Transfer device, method for operating a transfer device

Abstract

Charging device for a battery, wherein the battery comprises a series connection of at least two battery cells (BT1,..., BT12), wherein a positive terminal of each odd-numbered battery cell (BT1, BT3, ..., BT11) and a negative terminal of each even-numbered battery cell (BT2, BT4, ..., BT12) of the series connection of all battery cells (BT1,..., BT12) or a first subset of these battery cells (BT1,..., BT12) can be connected to a first connecting line (BL1) via a switching element (S1,...,S12), wherein a positive terminal of each even-numbered battery cell (BT2, BT4, ..., BT12) and a negative terminal of each odd-numbered battery cell (BT1, BT3, ..., BT11) of the series connection of all battery cells (BT1,..., BT12) or the first subset of these battery cells (BT1,..., BT12) can be connected to a first connecting line (BL1) via a switching element (S1,...,S12) is connectable to a further connecting line (BL2), wherein the transfer device (1) comprises at least one first transfer branch (2) with at least one capacitive element (C), characterized in that the first connecting line (BL1) is connectable via a first changeover switching element (WS1) to a first terminal (A1) as well as to a further terminal (A2) of the transfer branch (2), wherein the further connecting line (BL2) is connectable via a further changeover switching element (WS2) to the first terminal (A1) as well as to the further terminal (A2) of the transfer branch (2), wherein a connection-line-side terminal of the first changeover switching element (WS1) is connected via a first inductive connecting element (VL1) to the first connecting line (BL1) and / or a connection-line-side terminal of the further changeover switching element (WS2) is connected via a further inductive connecting element (VL2) to the further connecting line (BL2). is.

Description

The invention relates to a charge reversal device for a battery and to a method for operating such a charge reversal device. The invention further relates to a vehicle having such a transfer device.U.S. Pat. No. 10,446,880 B2 discloses a device for balancing a battery stack having two or more battery modules using a resonant circuit.DE 10 2010 029 015 A1 discloses a circuit for a battery which enables inductive cell balancing with reduced circuit complexity.U.S. Pat. No. 10,396,569 B2 discloses a system for battery cell balancing using an LC resonance.DE 10 2018 221 099 A1 discloses a charge reversal device for a battery, wherein a charge reversal branch comprises a series connection of at least one capacitive element and at least one inductive element.CN 103904740 A relates to the technical field of power management systems for energy stores, in particular to a method and system for voltage compensation in a management system for an energy store. WO 2018 / 134827 A1 relates to the field of battery charging and balancing. More particularly, the invention relates to a hybrid system and method for balancing series connected batteries.US 2017 / 093183 A1 relates generally to the field of power electronics, in particular to a device for compensating battery powers.The technical problem arises to create a recharging device for a battery, a method for operating such a recharging device, and a vehicle with such a recharging device, which ensure recharging with a high recharging current and thus a quick recharging over time.The solution of the technical problem is achieved by the subject matters having the features of the independent claims. Further advantageous embodiments of the invention are evident from the dependent claims.A charge reversal device for a battery is proposed, wherein the battery comprises a series connection of at least two battery cells. The battery preferably comprises a series connection of more than two battery cells, in particular three, four, five, six, seven, eight or nine or more than nine battery cells. The series circuit can in this case comprise an odd number of battery cells or an even number of battery cells.The battery can in particular form a vehicle battery or a part of a vehicle battery. The vehicle battery may be, in particular, a traction battery that serves to provide energy for the operation of an electric machine for driving the vehicle.A positive pole of each odd battery cell and a negative pole of each even battery cell of the series circuit of all battery cells or of each odd battery cell of a series circuit of a first subset of these battery cells can be connected to a first connecting line via a switching element. A first subset can comprise a plurality of, but not all, battery cells of the battery, wherein the battery cells of the first subset are, however, battery cells connected in series.An odd battery cell herein denotes an odd-numbered battery cell, the odd-numbered battery cell indicating the placement of the battery cell in the order of the series-connected battery cells. In other words, the ordinal number serves to identify the location at which the battery cell is located within the series of series-connected battery cells. An odd battery cell is therefore, for example, the first battery cell of the series circuit, the third battery cell of the series circuit, the fifth battery cell of the series circuit, etc. Accordingly, an even battery cell denotes a battery cell having an even atomic number. A straight battery cell is, for example, the second battery cell of the series circuit, the fourth battery cell of the series circuit, the sixth battery cell of the series circuit, etc.It is possible that each positive pole of each odd battery cell and each negative pole of each even battery cell can be connected to the first connecting line via a respective switching element, wherein the switching elements are formed separately from one another. However, if a negative pole of an even battery cell is connected to a positive pole of an odd battery cell, these poles can be connectable to the first connecting line via a common switching element.Furthermore, a positive pole of each even battery cell and a negative pole of each odd battery cell of the series circuit of all battery cells or of each even battery cell of the first subset of these battery cells can be connected via a switching element to a further connecting line, that is to say a second connecting line.It is possible that all positive poles of each even battery cell and all negative poles of each odd battery cell can be connected to the further connecting line via switching elements formed separately from one another. However, if a negative pole of an odd battery cell is connected to a positive pole of an even battery cell, these poles can be connectable to the further connecting line via a common switching element.The number of switching elements can thus be greater by one than the number of series-connected battery cells.In the sense of this invention, "connected" means that the elements connected to one another can be electrically connected, in particular directly connected. A direct connection may refer to a connection via an electrical connection element, e.g. a line, but not via an electrical or electronic component.The transfer device comprises the explained switching elements for connecting the poles of the battery cells to the corresponding connecting lines.Furthermore, the device comprises the explained connecting lines.Furthermore, the transfer device comprises at least one first transfer branch, which can also be referred to as a first transfer section. In this case, a first connection of the charge reversal branch can be connected or connected, in particular permanently connected, to the first connecting line, in particular via exactly or at least one switching element. Furthermore, a further connection of the charge reversal branch can be connected to the further connecting line, in particular via exactly one or at least one further switching element, or is connected, in particular permanently connected.The first and the further connecting line, which can also be referred to as second connecting line, are formed here as mutually different connecting lines.The first and the further connection of the transfer branch are connections of the transfer branch which are different from one another. The charge reversal branch can thus comprise a totality or an overall circuit of electrical or electronic components which is arranged between the first and the further connection of the charge reversal branch.Furthermore, the charge reversal device comprises at least one first charge reversal branch having at least one capacitive element. Preferably, the charge reversal branch comprises a series connection of at least one capacitive element and at least one inductive element. The fact that the charge reversal branch comprises a component can mean that the charge reversal branch comprises, in addition to this component, also further electrical or electronic components. A capacitive element can be designed in particular as a capacitor. An inductive element can be designed in particular as a coil. The series connection of at least one capacitive and at least one inductive element forms an oscillating circuit.The capacitive element of the charge reversal branch can also be referred to as a charge reversal capacitor. This capacitive element serves as a buffer for electrical energy / charge during charge balancing. A process for the charge equalization between different battery cells can in this case comprise a discharging process and a charging process.Thus, it is possible, for example, in a discharging process to transport charge from one or more battery cell(s) into the capacitive element, in particular via a corresponding current flow. After termination of this transport, electrical energy / charge can then be transported in a charging process from the capacitive element of the charge reversal branch into one or more battery cell(s), in particular likewise via a corresponding current flow. In this case, a battery cell, from which electrical energy is transported in the discharging process into the capacitive element of the charge reversal branch, is preferably not part of the battery cells, into which electrical energy / charge is transported in the charging process from the capacitive element of the charge reversal branch. Preferably, all battery cells from which electrical energy / charge is transported in the discharging process into the capacitive element of the charge reversal branch are different from the battery cells into which electrical energy / charge is transported in the charging process from the capacitive element of the charge reversal branch.The presence of the inductive element in the charge reversal branch advantageously means that no undesirably high currents can occur during the discharging process or the charging process. This advantageously ensures operability of the transfer device in an improved manner.The transfer device can of course comprise at least one control device for controlling the switching elements, in particular for setting switching times of the switching elements. This control device can be designed as a computing device or can comprise such a device. A computing device can be designed in particular as a microcontroller or as an integrated circuit, for example as an FPGA.Furthermore, the transfer device can comprise an evaluation device. The evaluation device and the explained control device can be designed as a common device. The evaluation device can also be designed as a computing device or can comprise such a computing device. By means of the evaluation device, variables explained in more detail below can be evaluated.It is possible that the first connection can be connected both to the first connecting line and to the further connecting line, in particular by means of a switching element, e.g. by means of a changeover switching element. However, the first terminal cannot be simultaneously connected to both the first and the further connection line. In other words, a first connection connectable to the first and further connecting line can be connected to the first connecting line, but not to the further connecting line, in a first state, and to the further connecting line, but not to the first connecting line, in a further state. As explained in more detail below, however, it is also possible in particular for the first connection to be connectable or connected to the first connecting line but not to the further connecting line. In other words, this can mean that the charge reversal device is configured such that no electrical connection can be established between the first terminal and the further connecting line.Accordingly, it is possible for the further connection to be connectable both to the first connecting line and to the further connecting line, in particular by means of a switching element, for example by means of a changeover switching element. However, the further connection cannot be simultaneously connected to both the first and the further connecting line. In other words, a further connection connectable to the first and further connecting line can be connected to the first connecting line, but not to the further connecting line, in a first state, and to the further connecting line, but not to the first connecting line, in a further state. As explained in more detail below, however, it is also possible in particular for the further connection to be connectable or connected to the further connecting line, but not to the first connecting line. In other words, this can mean that the charge reversal device is configured such that no electrical connection can be established between the first terminal and the further connecting line.According to the invention, the first connecting line can be connected to the first connection and also to the further connection via a first changeover switching element. However, the first connection line cannot be simultaneously connected to both the first and the further connection. In other words, the first connecting line which can be connected to the first and further connection can be connected to the first connection, but not to the further connection, in a first state, and to the further connection, but not to the first connection, in a further state.Furthermore, the further connecting line can be connected to the first connection and also to the further connection via a further changeover switching element. However, the further connecting line cannot be simultaneously connected to both the first and the further connection. In other words, the further connecting line which can be connected to the first and further connection can be connected to the first connection, but not to the further connection, in a first state, and to the further connection, but not to the first connection, in a further state.According to the invention, the connection line-side connection of the first changeover switching element is connected to the first connection line via a first inductive connection element and / or a connection line-side connection of the further changeover switching element is connected to the further connection line via a further inductive connection element. An inductive connecting element can be designed in particular as a coil. In other words, the connection line-side terminal of at least one alternating switching element is thus connected to the corresponding connection line via an inductive connecting element.The integration of inductive connecting elements into the electrical connection between the connecting line-side connections of the alternating switching elements and the connecting lines results in at least one battery cell being short-circuited via at least one inductive connecting element without the capacitive element of the charge reversal branch being arranged in the corresponding short-circuit circuit. This advantageously allows electrical energy to be buffered in the form of a magnetic field generated by the inductive element, wherein the buffered energy can then be supplied to the capacitive element after the short circuit has ended. This advantageously allows a high state of charge of the capacitive element to be achieved, which in turn accelerates the charge reversal process. It is also possible to carry out recharging, wherein a voltage across the capacitive element of the recharging branch is greater than the voltage across the battery cell(s) to be discharged, whereby, as explained in more detail below, a voltage swing during the recharging process across the capacitive element and thus also its thermal load is reduced. Furthermore, it is advantageously the result that high charge reversal currents can be conducted by the proposed configuration of the charge reversal branch, as a result of which a time duration for charge reversal between at least two battery cells is advantageously shortened.Furthermore, it is advantageously made possible that the charge reversal device does not have to comprise a voltage sensor for detecting a voltage across the capacitive element of the charge reversal branch in order to control the charge reversal. It is likewise not necessary for the recharging device to comprise a current sensor for detecting a current in the recharging branch in order to control the recharging. This advantageously reduces complexity, installation space requirement and costs of the proposed transfer device.In a further embodiment, the inductive connection elements have the same inductance. This advantageously simplifies a method for operating the charge reversal device, in particular since no different properties of differently dimensioned inductances on the time profile of the charge reversal current have to be taken into account.In a further embodiment, an alternating switching element is designed as a series circuit of two transistor switches or comprises such a series circuit. A transistor switch can be, in particular, a MOSFET or IGBT.This advantageously results in a simple circuit-related configuration of a changeover switching element, as a result of which production costs for producing the transfer device can be reduced while simultaneously ensuring reliable operation.In a further embodiment, the alternating switching elements are each designed as half-branches of a bridge circuit or comprise these half-branches. Thus, the entirety of the first alternating switching element and the further alternating switching element is provided by a bridge circuit having two half branches. This also advantageously results in a simple implementation of the transfer device in terms of circuitry, reliable operation being ensured.In a further embodiment, the capacitive element of the charge reversal branch is designed as a polarized capacitor or comprises such a capacitor. This advantageously reduces the installation space requirement for the realization of the charge reversal device, since the polarized capacitors, which can also be referred to as ELKO(s), require less installation space than non-polarized capacitors for a comparable capacitance.It is further possible that a switching element for connecting a pole of a battery cell to the first or the further connecting line is formed by at least two transistor switches connected in antiseries. In this case, a first transistor switch is connected to the pole of the battery cell and is connected to the further transistor switch via a connecting section. The further transistor switch is then connected to a connecting line.A transistor switch is preferably formed by a MOSFET, wherein a MOSFET can comprise an intrinsic free-wheeling diode which is electrically connected in parallel with the conduction path between drain and source of the MOSFET.Alternatively, the transistor switch may also comprise an IGBT. If a transistor switch comprises an IGBT, then the transistor switch can likewise comprise a freewheeling diode which is connected electrically in parallel with the conduction path between emitter and collector of the IGBT.Normally-off MOSFETs or IBGTs can preferably be used as transistor switches, more particularly so-called n-channel MOSFETs / IBGTs or p-channel MOSFETs / IBGTs. Alternatively, however, it is also possible to use normally-on MOSFETs / IBGTs, which can also be formed in this case as n-channel MOSFETs / IBGTs or p-channel MOSFETs / IBGTs.Antiseries here can mean that the forward directions of the free-wheeling diodes of the two transistor switches are oriented opposite to one another. For example, the transistor switches can be connected in series with one another in such a way that the forward direction of a first transistor switch is oriented from the connection line toward the pole and the forward direction of a further transistor switch is oriented from the pole toward the connection line. Alternatively, the transistor switches can also be connected in series with one another in such a way that the forward direction of the first transistor switch is oriented from the pole toward the connecting line and the forward direction of the further transistor switch is oriented from the connecting line toward the pole.In the case that the transistor switches of the switching element are formed by MOSFETs, the switching element can comprise, for example, a first MOSFET whose drain terminal is connected to the pole of a battery cell. The source terminal of this first MOSFET can be connected to a source terminal of a further MOSFET of the switching element. The drain terminal of this further MOSFET can then be connected to the connecting line. A forward direction of the intrinsic free-wheeling diode of the respective MOSFET can be oriented from the source to the drain.Furthermore, the transfer device comprises a driver circuit with a driver voltage connection for each switching element. This driving voltage terminal serves to provide the gate voltage for each transistor switch.Further, a gate terminal of each transistor switch of a switching element is connected to the driving voltage terminal of the driving circuit of the switching element, respectively. In other words, the gate terminals of all transistor switches of a switching element are connected to the same drive voltage terminal. Thus, all gate terminals are supplied with the same voltage, whereby all transistor switches of a switching element can be simultaneously switched on (i.e. switched on) or switched off (i.e. switched off).It is further possible that a supply voltage terminal of the driver circuit of a switching element, which is connected to a negative pole of a battery cell, is electrically connected to a positive pole of the battery cell and / or that the voltage at the driver voltage terminal is provided by means of a level converter and / or that the charge reversal device comprises a control device for controlling the driver circuits, wherein a supply voltage terminal of the control device is connected to a negative pole of the last battery cell of the series circuit of all battery cells or of the previously explained first subset of battery cells and / or that the positive pole of the first battery cell of the series circuit of all battery cells or of the first subset is connected via a first protective line to the first connecting line and via a second protective line to the further connecting line, wherein at least one diode is arranged in each protective line and / or that the negative pole of the last battery cell of the series circuit of all battery cells or of the first subset is connected via a third protective line to the first connecting line and via a fourth protective line to the further connecting line, wherein at least one diode is arranged in each protective line.It is further possible that the charge reversal branch comprises a series connection of at least one capacitive element, at least one inductive element and at least one resistive element and / or that the charge reversal device comprises at least one means for detecting or determining a voltage across the capacitive element of a charge reversal branch and at least one means for detecting or determining a voltage across the inductive element of a charge reversal branch. The means for detection can be designed in particular as a voltage sensor. However, it goes without saying that the invention is not limited to voltage sensors for detecting or determining the voltage. Alternatively or cumulatively, further means known to the person skilled in the art for detecting or determining such a voltage can be used. The means for detecting or determining can be connected here with the evaluation device explained above with data and / or signals. This advantageously results in an improved control of switching elements of the transfer device being made possible, namely a control depending on the detected or determined voltage. This will be explained in more detail below.It is further possible for the transfer device to comprise a further transfer branch. The further charge reversal branch comprises a series circuit of at least one capacitive element and at least one inductive element. It is also possible for the further charge reversal branch to comprise a series circuit of the at least one capacitive element, the at least one inductive element and at least one resistive element. The further charge reversal branch is preferably formed by one of the series connections mentioned. In other words, the further charge reversal branch is formed in accordance with the previously explained charge reversal branch.Furthermore, a first connection of the further charge reversal branch can be connected to a third connecting line, in particular via a switching element, or connected, in particular permanently connected. Furthermore, a further connection of the further charge reversal branch can be connected to a fourth connecting line, in particular via a switching element, or connected, in particular permanently connected.The third and fourth connection lines are formed as different connection lines from each other. Further, these connection lines are also different from the first and the second connection lines explained above. As already explained with regard to the first and the second connecting line, it may be possible that the first connection of the further charge reversal branch cannot be connected to the fourth connecting line. Likewise, the further connection of the further charge reversal branch cannot be connected to the third connecting line. These connections cannot also be connected to the first and the second connecting line.Furthermore, a positive pole of each odd battery cell and a negative pole of each even battery cell of all battery cells or of a further subset of these battery cells can be connected to the third connecting line via a switching element. The further subset of battery cells comprises a plurality of battery cells of the battery connected in series. However, the further subset of battery cells here comprises at least one battery cell which is not part of the first subset of battery cells explained above.Alternatively, it is possible that a positive pole of each odd battery cell and a negative pole of each even battery cell of a further battery can be connected to the third connecting line via a switching element.Furthermore, a positive pole of each even battery cell and a negative pole of each odd battery cell of all battery cells or of the further subset of these battery cells can be connected to the fourth connecting line via a switching element.Alternatively, it is possible that a positive pole of each even battery cell and a negative pole of each odd battery cell of the further battery can be connected to the fourth connecting line via a switching element.A method for operating a transfer device according to one of the embodiments disclosed in this description is further proposed. In this case, in a discharged state, a first subsection of the series circuit of all battery cells is connected to the charge reversal branch, wherein in a charged state, a further subsection of the series circuit of all battery cells is connected to the charge reversal branch, wherein at least one battery cell of the first subsection is not part of the further subsection.In this discharge state, electrical energy / charge can be transported from the battery cell(s) into the at least one capacitive element of the charge reversal branch. This can also be referred to as a discharging process. The discharge state can be set, for example, by driving corresponding switching elements and / or alternating switching elements. In the discharge state, in particular at least one battery cell of the first subsection can be discharged.The first subsection of the series circuit of all battery cells comprises at least one, but preferably a plurality of, series-connected battery cell(s) of the series circuit of all battery cells, more preferably, however, not all battery cells of the series circuit. However, it is also possible for the first subsection to comprise exactly one battery cell.In a state of charge, a further subsection of the series connection of all battery cells is connected to the charge reversal branch. The further subsection of battery cells here comprises at least one, but preferably a plurality of, series-connected battery cell(s) of the series circuit of all battery cells. However, it is also possible for the further subsection to comprise exactly one battery cell.The first subsection preferably comprises more battery cells than the further subsection. This advantageously results in a charge equalization that is quick in time.In this state of charge, electrical energy / charge can be transported from the at least one capacitive element of the charge reversal branch into the battery cell(s) of the further subsection. This can also be referred to as a charging process. The state of charge can also be set, in particular by actuating corresponding switching elements and / or alternating switching elements. Furthermore, at least one battery cell of the first subsection is not part of the further subsection. Preferably, no battery cell of the further subsection is a battery cell of the first subsection (and vice versa). However, it is also possible that a plurality of battery cells, but not all battery cells, of the first subsection are not part of the further subsection.The discharge state and the charge state can be set here by the control device explained above. In particular, the discharge state can be set until the at least one capacitive element of the charge reversal branch has reached a predetermined state of charge, in particular until the state of charge has increased to the predetermined state of charge, and / or until one or more battery cell(s) of the first subsection has reached a predetermined state of charge, in particular until the state of charge of this battery cell(s) has fallen to the predetermined state of charge.The state of charge can be set until one or more battery cells of the further subsection have each reached a predetermined (desired) state of charge, in particular until the state of charge of this battery cell(s) has increased to this predetermined state of charge, and / or until the state of charge of the at least one capacitive element has reached a predetermined threshold value, in particular until this state of charge has fallen to the predetermined threshold value.In this case, the charge reversal device can comprise at least one means for detecting or determining the state of charge of the at least one capacitive element of the charge reversal branch. Furthermore, the charge reversal device can comprise at least one means for detecting the state of charge of a battery cell, preferably each battery cell, of the series circuit of all battery cells.A sequence of the states "discharge state, charge state" or "discharge state, idle state, charge state" can be repeated periodically. In the mutually corresponding states of the different periods, battery cells different from one another can be discharged or charged in each case. It is possible, for example, for one of the odd battery cells to be charged in each case in the states of charge of periods following one another in time. After all odd battery cells have been charged, one of the even battery cells can then be charged in the states of charge of further periods following one another in time. Between the periodic sequence for charging the odd battery cells and the periodic sequence for charging the even battery cells, recharging of the capacitor in the recharging branch can take place, which is explained in more detail below.It is of course also possible that in the states of charge of time-consecutive periods one of the straight battery cells is charged in each case. After all even battery cells have been charged, one of the odd battery cells can then be charged in each case in the states of charge of further periods following one another in time. Between the periodic sequence for charging the even battery cells and the periodic sequence for charging the odd battery cells, recharging of the capacitor in the charge reversal branch can take place.This advantageously results in a method for carrying out a charge equalization between different battery cells of the series circuit of battery cells of a battery, which improves the ensuring of operability. In particular, the level of a charging or discharging current, i.e. of the current flowing in the discharging or charging state of the transfer device, is limited by the at least one inductive element.In a further embodiment, the discharge state is set when a voltage across the capacitive element of the charge reversal branch is less than the voltage across the first subsection of the series circuit of all battery cells. In other words, the discharge state is set when the charge-reversal capacitor voltage is lower than the voltage of one or more battery cell(s) connected in series. The discharge state can be set by closing switching elements for connecting a pole to a connecting line and by driving the alternating switching elements.In such a method, the first subsection is preferably short-circuited via the at least one inductive connecting element at a first point in time, wherein this short-circuit is cancelled at a later point in time, which can be referred to as a second point in time, for example. This can be effected, for example, by electrically connecting the capacitive element in the charge reversal branch to the first subsection of the series circuit, as a result of which the discharge state is set. The time period between the first and the second point in time can thus be situated temporally before the setting of the discharge state.In the short-circuited state, a current flow takes place through the at least one inductive connecting element, as a result of which a voltage builds up across the latter. If the capacitive element in the charge reversal branch is then connected via the inductive connecting elements to the first subsection of the series circuit of all battery cells, the capacitive element is charged both from the first subsection and on the basis of the current flow generated by the inductive connecting elements on the basis of the Lenz rule after the end of the short circuit, as a result of which the voltage across the capacitive element can become greater than the voltage across the first subsection of the series circuit, for example twice as high.At a third point in time, which can be in particular a zero current point in time, the further subsection of the series connection of all battery cells is connected to the connecting lines. Here, the zero current time point denotes a time point at which no current flows via the switching elements. At this time, no current can flow in the charge reversal branch either.At a fourth point in time, the further subsection can then be connected to the charge reversal branch, in particular by appropriate actuation of the switching elements. In this state, the charge reversal branch can in turn be connected to the further subsection via the at least one inductive connecting element. This corresponds to the state of charge explained above. In this state of charge, a current flows from the capacitive element of the charge reversal branch via the at least one inductive connecting element into the further subsection. At a fourth point in time, the charge reversal branch can then be electrically disconnected from the further subsection, in particular by actuating the switching elements. According to this, the at least one inductive connecting element can continue to drive a current, due to the Lenz rule, after the disconnection of the bypass branch, which current flows into the further subsection and charges the battery cell(s) arranged therein. At a fifth point in time, the further subsection can then be disconnected from the connecting lines, in particular by suitable actuation of the corresponding switching elements. The fifth time can also be selected here as the zero current time, that is to say a time at which no current flows via the switching elements.This advantageously results in a method for operating the recharging device, which allows a reliable recharging of battery cells.In an alternative embodiment, the discharge state is set when a voltage across the capacitive element of the charge reversal branch is greater than the voltage across the first subsection of the series circuit of all battery cells.In this embodiment as well, the first subsection can be short-circuited via the at least one inductive connecting element before the discharge state is set, in particular by suitable actuation of the alternating switching elements. Furthermore, the first subsection can be connected to the connecting lines at the first point in time, in particular by suitable actuation of the corresponding switching elements.At a second point in time, the short circuit can be canceled and the charge reversal branch can be electrically connected to the first subsection, whereby the discharge state is set. As explained above, the capacitive element is then charged both out of the first subsection and on the basis of the current flow generated by the inductive connecting elements on the basis of the Lenz rule after the end of the short circuit.At a third point in time, which is in particular a zero current point in time in the discharge state that occurs without switching the (alternating) current, the first subsection is disconnected from the connecting lines and the further subsection is connected to the connecting lines, in particular by suitable actuation of the corresponding switching elements. At a fourth point in time, the charge reversal branch can then be connected to the connecting lines, in particular by suitable actuation of the alternating switching elements. At a fourth time, which is in particular a zero current time in the state of charge that occurs without switching the (alternating) current, the further subsection can then be disconnected from the connecting lines. A new state of charge can be set thereafter.In a subsection between the third and the fourth point in time, the current can be (further) driven by the inductive connecting elements and can charge the battery cells of the further subsection.This advantageously results in operation of the charge reversal device with a small voltage swing at the capacitive element of the charge reversal branch, wherein a voltage swing denotes the difference between a maximum and a minimum voltage during a cycle "discharge state" "charge state". This advantageously results in a low thermal load on the capacitive element of the charge reversal branch.Furthermore, it is advantageously obtained that in such an embodiment, when the alternating switching elements are formed as half-branches of a bridge circuit, no disconnection of the further subsection from the connecting lines is necessary in the case of a zero current crossing in the state of charge, since freewheeling diodes of the transistor switching elements used prevent a further current flow in the half-branches and thus a renewed discharge of the battery cells of the further subsection. Thus, no disconnection of the further subsection from the connecting line, effected by active actuation of the switching elements, is necessary after the maximum charged state has been reached, as a result of which a switching operation and therefore also the corresponding generation of control signals are dispensed with. This advantageously results in simpler operation of the corresponding transfer device.In a further embodiment, a charge reversal current is detected. The charge reversal current may be a charging current or a discharging current. As already explained above, this can be detected in particular by a means for detecting the current flowing through the charge reversal branch, wherein the means can be designed in particular as a current sensor. The means for detecting the charge reversal current can be connected to the control and evaluation device explained above.Furthermore, switching instants for switching the changeover switches and / or switching instants for switching the switching elements, by means of which poles are connected to connecting lines, are then determined as a function of the current, that is to say as a function of the charge reversal current detected. In particular, switching instants are determined in such a way that the previously explained zero-current switching takes place, i.e. a switching at an instant at which the charge reversal current is zero or deviates from zero by a predetermined (low) measure, wherein at this instant the current flow through closed switching elements can also be zero.This advantageously results in improved operational reliability of the transfer device, in particular since it can be ensured that the switching elements (including the alternating switching elements) are not switched under current, whereby their service life is increased.In an alternative embodiment, a time profile of the charge reversal current is determined as a function of electrical properties of the elements of the charge reversal device.Such electrical properties can be, for example, a capacitance, a resistance and an inductance of the elements. The elements of the transfer device can be, in particular, the capacitive element of the transfer branch, an inductive element in the transfer branch, e.g. the at least one inductive connecting element, the switching elements, including the alternating switching elements, and the battery cells.It is thus possible to determine the electrical properties of a circuit closed in the charge reversal device, wherein such a circuit can comprise, for example, the capacitive element of the charge reversal branch, the at least one inductive connecting element, the switching elements and exactly one or more battery cells. The previously explained time profile of the charge reversal current can then be determined. This can be done in particular on a model basis. In this case, tolerances of the elements of the transfer device can also be taken into account, in particular.Furthermore, it is possible to detect a temperature of the at least one battery cell, wherein an electrical property of the battery cell, in particular an (internal) resistance of the battery cell, is then determined as a function of the temperature. In other words, the electrical property of at least one element of the transfer device is thus determined as a function of temperature, for example via a previously known temperature model. Furthermore, the time profile of the charge reversal current can then be determined as a function of the temperature-dependent property determined in this way. As explained above, switching instants for switching the changeover switches and / or switching instants for switching the switching elements for connecting poles to connecting lines can then be determined as a function of the current, that is to say as a function of the specific temporal profile explained above. In particular, the switching instants can be determined in such a way that zero-current switching is made possible.The determination of the time profile and of the switching times can be carried out in particular by the control and evaluation device explained above.This advantageously results in operation of the charge reversal device without direct current detection, whereby a current sensor is advantageously dispensed with and manufacturing costs for manufacturing the charge reversal device can thus be reduced.A vehicle, in particular a motor vehicle, is further proposed, wherein the vehicle comprises a battery having a plurality of series-connected battery cells and a charge reversal device according to one of the embodiments described in this disclosure.Overall, the transfer device described in this disclosure and the method for operating the transfer device can be embodied or further developed according to one of the embodiments described in the post-published DE 10 2018 221 099 A1, in particular a modification described in the claims of these post-published DE 10 2018 221 099 A1.The invention is explained in more detail on the basis of exemplary embodiments. The figures show: FIG. 1 shows a schematic circuit diagram of a transfer device according to the invention according to the prior art, FIG. 2 shows a schematic circuit diagram of a transfer device according to the invention, FIG. 3 shows a schematic circuit diagram of a charge reversal branch in a further embodiment, FIG. 4 shows a schematic circuit diagram of a transfer device according to the invention in a further embodiment, FIG. 5 shows schematic time curves of a voltage across a capacitive element in the charge reversal branch and a charge reversal current corresponding to a first operating mode of the charge reversal device, and FIG. 6 shows schematic time curves of a voltage across a capacitive element in the charge reversal branch and a charge reversal current corresponding to a further operating mode of the charge reversal device.In the following, the same reference numerals denote elements having the same or similar technical characteristics.FIG. 1 shows a schematic circuit diagram of a charge reversal device 1 according to the invention for a battery according to the prior art, wherein the battery comprises a series connection of a plurality of battery cells BT 1, BT 2, BT 3, BT 4,..., BT 11, BT 12. In FIG. 1, positive poles of the battery cells BT 1,..., BT 12 are represented with a "+" sign and negative poles of the battery cells BT 1,..., BT 12 are represented with a "-" sign. Also shown are battery cell voltages U1, U2, U3, U4,..., U11, U12, this battery cell voltage U1,..., U12 dropping across the respective battery cell BT1,..., BT12.Here, the first battery cell BT 1, the third battery cell BT 3, the fifth battery cell, the seventh battery cell, the ninth battery cell, and the eleventh battery cell BT 11 form odd battery cells of the series circuit. The second battery cell BT 2, the fourth battery cell BT 4, the sixth battery cell, the eighth battery cell, the tenth battery cell, and the twelfth battery cell BT 12 form straight battery cells of the series circuit.The transfer device further comprises switching elements S 1, S 2, S 3, S 4,..., S 12, S 13. In particular, the number of switching elements S 1,..., S 13 of the recharging device 1, which are used to establish or disconnect the electrical connection of positive or negative poles of the battery cells BT 1,..., BT 12 to a first connecting line BL 1 or a second connecting line BL 2, is greater by the number one than the number of series-connected battery cells BT 1,..., BT 12 of the battery.FIG. 1 shows that a positive pole of each odd battery cell BT 1, BT 3,..., BT 11 can be connected to the first connecting line BL 1 via a switching element S 1, S 3... It is also shown that a negative pole of each straight battery cell of the series circuit can also be connected to the first connecting line BL 1 via a switching element S 3,..., S 13. Here, positive poles of all the odd battery cells BT 3,..., BT 11 except for the first battery cell BT 1 are electrically connected to negative poles of the even battery cell BT 2, BT 4,... immediately preceding in the series circuit.Furthermore, it is shown that a positive pole of each straight battery cell BT 2, BT 4,..., BT 12 can be connected to the second connecting line BL 2 via a switching element S 2, S 4,..., S 12. It is further shown that the positive poles of the even battery cells BT 2, BT 4,..., BT 12 are electrically connected to negative poles of the odd battery cell BT 1, BT 3,..., BT 11 respectively immediately preceding in the series connection. Thus, the negative poles of all odd battery cells BT 1, BT 3,..., BT 11 are also electrically connectable to second connecting line BL 2 via switching elements S 2, S 4,..., S 12.It is further shown that the charge reversal device 1 comprises a charge reversal branch 2, wherein a capacitor C is arranged in the charge reversal branch. It is possible for the charge reversal branch to comprise a series circuit of a capacitor C and an inductance, for example an inductor, or to be formed by this. Alternatively, it is possible for the charge reversal branch to comprise a series circuit of a capacitor C and an inductance, e.g. an inductor, and a resistor or to be formed by said series circuit. The series connection of the resistor, the capacitor C and the coil form an oscillating circuit, in particular a damped oscillating circuit. If no resistor is present in the charge reversal branch 2, the series circuit in the charge reversal branch 2 forms an unattenuated resonant circuit.The charge reversal branch 2 has a first connection A 1 and a second connection A 2. The first terminal A 1 is electrically connected, in particular permanently, to the first connecting line BL 1. Furthermore, the first connection A 1 of the charge reversal branch 2 cannot be connected directly or directly to the second connecting line BL 2. In particular, an electrical connection between the first terminal A 1 of the charge reversal branch 2 and the second connecting line BL 2 can be established only via at least one battery cell BT 1,..., BT 12.It is further shown that the second connection A 2 of the charge reversal branch 2 is connected, in particular permanently, to the second connecting line BL 2.In particular, the second terminal A 2 cannot be directly connected to the first connecting line BL 1. Thus, the electrical connection of the second terminal A 2 to the first connection line BL 1 (and thus to the first terminal A 1) can be established only via at least one battery cell BT 1,..., BT 12.Also shown is a capacitor voltage UC which falls across the capacitor C of the charge reversal branch 2 and a coil voltage which falls across the coil L.Schematically shown is a control and evaluation device 3 which can control switching processes of the switching elements S 1,..., S 13. The control and evaluation device 3 can be designed, for example, as a microcontroller or integrated circuit. The switching elements S 1,..., S 13 can be embodied in particular as power switches, further in particular as MOSFETs or IGBTs.Various states, in particular an idling state and a discharging state and a discharging state, are explained in DE 10 2018 221 099.3 described at the beginning.FIG. 2 shows a schematic circuit diagram of a charge reversal device 1 according to the invention. the charge reversal branch 2 comprising a capacitive element C is shown. A first terminal A 1 of the charge reversal branch 2 can be connected to the first connecting line BL 1 via a first changeover switching element WS 1 and to a further connecting line BL 2 via a further changeover switching element WS 2. A further connection A 2 of the charge reversal branch 2 can be connected to the first connecting line BL 1 via the first changeover switching element WS 1 and to the further connecting line BL 2 via the further changeover switching element WS 2. In the state of the transfer device 1 illustrated in FIG. 2, the first terminal A 1 is connected to the first connecting line BL 1 via the first changeover switching element WS 1 and the further terminal A 2 is connected to the further connecting line BL 2 via the second changeover switching element WS 2. In other words, a connection line-side terminal of the first changeover switching element WS 1 can be connected via the first changeover switching element WS 1 to the first or the further terminal A 1, A 2 of the charge reversal branch 2. A connection line-side terminal of the further change-over switching element WS 2 can likewise be connected to the first or the further terminal A 1, A 2 of the charge reversal branch 2 via the further change-over switching element WS 2.It is also shown that the connection line-side terminal of the first alternating switching element WS 1 is connected to the first connection line BL 1 via a first inductive connection element VL 1. Likewise, the connection line-side terminal of the further alternating switching element WS 2 is connected to the further connection line BL 2 via a further inductive connection element VL 2. The inductances of the first and the further inductive connection element VL 1, VL 2 can be the same here.It is further shown that the charge reversal branch 2 or a section of the charge reversal branch 2 between the first and the further connection A 1, A 2 does not comprise a separate inductive element, in particular no coil. In particular, no series circuit comprising the capacitive element C and a separate inductive element is provided between the first and the further terminal A 1, A 2 of the charge reversal branch 2.Furthermore, FIG. 2 shows that the transfer device 1 comprises a series circuit of four battery cells BT 1, BT 2, BT 3, BT 4, wherein a positive pole of the first battery cell BT 1 can be connected to the first connecting line BL 1 via a first switching element S 1. Accordingly, a positive pole of the third battery cell BT 3 is connectable to the first connecting line BL 1 via a third switching element S 3. A positive pole of the second battery cell BT 2 is connectable to the further connecting line BL 2 via a second switching element S 2 and a positive pole of the fourth battery cell BT 4 is connectable to the further connecting line BL 2 via a fourth switching element S 4. It is further shown that a negative pole of the fourth battery cell BT 4 can be connected to the first connecting line BL 1 via a fifth switching element S 5.Also shown is a control and evaluation device 3, by means of which an operation of the switching elements S 1,..., S 5 and the alternating switching elements WS 1, WS 2 can be controlled. Corresponding control signal lines are shown by a dashed line.FIG. 3 shows a schematic circuit diagram of a charge reversal branch 2 in a further embodiment. A first terminal A 1 and a second terminal A 2 of the charge reversal branch 2 are shown, wherein a charge reversal capacitor C is arranged between the first and the further terminal A 1, A 2.It is further shown that the first alternating switching element WS 2 is formed by a series circuit of two MOSFETs M 1, M 2. Here, a drain terminal of the first MOSFET M 1 is connected to the first terminal A 1, and a source terminal of the first MOSFET M 1 is connected to a drain terminal of the second MOSFET M 2. Further, a source terminal of the second MOSFET M 2 is connected to the second terminal A 2. A first inductive connection element VL 1 is electrically connected to a connection section of the first alternating switching element WS 1, wherein the latter connects the source terminal of the first MOSFET M 1 to the drain terminal of the second MOSFET M 2. The series connection of the two MOSFETs M 1, M 2 forms a half branch of a bridge circuit. Accordingly, the further alternating switching element WS 2 is formed from a series circuit of a third MOSFET M 3 and a fourth MOSFET M 4.The capacitor C arranged in the charge reversal branch can be designed in particular as a polarized capacitor.FIG. 4 shows a schematic circuit diagram of a transfer device 1 according to a further embodiment of the invention. A charge reversal branch 2 is shown, having a capacitor C and a coil L which are connected in series. As explained above, the charge reversal branch 2 can also comprise only one capacitor C.A first terminal A 1 and a second terminal A 2 of the charge reversal branch 2 are also shown. Further illustrated is a first connection line BL 1 and a second connection line BL 2.The positive poles of each odd battery cell BT 1, BT 3 of the series circuit of battery cells BT 1,..., BT 4 are connectable to the first connecting line BL 1 via switching elements S 1, S 3. The negative poles of each straight battery cell BT 2, BT 4 are connectable to the first connection line BL 1 via switching elements S 3, S 5. The positive poles of each straight battery cell BT 2, BT 4 are connectable to the second connection line BL 2 via switching elements S 2, S 4. Correspondingly, negative poles of each odd battery cell BT 1, BT 3 can be connected to the second connecting line BL 2 via switching elements S 2, S 4.In the embodiment shown in FIG. 4, the first connecting line BL 1 can be connected to the first terminal A 1 and also to the further terminal A 2 by means of a first changeover switching element WS 1. Accordingly, the further connecting line BL 2 can be connected to the first terminal A 1 and also to the further terminal A 2, namely by means of a further changeover switching element WS 2.In this case, the switching elements S 1,..., S 5, via which poles of the battery cells BT 1,..., BT 4 can be connected to connecting lines BL 1, BL 2 or via which the connection between the poles and the connecting lines BL 1, BL 2 can be produced or disconnected, can be referred to as switching elements S 1,..., S 5 of a first switching element level. The switching elements WS 1, WS 2, via which an electrical connection can be established or disconnected between the terminals A 1, A 2 of the charge reversal branch 2 and the connecting lines BL 1, BL 2, can be referred to as switching elements of a second switching element level.Here, the embodiment shown in FIG. 4 includes switching elements of the first and second switching element levels. The embodiment shown in FIG. 1 comprises switching elements of the first switching element level, but no switching elements of the second switching element level.Also shown is a control device 7 for controlling the operation of the switching elements S1,..., S5 of the first level, wherein the control device 7 generates control signals for the operation of these switching elements S1,..., S5 and transmits them via control lines CS1, CS2, CS3, CS4, CS5. A supply voltage terminal of the control device 7 is connected to a negative pole of the fourth battery cell BT 4 of the series circuit of all battery cells BT 1,..., BT 4.Also shown is a control and evaluation device 3 which can control switching operations of the alternating switching elements WS 1, WS 2. It is possible for the control devices 3, 7 to be designed as separate or as common control devices.It is further shown that the positive pole of the first battery cell BT 1 is connected via a first protective line SL 1 to the first connecting line BL 1 and via a second protective line SL 2 to the further connecting line BL 2. A first protective diode SD 1 is arranged in the first protective line SL 1, wherein the forward direction of this first protective diode SD 1 is oriented from the first connecting line BL 1 to the positive pole. A second protective diode SD 2 is arranged in the second protective line SL 2, the forward direction of which is oriented from the second connecting line to the positive pole of the first battery cell BT 1.It is further shown that the negative pole of the fourth and thus last battery cell BT 4 is connected to the first connecting line BL 1 via a third protective line SL 3, wherein a third protective diode SD 3 is arranged in the third protective line SL 3, the forward direction of which is oriented from the negative pole toward the first connecting line BL 1. Correspondingly, a fourth protective diode SD 4 is arranged in a fourth protective line SL 4, the forward direction of which is oriented from the negative pole toward the second connecting line BL 2.FIG. 5 shows schematic time curves of a voltage UCover a capacitive element C (see, for example, FIG. 2 ) in the charge reversal branch 2 and a charge reversal current ILcorresponding to a first operating mode of the charge reversal device 1.At a first point in time t 0 at which the voltage UC across the capacitive element C of the charge reversal branch 2, which is referred to below as capacitor voltage, is zero or is less than a predetermined amount higher than 0 V, a first subsection of the series circuit of all battery cells BT 1,..., BT 4 illustrated in FIG. 2 is connected to the connecting lines BL 1, BL 2, in particular by driving the corresponding switching elements S 1,..., S 5. For example, the first battery cell BT 1, which exemplarily forms the first subsection in this exemplary embodiment, may be connected to the connection lines BL 1, BL 2 by closing the first and second switching elements S 1, S 2. Furthermore, by controlling the alternating switching elements WS 1, WS 2, a short circuit of the first battery cell BT 1 is produced via the inductive connecting elements VL 1, VL 2. This can be done by connecting the first changeover switching element WS 1 to the further terminal A 2 of the transfer branch 2 and also connecting the further changeover switching element WS 2 to the second terminal A 2 of the transfer branch.If the alternating switching elements WS 1, WS 2 are configured, for example, as in the embodiment shown in FIG. 3, this can be effected, for example, by switching the second MOSFET M 2 and the fourth MOSFET M 4 on in the embodiment shown in FIG. 3.After the first time t0, the charge reversal current ILincreases substantially linearly. At a second time t 1, the short circuit is canceled, in particular in that, for example, the further changeover switch WS 2 is no longer connected to the further terminal A 2 of the charge reversal branch 2. For example, for this purpose, the fourth MOSFET M 4 of the embodiment shown in FIG. 3 can be switched to the off state. If the voltage across the first battery cell BT 1 is greater than the voltage across the charge-reversal capacitor C, the current flow into the freewheeling diode of the MOSFET M 3 illustrated in FIG. 3 will commutate.It is also possible, at the second time t 1, to connect the first terminal A 1 of the charge reversal branch 2 via the first changeover switching element WS 1 to the first connecting line BL 1, for example by switching the third MOSFET M 3 illustrated in FIG. 3 on.The charge reversal current IL weiter increases until the voltage across the charge reversal capacitor UC erreicht the voltage of the first battery cell BT 1. Subsequently, the charge reversal current IL is further driven by the inductive connecting elements VL 1, VL 2 and further charges the charge reversal capacitor UC. It is shown that at a third point in time t 2, the charge reversal capacitor UC reaches approximately twice the cell voltage, i.e. a voltage which is twice as high as the voltage across the first battery cell BT 1. If the third MOSFET M 3 was switched on at the second time t 1, then this is switched off at the latest at the third time t 2. At the third time t 2, the charge reversal current IL becomes zero.Between the third time t 2 and a fourth time t 3, no charge reversal current IL fließt. In this period of time, the first battery cell BT 1 connected to the connecting lines BL 1, BL 2 can be disconnected from these connecting lines BL 1, BL 2, wherein the battery cell to be charged, for example the second battery cell BT 2, which exemplarily forms the further subsection of the series connection of all battery cells BT 1,..., BT 4, is then connected to the connecting lines BL 1, BL 2 via the actuation of the corresponding switching elements S 2, S 3.At the fourth time t 3, the charge reversal branch 2 is connected to the connecting lines BL 1, BL 2, in particular by the first terminal A 1 being connected to the second connecting line BL 2 via the further switching element WS 2 and the further terminal A 2 being connected to the first connecting line BL 1 via the first switching element WS 1. The charge reversal current IL now flows in the negative direction via the inductive connecting elements VL 1, VL 2 from the charge reversal capacitor UC into the second battery cell BT 2 until the voltage of the charge reversal capacitor UC has dropped to the cell voltage of this second battery cell BT 2. After this, charge reversal current IL is continued due to inductive connection elements VL 1, VL 2 and further charges second battery cell BT 2. If the alternating switching elements WS 1, WS 2 are formed by half branches of a bridge circuit, as illustrated in FIG. 3, then, for example, the third MOSFET M 3 and the second MOSFET M 2 can be switched to the off state after the fourth time t 3, wherein the charge reversal current IL can continue to flow through the corresponding free-wheeling diodes.At a fifth time t 4, the charge reversal current IL becomes zero, and the second battery cell BT 2 to be charged is then disconnected from the connecting lines BL 1, BL 2 by opening the corresponding switching elements S 2, S 3, so that the charge reversal capacitor C is not charged from this battery cell BT 2.FIG. 6 shows schematic time curves of a voltage UCover a capacitive element C (see, for example, FIG. 2 ) in the charge reversal branch 2 and a charge reversal current ILcorresponding to a further operating mode of the charge reversal device 1.At a first point in time t0, at which the voltage UC across the capacitive element C of the charge reversal branch 2, which is referred to below as capacitor voltage, is greater than the voltage of a first subsection of the series circuit of all battery cells BT 1,..., BT 4 illustrated in FIG. 2 to be discharged, said first subsection is connected to the connecting lines BL 1, BL 2, in particular by driving the corresponding switching elements S 1,..., S 5. For example, the first battery cell BT 1, which in this exemplary embodiment exemplarily forms the first subsection, can be connected to the connecting lines BL 1, BL 2 by closing the first and second switching elements S 1, S 2, wherein then the voltage across the charge reversal capacitor C is greater than the voltage across the first battery cell BT 1. Furthermore, by controlling the alternating switching elements WS 1, WS 2, a short circuit of the first battery cell BT 1 is produced via the inductive connecting elements VL 1, VL 2. This can be done by connecting the first changeover switching element WS 1 to the further terminal A 2 of the transfer branch 2 and also connecting the further changeover switching element WS 2 to the second terminal A 2 of the transfer branch.If the alternating switching elements WS 1, WS 2 are configured, for example, as in the embodiment shown in FIG. 3, this can be effected, for example, by switching the second MOSFET M 2 and the fourth MOSFET M 4 on in the embodiment shown in FIG. 3.After the first time t0, the charge reversal current ILincreases substantially linearly. At a second time t 1, the short circuit is canceled, in particular in that, for example, the further changeover switch WS 2 is no longer connected to the further terminal A 2 of the charge reversal branch 2. For example, for this purpose, the fourth MOSFET M 4 of the embodiment shown in FIG. 3 can be switched to the off state.It is also possible, at the second time t 1, to connect the first terminal A 1 of the charge reversal branch 2 via the first changeover switching element WS 1 to the first connecting line BL 1, for example by switching the third MOSFET M 3 illustrated in FIG. 3 on.The charge reversal current IL decreases, but is driven further into the charge reversal capacitor C because of the inductive connecting elements VL 1, VL 2 and charges this charge reversal capacitor UC further. It is shown that the charge-reversal capacitor UC reaches the highest voltage at a third point in time t2. If the third MOSFET M 3 was switched on at the second time t 1, then this is switched off at the latest at the third time t 2. At the third time t 2, the charge reversal current IL becomes zero.No charge-reversal current IL fließt between the third time t2and a fourth time t3, wherein the voltage across the charge-reversal capacitor C remains constant. In this period of time, the first battery cell BT 1 connected to the connecting lines BL 1, BL 2 can be disconnected from these connecting lines BL 1, BL 2, wherein the battery cell to be charged, for example the second battery cell BT 2, which exemplarily forms the further subsection of the series connection of all battery cells BT 1,..., BT 4, is then connected to the connecting lines BL 1, BL 2 via the actuation of the corresponding switching elements S 2, S 3.At the fourth time t 3, the charge reversal branch 2 is connected to the connecting lines BL 1, BL 2, in particular by the first terminal A 1 being connected to the second connecting line BL 2 via the further switching element WS 2 and the further terminal A 2 being connected to the first connecting line BL 1 via the first switching element WS 1. The charge reversal current IL now flows in the negative direction via the inductive connecting elements VL 1, VL 2 from the charge reversal capacitor UC into the second battery cell BT 2.At times, the charge reversal current IL is driven further because of the inductive connecting elements VL 1, VL 2 and further charges the second battery cell BT 2. If the alternating switching elements WS 1, WS 2 are formed by half branches of a bridge circuit, as illustrated in FIG. 3, then, for example, the third MOSFET M 3 and the second MOSFET M 2 can be switched to the off state after the fourth time t 3, in particular at a fifth time t 4, wherein the charge reversal current IL can continue to flow through the corresponding free-wheeling diodes.At a sixth time t 5, the charge reversal current ILbecomes zero, wherein the electrical energy of the inductive connection elements VL 1, VL 2 has then discharged into the second battery cell BT 2. Furthermore, no disconnection of the second battery cell BT 2 from the connecting lines VL 1, VL 2 is necessary, since freewheeling diodes of the MOSFETs M 1, M 2, M 3, M 4 used in the half-branches of the embodiment illustrated in FIG. 3 prevent a further current flow and thus a renewed discharge of the second battery cell BT 2.List of reference characters1 Charge transfer device 2 Charge transfer branch 3 Control and evaluation device 7 Control device C Capacitor L Coil R Resistance element S 1,..., S 12 Switching element BT 1,..., BT 12 Battery cell BL 1 First connecting line BL 2 Second connecting line A 1 First terminal A 2 Second terminal IL Charge transfer current UC Capacitor voltage UL Coil voltage M 1,..., M 4 MOSFET VL 1, VL 2 Inductive connecting element WS 1, WS 2 Alternating switching element SL 1,..., SL 4 Protective line SD 1,..., SD 4 Protective diodes CS 1,..., CS 5 Control signal lines t 1,..., t 5 Points in time

Claims

Recharging device for a battery, wherein the battery comprises a series connection of at least two battery cells (BT1,..., BT12), wherein a positive pole of each odd battery cell (BT1, BT3,..., BT11) and a negative pole of each even battery cell (BT2, BT4,..., BT12) of the series connection of all battery cells (BT1,..., BT12) or a first subset of these battery cells (BT1,..., BT12) can be connected via a switching element (S1,...,S12) to a first connecting line (BL1), wherein a positive pole of each even battery cell (BT2, BT4,.., BT12) and a negative pole of each odd battery cell (BT1, BT3,..., bt11) of the series connection of all battery cells (BT1,..., BT12) or of the first subset of these battery cells (BT1,..., BT12) can be connected via a switching element (S1,...,S12) to a further connecting line (BL2), wherein the transfer device (1) comprises at least one first transfer branch (2) having at least one capacitive element (C), characterized in that the first connecting line (BL1) can be connected via a first transfer switching element (WS1) to a first terminal (A1) and also to a further terminal (A2) of the transfer branch (2), wherein the further connecting line (BL2) can be connected via a further alternating switching element (WS2) to the first terminal (A1) and also to the further terminal (A2) of the charge reversal branch (2), wherein a connecting line-side terminal of the first alternating switching element (WS1) is connected via a first inductive connecting element (VL1) to the first connecting line (BL1) and / or a connecting line-side terminal of the further alternating switching element (WS2) is connected via a further inductive connecting element (VL2) to the further connecting line (BL2).Transfer device according to Claim 1, characterized in that a connection line-side connection of the first alternating switching element (WS1) is connected via a first inductive connecting element (VL1) to the first connecting line (BL1) and a connection line-side connection of the further alternating switching element (WS2) is connected via a further inductive connecting element (VL2) to the further connecting line (BL2), the inductive connecting elements (VL1, VL2) having the same inductance.Transfer device according to one of the preceding claims, characterized in that an alternating switching element (WS1, WS2) is designed as a series circuit of two transistor switches (M1, M2, M3, M4) or comprises such a series circuit.Transfer device according to Claim 3, characterized in that the alternating switching elements (WS1, WS2) are each designed as half-branches of a bridge circuit or comprise these half-branches.Transfer device according to one of the preceding claims, characterized in that the capacitive element (C) of the transfer branch (2) is designed as a polarized capacitor or comprises such a capacitor.Method for operating a charge reversal device (1) according to one of Claims 1 to 5, characterized in that, in a discharged state, a first subsection of the series connection of all battery cells (BT1,..., BT12) is connected to the charge reversal branch (2), wherein, in a charged state, a further subsection of the series connection of all battery cells (BT1,..., BT12) is connected to the charge reversal branch (2), wherein at least one battery cell (BT1,..., BT12) of the first subsection is not part of the further subsection.Method according to Claim 6, characterized in that the discharge state is set if a voltage across the capacitive element (C) of the charge reversal branch (2) is less than the voltage across the first subsection of the series connection of all battery cells (BT1,..., BT12).Method according to Claim 6, characterized in that the discharge state is set if a voltage across the capacitive element (C) of the charge reversal branch (2) is greater than the voltage across the first subsection of the series connection of all battery cells (BT1,..., BT12).Method according to one of Claims 6 to 8, characterized in that a charge reversal current is detected and switching instants for switching the changeover switches (WS1, WS2) and / or switching instants for switching the switching elements (S1,..., S12) are determined as a function of the current.Method according to one of Claims 6 to 8, characterized in that a temporal profile of the charge reversal current is determined as a function of electrical properties of the elements of the charge reversal device (1), and switching instants for switching the changeover switches (WS1, WS2) and / or switching instants for switching the switching elements (S1,..., S12) are determined as a function of the current.

Images