Balancing system for cells of a battery with integrated spectroscopic impedance measurement system

Abstract

The present invention concerns a balancing system for cells of a battery, for example a lithium battery, with an integrated spectroscopic impedance measurement system. The present invention also concerns a method for processing the impedance spectrum of at least one cell of a battery comprising the aforementioned balancing system.

Description

[0001] “BALANCING SYSTEM FOR CELLS OF A BATTERY WITH INTEGRATED SPECTROSCOPIC IMPEDANCE MEASUREMENT SYSTEM”

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] The present invention concerns a balancing system for cells of a battery, for example a lithium battery, with an integrated spectroscopic impedance measurement system.

[0004] The present invention also concerns a method for processing the impedance spectrum of at least one cell of a battery comprising the aforementioned balancing system.

[0005] STATE OF THE PRIOR ART

[0006] In the state of the art, different types of balancing systems for cells of a battery are known.

[0007] Balancing cells of a battery is a crucial process to ensure optimal operation and long battery life.

[0008] In general, a battery includes multiple cells connected in series or in parallel designed to provide the desired voltage and capacity. Cell balancing therefore refers to the management and balance of voltage and capacity differences between individual cells within a battery.

[0009] In this sense, several reasons emerge why a battery needs to have an adequate cell balance, including:

[0010] - cell uniformity: the cells of a battery can have intrinsic differences in their voltage and capacity, which can become further accentuated during charging and discharging. Cell balancing helps equalize the voltages and capacitances between cells, so they work smoothly as a single coherent system. This prevents some cells from discharging too quickly or charging too quickly compared to others, reducing the risk of damage and prolonging the life of the battery,

[0011] - performance optimization: correct cell balancing helps maintain optimal battery performance over time. Balanced cells allow to reach the maximum overall battery capacity and maintain a stable output voltage. Furthermore, appropriate balancing reduces cell deterioration, maintaining greater charging and discharging efficiency,

[0012] - safety: significant voltage differences between cells can cause safety problems. If a cell discharges too quickly or reaches too low a critical voltage, it can suffer permanent damage or even cause a thermal failure or hazardous situation such as fire. Cell balancing helps prevent situations like this by limiting voltage differences between cells and keeping the battery within safe parameters.

[0013] - maximizing lifespan: accurate cell balancing reduces stress on individual cells, preventing some from being overcharged or undercharged compared to others. This helps extend the overall life of the battery and delay battery degradation. Proper cell balancing can significantly improve battery longevity, reducing the need for premature replacement or repair.

[0014] In summary, balancing cells of a battery, particularly in a lithium battery, is essential to ensure reliable operation, optimal performance, safety and long battery life.

[0015] Batteries, in particular lithium batteries, use specialized electronic management devices, also called BMS or Battery Management System, which through measurements and algorithms, ensure that every single cell of a battery works within safety limits, as well as provide status indicators to users, for example charge level or SOC indicators, health status or SOH indicators, remaining life indicators, etc., which must be as accurate as possible. The main measures on which the operation of each typical state-of-the-art BMS is based are in general:

[0016] - voltage of single cells,

[0017] - temperature of single cells or groups of cells, and

[0018] - total battery current.

[0019] However, these parameters are usually not sufficient to accurately model the state of a cell and its complex possible evolutions over time.

[0020] For this reason, the research in this technical sector has focused on identifying other measurable quantities, which could allow for more accurate modeling of the state of health of cells. One of the quantity that is acquiring more and more importance in battery cell balancing systems is the impedance frequency spectrum.

[0021] However, the main difficulty not yet resolved in the sector is the practical application of these models based on the measurement of the impedance frequency spectrum, which requires the development of sensors, BMS and, in general, balancing systems capable to carry out these measurements in an integrated manner in the battery and during its operation.

[0022] These systems must then address the following issues:

[0023] - the current signals for impedance measurement that embedded circuits are capable of generating are typically of very small amplitude (tens or a few hundred mA), due to the complexity, size and cost that a circuit capable of generating signals of higher value should have,

[0024] - in the case of high-value signals, especially at low frequencies where the measurement time can be several tens of seconds, the power dissipated by the signal generation circuit poses temperature and heat disposal problems, which further limit the practical power obtainable,

[0025] - high-capacity cells such as those used, for example, in electric mobility, have very low internal impedances, for example in the 100 pQ scale,

[0026] - the use of limited current signals on very low value impedances implies that the measurement signal is of very low level, for example in the pV scale, which becomes very difficult to measure with sufficient resolution especially considering that it is often superimposed to a common mode value that corresponds to the opencircuit voltage of the cell, typically between 2.5 V and 4.5 V.

[0027] Document EP3840172A1 in the name of the Applicant illustrates a high- current balancing architecture which, however, does not provide for the measurement of the cell impedance spectrum.

[0028] It is therefore necessary and advantageous to design and create a balancing system which allows the disadvantages of the prior art listed above to be overcome.

[0029] OBJECTS OF THE INVENTION

[0030] The technical aim of the present invention is to improve the prior art relating to balancing structures for cells of a battery, in particular a lithium battery.

[0031] Within the scope of this aim, it is an object of the present invention to provide a balancing system for the cells of a battery that allows generating a high resolution or precision measurement of the impedance, even on large capacity cells.

[0032] Another object of the present invention is to provide a balancing system for cells of a battery which allows the generation, using already available commercial components, of current signals of high amplitude and in any direction (in the charge or discharge direction).

[0033] Another object of the present invention is to provide a balancing system for cells of a battery which allows to optimize the cost and size of the circuitry used, even on batteries composed of a large number of cells, making the solution also applicable to mass-produced batteries, for example for normal vehicle applications.

[0034] A further object of the present invention is to provide a balancing system for battery cells that exploits impedance measurement in order to obtain information on the state of health, dynamic behavior and operating conditions of the battery cells.

[0035] Finally, yet another object of the present invention is to provide a balancing system for cells of a battery which allows to obtain an optimal compromise between performance and impedance measurement precision, and cost and size of the system components.

[0036] This aim and these objects are achieved by a system according to claim 1, by a battery according to claim 15 and by a method according to claim 17.

[0037] The dependent claims refer to preferred and advantageous embodiments of the invention.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features and advantages of the invention will be more evident from the description of an embodiment of a balancing system for cells of a battery, in particular a lithium battery, illustrated for indicative purposes in the attached drawings in which: figure l is a schematic illustration of a balancing system for cells of a battery according to an embodiment of the present invention, figure 2 shows a detail of a balancing system according to the embodiment of figure 1, figure 3 schematically shows a switching device or slave device according to the embodiment of figure 1, figure 4 schematically shows a control and management unit or master management device according to the embodiment of figure 1.

[0040] In the attached drawings, identical parts or components are identified by the same reference numbers.

[0041] EMBODIMENTS OF THE INVENTION

[0042] With reference to the attached figures, the number 1 indicates as a whole a balancing system for cells C of a battery B, in particular a lithium battery, according to a non-limiting embodiment of the present invention.

[0043] Preferably, battery B is a battery that can be used together with other batteries B in a module or pack of batteries B usable in the electric mobility sector, for example for an industrial vehicle.

[0044] Each cell C of battery B has a positive terminal SP1 and a negative terminal SP2.

[0045] The balancing system 1 according to the present invention includes at least one control and management unit or master management device 4 of the battery B comprising at least one logic unit 4a and at least one power unit 4b.

[0046] The control and management unit or master management device 4 preferably constitutes the Battery Management System or BMS of battery B, and is configured to perform internal and external monitoring, protection and safety, charging and / or discharging functions of cells C

[0047] In particular, among the specific functions carried out by the control and management unit or master management device 4 it is possible to identify the monitoring of the total current and voltage of the battery B, the monitoring of the voltage and temperature levels of the individual cells C, the calculation of the state of charge (SOC) and the state of health (SOH) of battery B, the management of charging of battery B and communications with the system to which battery B is connected, the protection against overcurrents and / or undercurrents and / or overvoltages and / or undervoltages and the active and / or passive balancing functions of cells C.

[0048] Regarding the logic unit 4a, it is advantageously responsible for the processing of the data acquired by the sensors and by the monitoring circuits of the cells C of the battery B, as well as for the execution of control, decision-making and measurement algorithms, to guarantee an optimal battery B operation.

[0049] For example, the logic unit 4a can advantageously comprise a microcontroller configured to execute and / or implement the aforementioned functions.

[0050] With reference, instead, to the power unit 4b, it is advantageously responsible for managing the power supply and the energy flow within the balancing system 1. The power unit 4b can therefore include one or more electrical and / or electronic components configured to regulate voltage, current and energy distribution.

[0051] Optionally, the power unit 4b can comprise at least one switching power converter, if desired comprising inductors and / or capacitors and / or switching transistors and / or freewheeling transistors as well as a switching controller, for example an integrated controller or a microcontroller with digital control. In addition or alternatively, the power unit 4b can also include a transistor with resistive shunt and analog driving to produce the discharge currents or a converter with bidirectional topology, for example a bidirectional flyback converter.

[0052] The balancing system 1 according to the present invention also includes at least one active balancing component 5a configured to charge said plurality of cells C and / or at least one passive balancing component 5b configured to discharge the plurality of cells C.

[0053] Advantageously, system 1 includes both an active balancing component 5a and a passive balancing component 5b, preferably both integrated into the control and management unit or master management device 4.

[0054] According to a non-limiting embodiment of the present invention, the active balancing component 5a is a DC-DC converter configured to absorb energy from the total voltage of the battery B and transfer it into the cells C.

[0055] Optionally, the passive balancing component 5b may be a variable resistive load configured to absorb energy from the individual cell C and dissipate it into heat.

[0056] Advantageously, the power unit 4b is configured to act as a control interface of the logic unit 4a to drive the at least one active balancing component 5a and / or the at least one passive balancing component 5b of the cells C, so as to adjust it / them according to the balancing needs of the latter.

[0057] The balancing system 1 then includes a balancing line or bus 6 comprising at least one charge and / or discharge line 7, 8 designed to put the at least one active and / or passive balancing component 5a, 5b in electrical communication with each of cells C so as to allow the latter to be charged and / or discharged. For the effective connection of the at least one charge and / or discharge line 7, 8 with each cell C, the at least one charge and / or discharge line 7, 8 includes connectors or connection branches 7a, 8a towards and from each cell C.

[0058] According to the non-limiting embodiment of the present invention illustrated in figure 1, the balancing system 1 includes a charge line 7 designed to put the at least one active balancing component 5a in electrical communication with each of cells C so as to allow the charging of the latter and a discharge line 8, separated from the charge line 7, designed to put the at least one passive balancing component 5b in electrical communication with each of cells C so as to allow the latter to be discharged.

[0059] According to the non-limiting embodiment of the present invention illustrated in the figures, the charge and / or discharge line 7, 8, preferably both the charge line 7 and the discharge line 8, if two separate lines are provided, comprises a number of connectors or connection branches 7a, 8a towards and from each cell C equal to the number of cells C present in battery B.

[0060] In this regard, if four, six, eight cells C are present, preferably four, six, eight connectors or connection branches 7a, 8a respectively will be provided from the charge and / or discharge line 7, 8 to each cell C and four, six, eight connectors or connection branches 7a, 8a from each cell C to the charge and / or discharge line 7, 8. Naturally, in the case of a charge line 7 separated from the discharge line 8, four, six, eight connectors or connection branches 7a from the charge line 7 to each cell C and four, six, eight connectors 8a from each cell C to the discharge line 8 will be provided.

[0061] From a manufacturing point of view, the charge and / or discharge line 7, 8 as well as any connectors or connection branches 7a, 8a can be made using a connector element or wire, for example in a material chosen from the group consisting of copper or similar.

[0062] The balancing system 1 also includes a data and / or instructions communication line 10 between the control and management unit or master management device 4 and each of the plurality of cells C designed to allow the communication of data and / or instructions of cells C to the control and management unit or master management device 4 or vice versa.

[0063] In the balancing system 1, there are also included a plurality of switching devices or slave devices 9, each positioned to intercept a respective connector or connection branch or respective connectors or connection branches 7a, 8a and between the terminals SP1, SP2 of a respective cell C and each designed to open and / or close the passage of current to and from a respective cell C.

[0064] According to a non-limiting embodiment of the present invention, some or all of the switching devices or slave devices 9 comprise an electronic board 9a which includes a microcontroller 9b, and an interrupt or enabling element 9c of the electrical connection between the at least one charge and / or discharge line 7, 8 and a respective cell C on the basis of instructions that the control and management unit or master management device 4, via at least one data and / or instructions communication line 10, supplies to the microcontroller 9b.

[0065] Optionally, the interrupt or enabling elements 9c of the electrical connection between the at least one charge and / or discharge line 7, 8 and a respective cell C of the switching devices or slave devices 9 can be either of the mechanical or electronic type, but preferably of the electromechanical type since this type of switching device allows, in addition to the effective management of high currents, for example up to 30 A, also good electrical insulation between the lines and the various connectors or connection branches 7a, 8a of the balancing bus or line 6 as well as a notable reduction in the overall costs of the system 1.

[0066] According to the non-limiting embodiment example of the present invention illustrated in figure 1, the interrupt or enabling elements 9c are printed circuit or PCB relays.

[0067] Preferably, the interrupt or enabling elements 9c have a resistance lower than or up to a maximum of about 8 mQ, preferably between 4 and 8 mQ or about 6 m , to be able to limit energy losses during the passage of current.

[0068] Advantageously, the interrupt or enabling elements 9c have a breakdown voltage higher than 150 V.

[0069] Preferably, the balancing system 1 includes a sensor 14 of the state or level of charge associated with each cell C and used to monitor by means of the measurement of parameters, such as for example temperature and voltage parameters, the state of charge and the general operating conditions of each cell C.

[0070] In relation to the data and / or instructions communication line 10, it preferably comprises a bidirectional communication line or bus having a first end 10a operatively connected to the control and management unit or master management device 4 and a plurality of second ends 10b, preferably, equal to the number of switching devices or slave devices 9 present and operatively connected with the latter.

[0071] Advantageously, the control and management unit or master management device 4 or a component thereof, for example the logic unit 4a, is designed to control the plurality of switching devices or slave devices 9 so as to close a respective interrupt or enabling element 9c to allow the passage of electrical current between a single cell C, balancing bus or line 6 and at least one active and / or passive balancing component 4, 5 of the cells C, while the passage of current between the others cells C or the other connectors or connection branches 7a, 8a and the at least one active and / or passive balancing component 4, 5 of the cells C are interrupted or prevented.

[0072] The control of the plurality of switching devices or slave devices 9 can take place by means of commands, processed by the logic unit 4a of the control and management unit or master management device 4 and sent to the microcontroller 9b, if provided, via the data and / or instructions communication line 10, used to command the closing and / or opening of the interrupt or enabling elements 9c of the switching devices or slave devices 9.

[0073] In general, the balancing of the cells C of the battery B preferably requires the balancing task to be performed on a single cell C at a time, to maximize the effectiveness of the action, however, for example each time interval between 5 and 40 seconds, if desired every 10 seconds, the conditions of all the cells C present in the battery B can be re-evaluated by the logic unit 4a, for example on the basis of the values measured by the sensor 14 of the state or level of charge, if provided.

[0074] In this way, in cases in which only one cell C needs balancing, will be continue to act on it until it is aligned with the others in terms of charge while in the case in which multiple cells C have different or in any case too low energy levels compared to the others, will be act on each of them, preferably in an alternating manner, trying to obtain a homogeneous realignment of all the cells C present in battery B. Therefore, acting promptly on the misaligned cells C, by using the active balancing component 4 of cells C in case of need for active balancing or the passive balancing component 5 of cells C in case of need for passive balancing, it is possible to obtain the increase in the overall charge level of battery B in homogeneous way, thus improving its lifespan and efficiency.

[0075] The balancing system 1 according to the present invention also includes measuring means 11 of the impedance of the cells C.

[0076] More in detail, these measuring means 11 include a signal generation circuit or signal generator 12, controlled by the logic unit 4a and by the power unit 4b, designed to generate at least one alternating current signal or measurement signal at a given amplitude and frequency on at least one charge and / or discharge line 7, 8, and a measuring circuit or component 13, included in each switching device or slave device 9, designed to measure and communicate via the data and / or instructions communication line 10, the amplitude of the alternating voltage signal present between the terminals SP1, SP2 of a respective cell C induced by the alternating current signal or measurement signal generated by the signal generation circuit or signal generator 12 so that, by varying the frequency of the alternating current signals or measurement signals, the control and management unit or master management device 4 of the battery B can process the impedance spectrum of a respective cell C.

[0077] In particular, the processing of the impedance spectrum can advantageously be calculated by the logic unit 4a through the ratio between the amplitude of the alternating voltage signal measured between the terminals SP1, SP2 of the cell C considered and the amplitude value of the alternating current signal or measurement signal generated by the signal generation circuit or signal generator 12 at the given frequency: by varying the frequency of generation of the alternating current signal or measurement signal and carrying out the aforementioned calculation at each set frequency, the logic unit 4a is capable of processing the impedance spectrum of the cell C considered.

[0078] This information can possibly be used for diagnostics and evaluation of the state of health of the battery, the characterization of its dynamic behavior, the monitoring of operating conditions and / or the development and validation of battery models.

[0079] Preferably, the signal generation circuit or signal generator 12 is integrated into the control and management unit or master management device 4 and can use the power unit 4b thereof for generating the alternating current signal or measurement signal.

[0080] Preferably, the signal generation circuit or signal generator 12 comprises a digital signal synthesizer, advantageously including a microcontroller and a pulse width modulation or PWM peripheral or a digital-to-analog converter or DAC designed to generate a reference or set-point signal for the power unit 4b or, more particularly, for the at least one switching power converter thereof. In particular, the reference or set-point signal can be considered as a signal that represents a desired value that the power unit 4b or, better, the at least one switching power converter must reach and / or maintain.

[0081] In particular, the digital-to-analog converter or DAC can be used as an alternative to the pulse width modulation or PWM peripheral in order to convert the digital signal generated by the microcontroller into a discretized analog signal to be used as a reference or set-point signal for the power unit 4b.

[0082] To produce a high current signal compliant with the set-point signal, the switching power converter of the power unit 4b can advantageously be or comprise an isolated DC-DC converter, for example having a much higher switching frequency than the signal to be generated, if desired of a greater order of magnitude, for example around 20 kHz or a linear circuit or a combination of the latter.

[0083] Preferably, the signal generation circuit or signal generator 12 comprises a current sensor and a feedback circuit designed to reproduce an alternating current signal or measurement signal of set amplitude and frequency. In particular, the feedback circuit allows the desired alternating current signal or measurement signal to be obtained regardless of the series resistance of the balancing line or bus 6.

[0084] More in detail, the set amplitude and frequency is preferably selected using a measurement algorithm stored or implemented in the logic unit 4a.

[0085] With reference to the current sensor, it is advantageously designed to detect the phase of the alternating current signal or measurement signal and to detect the voltage at the ends of the balancing line or bus 6 so as to obtain an alternating current signal having the set amplitude.

[0086] Optionally, the current sensor may be or comprise a resistive shunt coupled to a specialized operational amplifier. If desired, the analog output of the current sensor can directly constitute the feedback of the switching controller of the signal generation circuit or signal generator 12, if provided, and also be digitally converted for the subsequent calculation of the impedance.

[0087] Preferably, the data and / or instructions communication line 10 is a digital communication line and the measurement circuit or component 13 includes an amplification circuit 13a of the alternating voltage signal measured between terminals SP1, SP2 of a respective cell C and an analog-digital converter 13b, operatively associated with a microcontroller, designed to convert the analog amplitude value of the alternating voltage signal measured between terminals SP1, SP2 of a respective cell C into a digital value and send it on the data and / or instructions communication line 10.

[0088] Optionally, the amplification circuit 13a includes at least one operational amplifier, preferably a low noise and low offset operational amplifier, where the term "offset" is to be understood as the voltage difference between the inverting input and the non-inverting input of the operational amplifier when the output is at zero or null, and a high-pass or band-pass circuit, if desired realized using passive RC stages or actively using other operational amplifiers.

[0089] As can be understood, each measuring circuit or component 13 is advantageously integrated into a respective switching device or slave device 9, optionally integrated into the electronic board 9a, if provided, so that it can be controlled directly by the control and management unit or master management device 4.

[0090] If desired, the given frequency of the alternating current signal or measurement signal generated by the signal generation circuit or signal generator 12 varies between or is a value between 0.1 Hz and 1 kHz.

[0091] Preferably, the signal generating circuit 12 generates an alternating current signal or measurement signal with an amplitude between 1 A and 20 A, for example about 5 A or 10 A.

[0092] It should be considered that, in the state of the art, the signal generation circuits used are capable of generating alternating current signals or measurement signals which are typically of very small amplitude, for example tens or a few hundred mA, due of the complexity, size and cost that a circuit capable of generating higher amplitude signals should have.

[0093] In this regard, in the state of the art, the use of limited alternating current signals or limited measurement signals on cells of high capacity and, therefore, having low internal impedance, for example in the 100 p scale, implies that the measure is in the pV scale, which becomes very difficult to measure with sufficient precision especially considering that it is superimposed on a common mode value that corresponds to the open-circuit voltage of the cell, typically between 2.5 V and 4.5 V.

[0094] This is advantageously overcome by the balancing system 1 thanks to the distribution of the elements of the signal generation circuit or signal generator 12 and of the elements of the measuring circuit or component 13 respectively in the control and management unit or master management device 4 and in the switching device or slave device 9, effectively obtaining an optimal compromise between performance and measurement precision and cost and size of the system's component 1.

[0095] Below is described a non-limiting operation example of the balancing system according to a non-limiting embodiment of the present invention with reference to the measurement and processing of the impedance of a cell C, an example which clearly can be replicated for all the desired frequencies or frequency bands and for all cells C of battery B.

[0096] Firstly, the power unit 4b or, more specifically, the switching power converter thereof, for example the isolated DC-DC converter, draws current from the total battery voltage, which thus acts as an energy source, or draws current from an auxiliary power supply available or included in the system 1, to generate a current signal.

[0097] In particular, the current signal is generated by the digital signal synthesizer of the signal generation circuit or signal generator 12 so as to obtain an alternating current signal or measurement signal according to a set amplitude and frequency and stored within a measurement algorithm contained in the logic unit 4a or, more specifically, in its microcontroller.

[0098] More specifically, the signal generation circuit or signal generator 12 or, better, the microcontroller thereof, reproduces or generates a sequence of digital samples in order to represent a digital signal having a set waveform, amplitude and frequency. This digital signal can be converted into a discretized analog signal by means of the pulse width modulation or PWM peripheral or by means of the digital- to-analog converter or DAC, preferably appropriately filtered, and this discretized analog signal can then constitute the reference or set-point signal for the power unit 4b or, more specifically, for the at least one switching power converter thereof, for example for the isolated DC-DC converter, so as to obtain the desired alternating current signal or measurement signal which can be transferred to the balancing bus 6 or, more specifically, to the at least one charge and / or discharge line 7, 8.

[0099] Clearly, the at least one interrupt or enabling element 9c of the cell C whose impedance is to be measured is closed so as to create a point-to-point connection between the control and management unit or master management device 4 and that cell C.

[0100] The alternating current signal or measurement signal reaches cell C and induces an alternating voltage signal whose amplitude is measured by the measuring circuit or component 13 present on the switching device or slave device 9 associated with cell C.

[0101] In more detail, the alternating voltage signal is amplified by the amplification circuit 13a, the amplitude value of the latter is detected by the microcontroller of the measuring component or circuit 13 and then converted into digital by the analog-to-digital converter or DAC 13b to be then sent via the data and / or instructions communication line 10 to the control and management unit or master management device 4.

[0102] The logic unit 4b can then process, by means of the ratio between the amplitude value of the alternating voltage signal measured between terminals SP1, SP2 of cell C and the amplitude value of the alternating current signal, measured by means of the current sensor, the impedance of cell C at the set frequency.

[0103] Subject-matter of the present invention is also a battery B, in particular a lithium battery, having a main positive pole or current supply end MP1 and a main negative pole MP2, comprising a plurality of cells C each having a positive terminal SP1 and a negative terminal SP2, and a balancing system 1 according to the present invention or according to non-limiting embodiments of the present invention electrically connected to the plurality of cells C.

[0104] Preferably, the capacity of the cells C is between 100 Ah and 600 Ah, for example about 200, 400 or 560 Ah.

[0105] Furthermore, the present invention also provides a method for processing the impedance spectrum of at least one cell C of a battery B according to the present invention or according to non-limiting embodiments of the present invention.

[0106] The method according to the present invention initially comprises the step of selecting a cell C of which to measure the impedance spectrum.

[0107] The step of commanding the switching device or slave device 9, by means of the control and management unit or master management device 4, to open the passage of current towards the selected cell C so as to create a point-to-point connection between the cell C and the control and management unit or master management device 4 is then provided.

[0108] Subsequently, the method comprises the step of generating, by means of the signal generation circuit or signal generator 12 and by means of the power unit 4b, an alternating current signal or measurement signal at a given amplitude and frequency on the at least one charge and / or discharge line 7, 8 of the balancing line or bus 6.

[0109] The step of indicating, by means of a measurement instruction sent by the control and management unit or master management device 4 via the data and / or instructions communication line 10, the execution of a measurement to the measurement circuit or component 13 associated with the selected cell C is therefore envisaged.

[0110] The method according to the present invention then comprises the step of measuring, by means of the measuring circuit or component 13, the amplitude of the alternating voltage signal between the terminals SP1, SP2 of the selected cell C.

[0111] Subsequently, the step of sending such measured amplitude value to the control and management unit or master management device 4 via the data and / or instructions communication line 10 is included. Next, the method according to the present invention comprises the step of processing the impedance value as a function of the amplitude of the generated alternating current signal and the amplitude of the measured alternating voltage signal.

[0112] Finally, the step of iterating the previous steps for all the desired frequencies or in any case for all the frequencies of at least one set frequency band so as to obtain an impedance spectrum of the selected cell C is provided.

[0113] Optionally, it is possible to iterate the above method for multiple cells C of battery B.

[0114] If desired, at the measurement frequencies for which the communication latency is negligible, it is also possible to provide for the step of measuring the reactive part of the impedance, by ensuring that the measuring circuit or component 13 communicates the peak instant of the measured alternating voltage signal, which the control and management unit or master management device 4 can compare with that measured on the alternating current signal or measurement signal, to compensate for the contribution of the parasitic values of the balancing line or bus 6, previously estimated by means of similar measurements.

[0115] As can be understood, the electronic balancing system described in document EP3840172A1 has been advantageously adapted in order to integrate electrical and / or electronic components that allow the impedance spectrum of each cell C of the battery B to be processed.

[0116] It should be noted that the method according to the present invention can advantageously be implemented directly during operation of battery B.

[0117] The balancing system 1, the battery B and the related method allow to generate a high resolution or precision measurement of the impedance, even on high capacity cells.

[0118] Furthermore, the balancing system 1, the battery B and the related method allow to generate, using commercial components already available, current signals of high amplitude and in any direction (in the charge or discharge direction).

[0119] The balancing system 1 allows to optimize the cost and the size of the circuitry used, even on batteries composed of a high number of cells, making the solution applicable also to mass-produced batteries, for example for normal vehicle applications.

[0120] Balancing system 1 is able to exploit impedance measurement in order to obtain information on the state of health, dynamic behavior and operating conditions of the battery cells.

[0121] In addition, balancing system 1 allows to obtain an optimal compromise between performance and impedance measurement precision, and cost and size of the system components. In general, the balancing system 1, the battery B and the related method allow to obtain the typical advantages of a four-point impedance measurement, while distributing the necessary electronics on a master device 4 and a slave device 9, and using a scheme for sharing the latter.

[0122] It has thus been seen how the invention fully achieves the proposed objects. Modifications and variations of the invention are possible within the scope of protection defined by the following claims.

Claims

CLAIMS1. Balancing system (1) for cells (C) of a battery (B), in particular a lithium battery, each cell (C) having a positive terminal (SP1) and a negative terminal (SP2), comprising:- at least one control and management unit or master management device (4) of the battery (B) comprising at least one logic unit (4a) and at least one power unit (4b),- at least one active balancing component (5a) for charging said plurality of cells (C) and / or at least one passive balancing component (5b) for discharging said plurality of cells (C),- a balancing bus or line (6) comprising at least one charge and / or discharge line (7, 8) designed to put said at least one active and / or passive balancing component (5a, 5b) in electrical communication with each of said cells (C) so as to allow the latter to be charged and / or discharged, said charge and / or discharge line (7, 8) comprising connectors or connection branches (7a, 8a) towards and from each cell (C ),- a plurality of switching devices or slave devices (9), each positioned to intercept a respective connector or connection branch or respective connectors or connection branches (7a, 8a) and between the terminals (SP1, SP2) of a respective cell (C), each designed to open and / or close the passage of current to and from a respective cell (C), and- at least one data and / or instructions communication line (10) between said control and management unit or master management device (4) and each of said plurality of cells (C) designed to allow communication of data and / or instructions of said cells (C) to said control and management unit or BMS (4) or vice versa, wherein said balancing system (1) comprises measuring means (11) of the impedance of said cells (C) which include:- a signal generation circuit or signal generator (12), controlled by said logic unit (4a) and by said power unit (4b), designed to generate at least one alternating current signal or measurement signal at a given amplitude and frequency on the atleast one charge and / or discharge line (7, 8), and- a measuring circuit or component (13), included in each switching device or slave device (9), designed to measure and communicate, via said data and / or instructions communication line (10), the amplitude of the alternating voltage signal present between the terminals (SP1, SP2) of a respective cell (C) induced by the alternating current signal or measurement signal generated by said signal generation circuit or signal generator (12) so that, by varying the frequency of the alternating current signals or measurement signals, said control and management unit or master management device (4) of the battery (B) can process the impedance spectrum of a respective cell (C), wherein said signal generation circuit or signal generator (12) is integrated in said control and management unit or master management device (4) and is configured to use the power unit (4b) thereof for generating the alternating current signal or measurement signal.

2. System (1) according to the preceding claim, wherein said signal generation circuit or signal generator (12) comprises a digital signal synthesizer.

3. System (1) according to the preceding claim, wherein said digital signal synthesizer comprises a microcontroller and a pulse-width modulation or PWM peripheral or a digital-to-analog converter or DAC designed to generate a reference or set-point signal for said power unit (4b).

4. System (1) according to the preceding claim, wherein said signal generation circuit or signal generator (12) comprises a current sensor and a feedback circuit designed to reproduce an alternating current signal or measurement signal of set amplitude and frequency.

5. System (1) according to the preceding claim, wherein said set amplitude and frequency is selected by means of a measurement algorithm stored or implemented in said logic unit (4a).

6. System (1) according to claim 4 or 5, wherein said current sensor is designed to detect the phase of the alternating current signal or measurement signal and to detect the voltage at the ends of the balancing bus or line (6) so as to obtain analternating current signal having the set amplitude.

7. System (1) according to any one of claims 4 to 6, wherein said current sensor is or comprises a resistive shunt coupled to a specialized operational amplifier.

8. System (1) according to any one of the preceding claims, wherein said data and / or instructions communication line (10) is a digital communication line and said measurement circuit or component (13) comprises an amplifying circuit (13a) of the alternating voltage signal measured between the terminals (SP1, SP2) of a respective cell (C) and an analog-to-digital converter (13b), operatively associated with a microcontroller, designed to convert the analog amplitude value of the alternating voltage signal measured between the terminals (SP1, SP2) of a respective cell (C) and send it on said data and / or instructions communication line (10).

9. System (1) according to the preceding claim, wherein said amplification circuit (12a) is a high-pass or band-pass amplification circuit.

10. System (1) according to any one of the preceding claims, wherein said given frequency varies between or is a value between 0.1 Hz and 1 kHz.

11. System (1) according to any one of the preceding claims, wherein said signal generation circuit or signal generator (12) generates an alternating current signal or measurement signal with an amplitude of between 1 A and 20 A.

12. System (1) according to any one of the preceding claims, wherein some or all of said switching devices or slave devices (9) comprise an electronic board (9a) which includes a microcontroller (9b), and an interrupt or enabling element (9c) of the electrical connection between said at least one charge and / or discharge line (7, 8) and a respective cell (C) on the basis of instructions that said control and management unit or master management device (4), by means of said at least one data and / or instructions communication line (10), supplies said microcontroller (9b).

13. System (1) according to any one of the preceding claims, wherein said at least one active and / or passive balancing component (5a, 5b) of the cells (C) comprises at least one active balancing component (5a) or charging component ofthe cells (C ) and at least one passive balancing component (5b) or discharging component of the cells (C) and in which said at least one charge and / or discharge line (7, 8) comprises a charge line (7) designed to put in electrical communication said at least one active balancing component (5a) with each of the cells (C) so as to allow charging of the latter and a discharge line (8), separate from said charge line (7), designed to put in electrical communication said at least one passive balancing component (5b) with each of the cells (C) so as to allow the latter to discharge.

14. System (1) according to any one of the preceding claims, wherein said power unit (4b) comprises at least one switching power converter.

15. Battery (B), in particular a lithium battery, having a main positive pole or current supply end (MP1) and a main negative pole (MP2), comprising a plurality of cells (C) each having a positive terminal (SP1) and a negative terminal (SP2), and a balancing system (1) according to any one of the preceding claims electrically connected to said plurality of cells (C).

16. Battery (B) according to the preceding claim, wherein the capacity of said cells (C) is between 100 Ah and 600 Ah.

17. Method for processing the impedance spectrum of at least one cell (C) of a battery (B) according to any one of claims 15 or 16, comprising the steps of: selecting a cell (C) to measure the impedance spectrum, commanding said switching device or slave device (9), by means of said control and management unit or master management device (4), the opening of the passage of current towards the selected cell (C) so as to create a point-to-point connection between said cell (C) and said control and management unit or master management device (4), generating, by means of said signal generation circuit or signal generator (12) and by means of said power unit (4b), an alternating current signal or measurement signal at a given amplitude and frequency on at least one charge and / or discharge line (7, 8) of said balancing bus or line (6), indicating, by means of a measurement instruction sent by the control and management unit or master management device (4) through said data and / orinstructions communication line (10), the execution of a measurement to said measuring circuit or component (13) associated with the selected cell (C), measuring, by means of said measuring circuit or component (13), the amplitude of the alternating voltage signal between the terminals (SP1, SP2) of the selected cell (C), sending this measured amplitude value to said control and management unit or master management device (4) through said data and / or instructions communication line (10), processing the impedance value as a function of the amplitude of the generated alternating current signal and the amplitude of the measured alternating voltage signal, iterating the previous steps for all the desired frequencies or for all the frequencies of at least one set frequency band so as to obtain an impedance spectrum of the selected cell (C).

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