Charging technology for rechargeable batteries connected in parallel
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- PHOENIX CONTACT GMBH & CO KG
- Filing Date
- 2026-01-15
- Publication Date
- 2026-08-06
Smart Images
Figure EP2026050872_06082026_PF_FP_ABST
Abstract
Description
[0001] Charging technology for parallel-connected batteries
[0002] The present disclosure relates to a technique for charging parallel-connected accumulators. In particular, but not limited to, a pre-charging circuit for connecting accumulators to a power outlet, an electrical energy storage device with such a pre-charging circuit, a system of multiple energy storage devices, and a method for pre-charging an accumulator are provided.
[0003] Rechargeable battery systems, i.e., accumulators, are key components of modern energy storage solutions, particularly in the areas of medical and information technology supply security, electromobility, renewable energies, and stationary storage. Connecting accumulators in parallel increases the total available capacity and power input and output, which is crucial for many applications.
[0004] Connecting batteries in parallel presents technical challenges. Different charge or aging states of the individual batteries can correspond to different open-circuit voltages. These drive equalizing currents, which lead to heat generation and reduce the battery lifespan.
[0005] Traditionally, these equalizing currents are limited by resistors. A corresponding pre-charge circuit was shown and described, for example, in an 'Application Brief' from Texas Instruments entitled "Why Pre-Charge Circuits are Necessary in High-Voltage Systems" in December 2021. However, a large portion of the energy exchanged during voltage equalization is lost across these resistors.
[0006] Existing solutions for pre-charging and balancing parallel-connected batteries are therefore often inefficient and time-consuming. They either require prior adjustment of the voltage levels or, due to the limited current-carrying capacity of the pre-charging components, result in long balancing times. This impairs the flexibility and cost-effectiveness of electrical energy storage systems.
[0007] The invention is therefore based on the objective of providing a technique for charging parallel-connected accumulators that enables fast and efficient balancing without requiring complex control mechanisms or additional communication signals.
[0008] The problem is solved using the characteristics of independent claims.
[0009] Suitable embodiments and advantageous further developments of the invention are specified in the dependent claims.
[0010] According to the first aspect, a pre-charging circuit is provided for connecting a battery to a power outlet. The pre-charging circuit includes a first switch between the first terminal of the battery and the first terminal of the power outlet, and a second switch between the second terminal of the battery and the second terminal of the power outlet. A series circuit is connected between the first terminal of the battery and the first terminal of the power outlet, comprising a third switch and a parallel circuit. The parallel circuit contains a resistor and a diode connected in parallel. The diode is polarized to allow energy flow from the power outlet to the battery and to block energy flow in the opposite direction.A battery management system (BMS) is designed to control the switches as follows: When the first switch is open, the second and third switches are closed to connect the battery to the power terminal via the resistor and diode. At a later time, the first switch is closed (with the third switch optionally opening).
[0011] Exemplary implementations of the pre-charge circuit enable efficient and rapid pre-charging of the battery. The diode allows higher pre-charge currents than the resistor alone, thus significantly reducing the balancing time between parallel-connected batteries with different charge levels. The diode's blocking effect also prevents unwanted reverse currents, increasing system safety. The battery management system controls the pre-charging and charging process without additional control signals, minimizing complexity and improving reliability.
[0012] Exemplary implementations enable an improved pre-charging circuit for the simple parallel connection of accumulators with minimal control effort and all-pole disconnection of the power connection. Integrating a diode in parallel with the pre-charging resistor allows accumulators with different charge levels to be quickly balanced by permitting higher currents during the pre-charging phase without requiring additional control signals. This results in efficient equalization of the accumulator voltage levels, enabling their safe parallel connection.
[0013] The power connection can be a multi-pole interface for charging and / or discharging the battery.
[0014] According to a second aspect, an electrical energy storage device is provided. The electrical energy storage device comprises a pre-charging circuit according to the first aspect and a battery which is electrically connected or connectable to the pre-charging circuit via the first and second terminals of the battery.
[0015] For example, the accumulator is located in the housing of the pre-charging circuit.
[0016] According to a third aspect, a system with multiple electrical energy storage devices is provided in accordance with the second aspect. The power connections of the pre-charging circuits of the electrical energy storage devices are connected in parallel.
[0017] According to a fourth aspect, a method for pre-charging and charging an accumulator is provided, wherein the accumulator is electrically connected to a power terminal via a pre-charging circuit as described in the first aspect. The method involves closing the second switch and the third switch of the pre-charging circuit to connect the accumulator to the power terminal via the resistor and diode. This selectively pre-charges the accumulator depending on its open-circuit voltage and the charging voltage applied to the power terminal. After pre-charging, the first switch is closed to charge the accumulator, for example, to balance it, which may involve charging or discharging.
[0018] This method enables effective adjustment of the charge state of parallel-connected batteries, for example, before charging them. The initial pre-charge via the diode allows for higher currents and thus faster charge equalization. Sequential switching ensures safe disconnection and connection of the components without the need for additional communication paths or complex control algorithms. This enables flexible and scalable design of energy storage systems that meet the requirements of modern energy storage applications.
[0019] Exemplary embodiments of the invention, which can be optionally combined with one another, are disclosed below with partial reference to the figures.
[0020] In particular, features mentioned in the context of a device (e.g., the circuit, memory, or system) can also be implemented accordingly in the process, for example, by a step of providing the corresponding feature or by a step of executing a function of the device. Furthermore, the device can include any feature mentioned in the context of the process and can be configured to execute any step mentioned in the context of the process.
[0021] The term "electrical" can be interpreted synonymously with "electrotechnical." In this context, "electrical" encompasses, for example, "electronic" or "electromechanical." That is, electrical modules can include electronic or electromechanical components. Examples of electronic components (such as switches) are semiconductors, in particular diodes, transistors (such as insulated-gate bipolar transistors, or IGBTs), and microprocessors. Examples of electromechanical components (such as switches) are contactors or mechanical relays. Generally, enumerations of the form "A, B, ... and / or C" reveal each enumerated feature individually ("A or B or ..."), each partial combination ("A and B," "A and C," ..."), and the entirety ("A and B and C").
[0022] Examples of how each of the four aforementioned aspects can be implemented include the following advantages and designs.
[0023] Exemplary embodiments (for example, the pre-charge circuit) enable rapid pre-charging of the accumulator in a heterogeneous system of several parallel-connected energy storage devices due to higher pre-charge currents during a pre-charge phase (i.e., in a pre-charge mode) through the diode, resulting in more energy-efficient and faster balancing when connecting energy storage devices in parallel.
[0024] These or other embodiments enable priority charging of the lowest-voltage battery, for example, without the need for additional communication between energy storage devices. Alternatively or additionally, using the pre-charge circuit, a system of multiple parallel-connected energy storage devices can be configured without a centralized (i.e., higher-level) BMS. This is advantageous for the interchangeability of batteries, for example, during system operation, or for the flexible manufacturing of systems with different capacities.
[0025] The accumulator (for example, of one or more energy storage devices) can comprise one or more electrochemical secondary cells. Within a system, cell equivalence can exist among the accumulators of different energy storage devices, meaning that the electrochemical cells within each accumulator, in their essential properties (e.g., capacity, internal resistance, charging and discharging behavior, and / or voltage), are as similar as possible. Any remaining or emerging inequalities can be efficiently compensated for after manufacturing or during operation by the pre-charging circuit.
[0026] The accumulator can be referred to simply as a battery.
[0027] The series circuit can be connected in parallel with the first switch. Alternatively or additionally, according to an internal circuit diagram of the series circuit, the third switch and the parallel circuit can be electrically connected. The series circuit can also consist solely of the third switch and the parallel circuit.
[0028] According to an external circuit of the series circuit, the third switch can be electrically connected to the first pole of the accumulator and the parallel circuit to the first pole of the power terminal, or the third switch can be electrically connected to the first pole of the power terminal and the parallel circuit to the first pole of the accumulator.
[0029] Each of the first, second, and third switches can be designed as a power contactor or a semiconductor switch. Alternatively or additionally, each switch can be a safety contactor, for example, in accordance with standard EN 60947-4-1 and / or standard EN ISO 13849-1.
[0030] In pre-charging mode, the second and third switches can be closed (i.e., electrically conductive) and the first switch can be open (i.e., electrically disconnected or locked).
[0031] In one embodiment, the diode is designed to allow currents greater than the current limited by the resistor (R). This can enable faster charge equalization during pre-charging, as the diode permits high charging currents, thus reducing the pre-charging time. In a first variant of each embodiment, the current limited by the resistor can refer to a maximum or average voltage difference between batteries of different energy storage devices, or to a voltage variation of the batteries (e.g., due to manufacturing or aging). In a second variant of each embodiment, the current limited by the resistor can refer to a maximum (e.g., maximum permissible) heat dissipation of the diode, for example, a maximum of 5% or 10% of the power (i.e., the charging power) of the current (i.e., the pre-charging current).
[0032] In one embodiment, the diode (i.e., the parallel circuit in place of said diode) comprises two or more diodes connected in series. This embodiment can provide redundancy in the event of a diode failure (for example, if the diode closes permanently) and improve the reliability of the pre-charge circuit.
[0033] In one embodiment, the BMS – or a separate switching logic dependent on the switching states of the first and second switches – is configured to open the third switch after or when the first switch closes. This allows a pre-charging circuit (e.g., a resistor and diode connected in parallel) to be disconnected after pre-charging is complete, increasing safety and reducing losses.
[0034] If Si and S2 are the closed state (e.g., "true" or "1" for "closed"; "false" or "0" for "open") of the first and second switches respectively, the closed state S3 of the third switch can be S3 = S2 AND NOT S1 or correspond to the following logic table:
[0035]
[0036] In one embodiment, a switching state of the third switch is derived from a combination of the switching states of the first switch and the second switch. Alternatively or additionally, a switching state of the third switch is defined according to...
[0037] S3 = S2 and not S1
[0038] is controlled. Here, the closed switching states of the first switch, the second switch, and the third switch can be specified by Si, S2, and S3, respectively. In a simplified version of each embodiment, the switching state of the third switch can be (at least temporarily) the same as the switching state of the second switch, i.e., S3 = S2. Furthermore, the switching state of the third switch can depend on the switching state of the first switch, for example, according to S3 = S2 AND NOT S1.
[0039] For example, the dependence of the switching state S3 of the third switch on the switching state S1 of the first switch is time-delayed compared to the dependence on the switching state S2 of the second switch. This means that the dependence on the switching state of the first switch can include a time delay. This time delay can allow for a temporal overlap during the transition from pre-charging (via the closed third switch) to regular charging (via the closed first switch), during which both the first and third switches are closed.
[0040] In one embodiment, the BMS is further configured to control the second and third switches via a single control signal (for example, to close and / or open them). Reducing the number of control signals can simplify the control and / or decrease the control overhead. For example, the switching state of the third switch can be the same as the switching state of the second switch, i.e., S3 = S2.
[0041] In one embodiment, the second switch is a safety contactor. Alternatively or additionally, the BMS is configured to open the first switch for both safety shutdown and pre-charging the battery. Such a dual function of the first switch can reduce the number of components required in the pre-charging circuit and / or simplify the pre-charging circuit, leading to cost and resource savings.
[0042] In one embodiment, the power connection and / or a housing (of the pre-charging circuit or the energy storage device) can be designed for connecting multiple electrical energy storage devices in parallel. Several energy storage devices, each comprising a pre-charging circuit, can be connected in parallel via the power connection. For example, the housing of the pre-charging circuit can have complementary profile structures on two opposite sides, e.g., to allow for detachable mechanical connection of the housing to an identical housing. For example, the complementary profile structures can be a tongue-and-groove system or a locking tab-and-groove system.
[0043] Alternatively or additionally, opposite sides of the housing or the complementary profile structures of the housing can be used for connector halves (e.g.
[0044] Plug contacts) have for connecting the first and second poles of adjacent power terminals in parallel in a mechanically connected state.
[0045] To scale an energy storage system, each aspect can be configured to add another energy storage device, each comprising an embodiment of the pre-charge circuit or an embodiment of the energy storage device itself. Due to the BMS, which closes the third switch and opens the first during pre-charging, and / or due to the diode, which selectively increases the pre-charge current for the battery with the lowest voltage, each aspect (for example, the pre-charge circuit) can enable efficient balancing of multiple electrical energy storage devices.
[0046] In one embodiment, complementary connector halves with contacts for the first and second poles of the power connection and complementary profile structures for mechanical connection to an identical housing can be arranged on opposite sides of the housing (of the pre-charging circuit or the energy storage device). The connector halves and the profile structures can be arranged to connect the first and second poles of the power connections of the housings mechanically connected via the profile structures in parallel to another housing when the housing is mechanically connected via the profile structures.
[0047] The first and second terminals of the battery can be an internal connection within the housing. Alternatively or additionally, the housing can have an external or externally accessible connection for the first and second terminals of the battery, for example, in a recess in the housing to accommodate the battery.
[0048] Alternatively or additionally, the connection encompassing the two terminals of the accumulator can be located on the underside of the housing. The housing can have recesses or projections (e.g., pins or locking tabs) that interact with complementary projections or recesses on another housing (for example, the housing of another energy storage device or the housing of an additional accumulator) to provide a mechanical connection. For example, the housing of the pre-charging circuit or a first energy storage device can be placed or plugged onto the housing of a second energy storage device or an additional accumulator.
[0049] Preferably, during the mechanical connection of the housings, the accumulators contained in the housings (i.e., the respective first and second poles of the accumulators) are connected in parallel. For this purpose, a terminal comprising both poles of the accumulator can be arranged on a top surface of the housing of the second energy storage device or the additional accumulator.
[0050] In one embodiment, the first pole of the accumulator can be a positive pole of the accumulator and the second pole of the accumulator can be a negative pole.
[0051] Alternatively, the first terminal of the battery can be the negative terminal and the second terminal can be the positive terminal. The positive and negative terminals of the battery can be technically referred to as the "highside" and "lowside" of the battery, respectively.
[0052] The series connection of the pre-charging circuit can be located on the high side of the battery. Furthermore, the first switch and / or the third switch can be a changeover switch. The changeover switch can be configured to alternately connect a base contact to a normally open contact and a normally closed contact. The base contact can be connected to the first terminal of the power terminal. The normally closed contact can be connected to the first terminal of the battery via a parallel connection (of a resistor and diode). Optionally, when both the first and third switches are open, the normally closed contact can be connected to ground or earth potential. This allows the first terminal of the power terminal to be grounded or de-energized.
[0053] Alternatively or additionally, the series connection of the pre-charging circuit can be arranged on the low side of the battery. This allows the BMS and / or a control line for closing the first switch and / or a control line for closing the third switch and / or a logic circuit for determining the switching state of the third switch (for example, depending on the switching states of the first and second switches) to be potential-free or to carry only a safety extra-low voltage (SELV).
[0054] The nominal and / or charging voltage of the battery can be above 100 V and / or below 1 kV, for example 400 V or 800 V.
[0055] In one variant of each embodiment, the pre-charging circuit can further include a capacitor connected in parallel to the first and second terminals of the power terminal, for example, as an intermediate circuit capacitor and / or for smoothing a voltage applied to the power terminal during the transition between the diode's reverse and forward states. Every electrical energy storage device (or energy storage device) can comprise one or more (e.g., stackable) accumulator modules (also called battery modules). For example, the energy storage device can comprise one or more accumulator modules, each of which has terminals on one upper side for the first and second terminals of the accumulator.The terminals on the top of an accumulator module contact corresponding terminals on the underside of another accumulator module in the stack above for a parallel connection of the secondary cells of the stacked accumulator modules or, as the topmost accumulator module, a bottom of the housing of the pre-charge circuit.
[0056] Each energy storage device in the system can comprise a battery and a pre-charging circuit with a BMS, a third switch and a diode according to an embodiment of the first-mentioned aspect.
[0057] By using energy storage devices, each containing a pre-charging circuit according to the first-mentioned aspect, embodiments of the system can enable the safe and efficient parallel connection of multiple energy storage devices. This can, for example, allow the system to be scalable, where each energy storage device can be pre-charged according to its individual voltage deficit (and thus its state-of-charge deficit), preferably without additional control communication between the energy storage devices.
[0058] When energy storage devices with accumulators of different voltage levels are connected in parallel, no high equalizing currents flow from the accumulator with the higher voltage level, because (in pre-charge mode) its diode blocks and its resistance limits the flowing equalizing current between the energy storage devices.
[0059] In each embodiment, the batteries of different energy storage devices can have different states of charge. The system allows batteries with different states of charge to be connected in parallel without prior balancing. The pre-charging circuit integrated into the energy storage device, with its diode (conducting in the charging direction), enables rapid balancing of the batteries, increasing the system's flexibility and efficiency.
[0060] In one embodiment, a central BMS can function as the BMS for all energy storage devices in the system. For example, the central BMS can control all first switches in the system via a common first system control line and / or all second switches in the system via a common second system control line. Furthermore, the third switch can be controlled depending on the switching state of the first and / or second switch.
[0061] Alternatively or additionally, each energy storage device can include the function of a BMS, and one of the BMS functions can act as the central BMS of the system. That is, each energy storage device can have its own BMS, whereby (e.g., at any given time) only one of the BMS functions as the central BMS and / or is active.
[0062] An implementation example where the (e.g., central or local) control system (for example, a BMS) controls the three switches of the energy storage device(s) via one or two control signals simplifies the system architecture and reduces the control effort. This leads to lower complexity and increases the reliability of the system.
[0063] The process for precharging and charging a battery can be executed by the (e.g., central or local) battery management system (BMS) of the precharging circuit or energy storage device, or by another controller (e.g., the system controller). This process enables the controller (e.g., the BMS) to quickly precharge the battery via the power terminal and / or efficiently balance the charge via the power terminal when energy storage devices are connected in parallel. The diode allows higher currents during the precharging phase than the precharging resistor, thus reducing the precharging time and improving the energy efficiency of balancing. During precharging, a charging voltage greater than the open-circuit voltage of all energy storage devices in the system can be applied to the (parallel-connected) power terminal of all energy storage devices in the system. This prevents any energy storage device from discharging during precharging.Alternatively or additionally, pre-charging can only begin above a threshold voltage (for example, from approximately 0.6 V to 0.7 V for a silicon diode) and / or pre-charging can be associated with a voltage drop (i.e., a forward voltage) across the diode (for example, from approximately 0.7 V to 1.0 V for a silicon diode).
[0064] The process can also include a gradual increase in the charging voltage. This allows only the energy storage device with the lowest open-circuit voltage of the battery to be pre-charged initially, as long as the charging voltage is above the lowest open-circuit voltage by the threshold voltage (or the forward voltage).
[0065] The invention is explained in more detail below with reference to the drawings and to preferred embodiments, which can optionally be combined with one another.
[0066] They show:
[0067] Fig. 1 shows an energy storage device with a conventional pre-charging circuit and load according to the state of the art;
[0068] Fig. 2 shows an energy storage device with a pre-charging circuit according to a first embodiment;
[0069] Fig. 3 shows an energy storage device with a pre-charging circuit according to a second embodiment;
[0070] Fig. 4 shows an energy storage device with a pre-charging circuit according to a variant of the first embodiment; Fig. 5 shows an energy storage system with energy storage devices according to the first embodiment;
[0071] Fig. 6 shows an energy storage system with energy storage devices according to the second embodiment; and
[0072] Fig. 7 shows a heterogeneous energy storage system with energy storage devices according to the first and second embodiments.
[0073] Fig. 1 shows a pre-charging circuit according to the prior art published by Texas Instruments in 2021, as mentioned above. Both poles of a high-voltage accumulator with battery cells (BC) can be disconnected from a load via switches Si and S2, respectively. A DC link capacitor is connected in parallel with the load.
[0074] In this prior art, the "pre-charging" with the second and third switches closed refers to a completely different current flow, namely the pre-charging of the intermediate circuit capacitor (C). Through this "pre-charging," the intermediate circuit capacitor charges to almost the same voltage as the accumulator, the only voltage source shown. There is no charging current source for pre-charging the accumulator and no indication of a parallel connection of the energy storage devices shown in Fig. 1.
[0075] The purpose of the DC link capacitor is that, once it is pre-charged, the pre-charge contactor S3 opens and the positive high-voltage contactor S1 closes, in order to drive the load or, in the case of energy recuperation, to charge the battery. Thus, the pre-charged DC link capacitor prevents a high inrush current for the load.
[0076] Fig. 2 shows a first embodiment of an energy storage device and a pre-charging circuit for the energy storage device. Herein, the pre-charging circuit and the energy storage device are generally designated by the reference numerals 100 and 200, respectively.
[0077] Figure 2 shows the first embodiment of a pre-charging circuit 100 for an energy storage device 200. The energy storage device 200 comprises an accumulator 202 with secondary cells (also referred to as battery cells, BZ), which is electrically connected to a power interface 104 via the pre-charging circuit 100. The pre-charging circuit 100 enables rapid and efficient adjustment of the state of charge with additional accumulators connected in parallel via the power interface 104 to ensure a safe parallel connection.
[0078] The accumulator 202 has a first terminal 102-1 and a second terminal 102-2. These terminals are selectively connected to the power terminal 104 via the pre-charging circuit 100, specifically to its first terminal 104-1 or its second terminal 104-2. This selective connection enables a controlled energy flow between the accumulator 202 and the power terminal 104.
[0079] A battery management system (BMS) 120 monitors and controls switches 106, 108, and 110 of the pre-charge circuit 100. Preferably, the BMS distinguishes between a regular charging phase, in which the first switch 106 and the second switch 108 are closed according to the control signal lines (2) and (1), respectively, shown with dashed lines, and a pre-charge phase. While the control unit for the charging phase and / or the pre-charge phase is referred to here as BMS 120, any control unit can be used for this purpose, for example, a control unit that exclusively controls the three switches 106, 108, and 110 for the charging and pre-charge phases.Preferably, the BMS 120 does not distinguish between a pre-charging phase, in which the accumulator 202 must be pre-charged due to its lower open-circuit voltage compared to the charging voltage applied at the power terminal, and a pre-charging phase in which the accumulator does not participate due to a sufficient open-circuit voltage. The first switch 106 is arranged between the first terminal 102-1 of the accumulator and the first terminal 104-1 of the power terminal. It allows the disconnection or connection of these two points and closes a main current path during the charging process in the charging phase. In the pre-charging phase, the first switch is open.
[0080] The second switch 108 is connected between the second terminal 102-2 of the accumulator and the second terminal 104-2 of the power connection. This switch enables all-pole disconnection of the power connection 104, thus increasing safety. The second switch 108 is open during the pre-charging and charging phases.
[0081] A series circuit 112 is located between the first terminal 102-1 of the accumulator 202 and the first terminal 104-1 of the power terminal 104. This circuit comprises a third switch 110 and a parallel circuit 114. The parallel circuit includes a pre-charge resistor 118 and a diode 116 connected in parallel. The diode is polarized to allow energy flow from the power terminal 104 to the accumulator 202 and to prevent reverse currents. In the first embodiment shown in Fig. 2, the parallel circuit is on the negative terminal side; that is, the first terminal 102-1 is the negative terminal. Accordingly, the diode 106 is forward-biased for conventional current flow to the negative terminal 102-1.
[0082] Optionally, a capacitor 122 is connected in parallel to the power terminal 104 and serves to smooth the voltage, which is particularly advantageous during transitions between different switching states. This ensures a stable voltage supply to the load connected to the power terminal 104 during discharge. During the pre-charging phase, the capacitor 122 (unlike the conventional DC link capacitor) can stabilize the on / off state of the diode 116 over time, for example, if the charging voltage at the power terminal 104 fluctuates while additional energy storage devices 200 are connected. This arrangement of the switches and the integration of the diode into the pre-charging circuit enable efficient charge balancing by allowing higher currents to flow during the pre-charging phase. This leads to faster balancing of the batteries and increases the efficiency and safety of the overall system.
[0083] Preferably, the switches 106, 108 and 110 mentioned herein are high-current contactors in one variant of each embodiment. The third switch 110 can be a separate pre-charging contactor for pre-charging the accumulator 202.
[0084] After pre-charging and charging, a load can be connected to the power connection 104 of the energy storage unit 200, e.g. a traction inverter of an electrically powered vehicle.
[0085] The second embodiment in Fig. 3 shows an energy storage device 200 with an optimized pre-charging circuit 100. This circuit 100 enables efficient adjustment of the charge states of parallel-connected accumulators 202. The energy storage device 200 comprises an accumulator 202, which is connected to a power terminal 104 via the pre-charging circuit 100.
[0086] In contrast to the first embodiment shown in Fig. 2, in this second embodiment the third switch 110 and the diode 116 (i.e., the entire series circuit 112) are arranged between the first terminal 102-1 of the accumulator 202 and the first terminal 104-1 of the power terminal 104 on the positive side of the accumulator 202. Similarly, the second switch 108 is arranged between the second terminal 102-2 of the accumulator 202 and the second terminal 104-2 of the power terminal 104 on the negative side of the accumulator 202.
[0087] The first switch 106 and the second switch 108 enable regular charging and discharging operation in the closed state and all-pole disconnection in the open state (including the third switch 110). As in the first embodiment, a series circuit 112 is connected between the first pole 102-1 of the accumulator 202 and the first pole 104-1 of the power terminal 104. This circuit includes the third switch 110 and the parallel circuit 114. The parallel circuit comprises a pre-charge resistor 118 and a diode 116. The diode 116 is polarized such that it allows energy flow from the power terminal 104 to the accumulator 202 and prevents unwanted reverse currents. That is to say, In the case of the arrangement of the diode 116 on the positive side of the accumulator 202, the conductive conventional current direction of the diode 116 is away from the positive terminal 102-1 of the accumulator 202.
[0088] Figure 4 shows a variant of the first embodiment of the pre-charging circuit 100 for the energy storage device 200. This variant includes a battery management system, BMS 120, which controls and monitors the first and second switches 106 and 108. The pre-charging circuit 100 enables efficient adjustment of the state of charge with additional accumulators 202 connected in parallel via the power connection 104.
[0089] As in the first embodiment of Fig. 2, the energy storage device 200 comprises an accumulator 202, which is electrically connected to a power terminal 104 via the pre-charging circuit 100. The accumulator 202 has a first terminal 102-1 and a second terminal 102-2, which can be connected to the first terminal 104-1 and the second terminal 104-2 of the power terminal 104, respectively, via the first and second switches 106 and 108. This connection enables an energy flow between the accumulator 202 and the power terminal 104, regulated by the BMS 120.
[0090] A first switch 106 is arranged between the first terminal 102-1 of the accumulator and the first terminal 104-1 of the power terminal. It closes the main current path during regular charging and discharging. A second switch 108 is located between the second terminal 102-2 of the accumulator and the second terminal 104-2 of the power terminal. It is closed during pre-charging, charging, and discharging, and otherwise, together with the first switch, ensures all-pole disconnection. The pre-charging circuit 100 (for example, the series circuit 112 or the BMS 120) further includes switching logic configured to control the switching state of the third switch 110 depending on the switching states of the first switch 106 and the second switch 108. The third switch 110 is closed when the second switch 108 is closed and the first switch 106 is open, according to the logic S3 = S2 and not S1.This logic ensures a safe and efficient pre-loading process.
[0091] This variant demonstrates that corresponding variations of the second embodiment shown in Fig. 3 exist, in which the switching logic can be applied in a similar manner to ensure fast and reliable balancing of the accumulators without additional signaling from the BMS 120. The integration of this switching logic leads to simplified control and reduces the need for additional control signals, thus increasing the efficiency and reliability of the system.
[0092] The first embodiment of a system 400 shown in Fig. 5 comprises a plurality of electrical energy storage devices 200, each containing a pre-charging circuit 100. These energy storage devices 200 are connected in parallel. That is, the energy storage devices 200 of the system 400 are connected in parallel via their respective power connections 104.
[0093] For pre-charging and / or charging, a central charging current source 402 supplies the energy storage devices 200 with a charging current, preferably with a charging voltage that increases over time, at the parallel-connected power terminals 104.
[0094] Each energy storage unit 200 contains an accumulator 202, which is connected to a power terminal 104 via the pre-charge circuit 100. The pre-charge circuit 100 enables effective adjustment of the charge states of the parallel-connected accumulators, thus supporting safe and efficient parallel operation. The pre-charge circuit 100 comprises a first switch 106 and a second switch 108, which control the energy flow between the accumulator 202 and the power terminal 104. The first switch 106 is located between the first terminal 102-1 of the accumulator and the first terminal 104-1 of the power terminal. The second switch 108 connects the second terminal 102-2 of the accumulator to the second terminal 104-2 of the power terminal.
[0095] A third switch 110 and a parallel circuit 114 consisting of a pre-charge resistor 118 and a diode 116 are connected in series between the first terminal 102-1 of the accumulator and the first terminal 104-1 of the power terminal. The diode 116 is polarized to allow energy flow from the power terminal to the accumulator and to prevent reverse currents. This allows higher pre-charge currents, thereby reducing the balancing time.
[0096] Preferably, a central battery management system (BMS) of system 400 controls the switches 106 and 108 of all energy storage units 200. This can be achieved by direct signaling to switches 106 and 108 (preferably eliminating the need for the decentralized BMS 120 in the individual energy storage units 200) or by centralized control of the distributed BMS 120 in the individual energy storage units 200. The control of the third switch can be identical to that of the first switch or, as described above, result from the switching states of the first and second switches 106 and 108, which reduces complexity and increases reliability.
[0097] This embodiment demonstrates how the clever integration of the pre-charging circuit 100 into each energy storage device 200 achieves energy storage-specific, fast, and efficient balancing without additional signaling paths. The parallel connection of the energy storage devices 200 enables a modular and scalable system configuration that can be flexibly adapted to the requirements of modern energy storage solutions. Corresponding systems 400 can be built, as shown in Fig. 6, based on the second embodiment of the energy storage devices 200, or in heterogeneous systems 400, as shown in Fig. 7, using either the first or second embodiment of the energy storage devices 200.
[0098] As can be seen from the above disclosed embodiments of all aspects, embodiments of the present technology include an optimized pre-charging circuit for parallel-connected batteries and enable a simple parallel connection of batteries with minimal control effort and all-pole disconnection of the contacts.
[0099] Such parallel-connected energy storage systems 200 in scalable systems 400 can be used, for example, in charging stations for electric vehicles or stationary energy storage systems. For example, each energy storage device 200 (i.e., each accumulator 202 within it) can have a capacity of 10 kWh or more.
[0100] The circuit shown in Fig. 1 is not satisfactory for connecting multiple batteries in parallel. The HV batteries would first need to be charged separately to exactly the same voltage and could be finely balanced via the pre-charge resistor R to avoid destructive equalizing currents later when directly connected (i.e., Si and S2 closed).
[0101] If highly unbalanced batteries are connected in parallel using the circuit of Fig. 1 and closed to balance S2 and S3, the charge equalization takes a very long time (e.g. several days or weeks), because the resistor, which is actually only designed for pre-charging capacitive loads, is either very high-impedance or can only be switched on briefly due to high pulse energy.
[0102] Exemplary embodiments of the pre-charging circuit 100 allow batteries 202 with different charge levels to be connected in parallel and subsequently balanced, i.e., charged to exactly the same potential level (e.g., open-circuit voltage). Balancing occurs relatively quickly.
[0103] Furthermore, poles 104-1 and 104-2 (e.g. connection terminals) of the power connection 104 can be completely disconnected by opening the three switches 106, 108 and 110.
[0104] No additional control signals are necessary to control the additional third switch 110.
[0105] In one variant of each embodiment of each aspect, the diode 116 can be added in parallel with the resistor 118 for the rapid balancing of parallel-connected batteries 202. To maintain the pre-charging functionality, the diode 116 must be installed in such a way that it can only accept charging current.
[0106] According to one embodiment of the method, the first switch S2 with reference numeral 106 and the third switch S3 with reference numeral 110 are first switched on (closed). Optionally, a capacitive load is then pre-charged and / or the balancing of parallel-connected batteries 202 is now possible. In this way, all parallel-connected batteries 202 can be quickly pre-charged to a common voltage level.
[0107] If required, two or more diodes 116 can be connected in series, e.g. for the case of a single fault where one diode is defective.
[0108] The charging voltage (optionally a charging voltage that increases over time at the end) is at least as high as that of battery 202 in system 400 with the highest charge level.
[0109] Depending on the current-carrying capacity of the third switch S3 and the diodes 116, the maximum current for balancing (i.e., the pre-charge current for pre-charging the batteries 202) may differ from the normal charging current. For example, third switches 110 with a lower current-carrying capacity are possible.
[0110] Fine balancing of parallel-connected batteries is possible via the pre-charge circuit 100 with the resistor 118.
[0111] For normal operation (for example, discharging or regular charging after pre-charging), the first switch Si is activated (closed). Optionally, the third switch is then opened.
[0112] Additional control signals for the third switch S3 110 can be omitted by using the control signal of the second switch 108 (for example a DC contactor S2) for the pre-charging circuit S3.
[0113] Dual use of the second switch S2 108 for safety shutdown and pre-charging can reduce the number of switches used.
[0114] In one variant of the embodiment, the BMS 120 can be installed internally or externally.
[0115] As can be seen from the exemplary embodiments of the pre-charging circuit 100, these circuits can have the following features and functions:
[0116] Diode 116 is connected in parallel to resistor 118. This enables rapid balancing of the batteries 202 by absorbing the (pre-)charging current and preventing reverse currents.
[0117] The three switches Si, S2, and S3 control the energy flow. The third switch, S3, performs the pre-charging function, while the first switch, S1, closes the main current path during normal operation.
[0118] The battery management system (BMS) monitors and controls the switches to ensure battery safety and efficiency. Its control lines, which activate and deactivate the switches, do not require a dedicated control line for the third switch. The addition of diode 116 and the optimized switch control enable rapid balancing of the batteries 202 without the need for additional control signals.
[0119] Exemplary embodiments of the pre-charging circuit 100 enable a modular and scalable solution for energy storage systems 400, which ensures efficient and rapid balancing of the batteries 202.
[0120] In a further development of each embodiment, the pre-charging circuit 100 also includes a temperature sensor that is thermally coupled to the diode 116. The battery management system 120 is further configured to monitor the temperature of the diode 116 during the pre-charging process and to modify the pre-charging process (for example, the switching positions of switches 106, 108 and / or 110) based on the measured temperature in order to prevent thermal overload of the diode 116.
[0121] By thermally coupling a temperature sensor to diode 116, the BMS 120 can monitor the diode's temperature in real time. During the pre-charging process, increased currents flow through diode 116 to enable rapid balancing of the parallel-connected batteries 202. These increased currents can lead to significant heating of diode 116.
[0122] The BMS 120 uses temperature measurements to control the pre-charging process and protect diode 116 from overheating. If the measured temperature exceeds a predefined threshold, the BMS 120 can adjust the pre-charging process, for example, by opening the third switch 110 to interrupt the current flow through the diode, or by limiting the current. Once diode 116 has cooled to a safe temperature, the BMS 120 can resume the pre-charging process.
[0123] This function solves the technical problem of potential thermal overload and failure of diode 116 due to high currents during the pre-charging process. It increases the safety and reliability of the pre-charging circuit 100 by preventing overheating of diode 116 and thus ensuring the proper operation of the circuit 100.
[0124] As can be seen from the preceding embodiments, these offer several advantages over the prior art. The diode 116 connected in parallel to the pre-charge resistor enables rapid balancing of parallel-connected accumulators 202 with different charge states. In contrast, conventional solutions involving a complex DC-DC conversion of a pre-charge voltage and individual application of the pre-charge voltage to each energy storage device are intricate, or the conventional solutions are very slow when balancing via a pre-charge resistor due to its high resistance. However, embodiments of the pre-charge circuit 100, with the diode 116, allow for a higher current flow and thus faster balancing of parallel-connected accumulators 202, which is more efficient because the power loss across the diode is lower than across a pre-charge resistor.
[0125] Furthermore, no energy storage-specific control of the third switch 110 is necessary. For example, during pre-charging, all third switches 110 of the parallel-connected energy storage devices can be closed. The energy storage-specific pre-charging of the accumulator 202, based on its voltage deficit compared to the pre-charging voltage applied at the power terminal 104, is controlled decentrally by the diode 116. Therefore, no energy storage-specific control signals and no complex control for faster balancing are necessary, as the diode 116 is connected in parallel to the pre-charging resistor 118.
[0126] A technical effect achieved only by the present invention is that, during the pre-charging phase, a higher current flows to those accumulators 202 where there is a residual voltage potential due to the diode connected in parallel to the pre-charging resistor. This leads to faster voltage balancing of the parallel-connected accumulators 202, since the diode 116 has a low resistance in the energy flow direction towards the weaker accumulator, thus facilitating charge exchange between the accumulators and / or prioritizing the charging current available in the system 400. This significantly reduces the time required for the accumulators to equalize their charge states, increasing efficiency and simultaneously ensuring safety when connecting batteries with different charge states in parallel.
[0127] Although the invention has been described with reference to exemplary embodiments, it is apparent to those skilled in the art that various modifications can be made and equivalents can be used as replacements. Furthermore, many modifications can be made to adapt the invention to a specific situation or material. Consequently, the invention is not limited to the disclosed embodiments but encompasses all embodiments that fall within the scope of the appended claims. List of reference numerals
[0128] Pre-charge circuit 100 First terminal of the accumulator 102-1 Second terminal of the accumulator 102-2 Power connection 104 First terminal of the power connection 104-1 Second terminal of the power connection 104-2 First switch 106 Second switch 108 Third switch 110 Series connection 112 Parallel connection 114 Diode 116 Pre-charge resistor 118 Battery management system (BMS) 120 Capacity 122 Energy storage 200 Accumulator 202 System 400 Charging current source 402
Claims
Patent claims 1. Pre-charging circuit (100) for connecting an accumulator (202) to a power connection (104), wherein the pre-charging circuit (100) comprises: a first switch (106) between a first pole (102-1) of the accumulator (202) and a first pole (104-1) of the power terminal (104); a second switch (108) between a second pole (102-2) of the accumulator (202) and a second pole (104-2) of the power terminal (104); a series circuit (112) connected between the first terminal (102-1) of the accumulator (202) and the first terminal (104-1) of the power terminal (104), wherein the series circuit (112) comprises a third switch (110) and a parallel circuit (114) connected in series with each other, and wherein the parallel circuit (114) comprises an ohmic resistor (118) and a diode (116) connected in parallel with each other, the diode being polarized such that it allows energy flow from the power terminal (104) to the accumulator (202) and blocks energy flow in the reverse direction; and a battery management system, BMS (120) which is designed to control the switches (106, 108, 110) as follows: - with the first switch (106) open, the second switch (108) and the third switch (110) closed to electrically connect the accumulator (202) to the power terminal via the resistor (118) and the diode (116), and - subsequent closing of the first switch (106).
2. Pre-charging circuit (100) according to claim 1, wherein the diode (116) is designed to allow currents that are greater than the current limited by the resistor (118).
3. Pre-charging circuit (100) according to claim 1 or 2, wherein the diode (116) comprises two or more diodes connected in series.
4. Pre-charging circuit (100) according to any one of claims 1 to 3, wherein the BMS (120) is further configured, or a switching logic dependent on the switching states of the first and second switches (106, 108) is configured, to open the third switch (110) after the first switch (106) has been closed.
5. Pre-charging circuit (100) according to one of claims 1 to 4, wherein a switching state of the third switch (110) is derived from a combination of the switching states of the first switch (106) and the second switch (108) or a switching state of the third switch (110) according to the logic S3 = S2 AND NOT Si is controlled, wherein a closed switching state of the first switch (106), the second switch (108) and the third switch (110) is indicated by Si , S2 and S3 respectively, optionally, the dependence of the switching state S3 of the third switch (110) on the switching state S1 of the first switch (106) is time-delayed compared to the dependence on the switching state S2 of the second switch (108).
6. Pre-charging circuit (100) according to one of claims 1 to 5, wherein the BMS (120) is further configured to close or control the second switch (108) and the third switch (110) via a single control signal.
7. Pre-charging circuit (100) according to one of claims 1 to 6, wherein the second switch (108) is a safety contactor and / or the BMS (120) is configured to open the first switch (106) both for safety shutdown and for pre-charging the accumulator (202). Such a dual function of the first switch can reduce the number of components required in the pre-charging circuit and / or simplify the pre-charging circuit, leading to cost and resource savings.
8. Pre-charging circuit (100) according to any one of claims 1 to 7, wherein the power connection (104) and / or a housing of the pre-charging circuit (100) is configured for connecting several electrical energy storage devices (200) in parallel.
9. Pre-charging circuit (100) according to claim 8, wherein on opposite sides of the housing of the pre-charging circuit (100) - complementary connector halves with contacts of the first pole (104-1) and the second pole (104-2) of the power connection (104) and - complementary profile structures for mechanical connection with an identical housing are arranged, wherein the connector halves and the profile structures are arranged to connect the first poles (104-1) and the second poles (104-2) of the power terminals (104) of the housings mechanically connected via the profile structures in a state mechanically connected with a further housing via the connector halves in parallel.
10. Pre-charging circuit (100) according to one of claims 1 to 9, wherein the first pole (102-1) of the accumulator (202) is a positive pole of the accumulator and the second pole (102-2) of the accumulator (202) is a negative pole; or wherein the first pole (102-1) of the accumulator (202) is a negative pole of the accumulator and the second pole (102-2) of the accumulator (202) is a positive pole.
11. Pre-charging circuit (100) according to one of claims 1 to 10, further comprising: a capacitor (122) connected in parallel to the first pole (104-1) and to the second pole (104-2) of the power terminal (104) for smoothing a voltage applied to the power terminal (104) during the transition between the reverse state of the diode (116) and the forward state of the diode (116).
12. Electrical energy storage (200), comprising: a pre-charging circuit (100) according to any one of claims 1 to 11, and an accumulator (202) whose first pole (102-1) and second pole (102-2) is electrically connected or connectable to the pre-charging circuit (100), optionally wherein the accumulator (202) is arranged in the housing according to claim 8 or 9.
13. System (400) comprising a plurality of electrical energy storage devices (200) according to claim 12, wherein the power terminals (104) of the pre-charging circuits (100) of the electrical energy storage devices (200) are connected in parallel.
14. System (400) according to claim 13, wherein the accumulators (202) of different energy storage devices (200) have different states of charge. The system allows accumulators with different states of charge to be connected in parallel without prior equalization. The pre-charging circuit integrated into the energy storage device with the (charging-direction conducting) diode enables rapid balancing of the accumulators, which increases the flexibility and efficiency of the system.
15. System (400) according to claim 13 or 14, wherein a central BMS (120) functions as the BMS (120) of all energy storage devices (200) in the system (400), optionally: wherein the central BMS (120) controls all first switches (106) in the system (400) via a common first control line and all second switches (108) in the system (400) via a common second control line, and wherein the third switch (110) is controlled depending on the switching state of the first and / or second switch, and / or wherein each energy storage device (200) includes the function of a BMS (120) and one of the BMS functions acts as the central BMS (120) of the system.
16. Method for precharging and charging an accumulator (202), wherein the accumulator (202) is electrically connected to a power connection (104) via a precharging circuit (100) according to one of claims 1 to 11, the method comprising: Closing the second switch (108) and the third switch (110) of the pre-charging circuit (100) to electrically connect the accumulator (202) to the power terminal (104) via the resistor (118) and the diode (116) for selective pre-charging depending on the open-circuit voltage of the accumulator (202) and the charging voltage at the power terminal (104); and subsequently closing the first switch (106) to charge the accumulator (202).