Battery pack system and method of operating the battery pack system

Abstract

The invention relates to a battery system and a method for operating a battery system. The invention relates to a battery system (1), which has a battery management system (2) for operating the battery system (1) in a controlled manner and at least two battery cells (10). The invention also relates to a method for operating the battery system (1).

Description

Technical Field

[0001] The present invention relates to a battery system and also to a method for operating the battery system. Background Art

[0002] In principle, it is known from the prior art that a battery system is constructed from a plurality of connected battery cells. On the other hand, these battery cells may also have a plurality of battery sub-units, such as battery cells. It is also known to equip each battery cell with a monitoring device, for example, see US 2012 / 0242144 A1. Such a monitoring device can perform various and comprehensive checks and monitoring of the battery sub-units of a battery cell, for example, see DE 10 2013 206 612 A1. Summary of the invention

[0003] The subject matter of the invention is a battery system and a method for operating a battery system. Further features and details of the invention are apparent from the description and the drawings. Features and details described in connection with the battery system according to the invention naturally also apply in connection with the method according to the invention, and vice versa, respectively, so that reference can always be made to each other with regard to the disclosure of the individual inventive aspects.

[0004] According to a first aspect, the present invention relates to a battery system, which has: a battery management system for operating the battery system in a controlled manner and at least two battery cells, wherein the at least two battery cells respectively have at least two battery sub-units, and the at least two battery sub-units respectively have at least one battery cell, wherein the battery management system also has a battery control device and a main bus system, and the battery control device is connected to the battery cells in a data communication manner via the main bus system. The battery system according to the present invention is characterized in that the battery management system has a communication device and a secondary bus system in each battery cell, and has a monitoring device for each battery sub-unit, and the communication device has a main communication interface and a secondary communication interface, wherein in each battery cell, the monitoring device is connected to the secondary communication interface of the communication device in a data communication manner via the secondary bus system, and the main bus system is connected to the main bus communication interface of the communication device in a data communication manner.

[0005] The battery system according to the invention has a plurality of battery cells, which can be electrically connected in series and / or in parallel with each other. Each battery cell in turn has at least two battery subunits, which in turn each consist of at least one battery cell. On the other hand, in the case of battery subunits, it is also conceivable that the battery subunits are electrically connected in series or in parallel, and within the battery subunits, it is also conceivable that the battery cells are electrically connected in series and / or in parallel. The battery cells themselves can preferably be constructed as lithium-ion batteries. Therefore, the battery system according to the invention can have a plurality of battery cells, in particular a number that can be adapted to any requirements, which can be electrically connected in series and / or in parallel with each other through multiple levels, so as to meet the requirements for the battery system according to the invention with respect to the voltage to be provided and / or the current to be provided. For the superior monitoring and / or control and / or regulation of the individual battery cells of the battery subunits, the battery system according to the invention has a battery management system, which in particular has a battery control device and a main bus system as main components. The individual battery cells are connected to the battery control unit in a data communication manner via the main bus system, whereby in particular bidirectional data communication can be provided between the battery control unit and the individual battery cells. In this way, state data determined in the battery cells can be transmitted to the battery control unit and at the same time control and / or regulation commands of the battery control unit can be conveyed to the individual battery cells.

[0006] The battery system according to the invention is characterized in particular in that the battery management system also has a communication device in each battery cell. The communication device in turn has a main communication interface for data communication with a main bus system. The communication device also has a secondary communication interface, via which a secondary bus system, which is also part of the battery management system, can be connected to the communication device in data communication. The secondary bus system is in turn used for data communication with a monitoring device, which is present in each battery subunit as part of the battery management system. The monitoring device in the individual battery subunit can, for example, provide monitoring of the state data (e.g. voltage, current or the like) of the respective battery subunit. The initial analysis of the determined state data and / or control and / or regulation, also at the level of the respective battery subunit, can also be performed in such a monitoring device. The essence of the invention is that, as described above, a cascaded bus architecture is used for data communication within the battery system according to the invention. In this way, the individual monitoring devices of the battery subunits are not directly connected to the battery control device of the battery management system. The data collected by the monitoring device of the battery subunit is first transmitted to the communication device of the corresponding battery unit via the secondary bus system and the secondary communication interface. From there, the communication device acts on the main bus system via the main communication interface and forwards the data to the battery control device via the main bus system. Therefore, in particular, in the case of a battery system with multiple battery cells according to the present invention, advantages are obtained relative to a battery system with only one bus system. Through the cascaded bus architecture, it can also be provided that the entire function of monitoring, regulating and / or controlling the battery system can be provided by the only battery control device as a central control entity. Within the battery unit, the secondary bus system can be constructed smaller and especially faster, and the main bus system can be constructed particularly robustly because the main bus system does not have to extend to each battery subunit. At the same time, the signal quality within each battery unit can be improved by using the secondary bus system. In this way, cost-effective and at the same time powerful communication can be provided for the battery management system. In this way, digital bus communication for hundreds of battery subunits can be provided. In this way, a high scalability of the entire battery system can also be provided, in particular with regard to the number of battery cells and battery subunits which can be selected essentially freely and is limited only by the bus capacity and also, for example, a spatially separated distribution.

[0007] In the battery pack system according to the present invention, it can also be provided that: at least one of the main bus system and / or the secondary bus system is constructed as a serial chain bus and / or as a parallel bus, preferably as a differential two-wire bus. Such a serial chain bus (which is often also referred to as a daisy chain bus) can be provided as a particularly robust design of the bus system of the battery pack system according to the present invention. On the other hand, a parallel bus is a particularly simple way and method of a bus system, because the parallel bus provides a high failure safety in particular. In a differential two-wire bus, electrical data is additionally transmitted as a voltage difference between the two wires of the two-wire bus. In this way, even safer data transmission can be achieved in the corresponding bus system.

[0008] The battery system according to the present invention can also be constructed as follows: the battery management system has a branch management unit and the main bus system has at least two bus branches, wherein the battery control device is connected to the at least two bus branches in a data communication manner via the branch management unit. In this way, it can be provided that the main bus system also has two or more bus branches instead of only one bus branch. Through the branch management unit, the safe distribution of data packets can be guaranteed, which are received from each battery unit via the corresponding bus branch. Through the branch management unit, it can also be guaranteed that the control and / or regulation instructions output by the battery control device to each battery unit are safely distributed to the correct bus branch and are therefore safely transmitted to the correct battery unit.

[0009] In the battery system according to the invention, it can also be provided that the battery subunits each have at least one safety device for deactivating the corresponding battery subunit, preferably each have a safety device for deactivating each battery cell in the battery cells of the corresponding battery subunit, wherein the corresponding monitoring device of the battery subunit is connected to the corresponding safety device in a data communication manner for triggering the safety device. In this particularly preferred embodiment of the battery system according to the invention, at least one safety device is respectively arranged in the battery subunit. Preferably, such a safety device can be configured, for example, to operate a safety switch, such as an electric switch or an electrochemical switch. The safety switch can be configured, for example, as an irreversible safety switch, and can therefore only be switched once to interrupt or establish a circuit. Possible embodiments of such a safety switch include, for example, a power semiconductor switch, a relay, a fast discharge element (Fast-Discharge-Element), an antifuse element (Antifuse-Element) or the like. In particular, the safety switch can be integrated in a current path with a battery cell or a battery subunit, for example, in series or in parallel with the battery cell or with the battery subunit. The safety device can be constructed to disable the corresponding entire battery subunit on the one hand, but it is preferably constructed to disable individual battery cells of the battery subunit separately. Here, the safety device can preferably be constructed so that the safety device disables the corresponding battery subunit or battery cell in an emergency, such as overcharging or mechanical damage of the corresponding battery subunit or battery cell. By the deactivation, in most cases, greater damage to a single battery cell, a single battery subunit and especially also to the corresponding battery unit or the entire battery system can be prevented. In order to trigger the corresponding safety device quickly and safely accordingly, the safety device is connected to the monitoring device of the corresponding battery subunit so that the safety device can be triggered by the monitoring device. On the other hand, the connection in the form of data communication can be realized, for example, through a secondary bus system. Thus, a particularly safer and especially independent triggering of the corresponding safety device can be provided that is independent of the upper battery control device. In other words, each battery subunit can be constructed safely by itself.

[0010] In addition, in the battery system according to the present invention, it can also be provided that the monitoring device of the battery subunit is supplied with electrical energy through the corresponding battery cells of the battery subunit and / or through an external energy supply device, and / or the communication device of the battery unit is supplied with electrical energy through the corresponding battery cells of the battery unit and / or through an external energy supply device. Supplying electrical energy to the monitoring device and / or communication device of each battery unit through its own battery cells is a particularly simple way and method for operating these units. In particular, by avoiding an external energy source, a particularly compact design of the corresponding unit, i.e., a battery subunit or an entire battery unit, can be provided. The advantage of an external energy source is that the operation of the corresponding monitoring device and / or communication device of the battery unit can be guaranteed even in the case of a complete failure of the battery cells of the battery unit. Thus, according to the requirements of the battery system according to the present invention, two ways and methods of supplying electrical energy can be used, or only one of the two possibilities of supplying electrical energy can be used.

[0011] The battery system according to the invention can also be designed as follows: the communication device of the battery cell and / or the monitoring device of the battery subunit is designed to determine and / or evaluate data of at least one of the following state variables of the respective battery cell and / or battery subunit:

[0012] -Voltage,

[0013] - current,

[0014] -temperature,

[0015] - leakage,

[0016] -Mechanical action.

[0017] The list is not complete here, so that other state variables can also be determined or analyzed if technically reasonable and possible. In particular, the necessary sensor devices can also be present in the individual battery cells in order to be able to measure the corresponding state variables safely and accurately. In this way, comprehensive monitoring of battery cells or battery subunits can thus already be provided decentralized at the corresponding level.

[0018] The battery system according to the invention may also be designed as follows: the communication device of the battery unit and / or the monitoring device in the battery subunit is designed to provide at least one of the following functions:

[0019] -Balancing of battery cells;

[0020] - analysis and / or manipulation of safety devices;

[0021] - detecting undershooting and / or exceeding of limit values ​​by analyzing the determined status data;

[0022] - Provides communication with the battery pack control unit.

[0023] This list is also not ended, so that other functions can also be provided if technically reasonable and possible. In this way, by balancing regulation, for example, temporary fluctuations in the effective power of individual battery cells can be balanced in particular, so that the total effective power of the battery cell or battery subunit according to the present invention can be provided as constantly as possible. In the case of damage that has occurred or is about to occur, by analyzing and / or manipulating the safety device, in particular the entire battery cell or battery subunit or also individual battery cells can be disabled in order to prevent damage to other battery cells or the entire battery cell or battery subunit. On the other hand, by analyzing the determined state data to be below and / or exceeding the limit value, it is possible to identify the overall state of the battery cell or battery subunit, in particular whether the overall state is adjusted to within the predetermined limits. By providing communication with the battery control device, in particular via a bus system, all measures and functions performed or the determined state data can be forwarded. Therefore, in the battery control device, all state data can be collected and analyzed, and functions performed by monitoring devices in the battery cell or battery subunit can also be collected and analyzed.

[0024] In the battery pack system according to the present invention, it can also be provided that the battery pack management system has at least one other communication device, and the at least one other communication device has an additional control communication interface, wherein the battery pack control device is connected to the at least one other communication device in a data communication manner through the control communication interface, and the at least one other communication device is connected to the main bus system in a data communication manner through the main communication interface. In this way, it can be provided that the communication device that can be used in the battery pack unit and already has a main communication interface and a secondary communication interface is also equipped with a control communication interface. Therefore, the communication device can be used not only in each battery pack unit to provide communication between the main bus system and the secondary bus system, but also in the battery pack control device for communication between the battery pack control device and the main bus system. In the first case, the main communication interface and the secondary communication interface of the communication device are used, and in the second case, the control communication interface and the main communication interface of the communication device are used. In this way, it can be avoided that another independent device must be designed and purchased in order to provide a connection between the battery pack control device and the main bus system in a data communication manner. Therefore, overall, by using one communication device for two applications, the cost of manufacturing the battery pack system according to the present invention can be saved.

[0025] According to a second aspect of the invention, this object is achieved by a method for operating a battery system according to the first aspect of the invention. The method according to the invention is characterized in that, in order to detect overcharging of at least one battery cell of the battery subunit when the battery control device is inactive, a monitoring device of the battery subunit monitors the voltage of at least one battery cell of the battery subunit with a measuring interval of >50 ms, in particular >100 ms, preferably >1 s, wherein the safety device of the battery subunit is activated by the monitoring device when the measured voltage exceeds a limit voltage, preferably when the voltage measured in two measurements, in particular ten measurements, preferably 25 measurements exceeds the limit voltage.

[0026] The method according to the invention is configured to operate a battery system according to the first aspect of the invention, or the battery system according to the first aspect of the invention has at least the capability to implement the method according to the second aspect of the invention. Therefore, the same advantages can be provided by the method according to the second aspect of the invention, which have been described in detail with respect to the battery system according to the first aspect of the invention.

[0027] The method according to the invention is particularly provided for a charging process of individual battery cells of a battery cell or a battery subunit of a battery system, which charging process is carried out when a battery control device is inactive. In order to detect overcharging of at least one battery cell, a monitoring device present in a battery subunit of a battery system according to the first aspect of the invention measures the voltage of at least one battery cell of the battery subunit undergoing the charging process. These measurements are carried out in such a way that they are not carried out continuously, but at measurement intervals of more than 50 ms, in particular more than 100 ms, preferably more than 1 s. As a result, on the one hand, the energy consumption of these measurements can be limited, and on the other hand, the amount of accumulated data can also be limited, without reducing the safety during monitoring. At the same time, the measured voltage is analyzed, in particular with respect to exceeding a limit voltage. When the limit voltage is exceeded, a safety device of the battery subunit is activated by the monitoring device to prevent damage to the battery subunit, in particular at least one battery cell of the battery subunit, the exceeding of the limit voltage being particularly preferably detected repeatedly, for example in two measurements, in particular ten measurements, preferably 25 measurements. In particular, therefore, in summary, the method according to the invention can provide that overcharging protection is provided at the battery level without having to activate a higher-level battery control device and without transmitting large amounts of data via the main bus system, which would increase when, for example, all battery cells of a battery system according to the invention are charged simultaneously.

[0028] The method according to the invention can also be extended so that: when the battery control device is active, the monitoring of the voltage of at least one battery cell of the battery subunit by the monitoring device is interrupted and / or the limit voltage is set higher than the total limit voltage, which is used in the battery control device to detect overcharging of at least one battery cell of the battery subunit. When the battery control device is active, the battery control device mostly bears the monitoring of the voltage of at least one battery cell of the battery subunit. Therefore, in a first alternative of this embodiment of the method according to the invention, it is provided that the monitoring of the voltage by the monitoring device is interrupted. In this way, unnecessary monitoring processes and therefore unnecessary loads on the monitoring device can be avoided. In addition or alternatively, in a second alternative of this embodiment of the method according to the invention, it can be provided that the monitoring of the voltage by the monitoring device is continued, wherein, however, the limit voltage used for comparison with the measured voltage is set higher than the total limit voltage, which is used in the battery control device to detect overcharging of at least one battery cell of the battery subunit. In this way it can be ensured that overcharging is first detected by the battery control unit before the monitoring device of the individual battery cells detects overcharging. Competition between the two monitorings, namely the monitoring by the battery control unit on the one hand and the monitoring by the monitoring device on the other hand, can thus be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other advantages, features and details of the present invention are apparent from the following description, in which embodiments of the present invention are described in detail with reference to the accompanying drawings. The features mentioned in the claims and in the description may reflect the essence of the invention individually or in any combination.

[0030] in:

[0031] Figure 1 A battery pack system having a serial main bus system according to the present invention is shown;

[0032] Figure 2 The enlarged image shows Figure 1 A battery system according to the present invention;

[0033] Figure 3 A battery pack system with a parallel main bus system according to the present invention is shown;

[0034] Figure 4 The enlarged image shows Figure 3 A battery system according to the present invention.

[0035] In the figures, identical technical features are respectively provided with the same reference symbols. DETAILED DESCRIPTION

[0036] exist Figure 1 and Figure 2 1 shows a battery system 1 according to the present invention, the main bus system 5 of which is designed as a serial data bus. Figure 1 In the detailed view shown in Figure 2 The two drawings are described together below.

[0037] The battery system 1 according to the invention has in particular a battery management system 2 which is used to monitor, control and / or regulate the battery system 1 according to the invention. The battery management system comprises in particular a plurality of components which are distributed throughout the battery system. Figure 1 In the figure, the following units are characterized as part of the battery management system 2, which basically include: a control device 3, a branch management unit 4 and a communication device 20 as well as a monitoring device 14 for each battery subunit 12 and a communication device 20 for each battery cell 10, without excluding other possibilities. In addition, other components can also be assigned to the battery management system 2, in particular devices that are necessary for communication between the components. Here, the battery management system 2 has in particular a battery control device 3, which is connected to the individual battery cells 10 in a data communication manner via a main bus system 5. In the illustrated embodiment of the battery system 1 according to the present invention, the main bus system 5 has a plurality of bus branches 6, wherein the branch management unit 4 ensures that the individual data and / or instructions are distributed to the individual bus branches 6. Each battery cell 10 (one of which is in Figure 1) each have a communication device 20, by means of which communication with the main bus 5 and thereby with the battery control device 3 of the battery management system 2 can be ensured. For this purpose, the communication device 20 has a main communication interface 21. Data communication within the individual battery cells 10 is ensured by means of a secondary communication interface 22. In particular, within each battery cell 10, a secondary bus system 11 is provided, which is also constructed as a serial bus in this embodiment, and is connected to the communication device 20 in a data communication manner via the secondary communication interface 22, and also connects the individual battery subunits 12 of the battery cell 10 to the communication device 20 in a data communication manner. Each battery subunit 12 in turn has a monitoring device 14 in order to monitor at least one battery cell 13 of the battery subunit 12. In each battery subunit 12, a safety device 15 is assigned to each battery cell 13 in order to deactivate the battery cell 13 in the event of a damage to the battery cell 13, in particular to deactivate the battery cell 13 automatically, in order to prevent damage to the battery subunit 12, the battery cell 10 or the entire battery system 1. By means of sensor devices, such as voltage sensors 16, current sensors 17 and / or crash sensors 18, state variables in the battery cell 10 or the battery subunit 12 can be collected, which can be evaluated by means of the communication device 20 and / or the individual monitoring units 14. It is also conceivable that the safety device 15 is activated by the monitoring device 14 based on these data. In this way, the communication device 20 and / or the monitoring device 14 of each battery subunit 12 can provide a variety of functions, such as balancing control of the individual battery cells 13 of the battery unit 10, the already mentioned analysis and / or control of the safety device 15, identification of undershooting and / or overshooting of limit values ​​by analyzing determined status data, and / or providing communication with the battery control device 3 via the main bus system 5.

[0038] As shown, the communication device 20 may also have a further interface, which is configured as a control communication interface 23. When the communication device 20 in the battery cell 10 is used, the control communication interface 23 is not functional. However, due to the presence of the control communication interface 23, the communication device 20 can also be used in the body of the battery management system 2, in particular for providing communication between the battery control device 3 and the main bus system 5. For this purpose, the control communication interface 23 establishes a connection in the form of data communication between the battery control device 3 and the communication device 20, which in turn is connected to the main bus system 5 via its main communication interface 21. In this way, the same communication device 20 can be used not only in the battery cell 10 itself but also in the central computing unit of the battery system 1 or the battery management system 2. As a result, cost savings can be achieved when manufacturing the battery system 1 according to the invention.

[0039] Furthermore, provision can also be made for the monitoring device 14 to continue monitoring the voltage of the individual battery cells 13 of the battery subunit 12 even when the battery control device 3 is deactivated. This has the advantage, in particular, that during a charging process of the battery system 1, for example, in which the battery control device 3 can be deactivated for test purposes, overcharging of the individual battery cells 13 can still be detected, for example by comparing the measured voltage with a limit value. Since the charging process usually takes place slowly, these monitorings can be carried out at relatively long time intervals, for example measuring intervals of more than 50 ms, in particular more than 100 ms, preferably more than 1 s, without thereby reducing the safety of the entire battery system 1. When an exceeding of the limit value by the measured voltage is detected, in particular when the exceeding is detected a plurality of times, for example in two measurements, in particular in ten measurements, preferably in 25 measurements, the monitoring device 14 can trigger the safety device 15. As a result, damage to individual battery cells 13, battery subunits 12, battery cells 10 or the entire battery system 1 can be avoided, up to the point of destruction of individual battery cells 13, battery subunits 12, battery cells 10 or the entire battery system 1. When the battery control device 3 is later reactivated, the monitoring of the voltage of the battery cell 13 by the monitoring device 14 described above can be interrupted and / or continued with a higher limit value, in particular a limit value that is higher than the overall limit voltage used in the battery control device 3 to detect overcharging of at least one battery cell 13 of the battery subunit 12. In this way, it can be ensured that the two monitorings do not interfere with each other.

[0040] exist Figure 2 It is shown in Figure 1 1 , wherein it becomes clear from this illustration that data communication within the battery system 1 is provided by a cascaded bus architecture. Starting from a battery control device 3, a branch management unit 4 controls a plurality of bus branches 6 of a main bus system 5, which in turn branch off in branches of a secondary bus 11 for each battery cell 1. In this way, a particularly high flexibility can be provided, in particular with regard to the number and spatial layout of individual battery cells 10, battery subunits 12 and in particular battery cells 13.

[0041] exist Figure 3 and 4 Another embodiment of the battery system 1 according to the present invention is shown in FIG. Figure 1 and2 as well as Figure 3 and 4 The only difference between the two embodiments shown in FIG. 1 is the bus architecture used for the primary bus system 5 and the secondary bus system 11. Thus, in Figure 1 and 2 In, as described, a serial bus architecture is used. On the other hand, in Figure 3 and 4 In the embodiment, both the main bus system 5 and the secondary bus system 11 are designed as parallel buses. This bus provides a particularly robust bus architecture. For all further details, see the Figure 1 and 2 Description.

Claims

1. A battery system (1), comprising: a battery management system (2) for operating the battery system (1) in a controlled manner and at least two battery cells (10), wherein the at least two battery cells (10) each have at least two battery sub-units (12), and the at least two battery sub-units each have at least one battery cell (13), wherein the battery management system (2) further comprises a battery control device (3) and a main bus system (5), wherein the battery control device (3) is connected to the battery cell (10) via the main bus system in a data communication manner, It is characterized in that The battery pack management system (2) has a communication device (20) and a secondary bus system (11) in each battery pack unit (10), and has a monitoring device (14) for each battery pack subunit (12), wherein the communication device has a main communication interface (21) and a secondary communication interface (22), wherein in each battery pack unit (10), the monitoring device (14) is connected to the secondary communication interface (22) of the communication device (20) via the secondary bus system (11) in a data communication manner, and the main bus system (5) is connected to the main communication interface (21) of the communication device (20) in a data communication manner.

2. The battery system (1) according to claim 1, It is characterized in that The primary bus system (5) and / or at least one of the secondary bus systems (11) is designed as a serial chain bus and / or as a parallel bus.

3. The battery system (1) according to claim 2, It is characterized in that The primary bus system (5) and / or at least one of the secondary bus systems (11) is designed as a differential two-wire bus.

4. The battery system (1) according to any one of claims 1 to 3, It is characterized in that The battery pack management system (2) has a branch management unit (4) and the main bus system (5) has at least two bus branches (6), wherein the battery pack control device (3) is connected to the at least two bus branches via the branch management unit (4) in a data communication manner.

5. The battery system (1) according to any one of claims 1 to 3, It is characterized in that The battery subunits (12) each have at least one safety device (15) for deactivating the corresponding battery subunit (12), wherein the corresponding monitoring device (14) of the battery subunit (12) is connected to the corresponding safety device (15) in a data communication manner for triggering the safety device (15).

6. The battery system (1) according to claim 5, It is characterized in that The safety device (15) is a safety device for deactivating each of the battery cells (13) of the corresponding battery subunit (12).

7. The battery system (1) according to any one of claims 1 to 3, It is characterized in that The monitoring device (14) of the battery subunit (12) is supplied with electrical energy via the corresponding battery cells (13) of the battery subunit (12) and / or via an external energy supply device, And / or the communication device (20) of the battery unit (10) is supplied with electrical energy via the corresponding battery cells (13) of the battery unit (10) and / or via an external energy supply device.

8. The battery system (1) according to any one of claims 1 to 3, It is characterized in that A communication device (20) of a battery cell (10) and / or a monitoring device (14) of a battery subunit (12) is designed to determine and / or evaluate data of at least one of the following state variables of the respective battery cell (10) and / or battery subunit (12): -Voltage, - current, -temperature, - leakage, -Mechanical action.

9. The battery system (1) according to any one of claims 1 to 3, It is characterized in that The communication device (20) of the battery unit (10) and / or the monitoring device (14) of the battery subunit (12) is designed to provide at least one of the following functions: - Balancing and regulating the battery cells (13); - analysis and / or control of the safety device (15); - detecting undershooting and / or exceeding of limit values ​​by analyzing the determined status data; - Providing communication with the battery pack control device (3).

10. The battery system (1) according to any one of claims 1 to 3, It is characterized in that The battery pack management system (2) has at least one other communication device (20), and the at least one other communication device has an additional control communication interface (23), wherein the battery pack control device (3) is connected to the at least one other communication device (20) in a data communication manner via the control communication interface (23), and the at least one other communication device (20) is connected to the main bus system (5) in a data communication manner via the main communication interface (21).

11. A method for operating a battery system (1) according to one of claims 1 to 10, It is characterized in that In order to identify overcharging of at least one battery cell (13) of a battery subunit (12) when a battery control device (3) is inactive, a monitoring device (14) of the battery subunit (12) monitors the voltage of at least one battery cell (13) of the battery subunit (12) at a measurement interval greater than 50 ms, wherein when the measured voltage exceeds a limit voltage, a safety device (15) of the battery subunit (12) is activated by the monitoring device (14).

12. The method according to claim 11, It is characterized in that The monitoring device (14) of the battery subunit (12) monitors the voltage of at least one battery cell (13) of the battery subunit (12) at a measuring interval of more than 100 ms.

13. The method according to claim 11, It is characterized in that The monitoring device (14) of the battery subunit (12) monitors the voltage of at least one battery cell (13) of the battery subunit (12) at a measuring interval of greater than 1 s.

14. The method according to claim 11, It is characterized in that When the voltage measured in both measurements exceeds the limit voltage, the safety device (15) of the battery subunit (12) is activated by the monitoring device (14).

15. The method according to claim 11, It is characterized in that When the voltage measured in ten measurements exceeds the limit voltage, the safety device (15) of the battery subunit (12) is activated by the monitoring device (14).

16. The method according to claim 11, It is characterized in that When the voltage measured in 25 measurements exceeds the limit voltage, the safety device (15) of the battery subunit (12) is activated by the monitoring device (14).

17. The method according to any one of claims 11 to 16, It is characterized in that When the battery control device (3) is active, the monitoring device (14) of the voltage of at least one battery cell (13) of the battery subunit (12) is interrupted, And / or the limit voltage is set higher than an overall limit voltage which is used in the battery control device (3) to detect overcharging of at least one battery cell (13) of the battery subunit (12).

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