FR3013007A1 - DEVICE FOR OPTIMIZING CONFIGURATIONS OF A BATTERY SET OF AN AIRCRAFT, AIRCRAFT - Google Patents

Abstract

The device (2) for optimizing a set (B1, B2) of batteries (b1, b2) embedded in an aircraft (1) with electric propulsion, comprises a switch allowing the passage of a first configuration (16) of the set (B1, B2) of batteries (b1, b2) for takeoff to a second configuration (15) for the cruise flight.

Description

DEVICE FOR OPTIMIZING CONFIGURATIONS OF A BATTERY SET OF AN AIRCRAFT AND AIRCRAFT.

FIELD The field of the invention relates to the devices managing the power supply of light aircraft with electric motorization using sets of batteries.

STATE OF THE ART Light aircraft with electric motorization, for example of the "mini-UAV" type, generally comprise an electric motor and a propulsion propeller. UAVs designate in the English terminology: "Unmanned Air Vehicle". Mini UAVs are aircraft generally weighing less than 10Kg. Such aircraft are generally designed to carry out surveillance missions of a geographical area, the mission having a predefined duration of the order of a few hours. The energy reserve must therefore be optimized to allow the accomplishment of the mission and thus allow the aircraft to return to a planned landing point. The energy reserve can be obtained from a set of batteries, also noted "battery pack", the number is provided in sufficient quantities. The autonomy is achieved by properly sizing the battery pack. A problem arises then to increase the duration of the missions. Missions of longer durations impose an increase in the capacity of the batteries or their number. This constraint generally imposes an increase in the weight of the aircraft and therefore requires more energy and power, in particular by increasing its consumption. An insoluble situation arises except to size the capabilities of the aircraft to the detriment of its volume, its discretion or to limit the duration of missions to missions of short duration. Moreover, the propulsion of the aircraft imposes different types of operations according to the flight phases, which do not have the same profiles of consumption and energy management.

A first operation corresponds to the operating phase of the takeoff. The aircraft must deploy maximum power to ensure takeoff and use the maximum of its resources. At a minimum, the battery capacities must allow the deployment of all the power necessary for take-off. A second operation is that of the cruise flight which is performed in optimal performance. The maximum power requirements are lower than at takeoff and the efficiency can be optimized for minimum consumption.

However, it is very difficult for a propulsion unit to be optimized in terms of efficiency for the two operating points: at takeoff and in cruising flight. In general, the dimensioning of a battery pack is carried out to achieve high powers at takeoff, at least to ensure the take-off of the aircraft. Because of this design, the cruise flight, which represents more than 90% of the mission's time, suffers from a non-optimized performance. The autonomy of the mission is therefore affected and its duration must be shortened.

One solution to overcome this problem is to use variable pitch propellers to optimize the performance of the propulsion at all engine speeds. Another solution is to change the rotational ratio between the propeller and the engine including through a gearbox.

Another solution is to use a take-off aid system such as a catapult so as to reduce the energy required for take-off. It can also be a contribution of momentum allowed by an operator who runs and launches the aircraft by giving the latter its momentum.

On some light aircraft, even very light, these solutions are sometimes difficult to implement or are complex to integrate and lead to overweight of the aircraft. Today's ultra-light aircraft or mini-drones fly more than 99% of the time with a suboptimal propulsion efficiency configuration, notably because of over-sizing of the batteries for this take-off phase. As a result, the battery packs are heavier and bulkier, some of their capacity flies in unnecessary calories. In addition, this configuration can cause overheating of the engine. SUMMARY OF THE INVENTION The invention aims to overcome the aforementioned drawbacks.

An object of the invention relates to a device for optimizing a set of batteries embedded in an electrically propelled aircraft, said device comprises a switching device allowing the passage of at least a first configuration of the set of batteries for taking off at least one second configuration for the cruise flight.

An advantage of the invention is to offer an optimized operating mode for take-off and an optimized operating mode for cruising flight. This dual optimization of the aircraft makes it possible to extend the duration of the missions of a light aircraft and its autonomy. In addition, the separation of the take-off and cruising flight regimes makes it possible to limit the dependence of the cruising speed on the size of the feed planned for taking off. Advantageously, the first configuration makes it possible to deliver a maximum current greater than the maximum current delivered by the second configuration of the set of batteries. One advantage is to allow a first configuration conducive to takeoff which requires a large current flow for a short period. Advantageously, the first configuration makes it possible to reach a regime comprising the delivery of a higher thrust at the first threshold of the aircraft and that the second configuration makes it possible to achieve a performance regime between the electrical energy and the higher mechanical energy. at second threshold.

The optimization device of the invention allows to offer at least two configurations that meet different operating requirements.

Advantageously, the first threshold corresponds to 90% of the maximum thrust of the aircraft and the second threshold corresponds to a coefficient of 0.65 relative to a maximum theoretical efficiency of 1. Advantageously, the set of batteries comprises a first sub-flight. a set of batteries and a second subset of batteries, the first configuration comprising putting in series the first and second battery subassemblies and the second configuration comprising paralleling the first and second battery subassemblies. This first possibility makes it possible to offer different levels of currents to the current controller of the motor or motors. Advantageously, the set of batteries comprises a first subset of batteries and a second subset of batteries, the first configuration comprising putting in series the first and second subsets of batteries, the optimization device comprising, in addition, a switch for alternating the power supply of the aircraft between the first subset of batteries and the second subset of batteries. This second possibility makes it possible to avoid a secondary problem: the paralleling of batteries with the possibility that a subset of 25 batteries will not charge or discharge in the second subset. Advantageously, the switch is a component of the switching device. Advantageously, the switch or the switching device comprises electromechanical relays. When two subsets of batteries are used, two electromechanical relays make it possible to provide the switching function and / or the alternator function (in the alternating direction of the electrical source) between the two subsets in the second configuration. Advantageously, the first and second subsets of batteries are identical. When the optimization device comprises a plurality of battery subassemblies, each subassembly may advantageously comprise the same number of unit elements and the same arrangement. Advantageously, the optimization device comprises a plurality of battery subassemblies and a switching device comprising a matrix of switching points making it possible to define a plurality of configurations of which at least one configuration corresponds to the serialization of all the subsets. battery packs. This configuration is advantageously used for the takeoff phase of the aircraft.

This embodiment makes it possible to define different flight phases optimized according to engine efficiency or thrust. A configuration could be adapted for example according to the duration of flight or other parameters. When a configuration does not correspond to the serialization of all the battery subassemblies, the device of the invention comprises means such as a switch for example in the form of an electromechanical relay and a switching matrix that allows alternate the power plug of each subassembly. According to one embodiment, the subassemblies can be configured to be in parallel. Advantageously, the device comprises a computer for calculating the value of a parameter and generating a switching setpoint enabling the commitment of a switchover from one configuration to another configuration as a function of the value of this parameter. Advantageously, the parameter may be a predefined parameter or a parameter relating to the flight plan of the aircraft or an airplane parameter. the predefined parameter can be a predefined duration; The airplane parameter can be included in the following list: {a speed of the aircraft; a weight of the aircraft; electricity consumption data; engine speed data, remaining range}; the parameter relating to the flight plan of the aircraft can be included in the following list: {altitude data; a heading datum; tilt data; coordinates of a point in the space to be reached}. Advantageously, the computer switches from one configuration to another as a function of a combination of values reached with at least one predefined parameter, at least one aircraft parameter, or at least one parameter relating to the flight plan. of the aircraft. Advantageously, the battery set comprises Lithium Polymer type batteries, for example: Lithium Ion. In addition, another object of the invention concerns an aircraft comprising an optimization device and a propulsion assembly comprising at least one engine and a propeller, the engine comprising a variator making it possible to regulate the speed of the propeller as a function of the current delivered by the optimization device. BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will become apparent on reading the detailed description which follows, with reference to the appended figures, which illustrate: FIG. 1: an ultra-light aircraft comprising a device for optimizing the invention for managing the configurations of a set of batteries B; FIG. 2: curves indicating the operating points of the rotational speed of the propeller and the thrust of the aircraft at takeoff and in cruise flight with a first arrangement of batteries; FIG. 3: curves showing the operating points of the rotational speed of the propeller and the thrust of the aircraft at takeoff and in cruise flight with a second battery arrangement; FIG. 4: an optimization device of the invention allowing a first configuration of the batteries; FIG. 5: an optimization device of the invention allowing a second configuration of the batteries; FIG. 6: an optimization device of the invention according to two configurations corresponding to the take-off and the cruising flight with an example of predefined battery arrangements. FIG. 7A: an optimization device in a first configuration comprising a switch for alternating between two sub-configurations of batteries in the second configuration; FIG. 7B: an optimization device in a second configuration comprising a switch for alternating between two sub-configurations of batteries in the second configuration; FIG. 7C: an optimization device of the invention comprising a switch for alternating between the two subsets of batteries in the first configuration. DESCRIPTION 1 represents an ultra-light aircraft 1 such as a drone equipped with a propeller 11, an electric motor M, a fuselage 10 and a battery pack B. A camera C embedded in the aircraft is shown for illustration. FIG. 2 represents a first graph 15, called "motor curve", illustrating the number of revolutions of the helix by a curve 22 associated with: - on the one hand to the motive power, on a scale denoted P [W], Corresponding to curve 20, and; - on the other hand to the motor efficiency, on a scale Eta [%], corresponding to the curve 21. According to the abscissa axis, a current scale 1 [A] indicates the levels for each point of each represented curve. Curve 21 represents the efficiency of engine M in the different phases of flight, takeoff and cruising. During takeoff, corresponding to the operating zone 31, the current delivered by all the necessary batteries is high, and is of the order of 75A. During the cruise flight the required current is of the order of 10A according to the second operating zone 32 of flight cruise. A curve 20 represents the motive power in the different phases of the flight, take-off and cruise.

These curves are obtained with a battery configuration rated 6S. A 6S configuration is a configuration in which 6 batteries are arranged in series. An equivalent 6S1P notation makes it possible to understand that 6 battery cells are in series and form only one branch. In this configuration no battery is in parallel.

It can be seen that the operating zone 31 corresponding to the take-off imposes a high power of the order of 1250 Watt and a yield close to 90%. It can also be seen that the operating zone 32 corresponding to the cruise flight for this same configuration of batteries requires a lower power of the order of 100 Watts and a degraded efficiency of the order of 57%. Similarly, a second graph 16, called "propeller curve", illustrates the thrust of the aircraft by a curve 24 associated with the driving power, curve 23. The thrust is expressed in grams on a scale denoted Thrust [g] . Curve 23 represents the motive power in the different phases of the flight: takeoff and cruising. These curves are obtained with the same configuration of batteries as the graph 15. It can be seen that the operating zone 33 corresponding to the take-off imposes a maximum thrust of the order of 9000 g, ie 9 kg, for the power previously recorded from the order 1250 Watt. To achieve take-off, this thrust must be maintained for a certain duration. In the case of example of Figure 2, a duration of 15s makes it possible to take off the aircraft. It is also noted that the operating zone 34 corresponding to the cruise flight for this same configuration of batteries requires a lower power of the order of 100 Watts and a thrust of the order of 2kg. This phase is also called the stabilized flight phase. On the other hand, graph 15 shows the yield in this stabilized flight phase is of the order of 55%, it constitutes a non-optimized regime. Graphs 15 and 16 illustrate that the aircraft has two operating points that can not be provided by a single battery configuration at the risk of penalizing engine performance in the cruising flight phase. Figure 3 illustrates the same graphs 17 and 18 with another battery configuration, denoted 3S2P. A 3S2P configuration is a configuration in which 2 sets of 3 series batteries are arranged in parallel. The 3S2P configuration delivers twice as much ampere hour and half the voltage as the 6S1P configuration, with a constant cell count and a constant mass. A graph 17 illustrates the motor curve. It represents, as the curve 15, the number of revolutions per minute of the helix by an associated curve 26: on the one hand, at the driving power, on a scale denoted P [W], corresponding to the curve 27, and ; - on the other hand, at engine efficiency, on a scale marked Eta [%], corresponding to curve 42. According to the abscissa axis, a current scale 1 [A] indicates the 25 levels for each point of each curve represent. Curve 42 represents the efficiency of the engine M in the different phases of flight including take-off and cruising flight. During takeoff, corresponding to the operating zone 41, the current delivered by all the necessary batteries is of the order of 30A. During the cruise flight the required current is of the order of 10A according to the second operating zone 42 of flight cruise The curve 27 represents the motive power in the various phases of flight: takeoff and cruising. It is noted that the operating zone 41 corresponding to the take-off imposes a driving power which can not be reached by the aircraft alone. Outside help such as a catapult must be put in place. This take-off aid makes it possible to obtain a yield close to 80%. It is also noted that the operating zone 42 corresponding to the cruise flight for the same configuration of batteries requires a lower power of the order of 100 Watts and a yield slightly greater than 70%. This performance is better than that of the 6S1P configuration in the cruising flight phase. Similarly, a second graph 18 illustrates the thrust curve by the representation of the thrust of the aircraft. A curve 28 associated with the driving power, curve 29. The thrust is expressed in 15 grams on a scale denoted Thrust [g]. Curve 29 represents the motive power in the different phases of flight: takeoff and cruising. These curves are obtained with the same configuration of batteries as the graph 17. It is noted that the operating zone 43 corresponding to the takeoff imposes a maximum thrust of just over 3kg. But such a thrust can not be achieved by the aircraft by its sole motive power. A catapult is needed to take off the aircraft. It is also noted that the operating zone 44 corresponding to the cruise flight for this same configuration of batteries requires a lower power of the order of 100 Watts and a thrust of 1.5kg. This last configuration of batteries, known as 3S2P, shows 30 best engine performance results especially for the cruise flight phase. On the other hand, it is necessary to use additional means to assist the aircraft during takeoff, such as a catapult or an equivalent device.

The optimization device of the invention makes it possible to switch from a battery arrangement, for example 6S1P, to a 3S2P arrangement corresponding to at least two battery configurations. These configurations are switched according to the flight phase of the aircraft. A switch toggles from one configuration to another. Figure 4 shows an embodiment of an optimization device 2 of a set of batteries of the invention. The set of batteries comprises two subsets B1 and B2 of batteries. The device 2 comprises a switch for switching from a first configuration in which B1 and B2 are in series in a second configuration in which B1 and B2 are in parallel. The first configuration, illustrated in FIG. 4, makes it possible to obtain two sets of batteries B1 and B2 in series. This configuration is conducive to release the power required for takeoff. This configuration is maintained for a relatively short period of time of the order of a few seconds to a few minutes. A planned duration is of the order of 15s during which the aircraft delivers maximum or near thrust.

The second configuration, illustrated in FIG. 5, makes it possible to obtain two sets of batteries B1 and B2 in parallel. This configuration is conducive to optimize engine performance in cruising flight. This phase of flight can last from a few minutes to a few hours. A target mission duration can be from 1h to 2h.

Switching from one configuration to another allows optimization of performance in all phases of the flight. The switch makes it possible to drive a set of relays 50, 51 simultaneously so as to allow the passage from one configuration to another during the flight.

FIG. 6 shows an embodiment in which each subset of batteries B1 and B2 comprises a set of batteries having a predefined arrangement, in particular in FIG. 6 are represented 12 battery cells in each circuit 19 and 19 '. Various embodiments are possible according to the battery arrangements of each subassembly B1, B2. A first arrangement defines a first 6S2P configuration which means that two sets of six series batteries are in parallel.

When the switch engages the first configuration in circuit 19, the two sets of 3S2P batteries define a 6S2P configuration in which two sets of six series batteries are in parallel. When the switch engages the second configuration according to the circuit 19 ', the two sets of 3S2P batteries define a 3S4P configuration in which four sets of 3 series batteries are in parallel. Other configurations may be defined such as a first configuration with a 12S2P arrangement and a second configuration with a 6S4P arrangement with two subsets of batteries each having a 6S2P array that are either in series or in parallel. In the second configuration, in order to prevent a first subset of batteries from charging or discharging into the second subset arranged in parallel with the first subset, battery balancing components may be implemented to improve the operation of this second configuration. According to one embodiment, these balancing elements may comprise, for example, diodes. These elements make it possible to avoid a loss of efficiency due to this undesirable effect of charge or electrical discharge of a subassembly in another subassembly when they are in parallel. Accordingly, to prevent a subset of batteries from emptying into another subset of batteries and to avoid any short circuit or electrical problem, the optimization device of the invention may include diodes of blocking arranged between the two subsets arranged in parallel. The diode system distributes the power of the two battery subassemblies alternately, which allows the energy of one subassembly to be consumed alternately with the second subassembly. According to another embodiment, to avoid the use of diodes, it can be implemented a connection between the motor M s comprising the electrical control member, not shown, and the two subsets B1 and B2 batteries allowing alternate use of each subassembly to avoid mutual charges and discharges. Fig. 7A shows an embodiment of this switch. Two relays 52 and 53 make it possible to pass from a first subset B1 of batteries to a second subset of batteries B2. Alternatively, the relays are in one position and then in the other to alternate the use of the two subsets of batteries. This possibility makes it possible to avoid the drawbacks of paralleling the two batteries while being adapted to obtain a cruising flight regime that offers optimized efficiency of the power supply resources. Figure 7A shows the device in a first sub-configuration of the second configuration in which the motor M is powered by the battery pack B1. Fig. 7B shows the device in a second sub-configuration of the second configuration in which the motor M is powered by the battery bank B2. The transition from the first sub-configuration of FIG. 7A to the second subconfiguration of FIG. 7B is accomplished by a switching of relay 52. FIG. 7C shows the device when the first configuration is activated, that is, say preferentially at takeoff. In this case, the motor is powered by the battery packs B1 and B2 which are then in parallel. An arrangement of the relays 52 and 53 allows the activation of this configuration. According to one embodiment as shown in FIGS. 7A-7C, the switches used for the transition from the first to the second configuration can be used to define sub-configurations of the second configuration. A first arrangement of the relays 52 and 53 allows different configurations to be defined which either correspond to a cruising configuration or a take-off configuration. A second arrangement makes it possible to define, in cruise flight, different energy sources that alternately deliver a current to the motor M. The alternation between the battery packs B1 and B2 then makes it possible to offer a good alternative to the set-up configuration. parallel of the two sets of batteries B1 and B2. In one example, the batteries can be LiPo type, lithium-ion polymer. Each unitary element of a battery or a battery pack or subassembly may in one embodiment have the following characteristics: A voltage of 3.7V and a capacity of 5Ah (ampere / hour). This allows to continuously deliver a current of 5A for one hour or a current of 10A for 1/2 hour or 2.5A for 2h. Other configurations are possible. A feature of each element is the ability to deliver a maximum current expressed as a function of the capacitance of the element. For example an element of 5Ah and max current 10C can deliver current peaks of 50A. This is a characteristic favoring the flight phase corresponding to take-off. A set of 3S2P configuration batteries includes 3x2 = 6 unit elements. Similarly, a set of 6S2P configuration batteries comprises 6x2 = 12 unit elements, i.e. the same number of elements as a 3S4P configuration. For a configuration of a 6S2P assembly, the following characteristics will be obtained: - Voltage 6 x 3.7V = 22.2V, calculated voltage vis-à-vis the 6 batteries in series - Capacity 2 x 5Ah = 10Ah, capacity calculated vis- to the two 30 sets of 6 batteries in parallel. Max current: 100A A 6S2P arrangement defined by the first battery configuration is used to the maximum of its peak current performance at takeoff, i.e., for a current of -50A to 100A. Another arrangement, noted 3S4P obtained by switching to the second configuration is then used to the maximum of its performance for the optimization of the electrical efficiency of the aircraft. The capacities of the battery subassemblies are optimized for the endurance of the aircraft and its autonomy. For the previous example, a current of about -6A on average provides a range of 13h0 approximately. The solution provided by the optimization device of the invention makes it possible to reconfigure the battery in flight according to an arrangement with a number of constant elements.

Keeping the assumptions of the previous example, a battery having a 6S2P arrangement consists of 12 elements that can be reconfigured into a 3S4P arrangement. this last arrangement makes it possible to define a second zone of operation of the aircraft more adapted to the cruising flight, one obtains: - Voltage 3 x 3.7V = 11.1V - Capacity 4 x 5 = 20Ah - Current max: 200A This reconfiguration can easily be carried out using two inverter relays typically shown in Figure 6. Other configurations are possible. Depending on the cases, in particular according to the engine, the weight of the aircraft and the expected mission times, the battery pack B is dimensioned so that it is delivered: - A voltage - A current - An electric charge expressed in amp hour. The maximum take-off thrust and the cruising flight efficiency are the corresponding input data requirements for choosing the best configuration of the battery pack and the two configurations that can be switched. The optimization device of the invention may include a control unit for engaging the tilting of the in-flight configurations. The control unit may comprise a computer which engages the switching of a configuration to another configuration according to airplane parameters, predefined parameters or parameters relating to the flight plan. The term "aircraft parameters", parameters that can be the speed of the aircraft, the weight of the aircraft, a power consumption data or a data engine speed. The term "predefined parameter" means a predefined duration that corresponds to a pre-calculated take-off time. "Parameters relating to the flight plan" of the aircraft, an altitude datum; a heading datum; tilt data; coordinates of a point in the space to be reached. The control unit may be the autopilot of the aircraft. According to one embodiment, the passage from one configuration to another can be engaged by means of a remote control of the aircraft which makes it possible to steer the aircraft from a distance. The autopilot makes it possible in particular to regulate the current delivered by the batteries and makes it possible to manage the speed of the aircraft. The device of the invention allows the autopilot to regulate the current in each of the possible configurations of the batteries and makes it possible to switch in a given configuration to obtain the best operating point of the aircraft according to the desired aircraft commands, of the type commands in speed, engine efficiency, altitude, etc. Relay control allows switching from a 6S2P configuration to a 3S4P configuration. The reverse tilting is also possible but does not correspond to the passage from takeoff to cruise flight. But it is this last passage that poses a problem in optimizing the flight of the aircraft. The technical advantage of this solution, in addition to adding little weight by adding 2 relays of about 100 grams, is that the motor can work at a better operating point for low power during its phase. flight cruise. Indeed, during the cruise flight phase, the voltage is reduced, therefore the shape of the yield curve shifts and the efficiency for a given power improves significantly. The improvement in efficiency means that the conversion of the energy consumed by the batteries into mechanical energy produced by the propeller is better. Consequently, by optimizing the performance of the cruise flight phase, for a constant electrical energy produced, the number of mechanical Watts produced during switching of the batteries in the second configuration is greater than the number of mechanical Watts without switching in the second configuration. . In the 3S4P configuration, the engine will no longer be able to deliver the maximum power required for take-off but will be adapted to a better performance during the cruising flight.

The efficiency improvement depends very much on the constituents of the aircraft such as the engine, the propeller (s) and possibly a gearbox such as a gearbox. The device of the invention could be adapted according to the configuration of the aircraft to a plurality of configurable battery configurations by means of a switch or a switching matrix controlled by a control member. For example, if 12 battery cells are present in the optimization device, they can define 3 different arrangements: a first arrangement corresponds to a subset of batteries in series: 12S1P.

A second arrangement corresponds to two subsets of 3S2P batteries that can be connected in series or used alternately or in series. A third arrangement corresponds to four subsets of 4S1P batteries that can be connected in series or used alternately or in series. Each subset can be used alternately when the aircraft is in cruise flight. The yield gain would be, in this case, calculated case by case according to the airplane configuration. Thanks to the device of the invention, an order of magnitude of the gain in performance is at least for previously mentioned arrangements of the order of 20%.

As this gain is achieved on the propulsion configuration corresponding to 99% of the time, this improvement of 20% of the output immediately translates into an improvement of equivalent autonomy. For an autonomy of 1h3Omn, we would spend about 1h5Omn. The optimization device of the invention allows the means at least two relays to extend the duration of the flight by maintaining a battery mass almost constant. As a result, the optimization device of the invention makes it possible to lengthen the distances of the missions. The device of the invention is particularly effective when a significant performance is required for takeoff, that is to say for a thrust greater than the weight of the aircraft. In this case, optimizing the low-end performance during the cruise flight phase is important. The optimization device of the invention nevertheless remains interesting when the initial thrust required for take-off is less than the mass of the aircraft, even if the difference in gain efficiency is lower. In this case, the device of the invention is compatible with an external take-off aid, such as a current operator to "launch" the aircraft on take-off. An advantage of the device of the invention is that it makes two possible flight phases with significant differences in the speeds associated with these phases. Because with a single battery configuration, a large deviation of the regime requires either the use of external means to take off or degradation of performance in cruising flight. As a result, the device of the invention allows large take-off thrust configurations. The first configuration makes it possible to reach a regime comprising delivering a higher thrust at first threshold S1 of the aircraft. This threshold may correspond to a percentage of the maximum thrust that can be delivered by the aircraft. In one embodiment, this first threshold S1 corresponds to 90% of the maximum thrust of the aircraft. On the other hand, the second configuration makes it possible to reach a performance regime between the electrical energy and the mechanical energy higher than the second threshold S2 which can be defined with respect to a maximum theoretical efficiency of 1. This second threshold can be according to the figures around 0.65 or 0.75 in cruise flight.

According to one embodiment, the change of configurations can be reversible and allow in case of urgent maneuver to return to the first configuration. For example, in case of a rapid rise to avoid an obstacle, the optimization device allows the passage of the second configuration to the first configuration. Thus the aircraft can benefit from a maximum thrust during flight. The optimization device of the invention also applies to switching to a plurality of configurations. For example, the flight phases can be segmented by taking into account different cruising speeds at descent phases. In the latter case, a matrix of switching points allows the passage from one configuration to another. The battery subassemblies comprise battery cells that can be connected in series or parallel with other battery cells of one or more other battery subassemblies. According to one embodiment, a computer makes it possible to optimize the configuration as a function of the engine speed. The invention is compatible with the use of a variable pitch of the propeller of the aircraft. When the aircraft comprises two engines, when it is twin engine, the device of the invention can drive two sets B of batteries each comprising a plurality of battery subassemblies B1, B2. 35

Claims (16)

REVENDICATIONS1. Device (2) for optimizing an assembly (B1, B2) of batteries (b1, b2) embedded in an aircraft (1) with electric propulsion, characterized in that the device (2) comprises a switching device enabling the passing at least a first configuration (16) of the set (B1, B2) of batteries (b1, b2) for takeoff to at least a second configuration (15) for the cruise flight. 2. Device (2) for optimizing a set (B1, B2) of batteries according to claim 1, characterized in that the first configuration allows to deliver a maximum current greater than the maximum current delivered by the second configuration of the set (B1, B2) of batteries (b1, b2). 3. Device (2) for optimizing a set (B1, B2) of batteries according to any one of claims 1 to 2, characterized in that the first configuration makes it possible to achieve a regime comprising the delivery of a thrust higher than the first threshold (S1) of the aircraft and the second configuration achieves a performance regime between the electrical energy and the mechanical energy higher than second threshold (S2). 4. Device (2) for optimizing a set (B1, B2) of batteries according to claim 3, characterized in that the first threshold (S1) corresponds to 90% of the maximum thrust of the aircraft and that the second threshold (S2) corresponds to a coefficient of 0.65 with respect to a theoretical maximum efficiency of 1. 5. Optimization device according to any one of claims 1 to 4, characterized in that the set (B1, B2) of batteries comprises a first subset (B1) of batteries (b1) and a second subset set (B2) of batteries (b2), the first configuration (16) - 21 - comprising putting in series the first (B1) and the second (B2) battery subassemblies (b1, b2) and the second configuration ( 15) comprising paralleling the first (B1) and the second (B2) battery subassemblies (b1, b2). 6. Optimization device according to any one of claims 1 to 4, characterized in that the set (B1, B2) of batteries comprises a first subset (B1) of batteries (b1) and a second subset set (B2) of batteries (b2), the first configuration (16) comprising putting in series the first (B1) and the second (B2) battery subassemblies (b1, b2), the optimization device comprising in in addition to a switch for alternating the power supply of the aircraft between the first subset (B1) of batteries (b1) and the second subset (B2) of batteries (b2). 7. Optimization device according to claim 6, characterized in that the switch is a component of the switching device. 8. Optimization device according to any one of claims 1 to 7, characterized in that the switch or the switching device comprises electromechanical relays. 9. Optimization device according to any one of claims 5 to 8, characterized in that the first (B1) and the second (B2) subsets of batteries are identical. 10. Optimization device according to any one of claims 1 to 9, characterized in that it comprises a plurality of battery subassemblies and a switching device comprising a matrix of switching points for defining a plurality of configurations of which at least one configuration corresponds to the serialization of all battery subassemblies. 11. Optimization device according to any one of claims 1 to 10, characterized in that the device comprises a computer for calculating the value of a parameter and to generate a switching setpoint allowing 1 "commitment d a switch from one configuration to another configuration depending on the value of this parameter. 12. Optimization device according to claim 11, characterized in that the parameter may be a predefined parameter or a parameter relating to the flight plan of the aircraft or an aircraft parameter. 13. Optimization device according to claim 12, characterized in that: the predefined parameter can be a predefined duration; the airplane parameter can be included in the following list: {a speed of the aircraft; a weight of the aircraft; electricity consumption data; engine speed data}; the parameter relative to the flight plan of the aircraft can be included in the following list: {altitude data; a heading datum; tilt data; coordinates of a point in the space to be reached}. 14. Optimization device according to claim 13, characterized in that the computer switches from one configuration to another according to a combination of values reached with at least one predefined parameter, at least one aircraft parameter, or at least one parameter relating to the flight plan of the aircraft. 15. Optimization device according to any one of claims 1 to 14, characterized in that the set of batteries (b1, b2) comprises batteries of Lithium Polymer type. 16. Aircraft comprising an optimization device according to any one of claims 1 to 15 and a propulsion assembly comprising at least one motor and a propeller, the motor comprising a variator for regulating the speed of the propeller according to the current delivered by the optimization device.