METHOD FOR DETERMINING THE CONDITION OF A MOTOR VEHICLE BATTERY

Description

[0001] The present invention claims priority from French application No. 1911502 filed on 16.10.2019.

[0002] The present invention relates to a method for determining the state of a battery equipping a motor vehicle.

[0003] A motor vehicle is typically equipped with a battery, such as a 12V battery, often a lead-acid battery, to power the vehicle's accessories. Knowing the battery's condition is essential, particularly for planning its replacement in case of failure. This condition refers to the battery's state of health, wear, or a similar indicator of its performance.

[0004] We know of methods for determining battery state that use measuring sensors, particularly temperature sensors, or even additional electrical loads to obtain a sufficiently high current, in particular on the order of 70 A. In the latter case, this also requires the installation of at least one switch. For example, see documents DE102007061112 and DE102009038663, which describe methods of this type that require the installation of components that add bulk and weight to the motor vehicle.

[0005] We also know from patent document JP-A-2002097974 a method according to the preamble of claim 1.

[0006] One aim of the present invention is to propose a method for determining the state of a battery equipping a motor vehicle, which is simple and quick to implement, the method not requiring the installation on the motor vehicle of elements which add weight and bulk to the motor vehicle.

[0007] In general, a method of the present invention is a method in which the health of a battery is determined by analyzing its internal resistance and the voltage drop during a current draw. The battery's health is assessed in relation to its ability to meet vehicle demands, specifically current draws from safety-critical components of the motor vehicle, such as power steering (PSS), electronic stability program (ESP), or similar systems.

[0008] More specifically, a method of the present invention is a method for determining the state of a first battery equipping a motor vehicle. The motor vehicle is equipped with a hybrid powertrain comprising at least one internal combustion engine and a gearbox including an electric machine connected to a first converter. The first converter is connected to a starter-generator via an electrical circuit. The motor vehicle is equipped with a second battery connected to a second converter.

[0009] According to the present invention, the determination method comprises: The first step involves configuring the second converter in reversible mode and activating a 48V load on the motor vehicle. This first step occurs either after the motor vehicle has started, or before the motor vehicle has started. The second step involves applying a 48V voltage to the first battery from the 48V load. The third step involves measuring the battery voltage across the terminals of the first battery during a current draw to determine its internal resistance. The fourth step involves comparing the measured internal resistance to a threshold resistance. The fifth step involves displaying a warning message to the motor vehicle user if the measured internal resistance exceeds the threshold resistance. The sixth step involves disconnecting the 48V load and restoring a normal start.If the measured internal resistance is less than or equal to the threshold resistance, the determination method advantageously includes at least one of the following characteristics, taken alone or in combination: the 48 V load consists of the second battery, the 48 V load consists of the alternator-starter, the 48 V load consists of the electric machine, the first battery is a 12 V battery, if the first step is prior to starting the motor vehicle, then the motor vehicle is started between the first and second steps, the second converter is connected in parallel with the alternator-starter, the first and second batteries are connected in parallel with the second converter.

[0010] It is understood that the method of the present invention is a method for determining the state of a battery equipping a motor vehicle which advantageously uses constituent elements of a hybrid traction chain and / or a facade architecture equipping the motor vehicle to determine the state of the battery.

[0011] More specifically, the method for determining the condition of the present invention uses 48 V loads installed in the motor vehicle to draw current and diagnose the condition of a battery under test, such as the aforementioned 12 V battery. The invention will be better understood upon reading the following non-limiting description, written with reference to the accompanying drawings, in which: [ Fig. 1 ] - there figure 1 schematically represents a hybrid powertrain and a front-end architecture equipping a motor vehicle with a first battery whose state is to be tested, [ Fig. 2 ] - there figure 2 schematically represents a first variant of a method for determining the state of the first battery illustrated on the figure 1 , [ Fig. 3 ] - there figure 3 schematically represents a second variant of a method for determining the state of the first battery illustrated on the figure 1 .

[0012] There figure 1 This schematically represents a hybrid powertrain 1a and a front panel architecture 1b equipping a motor vehicle, which are advantageously used to determine the state of a first battery 31 by means of a method of the present invention. It is understood that the hybrid powertrain 1a and the front panel architecture 1b are known in themselves but include elements that are advantageously used to test the first battery 31 and determine its state, commonly referred to as its "health status".

[0013] The hybrid powertrain 1a includes, in particular, an internal combustion engine 2 which is associated with a crankshaft 3. The crankshaft 3 includes a first end 3a provided with a first pulley 4 and a second end 3b equipped with a flywheel 5. The flywheel 5 is related to a first clutch 6 of a gearbox 7 which includes a second clutch 8 and a third clutch 9 which can be selectively coupled to wheels 10.

[0014] The gearbox 7 comprises an electrical machine 11, such as a 48 V electric motor, connected to a first converter 12, such as an alternating current / direct current converter, commonly referred to as an AC / DC converter, which is itself connected to a starter-alternator 13, such as a 48 V starter-alternator, via an electrical circuit 20. The starter-alternator 13 is provided with a second pulley 14. The first pulley 4 and the second pulley 14 are connected to each other by a belt 15, which is also connected to a third pulley 16, such as that of an air conditioning compressor 17 or similar. The pulleys 4, 14, 16 and the belt 15 are, in particular, integral components of the front panel architecture 1b of the motor vehicle.

[0015] A first electrical branch 21 is connected in parallel with the alternator-starter 13 on the electrical circuit 21. The first electrical branch 21 includes a second converter 18, such as a direct current / direct current converter, commonly referred to as a DC / DC converter. The second converter 18 also forms part of a second electrical branch 22 equipped with at least one electrical device 19 of the motor vehicle. On the first electrical branch 21, a second battery 32, such as a Li-ion battery, in particular a 48-volt battery, is connected in parallel with the second converter 18. On the second electrical branch 22, the first battery 31, such as a lead-acid battery, in particular a 12-volt battery, is connected in parallel with the second converter 18. The first battery 31 is the battery whose condition is to be determined.

[0016] On the figures 2 And 3, a method for determining 100 of a state E of a battery to be tested, such as the said first battery 31, in other words the 12 V lead-acid battery, is shown.

[0017] The determination process 100 includes a first step 101 which consists of configuring the second converter 18 in reversible mode and activating a 48 V load fitted to the motor vehicle. It is understood that the 48 V load is indifferently composed of the second battery 32, the electric machine 11 or the alternator-starter 13.

[0018] The determination process 100 includes a second step 102 which consists of stressing the first battery 31 by applying a voltage of 48 V to it from the 48 V load.

[0019] The determination process 100 includes a third step 103 which consists of measuring a battery voltage V across the terminals of the first battery 31 during a current draw A in order to deduce an internal resistance R of the first battery 31. The internal resistance R thus measured reflects the state E of the first battery 31.

[0020] The determination process 100 includes a fourth step 104 which consists of comparing the measured internal resistance R to a threshold resistance R1.

[0021] If the measured internal resistance R is greater than the threshold resistance R1, the determination procedure 100 includes a fifth step 105 which consists of displaying a warning message I to the motor vehicle user. The warning message I is, for example, the illumination of an electrical indicator light. Additionally, starting the motor vehicle is prohibited.

[0022] If the measured internal resistance R is less than or equal to the threshold resistance R1, no warning information is displayed and the determination procedure 100 includes a sixth step 106 which consists of disconnecting the 48 V load and restoring a normal start.

[0023] According to a first variant illustrated on the figure 2 , the first step 101 is carried out before a D start of the motor vehicle.

[0024] According to a second variant illustrated on the figure 3 The first step, 101, is performed immediately after the vehicle starts (D). It is understood that a time lapse on the order of a few hundred milliseconds elapses between the start (D) and the first step, 101.

Claims

1. Method for determining (100) the state (E) of a first battery (31) equipping a motor vehicle, the motor vehicle being equipped with a hybrid powertrain (1a) comprising at least one internal combustion engine (2) and a gearbox (7) including an electric machine (11) connected to a first converter (12), the first converter (12) being connected to a starter-alternator (13) via an electrical circuit (20), the motor vehicle being equipped with a second battery (32) connected to a second converter (18), the determination method (100) comprising: - a second step (102) which consists of applying a voltage of 48 V to the first battery (31) from the 48 V load (11, 13, 32), - a third step (103) which consists of measuring a battery voltage (V) across the terminals of the first battery (31) during a current draw (A) to deduce an internal resistance (R) of the first battery (31), - a fourth step (104) which consists of comparing the measured internal resistance (R) to a threshold resistance (R1), - a fifth step (105) which consists of displaying a warning message (I) to a user of the motor vehicle, if the measured internal resistance (R) is greater than the threshold resistance (R1), - a sixth step (106) which consists of disconnecting the 48 V load (11, 13, 32) and restoring a normal start, if the measured internal resistance (R) is less than or equal to the threshold resistance (R1), characterized in that it comprises: - a first step (101) which consists of configuring the second converter (18) in reversibility mode and activating a 48 V load (11, 13, 32) fitted to the motor vehicle, the first step (101) being subsequent to a start (D) of the vehicle automobile, or the first step (101) being prior to a starting (D) of the motor vehicle.

2. A method of determination (100) according to claim 1, characterized in that the 48 V load (11, 13, 32) consists of the second battery (32).

3. A method of determination (100) according to claim 1, characterized in that the 48 V load (11, 13, 32) consists of the alternator-starter (13).

4. A method of determination (100) according to claim 1, characterized in that the 48 V load (11, 13, 32) consists of the electric machine (11).

5. A method for determining (100) according to any one of the preceding claims, characterized in that the first battery (31) is a 12 V battery.

6. A method for determining (100) according to any one of the preceding claims, characterized in that if the first step (101) precedes a starting (D) of the motor vehicle, the starting (D) of the motor vehicle is carried out between the first step (101) and the second step (102).

7. A method for determining (100) according to any one of the preceding claims, characterized in that the second converter (18) is mounted in parallel with the alternator-starter (13).

8. A method for determining (100) according to any one of the preceding claims, characterized in that the first battery (31) and the second battery (32) are mounted in parallel with the second converter (18).