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

Abstract

The invention relates to a method for electrically connecting a group of battery packs (6) in parallel in order to reduce the balancing current (13) caused by non-uniform battery packs (6). In order to keep the balance current (13) at a minimum, a first battery pack (9) having either the highest (Ugrp, max) or the lowest (Ugrp, min) measured voltage value is selected and connected to the output (8) of the battery system (4). A maximum permissible deviation threshold ([Delta] Ulim) for selecting a second battery (10) from the remaining batteries (6) is determined by means of a decision matrix (18) on the basis of the selected input parameter (17). The second battery (10) is connected to the output (8) such that a difference between a measured voltage value (Uk) of the second battery (10) and a measured voltage value (Ugrp, max, Ugrp, min) of the first battery (9) is lower than or equal to a deviation threshold ([delta] Ulim).

Description

Technical Field

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

[0002] It is known to provide an electric vehicle with a high-voltage battery system comprising at least two battery packs, each of which may include one or a group of battery modules, wherein each battery module includes a group of battery cells. The battery packs together form a battery system and provide electrical energy for the electric drive or other auxiliary components of the vehicle. The battery packs are usually placed at different locations in the vehicle.

[0003] In order to safely connect several battery packs together electrically, for example at startup, 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 cause a large balancing current between the connected battery packs, which will shorten the life of the contactors and battery cells in the battery pack or even damage them.

[0004] In particular, connecting several battery packs will result in high balancing currents. This can lead to rapid capacity decay of battery cells, especially lithium-ion battery cells, due to differences in temperature, state of charge and voltage between the individual battery packs. This results in a lower energy throughput of the battery system overall, because the energy capacity in each battery pack remains unused when connecting uneven battery packs. In extreme cases, large current imbalances can cause damage to high-voltage components in the battery system, such as contactors or pre-charge resistors.

[0005] EP 3 078 073 B1 describes a method for balancing a battery consisting of a plurality of battery cells, wherein a first group of battery cells charged to a full state of charge (SOC) and a second group of battery cells partially charged to a preferred state of charge below the full state of charge are selected from a group of randomly selected battery cells to be balanced. In order to provide balancing, the battery cells in the first group are bypassed to charge the battery cells of the second group until the battery cells of both groups reach the preferred state of charge. The selection of battery cells within the battery can be permuted so that the state of charge is evenly distributed over all the battery cells of the battery. Because only a single group of battery cells is balanced, there is no problem of balancing currents that are high enough to damage the contactors of the battery system.

[0006] DE 10 2009 000 055 A1 shows a battery consisting of a plurality of battery cells, wherein the battery cells are balanced by an energy conversion circuit. A first group of battery cells having a higher state of charge than an average threshold state of charge is selected, which will transfer their excess electrical energy to a second group of battery cells having a state of charge below the average threshold state of charge via the energy conversion circuit until the first group and the second group of battery cells reach the average threshold state of charge.

[0007] DE 10 2018 000 581 A1 describes a method for balancing a battery consisting of a plurality of battery cells, wherein each battery cell is adjusted by an electronic control unit to a state of charge within the range of the average state of charge of all battery cells by means of individual charging or discharging of the respective battery cell by an electronic control unit. In addition, diagnostic information about the state of health of the respective battery cell is taken into account, wherein defective battery cells are completely discharged. Summary of the invention

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

[0009] The invention relates to a method for electrically connecting a group of battery packs to an output by means of a switching device to form a battery system preferably for a vehicle, wherein each battery pack comprises a plurality of battery cells and the voltage value of each battery pack is measured by means of a sensor device. The method comprises the following steps:

[0010] - 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;

[0011] - connecting said first battery pack to an output;

[0012] - setting a maximum permissible deviation threshold for connecting a second battery pack from said group of battery packs;

[0013] - selecting a second battery pack from the set of battery packs such that a difference between a measured voltage value of the second battery pack and a measured voltage value of the first battery pack is lower than or equal to a deviation threshold; and - connecting the second battery pack to the output.

[0014] In other words, the battery system may include a set of battery packs connected to an output of the battery system by means of a switching device to provide electrical energy to a high voltage component of the vehicle via the output or to receive electrical energy from a charging device (e.g., an onboard charger of the vehicle). Receiving electrical energy via the output may be a charging operation of the battery system, while transmitting electrical energy to the high voltage component via the output may be a discharging operation of the battery system.

[0015] The battery pack can be arranged in different locations in the vehicle.

[0016] The battery cells in a battery pack may be organized in battery modules within the battery pack. A battery module may include multiple battery cells connected in series or in parallel in the battery module to provide a desired voltage and / or capacity.

[0017] The battery modules in a battery pack may be connected in series or in parallel or in a series-parallel combination to provide a desired voltage and / or capacity of the battery pack, such as a 400V or 800V arrangement.

[0018] The battery pack may include a housing that houses the battery cells and / or battery modules. The housing preferably provides a sealed enclosure so that the battery pack can be arranged in a vehicle in a safe manner.

[0019] The battery packs of the vehicle may preferably be connected in parallel in order to achieve a desired total capacity of the battery system, but may also be connected in series if a desired output voltage of the battery system is achieved by combination.

[0020] It is known to provide a high-voltage battery system for an electric vehicle, which includes at least two battery packs, each of which may include one or a group of battery modules, wherein each battery module includes a group of battery cells. The battery packs together form a battery system and provide electrical energy for the electric drive device or other auxiliary components of the vehicle. The battery packs are usually placed in different locations in the vehicle.

[0021] A battery pack or battery module may include, for example, lithium-ion or lithium-polymer battery cells. A battery pack may also include at least one battery module, wherein each battery module includes a group of battery cells.

[0022] Battery packs may be connected in parallel to the output via a switching device, wherein each battery pack may include a group of battery modules and / or battery cells connected in series and / or parallel.

[0023] The battery system may further comprise a sensor device, in particular a measuring probe, which is connected to the electronic control unit and is suitable for measuring the voltage value of each battery pack and / or each battery module and / or each battery cell in the corresponding battery pack. The electronic control unit may measure the voltage value of each battery pack and / or each battery module and / or each battery cell in the corresponding battery pack by means of the sensor device. For example, the electronic control unit may calculate the voltage value of the corresponding battery pack by summing the measured voltage values ​​of each battery cell or each battery module in the battery pack. The voltage value of each battery pack and / or each battery module and / or each battery cell may preferably be measured in each cycle, in particular before selecting the first battery pack.

[0024] In addition, if the number of battery packs already connected to the output is zero, the electronic control unit can 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 greater than zero, the electronic control unit can skip the step of connecting the first battery pack to the output in each connection cycle.

[0025] If the number of battery packs already connected to the output is zero, a first battery pack having the highest or lowest measured voltage value may be selected from the group of all battery packs of the battery system and connected to the output. The maximum allowable deviation threshold is used to limit the balancing current between battery packs already connected to the output, the battery packs including the first battery pack and the second battery pack most recently connected. The deviation threshold may be a fixed voltage value, such as a voltage value less than or equal to 10V.

[0026] In order to limit the balancing current, the second battery pack or a group of second battery packs may be selected so that the deviation between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack is less than or equal to the deviation threshold. For the case of selecting the first battery pack with the highest measured voltage value, this can be expressed by the following equation:

[0027] 0≤|(U grp,max -U k )|≤ΔU lim (1)

[0028] The case of selecting the first battery group with the lowest measured voltage value can be expressed by the following formula

[0029] 0≤|(U grp,min -U k )|≤ΔU lim (2)

[0030] Among them U grp，max represents the highest voltage of the first battery group including a group of battery cells connected in series and / or in parallel, U grp，min The battery system may include a total of k battery packs, wherein the voltage value U of the battery pack k may be measured for each battery pack of the battery system by the electronic control unit with the aid of a sensor device. k This can be achieved by using the relation U grp，max ∈U k and U grp，min ∈U k Therefore, the highest or lowest measured voltage value can be:

[0031] U grp,max =max(U1, U2, ..., U k ) (3)

[0032] U grp，min=min(U1, U2, ..., U k ) (4)

[0033] For example, the battery system may include 10 different battery packs that are not yet connected to the output, so k ∈ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}. Each battery pack k may include n battery cells that may be connected in series, where the voltage of each battery cell n in the battery pack k may be represented as U k，n Therefore, the measured voltage value U of each battery pack k It can be calculated by the electronic control unit as:

[0034] U k =U k，1 +…+U k，n (5)

[0035] If the number of battery packs k that have not yet been connected to the output is zero, or if the number of battery packs connected to the output is equal to k, the cycle can terminate. The method minimizes the balancing current when multiple battery packs of different voltages and / or temperatures and / or state of charge levels are connected to the output of the battery system.

[0036] The battery system may be a 400V or 800V battery system suitable for a vehicle.

[0037] This has the advantage that the balancing current in a battery system including a group of multiple battery packs, in particular battery packs connected in parallel, is reduced compared to a method in which all battery packs are connected at the same time. This prevents damage to high-voltage components such as contactors due to high balancing currents that may occur after the battery packs are connected. This also prevents rapid capacity decay of the battery system, in particular the aging process of the battery cells, due to high balancing currents after connecting uneven battery packs. In addition, the energy throughput in the connected battery packs of the battery system can be increased. The battery system 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. In addition, during vehicle driving or charging, the disconnected battery packs of the battery system in the vehicle can be connected to the output of the battery system when the permitted connection level is reached.

[0038] Typically, the battery packs that have been connected to the output share the same voltage value. The shared voltage can be used as the highest U grp,max or minimum U grp,min Voltage value reference.

[0039] In a specific embodiment, if at least one of the battery packs in the group of battery packs is already connected to the output, a first battery pack is selected from the group of battery packs connected to the output. In other words, the charging or discharging operation performed on the battery packs already connected to the output may change the voltage value of the battery packs. In particular, the voltage value of each of the battery packs connected to the output may 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 with the highest or lowest measured voltage value can be selected from 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 skip the step of connecting the first battery pack to the output in each cycle. This is advantageous because the voltage value of the battery packs already connected to the output may change, in particular at different speeds, due to the charging or discharging operation of the battery system, while the voltage value of the battery pack disconnected from the output can remain substantially constant before a certain period of time has passed.

[0040] This has the advantage that changes in the energy level of the battery pack connected to the output due to charging or discharging operations can be taken into account. The charging operation of the battery pack can provide electrical energy to high-voltage components of the vehicle, such as an electric motor. The charging operation can be to receive electrical energy from an on-board charger of the vehicle via the output. In addition, this has the advantage that during driving or charging of the vehicle, a disconnected battery pack of the battery system in the vehicle can be connected to the output of the battery system when the permitted connection level is reached.

[0041] In one embodiment, the second battery group is selected so that the difference between the measured voltage value of the second battery group and the measured voltage value of the first battery group is the smallest among all pairs of the first battery group and the second battery group. k The measured voltage value U of the first battery pack grp，max or U grp，min The difference is lower than or equal to the deviation threshold in the second battery group, and the voltage value U can be selected to be measured k The measured voltage value U of the first battery pack grp，max or U grp，min The second battery group with the smallest difference. This condition can be expressed as: for all k, min(|U grp,max -U k |≤ΔU lim ) or min(|U grp,min -U k |≤ΔU lim). This has the advantage that in each cycle a second battery group is selected which has the smallest voltage deviation from the highest or lowest measured voltage value of the first battery group. This has the advantage that the equalization currents which occur after connecting the second battery group in parallel to the first battery group are minimized.

[0042] In one embodiment, the deviation threshold is determined by means of a decision matrix that records the corresponding deviation threshold based on the number and / or voltage of the battery packs that have been 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 or out of the battery system. In other words, the decision matrix can be a matrix that includes the deviation threshold ΔU lim A lookup table or database listing the deviation threshold ΔU lim is calculated by means of simulation or by means of statistical measurements of the balancing current of the battery system using at least one parameter selected as follows: the number N of battery packs connected to the output, the average state of charge SOC avg , average temperature T avg , the amount of current flowing into or out of the battery system |I| and the voltage U of the battery pack connected to the output N With the help of the corresponding values ​​of the corresponding parameters based on the sensor readings of the sensor device, the corresponding deviation threshold value can be accessed in the decision matrix, in particular in the database. Preferably, the parameters number N of battery packs, average state of charge SOC avg , average temperature T avg The sensor readings of the current |I| and the current amount |I| are used in the decision matrix.

[0043] For example, the deviation threshold ΔU lim It can be calculated by a function based on four parameters, for example:

[0044] ΔU lim =f(SOC avg , T avg ,|I|,N) (6)

[0045] The first boundary condition for the differential voltage can be

[0046]

[0047] Where N represents the number of battery packs connected to the output for the decision matrix.

[0048] Differential voltage ΔU lim The second boundary condition can be:

[0049]

[0050] If the number of battery packs connected to the output is zero, so N=0, then the differential voltage can be set to zero.

[0051] One parameter for the function of equation (6) may be the average state of charge SOC of the battery system including the N battery packs that have been connected to the battery system. avg The parameters can be calculated by the following equation:

[0052]

[0053] Among them, SOC avg，grpN represents the average state of charge of a group of battery cells in a corresponding battery pack N that has been connected to the output. For example, each battery pack includes a group of n battery cells that can be connected in series. Therefore, the state of charge of the corresponding battery pack can correspond to the lowest state of charge of the battery cells in the corresponding battery pack. This can be expressed by the following formula:

[0054] SOC avg,grpN =min(SOC N,1 , SOC N,2 , ..., SOC N,n ) (10)

[0055] Among them, SOC N，n Indicates the state of charge of the corresponding battery cell n in the battery pack N.

[0056] One parameter for the function of equation (6) may be the average temperature T of the battery pack connected to the output avg The average temperature can be determined by

[0057]

[0058] Where T avg，grpN represents the average temperature of a group of battery cells in the corresponding battery group that has been connected to the output. Therefore, the average temperature T of the corresponding battery group N avg，grpN It can be the battery with the highest temperature T in the corresponding battery pack N. max(N，1) The first battery cell and the one with the lowest temperature T min(N,2) The average value between the second battery cells is:

[0059]

[0060] Where T N，n The temperature of the corresponding battery cell n in the battery pack N is described.

[0061] One parameter for the function of equation (6) may be the amount of current |I| flowing into or out of the battery system via the output. For example, current may flow out of the battery system via the output during a discharge operation, and current may flow into the battery system via the output during a charge operation. The first battery pack to be connected to the output may be selected taking into account the direction of the current I. For example, in the case of a charge operation, the first battery pack may be the one with the lowest U grp，min The battery groups with the highest U grp，max Measure the voltage value of the battery pack.

[0062] One parameter of the function for 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, each of which may include n battery cells. For example, a battery pack may include a number of battery cells from 1 to 10, so n∈{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}.

[0063] If the total number of battery packs in the battery system is k, the maximum value for the decision matrix (including the value for connecting another battery pack to the output) representing the number of battery packs N already connected to the output can be 0 to N = k-1, so if k = 10, then N ∈ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}. However, if the number of battery packs already connected to the output is k, so N = k, then the loop can terminate because all battery packs are already connected.

[0064] Additionally, the voltage U of the battery pack connected to the output N can be considered as the deviation threshold ΔU lim This may be advantageous for dynamic situations where the voltage value of the corresponding battery pack connected to the output may change due to charging or discharging operations. For example, the voltage U N It may be the highest or lowest or average voltage of the battery packs connected to the output. Due to the charging or discharging operation performed on the battery system, the respective battery packs connected to the output may be charged or discharged at different speeds. This may be due to different life cycles or aging of the battery cells in the respective battery packs. Therefore, if the electronic control unit detects a charging or discharging operation, the highest U of the battery pack, preferably the battery pack that has been connected to the output, may be remeasured in each cycle. grp，max or minimum U grp，min Measure the voltage value.

[0065] This provides the following technical effect, namely, based on the selection of the corresponding operating parameters of the battery system, the maximum allowed deviation threshold is adapted to the corresponding operating mode of the battery system to maintain a low balancing current in each operating mode. In the case of using a limited number of input parameters to determine the deviation threshold, the use of the decision matrix, in particular as a database for accessing the corresponding deviation threshold based on the selection of the parameters, can further reduce the processing time of the electronic control unit. For example, in the case of selecting three of the parameters (such as the number of battery packs connected to the output, the average state of charge and the average temperature) for determining the deviation threshold, the time required to retrieve the deviation threshold from the database may be less than the time required for the electronic control unit to run the simulation.

[0066] In one embodiment, the deviation threshold is calculated by means of a simulation of the battery system, in particular a simulation of the balancing 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 the average temperature of the battery system, and / or the amount of current flowing into or out of the battery system. In other words, the simulation can calculate the maximum allowable voltage difference between the highest or lowest measured voltage value of the second battery pack to be connected to the output and the first battery pack based on the allowable amount of balancing current. The allowable balancing current can be simulated based on the sensor reading of the sensor device, the sensor reading being based on at least one parameter: the number N of battery packs connected to the output, the average state of charge SOC avg , average temperature T avg , the amount of current flowing into or out of the battery system |I| and the voltage U of the battery pack connected to the output N Preferably, the parameters are the number of battery packs N, the average state of charge SOC avg , average temperature T avg and the sensor readings of the current amount |I| are used for the simulation.

[0067] Using simulation to connect the second battery pack to the output in each cycle also provides the technical effect that the maximum allowed deviation threshold is adapted to the corresponding operating mode of the battery system to maintain a low balancing current in each operating mode. Using simulation may be advantageous in cases where several input parameters, such as more than three parameters, are used to determine the deviation threshold. In this case, the processing time of the simulation may be shorter than the time required to retrieve the corresponding deviation threshold from the database.

[0068] In one embodiment, in the case of a discharge operation of the battery system, the first battery pack with the highest measured voltage value is selected to be connected to the output by means of a switching device, and / or in the case of a charging operation of the battery system, the first battery pack with the lowest measured voltage value is selected to be connected to the output by means of a switching device. In other words, the electronic control unit can detect a charging or discharging operation based on a sensor reading of the current I by means of a sensor device and / or whether electrical energy is required or requested from the vehicle interface to the output of the battery system. In the case of a discharging operation, for example to provide electrical energy to an electric motor of the vehicle, the first battery pack with the highest measured voltage value and / or the highest state of charge can be first connected to the output of the battery system for discharging. The discharge can further reduce the voltage of the first battery pack so that after a specified period of time for the initial discharge of the first battery pack has passed, the measured voltage value U of the second battery pack is reduced. k The difference with the measured voltage value of the first battery pack can be further reduced.

[0069] Additionally or alternatively, in the case of a charging operation, such as receiving electrical energy from an onboard charger of a vehicle, the first battery pack having the lowest measured voltage value and / or the lowest state of charge may be first connected to the output of the battery system for charging. The charging may further increase the voltage of the first battery pack, such that after a specified period of time for initial charging of the first battery pack has elapsed, the difference between the measured voltage value of the second battery pack and the measured voltage value of the first battery pack may be further reduced.

[0070] Additionally, if the number of second battery groups for which the difference between the measured voltage value of the second battery group and the measured voltage value of the first battery group is lower than or equal to the deviation threshold is zero, the electronic control unit may charge or discharge the battery group connected to the output, in particular the first battery group, for a specified period of time before continuing to select the second battery group from the remaining disconnected battery groups.

[0071] 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 the second battery pack is connected.

[0072] The invention also relates to an electronic control unit for a battery system, preferably a battery management system, comprising means adapted to perform the steps of the method. In other words, the electronic control unit may comprise or be adapted to be connected to sensor means for measuring at least one of the following parameters: the number N of battery packs connected to the output, the average state of charge SOC avg , average temperature T avg , the current I flowing into or out of the battery system and the voltage U of the battery pack k(in particular the voltage of the battery modules and / or battery cells in the corresponding battery pack). The electronic control unit may also include a communication interface for sending a connection or disconnection command to the switching device, such as a command for opening or closing a corresponding switch that connects or disconnects the corresponding battery pack to the switching device. The electronic control unit may include at least one processor and a computer-readable storage medium, wherein the computer-readable storage medium includes instructions, which, when executed by at least one processor, cause the electronic control unit to perform the method on the battery pack of the battery system. To this end, the electronic control unit may be a battery management system for the battery, preferably 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).

[0073] The invention also relates to a computer program product comprising instructions for causing an electronic control unit to perform the steps of the method. In other words, the computer program can be installed on a computer readable storage medium of an electronic control unit of a battery, preferably a battery management system.

[0074] The invention further relates to a computer-readable storage medium on which the computer program is stored. In other words, the computer-readable storage medium may be a punch 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, wherein flash memory is particularly used. The computer-readable storage medium may also be a data communication network, such as the Internet or other systems, that allows downloading of program codes. The electronic control unit, preferably the battery management system, comprises the computer-readable storage medium. The computer program may preferably be an embedded system application, which may preferably be implemented in the C programming language.

[0075] The invention further relates to a battery system, preferably for a vehicle, comprising said electronic control unit, preferably said battery management system.The battery system may represent a battery, such as a lithium-ion or lithium-polymer battery, for a vehicle.

[0076] The battery system may include a sensor device for measuring at least one of the following parameters: the number N of battery packs connected to the output, the average state of charge SOC avg , average temperature T avg , the current I flowing into or out of the battery system and the voltage U of the battery pack k (In particular, the voltage of the battery cells in the corresponding battery pack).

[0077] The battery system may further comprise a communication line for sending a connection or disconnection command to the switching device, such as a command line for opening or closing a corresponding switch for connecting or disconnecting the corresponding battery pack from the switching device. Furthermore, the battery system may be adapted to be controlled by the electronic control unit and / or the computer program executed by at least one processor of the electronic control unit, such that a charging or discharging operation of the battery system may be detected by the electronic control unit and a method for connecting or disconnecting the battery pack from the output is executed by the electronic control unit. This has the advantage that the battery system may provide a constant operating voltage level and that a balancing battery system does not interfere with a current operating mode of the battery system.

[0078] The present invention also relates to a vehicle comprising the battery system and / or the electronic control unit.

[0079] The vehicle may include a high-voltage component adapted to receive electrical energy via a vehicle interface and an output of the battery system or to transmit electrical energy to the battery system. To this end, the vehicle may include 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 a motor vehicle, in particular a car or a truck, or a bus or a motorcycle, wherein the electric vehicle is in particular designed as an electric or hybrid vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] In the following, the present disclosure will be explained in more detail with reference to the accompanying drawings, in which:

[0081] Figure 1 is a schematic diagram of a battery system including a set of battery packs connected to high voltage components of a vehicle via an interface;

[0082] Figure 2 is a schematic diagram of a command circuit for an electronic control unit of a battery system, the command circuit being used to connect a battery pack to an output of the battery system; and

[0083] Figure 3 is a schematic flow chart of a method for connecting a battery pack to an output of a battery system. DETAILED DESCRIPTION

[0084] The embodiments explained below are preferred embodiments of the present invention. In the embodiments, the components of the embodiments each represent the individual features of the present invention that are considered to be independent of each other, and these features also further form the present invention independently of each other, and are therefore also considered to be individual components of the present invention or components of the combination form other than those shown. In the accompanying drawings, the same elements are represented by the same reference numerals, and in order to avoid repetition, their repeated descriptions can be omitted.

[0085] Figure 1A schematic diagram of a battery system 4 is shown, which is adapted to deliver electrical energy 15 to or receive electrical energy 15 from a high-voltage component 2 of a vehicle 1 via an output 8 of the battery system 4 and a corresponding vehicle interface 2 of the vehicle 1. The high-voltage component 2 may be, for example, an on-board charger or an electric engine.

[0086] For example, in an electric vehicle 1 with a high-voltage battery system 4, a plurality of battery packs 6 are integrated in the battery system 4, which together provide electrical energy 15 for high-voltage components 2 (e.g., electric drives or auxiliary components) of the vehicle 1. Each battery pack 6 has its own high-voltage contactor and can therefore be independently connected and disconnected with the switching device 11 by means of a switch 12 to provide the required electrical energy 15 to the vehicle 1 via the output 8 or to receive electrical energy 15 from the vehicle 1.

[0087] The battery system 4 includes a group of batteries with corresponding charge states SOC k k battery packs 6 are adapted to be electrically connected via a switch device 11, wherein closing or opening of a switch 12 can connect or disconnect the corresponding battery pack 6 to the switch device 11. For example, the switch device 11 can be adapted to electrically connect the battery packs 6 in parallel. In particular, the switch device 11 can be adapted to first connect the battery packs 6 to form a series string and then connect the series strings in parallel according to the required high-voltage architecture. The electronic control unit 3, such as a battery management system, can be adapted to control and / or measure the amount of current |I| flowing into or out of the battery system 4, in particular the corresponding battery pack 6 connected to the output 8, by means of a connection command loop 14 and by means of a sensor device.

[0088] The electronic control unit 3 may be adapted to connect or disconnect the battery packs 6 of the battery system 4 by means of the switching device 11, i.e. by closing or opening the corresponding switches 12, so as to adapt the battery system 4 to the amount of electrical energy 15 that is delivered to the high-voltage components 2 of the vehicle 1 in the current operating mode (e.g. charging or discharging mode) of the battery system 4. The corresponding battery pack 6 comprises a group of n battery cells 7 connected in parallel (or in an alternative embodiment connected in series), wherein the corresponding battery cell n in the battery pack k may have an individual state of charge SOC k,n .

[0089] This may result in the battery pack 6 having a different state of charge SOC accordingly. k , where an unbalanced current 13 occurs between the respective battery packs 6. When the battery packs 6 are connected in parallel to the output 8 by means of the switching device 11, this results in a balancing current 13 which may be high enough to cause damage to the battery system 4 (e.g. contactors or pre-charging resistors or electrical fuses). The balancing current 13 may be drawn from the battery pack with the highest state of charge SOC1 and / or the highest voltage U connected to the output 8. grp，maxThe first battery group 9 of the output 8 flows accordingly to the battery group 6 with a lower state of charge connected to the output 8, such as the module 6 with a corresponding state of charge SOC2. Conversely, the balancing current 13 can flow from the battery group 6 with a higher state of charge connected to the output 8 to the battery group 6 with the lowest state of charge SOC1 and / or the lowest voltage U connected to the output 8. grp，min The first battery pack 9.

[0090] In order to safely connect several battery packs 6 in parallel, the battery packs 6 should have the same voltage, temperature and charge state. Otherwise, an imbalance may cause a balancing current 13 to flow between the battery packs 6 electrically connected by means of the switching device 11. If the voltage and charge state of the connected battery packs 6 and 9 differ by more than a threshold value, in particular by a voltage threshold ΔU lim If the ground is different, a balancing current 13 may occur that is large enough to cause damage to the switch 12 and the battery pack 6. The amount of the balancing current 13 may depend on the number N of battery packs 6 connected in parallel by means of the switch device 11, and / or the average state of charge SOC of the N connected battery packs 6 and 9. avg and / or average temperature T avg , and / or the amount of current |I| flowing into or out of the battery system 4. Figure 1 In the example of FIG. 1 , the two battery packs 6 and 9 are connected in parallel by means of a switching device 11 , wherein the corresponding switch 12 is closed, so that Figure 1 In the example, N=2.

[0091] The amount of the balancing current 13 is reduced by means of a connection command circuit 14 which can be executed by an electronic control unit 3 which can convert said parameter of the amount of the balancing current 13 into a voltage threshold ΔU lim , for deciding whether to connect the second battery pack 10 to the switching device 11 by means of the decision matrix 18 and / or the simulation. Figure 2 is shown in more detail in .

[0092] Figure 2 Schematically depicted is a command loop 14 for an electronic control unit 3 of a battery system 4 for deciding by means of the electronic control unit 3 whether to connect a second battery pack 10 to the output 8 of the battery system 4, wherein the electronic control unit 3 may be adapted to execute said connection command loop 14. To this end, the electronic control unit 3 may be adapted to measure by means of sensor means the number N of battery packs 6 already connected to the output 8 and / or the average state of charge SOC avg and / or average temperature T avg and / or the current I flowing into or out of the battery system 4 via the output 8 and / or the current voltage value U of the battery pack 6 connected to the output 8 NFor example, the sensor device may be a measuring probe. Preferably, the number N of battery packs 6 connected to the output 8 and the average state of charge SOC avg and the average temperature T avg can be used as input parameter 17 . The input parameter 17 is thus based on sensor readings of the sensor device, which are transmitted to the electronic control unit 3 .

[0093] Based on the input parameters 17 , the deviation threshold ΔU is determined with the aid of a decision matrix 18 and / or a simulation. lim As output value 19, said output value 19 represents the maximum permissible voltage difference ΔU 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 lim The decision matrix 18 can thus be used as a database for retrieving the current deviation threshold ΔU based on the current sensor reading of the input parameter 17. lim The decision matrix 18 can combine the sensor readings of the combination of the input parameters 17 (preferably the number N of battery packs 6 connected to the output 8 and the average state of charge SOC avg and the average temperature T avg ) is converted into a voltage value ΔU as the maximum allowable deviation 20 lim .

[0094] The connection decision state machine 21 is adapted to decide whether to connect a corresponding second battery pack 10 of the remaining battery packs 6 in the battery system 4 to the output 8. To this end, if the measured voltage value U of the second battery pack 10 is k The measured voltage value U of the first battery group 9 grp，max or U grp，min The difference between them is lower than or equal to the deviation threshold ΔU lim , so |U grp，max -U k |≤ΔU lim or |U grp,min -U k |≤ΔU lim , then the connection decision state machine 21 is adapted to decide to connect the corresponding second battery pack 10 to the output 8 .

[0095] Preferably, the connection decision state machine 21 can select the second battery pack 10 with the smallest difference so that the measured voltage value U of the second battery pack 10 is k The measured voltage value U of the first battery group 9 grp，max or U grp,min The difference between them is the smallest among all first and second battery pack pairs, so for all k, min(|U grp,max -U k |≤ΔU lim ) or min(|Ugrp，min -U k |≤ΔU lim ).

[0096] The decision state machine 21 may be adapted to output a connection command 22 to connect the second battery pack 10 to the output 8 by means of a corresponding switch 12 of the switch arrangement 11. The electronic control unit 3 may comprise the decision state machine 21 and the connection algorithm 16. Furthermore, the electronic control unit 3 may comprise or have access to a database forming a decision matrix 18.

[0097] Additionally or alternatively, the electronic control unit 3 may be adapted to perform said simulation, said simulation outputting the deviation threshold value ΔU based on a combination of the input parameters 17 lim .

[0098] If the number N of battery packs 6 already connected to the output 8 is zero, the voltage value U of all battery packs 6 , in particular the first battery pack 9 and the second battery pack 10 , is measured. k If current flows out of the battery system 4, then the maximum measured voltage value U grp，max The first battery pack 9 is selected by the electronic control unit 3, and if current flows into the battery system 4, the one with the lowest voltage value U grp，min The first battery pack 9 is selected by the electronic control unit 3. The first battery pack 9 is connected to the output 8 by means of sending a connection command 22 for closing or disconnecting from the electronic control unit 3 to the corresponding switch 12 of the switching device 11. The electronic control unit 3 may be adapted to send the connection command 22 to open or close the corresponding switch 12 of the switching device 11 to connect or disconnect the corresponding 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 may measure the voltage value U of these battery packs 6. N , and determine the one with the highest U grp，max or minimum U grp，min voltage value of the first battery pack 6.

[0099] Figure 3 A flow chart of a method of connecting a group of battery packs 6 of a battery system 4 in parallel is depicted.

[0100] In a first step S1 , the voltage value U of each battery pack 6 of the battery system 4 is measured. k The electronic control unit 3 may be adapted to measure said voltage value of each battery pack 6 by means of a sensor device 11, for example a measuring probe for each battery pack 6, or a supplementary device for each battery cell 7 in the respective battery pack 6. k

[0101] In a second step S2, a battery having the highest U grp，maxor minimum U grp，min If the electronic control unit 3 detects a discharge operation of the battery system 4, so that current flows out of the battery system 4 via the output 8, the first battery pack 9 with the highest voltage value U grp，max If the electronic control unit 3 detects a charging operation, so that current flows into the battery system 4 via the output 8, the first battery pack 9 with the lowest voltage value U is selected. grp，min To this end, the electronic control unit 3 may be adapted to measure the direction of the current I via the output and determine a discharging or charging operation, and / or to receive a request or provision of electrical energy 15 from the vehicle interface 2 .

[0102] Typically, the battery packs 6 connected to the output share the same voltage value. The shared voltage can be used as the highest U grp，max or minimum U grp，min Voltage value reference.

[0103] In case the batteries 6 are discharged or charged at different speeds due to, for example, aging effects, an additional step may be added to step S2. If the number N of batteries 6 already connected to the output 8 is not zero, a first battery 9 may be selected among the batteries 6 already connected to the output 8. To this end, the electronic control unit 3 may be adapted to measure a voltage value U of each battery 6 already connected to the output 8. N , and select the one with the highest U grp，max or minimum U grp，min The battery group 6 with the same voltage value is used as the first battery group 9.

[0104] In a third step S3, the first battery pack 9 is connected to the output 8 by means of the switching means 11. To this end, the electronic control unit 3 may be adapted to send a connection command 22 to close the corresponding switch 12 for connecting the first battery pack 9 to the switching means 11 and thus to the output 8. If the number N of battery packs 6 already connected to the output 8 is not zero, step S3 is skipped.

[0105] In a fourth step S4, a maximum permissible deviation threshold ΔU for connecting the second battery pack 10 from the remaining battery packs 6 of the battery system 4 is set. lim , where the deviation threshold ΔU lim can be determined by means of a decision matrix 18 based on the selection of input parameters 17, which are preferably the number N of battery packs 6 that have been connected to the output 8 and the average state of charge SOC avg and the average temperature T avg .

[0106] Additionally or alternatively, the deviation threshold ΔU limcan be calculated by simulation of the battery system, preferably simulation of the balancing current 13 in the battery system, depending on input parameters 17, preferably the number N of battery packs 6 that have been connected to the output 8 and the average state of charge SOC avg and the average temperature T avg .

[0107] In the fifth step S5, if the voltage value U of the second battery pack 10 k The measured voltage value U of the first battery group 9 grp，max or U grp，min The deviation between them is lower than or equal to the deviation threshold ΔU lim , then the second battery pack 10 is selected from the remaining battery packs 6 of the battery system 4. Therefore, the condition for selecting the second battery pack 10 may be |U grp，max -U k |≤ΔU lim or |U grp,min -U k |≤ΔU lim .

[0108] Preferably, the voltage value U is selected k With the highest U grp,max or minimum U grp,min The deviation between the voltage values ​​is the smallest for the second battery pack 10, so for all battery packs k that have not yet been connected to the output 8, the condition may preferably be min(|U grp,max -U k |≤ΔU lim ) or min(|U grp，min -U k |≤ΔU lim ).

[0109] In a sixth step S6, the selected second battery pack 10 is connected to the output 8 and is thus connected in parallel with the battery pack 6 already connected to the output 8. Therefore, the balancing current 13 occurring after the connection is limited so that no damage is caused to the battery pack 6, in particular the contactor.

[0110] In a 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 terminate in step S8. In the case where at least one battery pack 6 remains disconnected, the voltage value U of each battery pack k in the battery system 4 k , preferably the voltage value U of the battery pack 6 connected to the output 8 kThe voltage of the battery 6 connected to the output 8 may change in case of a charging or discharging operation, which is measured by the electronic control unit 3 by means of the sensor device 11. The method is repeated starting from step S2, with step S3 being skipped, until the termination condition of step S7 is met. k k

[0111] It will be apparent to those skilled in the art that these embodiments and projects only describe examples of multiple possibilities. Therefore, the embodiments shown here should not be construed as limiting these features and configurations. According to the scope of the present invention, any possible combination and configuration of the features may be selected.

[0112] Reference numerals list

[0113] Vehicle 1

[0114] Vehicle interface for high voltage components 2

[0115] Electronic control unit for battery system 3

[0116] Battery System 4

[0117] A battery pack 5

[0118] Battery Pack 6

[0119] Battery Cell 7

[0120] Battery system output 8

[0121] First battery pack 9

[0122] Second battery pack 10

[0123] Switch device 11

[0124] Switch 12

[0125] Balance current 13

[0126] Connect command loop 14

[0127] Electricity 15

[0128] Connection Algorithm 16

[0129] Input Parameter 17

[0130] Decision Matrix 18

[0131] Output value 19

[0132] Deviation 20

[0133] Connection decision state machine 21

[0134] Connection command 22

[0135] State of charge SOC of battery pack n n

[0136] Deviation threshold ΔU lim

[0137] Maximum voltage value U grp，max

[0138] Minimum voltage value U grp，min

[0139] Voltage U of battery pack k k

[0140] The number of battery packs connected to the output N

[0141] The voltage of the battery connected to the output is U N

[0142] Average state of charge SOC of the battery system avg

[0143] Average temperature of the battery system T avg

[0144] The current flowing into or out of the battery system |I|

[0145] First step S1

[0146] Second step S2

[0147] Third step S3

[0148] Fourth step S4

[0149] Fifth step S5

[0150] Sixth step S6

[0151] Step S7

[0152] Eighth step S8

[0153] Ninth step S9

Claims

1. A method for electrically connecting a group of battery packs (5) in parallel to an output (8) by means of a switching device (11) to form a battery system (4) preferably for a vehicle (1), wherein: Each battery pack (6) includes a plurality of battery cells (7), and the voltage value (U k ) is measured by means of a sensor device, the method comprising the following steps: - selecting a first battery group (9) from the set of battery groups (5), the first battery group (9) having the highest measured voltage value (U grp,max ) or the lowest measured voltage value (U grp,min ); - connecting said first battery pack (9) to the output (8); -Set the maximum allowable deviation threshold (ΔU lim ), for connecting a second battery pack (10) from the set of battery packs (5); - selecting a second battery pack (10) from the set of battery packs (5) such that the measured voltage value (U k ) and the measured voltage value (U grp,max ,U grp,min ) is lower than or equal to the deviation threshold (ΔU lim );as well as - Connecting said second battery pack (10) to the output (8).

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

3. The method according to claim 1 or 2, characterized in that: The deviation threshold (ΔU lim ) is determined by means of a decision matrix (18) based on the number (N) and / or voltage (U) of battery packs (6) already connected to the output (8) N ), and / or the average state of charge (SOC) of the battery system (4) avg ) and / or average temperature (T avg ), and / or the current (|I|) flowing into or out of the battery system (4) to record the corresponding deviation threshold (ΔU lim ).

4. The method according to any one of the preceding claims, characterized in that Based on the number (N) and / or voltage (U) of battery packs (6) already connected to the output (8) N ), and / or the average state of charge (SOC) of the battery system (4) avg ) and / or average temperature (T avg ), and / or the current (|I|) flowing into or out of the battery system (4), by means of simulation of the battery system (4), in particular simulation of the balancing current in the battery system (4), to calculate the deviation threshold value (ΔU lim ).

5. The method according to any one of the preceding claims, characterized in that In the case of a discharge operation of the battery system (4), the maximum measured voltage value (U grp,max ) is selected to be connected to the output (8) by means of the switching device (11), and / or in the case of a charging operation of the battery system (4), the first battery group (9) having the lowest measured voltage value (U grp,min ) is selected to be connected to the output (8) by means of a switching device (11).

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

7. A computer program product comprising instructions for causing an electronic control unit (3) according to claim 6 to execute the steps of the method according to any one of claims 1-5.

8. A computer-readable storage medium having stored thereon the computer program product according to claim 7.

9. A battery system (4), preferably for a vehicle (1), comprising an electronic control unit (3) according to claim 6.

10. A vehicle (1) comprising a battery system (4) according to claim 10 and / or an electronic control unit (3) according to claim 6.

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