METHOD FOR PROGRESSIVELY HEATING A LITHIUM-ION BATTERY MOUNTED ON A HYBRID MOTOR VEHICLE

Abstract

The invention relates to a method for the gradual heating of a lithium-ion battery mounted on a hybrid motor vehicle, comprising a step of determining a setpoint torque applied to the primary shaft; a step of regulating the second torque; a step of measuring the battery power (PB); a step of measuring the cumulative battery power (IPB) over time (t) as a function of the battery power (PB); a step of forcing the discharge phase (PhD) when the cumulative battery power (IPB) is greater than a predetermined second threshold value (V2), said second threshold value (V2) being less than said first threshold value (V1), said second torque being positive; a step of gradually heating the battery without risk of lithium plating by a succession of discharge phases (PhD) and charge phases (PhC). Figure 1

Description

Title of the invention: METHOD FOR PROGRESSIVELY HEATING A LITHIUM-ION BATTERY MOUNTED ON A HYBRID MOTOR VEHICLE

[0001] The invention relates to the field of hybrid motor vehicles, and more particularly to the batteries of these vehicles.

[0002] Prior art patent application CN112428881 is known, describing a device and method for heating a battery in a hybrid motor vehicle. The vehicle comprises an electric motor, an internal combustion engine, and a battery. The vehicle is configured to control the charging and discharging of said battery. The vehicle generates alternating charge and discharge cycles of the battery to produce heat by Joule heating. This heat increases the battery temperature until it reaches a predefined target value. The invention aims to optimize battery heating by adjusting the alternating cycles according to the temperature in order to maintain said battery in an optimal operating state. When the battery temperature is below the target value, the vehicle alternately enters charging and discharging cycles.When the battery's state of charge exceeds a first power threshold, the vehicle enters the discharge phase. When the vehicle's state of charge falls below a second power threshold, it exits the discharge phase. However, a drawback remains. The described device and associated method do not account for the risk of lithium plating. Thus, if the target value is not reached, the vehicle continues to generate charge and discharge cycles, which can lead to lithium plating, reducing battery performance and shortening its lifespan.

[0003] The objective of the present invention is to remedy these drawbacks and to allow gradual heating of the battery without causing the detection of a risk of lithium plating.

[0004] To achieve this objective, the invention proposes a method for progressively heating a lithium-ion battery mounted on a motor vehicle, said vehicle comprising an accelerator pedal, wheels, an electric motor and a thermal engine, the electric motor and the thermal engine being connected to the wheels by a primary shaft configured to transmit the mechanical energy generated by the thermal engine and the electric motor to said wheels to move said vehicle, said electric motor being connected to said battery via a DC / AC converter configured to control a battery discharge phase during said DC / AC converter transforms a direct current from said battery into an alternating current to power said electric motor and of an AC / DC converter configured to control a battery charging phase during which said AC / DC converter transforms the alternating current from the electric motor into direct current to power said battery, the discharge phase and the charging phase being carried out alternately so as to generate heat dissipation by Joule effect to heat said battery, a first torque being applied to the internal combustion engine and a second torque being applied to the electric motor, said battery comprising an anode and a cathode, said battery comprising lithium capable of moving from the anode to the cathode during the discharge phase and from the cathode to the anode during the charging phase,a first threshold value for which the charging phase is interrupted to avoid the risk of lithium plating, lithium plating being the deposition of lithium in solid form on the surface of the anode during the charging phase, notable in that said process comprises the following steps: , - a step of determining a setpoint torque applied to the primary shaft as a function of the state of the accelerator pedal depressed by the driver, the setpoint torque being equal to the sum of the first torque and the second torque, said battery being in the discharge phase when said second torque is positive, said battery being in the charge phase when said second torque is negative; - a step of measuring the power of the battery; - a step of measuring the cumulative battery power over time as a function of the battery power measured during the battery power measurement step when the battery power is greater than a predetermined continuous charging power, said continuous charging power corresponding to the power admissible by said battery without time limitation and without generating the risk of lithium plating; - a forced execution step of the discharge phase when the cumulative battery power is greater than a second predetermined threshold value, said second threshold value being less than said first threshold value, said second couple being positive; - a step of progressive heating of the battery without risk of lithium plating by a succession of discharge phases and charge phases the cumulative battery power remaining below said second threshold value.

[0005] Thanks to the invention, the battery operates optimally by avoiding the detection of a risk of lithium plating. The battery temperature increases gradually.

[0006] Advantageously, the battery includes a temperature measurement sensor, said process comprising a stopping step when the temperature measured by said temperature measuring sensor reaches a predetermined temperature threshold value.

[0007] Preferably, during the shutdown stage, the battery power is greater than the predetermined continuous charging power.

[0008] The invention also relates to a heating device configured to implement said progressive heating method of a lithium-ion battery mounted on a previously described hybrid motor vehicle, characterized in that said device comprises a means for determining the setpoint torque, a means for regulating the second torque, a means for measuring the battery power, a means for measuring the cumulative battery power and a means for forcing the discharge phase when the cumulative battery power is greater than the second predetermined threshold value.

[0009] In addition, the invention relates to a hybrid motor vehicle comprising a heating device according to the invention.

[0010] The invention will be further detailed by the description of a non-limiting embodiment, and on the basis of the attached figure illustrating the invention, in which [Fig.1] schematically illustrates a graphical representation of the power of a lithium-ion battery mounted on a hybrid motor vehicle as a function of time, correlated with a graphical representation of the cumulative battery power as a function of time.

[0011] Figure 1 schematically illustrates a graph of the power of a lithium-ion PB battery mounted on a hybrid vehicle as a function of time t, correlated with a graph of the cumulative power of the IPB battery as a function of time t. The graphs illustrate a first period A during which the battery is at risk of lithium plating and a second period B during which the battery implements the progressive heating process of a lithium-ion battery mounted on a hybrid vehicle according to the present invention. The lithium-ion battery is a type of rechargeable battery in which lithium moves from the anode to the cathode during discharge and from the cathode to the anode during charging.Lithium-ion batteries are capable of providing stable power over a long period of time (t), which is advantageous for use in electric or hybrid vehicles. Lithium plating is a phenomenon that can occur in lithium-ion batteries when charging or discharging conditions are not optimal. Lithium plating is the process by which lithium is deposited on the anode surface in solid form during charging. Lithium plating occurs when the battery is overcharged, discharged at a particularly low temperature, or when the battery is... is subjected to excessively high charging currents. Lithium plating is likely to cause short circuits within the battery, thereby reducing its performance and consequently that of the vehicle. Furthermore, lithium plating is likely to cause premature battery deterioration, thus reducing its lifespan. In addition, the vehicle comprises wheels, an electric motor, and an internal combustion engine. The electric motor and the internal combustion engine are connected to the wheels by a primary shaft configured to transmit the mechanical energy generated by the internal combustion engine and the electric motor to the vehicle's wheels to enable its movement.The vehicle includes a DC / AC converter (acronym for Alternating Current / Direct Current) and an AC / DC converter (acronym for Direct Current / Alternating Current), each connecting the electric motor to the battery. The DC / AC converter is configured to control a high-power discharge (HPD) phase of the battery. The AC / DC converter is configured to control a high-power charging (HPC) phase of the battery. The HPD phase is characterized by a phase during which the DC / AC converter transforms direct current (DC) into alternating current (AC). The DC current is supplied by the battery. The DC current is then converted back to alternating current to power the electric motor.The PhC charging phase of the battery is a phase during which the AC / DC converter transforms the alternating current of the electric motor into direct current to power the battery. The PhD discharge phase and the PhC charging phase are performed alternately in a cyclic manner. This cycle of PhD discharge and PhC charging phases generates heat dissipation through the Joule effect. The Joule effect is a thermal phenomenon that occurs when an electric current passes through an electrically conductive material. When an electric current passes through an electrically conductive material, the electrical energy is converted into heat. During the PhC charging phase, the battery is susceptible to lithium plating if the battery's power output is too high or if the duration of the PhC charging phase is too long.To reduce the risk of battery deterioration, a first threshold value VI is predefined. In other words, the first threshold value VI is the value at which the PhC charging phase is interrupted to limit the risk of lithium plating. Over the period A illustrated in [Fig. 1], the graph shows the battery power PB, alternately in the PhD discharge phase and the PhC charging phase, as a function of time t when the battery is at risk of lithium plating. The first curve PB A represents the expected battery power over time t. The expected battery power is the power required for optimal vehicle operation. A second curve PBR re. This represents the actual battery power. The actual battery power takes into account the impact of lithium plating. During the PhC charging phase, and with lithium plating in place, the actual battery power is lower than the expected battery power. Therefore, vehicle performance is not optimal. The graph illustrating the cumulative battery power IPB as a function of time t shows the first threshold value V1. During period A, the cumulative battery power IPB quickly reaches the first threshold value VI, leading to the premature termination of the PhC charging phase and thus reduced heat dissipation through Joule heating, consequently lowering battery performance. In this way, the cumulative battery power IPB gradually decreases after two cycles of PhC charging and PhD discharging phases.The main consequence of the embodiment illustrated in Period A is a steady-state temperature of the battery. Indeed, the difference between the battery's power output (PB) during the charging phase (PhC) and its power output during the discharging phase (PB) does not generate sufficient heat dissipation through Joule heating to increase the battery's temperature. Period A illustrates the consequences of prior art battery heating methods. Period B represents the results observed when the progressive battery heating method, which is the subject of this patent application, is implemented. The method includes a step of determining a set torque applied to the primary shaft based on the driver's input. Torque is a measure of the rotational force that the electric motor and / or internal combustion engine can produce.The driver's intent is interpreted based on the degree to which the accelerator pedal is depressed. For example, if the pedal is depressed to 90%, this is interpreted as a significant power demand. A first torque is applied to the internal combustion engine, and a second torque is applied to the electric motor. The second torque is alternately positive or negative. The battery is in the discharge phase (PhD) when the second torque is positive. Conversely, the battery is in the charge phase (PhC) when the second torque is negative. The second torque is always the opposite of the first torque. Thus, the sum of the first and second torques equals the setpoint torque. The process includes a step to measure the battery power (PB), as shown in the graph illustrating the battery power (PB) as a function of time (t).In practice, the PB battery power varies between -20,000 W and 15,000 W. During the IPB cumulative battery power measurement step, the IPB cumulative battery power is calculated from the PB battery power measured during the PB battery power measurement step. The IPB cumulative battery power measurement step is only implemented when the power of the... The PB battery capacity exceeds the continuous charging power (PRC). The continuous charging power (PRC) is the maximum power the battery can withstand without time limitations and without incurring the risk of lithium plating. During a forced discharge stage, the PhD discharge phase is triggered when the cumulative battery capacity (IPB) exceeds a predetermined second threshold value (V2). This second threshold value (V2) is lower than the first threshold value (VL). The difference between the first threshold value (VI) and the second threshold value (V2) is a safety margin that drastically reduces, or even eliminates, the risk of lithium plating. During a gradual heating stage, the battery temperature increases progressively without inducing the risk of lithium plating because the cumulative battery capacity (IPB) remains below the second threshold value (V2).The battery is thus gradually heated through a succession of PhD discharge phases and PhC charge phases. Advantageously, the battery includes a temperature sensor, and the process includes a shutdown step when the temperature measured by the battery's temperature sensor reaches a predetermined temperature threshold. In other words, when the battery temperature is at least equal to the predetermined temperature threshold, the battery is no longer subjected to the PhC charge and PhD discharge phase cycles. Preferably, during the shutdown step, the battery's power (PB) is greater than the predetermined continuous charging power (PRC).Indeed, when the PB battery's power exceeds the continuous charging power (PRC), the PB battery's power is sufficient to allow the internal combustion engine to operate efficiently, even when the driver's input is low or negative, for example, during deceleration while the internal combustion engine is running. Furthermore, when the PB battery's power exceeds the PRC, the battery is capable of recovering kinetic energy during vehicle braking from high speed to a stop, without causing lithium plating.

[0012] Furthermore, the invention relates to a device configured to implement said progressive heating method for a lithium-ion battery mounted on a hybrid motor vehicle. The device comprises a means for measuring the battery power PB, a means for calculating the cumulative battery power IPB, and an inverter configured to interrupt the charging phase PhC and activate the discharging phase PhD when the battery is in the charging phase PhC and when the cumulative battery power IPB exceeds the second predetermined threshold value V2. The invention also relates to a hybrid motor vehicle comprising such a device as described above.

Claims

1. Demands A method for progressively heating a lithium-ion battery mounted on a motor vehicle, said vehicle comprising an accelerator pedal, wheels, an electric motor and a thermal engine, the electric motor and the thermal engine being connected to the wheels by a primary shaft configured to transmit the mechanical energy generated by the thermal engine and the electric motor to said wheels to move said vehicle,said electric motor being connected to said battery via a DC / AC converter configured to control a discharge phase (PhD) of the battery during which said DC / AC converter transforms a direct current from said battery into an alternating current to power said electric motor and an AC / DC converter configured to control a charge phase (PhC) of the battery during which said AC / DC converter transforms the alternating current from the electric motor into direct current to power said battery, the discharge phase (PhD) and the charge phase (PhC) being carried out alternately so as to generate heat dissipation by Joule effect to heat said battery, a first torque being applied to the internal combustion engine and a second torque being applied to the electric motor, said battery comprising an anode and a cathode,said battery comprising lithium capable of moving from the anode to the cathode during the discharge phase (PhD) and from the cathode to the anode during the charge phase (PhC), a first threshold value (VI) for which the charge phase (PhC) is interrupted to avoid the risk of lithium plating, lithium plating being the deposition of lithium in solid form on the surface of the anode during the charge phase (PhC), characterized in that said process comprises the following steps:, - a step of determining a setpoint torque applied to the primary shaft as a function of the state of depressment of the accelerator pedal by the driver, the setpoint torque being equal to the sum of the first torque and the second torque, said battery being in the discharge phase (PhD) when said second torque is positive, said battery being in the charge phase (PhC) when said second torque is negative; - a step to measure the battery power (PB); - a step of measuring the cumulative battery power (IPB) over time (t) as a function of the battery power (PB) measured during the battery power measurement step (PB) when the battery power (PB) is greater than a predetermined continuous charging power (PRC), said continuous charging power (PRC) corresponding to the power admissible by said battery without time limitation and without generating the risk of lithium plating; - a step of forced execution of the discharge phase (PhD) when the cumulative battery power (IPB) is greater than a second predetermined threshold value (V2), said second threshold value (V2) being less than said first threshold value (VI), said second couple being positive;- a step of progressive heating of the battery without risk of lithium plating by a succession of discharge phases (PhD) and charge phases (PhC), the cumulative battery power (IPB) remaining below said second threshold value (V2).;

2. A method according to claim 1 characterized in that the battery comprises a temperature measurement sensor, said method comprising a stopping step when the temperature measured by said temperature measurement sensor reaches a predetermined temperature threshold value.

3. The method according to claim 2 characterized in that, during the shutdown step, the battery power (PB) is greater than the predetermined continuous charging power (PRC).

4. Heating device configured to implement said progressive heating method of a lithium-ion battery mounted on a hybrid motor vehicle according to any one of claims 1 to 3, characterized in that said device comprises a means for determining the setpoint torque, a means for regulating the second torque, a means for measuring the battery power (PB), a means for measuring the cumulative battery power (IPB) and a means for forcing execution of the discharge phase (PhD) when the cumulative battery power (IPB) is greater than the second predetermined threshold value (V2).

5. Hybrid motor vehicle comprising a heating device according to claim 4.