Battery system, methods for charging battery modules, and methods for balancing battery modules

Abstract

Battery system (200, 300) comprising a battery with a plurality of battery modules (201) which are designed to be selectively activated or deactivated by means of control, such that in the activated state the battery module voltage of a respective battery module (201) contributes to an output voltage of the battery and in the deactivated state the battery module (201) is decoupled from the current path of the battery, characterized in that the battery system (200, 300) comprises a circuit for charging the battery modules (201) which has components (203, 204, 206, 207, 208) arranged according to a switching converter topology (202, 301) integrated into the battery system (200, 300) such that the battery modules (201) can be charged regardless of whether a respective battery module (201) to be charged is in the activated or deactivated state.

Description

[0001] The present invention relates to a modular battery system. More precisely, the invention relates to a battery system comprising a battery with a plurality of battery modules that can be selectively activated or deactivated by means of a control signal, wherein, in the activated state, the battery module voltage of a respective battery module contributes to an output voltage of the battery, and in the deactivated state, the battery module is decoupled from the current path of the battery. Furthermore, the invention relates to an associated method for charging battery modules and a method for balancing battery modules. The invention also relates to a motor vehicle with the battery system according to the invention. State of the art

[0002] It is becoming clear that battery systems will be increasingly used in the future, both in stationary applications and in vehicles such as hybrid and electric vehicles. To meet the voltage and available power requirements of a given application, a large number of battery cells are connected in series. Since the current supplied by such a battery must flow through all the battery cells, and each cell can only conduct a limited current, additional battery cells are often connected in parallel to increase the maximum current. Furthermore, it is often advantageous to be able to adjust the battery voltage, for example, to adapt it to the operating conditions of the motor.

[0003] Therefore, in previous patent applications of the applicant, battery systems were presented that have one or more battery module strings, the individual battery modules of which can be selectively switched on or off within the battery module string. An example of a battery system with such a battery module string is described in Fig. 1 schematically represented. According to Fig. 1 features a battery system 100 several battery modules connected in series 101 on, which form the battery module string. Each battery module 101 has one or more battery cells 102 , of which in the drawing per battery module 101 only one is shown. Furthermore, in Fig. 1 only two battery modules 101 Explicitly shown, however, in many applications a battery module string comprises more than two battery modules. 101 , which is indicated by points in the drawing. A battery module101 can use any number of battery cells 102 include. According to one embodiment, each battery module can include 101 the same number of battery cells 102 have, however, according to other embodiments, one of the battery modules may 101 a different number of battery cells 102 compared to the other battery modules 101 Furthermore, each battery module has 101 two switching elements each 103 , 104 on, depending on the switching position of the switching elements 103 , 104 Each battery module can be activated or deactivated. Thus, in a switch position where the... Fig. 1 upper switching element 103 a battery module 101 is in the closed state, whereas the lower switching element 104 in the open state, a respective battery module 101connected to the battery module string, so that the battery module voltage of the respective connected or activated battery module 101 contributes to a battery voltage that is present at both terminals 105 , 106 is available. However, if the upper switching element is in a different switching position, 103 opened and the lower switching element 104 closed, the respective battery module 101 deactivated. More precisely, in the deactivated state, a battery module 101 decoupled from the battery's current path and electrically bridged, so that only the remaining, activated battery modules 101 to contribute to the battery voltage and thus supply battery current and electrical energy.

[0004] One advantage of an arrangement according to Fig. The advantage is that a variable, selectable battery voltage can be set in this way. For example, with a sufficiently fine division of the battery module string into a large number of battery modules, this is possible. 101 and, with suitable control, a sinusoidal waveform of the battery voltage at the terminals. 105 , 106 The settings can be adjusted. Furthermore, if multiple battery module strings are used, each controlled to deliver a sinusoidal output voltage, the process can be optimized accordingly. For example, three phase-shifted sinusoidal voltages can be generated, allowing a three-phase electric motor to be driven without the need for an intermediate inverter.

[0005] However, a disadvantage of such a modular arrangement is that charging the battery cells requires... 102typically also via the switches provided for switching on and bypassing. 103 , 104 They must be confirmed as suitable so that each of the battery modules 101 is connected to the battery's power supply. More precisely, to, for example, convert a vehicle's electrical system into a battery module. 101 To charge, the respective battery module must 101 , if it was previously in a deactivated state, it can be reactivated. Furthermore, charging the battery modules is possible. 101 Generally, this is only possible from the vehicle's electrical system. In the Fig. Figure 1 illustrates the battery current I with the double arrow, where, depending on whether the battery is being charged or discharged, the current I flows into or out of the battery cells. Furthermore, to charge the battery, the necessary energy must first be transferred to the vehicle's electrical system so that the cells can then be charged by activating the respective modules. Disclosure of the invention

[0006] According to the invention, a battery system is provided that comprises a battery with a plurality of battery modules which can be selectively activated or deactivated by means of a control signal, wherein in the activated state the battery module voltage of a respective battery module contributes to an output voltage of the battery and in the deactivated state the battery module is decoupled from the current path of the battery. The battery system further comprises a circuit for charging the battery modules, which has components arranged according to a switching converter topology integrated into the battery system such that the battery modules can be charged regardless of whether a respective battery module to be charged is in the activated or deactivated state.

[0007] According to a further aspect of the invention, a method for charging battery modules which can be selectively activated or deactivated by means of control is disclosed, wherein the method is characterized by the use of the circuit arranged in the battery system according to the invention for charging battery modules.

[0008] According to a further aspect of the invention, a method for balancing battery modules of a battery system, which can be selectively activated or deactivated by means of a control signal, is provided. According to the method, a circuit is used for balancing the battery modules, which comprises components arranged according to a switching converter topology integrated into the battery system.

[0009] Furthermore, according to one aspect of the invention, a motor vehicle is provided which has an electric motor and the battery system according to the invention, wherein the battery system according to the invention is arranged in a drive train of the electric motor.

[0010] One advantage of the invention is that the battery modules or the battery cells of the battery modules can be charged in a special way, whereby, in contrast to the prior art, the invention does not require activating, i.e., switching on, individual battery modules. In particular, it makes it possible to charge the cell modules without having to draw energy from the vehicle's electrical system.

[0011] This is achieved in particular by providing additional means in the battery system for charging the battery modules, as described in independent claim 1. For this purpose, in addition to the existing conventional current path of the battery modules, which can be temporarily diverted by deactivating the battery modules, components according to a switching converter topology integrated into the battery system are provided. According to the invention, the battery system is modified such that it is designed, in particular, as a switching converter or has features or functions of a switching converter for the purpose of charging the battery modules.

[0012] According to the invention, energy from the vehicle's electrical system can also be transferred to the individual cell modules using the switching converter topology employed, without having to activate or switch on the individual battery modules, resulting in greater flexibility for modular battery systems.

[0013] The invention can be advantageously applied, in particular, to battery systems whose battery modules have two switching elements, each arranged such that a respective battery module is activated in a first switching position of the switching elements and deactivated in a second switching position of the switching elements. However, the invention is not limited to such a battery module. Instead, according to other embodiments, the switching converter topology according to the invention is used in battery modules that can be activated or switched on and off in a different way.

[0014] According to a preferred embodiment of the invention, one or more of the battery modules each have a secondary-side sub-circuit of the switching-wall topology, the output voltage of which corresponds to the battery module voltage of the respective battery module. For example, in a particularly preferred embodiment, the secondary-side sub-circuit can be configured such that it corresponds to a secondary-side sub-circuit of a conventional switching converter, wherein an output capacitor is replaced by one or more battery cells of the battery module.

[0015] The invention is not limited to a particular type of switching converter. Preferably, a flyback converter is used. According to one embodiment of the invention, a switch for generating a clock signal for the switching converter or for the switching converter topology is located on a primary side of the switching converter circuit.

[0016] In an advantageous embodiment of the invention, the switching converter topology is connected to a battery terminal via its primary side. This has the advantage that even cell modules that are actually switched off can be charged from the vehicle's electrical system, and balancing between the cell modules is enabled, particularly during inactive phases (e.g., when parked). For this purpose, the battery modules from which energy is to be drawn are switched on.

[0017] The inventive method thus allows energy to be extracted from activated battery modules by pulsing a switch and advantageously redistributed evenly to all battery modules, including the deactivated battery modules.

[0018] According to a preferred embodiment, a switching converter with galvanic isolation is used. It is particularly advantageous that the primary-side sub-circuit of the switching converter topology can be arranged galvanically isolated from the battery modules. This galvanic isolation makes it possible, in particular, to ensure isolation between the charging network, for example a 220 V household network, and the vehicle network.

[0019] The individual battery cell modules can be charged directly, meaning that charging can be done without using the battery terminals or without drawing energy from already charged, activated battery modules.

[0020] A power factor correction stage and a rectifier can typically be connected downstream of the switching converter on the primary side.

[0021] The battery cells according to the invention are preferably lithium-ion battery cells.

[0022] Advantageous embodiments of the invention are specified in the dependent claims and described in the description. Drawings

[0023] Exemplary embodiments of the invention are explained in more detail with reference to the drawings and the following description. The drawings show:

[0024] Fig. 1 a schematic representation of a battery with a modularly constructed battery module string according to the state of the art,

[0025] Fig. 2 a schematic representation of a battery system with an integrated switching converter topology according to a first embodiment of the invention, and

[0026] Fig. 3 a schematic representation of a battery system with an integrated switching converter topology according to a second embodiment of the invention, wherein direct charging of the battery modules is possible. Embodiments of the invention

[0027] In the Fig. Figure 2 is a schematic representation of a battery system. 200 shown according to a first embodiment of the invention. Compared to the battery system in Fig. 1 is the circuit diagram of each battery module 201 supplemented by components that conform to a switching converter topology 202 are arranged. More precisely, each battery module is assigned one 201 a series circuit consisting of a diode 203 and an inductor 204 connected in parallel. The parallel connection of the diode according to the invention. 203 and the secondary inductance 204 are components of a secondary-side sub-circuit 209 the switching converter topology 202 , which are integrated into the battery system 200 is integrated to provide a flexible solution that is independent of the switching state of the battery modules. 201 Largely independent charging of the battery modules 201to enable this. The switching converter, that is, the switching converter topology 202 features galvanic isolation 208 on, which can be implemented, for example, by the air gap of a storage transformer or a coil. The primary-side sub-circuit 205 the switching converter topology 202 exhibits a primary inductance 206 up and is activated by the switch 207 clocked to extract energy from the primary-side sub-circuit 205 to the secondary-side sub-circuits 209 , which are in the battery modules 201 are arranged to transmit. In this way, electrical energy can be transferred from the terminal. 105 the battery is taken from the battery, which is protected by galvanic isolation. 208 across to the battery modules 201 can be transferred evenly. Alternatively, the energy can be used to charge the battery modules. 201taken from the vehicle's electrical system, for example by drawing energy from the vehicle's electrical system via the battery terminals 105 , 106 is fed into the grid. This is particularly the case when the battery modules are being charged. 201 This is done and simultaneously all battery modules 201 are deactivated. According to one variant of this embodiment, the switching converter topology has 202 exactly one primary circuit 205 according to other variants, the switching converter topology is divided 202 in a different way, whereby the switching converter topology 202 multiple primary circuits 205 exhibits.

[0028] The arrangement according to the battery system 200 according to Fig. 2 enables, in particular, a very flexible balancing of the battery modules. 201 .

[0029] In the Fig. Figure 3 is a schematic representation of a battery system. 300shown according to a second embodiment of the invention. In contrast to the embodiment in Fig. 2 In the second embodiment of the invention, the battery modules 201 directly charged, for example without using the vehicle's electrical system. The embodiment according to Fig. 3 is particularly suitable for the battery modules 201 for example, to charge via a 220V household mains supply, since the primary-side sub-circuit 302 the switching converter topology 301 by means of galvanic isolation 208 from the rest of the battery system circuit 300 and from the battery modules 202 It is arranged in a galvanically isolated manner. This allows energy from an external network or the 220V household mains to flow directly into the primary-side sub-circuit. 302 be fed in. Typically, the input stage has 303 , which belong to the primary-side sub-circuit 302A power factor correction stage and a rectifier are connected upstream.

Claims

[1] Battery system ( 200 , 300 ), comprising a battery with a plurality of battery modules ( 201 ), which are designed to be selectively activated or deactivated by means of control, such that in the activated state the battery module voltage of a respective battery module ( 201 ) contributes to the battery's output voltage and, in the deactivated state, the battery module ( 201 ) is decoupled from the current path of the battery, characterized in that the battery system ( 200 , 300 ) a circuit for charging the battery modules ( 201 ) includes those that are installed in such a way according to a battery system ( 200 , 300 ) integrated switching converter topology ( 202 , 301 ) arranged building elements ( 203 , 204 , 206 , 207 , 208 ) shows that the battery modules ( 201) can be charged, regardless of whether a particular battery module to be charged ( 201 ) is in the activated or deactivated state. [2] Battery system ( 200 , 300 ) according to claim 1, wherein each of the battery modules ( 201 ) two switching elements ( 103 , 104 ) exhibits, each of which is arranged such that in a first switching position of the switching elements ( 103 , 104 ) a respective battery module ( 201 ) is activated and in a second switch position ( 103 , 104 ) the switching elements the respective battery module ( 201 ) is deactivated. [3] Battery system ( 200 , 300 ) according to claim 1 or 2, wherein one or more of the battery modules ( 201 ) each a secondary-side sub-circuit ( 209 ) the switching converter topology ( 202 , 301) exhibiting an output voltage that matches the battery module voltage of a respective battery module ( 201 ) corresponds. [4] Battery system ( 200 , 300 ) according to claim 3, wherein the switching converter topology ( 202 , 301 ) a galvanic isolation ( 208 ) exhibits. [5] Battery system ( 200 , 300 ) according to one of the preceding claims, wherein a primary-side sub-circuit ( 205 , 302 ) the switching converter topology ( 202 , 301 ) galvanically isolated from the battery modules ( 201 ) is arranged. [6] Battery system ( 200 , 300 ) according to one of the preceding claims, wherein the switching converter topology ( 202 , 301 ) on the primary side with a terminal ( 105 ) is connected to the battery. [7] Battery system ( 200 , 300 ) according to one of the preceding claims, wherein the battery system (200 , 300 ) furthermore includes a power factor correction stage and a rectifier, which is connected on the input side to the primary side ( 301 ) the switching converter topology ( 202 , 301 are coupled. [8] Battery system ( 200 , 300 ) according to one of the preceding claims, wherein the switching converter topology ( 202 , 301 ) is designed as a barrier converter. [9] Methods for charging battery modules ( 201 ) of a battery system ( 200 , 300 ), which can be selectively activated or deactivated by means of control, characterized by the use of the components in the battery system ( 200 , 300 ) a circuit arranged according to one of claims 1 to 8 for charging battery modules ( 101 ). [10] Method for balancing battery modules ( 201 ) of a battery system ( 200 , 300), which can be selectively activated or deactivated by means of control, characterized in that for balancing the battery modules ( 201 ) a circuit is used which, according to a system integrated into the battery ( 200 , 300 ) integrated switching converter topology ( 202 , 301 ) arranged building elements ( 203 , 204 , 206 , 207 , 208 ) exhibits. [11] Motor vehicle that has an electric motor and battery system ( 200 , 300 ) according to any one of claims 1 to 8, wherein the battery system ( 200 , 300 ) is arranged in a drive train of the electric motor.

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