Method for managing the charge level of a low-voltage battery in an electric motor vehicle

Abstract

Disclosed is a method for managing the charge level of a low-voltage battery (24) of an electric motor vehicle comprising a high-voltage battery module (12), the method being characterised in that it comprises: - a step (100) of initiating a rest phase of the vehicle and of starting a monitoring time period; - a step (101) of assessing a condition indicating whether the monitoring time period has elapsed; - when said time period has elapsed, one or more steps (102, 103, 104) of measuring a parameter of the low-voltage battery; - if at least one parameter exceeds a threshold, a verification step (105) in which the monitoring device (50) verifies whether the threshold continues to be exceeded for a predetermined length of time; - if the threshold continues to be exceeded for said length of time, a step (106) of recharging the low-voltage battery (24) by means of the at least one high-voltage battery module (12).

Description

[0001] Method for managing the charge level of a low-voltage battery in an electric motor vehicle

[0002] The invention relates to a method for managing the charge level of a low-voltage battery in an electric or hybrid motor vehicle. The invention further relates to a system and / or an electric or hybrid motor vehicle capable of implementing such a method.

[0003] In the field of electric vehicles, managing the power supply can be complex because even when the vehicle is in an inactive state, such as when parked for a certain period, some components may remain active or become intermittently active. These components continue to draw power from one or more of the vehicle's batteries. Therefore, accurately measuring, monitoring, and managing the battery charge level without excessive energy consumption can be challenging when the vehicle is in such an inactive state.

[0004] Generally, an electric vehicle includes a main drive system comprising a high-voltage battery, as well as a low-voltage battery which enables certain functions to be performed when the vehicle is in an inactive phase and the high-voltage battery is off.

[0005] The low-voltage battery of such an electric vehicle typically has a low capacity, yet this low-voltage battery provides the electrical power needed for the electronic standby components when the vehicle is inactive. To prevent the low-voltage battery from being completely discharged, it can be recharged at least once while the electric vehicle is in this inactive phase. Thus, a specific charging method, commonly called "top-up charging," involves partially and periodically recharging the low-voltage battery when the vehicle is stationary, in an inactive phase.

[0006] However, such charge-feeding is generally based on a theoretical battery consumption. Charge-feeding is usually triggered after a time delay has elapsed, the duration of which is estimated from this theoretical battery consumption. This time-based charge-feeding system thus ensures regular recharging of the low-voltage battery when the electric vehicle is inactive for an extended period, but it does not account for exceptional circumstances that could accelerate the discharge of the low-voltage battery.

[0007] Indeed, the limited capacity of the low-voltage battery poses a risk of deep discharge should unexpected power consumption and / or a significant drop in temperature cause the battery to fall below a level insufficient to properly power the electronic standby components. This could lead to a situation where the low-voltage battery is completely discharged before a temporary top-up can be performed. In such circumstances, the vehicle is rendered immobilized.

[0008] The aim of the invention is to overcome the drawbacks described above by providing a method for managing the battery charge level that takes into account specific circumstances that could lead to unusual battery discharge. The method also allows for exceptional low-voltage battery charging under certain circumstances to prevent a breakdown that would immobilize the vehicle. To this end, the invention relates to a method for managing the charge level of a low-voltage battery in an electric motor vehicle. The motor vehicle further comprises at least one high-voltage battery module. The method is characterized in that it comprises:

[0009] - an initiation step for a rest phase of the motor vehicle, for example when the vehicle is parked in a parking space, and the start of a monitoring timer; then

[0010] - an evaluation step for a condition at the end of the monitoring timer countdown; then

[0011] - when the monitoring time interval has elapsed, one or more measurement steps of at least one parameter of the low-voltage battery, during which a monitoring device measures the current delivered by the low-voltage battery and / or the voltage across the terminals of the low-voltage battery and / or the temperature of the low-voltage battery; then

[0012] - if at least one of these parameters exceeds a threshold specific to each parameter, a verification step during which the monitoring device checks whether this threshold exceedance persists for a predetermined period; then

[0013] - if the threshold is exceeded for a predetermined period, a step of recharging the low voltage battery by at least one high voltage battery module.

[0014] This process complements the previously mentioned time-based charging. It allows for simple and adequate onboard automatic recharging to cover various unforeseen or unusual situations that would otherwise lead to a deep discharge of the low-voltage battery.

[0015] In particular, the monitoring device regularly checks the battery's charge level and triggers an exceptional top-up when the situation requires it. In one embodiment, the monitoring time interval is between five and fifteen minutes inclusive, and in particular ten minutes.

[0016] According to one embodiment, the predetermined duration of the verification step is between five and thirty seconds inclusive, and more particularly equal to ten seconds.

[0017] According to one embodiment, the method includes a step of measuring the voltage across the terminals of the low-voltage battery, and the method proceeds to the step of checking if the monitoring device detects a voltage drop greater than or equal to 500mV.

[0018] According to one embodiment, the process includes a step of measuring the current delivered by the low voltage battery and the process proceeds to the step of verifying whether the monitoring device detects a current greater than or equal to 100mA, and more particularly greater than or equal to 200mA, or even greater than or equal to 300mA.

[0019] According to one embodiment, the process includes a step of measuring the temperature of the low voltage battery and the process proceeds to the step of checking if the monitoring device detects a temperature less than or equal to -10°C.

[0020] In one embodiment, the method further includes a step of heating the battery using a vehicle heating means when the monitoring device detects a low-voltage battery temperature of -10°C or lower, a heating step during which the heating means warms the battery until the low-voltage battery temperature reaches -5°C. In another embodiment, the vehicle's low-voltage battery is brought to a maximum charge level during the recharging step.

[0021] The invention also relates to a system for managing the charge level of a low-voltage battery for a motor vehicle, the system being configured to implement a method mentioned above, the system comprising:

[0022] - a high-voltage network comprising at least one high-voltage battery module and at least one component capable of driving the drive wheels of the motor vehicle;

[0023] - a low voltage network including a low voltage battery and at least one low voltage electrical device;

[0024] - a monitoring device configured to monitor at least one parameter of the low-voltage battery.

[0025] The invention also relates to a motor vehicle equipped with such a system. The invention also relates to a motor vehicle configured to implement a method mentioned above.

[0026] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0027] Figure 1 schematically illustrates a low-voltage battery management system according to one embodiment of the invention.

[0028] Figure 2 illustrates the steps of a process according to the invention.

[0029] In this description, the terms "first," "second," "third," etc., are not intended to imply or create a particular order of elements, nor to limit an element to a single element, unless expressly stated, for example, by using terms like "before," "after," "unique," and other such terms. Rather, the use of these terms serves to distinguish elements from one another. For example, a first element is distinct from a second element, and the first element may encompass more than one element and follow (or precede) the second element in an order of elements.

[0030] Figure 1 illustrates a low-voltage battery management system 1 suitable for implementing the claimed method. System 1 comprises a high-voltage network 10 and a low-voltage network 20. The high-voltage network 10 includes at least one high-voltage battery module 12 and at least one component 14, 16 suitable for driving the drive wheels of the motor vehicle. These components include, in particular, an electric motor 14 and an inverter 16, which are part of the motor vehicle's main drive system. The high-voltage battery 20 is used to power at least one component 14, 16 suitable for driving the drive wheels of the motor vehicle.

[0031] The low-voltage network 20 comprises an on-board network 22 and a low-voltage battery 24 configured to power at least one low-voltage electrical device in the vehicle. The low-voltage network 20 powers, for example, the radio and / or interior lighting in the vehicle's passenger compartment and / or other low-voltage electrical devices in the vehicle. The on-board network 22 comprises various electronic systems implemented in the vehicle. The low-voltage battery 24 can be a lithium battery or a lead-acid battery. Other battery types are also possible. The voltage of the low-voltage battery 24 can, for example, be 12 V.

[0032] A DC / DC converter 30 connects the high-voltage network 10 with the low-voltage network 20. The DC / DC converter 30 is capable of converting a high DC voltage from the high-voltage battery 12 to a lower DC voltage to allow the high-voltage battery 12 to charge the low-voltage battery 24. The DC / DC converter 30 is also configured to ensure the safety of potential passengers in the electric vehicle by isolating said passengers from the high-voltage electrical network 10.

[0033] The management system 1 also includes a low-voltage network management computer 40, which is connected on one side to the DC / DC converter 30 and on the other side to the low-voltage battery 24. The low-voltage network management computer 40 is connected to the DC / DC converter to enable voltage control. The computer 40 and the low-voltage battery 24 can communicate via a network 15, such as an Ethernet network or via a CAN data bus.

[0034] The management system 1 further includes a monitoring device 50 configured to monitor at least one parameter of the low-voltage battery 24, or even a plurality of parameters of said battery 24. This parameter or these parameters include, in particular, the current delivered by the low-voltage battery 24, the voltage across the terminals of the low-voltage battery 24, and / or the temperature of the low-voltage battery 24. Indeed, these parameters can be indicative of the state of charge of the low-voltage battery 24. Monitoring this at least one parameter by the monitoring device 50, in particular during an inactive phase of the vehicle, for example, a parking phase, makes it possible to verify the state of charge of the low-voltage battery and to prevent a deep discharge of this battery.The 50 monitoring device can, for example, be integrated into the battery management system (called "BMS" for "Battery Management System" in English).

[0035] To prevent deep discharge of the low-voltage battery 24, system 1 is configured to implement a charge level management process for the low-voltage battery 24 of the electric or hybrid vehicle. Figure 2 illustrates the steps of this process. This low-voltage battery level management process 24 complements a time-based charging process; the two processes can thus operate in parallel.

[0036] The process begins with a step 100 that initiates a rest phase for the motor vehicle, for example, when the vehicle is parked in a parking space. To do this, a mission end condition can be tested. The mission end condition is checked when the vehicle is no longer in use, for example, after the doors have been locked. The vehicle then transitions from an active phase to an inactive phase, commonly referred to as a "parking phase." If the mission end condition is met, a monitoring timer begins. The duration of the monitoring timer can, for example, be between five and fifteen minutes inclusive. It can also be ten minutes.

[0037] The process includes an evaluation step 101 to assess the end condition of the monitoring timer countdown. If the monitoring timer countdown has not finished, the end condition is not met, and the process proceeds to a vehicle status check step 107. If the vehicle is awake—that is, if an event such as unlocking and / or opening a door or turning on the ignition has caused the vehicle to transition from its inactive (parking) phase to an active phase—the monitoring process proceeds to a final termination step 108. The process is then terminated, and the countdown is stopped. However, if the vehicle is not awake—that is, if the vehicle has remained in its parking phase—the process loops back to step 101, and the monitoring timer countdown continues.

[0038] Thus, if at the end of step 101 the monitoring timer countdown is finished, the process proceeds to one or more measurement steps 102, 103, 104 of at least one parameter of the low voltage battery 24. During this or these measurement steps 102, 103, 104, the monitoring device 50 measures more particularly the current delivered by the low voltage battery 24 and / or the voltage across the terminals of the low voltage battery 24 and / or the temperature of the low voltage battery 24.

[0039] As illustrated in Figure 2, the process includes, in particular, a measurement step 102 during which the monitoring device 50 measures the voltage across the terminals of the low-voltage battery 24, followed by a measurement step 103 of the current delivered by the low-voltage battery, and then a measurement step 104 of the temperature of the low-voltage battery. The order of the parameter measurement steps 102, 103, and 104 in the process may vary, depending on the importance of the parameters relative to a discharge situation.

[0040] In general, when the value of at least one parameter measured by the monitoring device 50 exceeds a threshold for a predetermined period, the process initiates a recharging of the low voltage battery 24 by at least one high voltage battery module 12. Indeed, an exceedance of a threshold for at least one of the aforementioned parameters may reflect a significant consumption of the energy supplied by the low voltage battery 24 without this consumption waking the motor vehicle; the aim is then to prevent a deep discharge of said battery 24.

[0041] The process includes, in particular, a measurement step 102 during which the monitoring device 50 measures the voltage across the terminals of the low-voltage battery 24. If the voltage across the terminals of the low-voltage battery 24 is less than or equal to a threshold, for example, less than or equal to 12.5 volts, this is potentially an anomaly, and the process proceeds to a verification step 105, which is explained later in the description. Alternatively, if the monitoring device 50 detects a voltage drop greater than or equal to 500 mV during step 102, the process can proceed to the verification step 105.

[0042] If the voltage across the terminals of the low voltage battery 24 is not less than or equal to the threshold indicated previously, the process proceeds to a step 103 during which the monitoring device 50 measures the current delivered by the low voltage battery 24.

[0043] During this measurement step 103, if the current delivered by the low-voltage battery 24 exceeds a threshold, this is potentially an anomaly, and the process proceeds to a verification step 105, which is explained later in this description. The current threshold could be, for example, 100 mA, 200 mA, or even 300 mA. The value of this threshold can be adjusted according to the type of vehicle and its components.

[0044] If the current delivered by the low voltage battery 24 is not above this threshold, the process proceeds to a step 104 during which the monitoring device 50 measures the temperature of the low voltage battery 24.

[0045] During this measurement step 104, if the temperature of the low-voltage battery 24 falls below a certain threshold, this constitutes a critical situation for the low-voltage battery 24, which is then unable to perform its functions correctly. In this particular case, it is advisable to increase the charge of the low-voltage battery 24 and raise its temperature using energy from the high-voltage battery 12. The process then proceeds to a verification step 105, which is explained later in this description. The threshold for the temperature of the low-voltage battery 24 can, for example, be less than or equal to -10°C, or even less than or equal to -15°C. The value of this threshold can be adjusted according to the type of vehicle and the size of the low-voltage battery 24.

[0046] If the temperature of the low voltage battery 24 is not below this threshold, the process proceeds to step 107 of vehicle condition check.

[0047] When a threshold is exceeded during measurement step 102, measurement step 103, or measurement step 104, the process proceeds to a verification step 105 in which the monitoring device 50 checks whether the threshold exceedance persists for a predetermined period. This ensures that it is indeed due to excessive consumption of the energy supplied by the low-voltage battery 24 and not a measurement error. In particular, if the measured value for at least one of the parameters exceeds the threshold for a longer period than a predetermined period, the process proceeds to a recharging step 106 in which one or more actions are taken to remedy the situation.

[0048] The predetermined duration of the verification step 105 can be between five and thirty seconds inclusive. For example, the predetermined duration could be ten seconds, fifteen seconds, or even twenty seconds. Different values ​​can be considered for such a duration. However, an excessive duration could itself lead to overconsumption, which would trigger the feeding cycle, which is undesirable. Preferably, the duration is chosen so as to be able to confirm with near certainty whether exceeding a threshold for at least one of the aforementioned parameters actually indicates significant consumption of the energy supplied by the low-voltage battery 24.

[0049] The charging step 106 corresponds more specifically to an exceptional top-up. During this step, the monitoring device 50 signals the control unit 40 that the low-voltage battery 24 needs to be topped up, independently of the time-based top-up process operating in parallel. The low-voltage battery 24 can be fully recharged (100% charge) during this exceptional top-up. A 100% charge is easier to achieve and allows for the longest possible parking time before another top-up is required. However, a partial charge can also be considered, for example, an 80% charge or a 75% charge.

[0050] Optionally, the recharging step 106 may include a sub-step of warming the low voltage battery 24 when the monitoring device 50 detects a temperature of the low voltage battery 24 less than or equal to -10°C, or less than -15°C.

[0051] In this particular embodiment, the motor vehicle includes a heating means 60 configured to warm the low-voltage battery 24 when an exceedance of the temperature threshold has been detected by the monitoring device 50. Various embodiments can be envisaged for heating the low-voltage battery 24.

[0052] According to a first embodiment, the low-voltage battery 24 is, for example, enclosed in a housing, and a heating pad is placed in contact with one of the housing walls. The heating pad can, for example, take the form of a heating blanket or a mat comprising a resistive wire, such as a resistive coil. When a current flows through the resistive coil, it heats up, and the heat is then diffused to the battery through the housing wall, thus increasing its temperature. The heating pad then acts as a heating element 60. Alternatively, the low-voltage battery 24 includes an internal heating element 60, such as heating sheets arranged between the battery cells 24.Other heating means 60 may be considered to warm the low voltage battery 24 when the monitoring device 50 detects a temperature too low for said battery 24.

[0053] The sub-step of heating the low voltage battery 24 is notably controlled by the computer 40. Heating the low voltage battery 24 with a heating means 60 makes it possible to limit the loss of battery autonomy, or even to bring the battery back to an adequate operating temperature if the heating is powerful enough.

[0054] Battery heating can be interrupted, or even stopped, when the battery temperature reaches a reference value, which could be, for example, -5°C. Other reference values ​​for stopping battery heating, including higher temperature values, can be considered.

Claims

DEMANDS 1. A method for managing the charge level of a low-voltage battery (24) of an electric motor vehicle, the motor vehicle further comprising at least one high-voltage battery module (12), the method being characterized in that it comprises: - a step (100) for initiating a rest phase of the motor vehicle, for example when the vehicle is parked in a parking space, and starting a monitoring timer; then - a step (101) for evaluating an end-of-countdown condition for the monitoring timer; then - when the monitoring time interval has elapsed, one or more measurement steps (102, 103, 104) of at least one parameter of the low-voltage battery, during which a monitoring device (50) measures the current delivered by the low-voltage battery (24) and / or the voltage across the terminals of the low-voltage battery (24) and / or the temperature of the low-voltage battery (24); then - if at least one of these parameters exceeds a threshold specific to each parameter, a verification step (105) during which the monitoring device (50) checks whether this exceedance of the threshold persists for a predetermined period; then - if the threshold is exceeded for a predetermined period, a recharging step (106) of the low voltage battery (24) by at least one high voltage battery module (12).

2. Method according to the preceding claim, characterized in that the duration of the monitoring time delay is between five and fifteen minutes inclusive, and in particular equal to ten minutes.

3. A method according to any one of the preceding claims, characterized in that the predetermined duration of the verification step (105) is between five and thirty seconds inclusive, and more particularly equal to ten seconds.

4. A method according to any one of the preceding claims, characterized in that it comprises a measurement step (102) of the voltage across the terminals of the low voltage battery (24), and in that the method proceeds to the verification step (105) if the monitoring device (50) detects a voltage drop greater than or equal to 500mV.

5. A method according to any one of the preceding claims, characterized in that it comprises a measurement step (103) of the current delivered by the low voltage battery (24) and in that the method proceeds to the verification step (105) if the monitoring device (50) detects a current greater than or equal to 100mA, and more particularly greater than or equal to 200mA, or even greater than or equal to 300mA.

6. A method according to any one of the preceding claims, characterized in that it comprises a measurement step (104) of the temperature of the low voltage battery (24) and in that the method proceeds to the verification step (105) if the monitoring device (50) detects a temperature less than or equal to -10°C.

7. Method according to the preceding claim, characterized in that the method further comprises a step of heating the battery (24) by a heating means (60) of the motor vehicle when the monitoring device (50) detects a temperature of the low voltage battery (24) less than or equal to -10°C, a heating step during which the heating means (60) heats the battery (24) until the temperature of the low voltage battery (24) reaches -5°C.

8. A method according to any one of the preceding claims, characterized in that the low voltage battery (24) of the vehicle is brought to a maximum charge level during the recharging step (106).

9. System (1) for managing the charge level of a low-voltage battery (24) for a motor vehicle, the system being configured to implement a method according to any one of the preceding claims, the system comprising: - a high voltage network (10) comprising at least one high voltage battery module (12) and at least one component (14, 16) capable of driving the drive wheels of the motor vehicle; - a low voltage network (20) comprising a low voltage battery (24) and at least one low voltage electrical device; - a monitoring device (50) configured to monitor at least one parameter of the low voltage battery (24).

10. Motor vehicle characterized in that it is equipped with a system (1) according to the preceding claims or characterized in that it is configured to implement a method according to one of claims 1 to 8.

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