Diagnostic methods for motor vehicle batteries

Abstract

The invention relates to a diagnostic method for diagnosing the state of a battery (11) of an electrical network (10) of a motor vehicle, the network comprising electrical consumers (12) supplied with direct current via the battery and / or via a power converter (20) connected to the vehicle's transmission chain and to the network, the method comprising measuring at least one operating parameter (Ubat, Ibat) of the battery during its discharge and comparing the measured operating parameter with a predetermined state diagnostic threshold by calculating the discharge internal resistance (Rint) of the battery, the method comprising initializing the discharge of the battery before the measurement and then initializing the activation of the converter with an output voltage (Uconv) greater than or equal to the voltage (Urdb) required to power the electrical consumers, the initialization activation terminating the initialization discharge of the battery.

Description

Technical Field

[0001] The present invention relates to a diagnostic method for diagnosing a battery of a motor vehicle, and more precisely to the diagnosis of a battery of a vehicle configured to be able to travel without requiring high power to be delivered by said battery. Background Art

[0002] Motor vehicles, whether powered by heat, electricity or a hybrid heat / electric drive, generally comprise an on-board electrical network capable of supplying power to at least one electrical consumer of the vehicle.

[0003] The electrical consumer can also contribute to the comfort of the vehicle occupants, for example as a ventilation device for the passenger compartment of a motor vehicle, and to the safety of the vehicle occupants, for example as a brake assist device for a motor vehicle.

[0004] When electrical consumers are involved in passenger safety, the ability of the battery to provide sufficient power for the correct functioning of said electrical consumers needs to be verified each time the motor vehicle is used or regularly during vehicle use.

[0005] Furthermore, for some hybrid or electric vehicles, a driving phase of the vehicle can be implemented using only energy from a powertrain comprising an electric motor and a generator or a power battery, which is coupled to the electric motor, for example by means of a (DCDC) electric power converter, in order to implement the driving phase without requiring a high power to be sent by the battery of the onboard network.

[0006] Therefore, in some hybrid or electric vehicles, the ability of the onboard network battery to provide sufficient power for the correct operation of the electrical consumers of the onboard network cannot be verified before or during vehicle driving phases other than when the electrical consumers are activated. This is a greater problem if one or more of the electrical consumers involved are involved in safety functions such as braking, stopping, steering assistance or vehicle stability control.

[0007] This feature is not yet found in thermal-drive vehicles, since the battery of the onboard power system supplies the starter of the thermal engine before the vehicle is driven, which requires sufficient power to verify the battery's ability to enable the other electrical consumers of the onboard power system to operate correctly.

[0008] Document FR-A1-3044099 describes a diagnostic method for a battery of a first electrical network of a motor vehicle, the first network also comprising a first measuring member and an electrical consumer. A second measuring member is coupled to the first electrical network and isolates the first network from a second electrical network.

[0009] Diagnosis of the battery is performed by comparing a measurement of an operating parameter of the battery performed by a first measuring means with a measurement of the same operating parameter of the battery performed by a second measuring means.

[0010] This diagnosis effectively makes it possible to implement a double diagnosis of the battery, making it possible to check the battery's ability to supply high power even when the motor vehicle can travel without the need for such power to be sent by the battery of the first network.

[0011] However, such a diagnosis requires the use of several measuring members, which increases the weight of the motor vehicle, the bulk of its electrical network and its manufacturing price. Summary of the invention

[0012] The object of the present invention is to provide a diagnostic method for diagnosing the state of a battery of a motor vehicle, which diagnostic method does not require that a large power be sent by the battery that can be used for driving, while ensuring a predefined safety level at the start, end and / or during driving according to the vehicle equipment level (from the technical definition of the entry level in terms of driving assistance to the level defined in the autonomous vehicle standards), while allowing the manufacture of lighter, cheaper and smaller vehicles compared to vehicles of the prior art.

[0013] To this end, a first aspect of the present invention provides a diagnostic method for diagnosing the state of a battery of an electrical network of a motor vehicle, the electrical network comprising electrical consumers, the electrical consumers being supplied with direct current through the battery and through a power converter, the power converter being connected to a transmission chain of the motor vehicle and to the electrical network, the diagnostic method comprising measuring at least one operating parameter of the battery during discharge of the battery, and comparing the measured operating parameter with a predetermined state diagnostic threshold, the diagnostic method comprising initializing discharge of the battery before the measurement, and then initializing activation of the power converter with an output voltage greater than or equal to a voltage required to power the electrical consumers, the initialization activation terminating the initialization discharge of the battery.

[0014] Thus, this diagnostic method makes it possible to eliminate the polarization effects of the battery, thanks to this initial discharge and this initial activation, in order to obtain measurements that can be used to check the battery state of the vehicle. The method makes it possible to ensure this diagnosis of the battery while the vehicle is moving or before a driving phase, without the electrical consumers of the network requiring high power to be sent by the battery. The method requires only one measurement, which allows the manufacture of a lighter, cheaper and less bulky vehicle than the vehicles of the prior art.

[0015] Furthermore, eliminating the polarization effect of the battery can improve the inspection results, especially the reliability and repeatability of the results.

[0016] The state of the battery includes, for example, a charge state parameter, a health state parameter, and an internal resistance parameter.

[0017] Various additional features are available individually or in combination:

[0018] - the at least one measured operating parameter of the battery is a parameter pair comprising a terminal voltage of the battery and a current intensity flowing in a branch of the electrical network comprising the battery, and the comparison of the operating parameters is carried out by calculating the internal discharge resistance of the battery by dividing the terminal voltage by the current intensity;

[0019] - carrying out said initialization discharge and said initialization activation after a request to enter said motor vehicle or after a request to activate said motor vehicle;

[0020] - the diagnostic method comprises measuring the at least one operating parameter of the battery a plurality of times during successive discharges of the battery after initial activation of the power converter, and activating the power converter between each discharge at an output voltage greater than or equal to the voltage required to power the consumer, carrying out the comparison after each discharge, taking into account the most unfavourable comparison to diagnose the state of the battery;

[0021] - one or more discharges of the battery and / or one or more activations of the power converter last between 50 milliseconds and 250 milliseconds;

[0022] - said diagnostic method comprises, before said initial discharge and said initial activation, an initial supply of said electrical network with direct current by said power converter, then a comparison of the intensity of the current sent by said power converter with a predetermined initial diagnostic threshold, said initial diagnostic threshold being greater than or equal to the voltage required to power said electrical consumer, said comparison of the intensity of the current influencing the implementation of the subsequent steps;

[0023] - the diagnostic method comprises a classification according to the result of the comparison of the measured operating parameter of the battery with the state diagnostic threshold, according to which the battery is considered to be in a good state, a state to be renewed or a state to be recycled;

[0024] - the diagnostic method comprises verifying the result of the comparison by verifying that the intensity of the current flowing through the consumer is equal to the sum of the intensity of the current sent by the power converter and the intensity of the current flowing through the battery;

[0025] The diagnostic method comprises, after comparing the measured operating parameter of the battery with the condition diagnostic threshold, indicating the result of the comparison to a driver of the motor vehicle.

[0026] A second aspect of the present invention provides an electrically driven or thermal / electric hybrid driven motor vehicle, the motor vehicle comprising a first electrical network, a second electrical network and a DC / DC power converter, the power converter connecting the first electrical network with the second electrical network, the first electrical network comprising a battery and at least one electrical consumer, the at least one electrical consumer being supplied with DC current via the battery and / or via the power converter, the motor vehicle comprising a system for implementing the diagnostic method for diagnosing the battery as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other objects, features, details and advantages of the present invention will become more apparent from a reading of the following detailed description and the accompanying drawings which are given by way of example only to illustrate embodiments of the present invention, in which:

[0028] - Figure 1 is a schematic diagram of a power converter coupled to an electrical network including a battery and electrical consumers;

[0029] - Figure 2 The curves shown show the current intensity flowing in the battery as a function of time and the terminal voltage of the power converter as a function of time. DETAILED DESCRIPTION

[0030] Figure 1 An electrical network 10 is shown, which comprises a battery 11 and at least one electrical consumer 12 .

[0031] The DC / DC power converter 20 connects the network 10 to a second network (not shown).

[0032] According to one embodiment, the network 10 and / or the second network is coupled to the drive train of the vehicle.

[0033] According to one embodiment, the electrical network 10 belongs to a motor vehicle.

[0034] According to one embodiment, the motor vehicle is electrically driven or thermal / electrically hybrid driven.

[0035] The power converter 20 is configured to charge the battery 11 and / or supply electrical energy to the electrical consumer 12 .

[0036] According to one embodiment, the electrical network 10 is adapted for a current path having a voltage of approximately 12 volts.

[0037] According to one embodiment, said second network is adapted to a current path having a voltage higher than the voltage of the network 10 to which said battery 11 belongs.

[0038] Figure 2 From top to bottom:

[0039] - a graph showing the intensity Ibat of the current flowing in the battery 11 as a function of the time t,

[0040] - A graph showing the output voltage Uconv of the power converter 20 as a function of the time t.

[0041] like Figure 2 As shown, the power converter 20 is suitable for being activated so as to deliver a current having a non-zero output voltage Uconv, for example equal to 12.8 Volts.

[0042] When the power converter 20 is activated, the current sent through the power converter can charge the battery 11 and power the electrical consumers 12 of the electrical network 10. This charging Figure 2 The negative current intensity Ibat flowing in the battery 11 is shown above.

[0043] like Figure 2 As shown, the power converter 20 is adapted to be disabled so as not to deliver any current.

[0044] According to an embodiment not shown, the deactivation of the power converter 20 is not complete, so that the converter 20 sends a current with an output voltage Uconv which is lower than the voltage Urdb required, for example equal to 10.5 volts (its value is adjustable between 9.5 volts and 10.5 volts), to power the electrical consumers 12 of the electrical network 10. Thus, in the case that the battery 11 is capable of performing, the battery 11 is discharged to maintain in the electrical network 10 a voltage Urdb sufficient to power the electrical consumers 12. In the case that the battery 11 is not capable of performing, a minimum voltage Urdb in the electrical network 10 is ensured by the power converter 20. In the latter case, the battery 11 is declared to be defective.

[0045] When the power converter 20 is deactivated (i.e. not delivering any current, or delivering a current having an output voltage Uconv which is lower than the voltage Urdb required to power the consumer 12 with a minimum voltage level capable of ensuring the nominal performance of the consumer 12), the battery 11 is discharged to deliver a current capable of powering the consumer 12 of the electrical network 10. This discharge is Figure 2 The above is shown by the positive current intensity Ibat flowing in the battery 11.

[0046] According to one embodiment, the at least one electrical consumer 12 belongs to an electrical steering assistance device of the motor vehicle, a braking component of the motor vehicle, a thermal engine starting component of the motor vehicle and / or a lighting or signaling component of the motor vehicle.

[0047] The diagnostic method for diagnosing the state of the battery 11 includes a phase of initially supplying power to the on-board network 10 via the power converter 20 .

[0048] This initial power supply phase charges the battery 11 and supplies power to the electrical consumers 12 .

[0049] According to one embodiment, the initial power supply is triggered by opening a door of the motor vehicle.According to a different embodiment, the initial power supply is triggered by the ignition of the vehicle.

[0050] According to the exemplary embodiment shown, the initial power supply is carried out during a duration D0.

[0051] According to the embodiment shown, the initial power supply is implemented with a voltage Vs which is, for example, equal to 12.8 volts and which can be adjusted, for example, according to the static voltage of the battery 11 , which depends on the technology of the battery 11 .

[0052] According to various exemplary embodiments, the state of charge of battery 11 is measured before carrying out the diagnostic method.

[0053] After this initial power supply, the method consists in comparing the value of the current intensity Iconv sent by the converter 20 with a predetermined initial diagnostic threshold value Isd.

[0054] According to one embodiment, the initial diagnosis threshold Isd is greater than or equal to the demand of the electrical consumer 12 so that the battery 11 is not discharged.

[0055] According to various embodiments, after this initial power supply, the method consists in comparing the difference between the value of the current intensity Iconv sent by converter 20 and the value of the current intensity Ibat sent by battery 11 with a predetermined initial diagnostic threshold Isd equal to 70 Amps, for example.

[0056] If the comparison shows that the value of the current intensity Iconv transmitted by the converter 20 or the difference is greater than the respective threshold value, according to the embodiment shown, the method comprises an initialization period Ci consisting in deactivating the power converter 20 during a duration D1, such as Figure 2 shown.

[0057] According to one embodiment, duration D1 is approximately equal to 200 milliseconds.

[0058] Deactivation of the power converter 20 forces the battery 11 to discharge in order to power the electrical consumer 12. Initialization period Ci The deactivation of the power converter 20 is not necessarily complete, so that the converter 20 sends a sufficiently small current to discharge the battery 11, which discharge can therefore be called initialization discharge of the battery 11.

[0059] After this deactivation, the initialization period Ci comprises activating the power converter 20 during a duration D2, such as Figure 2 shown.

[0060] According to one embodiment, the duration D2 is approximately equal to 200 milliseconds.

[0061] Activation of the converter 20 supplies the consumers with electrical energy at a maximum voltage, for example the polarization voltage of the battery 11 of 12.8 volts, in order not to polarize the battery before starting the next cycle.

[0062] This initialization period Ci can eliminate the polarization effect of the battery 11.

[0063] The method then comprises at least one evaluation cycle Cm, each evaluation cycle Cm comprising a deactivation during a duration D1 and an activation of converter 20 during a duration D2.

[0064] like Figure 2 As shown, in the last evaluation period Cm, the activation is not constrained by the duration D2.

[0065] According to various embodiments, the durations of deactivation and activation are different from each other and / or from the initialization period Ci to the evaluation period Cm.

[0066] In each evaluation cycle Cm, the method consists in measuring the terminal voltage Ubat of the battery 11 and the intensity Ibat of the current circulating in the battery 11 when the power converter 20 is deactivated.

[0067] After each measurement, the method comprises calculating the discharge internal resistance Rint of the battery 11 by dividing the measured terminal voltage Ubat of the battery 11 by the measured current intensity Ibat flowing in the battery 11. The discharge internal resistance Rint represents the power supply capability of the battery 11.

[0068] According to one embodiment, the terminal voltage Ubat of the battery 11 and the current intensity Ibat circulating in the battery 11 are measured every millisecond (i.e. at a frequency of 1 kHz). For each evaluation cycle Cm of the converter 20, the average value of all measured voltages Ubat and current intensities Ibat or the average value of all calculated internal resistances Rint is calculated.

[0069] According to one embodiment, one or more measurements of the terminal voltage Ubat of the battery 11 and of the current intensity Ibat circulating in the battery 11 and one or more calculations of the internal discharge resistance Rint are performed, based on the gradient of the current intensity circulating in the battery 11 for a given duration greater than a predetermined threshold. This threshold is, for example, equal to 70 amperes for a duration of, for example, 5 milliseconds.

[0070] The internal resistance Rint or the average value of the internal resistance Rint is calculated in each evaluation cycle Cm and then compared with at least one predetermined health status diagnosis threshold value of the battery 11 , for example in an algorithm.

[0071] According to one embodiment, based on the result of comparing the calculated internal resistance Rint of the battery 11 with at least one health status diagnostic threshold, the battery 11 is considered to be in a good state, a state to be renewed, or a state to be recycled, for example, indicating that the ability of the battery 11 to provide power is considered to be nominal, temporarily degraded, degraded, or failed.

[0072] According to one embodiment, the comparison that resulted in the most unfavorable outcome is considered.

[0073] According to various embodiments, an average value of the results of the comparison is performed.

[0074] In the best case, the power generation of the battery 11 is sufficient to give it functional characteristics substantially identical to the nominal characteristics of a new battery.

[0075] The result of this comparison is sent to the power management system.

[0076] According to one embodiment, the method comprises subsequently processing the result of the comparison by the power management system.

[0077] According to one embodiment, in the event that the result fails to reach a predetermined diagnostic threshold, information is generated that enables the functions of the vehicle to be reconfigured, in particular by limiting the maximum current level of some functions, such as a steering assistance function.

[0078] According to one embodiment, the method comprises indicating the result, for example to a driver of the motor vehicle, so that the driver can adapt the use of his vehicle according to the severity level of the information presented to him.

[0079] According to one embodiment, this information is recorded and dated with the purpose of being able to be analyzed, for example, by the after-sales service of the vehicle manufacturer and / or to be used as objective evidence in legal proceedings when an accident occurs in conjunction with the occurrence of the information presented to the driver, in order to clarify the various responsibilities associated with the accident.

[0080] According to one embodiment, during all evaluation cycles Cm, it is verified that the intensity of the current Irdb circulating in the consumer 12 is equal to the sum of the intensity of the current Iconv sent by the power converter 20 and the intensity of the current Ibat circulating in the battery 11 .

[0081] According to the exemplary embodiment shown, the measurement of the terminal voltage Ubat of the battery 11 and of the current intensity Ibat flowing in the battery 11 is carried out by a battery state-of-charge box (BECB) 30 present on all vehicles.

[0082] According to one embodiment, it is verified that the terminal impedance of the electrical consumer 12 is less than a critical impedance.

[0083] This diagnostic method for diagnosing a battery 11 of a motor vehicle thus makes it possible to verify the ability of the battery 11 to provide sufficient power for the correct operation of the electrical consumers 12 without requiring a high power to be delivered by said battery 11 to enable driving.

[0084] This diagnostic method also allows for the manufacture of vehicles that are lighter, cheaper and smaller than prior art vehicles.

Claims

1. A diagnostic method for diagnosing the state of a battery (11) of an electrical network (10) of a motor vehicle, the electrical network (10) comprising electrical consumers (12) supplied with direct current via the battery (11) and via a power converter (20), the power converter being connected to the drive train of the motor vehicle and to the electrical network (10), the diagnostic method comprising measuring at least one operating parameter (Ubat, Ibat) of the battery (11) during discharge of the battery (11) and comparing the measured operating parameter (Ubat, Ibat) with a predetermined state diagnostic threshold, characterized in that The diagnostic method comprises the following steps in sequence before the measuring: Initially supplying the electrical network (10) with direct current via the power converter (20); The current intensity (Iconv) transmitted by the power converter (20) is then compared with a predetermined initial diagnostic threshold (Isd), the initial diagnostic threshold (Isd) being greater than or equal to the demand of the electrical consumer (12) so that the battery (11) is not discharged; If the value of the current intensity (Iconv) is greater than the initial diagnosis threshold (Isd), initializing discharge of the battery (11); The power converter (20) is then initially activated with an output voltage (Uconv) greater than or equal to the voltage (Urdb) required to power the electrical consumer (12), the initialization activation terminating the initialization discharge of the battery (11).

2. The diagnostic method according to claim 1, characterized in that The at least one measured operating parameter (Ubat, Ibat) of the battery (11) is a parameter pair, which includes the terminal voltage (Ubat) of the battery (11) and the current intensity (Ibat) flowing in the branch of the electrical network (10) including the battery (11), and the comparison of the operating parameters (Ubat, Ibat) is implemented by calculating the discharge internal resistance (Rint) of the battery (11) by dividing the terminal voltage (Ubat) by the current intensity (Ibat).

3. The diagnostic method according to claim 1 or 2, characterized in that: The initialization discharge and the initialization activation are carried out after a request to enter the motor vehicle or after a request to activate the motor vehicle.

4. The diagnostic method according to claim 1 or 2, characterized in that: The diagnostic method comprises measuring the at least one operating parameter (Ubat, Ibat) of the battery (11) several times during the continuous discharge of the battery (11) after initial activation of the power converter (20), activating the power converter (20) between each discharge with an output voltage (Uconv) greater than or equal to the voltage (Urdb) required to power the electrical consumer (12), carrying out the comparison after each discharge, and diagnosing the state of the battery (11) by taking into account the most unfavorable comparison.

5. The diagnostic method according to claim 4, characterized in that: One or more discharges of the battery (11) and / or one or more activations of the power converter (20) last between 50 milliseconds and 250 milliseconds.

6. The diagnostic method according to claim 1 or 2, characterized in that: The diagnostic method comprises classifying the battery (11) according to the result of comparing the measured operating parameters (Ubat, Ibat) with the state diagnostic threshold, according to which the battery (11) is considered to be in a good state, a state to be renewed or a state to be recycled.

7. The diagnostic method according to claim 1 or 2, characterized in that: The diagnostic method comprises verifying the result of the comparison by verifying that the intensity of the current (Irdb) circulating in the electrical consumer (12) is equal to the sum of the intensity of the current (Iconv) sent by the power converter (20) and the intensity of the current (Ibat) circulating in the battery (H).

8. The diagnostic method according to claim 1 or 2, characterized in that: The diagnostic method comprises, after comparing a measured operating parameter (Ubat, Ibat) of the battery with the state diagnostic threshold, indicating the result of the comparison to a driver of the motor vehicle.

9. An electrically driven or thermal / electrically hybrid driven motor vehicle, the motor vehicle comprising a first electrical network (10), a second electrical network and a DC / DC power converter (20), the power converter connecting the first electrical network (10) to the second electrical network, the first electrical network (10) comprising a battery (11) and at least one electrical consumer (12), the at least one electrical consumer being supplied with a DC current via the battery (11) and / or via the power converter (20), characterized in that: The motor vehicle comprises a system for implementing a diagnostic method for diagnosing the battery (11) according to any one of claims 1 to 8.

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