DE102014200206A1 - Power interruption device for traction batteries - Google Patents

Abstract

The invention relates to a battery pack (13) with a number of battery cells (12), with a battery disconnecting unit (18) having a charging and disconnecting device (24) for a positive pole (20) of the battery pack (13) and a Separator (26) for a negative terminal (22) of the battery pack (13). Furthermore, at least one current interrupt device (CID) (33) is associated with the battery pack (13). This is arranged in a current path (38, 40) such that the number of battery cells (12) form a first sub-battery (54) and at least one further second sub-battery (56, 58).

Description

State of the art

Traction batteries for use in electric and hybrid vehicles in the supply of electric drives. In order to achieve the required power and energy data for electric and hybrid vehicles, individual battery cells are connected in series and partially individual additional battery cells in parallel. In electric vehicles often 100 battery cells and more are connected in series, such batteries carry voltages up to 450 volts. Even in hybrid vehicles is more commonly exceeded the voltage limit of 60 volts, which is still classified as uncritical in contact with humans.

An in 1 shown traction battery has next to the battery cells even more functional groups such as a charging and disconnecting device at the positive pole of the battery, a separator at the negative pole of the battery, a service connector and a current interrupt device (CID). The above-mentioned further functional groups of a traction battery have the following tasks:
With the two circuit breakers in the separating devices, which are provided both at the positive pole, as well as at the negative pole of the traction battery, the battery cells can be switched off at both poles. This is called bipolar shutdown of battery cells. This makes it possible to disconnect the battery at a standstill or in safety-critical situations, such as the occurrence of an accident from the traction board network of the vehicle, or switch to the traction power supply while driving - depending on the requirement and driving situation.

The charging device, which may be provided, for example, at the positive pole of the battery, has the task of limiting equalizing currents in the traction power supply when switching on the traction battery to limit values. By means of the current interruption device (CID), the individual battery cells can be protected against overloading by impermissibly high currents in the event of an external short circuit of the traction battery. Without this measure, for example, the lithium-ion battery cells could undergo a "thermal runaway", whereby battery modules and the battery cells installed in them can be seriously damaged.

The representation according to 1 It can be seen that the above-mentioned charging and disconnecting devices at the two poles of the battery and the current interruption device (CID) according to the prior art in a battery disconnect unit (BDU) in the form of a housing community as a component are installed in the battery systems. An in 1 also shown service plug must be removed for safety reasons during maintenance of the battery. This can be enforced by the fact that the battery case can only be opened if the service plug was previously removed. The battery cells are therefore safely unipolar disconnected, even if the two disconnectors should not have opened in the disconnectors due to malfunction.

In the illustration according to 2 is an electrical equivalent circuit diagram of a Li-ion battery cell according to the prior art shown in more detail. Especially in battery cells for consumer applications, such as for laptops and tools, a power interruption device (CID) is integrated into the battery cell. This is usually a built-in battery cell overcurrent protection mechanism, which is similar to a fuse. If the battery cell in question is loaded with too high a current - for example due to an external short circuit of the battery system in which the battery is installed - the current interruption device (CID) is activated, for example by melting a tapered current-carrying element. As a result, the battery cell is protected from overloading, as a result of which it could come to an inadmissibly high temperature. This temperature limitation is especially important for Li-ion battery cells, as an inadmissibly high temperature rise could lead to thermal runaway of the battery cell.

Be battery systems, especially traction battery systems for hybrid and electric vehicles according to the in 1 architecture constructed and come in these traction battery systems battery cell integrated power interruption devices (CID) are used, the battery cells can be exposed to very high negative voltages in a tripping operation of an in-cell arranged power interruption device (CID). In magnitude, this negative voltage can assume values that can correspond to almost the entire battery voltage. As a result, very high demands are made with regard to the current turn-off capability on cell-internal current interruption devices (CID), since it is necessary to switch off against very high voltages. On the other hand, after activating its current interruption device (CID), a battery cell must be able to block very high negative voltages between its two cell terminals, ie between positive and negative poles, without resulting in electrical flashovers or electrochemical reactions, for example in the electrode ensemble of FIG Battery cell is coming.

Presentation of the invention

According to the invention, a battery pack is proposed, which is formed from a number of battery cells and comprises a battery disconnecting unit which contains a positive pole loading and disconnecting device and has a negative pole disconnecting device, the battery pack comprising at least one current interrupting device ( CID) and this is arranged such that the battery cells is divided into a first sub-battery and at least a second sub-battery.

By inventively proposed subdivision of the total number of more than a hundred individual battery cells in at least two sub-batteries or sub-modules by appropriately skillful choice of installation location of the at least one current interrupt device (CID) can be achieved that arranged at a tripping process of a cell internal power Interruption device (CID) occurring very high negative voltages can be at least halved. As a result, the requirements in terms of Stromabschaltfähigkeit can be significantly reduced at battery internally arranged power interruption units. At the same time can be achieved by the inventively proposed choice of installation of the at least one current interrupt device (CID) that a corresponding battery cell after activation of a respective power interruption device (CID) can block occurring voltages between two terminals, said Amount of voltages compared to solutions according to the prior art significantly reduced, at least halved. As a result, electrical flashovers or electrical reactions can be avoided.

In an advantageous embodiment of the invention underlying idea, the at least one current interrupt device (CID) is designed as a fuse. In a cost-effective and reliable embodiment, a design of a fuse is provided as a cross-sectional taper of an electrical conductor. Furthermore, the solution proposed according to the invention may be followed by the number of battery cells, of which up to a hundred and more are electrically interconnected, by the use of at least two current interrupt devices (CID) in a first sub-battery or a first battery module, a second Partial battery or a second battery module and a third sub-battery or a third battery module are divided. In this embodiment, it is possible to not only halve, but even further reduce the negative voltage that occurs during a tripping operation of a current interrupt device (CID).

In particularly simple manufacturing terms, there is the possibility, when using a cell-internal power interruption device (CID), to install them in such a way that mutually symmetrical first and second sub-batteries or battery modules are formed, d. H. the individual partial batteries or battery modules formed by the symmetrical subdivision each have an identical number of interconnected battery cells.

Advantageous embodiments of the inventively proposed choice of the installation location of the at least one current interrupt device (CID) are on the one hand that the at least one current interrupt device (CID) arranged in the current path between a first sub-battery or first battery module and a service connector becomes. A service connector is used on a housing of a battery pack or a battery module to ensure that only after removal of the service connector, a housing cover of the battery module or the battery pack can be opened so that the interior of the housing is accessible. Furthermore, the at least one current interrupt device (CID) can also be arranged between the service connector and a second sub-battery or second battery module arranged downstream of it. It is also possible to integrate the at least one power interruption device (CID) directly directly into the service connector.

The at least one inserted current interrupt device (CID) can be arranged for example in a high-current connector between two battery cells of a battery module, so that an internal short circuit between two adjacent battery cells can be secured. In the at least two formed sub-batteries or the at least two formed battery modules of a battery pack, the internal current interruption devices (CID) can also be arranged such that a short circuit within a respective sub-battery with respect to Stromabschaltfähigkeit and the residual voltage to be hedged can be hedged.

Advantages of the invention

Depending on the inventively proposed arrangement of at least one current interrupt device (CID) within a number of electrically interconnected battery cells, at least halving the negative voltage that occurs in a tripping operation of an in-cell current interruption device (CID) achieved become. This allows the requirements for in-battery power interruption devices (CID) in terms of Stromabschaltfähigkeit be reduced, since now no longer must be switched off against very high voltages, which are of the order of 400 volts and more, but that the voltage against which must be turned off, for example, in the order of 200 volts.

Furthermore, it can be achieved by the proposed solution according to the invention that a battery cell can reliably block voltages between the two cell terminals even after the activation of their respective current interruption device (CID), since the high negative voltages occurring there are halved. This ensures that electrical flashovers or electrochemical reactions in the electrode ensemble of a battery cell of traction batteries are avoided. The proposed solution according to the invention in its various possible embodiments, the safety of traction batteries, such as those used on electric and hybrid vehicles, can be significantly improved.

A current interrupt device (CID), as known in the art, can not prevent an internal short circuit that may have occurred due to an accident. A single isolated power interrupt device (CID) can not even detect a short circuit that has occurred.

With a number of current interruption devices (CID) installed in the current path, a much safer battery system can be offered. The positioning of at least one current interrupt device (CID) within the battery system and in particular its subdivision into battery modules or sub-batteries as individual units (representation according to the 4 and 5 ) offers a much safer battery system. The total voltage that is generated in each sub-battery or each battery module is significantly lower than that which would occur if the totality of battery cells operated as a separate unit. From the use of a plurality of power interruption devices (CIDs) it follows that the presence of individual battery cell fuses, ie within each battery cell to be provided current interruption device (CID) is no longer necessary. By the proposed solution according to the invention can be created battery systems that do without the additional requirement of individual battery cell fuses.

Brief description of the drawings

With reference to the drawing, the invention will be described below in more detail.

It shows:

1 the schematic diagram of a traction battery according to the prior art, which is electrically connected to a battery disconnecting unit,

2 Short-circuit paths occurring in traction batteries of electric and hybrid vehicles with an external and an internal short circuit,

3 a family of tripping characteristics which characterize a characteristic for the tripping of a current interruption device within an overcurrent range,

4 an arrangement possibility of power interruption units at different locations within a battery pack and

5 a number of battery cells, which are electrically interconnected and divided by the inventive arrangement of two power interruption units in sub-batteries or battery modules.

1 shows a schematic diagram of a traction battery according to the prior art, as it comes to electric and hybrid vehicles used.

1 shows a housing 10 in which a number of battery cells 12 , for example, a hundred and more are housed. The number of battery cells 12 forms a battery pack 13 , The individual battery cells 12 are interconnected via cell connectors 14 electrically interconnected, usually in series connection; however, there may also be groups of battery cells 12 electrically connected in parallel.

The case 10 with the number of battery cells 12 is a battery disconnecting unit 18 (Battery Disconect Unit = BDU). This is in turn both with a positive pole 20 of the battery pack 13 as well as with a negative pole 22 of the battery pack 13 connected. The battery disconnecting unit 18 includes a loading and separating device 24 that the plus pole 20 is assigned, further a separator 26 for the negative pole 22 , The loading and separating device 24 for the positive pole 20 includes a circuit breaker 28 for interrupting the electrical connection to the positive pole 20 and a charging switch 30 which has a charging resistance 32 is downstream. From the illustration according to 1 goes on to show that inside the battery disconnecting unit 18 a power interrupt device (CID) 33 located. This is for example as a fuse 34 educated. In addition, the battery separation unit includes 18 within the separator 26 that the negative pole 22 is assigned, a circuit breaker 36 , by which an electrically conductive connection to the negative pole 22 can be interrupted. For completeness, it should be mentioned that the housing 10 of the battery pack 13 a service plug 16 assigned. Once the service plug 16 from the case 10 of the battery pack 13 is removed, is the inside of the case 10 in which the electrically interconnected battery cells 12 are accessible from the outside. Through the service connector 16 is given an access protection. By removing the service plug 16 be in the case 10 recorded battery cells 12 safely disconnected from one pole, even if the two circuit breakers 28 respectively. 36 included in the battery disconnecting unit 18 are provided, may not be opened due to a malfunction.

The representation according to 2 Figure 3 shows short-circuit paths of currents when an external and an internal short-circuit occurs within a traction battery of electric and hybrid vehicles.

As already related to 1 discussed, shows 2 with reference to the already outlined above components of a traction battery, also a housing 10 in which a number of electrically interconnected battery cells 12 is housed. A plurality of battery cells 12 For example, more than a hundred pieces form a battery pack 13 , The individual battery cells 12 are electrically serial or parallel through cell connectors 14 connected. The service plug 16 is for safety reasons during maintenance work on the battery pack 13 deducted. The removal of the service plug 16 allows the opening of the housing 10 so only when removing the service plug 16 the interior of the case 10 is accessible. The battery cells 12 are safely disconnected in this way unipolar, even if the two circuit breakers 28 . 36 in the illustration according to 2 that the electrical connections to the positive pole 20 or to the negative pole 22 should not open due to a malfunction. Out 2 it also follows that in this embodiment, the battery disconnecting unit 18 , the loading and separating device 24 that the plus pole 20 is assigned and the power interrupt device (CID) 33 in the form of a fuse 34 includes. 2 shows that in the case of an external short circuit of the traction battery, a low-resistance short circuit path 38 is present. An external short circuit may occur, for example, when a "hot branch" occurs in an inverter of a traction drive, in which both circuit breakers of a phase are switched on due to an error, thereby forming a very low-resistance short-circuit path.

On the other hand, an internal short circuit path 40 arising as a result of an accident. In this case terminals of several battery cells are advised 12 due to mechanical deformation with electrically conductive battery parts, such as a metallic battery cover, which houses the housing 10 covers, in contact. In case of external short circuit path 38 the short-circuit current flows through the current interruption device (CID) 33 of the battery system. Become battery cells 12 using a battery cell internal power interruption device (CID) 33 have a matching of tripping characteristics of this power interruption device in the following form:
The power interruption device (CID) 33 included in the battery disconnecting unit 18 is provided triggers when occurring inadmissibly high currents much faster than arranged inside the cell Power Interrupt Devices (CID) 33 , Usually, the tripping characteristic has regard to the tripping time of a current interrupt unit (CID) 33 the battery disconnecting unit 18 over an overcurrent area 42 (compare illustration according to 3 ) one by one factor 10 Lower trip time, compared to the trip time, the in-cell power interruption units (CID) 33 exhibit. This ensures that if an external short circuit occurs according to the short circuit path 38 in 2 in the traction battery the power interrupt unit (CID) 33 of the battery system triggers quickly and at the same time no battery cell internal provided power interruption unit (CID) 33 triggers. This requires the power interrupt device (CID) 33 included in the battery disconnecting unit 18 is provided for the entire battery system, the short-circuit current, via the external short-circuit path 38 flows, can turn off against the entire battery voltage. This provides the design criterion for the shutdown capability of the power interruption device (CID) 33 represents.

If a battery internal short circuit occurs, compare the internal short circuit path 40 , the occurring short circuit current usually does not flow through the current interrupt unit 33 the battery disconnecting unit 18 ; it is rather a low-resistance short circuit, with inadmissibly high currents for the internal short circuit path 40 located battery cells 12 is connected so that at least one of the battery cell internal provided power interruption devices (CID) 33 triggers. The in-cell power interruption devices (CID) 33 are usually realized as a taper of conductors and therefore have in relation to each other large tolerances. Due to these high tolerances, there is a high probability that one of the battery cell internal power interruption devices (CID) 33 triggers faster than others in the internal short circuit path 40 current interruption devices (CID) 33 , A short-circuit current occurring in this case is against the sum voltage of all lying in the short circuit path battery cells 12 off.

In battery systems according to the prior art, this means that in the worst case, even with a battery-internal short circuit. according to the internal short-circuit path 40 all arranged there battery cells 12 must shut off against the entire battery voltage. Now that the current interruption device (CID) has occurred after the occurrence of a battery-internal short circuit 33 has responded with the shortest trip time blocks this battery cell 12 with further maintained internal short circuit path 40 the sum voltage of all in the internal short circuit path 40 lying battery cells 12 - In the worst case, the entire battery voltage - in the negative direction. This places very high demands on the battery-cell-internal current interruption units 33 , which can be fulfilled only with very high effort and therefore with considerable additional costs.

variants

The representation according to 3 are tripping characteristics of current interruption units faced, both for the battery system and the battery disconnecting unit as well as cell-internal for individual battery cells.

From the presentation 3 it turns out that a tripping characteristic flock 44 has a substantially asymptotic course. Placed over an overflow area 42 which, as shown in 3 between 800 amps and 8000 amps, is equivalent to each tripping characteristic 48 applied a tripping time.

Beyond a limit characteristic 46 arise different areas. The above the limit characteristic 46 lying tripping characteristics 48 show trip times for in-cell power interruption units 33 while with the reference numerals 50 identified tripping characteristics for a tripping time for the current interruption device (CID) 33 show, as shown in 2 in the battery disconnecting unit 18 the battery system of a traction battery is arranged.

The double arrows indicate that the tripping time corresponds to the tripping characteristics 50 below the limit characteristic 46 for a power interruption device (CID) 33 in a battery disconnecting unit 18 to at least the factor 10 is lower compared to the trip times for power interrupt units 33 , which are arranged inside the battery cell, according to the tripping characteristics 48 , which are above the limit characteristic 46 run.

In the illustration according to 4 are proposed according to the invention proposed installation locations for one or more power interruption devices (CID) 33 shown.

By relocating the installation location of the at least one power interruption device 33 for a battery system, or through the use of additional power interruption devices (CID) 33 can be achieved that the Stromabschaltfähigkeit and the voltage blocking behavior of a power interruption unit can be significantly improved. For example, in the illustration according to 4 built-in battery cells 12 the ability to turn off an overcurrent to at least half the battery voltage and, in addition, can be triggered by an in-cell Power Interrupt Device (CID) 33 disable at least half the battery voltage in the negative direction, the current interrupt device (CID) 33 of the battery system from the battery disconnecting unit 18 be relocated. In 4 it is shown that the power interruption device (CID) 33 at a first position 60 , a second position 62 , and at a third position 64 , in the middle of a series connection of battery cells 12 or a service plug 16 to be placed.

From the illustration according to 4 go the positions 60 . 62 . 64 , which according to the invention proposed installation sites for a power interruption device (CID) 33 are executed as a fuse 34 , can accept. The arrangement of the power interrupt unit 33 is not necessarily exactly symmetrical in the middle of the battery cells 12 For example, one hundred battery cells 12 not necessarily between the battery cells 12 No. 50 and no. 51 to choose. It is to be ensured that by the arrangement of the current interruption unit 33 either in the first position 60 or in the second position 62 or in the third position 64 ensures that an educated first part battery 54 , which can also be referred to as a battery module and a concomitant formation of at least one further, second sub-battery 56 (Battery module), which is defined by the location of the power interruption unit 33 can be protected.

4 shows that in the first position 60 the power interruption device (CID) 33 the first part battery 54 (Battery module) is created. There is also the possibility of the power interruption device 33 from its place of installation in the battery disconnecting unit 18 as shown in 2 directly into the service plug 16 to integrate. In this case, the installation location is through the second position 62 characterized.

There is also the possibility of the power interruption unit 33 downstream of the service connector 16 in the third position 64 to install, ie a second sub-battery 56 assigned. In the illustration according to 4 In addition, various internal battery short circuit paths are shown. Does the short circuit path include the power interrupt device (CID) 33 of the battery system, so it takes over the shutdown of the short-circuit current due to the shorter trip time. The worst case for which battery cell internal power interruption devices (CIDs) 33 are to be interpreted, is the one in which a shutdown along a short-circuit path 66 , the one complete partial battery, in this case the second partial battery 56 concerns to turn off. In this worst case, battery internal cell power interruption device (CID) 33 for half the battery voltage, or for the maximum voltage of those of the first or second sub-batteries 54 . 56 be designed, which has the largest number of battery cells 12 having.

For presentation according to 4 It should also be noted that the individual current interruption devices (CID) designed as a cross-sectional taper, for example 33 for example in cell connectors 14 within the sub-batteries 54 . 56 which the battery cells 12 electrically connected in series or in parallel, can be integrated. In the illustration according to 4 is also the battery disconnection unit 18 (Battery disconnec unit = BDU). This essentially corresponds to the battery separator units 18 already related to the 1 and 2 have been described in more detail. In the 4 is the battery-external short circuit path 38 as well as the internal short circuit path 40 , With reference number 52 is a cell internal short circuit path 52 designated, while reference numerals 66 the short-circuit path, which in the worst case by an entire sub-battery, in this case by the second sub-battery 56 and the individual battery cells connected in series there 12 extends.

In the event that battery cell internal power interruption devices (CID) 33 the battery cells 12 should not be able to turn off half the battery voltage at a low impedance short circuit, there is the possibility of the invention proposed solution following, multiple power interruption units 33 to integrate.

This embodiment of the proposed solution according to the invention can be according to the illustration 5 remove.

Out 5 it is apparent that in this embodiment the battery cell internal power interruption devices (CID) 33 safely switch off one third of the battery voltage. In this case, the use of at least two power interruption devices (CID) 33 required so that the battery pack 13 into three individual sub-batteries, namely the first sub-battery 54 , the second part battery 56 , and the third part battery 58 is divided. The individual sub-batteries 54 . 56 . 58 each comprise one third of the total number of battery cells 12 of the battery pack 13 ,

From the illustration according to 5 shows that in the case of the use of two power interruption devices (CIDs) 33 the voltage compared to the arrangement according to 2 not halve, but can further reduce and further - as in 5 by the reference numerals 68 and 70 indicated - optimized short-circuit paths also arise for unfavorable short-circuit paths.

The basis of the 3 . 4 and 5 described safety aspects significantly improved arrangements of at least one power interruption device (CID) 33 in the battery system of a traction battery for electric and hybrid vehicles, comes with the disadvantage that the at least one power interruption device (CID) 33 no longer in the battery disconnecting unit 18 is placeable, but are distributed as a separate component or components in the battery system to accommodate. Also in the in 5 illustrated embodiment of the invention is the housing 10 in which the number of battery cells 12 included is the battery disconnecting unit 18 (Battery disconnec unit = BDU) upstream. Inside the case 10 are the individual battery cells 12 through cell connectors 14 electrically interconnected. In the in 5 embodiment shown by the arrangement of the power interruption devices (CID) 33 , each designed as a fuse 34 the first part battery 54 , the second part battery 56 and the third part battery 58 formed so that this case in the event of a short circuit in the short circuit path 38 only one third of the battery voltage through the respective power interruption device (CID) 33 is to turn off. Also in the embodiment according to 5 The Battery Disconnect Unit (BDU) essentially corresponds to the battery disconnect units 18 already related to the 1 . 2 and 4 have been described.

The proposed solution according to the invention is not limited to the use of traction batteries for applications in vehicles, but can be used in the same way in batteries for stationary applications. The proposed solution according to the invention is particularly useful when used within a battery system, a plurality of battery cells 12 be connected in series, ie the voltage of the battery system can therefore assume very high maximum values.

Claims (9)

Battery pack ( 13 ) with a number of battery cells ( 12 ), with a battery disconnecting unit ( 18 ), which has a loading and separating device ( 24 ) for a positive pole ( 20 ) of the battery pack ( 13 ) and a separating device ( 26 ) for a negative pole ( 22 ) of the battery pack ( 13 ) and at least one power interruption device (CID) ( 33 ), characterized in that the at least one power interruption device (CID) ( 33 ) in rungs ( 38 . 40 ) is arranged so that the number of battery cells ( 12 ) in a first part of the battery ( 54 ) and at least one further second sub-battery ( 56 . 58 ) is divided. Battery pack ( 13 ) according to claim 1, characterized in that the at least one power interruption device (CID) ( 33 ) as a fuse ( 34 ), in particular designed as a cross-sectional taper of an electrical conductor. Battery pack ( 13 ) according to one of the preceding claims, characterized in that the number of battery cells ( 12 ) by at least two current interruption devices (CID) ( 33 ) in a first part of the battery ( 54 ), a second sub-battery ( 56 ) and a third sub-battery ( 58 ) is divided. Battery pack ( 13 ) according to one of the preceding claims, characterized in that the at least one power interrupt unit (CID) ( 33 ) in the current path ( 38 . 40 ) is arranged such that a plurality of mutually symmetrically arranged sub-batteries ( 54 . 56 . 58 ) are formed. Battery pack ( 13 ) according to one of the preceding claims, characterized in that the at least one current interruption device (CID) (CID) ( 33 ) in the current path ( 38 . 40 ) between the first sub-battery ( 54 ) and a service connector ( 16 ) is arranged. Battery pack ( 13 ) according to claim 1, characterized in that the at least one power interruption device (CID) ( 33 ) into a service connector ( 16 ) is integrated. Battery pack ( 13 ) according to one of the preceding claims, characterized in that in at least one of the sub-batteries ( 54 . 56 . 58 ) an internal power interruption device (CID) ( 33 ) is arranged that a short circuit within a respective sub-battery ( 54 . 56 . 58 ). Battery pack ( 13 ) according to one of the preceding claims, characterized in that at least in the first and second sub-battery ( 54 ) 56 ) each have an internal power interruption device (CID) ( 33 ), which is a short circuit between two adjacent battery cells ( 12 ). Battery pack ( 13 ) according to one of the preceding claims, characterized in that the at least one current interruption device (CID) (CID) ( 33 ) into a high-current path between the first and the second sub-battery ( 54 . 56 ) and / or the second and third sub-battery ( 56 . 58 ) is integrated.

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