METHOD FOR STOPPING THE PROPAGATION OF THERMAL RUNAWAY IN A BATTERY TANK OF AN ELECTRIC OR HYBRID MOTOR VEHICLE

Abstract

The invention relates to a method for stopping the propagation of thermal runaway in a battery tray of an electric or hybrid motor vehicle, comprising a step of measuring the temperature and / or voltage of a first electrochemical cell (E1), said dielectric fluid having a first level in said battery tray; a step of measuring the temperature and / or voltage of at least a second electrochemical cell (E2), thermal runaway propagation being detected when said second electrochemical cell has a measured temperature exceeding a second predetermined threshold temperature and / or an inconsistent voltage; and a control step (E3) of closing the first dielectric fluid distributor and the second dielectric fluid distributor, the dielectric fluid being exclusively redirected to said battery tray. Figure 1

Description

Title of the invention: METHOD FOR STOPPING THE PROPAGATION OF THERMAL RUNAWAY IN A BATTERY TANK OF AN ELECTRIC OR HYBRID MOTOR VEHICLE

[0001] The invention relates to cooling systems for battery trays of electric or hybrid motor vehicles.

[0002] Prior art patent application CN109361035 is known, describing a battery tray cooled by spraying an insulating coolant onto the electrochemical cells of the battery tray. The battery tray comprises a shell having an opening at its upper end. Furthermore, the battery tray includes a cover connected to said opening, a connection terminal electrically linking the battery tray to an external circuit, and a pump connected by a pipe to a hollow chamber located in the cover. The lower part of the cover includes a plurality of sprayers connecting the hollow chamber and the interior of the shell. The pump draws the coolant from the hollow chamber to allow the coolant to be sprayed into the shell by means of the sprayers. The coolant flows along the electrochemical cells to the bottom of said shell.During the charge and discharge cycles of electrochemical cells, the heat generated is dissipated by the coolant in the battery tray. However, a drawback remains. If an anomaly occurs during a charge or discharge cycle of an electrochemical cell, or if one of the electrochemical cells malfunctions, the temperature and volume of the affected cell increase significantly, which can prevent it from being effectively cooled by the coolant. Furthermore, the increased temperature and volume of one electrochemical cell can damage the other electrochemical cells in the battery tray. This creates a risk of thermal runaway of the entire battery, or even a fire if the thermal runaway is not addressed quickly.

[0003] The objective of the present invention is to remedy these drawbacks and reduce the risks of thermal runaway propagation from one electrochemical cell to another electrochemical cell.

[0004] To achieve this objective, the invention proposes a method for stopping the propagation of thermal runaway in a battery tray of an electric or hybrid motor vehicle, said vehicle comprising an electric machine, a voltage converter and a cooling circuit comprising a dielectric fluid configured to circulate in said battery tray, in said electric machine and in said voltage converter, said battery tray comprising a plurality of electrochemical cells, the cooling circuit comprising a first dielectric fluid distributor configured to permit or prohibit the passage of the dielectric fluid to said electric machine and a second dielectric fluid distributor configured to permit or prohibit the passage of the dielectric fluid to the voltage converter, each electrochemical cell comprising a voltage sensor, said vehicle comprising a controller configured to communicate with the voltage sensor of each electrochemical cell, the first dielectric fluid distributor and the second dielectric fluid distributor,remarkable in that said process comprises the following steps: - a step of measuring the voltage of a first electrochemical cell by said voltage sensor of the first electrochemical cell; thermal runaway of said first cell is detected when said first electrochemical cell presents a zero voltage, a negative voltage, or a voltage greater than a first predetermined threshold voltage, said dielectric fluid presenting a first level in said battery tray; - a step of measuring the voltage of at least a second electrochemical cell by said voltage sensor of the second electrochemical cell, a propagation of thermal runaway being detected when said second electrochemical cell presents a zero voltage, a negative voltage or a voltage greater than a second predetermined threshold voltage; - a control step for closing the first dielectric fluid distributor and the second dielectric fluid distributor by said controller when the propagation of thermal runaway is detected, the dielectric fluid being exclusively redirected to said battery tray so that said battery tray has a second level of dielectric fluid, said second level of dielectric fluid being higher than the first level of dielectric fluid.

[0005] Thanks to the invention, it is possible to reduce the risks of propagation, or even to stop the propagation, of the thermal runaway of an electrochemical cell.

[0006] Advantageously, during said step of measuring the voltage of at least a second electrochemical cell, the first predetermined threshold voltage being equal to the second predetermined threshold pressure.

[0007] Thus, the thermal runaway of the second electrochemical cell is proven from a given voltage, which increases the probability that there is a real propagation of the thermal runaway from the first electrochemical cell.

[0008] Preferably, at least said first electrochemical cell and said second electrochemical cell each comprise a temperature sensor, during said step of measuring the voltage of a first electrochemical cell, the temperature of said first electrochemical cell being measured, a thermal runaway of said first electrochemical cell is detected when said first electrochemical cell has a temperature greater than a first predetermined threshold temperature, during said step of measuring the voltage of a second electrochemical cell, the temperature of said second electrochemical cell being measured, a propagation of the thermal runaway being detected when said second electrochemical cell has a temperature greater than a second predetermined threshold temperature.

[0009] The presence of temperature sensors on certain electrochemical cells makes it possible to confirm by a measurement of the temperature, and in addition to the measurement of the voltage, whether the electrochemical cell is undergoing thermal runaway.

[0010] Advantageously, during said step of measuring the voltage of at least a second electrochemical cell, the first predetermined threshold temperature is equal to the second predetermined threshold temperature.

[0011] Thus, the thermal runaway of the second electrochemical cell is proven from a given temperature, which increases the probability that there is a real propagation of the thermal runaway from the first electrochemical cell.

[0012] Preferably, said cooling circuit includes a pump located at the outlet of the battery tray, the controller being configured to communicate with said pump, said pump being actuated by the controller to empty the dielectric fluid present in the electric machine and in the voltage converter so that said dielectric fluid is redirected to the battery tray.

[0013] Thus, the redirection of the dielectric fluid towards the battery tray is faster.

[0014] The invention also relates to an electric or hybrid motor vehicle comprising a computer configured to implement said method of stopping the propagation of a thermal runaway in a battery tray of an electric or hybrid motor vehicle previously described.

[0015] Furthermore, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the steps of the method for stopping the propagation of a thermal runaway in a battery tray of an electric or hybrid motor vehicle previously described.

[0016] The invention will be further detailed by describing a non-limiting embodiment, and based on the accompanying figure illustrating the invention, in which [Fig. 1] schematically illustrates, in the form of a flowchart, a stopping method of the propagation of a thermal runaway in a battery tray of an electric or hybrid motor vehicle.

[0017] A method for stopping the propagation of thermal runaway in the battery tray of an electric or hybrid motor vehicle is schematically illustrated in Figure 1 in the form of a flowchart. The battery tray comprises a plurality of electrochemical cells, including a first electrochemical cell and at least a second electrochemical cell, for storing electricity in chemical form. Each electrochemical cell includes a voltage sensor. The vehicle includes an electric machine and a voltage converter. The electric machine, or electric motor, converts the electrical energy stored in the electrochemical cells of the battery tray into mechanical energy to rotate the vehicle's wheels and thus enable its movement.The voltage converter regulates the voltage generated by the electrochemical cells so that electrical energy can be used by the other vehicle components. The vehicle also includes a cooling circuit containing a dielectric fluid. This dielectric fluid is configured to circulate within the battery tray, the electric motor, and the voltage converter. Preferably, the cooling circuit provides cooling to the battery tray by spraying. The battery tray has multiple spray nozzles that spray the dielectric fluid from the cooling circuit onto the electrochemical cells. The dielectric fluid then flows between the electrochemical cells to the bottom of the battery tray.Thus, the electrochemical cells are partially immersed in the dielectric fluid at all times because the battery tray contains a first layer of dielectric fluid. Furthermore, the cooling circuit includes a first dielectric fluid distributor configured to allow or prevent the flow of dielectric fluid to the electric motor and a second dielectric fluid distributor configured to allow or prevent the flow of dielectric fluid to the voltage converter. The vehicle also includes a controller configured to communicate with the voltage sensor of each electrochemical cell, as well as with the first and second dielectric fluid distributors. During a voltage measurement step for the first electrochemical cell, the voltage of the first electrochemical cell is measured by the voltage sensor.Thermal runaway of the first electrochemical cell is detected when the measured voltage of the first electrochemical cell is inconsistent, i.e., when the voltage is zero, when the voltage is negative, or when the voltage exceeds a predetermined threshold voltage. Initially, the battery tray contains the first level of dielectric fluid. During a measurement step... The voltage of at least one second electrochemical cell E2 is measured by the voltage sensor of the second electrochemical cell. Thermal runaway propagation from the first electrochemical cell is detected when the measured voltage of the second electrochemical cell is inconsistent, i.e., when the voltage is zero, negative, or greater than a predetermined second threshold voltage. In one embodiment, the first predetermined threshold voltage is equal to the second predetermined threshold voltage. Thus, thermal runaway of the second electrochemical cell is detected as a result of thermal runaway propagation from the first electrochemical cell. Preferably, the step of measuring the voltage of at least one second electrochemical cell E2 is performed on a plurality of electrochemical cells.In this case, the voltage of a plurality of electrochemical cells is measured, and thermal runaway is detected when a predetermined threshold number of electrochemical cells exhibits a zero voltage, a negative voltage, or a voltage higher than the first or second predetermined threshold voltage. In this way, it is possible to stop the propagation of thermal runaway before it reaches a large number of cells. Alternatively, thermal runaway is detected when all electrochemical cells exhibit a zero voltage, a negative voltage, or a voltage higher than the first or second predetermined threshold voltage. This ensures that thermal runaway has indeed occurred. Preferably, certain electrochemical cells, including the first and second electrochemical cells, each include a temperature sensor. Thus, during the voltage measurement step of the first electrochemical cell E1, the temperature of the first electrochemical cell is measured by the temperature sensor. Thermal runaway of the first electrochemical cell is detected when said first electrochemical cell has a temperature exceeding a predetermined threshold temperature. During the voltage measurement step of the second electrochemical cell E2, the temperature of the second electrochemical cell is measured. Thermal runaway propagation is detected when said second electrochemical cell has a temperature exceeding a predetermined threshold temperature.Preferably, the first predetermined threshold temperature is equal to the second predetermined threshold temperature. Temperature measurement, in addition to voltage measurement, confirms that the electrochemical cells in question exhibit anomalies, and that there is therefore a probable propagation of [electrochemical impedance]. Thermal runaway. Preferably, the first predetermined threshold temperature is between 50°C and 100°C. Alternatively, a temperature rise slope can be calculated to detect a sudden and significant temperature increase, indicating thermal runaway and likely its propagation. During a control step E3, the controller commands the closure of the first and second dielectric fluid distributors when thermal runaway propagation is detected during the voltage measurement step of at least one second electrochemical cell E2. Thus, the electric machine and the voltage converter are respectively deprived of dielectric fluid. All of the dielectric fluid is then redirected to the battery tray, primarily by gravity.Preferably, the cooling circuit includes a pump located at the outlet of the battery tray. The controller is configured to communicate with this pump to manage its operation. The pump is then activated by the controller to drain the dielectric fluid from the electric machine and the voltage converter. Thus, all of the dielectric fluid is efficiently directed into the battery tray. This results in an increase in the dielectric fluid level in the battery tray. Indeed, following the E3 control step, the battery tray has a second level, which is higher than the first.

[0018] The invention also relates to an electric or hybrid motor vehicle comprising a controller configured to implement such a method. Furthermore, the invention relates to a computer program configured to implement the aforementioned method.

Claims

1. Demands Method for stopping the propagation of thermal runaway in a battery tray of an electric or hybrid motor vehicle, said vehicle comprising an electric machine, a voltage converter and a cooling circuit comprising a dielectric fluid configured to circulate in said battery tray, in said electric machine and in said voltage converter, said battery tray comprising a plurality of electrochemical cells, the cooling circuit comprising a first dielectric fluid distributor configured to allow or prohibit the passage of the dielectric fluid to said electric machine and a second dielectric fluid distributor configured to allow or prohibit the passage of the dielectric fluid to the voltage converter, each electrochemical cell comprising a voltage sensor,said vehicle comprising a controller configured to communicate with the voltage sensor of each electrochemical cell, the first dielectric fluid distributor and the second dielectric fluid distributor, characterized in that said method comprises the following steps: - a step of measuring the voltage of a first electrochemical cell (El) by said voltage sensor of the first electrochemical cell, a thermal runaway of said first cell is detected when said first electrochemical cell has a zero voltage, a negative voltage or a voltage greater than a first predetermined threshold voltage, said dielectric fluid having a first level in said battery tray; - a step of measuring the voltage of at least a second electrochemical cell (E2) by said voltage sensor of the second electrochemical cell, a propagation of thermal runaway being detected when said second electrochemical cell has a zero voltage, a negative voltage or a voltage greater than a second predetermined threshold voltage; - a control step (E3) for the closure of the first dielectric fluid distributor and the second dielectric fluid distributor by said controller when the propagation of thermal runaway is detected, the dielectric fluid being exclusively redirected to said battery tray so that said battery tray presents a second level of dielectric fluid, said second level of dielectric fluid being higher than the first level of dielectric fluid.

2. A method according to claim 1 characterized in that, during said step of measuring the voltage of at least one second electrochemical cell, the voltage of a plurality of electrochemical cells are measured, the propagation of thermal runaway being detected when a predetermined threshold number of electrochemical cells exhibits a zero voltage, a negative voltage or a voltage greater than a second predetermined threshold voltage.

3. Method according to claim 1 or 2 characterized in that, during said step of measuring the voltage of at least a second electrochemical cell (E2), the first predetermined threshold voltage being equal to the second predetermined threshold pressure.

4. A method according to any one of claims 1 to 3 characterized in that at least said first electrochemical cell and said second electrochemical cell each comprise a temperature sensor, during said step of measuring the voltage of a first electrochemical cell (E1), the temperature of said first electrochemical cell being measured, a thermal runaway of said first electrochemical cell is detected when said first electrochemical cell has a temperature greater than a first predetermined threshold temperature, during said step of measuring the voltage of a second electrochemical cell (E2), the temperature of said second electrochemical cell being measured, a propagation of the thermal runaway being detected when said second electrochemical cell has a temperature greater than a second predetermined threshold temperature.

5. Method according to claim 4 characterized in that, during said step of measuring the voltage of at least a second electrochemical cell (E2), the first predetermined threshold temperature is equal to the second predetermined threshold temperature.

6. A method according to any one of claims 1 to 5, characterized in that said cooling circuit comprises a pump located at the outlet of the battery tray, the controller being configured to communicate with said pump, said pump being operated by the controller to empty the dielectric fluid present in the electrical machine and in the voltage converter so that said dielectric fluid is redirected to the battery tray.

7. Electric or hybrid motor vehicle comprising a computer configured to implement said method of stopping the propagation of a thermal runaway in a battery tray of an electric or hybrid motor vehicle according to any one of claims 1 to 6.

8. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method for stopping the propagation of a thermal runaway in a battery tray of an electric or hybrid motor vehicle according to any one of claims 1 to 6.

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