Method for communication between monitoring circuits internal to a battery, and battery implementing the method

Abstract

The invention relates to a method for communication in a battery (BT) comprising a plurality of cells (CLi), wherein the communication is between a management unit (BMU), connected to terminals (PTH, PTL) of the battery, and measurement units (MCi), each connected between two connection terminals (CTH, CTL) of one of the cells of the battery, the method comprising the steps of: transmitting a request (FR1) by the management unit by applying voltage drops across the terminals of the battery; receiving the request by each of the measurement units, by demodulating voltage drops detected at the terminals of the associated cell; transmitting a response (CFR_J) by each measurement unit, by applying voltage drops across the terminals of the cell; and receiving the response by the management unit, by demodulating the voltage drops detected at the terminals of the battery.

Description

[0001] DESCRIPTION

[0002] METHOD OF COMMUNICATION BETWEEN INTERNAL MONITORING CIRCUITS OF A BATTERY, AND A BATTERY IMPLEMENTING THE METHOD

[0003] technical field

[0004] The present invention relates to electrical energy storage batteries comprising a plurality of battery cells and communication between different monitoring and processing units within such batteries, in particular to transmit parameters representative of the operating state of the battery and the battery cells.

[0005] The present invention is particularly applicable to electrochemical cell batteries of the lithium-ion, sodium-ion, potassium-ion, magnesium-ion, lithium / sodium metal, or metal-air type, whether with liquid, solid, or gel electrolyte. Such batteries can be used in various applications such as electric vehicles, drones, power tools, and stationary energy storage.

[0006] State of the art

[0007] Electrical energy storage batteries are designed to be connected to a charging circuit to be charged and store electrical energy, and to discharge by producing an electrical current when connected to a load. Battery cells are connected in series and / or parallel within the battery to achieve the required voltage and energy level. Typically, a battery with cells, for example, lithium-ion cells, comprises several identical blocks of individual cells, each block containing one or more cells in series to achieve the desired total battery voltage. Multiple identical blocks are connected in parallel.The total energy capacity of the battery is determined by the number of blocks multiplied by the energy capacity of one block, itself dependent on the energy capacity of each of the identical individual cells assembled in series in each of the blocks.

[0008] Some batteries, particularly those of the types listed previously, can cause an explosion, combustion, and / or violent outgassing. To guarantee both battery lifespan and safe operation, it is important to be able to monitor, regularly or even continuously, representative functional parameters of the battery's condition, whether in operation or at rest. These functional parameters can relate to the battery as a whole, preferably to each group of cells within the battery, or even to each individual cell within the battery. These parameters may include, in particular, temperature and pressure values, as well as minimum discharge and maximum charging voltages.It is also desirable to be able to control the electrical balancing of all the cells, as well as the evolution of various battery parameters such as voltage and current during charge and discharge cycles. Using these functional parameters allows for the control of the charger's output voltage and current, and also for managing functions such as balancing the individual cells or cell blocks that make up the battery, as well as ensuring the battery's thermal safety. This controlled management can also be used to determine the battery's State of Health (SOH), extend its lifespan, and predict its Remaining Useful Life (RUL).

[0009] Generally, controlling the cells of a battery requires a multitude of wires and / or connections between the cells or blocks and a central management unit called a "BMS" (Battery Management System). It is therefore understandable that in the case of a complex series / parallel cell assembly, this interconnection with the central BMS proves complex, time-consuming, and industrially expensive, especially when the number of interconnected cells is large, as is the case with batteries intended for mobility applications and operating at voltages exceeding 350 volts, requiring a minimum of 100 cells or blocks connected in series (depending on the electrochemical pair used). Thus, some automotive batteries can contain several thousand cells. The same applies to stationary batteries.The resulting complexity of interconnection can represent a source of failure related to battery operating conditions. For example, batteries intended for mobility are subjected to vibrations and shocks, which can cause electrical disconnections, making reliable battery operation impossible, or even lead to short circuits or thermal runaways, jeopardizing the integrity of the application due to their inherent danger. The slightest failure of a single cell can thus prevent the entire battery from functioning, particularly in existing battery architectures where several cells or groups of cells are connected in parallel. Indeed, in a parallel cell assembly, if one cell short-circuits, it short-circuits the other cells connected in parallel, resulting in thermal runaway due to the sudden discharge of the other cells into the short-circuited one.This interconnection complexity is particularly evident in vehicles where the battery may consist of several blocks distributed across different locations within the vehicle. This complexity can be reduced by decreasing the number of measurement points, for example, by associating one measurement point with a block rather than with each individual cell. However, this solution requires significant safety margins on the detection thresholds to guarantee the necessary battery operating safety. Indeed, battery cells generally age unevenly (primarily due to variations in internal resistance). This results in behaviors, particularly thermal behavior, that can vary from one cell to another within the same battery.

[0010] It is therefore desirable to be able to measure the functional parameters of each cell in a battery with a very large number of cells, and to be able to transmit these measurements to the battery management unit. To this end, it is desirable to be able to associate each cell with a measuring device incorporating sensors for these functional parameters and a communication circuit with the battery management unit. It is also desirable to avoid having to provide specific connections between the measuring devices associated with the battery cells and the management unit. Finally, it is desirable to be able to maintain the battery's functionality as much as possible in the event of cell failure.

[0011] Summary

[0012] Embodiments relate to a communication method within a battery comprising a plurality of cells, between a management unit connected to battery terminals and measurement units, the battery comprising several parallel branches connected respectively to branch terminals and each comprising a plurality of cells connected in series, each cell being associated with one of the measurement units connected between two cell connection terminals, the method comprising steps consisting of: transmitting a request message by the management unit in a modulated form by applying pulse bursts in the form of voltage drops between the branch terminals; receiving the request message by each of the measurement units, by demodulating the pulse bursts between the cell terminals to which the measurement unit is connected;to emit by each measuring unit in response to the request message, a response message in a modulated form by applying bursts of pulses in the form of voltage drops between the terminals of the cell to which the measuring unit is connected, during a respective time slot allocated to the measuring unit, the response message containing data from a measurement of an operating parameter of the cell; and to receive the response message by the management unit, by demodulating the bursts of pulses detected on the terminals of the battery.

[0013] Thanks to these features, each cell can be monitored individually, with cell status data accessible and centralized by a single battery management unit. Furthermore, the transmission technique employed proves particularly effective for transmitting information between the battery management unit and the measurement units associated with each battery cell. Indeed, the transmission of messages via voltage drop bursts is not attenuated, as these bursts are immediately visible whether emitted by the management unit or by one of the measurement units. Moreover, this transmission technique is even more efficient because the messages emitted by the management unit are received simultaneously by all measurement units. Therefore, the management unit does not need to address each measurement unit individually.This transmission technique is therefore particularly well-suited to batteries with a large number of cells. Furthermore, each measuring unit can communicate with the control unit in turn. This avoids any risk of collision that can occur when two measuring units attempt to transmit a message simultaneously.

[0014] According to one embodiment, the process includes steps consisting of: measuring a cell voltage, by the measuring unit connected to the cell terminals, and deriving current at the cell terminals by the measuring unit for a balancing time which can be fixed, when the measured voltage is greater than a setpoint value, in order to balance the cell with the other cells of the battery.

[0015] Thus, the measuring units use the same components to communicate with the management unit and to balance the associated cell, in order to allow a maximum battery charge level to be reached.

[0016] According to one embodiment, voltage drops or current diversion are achieved by each of the measuring units, by controlling a transistor connected to the terminals of each cell.

[0017] According to one embodiment, the voltage drops are applied by the management unit by controlling a transistor connected to the branch terminals.

[0018] Thus, voltage drops can be applied using a very simple circuit that can easily be miniaturized. Furthermore, the amplitude of the voltage drops can be finely adjusted. In one embodiment, the voltage drops generated by each measuring unit to transmit a response message have an amplitude of a few tens of millivolts.

[0019] According to one embodiment, the measurement units are synchronized to a moment of detection of a first voltage drop upon receipt of a request message.

[0020] Thus, the measurement units can easily be synchronized, particularly to avoid collisions when communicating with the management unit.

[0021] According to one embodiment, the method further comprises steps of: detecting by the management unit that one of the battery cells is faulty on the basis of a failure to receive the response message from the cell measuring unit, or on the basis of a cell operating parameter measurement data received in the response message from the cell measuring unit, and if a cell failure is detected, controlling a switch to disconnect a branch of cells connected in series, to which the faulty cell belongs.

[0022] Thanks to the presence of a measuring unit for each battery cell and switches for each branch, a cell failure can be quickly detected and the battery can be rapidly shut down when a faulty cell is detected. Thus, the entire battery can be protected in the event of a single cell failure, without affecting the battery's voltage output.

[0023] According to one embodiment, several cell operating parameters are measured or calculated, and transmitted by each measuring unit, the cell operating parameters including at least one of the following parameters: a voltage across the cell, a cell temperature, a current through the cell, an internal resistance of the cell, and a pressure in the cell.

[0024] Thus, several parameters representative of the proper functioning of a battery cell can be measured for each battery cell.

[0025] According to one embodiment, operating parameters of each cell are acquired and stored at regular or irregular intervals in an event log stored in a secure memory area of ​​the measurement unit associated with the cell.

[0026] Embodiments may also relate to a battery comprising: a plurality of branches connected in parallel, respectively connected to branch terminals, each branch comprising a plurality of cells connected in series, a battery management unit connected to battery terminals and to branch terminals, and measurement units, each cell being associated with one of the measurement units connected between two cell connection terminals, the management unit and the measurement units being configured to implement the communication method defined above.

[0027] According to one embodiment, the control unit or each of the measurement units includes a transistor connected to the branch terminals, and respectively to the terminals of each cell, the transistor being controlled to apply voltage drops or derive current.

[0028] According to one embodiment, the management unit includes a power switch per branch to disconnect one of the branches when a cell in the branch is detected as faulty.

[0029] According to one embodiment, each measuring unit includes a wake-up circuit configured to detect a wake-up voltage drop between the cell terminals, and to activate a measuring unit processing unit upon detection of the voltage drop, the management unit being configured to generate the wake-up voltage drop.

[0030] According to one embodiment, each unit of measurement is realized in the form of a miniaturized integrated electronic component embedded in one of the battery cells.

[0031] According to one embodiment, the management unit incorporates a measurement unit to communicate with the measurement units associated with the battery cells.

[0032] Brief description of the figures

[0033] The present invention will be better understood with the aid of the following description of exemplary embodiments with reference to the accompanying figures, in which identical reference symbols correspond to structurally and / or functionally identical or similar elements.

[0034] Figure 1 schematically represents a battery comprising a plurality of cells, according to one embodiment,

[0035] Figure 2 schematically represents circuits of a measurement unit that can be associated with each of the battery cells, according to one embodiment,

[0036] Figure 3 schematically represents the circuits of a battery management unit, according to one embodiment,

[0037] Figure 4 schematically represents the transmission circuits of the measuring unit and the management unit, according to one embodiment. Figure 5 schematically represents the steps of a communication process between a measuring unit associated with a battery cell and the battery management unit, according to one embodiment.

[0038] Figure 6 schematically represents, as a function of time, data messages transmitted between the battery management unit and the measurement units associated respectively with the battery cells, according to one embodiment,

[0039] Figure 7 schematically represents circuits of a measurement unit that can be associated with each of the battery cells, according to another embodiment,

[0040] Figure 8 schematically represents circuits of a battery management unit, according to another embodiment.

[0041] Detailed description

[0042] Figure 1 depicts a low-voltage (LV) electrical energy storage battery comprising several CL1-, CL2, ..., CLn cells (n being an integer greater than or equal to 2) connected in series. Each of the CL1-CLn cells is configured to store electrical energy when electrically connected to a charging supply and to release this electrical energy when electrically connected to an electrical load. The CL1-CLn cells (i=1, ..., n) can belong to an electrochemical category, such as supercapacitor or rechargeable battery. Generally, an electrochemical cell consists of two electrodes, a separator between the two electrodes, and an electrolyte.There are different types of cells in the rechargeable electric battery category, for example lithium-ion cells, Nickel Cobalt Aluminium-Graphite, Nickel Manganese Cobalt-Graphite, Nickel Cobalt Aluminium-Silicon, Nickel Manganese Cobalt-Silicon, Lithium Cobalt Oxide-Graphite, Lithium Iron Phosphate-Graphite, Lithium-Sulfur, Lithium Sulfide-Silicon, Sodium-ion, etc.

[0043] The CL1-CLn cells are connected in series to form an RM1 branch connected between the BTH1 and BTL terminals of a BMU (Battery Management Unit), which is connected to the PTH and PTL terminals of the BT battery. The PTH and PTL terminals can be connected to an electrical load or a charging circuit. The BT battery can thus comprise several identical RM1, RM2, ..., RMp branches connected in parallel between a negative BTL terminal and the respective positive BTH1, BTH2, ..., BTHp terminals of the BMU.

[0044] In one embodiment, each CLi cell is associated with an MCi measuring unit (i = 1, ..., n) connected to the two terminals of the cell and comprising communication circuits for communicating with the BMU. Each MCi measuring unit is configured to acquire operating parameter values ​​for the cell and to transmit them to the BMU. The communication circuits of the MCi measuring units are configured to use the links between the CLi cells and the BMU to communicate with the latter.

[0045] Figure 2 illustrates the circuits of a measurement unit MC, which can be any of the measurement units MCi. The MC unit comprises a processing unit UC, a temperature sensor TS, a reference voltage generator VRG circuit, an ALM power supply circuit, a communication circuit TRC, a DC switching circuit controlled by the processing unit UC, and optionally other sensors such as a pressure sensor PS and a current measurement circuit IM. The current measurement circuit IM can, for example, be interposed on a current line of the measurement unit MC between the negative terminal CTL and the positive terminal CTH of the associated cell CLI.

[0046] The processing unit (PU) includes an analog-to-digital converter (ADC) with several inputs connected respectively to the temperature sensor (TS) and pressure sensor (PS), the reference voltage generator (VRG), the current measurement circuit (IM), and the positive terminal (CTH) of the cell (CLi) to which the measuring unit (MC) is connected for measuring the cell's voltage (Vc). The PU is thus configured to receive measurements of temperature, pressure, voltage (Vc), and current, if applicable, to compare these measurements to threshold values, and to transmit these measurements or the results of these comparisons via the communication circuit (TRC). The PU may include a microcontroller comprising the CVN and volatile and non-volatile memory (MEM) for storing, among other things, software executed by the PU.The ALM power supply circuit provides a supply voltage SV to the processing unit UC and the DC switching circuit. The VRG generator is configured to generate a highly stable voltage, independent of ambient temperature. Therefore, the reference voltage generated by the VRG generator can be used by the processing unit UC as a reference voltage, particularly for accurate operation of the CVN converter.

[0047] The TRC communication circuit includes a Tx input for transmit data and an Rx output for received data, connected to the processing unit (PU). The TRC communication circuit also includes an OTx output for the transmit signal and an IRx input for the received signal. Furthermore, the TRC circuit can be powered by VI and VG supply terminals connected to the output of the ALM power supply circuit and the CTL terminal, respectively. The OTx output of the TRC circuit controls a switch T1, which connects the negative CTL terminal of the CLi cell to a dissipative component R1, such as a resistor. R1 is connected to the positive CTH terminal of the CLi cell. Switch T1 can be a bipolar transistor, for example, of type npn (or pnp), with its base connected to the OTx output of the TRC circuit, its emitter connected to the negative CTL terminal, and its collector connected to the dissipative component R1.The IRx input of the TRC circuit is connected to the positive terminal CTH of the associated CLi cell via a capacitor C1. The capacitor C1 eliminates the DC component and thus extracts the transmission signal from the voltage at the CTH, CTL terminals of the cell.

[0048] The MC unit can also be configured to enter a low-power sleep state during periods when it is not required to transmit status data from the associated CLi cell. For this purpose, the MC unit includes a DC switching circuit controlled by the processing unit (CU). The DC switching circuit includes switches connecting the voltage output of the ALM power supply circuit to the VRG generator, the TS temperature sensor, and the TRC communication circuit, respectively. The DC switching circuit also includes an additional switch connecting the CTH positive terminal of the CLi cell to an input of the CVN converter.

[0049] The MC unit can also include a wake-up circuit (WU) configured to detect a wake-up signal on the CTH terminal and, upon detecting the wake-up signal, activate the UC processing unit by sending a signal to a designated input. The UC processing unit can be configured to control the CC switching circuit when it transitions to the active state, in order to selectively energize the TS temperature sensor, the VRG generator, and the TRC communication circuit. Conversely, the UC processing unit can be configured to enter an inactive state when the MC measuring unit is not being used by the BMU. The UC processing unit is then configured to control the CC switching circuit before transitioning to the inactive state, in order to de-energize the various TS and PS sensors, the VRG generator, and the TRC communication circuit.

[0050] Thanks to these arrangements, the various TS, PS sensors, the VRG generator and the TRC communication circuit can be powered and the cell voltage Vc can be supplied to the CVN converter, only when required.

[0051] The MC unit can also include a voltage monitoring circuit (VM) configured to monitor the voltage across the CTH and CTL terminals of the associated CLi cell, in redundancy with the processing unit (CU). For this purpose, the VM is connected to the CTH and CTL terminals of the associated CLi cell and is configured to compare the voltage across the CTH and CTL terminals of the CLi cell to maximum and minimum voltage safety threshold values. These maximum and minimum voltage safety thresholds are related to the electrochemical couple of the CLi cells. Indeed, depending on the electrochemical couple, the voltages reached at the end of charging and / or discharging are not the same. These voltage safety thresholds can be pre-programmed in the MC measuring units, independently of the software running on the processing unit (UC), which prevents them from being exceeded during normal operation.In the event of a hardware or software malfunction of the MC measuring unit, the VM circuit is configured to block transmissions via the TRC circuit to the BMU if these thresholds are exceeded, for example, using a SW switch connecting the control terminal of switch T1 to the CTL terminal. Furthermore, the BMU management unit can be configured to trigger an interruption of the charging or discharging process or to activate the BT battery protection mechanism if none of the MCi measuring units connected to the BMU receive a response.

[0052] The voltage thresholds applied by the VM circuit can be configured according to the desired operating range of the associated CLi cell and stored in the BMU's memory. These thresholds are then transmitted to the MCi measurement units and processed by their respective UCs. The high voltage at the end of charging can be lowered, and / or the minimum voltage at the end of discharge can be increased. Similarly, maximum and minimum temperature thresholds can be stored in the BMU's memory and adapted to the battery architecture. These thresholds are then transmitted to and stored in each UC's memory for processing. By avoiding exceeding these voltage thresholds, the structure of the active materials in the CLi cell degrades less rapidly, thus increasing the lifespan of the CLi cell and, consequently, the battery.

[0053] In one embodiment, the MC unit is implemented as a miniaturized integrated electronic component, for example, as an ASIC (Application-Specific Integrated Circuit) or a SoC (System on Chip). The MC unit can also be configured to connect easily to the CTH and CTL terminals of a CLi cell. This allows the MC unit to be readily integrated into each of the battery's CLi cells without increasing the battery's overall size. Sensors, particularly those for temperature, voltage, and pressure, can then be positioned as close as possible to the cell's electrochemical core, thus providing more accurate measurements. The IM current sensor can also be, for example, a Hall effect sensor connected to a link between the CTL and CTH terminals.

[0054] Figure 3 shows the circuits of the BT battery management and monitoring unit (BMU) according to one embodiment. The BMU comprises a processing unit (UC1), a power supply circuit (ALM1), and a communication circuit (TRC1). Figure 3 also shows the negative terminal (BTL) of the BMU connected to the negative terminals of branches RM1, RM2, ..., RMp, and the positive terminals (BTH1, BTH2, ..., BTHp) of the BMU connected to the positive terminals of the branches, respectively. The BMU may also include a wake-up circuit (WU1) that wakes up the MCi units present in the BT battery and connected to the BMU. Two positive terminals (PTH1, PTH2) and one negative terminal (PTL) form the terminals of the BT battery. The positive terminals are intended to be connected to an LD load and a CHC charging circuit, respectively, which are also connected to the negative terminal (PTL).However, the same positive terminal PTH1 or PTH2 can be used for both charging and discharging the BT battery. Furthermore, the BMU unit has as many positive terminals BTHj (j = 1, 2, ..., p) as there are RMj branches.

[0055] Each of the BTHj terminals is connected to a junction point EP at the battery voltage Vbt via a power switch SW11, ..., SW1p and a capacitor C11, ..., C1p connected in parallel with it. Each switch SW1j (j = 1, ..., p) allows the corresponding RMj branch to be disconnected, particularly when one of the branch's cells CLi is detected as faulty or when communication with a measuring unit MCi of the branch is lost. Furthermore, each of the SW1j power switches is connected in parallel with its respective capacitor C1j (C11, ..., C1p). The capacitors C1j maintain communication with the measuring units MCi of the corresponding RMj branch when the corresponding SW1j switch is open. The capacitance of the capacitors C1j is adjusted so as not to disrupt (attenuate, distort) the transmissions.SW1j switches are made for example by MOSFETs ("Metal-Oxide-Semiconductor Field-Effect Transistor").

[0056] Furthermore, the EP junction point is connected to each of the PTH1 and PTH2 terminals via an inductor L1 and a respective power switch SW3 and SW4. Switches SW3 and SW4 are controlled by the processing unit UC1, with only one switch being closed depending on whether the charging or discharging operation is in progress. The inductor L1 provides a filtering function. The EP junction point is also connected to the negative terminal BTL via a dissipative component R2 and a switch T2. The ALM1 power supply circuit generates a supply voltage SV1 for the processing unit UC1 and the communication circuit TRC1 from the internal voltage Vbt.The communication circuit TRC1 includes a power input VI connected to the output of the power supply circuit ALM1, a receive input IRx connected to the junction point EP via a capacitor C2 and to the input VI via an inductor L2 providing a filtering function, and a transmit output OTx connected to the control input of switch T2 via an amplifier AP. Switch T2 can be an N-type or P-type MOSFET, with a gate connected to the output OTx and conduction terminals connected respectively to the dissipative component R2 and the BTL terminal. Switch T2 is sized to be able to switch the high voltages present at the BTHj and BTL terminals of the battery. The amplifier AP amplifies the control voltage supplied by the SLC circuit to obtain a sufficient voltage to control switch T2. The dissipative component R2 can be a resistor.Furthermore, the TRC1 communication circuit includes a Tx input connected to a data output of the processing unit UC1 and an RX output of received data connected to an input of the processing unit UC1. The TRC1 communication circuit can be identical to the TRC communication circuit.

[0057] The processing unit UC1 includes an analog-to-digital converter CVN1 with several inputs receiving voltages Vh1, ..., Vhp taken respectively from the BTHj terminals, the internal voltage Vbt, and inputs connected to the terminals of a current sensor R3, for example, a resistive component interposed across the connection between the BTL and PTL terminals, to measure the current flowing between the terminals of the BT battery. The processing unit UC1 is also configured to control the SW1j switches, each of which is closed as long as a CLi cell belonging to the corresponding RMj branch is not detected as faulty. The SW1j switches can also be opened during periods of battery storage or transport, particularly to increase safety. The current sensor R3 can also be a Hall effect sensor placed across a connection between the BTL and PTL terminals.

[0058] The wake-up circuit WU1 can be implemented, for example, using a resistive or dissipative component coupled to a power switch controlled by the processing unit UC1, and connected to the junction point EP upstream of the inductor L1. The processing unit UC1 is configured to control the closing of the power switch in the WU1 circuit for a brief time, thereby generating a short voltage drop at the junction point EP. This voltage drop is transmitted to the cells CLi connected to the terminals BTHj and is detected by the wake-up circuit Wll of each of the MCi measuring units associated with these cells, thus "waking up" the MCi measuring units and synchronizing them.

[0059] Figure 4 shows the communication circuit TRC, TRC1 of the measuring unit MC and the unit BM1, according to one embodiment. The circuit TRC, TRC1 comprises a transmit stage TXT and a receive stage RXT. The transmit stage TXT includes a signal mixing circuit SMC that receives a data signal TXS to be transmitted at the Tx input of the circuit TRC, TRC1, provided by the processing unit UC, UC1; a low-pass filter F1 connected to the output of the SMC; and a slope control circuit SLC connected to the output of the filter F1. The output of the SLC is connected to the control terminal of the switch T1, T2. The SMC circuit is configured to modulate a carrier by the TXS signal, the carrier being a CK clock signal (or at a frequency defined by such a clock signal) provided for example by the processing unit UC, UC1 or a clock circuit provided in the MC measurement unit and the BMU unit.The clock signal frequency CK can, for example, be more than ten times the data rate in the TXS data signal. The signal produced by the SMC circuit can thus consist of bursts of square waves, each burst corresponding, for example, to a 1 in the TXS data signal, with the signal between bursts corresponding to one or more 0s. The SLC circuit is configured to transform the signal supplied by the filter F1 into a signal consisting of bursts of pulses with a substantially sinusoidal shape. Thus, the switch T1, T2 is controlled to produce bursts of pulses in the form of voltage drops across the CTH, CTL terminals of the associated CLi cell, or across the BTHj, BTL terminals of the BMU unit. The substantially sinusoidal shape of the pulses allows for signals with a Fourier spectrum consisting of essentially a single line.For example, the TXS data signal might have a rate of several tens of kHz, while the CK clock signal might have a frequency of a few MHz. TXS and RXS data signals are, for example, configured as frames conforming to the UART ("Universal Asynchronous Receiver Transmitter") protocol.

[0060] The voltage drops generated by the MCi measurement units have an amplitude of a few tens of millivolts, for example, 30 mV ±10%. Furthermore, the voltage drops generated by the BMU management unit are applied to the terminals of each RM1j branch. They are therefore distributed across the terminals of each cell connected in series within each branch. Thus, the voltage drops generated by the BMU management unit have a specific amplitude to be visible to all the MCi measurement units in the battery. To this end, the voltage drops generated by the BM1j management unit can have an amplitude corresponding to at least the amplitude of the voltage drop applied by each measurement unit, multiplied by the number of cells connected in series in each RMj branch, and taking into account the number of branches in parallel in the BT battery.Furthermore, inductance L1 prevents voltage drops generated by switch T2 from being dissipated in the LD load or in the CHC charging circuit connected to the BT battery. Conversely, inductance L1 isolates unit BM1 from interference that may originate from an external circuit (CHC, LD) connected to the battery.

[0061] The RXT receiver stage includes a resistor R4 connected to capacitors C1 and C2, a bandpass filter F2 connected to resistor R4, a voltage amplifier VA connected to the output of filter F2, an envelope detection EVD circuit connected to the output of the VA amplifier, and a comparator CP1 connected to the output of the EVD circuit. The EVD circuit generates an envelope signal from pulse bursts present in the data signal extracted from the voltage between the CTH and CTL terminals of the associated CLi cell. The comparator CP1 compares the envelope signal provided by the EVD circuit to a threshold voltage value Vrf to generate a square wave signal of 0 or 1 depending on whether the envelope signal is below or above the threshold value. The reference voltage Vrf is, for example, derived from the supply voltage SV provided by the ALM power supply circuit of the MC unit.The comparator CP1 provides an RXS signal of received data to the processing unit UC, UC1. The filter F2 eliminates Fourier spectrum lines from the received signal and removes parasitic frequencies from the environment or load, leaving only the frequency band of the useful communication signal.

[0062] It turns out that the voltage drops generated by the control of transistor T1 of one of the MCi units in an RMj branch are visible at the EP junction point, but not by the other MCi units in the branch. In contrast, the voltage drops generated by the control of transistor T2 of the BMU are visible simultaneously by all the MCi units connected to terminals BTH1, BTH2, and BTL. Furthermore, this modulation of the voltage across a cell or branch by voltage drops is inherently unaffected. Moreover, the inductor L1 prevents the voltage drops from being attenuated by the circuit connected to the battery.

[0063] This transmission method, which uses voltage drops on the cell power line, differs from power line communication (PLC) transmission, which involves injecting an amplitude-modulated carrier signal onto the power line, with the cell terminals interconnected by a capacitor. The modulated carrier signal injected in this way, as a current modulation, undergoes significant attenuation that increases as it propagates. Consequently, a signal transmitted via power line communication must be repeated at each cell to reach its intended recipient. Therefore, a transmitted message is necessarily processed by multiple cell circuits.Such repeated transmissions also result in significant transmission delays, an increased risk of errors, and high energy consumption, which, in the context of a battery, impacts battery life. Due to these significant transmission delays, power line communication (PLC) transmission technology cannot monitor a very large number of individual cells with sufficiently short response times to trigger effective battery protection measures following the detection of a cell failure.

[0064] In one embodiment, each MCi measuring unit implements a cell balancing function, CLI. This function aims to optimize the recovery of the highest possible battery capacity. Indeed, each cell evolves differently and has different charge and discharge rates, depending on its individual capacity. During battery charging, as soon as a cell reaches a maximum voltage, known as "Over Voltage," charging must be interrupted to prevent overheating or even battery destruction. This means that the entire battery is dependent on the cell that reaches the end of its charge the fastest. In this case, the other cells in the battery are not fully charged. Therefore, it is not possible to utilize the battery's total capacity.

[0065] The balancing function measures cell voltages during, for example, a battery charging operation. Based on these measurements, the charging of the fastest-charging cells (those with the fastest voltage changes) is slowed down by switching on a balancing resistor connected in parallel with the cell. This diverts a portion of the charging current away from the cell, thus preventing it from recharging. The diverted charging current is adjusted so that, at the end of the charge, all cells have the most homogeneous measured voltages possible. For example, the balancing function might aim for a final cell voltage difference of less than 1%. Thanks to the dissipative component R1 coupled to transistor T1, which is controlled by the processing unit UC, each MCi measuring unit can perform the balancing of its associated CLi cell.In addition, the cell balancing function can be performed on the basis of measurements that are all the more precise as the MCi measuring unit can be placed as close as possible to the associated CLI cell.

[0066] The balancing function can consist of controlling the closure of transistor T1 for a fixed duration, for example, 100 ms, or diverting a variable amount of current by acting on the control signal of transistor T1, when the voltage Vc of the CLi cell measured by the UC unit is greater than a minimum setpoint voltage Vmin plus a delta value, which depends on the difference between the minimum and maximum setpoint voltages. The minimum and maximum setpoint voltages can be provided by the BMU management unit. Thus, the UC processing unit can be configured to perform the balancing function during a battery charging operation. The balancing function can also be performed for long-term battery storage to limit the amount of energy stored in the cells, since in long-term storage, the more charged the battery is, the more dangerous it becomes and the more prematurely it ages.

[0067] Figure 5 illustrates steps S1 to S10 of a data exchange process between the BMU's processing unit UC1 and the processing unit UC of one of the MCi measuring units. In step S1, the BMU selects a type of FR message to transmit, for example, based on the battery's current state (charging, discharging) or based on any previous exchanges with the MCi units. This could be, for example, a configuration message containing battery operating and configuration parameters, or a message requesting measurement and / or status data following the detection of a fault in a cell.

[0068] In step S2, the BMU transmits a message FR1 of the selected type. In step S3, the message FR1 is received by all connected MCi units, approximately simultaneously. Each MCi unit receives the message FR1 and determines its type. If the type of the received message FR1 requires a response from the MCi unit, it triggers a time delay TMP in step S4. This time delay can depend on the type of the received message FR1 and a time slot J allocated to it. At the end of the TMP period, the MCi unit selects a message type to send in response to the message FR1, generates a message CFR_J corresponding to the selected type and containing the required data. In step S6, the MCi unit sends the CFR_J message (J=1, ..., N, where N is the number of cells in the battery) in response during its allocated time slot J. At step S7, the BMU unit receives the CFR_J message, and determines the type of the CFR_J message.Step S7 ends when the BMU has received messages from all MCi units or when all the time slots allocated to the MCi units for sending a reply message have elapsed. The following steps, S8 through S10, may be optional and depend on the type of CFR_J messages. In step S8, the BM11 unit selects a message type to send in response to the CFR_J message. In step S9, the BM11 unit generates an FR2 message corresponding to the selected type and containing the required data. In step S10, the MCi unit receives the FR2 message and executes step S3 again, and optionally steps S4 through S6 if a reply is required.

[0069] Figure 6 illustrates a message exchange between the BMU and the MCi units, according to one embodiment. This message exchange is initiated by the BMU sending a message FR1 of a given type (step S2). The FR1 message is received approximately simultaneously by all N MCi units connected to the BMU. The MCi units then send a response (step S6) with a CFR_J message of a type corresponding to the type of the FR1 message. For this purpose, each MCi unit uses a time slot that has been previously allocated to it. Upon receiving the CFR_N message corresponding to the last allocated time slot N, the BMU sends an FR2 message, which can be an end-of-exchange message or a request message for the status data of the CLI cells. In Figure 6, the width of the blocks representing the CFR_J messages illustrates the width of the time slots.

[0070] In one embodiment, a time slot is assigned to each MCi unit connected to the BMU by an initialization message (FR1). For example, the processing unit (CU) of each MCi unit stores a unique identifier known to the BMU connected to the MCi unit. The initialization message contains a list of all the identifiers of the MCi units connected to the BMU, each associated with a time slot number. The identifiers of the MCi units connected to the BMU can be provided to the BMU during a configuration phase when assembling the cells to form the battery.

[0071] In another example, each MCi unit randomly determines, or determines based on its unique identifier, a time slot number and responds to the initialization message FR1 with a CFR_J reply message containing, for example, its unique identifier during the corresponding time slot. In response, the BMU sends an allocation message containing the received MCi unit identifiers associated with a time slot number. If two MCi units have thus allocated themselves the same time slot, a collision occurs. In this case, the CFR_J messages sent by these two MCi units are not correctly received by the BMU, which detects, for example, a CRC error. If the BMU has not received a CFR_J message from each of the MCi units (considering the number of cells in the battery), the BMU retransmits the initialization message.Only MCi units that have not received a time slot number associated with their identifier respond during a new time slot determined randomly or from their identifiers.

[0072] This procedure can be performed branch by branch for all RMj branches of the BT battery, by controlling the SW1j switches so that only one branch is connected, so that only the MCi units of the connected branch receive and respond to the initialization message.

[0073] Each time an MCi unit has to transmit a CFR_J message (step S6), the TMP timing applied in step S4 corresponds to the duration of a time slot times J-1, from the moment of receipt of the FR1 message in step S3.

[0074] In one embodiment, the BM11 unit periodically sends a cell status request message (FR1) (step S2), and the MCi units respond with a CFR message containing a cell status (OK or KO), and optionally the unique identifier of the MCi unit or part of that identifier. Thus, the size of the exchanged messages is reduced to the bare minimum to provide a status for each battery cell, while also limiting the power consumption associated with these exchanges. Upon receiving the CFR_J messages sent by the MCi units in step S6, the BM11 unit determines whether all MCi units connected to it have responded and whether the responses indicate a cell failure. If no failure is detected and all MCi units have responded, the FR2 message sent by the BMU in step S9 terminates the communication.The MCi units can then enter an inactive state to minimize their power consumption. Otherwise, the FR2 message contains a request for measurement data to enable the BMU to determine the cause of the failure. In response (step S3), the MCi units send a CFR message containing a voltage measurement and / or a temperature measurement, and / or possibly a pressure measurement. Upon receiving all the measurement data transmitted by the MCi units, in step S7, the BMU can analyze this data (calculating averages, minimum / maximum voltage and temperature values, etc.) and send back, in step S9, an FR2 frame containing the calculated minimum and maximum values. Depending on the detected failure, the BMU can then decide to disconnect the RMj branch to which the faulty cell belongs using the corresponding SW1j switch.

[0075] According to one embodiment, each message FR1, FR2, CFR_J contains a header block, a termination block, and optionally a data block. The termination block may include a Cyclic Redundancy Check (CRC) code or a checksum to determine if the message was transmitted correctly. The message may also include transmission error correction codes. From the data transmitted by the MCi measuring units, the UC1 processing unit can perform various control operations. For example, the UC1 processing unit can calculate the internal resistance of each cell CLi, based on voltage measurements across the cell's terminals CTH and CTL, and the current measured in the RMj branch to which the cell is connected (for example, using the current sensor R3), such as during charging when the charging current is perfectly stabilized and controlled.The internal resistance of each CLi cell can be determined by dividing the difference in voltages measured across the cell, with and without current flowing in the branch to which the CLi cell belongs, by a measurement of that current. These two voltage measurements across the cell can be transmitted from the MCi measuring unit to the BMU.

[0076] In another embodiment, the BMU can transmit to each MCi measuring unit the current value measured in the branch where it is located, and each MCi can calculate and store the internal resistance of its associated CLi cell using the received branch current value and the voltage values ​​measured at the CTH and CTL terminals of the associated CLi cell, both in the presence and absence of current in the branch to which the CLi cell belongs. Knowing the internal resistance of each CLi cell and its evolution over time provides fundamental information regarding its state of health (SOH). Indeed, an abnormal drift in a cell's internal resistance indicates premature aging or a manufacturing defect.

[0077] Knowing the internal resistance of each Li-ion cell, combined with cell temperature measurements, can also optimize charging, either by adjusting the voltage and / or current delivered by the charger, or by limiting the charging time. This limits cell heating and maximizes energy recovery within an optimal timeframe. Using a "smart" charger that communicates with the BMU (Battery Management Unit) can facilitate this optimization.

[0078] Furthermore, the battery topology—that is, knowledge of the battery assembly configuration: the number of cells in series in each branch and the number of branches in parallel—is a determining parameter and impacts the communication method, particularly the data transmission rate between the MCi units and the BMU management unit. In one embodiment, this information is configurable and stored in the BMU management unit's memory for use by the UC1 processing unit. Additionally, the frequency of FR1 messages transmitted by the BMU can be adjusted according to the battery's operating regime. Thus, in a "power" operating regime where higher BT battery charge and / or discharge rates are required, it may be necessary to transmit the maximum and minimum voltage commands from the BM1 unit and the measurements taken by the MCi units more frequently.Conversely, in an "energy" operating regime, in which charge and / or discharge rates are slow, the frequency of FR1 message transmission does not need to be high.

[0079] In one embodiment, each MCi measuring unit maintains an event log stored in a secure, immutable memory area. To this end, each MCi unit can be configured to acquire, for example periodically, measurements from sensors, perform calculations of operating parameters of the associated CLi cell based on the acquired measurements, such as the internal resistance of the CLi cell, and store these parameters in the secure memory area. These parameters may include, in particular, the number of cycles of the CLi cell, its operating time since commissioning, its internal resistance, its remaining capacitance, its remaining energy, the number of high and low voltage overshoots, and the number of high temperature threshold overshoots.

[0080] Each MCi measuring unit can also store in the secure memory area information about the CLi cell to which it is associated, such as its electrochemical system, the nature and origin of its active materials, the name of its manufacturer, the place and date of its manufacture, its manufacturing batch number, its nominal capacity, its life in number of cycles, its maximum, minimum and nominal operating and safety voltages, its maximum discharge current, its minimum and maximum temperatures in charge and discharge, and the battery assembly architecture (number of branches and number of cells per branch).

[0081] Figure 7 shows circuits of a measurement unit MC', which can be any of the measurement units MCi, according to one embodiment. The MC' differs from the measurement unit MC in that it includes an output terminal TO connected to the output OTx of the communication circuit TRC, a data input terminal DTx for data to be transmitted by the TRC circuit, and a data output terminal DRx for data received by the TRC circuit. The DTx and DRx terminals are connected to the processing unit UC. The processing unit UC is configured to operate in a mode where the Rx signal data received from the TRC circuit is decoded and transmitted to the DRx terminal, and the data received by the DTx terminal is encoded and transmitted to the Tx terminal of the TRC circuit. Figure 8 shows circuits of a BT battery management and monitoring unit BMU', which can replace the BMU, according to one embodiment.The BMU' unit differs from the BMU unit in that the TRC1 communication circuit is replaced by the MC' measurement unit. The TO output of the MC' unit is connected to the AP amplifier input, the CTH terminal of the MC' unit is connected to the link between capacitor C2 and inductor L2, the CTL terminal of the MC' unit is connected to the BTL terminal, and the DTx and DRx terminals are connected to the UC1 processing unit.

[0082] The MC' unit exchanges transmit (TXS) and receive (RXS) data with the UC1 processing unit. The TXS signals and those from the Rx terminal are transformed by the MC' unit's UC processing unit. Signal transformation processes can include, for example, encryption / decryption to ensure that the data transmitted between the BMU' and the battery's MCi units is encrypted, thus preserving the confidentiality of the exchanged data.

[0083] In this way, communication between the BMU' control unit and the MCi measuring units is ensured exclusively between two MC' measuring units. Thus, the communication protocol between the MCi units and the BMU' control unit is implemented solely within the MC' units. Communications can therefore be encrypted without having to provide the secret data necessary for encryption, stored by the MC' units, to the BMU' manufacturer or the integrator assembling the batteries. Furthermore, these communications take place exclusively between a TXT transmit circuit and an RXT receive circuit of an MC' unit, which are specifically matched, particularly in terms of filtering. As a result, these communications are carried out optimally.

[0084] It will be readily apparent to those skilled in the art that the present invention is susceptible to various embodiments and applications. In particular, the invention is not limited to the message exchange described above. Indeed, in one embodiment, the BMU management unit may address the MCi measurement units individually by transmitting request messages containing a unique identifier of the recipient measurement unit, the MCi units being configured to send a reply message only when they detect their identifier in the request message.

[0085] Other circuits can be used to apply voltage drops across the terminals of a battery cell or battery. For example, transistor T1 and dissipative component R1 in MCi units can be replaced by a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The same applies to transistor T2 in the BMU. Dissipative components R1 and R2 can also be omitted if the MOSFET is gate-voltage controlled in linear mode. To perform cell balancing, the transistor can be controlled to divert current, for example, for a predefined fixed duration. Battery cell balancing can thus be carried out in successive stages.

Claims

DEMANDS 1. A method for communication within a battery (BT) comprising a plurality of cells, between a management unit (BM11) connected to terminals (PTH1, PTH2, PTL) of the battery and measurement units (MC1), the battery comprising several branches (RM1-RMp) in parallel connected respectively to branch terminals (BTH1-BTHp, BTL) and each comprising a plurality of cells (CL1) connected in series, each cell being associated with a measurement unit (MC1) connected between two connection terminals (CTH, CTL) of the cell, the method comprising steps consisting of: transmitting a request message (FR1) by the management unit in a modulated form by applying pulse bursts in the form of voltage drops between the branch terminals; receiving the request message by each of the measurement units, by demodulating the pulse bursts between the terminals of the cell to which the measurement unit is connected;to emit by each measuring unit in response to the request message, a response message (CFR_J) in a modulated form by applying pulse bursts in the form of voltage drops between the terminals of the cell to which the measuring unit is connected, during a respective time slot allocated to the measuring unit, the response message containing data from a measurement of an operating parameter of the cell; and to receive the response message by the management unit, by demodulating the pulse bursts detected on the battery terminals.

2. Method according to claim 1, comprising steps of: measuring a cell voltage (CLi), by the measuring unit (MCi) connected to the terminals (CTH, CTL) of the cell, and deriving current at the cell terminals by the measuring unit for a balancing time which can be fixed, when the measured voltage is greater than a setpoint value, in order to balance the cell with the other cells of the battery.

3. Method according to any one of claims 1 and 2, wherein the voltage drops or current shunting are carried out by each of the measuring units (MCi), by controlling a transistor (T1) connected to the terminals (CTH, CTL) of each cell (CLi).

4. Method according to any one of claims 1 to 3, wherein the voltage drops are applied by the control unit (BM11) by controlling a transistor (T2) connected to the branch terminals (BTH1-BTHp, BTL).

5. A method according to any one of claims 1 to 4, wherein the voltage drops generated by each of the measurement units (MCi) to emit a response message have an amplitude of a few tens of millivolts.

6. A method according to any one of claims 1 to 5, wherein the measurement units (MCi) are synchronized to a detection instant of a first voltage drop upon receipt of a request message.

7. A method according to any one of claims 1 to 6, further comprising steps of: detecting by the management unit (BM11) that one of the cells (CL1) of the battery is faulty on the basis of a failure to receive the response message (CFR_J) from the cell measuring unit, or on the basis of a cell operating parameter measurement data received in the response message from the cell measuring unit, and if a cell fault is detected, controlling a switch (SW11-SW1p) to disconnect a branch (RM1, RM2) of series-connected cells, to which the faulty cell belongs.

8. A method according to any one of claims 1 to 7, wherein several cell operating parameters (CLi) are measured or calculated, and transmitted by each measuring unit (MCi), the cell operating parameters comprising at least one of the following parameters: a voltage across the cell, a cell temperature, a current through the cell, an internal resistance of the cell, and a pressure in the cell.

9. A method according to any one of claims 1 to 8, wherein operating parameters of each cell (CLi) are acquired and stored at regular or non-regular intervals in an event log stored in a secure memory area of ​​the measuring unit (MCi) associated with the cell.

10. Battery comprising: a plurality of branches (RM1-RMp) connected in parallel, respectively connected to branch terminals (BTH1-BTHp, BTL), each branch comprising a plurality of cells (CLi) connected in series, a battery management unit (BMll) connected to battery terminals (PTH1, PTH2, PTL) and to branch terminals (BTH1-BTHp, BTL), and measuring units (MCi), each cell being associated with one of the measuring units connected between two connection terminals (CTH, CTL) of the cell, the management unit and the measuring units being configured to implement the communication method according to any one of claims 1 to 9.

11. Battery according to claim 10, wherein the management unit (BMU) or each of the measuring units (MCi) comprises a transistor (T2, T1) connected to the branch terminals (BTH1-BTHp, BTL), and respectively to the terminals (CTH, CTL) of each cell (CLi), the transistor being controlled to apply voltage drops or derive current.

12. Battery according to claim 10 or 11, wherein the battery management unit (BMU) includes a power switch (SW11-SW1p) per branch (RM1-RMp) to disconnect one of the branches when a cell in the branch is detected as faulty.

13. Battery according to any one of claims 10 to 12, wherein each measuring unit (MCi) comprises a wake-up circuit (WU) configured to detect a wake-up voltage drop between the cell terminals (CTH, CTL), and activate a processing unit (UC) of the measuring unit upon detection of the voltage drop, the management unit (BMU) being configured to generate the wake-up voltage drop.

14. Battery according to any one of claims 10 to 13, wherein each unit of measurement (MCi) is realized in the form of a miniaturized integrated electronic component embedded in one of the cells (CLi) of the battery (BT).

15. Battery according to claim 14, wherein the management unit (BMU) integrates a measuring unit (MC') to communicate with the measuring units (MC') associated with the cells (CLi) of the battery (BT).

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