METHOD FOR DETECTING AN UNDESIRABLE LIQUID IN AN ELECTRICAL ASSEMBLY.

Abstract

A method for detecting the undesired presence of an electrically conductive liquid in an assembly comprising: * a first electrical subassembly comprising: ** a housing (2) containing an electrical conductor (5, 6, 7, 8), ** an insulation testing means (102) for the electrical conductor (5, 6, 7, 8), * a second subassembly constituting a closed circuit for circulating the electrically conductive liquid, comprising: ** a portion internal to the housing (2), and a portion external to the housing (2) comprising an electric pump for circulating the liquid, and ** a means for diagnosing a leak of the liquid from the circuit, this method comprising: * a step performing a liquid leak diagnosis, and * a step performing an electrical insulation test of the electrical conductor (5, 6, 7, 8), and if the diagnosis establishes the leak and the insulation test establishes an insulation fault, the method performs a step for elaborating a fault of undesired presence of the liquid.Figure 1.

Description

Title of the invention: METHOD FOR DETECTING AN UNDESIRABLE LIQUID IN AN ELECTRICAL ASSEMBLY.

[0001] This invention applies, for example, to a motor vehicle comprising an electric traction battery, but can be applied to other technical fields concerning an electrical assembly.

[0002] Throughout this document, the term "battery" shall be understood to mean an assembly comprising at least one electrochemical cell. When there are several electrochemical cells, they are grouped into one or more modules. This battery may include electrical or electronic means for managing the electrical energy of this at least one module. When there are several modules, they are grouped in a casing or housing and thus form a battery pack, this battery pack being often referred to by the English expression "battery pack," this housing generally containing a mounting interface and connection terminals. This battery pack may, for example, be divided into several independent battery sub-assemblies, each comprising its own housing containing at least one module.These battery sub-assemblies are called modular batteries, and some or all of the modular batteries are removable and interchangeable to avoid downtime for recharging, for example, removable from a housing in an electric vehicle or from a fixed power supply station.

[0003] This battery pack, and this or these modular batteries, will also be referred to by the term battery throughout the text of this document.

[0004] Furthermore, the term electrochemical cell throughout the text of this document shall be understood to mean cells generating current by chemical reaction, for example of the lithium-ion (or Li-ion) type, of the Ni-Mh type, or Ni-Cd or lead type or even fuel cells.

[0005] This traction battery includes, for example, a device for detecting a serious thermal event internal to the battery, and must inform a vehicle supervisor as soon as such a situation is detected. This thermal event is, in particular, a thermal runaway, often referred to by the English acronym "Thermal Runaway Detection".

[0006] This device for detecting a serious thermal event includes, for example, a battery control unit and internal battery sensors that measure, for example, battery temperature, internal crankcase pressure, voltage, or more precisely, a sudden change in voltage. This control unit then sends a signal outside the battery, notably to the vehicle's monitoring system. This control unit determines, among other things, a state of charge of the battery, a state of health of the battery, and is often referred to by the abbreviation "BMS" for the English acronym "battery management system".

[0007] This signal is regulatory. In the event of a battery fire, it informs the driver via a dashboard display accompanied by an audible alert: "High battery temperature: Stop as soon as possible and leave the vehicle." The aim is to inform the driver while giving them enough time to stop the vehicle, ideally in an open area, and allow them to evacuate the occupants safely.

[0008] This thermal event is caused, for example, by an internal short circuit in a cell, leading to a fire that would spread from one cell to another, resulting in an "exponential" runaway effect. This detection is therefore intended to protect against production defects (impurities on the separator) or excessive lithium deposits (Li-plating) that could breach the separator of a single cell.

[0009] The principle of this detection is therefore to recognize the signatures of a fire starting in a cell and to trigger an alert. Several solutions exist; a pressure sensor can be placed in the casing to detect a rapid increase in pressure; an abnormal voltage drop, an increase in cell temperature, or a loss of insulation can also be detected.

[0010] This detection is therefore based on the principle that a first cell catches fire, and that the propagation is slow before the runaway.

[0011] But if several cells catch fire at the same time, the runaway effect will be immediate, and the warning time will be insufficient or even nonexistent.

[0012] One particular situation could potentially lead to a fire involving several cells simultaneously: A leak from a liquid cooling circuit internal to the battery casing, which would come into contact with several cells or conductors at the same time. A leak that could be linked, for example, to a vehicle accident. Although every measure is taken to prevent this from occurring in all reasonably foreseeable accident scenarios, exceptional cases must also be addressed.

[0013] Solutions are known in this area, and require the presence of a sensor specific to this problem, this sensor detecting the presence of this liquid in the crankcase. Unfortunately, this type of sensor is not reliable.

[0014] For example, we know from patent document EP-A1-3476645 of a battery comprising a first and a second humidity sensor, a comparison of the measurements being made between the two sensors so as to make the signal reported more reliable.

[0015] But this solution is complex to implement, and requires specific sensors and a complex development of a control that processes the information from the two sensors.

[0016] The invention aims to achieve reliable early detection of the presence of this liquid to prevent this thermal event due to leakage from the cooling circuit, without using specific sensors and in particular without humidity or liquid presence sensors.

[0017] To this end, the invention relates to a method for detecting the undesirable presence of an electrically conductive liquid in the internal volume of a housing of an assembly comprising: - a first electrical sub-assembly comprising: * the casing housing an electrical component and an electrical conductor which is at a first electrical potential, * a means of testing the insulation of an electrical conductor with respect to a second reference potential, - a second sub-assembly constituting a closed circuit for the circulation of the electrically conductive liquid, comprising: * an internal part within the casing, passing through the casing, and designed to exchange heat with the electrical element, * an external part to the crankcase, comprising an electric fluid circulation pump, and * a means of diagnosing a leak of fluid from the circuit, based on at least one electrical quantity measured from the circulation pump.

[0018] This process includes: - a step performing a leak diagnosis of the fluid from the circulation circuit, based on at least one measured electrical quantity from the circulation pump, and - a step performing an electrical insulation test of the electrical conductor with respect to the second reference potential, and if the diagnosis establishes the leak and the isolation test establishes an insulation fault, the process performs a step of elaborating a fault of undesirable presence of liquid in the internal volume of the crankcase.

[0019] According to one embodiment of the invention, if the diagnosis establishes the leak and the isolation test establishes an isolation fault, in the same time interval, the process performs a step of developing a fault of undesirable presence of the liquid in the internal volume of the casing.

[0020] The term "within the same time interval" in the entire text of this document shall be understood to mean a predetermined time interval during which at least one test Electrical isolation and fluid leak diagnostics are performed. Ideally, this interval is 0 seconds, but due to cycle time, load, or communication delays from one or more control units implementing the process, and depending on the system characteristics, particularly the initial electrical potential, this interval may be set at 1 second, 60 seconds, between 0 and 120 seconds, or any interval technically consistent with the system. For example, the test and diagnostic equipment stores the fluid leak and insulation faults during this interval.

[0021] According to one embodiment of the invention, the method performs a step of memorizing the fault of liquid leakage for a first determined duration, and a step of memorizing the fault of insulation for a second determined duration, and if these two memorized faults have a common period, the method performs the step of elaborating the fault of undesirable presence of liquid in the internal volume of the casing.

[0022] For example, the first and second determined durations are different or equal. For example, the first duration is greater than the second duration, because the isolation test is a continuous test that can detect a stealthy isolation fault.

[0023] The first and second determined durations, as well as the time interval, are not essential. Indeed, the insulation test is a continuous test that can detect a transient insulation fault, whereas the diagnosis of a fluid leak is by nature irreversible: as long as fluid is not added by external intervention (and the leak is sealed), the fluid leak will be permanent.

[0024] Throughout this document, "a closed circuit for circulating the electrically conductive liquid" will be understood to mean a circuit forming one or more loops recirculating the same liquid, the variation in volume of this liquid being due only to its variation in temperature without a change of state.

[0025] The electrical quantity is, for example, a current, a voltage, a power, an internal electrical resistance, a modulated electrical signal, or a variation or profile of this current, voltage, power, or internal electrical resistance.

[0026] According to one embodiment of the invention, the liquid leak diagnosis compares the measured electrical quantity to a predetermined expected threshold.

[0027] This threshold is for example a threshold in absolute value, or in relative value (variation), or even a curve representing a predetermined limit evolution as a function of time.

[0028] According to one embodiment of the invention, the first electrical subassembly comprises: - an electrical network external to the casing, to which the electrical element is connected via the electrical conductor, - a controllable isolation device, suitable for isolating the electrical element from the electrical network by severing the electrical conductor, the process executing, in the event of an undesirable presence of the liquid, a piloting step of the isolation means to isolate the electrical element, then executes the electrical insulation test step again, and if this insulation test again establishes an insulation fault, the process executes a step of generating an alarm warning of an electrical or thermal hazard.

[0029] According to one embodiment of the invention, the part external to the housing of the closed fluid circulation circuit includes several fluidically connected circulation pumps in series or parallel, and the fluid leak diagnostic step performs this diagnostic on each of the circulation pumps, and establishes a fluid leak if at least one of these diagnostics establishes a leak.

[0030] The invention also relates to an assembly comprising a calculator and including: - a first electrical sub-assembly comprising: * a casing housing an electrical component and also housing an electrical conductor which is at a first electrical potential, * a means of testing the insulation of an electrical conductor with respect to a second reference potential, * an electrical network external to the casing, to which the electrical element is connected via the electrical conductor, * a computer-controlled isolation method, designed to isolate the electrical component from the electrical network by severing the electrical conductor, - a second sub-assembly constituting a closed circuit for the circulation of the electrically conductive liquid and with a closed volume, comprising: * an internal part within the casing, passing through the casing, and designed to exchange heat with the electrical element, * an external part to the crankcase, comprising an electric fluid circulation pump, and * a means of diagnosing a leak of fluid from the circuit, based on at least one measured electrical quantity from the circulation pump, this computer includes the means of acquisition, processing by software instructions stored in a memory as well as the control means required to implement the process as previously described.

[0031] According to one embodiment of the invention, the part external to the housing of the closed liquid circulation circuit comprises several circulation pumps fluidly connected in series or parallel, the computer implementing the process as previously described.

[0032] According to one embodiment of the invention, the part external to the housing comprises a liquid reservoir and a means for measuring the level of the liquid in the reservoir, the diagnostic means being suitable for establishing the diagnosis of the leak based on at least the measured electrical quantity of the circulation pump, and the level of the liquid in the reservoir.

[0033] According to one embodiment of the invention, the second subassembly comprises a liquid pressure sensor, the diagnostic means being suitable for establishing the diagnosis of the leak based on at least the measured electrical quantity of the circulation pump and the liquid pressure.

[0034] According to one embodiment of the invention, the first electrical subassembly is a battery comprising the casing, and an electrochemical energy storage cell being the electrical element.

[0035] The invention also relates to a vehicle with at least electric drive comprising a battery and an electric drive machine powered by this battery, this vehicle comprising an assembly as previously described, the electrical network comprising the electric drive machine.

[0036] Indeed, the presence of unwanted liquid in the battery does not necessarily lead to a fire, but the probability is high if this conductive liquid comes into contact with electrically live parts (the electrical element and / or the conductor). This contact generates an insulation loss, which is detected by an insulation test, a regulatory requirement and therefore present. Conversely, an insulation loss alone is not necessarily a sign of a future fire, as the cause may be outside the battery, for example, in the electrical network external to the casing. Furthermore, an electrical insulation loss can be caused by small quantities of liquid, which are not sufficient to start a fire.

[0037] Thus, the invention uses only pre-existing means: the insulation test means, as well as the leak diagnosis means based on at least one measured electrical quantity of the pump, this means generally being integrated into the pump to stop it if it is no longer in the presence of the liquid (dry-run protection). With these pre-existing means, and therefore in particular without humidity sensors in the battery, the invention makes it possible to generate a reliable signal to warn of a risk of thermal runaway and / or an excessively high level of undesirable liquid in the battery.

[0038] Other features and advantages will become apparent from the following description of a particular, non-limiting embodiment of the invention, made with reference to the figures in which:

[0039] [Fig-1]: represents a schematic diagram of a first subset according to the invention, to which the method according to the invention applies.

[0040] [Fig.2]: represents a schematic diagram of a second subset according to the invention, to which the method according to the invention applies.

[0041] Figure 1 represents a first electrical sub-assembly 1 to which the invention applies. This first electrical sub-assembly 1 is, for example, a battery 1 comprising a casing 2 defining an internal volume 3, the casing 2 comprising a base 4 for retaining an unwanted conductive liquid, this base being optional.

[0042] The term “internal to the casing” in the entire text of this document shall be understood to mean any element or part of an element located entirely within this internal volume 3.

[0043] This retention base 4 is shown here with a recess forming a reservoir for the unwanted conductive liquid, but it can just as easily be of a flat or any other shape.

[0044] It should be noted that the term "undesirable" or "undesirable" means, throughout this document, an abnormality, such as, for example, the fact that the quantity of liquid present in the reservoir is excessive and presents an electrical or thermal risk. Generally speaking, this undesirable liquid originates from a leak in a section of the liquid circulation circuit, this section of the circuit 200, 201, 202 being internal to the casing 2. This circuit will be described in more detail later.

[0045] The internal volume 3 further comprises an electrical conductor 5, 6, 7, 8 electrically insulated from the housing 2. This electrical conductor 5, 6, 7, 8 comprises a conductive material, for example copper or aluminum, in forms such as wires, strips, bars, or rails. The electrical conductor 5, 6, 7, 8 may be in one piece or assembled from several constituent elements, each constituent element being in the form of a wire, strip, bar, or rail.

[0046] The diagram in [Fig. 1] shows an optional zone 9 of the electrical conductor 5, 6, 7, 8, located at a predetermined altitude h relative to the retention base 4. Zone 9 is, for example, the only zone of the electrical conductor 5, 6, 7, 8 that has electrical contact with the unwanted conductive liquid when the unwanted conductive liquid is present at the predetermined altitude h. This predetermined altitude h corresponds to a level of the unwanted conductive liquid beyond which there is a risk of an internal short circuit in the battery 1. For example, this short circuit could result from the electrical contact of two constituent elements of the electrical conductor 5, 6, 7, 8 at two different potentials, these two constituent elements not being not protected against unwanted electrical contact by the conductive liquid when at a level above the predetermined altitude h.

[0047] The diagram in [Fig.1] also shows two connection terminals 19, 20 to an external electrical network 101 to the housing 2, for example a current-consuming network 101 external to the battery 1, for example an on-board network, or a power network of a motor vehicle comprising power electronics and a reversible electric traction motor. For example, one terminal 19 is connected to a positive potential by a first constituent element 8 of the electrical conductor 5, 6, 7, 8, while the other terminal 20 is connected to a negative potential by a second constituent element 5 of the electrical conductor 5, 6, 7, 8. Thus, the two terminals 19, 20, as well as the first constituent element 8 and the second constituent element 5 of the electrical conductor 5, 6, 7, 8 are at different potentials, which can create a short circuit if they are not protected against electrical contact by the conductive liquid.

[0048] Still on the diagram of [Fig.1], is schematically shown, in the internal volume 3: - an isolation means 100 comprising a set of electrical breaking power relays called disconnectors, - an electrical element 17, 18 comprising two modules of electrochemical battery cells mounted in series 17, 18, - an electrical isolation test means 102, - a fuse 21 between the two modules of electrochemical cells 17, 18.

[0049] The first constituent element 8 and the second constituent element 5 connect the electrical switching power relay assembly 100 to the terminals 19, 20. The electrical conductor 6, 7 on the other hand connects the electrical switching power relay assembly 100 to the two electrochemical cell modules 17, 18 so that the isolation means 100 cuts the electrical conductor 5, 6, 7, 8 when its relays are open, and thus makes it possible to isolate the two terminals 19, 20 and the network connected to them 101 from the electrochemical cell modules 17, 18.

[0050] It should be noted throughout this document that the first component 8 and the second component 5 form a downstream zone of the electrical conductor 5, 6, 7, 8, while a third component 7 of the electrical conductor 5, 6, 7, 8 and a fourth component 6 of the electrical conductor 5, 6, 7, 8, connecting the electrochemical cell modules 17, 18 to the electrical switching power relay assembly 100, form an upstream zone of the electrical conductor 5, 6, 7, 8. The first component 8 and the third component 7 are thus, in this example, connected to the positive potential, while the second component 5 and the fourth component 6 are connected to the negative potential, the electrical switching power relay assembly 100, interposed between the upstream and downstream zones, interrupting the conductor Electrical circuits 5, 6, 7, and 8 are open if the relays are open. Isolation means 100 is controlled by a computer which controls the opening of all the electrical cut-off power relays 100 in the event of a fault in battery 1. This computer can be integrated into battery 1.

[0051] The two electrochemical cell modules 17, 18 are connected in series, but can just as easily be connected in parallel. Similarly, the fuse 21 between the two electrochemical cell modules 17, 18 can be mounted in another location on the battery 1.

[0052] In this example, the electrical insulation test means 102 is an electronic unit, for example integrated into the computer, which tests the electrical insulation of a component of the electrical conductor 5, 6, 7, 8 at a first potential, relative to a reference component at a second reference potential. The electrical insulation test means 102 is a known means, already in use and present on the majority of batteries, and is compliant with regulations. However, the electrical insulation test means 102 can also be external to the battery 1.

[0053] The first potential here is the potential of the fourth component 6 of the electrical interconnection means 5, 6, 7, 8, i.e., the negative potential. Thus, the electrical insulation test means 102 is electrically connected to the fourth component 6 by a first electrical connection 24. This fourth component 6 includes an optional first conductive branch 11, having a free end, this free end comprising the zone 9.

[0054] The reference element is the conductive liquid. Thus, the second reference potential is that of the conductive liquid. For example, the electrical insulation test means 102 is electrically connected to the housing 2 by a second electrical connection 22, the housing 2 exhibiting electrical conductivity to the conductive liquid, thus bringing it to the potential of the conductive liquid. For example, the housing 2 is made of a metallic material. Alternatively, the second electrical connection 22 is in direct electrical contact with the unwanted conductive liquid, without passing through the housing 2, with a portion immersed at an altitude lower than the predetermined altitude h. Alternatively still, the housing 2 comprises an outer skin and an inner skin, the inner skin being made of an electrically conductive material. These variations are not limiting, and other configurations of the housing 2 or of the second electrical connection 22 are conceivable.

[0055] The electrical insulation test means 102 can then detect an insulation fault of the zone 9 with respect to the undesired conductive liquid, and more generally of the electrical conductor with respect to the undesired conductive liquid.

[0056] It should be noted that the electrical insulation test means 102 also tests the electrical insulation of the third constituent element 7 at a third potential, relative to the reference element. This third potential is the positive potential. Thus, the Electrical insulation test means 102 is electrically connected to the third constituent element 7 by a third electrical link 23. It is evident that the electrical insulation test means 102 is not limited to this configuration, and that it can thus test the insulation of multiple constituent elements, for example the cells of modules 17, 18.

[0057] Zone 9 is connected to the negative potential. In a variant, not shown, this zone 9 is connected to the positive potential, in the upstream or downstream zone.

[0058] The electrical conductor 5, 6, 7, 8 is in electrical contact with a first conductive branch 11 comprising the zone 9.

[0059] Alternatively, zone 9 is any zone of the electrical conductor 5, 6, 7, 8.

[0060] The diagram in [Fig.2] represents a second sub-assembly to which the invention applies, this second sub-assembly constituting the closed circuit for circulating the electrically conductive liquid, comprising: - the internal part 200, 201, 202 in the casing 2, passing through the casing 2, and suitable for exchanging heat with the electrical element 17, 18, - an external part to the casing 2, comprising an electric pump PI, P2 for fluid circulation, and - a diagnostic means Cl, C2 of a leak of the fluid from the circuit, as a function of at least one electrical quantity measured from the circulation pump PI, P2.

[0061] The internal part 200, 201, 202 of the housing 2 includes, for example, a plate-shaped cooler 200, this plate comprising a chamber through which the electrically conductive liquid circulates, as well as inlet and outlet pipes 201, 202 of the liquid comprising hydraulic fittings for being connected to the chamber on the one hand, and for being connected to the external part on the other hand and in particular to one or more of the first pipes 203 of the liquid, of the external part.

[0062] These fittings are for example a potential source of liquid leakage, which then flows undesirably into the internal volume 3 of the casing 2.

[0063] This plate 200 is in particular in thermal contact on one of its largest faces, by thermal conduction, with the module(s) 17, 18, so as to be able to cool or heat the electrical element 17, 18, i.e. the modules in this example.

[0064] The external part of the housing 2 forms a first fluid circulation loop with the internal part. This external part, which closes this first loop, includes in particular: - a first PI circulation pump, and - the first pipe 203 hydraulically connected to the internal part and conveying the liquid propelled by the first PL pump

[0065] This external part, which closes this first loop, includes for example a heater 204 and / or a heat exchanger 205 hydraulically connected in series with the first pump PI, and the plate 200. This exchanger 205 is for example a radiator of a motor vehicle, and the heater 204 is for example a burner consuming a fuel.

[0066] As illustrated in [Fig. 2], this external portion further forms a second fluid circulation loop. This second loop includes a second fluid conduit 206 and a second pump P2 for circulating the fluid through the second conduit. This second loop is partially shown, with the second conduit 206 extended by dashed lines symbolizing the unshown portion of this second loop, for example, an electric motor for the vehicle cooled by this second loop.

[0067] Thus, the external part of the housing comprises several circulation pumps PI, P2 fluidically connected in series or in parallel, here connected in series. Indeed, this illustrated external part includes a hydraulic coupling valve V12 between the first loop and the second loop. This valve V12 is, for example, controlled by the computer to occupy several positions allowing: - either the first loop to be isolated from the second loop, - or the fluid from the first and second loops to be combined, by connecting them hydraulically in series as illustrated in [Fig. 2]. The valve V12 is illustrated in its position allowing the two pumps PI, P2 to be coupled in series. But of course, other configurations are possible.

[0068] The external part of the housing 2 may further include a reservoir (not shown) for the liquid and a means for measuring the liquid level (not shown) in the reservoir. This reservoir is, for example, an expansion vessel, well known to those skilled in the art, for absorbing variations in the volume of the liquid due to its temperature variation.

[0069] The second subassembly may further include a liquid pressure sensor (not shown), in the internal or external part of the housing 2. It is implied that this second subassembly includes a liquid temperature sensor (not shown).

[0070] This second subassembly comprises the diagnostic means Cl, C2 for detecting a leak of fluid from the circuit, based on at least one electrical quantity measured by the circulation pump PI, P2. This second subassembly may comprise a single diagnostic means Cl, in which case it will preferably be associated with the first pump PI of the first loop, but not necessarily; it may, for example, be associated with the second pump P2 if it is present, or with any one of the n pumps of the n loops of the second subassembly, these n loops all being hydraulically connected or connectable to each other by the valve(s) of hydraulic coupling V12. Alternatively, this diagnostic means Cl can be unique, but acquire each measured electrical quantity from each of the circulation pumps PI, P2.

[0071] This diagnostic means Cl, C2, is known to those skilled in the art and presents no technical difficulties. It can be integrated into each of the pumps PI, P2 in the form of a computer and constitute dry-run protection for the pump PI, P2 in its simplest form, but one that is nevertheless sufficient for the invention: detected dry running corresponds to a leak diagnosis of the liquid in one of the loops. For example, this diagnostic means Cl is suitable for implementing the liquid leak diagnosis by comparing the measured electrical quantity to a predetermined expected threshold.This comparison is, for example, the comparison of a current intensity to a low intensity threshold below which this current intensity should never be possible in the presence of a liquid completely filling the chamber containing the liquid propulsion element of the pump PI, P2, for example a piston or a turbine with blades for respectively a positive displacement pump and a kinetic pump.

[0072] It is entirely possible to envisage more precise diagnostics, and especially ones that detect leaks more quickly, for example if this diagnostic means Cl is capable of acquiring the pressure of the liquid in the loop associated with the pump PI. To this end, a method for detecting a leak in a closed-volume liquid system comprising a liquid cooling system in an aircraft is known, for example, from patent document EP-A1-2538193. The method comprises circulating a liquid through a closed loop with a pump driven by an electric motor, detecting a pressure in the closed loop, detecting the current consumption by the electric motor; and determining the presence of a liquid leak from the closed loop based on the detected pressure and the detected current consumption.Furthermore, the closed-volume liquid system includes a reservoir with a piston that expands the reservoir volume between a maximum and a minimum, preferably also including a liquid level detection step in the closed loop, and more preferably in which the level is determined by the position of the piston in the reservoir. This type of diagnostic is of course feasible within the scope of the present invention, provided that the liquid pressure sensor and the reservoir level sensor are present.

[0073] Thus, the invention relates to a method for detecting the undesirable presence of an electrically conductive liquid in the internal volume 3 of a casing 2 of an assembly comprising: - the first electrical sub-assembly comprising: * the casing 2 housing the electrical element 17, 18 and the electrical conductor 5, 6, 7, 8 which is at a first electrical potential, * the insulation test method 102 of the electrical conductor 5, 6, 7, 8 with respect to the second reference potential, - the second sub-assembly constituting the closed circuit for circulating the electrically conductive liquid, comprising: * the internal part 200, 201, 202 in the casing 2, passing through the casing 2, and suitable for exchanging heat with the electrical element 17, 18, * the part external to the casing 2, including the electric pump PI, P2 for fluid circulation, and * the diagnostic means Cl, C2 of the leak of the fluid from the circuit, as a function of at least the measured electrical quantity of the circulation pump PI, P2.

[0074] This process includes: - a step performing leak diagnosis of fluid from the circulation circuit, based on at least the measured electrical quantity of the circulation pump PI, P2 and - a step performing the electrical insulation test of the electrical conductor 5, 6, 7, 8 with respect to the second reference potential.

[0075] This method is such that if the diagnosis establishes the leak and the insulation test establishes an insulation fault, within the same time interval, the method executes a step of developing a fault of undesirable presence of liquid in the internal volume 3 of the casing 2. This step of developing a fault of undesirable presence of liquid can directly trigger a step of developing an alarm warning of an electrical or thermal risk, but can also be an intermediate step in which the fault of undesirable presence of liquid must be confirmed.

[0076] Thus, for example, the first electrical subassembly comprises: - the external electrical network 101 to the casing 2, network 101 to which the electrical element 17, 18 is connected via the electrical conductor 5, 6, 7, 8, - the controllable isolation means 100, suitable for isolating the electrical element 17, 18 from the external electrical network 101 by cutting the electrical conductor 5, 6, 7, 8, and the process executes, in the event of a fault in the presence of the undesirable liquid, a piloting step of the isolation means 100 to isolate the electrical element 17, 18, then executes again the electrical insulation test step, and if this insulation test again establishes an insulation fault, the process executes the step of generating an alarm warning of the electrical or thermal risk.

[0077] This control of the isolation means 100 thus confirms that the insulation fault does indeed occur in the internal volume 3 of the battery 1, and therefore that the probability of the undesirable presence of liquid in this internal volume 3 is very strong. However, as we saw earlier, the presence of this undesirable conductive liquid can cause a short circuit and generate an overcurrent in several modules 17, 18 and / or several electrochemical cells simultaneously, thus causing a very rapid thermal runaway. This process, and this assembly, makes it possible to detect this risk of thermal runaway as it occurs, or even before it occurs, giving the vehicle driver time to safely pull over and evacuate the passengers.

[0078] The external part includes, for example, several circulation pumps PI, P2 fluidically connected in series or in parallel, and the fluid leak diagnostic step performs this diagnostic on each of the circulation pumps PI, P2, and establishes a fluid leak if at least one of these diagnostics establishes a leak.

[0079] Thus, the object of the invention further relates to the assembly comprising the calculator and including: - the first electrical sub-assembly, the isolation means 100 being controllable by the computer, - the second sub-assembly, this computer comprising the means of acquisition, processing by software instructions stored in a memory as well as the control means required to implement the process as previously described.

[0080] Thus the invention proposes in particular to implement this method of detecting the undesirable presence of an electrically conductive liquid, within the assembly.

[0081] This implementation is carried out by means of the computer. This computer can be integrated into the first sub-assembly and, for example, include the insulation test means. This computer is, for example, if this sub-assembly is battery 1, the "BMS" for battery 1 (Battery Management System) and determines, among other things, the state of charge of battery 1, the health status of battery 1, and can be in network communication with a supervisor that handles the fault of unwanted presence of liquid and / or the alarm warning of electrical or thermal risk. This computer can also group the diagnostic means Cl, C2 for the liquid leak. However, this is not mandatory. Indeed, this computer could be external to the diagnostic means Cl, C2 and the insulation test means, while still being coupled to them.In the latter case, it can be arranged in the form of a dedicated computer including a possible dedicated program, for example. Consequently, a computer, according to the invention, can be implemented in the form of software modules (or computer modules (or "software")), or electronic circuits (or "hardware"), or a combination of electronic circuits and software modules.

[0082] Conversely, the supervisor can group the computer, the diagnostic means Cl, C2, and the isolation test means, and can also be implemented in the form of software modules (or computer modules (or "software")), or electronic circuits (or "hardware"), or a combination of electronic circuits and software modules.

[0083] Furthermore, if the part external to the housing includes the liquid reservoir and a means for measuring the level of the liquid in the reservoir, the diagnostic means is suitable for establishing the diagnosis of the leak based on at least the measured electrical quantity of the circulation pump PI, P2, and the level of the liquid in the reservoir.

[0084] Similarly, if the second subassembly includes the liquid pressure sensor, the diagnostic means is suitable for establishing the leak diagnosis based on at least the measured electrical quantity of the circulation pump PI, P2 and the liquid pressure.

[0085] The first electrical subassembly is for example the battery 1 comprising the casing 2, and the electrochemical energy storage cell is the electrical element 17, 18.

[0086] The invention applies for example to a vehicle with at least electric drive comprising the battery 1 and an electric drive machine powered by this battery 1, and comprising an assembly as previously described, the external electrical network 101 comprising the electric drive machine.

Claims

Claims

1. Method for detecting the undesirable presence of an electrically conductive liquid in the internal volume (3) of a casing (2) of an assembly comprising: * a first electrical subassembly comprising: ** the casing (2) housing an electrical element (17, 18) and an electrical conductor (5, 6, 7, 8) which is at a first electrical potential, ** an insulation testing means (102) of the electrical conductor (5, 6, 7, 8) relative to a second reference potential, ** an external electrical network (101) to the casing (2), network (101) to which the electrical element (17, 18) is connected via the electrical conductor (5, 6, 7, 8), ** a controllable isolation means (100), capable of isolating the electrical element (17, 18) from the external electrical network (101) by cutting the electrical conductor (5, 6, 7, 8), * a second subassembly constituting a closed circuit for circulation of the electrically conductive liquid, comprising: ** an internal part (200, 201, 202) to the casing (2),passing through the casing (2), and suitable for exchanging calories with the electrical element (17, 18), ** a part external to the casing (2), comprising an electric pump (PI, P2) for circulating the liquid, and ** a means (Cl, C2) for diagnosing a leak of the liquid coming from the circuit, as a function of at least one measured electrical quantity of the circulation pump (PI, P2), this method comprising: * a step carrying out a diagnosis of leakage of the liquid coming from the circulation circuit, as a function of at least the measured electrical quantity of the circulation pump (PI, P2) and * a step carrying out an electrical insulation test of the electrical conductor (5, 6, 7, 8) with respect to the second reference potential, characterized in that if the diagnosis establishes the leak and the insulation test establishes an insulation fault, the method executes: - a step of developing a fault of undesirable presence of the liquid in the internal volume (3) of the casing (2) then, - a step of controlling the insulation means (100) to isolate the electrical element (17, 18) then - executes the electrical insulation test step again, and if this insulation test establishes an insulation fault again, the method executes a step of generating an alarm warning of an electrical or thermal risk.

2. Method according to claim 1, the liquid leak diagnosis comparing the measured electrical quantity to a predetermined expected threshold.

3. Method according to one of the preceding claims, the external part comprising several circulation pumps (PI, P2) fluidically connected in series or in parallel, and the liquid leak diagnosis step performs this diagnosis on each of the circulation pumps (PI, P2), and establishes a liquid leak if at least one of these diagnoses establishes a leak.

4. Assembly comprising a computer and comprising: * a first electrical subassembly comprising: ** a casing (2) housing an electrical element (17, 18) and further housing an electrical conductor (5, 6, 7, 8) which is at a first electrical potential, ** an insulation testing means (102) of the electrical conductor (5, 6, 7, 8) with respect to a second reference potential, ** an external electrical network (101) to the casing (2), network (101) to which the electrical element (17, 18) is connected via the electrical conductor (5, 6, 7, 8), ** an isolation means (100) controllable by the computer, capable of isolating the electrical element (17, 18) from the external electrical network (101) by cutting the electrical conductor (5, 6, 7, 8), * a second subassembly constituting a closed circuit for circulation of the electrically conductive liquid and with closed volume, comprising: ** an internal part (200, 201, 202) to the casing (2), passing through the casing (2),and suitable for exchanging calories with the electrical element (17, 18), ** a part external to the casing (2), comprising an electric liquid circulation pump (PI, P2), and, ** a means for diagnosing a leak of liquid coming from the circuit (Cl, C2), as a function of at least one measured electrical quantity of the circulation pump (PI, P2), characterized in that this calculator comprises the means of acquisition, of processing by software instructions stored in a memory as well as the control means required for implementing the method according to any one of claims 1 to 2.

5. Assembly according to claim 4, the part external to the casing comprising several circulation pumps (PI, P2) fluidically connected in series or in parallel, the computer implementing the method according to claim 4.

6. Assembly according to claim 4 or 5, the part external to the casing comprising a liquid reservoir and a means for measuring the level of the liquid in the reservoir, the diagnostic means being capable of establishing the diagnosis of the leak as a function of at least the measured electrical quantity of the circulation pump (PI, P2), and the level of the liquid in the reservoir.

7. Assembly according to one of claims 4 to 6, the second subassembly comprising a liquid pressure sensor, the diagnostic means being capable of establishing the diagnosis of the leak as a function of at least the measured electrical quantity of the circulation pump (PI, P2) and the liquid pressure.

8. Assembly according to one of claims 4 to 7, the first electrical subassembly being a battery (1) comprising the casing (2), and an electrochemical energy storage cell being the electrical element (17, 18).

9. Vehicle with at least electric motor comprising a battery (1) and an electric motor powered by this battery (1), characterized in that it comprises an assembly according to claim 8, the external electrical network (101) comprising the electric motor.

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