Circuit arrangement and method for impedance spectroscopy excitation in multi-cell batteries

Abstract

This disclosure relates to circuit arrangements and methods for impedance spectrum excitation in multi-cell batteries. A method is described, comprising the steps of: switching on a plurality of switching elements coupled to the battery during corresponding on-times within a predetermined time period, thereby generating a current signal through the battery. The battery comprises a plurality of cell units, and each of the plurality of switching elements is arranged in parallel with at least one of the plurality of cell units. The on-times are determined by controller circuitry. The method further includes the step of measuring a voltage signal across the battery. Furthermore, the method includes the step of determining the impedance of the battery based on the measured voltage signal and the generated current signal.

Description

Technical Field

[0001] This application relates to the field of multi-cell batteries, and in particular to the use of electrochemical impedance spectroscopy to monitor multi-cell batteries. Background Technology

[0002] Multi-cell batteries are widely used in electric vehicles. They consist of a large number of interconnected battery cells, such as lithium-ion batteries. A typical multi-cell battery includes hundreds of battery cells and can produce voltage levels of 400 V or 800 V.

[0003] To obtain useful information about battery condition, such as state of charge, performance prediction, or temperature, multi-cell batteries can be monitored using electrochemical impedance spectroscopy (EIS). EIS is a diagnostic method that can predict near-term available power. Typically, a multi-cell battery is excited by an external circuit applying a sinusoidal signal to the battery, and the battery's impedance is measured.

[0004] However, conventional electrochemical impedance spectroscopy is energy-intensive and requires additional hardware. In particular, it either requires current measurements synchronized with voltage measurements or precise knowledge of the timing and amplitude characteristics of the excitation.

[0005] Therefore, there is a need for improved methods for monitoring multi-cell batteries, which have proven to be energy-efficient and require no additional hardware. Summary of the Invention

[0006] The aforementioned objective is achieved by the method of claim 1, particularly by activating the balance switches of the multi-cell batteries at corresponding predetermined on-times, and by the system of claim 15. By controlling the switching operations of the multiple balance switches of the battery, the load of the multi-cell batteries can be modulated, and a periodic excitation current is generated in the batteries. This excitation current can be used to determine the complex impedance of the batteries. Since the switching elements are part of the existing hardware of the battery management system, no additional circuitry is required. Furthermore, the on-time can be determined to obtain a variable signal waveform for the excitation current.

[0007] In one example, this disclosure relates to a method comprising the steps of: activating a plurality of switching elements coupled to a battery at corresponding on-times within a predetermined time period, thereby generating a current signal through the battery. The battery comprises a plurality of battery cells, and each of the plurality of switching elements is arranged in parallel with at least one of the plurality of battery cells. The on-times are determined by controller circuitry. The method further includes the step of measuring a voltage signal across the battery. Furthermore, the method includes the step of determining the battery impedance based on the measured voltage signal and the generated current signal.

[0008] In another example, this disclosure relates to a system including a battery comprising a plurality of battery cells. The system also includes a plurality of switching elements coupled to the battery. Each of the plurality of switching elements is arranged in parallel with at least one of the plurality of battery cells. The system also includes a controller circuit coupled to the plurality of switching elements. The controller circuit is configured to turn on the plurality of switching elements at corresponding on-times of a predetermined time period, thereby generating a current signal through the battery, wherein the on-times are determined by the controller circuit. The controller circuit is also configured to measure a voltage signal across the battery and determine the battery impedance based on the measured voltage signal and the generated current signal. Attached Figure Description

[0009] The embodiments described herein can be better understood by referring to the following description and accompanying drawings. The components in the drawings are not necessarily drawn to scale; the emphasis is on the principles of the illustrated embodiments. Furthermore, in the drawings, the same reference numerals designate corresponding parts. In the drawings:

[0010] Figure 1 The diagram illustrates the general structure of a multi-cell battery system based on one or more technologies described herein.

[0011] Figure 2 The illustration shows a first example circuit of a multi-cell battery system according to one or more technologies described herein.

[0012] Figure 3 The diagram illustrates the structure of a multi-cell battery system according to one or more technologies described herein, the system comprising multiple local controllers linked as a daisy chain.

[0013] Figure 4 A second example circuit of a multi-cell battery system with multiple local controllers according to one or more technologies described herein is illustrated.

[0014] Figure 5 An example circuit of a balancing device for diagnosing battery cells in a multi-cell battery, according to one or more techniques described herein, is illustrated.

[0015] Figure 6 The diagram illustrates a simplified circuit including a balancing circuit for the battery cell when the switching element is open (Figure (a)) and when the switching element is closed (Figure (b)).

[0016] Figure 7 The illustration shows a first example of switching operation of multiple switching elements according to one or more techniques described herein (Fig. (a)), switching operation of a balancing signal (Fig. (b)), and switching operation of an accumulation switching operation (Fig. (c)).

[0017] Figure 8 The illustration shows a second example of switching operation of multiple switching elements according to one or more techniques described herein (Figure (a)) and switching operation of a balance signal (Figure (b)).

[0018] Figure 9 The illustration shows a third example of switching operation of multiple switching elements according to one or more techniques described herein (Figure (a)) and switching operation of a balance signal (Figure (b)).

[0019] Figure 10 The illustration shows a fourth example of switching operation of multiple switching elements according to one or more techniques described herein (Figure (a)) and switching operation of a balance signal (Figure (b)).

[0020] Figure 11 The figure illustrates a time diagram of the load resistance for a multi-cell battery with different on-time modes, based on one or more techniques described herein.

[0021] Figure 12 This is a flowchart illustrating an example method for measuring the impedance of a multi-cell battery according to one or more techniques described in this disclosure. Detailed Implementation

[0022] Multi-cell batteries are widely used in electric vehicles. They consist of multiple interconnected battery cells. To enable in-depth battery analysis, multi-cell batteries are typically used in conjunction with a battery management system (BMS). The BMS is configured to provide battery state estimation and measure battery cell parameters such as voltage, current, and temperature, among other functions.

[0023] Balancing circuits are an essential component of battery management systems. They are used to balance the charge of battery cells or groups of cells, thus enabling individual diagnostics of each cell. Balancing circuits consist of resistors (also called balancing resistors) and switching elements. Balancing circuits are common in large lithium-ion batteries but can also be used in other types of batteries. The balancing circuits are connected to a controller circuit configured to control the balancing circuits, and specifically the switching elements, on and off. Each balancing switch can be controlled individually.

[0024] Figure 1An example of the overall structure of a multi-cell battery system 100 is illustrated. The system includes a multi-cell battery 110 comprising multiple battery cells. In one example, the battery is a 400 V or 800 V battery. Battery 110 may include hundreds of individual battery cells connected in series with each other. In one example, the battery includes 180 battery cells, each generating a DC voltage level of 4.2 V, resulting in a total DC voltage level of 756 V. In one example, a battery cell comprises a single battery element. In another example, at least one of the battery cells comprises multiple battery elements connected in parallel with each other.

[0025] System 100 includes a plurality of switching elements 130 coupled to a battery 110 and a controller 120 coupled to the plurality of switching elements 130. System 100 may also include a plurality of balancing resistors, wherein each of the plurality of switching elements 130 is arranged in series with at least one of the plurality of balancing resistors. The switching elements and balancing resistors are part of corresponding balancing circuits, as will be referenced below. Figures 2 to 6 As shown. In one example, controller circuit 120 is configured to turn on multiple switching elements 130. Controller circuit 120 and multiple switching elements 130 are part of a battery management system for multi-cell battery 110.

[0026] In one example, the controller circuit 120 is partially implemented in software using a suitable processor (e.g., a microcontroller). This processor can be configured to execute software instructions stored in memory. In another example, the controller circuit 120 is implemented entirely in hardware and does not require a programmable processor. The controller circuit 120 can also be implemented as a combination of hardware and software.

[0027] Figure 2 A first example of a multi-cell battery system 100 is illustrated in more detail. The multi-cell battery 110 includes a plurality of n battery cells BC1…BC1 connected in series with each other. n As described above, battery cells BC1…BC n It may include a single battery element B1…B n Or multiple battery elements arranged in parallel. Each battery element B1…B n It may include an internal resistor (not shown). System 100 also includes multiple balancing circuits 111…11 n Among them, the balancing circuit 111…11 n Each of them is connected to the corresponding battery cell BC1…BC n One of them. In the illustrated example, each balanced circuit 111…11 n Includes at least one switching element SW1…SW nand at least one balancing resistor R B1 R B2 ..., R Bn Each balancing circuit 111…11 n The switching elements and balancing resistors are connected in series. The controller circuit 120 is coupled to multiple switching elements SW1…SW1. n And is configured to control the switching elements SW1…SW n In the illustrated example, battery 110 is shown in a state where it is decoupled from external current and no current flows through it. In this state, battery 110 can be monitored by controller circuitry 120. In one example, battery 110 has no external load. This is schematically illustrated by open-circuit switching elements at both ends of battery 110.

[0028] The controller circuit 120 may be a microcontroller, configured to transmit signals to different balancing circuits 111…11 n Parallel control signals are sent to directly control the switching elements SW1…SW of battery 110. n Each of them. Alternatively, switching elements SW1…SW n This can be controlled via a local controller arranged in a serial daisy chain. This situation occurs in... Figure 3 Examples are provided in the text.

[0029] Figure 3The structure of a multi-cell battery system 100 is shown, comprising a plurality of local controllers 122 daisy-chained together. In the depicted example, controller circuitry 120 includes a master controller 121 and a plurality of local controllers 122. The first of the plurality of local controllers 122 is connected to the master controller 121. The local controllers 122 are connected to each other to form a daisy chain, i.e., they are connected sequentially to each other. Controllers 121, 122 may be electrically isolated, as schematically illustrated by capacitors between adjacent controllers. The master controller 121 may include a microcontroller communicating with a transceiver, for example via a UART interface. The microcontroller may be configured to transmit control signals including control signals for all local controllers 122. The transceiver may be connected to the first controller to transmit the microcontroller's control signals. The microcontroller's control signals are then transmitted from one local controller to the next, wherein each local controller 122 is configured to control at least one switching element of a balancing circuit for the battery cell based on the control signals. Local controllers may also be configured to send back messages to the master controller via the daisy chain. Local controllers 122 may have microcontrollers. However, this is not necessary. In one example, the local controller 122 is an integrated circuit. In one example, the local controller 122 is an integrated circuit of the TLE9012DQU type, wherein each local controller 122 is connected to twelve battery cells. In one example, the system includes ten local controllers 122. In one example, each local controller 122 is connected to up to eighteen battery cells of the battery. The local controller 122 is configured to control switching elements associated with the connected battery cells based on control signals from the main controller 121, and to measure the local voltage of the battery 110. In one example, the controller circuit 120 includes a plurality of local voltage sensors, wherein each local voltage sensor is configured to measure a local voltage signal over at least one of the plurality of battery cells. Additionally, the system 100 may include another local controller 140 connected to the battery 110 and configured to measure the current flowing through the entire battery 110, or the voltage level of the entire battery 110, or at least one of both. In one example, the other controller circuit 140 may include a microprocessor. In another example, the other controller circuit 140 is fully hardware implemented and does not require a programmable processor. The other controller circuit 140 can also be implemented as a combination of hardware and software.

[0030] Figure 4 The diagram shows Figure 2 Example of modification, where controller 120 is replaced with Figure 3 The system includes a main controller 121 and a local controller 122. Each local controller 122 is coupled to multiple switching elements SW1…SW1. nAt least one switching element is configured to control the corresponding switching element based on at least one signal from the main controller 121. Each local controller 122 can be connected to one or more battery cells BC1…BC n The daisy-chain configuration enables very short communication latency between local controllers 122. Communication between local controller 122 and the corresponding battery cell will refer to... Figure 5 A further detailed explanation is needed.

[0031] Figure 5 The diagram illustrates an example circuit for a conventional balancing system used with a local controller 122. This local controller 122 is configured to monitor multiple m battery cells BC1…BC m In one example, the local controller 122 is an integrated circuit of type TLE9012DQU, and the integer m equals 12. The local controller 122 includes multiple switching elements SW1…SW m In the illustrated example, the switching elements SW1…SW m It is a MOSFET. The local controller 122 is configured to control the MOSFET via the corresponding gate drivers GD1…GD. m To the switching elements SW1…SW m The gate sends a corresponding control signal to control the switching elements SW1…SW m However, the switching elements SW1…SW m Alternatively, it can be external to the local controller 122 and connected to the local controller 122 via corresponding pins. As described above, the local controller 122 can be daisy-chained to another local controller 122 and can receive control signals from the master controller 121 via a daisy chain.

[0032] Multiple battery cells BC1…BC m Each battery cell in the battery is connected to multiple switching elements SW1…SW m The corresponding switching elements are connected in parallel. In the illustrated example, each battery cell BC1…BC m Including battery components B1…B m and internal resistor R BC1 …R BCm Each battery cell BC1…BC m via the first pin U1…U of the local controller 122 respectively m Second pin G1…G m Connected to the corresponding MOSFETs SW1…SW m The drain and source terminals. The corresponding balancing resistor R. B1 …R Bm Arranged in battery cells BC1…BCm The first terminal and the second pin G1…G m Between. Filter resistor R F Arranged in battery cells BC1…BC m The second terminal and the first pin U1…U m Between. Additionally, battery cells BC1…BC m The first terminal is connected to the filter resistor R of the adjacent battery cell. F The first pin is connected to the adjacent battery cell. In one example, the local controller 122 is configured to measure battery cells BC1…BC m The local voltage drop between its first pin and the first pin of the adjacent battery cell. Additionally, to ensure electrical isolation, capacitor C... F1 Connected to each switching element SW1…SW m The drain and source, and capacitor C F2 It is connected to the drain of two adjacent switching elements.

[0033] Switching elements SW1…SW m It can be controlled independently by the local controller 122 for diagnostic purposes. In one example, the local controller 122 sends control signals to the switching elements SW1…SW based on the control signals from the main controller 121. m Send a balancing signal. This balancing signal can be a binary signal, where switching elements SW1…SW are activated when the balancing signal has a first value. m It is configured to be turned on, and configured to be turned off when the balancing signal has a second value. In one example, the balancing signal is a pulse width modulation (PWM) signal. The local controller 122 can turn on the corresponding switching elements SW1…SW m To monitor battery cells BC1…BC m During the monitoring process, no current flows through battery 110. When switching elements SW1…SW… m When switched on, the balancing current flows through the corresponding battery cells BC1…BC m The corresponding balancing resistor R B1 …R Bm and the corresponding filter resistor R F Battery cells BC1…BC m The voltage level drop between the first pin and the first pin of the adjacent battery cell is related to the filter resistor R. F The voltage drop is proportional to the resistance. The local controller 122 can then measure this voltage drop and diagnose the battery cell based on the measured voltage.

[0034] As mentioned above, the switching elements associated with the battery cell can be controlled individually to monitor the battery cell. However, according to one example, the switching elements can be controlled collectively to obtain more information about the battery cell.

[0035] Figure 6 A simplified example of a circuit including a battery cell BC1 and a corresponding balancing circuit 111 for the battery cell BC1 is shown. The battery cell BC1 and the balancing circuit 111 can be as follows: Figure 5 The example shown is configured as follows. Battery cell BC1 includes battery element B1 and internal resistor R. BDC1 In the depicted example, battery element B1 is a voltage source generating a voltage level of 4.2 V. In another example, battery cell BC1 comprises multiple battery elements arranged in parallel, wherein the voltage level of battery cell BC1 is equal to the sum of the voltage levels of the battery elements. In the depicted example, the internal resistor R... BDC1 The resistance is 200 µΩ. In other examples, the internal resistor R... BDC1 The resistance is between 100 µΩ and 500 µΩ. The balancing circuit 111 is connected in parallel with battery cell B1. The balancing circuit 111 has a switching element SW1 and a resistor R1 arranged in series with the switching element SW1, which represents the total resistance of the balancing circuit 111. Figure 5 In the example, resistor R1 is equivalent to the balancing resistor R B1 and filter resistor R F The switching element SW1 can be a transistor, such as a MOSFET. The balancing circuit 111 is controlled by a controller circuit 120 (not shown), as described above. The controller circuit 120 can be configured to measure the voltage between terminals C1 and C2 of the battery cell BC1.

[0036] Figure 6 (a) The diagram shows the case where the switching element SW1 is disconnected. Battery 110 is connected, resulting in no battery current I. bat Through battery cell B1, i.e., I bat =0 A. Therefore, the measured voltage V1 between terminals U1 and U2 of battery cell BC1 is equal to the voltage of battery element B1, which is 4.2 V in this case. Figure 6 (b) The diagram shows the state when the switching element SW1 is turned on. At this time, the balancing current i B It flows through battery cell BC1. In the depicted example, the balancing current i B equals i B =100 mA. In other examples, the balancing current i B Between 50 mA and 250 mA. The voltage drop between terminals U1 and U2 is equal to i B ·RBDC1 =20 µV voltage drop. When battery 110 includes 180 battery cells, the total DC voltage level of battery 110 is 756 V, the total internal resistance (internal load) of the battery is 36 mΩ, and the maximum voltage drop across battery 110 is 3.6 mV.

[0037] Therefore, the internal load of battery 110 can be modulated by collectively switching on and off the switching elements of the balancing circuit coupled to battery 110. Load modulation results in the generation of an excitation current across battery 110 that follows the load modulation; that is, if the load has a sinusoidal waveform, the excitation current will also have a sinusoidal waveform. In one example, a voltage signal is measured across the entire battery 110. In another example, a local voltage signal is measured across each cell of battery 110. In one example, an excitation current signal is also measured. In another example, the excitation current signal is evaluated based on the known characteristics of the balancing circuit and the cell. Based on the measured voltage and excitation current signals, the impedance of battery 110 can be determined. This impedance measurement does not require any additional hardware because the balancing circuit already exists in conventional battery systems. Only the corresponding software needs to be adjusted. Furthermore, power losses can be distributed across the entire battery, thus reducing power loss compared to conventional electrochemical impedance measurements.

[0038] Figure 7-10 The illustration shows how the switching elements of battery 110 can be switched in order to obtain the desired excitation current through battery 110. Figure 7 The diagram illustrates a method for controlling the switching operations of multiple switching elements during a predetermined time period T. Each switching element is arranged in parallel with at least one battery cell of a multi-cell battery, as shown in the preceding figures. The switching elements can be controlled by the same local controller 122, as described above regarding... Figure 6 As shown. In another example, the switching element can be controlled by a different local controller 122.

[0039] Figure 7 (a) illustrates the switching operation of four switching elements S1-S4. A value of "0" indicates that the switching element is open, and a value of "1" indicates that the switching element is closed. Switching elements S1-S4 are connected for a continuous on time t. on1 -t on4 The connection is established at the point of connection, and remains open for a continuous period of time t. off1 -t off4 The switch is disconnected. A brief transition time is required for the switching element to transition from the off state to the on state. As described above, the switching element can be controlled by the controller circuit 120, for example, based on a corresponding control signal. In the depicted example, the on-time is determined by the controller circuit 120.

[0040] Figure 7 (b) shows a timing diagram of the operating signal. This operating signal is a binary signal with low values ​​(i.e., "0") indicating that the switching element may not be turned on, and high values ​​(i.e., "1") indicating that the switching element may be turned on. In the depicted example, the operating signal is at the start time t1 of a predetermined time period T, and at time t... 12 It has a high value between, and at the midpoint of the predetermined time period T. 12 It has low values ​​between the end time t2 and the end time t2. In the example depicted, the intermediate time t 12 This corresponds to half of the predetermined time period T. Thus, the switching element operates during the first half T of the predetermined time period T. ON It is switched on during this period. Furthermore, the switching element is activated during the second half of the predetermined time period T. OFF The switching element is disconnected during this period. This allows the switching element to be switched on and off symmetrically. However, the operating signal can have different shapes. In one example, the switching element is switched on during a first period of a predetermined time period T and off during a second period of a predetermined time period T. In another example, the switching element is switched on during multiple first periods of a predetermined time period T. The first period can be separated by periods during which the switching element may not be switched on. The first period can be predetermined. In one example, the first period can be randomly determined.

[0041] Figure 7 (c) illustrates the cumulative operation of the switching element. In the depicted example, the on-time is determined such that the first half of the switching element is turned on during the first quarter of a predetermined time period, i.e., between time t1 and t2. 14 Between. In fact, in the example depicted, the on-time t on1 -t on4 They are evenly distributed over the first half of the predetermined time period. Similarly, the disconnection time t off1 -t off4 They are evenly distributed within the second half of a predetermined time period. In the depicted example, the time distance between the off-time and on-time of each switching element is equal to half of the predetermined time period T. In one example, the off-time t off1 -t off4 Determined by controller circuit 120. Specifically, the on-time and off-time t. off1 -t off4 This can be determined by the main controller 121. In another example, only the turn-on time is determined by the main controller 121. The local controller 122 is configured to turn off the switching element after a given switching time. As mentioned above, the given switching time can be equal to half of a predetermined time period T. Thus, the turn-on and turn-off operations of the switching element can be performed with respect to the midpoint t of the predetermined time period T. 12Symmetry. Specifically, in the depicted example, the off-time is determined such that the first half of the switching element is off during the third quarter of a predetermined time period, i.e., at time t. 12 With t 34 between.

[0042] As described above, the load on the battery cell changes when the corresponding switching element is turned on. Therefore, the total load on battery 110 varies according to... Figure 7 The shape of the curve in (c) changes, that is, during the first half of the predetermined time period T, the switching elements are sequentially turned on, and the total load gradually increases; and during the second half of the predetermined time period T, the switching elements are sequentially turned off, and the total load gradually decreases. Therefore, the load resistance of the battery has an approximately triangular shape. In addition, the current signal generated by the battery 110 also has a basic triangular shape. The load resistance curve determines the shape of the current flowing through the battery 110.

[0043] The switching operation can be repeated multiple times. The load resistance and current signal will have a periodic shape, where the frequency of the signal is... Figure 7 The reciprocal of the predetermined time period T. Please refer to... Figure 11 (a) illustrates the change in load resistance of the entire battery 110 over time. The load resistance has a triangular configuration. Therefore, a periodic excitation current can be generated through the battery 110 by controlling the switching operation of the switching elements coupled to the battery 110. A voltage signal can be measured across the battery 110, and the impedance of the battery 110 can be determined based on the measured voltage signal and the generated current signal. In one example, the total voltage is measured by an external voltage sensor 140. In another example, the controller circuit 120 includes a plurality of local voltage sensors, each configured to measure a local voltage signal across at least one of the plurality of battery cells. (Refer to above) Figure 6 As explained, the local voltage sensor can be configured to measure the voltage across the corresponding battery cell and another corresponding resistor in the balancing circuit. Furthermore, the current signal can be measured by an external voltage sensor 140. However, since all components of the balancing circuit are known, the current level can also be calculated without using any additional sensors.

[0044] Therefore, the impedance of a multi-cell battery can be determined by controlling the switching elements of the battery balancing device. Furthermore, the predetermined time period T can be modified to obtain excitation currents with different frequencies. Therefore, the complex impedance of the multi-cell battery can also be calculated by controlling the switching elements of the system. Since the balancing circuit already exists in a conventional system, this operation can be performed without altering the battery system.

[0045] The switching elements used to generate the periodic signal can always be the same switching elements. However, to prevent wear of the switching elements, at least some of the switching elements can be changed at each predetermined time period T. In one example, the controller circuit 120 switches the switching elements such that the switching elements are uniformly loaded over multiple predetermined time periods T. In one example, the controller circuit 120 is configured to associate a determined on-time with a switching element in the system. In another example, the determined on-time is pseudo-randomly associated with the switching element. The switching elements to be turned on and off can be selected by a pseudo-random generator arranged in the controller circuit 120. Furthermore, in one example, the order in which the switching elements are turned on and off is determined by the controller circuit 120. Alternatively, the order in which the switching elements are turned on and off can be pseudo-randomly determined.

[0046] Figure 7 The excitation signal can be generated using only four switching elements. However, the number of switching elements is not limited to four and can be fewer or more. Using a large number of switching elements results in a better approximation of the desired excitation curve. However, it is clear that the number of switching elements used should be kept as low as possible to prevent switching element degradation and reduce overall power consumption. Furthermore, the controller circuit 120 can be configured to turn on multiple switching elements at defined on-times. This allows for a very flexible design of the desired excitation curve.

[0047] Figure 8 An example of a method for controlling a system with a greater number of switching elements is shown. Figure 8 (a) shows a switching diagram for seventeen different switching elements among a plurality of switching elements during half of a predetermined time period. Therefore, Figure 8 (a) Only the switching operation of the switching element is shown. (and) Figure 7 Similar to the example, controller circuit 120 determines the on-time of the switching element such that the on-time is evenly distributed within the first half of a predetermined time period. (And...) Figure 7 (b) Similarly, Figure 8 (b) shows the timing diagram of the corresponding operating signal. The binary operating signal has a high value during the first half of the predetermined time period, meaning that the switching element can be turned on during this time period. The switching element can be turned off during the second half of the predetermined time period T, such that the off time is evenly distributed within the second half of the predetermined time period T. By repeating this switching pattern, the total load of the battery can vary according to a periodic triangular pattern. The resulting excitation current on the battery will also have a triangular shape. Since the on time is evenly distributed, this choice is particularly simple from a control perspective. In particular, since the number of switching elements involved in the switching process is greater than... Figure 7The example thus provides a better approximation of the triangular shape. As mentioned above, the number of switching elements involved in the switching process can be higher or lower depending on the desired pattern used for the excitation current. A higher number of switching elements turned on during a predetermined time period results in a smoother shape for the excitation signal.

[0048] However, by modifying the distribution of the switch-on time over a predetermined time period T, excitation currents for other shapes can also be obtained. Figure 9 An example of another approach to multiple switching elements in a control system is shown. Figure 9 (a) shows a switching diagram for seventeen different switching elements among a plurality of switching elements during the first half T / 2 of a predetermined time period T. Figure 9 (a) Only the switching operation of the switching element is shown. (and) Figure 7 and Figure 8 In contrast to the previous example, in this example, controller circuit 120 determines the on-time of the switching element such that the on-time is non-uniformly distributed within the first half of a predetermined time period. Specifically, controller circuit 120 determines the on-time such that a first time distance between two first consecutive on-times differs from a second time distance between two second consecutive on-times. Controller circuit 120 may determine the on-time based on a predetermined function. In the depicted example, controller circuit 120 determines the on-time such that the time distance between two consecutive on-times decreases during the first portion of the predetermined time period and increases during the second portion of the predetermined time period. In the depicted example, the first portion is equal to the first quarter of the predetermined time period T, and the second portion is equal to the second quarter of the predetermined time period T. In one example, the time distance between two consecutive on-times decreases linearly during the first portion of the predetermined time period. The time distance between two consecutive on-times may also increase linearly during the second portion of the predetermined time period. However, the time distance between two consecutive on-times can be determined based on other types of mathematical functions. To approximate a sinusoidal excitation signal, in the depicted example, the first half of the switching element is turned on during the first quarter of the predetermined time period T. Then, the end time of the first quarter of the predetermined time period T will correspond to the zero-crossing point of the generated periodic current signal.

[0049] and Figure 7 (b) and Figure 8 (b) Similarly, Figure 9(b) shows a timing diagram of the corresponding operating signal. The binary operating signal has a high value during the first half of a predetermined time period T, meaning that the switching element can be turned on during this time period. The switching element can be turned off during the second half of the predetermined time period (i.e., when the binary operating signal has a low value). In one example, the switching element is turned off in the same manner as it was turned on. In another example, the off times are not uniformly distributed within the second half of the predetermined time period. Specifically, the first time distance between two consecutive off times may decrease during the third part of the predetermined time period and increase during the fourth part. In one example, the time distance between the off time and the on time for each switching element is constant. This allows the switching elements to be evenly loaded. The time distance between the off time and the on time can be equal to half of the predetermined time period. In another example, the time distance between the off time and the on time varies depending on the switching element. This allows for more flexible control of the switching elements.

[0050] By repeating Figure 9 In the switching mode, the total load of battery 110 can vary according to the periodic pattern. The final excitation current on battery 110 will also be periodic. The shape of the load curve can be adjusted according to the function or pattern upon which the turn-on time is determined. Possible shapes of the load curve that can be obtained when the turn-on time is non-uniformly distributed are as follows: Figure 11 As shown in (b), (c), and (d), a trapezoidal or sinusoidal shape can be approximated based on the distribution of the turn-on time. Specifically, if the turn-on time decreases more rapidly in the first quarter of the predetermined time period, the slope of the load curve will be steeper. If the turn-on time decreases and increases linearly, the load curve can have a sinusoidal shape.

[0051] exist Figure 9 In the example, controller circuit 120 selects the switching elements to be turned on and the order in which they are turned on for each predetermined time period. Controller circuit 120 can also determine the order in which the selected switching elements are turned off.

[0052] Figure 10 A switching diagram for an alternative switching method is shown. In Figure 10In the example, the order in which the switching elements are turned on and off is determined pseudo-randomly. This order can be determined by a pseudo-random generator. Furthermore, the switching elements to be turned on can also be pseudo-randomly selected from among multiple switching elements in a multi-cell battery. The controller circuit 120 can monitor the switching operations of the switching elements and ensure that the switching elements are evenly loaded over multiple predetermined time periods to prevent degradation of the switching elements. In one example, when the controller circuit 120 determines that the number of times a switching element has been loaded over multiple predetermined time periods exceeds a threshold number, the controller circuit 120 sends a signal to the pseudo-random generator, causing the pseudo-random generator to disregard this switching element for subsequent impedance measurements.

[0053] In one example, at least one of the on-times is at least partially determined pseudo-randomly. The on-times can be determined by controller circuit 120 based on the desired excitation signal shape. Additionally, the determined on-times can be pseudo-randomly modified. In one example, the determined on-times can be modified by a pseudo-random generator of controller circuit 120. In one example, the variation in the determined on-times can be pseudo-randomly determined. The range of the variation, or the range of the variation to the on-time ratio, can be determined by controller circuit 120. Therefore, the determination of the on-times is both deterministic (i.e., based on a predetermined function) and pseudo-random. This results in the addition of artificial noise components to the excitation signal, in addition to natural noise components. The signal-to-noise ratio (SNR) of the excitation signal depends on the number of on-times determined at least partially pseudo-randomly. Controller circuit 120 can analyze the excitation signal and calculate its SNR. These data can be considered by controller circuit 120 when determining the on-times. Thus, the SNR can be reduced over multiple predetermined time periods of the excitation signal.

[0054] Figure 11 A timing diagram of the load resistance of the multi-cell battery 110 for different switching operations is shown. The solid line shows the change of the load resistance over time during two predetermined time periods T. The dashed line shows the change of the ideal sinusoidal excitation over time. The load resistance value is normalized to 1. Figure 11 (a) illustrates the load variation that results in a uniform distribution of turn-on time. The load resistance of battery 110 approximately has a triangular shape. However, the shape of the load resistance curve is not a perfect triangle. This is due to noise, which can be partly natural and partly artificially introduced by the pseudo-random modification of the turn-on time as described above. The symmetry of the load curve is due to the switching element being turned on during the first half of each predetermined time period T and turned off during the second half of each predetermined time period T.

[0055] Figure 11(b), (c), and (d) illustrate various non-uniform load variations that result in the turn-on time. The turn-on time decreases in the first quarter of a predetermined time period and increases in the second quarter, with half of the switching elements being turned on during the first quarter of the predetermined time period. Thus, a periodic sinusoidal excitation signal can be approximated. Figure 11 In the example of (b), the on-time decreases and increases linearly. The resulting load resistance curve has a shape very similar to that of a sinusoidal signal. Figure 11 In example (c), the decrease and increase in turn-on time are compared to Figure 11 Example (b) is faster. The resulting load resistance curve has a faster response than... Figure 11 (b) A steeper slope. In Figure 11 In example (d), the decrease and increase in turn-on time are even greater than Figure 11 Example (c) is faster. The resulting load resistance curve is trapezoidal with a very steep slope, approximating the edge signal.

[0056] Therefore, by determining the on-time of the switching elements in the balancing circuit, all possible types of load curves can be obtained. The load curve determines the signal shape of the excitation current that can be used for impedance measurement.

[0057] Figure 12 This is a flowchart illustrating an example method 1000 for controlling a system 100 including a multi-cell battery 110.

[0058] Example process 1000 can be used to operate the apparatus illustrated in this disclosure, such as according to Figure 2 The system or according to Figure 5 The system.

[0059] Process 1000 includes step 1010: turning on a plurality of switching elements SW1, SW2, ..., SW3 coupled to the battery 110 at corresponding turn-on times within a predetermined time period. n This generates a current signal through the battery 110. The battery 110 includes multiple battery cells B1…B n And multiple switching elements SW1…SW n Each switching element in 130 is associated with multiple battery cells B1…B nAt least one battery cell in the battery system 100 is arranged in parallel. The turn-on time is determined by controller circuit 120. Therefore, the load resistance of battery 110 can be modulated by controlling the switching elements already present in the common balancing circuit in battery system 100. When the switching operation is repeated multiple times, the predetermined time period is also the period of the resulting periodic signal. The shape of the load resistance determines the shape of the excitation current. Various types of excitation current can be obtained by changing the turn-on time. Controller circuit 120 can select a predetermined number of switching elements to be turned on during the predetermined time period T. In one example, the number of switching elements is equal to 200, and controller circuit 120 selects four switching elements to be turned on during the predetermined time period T. The switching elements can be controlled by the same local controller 122 of controller circuit 120. A larger number of switching elements results in a smoother current signal, but increases total power consumption and wear on the switching elements. The switching elements can also be pseudo-randomly determined. During this process, no external current flows through battery 110. In one example, battery 110 has no external load.

[0060] In one example, the switching elements SW1…SW n The switch is turned on during the first half of the predetermined time period. The control circuit can send a binary balance signal with a low value (i.e., "0") indicating that the switching element should not be turned on, and a high value (i.e., "1") indicating that the switching element can be turned on. Therefore, the resulting load resistance curve will rise during the first half of the predetermined time period.

[0061] In one example, the switching elements SW1…SW n The first half of the current is switched on during the first quarter of the predetermined time period. In this way, the symmetrical shape of the excitation current can be obtained.

[0062] In one example, controller circuit 120 determines the on-time such that the on-time is evenly distributed within the first half of a predetermined time period. This uniform distribution of the on-time results in a constant increase in the load resistance. In this way, the triangular shape of the excitation current can be obtained.

[0063] In another example, controller circuit 120 determines the on-time such that a first time distance between two consecutive first on-times differs from a second time distance between two consecutive second on-times. Therefore, the on-times are non-uniformly distributed. This allows for more varied shapes of the excitation current, particularly stepped edge shapes or sinusoidal shapes.

[0064] The controller circuit 120 can determine the on-time such that the time interval between two consecutive on-times decreases during the first portion of a predetermined time period and increases during the second portion of the predetermined time period. This allows for a steeper slope of the resulting excitation current and rounded edges of the current curve. This can help reduce energy loss when determining the impedance of the battery 110. The increase and decrease of the on-time can be linear. This allows for an approximation of the sinusoidal shape of the excitation current. The on-time can also be increased and decreased according to other mathematical functions, such as polynomials or exponential functions. This allows for tuning of desired characteristics of the excitation current curve, such as the slope and edge shape of the curve.

[0065] In one example, at least one of the turn-on times is determined at least partially by pseudo-randomization. The turn-on times can be determined deterministically by controller circuitry 120, and variations in these turn-on times can be determined pseudo-randomly. In one example, controller circuitry 120 includes a pseudo-random generator configured to pseudo-randomly determine variations in the turn-on times. In this way, artificial noise can be generated, which can be used to reduce overall noise caused by communication delays between components or between components.

[0066] In one example, process 1000 further includes disconnecting multiple switching elements SW1…SW at corresponding disconnection times within a predetermined time period. n The time interval between the off-time and on-time of each switching element can be equal to half a predetermined time period T. This allows for the generation of a symmetrical current signal. In one example, the off-time is determined by controller circuit 120. In another example, controller circuit 120 includes a main controller 121 and multiple local controllers 122. The main controller 121 determines the on-time of the switching elements and sends corresponding signals to the local controllers 122. The local controllers 122 control the switching elements to be turned on at the on-time and off after a switching cycle, which can be equal to the predetermined time period. In one example, switching elements SW1…SW n It is disconnected during the second half of the predetermined time period T.

[0067] In one example, the switching elements SW1…SW n The order in which the switching elements are switched on and off is determined by the controller circuit 120. This allows for simple monitoring of the load on the switching elements and prevents some switching elements from being overloaded by others. Alternatively, the switching elements SW1…SW n The order in which the circuit is switched on and off is determined pseudo-randomly. This reduces the computational complexity of the controller circuit 120.

[0068] In one example, controller circuit 120 switches elements SW1…SWn This allows the switching elements SW1…SW to operate over multiple predetermined time periods. n The switching element is uniformly loaded. This prevents degradation of the switching element. In one example, the switching element is uniformly loaded over ten impedance measurements. In another example, the switching element is uniformly loaded over a one-week cycle.

[0069] Process 1000 also includes step 1020: measuring a voltage signal across battery 110. In one example, the voltage signal is measured across the entire battery. In another example, measuring the voltage signal includes measuring multiple partial voltage signals, wherein each partial voltage signal is located across multiple battery cells B1…B n The voltage signal is measured over at least one battery cell; and partial voltage signals are summed to form a voltage signal. Partial voltage signals can be measured by local controllers 122 of controller circuitry 120, which are coupled to the balancing circuitry of battery 110.

[0070] Process 1000 further includes step 1030: determining the impedance of battery 110 based on the measured voltage signal and the generated current signal. The current signal can be measured by a corresponding current sensor. However, since the components of the balancing circuit are known, the current signal can also be calculated or evaluated by controller circuit 120.

[0071] This application describes a method for generating current curves as excitation signals for electrochemical impedance spectroscopy on a cell network of a multi-cell battery. For this purpose, switching elements of an available balancing circuit for monitoring battery operation can be collectively controlled to modulate the battery's internal load. Since the switching elements are part of the existing hardware of the battery management system, no additional circuitry is required. The controller circuit specifies the on-time of the switching elements to generate various signal shapes for excitation of the entire battery. By keeping the time distance between two consecutive on-times constant when the switching elements are turned on, a triangular shape of the excitation signal can be obtained. When the time distance between two consecutive on-times is not constant, other shapes of the excitation signal can be obtained, such as a sinusoidal shape or a stepped edge shape. A predetermined time period during which the switching elements are turned on and off corresponds to the period of the resulting signal. A symmetrical signal can be generated when the first half of the switching elements is turned on during the first quarter of the predetermined time period, and when all selected switching elements are turned on during the first half of the predetermined time period. Artificial noise can be generated by combining deterministic and pseudo-random determination of the on-time. In this way, actual signal noise can be reduced. To prevent degradation of the switching elements, the controller circuit can switch the switching elements so that they are evenly loaded over multiple predetermined time periods. Since measurements are performed using multiple balancing circuits, the overall power loss is shared by different balancing circuits, thus preventing the formation of hot spots in the battery and enabling good heat dissipation. Furthermore, because the switching operations are distributed over time, the battery's electromagnetic characteristics do not undergo any undesirable changes.

[0072] Although various embodiments have been illustrated and described with respect to one or more specific implementations, substitutions and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the features and structures described herein. In particular, regarding the various functions performed by the aforementioned components or structures (units, components, devices, circuits, systems, etc.), the terminology used to describe such components (including references to "means") is intended to correspond—unless otherwise stated—to any component or structure that performs the specified function of the described component (e.g., functionally equivalent), even if it is not structurally equivalent to the disclosed structure performing that function in the exemplary embodiments illustrated in this disclosure. Furthermore, the methods of this application can be implemented in all software implementations using appropriate processor instructions, or in hybrid implementations utilizing a combination of hardware and software logic to achieve the same result.

[0073] Although this disclosure is not limited thereto, the following numbered examples illustrate one or more aspects of this disclosure.

[0074] Example 1. A method comprising: activating a plurality of switching elements (SW1, SW2, ..., SW3) coupled to a battery (110) at corresponding activation times within a predetermined time period. n (130), thereby generating a current signal through the battery (110), wherein the battery (110) includes multiple battery cells (BC1, BC2, ..., BC3). n ), and multiple switching elements (SW1, SW2, ..., SW) n Each switching element in (130) is associated with multiple battery cells (BC1, BC2, ..., BC3). n At least one battery cell in the battery (110) is arranged in parallel, wherein the turn-on time is determined by the controller circuit (120); a voltage signal is measured on the battery (110); and the impedance of the battery (110) is determined based on the measured voltage signal and the generated current signal.

[0075] Example 2. According to the method described in Example 1, wherein the switching elements (SW1, SW2, ..., SW) n It is connected during the first half of the scheduled time period.

[0076] Example 3. The method according to Example 1 or 2, wherein the switching elements (SW1, SW2, ..., SW...) n The first half of the process is activated during the first quarter of the predetermined time period.

[0077] Example 4. The method according to any one of Examples 1 to 3, wherein the controller circuit (120) determines the turn-on time such that the turn-on time is evenly distributed in the first half of a predetermined time period.

[0078] Example 5. The method according to any one of Examples 1 to 3, wherein the controller circuit (120) determines the turn-on time such that a first time distance between two first consecutive turn-on times is different from a second time distance between two second consecutive turn-on times.

[0079] Example 6. The method according to any one of Examples 1 to 3 or 5, wherein the controller circuit (120) determines the on-time such that the time distance between two consecutive on-times decreases during a first portion of a predetermined time period and increases during a second portion of the predetermined time period.

[0080] Example 7. The method according to any one of Examples 1 to 6, wherein at least one of the turn-on times is determined at least partially by pseudo-randomization.

[0081] Example 8. The method according to any one of Examples 1 to 7 further includes: disconnecting a plurality of switching elements (SW1, SW2, ..., SW3) at corresponding disconnection times within a predetermined time period.n ), where the time distance between the off time and the on time of each switching element is equal to half of the predetermined time period.

[0082] Example 9. The method according to any one of Examples 1 to 8 further includes: disconnecting a plurality of switching elements (SW1, SW2, ..., SW3) at corresponding disconnection times within a predetermined time period. n The disconnection time is determined by the controller circuit (120).

[0083] Example 10. The method according to Example 8 or 9, wherein the switching elements (SW1, SW2, ..., SW...) n It was disconnected during the second half of the predetermined time period.

[0084] Example 11. The method according to any one of Examples 1 to 10, wherein the switching elements (SW1, SW2, ..., SW...) n The order in which the circuit is switched on and off is determined by the controller circuit (120).

[0085] Example 12. The method according to any one of Examples 1 to 10, wherein the switching elements (SW1, SW2, ..., SW...) n The order in which the connection and disconnection are made is determined pseudo-randomly.

[0086] Example 13. The method according to any one of Examples 1 to 12, wherein measuring the voltage signal comprises: measuring a plurality of partial voltage signals and summing the partial voltage signals to form a voltage signal, wherein each partial voltage signal is located in a plurality of battery cells (B1, B2, ..., B...). n The measurement is performed on at least one of the battery cells in the cell.

[0087] Example 14. The method according to any one of Examples 1 to 13, wherein the controller circuit (120) switches the switching elements (SW1, SW2, ..., SW1). n This allows the switching elements (SW1, SW2, ..., SW) to operate over multiple predetermined time periods. n It is uniformly loaded.

[0088] Example 15. A system (100) comprising: a battery (110), wherein the battery (110) includes a plurality of battery cells (BC1, BC2, ..., BC...). n ); multiple switching elements (SW1, SW2, ..., SW) n (130), which is coupled to the battery (110), wherein multiple switching elements (SW1, SW2, ..., SW) n Each switching element (SW1, SW2, ..., SW) in (130) n) and multiple battery cells (BC1, BC2, ..., BC n At least one battery cell in the battery is arranged in parallel; a controller circuit (120) is coupled to a plurality of switching elements (SW1, SW2, ..., SW1). n (130), wherein the controller circuit (120) is configured to: turn on multiple switching elements (SW1, SW2, ..., SW) at the corresponding on-time of a predetermined time period. n (130), thereby generating a current signal through the battery (110), wherein the on-time is determined by the controller circuit (120); measuring the voltage signal above the battery (110); and determining the impedance of the battery (110) based on the measured voltage signal and the generated current signal.

[0089] Example 16. The system (100) according to Example 15 further includes: a plurality of resistors (R B1 R B2 ..., R Bn ), including multiple switching elements (SW1, SW2, ..., SW) n Each switching element in (130) is associated with multiple resistors (R) B1 R B2 ..., R Bn At least one resistor in the series is arranged in series.

[0090] Example 17. A system (100) according to Example 15 or 16, wherein the controller circuit (120) includes a main controller (121) and a plurality of local controllers (122), wherein a first local controller of the plurality of local controllers (122) is connected to the main controller (121), and the local controllers (122) are connected to each other to form a daisy chain, and wherein each local controller (122) is coupled to a plurality of switching elements (SW1, SW2, ..., SW1). n At least one switching element in the main controller (121) is configured to turn on the corresponding switching element based at least on the signal of the main controller (121).

[0091] Example 18. The system according to Example 17, wherein each local controller (122) is configured to disconnect a corresponding switching element, wherein the time distance between the disconnection time and the turn-on time of the corresponding switching element is equal to half of a predetermined time period.

[0092] Example 19. A system according to any one of Examples 15 to 18, wherein the controller circuit (120) includes a plurality of local voltage sensors, wherein each local voltage sensor is configured to measure a plurality of battery cells (BC1, BC2, ..., BC...). n The local voltage signal above at least one battery cell in the battery cell.

Claims

1. A method comprising: At the corresponding turn-on time within a predetermined time period (T), multiple switching elements (SW1, SW2, ..., SW3) coupled to the battery (110) are turned on. n (130), thereby generating a current signal through the battery (110), wherein the battery (110) includes multiple battery cells (BC1, BC2, ..., BC3). n ), and the plurality of switching elements (SW1, SW2, ..., SW) n Each switching element in (130) is associated with the plurality of battery cells (BC1, BC2, ..., BC3). n At least one battery cell in the battery is arranged in parallel, wherein the turn-on time is determined by the controller circuit (120); Measure the voltage signal across the battery (110); and The impedance of the battery (110) is determined based on the measured voltage signal and the generated current signal.

2. The method according to claim 1, The switching elements (SW1, SW2, ..., SW) n It is switched on during the first half of the predetermined time period (T).

3. The method according to claim 1 or 2, The switching elements (SW1, SW2, ..., SW) n The first half of the circuit is switched on during the first quarter of the predetermined time period (T).

4. The method according to any one of claims 1 to 3, The controller circuit (120) determines the turn-on time such that the turn-on time is evenly distributed within the first half of the predetermined time period (T).

5. The method according to any one of claims 1 to 3, The controller circuit (120) determines the turn-on time such that the first time distance between two first consecutive turn-on times is different from the second time distance between two second consecutive turn-on times.

6. The method according to any one of claims 1 to 3 or 5, The controller circuit (120) determines the turn-on time such that during a first portion of the predetermined time period (T), the time distance between two consecutive turn-on times decreases, and during a second portion of the predetermined time period (T), the time distance between the two consecutive turn-on times increases.

7. The method according to any one of claims 1 to 6, At least one of the connection times is determined at least partially by pseudo-randomization.

8. The method according to any one of claims 1 to 7, further comprising: The plurality of switching elements (SW1, SW2, ..., SW) are disconnected at the corresponding disconnection time of the predetermined time period (T). n ), wherein the time distance between the off time and the on time of each switching element is equal to half of the predetermined time period (T).

9. The method according to any one of claims 1 to 8, further comprising: The plurality of switching elements (SW1, SW2, ..., SW) are disconnected at the corresponding disconnection time of the predetermined time period (T). n The disconnection time is determined by the controller circuit (120).

10. The method according to claim 8 or 9, The switching elements (SW1, SW2, ..., SW) n It is disconnected during the second half of the predetermined time period (T).

11. The method according to any one of claims 1 to 10, The switching elements (SW1, SW2, ..., SW) n The order in which the circuit is switched on and off is determined by the controller circuit (120).

12. The method according to any one of claims 1 to 10, The switching elements (SW1, SW2, ..., SW) n The order in which the connection and disconnection are made is determined pseudo-randomly.

13. The method according to any one of claims 1 to 12, The measurement of the voltage signal includes: Multiple partial voltage signals are measured and summed to form the voltage signal, wherein each partial voltage signal is measured in the plurality of battery cells (BC1, BC2, ..., BC3). n The measurement is performed on at least one of the battery cells in the cell.

14. The method according to any one of claims 1 to 13, The controller circuit (120) switches the switching elements (SW1, SW2, ..., SW) n This allows the switching elements (SW1, SW2, ..., SW) to operate over multiple predetermined time periods. n It is uniformly loaded.

15. A system (100) comprising: Battery (110), wherein the battery (110) includes multiple battery cells (BC1, BC2, ..., BC3). n ); Multiple switching elements (SW1, SW2, ..., SW) n (130), is coupled to the battery (110), wherein the plurality of switching elements (SW1, SW2, ..., SW1) are coupled to the battery (110). n Each switching element (SW1, SW2, ..., SW) in (130) n ) and the plurality of battery cells (BC1, BC2, ..., BC n At least one battery cell in the battery is arranged in parallel; The controller circuit (120) is coupled to the plurality of switching elements (SW1, SW2, ..., SW1). n (130), wherein the controller circuit (120) is configured to: At the corresponding turn-on time of the predetermined time period (T), the plurality of switching elements (SW1, SW2, ..., SW) are turned on. n (130), thereby generating a current signal through the battery (110), wherein the on-time is determined by the controller circuit (120); Measure the voltage signal across the battery (110); and The impedance of the battery (110) is determined based on the measured voltage signal and the generated current signal.

16. The system (100) according to claim 15, further comprising: Multiple resistors (R) B1 R B2 ..., R Bn The plurality of switching elements (SW1, SW2, ..., SW) n Each switching element in (130) is associated with the plurality of resistors (R) B1 R B2 ..., R Bn At least one resistor in the series is arranged in series.

17. The system (100) according to claim 15 or 16. The controller circuit (120) includes a main controller (121) and multiple local controllers (122). The first local controller of the plurality of local controllers (122) is connected to the main controller (121), and the local controllers (122) are connected to each other to form a daisy chain. Each local controller (122) is coupled to the plurality of switching elements (SW1, SW2, ..., SW1). n At least one switching element in the main controller (121) is configured to turn on the corresponding switching element based at least on a signal from the main controller (121).

18. The system (100) according to claim 17. Each local controller (122) is configured to disconnect the corresponding switching element, wherein the time distance between the disconnection time and the connection time of the corresponding switching element is equal to half of the predetermined time period (T).

19. The system (100) according to any one of claims 15 to 18. The controller circuit (120) includes a plurality of local voltage sensors, each configured to measure voltage in the plurality of battery cells (BC1, BC2, ..., BC3). n The local voltage signal above at least one battery cell in the battery cell.

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