WO2008107616A2

WO2008107616A2 - Method and system for monitoring the state of charge of, and conditioning, an electric power storage unit of a vehicle

Info

Publication number: WO2008107616A2
Application number: PCT/FR2008/050140
Authority: WO
Inventors: Nicolas Guerin; Mickaël Martino
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2007-02-01
Filing date: 2008-01-29
Publication date: 2008-09-12
Also published as: FR2912268B1; FR2912268A1; WO2008107616A3

Abstract

The invention relates to a method and a system for monitoring the state of charge of and conditioning a first electric power storage unit (12) of a motor vehicle comprising a second electric power storage unit (14) and means (16) for connecting the first unit to the second unit. According to the method, the level of charge (SOC(P)) of the first unit is monitored when the engine of the vehicle is shut off, and the connecting means (16) are instructed to periodically recharge, at predetermined time intervals, the first unit (12) using the second unit (14) when said level of charge is less than or equal to a predetermined level of charge (SOC(low)).

Description

Method and system for monitoring the state of charge and conditioning of an electrical energy storage member of a vehicle

The present invention claims the priority of the French application 0753007 filed 01/02/2007 whose content (description, claims and drawings) is incorporated herein by reference.

The present invention relates to a method and a monitoring system of the state of charge and conditioning of an electrical energy storage member, for example a supercapacitor, a thermal engine vehicle which comprises, in in addition, another organ for storing electrical energy, for example a battery. One of the two organs is used to start the engine.

In certain types of motor vehicles, such as hybrid vehicles (with thermal and electric engines), or for certain applications, such as the Stop & Start function, it is interesting to have a source of energy. additional electric (in addition to the conventional battery usually 12 volts). When this additional source of energy is used for starting the engine, it must provide a large amount of electrical power in a short period of time. In other words, this energy source must store a large electrical power. For this purpose, it is possible to use supercapacitors or batteries typed powers.

A major disadvantage of these electrical power organs, including supercapacitors, comes from the fact that their electrical load tends to decrease over time, by self-discharge. It can thus meet serious difficulties to start the engine during a prolonged immobilization of the vehicle, when the state of charge of the power unit is too weak (the starting torque, which depends directly on the state of charge, is then too low).

[Ooo5] The patent FR 2751 145 proposes a solution to limit the discharge of the battery when the alternator can not provide the current necessary for the normal operation of the electrical network of the automobile. To this end, a supercapacitor and a charge control system of the supercapacitor and the battery are used. Switching means provide the interruption or establishment of the electrical connection between the supercapacitor and the battery depending on whether the battery is charging or discharging. The method and the device described in this patent do not solve the problem of the self-discharge of the supercapacitor and the battery, in particular due to a prolonged stop of the vehicle.

Patent EP 1 013 506 discloses a control method of an onboard network for a motor vehicle which comprises a battery and a supercapacitor. A converter is used to charge the supercapacitor "while the motor vehicle rolls its momentum."

The patent application EP 1403143 teaches to maintain the state of charge at a supercapacitor to restart the vehicle, for a period for example of the order of 24 hours. During this period, a continuous monitoring of the state of charge of the supercapacitor is operated. Beyond this period, the state of charge is no longer controlled and recharging is no longer systematically performed. On the other hand, when the restart of the vehicle becomes probable (for example following the unlocking of a door), the recharging of the supercapacitor is controlled. Here, the self-discharge compensation can compromise the vehicle restart. The present invention proposes a solution to solve this problem.

More specifically, the invention relates to a method of monitoring the state of charge and conditioning of a first electrical energy storage member of a motor vehicle comprising a second storage member of electrical energy and means for connecting the first member to the second member. According to the method, the charge level of the first member is periodically checked at predetermined time intervals when the vehicle is stopped, and the connection means is controlled to recharge the first member with the second member when said charge level. is less than or equal to a predetermined load level.

[Ooio] The control means are therefore according to the invention only activated at predefined time intervals, which avoids unloading one of energy storage simply for these control means.

Advantageously, the control of the charge level of the first member is advantageously stopped after a predetermined number of checks.

Preferably, the charge level of the second member is compared to a predetermined low threshold level and the periodic control of the charge level of the first member is interrupted if the charge level of the second member is lower than the low threshold level. .

The invention also relates to a system for monitoring the state of charge and conditioning of a first electrical energy storage member of a motor vehicle comprising a second member storage of electrical energy, means for connecting the first member to the second member for transferring electrical energy between said members, an electric machine powered by the first member and means for controlling the connection means. According to the invention, the system comprises means for comparing the state of charge of the first member with a predetermined threshold, said comparison means operating periodically at predetermined time intervals when the engine of the vehicle is stopped.

For example, the first storage member may be a supercapacitor or a battery, the second storage member may be a battery, the electric machine may be a reversible alternator or a conventional alternator associated with a starter and the connection means may consist of a converter or a contactor connecting in parallel the storage members.

Other advantages and features of the invention will become apparent from the following description of several embodiments of the invention, given by way of non-limiting examples, with reference to the accompanying drawings and in which:

• Figure 1 shows schematically the architecture of the system,

FIG. 2 illustrates the successive steps of the method of monitoring and conditioning an electrical energy storage member while the ignition is off and without having received an annunciator signal for starting the engine, and

In FIG. 1, a motor vehicle (not shown) equipped with a heat engine, and possibly an electric motor in the case of a hybrid vehicle, is equipped with a system comprising an electric machine 10, for example a conventional alternator associated with a starter or a reversible alternator (acting as starter by driving the crankshaft of the engine when the alternator is supplied with electric current). A first member 12 for storing electrical energy is connected to the electrical machine 10 so as to supply it with electric power. A second member 14 for storing electrical energy is connected to electricity consumers 20, such as, for example, headlights or windscreen wipers.

The first member 12 is preferably an electrical power storage member, for example a supercapacitor or a battery, capable of supplying the machine 10 with a high intensity current in a short period of time (in other words , a high electric power), which makes it easier to start the engine. The second member 14 may be for example a conventional battery (usually 12VoItS), generally less sensitive to self discharge than a supercapacitor, the battery constituting a large and durable reserve of electrical energy.

Connection means 16 of the two members 12 and 14 are used to transfer electrical energy between these two bodies. The connection means 16 may be, for example, a contactor that can connect in parallel the two members 12 and 14, or a DC / DC converter when the voltage across the first member (for example 20 volts for a supercapacitor) is higher that the voltage at the terminals of the second member (for example 12 Volts for a conventional battery). The connection means 16 can be controlled using a computer 18 which can be a computer initially provided in the vehicle or be a dedicated computer, which is preferable because it consumes less energy than a non-dedicated computer (This is important since the computer must remain in standby while the vehicle is immobilized or waking up periodically). The calculator makes it possible in particular to compare the states of charges and / or the electrical voltages provided by the energy storage members, with each other or with predetermined thresholds, as explained below.

Figure 2 is a graph of the different states that can take the system and illustrates a method of implementation of the method. The method here consists, during the vehicle idle time, in monitoring the state or charge level of the power storage device 12 and conditioning / recharging if its state or charge level is too low to start engine.

Initially, the system is in an initial state A, engine stopped, and goes into a waiting state B in which the load state EDC (P) of the power store is periodically compared in the computer 18 to a predetermined low load state EDC (arrow 22), which is fixed to allow easy starting of the engine with the aid of the power storage member 12. By easy starting, it can be heard a level higher than the level necessary for a start using the power store as a power source - or a level possibly lower than this level, but which will nevertheless be sufficient to shorten the duration of the load of the power store, at the time of a restart command, so that this recharge is no longer a "dead time" which affects the approval of vehicle users.

While EDC (P) is above the EDC energy state threshold (low), the power store 12 does not need to be reloaded and the system remains in the waiting state B.

When EDC (P) becomes less than or equal to EDC (low), the power store 12 is recharged or conditioned. The system goes into state C (which may be a DC / DC converter) in which the computer 18 controls the connection means 16 to connect the storage members 12 and 14 in parallel so as to transfer energy from organ 14 to the member 12 (arrow 26), until EDC (P) reaches a predetermined high value EDC (high), this value being greater than or equal to EDC (low).

When the load of the member 12 reaches the value EDC (high), the system returns to the waiting state B (arrow 24). The monitoring method may however stop, the system going from state B to a state D (arrow 28) of inaction of the computer 18, if the number of checks of the value of the state of charge EDC (P ) of the power storage device is greater than or equal to a predetermined number. In other words, for EDC (P)> EDC (low), the system goes from state B to state D after a predetermined monitoring time. The system may also transition from state C to state D (arrow 30) if the level of charge EDC (E) of the energy storage member 14 is less than or equal to a predetermined energy threshold EDC (E, threshold). This energy level threshold corresponds to a charge level of the energy store 14 insufficient to ensure the raising of the level of the power unit 12 and the correct operation of the electrical consumers powered by the member 14.

The minimum acceptable state of charge of the energy store (EDC (E, min) and the threshold of the state of charge of the power store can be chosen variable depending on the outside temperature.

The method and system described can be used especially in a "Stop & Start" device, for which the vehicle engine stops and restarts automatically when the vehicle is stopped. The first energy storage member is then advantageously a supercapacitor forming part of the "Stop & Start" device.

Other embodiments than those described and shown may be designed by those skilled in the art without departing from the scope of the present invention. The examples indicated above indicate the recharging the power storage member 12 by the energy storage member: it is obvious that the method described could easily be applied to the conditioning of the energy storage member 14 by the storage member In addition, the power storage device 12 could be an energy storage device, as could the energy storage device 14 be a power storage device.

Claims

1. A method for monitoring the state of charge and conditioning of a first member (12) for storing electrical energy of a motor vehicle comprising a second member (14) for storing electrical energy and means connecting the first member (16) to the second member, the method being characterized periodically at predetermined time intervals to control the charge level (EDC (P)) of the first member when the vehicle engine is stopped, and controlling the connection means (16) to recharge the first member (12) with the second member (14) when said charge level is less than or equal to a predetermined charge level (EDC ( low)).

2. Method according to claim 1 characterized in that the charge level control (EDC (P)) of the first member is stopped after a predetermined number of checks.

3. Method according to one of claims 1 or 2 characterized in that the charge level (EDC (E)) of the second member (14) is compared to a predetermined low threshold level (EDC (E, threshold)) and in that the periodic check of the load level of the first member is interrupted if the load level (EDC (E)) of the second member is lower than said low threshold level (EDC (E, threshold)).

4. Method according to claim 3, characterized in that said low threshold level (EDC (E, threshold)) is chosen variable depending on the outside temperature.

5. System for monitoring the state of charge and conditioning of a first member (12) for storing electrical energy of a motor vehicle comprising a second member (14) for storing energy electrical means, connecting means (16) of said members between them for transferring electrical energy between said members, an electric machine (10) powered by the first member (12) and means for controlling the connection means, the characterized in that it comprises means (18) for comparing the state of charge (EDC (P) of the first member with a predetermined threshold (EDC (low)), said comparison means (18) operating when the vehicle engine is stopped, periodically at predetermined time intervals.

6. System according to claim 5 characterized in that the first member (12) for storage is a supercapacitor or a battery, the second storage member is a battery, the electric machine is a reversible alternator or a conventional alternator associated with a starter and the connection means (16) consist of a converter or a contactor connecting in parallel the storage members (12, 14).

7. System according to claim 5 or claim 6 characterized in that said vehicle is equipped with a device "Stop and Start" and in that said first member (12) is a supercapacitor equipping said device.