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

Abstract

Method for managing the charge level of a low-voltage battery in an electric motor vehicle. 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 characterized in that it comprises: - a step (100) of initiating a rest phase of the vehicle and starting a monitoring timer; - a step (101) of evaluating an end-of-countdown condition of the monitoring timer; - when said timer has elapsed, one or more measurement steps (102, 103, 104) of a parameter of the low-voltage battery; - if at least one parameter exceeds a threshold, a verification step (105) where the monitoring device (50) checks whether this exceedance persists for a predetermined duration;- if the threshold is exceeded for the said duration, a recharging step (106) of the low voltage battery (24) by at least one high voltage battery module (12). Figure for the abbreviation: Fig.1;

Description

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

[0001] 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.

[0002] In the field of electric vehicles, managing the power supply of said electric vehicles can be complex, because even when the vehicle is in an inactive phase, for example when the vehicle is parked in a parking space for a given period, certain parts of the electric vehicle may remain active or become active intermittently. These parts then continue to draw energy from one or more of the electric vehicle's batteries. It can therefore be difficult to accurately measure, monitor, and manage the battery charge level without consuming too much energy when the vehicle is in such an inactive phase.

[0003] 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.

[0004] The low-voltage battery of such an electric vehicle generally has a low capacity, yet this low-voltage battery provides the electrical energy required by the electronic standby components when the vehicle is in an inactive phase. To prevent complete discharge of the low-voltage battery, at least one recharge of said battery can be carried out while the electric vehicle is in this inactive phase. Thus, a particular charging method, commonly called "top-up charging," consists of partially and periodically recharging the low-voltage battery when the vehicle is stationary, in an inactive phase.

[0005] However, such battery charging is generally based on a theoretical battery consumption. Charging is usually triggered when a time delay has elapsed, the time delay being estimated from a theoretical battery consumption. Such time-based charging thus ensures regular low-voltage battery recharging when the electric vehicle undergoes a prolonged inactive phase, but it does not allow for consideration of exceptional circumstances that can accelerate the discharge of the low-voltage battery.

[0006] Indeed, the low-voltage battery's limited capacity poses a risk of deep discharge should unexpected power consumption and / or a significant drop in temperature cause the battery to operate 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.

[0007] The object of the invention is to remedy the disadvantages described above by proposing a method of managing the battery charge level that takes into account particular circumstances that may generate an unusual discharge of the battery, the method also allowing exceptional charging of the battery at low voltage in certain circumstances to avoid a breakdown immobilizing the vehicle.

[0008] To this end, the invention relates to a method for managing the charge level of a low-voltage battery of an electric motor vehicle, the motor vehicle further comprising at least one high-voltage battery module, the method being characterized in that it comprises: - 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

[0009] - an evaluation step of an end-of-countdown condition for the timer monitoring; then

[0010] - when the monitoring timer has expired, one or more steps of measurement 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

[0011] - 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 exceedance of the threshold persists for a predetermined period; then

[0012] - 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.

[0013] This method complements the temporal feeding mentioned above. This method allows for a simple and adequate on-board automatic refilling to cover various unforeseen or unusual cases that would lead to a deep discharge of the low-voltage battery.

[0014] In particular, the monitoring device regularly monitors the state of charge of said battery and triggers an exceptional top-up when the situation requires it.

[0015] According to one embodiment, the duration of the monitoring timeout is between five and fifteen minutes inclusive, and in particular equal to 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 method includes a step of measuring the current delivered by the low voltage battery and the method proceeds to the step of checking 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 method includes a step of measuring the temperature of the low voltage battery and the method proceeds to the step of checking if the monitoring device detects a temperature less than or equal to -10°C.

[0020] According to one embodiment, the method further comprises a step of heating the battery by a means of heating the motor vehicle when the monitoring device detects a temperature of the low voltage battery less than or equal to -10°C, a heating step during which the heating means heats the battery until the temperature of the low voltage battery reaches -5°C.

[0021] According to one embodiment, the vehicle's low-voltage battery is brought to a maximum charge level during the recharging step.

[0022] 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: - 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; - a low voltage network including a low voltage battery and at least one low voltage electrical device; - a monitoring device configured to monitor at least one parameter of the low-voltage battery.

[0023] 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.

[0024] 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:

[0025] Fig. 1 schematically illustrates a low-voltage battery management system according to one embodiment of the invention.

[0026] Figure 2 illustrates the steps of a process according to the invention.

[0027] In this description, the terms "first", "second", "third", etc. These terms 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 such as "before," "after," "unique," and other similar 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.

[0028] Figure 1 illustrates a low-voltage battery management system 1 suitable for implementing the claimed method. The 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 a main drive system of the motor vehicle. 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.

[0029] 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 the interior lighting of the vehicle 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 may be a lithium battery or a lead-acid battery. Other types of batteries may be considered. The voltage of the low-voltage battery 24 may, for example, be 12 V.

[0030] 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 DC 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.

[0031] 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 allow 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.

[0032] 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).

[0033] To prevent deep discharge of the low-voltage battery 24, the system 1 is configured to implement a method for managing the charge level of the low-voltage battery 24 of the electric or hybrid vehicle. Figure 2 illustrates the steps of this method. This method for managing the charge level of a low-voltage battery 24 complements a time-based charging method; the two methods can thus operate in parallel.

[0034] The method begins with a step 100 that initiates a rest phase of 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, in particular, be ten minutes.

[0035] The method includes an evaluation step 101 for evaluating an end-of-countdown condition for the monitoring timer. If the countdown of the If the monitoring timer has not finished, the countdown end condition is not met, and the process proceeds to step 107, which verifies the vehicle's status. If the vehicle is woken up—that is, if an event such as unlocking and / or opening a door or turning on the ignition has caused the vehicle to move from its inactive (parking) phase to an active phase—the monitoring process proceeds to a final step 108. The process is then terminated, and the countdown is stopped. However, if the vehicle is not woken up—that is, if the vehicle has remained in its parking phase—the process loops back to step 101, and the monitoring timer countdown continues.

[0036] 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.

[0037] As illustrated in [Fig. 2], the method 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 method may differ, depending on the importance of the parameters in relation to a discharge situation.

[0038] Generally, when the value of at least one parameter measured by the monitoring device 50 exceeds a threshold for a predetermined period, the method initiates a recharging of the low-voltage battery 24 by at least one high-voltage battery module 12. Indeed, exceeding 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.

[0039] The method 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 method proceeds to a verification step 105 explained later in the description.

[0040] In addition, or alternatively, if the monitoring device 50 detects a voltage drop greater than or equal to 500mV during step 102, the process can proceed to verification step 105.

[0041] 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.

[0042] 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 the description. The current threshold can, for example, be 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.

[0043] 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.

[0044] During this measurement step 104, if the temperature of the low-voltage battery 24 falls below a certain threshold, this situation becomes difficult for the low-voltage battery 24 to manage, as it is no longer able to perform its functions correctly. In this particular case, it is then desirable to increase the charge of the low-voltage battery 24 and raise its temperature using energy from the high-voltage battery 12. The process 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.

[0045] If the temperature of the low voltage battery 24 is not below this threshold, the process proceeds to step 107 of checking the condition of the vehicle.

[0046] 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.

[0047] 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 allow confirmation with near certainty as to whether exceeding a threshold for at least one of the aforementioned parameters actually reflects significant consumption of the energy supplied by the low-voltage battery 24.

[0048] The charging step 106 corresponds more specifically to an exceptional top-up. During this step, the monitoring device 50 signals to the control unit 40 that the low-voltage battery 24 needs to be topped up, independently of the time-based top-up process that operates 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 a further top-up is required. However, a partial charge can also be considered, for example, an 80% charge, or a 75% charge.

[0049] Optionally, the recharging step 106 may include a substep 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.

[0050] In this particular embodiment, the motor vehicle includes a heating means 60 configured to heat 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.

[0051] According to a first embodiment, the low-voltage battery 24 is, for example, confined within a housing, and a heating pad is placed in contact with one of the walls of the housing. 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 towards the battery through the wall of the housing, thus increasing its temperature. The heating pad then acts as a heating element 60.

[0052] Alternatively, the low-voltage battery 24 includes internal heating means 60 within said battery 24, such as heating sheets arranged between the cells of the battery 24. Other heating means 60 may be envisaged. to warm up 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 may, for example, be -5°C. Other reference values ​​for stopping battery heating, including higher temperature values, may be considered.

Claims

Demands

1. 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) of initiating a rest phase of the motor vehicle, for example when the vehicle is parked in a parking space, and of starting a monitoring timer; then - a step (101) of evaluating an end-of-countdown condition of 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 duration; then - if the exceedance of the threshold persists for a predetermined duration, a recharging step (106) of the low-voltage battery (24) by at least one high-voltage battery module (12).

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

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