EP2842215A2

EP2842215A2 - Device for supervising motor vehicle battery charge

Info

Publication number: EP2842215A2
Application number: EP13717783.8A
Authority: EP
Inventors: Bruno Beranger; Daniel Chatroux; Eric Fernandez
Original assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2012-04-25
Filing date: 2013-04-22
Publication date: 2015-03-04
Also published as: WO2013160266A2; WO2013160266A3; FR2990077B1; FR2990077A1

Abstract

The invention relates to a motor vehicle comprising: - an electric motor (33); - a battery (2) of power accumulator cells (21) which is intended selectively to power the electric motor (33) that drives the vehicle and to be recharged by this electric motor; - an interface (32, 33) providing connection to an electric power source; - a battery supervision device (1), comprising: - an altitude determining element (110); - a receiver interface (120) receiving a signal indicative of the stored energy; - a computer (100) configured so as to: - calculate a potential amount of energy with which the electric motor (33) can recharge the battery depending on the altitude; - calculate a recharge limit by subtracting the potential recharge energy from the maximum amount of energy that can be stored; - generate a signal to interrupt the charging of the battery when the energy stored in the battery reaches the recharge limit.

Description

DEVICE FOR SUPERVISION OF THE CHARGE OF A MOTOR VEHICLE BATTERY

The invention relates to vehicles whose drive is provided by an electric motor powered by a storage battery, and in particular the management of the charging of such a storage battery.

In certain types of electric traction vehicles, the electric motor is used as a generator in the downhill phases, both to provide engine braking to the vehicle and to recharge the accumulator battery. Thus, the potential energy of the vehicle is transformed into stored energy in electrochemical form during recuperative braking.

Unlike hybrid electric / electric vehicles, vehicles with electric traction only have a modest autonomy. Their range is therefore limited and the idea of being out of energy is a brake on the development and purchase of these vehicles. For such vehicles, the recovery of kinetic or potential energy during slowdowns or descents is particularly significant. On the hilly course, the range is slightly increased thanks to this energy recovery.

Most batteries, and especially those of Lithium ion technology (and the associated technology family), can not withstand being overloaded. A battery monitoring device thus ensures not to overload the accumulators of the battery, both during driving and during a normal or fast charging at a standstill by connection to an electrical network. When driving, the electrical energy passes mainly from the traction battery to the electric motor to overcome the friction related to the progress (aerodynamics and rolling of the tires), for the acceleration phases, or for the climbing phases. Conversely, during slowing down or downhill, the engine becomes generator and the electrical energy then passes from the engine to the traction battery.

For use of the vehicle in a hilly area, the presence of a form of engine braking is essential during the phases of descent. Indeed, in the absence of engine braking, the driver would find himself obliged to perform permanent braking by means of the mechanical brakes of the vehicle wheels. Continuously applying the brakes of the vehicle in a major descent would overheat them excessively, so that they could lose all effectiveness in carrying out emergency braking. For this purpose, the electric motor running as a generator provides engine braking during the descent phases to relieve mechanical brakes.

During the shutdown phases, users can, if possible, recharge the battery as much as possible by connecting it to the electrical network, in order to have maximum autonomy during a new start. In a hilly area, the vehicle can restart at altitude with a fully charged battery. During a descent with the battery fully charged, the battery monitoring device blocks charging the battery so as not to damage the batteries. To still provide an engine brake to the vehicle for safety reasons, a resistive load can be connected to the terminals of the electric motor. The kinetic energy of the vehicle is dissipated in heat by the Joule effect during the descent phases. It is indeed not possible to suddenly remove the generator operation of the electric motor when the battery reaches its full load during regenerative braking, otherwise the driver could be surprised by a sudden interruption of the engine brake, which could induce a risk of accident. Alternatively, it is known to dissipate the energy generated by the engine generator in useful electrical consumers, such as a heating of the passenger compartment, air conditioning ...

Therefore, such a vehicle does not achieve optimal use of the energy stored in its batteries, since a significant amount of recoverable energy is lost by the Joule effect. No known solution makes it possible in particular to avoid the problem of braking or dissipation of energy for a vehicle driven solely by an electric motor.

The invention aims to solve one or more of these disadvantages. The invention thus relates to a motor vehicle as defined in the appended claims. Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which:

FIG. 1 illustrates an electrical diagram of an example of a first example of an electric vehicle equipped with a device for monitoring the charge of the battery according to the invention;

FIG. 2 is a diagram illustrating the charging of the battery according to an example of downhill travel;

FIG. 3 is a diagram illustrating the charging of the battery according to another example of downhill travel;

FIG. 4 represents a table illustrating the energy consumed in rise as a function of various parameters;

FIG. 5 represents a table illustrating the downhill charging energy as a function of various parameters. The invention proposes to determine beforehand the potential charging energy by the electric motor as a generator for storage in a generator. storage battery, depending on the altitude of the vehicle. A battery supervision device then limits its recharge to a value equal to the difference between the maximum amount of energy that can store the battery and the recoverable potential recharge energy determined.

The limit value for recharging can be used either to restrain charging when the vehicle is shut down during a connection to the electric network, or to restrain charging when the vehicle is traveling and the electric motor is operating as a charging generator for the vehicle. drums.

The battery recharge limit can be set from a simple vehicle altitude measurement, by determining the height difference that the vehicle is likely to travel.

The battery recharge limit can also be set from a location on a global positioning system (GPS) with altimeter position information and altimetry mapping.

Figure 1 is a representation of a circuit diagram of a first example of implementation of the invention in a motor vehicle. The motor vehicle is in this case driven solely by an electric motor 33. The electric motor 33 is also not driven by another source of mechanical energy such as a heat engine. The electric motor 33 is powered by a power battery 2 comprising, in known manner, a plurality of electrochemical accumulators 21. A reversible inverter 34 is bidirectional in current. The reversible inverter 34 converts the DC voltage of the battery 2 into AC voltage to supply the electric motor 33 when this motor is in motor mode. The reversible inverter 34 also converts the AC voltage of the electric motor 33 into DC voltage when the electric motor 33 is in generator mode. The inverter 34 can be controlled in a manner known per se with appropriate current setpoints according to the needs of the pipe (acceleration, deceleration).

The vehicle of this example also includes a battery charger 31. The battery charger 31 includes an AC / DC converter controlled by a charge monitoring device 1. The battery charger 31 is intended to be connected to an alternating electric network 32. The vehicle further includes a discharge resistor 35 and an electrical consumer element 36, such as a compressor of a heat pump or an air conditioning unit. .

The battery charge monitoring device 1 comprises in this case a computer 1 00, an element 1 1 0 capable of providing altimetric information about the vehicle, and a communication interface 1 20 with the battery 2. The supervision device 1 can perform in a manner known per se a load balancing function of the different accumulators 21 of the battery 2, monitor the voltage or current across one or more accumulators, monitor the temperature of the battery 2, monitor its state of charge or determine the amount of energy stored in the battery 2. The charger 31 can adapt recharging parameters according to the information supplied to it by the supervision device 1.

The supervision device 1 can thus control the charging of the battery 2 by the electrical network 32 via the charger 31, when the vehicle is at a standstill. The supervision device 1 can control a complete recharging cycle by the network 32 at regular intervals, with a view to the maintenance of the battery 2. The supervision device 1 can also control the charging of the battery 2 by the electric motor by via the reversible inverter 34, during vehicle braking phases or during descent phases. Such a phase of operation makes it possible at the same time to increase the autonomy of the battery 2 and to guarantee the engine brake, which makes it possible both to secure the driver and to limit the heating of the mechanical brakes of the vehicle. The invention is therefore particularly advantageous in a vehicle driven solely by an electric motor.

For such a vehicle, the supervision device 1 according to the invention aims to set a charging limit of the battery 2 when stopping the vehicle. The supervision device 1 aims at setting an energy limit stored in the battery 2 when it is recharged by the electrical network 32. The supervision device 1 thus aims to prevent, when the vehicle leaves the vehicle, from descending, with the Battery 2 charged:

the generator operation of the motor 33 must be interrupted to avoid an excessive charge of the battery 2; or

energy is dissipated unnecessarily in an electric charge to keep the motor 33 running as a generator.

When stopped, the supervision device 1 has a vehicle altitude value provided by the element 1 10. According to this altitude, the computer 1 00 calculates a potential recharge energy of the battery 2 by the motor 33 operating as a generator during descents. Through the interface 1 20, the computer 1 00 also retrieves a value of the amount of energy stored in the battery 2. The calculator 1 00 also has a value representative of the maximum amount of energy that can be used. stored in the battery 2. The maximum amount of storage energy of the battery can be determined either by calculation or by factory configuration. The calculator 100 calculates a recharge limit of the battery 2 by subtracting the calculated potential recharge energy from the maximum amount of energy. During the recharging phase, when the energy stored in the battery 2 reaches the calculated recharge limit, the supervision device 1 interrupts charging by opening for example a switch connected between the charger 31 and the battery 2.

The element 1 1 0 advantageously includes a global positioning system (GPS). The GPS system may have altimeter position information provided by altimetric mapping. Such a GPS system generally has an altimetric positioning accuracy of the order of 10 meters.

The vehicle altitude signal provided by the Global Positioning System from the altimetric mapping may be insufficiently accurate (especially when a limited number of satellites are captured by the GPS system) to correctly determine the recharge energy potential of the battery 2 by the motor 33 generator. In addition, the altitude of the vehicle can be indeterminable by the GPS when the vehicle is out of the map stored therein.

Advantageously, the vehicle then has a barometric altimeter, determining the altitude of the vehicle according to the atmospheric pressure. Such an altimeter generally has a positioning accuracy of the order of 5 meters. Thus, the battery monitoring device can more accurately determine the amount of recoverable energy. In addition, such a barometric altimeter can precisely set the maximum recharge limit of the battery even when the vehicle is outside the limits of the map of the GPS system embedded in the vehicle.

Advantageously, the barometric altimeter or the GPS system comprises a variometer function, which measures the speed of descent and thus makes it possible to accurately anticipate the magnitude of the refills of the battery 2.

During a recharge, the supervision device 1 can interrogate the GPS system to determine the current altitude, as well as the negative elevation and the profile of the road that can be borrowed. Based on this information, the monitoring device 1 of the battery determines the potential recharge energy. From the maximum energy that the battery can store, the computer 1 00 then determines the recharge limit of the battery 2 by subtracting the potential recharge energy from the maximum energy that can be stored in the battery 2.

Thus, when recharged by the electrical network 32, the supervision device 1 limits the recharging of the battery 2 to the calculated limit, to ensure that the charging of the battery will not prevent braking by the engine 33 in downhill phases. This optimally uses the potential energy of the vehicle, without degrading the safety of use thereof and without risk of damaging the traction battery 2.

The invention goes against a technical prejudice according to which it would be preferable to charge a maximum power battery at a standstill to guarantee maximum autonomy. The invention makes it possible to substantially guarantee the same autonomy of the vehicle by making optimal use of the energy supplied by the electrical network. When charging the vehicle by connection to the electrical network

32, the supervisory device 1 can determine the potential recharge energy according to different paths provided by the GPS system. A first path taken into account may be a user-programmed route on the GPS system for future travel. A second path taken into account may be one of several common paths taken, this path being the one that can induce the maximum potential recharge energy. The second path can in particular be selected from a probability of use, based on the regularity of practice of a road depending on the day of the week for example. A third path taken into account may be the most critical path in terms of potential recharge energy, determined by the supervision device according to different potential paths indicated by the GPS system.

In a simplified version, the element 1 10 comprises a simple altimeter providing the vehicle altitude to the computer 1 00. The calculator 1 00 can then determine a maximum altitude difference from the vehicle altitude. The calculator 1 00 can then deduce the potential recharge energy for this maximum negative elevation. The supervision device 1 may include security functions, especially if the path taken by the user is more critical than the path taken into account to calculate the recharge limit of the battery 2.

For this purpose, the supervision device 1 can interrupt the operation of the generator 33 of the motor 33 by an appropriate command on the inverter 34, if it determines that the charge of the battery 2 approaches or reaches the maximum amount of energy that can be stored. in the battery 2. The mechanical brakes of the vehicle may be operated to prevent a sudden suppression of the engine brake. On the other hand, if the supervision device 1 determines that the charge of the battery 2 approaches or reaches the maximum quantity of energy, it can also activate the tripping of the electric charges 35 and 36 on power supply by the battery 2 or the inverter 34 , in order not uncoupling the electric motor 33 operating as a generator. The electric charge 35 may be dedicated to energy dissipation and may for example comprise a discharge power resistor immersed in a heat transfer fluid in order to absorb a high instantaneous power and be able to ensure a durable storage of the energy dissipated by Joule effect. The heat transfer fluid can be stored in an isothermal container to allow its subsequent use under appropriate conditions, for example for heating, defrosting or demisting the vehicle. If the conditions of use of the vehicle are suitable, another useful electrical consumer such as the compressor 36 of a heat pump or an air conditioning system is powered by the battery 2, for example to implement a dehumidification of the passenger compartment or cooling.

The compressor 36 can be powered from the traction battery 2 because the power it consumes is relatively high, typically from 2 to 3 kW. The discharge resistor 35, for example has a power of 10 to 15 kW, to absorb most of the excess electrical energy supplied by the inverter 34 in a particular case of descent. A dive resistor immersed in a volume of fifteen liters of water used as heat transfer fluid can store about 1 kWh of heat by heating the water by 60 ° C.

The powers of the discharge resistor 35 and the compressor 36 are advantageously chosen so that their sum is greater than the average power generated by the regenerative braking of the vehicle on roads open to the circulation of light vehicles and traveled at speed. authorized.

The variometer function included in the GPS makes it possible to anticipate the eventual necessity of activating the compressor 36 or the resistor 35 since, by coupling with the vehicle speedometer, this variometric function provides an image of the kinetic and potential energy stored. by the vehicle downhill.

The use of the safety functions of the supervision device 1 has been described when the battery 2 approaches its maximum amount of storable energy. However, these functions can also be activated to limit the power supplied by the engine 33 generator when the descent is very pronounced, when the vehicle is traveling at high speed or when significant braking is in progress. This operating mode can be signaled to the driver when it is triggered. The supervision device 1 can for example slave the maximum recharging current of the battery 2 as a function of voltage measurements made on the accumulators 21 of this battery 2. To determine the amount of potential recharge energy, the supervision device 1 can memorize the recharging characteristics of the battery according to the operating conditions of the vehicle: vehicle speed, speed of descent, engine / battery torque recharge efficiency when the engine is running as a generator ...

The calculator 100 can perform the calculation of the potential recharge energy according to different methodologies. The computer 1 00 may for example have stored tables, for determining a recoverable energy by the battery 2 for a given distance, depending on the slope of a section. Different tables may be available to accommodate different vehicle speeds. The GPS system can return presumed speeds for different sections. These tables can be established in the factory on the basis of real tests or simulations. These tables can also be acquired or corrected during the life of the vehicle.

The calculation of the recoverable energy can also be made from the potential energy of the vehicle, taking into account the conversion efficiencies between the motor 33 and the battery 2, the conversion efficiency between the wheels and the motor output. , or taking into account the vehicle parameters (aerodynamic resistance, rolling resistance, ....).

The calculation of the recoverable recharge energy can also be made based on the amount of energy consumed by the vehicle and recorded on the same uphill path, and applying a percentage corresponding to a conversion efficiency to that amount of energy. energy consumed. An example of a table illustrating the upward energy consumption as a function of the speed and the gradient is given in FIG. 4. An example of a table illustrating the energy recovery in the battery 2 as a function of the speed and the gradient is provided in Figure 5. It is noted that the climb and descent performance is relatively unfavorable at low speed, due to a lower efficiency of the engine 33. It is noted that the climb and descent performance is relatively unfavorable to high speed, because of the significant increase in aerodynamic losses.

The calculator 1 00 can perform calculations of recoverable recharge energy on different successive sections. The length of these sections may for example be between 100 and 500 m, depending on a compromise between the capacity or the necessary calculation time and the desired calculation accuracy.

The use of a GPS system with altimetric mapping makes it possible to accurately anticipate the profile of the path taken and thus makes it possible to fix as finely as possible the limit of recharge of the battery 2, which allows to optimize the autonomy of the vehicle. In particular, different road trip profiles can be identified by the GPS system.

A first example of a road profile is an altitude plateau. The GPS system constantly determines how far away the electric vehicle is from falling sections of the board. Thus the flat part that the vehicle travels before attacking a descent is well taken into account by the supervision device 1 in calculating the recharge limit of the battery 2. The supervision device 1 determines in particular that an initial roll on an altitude plateau induces a calculated discharge of the battery 2. Thus, the recharge limit the battery 2 can be raised from the amount of this discharge. The user can have a communication interface with the supervision device 1 to possibly raise the recharge limit of the battery 2, the user knowing beforehand that he will take a path with a small gradient and therefore an energy reduced potential recharge.

A second example of a road profile is a mountainside. The battery 2 then undergoes a heavy discharge if the vehicle rises higher in altitude, or a strong recharge if the vehicle descends. The learning of the most frequent route between the rise or the descent by the GPS system makes it possible to optimize the management of the energy by the device of supervision 1. Through the communication interface, the user can force the fixing of the recharge limit according to the rolling profile he wants to borrow.

A third example of a road profile is that where the vehicle is on a hill. In theory, in this case, the recharge limit of battery 2 is always set at less than 100%, since any path can only be descending. However, according to some load balancing strategies of the accumulators 21 of the battery 2 it may be necessary to periodically perform a recharge at 100% (for example, once every 10 recharges), or beyond the calculated recharge limit. In this case, the energy exceeding the limit is discharged into an electric charge such as the load 35 or the compressor 36.

To provide an encrypted example, it will be assumed that a vehicle has a battery 2 with a total capacity of 10 KWh. The GPS system tells the computer 1 00 that the vehicle must subsequently perform a descent of 7 km with 600 m of negative elevation (an average slope of 8.6%). It will be assumed that the descent will be covered at a speed of 70 km / h and will last 6 minutes. The vehicle includes a compressor 36 with a power of 3 kW and a discharge resistor 35 of 10 kW. In a first case illustrated in Figure 2, the planned route in the GPS system corresponds to the route taken. Information The calculator 100 identifies the slope sections that contribute to a significant recharge of the battery 2. The calculator 100 determines the potential recharge energy for the battery. each section. By accumulating the potential recharge energy for all the sections, the computer 100 determines the potential recharge energy of the battery 2 for the route taken. The computer 100 can of course subtract the power supply of the motor 33 in the rising sections.

In the example, the computer 100 determines that a potential recharge of 1 kWh of the battery 2 can be obtained on the planned route. Therefore, the supervision device 1 will limit the recharge of the battery 2 to a standstill up to a stored energy level of 9 kWh, which corresponds to a state of charge of 90%. Thus, for the planned route, the battery 2 will normally be recharged by 1 kWh to reach a state of charge of 100% at the end of descent.

In a second case, the vehicle takes a different path from that programmed in the GPS system at the time of charging. The supervision device limits the charging of the battery 2 to a standstill up to a stored energy level of 9.5 kWh (which corresponds to a state of charge of 95%) based on the path programmed in the GPS.

The path taken leads to a potential recharge of the battery 2 greater than the potential recharge calculated for the programmed path. Thus, at an intermediate point of the path traveled, the battery 2 reaches its maximum state of charge. The supervision device 1 then controls the limitation of the charging of the battery 2 by the motor 33 as a generator. The supervision device 1 then starts supplying the compressor 36 and the load 35 with the battery 2 or the inverter 34. The total power of the loads 35 and 36 is 13 kW. This power is for safety greater than the recharging power of the battery 2 by the regenerative braking (for example 10 kW). To account for an electrical power of the charges 35 and 36 greater than the charging power of the battery 2, these charges 35 and 36 will be fed by the battery with a suitable duty cycle, to maintain the charge of the battery at 100% until the end of the descent.

In the illustrated example, the charger 31 is embedded in the vehicle. It is of course conceivable that the charger is outside the vehicle and that the supervision device 1 limits the recharge of the battery 2 by such an external charger. Advantageously, the supervision device 1 takes into account a maximum amount of variable energy, to take account, for example, of the decrease in the capacity of the battery 2 during its life cycle.

Claims

Motor vehicle comprising:

an electric motor (33) for driving the vehicle, the vehicle being driven exclusively by said electric motor;

a battery (2) of accumulators (21) of power for selectively supplying the electric motor (33) driving the vehicle and being recharged by this electric motor;

a converter (34) connected to the electric motor (33) and the battery (2), and configured to selectively transfer energy from the battery to the electric motor or energy from the electric motor to the battery;

a connection interface to an alternating electric network (32, 33);

a monitoring device (1) for the battery, comprising:

an element (1 10) for determining the altitude of the vehicle;

an interface for receiving (120) a signal representative of the energy stored in the battery;

a calculator (100) configured for:

calculating a potential recharging energy of the battery by the electric motor (33) according to the altitude of the determined vehicle; -calculate a recharge limit by subtracting the calculated potential recharge energy from the maximum amount of energy that can be stored in the battery;

generating a signal for interrupting the charge of the battery when the energy stored in the battery reaches the calculated recharge limit; a switch (32) connected between the connection interface and the accumulator battery (2), the opening of which is controlled by the interrupt signal generated by the computer (100).

The vehicle of claim 1, wherein the vehicle altitude determination element includes an altimetric GPS location system (1 10).

Vehicle according to claim 2, wherein:

the GPS location system is configured to memorize a route, to determine elevation information for the stored route, and to provide the altitude information to the computer (100);

the computer (100) is configured to calculate the potential recharging energy of the battery (2) according to the level of information provided.

Vehicle according to claim 3, wherein the elevation information is determined for different sections of the stored route, the determined elevation information including the slope of said sections;

the locating system is configured to determine a predictable speed of a vehicle on the sections of the stored route;

the computer (100) is configured to calculate the potential recharging energy of the battery (2) by the motor (33) on each of said sections as a function of the slope of each section and the predictable speed on each section, and configured to calculate the potential recharge energy of the battery by the engine (33) on the stored route based on the cumulative potential recharge energies calculated for said sections.

Motor vehicle according to any one of the preceding claims, further comprising at least one electric load (35, 36), the computer (100) being configured to:

-determine that the vehicle is traveling downhill;

-determine that the battery (2) stores said maximum amount of energy; -commander power supply of said electric charge (35, 36) by the battery (2) when the vehicle rolls downhill and the battery stores said maximum amount of energy.