Patent Publication Number: US-2021167473-A1

Title: Method for disconnecting a battery

Description:
FIELD 
     The present invention relates to a method for disconnecting a battery, in particular a high-voltage battery, including at least two battery cells from at least one electrical component of a vehicle. Moreover, the present invention relates to a device for carrying out the method. 
     BACKGROUND INFORMATION 
     Conventionally, when a vehicle or an electric machine of the vehicle is stopped, the battery of the vehicle is disconnected from the power electronics by a relay. Conventionally, the relay is opened in emergency situations, for example in the event of an accident. Generally, one relay is integrated into a positive “high-side” path, and a further relay is integrated into a negative “low-side” path, the paths denoting the two lines that connect the battery to the electric machine. 
     German Patent Application No. DE 10 2015 002 069 A1 describes a battery cell for a battery of a motor vehicle. The battery cell may be connected to further battery cells of the battery via two electrical terminals. It is also described that a transport state for the battery may be provided. 
     A battery system including a battery with a plurality of battery modules is described in German Patent Application No. DE 10 2012 205 395 A1. 
     German Patent Application No. DE 10 2015 215 797 A1 describes a battery that includes an integrated discharge circuit. 
     SUMMARY 
     The present invention relates to a method for disconnecting a battery, and a device for disconnecting a battery. Further features and details of the present invention result from the description herein, and the figures. Of course, features and details that are described in conjunction with the method according to the present invention also apply in conjunction with the device according to the present invention, and vice versa in each case, and mutual reference is or may always be made to the individual aspects of the present invention. 
     In particular, in accordance with an example embodiment of the present invention, protection is provided by a method for disconnecting an (in particular rechargeable) battery, preferably a high-voltage battery, including at least two battery cells from at least one electrical component, in particular a drive component, of a vehicle. The disconnection advantageously takes place when the component, in particular the drive component, which is preferably designed as an electric motor or an electric machine (E-machine), is switched off. 
     The electrical component may be designed as power electronics and/or as an electrical consumer of a vehicle electrical system of the vehicle. In addition, the electrical component may be designed as a high-voltage component and/or as a drive component of the vehicle, such as an electric motor. Similarly, it is possible for the battery to be designed as a rechargeable high-voltage battery for supplying power to the high-voltage component to allow a movement of the vehicle. As an example, the battery is a 400 V or 800 V battery. 
     In the method according to an example embodiment of the present invention, it is advantageous for the vehicle to be designed as a passenger automobile or truck or the like. The vehicle is advantageously designed as an electric vehicle that includes a hybrid drive or only an electric drive. Similarly, the component may be a component of a high-voltage drive train of an E-machine of the vehicle. In these types of electric vehicles it is thus possible to provide a topology made up of a high-voltage battery pack (i.e., the battery), a DC link, and power electronics of the E-machine. 
     In a method according to an example embodiment of the present invention, it may be provided that at least two switching units are associated with each of the battery cells of the battery. In other words, for each battery cell, a system including two switching units may be provided and in particular integrated into the battery cell. It is also possible for all battery cells of the battery to include these two switching units, and thus to be disconnectable from the component. This allows a complete disconnection of the battery from the component. Alternatively, in addition to these battery cells including the switching units, other types of battery cells are provided in the battery which cannot be disconnected in the manner described according to the present invention. 
     According to an example embodiment of the present invention, the battery cells (in particular in each case as a function of the at least two switching units in each case) may be electrically connected to the component via the particular switching units, so that a power supply for the component is provided by the battery. This allows an operation of the component, for example a rotational movement of a drive component and/or a movement of the vehicle. In contrast, by the disconnection from the component, the power supply may be deactivated, and the above-mentioned operation of the component may thus be stopped. 
     In a method according to an example embodiment of the present invention, the following steps for the disconnection from the component may be carried out, preferably in succession in the indicated order or in an arbitrary order, it also being possible to carry out individual steps repeatedly:
     a) switching the at least two switching units of a first of the battery cells,   b) switching the at least two switching units of at least one second (and optionally of a third and fourth, etc.) of the battery cells, in particular gradually, in each case after the preceding switching has occurred, preferably until all switching units of all battery cells have been switched.   

     In other words, at least two battery cells of the battery may be electrically disconnected from the at least one component via at least two switching units in each case. The switching may involve a closing as well as an opening, the switching units in each case being designed as electronic switching units, for example. Thus, the switching in particular does not relate to a mechanical switching (mechanical opening or closing), but, rather, a switching over from the blocking state into the conducting state and/or vice versa. This allows a reliable and flexible switching of the battery cells. In addition, the use of relays may be avoided. In particular, for relays it is known that spark gaps may result from the mechanical disconnection in the direct voltage line. It is often technically complicated to avoid a defect in the relay (such as sticking) which is thus possible. Furthermore, the use of relays is associated with higher costs. In addition, these disadvantages may be at least reduced by a method according to the present invention. 
     In a method according to an example embodiment of the present invention and/or a device according to an example embodiment of the present invention, it may be provided to dispense with the relays that generally connect the battery to the component and/or that are integrated into the high-side and/or low-side path. Instead, switching units that are not designed as relays and/or as electronic switching units and/or integrated into the battery cells may be used. The failure rate with respect to the relay may thus be reduced. In addition, installation space may be saved. 
     The disconnection and/or the carrying out of the described method steps of a method according to the present invention may be initiated, for example, when an electronics system of the vehicle detects a user input for stopping the motor of the vehicle and/or an emergency involving the vehicle. 
     In a method according to an example embodiment of the present invention, it may be advantageous to gradually carry out the switching of the at least two switching units of at least the second (and optionally further) of the battery cells, in each case after the preceding switching is carried out. In other words, a first of the two switching units (of a certain battery cell) may be initially switched, and a second of the two switching units (of the certain battery cell) is not switched until after a delay time. This switching sequence may optionally be subsequently repeated for further battery cells. The sequential switching of the switching units for each battery cell may thus take place sequentially, battery cell by battery cell. Jumps in voltage and/or current during the disconnection may thus be reduced. 
     A switching duration for each switching unit and/or the delay time may be, for example, in the range of 1 ns to 100 ns, preferably 10 ns to 50 ns. The switching duration or delay time is preferably less than 100 ns, which for the disconnection may result in a total time period of several 10 μs for the battery. The time period for the disconnection is thus also reduced in comparison to the relay. An improved and controlled secure state may thus be generated. 
     According to one advantageous refinement of the present invention, it may be provided that step b) is carried out only after step a), and in particular each further gradual switching after the preceding switching is not carried out until a switch-on condition is present, the gradual switching preferably taking place in each case as a function of time and/or current, preferably as a function of an electric current detection in the current path of the switching unit utilized for the preceding switching. Thus, for example, the switching according to step b) may also take place as a function of an electric current detection in the current path of the switching unit utilized for the switching according to step a). The switch-on condition may preferably be the current intensity exceeding, falling below, or reaching a predetermined current intensity, which is detected in particular after the switching in the current path in the switching unit utilized for this switching. 
     Furthermore, within the scope of the present invention, it is possible that for switching the at least two switching units of the first and/or second and/or at least one further of the battery cells, in each case the two switching units are sequentially switched after a delay time. The delay time may be predefined, for example, by electronics of the battery cell (in particular by an appropriate activation of the switching units by the electronics). Such electronics are, for example, integrated into each of the battery cells of the battery. 
     In addition, it may be possible for the at least two switching units in each case to be designed as at least one coupling switching unit and one short-circuit switching unit, the coupling switching unit preferably being integrated into a current path of the particular battery cell (in series with same), and the short-circuit switching unit being integrated into a current path in parallel to the particular battery cell, these switching units preferably being sequentially switchable for the disconnection. All battery cells or switching units of the battery cells may be designed according to this arrangement. To disconnect one of the battery cells from the component, the short-circuit switching unit of this battery cell may initially be closed, and the coupling switching unit of this battery cell may be opened only afterwards (after a delay time, for example). This operation may be repeated for the further battery cells for the complete (electrical) disconnection of the battery. 
     In a method according to an example embodiment of the present invention, the disconnection may be understood to mean that the disconnection takes place not in the sense of a physical separation of the electrical connection, but rather, takes place electrically in such a way that an electric current flow is blocked by electronic switches (such as transistors or field effect transistors). Similarly, the switching units may be such electronic switches, preferably power switches. 
     In addition, it is optionally possible that for the particular disconnection of the battery cells, the short-circuit switching unit of the particular battery cell is initially switched, in particular closed, and after a delay time the coupling switching unit is switched, in particular opened. A reliable disconnection of the battery cells is thus possible. This switching pattern may be sequentially repeated for further battery cells. 
     In a further option, it may be provided that for disconnecting further battery cells, they are gradually disconnected from the at least one component, at least 5 or at least 10 or at least 20 battery cells being disconnected in succession. The voltage or the electric current delivered to the component by the battery may be gradually reduced in this way. 
     Furthermore, it is advantageous when, within the scope of the present invention, the battery is designed as a high-voltage battery, for example a 400 V (volt) or 800 V battery. Alternatively or additionally, the switching units may be integrated into the battery. This allows a very space-saving design. 
     Moreover, the present invention relates to a device for disconnecting a battery including at least two battery cells from at least one electrical component of a vehicle. In accordance with an example embodiment of the present invention, It is provided that the device is designed to carry out a method according to the present invention. The device according to the present invention thus yields the same advantages as those described in detail with regard to a method according to the present invention. 
     Further advantages, features, and particulars of the present invention result from the following description in which exemplary embodiments of the present invention are described in greater detail with reference to the figures. The features mentioned in the description may in each case be important to the present invention, alone or in any arbitrary combination. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic representation for illustrating a method according to an example embodiment of the present invention. 
         FIG. 2  shows a schematic representation of a device according to the present invention for illustrating a method according to an example embodiment of the present invention. 
         FIG. 3  shows a schematic representation of a sequence of a method according to an example embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     In the figures, identical reference numerals are used for the same technical features, even of different exemplary embodiments. 
     A method according to an example embodiment of the present invention is schematically illustrated with reference to  FIGS. 1 through 3 , it being possible in particular for component  11  to be a drive component  11  of a vehicle  10 . This component is supplied with power by a battery  12 , in particular a high-voltage battery  12 , and thus operated. For this purpose, battery  12  may be connected to component  11  via two current paths  15 ,  16  (high-side  15  and low-side  16 ). 
       FIG. 2  shows a device  100  according to an example embodiment of the present invention for carrying out a method according to the present invention in greater detail. 
     At least two battery cells  30   a,    30   b  of battery  12  may be electrically connected to the at least one component  11 , and thus switched on, via at least two switching units  20   a,    20   b  in each case. 
     It is apparent that at least two switching units  21  are associated with each of battery cells  30 , battery cells  30  in each case being electrically connected to component  11  as a function of the at least two switching units  21  in each case, so that a power supply for component  11  is provided by battery  12 . 
     Battery  12  may include a first battery cell  30   a,  a second battery cell  30   b,  and optionally further battery cells  30  up to an nth battery cell  30   n.  Each of these battery cells  30  may be associated with at least two or exactly two switching units  20 . Similarly, at least two first switching units  20   a  may be associated with first battery cell  30   a,  at least two second switching units  20   b  may be associated with second battery cell  30   b,  and at least two nth switching units  20   n  may be associated with nth battery cell  30   n  (n is an arbitrary integer). The at least two switching units  20  for each battery cell  30  may also be subdivided into a coupling switching unit  22  and a short-circuit switching unit  23 . Coupling switching unit  22  is integrated, for example, into the same current path  21  as that of associated battery cell  30 . Short-circuit switching unit  23  together with further short-circuit switching units  23  is integrated, for example, into a current path that leads from the DC link of the vehicle or from component  11  to a ground potential  40 . Coupling units  22  may connect associated battery cell  30  to component  11 , whereas short-circuit switching units  23  may bridge battery cells  30  associated with the component. 
       FIG. 2  is to be understood only in a representative sense, so that even further battery cells  30  may be provided and gradually added and/or disconnected, it being possible only by way of example for at least 5 or at least 10 or at least 20 battery cells  30  to be added in succession and/or subsequently again disconnected. In particular, the at least one particular switching unit  20  may include at least one coupling switching unit  22  and one short-circuit switching unit  23  that is associated with the particular battery cell  30 , and that may be reciprocally switched over to add and/or disconnect this battery cell  30 . 
     According to  FIG. 3 , a gradual adding and subsequently a gradual disconnection are initially illustrated for better understanding of the present invention. An example of a profile of a voltage  2  and of an electric current  3  in the current path between battery  12  and component  11  is shown as a function of time t. 
     The addition or the disconnection may take place in each case only when a switch-on condition for the preceding addition or disconnection is present. For this purpose, the gradual addition or disconnection may each be carried out as a function of an electric current detection in the current path of switching unit  20  that is utilized for this addition or disconnection. 
     The addition may take place, for example, until a total voltage U is reached by a voltage  2  of battery  12 . 
     For a first addition  1   a , initially switching unit S 2 _ n  (shown in  FIG. 2 ) may be closed and S 1 _ n  may be opened. A time period may then be awaited until current  3  has died down (i.e., remains at 0 ampere). The maximum current intensity of current  3  is limited in this way. This may be carried out in a time-controlled or current-controlled manner, for example, by electronics in battery  12 . For a second addition  1   b , switching unit S 2 _ 2  may be subsequently closed and switching unit S 1 _ 2  may be opened. Likewise, after the presence of the switch-on condition, i.e., in particular the time period, a third addition  1   c  may take place. The addition may be carried out multiple times for further battery cells  30 , up to an nth addition in which a switching unit S 2 _ 1  is closed and a switching unit S 1 _ 1  is opened. The switching units, which are associated with a shared battery cell  30 , may optionally be reciprocally opened. When all switches S 1 _ 1  through S 1 _ n  are opened and correspondingly all switches S 2 _ 1  through S 2 _ n  are closed, the full DC link voltage is present and the power electronics may start E-motor  11  or component  11 . 
     To subsequently allow a disconnection of battery  12  from component  11  in order to stop E-motor  11  and/or in the event of an emergency, according to a method according to the present invention a switching of the at least two switching units  21  of a first battery cell  30   a  of battery cells  30  may initially take place, and then a switching of the least two switching units  21  of at least one second battery cell  30   b  of battery cells  30  may take place. The switching may also be carried out for further battery cells  30 , so that a first disconnection  2   a  of first battery cell  30   a  initially takes place in that switching unit S 1 _ 1  is closed, and after a delay time switching unit S 2 _ 1  is opened. Switching unit S 1 _ 2  may subsequently be closed and S 2 _ 2  may be opened in order to carry out a second disconnection  2   b  for second battery cell  30   b  of battery cells  30 . A third disconnection  2   c  may similarly be carried out for a further battery cell  30 . Lastly, an nth disconnection may be effectuated by closing switching unit S 1 _ n  and opening switching unit S 2 _ n  (in particular after the delay time). In particular, the disconnection of battery cells  30  is thus carried out in the reverse order as for the addition. 
     The above explanation of the specific embodiments describes the present invention solely in terms of examples. Of course, individual features of the specific embodiments, if technically feasible, may be freely combined with one another without departing from the scope of the present invention.