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

Abstract

The invention relates to a communication method in a battery (BT) comprising a plurality of cells (CLi), between a battery 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 battery cells. The method comprises the steps of: sending a request (FR1) by the management unit by applying voltage drops across the battery terminals; receiving the request by each of the measurement units, by demodulating voltage drops detected across the terminals of the associated cell; sending a response (CFR_J) by each measurement unit, by applying voltage drops across the cell terminals; and receiving the response by the management unit, by demodulating the voltage drops detected across the battery terminals. Figure 1

Description

Title of the invention: Method for communication between internal monitoring circuits of a battery, and a battery implementing the method. Technical field

[0001] 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.

[0002] The present invention applies in particular 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. State of the art

[0003] Electrical energy storage batteries are configured to be connected to a charging circuit to be charged and store electrical energy, and to discharge by producing an electric current when connected to an electrical load. The battery cells are connected in series and / or parallel within the battery to achieve a required voltage and energy level. Typically, a battery with cells, for example, lithium-ion cells, comprises several identical blocks of individual cells, each block comprising one or more cells in series to achieve the desired total battery voltage. Several 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, which itself depends on the energy capacity of each of the identical individual cells assembled in series in each of the blocks.

[0004] Certain batteries, particularly those of the types listed above, can cause an explosion, combustion, and / or violent outgassing. In order to guarantee both the lifespan and operational safety of the batteries, 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. The functional parameters to be monitored may relate to the battery as a whole, or preferably to each group of cells within the battery, or even to each individual cell of the battery. These parameters may include, in particular, temperature parameters. and pressure, minimum discharge voltages, and maximum charge voltages. It is also desirable to be able to control the electrical balance 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 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).

[0005] Generally, controlling the cells of a battery requires a multitude of wires and / or wired 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, particularly when the number of interconnected cells is large, as in the case of batteries intended for mobility applications with voltages exceeding 350 volts, i.e., 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 is true for 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.

[0006] This interconnection complexity is particularly apparent in vehicles where the battery may consist of several blocks distributed in different locations within the vehicle. This interconnection 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 cell. However, this solution requires taking certain precautions. Significant safety margins are maintained on the detection thresholds to guarantee the required safety of battery operation. 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.

[0007] 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 with each cell a measuring device integrating 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. It is also desirable to be able to maintain the battery's functionality as much as possible in the event of cell failure. Summary

[0008] Embodiments relate to a communication method within a battery comprising a plurality of cells, between a management unit connected to terminals of the battery and measuring 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 measuring units connected between two connection terminals of the cell, the method comprising steps consisting of: transmitting a request message by the management unit in a modulated form by applying bursts of pulses in the form of voltage drops between the branch terminals; receiving the request message by each of the measuring units, by demodulating the bursts of pulses between the terminals of the cell to which the measuring unit is connected;to emit by each measuring unit, in response to the request message, a response message 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.

[0009] Thanks to these arrangements, 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 the battery cells. Indeed, the transmission of messages via bursts of voltage drops is not attenuated, as these are immediately visible whether emitted by the control unit or by one of the measuring units. Furthermore, this transmission technique is all the more efficient because the messages emitted by the control unit are received simultaneously by all the measuring units. Therefore, it is not necessary for the control unit to address each measuring unit individually. This transmission technique is thus particularly well-suited to batteries with a large number of cells. Moreover, 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 at the same time.

[0010] According to one embodiment, the method 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.

[0011] 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.

[0012] According to one embodiment, the voltage drops or current diversion are carried out by each of the measuring units, by controlling a transistor connected to the terminals of each cell.

[0013] According to one embodiment, the voltage drops are applied by the management unit by controlling a transistor connected to the branch terminals.

[0014] Thus, voltage drops can be applied using a very simple circuit that can easily be miniaturized. Furthermore, the magnitude of the voltage drops can be finely adjusted.

[0015] According to one embodiment, the voltage drops generated by each of the measurement units to emit a response message have an amplitude of a few tens of millivolts.

[0016] 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.

[0017] Thus, the measurement units can easily be synchronized, in particular to avoid collisions when communicating with the management unit.

[0018] According to one embodiment, the method further comprises steps consisting of: detecting by the management unit that one of the battery cells is faulty based on the absence of a response message from the cell's measurement unit, or based on a measurement of an operating parameter. cell received in the response message of the cell measurement unit, and if a cell failure is detected, command a switch to disconnect a branch of series-connected cells, to which the faulty cell belongs.

[0019] 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 cell failure, without affecting the voltage supplied by the battery.

[0020] According to one embodiment, several cell operating parameters are measured or calculated, and transmitted by each measuring unit, the cell operating parameters comprising at least one of the following parameters: a voltage across the cell terminals, a cell temperature, a current through the cell, an internal resistance of the cell, and a pressure in the cell.

[0021] Thus, several parameters representative of the proper functioning of a battery cell can be measured for each battery cell.

[0022] According to one embodiment, operating parameters of each cell are acquired and stored at regular or non-regular intervals in an event log stored in a secure memory area of ​​the measurement unit associated with the cell.

[0023] 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.

[0024] According to one embodiment, the control unit or each of the measuring units comprises 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.

[0025] 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.

[0026] 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 activate a measuring unit processing unit upon detection of the voltage drop, the management unit being configured to generate the wake-up voltage drop.

[0027] According to one embodiment, each unit of measurement is made in the form of a miniaturized integrated electronic component embedded in one of the battery cells.

[0028] According to one embodiment, the management unit incorporates a measuring unit for communicating with the measuring units associated with the battery cells. Brief description of the figures

[0029] 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 signs correspond to structurally and / or functionally identical or similar elements.

[0030] [Fig. 1] Figure 1 schematically represents a battery comprising a plurality of cells, according to one embodiment,

[0031] [Fig.2] Figure 2 schematically represents circuits of a measuring unit that can be associated with each of the battery cells, according to one embodiment,

[0032] [Fig.3] Figure 3 schematically represents the circuits of a battery management unit, according to one embodiment,

[0033] [Fig.4] Figure 4 schematically represents the transmission circuits of the measuring unit and the control unit, according to one embodiment,

[0034] [Fig. 5] Figure 5 schematically represents steps in a communication method between a measuring unit associated with a battery cell and the battery management unit, according to one embodiment,

[0035] [Fig. 6] 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,

[0036] [Fig.7] Figure 7 schematically represents circuits of a measuring unit that can be associated with each of the battery cells, according to another embodiment,

[0037] [Fig.8] Figure 8 schematically represents circuits of a battery management unit, according to another embodiment. Detailed description

[0038] Figure 1 shows 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 cells (i=l, ..., n) can belong to a Electrochemical cells, such as supercapacitors or rechargeable batteries, are generally composed of two electrodes, a separator between them, and an electrolyte. Various types of cells exist within the rechargeable battery category, including lithium-ion, nickel-cobalt aluminum-graphite, nickel-manganese-cobalt-graphite, nickel-cobalt aluminum-silicon, nickel-manganese-cobalt-silicon, lithium-cobalt oxide-graphite, lithium-iron-phosphate-graphite, lithium-sulfur, lithium-silicon sulfide, sodium-ion, and others.

[0039] The CL1-CLn cells are connected in series to form an RMI branch connected between terminals BTH1 and BTL of a BMU (Battery Management Unit), which is connected to terminals PTH and PTL 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 RMI, RM2, ..., RMp branches connected in parallel between a negative terminal BTL and the respective positive terminals BTH1, BTH2, ..., BTHp of the BMU.

[0040] According to 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 management unit. Each MCi measuring unit is configured to acquire operating parameter values ​​of the cell and to transmit them to the BMU management unit. The communication circuits of the MCi measuring units are configured to use the links between the CLi cells and the BMU management unit to communicate with the latter.

[0041] Figure 2 shows circuits of a measuring unit MC, which can be any of the measuring 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 measuring unit MC between the negative terminal CTL and the positive terminal CTH of the associated cell CLI.

[0042] The processing unit UC includes an analog-to-digital converter CVN comprising 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 associated for measuring the cell voltage Vc. The processing unit UC is thus configured to receive measurements of temperature, pressure, and The voltage (Vc) and current (if applicable) are used to compare these measurements to threshold values ​​and transmit these measurements, or the results of these comparisons, via the communication circuit (TRC). The processing unit (PU) may include a microcontroller comprising the CVN converter and volatile and non-volatile MEM memories for storing, among other things, software executed by the processing unit. The power supply circuit (ALM) provides a supply voltage (SV) to the processing unit (PU) and the DC switching circuit. The generator (VRG) is configured to generate a very stable voltage, independent of ambient temperature. Therefore, the reference voltage generated by the generator (VRG) can be used by the processing unit (PU) as a reference voltage, particularly for achieving accurate operation of the CVN converter.

[0043] The TRC communication circuit includes a Tx input for data to be transmitted and an Rx output for received data, connected to the processing unit UC. The TRC communication circuit also includes an OTx output for the signal to be transmitted and an IRx input for the received signal. Furthermore, the TRC circuit can be powered by supply terminals VI and VG connected respectively to the output of the ALM power supply circuit and to the CTL terminal. The OTx output of the TRC circuit controls a switch Tl connecting the negative terminal CTL of the CLi cell to a dissipative component RI, such as a resistor. The RI component is connected to the positive terminal CTH of the CLi cell.The switch Tl can be a bipolar transistor, for example of type npn (or pnp), whose base is connected to the output OTx of the TRC circuit, the emitter is connected to the negative terminal CTL and the collector is connected to the dissipative component RL. The input IRx of the TRC circuit is connected to the positive terminal CTH of the associated cell CLi via a capacitor CL. The capacitor Cl allows the DC component to be eliminated and thus the transmission signal of the voltage to the terminals CTH, CTL of the cell to be extracted.

[0044] 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 UC. 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 includes an additional switch connecting the positive terminal CTH of the CLi cell to an input of the CVN converter.

[0045] The MC unit may also include a wake-up circuit WU configured to detect a wake-up signal on the CTH terminal and, when it detects the wake-up signal, activate the processing unit UC by sending it a signal on an input provided at This effect is achieved by the processing unit (CU) which can be configured to control the DC switching circuit when it enters the active state, selectively powering on the temperature sensor (TS), the generator (VRG), and the communication circuit (TRC). Conversely, the processing unit can be configured to enter an inactive state when the measurement unit (MC) is not being used by the BMU. In this case, the processing unit is configured to control the DC switching circuit before entering the inactive state, thus de-energizing the various sensors (TS, PS), the generator (VRG), and the communication circuit (TRC).

[0046] Thanks to these arrangements, the various sensors TS, PS, the generator VRG and the communication circuit TRC can be powered and the cell voltage Vc can be supplied to the CVN converter, only when necessary.

[0047] The MC unit may 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. The 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 executed by the processing unit (CU), 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 the Tl switch to the CTL terminal. Furthermore, the BMU management unit can be configured to trigger an interruption of the charging or discharging process or a BT battery safety shutdown if there is no response from one of the MCi measuring units connected to the BMU management unit.

[0048] 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 for subsequent transmission to the MCi measuring units and processing 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, adapted to the battery architecture, and transmitted to and stored in the memory of each UC for processing. Lastly, by avoiding exceeding these voltage thresholds, the structure of the active materials in the CLi cell degrades less rapidly, which increases the lifespan of the CLi cell and therefore the battery.

[0049] According to 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. Thus, the MC unit can be easily 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 therefore be placed as close as possible to the cell's electrochemical core, thereby providing more precise measurements. The IM current sensor can also be, for example, a Hall effect sensor connected to a link between the CTL and CTH terminals.

[0050] Figure 3 shows circuits of the BT battery management and monitoring 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 RMI, RM2, ... RMp, and the positive terminals BTH1, BTH2, ... BTHp of the BMU connected respectively to the positive terminals of the branches. The BMU may also include a wake-up circuit WU1 performing a wake-up function for the MCi units present in the BT battery and connected to the BMU, two positive terminals PTH1, PTH2, and a negative terminal PTL forming the terminals of the BT battery, the positive terminals being intended to be connected respectively to an LD load and a CHC charging circuit, 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 branches RMj.

[0051] Each of the BTHj terminals is connected to a junction point EP at the battery voltage Vbt via a power switch SW11, ..., SWlp and a capacitor Cil, ..., Clp connected in parallel with it. Each SWlj switch (j = 1, ..., p) allows the corresponding RMj branch to be disconnected, in particular when one of the cells CLi of the branch is detected as faulty or when communication with a measuring unit MCi of the branch is no longer ensured. In addition, the SWIj power switches are each connected in parallel with a respective capacitor Clj (Cil, ..., Clp). The capacitors Clj allow communication with the measuring units MCi of the corresponding RMj branch to be maintained when the corresponding SWlj switch is open. The capacitance of the capacitors Clj is adjusted so as not to disturb (attenuate, distort) the transmissions. SWlj switches are made for example by MOSFETs ("Metal-Oxide-Semiconductor Field-Effect Transistor").

[0052] Furthermore, the junction point EP is connected to each of the terminals PTH1, PTH2 via an inductor L1 and a respective power switch SW3, SW4. The switches SW3, SW4 are controlled by the processing unit UC1, with only one of the switches being in the closed state depending on whether the charging or discharging operation is in progress. The inductor L1 provides a filtering function. The junction point EP is also connected to the negative terminal BTL via a dissipative component R2 and a switch T2.

[0053] 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 ALM1 power supply circuit, a receive input IRx connected to the junction point EP via a capacitor C2 and to the VI input 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, comprising a gate connected to the OTx output, 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 AP amplifier amplifies the control voltage supplied by the SLC circuit to provide 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.

[0054] The processing unit UC1 includes an analog-to-digital converter CVN1 comprising several inputs receiving voltages Vhl, ..., Vhp respectively taken 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 on 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 SWlj switches, each of which is in the closed state as long as a CLi cell belonging to the corresponding RMj branch is not detected as faulty. The SWIj switches can also be opened during periods of battery storage or transport, in particular to increase the safety. The R3 current sensor can also be a Hall effect sensor placed on a link between the BTL and PTL terminals.

[0055] 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 LL. The processing unit UC1 is configured to control the closing of the power switch in the WU1 circuit for a short time so as to generate a brief 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 WU of each of the measuring units MCi associated with these cells, thus "waking up" the measuring units MCi and synchronizing them.

[0056] Figure 4 shows the communication circuit TRC, TRC1 of the measuring unit MC and the unit BMU, according to one embodiment. The circuit TRC, TRC1 comprises a transmit stage TXT and a receive stage RXT. The transmit stage TXT comprises a signal mixing SMC circuit receiving 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 type filter Fl connected to the output of the SMC circuit, and a slope control SLC circuit connected to the output of the filter FL. The output of the SLC circuit 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 Fl filter 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 may have a rate of a few tens of kHz, while the CK clock signal may have a frequency of a few MHz. The TXS and RXS data signals are, for example, configured as frames conforming to the UART ("Universal Asynchronous Receiver Transmitter") protocol.

[0057] The voltage drops generated by the MCi measuring 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 in each branch. Thus, the voltage drops generated by the BMU management unit have an amplitude determined to be visible to all the MCi measuring units in the battery. To this end, the voltage drops generated by the BMU management unit can have an amplitude corresponding to at least the amplitude of the voltage drop applied by each measuring 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 the BMU unit from interference that may originate from an external circuit (CHC, LD) connected to the battery.

[0058] The RXT receiver stage includes a resistor R4 connected to capacitor C1, 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 amplifier VA, and a comparator CPI 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 terminals CTH, CTL of the associated cell CLi. The comparator CPI compares the envelope signal provided by the EVD circuit to a threshold voltage value Vrf in order 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, produced from the supply voltage SV provided by the ALM power supply circuit of the MC unit.The CPI comparator provides an RXS signal of received data to the processing unit UC, UC1. The F2 filter eliminates Fourier spectrum lines from the received signal and removes parasitic frequencies from the environment or load, retaining only the frequency band of the useful communication signal.

[0059] It turns out that the voltage drops generated by the control of transistor T1 of one of the MCi units of an RMj branch are visible at the EP junction point, but not by the other MCi units of the branch. On the other hand, the voltage drops generated by the control of transistor T2 of the BMU unit 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 does not undergo, by nature, no attenuation. Furthermore, the inductance L1 prevents voltage drops from being attenuated by the circuit connected to the battery.

[0060] This transmission method, which involves applying voltage drops to the cell power line, differs from the power line communication (PLC) technique, which consists of injecting an amplitude-modulated carrier signal onto the power line, with the cell terminals interconnected by a capacitor. Indeed, the modulated carrier signal injected in this way, in the form of a current modulation, undergoes significant attenuation that increases as it propagates. As a result, a signal transmitted by power line communication must be repeated at each cell in order to reach the signal's recipient. Consequently, a transmitted message is necessarily processed by several cell circuits.Such repetitions also lead to significant transmission delays, an increased risk of errors, and high energy consumption, which in the context of a battery affects 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.

[0061] According to one embodiment, each MCi measuring unit implements a balancing function for the associated cell 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. It is therefore not possible to utilize the battery's total capacity.

[0062] The balancing function consists of measuring the cell voltages during, for example, a battery charging operation, and based on these measurements, slowing down the charging of the fastest-charging cells (whose voltage changes most rapidly) by switching on a balancing resistor connected in parallel with the cell. In this way, a portion of the charging current is diverted away from the cell and therefore does not contribute to its recharging. The diverted portion of the charging current is adjusted so that, at the end of charging, all the cells have the most homogeneous measured voltages possible. For example, the balancing function may aim to achieve a voltage difference between the cells in The load is less than 1% at the end of charging. Thanks to the dissipative component RI coupled to the transistor Tl controlled by the processing unit UC, each measuring unit MCi can balance its associated cell CLi. Furthermore, the cell balancing function can be performed based on increasingly precise measurements the closer the measuring unit MCi can be positioned to the associated cell CLi.

[0063] The balancing function can consist of controlling the switching of transistor Tl for a fixed duration, for example 100 ms, or diverting a variable amount of current by acting on the control of transistor Tl, when the voltage Vc of the cell CLi measured by the UC unit is greater than a minimum setpoint voltage Vmin plus a delta value, depending on the difference between the minimum setpoint voltage and a maximum setpoint voltage. 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, knowing that in long-term storage, the more the battery is charged, the more dangerous it becomes and the more prematurely it ages.

[0064] Figure 5 illustrates steps SI to S10 of a data exchange process between the processing unit UC1 of the BMU and the processing unit UC of one of the MCi measuring units. In step SI, the BMU selects a type of FR message to transmit, for example, based on the current state of the battery (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.

[0065] In step S2, the BMU transmits an FRI message of the selected type. In step S3, the FRI message is received by all connected MCi units, substantially simultaneously. Each MCi unit receives the FRI message and determines its type. If the type of the received FRI message requires a response from the MCi unit, the latter triggers a TMP timer in step S4. This timer can depend on the type of the received FRI message and a time slot J allocated to it. At the end of the TMP timer, the MCi unit selects a message type to send in response to the FRI message, generates a CFR_J message 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. In step S7, the BMU receives the CFR_J message and determines its type. Step S7 ends when the BMU has received messages from all MCi units or when all the time slots allocated to MCi units to issue a reply message have expired.

[0066] The following steps S8 to S10 may be optional and depend on the type of CFR_J messages. In step S8, the BMU selects a message type to send in response to the CFR_J message. In step S9, the BMU 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 S4 to S6 if a response is required.

[0067] Figure 6 illustrates a message exchange between the BMU and the MCi units, according to one embodiment. Such a message exchange is initiated by the BMU sending an FRI message of a given type (step S2). The FRI message is received substantially simultaneously by all N MCi units connected to the BMU. The MCi units then send a CFR_J message in response (step S6) with a type corresponding to the type of the FRI 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 message requesting state data from the CLI cells. In Figure 6, the width of the blocks representing the CFR_J messages illustrates the width of the time slots.

[0068] In one embodiment, a time slot is assigned to each MCi unit connected to the BMU by means of an initialization-type FRI message. For example, the processing unit (PU) 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.

[0069] According to another example, each MCi unit randomly determines, or determines based on its unique identifier, a time slot number and responds to the initialization-type FRI message 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 the MCi units that have not received a CFR_J message are retransmitted. time slot number associated with their identifier respond during a new time slot determined randomly or from their identifiers.

[0070] This procedure can be carried out branch by branch for all the RMj branches of the BT battery, by controlling the SWlj 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.

[0071] 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 instant of receipt of the FRI message in step S3.

[0072] According to one embodiment, the BMU periodically sends a cell status request message (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 limiting the power consumption associated with these exchanges. Upon receiving the CFR_J messages sent by the MCi units in step S6, the BMU determines whether all MCi units connected to the BMU 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 SWlj switch.

[0073] According to an exemplary embodiment, each FRI, FR2, CFR_J message 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 whether the message was transmitted correctly. The message may also include transmission error correction codes.

[0074] Based on the data transmitted by the MCi measuring units, the UC1 processing unit can perform various control processes. For example, the unit The UC1 processing unit can calculate the internal resistance of each CLi cell from voltage measurements across the cell's terminals (CTH and CTL) and the current measured in the branch RMj to which the cell is connected (for example, using the current sensor R3). This calculation is performed, for instance, 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 terminals can be transmitted from the MCi measuring unit to the BMU.

[0075] According to 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 unit can calculate and store the internal resistance of the CLi cell to which it is associated 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 the internal resistance of a cell indicates premature aging or a manufacturing defect.

[0076] Knowledge of the internal resistance of each CLi cell, combined with cell temperature measurements, can also be used to optimize charging, either by adjusting the voltage and / or current delivered by the charger, or by limiting the charging time. This limits the heating of the battery cells and allows for maximum energy recovery within an optimal timeframe. The use of a so-called "smart" charger, which communicates with the BMU, can enable this optimization.

[0077] 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, are determining parameters and have an impact on the communication mode, and in particular on the data transmission rate between the MCi units and the BMU management unit. According to one embodiment, this information is configurable and stored in the BMU management unit's memory to be taken into account by the UC1 processing unit. Also, the frequency of the FRI messages sent by the BMU can be adapted to the battery's operating regime. Thus, in a "power" operating regime in which higher BT battery charge and / or discharge rates are required, it may be necessary to transmit the maximum and minimum voltage commands and measurements more frequently by the BMU. carried out by the MCi units. Conversely, in an "energy" operating regime, in which charge and / or discharge rates are slow, the frequency of FRI message transmission does not need to be high.

[0078] According to one embodiment, each MCi measuring unit maintains an event log stored in a secure, non-modifiable memory area. For this purpose, 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.

[0079] Each MCi measuring unit can also store in the secure memory area information on 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).

[0080] Figure 7 shows circuits of a unit of measurement MC' which can be any of the units of measurement MCi, according to one embodiment. The unit MC' differs from the unit of measurement MC in that it comprises an output terminal TO connected to the output OTx of the communication circuit TRC, a data input terminal DTx to be transmitted by the circuit TRC, and a data output terminal DRx received by the circuit TRC. The DTx and DRx terminals are connected to the processing unit UC. The processing unit UC is configured to exhibit an operating mode in which the data of the signal Rx received from the circuit TRC is decoded and transmitted on the DRx terminal, and the data received by the DTx terminal is encoded and transmitted on the Tx terminal of the circuit TRC.

[0081] Figure 8 shows the circuits of a BT battery management and monitoring unit (BMU'), which can replace the BMU, according to one embodiment. The BMU' differs from the BMU in that the communication circuit TRC1 is replaced by the measurement unit MC'. The TO output of the MC' unit is connected to the input of the amplifier AP, the CTH terminal of the MC' unit is connected to the connection 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 transmittable TXS and received RXS data with the processing unit UC1. The TXS signals and those from the Rx terminal are transformed by the processing unit UC of the MC' unit. Signal transformation processes may include, for example, encryption / decryption processes to ensure that the data transmitted between the BMU' unit and the battery's MCi units are encrypted, thereby 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 exclusively within the MC' units. Communication can therefore be encrypted without having to provide the secret data necessary for encryption, stored by the MC' units, to the manufacturer of the BMU' units or to the integrator assembling the batteries. Furthermore, this communication takes 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, this communication is carried out optimally.

[0084] It will be evident 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 measurement unit receiving the request message, 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 implemented to apply voltage drops across the terminals of a battery cell or battery. For example, transistor T1 and the dissipative component RI in MC1 units can be replaced by a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The same applies to transistor T2 in the BMU unit. The dissipative components RI 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. 1. A method of communication within a battery (BT) comprising a plurality of cells, between a management unit (BMU) connected to terminals (PTH1, PTH2, PTL) of the battery and measurement units (MCi), the battery comprising several branches (RMl-RMp) in parallel connected respectively to branch terminals (BTH1-BTHp, BTL) and each comprising a plurality of cells (CLi) connected in series, each cell being associated with one of the measurement units (MCi) connected between two connection terminals (CTH, CTL) of the cell, the method comprising steps of: transmitting a request message (FRI) 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. 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 may 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. 3. A method according to any one of claims 1 and 2, wherein the voltage drops or current diversion are achieved by each of the measurement units (MCi), by controlling a transistor (Tl) connected to the terminals (CTH, CTL) of each cell (CLi).

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

5. 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 reply message have an amplitude of a few tens of millivolts.

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

8. 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. 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 irregular intervals in a log of events stored in a secure memory area of ​​the measurement unit (MCi) associated with the cell.

10. 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 (BMU) connected to battery terminals (PTH1, PTH2, PTL) and to branch terminals (BTH1-BTHp, BTL), and measurement units (MCi), each cell being associated with one of the measurement units connected between two connection terminals (CTH, CTL) of the cell, the management unit and the measurement units being configured to implement the communication method according to any one of claims 1 to 9.

11. 11. Battery according to claim 10, wherein the management unit (BMU) or each of the measuring units (MCi) comprises a transistor (T2, Tl) connected to the branch terminals (BTHl-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. 12. Battery according to claim 10 or 11, wherein the battery management unit (BMU) includes a power switch (SW 11-SWlp) per branch (RMl-RMp) to disconnect one of the branches when a cell in the branch is detected as faulty.

13. 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 across 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. 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. 15. Battery according to claim 14, wherein the battery management unit (BMU) incorporates a measuring unit (MC') for communicating with the measurement units (MC') associated with the cells (CLi) of the battery (BT).

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