DETERMINATION OF INFORMATION REPRESENTATIVE OF A CHANGE IN STATE OF CHARGE OF A RECHARGEABLE CELLULAR BATTERY OF A SYSTEM

Abstract

A method is used to determine information about a rechargeable battery that is part of a system, comprising cells and having determined initial cell voltages and open-circuit voltage, and an estimated capacity, by dividing the quantity of ampere-hours supplied during a discharge phase or received during a recharge phase by a change in the state of charge during that discharge or recharge phase. This method includes a step (10-20) in which information is determined that represents a minimum change in the state of charge for estimating the capacity with a chosen accuracy, based on at least a first estimated error in the change in the state of charge and a second estimated error in the quantity of ampere-hours. Figure 3

Description

Title of the invention: DETERMINATION OF INFORMATION REPRESENTATIVE OF A CHANGE IN STATE OF CHARGE OF A RECHARGEABLE CELLULAR BATTERY OF A SYSTEM Technical field of the invention

[0001] The invention relates to systems comprising at least one rechargeable battery having cells, and more specifically the determination of information relating to such a rechargeable battery. State of the art

[0002] In many systems, such as for example in vehicles (possibly automobiles), rechargeable batteries are used which have cells designed to store electrical energy intended to power at least one electrical machine (possibly a motor) and / or an electrical power supply circuit.

[0003] For example, the cells can be electrochemical (in particular lithium-ion (or Li-ion) or Ni-Mh or Ni-Cd). Furthermore, in the case of a vehicle, the rechargeable battery can be either a so-called "main" battery (or traction or power battery) when it is responsible for supplying electrical current to an on-board network, via a converter, and at least one electric drive unit of the powertrain (or powertrain), or a so-called "service" battery when it is of the very low voltage type (typically between 12 V and 48 V) and responsible for supplying electrical current to the on-board network in the absence of a main battery (and therefore of an electric drive unit) or in place of or in addition to the main battery.

[0004] In what follows and what precedes, "on-board network" means an electrical power supply network to which electrical (or electronic) equipment (or components) consuming electrical energy are coupled.

[0005] Current rechargeable cellular batteries are subject to the management of certain parameters in order to maximize their lifespan and optimal performance, minimizing the risk of failure and incidents, for example, for the safety and peace of mind of vehicle users. This management system enables, in particular, diagnostics designed to optimize the use of the rechargeable cellular battery, reduce repair costs, and anticipate end-of-life or major malfunctions.

[0006] Among the parameters managed, one can notably mention the current capacity, which is equal to the ratio between the quantity of ampere-hours (AQ) supplied in a phase of The discharge or charge received during a charging phase of the battery (rechargeable cell) and the change in state of charge (ASOC) during this discharge or charging phase, and the state of health capacity (SOHC), which is equal to the current capacity divided by the initial capacity (i.e., at the beginning of the battery's life). Currently, the SOHC degradation of a battery is subject to error, which can lead to an overestimation or underestimation of battery performance.

[0007] In some countries or regions, standards regulate the magnitude of this error to varying degrees in order to ensure transparency from battery system manufacturers towards their users. For example, a verification of the error magnitude may be required every two years, with a penalty if the actual error does not prevent an overestimation by a predefined percentage.

[0008] The aforementioned error must therefore meet a precision requirement because, depending on the precision chosen, there may be a significant impact on the failure rate of the batteries and the same could be true of the impact on the warranty coverage of the batteries.

[0009] As an illustrative example in the case of automotive vehicle batteries, proper operation is guaranteed as long as their SOHC is greater than or equal to a predefined threshold, for example, 70%. In this case, if a maximum error of 5% on the SOHC estimate is considered to be tolerated under the warranty, an alarm will be triggered in the system as soon as the estimated SOHC becomes equal to 75% (70% + 5%).

[0010] Currently, the maximum error is chosen based on a predefined state of charge variation (ASOC). However, if too large a predefined state of charge variation (ASOC) is imposed, there is a risk of failure to learn during battery use because the user-side occurrence assumption is too pessimistic.

[0011] It would certainly be possible to use the worst-case error scenario to avoid overestimating the battery capacity. However, this would lead to a significant underestimation of the battery capacity, resulting in premature battery shutdown and user complaints.

[0012] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0013] In particular, it proposes a determination method for determining information relating to a rechargeable battery forming part of a system, comprising cells and having determined initial voltages across its cells and an open-circuit voltage and an estimated capacity by dividing a quantity ampere-hour supplied in a discharge phase or received in a recharge phase by a change in state of charge during that discharge or recharge phase.

[0014] This information determination method is characterized by the fact that it includes a step in which information representative of a minimum charge state variation is determined to estimate the capacity with a chosen accuracy, based on at least a first estimated error on the charge state variation and a second estimated error on the quantity of ampere-hours.

[0015] This consideration of possible errors that may impact the calculation of the capacity now makes it possible to impose rules for choosing the variation of the state of charge which guarantee a coverage rate in accuracy of the estimated capacity (and therefore of the SOHC) with a chosen accuracy (or error), and therefore to have a better accuracy on the estimation of the estimated capacity (and therefore of the SOHC) which allows a better exploitation of the electrical energy stored in the rechargeable battery.

[0016] The information determination method according to the invention may include other features which may be taken separately or in combination, and in particular:

[0017] - in its step, the first error can be estimated as a function of at least one estimated error on the determined open-circuit voltage;

[0018] - in the presence of the first option, in its step, one can estimate the error on the open-circuit voltage determined as a function of the linearity of an open-circuit voltage evolution curve as a function of the state of charge of the rechargeable battery and / or of an open-circuit voltage hysteresis observed between a discharge phase and a charging phase and / or of an influence on this evolution curve of a temperature of the rechargeable battery and / or of an aging of the rechargeable battery;

[0019] - also in the presence of the first option, in its stage, one can estimate the first error depending further on an estimated error on the first determined voltages;

[0020] - also in the presence of the first option, in its stage, one can estimate the first error depending also on a statistical distribution of rechargeable battery uses of systems similar to the system considered and / or on a rechargeable battery usage profile by a user of the system considered;

[0021] - in its step, the second error can be estimated as a function of an estimated error based on a measurement of the current flowing through the rechargeable battery;

[0022] - in its step, the minimum load state variation can be determined from of a function that defines the chosen precision of the estimated capacity and that is defined by multiplying by one hundred the difference between a product of first and second values ​​and the number 1, this first value being equal to the ratio between the variation of state of charge and the variation of state of charge increased by the first error, and this second value being equal to the second error increased by the number 1.

[0023] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing a method of determining information of the type presented above in a system comprising a rechargeable battery having cells and having first voltages across its cells and a determined open-circuit voltage and a capacity estimated by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during this discharge or recharge phase, to determine information representative of a minimum change in state of charge to estimate the capacity with a chosen accuracy.

[0024] The invention also proposes a determination device for determining information relating to a rechargeable battery forming part of a system, comprising cells and having first voltages across its cells and a determined open-circuit voltage and an estimated capacity by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during this discharge or recharge phase.

[0025] This information determination device is characterized by the fact that it includes at least one processor and at least one memory arranged to perform the operations consisting of determining information representative of a minimum charge state variation to estimate the capacity (and therefore also the SOHC) with a chosen accuracy, as a function of at least a first estimated error on the charge state variation and a second estimated error on the quantity of ampere-hours.

[0026] The invention also proposes a system comprising, on the one hand, a rechargeable battery having cells and having first voltages across its cells and a determined open-circuit voltage and a capacity estimated by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during this discharge or recharge phase, and, on the other hand, an information determination device of the type of that presented above. Brief description of the figures

[0027] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0028] [Fig. 1] schematically and functionally illustrates an example of an embodiment of a vehicle comprising a powertrain with an electric drive unit powered by a a rechargeable cellular battery associated with a battery calculator, and an information determination device according to the invention,

[0029] [Fig.2] schematically and functionally illustrates an example of the realization of a battery calculator comprising an information determination device according to the invention,

[0030] [Fig.3] schematically illustrates an example of an algorithm implementing an method for determining information according to the invention, and

[0031] [Fig.4] schematically illustrates within a diagram an example of curves evolution, for five different SOC errors (in %), of the error (or accuracy in %) of SOHC of a rechargeable cellular battery as a function of the variation of state of charge of this same rechargeable cellular battery. Detailed description of the invention

[0032] The invention aims in particular to propose a method for determining information, and an associated information determination device DD, intended to allow the determination of information ivec representative of a minimum charge state variation ASOCmin for a rechargeable battery BR equipping a system S and comprising CE cells responsible for storing electrical energy.

[0033] In what follows, system S is considered, by way of non-limiting example, to be a motor vehicle, such as a car, as illustrated in [Fig. 1]. However, the invention is not limited to this type of system. It relates to any type of system comprising at least one rechargeable cellular battery. Thus, it relates to vehicles (land, sea (or river), and air), mobile equipment (including those that perform a lifting function), electronic devices (possibly household appliances and / or possibly mobile), fixed or stationary installations (possibly industrial), such as electrical power supply installations, and buildings, for example. By way of purely illustrative example, the rechargeable cellular battery BR of a system S can be connected to a renewable energy source (in particular photovoltaic or wind).

[0034] Furthermore, in what follows, by way of non-limiting example, system S (here a vehicle) is considered to comprise a powertrain (or PWM) of the all-electric type (and therefore whose propulsion is ensured exclusively by at least one electric motor). However, the PWM could be of the hybrid type (thermal and electric) or purely thermal.

[0035] Furthermore, in what follows, the BR cellular rechargeable battery is considered, by way of non-limiting example, to be a main (or traction or power) battery. But the cellular rechargeable battery that is the subject of the estimates information could be a service battery (possibly rechargeable via a converter powered by electrical energy from a main battery).

[0036] A system S (here a vehicle) comprising an electric GMP transmission chain, an on-board network RB, a power supply group comprising a service battery BS and (here) a CV converter associated with a rechargeable cellular battery BR (itself associated with a battery computer CB), and an information determination device DD according to the invention, has been schematically represented in [Fig.1].

[0037] The RB on-board network is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0038] The auxiliary battery BS is responsible for supplying electrical power to the vehicle's electrical system RB, supplementing that supplied by the CV converter powered by the rechargeable cellular battery BR, and sometimes replacing this CV converter (particularly when the engine is off and the CV converter is inactive). For example, this auxiliary battery BS can be configured as a very low voltage type battery (typically 12 V, 24 V, or 48 V). It is rechargeable at least by the CV converter. In the following, for the sake of non-limiting example, the auxiliary battery BS is considered to be a 12 V lithium-ion type.

[0039] The transmission system has a powertrain which, in this case, is purely electric, and therefore includes, in particular, an electric drive machine MME, a drive shaft AM, and a transmission shaft AT. The term "electric drive machine" here refers to an electric machine arranged to supply or recover torque to move the system S (here, a vehicle). The operation of the powertrain is supervised by a control unit CS.

[0040] The electric drive unit MME (here an electric motor) is coupled to the rechargeable cellular battery BR, in order to be supplied with electrical energy, and also possibly to supply this rechargeable cellular battery BR with electrical energy (for example, during a regenerative braking phase). It is coupled to the motor shaft AM, to provide it with torque by rotational drive. This motor shaft AM is here coupled to a reduction gear RD which is also coupled to the transmission shaft AT, itself coupled to a first set of wheels Tl, preferably via a differential DI.

[0041] This first train Tl is here located in the front part PVV of the vehicle S. But in a variant this first train Tl could be the one which is here referenced T2 and which is located in the rear part PRV of the vehicle S.

[0042] The MME drive machine is, here, also coupled to the CV converter which is also indirectly coupled to the BS auxiliary battery, in particular to recharge it with electrical energy from the BR rechargeable cellular battery and converted.

[0043] This CV converter is an electrically coupled current converter, here, for example, to a CN charging connector of vehicle S. It is also responsible for supplying the on-board network RB with electrical energy from the rechargeable cellular battery BR, converted when the engine is running or when the engine is asleep but vehicle S is charging its rechargeable cellular battery BR, in addition to charging the auxiliary battery BS.

[0044] For example, the BR cellular rechargeable battery may comprise CE electrochemical energy storage cells. Also, for example, each CE (electrochemical energy storage) cell may be of the lithium-ion (or Li-ion) type. However, this is not mandatory. Indeed, it could be of the Ni-MH or Ni-Cd type, for example. Also, for example, the BR cellular rechargeable battery may be of the low-voltage type (typically 450 V or 600 V, by way of illustration). But it could also be of the medium-voltage or high-voltage type.

[0045] It should be noted, as illustrated (though not exhaustively) in [Fig. 1], that the CE cells can be part of MC modules which are coupled together, for example in series, within the BR rechargeable cellular battery. Here, "MC module" means a group of at least one CE cell. When an MC module comprises several CE cells, these cells (CE) can be connected together in series and / or in parallel.

[0046] It should also be noted that the BR cellular rechargeable battery is associated with a BB battery case which includes, in particular, means for measuring voltage, current and internal temperature (not illustrated) and the CB battery calculator. The latter (CB) centralizes the current measurements, the determined voltage measurements (and in particular the first ucl voltages across the terminals of the different CE cells), the measurement of the current through the BR cellular rechargeable battery, the measurement of the open circuit voltage (or equilibrium voltage) OCV of the BR cellular rechargeable battery, and the internal temperature measurements (in particular those relating individually to each of the CE cells).Furthermore, the CB battery calculator can estimate parameters of the BR cellular rechargeable battery based on these measurements, including its internal resistance, minimum voltage, current state of charge (SOC), current capacity (CC), and estimated capacity health (SOHC).

[0047] It is recalled that the current capacity DC is equal to the ratio between the quantity of ampere-hours AQ supplied in a discharge phase or received in a recharge phase of the rechargeable cellular battery BR and the change in state of charge ASOC during that same discharge or recharge phase, and that the state State of Health Capacity (SOHC) is equal to the current DC capacity divided by the initial Cini capacity (i.e., at the beginning of the rechargeable battery's life), or SOHC = CC / Cini. Currently, the degradation of a battery's current DC capacity (and therefore also its SOHC) is subject to error, which can lead to an overestimation or underestimation of battery performance.

[0048] The change in state of charge ASOC is therefore determined by subtracting two states of charge SOC1 and SOC2 obtained respectively at two different times t1 and t2 of a discharge phase or a recharge phase of the rechargeable cellular battery BR, i.e. ASOC = SOC2 - SOC1. Preferably, these two times t1 and t2 are chosen in a life phase in which the rechargeable cellular battery BR is relaxed (sufficiently long period without supply or receipt of current (typically on the order of one hour at 25°C)).

[0049] It should also be noted that in the example illustrated, but not limited to, in [Fig. 1], the vehicle S also includes a distribution box BD to which the auxiliary battery BS, the CV converter, and the on-board network RB are coupled. This distribution box BD is responsible for distributing the electrical energy produced by the CV converter or stored in the auxiliary battery BS into the on-board network RB to power the electrical components (or equipment) connected to the on-board network RB, according to power demands received (in particular from the powertrain control unit CS).

[0050] As mentioned above, the invention proposes in particular a method for determining information intended to allow the determination of an ivec information which is representative of a minimum charge state variation ASOCmin for the BR cellular rechargeable battery.

[0051] This method (of information determination) can be implemented at least partially by the information determination device DD (illustrated in Figures 1 and 2), which for this purpose comprises at least one processor PR1, for example a digital signal processor (or DSP), and at least one memory MD. This information determination device DD can therefore be implemented in the form of a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software").

[0052] The MD memory is random access memory (RAM) for storing instructions for the implementation by the PR1 processor of at least part of the information determination process. The PR1 processor may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is defined as any type of device capable of performing at least one electrical or electronic operation.

[0053] In the example illustrated, but not limited to, Figures 1 and 2, the DD information determination device is part of the CB battery computer (and therefore, in this case, of the BB battery housing). However, this is not mandatory. Indeed, the DD information determination device could comprise its own dedicated computer, which could then be coupled to the CB battery computer, for example.

[0054] As illustrated non-limitingly in [Fig.3], the method (of determining information), according to the invention, comprises a step 10-20 which is implemented in the system S (here a vehicle) whenever a determination of the information ivec, representative of a minimum state of charge variation ASOCmin, is requested, for example by the battery computer CB (but this could be requested by the supervisory computer CS or by a server that can access the system S via radio waves).

[0055] This step 10-20 includes a substep 20 in which information is determined (for example, by the information determination device DD) which is representative of a minimum state-of-charge variation ASOCmin, allowing the current capacity CC (and therefore also the state of health in terms of capacity SOHC) to be estimated with a chosen accuracy (or error) SOHC err (for example, as a percentage (%)). This determination is made based on at least a first error e1 estimated on the state-of-charge variation ASOC and a second error e2 estimated on the quantity of ampere-hours AQ.

[0056] It is important to note that the ivec information can be equal to the minimum state of charge variation ASOCmin or can only be representative of the latter (ASOCmin). This ivec information is then used by the CB battery computer, in particular to estimate the current capacity (and therefore also the state of health in terms of SOHC capacity).

[0057] By taking into account potential errors that may affect the calculation of the DC current capacity (and therefore also the SOHC capacity health status), and at least the AQ ampere-hour quantity and the ASOC state of charge variation, it is now possible to impose rules for choosing the ASOC state of charge variation that advantageously guarantee a coverage rate in accuracy of the estimated SOHC with a chosen (or target) SOHC error accuracy. This provides better accuracy in estimating the DC current capacity (and therefore also the SOHC capacity health status), which allows for better use of the electrical energy stored in the BR cellular rechargeable battery, without risk of interruption or failure. Furthermore, this increases the lifespan of the BR cellular rechargeable battery while statistically respecting the warranty offered by the manufacturer of the system S.

[0058] It will be noted that step 10-30 may include, as illustrated non-limitingly in [Fig.3], a substep 10 in which one (for example the information determination device DD) can estimate at least the first error el as a function of at least one error OCV err estimated on the determined open-circuit voltage OCV (which is a function of the current state of charge SOC of the rechargeable cellular battery BR (OCV = f(SOC))).

[0059] In this case, in this substep 10, one (for example, the information determination device DD) can estimate the error OCV err on the determined open-circuit voltage OCV as a function of:

[0060] - of a linearity of the evolution curve of the open-circuit voltage OCV as a function of the state of charge SOC of the rechargeable battery BR (i.e., OCV = f(SOC)), and / or

[0061] - of a hysteresis hocv of the open-circuit voltage OCV observed between a discharge phase (OCVch) and a recharge phase (OCVdc), and / or

[0062] - of the influence on this evolution curve OCV = f(SOC) of the temperature of the BR cellular rechargeable battery and / or aging of the BR cellular rechargeable battery.

[0063] Preferably, all the variables mentioned above are taken into account, as this allows for the greatest accuracy in the estimated OCV error. However, it is possible to take into account only one or more of the variables mentioned above.

[0064] It should also be noted that in substep 10, the first error el can be estimated (for example, by the information determination device DD) as a function of an estimated error on the first voltages ucl determined across the different CE cells. This latter error is known internally because it is specific to the sensors that measure the voltages of the different CE cells. This allows for greater accuracy in estimating the first error el.

[0065] It should also be noted that in substep 10, one (for example, the information determination device DD) can estimate the first error el based also on a statistical distribution of cellular rechargeable battery usage patterns in systems similar to system S and / or a usage profile of the cellular rechargeable battery BR by the user of system S. This statistical distribution of usage patterns and / or this usage profile can be transmitted wirelessly to system S by a server. This also allows for greater accuracy in estimating the first error el, and even greater accuracy in estimating the first error el when the error estimated on the first voltages ucl is also taken into account.

[0066] It should also be noted that in substep 10 (or in another dedicated substep of step 10-20) one (for example, the information determination device DD) can estimate the second error e2 as a function of an error that is estimated on the measurement of the current flowing through the rechargeable cellular battery BR. This latter error is known internally because it is specific to the sensor that measures the current going in or out of the BR cellular rechargeable battery.

[0067] It should also be noted that in substep 20, one (for example, the information determination device DD) can determine the minimum state of charge variation ASOCmin from a function f(ASOC, el, e2) which defines the chosen accuracy (or error) SOHC err of the health state in estimated capacity SOHC and which is defined by multiplying by one hundred the difference between a product of first vl and second v2 values ​​and the number 1, i.e. SOHC err = f(ASOC, el, e2) = 100*[(vl*v2) -1]. In this case, the first value vl is equal to the ratio between the state of charge variation ASOC and the state of charge variation ASOC increased by the first error el, i.e. vl = ASOC / (ASOC + el). Also in this case, the second value v2 is equal to the second error e2 increased by the number 1, i.e. v2 = e2 +1.We then have, in expanded form, SOHC err = f(ASOC, el, e2) = 100*[( ASOC / (ASOC + el)*(e2 + 1)) -1],

[0068] It will be understood that by using the inverse function (SOHC err) 1 = f '(ASOC, el, e2) we (for example the information determination device DD) can obtain curves of evolution of the variation of the state of charge ASOC as a function of the chosen accuracy (or error) SOHC err for different values ​​of the first el and second e2 errors, of the type illustrated as an example in [Fig.4]. Then, we (for example the information determination device DD) can determine from these evolution curves the minimum variation of the state of charge ASOCmin, according to the initially defined requirements.

[0069] In the diagram in [Fig. 4], the box in the upper right corner indicates the types of points and / or lines used to differentiate the curves corresponding to five different ASOC state of charge variation values. A position above the evolution curves indicates an overestimation of the current DC capacity (or the SOHC capacity state of health), while a position below the evolution curves indicates an underestimation of the current DC capacity (or the SOHC capacity state of health). It should be noted that overestimating the current DC capacity (or the SOHC capacity state of health) implies that the BR rechargeable cellular battery can still be used even though it is physically near the end of its life.

[0070] It should also be noted that the determination of the minimum charge state variation ASOCmin can depend on (or guide the) choice of the two instants t1 and t2 at which the two charge states SOC1 and SOC2 are determined respectively, allowing the charge state variation ASOC to be obtained.

[0071] It should also be noted that the driving information of each vehicle S can be transmitted wirelessly by the vehicle (S) to a server, then stored in a database for dedicated analysis to determine when must be carried out in this vehicle S a determination of the ASOC state of charge variation. Thus, when such a determination of the ASOC state of charge variation must be carried out in a vehicle S, the server sends to the latter (S) a message indicating the need to make an internal determination of the ASOC state of charge variation, preferably deep, and of the quantity of ampere-hour AQ associated, to improve the accuracy coverage of the current DC capacity (and therefore also of the SOHC capacity health status).

[0072] It will also be noted, as illustrated non-limitingly in [Fig.2], that the battery calculator CB (or the dedicated calculator of the information determination device DD) may also include a mass memory MM1, in particular for the temporary storage of the states of charge SOC1 and SOC2 (or the corresponding variation of the state of charge ASOC), the quantity of ampere-hours AQ, the determined open-circuit voltage, the current capacity CC (and therefore also the state of health in capacity SOHC), the current value of each variable participating in the estimation of the first or second error, the measurements of voltage, current and possibly internal temperature, and any intermediate data involved in all its calculations and processing.Furthermore, this CB battery calculator (or the dedicated calculator of the DD information determination device) may also include an IE input interface for receiving at least the SOC1 and SOC2 charge states (or the corresponding ASOC charge state variation), the AQ ampere-hour quantity, the determined open-circuit voltage, the current capacity CC (and therefore also the SOHC capacity health state), the current value of each variable involved in estimating the first or second error, voltage, current and possibly internal temperature measurements, for use in calculations or processing, possibly after shaping and / or demodulating and / or amplifying them, in a manner known per se, by means of a PR2 digital signal processor.Furthermore, this CB battery calculator (or the dedicated calculator of the DD information determination device) may also include an IS output interface, notably for delivering IVEC information.

[0073] It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the type of electronic circuits (or hardware), such as for example the PR1 processor, is suitable for implementing the information determination process described above to determine an ivec information representative of a minimum charge state variation ASOCmin to estimate the current capacity CC (and therefore also the state of health in capacity SOHC) of the BR rechargeable cellular battery of the S system.

Claims

Demands

1. A method for determining information relating to a rechargeable battery (BR) forming part of a system (S), comprising cells and having determined first voltages across said cells and open-circuit voltage and an estimated capacity by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during that discharge or recharge phase, characterized in that it comprises a step (10-20) in which information representative of a minimum change in state of charge is determined to estimate said capacity with a chosen accuracy, as a function of at least a first estimated error on said change in state of charge and a second estimated error on said quantity of ampere-hours.

2. Method according to claim 1, characterized in that in said step (10-20) said first error is estimated as a function of at least one estimated error on said determined open-circuit voltage.

3. Method according to claim 2, characterized in that in said step (10-20) said error on the open-circuit voltage is estimated as a function of a linearity of a curve of evolution of said open-circuit voltage as a function of a state of charge of said rechargeable battery (BR) and / or a hysteresis of said open-circuit voltage observed between a discharge phase and a recharge phase and / or an influence on said curve of evolution of a temperature of said rechargeable battery (BR) and / or an aging of said rechargeable battery (BR).

4. Method according to claim 2 or 3, characterized in that in said step (10-20) said first error is estimated further as a function of an error estimated on said first determined tensions.

5. A method according to any one of claims 2 to 4, characterized in that in said step (10-20) said first error is estimated further based on a statistical distribution of uses of rechargeable batteries of systems similar to said system (S) and / or a usage profile of said rechargeable battery (BR) by a user of said system (S).

6. A method according to any one of claims 1 to 5, characterized in that in said step (10-20) said second error is estimated as a function of an error estimated on a measurement of current through said rechargeable battery (BR).

7. A method according to any one of claims 1 to 6, characterized in that in said step (10-20) said minimum state of charge variation is determined from a function which defines said chosen accuracy of the estimated capacity and which is defined by a multiplication by one hundred of a difference between a product of first and second values ​​and the number 1, said first value being equal to the ratio between said state of charge variation and said state of charge variation increased by said first error, and said second value being equal to said second error increased by the number 1.

8. Product computer program comprising a set of instructions which, when executed by processing means, is suitable for implementing the information determination method according to any one of claims 1 to 7, in a system (S) comprising a rechargeable battery (BR) having cells and having determined first voltages across said cells and an open-circuit voltage and a capacity estimated by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during that discharge or recharge phase, to determine information representative of a minimum change in state of charge to estimate said capacity with a chosen accuracy.

9. A determination device (DD) for determining information relating to a rechargeable battery (BR) forming part of a system (S), comprising cells and having determined initial voltages across said cells and an open-circuit voltage, and an estimated capacity by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during that discharge or recharge phase, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to perform the operations of determining information representative of a minimum change in state of charge to estimate said capacity with a chosen accuracy, as a function of at least a first estimated error on said variation of state of charge and a second estimated error on said quantity of ampere-hour.

10. System (S) comprising a rechargeable battery (BR) having cells and having determined first voltages across said cells and open-circuit voltage and a capacity estimated by dividing a quantity of ampere-hours supplied in a discharge phase or received in a recharge phase by a change in state of charge during that discharge or recharge phase, characterized in that it further comprises a determination device (DD) according to claim 9.

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