Method for determining the remaining capacity of a battery

Abstract

One aspect of the invention relates to a computer-implemented method 100 for determining the remaining capacity of a battery, comprising the steps of: Obtaining 110 a date of manufacture and / or initial charge and / or recharging of the battery and a second date; Determining 120 a self-discharge value between the date of manufacture and / or initial charge and / or recharging of the battery and the second date; and Calculating 130 the remaining capacity of the battery from the determined self-discharge value, the date of manufacture and / or initial charge and / or recharging of the battery, and the second date. Figure to be published with the abstract: Figure 1

Description

Title of the invention: Method for determining the remaining capacity of a battery. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of batteries.

[0002] The present invention relates to a method for determining the remaining capacity of a battery and in particular a method for determining the remaining capacity of a battery taking into account the self-discharge of the battery. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0004] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and 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 employing methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and finally aviation biofuels.

[0006] In this context, the determination of a battery's remaining capacity needs to be improved. Indeed, when electronic equipment is powered by a battery, it is essential to be able to determine the battery's remaining capacity in order to know whether the battery needs to be replaced or recharged. A battery is an electrochemical device that produces electricity by converting chemical energy into electrical energy. There are different types of batteries, such as saline, alkaline, and lithium batteries. The term "battery," in this application, is used to refer to both a primary and a secondary battery. A primary battery is a battery designed for single use and disposal. Conversely, a secondary battery is a battery that can be recharged and reused. A secondary battery is sometimes called a rechargeable battery. The capacity of a battery is the amount of electrical charge that the battery can supply. The remaining capacity of a battery is therefore the remaining amount of electrical charge that the battery can supply.

[0007] The life cycle of a battery comprises several stages. The first stage is the manufacturing of the battery. The second stage is the storage of the battery. This second stage has a highly variable duration, for example, from a few days to several years. The third stage is the commissioning of the battery. This stage begins when the battery is installed in electrical equipment to provide its power supply. Once the battery is installed, the electrical equipment can remain off, be put into standby mode, or be switched on. Thus, this third stage of battery commissioning can be divided into three categories depending on the state of the electrical equipment. The first category consists of commissioning the battery when the device is off. The second category consists of commissioning the battery when the device is in standby mode.A third category involves the activation of the battery when the device is in operation. The first category of activation for an electrical device generally precedes the second category, which itself precedes the third category of standby mode. However, it is also possible for these three categories of standby mode to be ordered differently and for them to occur several times for the same electrical device. Finally, the last stage is the end of the battery's life. This stage begins when the battery's capacity is too low to allow the electrical equipment in which the battery is installed to function. Indeed, during the battery's life cycle, the remaining capacity of the battery decreases. Thus, it is common to consider the remaining capacity of the battery to be 100% until the third stage of battery activation.A remaining battery capacity of 100% means that the battery's remaining capacity is equal to its initial capacity. A remaining battery capacity of 0% means that the battery can no longer supply electricity. When a battery reaches the end of its life, it is discarded if it is a primary battery or recharged if it is a secondary battery.

[0008] Several methods exist for determining the remaining capacity of a battery. One method consists of using a battery life counter. This counter is set to 100% at the beginning of the third commissioning stage of the battery's life cycle. battery. Then, this counter is decremented each time the electrical device powered by the battery is switched on. This method is simple to implement but lacks precision in determining the battery's remaining capacity. A second known method consists of measuring the voltage across the battery terminals to deduce the remaining capacity. This method has several drawbacks. First, this method cannot be used for all types of batteries. Indeed, lithium batteries have a constant voltage when their remaining capacity is above a threshold, for example, above 20%, then the voltage drops very rapidly to almost zero when the remaining capacity is below this threshold. Thus, it is not possible to determine the remaining capacity of a lithium battery by measuring the voltage across its terminals.Furthermore, this method is lengthy and tedious to implement when the battery is mounted on electrical equipment. Indeed, to access the battery terminals, it is necessary to remove the battery from the equipment or at least manipulate part of the electrical equipment in order to access the battery terminals.

[0009] There is therefore a need to provide a method for determining the remaining capacity of a battery that at least partially resolves the drawbacks of prior art methods. Summary of the invention

[0010] The invention provides a solution to the problems mentioned by taking into account the self-discharge value of the battery in order to determine the remaining capacity of the battery. This self-discharge value is calculated from the date of manufacture and / or initial charging and / or recharging of the battery, as well as a second date, for example, the date of the first commissioning of the battery.

[0011] One aspect of the invention relates to a computer-implemented method for determining the remaining capacity of a battery, comprising the steps of: • Obtaining a manufacturing date and / or initial charging date and / or battery recharging date and a second date, • Determination of a self-discharge value between the date of manufacture and / or initial charge and / or recharge of the battery and the second date, and • Calculation of the remaining battery capacity from the determined self-discharge value, the date of manufacture and / or initial charge and / or recharge of the battery and the second date.

[0012] Thanks to the invention, the accuracy of determining the remaining battery capacity is improved. Indeed, the method according to the invention takes into account the self-discharge of the battery, which is a phenomenon influencing the remaining battery capacity. Furthermore, the method according to the invention can be used for any type of battery and does not require to access the terminals of the battery.

[0013] In addition to the characteristics mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: • The second date is the date of the first commissioning of the battery. • the second date is subsequent to the initial commissioning of the battery, the The process according to the invention further comprises the steps of: • Obtaining at least one battery commissioning time and at least one value for an electrical consumption profile during battery commissioning, • Determination of a battery discharge based on the duration of the battery's commissioning period and at least one value from the power consumption profile during battery commissioning, and • Update of the remaining battery capacity based on the determined battery discharge, • The battery temperature is taken into account when determining the self-discharge value. • The method according to the invention further comprises a preliminary step of characterizing the self-discharge value, including a measurement of the battery's self-discharge value for a predetermined duration and for at least one battery temperature, and • The method according to the invention further includes sending an alert when the determined remaining capacity is less than a predetermined remaining capacity.

[0014] A second aspect of the invention relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the process according to the invention.

[0015] A third aspect of the invention relates to a computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to implement the process according to the invention.

[0016] A fourth aspect of the invention relates to a system comprising means adapted to carry out the process according to the invention.

[0017] A fifth aspect of the invention relates to an aircraft comprising a system according to claim 9 and a battery whose remaining capacity is determined by said system.

[0018] The invention and its various applications will be better understood upon reading the description which follows and examination of the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0019] The figures are presented for illustrative purposes only and are in no way limiting of the invention. • Fig. 1 shows a block diagram of an example of a method for determining the remaining capacity of a battery according to the invention. • Fig. 2 shows a diagram illustrating an example of variation of a self-discharge value as a function of battery temperature. DETAILED DESCRIPTION

[0020] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0021] Figure 1 is a block diagram illustrating the steps of an example of process 100 according to the invention. The mandatory steps of the example of process 100 are indicated by a solid rectangle and the optional steps are indicated by a dashed rectangle.

[0022] The method 100 is implemented by a computer or a processor. For example, the method 100 can be implemented by a processor within a management system for a stack of an embedded system such as an aircraft. The management system preferably has the structure of a computer, in this case an onboard computer, and / or a computer. It comprises an electronic circuit in one or more parts equipped with at least one non-volatile memory and a processor for executing logical operations. It may also include one or more other memories, of the RAM type or another type, and one or more other processors.

[0023] By "computer-implemented," it is meant that the steps, or virtually all of the steps, are executed by at least one computer or processor or other similar system. Thus, steps are carried out by the computer, possibly in a fully automatic or semi-automatic manner. In some examples, the triggering of at least some of the steps of the process can be achieved through user-computer interaction. The level of user-computer interaction required may depend on the intended level of automation and be balanced against the need to implement the user's requirements. In some examples, this level may be defined by the user and / or predefined.

[0024] A typical example of computer implementation of a process consists of executing the process with a system adapted for this purpose. The system may include a processor coupled with memory and a graphical user interface (GUI), with a computer program comprising instructions for implementing the process being stored in memory. The memory may also store a database of Data. Memory is any hardware adapted for such storage, possibly comprising several distinct physical parts.

[0025] Method 100 is a method for determining the remaining capacity of a battery. The method can determine the decrease in the battery's remaining capacity due to self-discharge before the battery is put into service, where the second date is the date of the battery's first put into service. The method can also determine the decrease in the battery's remaining capacity due to self-discharge at the end of a first-category battery put into service, as defined above, where the second date is the end of the period during which the electrical device is off. The method can also determine the decrease in the battery's remaining capacity due to self-discharge at the end of a first-category battery put into service, as defined above, where the second date is the end of the period during which the electrical device is in standby mode.Indeed, in some cases, depending on the temperature and / or the power consumption of the electronic equipment in standby mode, battery self-discharge can lead to a decrease in remaining battery capacity exceeding 50%. It is therefore essential to accurately determine this self-discharge if one wishes to reliably indicate the remaining battery life. Furthermore, process 100 can also be used to determine the battery capacity decrease related to the power consumption induced by the equipment's operation, with optional steps 140 to 160.

[0026] The process 100 includes a first step 110 of obtaining a first date and a second date. The first date may be a date of manufacture of the battery. The first date may also be a date of initial charging and / or recharging of the battery if the battery is a secondary battery. The term "obtaining" means, in this application, receiving and / or measuring and / or calculating. For example, the first date may be stored in memory during the manufacture of the battery. In a second example, consistent with the previous example, the first date may be stored or updated in memory during the initial charging and / or recharging of the battery. The memory containing the first date may, for example, be a memory of the electrical equipment that the battery powers or will power. The second date may be any date equal to or later than the first date, for example, the date on which the process 100 is implemented.The first and second dates can be in different formats and, for example, include all or part of the following information: year, month, day, and time. The first and second dates can be stored in any form that allows the previously described information to be retrieved, for example, by calculation.

[0027] In an example consistent with the preceding examples, the second date is the date of the first commissioning of the stack. By "first commissioning of the stack", The term "first commissioning" refers to the initial activation of the battery following its manufacture, initial charging, and / or recharging. Therefore, a secondary battery will have several "first commissionings" during its use.

[0028] The process 100 includes a second step 120 of determining a self-discharge value between the first and second dates. The self-discharge of a battery is an electrochemical reaction causing a gradual reduction in the remaining capacity of a battery, in the absence of a current-consuming device, when the battery is not used for a given period. This is a technological limitation to the storage of electrical energy by a battery. The self-discharge value is commonly called "self-discharge current" in English and can also be called "couroir de déscharge" in French. The self-discharge value therefore corresponds to the loss of capacity of the battery over a given period due to this self-discharge phenomenon. The determination of the self-discharge value can be carried out experimentally. The self-discharge value is specific to each battery model.Therefore, this determination of the self-discharge value must be performed on the same battery model as the battery for which the remaining capacity is being determined. For example, it is possible to measure the capacity loss of a battery over a predetermined period. This predetermined period can be determined based on the estimated lifespan of the battery. For example, the predetermined period could be between 10% and 50% of the estimated lifespan, preferably 25%. In another example, the predetermined period could be between one day and one year, preferably one month.

[0029] In one example, consistent with the preceding examples, the battery temperature is taken into account in determining the self-discharge value. The battery temperature, measured in degrees Celsius (°C), can be obtained in various ways. For example, by measuring the temperature of a part of the battery and / or the temperature of the battery's environment and / or the temperature of the electrical device powered by the battery. Furthermore, since the self-discharge value is determined over a period between the first and second dates, the battery temperature can be the average battery temperature during this period. For example, the temperature can be measured daily to weekly between the first and second dates. In another example, the battery temperature can be constant throughout the entire period considered.

[0030] In an example consistent with the preceding example, the method 100 includes an optional initial step 105 for characterizing the self-discharge value of the battery, comprising a measurement of the self-discharge value of the battery for a predetermined time and for at least one battery temperature. For example, it is possible to measure the self-discharge value of the battery for a predetermined time and for a A predetermined temperature range can correspond to the range of temperatures to which the battery may be exposed during its lifetime. For example, the temperature range could be between -50°C and 130°C. To measure the capacity loss of a battery over a predetermined period, a two-step self-discharge characterization method can be implemented. The first step involves storing the battery for a predetermined duration. The second step involves applying a constant and known direct current to the battery until its remaining capacity reaches 0%. By measuring the duration of the second step, it is possible to determine the remaining capacity of the battery at the beginning of the second step. Then, from this remaining capacity at the beginning of the second step, it is possible to deduce the self-discharge value for the duration of the first step.Furthermore, to account for the battery temperature, this self-discharge value characterization process can be repeated for different battery temperatures within the predetermined temperature range. This characterization process yields a diagram like the one shown in [Fig. 2], illustrating the self-discharge value of a Tadiran® ​​SL-560 lithium battery with an average current of 90 microamperes (pA) as a function of temperature. The vertical axis 210 of diagram 200 represents the self-discharge value measured in microamperes. The horizontal axis 220 of diagram 200 represents the temperature, measured in degrees Celsius. As shown in curve 230 of [Fig. 2], for this battery model, the self-discharge value varies between 2.5 and 150 pA for a temperature between -40°C and 125°C.

[0031] The method 100 includes a third step 130 for calculating the remaining battery capacity based on the self-discharge value determined in step 120, the first date, and the second date. Thus, by calculating the time between the first and second dates, it is possible to determine the battery capacity loss during this time and then deduce the remaining battery capacity. When the battery temperature is taken into account, it is possible to divide the time between the first and second dates into several distinct periods based on the temperature change between the first and second dates. Each distinct period corresponds to a given temperature and therefore to a given self-discharge value. For example, a first distinct period corresponds to a first battery temperature, and a second distinct period corresponds to a second battery temperature.In this example, the self-discharge value for the period between the first and second dates will be the weighted average of the self-discharge value for the first distinct period and the self-discharge value for the second distinct period. The weighting of each distinct period depends on the relative duration of each period. distinct in relation to the duration between the first and second dates. For example, if the first distinct duration represents 30% of the duration between the first and second dates and the second distinct duration represents 70% of the duration between the first and second dates, the first distinct duration will have a weighting of 0.3 and the second distinct duration will have a weighting of 0.7.

[0032] When the second date is the date of initial commissioning, method 100 allows the remaining capacity of the battery to be determined at the time of its initial commissioning. Thus, unlike commonly used methods for determining remaining battery capacity, the remaining capacity of the battery at the time of initial commissioning is not considered to be equal to 100%.

[0033] The method 100 comprises three optional steps 140 to 160 when the second date is later than the initial commissioning of the battery. The first optional step 140 consists of obtaining at least one battery commissioning time. For example, during this step 140, the initial commissioning date is obtained. Thus, it is possible to calculate the battery commissioning time using the second date and the initial commissioning date. In addition, at least one value for an electrical consumption profile during the battery commissioning is obtained. The electrical consumption profile depends on the electrical device and, in particular, on the operating state of the electrical device.For example, a first power consumption profile obtained might correspond to the power consumption profile when the battery-powered device is off, a second power consumption profile obtained might correspond to the power consumption profile when the battery-powered device is in standby mode, and a third power consumption profile obtained might correspond to the power consumption profile when the battery-powered device is in operation. The power consumption profile can be measured and is expressed in microamperes or amperes.

[0034] The optional second step 150 consists of determining a battery discharge from the battery's on-time and at least one value from the power consumption profile during the battery's on-time. It should be noted that when the electrical device powered by the battery has alternated between different operating states, the battery's on-time can be divided into several distinct durations. For example, for a first distinct duration, the discharge can be calculated from a first power consumption profile, and for a second distinct duration, the discharge can be calculated from a second power consumption profile. As in step 120, the different distinct durations can be weighted. The weighting of each distinct duration depends on the relative duration of each distinct duration in relation to the battery commissioning time.

[0035] The optional third step 160 consists of updating the remaining battery capacity based on the determined battery discharge. For example, if the battery discharge corresponds to 10% of the total battery capacity and the remaining battery capacity at the start of commissioning was 60%, then the remaining battery capacity will be 50%. Furthermore, it should be noted that during this battery commissioning, the self-discharge phenomenon, taken into account by method 100, may not be negligible, i.e., represent at least 1% of the total battery capacity. In particular, if the commissioning period is sufficiently long and / or the battery temperature during commissioning is high. For example, if the commissioning period exceeds one day or one week, the self-discharge value of the battery during this period is not negligible.Similarly, if the battery temperature is above 40°C, the battery's self-discharge rate during this period is not negligible.

[0036] It should be noted that once in operation, the electrical equipment has a power consumption that can be considered average or may include current peaks. Thus, it is possible to determine the battery capacity degradation beforehand, experimentally, based on these consumption profiles. Furthermore, it is possible to determine the battery capacity degradation based on these consumption profiles for different temperatures of the electrical equipment. In the case of power consumption that can be considered average, the remaining capacity of the battery can be regularly reassessed by recording the time elapsed since the equipment was put into operation in a counter, or several counters if the equipment has multiple operating modes. In the case of consumption including current peaks, a counter can be incremented for each event that generates a current peak.Furthermore, it is possible to use as many event counters as there are electrical consumption profiles of the equipment, depending on the equipment's operating phases and / or the temperature measured by the equipment itself. Based on the values ​​of these event counters, the remaining capacity can be regularly reassessed. The two preceding elements can be weighted by knowledge of the temperature. This weighting can be modeled in the case of a repetitive thermal profile, or linked to a measurement of the battery temperature, or even a measurement that mirrors the battery temperature, such as the temperature of the electrical equipment.

[0037] The method 100 may include a final optional step 170 of sending an alert when the determined remaining capacity is less than a predetermined remaining capacity. The predetermined remaining capacity may, for example, be between 5 and 30% of the battery's total capacity, for example, 20%. This final step 170 can, for example, warn a user that the remaining battery capacity is insufficient and that the battery must be changed or recharged. This final step 170 can also, for example, automatically switch the power source of the electrical device. Thus, when a remaining capacity threshold is reached, the electrical device can be powered by a second battery with a remaining capacity greater than the predetermined remaining capacity. This change of power source therefore prevents any power interruption to the electrical equipment.

Claims

Claims

1. A computer-implemented method (100) for determining a remaining capacity of a battery comprising steps of: - Obtaining (110) a date of manufacture and / or initial charge and / or recharge of the battery and a second date, - Determining (120) a self-discharge value between the date of manufacture and / or initial charge and / or recharge of the battery and the second date, and - Calculating (130) the remaining capacity of the battery from the determined self-discharge value, the date of manufacture and / or initial charge and / or recharge of the battery and the second date.

2. The method (100) of claim 1 wherein the second date is a date of first commissioning of the cell.

3. Method (100) according to claim 1 wherein the second date is subsequent to a first commissioning of the battery, the method (100) further comprising steps of: - Obtaining (140) at least one duration of commissioning of the battery and at least one value of an electrical consumption profile during the commissioning of the battery, - Determining (150) a discharge of the battery from the duration of the period of commissioning of the battery and the at least one value of the electrical consumption profile during the commissioning of the battery, and - Updating (160) the remaining capacity of the battery from the discharge of the battery determined (150).

4. A method (100) according to any preceding claim wherein a temperature of the battery is taken into account in determining (120) the self-discharge value.

5. Method (100) according to the preceding claim further comprising a prior step (105) of characterizing the self-discharge value comprising a measurement of the self-discharge value of the battery for a predetermined duration and for at least one temperature of the battery.

6. A method according to any preceding claim. further comprising sending (170) an alert when the determined remaining capacity is less than a predetermined remaining capacity.

7. Computer program product comprising instructions which, when the program is executed by a computer, cause the latter to implement the method according to any one of claims 1 to 6

8. 1 d O. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of claims 1 to 6.

9. System comprising means adapted to carry out the method according to any one of claims 1 to 6.

10. Aircraft comprising a system according to claim 9 and a battery whose remaining capacity is determined by said system.

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