Device for estimating two states of charge of a battery, and associated system, aircraft and method

Abstract

The invention relates to a device (9) for estimating two states of charge (SOC1, SCO2) of a battery (8) comprising a plurality of cells (12) connected to one another, at least a fraction of the plurality of cells forming at least one set of cells (13, 14, 15) comprising at least two cells, the device comprising: first determining means (20) that are configured to determine a first state of charge (SOC1) of the battery from the voltage across the terminals of each cell (12) and the temperature in the vicinity of each cell, and the current flowing through the terminals of the plurality of cells. The device further comprises second determining means (21) configured to determine a second state of charge (SCO2) of the battery from at least one variable measured across the terminals of the set of cells.

Description

[0001] DESCRIPTION

[0002] TITLE: Device for estimating two states of charge of a battery, associated system, aircraft and method

[0003] Technical field of the invention

[0004] The invention relates to the estimation of battery charge states, and more particularly to devices for estimating two charge states of a battery.

[0005] The invention further relates to an electrical power supply system for an aircraft comprising such a device, an aircraft comprising such a system, and a method for redundantly estimating two states of charge of a battery.

[0006] State of the prior art

[0007] Generally, aircraft are powered by turbomachinery of the turboprop, turbojet or turbine type.

[0008] However, the use of turbomachines is accompanied by significant noise emissions and high consumption of fossil fuel, particularly kerosene, generating equally significant polluting emissions.

[0009] In order to reduce pollutant and noise emissions, aircraft propulsion can be electric or hybrid, replacing all or part of the turbomachines intended to produce the aircraft's thrust with electric motors.

[0010] The electric motors are powered by propulsion batteries.

[0011] In order to ensure the flight safety of an aircraft equipped with an electric or hybrid propulsion system, it is necessary to determine the state of charge (SOC) of each propulsion battery, defined as the ratio between the charge stored in the battery divided by the maximum charge admissible by the battery. The state of charge provides an indirect image of the energy available in the propulsion battery.

[0012] The charge available in the battery is determined from battery state estimators implementing algorithms from measurements such as measuring the temperature in the vicinity of the battery cells, the individual cell voltage and the current flowing in the battery.

[0013] Each cell is equipped with a voltage sensor measuring the voltage across its terminals.

[0014] The battery has temperature sensors placed near the cells to estimate the temperature of the cells, and is equipped with a current sensor measuring a current flowing at its terminals.

[0015] To simplify battery construction, the number of temperature sensors is usually less than the number of battery cells.

[0016] Since the battery state of charge (SOC) is a critical data, it is necessary to detect an erroneous SOC value.

[0017] It is known to determine two redundant SOC estimates by two independent estimators and to compare the SOC estimates delivered by the two estimators with each other. To perform the two estimators, it may be necessary to redundant the sensors and the state of charge estimators to detect an erroneous SOC value by comparing the SOC estimates delivered by the estimators with each other.

[0018] Furthermore, it is necessary to implement dissimilar technology estimators to overcome common mode failures.

[0019] However, the implementation in an aircraft of redundant sensors of dissimilar technology on each battery cell and the integration of charge estimators of dissimilar technology result in a duplication of voltage, temperature and current measurement sensors, electronic cards, calculation components and algorithms of the estimators, and communication buses connecting the measurement means to the estimators, complicating the production of the communication harnesses connecting said components, and the installation of the harnesses, the measurement sensors in the battery and the estimators in the aircraft. The document entitled “State-of-the-art of battery state-of-charge determination” published in December 2005 in the journal “Measurement Science and Technology” and the document US2022024438 disclose a battery state-of-charge estimator implementing a Kalman filter.

[0020] US 2022 / 024438 implements a Kalman filter comprising a battery pack model from measurements of battery pack temperature, current and voltage.

[0021] Document US 2022 / 024438 further discloses a measurement of the state of charge of a battery pack from temperature, current and voltage sensors of the battery pack, and Coulomb counting.

[0022] US 2015 / 0198671 discloses a system for monitoring and balancing cells of a battery. The system estimates the state of charge of a cell from variations in the voltage across the cell during charging or discharging of the cell. It further discloses using a sum of voltages to perform a consistency test of individual voltage measurements.

[0023] However, the monitoring system does not provide two redundant SOC estimates.

[0024] Statement of the invention

[0025] The aim of the invention is to overcome all or part of these drawbacks.

[0026] The subject of the invention is a method for estimating two states of charge of a battery comprising a plurality of cells connected together, the method comprising the determination of a first state of charge of the battery from the voltage at the terminals of each cell and at least one temperature in the vicinity of each cell, a current flowing at the terminals of the plurality of cells, and predetermined parametric tables, each parametric table linking a state of charge of a cell to the voltage at the terminals of said cell, to the temperature in the vicinity of said cell, and to the current at the terminals of the plurality of cells.

[0027] The method comprises determining a second state of charge of the battery from at least one quantity at the terminals of at least one set of cells of the battery, at least a fraction of the plurality of cells forming the set of cells comprising at least two cells.

[0028] The two estimates of the state of charge of the battery made from measurements taken on each cell, in the vicinity of each cell and on a set of cells, make it possible to obtain two estimates of the state of charge by two different measurement channels without redundant all of the sensors and acquisition and processing chains implemented by the two measurement channels, making it possible to simplify the production of the battery and the harnesses connecting the sensors to means of determining the states of charge.

[0029] Preferably, the battery comprises the set of cells forming a pack, the determination of the second state of charge comprises

[0030] - the determination of a first quantity comprising the voltage at the terminals of each pack and of a second quantity comprising the current at the terminals of said pack,

[0031] - the determination of the temperature of said pack, and

[0032] - determining the second state of charge of the battery from the voltage and current at the terminals of each pack, the temperature of each pack, and a predetermined parametric table linking a state of charge of each pack to the voltage and current at the terminals of each pack, and to the temperature of each pack.

[0033] Advantageously, the battery comprises at least two sets of cells, each set forming a module, the determination of the second state of charge comprises:

[0034] - the determination for each module of a first quantity comprising the voltage at the terminals of said module and of a second quantity comprising the current at the terminals of said module,

[0035] - determining the temperature of each module, and

[0036] - determining the second state of charge of the battery from the voltage and current at the terminals of each module, the temperature of each module, and at least one predetermined parametric table linking a state of charge of each module to the voltage and current at the terminals of said module, and to the temperature of said module. Preferably, the battery comprises the set of cells forming a pack, each pack comprising a fraction of the plurality of cells, determining the second state of charge comprises:

[0037] - the determination of the quantity comprising the current at the terminals of each pack,

[0038] - the determination of the quantity of instantaneous electricity passing through the terminals of each pack from the current at the terminals of said pack, and

[0039] - the determination of the second state of charge from the capacity of each pack and the quantity of instantaneous electricity passing through the terminals of each pack.

[0040] Advantageously, the set of battery cells comprises the plurality of battery cells, the determination of the second state of charge comprises:

[0041] - the determination of a first quantity comprising the voltage at the terminals of the battery and a second quantity comprising the battery current

[0042] - determination of the battery temperature, and

[0043] - determining the second state of charge from the voltage and current at the battery terminals, the battery temperature, and a predetermined chart linking the second state of charge to the voltage and current at the battery terminals, and to the battery temperature.

[0044] Preferably, the method further comprises a comparison of the first state of charge and the second state of charge, and wherein:

[0045] - if the difference in absolute value between the first state of charge and the second state of charge is less than a predetermined threshold, the method comprises the delivery of a signal indicative of the first state of charge,

[0046] - if the absolute value difference between the first state of charge and the second state of charge is greater than a predetermined threshold, the method includes the delivery of an alert signal.

[0047] Comparing the two states of charge determined by two different measurement channels makes it possible to detect and alert of the failure of one of the measurement channels. Also provided is a device for estimating two states of charge of a battery comprising a plurality of cells connected together, at least a fraction of the plurality of cells forming at least one set of cells comprising at least two cells, the device comprising:

[0048] - first determination means comprising predetermined parametric tables and configured to determine a first state of charge of the battery from the voltage at the terminals of each cell and the temperature in the vicinity of each cell, the current flowing at the terminals of the plurality of cells, and the parametric tables, each parametric table linking a state of charge of a cell to the voltage at the terminals of said cell, to the temperature of said cell, and to the current at the terminals of the plurality of cells.

[0049] The device further includes:

[0050] - second determination means configured to determine a second state of charge of the battery from at least one quantity measured at the terminals of the set of cells.

[0051] Preferably, the device further comprises means for comparing the first state of charge and the second state of charge configured to:

[0052] - deliver a signal indicative of the first state of charge if the difference in absolute value between the first state of charge and the second state of charge is less than a predetermined threshold; and

[0053] - deliver an alert signal if the absolute value difference between the first state of charge and the second state of charge is greater than a predetermined threshold.

[0054] There is also proposed an electrical power supply system for aircraft, comprising a battery comprising a plurality of cells connected together, each cell comprising a voltage sensor measuring the voltage at the terminals of said cell, the battery further comprising at least one temperature sensor measuring the temperature in the vicinity of the cells, and a current sensor measuring a current flowing at the terminals of the plurality of cells, the system further comprising measuring means for determining a quantity at the terminals of the set of cells, and a device as defined previously connected to the voltage, temperature and current sensors and to the measuring means.

[0055] Also provided is an aircraft comprising an electrical power system as defined above.

[0056] Brief description of the drawings

[0057] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0058] [Fig 1] schematically illustrates an aircraft according to the invention;

[0059] [Fig 2] schematically illustrates a first example of an electrical power supply system according to the invention;

[0060] [Fig 3] schematically illustrates a second example of an electrical power supply system according to the invention;

[0061] [Fig 4] schematically illustrates a third example of an electrical power supply system according to the invention; and

[0062] [Fig 5] schematically illustrates a fourth example of an electrical power supply system according to the invention.

[0063] Detailed description of at least one embodiment

[0064] We refer to figure 1 which schematically illustrates an aircraft 1 comprising a propulsion system 2.

[0065] The propulsion system 2 comprises two rotating electrical machines 3, 4 each arranged on either side of a longitudinal axis of the aircraft 1 and each provided with a propeller to propel the aircraft 1.

[0066] Alternatively, the aircraft 1 may comprise more than two rotating electrical machines 3, 4 arranged in equal numbers on either side of the longitudinal axis of the aircraft 1 or a single electrical machine arranged on the longitudinal axis of the aircraft 1.

[0067] According to yet another variant, the aircraft 1 may comprise a single rotating electrical machine. According to yet another variant, the aircraft 1 is of the hybrid type and comprises at least one rotating electrical machine and at least one turboprop or turbojet comprising a turbomachine.

[0068] The propulsion system 2 further comprises two identical electrical power conversion devices 5, 6 each supplying one of the rotating electrical machines 3, 4, and an electrical power supply system 7 supplying the conversion devices 5, 6.

[0069] Each conversion device 5, 6 comprises at least one power converter supplying a different rotating electrical machine 3, 4.

[0070] The power supply system 7 comprises a propulsion battery 8 supplying the conversion devices 5, 6, a redundant estimation device 9 of two charge states of the battery 8 connected to the battery 8, and an electrical energy distribution device 10 connected to the battery 8 and to the conversion devices 5, 6.

[0071] The battery 8 supplies the rotating electrical machines 3, 4 operating in motor mode via the conversion devices 5, 6 and the distribution device 10.

[0072] Alternatively, the rotating electrical machines 3, 4 operate in generator mode and charge the battery 8 via the conversion devices 5, 6 and the distribution device 10.

[0073] The estimation device 9 is incorporated in the battery 8.

[0074] Alternatively, the estimation device 9 is located outside the battery 8.

[0075] Alternatively, the power supply system 7 comprises at least two propulsion batteries, each battery being connected to an estimation device 9.

[0076] The estimation device 9 determines two states of charge of the battery 8.

[0077] The estimation device 9 is further connected to a data bus 11 of the aircraft 1.

[0078] Figure 2 schematically illustrates a first example of the power supply system 7. The battery 8 comprises a plurality of cells 12 storing electrical energy.

[0079] The cells 12 are connected together to form two modules 13, 14.

[0080] The modules 13, 14 are connected together to form a pack 15 connected to the distribution device 10.

[0081] The cells 12 are connected together in series or in parallel, and the modules 13, 14 are connected together in series or in parallel.

[0082] It is assumed that modules 13, 14 are connected in series.

[0083] Each module 13, 14 comprises the same number of cells 12 and at least one temperature sensor 17 measuring the temperature in the vicinity of the cells 12 so that the measured temperature is indicative of the temperature of the cells 12.

[0084] Each module 13, 14 may comprise several temperature sensors 17 distributed between the cells 12 so that the number of sensors 17 is less than the number of cells 12.

[0085] Two temperature sensors are for example separated by at least two cells 12 as shown in FIG. 2, each module 13, 14 comprising two temperature sensors 17.

[0086] Alternatively, two temperature sensors are separated by more than two cells 12, for example by ten cells.

[0087] When each module 13, 14 comprises several sensors 17, the temperature in the vicinity of a cell 12 is for example equal to the average of the temperatures recorded by the sensors 17 adjacent to said cell 12 or is for example equal to the temperature recorded by the sensor 17 adjacent closest to said cell 12 among all the sensors 17.

[0088] It is assumed in the following that the temperature in the vicinity of a cell 12 is equal to the temperature recorded by the sensor 17 adjacent to said cell 12 among all the sensors 17.

[0089] Of course, the battery 8 may comprise more than one pack 15, and each pack 15 may comprise more than two modules 13, 14.

[0090] Each cell 12 comprises a voltage sensor 16 measuring the voltage at its terminals. A first current sensor 18 measures the current flowing at the terminals of the battery 8.

[0091] The estimation device 9 comprises first storage means 19, for example a non-volatile memory, storing predetermined parametric tables TAB 1 , TAB 2 ... TAB n , n being an integer equal to the number of cells 12.

[0092] Each parametric table is associated with a different cell 12 and relates a state of charge of a cell 12 to the voltage across said cell 12, to the temperature in the vicinity of said cell 12, and to the current across the pack 15.

[0093] The parametric tables are determined for example from an equivalent electrical circuit of cell 12 making it possible to calculate the transfer function between the current and the voltage of cell 12 for a given state of charge and temperature.

[0094] The equivalent circuit is for example of the resistive or resistive and capacitive type.

[0095] Alternatively, cells 12 are identical so that the parametric tables are identical.

[0096] Furthermore, the first determination means 20 determine a first state of charge SOC 1 of the battery 8 from the voltage at the terminals of each cell 12 measured by the voltage sensor 16 associated with said cell 12, from the temperature in the vicinity of each cell 12 measured by the temperature sensors 17 associated with said cell 12, from the current flowing at the terminals of the pack 15 measured by the current sensor 18, and from the predetermined parametric tables TAB 1, ...TABn.

[0097] The first determination means 20 determine an intermediate state of charge of each cell 12 by identifying the value of the intermediate state of charge of said cell 12 associated by the parametric table TABn of said cell 12 with the voltage and temperature values ​​in the vicinity of said cell 12, and with the measured current value.

[0098] The first determination means 20 are produced for example from a first processing unit and comprise the storage means 19. The first determination means 20 determine the intermediate state of charge for each cell 12 and deduce the first state of charge SOC 1 for example by averaging all the intermediate states of charge or by retaining the largest value of the intermediate state of charge, or by retaining the smallest value of the intermediate state of charge.

[0099] The highest value of the intermediate state of charge is retained, for example, when charging the battery 8 to define the instant at which charging stops. When the highest value of the intermediate state of charge reaches a maximum charge value, charging of the battery 8 is stopped in order to prevent deterioration of the cell(s) 12 having reached the maximum charge value. The battery 8 is considered to be fully charged.

[0100] The smallest value of the intermediate state of charge is retained, for example, to determine when battery 8 is discharged.

[0101] When the smallest value of the intermediate state of charge reaches a maximum discharge value, the battery charge 8 is considered to be completely discharged.

[0102] The sensors 16, 17, 18, first storage means 19, the first determination means 20 form a first measurement channel.

[0103] The estimation device 9 further comprises measuring means for determining at least one quantity at the terminals of at least one set of cells, and second determining means 21 for determining a second state of charge SOC2 of the battery 8 from the quantity measured by the measuring means.

[0104] The cell assembly comprises at least a fraction of the plurality of cells 12, the number of cells 12 incorporated in the cell assembly being able to extend from two cells 12 to the plurality of cells 12 of the battery 8.

[0105] The second determining means 21 and the measuring means form a second measuring channel.

[0106] In this example, the set of cells comprises the plurality of cells 12 forming the pack 15 of the battery 8, and the measuring means comprise a second temperature sensor 22 measuring the temperature of the pack 15, a second current sensor 23 measuring the current flowing at the terminals of the pack 15, and a second voltage sensor 24 measuring the voltage at the terminals of the pack 15.

[0107] The second determination means 21 comprise second storage means 25 comprising for example a non-volatile memory and storing a predetermined parametric table TP I linking a state of charge of the pack 15 to the voltage measured by the second voltage sensor 24, to the current measured by the second current sensor 23 of each pack, and to the temperature measured by the second temperature sensor 22.

[0108] Since battery 8 comprises a single pack 15, the second state of charge SOC2 of battery 8 is equal to the state of charge of pack 15.

[0109] The parametric table TP I is for example determined from an equivalent electrical circuit of pack 15 allowing the calculation of the transfer function between the current and the voltage of pack 15 for a given state of charge and temperature.

[0110] The equivalent circuit is for example of the resistive or resistive and capacitive type.

[0111] The second determination means 21 further comprise means 26 for implementing the second storage means 25.

[0112] The implementation means 26 determine the value of the second state of charge SOC2 of the battery 8 by identifying the value of the state of charge associated by the parametric table TP I with the voltage and temperature values ​​measured by the second sensors 22, 24 and with the value of the current measured by the second current sensor 23.

[0113] The implementation means 26 comprise, for example, a second processing unit.

[0114] If the battery 8 comprises several packs, each pack comprises a second temperature sensor, a second current sensor if the packs are connected in parallel in order to measure the current flowing in said pack, and a second voltage sensor, the second determination means 21 determining an intermediate state of charge for each pack and adding the intermediate states of charge of the packs to determine the second state of charge SOC2 of the battery 8.

[0115] The first and second estimation means, the voltage sensors 16 and the second voltage sensor 24, the current sensor 18 and the second current sensor 23, and the temperature sensors 17 and the second temperature sensor 22 are of dissimilar technology to overcome common mode failures.

[0116] The estimation device 9 further comprises means 27 for comparing the first state of charge SOC 1 and the second state SOC2 delivering a signal indicative of the first state of charge SOC 1 if the difference in absolute value between the first state of charge SOC 1 and the second state of charge SOC2 is less than a predetermined threshold.

[0117] The predetermined threshold is determined so that the difference between the values ​​of the first state of charge SOC 1 and the second state of charge SOC2 is within an acceptable uncertainty range determined from the measurement uncertainty of the sensors, the dispersion of the cells 12, the temperature, and the precision of the signal acquisition and processing chain.

[0118] The indicative signal is transmitted by the comparison means 27 to the bus 11 so that the value of the first state of charge SOC 1 is used by other components of the aircraft 1, for example by a display located in the cockpit of the aircraft 1 to visually indicate to the pilots the state of charge of the battery 8.

[0119] The comparison means 27 comprise, for example, a third processing unit.

[0120] If the difference in absolute value between the first state of charge and the second state of charge is greater than a predetermined threshold, one of the determination means 20, 21 is considered to be faulty. The comparison means 27 deliver an alert signal on the bus 11.

[0121] The measures taken following receipt of the alert signal are, for example, conditioned by the architecture of the aircraft 1 and the operational safety strategy adopted.

[0122] Figure 3 schematically illustrates a second example of the power supply system 7. We find the battery 8 comprising the pack 15, and the estimation device 9 comprising the first estimation means 20, the first storage means 19, and the comparison means 27.

[0123] This example differs from the previous example illustrated in Figure 2 in that the battery 8 comprises two sets of cells, each set of cells being formed by a different module 13, 14, and the measuring means comprise, for each set of cells formed by a module 13, 14, a third temperature sensor 28, 29 measuring the temperature of said module 13, 14, a third voltage sensor 30, 31 measuring the voltage at the terminals of each set of cells, and a third current sensor 30 measuring the current flowing at the terminals of each set of cells.

[0124] As the modules 13, 14 are connected in series, the current flowing across the terminals of the modules 13, 14 is identical, a single third sensor 32 measures the current across the terminals of the second module 14.

[0125] Furthermore, the second determining means 21 differ from the second determining means 21 illustrated in FIG. 2 in that the second storage means 25 stores for each module

[0126] 13, 14, a predetermined parametric table TP2, TP3 linking a state of charge of each module 13, 14, to the voltage and current measured at the terminals of said module 13, 14, and to the temperature of said module 13,

[0127] 14.

[0128] Each parametric table TP2, TP3 is determined for example from an equivalent electrical circuit of each module 13, 14 making it possible to calculate the transfer function between the current and the voltage of each module 13, 14 for a given state of charge and temperature.

[0129] The equivalent circuit is for example of the resistive or resistive and capacitive type.

[0130] The implementation means 26 determine the state of charge of each module 13, 14 by identifying the value of the state of charge of each module 13, 14 associated by the parametric table TP2, TP3 with the voltage and temperature values ​​measured by the third sensors 28, 30 and 29, 32, and with the current value measured by the third current sensor 32. The implementation means 26 determine the value of the second state of charge SOC2 by adding the states of charge of the modules 13, 14.

[0131] The first and second estimation means 20, 21, the voltage sensors 16 and the third voltage sensors 30, 31, the current sensor 18 and the third current sensor 32, and the temperature sensors 17 and the third temperature sensors 28, 29 are of dissimilar technology to overcome common mode failures.

[0132] Figure 4 schematically illustrates a third example of the power supply system 7.

[0133] We find the battery 8 comprising the pack 15 and the estimation device 9 comprising the first estimation means 20, the first storage means 19, and the comparison means 27.

[0134] This example differs from the previous example illustrated in Figure 2 in that the measuring means comprise a fourth current sensor 33 measuring the current at the terminals of the pack 15 forming the set of cells.

[0135] Furthermore, the second determination means 21 differ from the second determination means 21 illustrated in FIG. 2 in that the second storage means 25 store the value of the total capacity Co of the pack 15, and the implementation means 26 determine the value of the second state of charge SOC2 by determining the instantaneous quantity of electricity passing through the terminals of the pack 15 from the measurements of the fourth current sensor 33 by adding or subtracting said quantity of electricity from the total capacity Co depending on whether the pack 15 delivers or receives electrical energy. The implementation means comprise, for example, a current sensor of the shunt or Hall effect type.

[0136] The first and second estimation means 20, 21, the current sensor 18 and the fourth current sensor 33 are of dissimilar technology to overcome common mode failures.

[0137] Figure 5 schematically illustrates a fourth example of the power supply system 7. We find the battery 8 comprising the pack 15 and the estimation device 9 comprising the first estimation means 20, the first storage means 19, and the comparison means 27.

[0138] This example differs from the previous example illustrated in Figure 2 in that the measuring means comprise a fifth current sensor 34 measuring the current at the terminals of the battery 8, a fifth voltage sensor 35 measuring the voltage at the terminals of the battery 8, and a fifth temperature sensor 36 measuring the temperature of the battery 8.

[0139] The set of cells 12 of the battery 8 forms the cell set.

[0140] Furthermore, the second determination means 21 differ from the second determination means 21 illustrated in FIG. 2 in that the second storage means 25 stores a predetermined chart ABQ linking the second state of charge SCO2 to the voltage and current flowing across the terminals of the battery 8 measured by the fifth sensors 34, 35, and to the temperature measured by the fifth temperature sensor 36.

[0141] The implementation means 26 determine the second state of charge SCO2 by identifying the value of the second state of charge SCO2 associated by the chart ABQ with the voltage and temperature values ​​measured by the fifth sensors 36, 35 and with the value of the current measured by the fifth current sensor 34.

[0142] The first and second estimation means 20, 21, the voltage sensors 16 and the fifth voltage sensor 35, the current sensor 18 and the fifth current sensor 34, and the temperature sensors 17 and the fifth temperature sensor 36 are of dissimilar technology to overcome common mode failures.

[0143] The estimation device 9 comprising two different measurement channels makes it possible to obtain two estimates of the state of charge without redundant all of the sensors implemented by the two measurement channels, making it possible to simplify the production of the battery and the harnesses connecting the sensors to the means for determining the states of charge of the measurement channels. These simplifications make it possible to reduce the size and mass of the system 7.

[0144] Furthermore, the installation in the first channel of sensors 16, 17, 18 and first determination means 20 and in the second measurement channel of sensors 22, 23, 24, 28, 29, 30, 31, 32, 33, 34, 35, 36 of technology dissimilar to that of the first measurement channel, and of second determination means 21 in the second measurement channel of technology dissimilar to that of the first measurement channel makes it possible to improve the operational safety of the system 7. The estimations of the state of charge SOC 1, SOC2 of the battery 8 and the comparison of the states of charge with each other make it possible to detect and alert of the failure of one of the determination means 20, 21 of the state of charge of the battery 8.

Claims

DEMANDS 1. A method for estimating two states of charge (SOC1, SOC2) of a battery (8) comprising a plurality of interconnected cells (12), the method comprising determining a first state of charge (SOC1) of the battery from the voltage across each cell and at least one temperature in the vicinity of each cell, a current flowing across the plurality of cells, and predetermined parametric tables (TAB1, TAB2, TABn), each parametric table relating a state of charge of a cell to the voltage across said cell, to the temperature in the vicinity of said cell, and to the current across the plurality of cells, characterized in that the method comprises determining a second state of charge (SOC2) of the battery from at least one quantity measured across at least one set of cells (13, 14, 15) of the battery,at least a fraction of the plurality of cells forming the cell group comprising at least two cells.

2. Method according to claim 1, the battery comprising the set of cells forming a pack (15), the determination of the second state of charge comprises: the determination of a first quantity comprising the voltage across each pack and a second quantity comprising the current across said pack, the determination of the temperature of said pack, and the determination of the second state of charge (SCO2) of the battery (8) from the voltage and current across each pack, the temperature of each pack, and a predetermined parametric table (TP1) relating a state of charge of each pack to the voltage and current across each pack, and to the temperature of each pack.

3. Method according to claim 1, the battery comprising at least two sets of cells, each set forming a module (13, 14), the determination of the second state of charge comprises: the determination for each module (13, 14) of a first quantity comprising the voltage across said module and a second quantity comprising the current across said module, the determination of the temperature of each module (13; 14), and the determination of the second state of charge of the battery from the voltage and current across each module, the temperature of each module, and at least one predetermined parametric table (TP2, TP3) relating a state of charge of each module to the voltage and current across said module, and to the temperature of said module.

4. Method according to claim 1, the battery comprising the set of cells forming a pack (15), each pack comprising a fraction of the plurality of cells, the determination of the second state of charge comprises: the determination of the quantity comprising the current at the terminals of each pack, the determination of the instantaneous quantity of electricity passing through the terminals of each pack from the current at the terminals of said pack, and the determination of the second state of charge from the capacity of each pack (Co) and the instantaneous quantity of electricity passing through the terminals of each pack.

5. A method according to claim 1, wherein the battery cell assembly (8) comprises the plurality of cells (12) of the battery, the determination of the second state of charge comprises: the determination of a first quantity comprising the voltage across the battery terminals and a second quantity comprising the battery current; the determination of the battery temperature; and the determination of the second state of charge from the voltage and current across the battery terminals, the battery temperature, and a predetermined nomogram (ABQ) relating the second state of charge to the voltage and the current at the battery terminals, and the battery temperature.

6. A method according to any one of the preceding claims, further comprising a comparison of the first state of charge (SOC 1) and the second state of charge (SOC2), and wherein: if the difference in absolute value between the first state of charge and the second state of charge is less than a predetermined threshold, the method comprises the delivery of an indicator signal of the first state of charge; if the difference in absolute value between the first state of charge and the second state of charge is greater than a predetermined threshold, the method comprises the delivery of an alert signal.

7. Device (9) for estimating two states of charge (SOC 1, SCO2) of a battery (8) comprising a plurality of interconnected cells (12), at least a fraction of the plurality of cells forming at least one set of cells (13, 14, 15) comprising at least two cells, the device comprising: first determination means (20) comprising predetermined parametric tables (TAB 1, TBA2, TABn) configured to determine a first state of charge (SOC 1) of the battery from the voltage across each cell (12) and the temperature in the vicinity of each cell, the current flowing across the plurality of cells, and parametric tables, each parametric table relating a state of charge of a cell to the voltage across said cell, to the temperature of said cell, and to the current across the plurality of cells,characterized in that the device further comprises second determination means (21) configured to determine a second state of charge (SCO2) of the battery from at least one quantity measured across the terminals of the cell assembly.

8. Device according to claim 7, further comprising means (27) for comparing the first state of charge (SOC 1) and the second state of charge (SOC 2) configured for: to deliver an indicator signal of the first state of charge if the difference in absolute value between the first state of charge and the second state of charge is less than a predetermined threshold; and to deliver an alert signal if the difference in absolute value between the first state of charge and the second state of charge is greater than a predetermined threshold.

9. Aircraft power supply system (7), comprising a battery (8) comprising a plurality of interconnected cells (12), each cell comprising a voltage sensor (16) measuring the voltage across said cell, the battery further comprising at least one temperature sensor (17) measuring the temperature in the vicinity of the cells, and a current sensor (18) measuring a current flowing across the terminals of the plurality of cells, the system further comprising measuring means (22, 23, 24, 28, 29, 30, 31, 32, 33, 34, 35) for determining a quantity across the terminals of the set of cells, and a device (9) according to any one of claims 7 and 8 connected to the voltage, temperature, current sensors and to the measuring means.

10. Aircraft (1) comprising a power supply system (7) according to claim 9.

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