DE102013204509A1 - Battery module and method for monitoring a battery module - Google Patents

Abstract

A battery module (221) having a plurality of battery cells (21) equipped with cell monitoring electronics (228, 229) and a monitoring and driving unit (230) adapted to monitor the battery module (221) will be described. The battery module (221) has a coupling unit (227) which comprises a half-bridge (240) with power semiconductors (241, 242) for coupling the battery cells (21) to output terminals (224, 225) of the battery module (221). Furthermore, the monitoring and control unit (230) is configured to detect an operating state deviating from normal operation of the battery module (221) and to control the power semiconductors (241, 242) in such a way that a safe operating state of the battery module is established.

Description

The present invention relates to a battery module with a plurality of battery cells, which are equipped with cell monitoring electronics, and a monitoring and control unit, which is set up for monitoring the battery module. Furthermore, the invention relates to a method for monitoring a battery module having a plurality of battery cells by means of a monitoring and control unit arranged in the battery module.

State of the art

It is common to refer to batteries for use in hybrid and electric vehicles as traction batteries, as these batteries are used for the supply of electric drives. In the 1 is the schematic diagram of a battery system with such a traction battery 20 shown. The battery 20 includes several battery cells 21 , To simplify the illustration in 1 were only two battery cells by the reference numeral 21 Mistake. Traction batteries in hybrid and electric vehicles are usually modular. Here are from at least two individual battery cells 21 , which are connected in series or in parallel, battery modules (in 1 not shown).

The battery 20 is from two battery cell series circuits 22 . 23 formed, each having a plurality of battery cells connected in series 21 include. These battery cell series circuits 22 . 23 or cell modules are each with a battery terminal 24 . 25 and with a connection of a service connector 30 connected.

The positive battery terminal 24 is with the battery 20 via a separating and charging device 40 connectable, which is a circuit breaker 41 which is parallel to a series connection of a charging switch 42 and a charging resistor 43 is switched. The negative battery terminal 25 is with the battery 20 via a separating device 50 connectable, which is another disconnector 51 includes.

Further shows 2 a diagram 60 in which different error mechanisms 61 lithium-ion batteries and their consequences 62 are represented very schematically. These illustrated failure mechanisms 61 can cause an unacceptable temperature increase 63 induced thermal runaway (thermal runaway) 64 the battery cells 21 to lead. When a thermal runaway occurs 64 It may be due to an emission of gas 65 , which may occur, for example, when opening a bursting valve as a result of increased battery cell internal pressure, to a fire of the battery cells 66 or in extreme cases even bursting 67 the battery cells 21 come. Therefore, the occurrence of thermal runaway must be 64 when using the battery cells 21 be excluded in traction batteries with a high probability close to 1.

A thermal runaway 64 can be overcharged 70 a battery cell 21 , as a result of a total discharge 80 a battery cell 21 during the subsequent charging process or in the presence of impermissibly high charging and discharging currents of the battery cell 21 for example, an external short circuit 90 can arise, occur. Furthermore, a thermal runaway 64 even in the presence of a battery cell internal short circuit 100 occur, for example, as a result of a strong mechanical force during an accident 101 or as a result of the formation of battery cell internal dendrites 102 may arise, for example, in the presence of excessive charging currents at low temperatures. Furthermore, a thermal runaway 64 also occur as a result of battery cell internal short circuits caused by in the manufacturing impurities of the battery cells 21 , in particular by metallic foreign particles present in the battery cells 103 , can be caused. Also, a thermal runaway 64 in the presence of an impermissible heating of the battery cells 110 , which may arise, for example, as a result of a vehicle fire, or in the presence of an overload of the battery cells 120 occur.

In the 3 the schematic diagram of a known from the prior art battery system is shown, which is a traction battery 20 with several battery cells 21 and a battery management system (BMS). The electronics of the battery management system has a decentralized architecture in which the cells of the cell monitoring electronics (CSC electronics) of the battery cells 21 trained monitoring and control units 130 are designed as satellites, each for monitoring the functional state of one or more battery cells 21 are provided and via an internal bus system 141 with a central battery control unit (BCU) 140 communicate.

The electronics of the battery management system, in particular the monitoring electronics of the battery cells 21 , is required to the battery cells 21 from the critical, in 2 Protected states that can lead to a thermal runaway. In the electronics of the battery management system, a high effort is operated, on the one hand, the battery cells 21 to protect against overload by external causes, such as by a short circuit in the inverter of an electric drive, and on the other hand to avoid that the battery cells 21 by a malfunction of the electronics of the battery management system, such as by a faulty detection of the battery cell voltages by the monitoring and control units 130 to be endangered.

Just like the one in the 1 shown battery system is in the in the 3 shown battery system, the traction battery via a separating and charging device 40 with a positive battery terminal 24 connectable and via a separator 50 with a negative battery terminal 25 connectable. In this case, to designate the same or similar components for in the 1 and 3 shown battery systems each used the same reference numerals.

Further, the central battery control device 140 adapted to disconnect (relay) 41 and the charging switch (relay) 42 the separating and charging device 40 head for. The activation of the disconnector 41 and the charging switch 42 by means of the battery control device 140 is in the drawing with the arrow 142 symbolizes. Also is the central battery control unit 140 adapted to the other disconnector (relay) 51 the separator 50 head for. The activation of the disconnector 51 by means of the battery control device 140 is with the arrow 143 symbolizes.

The central battery control unit 140 is via a high-voltage line 144 . 145 with a different battery terminal 24 . 25 connected. Furthermore, the central battery control device comprises 140 current sensors 150 . 160 , which are intended by the traction battery 20 to measure flowing electricity. The battery control unit 140 also communicates with a vehicle interface via a CAN bus 146 , Via the CAN bus, the battery control unit can 140 Information about the functional state of the vehicle can be provided.

When using a battery management system of a battery system known from the prior art, it is thus desirable to increase the safety of the battery system so that no unreasonable risk arises. It will be in accordance with the ISO 26262 high demands placed on the functional safety of the battery management system, as a malfunction of the electronics, as explained above, can lead to a hazard. Furthermore, safety tests are required for lithium-ion battery cells. To be able to transport the battery cells, for example, UN transport tests have to be carried out. The test results must be assessed according to the EUCAR Hazard Levels (EUCAR Hazard Levels). The battery cells 21 must comply with given minimum safety levels. To achieve this, extensive additional measures are taken in the battery cells, which are intended for use in traction batteries.

For battery management systems for battery systems with traction batteries 20 For electric vehicles and plug-in hybrids (plug-in hybrids), a classification according to the danger level ASIL C is expected to establish, if the safety of the battery cells 21 can not be significantly increased. Such additional measures are taken by integrating so-called safety devices in the battery cells. Thus, the following safety devices are typically integrated in the battery cells.

A battery cell incorporates an Overcharge Safety Device (OSD). Such a Überladesicherheitsvorrichtung causes the battery cell during an overcharge does not exceed an EUCAR security level 4. The permissible range of the battery cell voltage ends at 4.2 V. During an overcharging operation, the battery cell builds up such a high internal pressure from a battery cell voltage of about 5 V that a membrane of the overcharging safety device is arched outward and the battery cell is electrically short-circuited. As a result, the battery cell is discharged until a battery-internal fuse is activated. The short circuit of the battery cell between the two poles of the battery cell is maintained via the overcharging safety device.

Furthermore, a battery cell fuse (Cell Fuse) is integrated into the battery cell. This integrated in the battery cell fuse is a very effective protection instrument at the battery cell level, but causes considerable problems in the installation of the battery cells in a series circuit of a battery module or in a battery system. There, these measures are rather counterproductive.

A nail cell penetration safety device (Nail Penetration Safety Device (NDS)) is also integrated in a battery cell. A nail penetration safety device protects the battery cell by establishing such a defined short-circuit path upon penetration of a nail or a pointed object into the battery cell, which does not lead to such strong local heating of the battery cell in the area of nail entry, which leads to a local melting of the existing separator could.

In a battery cell is also a functional safety layer (SFL) integrated. The functional safety layer is realized by the ceramic coating of one of the two electrodes of the battery cell, preferably by the ceramic coating of the anode. By means of the functional safety layer, a surface short circuit of the battery cell and thus an extremely rapid conversion of the electrical energy of the battery cell into heat loss can be prevented when the separator melts.

In a battery cell also a shock safety device (Crush Safety Device) is integrated. The shock safety device has a similar operation as the nail penetration safety device. With a strong mechanical deformation of the battery cell housing, a defined short-circuit path is provided in the battery cell, which prevents strong local heating of the battery cell and thereby increases the safety of the battery cell.

In the case of the battery cells currently being developed, the measures for electrical safety, which for example protect against overcharging or ensure overcurrent protection, are associated with considerable expense. Moreover, these measures tend to be rather counterproductive rather than meaningful after the installation of a battery cell in a battery module or in a battery system. For example, when the fuse of a battery cell is activated, the situation arises that the electronics of the existing battery management system (BMS) are exposed to very high negative voltages. This creates an additional expense on the battery system level, since the transport regulations must be met at the battery cell level, without any other benefit would be connected.

Disclosure of the invention

According to the invention, a battery module with a plurality of battery cells, which are equipped with cell monitoring electronics, and a monitoring and control unit, which is set up to monitor the battery module, are provided. The battery module has a coupling unit which comprises a half-bridge with power semiconductors for coupling the battery cells to output terminals of the battery module. Furthermore, the monitoring and control unit is set up to detect a mode of operation deviating from normal operation of the battery module and to control the power semiconductors in such a way that a safe operating state of the battery module is established.

Furthermore, a method is provided for monitoring a battery module having a plurality of battery cells by means of a monitoring and control unit arranged in the battery module, in which the battery module is operated by means of a coupling unit arranged in the battery module and comprising a half-bridge of power semiconductors. According to the method, the battery module is set by means of a control of the coupling unit in a safe state, if detected by the monitoring and control unit deviates from a normal operation of the battery module error situation or danger situation.

According to one aspect of the invention, a motor vehicle with an electric motor and a traction battery for supplying the electric motor is also provided, wherein the traction battery comprises the battery module according to the invention.

The dependent claims show preferred developments of the invention.

The invention advantageously provides an electrically intrinsically safe battery module, with which the safety, in particular of large battery systems, as e.g. used in electric and hybrid vehicles, can be significantly increased. The battery module with the monitoring and control unit according to the invention can protect itself against impermissible electrical operating states, without having to rely on the function of electronics of a battery management system.

Overall, the battery module can be carried out so securely that much lower requirements can be made of a battery management system than is usual in the prior art. Thus, due to the invention, an intrinsically safe battery cell is available as a basic building block from which safe battery systems can be constructed in a simple manner. In this case, the conventionally performed, non-targeted measures for the electrical safety of the battery cells, such as an overcharge protection device or a cell fuse omitted.

The monitoring and control unit can be connected to the battery cells via cell monitoring electronics. Thus, according to one embodiment of the invention, each of the battery cells is equipped with its own cell monitoring electronics. Additionally or alternatively, the battery module may have a central cell monitoring electronics, which is connected to each battery cell directly or via the respective battery cell's own cell monitoring electronics. In this case, the monitoring and control unit is to is designed to communicate with the central cell monitoring electronics or, depending on the embodiment, with the battery cell's own cell monitoring electronics.

According to a particular embodiment of the invention, the monitoring and control unit is designed to monitor a battery cell voltage and / or a battery module voltage and / or a current flowing through the battery module current.

In this case, the drive and monitoring unit can preferably determine whether there is a battery cell voltage or battery module voltage whose magnitude exceeds an upper voltage limit. Furthermore, the coupling unit can have diodes, each of which is in each case connected inversely to one of the power semiconductors.

In this particular embodiment of the invention, the monitoring and control unit can thus advantageously detect, starting from normal operation, impending overcharge of the battery module on the basis of an exceeding of an upper voltage limit value of a cell voltage or battery module voltage. In normal operation, for example, a first power semiconductor of the battery module can be switched on and a second power semiconductor switched off, so that the battery cells are connected to both output terminals of the battery module. Thus, according to the invention, when the excess voltage threshold has been exceeded, the first power semiconductor of the half-bridge is turned off and the lower power semiconductor is turned on. Since the battery _{module voltage} is within the range U _{min_module} and U _{max_module} , the inverse diode of the first power semiconductor advantageously blocks even in the event of imminent overcharging, for example in the event of a malfunction during charging of the battery. As a result, further charging of the cells or of the battery module can be reliably prevented.

Furthermore, the monitoring and control unit can determine whether a battery cell voltage or battery module voltage is present, the amount of which falls below a lower voltage limit.

Detects the monitoring and control unit thus starting from normal operation impending deep discharge of the battery module based on falling below a lower voltage limit of the battery module voltage or the battery cell voltage, the first power semiconductor of the half-bridge is turned off and the lower power semiconductor is turned on. The battery current then flows through the second power semiconductor and the battery module is not discharged further.

In yet another embodiment, the monitoring and driving unit may further determine whether there is a charging current whose amount exceeds a predetermined charging current limit.

Detects the monitoring and control unit thus starting from normal operation impending overload of the battery module due to excessive discharge, for example as a result of external short circuit of the battery by a fault in an inverter, the first power semiconductor of the half-bridge can be turned off and the second power semiconductor. The battery current then flows through the second power semiconductor and the battery module is not loaded with unacceptably high discharge currents.

In still another embodiment, the monitoring and driving unit may further determine whether there is a discharge current whose amount exceeds a predetermined discharge current limit.

Detects the monitoring and control unit thus starting from normal operation impending overload of the battery module by excessive charging currents, for example at very low temperatures of a battery cell, where the cell is particularly sensitive to the so-called lithium plating, which can be adjusted on the anode, the first Power semiconductor of the half-bridge turned off and the second power semiconductor are turned on. The battery current then flows through the second power semiconductor, the battery cell and / or the battery module is not loaded with unacceptably high charging currents.

According to another particularly advantageous embodiment, the monitoring and control unit is designed to determine, on the basis of information communicated in particular by a battery management system, whether there is a danger situation in which the battery module can be damaged.

In this case, the monitoring and control unit is preferably designed to trigger the power semiconductor of the coupling unit in such a way that one of the power semiconductor is turned on and the other power semiconductor is put into an active operation for producing the safe operating state of the battery module in the presence of a dangerous situation.

For example, when the monitoring and control unit of the invention electrically intrinsically safe battery cell gets notified by a battery management system that the vehicle had an accident, the battery module can be discharged by means of the coupling unit, that is, over the half-bridge. For example, a power semiconductor can be switched on and a second can be operated as an active resistor. The battery module does not supply any voltage at its output terminals and is nevertheless slowly discharged. The realizable discharge currents are limited only by the thermal power loss that can be imposed on the power semiconductor in continuous operation. Preferably, the power semiconductor operated as an active resistor, including its thermal connection and cooling, is designed in accordance with the respective requirements.

The claimed battery module preferably has lithium-ion battery cells.

Advantageous developments of the invention are specified in the subclaims and described in the description.

drawings

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

1 the block diagram of a known from the prior art battery system with a traction battery,

2 FIG. 2 is a diagram illustrating various failure mechanisms of a prior art lithium-ion battery that may cause thermal cycling of this lithium-ion battery. FIG.

3 3 is a block diagram of a battery system known from the prior art with a traction battery formed from a plurality of battery cells and a decentralized battery management system;

4 the schematic diagram of a battery module according to an embodiment of the invention,

5 the schematic diagram of a battery module according to another embodiment of the invention,

6 the block diagram of a battery module according to yet another embodiment of the invention,

7 the block diagram of a battery module according to yet another embodiment of the invention,

8th the block diagram of a battery module according to yet another embodiment of the invention,

9 the block diagram of a battery module according to yet another embodiment of the invention,

10 the block diagram of a battery module according to yet another embodiment of the invention, and

11 a block diagram of a battery that is equipped with intrinsically safe battery modules according to the invention.

Embodiments of the invention

In the 4 is the schematic diagram of a battery module 221 illustrated according to a first embodiment of the invention. The battery module 221 includes several battery cells 21 connected in series in a cell module 260 are arranged. The battery cells are equipped with cell monitoring electronics 228 connected to monitor the individual battery cells 21 is provided. According to the embodiment shown here, the cell monitoring electronics 228 by a central cell monitoring electronics 229 (CSC) implements that with all battery cells 21 and, in particular, can control cell balancing.

The battery module also has a coupling unit 227 on, which consists of a half-bridge with a first power semiconductor 241 and a second power semiconductor 242 is trained. Parallel to the power semiconductors 241 . 242 is each a diode 260 whose forward direction is opposite to the forward direction of the corresponding power semiconductor 241 . 242 runs.

The coupling unit 227 is at a first, the first power semiconductor (the upper power semiconductor switch of the half-bridge from the 4 ) 241 associated port with the positive pole 222 of the cell module 260 and at a second, the second power semiconductor 242 (The lower power semiconductor switch of the half-bridge from the 4 ) associated with the negative terminal 223 of the cell module 260 connected. The half bridge of the coupling unit 227 is also at a center terminal with a first output terminal 224 of the battery module 221 connected.

The battery module according to the invention 221 includes one to the cell module 260 Parallel monitoring and control unit 230 for monitoring the functional state of the battery module 221 , The monitoring and control unit 230 is according to the invention with a integrated control for the power semiconductors 241 . 242 set up. According to the in 4 shown embodiment of the invention is the coupling unit 227 on or in the monitoring and control unit 230 arranged. However, the invention is not limited to such an embodiment. Thus, according to other embodiments of the invention, the coupling unit 227 separately to the monitoring and control unit 230 be arranged. In the 4 is also a battery management system 211 for a battery system. The battery management system 211 is designed to work with the monitoring and control unit 230 Exchange information. The information exchange between the battery management system 211 and the monitoring and driving unit 230 is by means of the double arrow 215 symbolizes.

Furthermore, the monitoring and control unit communicates 230 with the central cell monitoring electronics 229 , The communication can be for example via a bus 235 respectively. In this way, the monitoring and control electronics 230 from cell monitoring electronics 229 In particular, voltage and / or current measured values transmitted by the monitoring and control unit 230 for safety monitoring, as shown below.

Detects the monitoring and control unit 230 starting from a normal operation of the battery module 221 a threatening overload of a battery cell 21 on exceeding a first limit value of a battery cell voltage and / or the entire battery module voltage, the first power semiconductor 241 the half bridge 240 switched off and the second power semiconductor 242 switched on. Since the battery _{cell voltage} is within the range of U _{min_modul} and U _{max_modul} , the diode blocks 260 of the first power semiconductor 241 even with imminent overload, for example in case of malfunction when charging the battery or the battery module 221 , This can be a further charge of the battery cell or the battery module 221 safely prevented.

Detects the monitoring and control unit 230 starting from the normal operation of the battery module 221 a threatening deep discharge of the battery module 221 based on a shortfall of a second limit value of a battery cell voltage and / or the battery module voltage, the first power semiconductor 241 the half bridge 240 switched off and the second power semiconductor 242 is turned on. Then no current flows through the battery module 221 , One possibly over an entire battery system in which the battery module according to the invention 221 is disposed outwardly discharged current flows in the battery module 221 only via the first power semiconductor (semiconductor switch) 241 the coupling unit 227 ,

Detects the monitoring and control unit 230 starting from the normal operation of the battery module 221 a threatening overload of the battery module 221 too high discharge currents, which may occur as a result of an external short circuit of the battery due to an error in the inverter, is the first power semiconductor 241 the half bridge 240 switched off and the second power semiconductor 242 is turned on. Then no current flows through the battery module 221 , The battery module 221 is thus protected against loading with impermissibly high discharge currents.

Detects the monitoring and control unit 230 starting from the normal operation of the battery module 221 a threatening overload of the battery module 221 due to excessive charging currents, for example at very low temperatures of a battery cell 21 in which the battery cell 21 is particularly sensitive to an educated especially on the anode lithium coating is by means of the monitoring and control unit 230 the first power semiconductor 241 the half bridge 240 switched off and the first power semiconductor 242 is turned on. It then flows no more electricity through the actual battery cell 21 , The battery cell is thus protected against loading with impermissibly high charging currents.

Will the monitoring and control unit 230 the intrinsically safe battery module according to the invention 221 For example, in a vehicle of a battery management system 211 informed that the vehicle had an accident, the battery module 221 over the half bridge 240 discharged. This is the second power semiconductor 242 switched on and first power semiconductors 241 operated in the so-called active operation as a controllable resistor. The battery module 221 gives at its exit terminals 224 . 225 then no more voltage and is still slowly discharged. The realizable discharge currents are limited only by the thermal power loss, the power semiconductors operated as a controllable resistor 241 can be imposed in continuous operation. A powered in particular as a controllable resistor power semiconductors 241 including its thermal connection and cooling is therefore designed according to the requirements.

In the 5 the block diagram of a battery module according to another embodiment of the invention is shown. Unlike the in 4 embodiment shown are the battery cells 21 here each with its own cell monitoring electronics 231 fitted. Further, similar as in 4 , also a central cell monitoring electronics 229 There are, however, some functions of cell monitoring rather than in the central cell electronics 229 now in the individual battery cells 21 or in the corresponding battery cell own cell monitoring electronics 231 be executed. For this purpose, the central cell monitoring electronics communicate 229 with the individual cell monitoring electronics 231 in the battery cells. This communication can be done by means of a bus 235 carried out on both the central cell monitoring electronics 229 as well as the battery cell's own cell monitoring electronics 231 are connected. The monitoring and control unit according to the invention 230 on the other hand communicates, similar to after 4 , with the central cell monitoring electronics 229 ,

In the 6 the schematic diagram of a battery module according to yet another embodiment of the invention is shown. Unlike the embodiment according to 5 are the battery cell's own cell monitoring electronics 231 here each with its own, that is separate communication bus 235 with the central cell monitoring electronics 229 connected, the output side has a correspondingly higher number of interfaces.

The 7 shows the block diagram of a battery module according to yet another embodiment of the invention, according to this embodiment, a communication link 235 between a battery cell own cell monitoring electron 231 and the central cell monitoring electronics 229 is present, so the central cell electronics 229 only with a single one of the cell monitoring electronics 228 directly communicates. The battery cell's own cell monitoring electronics 228 communicate with each other, for example via a daisy chain, so that all relevant battery cell data first on the daisy chain and then on the communication link, in the figures with the reference numeral 235 is designated to be transmitted.

The invention is not limited to such battery cell own cell monitoring electronics 231 limited within a respective battery cell 21 are arranged. Alternatively, it is conceivable that for each battery cell 21 a corresponding separate cell monitoring electronics 231 outside the battery cell 21 arranged and connected to the battery cell, optionally a central (main) cell monitoring electronics may be present.

The 8th to 10 show further embodiments of the invention, wherein in these embodiments, the monitoring and control unit 230 directly with the battery cell's own cell monitoring electronics 231 is connected, without requiring a central cell monitoring electronics 229 is available. Thus, some cell monitoring tasks become directly in / on the battery cells 21 executed, wherein determined measurement results and outputs of cell monitoring electronics 231 directly to the monitoring and control unit 230 be communicated.

The communication 235 between the monitoring and control unit 230 and cell monitoring electronics 231 takes place similar to the embodiments described above in connection with the 5 to 7 were discussed, with the difference that the or the corresponding communication buses 235 to the monitoring and control unit 230 and not connected to a central cell monitoring unit. So shows 8th an embodiment of the invention, in the monitoring and control unit 230 over a bus 235 with cell monitoring electronics 231 connected, and in 9 are several communication links or buses 235 between the monitoring and control unit 230 on the one hand and the respective cell monitoring electronics 231 on the other hand available. Further shows 10 an embodiment in which the cell monitoring electronics 231 communicate with each other, one of the cell monitoring electronics 231 with the monitoring and control unit 230 connected is.

In the 11 The structure of a battery in which several battery modules according to the invention 221 are shown. How out 11 can be seen, assigns each battery module 221 the battery shown there several battery cells 21 and a coupling unit with a half-bridge 240 on. For the sake of simplicity of illustration, emphasis has been placed on the explicit representation of the in each battery module 221 arranged monitoring and control unit 230 waived.

The battery modules according to the invention presented here 221 are not limited to the use of lithium-ion battery cells. They may also include other battery cell technologies, such as for nickel-metal hybrid battery cells.

In the inventive intrinsically safe battery modules shown here 221 The overcharge safety devices (Overcharge Safety Devices (OSDs) and the battery cell fuse (Cell Fuses) used so far can be used as far as possible omitted. With the battery modules according to the invention presented here 221 Battery systems can be set up, the battery management systems 211 have to be placed on the much lower requirements than the known from the prior art battery systems. The electronics of a battery management system 211 Therefore, thanks to the invention, it is expected that it can only be developed with the usual quality assurance measures (ASIL classification QM) and does not have to fulfill the ASIL C. Overall, the safety of battery systems can thus be significantly improved over the current state of the art.

According to the invention, the battery cells or battery modules are controlled such that their operating parameters are within the respective limits which are necessary for safe operation.

Thus, lithium ion battery cells are typically operated within a voltage range of Umin to Umax of 2.8V to 4.2V, or preferably 3.0V to 4.2V volts. This applies in particular to safety-relevant values Umin_safety or Umax_safety. However, these specifications apply to the voltages to be measured U battery cell at idle, that is, when no current flows through the battery cell. It is important to observe these limits, otherwise the electrodes may be damaged.

The open circuit voltage of the battery cells depends essentially on their state of charge. In this case, typically a charge state SOC of 0%, at 3.5 V a charge state of 20%, and at 4.2 V a state of charge of 100% is assumed for a voltage U battery cell of 2.8 V, these values being in each case of type and Material of the cathode, the anode, and / or the electrolyte used.

When a current flows through a battery cell, the battery cell voltages UBatteriezelle may differ from the above figures. Suppose the open circuit voltage is 3.5 V and the internal resistance of the battery cell at 25 ° C is 10 mΩ. At a charging current of 100 A, this would then give a voltage value U battery cell of 3.5 V + 1.0 V = 4.5 V. The internal resistance of the battery cell can be as high as 50 mΩ, for example, at a temperature of 0 ° C For example, for an exemplary discharge current of 50A, a voltage would be U battery cell of 3.5V minus 2.5V = 1.0V. Due to the applied control and the sensors used, these voltage values are not reached at room temperature or at 0 ° C. Generally, during operation of the battery cells, the Umax value may be between 4.2V and 5.0V and the Umin value between 1.5V and 4.2V, preferably between 1.8V and 4.15V Values, however, do not refer to the open circuit voltage.

The above voltage values apply to a single battery cell. For a battery module, it depends on how many cells are connected in series or in parallel. Thus, the allowable module open circuit voltage UBatteriemodul is between n × 2.8V to n × 4.2V, where n is the number of battery cells connected in series.

Limit values for temperatures in lithium-ion battery cells are approximately at Tmin = -40 ° C and Tmax = 30 ° C to 50 ° C, preferably 30 ° C to 45 ° C, most preferably 35 ° C to 40 ° C. For safety reasons, a maximum temperature Tmax-safety of 46 ° C to 80 ° C, preferably 50 ° C to 60 ° C should not be exceeded. Furthermore, the maximum outdoor temperature Taußen, at which the battery cells are operated, should not exceed 40 ° C.

The battery currents through the battery cells should not be outside a range of -1000 A to +1000 A, preferably -600 A to +600 A, more preferably -500 A to +500 A, even more preferably -450 A to +450 A, and more preferably -350 A to + 350 A, are.

The internal pressure of a battery cell should not leave the pressure range of 2 bar to 8 bar, preferably 3 bar to 7 bar.

The above discussion has been made by way of example for lithium-ion battery cells or lithium-ion battery modules, the values given in particular for lithium-ion battery cells with lithium manganese cobalt oxide as active material for the cathode. However, the invention is not limited to such battery cells, in particular not to lithium-ion battery cells. In practice, the numerical values of the operating parameters to be selected thus depend on the particular battery cell type.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• ISO 26262 [0012]

Claims (10)

Battery module ( 221 ) with several battery cells ( 21 ) equipped with cell monitoring electronics ( 228 . 229 . 231 ) and a monitoring and control unit ( 230 ) used to monitor the battery module ( 221 ), characterized in that the battery module ( 221 ) a coupling unit ( 227 ) having a half-bridge ( 240 ) with power semiconductors ( 241 . 242 ) for coupling the battery cells ( 21 ) with exit terminals ( 224 . 225 ) of the battery module ( 221 ), and the monitoring and control unit ( 230 ) is adapted to one of a normal operation of the battery module ( 221 ) deviating operating state and the power semiconductors ( 241 . 242 ) such that a safe operating state of the battery module ( 221 ) will be produced. Battery module ( 221 ) according to claim 1, wherein the monitoring and control unit ( 221 ) is formed, a battery cell voltage and / or a battery module voltage and / or by the battery module ( 221 ) and a presence of a battery cell voltage or battery module voltage whose magnitude exceeds an upper voltage limit, and / or a battery cell voltage or battery module voltage whose magnitude is less than a lower voltage limit, and / or a charge current whose magnitude exceeds a predetermined charging current limit, and / or a discharge current whose amount exceeds a predetermined discharging current limit. Battery module according to claim 1 or 2, wherein the monitoring and control unit ( 230 ) is configured to determine on the basis of information communicated in particular by a battery management system, whether a dangerous situation in which the battery module ( 221 ) is damaged. Battery module ( 221 ) according to one of the preceding claims, wherein the monitoring and control unit ( 230 ) is adapted for establishing a safe operating state of the battery module ( 221 ), in particular in the presence of a dangerous situation, the power semiconductors ( 241 . 242 ) of the coupling unit ( 227 ) such that one of the power semiconductors ( 241 . 242 ) is turned on and the other power semiconductor ( 241 . 242 ) is put into active operation. Battery module ( 221 ) according to one of the preceding claims, wherein each of the battery cells ( 21 ) with its own cell monitoring electronics ( 231 ) and / or the battery module ( 221 ) a central cell monitoring electronics ( 229 ) connected to each battery cell ( 21 ) directly or via a respective battery cell's own cell monitoring electronics ( 231 ), the monitoring and control unit ( 230 ) is designed to communicate with the central cell monitoring electronics ( 229 ) or with the battery cell-specific cell monitoring electronics ( 231 ) to communicate. Battery module ( 221 ) according to one of the preceding claims, wherein the coupling unit ( 227 ) Diodes ( 260 ), each of which is assigned to one of the power semiconductors ( 241 . 242 ) is inversely connected. Method for monitoring a battery module ( 221 ) with several battery cells ( 21 ) by means of a in the battery module ( 221 ) arranged monitoring and control unit ( 230 ), characterized in that the battery module ( 221 ) by means of a in the battery module ( 221 ) arranged coupling unit ( 227 ), which is a half-bridge ( 240 ) from power semiconductors ( 241 . 242 ) is operated, if, by the monitoring and control unit ( 230 ) one of a normal operation of the battery module ( 221 ) deviating fault situation or danger situation, the battery module ( 221 ) by means of a control of the coupling unit ( 227 ) is put in a safe state. Method according to claim 7, wherein by means of the monitoring and control unit ( 230 ) a battery cell voltage and / or a battery module voltage and / or by the battery module ( 221 ) is monitored and in the presence of a battery cell voltage or battery module voltage whose amount exceeds an upper voltage limit, and / or in the presence of a battery cell voltage or battery module voltage whose amount falls below a lower voltage limit, and / or in the presence of a charging current, the amount of a predetermined charging current limit exceeds, and / or in the presence of a discharge current whose amount exceeds a predetermined discharge current limit, the power semiconductors ( 241 . 242 ) of the coupling unit ( 227 ) are put into a switching state in which by the battery module ( 221 ) no electricity flows. Method according to claim 7 or 8, wherein the monitoring and control unit ( 230 ) the existence of a danger situation is determined on the basis of information communicated in particular by a battery management system, and the coupling unit ( 227 ) is controlled in the presence of a danger situation such that at the half-bridge ( 240 ) one of the power semiconductors ( 241 . 242 ) and the other power semiconductor ( 241 . 242 ) in an active operation as controllable Resistor is operated so that the battery module ( 221 ) is unloaded. Motor vehicle with an electric motor and a traction battery for supplying the electric motor, which is a battery module ( 221 ) according to one of claims 1 to 6.

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