WO2012116967A1

WO2012116967A1 - Battery module and battery with redundant cell voltage detection

Info

Publication number: WO2012116967A1
Application number: PCT/EP2012/053309
Authority: WO
Inventors: Stefan Butzmann
Original assignee: Sb Limotive Germany Gmbh; Sb Limotive Company Ltd.
Priority date: 2011-03-02
Filing date: 2012-02-28
Publication date: 2012-09-07
Also published as: DE102011004980A1

Abstract

The invention introduces a battery module having a plurality of series-connected battery cells (1) and a cell voltage detection module (114) connected to the battery cells (1). The cell voltage detection module (114) is designed to detect and digitize cell voltages of the battery cells (1) and to transmit the digitized cell voltages via a bus. The battery module contains first measuring electronics (117) which are connected to the battery cells (1) and are designed to output a first analogue measurement variable proportional to an extreme cell voltage of the cell voltages of the battery cells (1). The invention also relates to a battery having such a battery module and to a motor vehicle having such a battery.

Description

Description title

Battery module and battery with redundant cell voltage detection

The present invention relates to a battery module with a redundant cell voltage detection and a battery with such a battery module.

State of the art

It is becoming apparent that in the future both in stationary applications as well as in vehicles such as hybrid and electric vehicles increased

Battery systems will be used. To those for a respective

To meet given voltage requirements and available power, a large number of battery cells are connected in series. The failure of a battery cell can because of

Series connection to the failure of the battery and this in turn lead to a failure of the overall system, which is why high demands are placed on the reliability of the battery, especially for safety-related applications. In order to detect the condition of the battery and the individual battery cells as accurately as possible and to detect an imminent failure of a battery cell in time, the voltages of the battery cells 1 are regularly measured in known battery systems such as that of Figure 1 in addition to other parameters of the battery or battery cells 1 , The battery is for this purpose usually equipped with units 14, the cell voltages of the individual battery cells 1 and optionally further

Determine measured variables such as battery temperature and battery current and transmit them to a central control unit 16 (for example, a microcontroller). The central control unit 16 may be part of a battery module, the battery or a battery management system connected to the battery. The

Control unit 16 has among other things the task of measuring Check cell voltages to see if they are within a permissible range

Voltage range are. Both under- and overvoltages can negatively affect the life of the battery cells 1 and in the worst case even lead to a hazardous situation.

In order to ensure the safety of such a battery system, a so-called companion chip 15 is typically used in parallel to the cell voltage detection module 14, which monitors the cell voltages of the battery cells 1 to certain limits. Will one

Violated limit of a battery cell 1, an alarm is triggered and usually prescribed by safety regulations Sagittarius 7 and 8 for electrically disconnecting the battery from its environment opened

A disadvantage of this procedure, however, is that an error in the cell voltage measurement is detected only when a cell under- or undercuts one of the two limits for the emergency shutdown Reference voltage or a line break can only be detected by complex plausibility checks, which is the

Programming complex algorithms and proving their functional safety makes it difficult.

Disclosure of the invention

According to the invention, therefore, a battery module is introduced with a plurality of series-connected battery cells and a cell voltage detection module connected to the battery cells. Of the

Cell voltage detection module is formed, cell voltages of

To capture and digitize battery cells and digitized the ones

To send cell voltages over a bus. The battery module contains a first measuring electronics connected to the battery cells, which is designed to output a first analog measured variable proportional to an extreme cell voltage below the cell voltages of the battery cells. The invention has the advantage that a plausibility check of the measurements of the cell voltage detection module is made possible simply by an associated with the cell voltage detection module via the bus control unit from the transmitted digitized cell voltages an extreme cell voltage and compares the value with the first analog measured variable. When working correctly, the two values must match (taking into account measurement inaccuracies). If the two values are too large, there is obviously a malfunction. Opposite one

Combination of cell voltage detection module and companion chip also has the advantage of less effort and a

mutual control of cell voltage detection module and the first measuring electronics, wherein the evaluation according to the invention outside the

Battery module takes place, which causes further advantages in terms of robustness of the overall device.

Particularly preferably, the first analog measured variable is a measuring current or a measuring voltage. A measuring current can easily be independent of

Potential differences between the battery module and the control unit are transmitted, but usually has to be converted into a voltage before detection. A measuring voltage, however, can be processed very easily.

The extreme cell voltage may be a minimum cell voltage or a maximum cell voltage below the cell voltages of the battery cells. It is also possible, in each case a measuring electronics for the minimum and the maximum

Provide cell voltage to ensure protection against falling below both limits.

The battery module can also have a second measuring electronics, which is designed to output a proportional to an extreme operating parameters of the battery cells second analog measurement. The extreme

Operating parameter is preferably a minimum or maximum

Cell temperature below the cell temperatures of the battery cells. Such an embodiment of the battery module is particularly advantageous when the cell voltage detection module is also designed to detect cell temperatures and to send over the bus, or additional for this purpose Circuit components are provided so that the detected

Cell temperatures can be plausibility.

The battery module can have an analog-to-digital converter which is designed to convert the first analog measured variable into a digital measured value and to transmit the digital measured value over the bus. In this case, there is the advantage that the first analog measured variable is over the same

Communication link as the digitized cell voltages can be sent. Due to the often high battery voltage usually expensive isolation measures are required, which must be provided for each connection between the battery cells and the rest of the battery system, so that additional communication connections also mean a correspondingly increased effort.

In all embodiments and aspects of the invention, the battery cells are preferably lithium-ion battery cells, which have the advantages of high

Energy density and a high cell voltage to unite.

A second aspect of the invention relates to a battery having at least one

Battery module according to a first aspect of the invention and a

Microcontroller. The microcontroller is connected to the bus and configured to receive the digitized cell voltages and to determine an extreme cell voltage among the received digitized cell voltages.

In this case, the at least one battery module via a

Analog-to-digital converters and the microcontroller additionally be designed to receive the digital reading and compare it with the extreme cell voltage among the received digitized cell voltages.

Alternatively or additionally, the microcontroller may comprise a digital-to-analog converter, which is designed to convert the extreme cell voltage into an analog comparison value. The battery will also contain one

Comparator, which is designed to compare the first analog measured variable with the analog comparison value. Here, a check of the transmitted values alternatively or additionally by analog

Circuit components take place. Particularly advantageous is an embodiment, in the at least one battery module includes an analog-to-digital converter and the battery includes a digital-to-analog converter, because in this case the

mutual plausibility of the measured values can also be done twice, namely once in the analog and once in the digital domain.

In all embodiments of the invention, the microcontroller may be configured, depending on a result of the comparison, an emergency routine

perform. In this case, the battery may, for example, have contactors which are opened when the emergency routine is executed in order to galvanically separate the battery cells from their surroundings.

Another aspect of the invention relates to a motor vehicle with a

electric drive motor for driving the motor vehicle and a battery connected to the drive motor according to the second aspect of the invention.

drawings

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below. Show it:

1 shows a battery system with a cell voltage detection module and a companion chip according to the prior art,

Figure 2 shows a first example of a measuring device for explaining the

Operation of a measuring electronics of the invention,

3 shows a second example of a measuring device for explaining the

Operation of a measuring electronics of the invention,

Figure 4 shows an embodiment of a measuring electronics for use in the

Invention, and

Figure 5 shows an embodiment of the invention. Embodiments of the invention

Figure 2 shows a first example of a measuring device for explaining the operation of a measuring electronics of the invention. A battery cell 1, which is connected in a battery module with the measuring electronics, can with other

Battery cells to be connected in a string in series. A first pole of the battery cell 1 is connected to one of two inputs of a

Transimpedance amplifier 2 connected. The second entrance of the

Transimpedance amplifier 2 is connected to one terminal of a resistor 3, whose further terminal is in turn connected to a remaining pole of the battery cell 1. The output of the transimpedance amplifier 2 is connected to a control electrode of a flow control valve 4, which is designed in the example shown as npn transistor. However, other transistor types or even more complex circuits can be used as the flow control valve 4. The flow control valve 4 is between the with the

Transimpedance amplifier 2 connected terminal of the resistor 3 and the actual voltage measuring device connected in all

Embodiments shown only as an example and not part of the measuring electronics. This voltage measuring device may comprise a reference resistor 5 with a known resistance value and a voltmeter 6, which measures the voltage drop across the reference resistor 5.

The transimpedance amplifier 2 compares the cell voltage of the battery cell 1 with the voltage drop across the resistor 3 and generates an output current whose magnitude is proportional to the difference between the two

Tension is. This output current reaches the control electrode of the flow control valve 4, to which an optional setpoint current source 9 can be connected. This nominal current source 9 carries a constant current and serves for operating point adjustment of the flow control valve 4

Transimpedance amplifier 2 - optionally less the constant current of the target current source 9 - controls the current that allows the flow control valve 4 to pass. However, the more current that can flow through the flow control valve 4, the greater will be the voltage that drops across the heat exchanger 3. This results in that the voltage at one input of the transimpedance amplifier 2 increases relative to the voltage at the other input, whereby the difference of the

Input voltages decreases and the transimpedance amplifier 2 also its Output current reduced accordingly. However, if too little current flows through the resistor 3, the transimpedance amplifier 2 will correspondingly again flow more current to the control electrode of the flow control valve 4. This results in a feedback, which causes the voltage across the resistor 3 due to the control effect of the

Transimpedance amplifier 2, the Wderstand 3 and the flow valve. 4

comprehensive control loop is kept equal to the cell voltage. Since the inputs of the transimpedance amplifier 2 are ideally made high-impedance, the entire current flowing through the resistor 3, also flows through the flow control valve 4 and represents an exact measure of the cell voltage due to the linear relationship between voltage, Wderstand and current. He could now be measured elsewhere, if there is interest in its actual value, for example by being passed over a self-not belonging to the measuring device reference resistor 5 and thereby converted into a voltage whose height results directly from the cell voltage and independent in their place from the usually high and variable potentials at the battery terminals of the battery cell 1 and thus can be measured safely. In this case, if necessary, a correction factor is to be taken into account which determines the ratio of the amount of the resistor 3 to that of the

Reference resistance 5 indicates. In order to avoid a corruption of the current output by the flow control valve 4 through the base current of the current in the example shown as a bipolar transistor 4, can

For example, a MOSFET or an IGBT (Insulated Gate Bipolar Transistor) can be used.

In the measuring devices or measuring electronics shown in FIGS. 2 to 4, instead of a battery cell 1, it is also possible to provide a sensor, for example a temperature sensor, which outputs a sensor voltage which is dependent on a cell temperature.

Figure 3 shows a second example of a measuring device for explaining the operation of a measuring electronics of the invention, in which the

Transimpedance amplifier 2 is designed as a differential amplifier. Of the

Transimpedance amplifier 2 has a connection for a current source 10, which impresses a current in the differential amplifier. Depending on which of the two transistors 2-1 and 2-2 of the two branches of

Differential amplifier receives the larger input voltage, the current of the power source 10 will flow either through one transistor or the other. The current flowing through the transistor 2-1 is mirrored and output through a current mirror including the transistors 2-3 and 2-4. Because the

Operation of a differential amplifier is well known in the art, will not be discussed further here.

In contrast to the embodiment of Figure 1, the flow control valve 4 is designed as a PNP transistor, whereby a lower output current of

Transimpedance amplifier 2, output by the transistor 2-4, leads to a drop in the voltage at the control electrode of the flow control valve 4 and thereby leads to an increase in the base-emitter voltage of the pnp transistor designed as a current valve. The increased base-emitter voltage, in turn, causes an increase in the current through the flow control valve 4, which in turn results in the desired feedback.

The flow valve 4 could also be designed as an NPN transistor. In this case, the transistor 2-3 could simply be switched into the other branch of the differential amplifier (between the positive pole of the battery cell 1 and the transistor 2-2).

The current source 9 preferably carries a current which corresponds to half the current of the current source 10. In the steady state state of the control loop, the current of the current source 10 will ideally be equally divided between the two branches of the differential amplifier. In this case, the transistor 2-4 will also output a current that is half the current of the

Current source 10 corresponds, so that the voltage at the control electrode of the flow control valve 4 remains constant. However, instead of the current source 9, for example, a simple resistor or other suitable switching means could be used.

FIG. 4 shows an exemplary embodiment of measuring electronics for use in the invention. In this embodiment, multiple control loops are built and cascaded. The transimpedance amplifier 2 are constructed as in the illustrative Figures 2 and 3 as a differential amplifier, but the Current flowing through a branch of a respective differential amplifier serves as a current source for the superordinate differential amplifier. Only the lowest differential amplifier is connected to a power source 10, which

for example, is constructed together with the power source 9 as a current mirror. However, of course, other forms of implementation of the current sources 9 and 10 are possible.

Apart from the transimpedance amplifiers 2, the resistors 3 are also cascaded. Because the cascade of transimpedance amplifiers but only a single

Output current output, only one flow control valve 4 is further provided, which can be implemented as a transistor or in another of the types shown. In order to equalize the potential above each of the resistors 3 to that of the positive pole of the respective associated battery cell 1 (or the respective associated sensor), without affecting the current flow through the resistors 3, a potential replication device is also provided at the lower control cells, for example, a pair of complementary transistors 12 and 13. In order to limit the current through the cascaded transistors 13, a resistor 11 is also preferably provided. Instead of the transistors 12 and 13 and the Wderstandes 11 but other circuits can be provided which the potential to the

Resistors 3 match that of the positive poles of the battery cells 1.

The input of the differential amplifiers connected to the battery cells 1 may have a voltage divider formed of resistors 2-7 and 2-8, since otherwise the highest differential amplifier is not sufficiently high

Potential at the collectors or for the lowest one

Differential amplifier at the emitters of the transistors 2-1 and 2-2 would be more available.

The measuring electronics of Figure 4 has the special property that the cell voltages of several battery cells 1 can be measured simultaneously, but only the minimum cell voltage of all battery cells 1 is measured. That is, in the embodiment of FIG. 3, the current output by the cascade of the differential amplifiers is proportional to the smallest of all cell voltages. The measuring device of Figure 3 can thereby Of course, also be carried out for only two battery cells or a larger number of battery cells.

The circuit of FIG. 4 can also be used to determine a maximum

Cell voltage can be designed, which is advantageous for example in the

Monitoring cargo operations where overcharging can pose a security risk. For this purpose, the

Differential amplifier connected in an alternative manner, wherein the in Figure 4 respectively connected to the pole of the associated battery cell branch of

Differential amplifier with the base of the respective parent

Differential amplifier and therefore the cascaded in Figure 4 branch is connected to the pole of the battery cell. In order to be able to detect both the minimum and maximum cell voltage, the circuit of FIG. 4 can be used

Accordingly, each be executed once in each of the two possible variants.

FIG. 5 shows an embodiment of the invention. The battery of Figure 5 includes a battery module with battery cells connected in series. The poles of the battery module are connected via optional contactors 107 and 108 to the terminals of the battery. The battery module has one

Cell voltage detection device 114, which is executed in a known manner and connected to a microcontroller 116. The microcontroller 116 may be part of the battery module, the battery or one connected to the battery

Be battery management system. In the present example, it includes an analog-to-digital converter 120 and a digital-to-analog converter 121.

In addition to the cell voltage detection module 1 14, a measuring electronics 1 17 is provided, which is connected to the battery cells 1 and designed to determine an extreme cell voltage of the battery cells 1 and output a proportional to the extreme cell voltage analog reading. In the illustrated embodiment of the invention, the analog measurement is supplied to both analog-to-digital converter 120 and comparator 118. The analog-to-digital converter 120 converts the analog measured value into a digital measured value, which the microcontroller converts to a measured value from the output of the microcontroller

Cell voltage detection module 114 received digital

Cell voltage values determined compared extreme cell voltage value. at the proper functioning of the overall device, the two values should correspond to one another, advantageously a given one

Margin of error is taken into account. As additional protection, the

Digital-to-analog converter 121 to the determined by the microcontroller extreme cell voltage value to an analog value, which is applied to a second input of the comparator 118. The comparator 118 compares the two values in addition to the computational comparison within the

Microcontroller in the analog domain to allow even greater security in verifying the correct functioning of the device. Both the microcontroller 116, and the comparator 1 18 generate an output signal dependent on a result of the comparison, which are both given to a logic module 1 19. The logic device 119 may also be integrated into the microcontroller 116, in which case the output of the comparator 118 is connected to the microcontroller 116. The output of the logic module 119 may be connected, for example, to shooters 107 and 108 or else to a signal generator for an alarm signal. The output of the logic module 1 19 may also be connected to an input of the microcontroller 116.

The logic module 1 19 takes a logical link between the two

Output signals before. The type of logical connection can be selected depending on requirements for the security of the device. If a logical OR operation is selected, a safety routine is already executed if one of the two comparisons causes an excessive deviation of the digital data transmitted from the cell voltage detection module 1 14

Cell voltages detected extreme cell voltage from that of the

Measuring electronics 117 determined determines. Alternatively, a logical UN D link can also be provided. In this case, the safety routine is only performed if both comparisons consistently signal an error. As a result, unnecessary alarm situations that would lead to the shutdown of the system powered by the battery, can be avoided.

In addition, a mutual plausibility of the two comparisons is achieved.

Claims

claims

A battery module having a plurality of series-connected battery cells (1) and one connected to the battery cells (1)

Cell voltage detection module (114), which is designed

Detect and digitize cell voltages of the battery cells (1) and send the digitized cell voltages over a bus,

characterized by a with the battery cells (1) connected first measuring electronics (117), which is designed to output a proportional to an extreme cell voltage among the cell voltages of the battery cells (1) first analog measured variable.

The battery module according to claim 1, wherein the first analog

Measured variable is a measuring current or a measuring voltage.

The battery module according to one of claims 1 or 2, wherein the extreme cell voltage is a minimum cell voltage or a maximum cell voltage among the cell voltages of the battery cells (1).

The battery module according to one of the preceding claims, having a second measuring electronics which is designed to output a second analog measured variable proportional to an extreme operating parameter of the battery cells (1), the extreme operating parameter having a minimum or maximum cell temperature below the cell temperatures of the battery cells (1). is.

The battery module according to one of the preceding claims, comprising an analog-to-digital converter (120), which is designed to convert the first analog measured variable into a digital measured value and to transmit the digital measured value via the bus. A battery having at least one battery module according to one of the preceding claims and a microcontroller (116), wherein the microcontroller (116) is connected to the bus and adapted to receive the digitized cell voltages and an extreme

To determine cell voltage among the received digitized cell voltages.

The battery according to the preceding claim, wherein the at least one battery module according to claim 5 is formed, wherein the

Microcontroller (116) is additionally designed to receive the digital measured value and to compare it with the extreme cell voltage among the received digitized cell voltages.

The battery according to one of claims 6 or 7, wherein the at least one battery module according to any one of claims 1 to 5 is formed and wherein the microcontroller (1 16) comprises a digital-to-analog converter (121), which is formed convert extreme cell voltage into an analog comparison value, wherein the battery also includes a comparator (118), which is designed to compare the first analog measured variable with the analog comparison value.

9. The battery according to one of claims 7 or 8, wherein the

Microcontroller (116) is adapted to perform an emergency routine depending on a result of the comparison.

10. A motor vehicle having an electric drive motor for driving the motor vehicle and a battery connected to the drive motor according to one of claims 6 to 9.