Method for managing the available charge state of an electric battery

Abstract

One aspect of the invention relates to a method (100) for managing an available state of charge SOCDisp of an aircraft electric battery comprising steps of: Obtaining (110) a first intermediate available state of charge SOCDisp1 from a battery capacity table as a function of a battery temperature, Obtaining (120) a second intermediate available state of charge SOCDisp2 from a stored state of charge, a first instantaneous voltage, an instantaneous open circuit voltage, and a predetermined minimum admissible voltage, Measuring (130) a second instantaneous voltage Ucell at the terminals of the battery, and Determining (140) an available state of charge SOCDisp from the first intermediate available state of charge SOCDisp1, the second intermediate available state of charge SOCDisp2 and the second instantaneous voltage Ucell measured (130). Figure to be published with the abstract: Figure 3

Description

Title of the invention: Method for managing an available charge state of an electric battery TECHNICAL FIELD OF THE INVENTION

[0001] The technical field is that of the management of electric batteries, in particular batteries on board a vehicle, notably in an aircraft.

[0002] The present invention relates to a method for managing an available charge state of an electric battery and an associated system. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various States. In particular, an ambitious standard applies both to new types of aircraft and those currently in circulation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0004] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the factors impacting all phases of design and development, to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft. The Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible to reduce the environmental footprint of its activity.

[0005] This sustained research and development work covers new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and finally aeronautical biofuels.

[0006] In this context, the use and management of electric batteries within aircraft must be optimized. It is particularly essential to be able to manage the state of charge of an electric battery. The state of charge, sometimes called charge level and noted SOC for "State of Charge" in English, is a quantity representing the electrical charge stored in a battery at a given moment. The state of charge SOC, often expressed as a percentage of the total capacity of the battery, is generally equal to the ratio between, on the one hand, a charge stored in the battery at the moment in question, and, on the other hand, a maximum or nominal charge that can be stored in this battery, i.e.: stored charge divided by the total capacity (maximum or nominal charge) of the battery.

[0007] The most commonly used method for calculating the state of charge SOCstock is coulomb counting, which consists of integrating the current over time. This is applicable when the initial state of charge SOCstockj0 is known. The state of charge SOCstock at a time t is therefore expressed in ampere hours, denoted Ah, by:

[0008] ( i . [Eq. 1] SOCstock(t) - SOC^.^ + 3^5J0 / (t)dt

[0009] It is also possible to express the state of charge SOCstock as a percentage relative to a total reference capacity of the battery.

[0010] The state of charge SOCstock estimated by coulomb-metric counting provides information on the capacity stored in the battery. This information on the capacity stored in the battery is however insufficient because a part of this capacity can potentially be unavailable, especially at low temperature and / or high current. These variations in available capacity result from voltage variations; the voltage variations being a consequence of the variation in current or internal impedance, which varies according to the temperature of the battery, the current and the state of charge SOCstock. Indeed, when a discharging current flows through the battery, the voltage at the terminals of the battery decreases proportionally to the impedance of the battery and the current between its terminals.

[0011] [Fig. 1] shows the evolution of the voltage at the terminals of the battery during the time during a discharge at IC current at two different temperatures, 10°C and 25°C. The thick line curves are associated with the temperature 25°C while the thin line curves are associated with the temperature 10°C. The battery impedance increases as the temperature decreases, so the voltage drop caused during discharge is greater. Similarly, if the impedance is the same, the voltage drop will be higher for a higher current. It is important to note that the battery discharge stops when the lowest allowed voltage is reached. However, for the same stored state of charge SOCstoCk, this voltage is reached more quickly if the current is high or if the temperature is low. In these circumstances, the available state of charge SOCDisp is lower.

[0012] Thus, the stored state of charge SOCstoCk and the available state of charge SOCDisp must be differentiated when managing an electric battery. The available state of charge SOCDisp is theoretically a function of the stored state of charge SOCstoCk, the temperature T and the current I:

[0013] SOCDis„ = flSOC^ T, I) [Eq. 2]

[0014] A first problem to be solved therefore consists of determining the function between the available state of charge SOCDisp, the current and the temperature, or finding another way of taking into account the effects of the current and the temperature on the available state of charge SOCDisp.

[0015] As regards the temperature, it is possible to carry out a series of battery charge and discharge tests at a sufficiently low current, so as not to heat the battery during the test, to obtain the limit values ​​of charge stored in the battery. [Fig. 2] illustrates the available battery capacity as a function of temperature, and with respect to the charging or discharging operations. Zone 1 corresponds to the unavailable capacity in charge as a function of temperature. Zone 3 corresponds to the unavailable capacity in discharge as a function of temperature. Zone 2 corresponds to the available capacity in charge and discharge as a function of temperature. The curve delimiting zone 1 from zone 2 corresponds to the lower capacity limit of the battery and the curve delimiting zone 3 from zone 2 corresponds to the upper capacity limit of the battery. For example, at the end of discharge at a temperature of 0°C, approximately 0.24 Ah remain stored in the battery and are not available for discharge. We thus deduce that the available state of charge SOCDisp at 0°C is lower than the stored state of charge SOCstoCk at 0°C of 0.24 Ah. An example of such a method is for example disclosed in the French patent application FR3126812A1, the Applicant of which is Safran Electrical and Power SAS, entitled “Method for monitoring a charge level of a battery, and associated storage system”.

[0016] However, this approach cannot be adopted to study the dependence of the available capacity on the electric current, because high currents heat the battery and the measured capacity value cannot therefore be associated with a specific operating point.

[0017] To address this limitation, it is necessary to be able to take into account strong electric currents in determining the available state of charge SOCDisp.

[0018] In summary, the available state of charge SOCDisp in a battery is different from the stored state of charge SOCstoCk of the battery and depends on the temperature and the electric current. A first group of known methods makes it possible to determine the available state of charge SOCDisp in a battery at different temperatures and at low constant current. However, this cannot be done for high currents because they significantly increase the temperature of the battery, which prevents having a measurement of the available state of charge SOCDisp at a given temperature for different currents. However, the battery voltage is directly influenced by the temperature and the current. Moreover, the voltage is the main criterion for stopping a discharge. This information can therefore be used to find the available state of charge SOC from the stored SOC. The available state of charge SOCDisp in a battery could be determined by taking into account the effect of temperature and current, even for high currents, but such methods tend to underestimate the available state of charge SOCDisp of the battery when the latter is average or high.

[0019] There is therefore a need for a method for managing the available state of charge SOCDisp of a battery making it possible to solve, at least partially, the aforementioned problems of the prior art. Summary of the invention

[0020] The invention offers a solution to the problems mentioned above by proposing a method and system for managing an available charge state SOCDisp which is reliable, in particular by precisely determining the available charge state SOCDisp from three data: • a first intermediate state of charge SOCDispi obtained from a table of battery capacity as a function of temperature, • a second intermediate state of charge SOCDisp2 obtained from a stored state of charge, a first instantaneous voltage, an instantaneous open circuit voltage (OCV for Open Cell Voltage) and a minimum admissible voltage, and • a second instantaneous voltage.

[0021] A first aspect of the invention relates to a method for managing an available state of charge SOCDisp of an electric battery comprising computer-implemented steps of: • Obtaining a first intermediate available state of charge SOCDispi, the first intermediate state of charge SOCDispi being obtained from a battery capacity table as a function of a battery temperature, the battery capacity table making it possible to obtain, for a predetermined set of temperatures, a lower battery capacity limit and an upper battery capacity limit, The "lower limit of battery capacity" corresponds to the capacity stored at the end of a complete discharge with a standard current and the "upper limit" corresponds to the capacity stored at the end of a complete charge with the standard current. The standard current can vary, and for example be a constant current at C / 2 for the discharge, and a constant current at C / 2 followed by a step at a constant voltage Umax corresponding to a predetermined maximum voltage ensuring the integrity of the battery for charging. • Obtaining a second intermediate available state of charge SOCDisp2, the second intermediate state of charge SOCDisp2 being obtained from a stored state of charge, a first instantaneous voltage, an instantaneous open circuit voltage and a minimum admissible voltage, the minimum admissible voltage being a predetermined datum, • Measurement of a second instantaneous voltage Ucen at the battery terminals, and • Determination of an available charge state SOCDisp from the first state of intermediate available charge SOCDispi. of the second intermediate available charge state SOCDisp2 and of the second measured instantaneous voltage Ucen.

[0022] Thanks to the invention, it is therefore possible to determine and manage an available state of charge SOCDisp of a battery reliably for all possible state of charge domains. The method according to the invention allows in particular the precise determination of an available state of charge SOCDisp of a battery in a context of high intensity electric currents, i.e. causing heating of the battery. Changes in the behavior of the battery cells between an average or high SOC and a low SOC are taken into account.

[0023] In addition to the characteristics which have just been mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the determination of the available state of charge SOCDisp comprises a calculation of the available state of charge SOCDispen carrying out a weighted sum of the first intermediate available state of charge SOCDispi and the second intermediate available state of charge SOCDisp2, the weighting of the sum being dependent on the second instantaneous voltage Ucen measured. • the weighted sum is carried out as follows: SOC^t) = w^OC^t} + w / tjSOCn^

[0024] With: • t ' a current instant, • ,,, ^ceir^celbim W] - TT J, ceihnax celkmm • W7 —— 1 — • U celLmin, a predetermined minimum voltage ensuring battery integrity, and • Uceit^iax, a predetermined maximum voltage ensuring the integrity of the battery, obtaining the first intermediate available state of charge SOCDispi includes steps of: • measurement of an electric current delivered by the battery, • measurement of battery temperature, • calculation, by an electronic processing and control system, of a total electrical charge stored in the battery at a current instant, by coulomb-metric counting, as a function of a total electrical charge stored in the battery at a previous instant and as a function of the measured electrical current, • calculation of a stored state of charge, equal to the total electrical charge stored in the battery at the current time, divided by a maximum total charge that can be stored in the battery, • calculation of an available electrical charge based on a difference between, • the total electrical charge stored in the battery at the current time, and • a non-extractable electrical charge, which cannot be extracted from the battery given its temperature, the non-extractable electrical charge being determined as a function of at least said measured temperature, from operating characteristics of the battery stored in a memory of the electronic processing and control system, • calculation of the first intermediate available state of charge SOCDispi, equal to the available electrical charge, divided by a maximum available charge, the maximum available charge being equal to the difference between, on the one hand, a maximum achievable charge, which can be stored to the maximum in the battery when it is charged at said temperature, and on the other hand, said non-extractable electrical charge. obtaining the second intermediate available state of charge SOCDisp2 includes steps of: • determination of a stored charge state, • measurement of battery temperature, • determination of an instantaneous open circuit voltage of the battery based on an instantaneous open circuit voltage map as a function of the stored state of charge and the temperature battery temperature, measurement of the first instantaneous voltage at the battery terminals, • determination of the second intermediate available state of charge SOC Disp2 as a function of the stored state of charge, the first instantaneous voltage, the instantaneous open circuit voltage and the minimum admissible voltage, the minimum admissible voltage being a datum predetermined by design. The method according to the invention further comprises a modification of the conditions of use of the battery as a function of the available state of charge SOCDispdetermined.

[0025] A second aspect of the invention relates to a system for managing an electric battery comprising means for implementing the method according to the invention.

[0026] A third aspect of the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement a method according to the invention.

[0027] A fourth aspect of the invention relates to a non-transitory computer-readable data carrier on which the computer program according to the invention is recorded.

[0028] The invention and its various applications will be better understood upon reading the description which follows and the examination of the figures which accompany it. BRIEF DESCRIPTION OF THE FIGURES

[0029] The figures are presented for information purposes only and in no way limit the invention. [Fig.l] illustrates an example of discharging an IC current battery at two different temperatures, [Fig.2] illustrates an example of stored capacity at the end of charge and at the end of discharge as a function of temperature, [Fig. 3] is a block diagram illustrating the steps of an example of the method according to the invention, [Fig.4] illustrates an example of the evolution of an instantaneous battery voltage as a function of time, and an example of the evolution of the value of the stored state of charge SOCstoCk as a function of time, during a discharge of the battery, and [Fig.5] illustrates an example of a result that can be obtained using the method according to the invention. DETAILED DESCRIPTION

[0030] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0031] [Fig. 3] is a block diagram illustrating the steps of an example of the method 100 according to the invention. The optional steps of the example of the method 100 are indicated by a dotted rectangle.

[0032] The method 100 is a method for managing an available state of charge SOCDisp of one or more electric batteries. It allows more reliable management of the available state of charge SOCDisp of one or more electric batteries by precisely determining this available state of charge SOCDisp.

[0033] The electric battery to which the method 100 is applied is, for example, a battery on board an aircraft. The battery is for example used to store and / or deliver electrical energy to equipment of an aircraft turbomachine. The battery is for example used for electric propulsion functions within the turbomachine. Alternatively, the electric battery is a battery of an on-board automotive, railway, maritime, etc. system.

[0034] A first step 110 of the method 100 comprises obtaining a first intermediate available state of charge SOCDispi. The term “obtaining” may mean, in the present application, “receiving” and / or “calculating” and / or “determining by implementing a method”. This first intermediate available state of charge SOCDispi is obtained from a battery capacity table as a function of a battery temperature. Thus, the battery capacity table makes it possible to obtain, for a predetermined set of temperatures, a lower battery capacity limit and an upper battery capacity limit. An example of such a capacity table is illustrated in [Fig.2].

[0035] In a first example, the battery capacity table is obtained according to a first protocol. The first protocol is carried out at different temperatures, called "test temperatures", of the battery covering the operational range of the battery. The first protocol comprises, for each test temperature of the set of test temperatures, steps of: • 1 - Stabilization of the battery at a test temperature, • 2 - Complete battery charge using for example a protocol CCCV, for "constant current - constant voltage" in English, comprising charging at a low current (for example, a current at C / 2) up to a maximum battery voltage, and then charging at a fixed maximum voltage until the battery current decreases to an even lower current value, for example equal to C / 20, • 3 - Break for example lasting between thirty minutes and three hours, for example one hour, and • 4 - Complete discharge of the battery using for example a CC protocol, for "constant current" in English, including a discharge at a current for example at C / 2.

[0036] The last step 4 of the protocol provides the battery capacity at the test temperature. In this first example, it is therefore considered that after full charging, especially if the protocol used in step 2 is of the CCCV type, the quantity of electric charge stored in the cell is the same regardless of the temperature. Then, it is preferable to fit an equation of the type Q = fQ(T), with Q the battery capacity and T the battery temperature, to the measured points of step 4. This equation depends on the results obtained and can be, for example, a third-order polynomial. Finally, it is possible to calculate the limits of the minimum capacity Qmin of the battery and the maximum capacity Qmax of the battery with the following equations:

[0037] q (J1) = max / f \ [Eq. 4] ^TIUÏX v 7 \JQ /

[0038] Q. (T) =Q (T) -fJr} 53

[0039] This first example makes it possible to obtain a capacity table similar to the capacity table of [Fig.2], with the difference that the maximum capacity Qmax of the battery is the same for all temperatures, so all the difference in capacity from one temperature to another is attributed to the end of the discharge.

[0040] In a second example, the battery capacity table is obtained according to a second protocol. The second protocol is carried out at different temperatures, called "test temperatures", of the battery covering the operational range of the battery. The second protocol comprises, for each test temperature of the set of test temperatures, steps of: • 1 - Stabilization of the battery at a test temperature, • 2 - Complete battery charge using for example a protocol CCCV comprising a charge, for example at a current C / 2, up to a maximum battery voltage and then a charge at a fixed maximum voltage until the battery current decreases to a current value for example equal to C / 20, • 3 - Break for example lasting between thirty minutes and three hours, for example one hour, • 4 - Complete discharge of the battery using for example a CC protocol including a discharge for example at a current C / 2, • 5 - Stabilization of the battery at a reference temperature, for example, 25°C, and • 6 - Fully charge the battery using for example a protocol CCCV comprising charging for example at a current C / 2 up to a maximum battery voltage and then charging at a fixed maximum voltage until the battery current decreases to a current value for example equal to C / 20. • 7 - Break for example lasting between thirty minutes and three hours, for example one hour, • 8 - Stabilization of the battery at the test temperature, and • 9 - Complete discharge of the battery using, for example, a CC protocol including a discharge at a current for example equal to C / 2.

[0041] In this second example, it is therefore not considered that after full charging, the quantity of electrical charge stored in the cell is the same regardless of the temperature. Indeed, this second example makes it possible to attribute the difference in battery capacity between the different temperatures partly to charging and partly to discharging, as illustrated in [Fig.2].

[0042] Steps 1 to 4 of the second protocol are identical to those of the first protocol. Steps 5 to 9 allow to evaluate the proportion of the difference in the battery capacity due to the discharge. For this reason, the second full charge of the battery in step 6 is carried out at a reference temperature, which is identical for all test temperatures, which allows to define the same starting point. Then, it is necessary to adjust an equation of type QA = fç^T), with QA the battery capacity determined at the reference temperature and T the battery temperature, at the points measured during step 9. This equation depends on the results obtained and can be, for example, a third-order polynomial. Then, it is possible to calculate the limit Qmin with the following equation:

[0043] q Çt) ~ max( fn , ) - f (f\ [Ecb 7]

[0044] It is also necessary to adjust an equation of type QB = fQ,B(T) with QB the battery capacity determined at the test temperature and T the battery temperature, at the points measured during step 4. This equation depends on the results obtained and can be, for example, a third-order polynomial. Finally, it is possible to calculate the limit Qmax with the following equation:

[0045] q (r) =2. (r)+ / „JrHEq-8]

[0046] When the battery capacity table is obtained, for example with the first or the second method described above, it is possible to calculate the intermediate available state of charge SOCDispi, expressed in Ah, using the following equation:

[0047] SOC^i = SOCsmt - qJt) [Eq. 9]

[0048] With: • SOC the stored state of charge expressed in Ah, • Qmin(T) the lower limit of battery capacity, expressed in Ah, in function of temperature T, i.e. corresponding to the line defining zone 3 on [Fig.2].

[0049] When the battery capacity table is obtained, it is possible to calculate the intermediate available state of charge SOCDispien percentage, using the following equation:

[0050]

[0051]

[0052] rnr „ % [Eq. 10] q(t)-Q(T)X With : • Qmax(T) the upper limit of battery capacity, expressed in Ah, as a function of temperature T, ie corresponding to the line defining zone 1 in [Fig.2]. In one example, consistent with the previous examples, obtaining the first intermediate available state of charge SOCDispi includes steps of: • measurement of an electric current delivered by the battery, • measurement of battery temperature, • calculation, by an electronic processing and control system, of a total electrical charge stored in the battery at a current instant, by coulomb-metric counting, as a function of a total electrical charge stored in the battery at a previous instant and as a function of the measured electrical current, • calculation of a stored state of charge, equal to the total electrical charge stored in the battery at the current time, divided by a maximum total charge that can be stored in the battery, • calculation of an available electrical charge based on a difference between, • the total electrical charge stored in the battery at the moment current, and • a non-extractable electrical charge, which cannot be extracted from the battery given its temperature, the non-extractable electrical charge being determined as a function of at least said measured temperature, from operating characteristics of the battery stored in a memory of the electronic processing and control system, • calculation of the first intermediate available state of charge SOCDispi, equal to the available electrical charge, divided by a maximum available charge, the maximum available charge being equal to the difference between, on the one hand, a maximum achievable charge, which can be stored to the maximum in the battery when it is charged at said temperature, and on the other hand, said non-extractable electrical charge.

[0053] In one example, consistent with the previous examples, when the battery is at rest and a coulomb-metric count is used to determine the state of charge SOCstockinitial, obtaining the first intermediate available state of charge SOCDispi further comprises a step of measuring the open circuit voltage OCV in order to determine the state of charge SOCstockinitial. Indeed, the determination of the initial stored SOC can be used to calculate the first intermediate available state of charge SOCDispi and the second intermediate available state of charge SOCDisp2.

[0054] In one example, compatible with the previous examples, the first intermediate available charge state SOCDispiest is obtained by implementing the method described in patent application FR3126812A1.

[0055] A second step 120 of the method 100 comprises obtaining a second intermediate available state of charge SOCDisp2. The second intermediate state of charge SOC Disp2 is obtained from a stored state of charge, a first instantaneous voltage, an instantaneous open circuit voltage and a minimum admissible voltage, the minimum admissible voltage being a datum predetermined by design, i.e. linked to the battery design.

[0056] In one example, it is possible to obtain the second intermediate available state of charge SOCDisp2 of the battery, expressed in Ah, from a mapping of an open circuit voltage OCV as a function of the intermediate available state of charge SOCDisp2 of the battery and as a function of the temperature of the battery. This mapping can be determined or already available since it can also be used for calculating the stored state of charge SOCstock. In this example, the second intermediate available state of charge SOCDisp2> expressed in Ah, can be calculated using the following equation:

[0057] [Eq. 11] MJCDisp2 -

[0058] Alternatively, the second intermediate available state of charge SOCDisp2, expressed as a percentage relative to the reference capacity of the battery, can be calculated using the following equation: [°° 59 1 SOC^a = A— X 100%11 “ 121

[0060] With: • Qref> the reference capacity of the battery.

[0061] The reference capacity of the battery can be obtained from a complete discharge at a reference temperature, for example 25 °C, and a reference current, for example a current C / 2. It is also possible to express the second intermediate available state of charge SOCDisp2 of the battery relative to the upper capacity limit of the battery Q (.T).

[0062] In one example, advantageously compatible with the preceding examples, obtaining 120 of the second intermediate available state of charge SOCDisp2 includes steps of: • determination of a stored charge state, • measurement of battery temperature, • determination of an instantaneous open circuit voltage of the battery based on an instantaneous open circuit voltage map as a function of the stored state of charge and the battery temperature, • measurement of the first instantaneous voltage at the battery terminals, • determination of the second intermediate available state of charge SOCDisp2 as a function of the stored state of charge, the first instantaneous voltage, the instantaneous open circuit voltage and the minimum admissible voltage, the minimum admissible voltage being a datum predetermined by design.

[0063] A third step 130 of the method 100 comprises the measurement of a second instantaneous voltage Uœn at the terminals of the battery, by any standard means conventionally used for this purpose. In one example, step 130 can be carried out before step 120 and the second instantaneous voltage Uceu can be used as the first instantaneous voltage to determine the second intermediate available state of charge SOCDisp2. Thus, in this example, the first and second instantaneous voltages are identical and obtained by the measurement step 130.

[0064] A fourth step 140 of the method 100 comprises determining an available state of charge SOCDisp from the first intermediate available state of charge SOCDispi, the second intermediate available state of charge SOCDisp2 and the second instantaneous voltage Ucen of the battery measured in step 130. Thus, the second instantaneous voltage Uœnest is used to determine the available state of charge SOCDisp from the first intermediate available state of charge SOCDispi and the second intermediate available state of charge SOCDisp2.

[0065] Indeed, the evolution of the second instantaneous voltage Ucen as a function of time and the evolution of the stored state of charge SOCstoCk of the battery as a function of time can be used to determine whether the state of charge of the battery is low, medium or high from the second instantaneous voltage Ucen of the battery. It should be noted that the characteristic behavior of a low state of charge SOC varies depending on the operating conditions. Thus, knowledge of the current state of charge SOC is not necessarily sufficient to characterize a low state of charge SOC.

[0066] [Fig.4] is a graph 200 describing, for a discharge of a battery, a example of evolution of the instantaneous voltage of the battery as a function of time, by a curve 201, and an example of evolution of the value of the stored state of charge SOCstock as a function of time, by a line 202. The left vertical axis corresponds to the value of the instantaneous voltage Uceude the battery and the right vertical axis corresponds to the value of the stored state of charge SOCstoCk of the battery, expressed as a percentage. The horizontal axis corresponds to time and is expressed in minutes. Thus, using [Fig.4], we note for example that a low stored state of charge SOCstoCk, noted 203, is characterized by an accelerated drop in the instantaneous voltage Ucende the battery.

[0067] An example of a result that can be obtained using the method according to the invention is illustrated in [Fig. 5]. [Fig. 5] is a graph 300 describing the evolution of an example of available state of charge SOCDisp noted 304 determined using the method 100. The curves 301 and 302 are respectively an example of a first intermediate available state of charge SOCDispi and an example of a second intermediate available state of charge SOCDisp2 having made it possible to obtain the example of available state of charge SOCDisp noted 304. The vertical axis on this graph 300 corresponds to the available state of charge of the battery expressed in Ah and the horizontal axis corresponds to the time expressed in minutes. The curve 303 corresponds to the reference state of charge SOC.

[0068] In one example, consistent with the previous examples, the determination 140 of the available state of charge SOCDisp comprises a calculation of the available state of charge SOCDisp by performing a weighted sum of the first intermediate available state of charge SOCDispi and the second intermediate available state of charge SOCDisp2- Thus, the following equation is used to determine the available state of charge SOCDisp: [00691 [Eq. 13]

[0070] With: • ' a current moment, • wi and w2, the weighting weights determined for example as a function of the second instantaneous voltage Ucen measured in step 130.

[0071] In one example, consistent with the previous examples, the weighting weights and w2 are determined using the following equations:

[0072] w _ [Eq. 14] Vl- 1 TT T • cell / nax'

[0073] w2= 1-nq [Eq. 15]

[0074] A fifth optional step 150 of the method 100 comprises a modification of the conditions of use of the battery as a function of the available state of charge SOCDisp determined in step 140. This modification of the conditions of use of the battery may be automatic, semi-automatic or manual, i.e. requiring human intervention. In examples, this modification of the conditions of use of the battery may comprise at least one action from among: • decision-making, by a user, concerning an aircraft maneuver such as a landing, • estimation, by the system, of a remaining charging time, of a remaining time discharge and therefore flight of an aircraft or a distance that can be covered before the battery is completely discharged, • display of the available charge status SOCDisp, • changing a first battery powering a system, such as a system contained in an aircraft or of an aircraft, and whose available state of charge SOCDisp is determined by the method 100, by a battery whose available state of charge SOCDisp is greater than the available state of charge SOCDisp of the first battery, • stopping a system, such as a system contained in an aircraft or an aircraft, powered by the battery whose available charge state SOCDisp is determined by the method 100, • prediction of a remaining battery charge duration whose available charge state SOCDisp is determined, and • implementation of a maintenance operation of a system, such as a system contained in an aircraft or of an aircraft, powered by the battery whose available charge state SOCDisp is determined.

[0075] The present invention also relates to a system for managing an electric battery comprising means for implementing the method 100. For example, the management system according to the invention may comprise an electronic processing and control system, otherwise called a “computer”, comprising at least one processor and one memory, the electronic processing and control system being configured to execute the steps of the method 100. In addition, optionally, the system for managing an electric battery may comprise a means for displaying the available state of charge SOCDispidetermined by the method 100, at least one means for measuring the temperature of the battery, at least one means for measuring the voltage at the terminals of the battery, and at least one means for measuring the current flowing between the terminals of said battery.

Claims

Claims

1. Method (100) for managing an available state of charge SOCDisp of an electric battery comprising computer-implemented steps of: - Obtaining (110) a first intermediate available state of charge SOCDisp of said battery, the first intermediate state of charge SOCDisp being obtained from a battery capacity table as a function of a battery temperature, the battery capacity table making it possible to obtain, for a predetermined set of battery temperatures, a lower battery capacity limit and an upper battery capacity limit, - Obtaining (120) a second intermediate available state of charge SOCDisp2 of said battery, the second intermediate state of charge SOCDisp2 being obtained from a stored state of charge, a first instantaneous voltage, an instantaneous open circuit voltage, and a predetermined minimum admissible voltage,- Measurement (130) of a second instantaneous voltage Ucen at the terminals of the battery, and - Determination (140) of an available state of charge SOCDisp of the battery, from the first intermediate available state of charge SOCüispi, the second intermediate available state of charge SOCDisp2 and the second instantaneous voltage Ucen measured (130).,

2. Method (100) according to the preceding claim in which the determination (140) of the available state of charge SOCDisp comprises a weighted sum of the first intermediate available state of charge SOCDispi and the second intermediate available state of charge SOCDisp2, the weighting of the sum being dependent on the second measured instantaneous voltage UCeii (130).

3. Method (100) according to the preceding claim in which the weighted sum is carried out in the following manner: SOCBi,r(t) = + w^OCDkpl(t} With:

4. - 1 a current moment, — . célfytùn VI 1 --- i : r J 1 ° cdlflmU a-lbma _ w2 = 1 - - Ueell.min a predetermined minimum voltage ensuring battery integrity, and - Uceiijnax a predetermined maximum voltage ensuring battery integrity. Method (100) according to any one of the preceding claims wherein obtaining (110) the first intermediate available state of charge SOCDisPi comprises steps of: - measurement of an electric current delivered by the battery, - battery temperature measurement, - calculation, by an electronic processing and control system, of a total electrical charge stored in the battery at a current instant, as a function of a total electrical charge stored in the battery at a previous instant and as a function of the measured electrical current, - calculation of a stored state of charge, equal to the total electrical charge stored in the battery at the current time, divided by a maximum total charge that can be stored in the battery, - calculation of an available electrical charge based on a difference between, • the total electrical charge stored in the battery at the current time, and • a non-extractable electrical charge, which cannot be extracted from the battery given its temperature, the non-extractable electrical charge being determined as a function of at least said measured temperature, from operating characteristics of the battery stored in a memory of the electronic processing and control system, - calculation of the first intermediate available state of charge SOC Dispi, equal to the available electrical charge, divided by a maximum available charge, the maximum available charge being equal to the difference between, on the one hand, a maximum achievable charge, which can be stored to the maximum in the battery when it is charged at said temperature, and on the other hand, said non-extractable electrical charge.

5. Method (100) according to any one of the preceding claims wherein obtaining (120) the second intermediate available state of charge SOCDisp2 comprises steps of: - determining the stored state of charge, - measuring the temperature of the battery, - determining an instantaneous open circuit voltage of the battery as a function of a mapping of instantaneous open circuit voltage as a function of the stored state of charge and the temperature of the battery, - measuring the first instantaneous voltage at the terminals of the battery, - determining the second intermediate available state of charge SOCDisp2 as a function of the stored state of charge, the first instantaneous voltage, the instantaneous open circuit voltage and the minimum admissible voltage, the minimum admissible voltage being a datum predetermined by design.

6. Method (100) according to any one of the preceding claims, further comprising a modification (150) of the conditions of use of the battery according to the determined available state of charge SOCDisp (140).

7. System for managing an electric battery comprising a processing unit configured to implement a method according to one of the preceding claims.

8. An aircraft comprising a battery and a battery management system according to the preceding claim.

9. A computer program comprising instructions which, when the program is executed by a computer, causing the latter to implement a method according to any one of claims 1 to 6.

10. A non-transitory computer-readable data carrier on which a computer program according to claim 9 is recorded.

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