NL2023697B1 - Electrically-powered agricultural machine - Google Patents

Abstract

An electrically-powered agricultural machine, which comprises at least one main equipment (2) and a traction assembly (3) adapted to move the equipment (2) along a piece of agricultural land to be worked. The assembly (3) comprises a rechargeable battery (4) of electricity storage cells and an electric motor (5), powered by the battery (4); the battery (4) comprises a plurality of accumulators (6) connected in series and each accumulator (6) comprises a plurality of rechargeable lithium-ion cells (7) connected in parallel; the accumulators (6) and the cells (7) are configured to define a maximum voltage, between the terminals (4a) of the battery (4), which is comprised between 28 volts and 40 volts; such maximum voltage between the terminals (4a) is chosen to be higher, at least by 20%, than the rated operating voltage of the motor (5).

Description

P34205NLOO/TRE Title: ELECTRICALLY-POWERED AGRICULTURAL MACHINE The present invention relates to an electrically-powered agricultural machine.

As is known, in the known art various types of agricultural machine are widespread, which are designed for harvesting vegetables.

Often, the very peculiarity of the specific vegetable and of the method of cultivation it requires, conditions or suggests the design and structure of the agricultural machine designed for harvesting it.

For example, harvesting courgettes or asparagus entails the use of dedicated machines and, for asparagus, machines for white asparagus must be designed differently from machines for green asparagus.

In any case, both in the above-mentioned examples and in other applications, for different vegetables, such machines are often powered by batteries of electricity storage cells, mounted on board the machine. They supply the energy necessary for the movement along the field to be harvested and they are preferred to heat engines and/or motors using other energy sources.

However, one of the drawbacks that most afflicts electrically-powered agricultural machines is the limited battery capacity they can draw on.

This forces the operator to make long stops in order to allow the batteries to be recharged, during which it is evidently necessary to interrupt work in the field, with unwanted delaying of the harvest operations.

Moreover, an imprudent increase in the capacity of the batteries, which does not take into consideration all the risk factors, can lead to even worse problems: for example, such an increase can be accompanied by extensive overheating, which increases the risk of fires.

Furthermore, the conventional batteries that provide the greatest capacity (which in any case is now insufficient) are very heavy and it is therefore not possible to remove them and transport them to the recharging area separately from the agricultural machine.

It should be noted finally that, typically, information about the status of the batteries, and about the remaining capacity that they are capable of providing, is critically important in order to prevent the risk of the machine coming to a stop with no energy in the open countryside. That notwithstanding, with traditional solutions it is often difficult to ensure such information in real time with an adequate degree of reliability.

The aim of the present invention is to solve the above mentioned problems, by providing an electrically-powered agricultural machine that ensures high capacity.

Within this aim, an object of the invention is to provide an agricultural machine with high capacity and low weight, while at the same time ensuring optimal operability of the devices connected to it.

Another object of the invention is to provide an agricultural machine in which the accumulator battery ensures a high reliability of operation and is provided with effective measures against the risk of fire.

Another object of the invention is to provide an agricultural machine that makes it possible to easily and reliably verify the status of its accumulator battery and in particular the remaining capacity.

Another object of the invention is to provide an agricultural machine that adopts an alternative technical and structural architecture to those of conventional agricultural machines.

Another object of the invention is to provide an agricultural machine that can be easily implemented using elements and materials that are readily available on the market.

Another object of the invention is to provide an agricultural machine that is of low cost and safely applied.

This aim and these and other objects which will become better apparent hereinafter are achieved by an electrically-powered agricultural machine, which comprises at least one main equipment and a traction assembly adapted to move said equipment along a piece of agricultural land to be worked, said assembly comprising a rechargeable battery of electricity storage cells and an electric motor, powered by said battery, characterized in that said battery comprises a plurality of accumulators connected in series, each one of said accumulators comprising a plurality of rechargeable lithium-ion cells connected in parallel, said accumulators and said cells being configured to define a maximum voltage, between the terminals of said battery, which is comprised between 28 volts and 40 volts, said maximum voltage between said terminals being chosen to be higher, at least by 20%, than the rated operating voltage of said motor.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred, but not exclusive, embodiment of the agricultural machine according to the invention, which is illustrated by way of non-limiting example in the accompanying drawings wherein:

Figure 1 is a schematic perspective view of the traction assembly and some further components of the agricultural machine according to the invention; Figure 2 is a perspective view of the accumulator battery comprised in the traction assembly in Figure 1; Figure 3 is a perspective view of an accumulator of the battery in Figure 2; Figures 4 and 5 are schematic perspective views of two respective methods of recharging the battery in Figure 2; Figures 6 to 9 are perspective views of respective examples of agricultural machines according to the invention.

With particular reference to the figures, the reference numeral 1 generally designates an electrically-powered agricultural machine, which comprises at least one main equipment 2 and a traction assembly 3 which is adapted to move the equipment 2 along a piece of land to be worked.

In the present discussion, the term equipment 2 refers to the supporting structure and to the set of all elements and components, directly or indirectly connected to the supporting structure, which cooperate to carry out the specific work the machine 1 is adapted to.

The supporting structure and in general the equipment 2 can be moved by an assembly 3 which is mounted directly on the structure, or it can also be moved by an assembly 3 mounted on board a tractor, designed to tow a trailer on which the equipment 2 is placed.

Each one of the possibilities outlined briefly above should be understood as comprised in the scope of protection claimed herein, which moreover further includes any type of working of the soil and therefore to equipment 2 adapted to work agricultural lands of any kind.

More specifically, the piece of agricultural land to be worked will typically (but not exclusively) be used for the cultivation of a specific vegetable, and the best-suited equipment 2 can be chosen for that precise cultivation, while still remaining within the scope of protection claimed herein.

Purely for the purposes of non-limiting example therefore, Figures 6-9 show some examples of agricultural machines 1 that implement the invention that is the subject matter of the present description. Such machines 1 are respectively designed for working land used to cultivate courgettes (Figures 6-7), white asparagus (Figure 8) and green asparagus (Figure 9).

An application of the invention that is of particular interest consists of harvesting courgettes, asparagus and the like.

It should be noted however that it is possible to provide the machines 1 according to the invention for working of another nature, including for uncultivated land or land being prepared for future cultivation.

In any case, the assembly 3 comprises a rechargeable battery 4 of electricity storage cells and an electric motor 5, powered by the battery 4. Therefore it is precisely the electric motor 5 that acts to move the equipment 2, by virtue of the mechanical energy output, which in turn is obtained from the electric power input, which is supplied by the battery 4.

The electric motor 5 can also be chosen to be of any type, as a function of the requirements and of the specific application.

According to the invention, the battery 4 comprises a plurality of accumulators 6 connected in series (Figure 3), each one of which comprises in turn a plurality of rechargeable lithium-ion cells 7 connected in parallel. The accumulators 6 and the cells 7 are configured to define a maximum voltage, between the terminals 4a of the battery 4, which is comprised between 28 volts and 40 volts. Furthermore, such maximum voltage between the terminals 4a is chosen to be higher, at least by 20%, than the rated operating voltage of the motor 5.

This makes it possible from this point onward to achieve the set aim: in fact, by virtue of the choice to ensure such a high maximum voltage (conventional solutions keep it much lower), thanks to a motor 5 that has a lower rated operating voltage, at least in the first step of supplying energy to the motor 5 the current value is very low (since the voltage value is very high), and therefore the battery 4 can discharge very slowly, thus ensuring high capacity.

In particular, in an embodiment of significant practical interest, the accumulators 6 and the cells 7 are configured to define a maximum voltage, between the terminals 4a of the battery 4, equal to 33.6 volts. In such context, the motor 5 can for example have a rated operating voltage of 24 volts.

Even more specifically, in the preferred embodiment, which however does not limit the application of the invention, the battery 4 comprises eight accumulators 6; since a maximum voltage needs to be defined between the terminals 4a equal to 33.6 volts, a maximum voltage equal to 4.2 volts is therefore defined between the terminals 6a of each accumulator 6.

Typically, but not exclusively, such accumulators 6 will define a minimum voltage value between the terminals 4a equal to 24 volts, while between each pair of terminals 6a a minimum voltage value will be defined equal to 3 Volt.

It should be noted however that the possibility is not ruled out of providing the 5 battery 4 with a different number of accumulators 6, with a maximum voltage between the terminals 6a equal to or less than 4.2 volts and a maximum voltage between the terminals 4a also different from 33.6 volts (and for example equal to 28.8 volts). Likewise, the motor 5 can also have different values of rated operating voltage.

With further reference to the preferred embodiment (and to the accompanying figures), each accumulator 6 comprises twenty-three cells 7 (arranged in parallel as we have already seen).

The maximum/minimum amperage ensured by each cell 7 can also be chosen freely, while remaining within the scope of protection claimed herein.

For example, each cell 7 that defines a maximum voltage between the terminals 6a equal to 4.2 volts can provide a rated current of 2.6 amps, under conditions of maximum charge. If twenty-three cells 7 are used, each element 8 can provide up to 59.8 amps.

Conveniently, the agricultural machine 1 according to the invention comprises an electronic unit 8 for the control and management of the battery 4.

The electronic unit 8 can be of any type, and preferably it is constituted by a control unit mounted directly on the battery 4 (between its terminals 4a, as in the accompanying figures). It is however possible to use different types of electronic unit 8 (whether mounted on the battery 4 or not), which could therefore be any hardware platform, reprogrammable or otherwise, that is capable of acting (automatically and/or as a consequence of user intervention) according to the methods that will be described in the next paragraphs.

The electronic unit 8 is provided with a reading module for reading the instantaneous voltage value at the terminals 6a of each accumulator 6 of the battery 4, with a first module for cutting the electrical connection between the battery 4 and the motor 5 and with a second module for cutting the electrical connection between the battery 4 and an electric recharging instrument (of any type, but one that can be associated with the battery 4 in order to begin the recharging phase of the latter).

The first module for cutting an electrical connection can therefore be activated as a result of reading an instantaneous voltage value, at the terminals 6a of even only one of the accumulators 6, equal to a minimum predefined threshold voltage, chosen forexample to correspond to the minimum rated value (for example 3 volts, as we have already seen).

Likewise, the second module for cutting an electrical connection can be activated as a result of reading an instantaneous voltage value, at the terminals 6a of even only one of the accumulators 8, equal to a maximum predefined threshold voltage, chosen for example to correspond to the maximum voltage mentioned earlier (for example 4.2 volts, as we have already seen).

It should be noted that operating outside of the envisaged rated range brings the risk of overheating and fire in the battery 4: the modules for cutting the electrical connections are found to be very useful for preventing such hazard, in that (by conveniently choosing the threshold voltages) they cut the flow of energy in input to and in output from the battery 4 when, even for only one accumulator 8, the readings approach the limits of the optimal operating range.

Conveniently, the electronic unit 8 is provided with a module for balancing (or equalizing) the energy supplied to each accumulator 6 during the recharging phase, as a function of the instantaneous voltage value detected by the reading module.

This ensures better conditions of safe operation for the battery 4: in fact, it must be noted that during the current dispensing or recharging phases, there may be an unbalancing of the voltage values among some accumulators 8. This can lead to an arrest during the recharging phase, without the recharging being completed. Precisely to this end, the electronic unit 8 ensures, by virtue of the module for balancing the energy, that any different values are matched during the recharging phase.

Conveniently, the agricultural machine 1 can comprise at least one photovoltaic panel 9, which can be moved by the traction assembly 3 integrally with the equipment 2 along the soil to be worked. To this end, the panel 9 can be mounted on the top of the agricultural machine 1, or it can in any case be conveniently arranged and inclined in order to receive the maximum solar radiation during movement along the piece of agricultural land (or even while stopped, obviously).

The photovoltaic panel 9 is functionally associated with the battery 4, so as to supply electric power (obtained by converting the energy conveyed by solar radiation) to the accumulators 6, in order to actuate the recharging phase of the battery 4. In this case therefore, the recharging instrument mentioned above, is the panel 9.

The use is also envisaged of a voltage regulator 10, functionally interposed between the panel 9 and the battery 4, which acts to stop the recharging phase when the voltage value between the terminals 4a is just below the maximum predefined thresholdvoltage (for example 33.4 volts). The regulator 10 can likewise be configured to stop the recharging phase when the voltage value between the terminals 6a of even only one of the accumulators 6 drops below a preset limit. Actually, the regulator 10 provides a safety function in addition to the second module for cutting an electrical connection, leaving the latter the task of intervening as a last resort, in the event of malfunction of the regulator 10, as a further assurance of reliability of the invention.

The active configuration that includes the panel 9, the regulator 10 and the battery 4 is schematically shown in Figure 4.

It should be noted in any case that the recharging phase can also be actuated in another manner, by using other types of recharging instruments, and for example by connecting the battery 4 to a battery charger 11 (which may be conventional) which in turn is connected or can be connected, for example, to the mains electricity supply 12 (Figure 5).

In this latter case as well, it is possible to provide the battery charger 11 with a functionality similar to that of the regulator 10, i.e. capable of stopping the recharging phase before reaching the maximum predefined threshold voltage (for each accumulator 6 or for the battery 4), for the purpose of adopting an additional precaution against the risk of exceeding such limit (with consequent hazard of overheating and fire).

Advantageously, the agricultural machine 1 according to the invention comprises an electronic device 13 for verifying the charge status of the battery 4, which is associated with a respective display 14 for displaying that charge status.

As with the unit 8, the electronic device 13 can also be of any type, but preferably it is constituted by a microprocessor circuit board (while not ruling out the use of a control unit or of any other hardware platform, reprogrammable or otherwise). The device 13 can also be integrated into the unit 8 (or vice versa) or in any case it can interact with the latter, for example in order to exchange relevant data or information and/or in order for one to take advantage of the functionality of the other, and vice versa.

The display 14, which is also chosen to be conventional per se, can be mounted in an appropriately chosen position, so as to make it easily and quickly accessible to a user.

The device 13 comprises first instructions for the periodic testing of the instantaneous voltage value at the terminals 4a of the battery 4; for example such first instructions can entail a test every 3 seconds. It should be noted that such functionality can be carried out using the reading module of the unit 8.

The device 13 further comprises second instructions for the periodic calculation of the mean of the instantaneous voltage values over predefined time intervals (chosen for example to be equal to 10 minutes), for an estimate of the charge status.

The device 13 then comprises third instructions for carrying out, at the end of each interval (every 10 minutes), the comparison of the most recent calculated status with the previous calculated status, and for displaying the most recent status on the display 14, in substitution for the previous one, only when the most recent status is lower than the previous one.

It should be noted that in identifying the actual charge status (and of the actual voltage value) of a battery 4 a problem can arise: when the motor 5 draws a great deal of energy from the battery 4 the voltage value can drop below the actual voltage, while when the motor 5 is stationary the voltage value can rise, indicating the maximum value of the battery 4.

The device 13 remedies these problems by updating the display 14 on the basis of means (which therefore do not take account of momentary oscillations) and only when these indicate a progressive fall (a rise, under working conditions, obviously needing to be considered a reading error).

The device 13 can be provided with further useful functionalities, such as for example an audible and/or visual alarm, automatically activatable upon reading an instantaneous voltage value (or a mean) that is close to the charge-depleted condition (for example the alarm can be activated when the voltage value is equal to 25 volts).

Advantageously, the electronic device 13 is provided with an inhibition module for inhibiting the traction assembly 3, which can therefore stop the machine 1, preventing any further advancement.

The inhibition module can be automatically activated upon an instantaneous voltage value at the terminals 4a of the battery 4 which is equal to a preset lower limit value (for example when a voltage value is detected equal to 24.2 volts). In turn, the inhibition module can be selectively deactivated (by way of a special button for example) in order to allow small-scale movements of the equipment 2 and for it to be made safe.

Actually, the inhibition module can immobilize the machine 1 just before the charge is exhausted, while still retaining an amount of residual energy that can be used to allow the user to bring the machine 1 back to the recharging station, thus preventing carelessness and misuse that would otherwise presage inconveniences and problems.

The device 13 can likewise be provided with a module for storing the minimum mean, until the recharging phase has been completed (33.6 volts): at this point thesystem can reset automatically in order to allow a new calculation. This has the function of alerting the user if during the night {or in any case during the recharging phase) the recharging has not been completed. Conveniently, the agricultural machine 1 comprises an amperometric sensor, interposed between the battery 4 and the motor 5. The sensor is configured to read, instant by instant, the electrical input of the motor 5 and to transmit the related data to an electronic card which in turn is configured to compare such data, during the operation of the motor 5, with a predefined optimal discharge curve of the battery 4. It should be noted in fact that in conventional batteries (and therefore also in the battery 4) it is possible to identify an optimal discharge curve (specified by the manufacturer for example), which gives the best performance and the maximum capacity. By contrast, the working conditions in which the machine 1 actually operates can be such as to skew the discharge curve from the optimal curve (for example when the traveled soil is not compact).

To prevent an excessive skewing from the optimal curve, the card is therefore provided with instructions for temporarily deactivating the traction assembly 3, upon reading an electrical input value higher than that of the optimal curve for a period longer than a predefined time threshold. The time threshold can be chosen to be equal to 10 minutes, in order to compensate for any requirement for more power, required for short periods in order for example to get past a ditch or an obstacle.

In general, the optimal curve can for example entail an energy consumption of 12 amps*h in a battery rated at 60 amps*h (30 amps*h in a battery rated at 150 amps).

Operation of the agricultural machine according to the invention is therefore evident from the foregoing description.

It has been already stated in fact that the agricultural machine 1 can be moved along the piece of agricultural land of interest by its traction assembly 3, with its electric motor 5 which moves the equipment 2, which can move over ground for example by virtue of wheels 15.

The electric motor 5 is powered by the battery 4, which is entirely innovative and capable of ensuring high capacity, well above that obtainable with conventional solutions.

In fact, by providing a battery 4 with at least eight accumulators 6 connected in series (and preferably indeed with eight elements 6), each one of which is provided with a plurality of lithium-ion cells 7 connected in parallel, it is possible to obtain substantially the same amperage as with traditional batteries but with a yield higher than 30%. This is byvirtue of the maximum voltage between the terminals 4a which is conveniently higher, at least by 20%, than the rated operating voltage of the motor 5.

In more detail, in the first part of the discharging phase, i.e. when the battery 4 supplies energy to power the motor 5, the corresponding current value is very low, and therefore the battery 4 can discharge very slowly, thus ensuring high capacity.

Furthermore, the overheating of the motor 5 and of the other components affected is appreciably less than that observed in conventional solutions.

The electronic components also heat up less, and their efficiency is therefore increased.

For example, a battery 4 is provided with eight accumulators 6 with a maximum voltage equal to 4.2 volts (and a minimum voltage equal to 3 volts), each one of which is composed of twenty-three cells 7: therefore the maximum voltage between the terminals 4a of the battery 4 is equal to 33.6 volts. It should be noted that the motor 5 (even if chosen, as seen, with a lower rated voltage) and all the electronic components to be connected to the battery 4 can operate correctly at voltage values equal to 33.6 volts (or even more, and therefore the desired increase in capacity is obtained without compromising the optimal operability of the components (electronic and non-electronic) connected to it.

Furthermore, such results of undoubted interest are obtained with a battery 4 that has eight or more accumulators 6, and therefore with a minimal increase in weight with respect to conventional solutions (which have batteries with a smaller number of accumulators). It should be noted in this regard that each accumulator 6 can have a weight equal to about 1.2 kg (and therefore entails a very limited overall increase). The increase in cost associated with adopting the battery 4 instead of traditional batteries is also low, in that the outer shell and its assembly are substantially the same, as are the costs for their disposal.

More generally, by virtue of the battery 4 it is possible to obtain results that are comparable (in terms of capacity and performance) to those that are traditionally obtained with much higher weights and costs, by using a plurality of batteries or in any case by appreciably complicating the configuration of the machine.

The battery 4 can therefore be implemented on agricultural machines 1 that are intended for harvesting (or other processing) of vegetables, by being capable of ensuring high capacity with evident benefits in terms of productivity. By virtue of the low weight, the battery 4 can furthermore be easily dismantled and transported separately (from the machine 1) if the specific circumstances require it.

It has furthermore already been seen that the modules for cutting the electrical connections of the unit 8, which cooperate with the reading module, are found to be very useful for guarding against the danger of fire, in that they act to cut the flow of energy in input to and in output from the battery 4, when conditions are approached that could generate overheating. This evidently increases the reliability of operation.

The presence of the display 14, and the peculiar methods with which the electronic device 13 displays the charge status on it (already described in the foregoing pages) make it possible to easily and reliably verify the status of the battery 4 and in particular the remaining capacity. The practicality of use of the display 14 (and the reliability of the data supplied) are evidently very useful: in fact the machine 1 is designed to work on agricultural land even if far from energy sources, and it is therefore essential for the user to be able to quantify how much time is available for the work and avoid leaving the machine 1 stopped in the middle of the countryside.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be substituted with other, different characteristics, existing in other embodiments.

In practice, the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims (10)

-12- CONCLUSIONS An electrically powered agricultural machine, comprising at least a main implement (2) and a drive assembly (3) adapted to move the implement (2) over a piece of land for cultivation, the assembly (3) having a rechargeable battery (4) comprises of electric storage cells and comprises an electric motor (5), driven by the battery (4), characterized in that the battery (4) comprises a plurality of accumulators (6) connected in series, each of the accumulators (6) comprises a plurality of rechargeable lithium ion cells (7) connected in parallel with each other, wherein the accumulators (8) and the cells (7) are arranged to define a maximum voltage between the terminals (4a) of the battery ( 4), which is comprised between 28 volts and 40 volts, the maximum voltage between the terminals (4a) being chosen to be greater, by at least 20%, than the rated operating voltage of the motor (5). Agricultural machine according to claim 1, characterized in that the accumulators (6) and the cells (7) are arranged to define a maximum voltage between the terminals (4a) of the battery (4) which is equal to 33.6 volts. Agricultural machine according to claim 2, characterized in that the battery (4) comprises eight accumulators (6), a maximum voltage equal to 4.2 volts being defined between the terminals (6a) of each of the accumulators (6). Agricultural machine according to one or more of the preceding claims, characterized in that each of the accumulators (8) comprises twenty-three cells (7). Agricultural machine according to one or more of the preceding claims, characterized in that it comprises an electronic device (8) for regulating and controlling the battery (4), the electronic device (8) being provided with a display module for the reading the instantaneous voltage value at the terminals (6a) of each of the accumulators (8), with a first module for breaking the electronic connection between the battery (4) and the motor (5) and with a second module for disconnection of the electronic connection between the battery (4) and an electrical recharging device, the first module and the second module being respectively activatable as the result of reading a value for the instantaneous voltage, at the terminals (6a) of even a of the accumulators (8), equal to a minimum and maximum predetermined threshold voltage. -13- Agricultural machine according to claim 5, characterized in that the electronic device (8) is provided with a module for balancing the energy supplied to each of the accumulators (6) during the recharge phase, as a function of the instantaneous voltage value detected by the readout module. Agricultural machine according to one or more of the preceding claims, characterized in that it comprises at least one photovoltaic panel (9), which can be moved by the drive assembly (3), integral with the implement (2) along the land in order to The photovoltaic panel (9) is operatively connected to the battery (4) to provide electrical power to the accumulators (6) and activate the recharge phase of the battery (4). Agricultural machine according to one or more of the preceding claims, characterized in that it comprises an electronic device (13) for verifying the charge status of the battery (4), which is connected to a respective screen (14) for displaying of the state, wherein the device (13) comprises first instructions, for periodically testing the instantaneous voltage at the terminals (4a), and includes second instructions, for periodically calculating the average of the instantaneous voltage values over predetermined time intervals for an estimate of the mean of the state of charge, the device (13) comprising third instructions for performing, at the end of each of the intervals, a comparison of the most recent calculated status with the previous calculated status, and for displaying of the most recent status on the display (14), replacing the previous status, only when the most recent status is lower than the previous status status. Agricultural machine according to claim 8, characterized in that the electronic device (13) is provided with a braking module for the drive assembly (3), which can be activated automatically upon reaching a momentary voltage value at the terminals (4a) which is equal to a pre-set set lower limit value, whereby the braking module can be selectively deactivated to allow small-scale movements of the implement (2) and to make it safe. Agricultural machine according to one or more of the preceding claims, characterized in that it comprises an amperage sensor, which is placed between the battery (4) and the motor (5), which is arranged to, moment by moment, the electrical input of to read the motor (5) and to send the related values to an electronic card arranged to compare the values, during the operation of the motor (5), with a predetermined optimal discharge curve of the battery -14 - (4), the card having instructions for temporarily deactivating the drive assembly (3), when reading an electrical input value higher than that of the optimal curve for a period longer than a predetermined time limit .