ANALYSIS OF CELL(S) SELF-DISCHARGE IN A CELLULAR BATTERY

Abstract

A method allows for the analysis of a cellular battery equipping a system and comprising at least one electrical energy storage cell, by which voltage measurements are taken across its terminals. This method includes a step (10⁻⁷⁰) in which, for each cell, first and second information values ​​are determined as functions of first and second voltage measurements taken at first and second instants occurring after a first duration has elapsed following the cessation of current flow and just before the next current flow in the cellular battery. A third piece of information representing self-discharge is determined as a function of a subtraction between the first and second determined information values ​​when the time difference between these first and second instants exceeds a chosen threshold. Figure 3

Description

Title of the invention: ANALYSIS OF THE SELF-DISCHARGE OF CELL(S) IN A BATTERY CELL Technical field of the invention

[0001] The invention relates to cellular batteries comprising at least one electrical energy storage cell, and more specifically to the analysis of such cellular batteries. State of the art

[0002] Some systems, such as for example certain vehicles (possibly automobiles), include a cellular battery, comprising at least one cell suitable for storing electrical energy, and in which an electric current (discharge or recharge) can flow.

[0003] It should be noted that such a cellular battery generally comprises many cells (usually electrochemical) arranged within modules.

[0004] It should also be noted that in a vehicle, the cellular battery is generally coupled to at least one electric drive unit of the powertrain (or powertrain), in order to supply it with electrical energy so that it can produce torque to move the vehicle. It is understood that during such a power supply, the cellular battery discharges. Such a cellular battery is generally called the "main" (or "traction" or "power") battery.

[0005] As those skilled in the art know, for safety reasons it is necessary to monitor the electrical, thermal, and possibly electrochemical states of the cellular battery and, if possible, of each of its cells. To do this, the state of charge and / or health and self-discharge are determined or estimated, in particular, from direct or indirect measurements, using software (or a program) running in the computer associated with the cellular battery.

[0006] The invention relates more particularly to the analysis of cellular self-discharge. The concept of self-discharge describes the fact that the state (or level) of charge of an unused cell gradually decreases. In fact, depending, in particular, on the manufacturing parameters, the use, and the thermal exposure of the battery cell, each cell can experience a greater or lesser increase in its self-discharge level during its battery life. For a given cell, the effect of self-discharge can be modeled as a short-circuit current caused by a self-discharge resistor connected in parallel with that cell.

[0007] The self-discharge level of a cell is an indicator of its health. If the self-discharge becomes too high, the cell should no longer be used. concerned for security reasons.

[0008] Currently, the self-discharge of a cell is estimated from the value of the aforementioned self-discharge resistance or the aforementioned self-discharge current (flowing through it). The higher the self-discharge level, the lower the self-discharge resistance and the higher the self-discharge current. However, for an electrochemical cell with an open-circuit voltage of approximately 4 volts, the value of the self-discharge resistance is approximately 500 ohms for a self-discharge current of approximately 8 mA. Therefore, it proves very difficult to measure the effect of a current diverted in parallel by a few milliamperes on cells, even though these cells are capable, in operation, of supplying a current exceeding 100 A to an electric motor. Consequently, with prior art methods, it proves very difficult to estimate the self-discharge of a cell with good accuracy.

[0009] The invention therefore aims in particular to improve the situation. Presentation of the invention

[0010] In particular, it proposes for this purpose an analysis method intended to allow an analysis of a cellular battery suitable for equipping a system and comprising at least one electrical energy storage cell, subject to voltage measurements at its terminals.

[0011] This analysis method is characterized by the fact that it includes a step in which, for each cell, the following is determined:

[0012] - of the first and second information functions respectively of first and second voltage measurements taken respectively at first and second instants occurring after the elapsed time following the end of a current flow and just before the next current flow in the cellular battery, and

[0013] - a third piece of information representative of a self-discharge as a function of a subtraction between these first and second determined pieces of information, when a time difference between the first and second moments is greater than a chosen threshold.

[0014] Thanks to the invention, we now have a third piece of information (representative of cellular self-discharge) that is quite precise, and above all significantly more precise than what is permitted by the methods of the prior art.

[0015] The analysis method according to the invention may include other features which may be taken separately or in combination, and in particular:

[0016] - in a first embodiment, in its stage, the first and second in formations of each cell can each be a state of charge which is determined according to a voltage measurement;

[0017] - in the presence of the first option, in its step, it is possible to determine, for each cell, each state of charge as a function of an electromotive voltage of the cell concerned, itself determined as a function of a corresponding voltage measurement;

[0018] - in the presence of the last sub-option, in its step, it is possible to determine, for each cell, each electromotive voltage also depends on an internal temperature measured in the vicinity of the cell concerned;

[0019] - also in the presence of the last sub-option, in its step, one can de to conclude, for each cell, each electromotive voltage as a function of an estimated state of health of the cell concerned;

[0020] - in a second embodiment, in its step, the first and second in formations can be respectively the first and second tension measurements;

[0021] - in its step one can determine a self-discharge rate which is equal to a ratio between the third piece of information determined and the time gap.

[0022] The invention also proposes a computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing an analysis method of the type presented above, in a system comprising a cellular battery including at least one electrical energy storage cell, the voltage of which is measured at its terminals, in order to determine at least one cellular self-discharge.

[0023] The invention also proposes an analysis device intended to be part of a system comprising a cellular battery including at least one electrical energy storage cell, subject to voltage measurements at its terminals.

[0024] This analysis device is characterized in that it comprises at least one processor and at least one memory arranged to perform the operations consisting, for each cell, of determining:

[0025] - of the first and second information functions respectively of first and second voltage measurements taken respectively at first and second instants occurring after the elapsed time following the end of a current flow and just before the next current flow in the cellular battery, and

[0026] - a third piece of information representative of a self-discharge as a function of a subtraction between these first and second determined pieces of information, when a time difference between the first and second moments is greater than a chosen threshold.

[0027] The invention also proposes a system comprising, on the one hand, a cellular battery including at least one electrical energy storage cell, the voltage of which is measured at its terminals, and, on the other hand, an analysis device of the type presented above.

[0028] For example, this system may constitute a vehicle, possibly of the automobile type. In this case, the vehicle may also include at least one electric drive unit capable of being powered by the cellular battery. Brief description of the figures

[0029] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0030] [Fig.1] schematically and functionally illustrates an example of an embodiment of a vehicle comprising an analysis device according to the invention and a powertrain with an electric drive unit associated with a battery assembly comprising a cell battery and a battery box with an interface device and battery computer,

[0031] [Fig.2] schematically and functionally illustrates an example of an embodiment of a battery calculator comprising an example of an analysis device according to the invention, and

[0032] [Fig.3] schematically illustrates an example of an algorithm implementing an analysis method according to the invention. Detailed description of the invention

[0033] The invention aims in particular to propose an analysis method, and an associated DA analysis device, intended to allow in particular the determination of the self-discharge adcn of each CEn cell of a BC cellular battery equipping a system S.

[0034] In what follows, the 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. Indeed, BC cellular batteries can be part of any system, and in particular vehicles (land, sea (or river), or air), electronic devices (possibly household appliances), mobile machinery (including those that perform a lifting function), installations (possibly industrial), and buildings, for example.

[0035] Furthermore, in what follows, by way of non-limiting example, system S (here a vehicle) is considered to comprise a powertrain with an all-electric power unit (or PMU) (and therefore whose drive is provided exclusively by at least one electric motor). However, the PMU could be of the hybrid type (thermal and electric).

[0036] Figure 1 schematically represents a system S (here a vehicle) comprising a DA analysis device, a power supply system, a transmission chain to electric GMP (here) (and therefore to electric motive machine MME), a CS supervisory computer, an RB on-board network, a BS service battery, a CV converter, and an EB battery assembly comprising a BC cellular battery and a BB battery box comprising a DI interface device and a CB battery computer.

[0037] The power supply system includes a main electrical circuit connected to a CH charger, comprising an AC charger computer as well as here a CV converter, the electric drive machine MME, and (here) a CR power connector.

[0038] 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.

[0039] 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 cellular battery BC via the main electrical circuit, and sometimes replacing this CV converter. For example, this auxiliary battery BS may 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.

[0040] The main electrical circuit (or "high voltage" or power circuit) is more precisely connected, on the one hand, to the cellular battery BC via the battery box BB (and more specifically its interface device DI), and, on the other hand, to electronic equipment, such as the CV converter and the electric motor MME. It also allows the cellular battery BC to be recharged by an external power source and, for example, temporarily connected to the optional power connector CR. In the example illustrated, but not limited to, in [Fig. 1], the main electrical circuit allows the cellular battery BC to be recharged not only with direct current (or mode 4), but also with alternating current (or mode 2 or 3), under the control of the charger computer CA (of the charger CH) and the battery computer CB (of the battery box BB).However, in unillustrated alternative embodiments, the main electrical circuit might only allow direct current charging (or mode 4) or only alternating current charging (or mode 2 or 3).

[0041] The transmission chain 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. Here, "electric drive machine" means an electric machine arranged to provide torque to move the vehicle S when it is supplied with electrical energy, as well as possibly to recover torque in the transmission chain.

[0042] The operation of the transmission chain (and therefore of the powertrain) is supervised by a CS supervisory computer.

[0043] The electric drive machine MME (here an electric motor) is here coupled to the cellular battery BC via the main electrical circuit and the battery box BB (and more specifically its interface device DI), in order to be supplied with electrical energy, as well as possibly to supply this cellular battery BC with electrical energy, for example during a regenerative braking phase.

[0044] Furthermore, this electric drive machine MME is coupled to the motor shaft AM to supply 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 DF.

[0045] 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.

[0046] The CV converter can also be charged, during the driving phases of the vehicle S, with converting part of the electrical energy stored in the cellular battery BC to supply converted electrical current to the on-board network RB and the auxiliary battery BS (to recharge it).

[0047] It will be noted, as illustrated non-limitingly on [Fig.1] and as indicated above, that the CV converter can be part of the CH charger which also includes the AC charger computer responsible, at least, for controlling the charging of the BC cellular battery.

[0048] The cellular battery BC, which here powers the electric motor MME, constitutes a main (or traction or power) battery. It (BC) comprises at least one cell CEn designed to store electrical energy. It should be noted that in the example illustrated (non-limitingly) in [Fig. 1], the cellular battery BC comprises numerous CEn cells. It should also be noted that in the example illustrated (non-limitingly) in [Fig. 1], the CEn cells are grouped into several modules MC where they are coupled to each other (CEn-1 and CEn) or (CEn and CEn+1) via conductive inter-cell physical connections. During operation (discharge or recharge), a current (discharge or recharge) flows through the cellular battery BC.

[0049] It should also be noted that in the example illustrated, but not limited to, in [Fig. 1], each MC (cellular) module comprises four CEn cells (n = 1 to 4) coupled to one another. However, the number of CEn cells in an MC cellular module can take any value greater than or equal to one.

[0050] It should also be noted that in the example illustrated, but not limited to, in [Fig. 1], the BC cell battery comprises six MC cell modules. However, the number of MC cell modules can take any value greater than or equal to one.

[0051] The interface device DI has, for example, an open (or non-conducting) state in which it prevents the flow of the aforementioned current, and a closed (or conducting) state in which it allows the flow of the aforementioned current. It is therefore arranged so as to isolate, if necessary, the cellular battery BC from the entire main electrical circuit. It includes, in particular, contactors (or switches or relays), possibly based on MOSFET(s), and protective fuses.

[0052] Each cell CEn is subjected to successive measurements of the cell voltage at its terminals ucn when the battery computer CB is woken up. For example, these measurements can be carried out periodically (the period can be between 50 milliseconds and 100 milliseconds, for example).

[0053] For example, CEn cells can be electrochemical. In this case, they can be of the lithium-ion (or Li-ion) or Ni-MH or Ni-Cd type, for example. Also, for example, the BC cell battery can be of the low-voltage type (typically 450 V by way of illustration). But it could also be of the medium-voltage or high-voltage type.

[0054] Furthermore, the cellular battery BC is (here) housed in a battery casing (or enclosure) BB, preferably waterproof, which also houses, in particular, the interface device DI, information acquisition devices (not shown), and the battery calculator CB. For example, the cellular battery BC, the battery casing BB, the interface device DI, the analysis devices, and the battery calculator CB can constitute a battery assembly (or "pack") EB.

[0055] The information-gathering devices are suitable for determining current values ​​of quantities representative of the cells CEn (and in particular their respective cell voltages ucn as well as possibly the internal temperature tin in their vicinity), and communicate with the battery computer CB so that the latter (CB) can receive these determined current values ​​and control the operation of the cell battery BC according to these determined and received current values.

[0056] 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 stored in the auxiliary battery BS or produced by the CV converter 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).

[0057] As mentioned above, the invention proposes in particular an analysis method intended to allow the analysis of the BC cellular battery at least to determine (or estimate) the self-discharge adcn of each CEn cell.

[0058] This (analysis) method can be implemented at least partially by the DA analysis device (illustrated at least partially in Figures 1 and 2), which for this purpose comprises at least one PR1 processor, for example a digital signal processor (or DSP), and at least one MD memory. This DA analysis device can therefore be implemented as a combination of electrical or electronic circuits or components (or "hardware") and software modules (or "software"). For example, it could be a microcontroller.

[0059] The MD memory is random access memory (RAM) to store instructions for the implementation by the PR1 processor of at least part of the analysis process. The PR1 processor may include integrated circuits (or printed circuit boards), or several integrated circuits (or printed circuit boards) connected by wired or wireless connections. An integrated circuit (or printed circuit board) is defined as any type of device capable of performing at least one electrical or electronic operation.

[0060] In the example illustrated, but not limited to, in Figures 1 and 2, the DA analysis device is part of the CB battery control unit. However, this is not mandatory. Indeed, the DA analysis device could comprise its own dedicated control unit, which is then coupled to the CB battery control unit, or it could be part of another control unit embedded in the S system and performing at least one other function.

[0061] As illustrated non-limitingly in [Fig.3], the (analysis) method according to the invention includes a step 10-70 which is implemented each time the CB battery calculator is woken up and is therefore able to obtain the measurement of the voltage ucn of each CEn cell of the BC cellular battery.

[0062] Step 10-70 of the process includes a substep 20 in which, for each cell CEn, the first iln and second i2n information is determined, which are functions respectively of at least the first ucn(tl) and second ucn(t2) voltage measurements taken respectively at a first instant tl occurring after the elapsed time dr following the cessation of current flow in the cell battery BC (instant tfc) and a second instant t2 occurring just before the next current flow in the cell battery BC. Information of the form iln = f(ucn(tl)) and i2n = f(ucn(t2)) is thus determined, with tl - tfc > dr.

[0063] It will be understood that between the end of current flow and the next current flow, there is a state of operation during which the cellular battery BC neither supplies electrical energy to an electrical consumer of the system S (discharge) nor receives electrical energy (recharge). This state of operation can occur, by for example, when the DI interface device is in its open state.

[0064] The minimum time interval dr that must elapse before time tl corresponds to the average time required for the relaxation of the CEn cells. It is considered here that a CEn cell reaches a state of electrochemical and thermal equilibrium after a rest period, that is, without being used. Once relaxed, the CEn cell has a voltage ucn across its terminals that is relatively stable and therefore usable. For example, this time interval dr can be between 15 and 45 minutes.

[0065] Step 10-70 of the process also includes a substep 30 in which, for each cell CEn, a third piece of information i3n is determined, which is representative of its (cellular) self-discharge adcn as a function of the subtraction between the first iln and second i2n determined pieces of information, when a time difference ect between the first t1 and second t2 instants is greater than a first threshold, if chosen. Thus, i3n = iln - i2n is determined, provided that ect (= t2 - t1) > si.

[0066] For example, in substep 30 of step 10-70, the first threshold si can be between 6 and 10 hours. As an illustrative example, this first threshold si can be equal to 8 hours. However, other values ​​for the first threshold si can be used. For example, the value of the first threshold si can be chosen during the system S (or BC cell battery) development phase.

[0067] It should be noted that the instant t2 can be that when the cellular battery BC is woken up within the system S. The battery calculator CB generally has an internal digital clock which allows to determine the time intervals during which it has remained asleep and which corresponds approximately to the rest time ect of the cellular battery BC.

[0068] Thanks to the use of first ucn(tl) and second ucn(t2) voltage measurements carried out at first tl and second t2 instants guaranteeing cellular relaxation and a sufficiently large flow of time to allow a significant self-discharge adcn of each CEn cell, we now have a third piece of information i3n (representative of this self-discharge adcn) that is quite precise, and above all significantly more precise than what is allowed by the methods of the prior art.

[0069] It will be noted that the third determined (or estimated) piece of information i3n can be equal to the self-discharge adcn, or equal to a parameter or index which represents the self-discharge adcn.

[0070] For example, and as illustrated, but not limited to, in [Fig. 3], step 10-70 may also include a substep 10 in which one (for example, the analysis device DA) is informed of the time tfc from which the cell battery BC no longer supplies or receives electrical energy. As indicated previously, this time tfc may be the time when the interface device DI transitions to its open state. Upon receiving this tfc information, one (for example, the DA analysis device) can trigger a first time delay of duration dr. Then, at the expiration of this duration dr (and therefore at time tl), one (for example, the DA analysis device) can record the first voltage measurement ucn(tl), provided that during this duration dr, no current has flowed again in the cellular battery BC. Next, one (for example, the DA analysis device) can trigger a second time delay of a duration equal to the first threshold si, and at the expiration of this duration si, one (for example, the DA analysis device) can record that the minimum waiting time si has elapsed, provided that during this time si, no current has flowed again in the cellular battery BC.

[0071] At least two embodiments can be envisaged for the implementation of the invention.

[0072] In a first embodiment, in substep 20 of step 10-70, the first iln and second i2n information of each cell CEn can each be a state of charge (or SOC (“State Of Charge”)) edcn which is determined (or estimated) based on at least one voltage measurement ucn(tl) or ucn(t2). Thus, in this substep 20, information of the type iln = edcn(ucn(tl)) and i2n = edcn(ucn(t2)) is determined, and in substep 30, a third piece of information i3n of the type i3n = edcn(ucn(tl)) - edcn(ucn(t2)) is determined.

[0073] In the first embodiment, in substep 20 of step 10-70, one (for example, the analysis device DA) can determine, for each cell CEn, each state of charge edcn(tl) or edcn(t2) as a function of an electromotive voltage tecn(tl) or tecn(t2) of the cell CEn concerned, itself determined as a function of a corresponding voltage measurement ucn(tl) or ucn(t2).

[0074] In this case, we therefore determine charge states edcn(tl) and edcn(t2) of the type edcn(tl) = g(tecn(tl, ucn(tl))) and edcn(t2) = g(tecn(t2, ucn(t2))).

[0075] Indeed, when each cell CEn is modeled by an assembly comprising its electromotive voltage tecn in series with an internal resistance rin, and connected in parallel with a self-discharge resistance rad, with only a self-discharge current iad flowing (and therefore neither charging nor discharging), we have the relation tecn = ucn - rin*iad (ucn being here the voltage across the assembly). Since the internal resistance rin is on the order of ten milliohms and the self-discharge current iad is on the order of a few milliamperes, we can then neglect the voltage drop across the resistance rin and arrive at the new relation tecn = ucn.Now, since the electromotive voltage tecn is a first-order function of the state of charge edcn, we deduce that when the cell CEn is in its relaxed state (from the first instant tl), we have the relations edcn(tl) = g(tecn(tl, ucn(tl))) and edcn(t2) = g(tecn(t2, ucn(t2))) where g is the inverse function of the electromotive voltage tecn (i.e. edcn(tl) = . tecn '(ucn(tl)) and edcn(t2) = tecn *(ucn(t2))).

[0076] In the first embodiment, in substep 20 of step 10-70, one (for example, the analysis device DA) can determine, for each cell CEn, each electromotive voltage tecn as a function not only of a voltage measurement ucn(t1) or ucn(t2) but also of the internal temperature tin measured in the vicinity of the cell CEn concerned. Information of the form iln = edcn(t1) = tecn '(ucn(t1), tin(t1)) and i2n = edcn(t2) = tecn *(ucn(t2), tin(t2)) is thus determined. This follows from the fact that the electromotive voltage tecn is also a second-order function of the internal temperature tin.

[0077] Taking into account the internal temperature tin makes it possible to improve the accuracy of the third piece of information i3n.

[0078] It should be noted that the internal temperature tin can be measured at the level of the cell concerned CEn if a temperature sensor is associated with each cell CEn, or the internal temperature tin can be measured at the level of a group of cells CEn if a temperature sensor is associated with each group of cells CEn within an MC module.

[0079] It should also be noted that in the first embodiment, in substep 20 of step 10-70, one (for example, the analysis device DA) can determine, for each cell CEn, each electromotive voltage tecn as a function not only of a voltage measurement ucn(tl) or ucn(t2) but also of the estimated state of health (or SOH) escn of the cell CEn concerned. Information of the type iln = edcn(tl) = tecn '(ucn(tl), escn(tl)) and i2n = edcn(t2) = tecn 1 (ucn(t2), escn(t2)) is then determined.

[0080] It is recalled that the estimated health state escn is representative of the aging of a CEn cell and that it can be taken into account in the law defining the electromotive voltage tecn. The estimated health state escn represents, in fact, the current capacity can (Ah) of a CEn cell relative to the capacity at the beginning of its life cinin (Ah) of that same CEn cell (i.e., escn = can / cinin). It should be noted that the health state escn is generally estimated by the battery computer CB.

[0081] It should also be noted that in the first embodiment, in substep 20 of step 10-70, one (for example, the analysis device DA) can determine, for each cell CEn, each electromotive voltage tecn(tl) or tecn(t2) as a function not only of a voltage measurement ucn(tl) or ucn(t2) but also of the internal temperature tin(tl) or tin(t2) and the estimated health status escn(tl) or escn(t2). Information of the type iln = edcn(tl) = tecn '(ucn(tl), tin(tl), escn(tl)) and i2n = edcn(t2) = tecn *(ucn(t2), tin(t2), escn(t2)) is then determined.

[0082] In a second embodiment, in substep 20 of step 10-70 the first i1n and second i2n information can respectively be the first ucn(t1) and second ucn(t2) are voltage measurements. In this case, we have i1n = ucn(t1) and i2n = ucn(t2), and therefore i3n = ucn(t1) - ucn(t2). Note that in this second embodiment, the third piece of information i3n is less precise than when it is determined (or estimated) according to the first embodiment.

[0083] Also, for example, and as illustrated non-limitingly in [Fig.3], step 10-70 can also include a substep 40 in which one (for example the DA analysis device) can determine for each cell CEn a self-discharge rate tadn which is equal to the ratio between the third determined information i3n and the time gap ect, i.e. tadn = i3n / ect.

[0084] Then, step 10-70 can also include a substep 50 in which the self-discharge rate tadn can be compared to a second threshold s2 chosen for each cell CEn (for example, the DA analysis device). If, for a cell CEn, the self-discharge rate tadn is greater than the second threshold s2 chosen, then in a substep 60 of step 10-70, an alert message can be generated (for example, the DA analysis device can trigger the generation of an alert message) for a user of the system S (for example, the driver in the case of a vehicle).

[0085] When the warning message is intended for the driver, its purpose is to prompt them to have their vehicle S checked as soon as possible at a service center. This is because the cellular battery BC is assumed to need to be checked (and probably repaired or replaced). In this case, the warning message may be delivered by illuminating a warning light on the vehicle S and / or displaying a text message and / or emitting an audible message. The warning light may be part of the vehicle S's instrument panel or displayed on a vehicle S display screen (possibly the central instrument cluster screen mounted on or in the instrument panel). It may be a dedicated warning light or a non-dedicated service light. The text message may be displayed on at least one screen on the vehicle S (for example, the instrument panel or the central instrument cluster) or on the screen of the driver's smartphone.The audio message can be played through at least one speaker in the vehicle S or the aforementioned smartphone.

[0086] On the other hand, if all the self-discharge rates tadn are below the second threshold s2, then the process ends in a substep 70 of step 10-70 because the BC cellular battery can continue to be used normally.

[0087] It should be noted that when using the internal temperature tin, an error in estimating the internal temperatures tin can be taken into account in determining a sufficient margin with respect to the determination of the second threshold (self-discharge) s2 from which the use of the cellular battery BC must be stopped.

[0088] It should also be noted that when using the escn health status, an error in estimating escn health statuses can be taken into account in determining a sufficient margin with respect to the determination of the second (self-discharge) threshold. s2 from which the use of the BC cellular battery must be stopped.

[0089] It should also be noted that it is possible to establish a confidence level for the third determined piece of information i3n (representing self-discharge) as a function of the time difference ect (= t2 - t1), and therefore of the rest time of the BC cell battery. Indeed, the longer the rest time ect, the more reliable the determined self-discharge value adcn will be. This confidence level can, for example, be a confidence index ic. As an illustrative example:

[0090] - if the rest period ect is greater than 30 days, then ic = 100%,

[0091] - if the rest period ect is greater than 20 days and less than 30 days, then ic = 90%,

[0092] - if the rest period ect is greater than 10 days and less than 20 days, then ic = 60%,

[0093] - if the rest time ect is less than 10 days, then ic = 40%.

[0094] Depending on the confidence index ic determined, it is also possible:

[0095] - to exclude certain of the self-discharges determined adcn,

[0096] - to wait until several measures with a low confidence index ic have been taken before making any decisions includes the corresponding ADCN self-discharges,

[0097] - to calculate an average of the self-discharge adcn weighted by the confidence index ic.

[0098] It should also be noted, as illustrated but not limited to [Fig. 2], that the battery calculator CB (or the calculator of the analysis device DA) may also include a mass memory MM1, in particular for storing each voltage measurement ucn, each possible internal temperature tin, and each possible estimated health status escn, as well as any intermediate data involved in all its calculations and processing. Furthermore, this battery calculator CB (or the calculator of the analysis device DA) may also include an input interface IE for receiving at least the voltage measurements ucn, the possible internal temperatures tin, and the possible estimated health status escn, possibly after having shaped and / or demodulated and / or amplified them, in a manner known per se, by means of a digital signal processor PR2.Furthermore, this CB battery calculator (or the DA analysis device calculator) may also include an IS output interface, specifically for generating and delivering each warning message.

[0099] 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 analysis process described above to determine at least the cellular self-discharge adcn in the cellular battery BC of the S system.

Claims

Claims

1. Method for analyzing a cellular battery (BC) suitable for equipping a system (S) and comprising at least one cell (CEn) for storing electrical energy, subject to voltage measurements at its terminals, characterized in that it comprises a step (10-70) in which, for each cell (CEn), i) first and second information are determined as a function respectively of first and second voltage measurements carried out respectively at first and second times occurring after the elapse of a first duration following an end of current flow and just before a next flow of current in said cellular battery (BC), and ii) third information representative of a self-discharge as a function of a subtraction between said first and second determined information, when a time difference between said first and second times is greater than a chosen threshold.

2. Method according to claim 1, characterized in that in said step (10-70) said first and second information of each cell (CEn) are each a state of charge determined as a function of a voltage measurement.

3. Method according to claim 2, characterized in that in said step (10-70) each state of charge is determined for each cell (CEn) as a function of an electromotive voltage of said cell (CEn), itself determined as a function of a corresponding voltage measurement.

4. Method according to claim 3, characterized in that in said step (10-70) each electromotive voltage is determined, for each cell (CEn), as a function, in addition, of an internal temperature measured in the vicinity of said cell (CEn).

5. Method according to claim 3 or 4, characterized in that in said step (10-70) each electromotive voltage is determined for each cell (CEn) as a function, in addition, of an estimated state of health of said cell (CEn).

6. Method according to claim 1, characterized in that in said step (10-70) said first and second information are respectively said first and second voltage measurements.

7. Method according to one of claims 1 to 6, characterized in that in said step (10-70) a self-discharge rate is determined equal to a ratio between said third determined information and said difference temporal.

8. Computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing the analysis method according to one of claims 1 to 7, in a system (S) comprising a cellular battery (BC) comprising at least one cell (CEn) for storing electrical energy, subject to voltage measurements at its terminals, to determine at least one cellular self-discharge.

9. Analysis device (DA) for a system (S) comprising a cellular battery (BC) comprising at least one cell (CEn) for storing electrical energy, subject to voltage measurements at its terminals, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting, for each cell (CEn), in determining i) first and second information as a function respectively of first and second voltage measurements carried out respectively at first and second times occurring after the elapse of a first duration following an end of current flow and just before a next flow of current in said cellular battery (BC), and ii) third information representative of a self-discharge as a function of a subtraction between said first and second determined information,when a time difference between said first and second instants is greater than a chosen threshold.,

10. System (S) comprising a cellular battery (BC) comprising at least one cell (CEn) for storing electrical energy, subject to voltage measurements at its terminals, characterized in that it further comprises an analysis device (DA) according to claim 9.

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