WO2006024802A1

WO2006024802A1 - Method for determining the state of an electrochemical battery and device for carrying out the same

Info

Publication number: WO2006024802A1
Application number: PCT/FR2005/002146
Authority: WO
Inventors: Benoit Soucaze-Guillos; Matthieu Treguer; Antoine De Monts De Savasse
Original assignee: Valeo Equipements Electriques Moteur
Priority date: 2004-08-26
Filing date: 2005-08-26
Publication date: 2006-03-09
Also published as: FR2874701B1; FR2874701A1

Abstract

The invention relates to a method for determining the state of an electrochemical battery, forming part of an electrical system on a motor vehicle, comprising in addition to a battery (2), at least one controllable source of electrical energy (1) and electrical energy users (3), comprising the application (E1 ) of a variation with time (DG) of voltage or current applied to the battery terminals (2), measuring (E3) the response of the battery (B) and to calculate the state of the battery (Etat_Batt) as a given function (f1 )) which is dependant on said variation (DG), said response (B) and the temperature (Tbat) of the battery.

Description

"Method for evaluating the state of an electrochemical battery and implementation device"

Field of the invention

The invention relates to a method for evaluating the state of an electrochemical battery, belonging to an electrical network, in particular an onboard network of a motor vehicle, comprising in addition to the battery, at least one source of controlled electric energy. and consumers of electrical energy.

The present invention also relates to an implementation device which makes it possible to signal and also to regulate the charging device of the battery for the operation of the onboard network of the motor vehicle. The invention makes it possible to remedy situations in which the state of the battery is critical, as in the case of modern motor vehicles where more and more safety equipment is supplied with electrical energy.

State of the art

Several methods for evaluating the state of an electrochemical battery are already known in the state of the art. A method exploits the weighing of the liquid electrolyte of the battery but remains complex to set up, and is not applicable in the case of a gelled or absorbed electrolyte battery. The comparison between the weighing of the electrolyte and a predefined theoretical value makes it possible to determine the qualitative state of the battery. Another drawback is that it is necessary to redefine the comparison value used for each type of battery, because each battery has an electrolyte of its own. Another method exploits a mapping of a characteristic of the battery but it is heavy to implement and requires a large memory size for the computing unit. For example, the evaluation of the state of the battery is obtained by comparison between the measured current delivered by the battery during normal operation of the motor vehicle and a theoretical value read on the characteristic mapping of the battery. This method only applies to one type of battery in particular since a battery corresponds to a map of its own. In addition, the mapping does not take into account the aging of the battery.

Another method exploits the measurement of impedance of the battery in the frequency domain. Only it is complex, expensive and requires a frequency generator and frequent registration.

There are also methods of testing the condition of an electrochemical battery, known as "high current test methods" and "low current test methods", by which an operator can measure, as a verification , this state of the battery. Only such verification has no impact on the electrical system of the motor vehicle and it is not implementable within the electrical system. The defect of this method is that the test device is a module external to the onboard network of the motor vehicle and therefore it does not use the electrical architecture already present in the motor vehicle. In addition, this method is only for signaling the state of the battery, it has no influence on the systems related to the battery, such as the battery charging device.

In US-B1-6.515.456 is described a system for the maintenance and charging of a battery connected to the onboard network comprising a controlled alternator. The document teaches using an open-circuit voltage measurement of the battery to estimate the state of charge before each resumption of activity following an extended stop. Only one disadvantage of such a method is that a significant measurement of the open circuit voltage is very difficult to obtain, which distorts the evaluation of the state of charge SOC. Therefore, the teaching of this document is reliable only when the battery is new.

Object of the invention

The present invention provides a remedy for these disadvantages of the state of the art. Indeed, the invention relates to a method of the kind recalled above, which is applicable to all batteries, which is achievable in a simple, realistic and economical manner including the use of electrical elements already present in the electrical network and which is capable of providing the necessary control parameters for the battery charging device.

An advantage of the method is to allow the evaluation of the state of the battery in situ, that is to say during its actual operation when connected to the on-board vehicle network. Another advantage of the method is to dispense with the management of battery maps that has been used until now.

Another advantage of the invention is to simplify the management of the battery state by resorting to a binary type implementation. Indeed, for the management of the battery charging device, one does not need to know precisely the state of the battery. In one embodiment of the method, it would be useless to indicate to the user that the battery is in an intermediate state, if this state does not guarantee the proper electrical operation of the motor vehicle. The invention also relates to an implementation device that makes it possible to reduce the cost of the electrical system by using the existing components in the electrical architecture of the vehicle. automobile. The establishment of the device according to the invention is therefore inexpensive.

Another advantage of the invention is that the method is applicable to any type of electrochemical batteries. Another advantage is that the device according to the invention can be implemented in different types of motor vehicle electrical systems. These systems include single-voltage and dual-voltage systems, and combined systems in which the same electrical machine serves as alternator or starter or electric traction motor.

To this end, the present invention relates to a method for evaluating the state of an electrochemical battery.

The state variable of an electrochemical battery provides information on SOC state of charge and / or SOH health status. The state of charge SOC of an electrochemical battery is representative of the ratio to an effective and / or initial charge of the electric charge stored by the electrochemical battery. The state of charge SOC can be modified by an electric charging procedure using a source of electrical energy such as an alternator or by the current consumption on the on-board network by a consumer such as the heated seat of a vehicle. Knowledge of the state of charge SOC allows in particular to control and regulate the charge of the battery and control the operation of the various consumers connected to the onboard network. The state of health SOH of an electrochemical battery is representative of its degree of aging, that is to say its state of wear. The battery wear factors are, in addition, the temperature, the voltage variations at the terminals of the battery and the operation at the intermediate state of charge. For example, the state of health SOH can be defined as the ratio of the effective capacity of the electrochemical battery to the nominal capacity of the electrochemical battery. The method according to the invention consists in applying, for a predetermined duration, to the battery terminals a variation of an electrical quantity, such as a variation of voltage or current, linked to the battery, and to evaluate the response. an electrical quantity, such as a variation in voltage or current, related to the battery and comparing this response with an electrical reference quantity, such as a voltage or a current, in order to determine the state of the drums. The method also consists in taking into account only the pairs of values for which the temperature of the combination of the battery, the starter chain and the internal combustion engine is homogeneous, ie that all the components of this association has the same overall temperature.

The method according to the invention is executed at each start of the motor vehicle, and is executed periodically during normal operation of said motor vehicle.

The method of the invention comprises three steps: a step of applying a temporal variation of an electrical quantity applied to the battery; A step of determining the response of an electrical quantity related to the battery; and

A step of calculating a state variable as a function of the temporal variation and the response related to the battery.

The invention also relates to a device for evaluating the state of an electrochemical battery when it is connected to the electrical network of a motor vehicle said network. This network consists of a source of electrical energy such as an alternator, an electrochemical battery and electrical consumers such as the starter, the lighting, etc. The invention also relates to an implementation device which comprises means for regulating a charging device of the battery. The invention also relates to an implementation device which comprises means for signaling the state of the battery.

Brief description of the drawings

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which follows, with reference to the appended drawings among which:

FIG. 1 illustrates, in flowchart form, a first embodiment of the method according to the invention;

FIG. 2 schematically represents the edge network to which the method according to the invention is applied; FIG. 3 represents a flowchart describing an embodiment of the method for evaluating a state of health component SOH of the state variable of the electrochemical battery;

FIG. 4 represents a flowchart describing another embodiment of the method for evaluating a state of charge component SOC of the state variable of the electrochemical battery;

- Figure 5 shows a flowchart describing another embodiment of the method according to the invention by processing voltage profiles, consecutive to a temporal variation applied to the battery as the solicitation of the starting device;

FIG. 6 is a graph representing the voltage profiles resulting from the application of a strong load on the largest consumer of the on-board network such as the starter;

- Figure 7 illustrates, schematically, another embodiment of the method according to the invention. Description of embodiments of the invention

FIG. 1 represents, schematically, a first embodiment of the method for evaluating the state of an electrochemical battery when it is connected to at least one electrical network of a motor vehicle called an onboard network. This network consists of a source of electrical energy, such as an alternator, alternator-starter or a voltage converter, a battery and consumers or electrical loads such as a starter, lighting, heated seats, the device wiper, the heater of the rear window of the vehicle to defrost it, the air conditioning device and the braking device of a motor vehicle ....

The presence or absence of these consumers depending on the degree of equipment of the vehicle.

In Figure 1, there is shown an embodiment of the method which comprises mainly three steps.

In a first step E1, a predetermined time variation DG of an electrical quantity G connected to the electrochemical battery is executed for a predetermined duration Dt. In a first example, the electrical quantity G is the voltage measured at the terminals of the battery. This DG time variation is then performed during the normal operation of the vehicle by the source of electric power controlled, such as an alternator. In a second example, the electrical quantity G is the current flowing through the electrochemical battery. This DG time variation is then performed at the start of the motor vehicle by one of the largest consumer of the onboard network, such as the starter or the heated seats, or the heating device of the rear window of the motor vehicle.

In a second step E3, the response of the on-board network to the variation DG of the first step E1 is evaluated on the basis of the measurement of an electrical quantity B related to the operation of the electrochemical battery as the voltage at the terminals of the battery, Ub, or as the current passing through the electrochemical battery Ib.

In a third step E4, a state variable of the state_Batt battery is evaluated on the basis of a function f1 determined, dependent on the temporal variation DG, of the corresponding response B according to a relation of the form: Etat_Batt = f1 ( DG, B). The function f1 is determined in advance. It is stored in a memory of the device which implements the method of the invention with the aid of a computer executing the predetermined function f1.

In one embodiment, the determined function f1 also depends on the temperature Tbat of the battery. In an exemplary embodiment, the electrochemical battery of the vehicle is equipped with a temperature sensor which returns the temperature measurement information Tbat to a computer, such as a microcontroller, executing the predetermined function f1 which then takes the regular form: State_Batt = f1 (DG, B, Tbat).

In another embodiment of the method according to the invention, in a further step E2 inserted between the steps E1 of the application of a temporal variation DG and E3 of the measurement of the response B, the method consists in eliminating the transients of the power supply, the battery, the electrical consumers of the on-board electrical network and the switching of loads resulting from the application of the DG time variation at the terminals of the battery when the transient responses do not provide information on the state of the battery. This additional step E2 consists, for example, in delaying the beginning of the measurement step E3 while waiting for the end of the disturbed states of the network. In a variant, the delay is constituted by a predetermined predetermined period.

The knowledge of the State_Batt state variable of the electrochemical battery makes it possible to ensure a correct recharge of the electrochemical battery according to said variable State_Batt state of the electrochemical battery. This knowledge makes it possible to prevent the on-board system from operating in a cant, which happens when the power supply, such as an alternator or a voltage converter, no longer supplies the necessary electrical energy to the consumers of the transmission network. edge. The operation of the on-board on-board network degrades the electrochemical battery.

FIG. 2 schematically represents the edge network to which the method according to the invention is applied. The on-board network is an electrical network composed of an electrical energy source 1, an electrochemical battery 2 and consumers or electrical charges 3. The consumers 3 and the energy source 1 are connected to the positive terminal of battery. This figure also shows the connections to the ground of the consumers 3, the source 1 and the battery 2. The device of the invention comprises a unit 4, called BMS (battery management system), battery management 2, a unit 5, called LMU (Load Management Unit), of the management of the loads of the on-board network, a computing unit 6, such as a microcontroller, of the state variable of the battery 2, which implements the method of the invention, optionally a signal unit 7 of the state of the battery 2 and a clock 16.

The electrical consumers 3 comprise for example at least one of the following consumers: starter, heated seats, air conditioning system compressor, electric motor of the power steering, heating device of the rear window of the vehicle.

The electric power source 1 supplies electricity to the on-board network to supply electrical energy to the electrical consumers 3 and to allow charging of the battery 2 which stores the electrical energy. The calculation unit 6 comprises an input-output management unit 9, which allows the exchange of information between the unit 4 and the calculation unit 6 of the state_Batt state variable of the battery 2, said information concerning the current 13 flowing in the battery 2, the voltage 14 measured at the terminals of the battery 2, the temperature 15 of the battery, said information being denoted respectively Ib, Ub and Tbatt in the embodiment of FIG.

In one embodiment, the I / O management unit 9 comprises means for interpreting a request 12 for executing the evaluation method of the State_Batt state variable of the battery 2.

In one embodiment, the management unit 9 is connected to a clock 16 in order to synchronize the execution of the method of evaluating the state of the battery 2 on the clock 16, so that the method of evaluation of the State_Batt variable is performed periodically.

The computing unit 6 also comprises a unit 8 comprising a memory of a program implementing the method according to the invention, in particular allowing the execution of the function f1 for calculating the battery state and produces a signal representative of the state of the battery, such as SOC state of charge and / or SOH health state thereof.

The calculation unit 6 also comprises a register 10 storing the state of charge variable of the battery, said register being connected to the battery management unit 4 as well as to the signaling unit 7 when the latter is connected to the battery management unit 4. this is present.

The calculation unit 6 also comprises a register 11 storing the state of health variable SOH of the battery, said register being connected to the signaling unit 7 when it is present.

As will be understood, the permanent presence of the signaling unit is not essential. Indeed this one can consist of a diagnostic device that is connected on site during a maintenance session on at least one of the registers 10, 11 to have a display on the state of the battery, that is to say a signaling of the state of the battery. Alternatively this diagnostic device is in the network of the car manufacturer, the information being transmitted remotely over the phone. As a variant, the signaling unit is on board the vehicle and the display of the state of the battery is indicated on the driving position.

The computing unit 6 comprises means for controlling electrical devices of the on-board network, such as the electric power source 1, to implement the method of the invention. In particular, said unit 6 drives the source of electrical energy 1 so that it produces, as in FIG. 1, a time variation DG during a determined duration Dt. In one embodiment, the computing unit 6 is distributed over computing resources, such as microcontrollers, already existing on the motor vehicle such as the engine control computer of the vehicle and the microcontrollers, for example from the source of the engine. power supply, as the alternator transforming as we know the mechanical energy into electrical energy.

In one embodiment, the electric power source 1 comprises a polyphase alternator, for example three-phase or hexaphase, comprising a voltage regulator as described for example in the document EP 0 802 464 to which reference will be made for more details.

As is known, a conventional alternator, cooled by water or by air, comprises a casing intended to be mounted on a fixed part of the vehicle, a stator mounted inside the casing comprising at least one front bearing and a bearing. rear, a rotor mounted within the stator, a shaft rotatably mounted by its axial ends respectively in the front bearing and the rear bearing each with for example a ball bearing for this purpose. The rotor is for example a claw rotor having two pole wheels between which is mounted the excitation coil as described for example in EP A 0 515 259 describing an alternator with internal ventilation. In a variant, the rotor has salient poles around each of which is mounted an excitation winding as described in document WO 02/054566.

The rotor is secured to the shaft and therefore comprises at least one excitation winding, constituting an inductor winding enabling when it is electrically powered to create magnetic poles on the rotor and a current induced in the stator.

The ends of this excitation winding are connected by wire links to two slip rings belonging to the rear end of the rotor shaft adjacent to the rear bearing of the housing. The front end of this shaft, adjacent to the front bearing housing, carries a drive member, such as a pulley, intended to be driven via a transmission device, for example by belt, by the engine of the vehicle. Brushes rub on the slip rings. These brushes are carried by a brush holder and are electrically connected to the voltage regulator usually carried by the rear bearing housing, alternatively placed in a housing mounted outside the alternator. Alternatively the alternator is brushless and the excitation coil is fixed so that these ends are electrically connected to the voltage regulator.

The presence of slip rings is not required.

The stator comprises a body, advantageously in the form of a pack of sheets mounted in the housing. This stator body is grooved for carrying phase windings mounted for example in a star or in a triangle and connected to a rectifying device, such as a diode bridge in the case of an alternator or a bridge of MOSFET type transistors in the case of an alternator, said alternator-starter, operating in a reversible manner and thus also making it possible to transform electrical energy into mechanical energy in order to drive the shaft integral with the rotor. Such an alternator-starter is described for example in document FR A 2,745,445, the rectifier operating in the inverter when the alternator-starter operates in electric motor mode. The unit 6, in one embodiment, takes advantage of the control and control module, which this alternator-starter presents, in particular to drive the gates of the MOSFET transistors using signals. Unit 6, in this embodiment, is associated with this module, which has a microcontroller so that we take advantage of this microcontroller.

The rectifier device rectifies the induced alternating current produced in the DC stator so as to deliver a DC voltage to the battery and to the onboard network. The function of the voltage regulator is to keep the voltage of the alternator substantially constant at all engine speeds, even in the case of a large variation of the alternator load.

The output of the rectifier is connected to the voltage regulator for regulating the excitation current of the excitation coil. This excitation current is regulated in all or nothing or numerically as described in the aforementioned EP A 0 802 464 document comprising a microcontroller. For this purpose, this type of regulator comprises a pulse width modulation control means which drives the current and / or the output voltage, for example by means of a MOS switch arranged in series with the winding. excitation of the inductor rotor The voltage regulator makes it possible to deliver a substantially constant electromotive force and advantageously comprises, as described in the aforementioned document EP A 0 802 464, a control stage electrically connected to a computer, for example that of the control vehicle engine, and a power stage for amplifying the signals delivered by the control stage and applied thereto the excitation coil or inductor winding of the rotor.

The unit 6 advantageously takes advantage of this configuration, in particular the microcontroller of this regulator being associated with it.

According to the invention, the calculation unit 6 controls the voltage regulator in order to achieve a DG time variation of an electrical quantity related to the operation of the battery as a voltage step in one embodiment of the invention.

Thus the implementation of the voltage variation of the battery is achieved through the controlled controller.

In another embodiment, the electric power source 1 comprises a DC / DC voltage converter. According to the invention, the calculation unit of the state variable 6 modifies the transformation coefficient of the DC / DC converter during a predetermined short duration Dt in order to achieve a DG time variation of an electrical quantity related to the operation of the battery, preferably in the form of an overvoltage step in one embodiment of the invention.

Thus the implementation of the voltage variation of the battery is achieved through the DC / DC converter.

In another embodiment, the electric power source 1 is an alternator-starter. The alternator-starter is an electrical machine that provides the combined functions of alternator, operation in current generator mode, including starter, operation in electric motor mode. In some cases, the alternator-starter makes it possible to suppress the conventional starter and to achieve a silent and rapid start of the heat engine fitted to the vehicle. Of course alternatively a starter can be associated with the alternator-starter for a start in extreme conditions, for example cold weather, the engine of the vehicle. As aforesaid, this alternator-starter is an alternator operating in a reversible manner.

In a first embodiment of this alternator-starter to the constitution of a conventional alternator supra, its rectifying device being for example constituted by a bridge of MOSFET type transistors. Thus one can inject current into the windings of the stator to operate the alternator in electric motor.

For more details, see for example the document FR A 2,745,445 mentioned above. In the aforementioned manner, the microcontroller that the alternator / starter control and control unit uses to control the transistors when the alternator-starter operates in an electric motor mode, in particular to start the engine of the motor vehicle. In another embodiment, as described in the document US Pat. No. 6,561,336 to which reference will be made, the alternator-starter is associated with the clutch of the motor vehicle, its rotor being integral with the flywheel, possibly in two parts for to form a double damping flywheel. The alternator-starter in all cases operates as an electric motor to start the engine of the vehicle and can be used to restart the engine for example after a stop at red light.

In this case, the microcontroller, which comprises the alternator-starter and acting on the rectifying device, for example a MOSFET-type transistor, is used to function either as an electric motor for starting the vehicle engine or as a current generator. ie as a power source. Thus the implementation of the voltage variation of the battery is achieved through the alternator-starter. In another embodiment, this alternator / starter is designed to perform other functions, for example to perform an assistance function to prevent the engine of the vehicle from stalling for example at idle speed, this function being said function boost. It can perform a training function to temporarily move the vehicle for example during parking maneuver. It can function as an auxiliary electric motor for example to drive the compressor of the air conditioning system when the vehicle is stationary at a red light, engine stopped, as described for example in WO 02/060711. These various combinations of functions are used in particular in the realization of a strategy of "stop and go" which will be detailed further with the aid of FIG. 8, knowing that the alternator-starter advantageously comprises a microcontroller for passing from the alternator mode of operation to the mode of operation in the electric motor mode, in particular to start the engine of the vehicle.

Of course, in a variant, the vehicle is a vehicle of the hybrid type and comprises, in known manner, a heat engine and an electric motor for driving respectively outside the city and in the city. In this case the electric motor is the biggest consumer.

In a current generating mode, this alternator-starter, which is a combined machine, transforms the mechanical energy into electrical energy to supply electricity to the electrical consumers 3 and the electrochemical battery 2 which stores the electrical energy. Here, the computing unit 6 will act on the microcontroller of the alternator-starter to realize a time variation DG, Dt of an electrical quantity related to the operation of the battery, such as an overvoltage step in an embodiment of the invention. invention, and the computing circuit 6 of the invention will establish the state of charge SOC of the battery. In a mode of consumption, starter mode or electric motor mode, the alternator-starter transforms the electrical energy available on the on-board network into mechanical energy to start the engine or drive the vehicle. Here, the calculation unit of the state variable 6 will act on the microcontroller of the alternator-starter to achieve a time variation DG, Dt of an electrical quantity related to the operation of the battery as a circuit in a embodiment of the invention and the calculation circuit 6 of the invention will establish the state of health SOH of the battery.

The unit 4 of management of the battery 2 receives from sensors, advantageously present on the on-board network, measurement values of electrical quantities representative of the operation of the devices of the on-board network such as the current and the voltage of the source of power. electrical energy 1 and electrical consumers 3, and also receives a measurement value of the temperature Tbatt of the battery 2. In one embodiment of the method, the unit 4 comprises means for controlling the electric power source 1 for the charging procedure of the electrochemical battery 2.

In one embodiment of the invention, the computing unit 6 evaluates the state of health SOH. The health status information SOH is transmitted to the signaling unit 7, optionally, for displaying and / or testing at a predetermined critical situation. In turn, the signaling unit 7 sends a warning message of sound or light type for example on the diagnostic device or on the driving position of the vehicle.

As a variant, the health status information SOH is transmitted to a maintenance device which is connected to the computing unit 6 during a maintenance session for the display of the information. In another embodiment of the invention, the state variable calculating unit 6 evaluates the SOC state of charge. The electrochemical battery management unit 4 controls the source for electrical energy 1 for the electrochemical battery charging procedure 2. In this case, the on-board network load management unit 5 drives the consumers 3 during their operation. Unit 5 is a unit that discharges loads from the on-board electrical network.

In one embodiment, the load management unit 5 of the on-board network discharges charges, with the engine running, when the network is in a slope, ie when the power supply source 1 no longer has sufficient power. energy to meet the needs of the onboard network. When the engine is idle and the energy balance of the network is negative, the unit 5 comprises a means for raising the idle level and raise the level of the charging current delivered by the electric power source 1. If this is not enough, it proceeds to load shedding according to a preestablished order of preference.

In another embodiment, the on-board network load management unit 5, by reducing the consumption of the consumers, limits the current drawn into the battery. Examples of reduction of consumption include the wiper control at minimum speed and the reduction of the sound level of the car radio.

In another embodiment, the unit 5 gradually cuts the consumers on the vehicle to arrive at a minimum consumption level during the final stop of the vehicle.

FIG. 3 represents a flowchart describing an embodiment of the method for evaluating the state of the electrochemical battery 2, where the state variable of the battery comprises the only health state component SOH. The state of health SOH of the battery informs about the degree of aging of the battery, and is reported, through the signaling unit 7, present permanently or not. We understand that the user only needs information whether the battery is in good health or not. It does not need to know the intermediate states that do not guarantee absolutely good operation of consumers especially the starter. The SOH health status evaluation method is performed at each start of the motor vehicle for homogeneous temperatures. Indeed, the object of the method is to solicit the electrochemical battery by one of the largest consumer of the network, such as the starter or the heating device of the rear window, and to determine the response of the battery to this solicitation so to evaluate the state of health SOH.

In one embodiment, the method according to the invention consists in correlating the responses, consecutive to two starts under identical conditions, from the on-board network to a DS power demand using one of the largest consumers connected to the on-board network, such as the starter or the heating device of the rear window of the motor vehicle. The method thus tests the response of the battery to the most stringent demand of the network. Thus, the method consists, for each startup, in storing in a memory the voltage response of the electrochemical battery for a next evaluation of the state of health SOH. The voltage response thus stored constitutes a history. The SOH health status assessment is thus obtained by comparing the current response to a DS solicitation with the history. This history has a predetermined duration. For example after 18 months we consider that the battery is no longer new. Likewise after a certain number of kilometers of the vehicle, the battery is considered to be new. This history is therefore done after a time T, for example 18 months, and / or a certain number of kilometers for example 20000. There is an evolution during the period of break-in of the vehicle and at the end of its life. vehicle with starter wear and connecting cables. The parameter measured is the voltage across the battery and the consumer.

The voltage drop under identical conditions makes it possible to establish the degree of aging of the battery. Between two start-ups performed under similar conditions, the difference between the voltage profiles will therefore be mainly related to the evolution of the battery state variable.

Knowing these parameters before the starter stroke makes it possible to estimate a second parameter by comparing the voltage profiles. Thus, two start-ups in similar conditions with a fully charged battery make it possible to follow the evolution of its state of health SOH.

The recent battery history is updated with each SOH health assessment. The recent history is replaced by the last response in voltage following the application to the terminals of the battery of a DS solicitation of the largest consumer of the onboard network.

Thus, in a first step A1, the method consists in applying to the terminals of the battery a high DS load of one of the largest consumers of the electrical network, such as the starter or the heating device of the rear window of the motor vehicle.

In a second step A2, the electrochemical battery management unit acquires the voltage at the terminals of the battery and stores the information obtained in memory. The information is then transmitted to the calculation unit of the battery state variable which analyzes the voltage profile across the electrochemical battery. The analysis of the voltage profile makes it possible to draw up a list of characteristic parameters of the voltage signal. These parameters prevent electrochemical battery failure 2. The characteristic parameters are: - the initial charge voltage of the battery before starting Vinit;

the minimum voltage reached by the battery Vmin;

- the average voltage across the battery Vmoy on the first moments of startup (between 10ms and 1 s); the frequency of the ripple Background generated on the instantaneous voltage of the battery, its average value Fmoy and its amplitude Aond, for example in first harmonic;

- the start time Td;

the number of compressions Nc of the engine of the vehicle at start-up.

The voltage profile at the terminals of the battery is therefore characterized by an analysis vector VA whose components are the parameters mentioned above such that VA = (Vinit, Vmin, Vmoy, Background, Fmoy, Aond, Td, Nc). Step A2 is therefore a step of recording and extracting the data.

In a third step A3, the unit for calculating the battery state variable correlates a history of the VA analysis vector (history) of the electrochemical battery 2 with the analysis vector VA (measured). determined and stored in memory during step A2. The history of the analysis vector VA (history) of the electrochemical battery 2 is obtained during the learning phase of the voltage response of the electrochemical battery.

The evolution of the VA analysis vector into operating phases makes it possible to establish the degree of aging of the battery or state of health SOH. The unit for calculating the state variable of the battery 6 determines the variations of each component DVAi of the variation DVA of the analysis vector VA (measured) with respect to its history VA (history). Signaling a critical variation of one of these parameters therefore makes it possible to establish the degree of aging of the battery and to warn the driver of a future failure of the battery. The electrochemical battery management unit measures the temperature T of the electrochemical battery. The unit for calculating the battery state variable contains a program that performs a SOHi state evaluation function g for each characteristic parameter, ie for each DVAi component, such as:

SOHi = [g (DVAi, DS, T)> SOH_SEUILi] where SOH_SEUILi is a predetermined threshold for each variation DVAi and where SOHi is a value which is worth 1 if the state of health relative to the parameter i of the vector VA considered is critical and 0 otherwise.

Then, a combination function of the calculated SOHi values makes it possible to establish the state of health SOH of the electrochemical battery.

In a step A4, in response to a critical state of health SOH, the signaling unit 7 warns by an alert message of the poor state of the battery. Thus, a failure of the battery will be reported, in one embodiment of the method, by means of a sound or light signal.

FIG. 4 represents a flowchart describing another embodiment of the method for evaluating the state of the electrochemical battery 2, where the state of the battery indicates the state of health SOC of the battery.

The method according to the invention makes it possible to determine whether the battery is charged or not. The charged state of the battery is predetermined. This information is essential in the case of systems where the battery management strategy aims to have a permanently charged battery.

Indeed, the state of charge SOC is a regulation parameter of a charging device of the battery. So the necessary information regarding the state of charge SOC is whether the battery charge is sufficient or not, in order to start or not the charging process of the battery. The process ensures a correct charging, avoiding overload and under load, thanks to the controlled controller and the knowledge of the temperature of the battery. The method makes it possible to inform the driver or the various computers on board of the state of charge and health of the battery, which makes it possible to privilege a fast recharge of the battery by increasing the voltage of the on-board network.

The method of evaluating the state of charge variable SOC is periodically performed during the normal operating mode of the motor vehicle.

A first step A'1 consists of applying a first voltage variation across the battery, particularly a voltage step DU. In a first embodiment, the implementation of the voltage variation is carried out thanks to a controller controlled in the case of an alternator described with reference to FIG.

In another embodiment, the implementation of the voltage variation is carried out thanks to the DC / DC converter in the described with reference to FIG. 2. In another embodiment, the implementation of the variation of voltage is achieved thanks to the control electronics in the case of an alternator-starter with reference to FIG.

As a result of the voltage step DU applied to the battery, transients occur at the power supply, the battery, the consumers and the load switching. For specific measures, permanent regimes must be achieved. Thus, the method comprises a step A'2 for eliminating the transient conditions. In one embodiment, the elimination of the transients is performed by a filtering device or a delay device. Thus, in steady state, the electricity grid is comparable to a resistive circuit and reacts linearly. We thus established the following relations: Vconso = Rconso * Iconso DVconso / DIconso = Rconso DVconso / Vconso = Dlconso / lconso

Where Vconso is the voltage across consumers, Iconso, the current crossing consumers and Rconso consumer resistance. DVconso and Dlconso are respectively the relative variations of the voltages across consumers and the relative variations of currents passing through consumers.

Thus, the knowledge of these parameters and the current delivered by the electric power source 1 make it possible to calculate the current flowing through the battery.

Next, the method according to the invention comprises a step A'3 of evaluation of the current response of the battery which will serve as reference R. The determination of the current is carried out thanks to the unit of calculation of the variable of state of the battery, which in knowledge of the currents delivered by the alternator and electrical consumers can determine the current through the battery. The values of these currents are obtained thanks to the sensors already present in the motor vehicle so that we do not add sensors on the on-board network. The index response is stored in memory. In steady state and according to the law of meshes, the current, passing through the battery, is determined in knowledge of the current delivered by the source of electrical energy 1 and the current used by the electrical consumers with reference to FIG.

Ibat = IaIt - Iconso and therefore Dlbat = DIaIt - Dlconso.

A good knowledge of the electrical characteristics of the onboard network makes it possible to calculate Dlconso with precision and thus Dlbat. In one embodiment of the method, and particularly in the case where the system comprises a DC / DC converter or a combined machine such as an alternator-starter, the current delivered by the alternator is known and is calculated by an abacus: IaIt = f (lexc, NaIt, TaIt) where lexc is the excitation current with: lexc = f (DF), and NaIt is the rotation speed of the alternator and TaIt the temperature of the alternator. The determination of the current IaIt is carried out for a temperature TaIt within a predetermined temperature range.

Then, we repeat the steps A'1, A'2 and A'3 a second time. Thus, there are two battery current index responses, one of which serves as a reference R. A step A'4 consists of evaluating the relative variation of the battery current, taking as a reference the first measured index response and thereafter consists of evaluating SOC state of charge.

The battery management unit determines the temperature T of the battery and transmits the information to the calculation unit of the battery state variable.

The calculation unit of the battery state variable comprises means for implementing the method for calculating the state of charge SOC on the basis of a function h such that: SOC = [h (DI, DU , T)> SOC_seuil].

In this embodiment, the state of charge SOC is therefore a boolean parameter which is equal to 0 if the battery is discharged and 1 otherwise, thanks to the predetermined choice of a SOC_Seuil parameter.

The SOC state of charge information is then transmitted to the battery management unit BMS 4 which drives the battery charging device. The method according to the invention therefore comprises a step A'5 for controlling the charging device of the battery. This SOC information is essential to ensure a good charge of the battery by avoiding any overload and under load, ie to avoid any overvoltage or undervoltage at the terminals of the battery. FIG. 5 represents, in flowchart form, in one embodiment of the method according to the invention, the procedure for processing the voltage profiles, consecutive to a temporal variation applied to the battery as the solicitation of the starting device. This embodiment relates to the evaluation of the state of health SOH of an electrochemical battery 2. In a step D1, the method consists in acquiring the voltage profile subsequent to the solicitation, via the BMS unit. battery management 4.

In a step D2, the method consists in analyzing and evaluating the various parameters of the voltage profile. In this, the calculation unit of the state variable 6 comprises means for detecting the various parameters of the voltage profile.

In a step D3, the method consists in establishing an analysis vector VA (measured) consisting of the parameters determined during step D2.

In a step D4, the method consists in analyzing the relative variations of the vector VA (measured) with respect to its history VA (history) previously determined during the learning phase of the state of health SOH and stored in memory. A relative variation of one of the components of the analysis vector VA (measured) indicates a battery failure and thus makes it possible to determine the state of health variable SOH of the battery in a step D5.

A step D6 consists, in case of critical state of health, of controlling the signaling unit 7 which warns the driver of the poor state of the battery.

FIG. 6, with reference to FIG. 3, describes the characteristic signals of the voltage profiles consecutive to the application. at the terminals of the battery a strong demand of the largest consumers of the onboard network such as the starter. Each voltage profile is defined by its analysis vector VA whose components are described above. These components are evaluated by the unit of calculation of the battery state variable and are as in Figure 4,

• The initial battery voltage before starting Vinit;

• The minimum voltage reached by the battery Vmin;

• The average battery voltage Vmoy on the first moments of the start (between 10ms and 1 s);

• The frequency of the ripple Fund generated, its average value Fmoy, its amplitude Aond;

• The start time Td;

• The number of compressions Nc of the engine at start-up.

The vector thus obtained for each voltage profile is expressed by the list:

VA = (Vinit, Vmin, Vmoy, Background, Fmoy, Aond, Td, Nc)

Figure 7 describes another embodiment of the method according to the invention. The battery management strategy is always oriented to have a state of charge SOC close to 100% permanently.

In the absence of data making it possible to evaluate the state of charge of the battery, the method according to the invention consists of a configuration in charging mode of the battery until having a relevant information of the state of charge SOC. The charging mode will be set using the battery temperature to prevent overcharging or under load. The application of the SOC state of charge measurement is useful if and only if the measured SOC parameter is not 100% when the engine is running. A first step CO consists in checking whether the engine of the motor vehicle is running, that is to say whether the engine is in phase "Go" or not.

In phase "Go", a step C1 checks whether the state of charge SOC of the electrochemical battery is greater than a minimum state of charge SOC_min predefined.

If the state of charge SOC is lower than a minimum state of charge SOC_min, the method according to the invention executes a step C3 charging procedure of the battery. Once the charging procedure is completed, the method according to the invention returns to step CO possibly after a delay step.

If the state of charge SOC is greater than a minimum state of charge SOC_min, the method switches to monitoring mode of the on-board network, in a step C2, where the method according to the invention monitors, in a step C4, whether the voltage of the network U_network is greater than a minimum voltage of the network of U_eaueau_min and the efficiency of the energy source, that is to say for example if the excitation rate of the inductor coil that includes the rotor alternator or alternator-starter, is different from 100%. Of course, it is also possible to monitor the voltage of the energy source, such as the voltage of the alternator, and this, in a variant, in combination with the aforementioned excitation rate.

If these conditions are not verified, the method executes a step C5 which consists of a step taking advantage of the LMU (Load Management Unit).

More specifically, step C5 is implemented by the LMU load management unit. In one embodiment, the load management unit discharges charges, with the engine running, when the battery is in an overhang (a source of energy such as the alternator or alternator-starter not delivering enough) and provides current to the onboard network. It can, for example when the engine is idling and the load balance is negative, raise the level of idling and raise the level of the flow of the electric generator, that is to say for example of the alternator or the alternator-starter. If this is not enough, it proceeds to load shedding according to a pre-established order of preference.

The load management unit reduces the consumption of the electrical consumers so that the voltage of the network network U_network increases and become greater than a minimum voltage of the network network U_network_min. The method according to the invention performs again a step of checking the network voltage U_network and the efficiency of the energy source in a step C6.

If U_Network becomes greater than U_Network_min, then the method according to the invention returns to step CO. In the opposite case, the method according to the invention returns to step C5.

If the heat engine is considered to be non-rotating and is thus in the "Stop" phase, in a step C7, the method according to the invention executes an "LMU" phase in a step C8 using the management unit of the loads. During an "LMU" phase, the load management unit minimizes the load on consumers to limit the current drawn in the battery, for example by wiping ice wipes at minimum speed, by correcting the sound level of the car. radio.

The method comprises performing the aforementioned steps as long as a predetermined time limit, following a measurement of the duration of time TD in a step C11, is not reached. If the time limit is reached (step C12), the method triggers the restart step C13, that is, restarting the heat engine (Go phase).

If the heat engine is considered to be non-rotating and not in the Stop phase, in step C7, the method consists of a stop step C14 and then a long-term step C15 LMU. Step C15 is to gradually cut the consumers on the vehicle to reach a minimum consumption level when the vehicle is abandoned.

It is clear that the invention applies to the management of more than one battery operating independently or concurrently on the on-board network.

It will be appreciated that the battery (s) may be remote from the power source.

For example, the battery is in an embodiment implanted in the trunk or under one of the seats of the motor vehicle. This is made possible by the fact that the measuring step E3 is preceded by a step E2 of elimination of the transient states. It will also be appreciated that the temporal variation of the electrical quantity during step E1 is carried out in a discrete manner and that the consumer used during the step of switching on at least one electricity consumer is not necessarily the starter.

Claims

1. Method for evaluating the state of an electrochemical battery (2), connected to an on-board network of a motor vehicle, comprising in addition to the battery (2), at least one source of electrical energy (1) , electrical consumers (3), at least one battery management unit (4), a management unit (5) of the on-board network charges (5) and a calculation unit (6) of a variable d state of the battery, characterized in that it comprises three steps: a step (E1) of applying a temporal variation (DG, Dt) of an electrical quantity applied to at least one terminal of the electrochemical battery; ; - A step (E3) for determining the response of an electrical quantity (B) related to the electrochemical battery; A step (E4) for calculating a representative variable (Batch_State) of the state of the electrochemical battery on the basis of a determined function (f 1) of the temporal variation (DG), of the response (B) related thereto; to the electrochemical battery

2. Method according to claim 1, characterized in that the step of applying (E1) a temporal variation (DG) of an electrical quantity comprises a step of applying an overexcitation of the energy source electrical (1) connected to the onboard network so that a predetermined overvoltage is produced across the battery (2) for a predetermined time.

3. Method according to claim 2, characterized in that the step of applying (E1) a temporal variation (DG) of an electrical quantity comprises a step of applying an overexcitation of the energy source electrical (1) connected to the on-board network by controlling the output voltage of a voltage regulator of the electric power source (1).

4. Method according to claim 2, characterized in that the step of applying (E1) a temporal variation (DG) of an electrical quantity comprises a step of applying an overexcitation of the energy source electrical connector (1) connected to the on-board network by controlling at least one output voltage of a DC-DC voltage converter.

5. Method according to claim 1, characterized in that, during the step (E4) of calculation, an evaluation of the temperature

(Tbatt) of the battery is carried out, then an evaluation function f1 is determined on the basis of a relation State_Batt = f1 (DG, B, Tbatt).

6. Method according to claim 1, characterized in that the calculation step (E4) comprises a step of calculating, as the state of the battery, the state of charge SOC according to a relation SOC = [h ( B, DG, T)> SOC_seuil], h being a predetermined function, preceded by a step (E3) for determining the battery response B in the form of an estimation / calculation of the current flowing through the battery, where (SOC_seuil ) is a predetermined threshold for which a SOC state of charge value higher than said threshold defines a SOCcharged state of charge.

7. Method according to claim 1, characterized in that the measuring step (E3) of an electrical response quantity of the battery is preceded by a step (E2) of elimination of the transient states.

8. Method according to claim 1, characterized in that the step of applying a variation of electrical magnitude comprises a step of switching on at least one consumer of electricity on the on-board network for a predetermined duration (dt).

9. Method according to claim 8, characterized in that the measuring step (E3) of an electrical response quantity of the battery comprises a step of measuring the voltage across the battery and that the step (E4) comprises a step of calculating, as a state of the battery, the state of health SOH according to a relation SOH = [g (B, DG, T)> SOH_seuil] where g () is a predetermined function and where (SOH_seuil) is a predetermined threshold for which a health state value SOH greater than said threshold defines a critical state of health SOH.

10. The method of claim 9, characterized in that the step (E3) for measuring the voltage at the terminals of the battery also comprises a step for constituting a history of the measurements of the voltage at the terminals of the battery during previous starts. .

11. Method according to Claim 7, characterized in that the step (E3) for measuring the voltage at the terminals of the battery also comprises a step for constituting an analysis vector (VA) comprising at least one of the quantities derived from the profile of voltage.

12. The method of claim 11, characterized in that the step (E4) for calculating the state of health SOH comprises a step for forming a difference between the analysis vector (VA (measured)) measured and a vector. analysis (VA (history)) deduced from the history, then a step to perform a predetermined test (g)) of at least one of the differences values to deduce the aging of the battery.

13. The method as claimed in claim 1, characterized in that it comprises, during the step (E4) of calculating the state of the battery, a step for determining trigger thresholds and a step for determining test results. at least a part of the values measured during the step (E3) so that at least part of the function (f1) for determining the state of the battery is of Boolean type.

14. Apparatus for implementing the method according to claim 1, of the kind intended to be mounted on a vehicle having an electrical network on board including at least one power source (1), electrical consumers (3) as a starter or an electric motor, an electrochemical battery (2) whose state is to be monitored, a management unit (5) of the onboard network loads, a unit (6) for calculating a state variable of the battery and a management unit (4) of the battery (4) in particular for controlling the state of charge of the battery and the switching on of the consumers as well as the state of the energy source, characterized in that it also comprises: a plurality of means for estimating or measuring a variation of an electrical quantity (DG) applied across the terminals of the electric battery and / or the response of an electrical quantity (B) connected to the electrochemical battery; - a computing unit (6) provided with means for controlling the source of electrical energy (1) so that said variation of an electrical quantity (DG) is produced, means for deriving a state of the battery (SOC, SOH) on the basis of said applied electrical magnitude variation (DG), said electrical response (B) and the temperature T of the battery (2) by performing a determination function (f1)).

15. Device according to claim 14, characterized in that the computing unit (6) is also provided with means for controlling the battery management unit (4) according to the determination of the state of the battery (SOC, SOH).

16. Device according to claim 15, characterized in that the means for controlling the calculation unit (6) comprises means for determining the state of charge during a restart strategy of the vehicle.

RECTIFIED SHEET (RULE 91) ISA / EP