Battery pack system for electric vehicle, method for operating battery pack system, and electric vehicle

Abstract

A battery system for an electric vehicle, a method for operating the battery system, and an electric vehicle. The present invention relates to a battery system for an electric vehicle, comprising at least two battery branches and a battery control device for controlling the at least two battery branches, wherein each of the battery branches comprises at least one battery module, and wherein at least one battery module comprises: at least one battery cell having a fast discharge device; and a module control device for controlling at least one battery cell. A current measuring device is respectively provided in each of the battery branches, which sends the magnitude of the current flowing in the battery branch and the direction of the current flowing in the battery branch to at least one control device. Each of the battery branches respectively comprises an isolation device for shutting down the battery branch, which can be controlled by at least one control device. The present invention also relates to a method for operating the battery system according to the present invention.

Description

Technical Field

[0001] The present invention relates to a battery system for an electric vehicle, the battery system comprising at least two battery branches and a battery control device for controlling the at least two battery branches. Here, each of the battery branches comprises at least one battery module, and the at least one battery module comprises: at least one battery cell having a fast discharge device; and a module control device for controlling the at least one battery cell. The present invention also relates to a method for operating the battery system according to the present invention and a corresponding electric vehicle. Background Art

[0002] It is found that in the future, battery systems will be increasingly used, especially in electric vehicles, which place high demands on reliability, efficiency, safety and service life. Battery systems with lithium-ion battery cells are particularly suitable for such applications. These battery systems are particularly characterized by high energy density, thermal stability and extremely low self-discharge.

[0003] A battery cell has an anode connected to a negative terminal and a cathode connected to a positive terminal. A plurality of such battery cells are electrically connected to one another in series and also in parallel and are connected to form a battery module. A plurality of such battery modules are connected to one another, in particular in series, to form a battery branch. A plurality of battery branches constructed in this way are then connected to one another, in particular in parallel, and thus form a battery system for an electric vehicle.

[0004] Battery systems with lithium-ion battery cells are subject to high demands regarding functional safety. Improper operation of the battery cells can lead to exothermic reactions up to and including fire and / or degassing. Fires or explosions can occur in particular if metal parts penetrate into the battery cells. However, deformations of the cell housing of the battery cells can also trigger exothermic reactions.

[0005] In the event of a fault in a battery cell, for example an internal short circuit between the anode and the cathode, it may be necessary to discharge the battery cell in order to avoid a critical state which could lead to overheating and explosion of the battery. Rapid discharge devices are known for this purpose. Such rapid discharge devices are jumper elements which are connected to the terminals of the battery cell. In normal operation, the rapid discharge device is disconnected and electrically insulates the terminals of the battery cell from one another. In the event of a fault, the rapid discharge device is activated and then electrically connects the terminals of the battery cell to one another. Subsequently, a discharge current flows through the rapid discharge device and the battery cell is discharged. Document DE 10 2012 005979 B4 discloses such an electrical jumper element for bridging battery cells in the event of a fault. Summary of the invention

[0006] A battery system for an electric vehicle is provided. The battery system comprises at least two battery branches and a battery control device for controlling the at least two battery branches. The at least two battery branches are preferably connected electrically in parallel with each other.

[0007] Each of the battery branches of the battery system comprises at least one battery module, preferably a plurality of battery modules, which are electrically connected in series with one another. The at least one battery module comprises at least one battery cell, preferably a plurality of battery cells, which are electrically connected in series and also in parallel with one another. The at least one battery cell has a rapid discharge device. The at least one battery module also comprises a module control device for controlling the at least one battery cell.

[0008] According to the present invention, a current measuring device is provided in each of the battery branches, which detects the magnitude of the current flowing in the battery branch and the direction of the current flowing in the battery branch and sends it to at least one control device. In addition, each of the battery branches of the battery system includes an isolation device for shutting down the battery branch. The isolation device can be controlled by at least one control device, that is, by the battery control device and / or by at least one module control device.

[0009] The current measuring device comprises, for example, a shunt resistor. The current measuring device may also comprise a magnetic sensor, for example a Hall sensor. The isolating device may be, for example, an electromechanical contactor or a relay. However, the isolating device may also be configured, for example, as a pyrotechnic fuse or a semiconductor switch, in particular in the form of a metal oxide field effect transistor (MOSFET).

[0010] According to an advantageous development of the invention, a device is provided for measuring the voltage applied to the battery branches. The device is, for example, at least one voltage measuring device, which also sends the magnitude of the measured voltage to at least one control device, i.e. to at least one of the battery control device and / or the module control device. As long as all battery branches of the battery system are connected electrically in parallel to each other, the same voltage is applied to the battery branches. In this case, a single voltage measuring device is sufficient.

[0011] According to an advantageous embodiment of the invention, at least one battery module comprises a deformation sensor which monitors the battery module, in particular the housing of the battery module. In the event of a detected fault, for example in the event of penetration of a metal part into the housing of the battery module or in the event of a deformation of the housing, the deformation sensor causes the activation of all rapid discharge devices of the battery cells of the battery module in question.

[0012] Preferably, the battery control device, the module control device and the current measuring device communicate with one another via a data line, which is, for example, part of a bus system.

[0013] A method for operating a battery system according to the invention is also proposed. After activation of at least one rapid discharge device, for example after detection of a fault by a deformation sensor of a battery module, according to the invention in each of the battery branches the magnitude of the current flowing in the battery branch and the direction of the current flowing in the battery branch are detected by a current measuring device and are transmitted to at least one control device, namely to the battery control device and / or to one of the module control devices.

[0014] In this case, in each of the battery branches, the isolating device can be controlled by at least one control device, i.e. by the battery control device and / or by at least one of the module control devices, when the current is a charging current and flows at least during a first duration, or when the current is a discharging current and flows at least during a second duration. In this case, the second duration is greater than the first duration. The first duration is, for example, 10 seconds, and the second duration is, for example, 30 seconds. The second duration is preferably 2 to 5 times greater than the first duration.

[0015] After the rapid discharge device of the battery cell has been activated, the battery module concerned is short-circuited. As a result, the voltage of the battery branch in which the short-circuited battery module is arranged is reduced. A discharge current now flows in each of the remaining intact battery branches, and a charging current flows in the battery branch with the short-circuited battery module.

[0016] If the amount of charge transferred by the charging current exceeds a predetermined limit value, this can lead to damage and overloading of the battery cells in the battery branch with the short-circuited battery module. Similarly, an amount of charge transferred by the discharging current that exceeds a predetermined limit value can lead to damage of the battery cells in the intact battery branch. Such damage can be avoided if the corresponding battery branch is disconnected by means of an isolating device.

[0017] The method according to the invention allows a two-stage shutdown of the battery branches of a battery system after activation of at least one rapid discharge device. In this case, in each battery branch, the direction of the flowing current is checked.

[0018] If a charging current is detected in a battery branch, at least one battery module of the battery branch is short-circuited. The battery branch is then switched off after a first duration, i.e. relatively quickly. No more dangerous charging currents then flow in the battery branch with the short-circuited battery module. No more dangerous discharging currents then flow in the other intact battery branches either.

[0019] If a discharge current is detected in the battery branch, at least one battery module of another battery branch is short-circuited. If the discharge current still flows after a second duration that is greater than the first duration, the battery branch with the short-circuited battery module has not yet been switched off. This may occur, for example, when the isolation device of the battery branch with the short-circuited battery module fails. In this case, the intact battery branch is then switched off after the second duration, i.e. with a time delay. Then, no dangerous discharge current flows in the intact battery branch. Then, no dangerous charging current flows in the battery branch with the short-circuited battery module either.

[0020] Preferably, the isolating device is activated only when the amount of charge transferred by the current flowing through the battery branch exceeds a predetermined limit value. If the amount of charge transferred by the current flowing through the battery branch does not exceed a predetermined limit value, the isolating device is not activated. The predetermined limit value is, for example, between 0.5AH and 2AH.

[0021] According to an advantageous embodiment of the method according to the invention, after activating at least one rapid discharge device, the voltage present at each of the battery branches is first measured. The isolating device is activated only if the voltage present at the battery branch exceeds a predetermined threshold value. If the voltage present at the battery branch does not exceed a predetermined threshold value, the isolating device is not activated. The predetermined threshold value is, for example, between 65% and 70% of the rated voltage of the battery branch.

[0022] According to a preferred embodiment of the method according to the invention, after activating at least one fast discharge device, a control signal is sent to the battery control device and / or to the module control device. The control signal is in particular a wake-up signal, which is used to switch on the control device when it is switched off.

[0023] Preferably, the battery control unit and / or the module control unit is switched off when the magnitude of the current flowing in the battery branch does not exceed a predefined limit value.

[0024] An electric vehicle is also proposed, which comprises a battery system according to the invention and which is operated using the method according to the invention.

[0025] Advantages of the present invention:

[0026] The method for operating a battery system according to the invention allows that the remaining battery system continues to remain effective when all rapid discharge devices of the battery cells of a damaged battery module are activated. The electric vehicle thus continues to remain operational and can, for example, also be driven to a workshop for replacing a damaged battery module. In particular, damage to the battery cells in other battery modules is also effectively prevented by the balancing current. The damage caused to the battery system is therefore minimized. The method according to the invention is also effective after an erroneous triggering of a deformation sensor, which monitors, for example, the housing of the battery module. If the rapid discharge device of the battery cells of an intact battery module is also accidentally activated, damage to the battery cells in other battery modules is prevented. With the method according to the invention, if the isolation device fails and the battery branch involved cannot be shut down, damage to the battery cells can be avoided by the balancing current itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the present invention are further explained with reference to the drawings and the following description.

[0028] Figure 1 A schematic diagram showing a battery module having a plurality of battery cells;

[0029] Figure 2 A schematic diagram showing a battery system having multiple battery branches; and

[0030] Figure 3 Shown for running on Figure 2 Flowchart of a method for a battery system shown in FIG. DETAILED DESCRIPTION

[0031] In the following description of embodiments of the invention, identical or similar elements are denoted by the same reference numerals, wherein a repeated description of these elements is omitted in individual cases. The figures merely schematically illustrate the subject matter of the invention.

[0032] Figure 1The schematic diagram of a battery module 5 is shown with a plurality of, in the present case, ten, battery cells 2. The battery cells 2 are here electrically connected in series. Each battery cell 2 comprises an electrode unit 10, which each comprises an anode 11 and a cathode 12. The anode 11 of the electrode unit 10 is here connected to a negative terminal 15. The cathode 12 of the electrode unit 10 is connected to a positive terminal 16. For the series connection of the battery module 5, the negative terminal 15 of a battery cell 2 is respectively electrically connected to the positive terminal 16 of an adjacent battery cell 2.

[0033] Each battery cell 2 further comprises a rapid discharge device 20. The rapid discharge device 20 is electrically connected to the negative terminal 15 and to the positive terminal 16 of the battery cell 2. In the illustration shown here, the rapid discharge device 20 is switched off, i.e. in a passive state. This means that the negative terminal 15 and the positive terminal 16 of the battery cell 2 are not electrically connected to one another via the rapid discharge device 20.

[0034] The battery module 5 also comprises a module control device 50 for controlling the battery cells 2. The battery module 5 also comprises a deformation sensor 51, which in particular monitors the housing of the battery module 5. If the deformation sensor 51 detects a fault, such as a metal part penetrating into the housing or a deformation of the housing, the deformation sensor 51 causes the activation of all the rapid discharge devices 20 of the battery cells 2 of the battery module 5. The deformation sensor 51 can directly activate the rapid discharge device 20 or the deformation sensor 51 sends a signal to the module control device 50, which then activates the rapid discharge device 20.

[0035] After activation, the fast discharge device 20 is in an activated state in which it forms a short circuit between the negative terminal 15 and the positive terminal 16 of the battery cell 2. Then, a discharge current flows through the fast discharge device 20 and the battery cell 2 is thereby discharged. After activation of the fast discharge device 20 of the battery cell 2, the entire battery module 5 is short-circuited.

[0036] Figure 2 The schematic diagram shows a battery system 7 of an electric vehicle having a plurality of, in the present case ten, battery branches 6 . In the present case the battery branches 6 are electrically connected in parallel. The battery system 7 also comprises a battery control device 70 for controlling the battery branches 6 .

[0037] Each of the battery branches 6 of the battery system 7 comprises a plurality of, in the present case ten, battery modules 5 which are electrically connected in series with one another. In addition, each of the battery branches 6 comprises an isolating device 62 for shutting down the battery branch 6. The isolating devices 62 are here respectively electrically connected in series with the battery modules 5. If the isolating devices 62 are actuated, the electrical connection is interrupted and the battery branch 6 is shut down. The isolating devices 62 are, for example, electromechanical contactors or relays, pyrotechnic fuses or semiconductor switches, in particular in the form of metal oxide field effect transistors (MOSFETs).

[0038] The isolating device 62 of each battery branch 6 can be controlled by a battery control device 70 of the battery system 7. Furthermore, the isolating device 62 of each battery branch 6 can also be controlled by a module control device 50 of the battery module 5 in the respective battery branch 6.

[0039] Each of the battery branches 6 also comprises a current measuring device 61, which measures the current I flowing through the battery branch 6. The current measuring devices 61 of the battery branches 6, the module control devices 50 of the battery modules 5 and the battery control device 70 of the battery system 7 are connected to one another via the data line 30 and communicate with one another via the data line 30.

[0040] The current measuring device 61 measures the magnitude of the current I flowing in the battery branch 6 and the direction of the current I flowing in the battery branch 6. The current measuring device 61 sends the corresponding values ​​to the module control device 50 in the battery branch 6 and the battery control device 70 of the battery system 7 via the data line 30.

[0041] Figure 3 Shown for running Figure 2 Flow chart of a method for a battery system 7 is shown in FIG. 1 . At a starting point in time 100, a rapid discharge device 20 of a battery cell 2 in one of the battery modules 5 is activated. The battery module 5 concerned is then short-circuited. As a result, the voltage of the battery branch 6 in which the short-circuited battery module 5 is arranged is reduced. A discharge current now flows from each of the remaining intact battery branches 6, and a charging current now flows in the battery branch 6 having the short-circuited battery module 5.

[0042] In step 101, a control signal is then sent to the battery control device 70 and the module control device 50. The control signal is a wake-up signal, which is used to turn on the battery control device 70 and the module control device 50 when they are turned off.

[0043] In step 102 , the charging current of the battery cells 2 , in particular in the battery branch 6 in which the short-circuited battery module 5 is arranged, is controlled.

[0044] In step 103 , the voltage present at the battery branch 6 is measured and compared with a predefined threshold value, which lies, for example, between 65% and 70% of the nominal voltage of the battery branch 6 .

[0045] If the voltage present at the battery branch 6 exceeds a predefined threshold value, then in step 104 the direction of the current I flowing in the battery branch 6 is detected in each of the battery branches 6 .

[0046] If the current I is a charging current, a first time period is waited in step 105. If the current I is a discharging current, a second time period is waited in step 106. After the first time period has elapsed or after the second time period has elapsed, the magnitude of the current I flowing in the battery branch 6 is compared with a predefined limit current in step 107.

[0047] If the magnitude of the current I flowing in the battery branch 6 still exceeds a predefined limit value after the first time period or after the second time period, the isolating device 62 of the battery branch 6 is activated in a triggering step 120 .

[0048] If the magnitude of the current I flowing in the battery branch 6 no longer exceeds a predefined limit value after the first period of time or after the second period of time, the battery control device 70 and the module control device 50 can be switched off in an optional switching-off step 130 .

[0049] If the voltage present at the battery branch 6 measured in step 103 does not exceed a predetermined threshold value, the voltage at the battery branch 6 is further measured and monitored in step 108. In step 109, the voltage present at the battery branch 6 is compared with a predetermined threshold value.

[0050] If the voltage present at the battery branch 6 measured in step 108 exceeds a predefined threshold value, the isolating device 62 of the battery branch 6 is actuated in a control step 120 .

[0051] If the voltage present at the battery branch 6 measured in step 108 does not exceed a predefined threshold value, then in step 110 the magnitude of the current I flowing in the battery branch 6 is compared with a predefined limit value.

[0052] If the magnitude of the current I flowing in the battery branch 6 no longer exceeds a predefined limit value, the battery control device 70 and the module control device 50 can be switched off in an optional switching-off step 130 .

[0053] If the magnitude of the current I flowing in the battery branch 6 exceeds a predefined limit value, the voltage across the battery branch 6 is further measured and monitored in step 108 .

[0054] The invention is not limited to the embodiments described here and the aspects highlighted here. Rather, numerous variations are possible within the scope of the expert's purview within the scope of the claims.

Claims

1. A battery pack system (7) for an electric vehicle, the battery pack system comprising at least two battery pack branches (6) and a battery pack control device (70) for controlling the at least two battery pack branches (6), wherein Each of the battery branches (6) comprises at least one battery module (5), And among them The at least one battery module (5) comprises: at least one battery cell (2), the battery cell having a rapid discharge device (20); and a module control device (50) for controlling the at least one battery cell (2), It is characterized in that A current measuring device (61) is respectively arranged in each of the battery branches (6), and after activating at least one rapid discharge device (20), the current measuring device sends the magnitude of the current (I) flowing in the battery branch (6) and the direction of the current (I) flowing in the battery branch (6) to at least one control device (50, 70), and each of the battery branches (6) includes an isolation device (62) for shutting down the battery branch (6), and the isolation device can be controlled by at least one control device (50, 70). The at least one control device (50, 70) is a battery pack control device (70) and / or at least one module control device among the module control devices (50), The at least one control device (50, 70) is configured to control the isolation device (62) in each of the battery pack branches (6) when the current (I) is a charging current and flows at least during a first duration or when the current (I) is a discharging current and flows at least during a second duration, wherein the second duration is greater than the first duration.

2. The battery system (7) according to claim 1, characterized in that: Means are provided for measuring the voltage applied to the battery branches (6).

3. The battery system (7) according to any one of the preceding claims, characterized in that At least one battery module (5) comprises a deformation sensor (51) which monitors the battery module (5) and, in the event of a fault, causes the activation of all rapid discharge devices (20) of the battery cells (2) of the battery module (5).

4. The battery system (7) according to any one of the preceding claims, characterized in that The battery pack control device (70), the module control device (50) and the current measurer (61) communicate with each other via a data line (30).

5. A method for operating a battery system (7) according to any one of the preceding claims, wherein after activating at least one rapid discharge device (20), in each of the battery branches (6), a current meter (61) sends the magnitude of the current (I) flowing in the battery branch (6) and the direction of the current (I) flowing in the battery branch (6) to at least one control device (50, 70), and The isolating device (62) in each of the battery branches (6) is controlled by at least one control device (50, 70) when the current (I) is a charging current and flows at least during a first duration or when the current (I) is a discharging current and flows at least during a second duration, wherein the second duration is greater than the first duration, and The at least one control device (50, 70) is a battery pack control device (70) and / or at least one module control device among the module control devices (50).

6. The method according to claim 5, wherein The isolating device (62) is activated only when the amount of charge transferred by the current (I) flowing in the battery branch (6) exceeds a predetermined limit value.

7. The method according to any one of claims 5 to 6, wherein After activating at least one rapid discharge device (20), firstly the voltage applied to each of the battery branches (6) is measured, and wherein The isolating device (62) is only activated when the voltage present at the battery branch (6) exceeds a predefined limit value.

8. The method according to any one of claims 5 to 7, wherein After activating at least one fast discharge device (20), a control signal is sent to the battery pack control device (70) and / or the module control device (50).

9. The method according to claim 8, wherein The battery control device (70) and / or the module control device (50) are switched off when the magnitude of the current (I) flowing in the battery branch (6) does not exceed a predetermined limit value.

10. An electric vehicle comprising at least one battery system (7) according to any one of claims 1 to 4, wherein the battery system is operated using the method according to any one of claims 5 to 9.

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