DE102015200316A1 - Battery and battery system comprising a battery - Google Patents

Abstract

The present invention relates to a battery system (10), comprising at least one battery module (12) with a plurality of battery cells (14) connected in series or in parallel, and comprising a plurality of current conductors (16), wherein the current conductors (16) are each connected to at least one battery cell (16). 14), and comprising at least one current sensor (11) for determining the current flowing through the battery module (12), wherein at least one current conductor (16) at least one inductance increasing means (19) for selectively increasing the total inductance of the battery system such that the at least one inductance-increasing means (19) is adapted to a measuring frequency of the current sensor (11), wherein the current rise speed of a short-circuit current flowing through the at least one battery module (12) is limited such that at least two measuring points of the short-circuit current in the duration of the current increase Current sensors (11) fall. A battery system (10) described above allows in a simple and cost-effective manner an improved short-circuit detection or short-circuit current limitation and thereby improved safety in the operation of such a battery system (10), in particular in an electrically driven vehicle.

Description

The present invention relates to a battery with improved safety. The present invention further relates to a battery system having such a battery.

State of the art

Various energy storage systems, such as lithium-based energy storage or lithium-ion batteries, are almost indispensable in today's life. Areas of application include fully electrically powered vehicles or hybrid vehicles, as well as electrical tools, electrical entertainment electronics, computers, mobile phones, and other applications.

In electrically driven vehicles, for example, today are used as electrical energy storage (EES) often based on lithium chemistry accumulators, since they have a particularly high energy density at the same time low weight compared to nickel or lead-based energy storage. Typically, electrical energy stores are realized as a series connection of individual cells or as a series circuit of cells connected in parallel. Most of the individual cells are grouped in modules, so that the total battery is constructed as a series of modules.

In order to reduce a danger emanating from the energy stores or batteries, disconnecting devices are often provided which can interrupt an electrical conductor in the event of a short circuit.

The document DE 10 2011 121 604 A1 , for example, discloses a method of protecting an electrical or electronic system, particularly a high voltage battery system in an electric or hybrid vehicle, from electrical overcurrent and / or short circuit. Provided for this purpose are at least one measuring device for measuring an operating current, a circuit breaker for interrupting power and a control device for triggering the circuit breaker. An unusually high current increase is used as an indicator of a coming short circuit. Furthermore, provision can be made for a setpoint value for the current interruption to be adapted to the inductance of the system.

From the document WO 2005/115805 A1 Further, an electronic battery circuit breaker is known, which is connected in motor vehicles between the battery and the vehicle electrical system. In this case, a purely electronic overcurrent or short-circuit shutdown is provided, which should allow a much faster shutdown. It is also generally described that at the time of switching off the load circuit, a small current flows due to the finite current rise speed, caused by the inductance of the load circuit.

From the document EP 0 590 167 A1 Further, a line switch for high-frequency applications with low currents up to 16A is known which operates with a semiconductor element whose internal resistance at a certain control voltage at a control electrode and a working voltage lying in the direction of passage in a line lying working electrode has a low value and its internal resistance with increasing voltage the working electrodes jump up. It is provided that in the load current, a small inductance of up to 100nH is connected.

The document DE 10 2009 007 969 A1 describes a short-circuit protection device for limiting short-circuit currents in high-energy DC networks, in particular battery installations in submarine DC networks. Such a device comprises an ohmic resistor for limiting the short-circuit current and a switch connected in parallel with the resistor for bridging the resistor in the event of short-circuit freedom.

Disclosure of the invention

The present invention relates to a battery system, comprising at least one battery module with a plurality of serially or parallel connected battery cells, and comprising a plurality of conductors, wherein the conductors are each connected to at least one battery cell, and comprising at least one current sensor for determining the flowing through the battery module Electricity, wherein at least one conductor has at least one inductance-increasing means for selectively increasing the total inductance of the battery system such that the at least one inductance increasing means is adapted to a measuring frequency of the current sensor, wherein the current rise rate of a current flowing through the at least one battery module short-circuit current is limited such at least two measuring points of the current sensor fall in the duration of the current increase to the short-circuit current.

A battery described above allows a simple and cost-effective manner an improved short-circuit detection or short-circuit current limiting and thereby improved safety in the operation of such Battery, especially in an electrically driven vehicle.

Under a battery can be understood in a manner understandable to the skilled artisan both a primary battery, and more preferably a secondary battery, so a rechargeable battery, which can be preferably operated in DC. For example, the battery may be a lithium battery, such as a lithium-ion battery. In particular, a prescribed battery may be a traction battery of an electrically powered vehicle.

The battery described above has at least one battery module with a plurality of battery cells connected in series or in parallel. The battery cells can be configured, for example, as lithium-ion cells, as these are known in principle to those skilled in the art. In this case, the number and configuration of the battery cells can be adapted to the desired field of application. For example, for the exemplary case of an electrically powered vehicle, the battery cells in their entirety, for example distributed across multiple battery modules of the battery system, may have a nominal voltage greater than or equal to 200V, such as 400V or greater, and a nominal maximum current of up to 100A or greater or equal 100A, for example greater than or equal to 120A, about 240A or above.

Further, a plurality of conductors is provided, which are each connected to at least one battery cell. The current leads allow the battery cells to be connected in series or in parallel with one another in battery modules, for example in a manner known per se, or the current conductors can interconnect a plurality of battery modules, such as two battery modules. Furthermore, the current conductors can connect the battery cells or the modules to an external connection. For example, the current conductors can be high-current connectors, that is to say connecting conductors which can withstand the aforementioned currents. Thus, the current conductors are in particular designed such that they can withstand currents of at least 100A, thus remain stable when driving 100A. This includes, in a manner understandable to a person skilled in the art, that in embodiments it may also be possible to carry higher currents than 100A.

The battery also has at least one current sensor for determining the current flowing through the battery module, wherein the current sensor can operate at a defined measurement frequency. The measuring frequency indicates in which time interval individual measurements can take place.

The measured values of such a current sensor, such as, for example, a shunt sensor or a Hall sensor, can be evaluated at discrete points in time which can be defined by the measurement frequency as described above and averaged by software to reduce the computing power of a control unit and / or or filtered and processed at a lower repetition rate. The measuring range of these current sensors may be designed, for example, to the specified system current, so it can go only slightly beyond the maximum operating current, such as up to 50% above.

At least one current conductor can have an inductance-increasing means. In the context of the present invention, this may mean, in particular, that the total inductance of the battery module or of the battery system increases by the insertion of this means in comparison to a battery module without this means. In particular, an electrical conductor which has the same length as the conductor equipped with the inductance-increasing means and which is formed in a straight line can serve as comparison.

The current conductor with the inductance-increasing means is preferably such a conductor, which is for example directly connected to at least one battery cell and thereby preferably can be arranged directly within a battery. For example, the current conductor may be a high current connector. Such a component can thus be adapted individually to the desired application. In addition, this in turn can allow a particularly simple implementation and retrofitting.

The inductance-increasing means or the plurality of inductance-increasing means can thereby enable the total inductance L of the battery module to increase significantly in comparison to conventional battery modules. By increasing the inductance, the time constant t = L / R can be increased, wherein R indicates the internal resistance of the battery, and thus the step response of the battery to the short circuit are delayed such that the battery management system detects an overcurrent safely and optionally a separator can activate, as explained in detail below.

In this case, the at least one inductance-increasing means is selected such that the at least one inductance-increasing means is adapted to a measurement frequency of the current sensor, so that the current rise rate of a current flowing through the battery module short-circuit current is limited such that in the duration of the current increase to the short-circuit current at least two Measuring points of the current sensor, in particular at least five measuring points of the current sensor fall. Such adaptation or selection of the inductance-increasing means or means has significant advantages over the prior art solutions.

For example, in electrically powered vehicles may be provided in a prescribed battery or in a battery system having such a battery one or more devices to limit a short-circuit current or to separate an electrical line in the occurrence of short-circuit currents. For this purpose, for example, fuses may be provided in the electrical lines. This can prevent the risk of fire or cell damage. The fuses may be formed of tapered conductors, such as copper conductors, which have approximately several serially or parallel realized bottlenecks in the conductor. With short-circuit currents, these bottlenecks can melt and thus interrupt the conductor.

However, such rejuvenations weaken the structure of the conductor, which can break the bottlenecks under vibration and lead to a changed fuse characteristic and to an unauthorized or unwanted interruption of the circuit. Even when operating with specified peak currents, it can come at the tapers or bottlenecks to a warming and thus aging of the fuse, which can also lead to a change in the safety characteristics and unauthorized interruptions of the circuit.

In addition, fuses have a specific characteristic: if the flowing current is only slightly above the value specified for a fuse break, it may take several seconds, such as up to more than 100s, for the current to be interrupted. At very high currents, however, the fuse can already disconnect after less than 1ms. Therefore, fuses, at least one of which may be provided in a battery as described above, can increase safety significantly, but still provide room for improvement.

It may therefore be advantageous that can be dispensed with the provision of a fuse in a battery system described above. As a result, the battery system on the one hand be designed to be particularly cost-effective and can be increased on the other hand, the long-term stability.

Furthermore, in a previously described battery system, for example in vehicles, one or more, for example, irreversible or reversible separating devices, such as contactors, may be provided, which disconnect the battery from the electrical system or traction network, for example, when the battery is not in use, such as the vehicle, for example, bipolar to limit the area of the vehicle, which is under voltage of, for example,> 60 V, to the interior of the battery. These separators are also used to protect the battery, for example, before deep discharge under overload. For this purpose, the separation devices can not only carry and separate the specific operating current, but can also separate significantly higher currents, for example up to 400%, at least a few times. Further, the separator may serve to disconnect a current conductor in the presence of a short-circuit current. The disconnecting devices are usually controlled by the control unit, such as the battery management system. In this case, the control unit is supplied by the detection device for detecting current flowing through the battery module with current current values and in the presence of a current which is above a limit, the disconnecting device for disconnecting a short-circuit current to control.

Due to the low internal resistance, for example of lithium-ion batteries very high short-circuit currents are possible, which can exceed both the measuring range of the current sensors used, as well as the separation capability of the separator at least in current peaks.

Since, in the event of a short circuit, the current typically increases very rapidly, for example due to a faulty drive or breakdown of an IGBT, or due to the contact of two live parts, the measured value of the current sensor can conventionally jump from one sensing step to the next from the instantaneous measured value to the measuring range stop. In this case, between the sampling steps, a time duration in a range of greater than 0.5 ms, for example 1 ms or above. In this state, it is difficult for the control unit to detect whether the current is still in a range that can be separated by the separator. In this case, it is therefore necessary to rely on the function of the fuse. After removing the external short circuit, the system can only be put back into operation by replacing the fuse.

Since damage to the cells can occur due to high short-circuit currents despite triggering fuse, and since the current is separated very quickly by the fuse at high short-circuit currents, it may happen that the Measuring range stop of the current sensor is not detected, since the short-circuit current and the separation between two sampling steps may be, or that the measuring range stop is present only for a sampling step. In the latter case may have the effect that, since it may lead to incorrect measurement in the vehicle environment, for example by interference, vehicle electrical system fluctuations, etc., a single detection of a measuring range stop often does not lead to an entry in a fault memory. Therefore, it is often questionable whether after the failure of the fuse the affected cells and thus the battery stack may continue to operate.

However, this problem does not occur using the battery described above. Characterized in that the at least one inductance-increasing means is adapted to a measuring frequency of the current sensor, so that the current rise rate of a current flowing through the battery module short-circuit current is limited so that in the duration of the current increase to the short-circuit current at least two measuring points of the current sensor, it is possible at least two, preferably at least five, to determine measurements for the current flowing through the battery module current before the current has reached the strength of a short-circuit current. In this way, it can be ensured that a short-circuit current is determined reliably and reliably, wherein a faulty measurement or a faulty closing of a circuit breaker can furthermore be ruled out by the plurality of measurement results. This can be determined in a secure manner, whether and to what extent a battery can still be operated after closing a circuit breaker.

In addition, since the physically possible rate of increase of the current through the at least one inductance-increasing means of the conductor is significantly limited by an increase in inductance, the control unit can activate the battery's own disconnecting means in good time before the rise-limited short-circuit current exceeds the range still passing through the disconnecting means can be separated. As a result, the battery can continue to operate despite externally occurred short circuit, as the fuse does not trip due to the separation of the short-circuit current through the disconnecting device. However, it should be noted that the fuse has aged and should be replaced promptly. If it is also possible to interpret the detection and shutdown sufficiently reliable, can be completely dispensed with the fuse.

Thus, a control device such as a battery management system can be made particularly advantageous in that a short circuit is surely detected. In particular, it can be distinguished whether an optionally present fuse has broken due to aging or vibration or due to a short circuit the circuit. It is thus particularly advantageous to decide on the basis of fault memory entries on the possible whereabouts of the battery.

In the case of a previously described battery, therefore, there is no adaptation of the control technology or of the measuring cycles to the given inductance of the battery, but rather the inductance is adapted to the existing periphery of the battery system or of the respective battery module and to the adjustable measuring cycles. As a result, the battery system may be particularly advantageous for battery modules with low internal resistance, such as for lithium batteries, such as lithium-ion batteries. An implementation of the above-described battery in existing battery systems is particularly easy to carry out. Furthermore, by suitable adaptability, the risk posed by a short circuit can be reduced particularly reliably.

Within the scope of an embodiment, the at least one inductance-increasing means may be selected such that the current rise rate of a short-circuit current flowing through the battery module is limited such that at least two measuring points of the current sensor fall within the duration of the current increase to a tripping current of a protective device for interrupting the short-circuit current. In particular, in this embodiment, a particularly safe operation of the battery may be possible because not only a short circuit can be detected safely, but in response to the detection of the short-circuit current this can also be safely separated. Because it can be ruled out substantially that the short-circuit current exceeds the separation capability of the protective device or the separating device. This may be particularly advantageous for batteries with low internal resistance, such as in lithium-ion batteries.

In the context of a further embodiment, the at least one inductance-increasing means may be selected such that the battery system has a total inactivity which is in a range of greater than or equal to 10mH, for example greater than or equal to 20mH, greater than or equal to 25mH, less than or equal to 500mH, in particular to less than or equal to 250mH, and that the measuring frequency determines measurements at a time interval of greater than or equal to 1 ms to less than or equal to 100 ms. In particular, in this embodiment, it is possible by a significant increase in the total inductance of the battery module be that cost-effective measuring devices or control devices can be used with relatively low measurement frequencies. For measuring frequencies in the above-described range are customary in the ON-board diagnosis in motor vehicles systems, in particular battery management systems, and usually easily and inexpensively applicable, whereby by the aforementioned parameters, in particular a suitable combination of increasing the inductance and inexpensive and easy to use measuring and evaluation systems is possible.

For example, the inductance, such as the inductance of the entire system can be determined by impedance spectroscopy or in a conventional manner by means of an LCR bridge or AC bridge.

Furthermore, as a result of the inductance-increasing means increasing the inductance to an amount of greater than or equal to 10mH, in particular greater than or equal to 20mH, for example greater than or equal to 25mH realized, in a particularly simple manner a usability in battery systems with high currents, for example an electrically powered vehicle, be possible. By way of example and not limitation, for a battery having typically 0.1 ohm internal resistance, 400 volts nominal voltage and a nominal maximum current of 240 amperes and a current sensor having a measurement range of 330 amps for a total of five measurements at one milisecond each Inductivity of 20 mH be advantageous.

In the context of a further embodiment, at least one current conductor may be formed in or have an inductance-increasing structure. This means that the current conductor deviates from its conventional shape, such as a straight line or a right angle or an arc shape, and rather has a particular locally limited structure, by which an increased inductance is generated, wherein the inductance increase in particular on a straight ladder same Can relate length. In this case, in particular the total length of the conductor may be meant and not necessarily the geometric length, ie the length of the component. The inductance can be determined, as is generally known to the person skilled in the art.

Because at least one current conductor has an inductance-increasing structure or the inductance-increasing means is formed by the inductance-increasing structure, an increased inductance can thus be made possible by the conductor as such and optionally without the provision of further elements. This allows a particularly simple and inexpensive while effective training of the inductance. Furthermore, in this way, further components of the battery system can be configured substantially in a conventional manner, which allows a particularly simple implementation in already existing systems.

For example, the current conductor in the form of a loop or a coil can be designed as an inductance-increasing structure. In particular, by a coil or a loop inductance can be greatly increased, so as to limit current spikes or high short-circuit currents can. The number of coil turns or loops can be adapted to the desired field of application. For example, the U-shape current conductor may be configured as the simplest loop shape or in the form of a meander as a multiple loop shape.

In the context of a further embodiment, the inductance-increasing means may comprise a magnetically highly permeable material. In this case, a magnetically highly permeable material can be understood in particular to be a material having a relative magnetic permeability μ _r in a range of greater than or equal to 200, for example greater than or equal to 300, approximately smaller or equal to 10,000. The relative magnetic permeability μ _r can be determined according to the Standard DIN IEC 60404 , By providing such materials to the inductance-increasing structure, the inductance can be effectively increased.

For example, the magnetically highly permeable material may be present on an inductance-increasing structure. As a result, the design of the inductance-increasing structure, such as a coil or a loop, be particularly small dimensions, which may allow for example in electrically powered vehicles, the implementation in small spaces and with low weight.

For example, a ferrite can be used as the magnetically highly permeable material. In particular, ferrites can allow a particularly high increase in inductance, so that a particularly compact design can be possible. Manganese-zinc ferrites (MnZn), for example in the composition Mn _a Zn _(1-a) Fe ₂ O ₄ , or else nickel-zinc ferrites (NiZn), for example in the composition Ni _a , may be used as examples of ferrites Zn _(1-a) Fe ₂ O ₄ .

It may further be provided that the magnetically highly permeable material in the interior of Coil windings of a coil shaped in the form of a current conductor is arranged, or that the highly permeable material is surrounded by the coil turns. This arrangement can in turn be arranged very space-saving, so that an application is possible even in small spaces. Furthermore, a particularly good inductance increase can thus be made possible.

Alternatively, it may be possible for the magnetically highly permeable material to at least partially, in particular completely, surround at least one current conductor, for example in the region of the inductance-increasing structure. For example, the highly permeable material in the region of the inductance-increasing structure can serve as a sheath for the current conductor. This embodiment can in turn allow a particularly space-saving implementation.

drawings

Further advantages and advantageous embodiments of the objects according to the invention are illustrated by the drawings and explained in the following description, wherein the features described individually or in any combination may be an object of the present invention, as far as the context does not clearly indicate the opposite. It should be noted that the drawings have only descriptive character and are not intended to limit the invention in any way. Show it

1 a schematic view of an embodiment of a battery system of modules with two increased according to the invention in its inductance module connectors; and

2 a schematic view of another embodiment of a battery subsystem of modules with a battery module connector between two modules according to the invention.

In the 1 is an embodiment of a battery system 10 shown. The battery system 10 , which may be about a lithium-ion battery system, has at least one battery module 12 with a plurality of serially connected battery cells 14 on, in the 1 eight battery modules 12 are shown. Further, a plurality of conductors 16 provided to the battery modules 12 to connect with each other. The power conductors 16 can be designed to carry currents of 100A. In detail are the power conductors 16 according to 1 between two battery cells 14 arranged or connected to these, the battery cells 14 then one end of a battery module 12 training battery string are arranged. It is provided that at least one conductor 16 with an inductance increasing means 19 is provided such that the at least one inductance-increasing means 19 to a measuring frequency of a current sensor 11 is adjusted, the rate of increase of the current through the battery module 12 flowing short-circuit current is limited such that in the duration of the current rise to the short-circuit current at least two measuring points of the current sensor 11 fall.

In the 1 is to recognize that the inductance-increasing means 19 , a magnetically highly permeable material 18 , such as a ferrite, which is the current conductor 16 encases or encloses.

Further, a current sensor 11 for detecting by the battery 10 shown flowing current, in addition to the arrangement shown on the positive conductor and the negative current conductor of the battery, between the modules 12 or within one of the modules 12 can be arranged. Furthermore, there are two guards 13 shown for interrupting the short-circuit current, one of which may be sufficient. It is also a control unit 15 to activate the protection device 13 provided further with the current sensor 11 can be connected. The control unit may be, for example, the battery management system comprising the current sensor 11 control or the data of the current sensor 11 evaluate and the protection device 13 or control separation device. Finally, there is an electrical connection 17 , such as a connector socket, of the battery system 10 shown.

In the 2 is another embodiment of a battery 10 shown, with a conductor 16 that has one port each 20 with two battery cells 14 in the form of a coil as an inductance-increasing structure as an inductance-increasing means 19 is trained. With respect to the further description, the description to 1 refer, wherein the same or similar components are provided with the same reference numerals.

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 patent literature

• DE 102011121604 A1 [0005]
• WO 2005/115805 A1 [0006]
• EP 0590167 A1 [0007]
• DE 102009007969 A1 [0008]

Cited non-patent literature

• Standard DIN IEC 60404 [0039]

Claims (10)

Battery system ( 10 ), comprising at least one battery module ( 12 ) with a plurality of series or parallel connected battery cells ( 14 ), and comprising a plurality of conductors ( 16 ), the conductors ( 16 ) each with at least one battery cell ( 14 ), and comprising at least one current sensor ( 11 ) for determining by the battery module ( 12 ) flowing stream, characterized in that at least one conductor ( 16 ) at least one inductance-increasing agent ( 19 ) for selectively increasing the total inductance of the battery system ( 10 ) such that the at least one inductance-increasing means ( 19 ) to a measuring frequency of the current sensor ( 11 ), wherein the rate of increase of the current through the at least one battery module ( 12 ) is limited such that in the duration of the current rise to the short-circuit current at least two measuring points of the current sensor ( 11 ) fall. Battery system ( 10 ) according to claim 1, characterized in that the at least one inductance- increasing means ( 19 ) is selected such that the rate of current rise of a through the at least one battery module ( 12 ) short-circuit current is limited such that in the duration of the current increase to a trip current of a protective device ( 13 ) for interrupting the short-circuit current at least two measuring points of the current sensor ( 11 ) fall. Battery system ( 10 ) according to claim 1 or 2, characterized in that the at least one inductance- increasing means ( 19 ) is selected such that the battery system ( 10 ) has a total inductivity that is greater than or equal to 10mH, and that the measurement frequency defines measurements at a time interval greater than or equal to 1ms less than or equal to 100ms. Battery system ( 10 ) according to one of claims 1 to 3, characterized in that at least one conductor ( 16 ) is formed in an inductance-increasing structure, in particular in the form of a loop or a coil. Battery system ( 10 ) according to one of claims 1 to 4, characterized in that the at least one inductance- increasing means ( 19 ) a magnetically highly permeable material ( 18 ), in particular having a relative magnetic permeability μ _r in a range of greater than or equal to 200. Battery system ( 10 ) according to claim 5, characterized in that the magnetically highly permeable material ( 18 ) is a ferrite. Battery system ( 10 ) according to one of claims 5 or 6, characterized in that the magnetically highly permeable material ( 18 ) inside coil turns of a coil-shaped conductor ( 16 ) or that the magnetically highly permeable material ( 18 ) at least one conductor ( 16 ) at least partially encloses. Battery system ( 10 ) according to one of claims 1 to 7, characterized in that the current conductors ( 16 ) are designed to carry currents of 100A. Battery system ( 10 ) according to one of claims 1 to 8, characterized in that the battery ( 10 ) is a lithium battery, in particular a lithium-ion battery. Battery system ( 10 ) according to one of claims 1 to 9, characterized in that the battery system has no fuse.

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