WO2008034991A1

WO2008034991A1 - Method for controlling the charge of a vehicle battery

Info

Publication number: WO2008034991A1
Application number: PCT/FR2007/051921
Authority: WO
Inventors: Franck Ragot; Bernard Sahut; Christine Chabot Petrault; Nathalie Le Beuze
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2006-09-20
Filing date: 2007-09-12
Publication date: 2008-03-27
Also published as: FR2905915B1; FR2905915A1

Abstract

The invention relates to a method for deciding the application of an optimised charge voltage to the battery of a vehicle, said optimised voltage being higher than the regular charge voltage. The decision to apply an optimised charge voltage is taken in a charge control unit fitted in the vehicle and upon activation of the vehicle. According to the invention, the control unit measures the electric energy used by the electric receivers since the last stop of the engine, and if the time elapsed since the last stop is longer than a minimal duration, a charge state of the battery is estimated based on a measurement of the open-circuit voltage (U). The optimised charge voltage is applied if the amount of energy used is higher than a first threshold value or if the charge is lower than a second threshold value. The invention pertains to automotive vehicles with a thermal engine.

Description

Method of managing the charge of a vehicle battery

The invention relates to the charging of a battery of a vehicle equipped with electrical receivers that can be used in particular when the vehicle engine is not running.

The number and power of electric receivers equipping motor vehicles are continuously increasing. These receivers are, for example, power windows, remote control receivers, burglar alarms, internal lights, mobile phone chargers, or LCD video screens. These new receivers help to increase the consumption of electrical energy that is taken from the vehicle's battery. This is for example the case when an LCD screen or a window lifter is used by a vehicle occupant when the engine is not running, the electric current consumed then coming only from the battery.

But the energy taken from the battery is significant even in the absence of occupant in the vehicle. For example, the remote control receiver is continuously powered to be sensitive at all times to an opening signal emitted by an opening remote control.

This increase in electrical energy taken from the battery is currently resulting in an increase in vehicle failures whose cause is only a discharge of the battery.

One way of remedying this problem is to equip the vehicle with a battery charge level evaluation box, which makes it possible to know continuously this level of charge. This housing takes into account various parameters conditioned by the state of Battery charge, such as voltage, current, temperature.

When the case reveals that the battery is too discharged, an optimized charge voltage is applied to it as soon as the engine is running so as to accelerate the charging process. Such a housing thus makes it possible to refine the management of the charge of the battery, to limit as much as possible the situations in which this battery could be completely discharged.

The cost of such a housing as well as the need to integrate it into the battery environment, however, are two significant obstacles to this solution. The object of the invention is to propose a solution that significantly improves the management of the charge level of the battery without having to implant a battery charge evaluation box.

For this purpose, the subject of the invention is a method of deciding to apply a so-called optimized charging voltage to a battery of a vehicle, from a load management unit equipping this vehicle, in which the unit of managing the electrical energy consumed by the electrical receivers of the vehicle since the last engine stop, in which if the time elapsed since the last stop of the vehicle is greater than a minimum duration, it is estimated in the management unit a charging state of the battery based on a measurement of the empty voltage of this battery when the vehicle awakes, and in which it is decided in the management unit to apply an optimized charging voltage if the amount of energy consumed is greater at a first threshold value or if the charge of the battery is less than a second threshold value. The invention also relates to a method as defined above, in which it is also decided to apply the optimized charging voltage if a temperature resulting from a temperature sensor fitted to the vehicle is below a threshold temperature.

The invention also relates to a method as defined above, wherein it is also decided to apply an optimized charging voltage if the vehicle has traveled a total mileage less than a mileage threshold.

The invention also relates to a method as defined above, wherein it is also decided to apply an optimized charging voltage if the time elapsed since the last stop is greater than a predetermined value, such as a week.

The invention also relates to a method as defined above, in which the determination of the state of no-load charge of the battery based on an empty voltage measurement is corrected with a temperature value resulting from a probe located out of the battery.

The invention also relates to a method as defined above, wherein the electrical energy consumed by the receivers since the last stop is counted on the basis of the time of use of each receiver determined from information circulating on a network of the vehicle to which the management unit is connected, and average consumption of these receivers registered in the management unit.

The invention also relates to a method as defined above, further comprising prohibiting the use of certain receivers of the vehicle if the energy consumed is greater than a third threshold value greater than the first threshold value if the state of charge of the battery is less than a fourth threshold value lower than the second threshold value.

The invention will now be described in more detail, and with reference to the single figure which is a representation of the method according to the invention, in block diagram form. The invention provides a method for deciding to apply a so-called optimized charging voltage to a battery identified by Batt, this optimized charging voltage being substantially greater than a normal charging voltage.

The choice of the charging voltage to be applied to the battery is made during the wake up of the vehicle, which follows a standby phase during which the majority of the vehicle's electrical receivers such as its computers are disabled.

The alarm clock corresponds to a phase during which different computers are reactivated, this alarm being caused in particular by the unlocking of the vehicle, or by the fact that an electric receiver is actuated by a user.

The vehicle comprises a battery charge management unit, not shown, including a processor and memory means. This management unit is advantageously connected to an on-board network of the vehicle, such as a CAN-type network, it is deactivated when the vehicle is in standby, and it is reactivated at the beginning of the wakeup phase of the vehicle.

When the management unit is active while the engine of the vehicle is stopped, the management unit records the energy taken from the battery since the engine stopped.

This accounting is done by counting the time of use of each receiver, and using data stored in the memory of the management unit, which are representative of the average consumption of each receiver.

The amount of electrical energy thus evaluated is stored by the management unit before falling asleep of the vehicle. It should be noted that the management unit can be configured to make evaluations of the state of charge of the battery at regular intervals, when the motor is stopped while receivers are in operation. It can thus gradually determine the average consumption of each receiver to memorize it. But the average consumption data of the receivers can also be prerecorded in the management unit, the values being derived from more precise measurements of the receivers, these measurements being for example carried out on a test bench. The management unit also determines the elapsed time since the last stopping of the engine, or the idle time elapsed since the last stopping of the engine. This determination can be made during the wake up of the management unit by consulting data representative of the date and time, circulating on the network.

When the vehicle wakes up, the management unit determines whether the elapsed time is greater than a minimum duration of, for example, six or seven hours. If so, the state of empty charge of the battery is determined, from the voltage U of the empty battery, and a temperature data T ° resulting from a thermal probe equipping the vehicle.

To do this, the management unit interrogates through the on-board network a sensor of the battery U voltage Batt and a temperature sensor. It then determines in block 1 the state of no load from this vacuum voltage U and temperature T °, and recorded charts to deduce the state of charge.

By sensor of the voltage U, here means a sensor that can be integrated into a computer fitted to the vehicle. In this case, the computer in question measures its supply voltage which it corrects to estimate the voltage U at the terminals of the battery.

The estimation of the state of charge is carried out only if the vehicle has been stopped for a period longer than the minimum duration, which allows the battery voltage to stabilize, so as to accurately reflect the battery charge level.

This estimate is made first when the vehicle wakes up, that is to say say before the commissioning of other electrical receivers. The voltage supplied by the sensor thus corresponds to a vacuum voltage U of the battery, which constitutes information making it possible to accurately and simply determine the state of charge of the battery at this time.

This minimum duration also ensures that the temperature of the battery is identical to that of the environment of the probe used. The temperature sensor is advantageously an engine temperature sensor, so that it is not necessary to provide a temperature sensor specifically dedicated to the battery.

After being determined, the idle state of charge is stored by the management unit. After determining the energy consumed and possibly the state of charge of the battery, the management unit is thus able to decide the charging voltage to be applied, which corresponds to block 2. Thus, after starting the engine thermal, the management unit can control the alternator Alt so that it applies a load voltage is normal or optimized, which is shown in block 3.

After stopping for a few hours, during which the occupant of the vehicle listened to the radio and used a video screen, a reliable estimate of the state of charge of the battery can not be established if the downtime is less than minimum duration.

But in this case, if the amount of energy consumed is greater than a first threshold value, the management unit decides to apply an optimized voltage to the battery to facilitate recharging. The first threshold value is for example a certain fraction, such as a third, of the total capacity of the battery.

In the more common case where the vehicle was not used all night, that is to say for more than six or seven hours, when the alarm clock, the energy consumed is close to zero, that is to say say not involving the application of an optimized charging voltage. But in this case, the management unit is able to establish a reliable estimate of the state of charge of the battery to apply an optimized voltage if this state of charge turns out to be less than a second threshold value.

The second threshold value is for example two-thirds of the capacity of the battery.

Advantageously, the management unit also decides to automatically apply an optimized charging voltage if the temperature T ° resulting from the temperature probe is in itself lower than a low temperature threshold. Indeed, it appears that the low temperatures make charging the battery more difficult, so that an optimized voltage is then desirable.

It is also advantageous if the management unit decides to automatically apply an optimized charging voltage if the vehicle is new, that is to say if its mileage is less than a lower mileage threshold, for example worth a few hundreds of kilometers.

Indeed, it appears that when a new vehicle has been acquired, his or her users tend in a first time to strongly solicit their electrical equipment they discover. It follows that at the beginning of life, the battery is more heavily stressed than later, so that an optimized charging voltage is also desirable.

Advantageously, the management unit also decides to automatically apply an optimized charging voltage if the stopping time of the vehicle is greater than a maximum duration of, for example, one week. This aims to to compensate for the discharge due to the receivers which are not put on standby, such as, for example, the one or more vehicle opening remote control sensors which are continuously active. The different threshold values mentioned above are stored in the management unit, for example during its configuration on a production line, the threshold values above being given for information only. The management unit whose function is to limit the risk of significant discharge of the battery can also intervene on the receivers to prohibit operation if the situation warrants.

This is the case if, after waking the vehicle, it turns out that the amount of energy consumed since the last stop is greater than a third threshold value corresponding to a very high consumption involving a large discharge of the battery.

This third threshold value is greater than the first threshold value, and is for example two thirds of the total capacity of the battery.

This is also the case if, after waking the vehicle, it turns out that the state of charge of the battery is less than a fourth threshold value corresponding in itself to a very low level of charge. This fourth threshold value is less than the second threshold value and is for example one third of the total capacity of the battery.

The management unit then transmits data on the CAN network to prohibit the operation of certain receivers considered non-vital. These receivers considered non-vital are for example the radio or video screens fitted to the vehicle, which have a significant consumption that could penalize the charging of the battery.

The value of the optimized charging voltage is obtained by driving the alternator of the vehicle so that it delivers a certain output voltage during a predetermined charging time. The application of this optimized voltage can be controlled directly by the management unit, or by another body interrogating this management unit and driving the alternator.

Advantageously, the optimized charging voltage and the duration during which it is applied both depend on the temperature, the optimized charging voltage and its duration of application being even lower than the temperature T ° is high.

Such a correspondence law is represented in the table below, this law being advantageously memorized in the management unit.

Charge duration voltage charge

T ° <0 ° c 14.5 to 15.5 30 to 120 volts minutes

0 ° c <T <14 to 15 volts 10 to 60 30 ° c minutes

30 ° C <T ° 13 to 14 volts 10 to 60 minutes

It should be noted that the estimation of the state of charge of the battery which is carried out as soon as the vehicle awakes can be corrected by taking into account the energy consumed between the instant when the estimate based on the no-load voltage U is performed and the subsequent moment when the engine is started, which improves the accuracy of the evaluation.

The state of charge after starting results from the difference between the state of charge based on the no-load voltage and the electrical energy consumed during the waking phase.

If for example the user listens to a vehicle radio after the start of the alarm, but before switching on the starter, the radio consumption is then counted to allow an accurate assessment of the state of charge of the battery after starting the engine.

Claims

REVENDI CATIONS

A method for deciding to apply a so-called optimized charging voltage to a battery (Batt) of a vehicle, from a charge management unit equipping said vehicle and when waking up this vehicle, in which it is counted in the management unit the electrical energy consumed by the vehicle's electrical receivers since the last engine stop, in which, if the time elapsed since the last stop of the vehicle is greater than a minimum time, the management unit shall be deemed to be in a state of charging the battery based on a measurement of the empty voltage (U) of this battery, and in which it is decided in the management unit to apply an optimized charging voltage if the amount of energy consumed is greater than at a first threshold value or if the charge of the battery is less than a second threshold value.

2. The method of claim 1, wherein it is also decided to apply the optimized charging voltage if a temperature (T °) resulting from a temperature sensor fitted to the vehicle is less than a threshold temperature.

3. The method of claim 1 or 2, wherein it is also decided to apply an optimized charging voltage if the vehicle has traveled a total mileage less than a threshold mileage.

4. Method according to one of claims 1 to 3, wherein it is also decided to apply an optimized charging voltage if the time elapsed since the last stop is greater than a predetermined value, such as a week.

5. Method according to one of claims 1 to 4, wherein the determination of the state of empty charge of the battery (Batt) based on a measurement of no-load voltage (U) is corrected with a temperature value ( T °) resulting from a probe located outside the battery (Batt).

6. Method according to one of claims 1 to 5, wherein the electrical energy consumed by the receivers since the last stop is counted on the basis of the time of use of each receiver determined from information circulating on a network. of the vehicle to which the management unit is connected, and average consumption of these receivers registered in the management unit.

7. Method according to one of the preceding claims, further comprising prohibiting the use of certain receivers of the vehicle if the energy consumed is greater than a third threshold value greater than the first threshold value if the state of charge of the battery (Batt) is less than a fourth threshold value lower than the second threshold value.