FR3094680A1 - MOTOR VEHICLE INCLUDING AN ELECTRICAL POWER SUPPLY CIRCUIT WITH DOUBLE LITHIUM ACCUMULATOR - Google Patents

Abstract

Motor vehicle comprising a heat engine and an electrical supply circuit (10) comprising: at least one electrical energy consuming device (14); a starter (16) for starting the engine; a lithium power accumulator (20) configured to supply the starter (16) with a quantity of electrical energy allowing the starting of the engine, a lithium energy accumulator (22) configured to supply electrical energy to said at least one component electrical energy consumer (14), wherein said at least one electrical energy consuming member (14), the alternator (18), the starter (16), the power accumulator (20) and the accumulator energy (22) are electrically connected in parallel with respect to each other. Figure for the abstract: Fig. 1

Description

MOTOR VEHICLE COMPRISING A DUAL LITHIUM BATTERY POWER SUPPLY CIRCUIT

The present invention relates to a motor vehicle comprising a dual lithium battery power supply circuit. The present invention also relates to a method for controlling such a power supply circuit.

For nearly a century, all motor vehicles have been equipped with a lead-acid battery (otherwise called an accumulator). The evolution of technologies and regulatory constraints tends today to replace lead batteries by alternative systems. However, this replacement is not easy to operate because the lead battery has technical characteristics suitable for application to a motor vehicle while having a limited cost.

Among other things, lead-acid batteries have two fundamental qualities: cold power and energy reserve to compensate for standby currents (otherwise called "off currents") when the vehicle is parked for a long period of time.

The power of a battery, expressed in Ampere-hour (A.h), is the capacity of a battery to deliver a predetermined quantity of electricity. In the automotive context, the battery must guarantee the starting of the cold combustion engine after prolonged parking, i.e. after a partial discharge of the battery. Very conventionally, a lead-acid battery can perfectly start an engine at -20°C or -30°C after a parking period of 1 or 2 months. Its state of charge (otherwise called “SOC”) is still above 60% and 20 to 30% of its capacity has been discharged by “off currents”.

The energy reserve, or mass density or specific energy, expressed in watt-hours per kilogram (W.h/kg), corresponds to the amount of energy that the battery can restore in relation to its mass.

In addition, a lead-acid battery resists well to the difficult conditions present under the bonnet of a vehicle where the temperature can reach 80°C and where the battery can remain several hours a day at more than 60°C. This “hot” environment has a significant impact on its aging. However, the low cost of lead batteries allows them to be changed regularly (every 5 years on average in Europe) like all wearing parts of the vehicle. In addition, the recyclability rate of a lead battery is very high (>95%) and it can be converted into new batteries.

It should be noted that this ability to withstand high temperatures makes it possible to place the lead-acid battery close to the internal combustion engine and therefore to the alternator and the starter. Thus, the lead battery connection cables are short and the resistive losses are low.

Many solutions exist to supplement the lead battery but only during certain operating phases of the motor vehicle so that all these solutions include a lead battery accompanied by an additional battery of different technology. By way of example, document WO 2017163959 A1 describes a power supply circuit comprising two batteries in parallel for a micro-hybrid system. The electrical supply circuit includes a lead-acid battery accompanied by a lithium battery to ensure the recovery of energy during braking. It is understood that such a system comprising a lead-acid battery risks in the long term no longer satisfying the regulatory constraints.

There is therefore a need for a motor vehicle comprising an electrical energy supply system making it possible to completely supplement a lead-acid battery.

For this, the invention proposes a motor vehicle comprising a motor and an electrical supply circuit comprising:
at least one electrical energy consuming member;
a starter to start the engine;
a lithium power accumulator configured to supply the starter with a quantity of electrical energy allowing the engine to be started,
a lithium energy accumulator configured to supply electrical energy to said at least one electrical energy consuming member,
wherein said at least one electrical energy consuming member, the alternator, the starter, the power accumulator and the energy accumulator are electrically connected in parallel with each other.

The combination of two lithium accumulators (or batteries) each dedicated to a specific function makes it possible to adapt more effectively to the constraints and expectations of the motor vehicle's electrical supply circuit. The two lithium accumulators can for example be of different technologies, at different locations in the motor vehicle and/or be controlled differently.

More specifically, one of the so-called "power" accumulators is configured to deliver a predetermined quantity of electricity allowing the engine to be started. The other, so-called “energy” accumulator, is configured to supply electrical energy to said at least one electrical energy consuming member and to compensate for the “current off” when the motor vehicle is in long-term parking.

This dual lithium battery configuration makes it possible to obtain a complementary battery system with equivalent or even better technical characteristics than a lead-acid battery. In addition, this configuration allows great flexibility in the choice of the amount of energy on board the motor vehicle without excessive installation constraints, unlike lead-acid batteries for which this problem is recurrent.

According to one embodiment of the motor vehicle, the power accumulator and the energy accumulator have negative electrodes of different compositions from one another.

According to one embodiment of the motor vehicle, the power accumulator comprises an anode comprising Lithium-Titanate and/or the energy accumulator comprises an anode comprising graphite.

According to one embodiment of the motor vehicle, the power accumulator is placed at the level of a hot zone of the motor vehicle and the energy accumulator is placed at the level of a cold zone of the motor vehicle.

According to one embodiment of the motor vehicle, the power accumulator is arranged close to the engine, the energy accumulator being arranged inside the passenger compartment of the motor vehicle.

According to one embodiment of the motor vehicle, the power accumulator, the energy accumulator and the starter are each arranged on a branch of the electrical supply circuit, each branch being mounted in parallel with respect to the others and comprising a selectively operable relay to electrically connect the power accumulator, the energy accumulator or the starter present on the branch to the rest of the electrical supply circuit.

According to one embodiment of the motor vehicle, the electrical power supply circuit defines a first sub-circuit comprising the power accumulator, the starter and the alternator, and a second sub-circuit comprising the energy accumulator and said at least one electrical energy consuming member, the electrical power supply circuit further comprising a separation relay configured to allow the selective connection of the first and second sub-circuits to one another.

According to one embodiment of the motor vehicle, the electrical supply circuit further comprises:
a heater of the energy accumulator connected in parallel with respect to the energy accumulator, and
an additional relay selectively operable to electrically connect the heating member and the rest of the electrical supply circuit.

According to one embodiment of the motor vehicle, the heating member extends at least partially inside the energy accumulator.

The invention also relates to a method for controlling an electrical power supply circuit for a motor vehicle as described above, the electrical power supply circuit further comprising an alternator for generating electrical energy from the motor , the alternator being mounted on a branch parallel to the other branches of the power supply circuit, comprising at least one of the following steps:
when the engine is off in the parking phase of the motor vehicle, controlling the relays so as to electrically connect the energy accumulator to said at least one electrical energy consuming member and to electrically disconnect the power accumulator and the starter from the rest of the power supply circuit,
for starting the engine, controlling the relays so as to electrically connect the power accumulator to the starter and to electrically disconnect the energy accumulator from the rest of the supply circuit,
for carrying out a micro-hybrid operation in which the power accumulator recovers electrical energy during braking of the motor vehicle and distributes electrical energy during acceleration of the motor vehicle, controlling the relays so as to electrically disconnect the energy accumulator and the starter from the rest of the supply circuit and control the relays so as to electrically connect the alternator to the power accumulator.

The accompanying drawings illustrate the invention:

shows a first embodiment of an electric power supply circuit for a motor vehicle comprising a lithium power accumulator and a lithium energy accumulator.

shows a layout diagram of the first embodiment of the electric power supply circuit of FIG. 1 in the motor vehicle.

represents an example of evolution of the state of charge or “SOC” of power and energy accumulators as a function of their voltage at zero current or “OCV”.

represents the state of charge or “SOC” of the power and energy accumulators as a function of their voltage at zero current or “OCV” at the time of a parking or parking phase of the motor vehicle.

represents the state of the electric power supply circuit at the time of a parking or parking phase of the motor vehicle.

represents the state of charge or “SOC” of the power and energy accumulators as a function of their voltage at zero current or “OCV” at the time of an engine starting phase.

represents the state of the electrical supply circuit at the time of an engine starting phase.

represents the evolution of the state of charge for a cold start or “SOCminDem” as a function of the temperature at the time of a recharging phase of the power accumulator.

represents the state of charge or “SOC” of the power and energy accumulators as a function of their voltage at zero current or “OCV” at the time of a recharging phase of the power accumulator.

represents the state of the electrical supply circuit at the time of a recharging phase of the power accumulator.

represents the state of charge or "SOC" of the power and energy accumulators as a function of their voltage at zero current or "OCV" at the time of a switching phase from the load of the power accumulator to the load of the energy accumulator.

represents the state of the electrical power supply circuit at the time of a phase of switching from the charge of the power accumulator to the charge of the energy accumulator.

represents the state of charge or “SOC” of the power and energy accumulators as a function of their voltage at zero current or “OCV” at the time of a recharging phase of the energy accumulator.

represents the state of the electrical power supply circuit at the time of a recharging phase of the energy accumulator.

shows an example of laws for determining the charging current of the energy accumulator depending on its state of charge and temperature.

represents the state of charge or "SOC" of the power and energy accumulators as a function of their voltage at zero current or "OCV" at the time of a switching phase of the charge from the energy accumulator to the micro-hybrid and “start and stop” functions.

represents the state of the electrical power supply circuit at the time of a switching phase from the charge of the energy accumulator to the micro-hybrid and “start and stop” functions.

represents the state of charge or "SOC" of the power and energy accumulators as a function of their voltage at zero current or "OCV" at the time of a supply phase of the micro-hybrid functions and of the "start" function and stop”.

represents the state of the power supply circuit at the time of a supply phase of the micro-hybrid functions and of the “start and stop” function.

shows a second embodiment of the power supply circuit comprising a separation relay.

represents the influence of temperature on the ability of a lithium energy accumulator to sustain a discharge current of 1C for a third embodiment of the electrical power supply circuit comprising a heater of the accumulator of energy.

represents the state of the third embodiment of the electrical power supply circuit at the time of a parking or parking phase of the motor vehicle.

represents the state of the third embodiment of the electrical power supply circuit at the time of an engine starting phase.

represents the state of the third embodiment of the electrical power supply circuit at the time of an engine starting phase if the energy accumulator has a temperature below 0°C.

schematically shows a sectional front view and a sectional side view of an embodiment of an energy accumulator with an integrated heater.
Description of embodiment(s)

As represented in FIG. 1, an electric power supply circuit 10 is proposed for the electric power supply of a motor vehicle 12 comprising a heat engine 11 allowing the driving of the motor vehicle 12. The electric power supply circuit 10 is a low voltage network, in particular less than 20V. The motor vehicle 12 is in particular a micro-hybrid vehicle having a “Start-and-Stop” function (also called automatic start-stop). This function makes it possible to automatically cut the engine during stops and to restart it automatically as soon as the driver starts again. The micro-hybrid functions correspond to a recovery of electrical energy by an accumulator of the electrical energy circuit during braking of the motor vehicle 12 and a distribution of electrical energy during an acceleration of the motor vehicle 12.

The electrical power supply circuit 10 comprises at least one electrical energy consuming member 14. Usually and preferably, the motor vehicle 12 includes a plurality of electrical energy consuming members 14. The electrical energy consuming members 14 correspond to the systems on board the motor vehicle 12 requiring a supply of electrical energy to operate. By way of example, the power steering is an electrical energy consuming member 14 within the meaning of the present invention. When the electrical power supply circuit 10 comprises a plurality of electrical energy consuming members 14, these are connected in parallel with respect to each other.

The electrical supply circuit 10 also includes a starter 16 and an alternator 18. The starter 16 makes it possible, once supplied with electrical energy, to start the motor 11 when the latter is stopped. The alternator 18 makes it possible to generate electrical energy when the motor vehicle 12 is in motion for recharging an accumulator. The starter 16 and the alternator 18 are arranged in parallel with respect to each other and also with respect to said at least one electrical energy consuming member 14. In other words, the starter 16, the alternator 18 and said at least one electrical energy consumer member 14 are arranged on parallel branches of the electrical supply circuit 10.

The power supply circuit further comprises a power accumulator 20 and an energy accumulator 22. The power 20 and energy accumulators 22 are arranged in parallel with respect to each other and in parallel with respect to the other components of the power supply circuit 10.

The power accumulator 20 is configured to supply the starter with a quantity of electrical energy allowing the engine 11 to be started. In other words, the power accumulator 20 is chosen and sized to be used for starting the engine a parking phase than for a “start and stop” function, ie an automatic restart of the engine 11 during a phase of use of the motor vehicle 12.

The energy accumulator 22 is configured to supply electrical energy to said at least one electrical energy consuming member 14. In other words, the energy accumulator 22 is chosen and sized to supply the consuming members of electrical energy 14 during a driving phase of the motor vehicle 12 or the “off” currents in the parking phase. The “off currents” are of the order of a few mA. For reasons of safety of the electrical supply in the event of malfunction of the alternator or of a converter or of the power accumulator 20, the energy accumulator 22 must also be able to provide a minimum of power functions from time to time. . The choice of the technology of the energy accumulator 22 therefore preferably meets this requirement. This energy source redundancy makes it possible to secure the motor vehicle 12.

The power accumulator 20 and the energy accumulator 22 are lithium accumulators. A lithium battery is an electrochemical battery whose reaction is based on the lithium element. In particular, the lithium accumulators are here preferably accumulators called “lithium-ion” where the lithium remains in the ionic state thanks to the use of an insertion compound both at the negative electrode (for example in graphite or titanate) than at the positive electrode (e.g. cobalt dioxide, manganese, iron phosphate). This "lithium-ion" technology is advantageous because it has a high specific energy and the "self-discharge" phenomenon is relatively low compared to other battery technologies. In addition, the wide variety of possible combinations between the negative and positive electrodes allows great operating flexibility.

To obtain complementary operation between the power 20 and energy 22 accumulators, these are preferably of different lithium technologies. In other words, the positive and/or negative electrodes of the power 20 and energy 22 accumulators have different compositions from each other.

The power accumulator 20 preferably comprises a negative electrode composed of titanate (otherwise called “LTO” or “Lithium-Titanate” electrode). It has been observed that a negative electrode made of titanate makes it possible to withstand, for relatively short periods of time, high currents in charge as well as in discharge, i.e. to develop a high power density. A lithium battery with a negative electrode made up of titanate is therefore suitable for starting the motor 11. In addition, such a battery has good resistance to high temperatures, it can therefore be placed close to the motor 11. In the present application, use is made of the terms “power accumulator” and “high power density accumulator”.

The energy accumulator 22 preferably includes a negative electrode made of graphite. It has been observed that a negative electrode made of graphite makes it possible to supply low to medium currents for relatively long durations, i.e. to develop a high energy density. A lithium accumulator with a negative electrode composed of graphite is therefore suitable for supplying electrical power to the electrical energy consuming members 14 of the motor vehicle 12. In addition, the cost of such an accumulator is very reasonable, in particular much lower than the cost an accumulator with a negative electrode composed of titanate. In the present application, the terms “energy accumulator” and “high energy density accumulator” are used interchangeably.

The combination of a lithium accumulator with a negative titanate electrode for the power functions and a lithium accumulator with a negative graphite electrode for the energy functions makes it possible to satisfy all of the electrical supply requirements of the motor vehicle 12. Therefore, this combination of accumulators makes it possible to supplement a lead-acid battery.

As shown in Figure 2, the power accumulator 20 is preferably arranged close to the engine 11, in particular under the engine cover. This arrangement close to the motor 11, the starter 16 and the alternator 18 makes it possible to limit the length of the connection cables and therefore the resistive losses. Given the heat released by the engine 11 in use of the motor vehicle 12, the area under the engine hood is called "hot area" 24. The temperature near the engine 11 can reach 80 ° C and can remain several hours at 60°C. In comparison, the passenger compartment 28 of the motor vehicle 12 is considered to be a "cold zone" 26. The use of a lithium power accumulator 20 with a negative electrode composed of titanate allows installation of the power accumulator 20 in areas with high temperatures, in particular above 60°C. The cables connecting the power accumulator 20 to the starter 16 and to the alternator 18 are preferably of large cross section, ie having a larger cross section than the cross section of the cables connecting the energy accumulator 22 to the rest of the circuit of power supply 10. The location of the power accumulator 20 at the level of the motor 11 is preferred because it will easily withstand high temperatures so that its service life can even equal the service life of the motor vehicle 12. Thus, the installation constraints in the engine compartment are greatly reduced because the accumulator placed in the engine compartment is no longer a wearing part and therefore will no longer need to be easily accessible. Indeed, the lead-acid accumulator requires several replacements during the life of the motor vehicle, which implies that its access must be simplified.

The energy accumulator 22 is preferably placed at the level of a “cold zone”, in comparison with the zone under the bonnet which is considered as a “hot zone”. Indeed, the performance of accumulators with a negative electrode made of graphite is reduced below 10°C and high temperatures (in particular above 50°C) lead to premature degradation of the accumulator. Therefore, the energy accumulator 22 is preferably arranged inside the passenger compartment 28 of the motor vehicle 12 so as to guarantee optimum operating performance. Even more preferably, the energy accumulator 22 is arranged inside the trunk of the motor vehicle 12, for example at the level of the location of a spare wheel. This location makes it possible not to subject the energy accumulator 22 to temperatures and a level of sunlight that are detrimental to its lifespan. In addition, the location in the boot facilitates maintenance and/or replacement of the energy accumulator 22.

The provision of only one of the power 20 and energy 22 accumulators at the level of the engine compartment allows a standardization of the layout of the engine compartment because the volume allocated to the accumulator will always be the same whatever the level of motor vehicle equipment 12.

The positive electrode of each of the power 20 and energy 22 accumulators can be chosen from among different types of electrodes, such as lithium-manganese-cobalt electrodes (called “NMC”, lithium-iron-phosphate (called “LFP ), lithium-manganese-spinel (called "LMO") or lithium-cobalt dioxide (called "LCO"). Each type of positive electrode has its own electrical performance, lifetime and cost. In this context, the intrinsic voltage or voltage at zero current (called "OCV" for Open Circuit Voltage in English) of a lithium technology according to the state of charge (called "SOC" for State Of Charge in English) is also singular. Moreover, the average voltage of a battery cell comprising a pair of positive and negative electrodes is very dependent on the technology of the negative electrode. The most suitable pair of electrodes therefore corresponds to the conditions in which the accumulators are u used.

In the case of a motor vehicle, the voltage range used is framed by two constraints: the lower limit corresponds to the voltage that the electrical network can withstand without the functions being degraded and the upper limit which is adjusted only for recharging. of the accumulator(s). Usually, these low and high limits are set according to a lead-acid accumulator. The lower limit is of the order of 10 to 11 V and the upper limit of the order of 15 to 16 V. To limit the costs of modifying this voltage range, the power 20 and energy accumulators 22 are preferably configured to operate in this voltage range. For this, the power accumulator 20 preferably comprises a negative electrode "LTO" (Lithium-Titanate) associated with a positive electrode "LMO" (lithium-manganese-spinel). The energy accumulator 22 preferably comprises a negative electrode composed of graphite associated with a positive electrode "LMO" (lithium-manganese-spinel).

In addition, the number of cells inside the power 20 and energy 22 accumulators is chosen so as to optimize the control thereof and the operation of the electric power supply circuit 10. The number of cells is preference limited to the maximum for the economic interest and the reduction of the internal resistance of the accumulators. It was observed that a number of five cells connected in series for the power accumulator 20 and three cells connected in series for the energy accumulator 22 was the optimum configuration. Lithium energy accumulators generally have four cells. The control and technologies chosen for the power 20 and energy 22 accumulators therefore make it possible to save 25% of the cost of the energy accumulator 22.

The cells of the power 20 and energy 22 accumulators are preferably reformed cells originating from the energy accumulators of electric vehicles.

The capacity of the power accumulator 20 is preferably chosen so as to be less than or equal to 15Ah, preferably less than or equal to 10Ah The capacity of the energy accumulator 22 is preferably chosen so as to be equal to 30Ah to provide the electrical energy needed for the parking phase.

The electrical energy consuming devices 14 are preferably arranged between the power 20 and energy accumulators 22. The electrical energy consuming devices 14 are supplied either by the alternator 18 or one of the two power accumulators 20 and energy 22.

To allow the power 20 and energy 22 accumulators to be used as a replacement for a lead-acid battery in the motor vehicle 12, the electrical supply circuit preferably comprises a first relay A, a second relay B and a third relay C respectively allowing the selective connection of the power accumulator 20, of the energy accumulator 22 and of the starter 16 to the rest of the electrical supply circuit 10. For this, the first A, second B and third C relays are arranged between the power accumulator 20, the energy accumulator 22 and the starter 16, respectively, and the rest of the power supply circuit 10. The opening of the first A, second B and third C relays allows the disconnection of the power accumulator 20, of the energy accumulator 22 or of the starter 16, respectively. Thus, said in a different way, the first A and second B relays make it possible to put into service one or the other of the power 20 and energy 22 accumulators.

The first A and second B relays are shown outside the power 20 and energy 22 accumulators for greater clarity. Preferably, the first relay A is integrated directly into the power accumulator 20 and the second relay B is integrated directly into the energy accumulator 22 to ensure the safety of the accumulators. The third relay C corresponds to a starter control relay 16.

The power supply circuit 10 further comprises a computer 30 making it possible to control the opening or closing of the first A, second B and third C relays and to control the voltage of the alternator 18. The computer 30 (otherwise called Energy management in English) is configured to receive voltage, current, temperature and state of charge information from each of the power 20 and energy 22 accumulators. The computer 30 is configured to implement strategies allowing the power 20 and energy 22 accumulators of different technologies and voltage ranges to be able to operate together. These control strategies are presented below in certain characteristic phases of the operation of the motor vehicle 12.

The control of the power 20 and energy 20 accumulators is carried out in particular according to a characteristic curve representing the state of charge of the accumulator considered (otherwise called “SOC” for State Of Charge in English) according to its zero-current voltage (otherwise called "OCV" for Open-Circuit Voltage in English). FIG. 3 represents a first curve 32 representing the SOC as a function of the OCV for the power accumulator 20 and a second curve 34 representing the SOC as a function of the OCV for the energy accumulator 22. A third curve 36 represents the minimum voltage of the electrical supply circuit 10 for the vital functions of the motor vehicle to operate, for example the power steering. This minimum voltage is here 10.5V in the example presented.

As seen in Figure 3, the voltage of the energy accumulator 22 is much lower than that of the power accumulator 20. This is perfectly suited to the functions required of the accumulators in the power supply circuit. The energy accumulator 22 is configured to supply the "off currents" of the motor vehicle when the latter is parked, these currents being of the order of 10 to 20 mA, the ohmic losses in the cables are very low and therefore the general voltage of the power supply circuit 10 always remains well above the minimum voltage required. Conversely, the power accumulator 20 is configured to undergo high discharge currents during start-up or micro-hybrid operation and it is suitable for its voltage at zero current or “OCV” to be higher.

The power 20 and energy 22 accumulators are configured to be used independently, ie not to be connected together simultaneously to the rest of the electrical supply circuit 10. Indeed, given their technical characteristics, the power accumulator 20 would be discharged into the energy accumulator 22 or would impose too high a voltage on it, risking damaging it if a simultaneous connection were to be made. This selective connection is achieved by controlling the first A and second B relays.

The control of the electrical power supply circuit 10 is presented below in correspondence with FIGS. 4 to 20. For greater clarity, this control is described in connection with the different phases of life of the motor vehicle, associated with the respective management of the power 20 and energy 22 accumulators. For simplicity, the voltages of each accumulator will be represented by its voltage at zero current or “OCV”. A person skilled in the art will of course understand that under current, they would be different, the ohmic losses would be added to or subtracted from them.

FIGS. 4 and 5 represent the state of charge or “SOC” of the power 20 and energy 22 accumulators as a function of their voltage at zero current or “OCV” as well as the state of the electrical supply circuit at the time of a parking or parking phase of the motor vehicle 12. The engine is off.

The second B relay is controlled so as to electrically connect the energy accumulator 22 to said at least one consumer member 14. The first A and third C relays are controlled so as to electrically disconnect the power accumulator 20 and the starter 16 from the rest of the power supply circuit 10. The first A and third C relays are therefore open and the second relay B is closed.

The energy accumulator 22 provides currents of the order of milliamperes. The state of charge of the power accumulator 20 is preserved above that required to ensure the state of charge required for a cold start (called "SOCminDem") and will not change because it does not supply the motor vehicle in the parking lot.

If the state of charge of the energy accumulator 22 reaches its minimum "SOCmin STO", then the second relay B opens to preserve the state of health of the energy accumulator 22, the currents of the order of the milliampere are no longer guaranteed. A degraded mode makes it possible to close the first relay A from the cells of the power accumulator 20 then to close the third relay C with the same source of energy and to start.

The state of charge or “SOC” of the power 20 and energy 22 accumulators during the parking phase is represented respectively for the cursors 40 and 42 in FIG. 4.

FIGS. 6 and 7 represent the state of charge or “SOC” of the power 20 and energy 22 accumulators as a function of their voltage at zero current or “OCV” as well as the state of the electric power supply circuit at the moment of an engine starting phase 11.

To start the motor 11, the first relay A is controlled so as to electrically connect the power accumulator 20 to the rest of the electrical supply circuit 10. The second relay B is controlled so as to electrically disconnect the accumulator from energy 22 from the rest of the power supply circuit 10. The opening of the second relay B is offset from the closing of the first relay A with a time delay to avoid any transfer of energy from the power accumulator 20 to the energy accumulator 22. This delay is preferably less than 1s, preferably less than 50ms. The third relay C is then controlled so as to electrically connect the power accumulator 20 to the starter 16 to ensure the starting in rotation of the motor 11. The third relay C is open after starting the motor 11.

The state of charge or “SOC” of the power 20 and energy 22 accumulators during the start-up phase is represented respectively for the cursors 40 and 42 in FIG. 6.

FIGS. 8 to 10 represent the evolution of the state of charge for a cold start or “SOCminDem” as a function of the temperature, the state of charge or “SOC” of the power 20 and energy 22 accumulators in function of their voltage at zero current or "OCV" as well as the state of the electrical supply circuit at the time of a recharging phase of the power accumulator 20.

After starting the motor 11, it is important to regenerate the starting capability of the power accumulator 20 while protecting the energy accumulator 22 from an overvoltage.

The second relay B is controlled to remain open so as to disconnect the energy accumulator 22 from the rest of the electrical supply circuit 10. The voltage of the alternator 18 "VALT" is therefore adjusted to a high value, ie greater than or equal to the zero current voltage or "OCV" of the power accumulator 20, to supply the network and at the same time to recharge the power accumulator 20. When the state of charge or "SOC" of the power accumulator 20 reaches a predetermined state of charge value for a cold start “SOCminDem”, the alternator voltage “VALT” is reduced and the charging currents will also be reduced.

The predetermined state of charge value for a cold start "SOCminDem" is determined as a function of the temperature outside the motor vehicle 12. FIG. 8 shows a curve representing the evolution of the state of charge or "SOC" in function of the temperature of the temperature of the power accumulator 20 making it possible to carry out this determination.

The control of the recharging of the power accumulator 20 can be carried out with the following steps. The voltage across the alternator 18 is determined. If the voltage across the terminals of the alternator 18 is below a predetermined voltage threshold for recharging the power accumulator 20, the voltage across the terminals of the alternator 18 is increased. The second B and third C relays are then controlled so as to electrically disconnect the energy accumulator 22 and the starter 16 from the rest of the electrical supply circuit 10. The first relay A is then controlled so as to electrically connect the power accumulator 20 to the alternator 18.

FIGS. 11 and 12 represent the state of charge or “SOC” of the power 20 and energy 22 accumulators as a function of their voltage at zero current or “OCV” as well as the state of the electric power supply circuit at the moment a phase of switching from the charge of the power accumulator 20 to the charge of the energy accumulator 22.

When the state of charge or "SOC" of the power accumulator 20 is found, the computer 30 preferably undertakes to recharge the energy accumulator 22. This recharge makes it possible to ensure that the energy accumulator 22 is capable of supplying currents of the order of milliamperes and “off currents” during a potential subsequent parking phase.

It is preferable to check the docking or the convergence of the voltages of the alternator 18 “VALT”, of the power accumulator 20 “VLTO” and of the energy accumulator 22 “VGRA”. It is also preferable to avoid strong exchange currents between the two accumulators as well as an uncontrolled charging of the energy accumulator 22. For this, the voltage of the alternator 18 "VALT" is reduced to a value situated between the voltage of the energy accumulator 22 “VGRA” and the voltage of the power accumulator 20 “VLTO”. This reduction is preferably carried out according to a slope that is not sensitive to the driver. The voltage of the alternator 18 can for example be reduced by a value situated between 1 and 2 V/s so that this reduction is not or barely perceptible by the driver.

The second relay B is controlled so as to electrically connect the energy accumulator 22 to the rest of the power supply circuit 20. Then, the first relay is controlled to electrically disconnect the power accumulator 20 from the rest of the power supply circuit. power supply 10. The control of the first relay A is preferably carried out after a time delay of less than 1s, preferably less than 50ms. The voltage of the alternator 18 "VALT" then governs the charging currents of the energy accumulator 22.

FIGS. 13 and 14 represent the state of charge or “SOC” of the power 20 and energy 22 accumulators as a function of their voltage at zero current or “OCV” as well as the state of the electrical supply circuit 10 at the moment of a recharging phase of the energy accumulator 22.

The speed of charging the energy accumulator 22 is highly dependent on its state of charge or “SOC” and its temperature. These data are supplied to the computer 30 by a control system (called “BMS” for Battery Management System in English) integrated into the energy accumulator. The same control system is also present in the power accumulator 20. The alternator voltage “VALT” is therefore controlled by the computer 30 according to the state of charge or “SOC” and the temperature. supplied by the control system of the energy accumulator 22. The voltage of the alternator 18 "VALT" is thus adjusted to supply the electrical energy consuming components 18 of the motor vehicle 12 and also to finely control the current of charges the energy accumulator 22. This control is thus carried out according to laws Icharge=f(T°C; SOC%, VAcc), “Icharge” being the intensity of the charging current of the energy accumulator 22, "T°C" being the temperature of the energy accumulator 22, "SOC%" being the state of charge of the energy accumulator 22 and "VACc" being the voltage of the energy accumulator. energy 22. The recharging of the energy accumulator 22 is preferably carried out until its state of charge reaches its maximum, ideally 100%. The fact of controlling the charging current directly by the voltage of the alternator 18 makes it possible to overcome the wiring resistances and their aging unique to each motor vehicle as well as the consumption of the motor vehicle.

FIG. 15 presents an example of laws making it possible to determine the charging current CHA of the energy accumulator 22 according to its state of charge and its temperature. This charging current is defined in such a way as to limit accelerated aging mechanisms such as the deposition of lithium at the anode. It appears that the admissible charging current is considerably reduced when the temperature of the energy accumulator 22 drops and the state of charge increases. By following these laws, the computer 30 can control the voltage of the alternator 18 so that the charging current seen by the control system of the energy accumulator 22 takes on the correct value.

The control of the recharging of the energy accumulator 22 can be carried out with the following steps. The voltage across the alternator 18 is determined. If the voltage across the terminals of the alternator 18 is above a predetermined voltage threshold for recharging the energy accumulator 22, the voltage across the terminals of the alternator 18 is reduced. The second relay B is then controlled so as to electrically connect the energy accumulator to the alternator 18. The first A and third C relays are then controlled so as to electrically disconnect the power accumulator 20 from the rest of the circuit d power supply 10.

FIGS. 16 and 17 represent the state of charge or “SOC” of the power 20 and energy 22 accumulators as a function of their voltage at zero current or “OCV” as well as the state of the electrical supply circuit 10 at the moment of a switching phase of the charge of the energy accumulator 22 towards the micro-hybrid and “start and stop” functions. The micro-hybrid functions correspond to a recovery of electrical energy by the power accumulator 20 during braking of the motor vehicle 12 and a distribution of electrical energy during an acceleration of the motor vehicle 12.

Once the states of charge "SOC%" of the power 20 and energy 22 accumulators are adjusted to their nominal values, the voltages of the alternator 18 "VALT", of the power accumulator 20 "VLTO" and of the energy accumulator 22 “VGRA” are controlled to allow the reconnection/disconnection of each of the elements. For this, the voltage of the alternator 18 "VALT" is increased to take an intermediate value between those of the power 20 and energy accumulators 22. The adjustment of the voltage of the alternator 18 "VALT" is preferably made on a slope that is not sensitive to the driver. The voltage of the alternator 18 can for example be reduced by a value situated between 1 and 2 V/s so that this reduction is not or barely perceptible by the driver.

The first relay A is controlled to electrically connect the power accumulator 20 to the rest of the power supply circuit 10. The second relay B is then controlled to disconnect the energy accumulator 22 from the rest of the power supply circuit 10 The control of the second relay B is preferably carried out after a time delay of less than 1s, preferably less than 50ms. The power supply circuit 10 then operates only on the power accumulator 20 and can perform the micro-hybrid functions and the “start and stop” function.

FIGS. 18 and 19 represent the state of charge or “SOC” of the power 20 and energy 22 accumulators as a function of their voltage at zero current or “OCV” as well as the state of the electrical supply circuit 10 at the moment of a supply phase of the micro-hybrid functions and of the "start and stop" function. During micro-hybrid operation, the electrical supply circuit 10 is controlled so that the power accumulator 20 recovers electrical energy generated during braking of the motor vehicle 12 and distributes electrical energy during an acceleration of the motor vehicle 12.

To allow the operation of the micro-hybrid functions, the first relay A is controlled to electrically connect the power accumulator to the rest of the power supply circuit 10. The second relay B is controlled to remain open so as to disconnect the accumulator energy from the rest of the power supply circuit 10. Thus, only the power accumulator 20 is connected to the power supply circuit so as to ensure energy recovery during braking, corresponding to the high voltage "VALT h" , and its restitution during acceleration, corresponding to the low voltage “VALT b”.

It is also the power accumulator 20 which provides power to the motor vehicle 12 during the automatic stop and the restarting of the engine 11 during the course of the “start and stop” function.

The association of two lithium accumulators in parallel for the selective performance of the functions of the motor vehicle 12 makes it possible to obtain a simple and efficient operation for replacing a lead-acid battery. Thanks to appropriate control of the existing relays in the batteries and adjustment of the alternator regulation voltage, it becomes possible to use lithium accumulators with very different nominal voltages, which makes it possible to very precisely adjust the size just as needed.

As shown in Figure 20, a second embodiment of the power supply circuit 10 is proposed. The power supply circuit 10 of FIG. 20 is identical to that of the first embodiment except that a separation relay D is added to the power supply circuit 10 so as to be able to separate the power supply circuit into a first sub-circuit 44 comprising the power accumulator 20, the starter 16 and the alternator 18 as well as a second sub-circuit 46 comprising the energy accumulator 22 and the electrical energy consuming elements 14. The separation relay D thus makes it possible to selectively connect the first 44 and second 46 sub-circuits to each other. The disconnection of the first 44 and second 46 sub-circuits is particularly useful during restarting because the electrical energy consuming members 14 can continue to be powered by the energy accumulator 22 and the electrical power supply circuit 10 does not undergo no undervoltage during peak power. For this, the second relay B is closed at the same time as the third relay C and the separation relay D are open.

As shown in Figures 21 to 24, a third embodiment of the power supply circuit 10 is proposed.

This second embodiment also makes it possible to process the case of degraded use where the motor vehicle 12 is unavailable because of the too low outside temperature. The configuration of the power supply circuit 10 here makes it possible to preheat the energy accumulator 22 by means of a heating device 52. Advantageously, the heating device 52 is powered by the power supply circuit 10 itself. same. Preferably, the heating member 52 extends at least partially inside the energy accumulator 22 to directly heat the cells of the energy accumulator 22.

The principle consists in heating the energy accumulator 22 by using as a priority the energy coming from the power accumulator 20 connected in parallel. After starting the motor 11 or the converter, the energy accumulator 22 continues to be heated by the network. The advantage of this configuration according to the third embodiment is to be able to use an accumulator built for the energy, ie the energy accumulator 22, even under very cold temperature conditions and by limiting the latency time as much as possible. between the moment when the driver intends to use his motor vehicle and the moment when he can do so in complete safety.

Figure 21 shows the influence of temperature on the ability of a lithium energy accumulator to sustain a discharge current of 1C (for a 50Ah battery, this represents 50A). It appears that for low temperatures and a typical state of charge after parking of 75%, the accumulator cannot provide a safety current for temperatures below 0°C. This safety current is around 50A for 2 to 3 minutes.

As indicated previously, each of the power 20 and energy 22 accumulators is preferably capable of compensating for the loss of one of the accumulators and of the alternator 18 for safety reasons. This means that each accumulator should supply a minimum current profile above a certain voltage threshold in order, for example, to supply the braking or the power steering for the time required to stop the motor vehicle 12 in complete safety.

The power of a Lithium accumulator is very dependent on its state of charge and its temperature so that, to meet these requirements, the battery must be at a sufficiently high temperature and/or sufficiently charged. The specifications for a motor vehicle usually require that it be able to start at -30°C. At this temperature, it is not possible for a lithium energy accumulator to deliver the current profile required to ensure the safety of the vehicle. It needs to be warmed up.

The third embodiment proposes heating the energy accumulator 22 using a sequence calling on electrical energy from the power accumulator 20 then energy from the network.

The power supply circuit 10 of the third embodiment is identical to that of the first embodiment except that a heating branch 50 is added in parallel with the branch receiving the energy accumulator 22. The heating branch heater 50 comprises a heater 52 of the energy accumulator 22 and an additional relay E for selective power supply of the heater 52. The third relay C is not shown but it is also present in the circuit power supply 10. A separation relay D can also be integrated.

With reference to Figures 22 to 24, a control sequence of the supply circuit 10 according to the third embodiment by the computer 30 is proposed.

Figure 22 shows the state of the first A and second B relays as well as the additional relay E during a parking phase. The "off currents" which supply the motor vehicle 12 when stationary are supplied by the energy accumulator 22, thus preserving the state of charge of the power accumulator 20 for starting.

FIG. 23 represents the state of the first A and second B relays as well as of the additional relay E during start-up if the energy accumulator 22 has a temperature above 0°C. In this case, the energy accumulator 22 is able to ensure its safety function so that the first relay A is closed which allows the power accumulator 20 to start the motor 11. The computer 30 adjusts then the voltage of the alternator 18 so as to best charge the two accumulators and to supply the electrical energy consuming devices 18.

Figure 24 shows the state of the first A and second B relays as well as of the additional relay E during start-up if the energy accumulator 22 has a temperature below 0°C. As soon as the customer's "intention to start" is known, for example via a pre-programming done previously or on a command made via his smartphone or when unlocking the doors of the motor vehicle 12, the first relay A and the additional relay E are closed. The second relay B can possibly be opened if the voltage difference between the two accumulators is too great. In this configuration of the relays, the power accumulator 20 supplies the heating device 52 thus making it possible to raise the temperature of the energy accumulator 22 to limit the time during which the motor vehicle 12 is not fully operational. . It is considered that the motor vehicle is fully operational as soon as the temperature of the energy accumulator is above 0°C and ensures sufficient discharge current to ensure safety.

Advantageously, the state of charge of the power accumulator 20 is predetermined so that it has sufficient energy allowing the heating of the energy accumulator 22 without altering its starting capacity at -30° vs. Thus, for example, if the general climate is hot, the state of charge of the power accumulator 20 can be adjusted to 70% so that the energy recovery functions during braking are optimum. Indeed, the power accumulator 20 has a good charging capacity at this state of charge. On the other hand, if the climate is cold, the computer 30 favors a state of charge of around 100% for the power accumulator 20, by prioritizing the next day's restart to the detriment of energy recovery from braking. Thus, the power accumulator 20 will have enough energy for the preheating of the energy accumulator 22 and the start.

For example, a 10 Ah battery that is sized to be powerful enough to start at -30°C and 70% state of charge has about 35 Wh available for heating. The rate of rise in temperature obviously depends on the power and the mass and composition of the energy accumulator 22, but by way of example, 35Wh are sufficient to increase the temperature of 5 kg of aluminum by about thirty °C, which makes it possible to heat the energy accumulator 22.

An embodiment of the energy accumulator 22 is shown in Figure 25. The energy accumulator 22 comprises four cells 54 mounted in series with respect to each other via inter-cell connections 56. As indicated previously, the energy accumulator 22 can advantageously comprise only three cells 54. The cells 54 are connected to a positive terminal 60 and to a negative terminal 62 of the energy accumulator via a control system 64. The control system 64 also comprises a fuse as well as a relay (not shown) corresponding to the second relay B described above, if the latter is integrated into the energy accumulator 22.

The energy accumulator 22 comprises a casing 68 in which the cells 54 are arranged. The casing 68 is preferably made of thermally insulating material, for example plastic material. The function of the box 68 is to ensure the tightness and protection of all the elements constituting the energy accumulator 22.

The energy accumulator 22 further comprises a body 66 arranged inside the casing 68 and around the cells 54. The body 66 can be formed of two parts cooperating together to surround the cells 54. The body 66 is made of a material thermal conductor, preferably aluminum.

The heater 52 is arranged inside the casing 68, preferably in contact with the body 66 to allow good heat diffusion. Even more preferably, the heating member 52 is arranged inside the body 66. The heating member 52 comprises two plates 70 forming plates heating the cells 54 via the body 66 by Joules effect. A connector 72 allows the plates 70 to be supplied with electrical energy. The heater 52 may comprise at least one plate 70. The plates 70 may be of any shape allowing the transfer of heat to the body 66.

The body 66 fixes and protects the cells 54 and at the same time, crossed by the heating plates 70, the body 66 ensures rapid diffusion of the heat produced towards all the faces of the cells 54.

This isolation is made possible because the energy accumulator 22 does not deliver high currents and, therefore, does not need to be cooled. Thus, the thermal insulation, by greatly limiting the cooling rate when the motor vehicle is parked, makes it possible not to need to heat the energy accumulator 22 too quickly, in particular the day after use of the motor vehicle. Thus, if the vehicle is used daily or every other day, all the functions will be immediately available from start-up, even in very low outside temperatures. It is also possible to adjust the temperature of the energy accumulator 22 according to the outside temperature so as to further increase the cooling time. With a temperature outside the motor vehicle of -30° C., the temperature inside the energy accumulator 22 can be adjusted to 40° C., whereas with an ambient of 0° C., the temperature inside inside the energy accumulator 22 can be adjusted to 20°C or 30°C.

This embodiment of the energy accumulator 22 makes it possible to provide a solution to the problem of the lack of intrinsic power (in charge and in discharge) of lithium energy accumulators with a graphite anode. Indeed, the preheating of the energy accumulator 22 in parallel and its thermal insulation makes it possible to limit the period when the motor vehicle is not fully operational. This parallel assembly also allows us to exploit the fact that the energy accumulator 22 does not have to be cooled and therefore can be thermally insulated, which makes it possible to considerably increase the availability of the functions of the motor vehicle 12 itself. by very cold outside temperatures.

Claims (10)

Motor vehicle (12) comprising a heat engine (11) and an electrical supply circuit (10) comprising:
at least one electrical energy consuming member (14);
a starter (16) for starting the engine (11);
a lithium power accumulator (20) configured to supply the starter (16) with a quantity of electrical energy enabling the engine (11) to be started,
a lithium energy accumulator (22) configured to supply electrical energy to said at least one electrical energy consuming member (14),
wherein said at least one electrical energy consuming member (14), the alternator (18), the starter (16), the power accumulator (20) and the energy accumulator (22) are electrically connected in parallel with each other. A motor vehicle (12) according to claim 1, wherein the power accumulator (20) and the energy accumulator (22) have negative electrodes of different composition from each other. Motor vehicle (12) according to claim 1 or 2, wherein the power accumulator (20) comprises an anode comprising Lithium-Titanate and / or the energy accumulator (22) comprises an anode comprising graphite. Motor vehicle (12) according to one of claims 1 to 3, wherein the power accumulator (20) is arranged at a hot zone of the motor vehicle (12) and the energy accumulator (22) is arranged at a cold zone of the motor vehicle (12). A motor vehicle (12) according to any one of claims 1 to 4, wherein the power accumulator (20) is disposed near the engine (11), the energy accumulator (22) being disposed at the interior of the passenger compartment of the motor vehicle (12). Motor vehicle (12) according to any one of the preceding claims, in which the power accumulator (20), the energy accumulator (22) and the starter (16) are each disposed on a branch of the circuit. power supply (10), each branch being connected in parallel with respect to the others and comprising a relay (A, B, C) selectively actuable for electrically connecting the power accumulator (20), the energy accumulator (22) or the starter (16) present on the branch to the rest of the electrical supply circuit (10). A motor vehicle (12) according to any preceding claim, wherein the power supply circuit (10) defines a first sub-circuit (44) comprising the power accumulator (20), the starter (16) and the alternator (18), and a second sub-circuit (46) comprising the energy accumulator (22) and said at least one electrical energy consuming member (14), the electrical supply circuit (10) further comprising a separation relay (10) configured to allow selective connection of the first (44) and second (46) subcircuits to each other. Motor vehicle (12) according to any one of the preceding claims, in which the electric power supply circuit (10) further comprises:
a heater (52) of the energy accumulator (22) mounted in parallel with the energy accumulator (22), and
an additional relay (E) selectively actuable to electrically connect the heater (52) and the rest of the electrical supply circuit (10). Motor vehicle (12) according to claim 8, wherein the heater (52) extends at least partially inside the energy store (22). A method of controlling an electrical supply circuit (10) for a motor vehicle (12) according to any one of the preceding claims in combination with claim 6, the electrical supply circuit (10) further comprising an alternator (18) for generating electric power from the engine (11), the alternator (18) being mounted on a branch parallel to the other branches of the power supply circuit (10), comprising at least one of the following steps:
when the engine (11) is off during the parking phase of the motor vehicle (12), control the relays so as to electrically connect the energy accumulator (22) to said at least one electrical energy consuming member (14) and electrically disconnecting the power accumulator (20) and the starter (16) from the rest of the supply circuit (10),
to start the engine (11), control the relays (A, B, C) so as to electrically connect the power accumulator (20) to the starter (16) and to electrically disconnect the energy accumulator (22) the rest of the supply circuit (10),
for carrying out a micro-hybrid operation in which the power accumulator (20) recovers electrical energy during braking of the motor vehicle (12) and distributes electrical energy during acceleration of the motor vehicle (12), control the relays (B, C) so as to electrically disconnect the energy accumulator (22) and the starter (16) from the rest of the supply circuit (10) and control the relays (A ) so as to electrically connect the alternator (18) to the power accumulator (20).