Method for controlling an electrochemical battery on board a motor vehicle

Abstract

The invention relates to a method for controlling an electrochemical battery provided with electrodes comprising lead and an electrolyte comprising sulfuric acid, in particular a low-voltage battery of the order of 12 to 14 volts, the battery being on board a motor vehicle, the method comprising a test step (20) in which at least one parameter is periodically evaluated at a given time interval, referred to as a test period, in order to provide one or more items of information on a state of the battery, in particular a sulfation state, the method further comprising a step (30) of charging the battery using a charging current having a voltage higher than a nominal charging voltage, referred to as an overvoltage charging step, the overvoltage charging step (30) being carried out for a duration set in advance, as a function of the information on the state of the battery.

Description

[0001] Method for controlling an electrochemical accumulator installed on a motor vehicle

[0002] The invention relates to a method for controlling an electrochemical accumulator equipped with electrodes comprising lead and an electrolyte comprising sulfuric acid, in particular a 12V battery, mounted on a motor vehicle.

[0003] Motor vehicles today are equipped with electrical consumers, enabling the starting of a vehicle's engine, waking up the vehicle and / or other "life on board" functions.

[0004] Such vehicles include lead-acid batteries, also known as "12V batteries," as a supplementary electrical power source, working in conjunction with an alternator in the case of internal combustion engine vehicles or a converter in the case of hybrid or electric vehicles, to perform these functions. However, this battery usage imposes significant constraints, particularly regarding the battery's state of charge. Indeed, the performance of such batteries can be impaired by sulfation, a phenomenon known as battery sulfation. Sulfation is one of the causes of aging in a lead-acid battery that has remained discharged for a certain period before being recharged. This phenomenon reduces the performance of these batteries, and can even permanently diminish their capacity if they are not properly recharged.

[0005] In particular, the vehicle's 12V lead-acid battery exhibits a well-known wear factor due to sulfation, typical of low-mileage drivers. For example, a vehicle used less than 5,000 km per year will experience battery sulfate buildup and a lower than average state of charge. The discharged portion of the battery consists of a mixture of lead sulfate and water, while the undischarged portion consists of a mixture of lead and sulfuric acid. Regular charging, via the alternator in the case of a combustion engine vehicle or the DC converter in the case of an electric or hybrid vehicle, reduces the lead sulfate during vehicle use, converting it back to metallic lead according to the chemical reaction: [PbSO4 + H2O] -> [Pb + H2SO4], a simplified expression of the transformations occurring during charging.Infrequent use of the vehicle, for example a few kilometers once or twice a week, does not allow this transformation to occur completely, and the sulfate in the uncharged portion accumulates and gradually becomes unusable: the battery is sulfated. It loses part of its initial capacity.

[0006] To overcome this drawback, it has already been proposed to charge the battery at a higher voltage than a standard charging voltage.

[0007] Document EP 3 480 882 B1 uses such a principle. However, the proposed solution is relatively complex to implement and may not adequately address the needs of "small-scale drivers".

[0008] The invention aims to overcome, at least in part, the aforementioned drawbacks and, to this end, proposes a method for monitoring an electrochemical accumulator equipped with lead electrodes and an electrolyte comprising sulfuric acid, in particular a low-voltage battery of the order of 12 to 14 volts. This method comprises a test step in which at least one parameter is periodically evaluated at a given time interval, referred to as the test period, to provide information on the state of the accumulator, in particular a sulfation state. The method further comprises a charging step for the accumulator using a charging current with a voltage higher than the nominal charging voltage, referred to as the high-voltage charging step. This high-voltage charging step occurs for a predetermined duration, depending on the information regarding the state of the accumulator.

[0009] The method according to the invention makes it possible to treat any sulfation of the accumulator using an elevated voltage in a simple way, thanks to a test which takes place periodically and thanks to a duration of charge at elevated voltage which does not depend on a driving profile of the vehicle during a period preceding the test since the duration of this charge at elevated voltage, even if it can vary according to the parameters recorded during the test, is fixed in advance.

[0010] Furthermore, thanks in particular to the periodic testing, the method of the invention prevents the battery from degrading significantly and thus maintains its efficiency. The solution proposed by the invention is simpler than those of the prior art and maintains the battery at a level of sulfation that is reversible through its periodicity.

[0011] The process of the invention also makes it possible to treat any sulfation of the accumulator without removing the batteries from the vehicle and therefore without immobilizing the vehicle.

[0012] According to various additional features of the invention, which may be taken together or separately and which constitute so many embodiments of the invention:

[0013] - said testing period is several months, specifically four months,

[0014] - said testing step includes an evaluation step of a first parameter, called the acceptance parameter,

[0015] - the said pre-determined duration takes on a value, called the adapted value, chosen from a limited number of pre-determined values, said adapted value depending on a value of said acceptance parameter,

[0016] - said testing step includes a step of comparing said acceptance parameter to an acceptance threshold,

[0017] - the possible number of suitable values ​​for the said pre-determined duration is two, and the said pre-determined duration takes a first of said suitable values ​​if the acceptance parameter is greater than the acceptance threshold and a second of said suitable values ​​if the acceptance parameter is less than the acceptance threshold,

[0018] - the first suitable value, in particular 6 hours, is approximately half of the second suitable value, in particular 12 hours,

[0019] - said acceptance parameter is the intensity of the charging current after a given charging time,

[0020] - said acceptance threshold is a value proportional to the average size of said accumulator, measured in Ampere-hours,

[0021] - Another of the parameters of the test stage is the state of charge of said accumulator,

[0022] - said test step includes a step for evaluating said state of charge,

[0023] - said acceptance parameter evaluation step is executed if the state of charge of said accumulator is less than 100%, - said test step includes a time counting step providing elapsed time information,

[0024] - said load state evaluation step and / or said acceptance parameter evaluation step are executed when said elapsed time information reaches a value corresponding to said test period,

[0025] - the voltage of the charging current during said high-voltage charging stage is constant during said high-voltage charging stage,

[0026] - said elevated voltage charging step includes a step of transmitting information, called deep desulfation, when said predetermined duration is equal to said second adapted value,

[0027] - said process includes a step of forcing said test step,

[0028] - said elevated voltage charging step is further executed based on the results of said forcing step,

[0029] - said nominal voltage is less than 13 V, specifically by approximately 12.8 V,

[0030] - said elevated voltage is greater than 13 V, specifically by approximately 15 V,

[0031] - said elevated voltage charging stage includes a temperature control stage for said accumulator,

[0032] - said elevated voltage is reduced to approximately 14 V if and / or as long as said battery temperature is above a threshold, in particular 50°C,

[0033] - said elevated voltage charging stage is carried out using charging components of said accumulator intended to be used in addition during a charging stage of said accumulator at nominal voltage,

[0034] - said elevated voltage charging stage is carried out during successive rolling phases,

[0035] - the said duration fixed in advance is accounted for by summing the duration of each of the said driving phases.

[0036] - said high voltage charging stage is interrupted in the event of a stoppage of a vehicle motor while electrical consumers of said vehicle are active, - said high voltage charging stage is carried out during successive phases of activity of a voltage converter between a high voltage direct current and said charging current.

[0037] The invention also relates to a management system, intended to be embedded in a motor vehicle, said management system comprising hardware and / or software elements implementing the control process as described above.

[0038] The invention further relates to a motor vehicle comprising a management system as described above.

[0039] The invention also relates to a computer program product comprising program code instructions recorded on a computer-readable medium to implement the steps of the control process as described above, when said program is running on a computer.

[0040] The invention further relates to a computer-readable data recording medium on which is recorded a computer program comprising program code instructions to implement the steps of the control process as described above, when said program is running on a computer.

[0041] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent in the course of the detailed explanatory description which follows, of at least one embodiment of the invention given by way of purely illustrative and non-limiting example, with reference to the accompanying schematic drawings, among which:

[0042] [Fig. 1] Figure 1 schematically illustrates a charging system for a battery in a vehicle; and

[0043] [Fig. 2] Figure 2 represents a logic diagram relating to a method of controlling an electrochemical accumulator according to an embodiment of the invention.

[0044] In the description that follows, identical reference numbers denote identical parts or parts with similar functions.

[0045] Figure 1 shows a charging system 1 for an electrochemical accumulator included in a vehicle, for example, a marine, aerial, or land vehicle. In this embodiment, the vehicle is preferably a motor vehicle with a thermal, hybrid, or electric motor. Within the scope of the invention, the accumulator is equipped with electrodes comprising lead and an electrolyte comprising sulfuric acid, advantageously grouped in the form of electrical cells connected in series and / or parallel to create an electrical generator of the desired voltage and capacity. These cells are preferably housed in a single casing. The accumulator delivers an electrical current at a voltage described as low voltage. Such an accumulator is more commonly called a "12 V battery" and / or a "lead-acid battery." The accumulator is, in particular, installed in the motor vehicle.

[0046] The said accumulator is intended, in particular, for starting the engine, waking up the vehicle and / or powering one or more electrical consumers of the vehicle when the engine is not active, for example during engine shutdown phases, such as those occurring when the vehicle is equipped with a function known as Stop&Start and / or phases called "life on board" where the driver uses, for example, his radio without running the engine.

[0047] For this purpose, the said accumulator is configured to supply a direct current, in particular a low voltage current, for example a current with a voltage between 12 and 15 V, in particular in the order of 12 to 14 V.

[0048] The charging system 1 is designed to supply the battery with a current to recharge it, specifically a current with characteristics such as those mentioned above. This charging system 1 is, in particular, installed on the motor vehicle.

[0049] The charging system 1 comprises, but is not limited to, the following elements: a processing unit 2; a vehicle electrical power source 3; one or more sensors 4 for one or more indicators of the battery's operation; and / or a detection system 5 configured to detect phases in which the battery and / or the power source 3 supply power to the vehicle's electrical consumers without running the engine, such as Stop&Start phases and / or "on-board" operation phases. Such a system 5 is particularly capable of transmitting information on the activation / deactivation of the Stop&Start function and / or the vehicle's electrical consumers when the engine is not running.

[0050] In this load system 1, the processing unit 2 is connected to each element of this set. In particular, it should be noted that insofar as each element of this set and the processing unit 2 are arranged separately from a construction and / or functional point of view, each of these elements and the processing unit 2 can be connected to each other by a link network 7, for example by means of a CAN bus or another electrical link for data exchange.

[0051] This processing unit 2 comprises at least one computing unit with hardware and software resources, specifically at least one processor cooperating with memory elements. This computing unit is capable of executing instructions for the implementation of a computer program. Such a processing unit 2 forms, for example, a management system.

[0052] The aforementioned electrical energy producer 3 includes, for example, an alternator in the case of a vehicle with an internal combustion engine or, in the case of a hybrid or electric vehicle, a device that converts a direct current at a first voltage, in particular a high voltage of several hundred volts, for example 400 V, into a direct current at another voltage, here the low-voltage current mentioned above. Such a device is commonly called a DC / DC converter.

[0053] In the case of a vehicle with an internal combustion engine, the vehicle's alternator, which rotates continuously at a speed dependent on the engine speed, is connected to the battery terminals and / or supplies power to the vehicle's electrical components. This alternator 3 is capable of being controlled by the processing unit 2 in order to generate a voltage, specifically a charging voltage, at the battery terminals, which is essentially constant, by continuously drawing torque from the vehicle's internal combustion engine.

[0054] In an example of a hybrid or electric vehicle, the DC / DC converter is connected to the battery terminals and / or supplies power to the vehicle's electrical consumers. This converter 3 is capable of being controlled by the processing unit 2 to generate a voltage, specifically a charging voltage at the battery terminals, which is essentially constant, by drawing energy from the vehicle's high-voltage network, that is to say, in particular, the network connected to the vehicle's motor.

[0055] In this system 1, the sensor 4 for an indicator quantity of the battery's operation is preferably a current sensor. This sensor 4 includes a module for measuring the battery current, which is preferably integrated into the battery's electrical circuit by being connected to its terminals.

[0056] With reference to Figure 2, the invention relates to a method for controlling an accumulator, for example an accumulator as described above.

[0057] The method according to the invention includes a test step 20 in which at least one parameter is periodically evaluated at a given time interval, referred to as the test period, to provide information about the state of the accumulator. This information advantageously represents the sulfation state of the accumulator.

[0058] The process further includes a step 30 for charging the battery using a charging current with a voltage higher than the nominal charging voltage, referred to as step 30, the high-voltage charging step. The nominal voltage is, for example, less than 13 V, specifically around 12.8 V. The charging current voltage during the high-voltage charging step 30 is, in particular, constant throughout the step, unless the battery overheats, as will be discussed later. The high voltage is, in particular, greater than 13 V, specifically around 15 V.

[0059] Stage 30, the high-voltage charging stage, is carried out using battery charging devices, specifically the vehicle's power producers (3). As previously mentioned, these charging devices are also intended to be used during charging stages of the battery at nominal voltage and / or for supplying low-voltage current to the vehicle's electrical consumers. Stage 30, the high-voltage charging stage, is performed in particular by the charging system (1).

[0060] Stage 30, the high-voltage charging stage, is performed for a predetermined duration based on the battery's condition information. This high-voltage charging stage is advantageously triggered based on the aforementioned battery condition information. The test period is typically several months, for example, four months. Thus, charging stage 30 is performed periodically, specifically every four months during the vehicle's lifespan, regardless of its usage.

[0061] The method according to the invention thus makes it possible to treat any sulfation of the accumulator using an elevated voltage in a simple way, thanks to a test which takes place periodically and thanks to a duration of charge at elevated voltage which does not depend on a driving profile of the vehicle during a period preceding the test since the duration of this charge at elevated voltage, even if it can vary according to the parameters recorded during the test, is fixed in advance.

[0062] In other words, the charging time is constant or at the very least depends solely on parameters recorded during the test stage and not on the driving profile of the vehicle preceding said test stage.

[0063] Test step 20 includes in particular a step 26 of evaluation of a first of the parameters recorded periodically, called the acceptance parameter.

[0064] The predetermined duration, for example, takes on a value, called the adapted value, chosen from a limited number of predetermined values. The adapted value depends, in particular, on a value of the acceptance parameter.

[0065] Test step 20 includes in particular a step 28 of comparison of the acceptance parameter to an acceptance threshold.

[0066] The number of possible values ​​adapted for the predetermined duration is, for example, two. The predetermined duration takes, in particular, a first of the adapted values ​​if the acceptance parameter is greater than the acceptance threshold and, in particular, a second of the adapted values ​​if the acceptance parameter is less than the acceptance threshold.

[0067] The first suitable value, namely 6 hours, is approximately half the size of the second suitable value, namely 12 hours. In the remainder of this description, we will use 6 hours and 12 hours in examples including the first and second suitable values ​​respectively, but other values ​​may be used without departing from the scope of the invention.

[0068] Thus, charging step 30, designed to treat sulfation, is carried out under increased voltage and lasts 6 hours if the acceptance parameter is above the acceptance threshold, or 12 hours if the acceptance parameter is below the acceptance threshold. This double charge (here, 12 hours) has demonstrated its ability to desulfate batteries exhibiting high sulfation levels, more effectively than prior art methods. The invention thereby prevents sulfation from reaching an irreversible level.

[0069] In the case of a vehicle with an internal combustion engine, charging stage 30 is carried out during successive driving phases. The predetermined duration is calculated by summing the duration of each driving phase during which the battery is charged at a higher voltage. High-voltage charging stage 30 is interrupted if the vehicle's engine is switched off while electrical consumers are active, particularly those involved in the operation of the stop-start system and / or the "life on board" functions. The duration of the interruption is equal to the duration the vehicle's engine is switched off. Therefore, specific operating phases of internal combustion engine vehicles that prevent the application of high-voltage charging stage 30, such as engine shutdowns for the stop-start function or "life on board" functions, are not counted as driving phases.

[0070] In the case of an electric and / or hybrid vehicle, charging step 30 is carried out during successive phases of DC / DC converter activity. The predetermined duration is calculated by summing the duration of each period during which the converter is active and maintains the charging voltage at the elevated voltage.

[0071] The acceptance parameter is, for example, the charging current intensity per unit of time. It is understood here that charging has already begun during step 26 of the acceptance parameter evaluation. The invention thus makes it possible to assess the sulfation state of the battery using a battery charging current sensor, in particular sensor(s) 4, and then to perform a battery regeneration charge, i.e., a battery desulfation, periodically using an embedded algorithm that utilizes the vehicle's electrical power generator.

[0072] For example, during step 26 of the acceptance parameter assessment, the charging current of the battery under elevated voltage is measured after, for example, 5 minutes of charging. If this current is above the acceptance threshold, which is proportional to the battery's capacity, the battery is in good condition, and step 30, charging for 6 hours (first suitable value) under elevated voltage, will remove the sulfate that is forming. If this charging current after 5 minutes is below the acceptance threshold, the battery contains a significant amount of lead sulfate, which is relatively "consolidated." To restore the battery to good condition, the duration of step 30, charging under elevated voltage, will be doubled, and the cumulative charging time increased to 12 hours (second suitable value) instead of 6 hours, as explained previously.

[0073] The acceptance threshold is proportional to the average size of the battery, measured in Ampere-hours (Ah). For example, for an average-sized 60 Ah battery, the acceptance threshold is set at 6 A for five minutes. It follows that an average-sized 60 Ah battery will be considered to be in good condition if the charging current after 5 minutes is greater than 6 A.

[0074] Another parameter in step 20 of the test is, for example, the state of charge of the battery.

[0075] In this sense, test step 20 here includes a step 24 for evaluating this state of charge.

[0076] Thus, charging step 30, and in this case, acceptance parameter evaluation step 26, are preceded by state-of-charge evaluation step 24. The purpose of this state-of-charge evaluation step 24 is to avoid performing charging step 30, and even acceptance parameter evaluation step 26, if the battery is fully charged. This indicates that it is not suffering from sulfation. In this rare case, the process of the invention is postponed to the next deadline, specifically to the end of the next testing period.

[0077] Step 26, evaluating the acceptance parameter, is performed in particular if the battery's state of charge is less than 100%, that is, if step 24, evaluating the state of charge, detected a battery state of charge below 100%. In this case, if the state of charge is, for example, 88%, the method of the invention can proceed to step 26, evaluating the acceptance parameter.

[0078] Test step 20, for example, also includes a time-counting step 22 that provides elapsed time information. This time-counting step 22 allows us to determine whether the test period has ended. Therefore, load state evaluation step 24 and / or acceptance parameter evaluation step 26 are executed specifically when the elapsed time information reaches a value corresponding to the test period.

[0079] Since the vehicle charges the battery during use, a protective device, possibly already in place, is advantageously used to prevent damage should the battery become too hot. This device, for example, limits the charging voltage to 14 volts if the battery temperature exceeds a certain threshold, such as 50°C.

[0080] Step 30 of the elevated voltage charging process includes, for example, a step for monitoring the temperature of the battery.

[0081] Step 30 of the high-voltage charging process may include a step for transmitting information, known as deep desulfation, when the predetermined duration equals the second suitable value (here, 12 hours). This deep desulfation information is intended, in particular, for use during vehicle maintenance. This information may be transmitted using an indicator. The invention thus combines deep desulfation with a monitoring system that assists the mechanic in the periodic maintenance of the vehicle. For example, the mechanic may suggest to the customer a battery replacement suited to their vehicle usage.

[0082] The method of the invention includes, in particular, a step for forcing test step 20. This forcing step takes place specifically during vehicle maintenance phases. It is understood here that test step 20 can be performed at any time, and not only when time-counting step 22 has provided elapsed time information and this information has reached a value corresponding to the test period.

[0083] Step 30, the high-voltage loading step, can then be performed based on the results of the forcing step. Thus, when the conditions are met following the forcing step of test step 20, the method of the invention provides for carrying out step 30, the high-voltage loading step, in the same way as following test step 20, which is performed without forcing.

[0084] During the scheduled maintenance at the garage, another possibility of the invention's method involves performing a battery check using an external protocol, as detailed in the repair methods. The mechanic can then, using their diagnostic / repair tools, force the activation of the desulfation strategy according to the invention by forcing step 30 of the high-voltage charging process, again without waiting for the end of the current four-month period.

[0085] In summary, and describing only the steps of the process of the invention illustrated in Figure 2, said process first comprises test step 20. This test step 20 includes, in particular, time-counting step 22, which provides elapsed time information. If the elapsed time information is less than a predetermined period, here 4 months, the process continues with the same time-counting step 22.

[0086] If, however, the elapsed time is equal to the predetermined time, the process continues with step 24, which assesses the battery's state of charge. If the state of charge is assessed at 100%, the process restarts step 22, which counts the time, for a new period.

[0087] If, on the other hand, the state of charge is evaluated here as less than 100%, the process continues with step 26 of evaluating the acceptance parameter, namely an intensity of the charging current after a given charging time.

[0088] The process then includes step 28 of comparing the acceptance parameter to an acceptance threshold.

[0089] The process further includes step 30 of triggered elevated voltage charging occurring for a predetermined duration, in particular 6 hours if the acceptance parameter is above the threshold and 12 hours if the acceptance parameter is below the threshold.

[0090] At the end of the charging step 30, the process restarts the time counting step 22 for a new period.

[0091] The invention also relates to the management system as described above. The management system thus comprises hardware and / or software components implementing the control process as described above.

[0092] The invention also relates to a motor vehicle including the management system.

[0093] The invention further relates to a computer program product comprising program code instructions stored on a computer-readable medium for implementing the steps of the control process as described above, when said program is running on a computer. The invention also relates to a computer-readable data storage medium on which is stored a computer program comprising program code instructions for implementing the steps of the control process as described above, when said program is running on a computer.

Claims

DEMANDS 1. A method for testing an electrochemical accumulator equipped with electrodes comprising lead and an electrolyte comprising sulfuric acid, in particular a low-voltage battery of the order of 12 to 14 volts, said method comprising a test step (20) in which at least one parameter is periodically evaluated at a given time interval, referred to as the test period, to provide information on a state of said accumulator, in particular a sulfation state, said method further comprising a charging step (30) of said accumulator using a charging current having a voltage higher than a nominal charging voltage, referred to as the raised-voltage charging step (30), said raised-voltage charging step (30) occurring for a predetermined duration, depending on the information on the state of the accumulator.

2. Control method according to claim 1, wherein said test step (20) includes a step (26) for evaluating a first of the parameters, called the acceptance parameter.

3. Control method according to claim 2, wherein said time fixed in advance takes a value, said adapted value, chosen from a limited number of values, fixed in advance, said adapted value depending on a value of said acceptance parameter.

4. Control method according to claim 3, wherein the number of possible values ​​adapted for said predetermined duration is two and wherein, said test step (20) comprising a step (28) of comparison of said acceptance parameter to an acceptance threshold, said predetermined duration takes a first of said adapted values ​​if the acceptance parameter is greater than said acceptance threshold and a second of said adapted values ​​if the acceptance parameter is less than said acceptance threshold.

5. Control method according to any one of claims 2 to 4, wherein said acceptance parameter is a charging current intensity after a given charging time.

6. A control method according to any one of claims 2 to 5, wherein said test step (20) comprises a step (24) for evaluating a state of charge of said accumulator, another of said parameters being said state of charge.

7. Control method according to claim 6, wherein said step (26) of evaluating the acceptance parameter is carried out if the state of charge of said accumulator is less than 100%.

8. Control method according to claim 6 or 7, wherein said test step (20) comprises a time counting step (22) delivering elapsed time information.

9. Control method according to claim 8, wherein said step (24) of evaluating said state of charge and / or said step (26) of evaluating said acceptance parameter are executed when said elapsed time information reaches a value corresponding to said test period.

10. Management system (1), intended to be embedded in a motor vehicle, said management system (1) comprising hardware and / or software elements implementing the control method according to any one of the preceding claims.

11. Motor vehicle comprising a management system (1) according to the preceding claim.

12. Product computer program comprising program code instructions recorded on a computer-readable medium to implement the steps of the control process according to any one of claims 1 to 9, when said program is run on a computer.

13. Computer-readable data storage medium on which is stored a computer program comprising program code instructions for implementing the steps of the control method according to any one of claims 1 to 9, when said program is running on a computer.

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