METHOD FOR DISCHARGING BATTERY MODULES AND CONTROL DEVICE

Abstract

A method of discharging battery modules of a battery in case of a fault state of at least one of the battery modules, a respective battery module of the plurality of battery modules having at least one battery cell includes, under at least one first condition that at least one first battery cell of a first battery module of the plurality of battery modules has at least one critical state, respective second battery modules, from among the battery modules which are different from the first battery module are at least partly discharged in accordance with an order at least under a second condition. The order depending on a spatial distance between the respective second battery modules different from the first battery module and the first battery module and/or depending on a thermal resistance between the respective battery modules different from the first battery module and the first battery module.

Claims

1. A method of discharging a plurality of battery modules of a battery in case of a fault state of at least one of the battery modules, a respective battery module of the plurality of battery modules having at least one battery cell, the method comprising: under at least one first condition that at least one first battery cell of a first battery module of the plurality of battery modules has at least one critical state, respective second battery modules, from among the battery modules, which are different from the first battery module, are at least partly discharged in accordance with a determined order at least under a second condition, the order being determined depending on a spatial distance between the respective second battery modules different from the first battery module and the first battery module and/or depending on a thermal resistance between the respective second battery modules different from the first battery module and the first battery module.

2. The method according to claim 1, wherein respective battery cells comprised by the respective second battery modules and different from the first battery cell are at least partly discharged in accordance with a determined order at least under the second condition, the order being determined depending on a spatial distance with respect to the first battery cell and/or depending on a thermal resistance between the respective battery cells different from the first battery cell and the first battery cell.

3. The method according to claim 1, wherein the second condition comprises a present state of charge (SOC) of a second battery module, from among the respective second battery modules being greater than a determined state of charge limit value (G), which is between about 30% and about 50%.

4. The method according to claim 3, wherein, the plurality of battery modules comprise at least one second battery module and at least one third battery module, the at least one second battery module being at a smaller distance from the first battery module than the at least one third battery module and/or a thermal resistance between the first and second battery modules being smaller than a thermal resistance between the first and third battery modules, a discharge process of the at least one third battery module being initiated under at least one third condition that a state of charge (SOC) of at least the at least one second battery module has a maximum magnitude equal to a determined state of charge limit value (G).

5. The method according to claim 1, wherein second battery modules, from among the second battery modules, which are at a distance from the first battery module which is in a common distance range and/or have a thermal resistance with respect to the first battery module which is in a common resistance range, are discharged at least partly simultaneously.

6. The method according to claim 1, wherein the first battery module is not discharged if the at least one critical state is a state in which a temperature assigned to the first battery module or to the at least one first battery cell is greater than a determined first temperature limit value, and/or a state of charge (SOC) of the first battery module has a maximum magnitude equal to a predetermined state of charge limit value (G).

7. The method according to claim 3, wherein to at least partly discharge the respective second battery modules, during discharging of at least one second battery module of the battery modules, charge is transferred to the at least one battery module which is to be discharged later in accordance with the determined order, or is not to be discharged in accordance with the second condition and which has a state of charge (SOC) different from a full charge.

8. The method according to claim 1, wherein to at least partly discharge the respective second battery modules, at least one of the second battery modules to be discharged is discharged by a vehicle-external energy sink according to at least one measure among measures including: electrical connection to a motor vehicle-external energy store and/or electrical consumer; and/or electrical connection to a motor vehicle-external electricity grid; and/or electrical connection to a ground terminal.

9. The method according to claim 1, wherein to at least partly discharge the respective second battery modules, at least one of the second battery modules to be discharged is discharged by a motor vehicle-internal electrical consumer which is different from the battery modules and/or the at least one battery cell according to at least one electrical consumer, among the following electrical consumers: a high-voltage heater and/or heating device; an air-conditioning apparatus and/or a radiator fan; an energizable chassis component; an electric motor of the motor vehicle that is operated in idle mode; an electronic component; a charger in a power loss mode; an illuminant; an electric transmission controller; a loudspeaker and/or a horn; a pump; an antenna; an infotainment system; and/or a medium-voltage and/or low-voltage battery.

10. A control device of a motor vehicle to control discharging a plurality of battery modules of a battery of the motor vehicle in case of a fault state of at least one of the battery modules among the plurality of battery modules, a respective battery module of the plurality of battery modules having at least one battery cell, the control device comprising: a memory to store a program code; and a processor coupled to the memory and to execute the program code to control a process to, under at least one first condition that at least one first battery cell of a first battery module of the plurality of battery modules has at least one critical state, initiate at least partial discharging of respective second battery modules, from among the battery modules, which are different from the first battery module, in accordance with a determined order at least under a second condition, the order being determined depending on a spatial distance between the respective second battery modules different from the first battery module and the first battery module and/or depending on a thermal resistance between the respective second battery modules different from the first battery module and the first battery module.

11. The control device according to claim 10, wherein the process is to control to at least partially discharge respective battery cells comprised by the respective second battery modules and different from the first battery cell in accordance with a determined order at least under the second condition, the order being determined depending on a spatial distance with respect to the first battery cell and/or depending on a thermal resistance between the respective battery cells different from the first battery cell and the first battery cell.

12. The control device according to claim 10, wherein the second condition comprises a present state of charge (SOC) of a second battery module, from among the respective second battery modules being greater than a determined state of charge limit value (G), which is between about 30% and about 50%.

13. The control device according to claim 12, wherein, the plurality of battery modules comprise at least one second battery module and at least one third battery module, the at least one second battery module being at a smaller distance from the first battery module than the at least one third battery module and/or a thermal resistance between the first and second battery modules being smaller than a thermal resistance between the first and third battery modules, a discharge process of the at least one third battery module being initiated under at least one third condition that a state of charge (SOC) of at least the at least one second battery module has a maximum magnitude equal to a determined state of charge limit value (G).

14. The control device according to claim 10, wherein the process is to control to discharge at least partly simultaneously the second battery modules, from among the battery modules, which are at a distance from the first battery module which is in a common distance range and/or have a thermal resistance with respect to the first battery module which is in a common resistance range.

15. The control device according to claim 10, wherein the first battery module is not discharged if the at least one critical state is a state in which a temperature assigned to the first battery module or to the at least one first battery cell is greater than a determined first temperature limit value, and/or a state of charge (SOC) of the first battery module has a maximum magnitude equal to a predetermined state of charge limit value (G).

16. The control device according to claim 12, wherein to at least partly discharge the respective second battery modules, during discharging of at least one second battery module of the battery modules, the process is to control transfer a charge to the at least one battery module which is to be discharged later in accordance with the determined order, or is not to be discharged in accordance with the second condition and which has a state of charge (SOC) different from a full charge.

17. The control device according to claim 10, wherein to at least partly discharge the respective second battery modules, the process is to control to discharge at least one of the second battery modules to be discharged by a vehicle-external energy sink according to at least one measure among measures including: electrical connection to a motor vehicle-external energy store and/or electrical consumer; and/or electrical connection to a motor vehicle-external electricity grid; and/or electrical connection to a ground terminal.

18. The control device according to claim 10, wherein to at least partly discharge the respective second battery modules, the process is control to discharge at least one of the second battery modules to be discharged by a motor vehicle-internal electrical consumer which is different from the battery modules and/or the at least one battery cell according to at least one electrical consumer, among the following electrical consumers: a high-voltage heater and/or heating device; an air-conditioning apparatus and/or a radiator fan; an energizable chassis component; an electric motor of the motor vehicle that is operated in idle mode; an electronic component; a charger in a power loss mode; an illuminant; an electric transmission controller; a loudspeaker and/or a horn; a pump; an antenna; an infotainment system; and/or a medium-voltage and/or low-voltage battery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] These and other aspects and advantages will become more apparent and more readily appreciated from the following description of the examples, taken in conjunction with the accompanying drawings of which:

[0038] FIG. 1 shows a schematic illustration of a high-voltage battery with a plurality of battery modules at a first point in time, one of which battery modules is in a critical state and is discharged via a consumer in accordance with an example;

[0039] FIG. 2 shows a schematic illustration of the battery from FIG. 1 at a later point in time, the battery modules closest to the critical battery module being discharged via the consumer, in accordance with a further example;

[0040] FIG. 3 shows a schematic illustration of the battery from FIG. 1 and FIG. 2 at an even later point in time, at which the battery modules that are even further away from the critical battery module are discharged, in accordance with an example;

[0041] FIG. 4 shows a schematic illustration of a battery with a defective battery module in accordance with a further example; and

[0042] FIG. 5 shows a schematic illustration of the battery from FIG. 4, in which the battery modules closest to the critical battery module are discharged by their charge being transferred to battery modules further away, in accordance with a further example.

DETAILED DESCRIPTION

[0043] The examples explained below may be examples of an invention. In the examples, the described components may each constitute individual features which may be considered independently of one another and which each may also develop the examples of the invention independently of one another. Therefore, the disclosure is also intended to encompass combinations of the features of the examples other than those presented. Furthermore, the described examples are also able to be supplemented by further features from among those already described.

[0044] In the figures, identical reference signs in each case designate functionally identical elements.

[0045] FIG. 1 shows a schematic illustration of a battery 10, embodied as a high-voltage battery in this example, at a first point in time t1 in accordance with the example. In this example, the battery 10 has a plurality of battery modules 12, each of which in turn can comprise a plurality of battery cells, which are not explicitly illustrated in the present case. Furthermore, only some of the battery modules 12 are provided with a reference sign, for reasons of clarity. The battery modules 12 can additionally be arranged in a common high-voltage battery housing 14. Such a high-voltage battery 10 can be arranged for example in an underbody region of a motor vehicle.

[0046] In this case, the fire hazard stemming from such a high-voltage battery 10 scales with the state of charge thereof. In other words, a fully charged battery 10 has the greatest energy content and thus the greatest fire hazard in the event of an accident. Accordingly, a fully charged battery burns very intensely, while a half fully charged battery often only outgasses and does not catch figure. A significantly drained battery has a very high probability of not catching fire at all. The examples use this insight, then, in order to enable targeted draining or consuming of the energy stored in such a battery 10 according to the “star method” described in greater detail below. In principle, such a battery 10 can be discharged with the aid of consumers 16, which can be manifested in various ways. One such consumer 16 is illustrated by way of example in FIG. 1, FIG. 2 and FIG. 3. Said consumer 16 can be either a vehicle-internal consumer or a vehicle-external consumer. Once again various consumers are in each case suitable here. In principle, appropriate vehicle-internal consumers are any high-voltage, medium-voltage or low-voltage electrical systems and/or electronic systems (collectively may be referred to as electrical consumers), which entail the potential of consuming a high electrical energy content within a relatively short time, in particular by way of reactive power. Besides such consumers which are present in the vehicle anyway and which perform other tasks and functions in the normal state, components introduced separately for this purpose can optionally also be provided as such consumers 16, which components are then configured to convert electrical energy into heat and/or light and/or sounds and/or electromagnetic waves having any desired wavelengths and/or kinetic energy. In order to draw energy from the battery 10 by use of vehicle-external consumers, it is also possible to use bidirectional charging, for example. By this way, the vehicle battery 10, via a charging cable not illustrated in more specific detail here, can be connected to other electrical storage media, for example other high-voltage batteries of another vehicle, or from the fire department, or a connector which can be grounded could also be used in order to dissipate the energy to be drawn from the battery 10 into the ground.

[0047] There are in turn a number of possibilities in order then to discharge the battery 10 as efficiently as possible; these possibilities will now be explained in greater detail below. These discharge methods begin firstly with the detection of a specific critical state of at least one of the battery modules 12a, as is illustrated at the first point in time t1 in FIG. 1. Such a critical state may be present if for example an irregularly boosted temperature, for example of between 80° C. and 140° C. is detected in a cell module 12, such as in a first cell module 12a in this example. A critical state may also be deemed to have been detected if an even higher temperature is detected. In this case, it may be advantageous primarily if a distinction is drawn between at least two different critical states Z1, Z2. A first critical state Z1 is illustrated for the first battery module 12a in FIG. 1, for example, and the second critical state Z2 in FIG. 2. If the temperature of the relevant cell 12a is for example in a first temperature range, for example between 80° C. and 140° C., then this can correspond to the first critical state Z1, and if by contrast the temperature is even higher then this can correspond to the second critical state Z2. The temperature of the cells of the individual battery modules 12 can moreover be detected by one or more temperature sensors per battery module 12, which are installed in particular within each battery module 12. Already existing temperature sensors can primarily be used for this purpose in an efficient way. Thus, if a critical state Z1, Z2 of a relevant battery module 12a is detected, then it is possible to initiate selective discharging, e.g. firstly of this corresponding battery module 12a, via the electrical consumers 16 mentioned. A reduction of the state of charge of the relevant cell module 12a can be achieved as a result, and so possible development of a fire can be prevented early and the battery module 12a only outgasses without flames. In an example, discharging of the battery module 12a, as is illustrated in FIG. 1, may take place or to be initiated only if said battery module 12a is in the defined first critical state Z1. If the thermal propagation within the battery module 12a has already progressed too far, for example, and if the temperature of the battery module 12a has already indeed increased too much, such that it is no longer possible to stop this module 12a from catching fire, which is characterized by the second critical state Z2, then discharging of the relevant module 12a is dispensed with and the method proceeds directly to the discharging of adjacent battery modules 12b, as is illustrated for a later second point in time t2 in FIG. 2.

[0048] In this case, FIG. 2 shows in particular the battery module 10 from FIG. 1 at the later point in time t2 relative to the first point in time t1. The battery modules closest to the critical battery module 12a are designated by 12b in the present case. These battery modules 12b may then be discharged next, in particular once again via one or more of the consumers 16 mentioned above. The battery modules 12 need not necessarily be completely discharged in accordance with this discharge strategy. On the contrary, these battery modules 12b may be discharged only until a specific state of charge limit value G is reached or undershot, which may be between 30 and 50%. If one or more of these closest battery modules 12b already has a state of charge SOC that is less than this limit value G, then targeted discharging of these modules 12b can also be dispensed with and it is possible to proceed directly to the next battery modules 12. The trigger for discharging these battery modules 12b thus constitutes a battery module 12a in a critical state, in particular in the first critical state Z1 or, as in the present case, in the second critical state Z2. Discharging of the battery module 12a which is in the first critical state Z1 can likewise be dispensed with as well if this battery module already has an initial state of charge SOC that is less than this predetermined state of charge limit value G. In other words, if an initial battery module 12a is present whose initial temperature exceeds 140° C., or an initial battery module 12a with an increased temperature below a noncritical state of charge value G, for example between 30 and 50%, then initial discharging of this first battery module 12a can be dispensed with, and the closest battery modules 12b can directly be selectively discharged. In other words, if these closest battery modules 12b are all discharged below the predefined critical state of charge value G, then the nearest adjacent cell modules 12c can in turn be discharged, as is illustrated at an even later third point in time t3 in FIG. 3. In this regard, the method can continue progressively until all the battery modules 12 are discharged or are at least discharged below the predefined critical state of charge limit value G. The thermal resistance between the battery modules 12 can optionally also be taken into account when defining the discharge order. By way of example, if one of the modules 12b closest to the first module 12a is thermally insulated from the first module 12a better than a module 12c that is further away is thermally insulated from the first module 12a, then firstly the module 12c that is further away can also be discharged before the closest module 12b. Often, however, the modules 12 are embodied identically and are thermally insulated from one another in an identical manner, such that the thermal resistance increases with increasing spatial distance with respect to the first battery module 12a, such that even taking the thermal resistance into account, the resulting discharge order may be the same as may result if only the spatial distance were taken into account.

[0049] However, discharging in accordance with this procedure can be realized not just by use of the electrical consumers 16 described, but additionally or alternatively also by battery-internal redistribution of the states of charge SOC between the individual high-voltage battery modules 12, as is illustrated in FIGS. 4 and 5. FIGS. 4 and 5 each show a further example of a high-voltage battery 10, which can be constructed in particular as described above. In this example, the first battery module 12a once again has a critical state Z1, Z2. In particular, FIG. 4 already shows a state of this battery module 12a in which its state of charge SOC is already very low and is only 35% in this example. This may have been achieved for example by previous targeted discharging of this battery module 12a as described for example in relation to FIG. 1, or, as is intended to be illustrated in this example, by transfer of charge to battery modules 12c that are further away.

[0050] In this example, the other battery modules 12 have a respective state of charge SOC that is different from full charge, that is to say is different from 100%. In this example, the battery modules 12c that are the furthest away or at least further away from the critical cell or the critical battery module 12a are then used in order to take up energy from the critical battery module 12a and the battery modules 12b closest to the critical battery module. In other words, here as well once again the battery modules 12b closest to the critical cell module 12a are discharged first, in particular before the battery modules 12c that are even further away, by at least part of the charge taken up in said closest battery modules 12b being transferred to the modules 12c that are further away. As is illustrated in FIG. 5, the closest battery modules 12b may be for example correspondingly discharged from an initial state of charge of 90%, as is illustrated in FIG. 4, to now 45%, as illustrated in FIG. 5, while the modules 12c that are further away were charged from initially 90% firstly to 93% by taking up the charge of the defective module 12a, as illustrated at an earlier point in time t4 in FIG. 4, and then to now 100% by taking up charge of the module 12b, as illustrated at a later point in time t5 in FIG. 5. This concept thus involves implementing a redistribution of the charge within the battery 10. What is prioritized is the discharge of the overheated module 12a until for example a noncritical state of charge SOC in relation to fire behavior is reached, for example of 35%. The electrical energy is taken up by the other cell modules 12c, which accordingly become charged further. In this case, cell modules 12c that are further away may be charged, in particular once again according to the star method already described above. If permitted by the capacitive reserves, the adjacent battery modules 12b can also be discharged at the expense of the battery modules 12c that are further away.

[0051] This strategy may be particularly advantageous primarily in combination with the above-described discharge via a consumer 16. The battery-internal charge transfer additionally makes it possible to gain a time advantage in order to inhibit the thermal propagation. The outer battery modules 12c can then be discharged via battery-external consumers 16, for example.

[0052] In order to implement the discharge strategies described, the individual battery modules 12 or the cells thereof can be interconnected with one another in a correspondingly suitable manner. Suitable implementations are sufficiently known here to the person skilled in the art and are therefore not explained in any greater detail.

[0053] Overall, the examples show use of energy consumers to reduce the capacity of a high-voltage battery in the imminent event of an accident. The state of charge of overheated battery modules can be lowered in a targeted manner by the star method described. A lower state of charge of an overheated battery module can avert a fire of the corresponding battery module and thus spreading of a fire. Battery modules having a low state of charge can maximally outgas and are significantly less dangerous than a fire. If the overheated battery module is past saving, that is to say a fire arises there, the states of charge of the adjacent battery modules can accordingly be reduced to a noncritical state of charge, with the result that the fire cannot spread.

[0054] A description has been provided with particular reference to examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims, which may include the phrase “at least one of A, B and C” as an alternative expression that refers to one or more of A, B or C, contrary to the holding in Superguide v. DIRECTV, 358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).