for accessing each deviation threshold based on the selection of the above-described parameters can further reduce the processing time of the electronic control unit when a limited number of input parameters are used to determine the deviation threshold. For example, when three selections among the above-described parameters such as the number of battery packs connected to the output, the average state of charge, and the average temperature are used to determine the deviation threshold, the time required to obtain the above-described deviation threshold from the database may be shorter than performing a simulation by the electronic control unit.

[0063] In one embodiment, the deviation threshold is calculated by simulation of the battery system, particularly simulation of the equalization current in the battery system, based on the number and / or voltage of the battery packs already connected to the output, and / or the average state of charge and / or average temperature of the battery system, and / or the amount of current flowing into / flowing out of the battery system. In other words, the simulation may calculate the maximum allowable voltage difference between the second battery pack connected to the output and the highest or lowest measured voltage value of the first battery pack based on the allowable equalization current. The allowable equalization current is based on at least one of the number N of battery packs connected to the output, the average state of charge SOC avg , the average temperature T avg , the amount of current |I| flowing into / flowing out of the battery system, and further the voltage U of the battery packs connected to the output N . The simulation is preferably based on sensor readings of a sensor configuration based on at least one of these parameters. Preferably, the sensor readings of each parameter such as the number N of battery packs, the average state of charge SOC avg , the average temperature T avg , and the amount of current |I| are used for the simulation.

[0064] The use of simulation in each cycle for connecting the second battery pack to the output also provides the technical effect that the maximum allowable deviation threshold conforms to each operating mode of the battery system and keeps the equalizing current low in each operating mode. The use of simulation can be advantageous when several input parameters, for example more than three parameters, are used to determine the deviation threshold. In this case, the processing time of the simulation can be shorter than the time required to obtain each deviation threshold from the database.

[0065] In one embodiment, the first battery pack having the highest measured voltage value is selected to be connected to the output by a switching configuration in the case of the discharging operation of the battery system, and / or the first battery pack having the lowest measured voltage value is selected to be connected to the output by a switching configuration in the case of the charging operation of the battery system. In other words, the electronic control unit may detect a charging or discharging operation based on the sensor reading value of the current flow I by the sensor configuration and / or whether electrical energy is required at the vehicle interface with the output of the battery system. In the case of a discharging operation, for example when supplying electrical energy to the electric motor of the vehicle, the first battery pack having the highest measured voltage value and / or the highest state of charge may be first connected to the output of the battery system for discharging. The discharging may further reduce the voltage of the first battery pack such that the difference between the measured voltage value U k of the second battery pack and the measured voltage value of the first battery pack can further decrease after a predetermined time of initial discharge of the first battery pack.

[0066] Additionally or alternatively, in the case of a charging operation, for example when receiving electrical energy from an in-vehicle charger of a vehicle, a first battery pack having a lowest measured voltage value and / or a lowest state of charge can be first connected to the output of the battery system for charging. Charging can further increase the voltage of the first battery pack such that the difference between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack can further decrease after a predetermined time of initial charging of the first battery pack.

[0067] Additionally, when the number of second battery packs for which the amount of the difference between the measured voltage value of the second battery pack described above and the measured voltage value of the first battery pack described above is below the deviation threshold is zero, the electronic control unit may charge or discharge the battery pack connected to the output, particularly the first battery pack, for a predetermined time before resuming the selection of the second battery pack from the remaining disconnected battery packs.

[0068] This has the advantage that the imbalance between the first battery pack and the second battery pack can be further reduced by reducing the difference between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack before connecting the second battery pack.

[0069] The present invention also relates to an electronic control unit of a battery system, preferably a battery management system, and comprises means adapted to perform the steps of the method described above. In other words, the electronic control unit determines the number N of battery packs connected to the output, the average state of charge SOC avg , the average temperature T avg , the current I flowing into / out of the battery system, and further the voltage U of the battery pack k、 and may be provided with, or adapted to be connected to, a sensor configuration for measuring at least one parameter of the voltage of the battery cells, particularly in the battery module and / or each battery pack. The electronic control unit may further comprise a communication interface for sending a connection or disconnection command, for example, a command for opening and closing each switch for connecting / disconnecting each battery pack to / from the switching configuration, to the switching configuration. The electronic control unit may comprise at least one processor and a computer-readable storage medium, where the computer-readable storage medium, when executed by the at least one processor, comprises instructions for causing the electronic control unit to execute the method described above for the battery packs of the battery system. For this purpose, the electronic control unit may be a battery management system of the battery, and preferably may be for a vehicle. The at least one processor may be a microprocessor and / or a microcontroller and / or an FPGA (Field Programmable Gate Array) and / or a DSP (Digital Signal Processor).

[0070] The present invention also relates to a computer program comprising instructions for causing an electronic control unit to execute the steps of the method. In other words, the computer program may be installed on a computer-readable storage medium of an electronic control unit of a battery, preferably a battery management system.

[0071] The present invention also relates to a computer-readable storage medium storing the above-described computer program. In other words, the computer-readable storage medium may be a punched card, a (floppy) disk storage medium, a hard disk, a CD, a DVD, a USB (Universal Serial Bus) storage device, a RAM (Random Access Memory), a ROM (Read Only Memory), and / or an EPROM (Erasable Programmable Read Only Memory). Preferably, the computer-readable storage medium may be a RAM or a ROM, and in particular, a flash memory is used. The computer-readable storage medium may also be a data communication network, such as the Internet, that enables downloading of program code, or a further system. The electronic control unit, preferably the battery management system, comprises the above-described computer-readable storage medium. The computer program may preferably be an embedded system application and may preferably be implemented in the C programming language.

[0072] The present invention also relates to a battery system, preferably for a vehicle, comprising the above-described electronic control unit, preferably the above-described battery management system. The battery system may represent a vehicle battery, such as a lithium-ion or lithium-polymer battery, for example.

[0073] The battery system may comprise a sensor configuration for measuring at least one parameter of the number N of battery packs connected to the output, the average state of charge SOC avg , the average temperature T avg , the current I flowing into / out of the battery system, and furthermore the voltage U of the battery packs k , in particular at least one of the voltages of the battery cells within each battery pack.

[0074] The battery system may further comprise a communication line for sending a connection or disconnection command, for example, a command line for opening and closing each switch for connecting / disconnecting each battery pack to / from the switching configuration, to the switching configuration. Further, the battery system is adapted to be controlled by the computer program described above, which is executed by the electronic control unit and / or at least one processor of the electronic control unit, such that the charging or discharging operation of the battery system is detected by the electronic control unit and the method of connecting / disconnecting the battery pack to / from the output is executed by the electronic control unit. This has the advantage that a constant operating voltage level can be provided by the battery system and balancing the battery system does not interfere with the current operating mode of the battery system.

[0075] The present invention further relates to a vehicle comprising the battery system described above and / or the electronic control unit described above.

[0076] The vehicle may comprise high-voltage components adapted to receive / transfer electrical energy from / to the battery system via the vehicle interface and the output of the battery system. For this purpose, the vehicle may comprise an interface connected to the output of the battery system. For example, the high-voltage component may be an electric motor or an on-board charger. The vehicle may be designed as an automotive vehicle, in particular a passenger car or a truck, or as a passenger bus or a motorcycle, where the electric vehicle is in particular designed as an electric vehicle or a hybrid vehicle.

Brief Description of the Drawings

[0077] In the following, the present disclosure will be described in more detail with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

[0078] The embodiments described below are preferred embodiments of the present invention. In the embodiments, the components described in the embodiments represent individual features of the invention that should be considered independently of each other. This also further forms an invention independently of each other in each case, and therefore, should be regarded as components of the invention in combinations other than those individually or illustrated. In the figures, similar elements are denoted by the same reference numerals, and repeated descriptions are omitted to avoid duplication.

[0079] Figure 1 shows a schematic diagram of a battery system 4 adapted to supply electrical energy 15 to high-voltage components 2 of a vehicle 1 or receive electrical energy 15 from the high-voltage components 2 of the vehicle 1 via an output 8 of the battery system 4 and a corresponding vehicle interface 2 of the vehicle 1. The high-voltage components 2 may be, for example, an on-vehicle charger or an electric engine.

[0080] For example, in an electric vehicle 1 having a high-voltage battery system 4, several battery packs 6 are integrated into the battery system 4, and together they provide electrical energy 15 to high-voltage components 2 of the vehicle 1 such as an electric drive device and auxiliary components. Each of the battery packs 6 has its own high-voltage contactor and can therefore be individually connected / disconnected to / from the switching configuration 11 by a switch 12 and provide the required electrical energy 15 from / to the vehicle 1 via the output 8.

[0081] The battery system 4 is adapted to be electrically connected via a switching configuration 11 to respective states of charge SOC k and comprises a set of k battery packs 6 each having a state of charge SOC. The opening and closing of the switches 12 may connect / disconnect the respective battery packs 6 to / from the switching configuration 11. For example, the switching configuration 11 may be adapted to electrically connect the battery packs 6 in parallel. In particular, the switching configuration 11 may be adapted to first connect the battery packs 6 to form a series string and then connect the series strings in parallel, depending on the required high-voltage architecture. The electronic control unit 3, for example a battery management system, may be adapted to control and / or measure by means of a sensor configuration the amount of current |I| flowing into / out of the battery packs 6 connected to / from the output 8 by the battery system 4, in particular by the connection command loop 14.

[0082] The electronic control unit 3 may be adapted to connect or disconnect the battery packs 6 of the battery system 4 via the switching configuration 11, i.e. by opening and closing the respective switches 12, and to adapt the battery system 4 to the amount of electrical energy 15 transmitted in the current operating mode of the battery system 4, such as a charging or discharging mode, to the high-voltage components 2 of the vehicle 1. Each battery pack 6 comprises a group of n battery cells 7 connected in parallel (or in series in an alternative embodiment), and each battery cell n within the battery pack k may have an individual state of charge SOC k,n and may have.

[0083] This may result in the battery packs 6 each having a different state of charge SOC k and an imbalance current 13 occurring between the respective battery packs 6. When the switching configuration 11 connects the battery packs 6 in parallel to the output 8, this may result in a flow 13 of balancing current high enough to damage the battery system 4, such as contacts, pre-charge resistors, fuses. The balancing current 13 is the highest state of charge SOC1 and / or the highest voltage U grp,maxFrom the first battery pack 9 connected to the output 8 having, it may flow to the battery pack 6 connected to the low-charged output 8, for example, to the modules 6 each having a charge state SOC2. Otherwise, the equalization current 13 flows from the battery pack 6 with a higher charge state connected to the output 8 to the lowest charge state SOC1 and / or the lowest voltage U grp,min having the first battery pack 9.

[0084] To safely connect a plurality of battery packs 6 in parallel, the battery packs 6 should have the same voltage, temperature, and charge state. Otherwise, the imbalance can result in an equalization current 13 flowing between the battery packs 6 electrically connected by the switching configuration 11. The voltages and charge states of the connected battery packs 6 and 9 are different, and when the threshold value, particularly the voltage threshold value ΔU lim is exceeded, an equalization current 13 large enough to damage the switch 12 and the battery pack 6 can occur. The amount of the equalization current 13 depends on each parameter such as the number N of battery packs 6 connected in parallel by the switching configuration 11, and / or the average charge state SOC avg and / or the average temperature T avg , and / or the amount |I| of the current flowing into / out of the battery system 4. In the example of FIG. 1, two battery packs 6 and 9 are connected in parallel by the switching configuration 11, and each switch 12 is closed. Therefore, in the example of FIG. 1, N = 2.

[0085] The amount of the equalization current 13 is reduced by a connection command loop 14 that can be executed by the electronic control unit 3. The electronic control unit 3 converts the above-described parameters for the amount of the equalization current 13 into a voltage threshold value ΔU for determining whether to connect the second battery pack 10 to the switching configuration 11 by the determination matrix 18 and / or simulation. This is shown in more detail in FIG. 2. lim

[0086] Figure 2 schematically shows a command loop 14 for an electronic control unit 3 of a battery system 4 for determining whether the electronic control unit 3 should connect a second battery pack 10 to an output 8 of the battery system 4. The electronic control unit 3 may be adapted to execute the connection command loop 14 described above. For this purpose, the electronic control unit 3 determines the number N of battery packs 6 already connected to the output 8, and / or the average state of charge SOC avg , and / or the average temperature T avg , and / or the current I flowing into / out of the battery system 4 via the output 8, and / or the current value U of the battery pack 6 already connected to the output 8 by the sensor configuration N . The sensor configuration may be, for example, a measurement probe. Preferably, the number N of battery packs 6 already connected to the output 8 and the average state of charge SOC avg and the average temperature T avg may be used as input parameters 17. The input parameters 17 are thereby based on the sensor readings of the sensor configuration transmitted to the electronic control unit 3.

[0087] Based on the input parameter 17, a deviation threshold ΔU lim is determined as an output value 19 by a decision matrix 18 and / or simulation. This output value 19 represents the maximum allowable voltage difference ΔU lim between the measured voltage value of the first battery pack 9 already connected to the output 8 and the voltage value of the second battery pack 10 to be connected to the output. The decision matrix 18 can thus function as a database for obtaining the current deviation threshold ΔU lim based on the current sensor readings of the input parameter 17. The decision matrix 18 and / or can convert the sensor readings of the combination of the input parameters 17 described above, preferably the number N of battery packs 6 already connected to the output 8 and the average state of charge SOC avg and the average temperature T avg into a voltage value ΔU lim as the maximum allowable amount of deviation 20.

[0088] The connection determination state machine 21 is adapted to determine whether to connect each second battery pack 10 from the remaining battery packs 6 in the battery system 4 to the output 8. For this purpose, the connection determination state machine 21 determines whether the difference between the measured voltage value U k of the second battery pack 10 and the measured voltage value U grp,max or U grp,min of the first battery pack 9 is less than or equal to the deviation threshold ΔU lim . Accordingly, if

[0089]

Number

[0090]

Number

[0091] Preferably, the connection determination state machine 21 selects the second battery pack 10 having the smallest difference value such that the difference between the measured voltage value U k of the second battery pack 10 and the measured voltage value U grp,max or U grp,min of the first battery pack 9 is the smallest among all pairs of the first and second battery packs. Accordingly, for all k,

[0092]

Number

Number

[0093] The decision state machine 21 may be adapted to output a connection command 22 for connecting the second battery pack 10 to the output 8 by means of each switch 12 of the switching configuration 11. The electronic control unit 3 may comprise a decision state machine 21 and a connection algorithm 16. Furthermore, the electronic control unit 3 may comprise a database forming a decision matrix 18 or may have access to a database.

[0094] Additionally or alternatively, the electronic control unit 3 may be adapted to execute the above-described simulation for outputting a deviation threshold ΔU lim based on a combination of input parameters 17.

[0095] If the number N of battery packs 6 already connected to the output 8 is zero, the voltage values U k of all battery packs 6, in particular of the first battery pack 9 and the second battery pack 10, are measured. If current flows out of the battery system 4, the first battery pack 9 having the highest measured voltage value U grp,max is selected by the electronic control unit 3, while if current flows into the battery system 4, the first battery pack 9 having the lowest voltage value U grp,max is selected by the electronic control unit 3. The first battery pack 9 is connected to the output 8 by sending a connection command 22 for opening and closing to each switch 12 of the switching configuration 11 from the electronic control unit 3. The electronic control unit 3 may be adapted to send a connection command 22 for opening and closing each switch 12 of the switching configuration 11 in order to connect or disconnect each battery pack 6. If the number N of battery packs 6 already connected to the output 8 is greater than zero, the electronic control unit 3 measures the voltage values U N of these battery packs 6 and may determine the first battery pack 6 having the highest voltage value U grp,max , or the lowest voltage value U grp,min .

[0096] Figure 3 shows a flowchart of the method for connecting in parallel a set of battery packs 6 of the battery system 4.

[0097] In a first step S1, a voltage value U is measured for each battery pack 6 of the battery system 4. k The electronic control unit 3 may be adapted to measure the above-mentioned voltage value of each battery pack 6 by means of a sensor arrangement 11, such as measurement probes for each battery pack 6 or for each battery cell 7 within an auxiliary respective battery pack 6.

[0098] In a second step S2, a first battery pack 9 having the highest voltage value U grp,max or the lowest voltage value U grp,min is selected from the battery packs 6 of the battery system 4. If the discharging operation of the battery system 4 is detected by the electronic control unit 3 and thus current flows out of the battery system 4 via the output 8, the first battery pack 9 having the highest voltage value U grp,max is selected, and if the charging operation is detected by the electronic control unit 3 and thus current flows into the battery system 4 via the output 8, the first battery pack 9 having the lowest voltage value U grp,min is selected. For this purpose, the electronic control unit 3 may be adapted to measure the direction of the current flow I via the output, to determine the discharging or charging operation, and / or to receive a request or provision of electrical energy 15 from the vehicle interface 2.

[0099] Typically, the battery packs 6 already connected to the output share the same voltage value. This shared voltage may be used as a reference for the highest voltage value U grp,max or the lowest voltage value U grp,min .

[0100] For example, when the above-described battery pack 6 discharges or charges at different speeds due to the influence of aging, an additional step may be added to step S2. When the number N of battery packs 6 already connected to the output 8 is different from zero, a first battery pack 9 may be selected from among the battery packs 6 already connected to the output 8. For this purpose, the electronic control unit 3 measures the voltage value U N of each battery pack 6 already connected to the output 8, and may be adapted to select the first battery pack 9 having the highest voltage value U grp,max or the lowest voltage value U grp,min .

[0101] In a third step S3, the first battery pack 9 is connected to the output 8 by the switching configuration 11. For this reason, the electronic control unit 3 may be adapted to send a connection command 22 for closing each switch 12 for connecting the first battery pack 9 to the switching configuration 11 and thus to the output 8. When the number N of battery packs 6 already connected to the output 8 is different from zero, step S3 is skipped.

[0102] In a fourth step S4, a maximum allowable deviation threshold ΔU lim for connecting a second battery pack 10 from the remaining battery packs 6 of the battery system 4 is set, and the deviation threshold ΔU lim may be determined by a decision matrix 18 based on the selection of the input parameter 17, preferably the number N of battery packs 6 already connected to the output 8, and the average state of charge SOC avg , and the average temperature T avg .

[0103] In addition or alternatively, the deviation threshold ΔU lim may be calculated by simulation of the battery system, preferably simulation of the balancing current 13 in the battery system depending on the input parameter 17, and the input parameter 17 is preferably the number N of battery packs 6 already connected to the output 8, and the average state of charge SOC avgand the average temperature T avg is.

[0104] In the fifth step S5, the voltage value U of the second battery pack 10 k and the measured voltage value U of the first battery pack 9 grp,max or U grp,min when the amount of deviation from is less than or equal to the deviation threshold ΔU lim the second battery pack 10 is selected from the remaining battery packs 6 within the battery system 4. Therefore, the condition for selecting the second battery pack 10 is

[0105]

Number

Number

[0106] Preferably, the second battery pack 10 with the smallest amount of deviation between the voltage value U k and the maximum voltage value U grp,max or the minimum voltage value U grp,min is selected. Therefore, the condition is that for all battery packs k that are not yet connected to output 8, preferably

[0107]

Number

Number

[0108] In the sixth step S6, the selected second battery pack 10 is connected to output 8, and thus is connected in parallel with the battery pack 6 already connected to output 8. The balancing current 13 that appears after the connection is therefore limited so as not to damage the battery pack 6, especially the contacts.

[0109] In the seventh step S7, the electronic control unit 3 may check whether at least one battery pack 6 of the battery system 4 remains disconnected from the output 8. If the number of disconnected battery packs 6 is zero, the method may end at step S8. In the case where at least one battery pack 6 remains disconnected, the voltage value U k of each battery pack k in the battery system 4, preferably the battery packs 6 already connected to the output 8, is measured by the sensor arrangement 11 in the electronic control unit 3 as in the case of a charging or discharging operation, and the voltage of the battery packs 6 already connected to the output 8 may change. The method starts from step S2, skips step S3, and is repeated until the end condition of step S7 is met.

[0110] It will be apparent to those skilled in the art that these embodiments and items merely depict examples of a plurality of possibilities. Therefore, the embodiments shown herein should not be understood to form limitations of these features and configurations. Any possible combination and configuration of the described features may be selected in accordance with the scope of the present invention.

Explanation of Reference Numerals

[0111] Vehicle 1 Vehicle interface with high-voltage components 2 Electronic control unit for battery system 3 Battery system 4 Set of battery packs 5 Battery pack 6 Battery cell 7 Output of battery system 8 First battery pack 9 Second battery pack 10 Switching arrangement 11 Switch 12 Flow of balancing current 13 Connection command loop 14 Electrical energy 15 Connection algorithm 16 Input parameter 17 Decision matrix 18 Output value 19 Amount of deviation 20 Connection determination state device 21 Connection command 22 State of charge SOC of battery pack n n Deviation threshold ΔU lim Maximum voltage value U grp,max Minimum voltage value U grp,min Voltage U of battery pack k k Number N of battery packs connected to the output Voltage U of the battery packs connected to the output N Average state of charge SOC of the battery system avg Average temperature T of the battery system avg Current |I| flowing into / out of the battery system First step S1 Second step S2 Third step S3 Fourth step S4 Fifth step S5 Sixth step S6 Seventh step S7 Eighth step S8 Ninth step S9

Claims

1. A method for forming a battery system (4) by electrically connecting a set of battery packs (5) in parallel with an output (8) using a switching configuration (11), wherein each of the battery packs (6) comprises a plurality of battery cells (7), and the voltage value (U k ) is measured by the sensor configuration, and the method is A step of selecting a first battery pack (9) from the set of battery packs (5), wherein the first battery pack has a maximum measured voltage value (U grp,max ) or minimum measured voltage value (U grp,min ) has a step and The steps include connecting the first battery pack (9) to the output (8), The maximum allowable deviation threshold (ΔU) for connecting the second battery pack (5) from the aforementioned battery pack set (5) lim The steps to set ) and The measured voltage value (U) of the second battery pack (10) k ) and the measured voltage value (U) of the first battery pack (9) grp,max , U grp,min The difference between this and the aforementioned deviation threshold (ΔU lim ) The step of selecting the second battery pack (10) from the set of battery packs (5) so that the following conditions apply, The steps include connecting the second battery pack (10) to the output (8) and A method that includes [a certain feature].

2. The second battery pack (10) is such that the measured voltage value (U k ) of the second battery pack (10) and the measured voltage value (U grp,max , U grp,min ) of the first battery pack (9) are selected such that the difference therebetween is minimized among all pairs of the first battery pack (9) and the second battery pack (10). The method according to claim 1, characterized in that.

3. The aforementioned deviation threshold (ΔU lim ) is the number (N) and / or voltage (U) of the battery packs (6) already connected to the output (8). N ), and / or the average charge state (SOC) of the battery system (4) avg ) and / or average temperature (T avg Based on the amount of current (|I|) flowing into and out of the battery system (4), the deviation threshold (ΔU lim The method according to claim 1, characterized in that it is determined by a decision matrix (18) that registers ).

4. The aforementioned deviation threshold (ΔU lim ) is the number (N) and / or voltage (U) of the battery pack (6) already connected to the output (8). N ), and / or the average charge state (SOC) of the battery system (4) avg ) and / or average temperature (T avg The method according to claim 1, characterized in that it is calculated by simulating the battery system (4), particularly simulating the balancing current within the battery system (4), based on the amount of current (|I|) flowing into and out of the battery system (4), and / or the amount of current (|I|) flowing into and out of the battery system (4).

5. The aforementioned highest measured voltage value (U grp,max The first battery pack (9) having ) is selected to be connected to the output (8) by the switching configuration (11) in the event of a discharge operation of the battery system (4), and / or the minimum measured voltage value (U grp,min The method according to claim 1, wherein the first battery pack (9) having ) is selected to be connected to the output (8) by the switching configuration (11) in the event of a charging operation of the battery system (4).

6. The method according to claim 1, wherein the battery system (4) is for a vehicle (1).

7. A battery system (4), preferably an electronic control unit (3) for a battery management system, comprising means adapted to perform the steps of the method according to any one of claims 1 to 6.

8. A computer program comprising an instruction causing the electronic control unit (3) described in claim 7 to perform the steps of the method according to any one of claims 1 to 6.

9. A computer-readable storage medium for storing the computer program described in claim 8.

10. A battery system (4) for a vehicle (1), preferably comprising the electronic control unit (3) described in claim 7.

11. A vehicle (1) comprising the battery system (4) according to claim 10 and / or the electronic control unit (3) according to claim 7.

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