# Patent

## Title
Battery sensor data transmission unit and a method for transmitting battery sensor data

## Abstract

A battery sensor data transmission unit is described as including a connection state ascertainment unit for ascertaining a series connection state in which a battery cell is connected in series to one other battery cell with the aid of a power transmission line and/or for determining a bypassing state in which at least one pole of the battery cell is decoupled from at least one other battery cell. Furthermore, the battery sensor data transmission unit includes a data transmission unit designed for outputting a sensor signal, which represents a physical variable in or at the battery cell, in the series connection state to an evaluation device using the power transmission line and/or outputting the sensor signal in the bypassing state to the evaluation device using a battery housing wall as the transmission medium.

## Background
FIELD OF THE INVENTION
The present invention relates to a battery sensor data transmission unit, a method for transmitting battery sensor data, as well as an appropriate computer program product.
BACKGROUND INFORMATION
In particular in automotive engineering, batteries are increasingly being used to make it possible to operate an electric motor as a means of moving the vehicles. In this context, monitoring the state of the batteries is increasingly important in order to communicate to a user of the vehicle a possibly upcoming problem with the drive unit or a possible battery failure at an early state. For this purpose it was provided to carry out a detection and transmission of sensor signals over dedicated data lines, for example, the CAN Bus. Relevant data about a state of the battery are detected by one or multiple battery sensors and transmitted to a control unit or evaluation device.
German Published Patent Application No. 10 2009 036 086 describes a monitoring electronic system for a battery having a plurality of cells, the monitoring electronic system having a plurality of cell monitoring circuits which are attached to a flexible circuit board. In particular, the monitoring electronic system may be set up in such a way that it includes a cell monitoring circuit for each cell pole of the battery. In particular, the provision of preferably many integrally bonded connections between an electronic system and the flexible circuit board and/or the flexible circuit board including the cells and optional temperature sensors may result in a longer service life with lower error rates.
SUMMARY
Against this background, the present invention relates to a battery sensor data transmission unit, a method for transmitting battery sensor data, as well as an appropriate computer program product according to the main claims. Advantageous embodiments are derived from the subclaims and the following description.
The present invention provides a battery sensor data transmission unit including the following features:

    
    
        a connection state ascertainment unit for ascertaining a series connection state in which one battery cell is connected in series to one other battery cell with the aid of a power transmission line and/or for determining a bypassing state in which at least one pole of the battery cell is decoupled from at least one other battery cell; and
        a data transmission unit designed for outputting a sensor signal, which represents a physical variable in or at the battery cell, in the series connection state to an evaluation device using the power transmission line and/or outputting the sensor signal in the bypassing state to the evaluation device using a battery housing wall as the transmission medium.
    
    


(Battery sensor data transmission) unit may be understood in the present case as a device or an electric device which processes sensor signals and as a function of those sensor signals outputs control and/or data signals. The device may include an interface which may be designed as hardware and/or software. In a hardware design, the interfaces may, for example, be part of a so-called system ASIC, which includes various functions of the device. However, it is also possible that the interfaces are separate integrated circuits or are made, at least in part, of discrete components. In a software design, the interfaces may be software modules, which, for example, are present on a microcontroller together with other software modules.
Furthermore, the present invention also provides a method for the transmission of battery sensor data, the method including the following step:

    
    
        ascertaining a series connection state in which one battery cell is connected in series to at least one other battery cell with the aid of a power transmission line and/or ascertaining a bypassing state in which the pole of one battery cell is decoupled from at least one other battery cell; and
        outputting a sensor signal, which represents a physical variable in or at the battery cell, in the series connection state to an evaluation device using the power transmission line and/or outputting the sensor signal in the bypassing state to the evaluation device using a battery housing wall as the transmission medium.
    
    


Also advantageous is a computer program product having program code, which may be stored on a machine-readable medium, such as a semiconductor memory, a hard disk memory, or an optical memory, and is used for carrying out the method according to one of the previously described specific embodiments, if the program is executed on a unit, a computer, or a device.
A connection state ascertainment unit may be understood as a device or a module which is designed to determine a series connection state and/or a bypassing state in an electrical coupling (or decoupling) of multiple battery cells. A power transmission line may be understood to be an electrical line via which in addition to a current flow for the transmission of electrical energy, a data signal may be modulated. A series connection state may be understood to be a state in which a pole of one battery cell is connected in series to at least one pole of one other battery cell in an electrically conductive way as a power transmission line. In the series connection state, the battery cell may thus be understood to be connected in series to at least one other battery cell so that at two end tapping terminals of such a series connection the voltages at the respective poles of the two battery cells connected in series are summed up. A bypassing state may be understood to be a state in which the pole of the battery cell is not connected to another pole of one other battery cell, i.e., the pole of the battery cell is decoupled from another pole of one other battery cell. If, on the other hand, multiple other battery cells are connected in series without the battery cell in question being included in the series connection, the connection state ascertainment unit determines the transmission state in which the battery cell in question is connected electrically only in a side branch of the power transmission line. In such a transmission state, the voltage between the two poles of the battery cell in question is not usable to increase the voltage between the end tapping terminals. A data transmission unit may be understood as a device or a module used to process a sensor signal and to transmit that signal via a predetermined transmission path to an evaluation device. This predetermined transmission path may be chosen as a function of the particular series connection state or the bypassing state of the data transmission unit. A sensor signal may be understood to be a signal, which represents a physical variable, for example, a pressure or a temperature in or at the respective battery cell. In the series connection state, the sensor signal may be transmitted directly via the power transmission line. In this case, the sensor signal may be transmitted to the evaluation device using a powerline transmission method without using an additional data line. In the bypassing state, in which at least one pole of the battery cell in question is not integrated into and connected to the power transmission line (i.e., in which the pole of the battery cell is decoupled from another pole of one other battery cell) the sensor signal may be transmitted to the evaluation device using the battery housing wall. In this case, this battery housing wall may be used as an element in order to establish an electrical line to the evaluation device through the side branch in which the battery cell in question is electrically located in the transmission state.
The present invention is based on the finding that, when the individual battery cells are connected differently in order to provide different voltage levels, data may be transmitted via the same line which is also used by the individual battery cells to transfer electrical energy. Such an approach has the advantage that a separate data transmission line is not necessary, whereby manufacturing costs for a battery sensor data transmission unit may be reduced and, at the same time, a lower error rate through a smaller number of components may be ensured. If, however, a battery cell is decoupled from this series connection, it would no longer be possible to transmit the sensor data representing a physical variable of this specific decoupled battery to the evaluation device. In such a case, the battery cell in question, which is partly decoupled from the power transmission line, may be connected to a “separate” circuit, which is closed via a battery housing wall, thus enabling in this way the transmission of the sensor signal in the transmission state to the evaluation device. In this simple and reliable way, a continuous and largely interruption-free evaluation of one or multiple physical variable(s) contained in one or multiple sensor signals is made possible.
According to one advantageous specific embodiment of the present invention the connection state ascertainment unit may be designed to determine the series connection state when poles of at least three battery cells are connected in series using the power transmission line. Such a specific embodiment of the present invention has the advantage that a power transmission line may be set up, via which different voltage levels are achievable at the tapping terminals of the power transmission line, for example, by multiplexing different combinations of a connection of the individual battery cells. In such a flexibly connectable power transmission line there is a particularly high need for a reliable and stable transmission of data signals via this power transmission line even when individual battery cells are decoupled from the series connection of this power transmission line.
According to another specific embodiment of the present invention, the connection state ascertainment unit may also be designed to determine the series connection state or the bypassing state by evaluating the position of a switch which is designed to carry out an electrical coupling of the pole of the battery cell to the power transmission line. Such a switch may, for example, be a multiplexer, which connects the poles in question of individual battery cells in different ways. Such a specific embodiment of the present invention has the advantage that predefined switch positions may be evaluated and allows a conclusion to be drawn as to whether a particular battery cell is presently integrated into a series connection of a power transmission line. In this way, the bypassing state or the series connection state of a certain battery cell may be ascertained very quickly and in a technical manner.
According to one specific embodiment of the present invention the connection state ascertainment unit may be designed to ascertain the series connection state or the bypassing state using a measuring result in relation to a current flow, energy flow and/or power flow via the power supply line. Such a specific embodiment of the present invention has the advantage of a technically simple detection of whether the battery cell, which is coupled to the battery sensor data transmission unit, is connected in series to other battery cells so that power is transmitted via the power supply line.
In one specific embodiment of the battery sensor data transmission unit according to the present invention, in which the switch is activated using a control signal, in particular using a pulse-width modulated control signal, the data transmission unit may be advantageously designed to synchronize the ascertainment or output of the sensor signal with the control signal. Such a specific embodiment of the present invention has the advantage that by evaluating the previously known pulse-width modulated control signal, a conclusion may be drawn regarding the instantaneously present series connection state or the bypassing state for a battery cell in question without requiring a measurement or a determination of the instantaneous connection state. By synchronizing the output or the ascertainment of the sensor signal with the control signal, a fast and virtually interruption-free transmission of the sensor signal to the evaluation device is possible.
In a particularly advantageous specific embodiment of the present invention, a data transmission unit designed for outputting the sensor signal in the series connection state to an evaluation device using the power transmission line and/or outputting the sensor signal in the bypassing state to the evaluation device using a battery housing wall as the transmission medium. Such a specific embodiment of the present invention has the advantage that it is ensured that the battery housing wall is used as the transmission medium for a sensor signal from a specific battery cell to the evaluation device only in the bypassing state. This enables a simpler evaluation or a simpler reception of the sensor signals at the evaluation device, since the evaluation device needs to expect at predetermined points in time sensor signal 168 of a particular battery cell via a single transmission path only. At the same time, it is ensured that the power transmission line is preferably frequently used to transmit the sensor signal, in this way minimizing interferences.
To ensure that data signals are unambiguously assigned in the evaluation device, according to one specific embodiment of the present invention the data transmission unit may be designed to encode sensor signal 168 in a sensor signal package unambiguously assignable to the battery cell. Such a specific embodiment of the present invention has the advantage that multiple sensor signals representing physical variables from different battery cells may be unambiguously assigned to the battery cells in question in the evaluation device.
Furthermore, it is advantageous when according to another specific embodiment of the present invention a battery unit is provided having the following features:

    
    
        a battery cell assembly which includes at least two battery cells, the battery cells being connectable in series with the aid of a power transmission line;
        at least one sensor which provides a measured value, the measured value representing a physical variable in or at one of the battery cells; and
        at least one battery sensor data transmission unit according to a previously described variant.
    
    


Such a specific embodiment of the present invention has the advantage that the individual components may be optimally coordinated so that a preferably interference-free transmission of sensor signal 168 to an evaluation unit or an evaluation device may be carried out.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of a battery unit in which one exemplary embodiment of the present invention is used.
FIG. 2 shows diagrams showing a synchronization of a switch signal for a switch having one output of the sensor signal.
FIG. 3 shows a flow chart of one exemplary embodiment of the present invention as a method.



DETAILED DESCRIPTION
In the following description of preferred exemplary embodiments of the present invention the same or similar reference numerals are used for similar elements in the different figures, a repeated description of those elements being omitted.
FIG. 1 shows a block diagram of a vehicle 100 including a battery unit 110 for providing electrical power to a power electronics unit 115, an electric motor 120 being operatable by the power supplied by battery unit 110. In battery unit 110, multiple battery cells 130 are situated, which are denoted by reference numerals 130a, 130b and 130c for better differentiation. In the exemplary embodiment of FIG. 1, all battery cells 130 are configured identically, which is not always absolutely necessary. Poles 135 of battery cell 130 are connected in series to each other in power transmission line 140 so that, in the connection state shown in FIG. 1 with a solid line, voltage is available to battery unit 110 at tapping terminals 145, which in sum equals the voltages between poles 135 of each of the three shown battery cells 130. In order to supply alternating voltage or at least a varying voltage level at terminals 145, the connection state of individual battery cells 130 may be controlled with the aid of connection control unit 150. In a very simple case shown in FIG. 1 intended to show only the operating mode in principle of such a change of the connection state, a switch 160 may be activated by connection control unit 150 with the aid of a control signal 155 in such a way that this switch is brought from a position shown with a solid line in FIG. 1 to a position shown with a broken line in FIG. 1, whereby middle battery cell 130b shown in FIG. 1 is decoupled from the series connection of power transmission line 140. If, however, poles 135 of middle battery cell 130b and right battery cell 130c (for example, for reasons of a preferably error-resistant circuit configuration) middle battery cell 130b is connected as a side branch of power supply line 140 which is not relevant for the supply of the voltage level at terminals 145. In this state, in which the middle battery cell 130b is decoupled from the series connection, this battery cell is in a state which in the following description is referred to as bypassing state. If, however, switch 160 is in the position shown with a solid line in FIG. 1, the middle battery cell 130b shown in FIG. 1 is in a state which in the following description is referred to as series connection state.
All battery cells 130 shown in FIG. 1 each include one battery sensor data transmission unit 165. Battery sensor data transmission unit 165 includes one connection state ascertainment unit 166 and one data transmission unit 167 coupled to connection state ascertainment unit 166. The circuit state ascertainment unit 166 is designed to ascertain a connection state of battery cell 130 in question (for example, the series connection state or bypassing state), for example by measuring the current flowing over the poles of battery cell 130 or the energy/power flowing over same. Data transmission unit 167 is designed to convert a physical variable detected by a sensor 162 into a sensor signal 168 and to transmit this sensor signal to an evaluation device 170. The physical variable detected by sensor 162 in question may, for example, be a pressure or a temperature in or at battery cells 130a, 130b or 130c in question. In evaluation device 170, the state of the individual battery cells 130 may be monitored and, when a deviating physical variable is detected in or at one of battery cells 130, a warning or a handling recommendation may be output to a user of battery unit 110.
In the series connection state, battery sensor data transmission unit 165 may modulate sensor signal 168 of battery cells 130 in question as a powerline signal transmission in addition to the energy flowing in power supply line 140 so that evaluation device 170 is able to filter out and evaluate the sensor signals of power supply line 140. If, however, middle battery cell 130b shown in FIG. 1 is switched to the transmission state by switching switch 160 in order to provide a changing voltage level at terminals 145 with technically simple means, there is no longer a closed circuit between battery sensor data transmission unit 165, middle battery cell 130b and evaluation device 170. A sensor signal including a physical variable pertaining to middle battery cell 130b could then no longer be transmitted to evaluation device 170.
In order to nonetheless ensure a transmission of the sensor signal from battery sensor data transmission unit 165 of middle battery cell 130b, at a point in time when the battery cell in question is decoupled from power supply line 140 or when it is at least no longer connected in series to other battery cells 130, battery sensor data transmission unit 165 of middle battery cell 130b may, for example, close a high-frequency electrical circuit with evaluation device 170. This may, for example, be achieved by establishing a connection which is capable of transmitting data under certain circumstances (for example, as a capacitive coupling) to evaluation device 170 via wall 175 of middle battery cell 130b and battery unit housing wall 180, evaluation device 170 also being connected to battery unit housing wall 180 via a connection which is also capable of transmitting data under certain circumstances (for example, also as a capacitive coupling). In this case, the transmission of the sensor signal to battery cell wall 175 or to battery unit housing wall 180 is shown in FIG. 1 as a broken feed-in of sensor signal 168 to battery cell wall 175. Now, even without a current path between battery sensor data transmission unit 165 and evaluation device 170 there is the option of transmitting sensor signal 168 from middle battery cell 130b to evaluation device 170, since a path is now established, for example, via the capacitive coupling between battery cell wall 175 and battery housing wall 180, as well as between the capacitive coupling between the battery housing wall and evaluation device 170, at least for high-frequency signals. Alternatively to or in addition to the transmission of sensor signal 168 via power supply line 140, sensor signal 168 may also be completely transmitted from respective battery cell 130b using wall 180 of battery unit 110. A wall of battery cell 130 and/or of battery unit 110 may be understood to be an exterior wall which is different from a pole, this pole being intended specifically for electrical contacting of battery cell 130 and/or of battery unit 110. In particular in a case in which many or all battery cells 130 of battery unit 110 are connected in a fixed manner, this means statically, and not separably during operation, a transmission of the sensor signals from individual battery cells 130 or corresponding battery sensor transmission units 165 may be achieved very easily in such a way. In this case, it could, on the one hand, be ensured that each battery sensor data transmission unit 165 is capable of transmitting a corresponding sensor signal 168 to the evaluation unit or evaluation device 170, and, at the same time, the determination of the connection state of the battery cell in question in the series connection state or the bypassing state may be avoided. On the other hand, such a transmission of information via a housing wall 180 of battery unit 110 may possibly be more susceptible to interferences than the transmission of information via power supply line 140. It is also conceivable, for example, that a hybrid form of data transmission takes place using the two methods mentioned above, for example, in that state information about the general operational readiness of individual battery sensor data transmission unit 165 via a wall 180 of the battery unit 110 is transmitted to evaluation device 170, whereas the sensor signals, which each represent a physical variable within battery cell 130 in question, are transmitted via power supply line 140. In this case, for example, the information transmitted via power supply line 140 could be reduced, whereas data, which do not require an update rate this high, are transmitted to evaluation device 170 via an alternative transmission path, which is wall 180 of battery unit 110.
In order to switch particularly quickly and effectively between the transmission of the sensor signal from middle battery cell 130b to the evaluation device, the output of the sensor signal of middle battery cell 130b may be synchronized on the one hand to the power supply line 140 and on the other hand to battery cell wall 175. For this purpose, the battery sensor data transmission unit may receive a signal from connection control unit 150 representing a switchover of switch 160 so that battery sensor data transmission unit 165 may detect very early and without, for example, measuring a flow of power via power supply line 140, that it was switched to the bypassing state. In this way, it may be ensured that the sensor signal is transmitted to evaluation device 170 nearly interruption-free, or that the data transmission is at least only briefly interrupted.
FIG. 2 shows in the upper partial diagram a progression of positions 1 (in FIG. 1 shown with a solid line) and 2 (in FIG. 1 shown with a broken line) of switch 160 as it is activated by connection control unit 150. The middle diagram shows a change over time between series connection X and bypassing Y of middle battery cell 130b. Here it is apparent that a very simple and stable transmission of the sensor signal from middle battery cell 130b to evaluation device 170 may be ensured by synchronizing the position of switch 160 and the switch to a particular path for the transmission of the sensor signal required by the connection state of middle battery 130b according to the lower partial diagram of FIG. 2 (x stands for the transmission of the sensor signal via power supply line 140, y stands for the transmission of the sensor signal via the ground connection.)
In FIG. 1, to better illustrate the basics of the approach presented here, the explanation of the basic idea of an exemplary embodiment of the present invention has been limited to the bypassing of only one battery cell 130. The connection or bypassing option shown in FIG. 1 may, of course, also be extended to any desired number of individual battery cells 130 or extended to bypassing multiple battery cells 130 at the same time, the concept presented above being adjustable easily to the individual case used. Bypassing states that differ in length of time may also be specified for individual battery cells 130 in order to obtain the desired voltage at terminals 145. For this purpose, switch or switches 160 of connection control unit 150 may (each) be activated by a pulse-width-modulated signal so that the desired sequence of series connection states and bypassing states for the individual battery cells may be implemented.
FIG. 3 shows a flow chart of one exemplary embodiment of the present invention as method 300 for the transmission of battery sensor data. The method includes a step of determining 310 a series connection state in which one pole of a battery cell is connected in series to one pole of at least one other battery cell with the aid of a power transmission line and/or determining a bypassing state in which the pole of the battery cell is not connected in series to the pole of the at least one other battery cell, i.e., in which a pole of the battery cell is decoupled from at least one pole of one other battery cell. Method 300 furthermore includes a step of outputting 320 a sensor signal, which represents a physical variable in or at the battery cell, in the series connection state to an evaluation device, using the power transmission line, and/or outputting the sensor signal in the bypassing state to the evaluation device by using a battery housing wall as the transmission medium.
In summary, it should be noted that for the implementation of the present invention one specific embodiment of a battery may be used, in which a change in the battery voltage caused by an interconnection of different battery cells may be enabled, it being possible in the basic state that all battery cells 130, for example, are connected in series. In order to generate an alternating voltage at the output of battery 110, modules, i.e., battery cells 130 or groups of those battery cells (logic and circuitry-wise grouping of multiple cells within the battery), are bypassed in this series connection. In this way, the output voltage of battery 110 may be varied as a sum of the non-bypassed modules.
One aspect of the approach presented here includes enabling the communication on the part of a sensor system 165, 162 within a battery having a variable output voltage 110, while individual battery cells are decoupled or bypassed from power supply line 140 due to the operating mode of the battery. In bypassed module 130b at least one of its terminals 135 is decoupled by a power switch 160. At the same time, terminals 135 are bypassed on the battery level in order to maintain the series connection of the remaining modules 130a and 130c. In this way, module 130b forms a side-branch with a dead end in power supply line 140 and a powerline communication is no longer possible.
The previously presented aspect in particular intends to the limitation of a communication via powerline to the phases in which the data transmitting cell 130 does not depend on the rest of power supply line 140. This may take place by synchronizing the communication with the pulse-width modulated frequency of the battery having a variable output voltage. Such an approach has several advantages, for example, the option of enabling a communication despite a temporarily interrupted transmission path. A powerline communication within a battery having a variable output voltage is also enabled without any additional switching effort. Such an approach may generally be used for all such batteries.
Another aspect of the present invention according to one exemplary embodiment enables the use of the battery (cell) housing in order to restore the transmission path from the side-branch to the evaluation device. A transmission path requires a DC circuit or, at least, a high-frequency closed circuit. This is not the case when side-branch 130b is decoupled; this side-branch may, however, be restored via a capacitive coupling of the sensor system to the battery housing, which is connected to the vehicle mass. This aspect of the present invention also has several advantages; for example, a communication within a battery having a variable output voltage is possible, in which individual cells or cell modules are decoupled. This aspect may also generally be used in all batteries having a variable output voltage.
The present invention may particularly advantageously be used as a device or configuration of a sensor system having electric and electronic components, which may be installed in or attached to a battery cell (for example, a lithium-ion battery of an electric vehicle.) The previously presented approach serves to exchange data between the sensor system and a central evaluation device, while individual battery cells are decoupled from the power supply line or bypassed due to the operating mode of the method used in the battery for generating a variable output voltage.
The exemplary embodiments described and shown in the figures are selected only as examples. Different exemplary embodiments may be combined with each other completely or in regard to individual features. One exemplary embodiment may also be supplemented by features of another exemplary embodiment.
Furthermore, method steps according to the present invention may also be repeated or carried out in a sequence different from the sequence described.
If one exemplary embodiment includes an “and/or” link between a first feature and a second feature, this is to mean that the exemplary embodiment according to one specific embodiment includes both the first and the second feature, and according to another specific embodiment includes only the first feature or only the second feature.

## Claims

1. A battery sensor data transmission unit for a battery cell of a battery unit, the battery unit having multiple battery cells connected in series, comprising:
a connection state ascertainment unit for the battery cell, and configured for:
ascertaining a series connection state in which the battery cell is connected in series to another battery cell with the aid of a power supply line, and
determining a bypassing state in which at least one pole of the battery cell is decoupled from at least the other battery cell; and

a data transmission unit for the battery cell, and configured for:
outputting, if the battery cell is in the series connection state, a sensor signal that represents a physical variable one of in and at the battery cell in the series connection state to an evaluation device of the battery unit with the power supply line, and
outputting, if the battery cell is in the bypassing state, the sensor signal in the bypassing state to the evaluation device with a battery housing wall as a transmission medium;
wherein the data transmission unit is coupled to the connection state ascertainment unit.

2. The battery sensor data transmission unit as recited in claim 1, wherein the connection state ascertainment unit determines the series connection state when poles of at least three battery cells are connected in series with the power supply line.

3. The battery sensor data transmission unit as recited in claim 1, wherein the connection state ascertainment unit determines one of the series connection state and the bypassing state by evaluating a position of a switch that carries out an electrical coupling of the pole of the battery cell to the power supply line.

4. The battery sensor data transmission unit as recited in claim 3, wherein the switch is activated with a control signal, and wherein the data transmission unit synchronizes one of an ascertainment and an output of the sensor signal with the control signal.

5. The battery sensor data transmission unit as recited in claim 4, wherein the control signal is a pulse-width modulated control signal.

6. The battery sensor data transmission unit as recited in claim 1, wherein the connection state ascertainment unit ascertains one of the series connection state and the bypassing state with a measuring result relating to at least one of a current flow, an energy flow, and a power flow via the power supply line.

7. The battery sensor data transmission unit as recited in claim 1, wherein the data transmission unit encodes the sensor signal in a sensor signal package unambiguously assignable to the battery cell.

8. A battery unit, comprising:
a battery cell assembly that includes at least two battery cells, the battery cells being connectable in series with a power supply line;
at least one sensor for providing a measured value that represents a physical variable one of in and at one of the battery cells; and
at least one battery sensor data transmission unit that includes:
a connection state ascertainment unit configured for:
ascertaining a series connection state in which one of the battery cells is connected in series to another of the battery cells with the power supply line, and
determining a bypassing state in which at least one pole of the battery cell is decoupled from at least the other battery cell; and

a data transmission unit configured for:
outputting, if the battery cell is in the series connection state, a sensor signal that represents the physical variable in the series connection state to an evaluation device with the power supply line, and
outputting, if the battery cell is in the bypassing state, the sensor signal in the bypassing state to the evaluation device with a battery housing wall as a transmission medium.

9. A method for transmitting battery sensor data, the method comprising:
ascertaining at least one of:
a series connection state in which a battery cell is connected in series to another battery cell with a power supply line, and
a bypassing state in which a pole of the battery cell is decoupled from at least the other battery cell; and

outputting, if the battery cell is in the series connection state, a sensor signal that represents a physical variable one of in and at the battery cell, in the series connection state to an evaluation device with the power supply line, and
outputting, if the battery cell is in the bypassing state, the sensor signal in the bypassing state to the evaluation device with a battery housing wall as a transmission medium.

10. A computer readable medium having a computer program, which is executable by a processor, comprising:
a program code arrangement having program code for transmitting battery sensor data by performing the following:
ascertaining at least one of:
a series connection state in which a battery cell is connected in series to another battery cell with the aid of a power supply line, and
a bypassing state in which a pole of the battery cell is decoupled from at least the other battery cell; and

outputting, if the battery cell is in the series connection state, a sensor signal that represents a physical variable one of in and at the battery cell, in the series connection state to an evaluation device with the power supply line, and
outputting, if the battery cell is in the bypassing state, the sensor signal in the bypassing state to the evaluation device with a battery housing wall as a transmission medium.