Measuring leakage current of battery

Abstract

A method for measuring a leakage current of a battery (BAT), the method comprising the following consecutive steps: performing a first plurality of measurements (Vmid1) of a difference between an intermediate potential (Vmid) and a high voltage ground (GND) of a vehicle; using a switching device such that the third resistor (R3) is electrically connected between the intermediate potential (Vmid) and the high potential (BAT +) of the battery (BAT); performing a second multiple measurement (Vmid2) on the intermediate voltage; deriving a second stable value (Vstab2) of the intermediate voltage from the second plurality of measurements (Vmid2); deriving values of the first parasitic resistor (RIP) and the second parasitic resistor (RIM); and deriving a leakage current at the terminals of the first parasitic resistor (RIP) and the second parasitic resistor (RIM).

Description

Technical Field

[0001] The present invention relates to a current sensor designed to measure high-intensity currents, particularly currents with an intensity greater than or equal to 200 A DC.

[0002] A particularly advantageous application of this current sensor is in the field of electric or hybrid motor vehicles, and specifically in measuring the current at the input and / or output terminals of the battery in such vehicles. Background Technology

[0003] Current sensors designed to measure the current at the input and / or output of a battery intended to supply power to an electric motor in an electric or hybrid motor vehicle are known from the prior art. Such current sensors can be based on a resistor bar type, or more commonly a busbar shunt type sensitive component. This sensitive component consists of a resistor bar (or shunt) surrounded by two interconnecting (or busbar) plates.

[0004] The resistor bar is made of resistive material and thus forms a measuring resistor. It is soldered to a corresponding interconnect on each side, the interconnect simply ensuring the flow of current. In use, each corresponding interconnect is connected to a circuit containing a battery.

[0005] A sensitive component is connected to a printed circuit board that houses current-measuring electronics. The current-measuring electronics are configured to perform voltage measurements and derive the current value from the known resistance of a resistor bar. The printed circuit board is advantageously stacked on top of the sensitive component and connected to it at solder joints between the sensitive component and the printed circuit board.

[0006] The known approach from existing technology is to use, as... Figure 1 The circuitry is used to measure the leakage current of a motor vehicle's traction battery. In particular, this leakage current measurement indicates whether there is a risk if a user comes into contact with the circuit.

[0007] The architecture of circuit 2 includes: - A battery BAT having a high potential BAT+ and a low potential BAT-, wherein the difference between the high potential BAT+ and the low potential BAT- defines the voltage VBAT. - Voltage divider bridge P1, which includes a first resistor R1 and a second resistor R2 electrically connected to each other at the midpoint defining an intermediate potential Vmid. The first resistor R1 is electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery, and the second resistor R2 is electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery BAT. - A third resistor R3, which can be electrically connected or not electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery BAT via a switching device SW1, and - A fourth resistor R4, which can be electrically connected or not electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery BAT via the switch SW2 of the switching device, the intermediate potential Vmid being intended to be electrically connected to the high-voltage ground terminal GND of the vehicle.

[0008] In addition, the vehicle has the following limitations: -A first structural capacitor CyP and a first parasitic resistor RIP connected in parallel between the intermediate potential Vmid and the high potential BAT+, and A second structural capacitor CyM and a second parasitic resistor RIM are connected in parallel between the intermediate potential Vmid and the low potential BAT-.

[0009] The first constructed capacitor CyP and the second constructed capacitor CyM have a capacitance that is typically equal to 1 μF.

[0010] The first and second parasitic resistors carry a potential that the user can contact.

[0011] The leakage current of the battery is represented by the values ​​of the first parasitic resistor RIP and the second parasitic resistor RIM, which are related to the value of the intermediate voltage Vmid.

[0012] However, it is necessary to wait for the charging time of the first constructed capacitor CyP and the second constructed capacitor CyM before the value of the steady-state intermediate voltage can be measured.

[0013] Typically, the potential difference between the intermediate potential Vmid and the high-voltage ground terminal GND stabilizes approximately five times the charging time constant of the first construction capacitor CyP and the second construction capacitor CyM. This difference is called the intermediate voltage.

[0014] Before reaching steady state, the intermediate voltage is in a so-called transient state, during which the stable value of the intermediate voltage cannot be measured.

[0015] Because the measurement time is limited, there is a risk that the measurement may be performed during this transient period. Since the measured value is false, the leakage current may appear too high for a user in contact with the circuit, and the circuit may not be able to indicate this danger. Summary of the Invention

[0016] Therefore, this document relates to a method for measuring the leakage current of a battery in a circuit, said circuit comprising: - This battery, which is a traction battery for motor vehicles, has a high potential and a low potential. - A voltage divider bridge comprising a first resistor and a second resistor electrically connected to each other at the midpoint defining an intermediate potential, the first resistor being electrically connected between the intermediate potential and the high potential of the battery, and the second resistor being electrically connected between the intermediate potential and the low potential of the battery. - A third resistor, which can be electrically connected or not electrically connected between the intermediate potential and the high potential of the battery via a switching device. - A fourth resistor, which can be electrically connected or not electrically connected between an intermediate potential and the low potential of the battery via the switching device, the intermediate potential being intended to be electrically connected to the high-voltage ground terminal of the vehicle. The vehicle defines a first structural capacitor and a first parasitic resistor connected in parallel between an intermediate potential and a high potential. The vehicle defines a second structural capacitor and a second parasitic resistor connected in parallel between an intermediate potential and a low potential. The method comprises the following sequential steps: a) Using the switching device, the third resistor is not electrically connected between the intermediate potential and the high potential of the battery, and the fourth resistor is not electrically connected between the intermediate potential and the low potential of the battery. b) Measure the initial value of the intermediate voltage. If the initial value of the intermediate voltage is less than or equal to half the difference between the high potential and the low potential of the battery, then proceed with the subsequent steps of the method according to the first case; otherwise, proceed with the subsequent steps of the method according to the second case. c) In this first case, a switching device is used such that the third resistor is electrically connected between the intermediate potential and the high potential of the battery, and the fourth resistor is not electrically connected between the intermediate potential and the low potential of the battery. In this second case, a switching device is used such that the third resistor is not electrically connected between the intermediate potential and the high potential of the battery, and the fourth resistor is electrically connected between the intermediate potential and the low potential of the battery. d) Perform a first multiple measurement on the difference between the intermediate potential and the high-voltage ground terminal of the vehicle, the difference corresponding to the intermediate voltage, the first multiple measurements being time-spaced within a first time interval and including a measurement of the intermediate voltage at the upper limit of the first time interval; e) Derive the first stable value of the intermediate voltage from the results of the first multiple measurements; f) Using a switching device, the third resistor is not electrically connected between the intermediate potential and the high potential of the battery, and the fourth resistor is not electrically connected between the intermediate potential and the low potential of the battery. g) Perform a second multiple measurement on the intermediate voltage, the second multiple measurement being time-spaced within a second time interval and including the measurement of the intermediate voltage at the upper limit of the second time interval; h) Derive the second stable value of the intermediate voltage from the results of the second multiple measurements; i) Using the first and second stable values ​​of the intermediate voltage, the values ​​of the first and second parasitic resistors are derived by calculation; and j) The leakage current at the terminals of the first and second parasitic resistors is derived by calculation.

[0017] In the remainder of this document, intermediate voltage is understood to refer to the potential difference between the midpoint and the high-voltage grounding terminal of the vehicle.

[0018] In this way, even if the first or second multiple measurement results do not include the first or second stable value of the intermediate voltage, an approximate value of the first or second stable value of the intermediate voltage can be derived from them.

[0019] In other words, this method allows us to get rid of the limitations imposed by the charging time of the first and second constructed capacitors.

[0020] Even if the first and second multiple measurements are performed transiently, the method allows the values ​​of the first and second stable values ​​of the intermediate voltage to be derived from them, and thus the leakage current at the terminals of the first and second parasitic resistors to be derived.

[0021] Therefore, calculating leakage current more quickly (in less time) reduces the risk of leakage current being too high for users in contact with the circuit, and the circuit failing to indicate this danger.

[0022] The circuit may further include a first additional voltage divider bridge, which includes a second resistor and a measuring resistor electrically connected to each other at a first additional midpoint defining the measuring potential. The difference between the measuring potential and the vehicle's ground terminal is the measuring voltage, which is a fraction of the intermediate voltage.

[0023] Since the magnitude of the intermediate voltage can be too large for voltage measuring instruments, measuring this voltage allows us to overcome this limitation and measure changes in the intermediate voltage. Typically, the intermediate voltage is between 400 V and 800 V.

[0024] The circuit may further include a second additional voltage divider bridge, which includes a fourth resistor and a diagnostic resistor electrically connected to each other at a second additional midpoint defining a diagnostic potential. The difference between the diagnostic potential and the vehicle's ground terminal is a diagnostic voltage that allows checking the operating status of the switching device.

[0025] The switching device may include a first switch disposed between the midpoint and the third resistor and / or a second switch disposed between the midpoint and the fourth resistor.

[0026] Choosing between the first and second options allows for the measurement of more significant changes in the intermediate voltage.

[0027] This is why, in the first case, we want to increase the intermediate voltage by using a switching device to electrically connect the third resistor between the intermediate potential and the high potential of the battery, and not to electrically connect the fourth resistor between the intermediate potential and the low potential of the battery.

[0028] Conversely, in the second case, we want to reduce the intermediate voltage by using a switching device to prevent the third resistor from being electrically connected between the intermediate potential and the high potential of the battery, and to electrically connect the fourth resistor between the intermediate potential and the low potential of the battery.

[0029] If the difference between the measurement result of the intermediate voltage at the upper limit of the first time interval and the previous measurement result of the first multiple measurements of the intermediate voltage is greater than the first threshold voltage, then step (e) includes the following sub-steps: (e1) Perform a first extrapolation on the first multiple measurement result of the intermediate voltage using a first extrapolation function. In the second case, the first extrapolation function is a decreasing exponential function representing the discharge of the first and second structural capacitors of the vehicle. In the first case, the first extrapolation function is an increasing exponential function representing the charging of the first and second structural capacitors of the vehicle. (e2) The first stable value of the intermediate voltage is derived by calculation; Otherwise, the first stable value of the intermediate voltage is equal to the measurement result of the intermediate voltage at the upper limit of the first time interval.

[0030] During the transient period of charging or discharging of the first and second structural capacitors of the vehicle, the value of the intermediate voltage increases or decreases with time, respectively. Therefore, the difference between the measured result of the intermediate voltage at the upper limit of the first time interval and the previous measurement result in the first multiple measurements of the intermediate voltage is large during this transient period (i.e., greater than the first threshold voltage).

[0031] Furthermore, steps (e1) and (e2) are performed to determine the first stable value of the intermediate voltage.

[0032] On the other hand, during the steady-state charging of the vehicle's first and second structural capacitors, the value of the intermediate voltage remains substantially constant and equal to the first stable value of the intermediate voltage.

[0033] Therefore, the difference between the measurement result of the intermediate voltage at the upper limit of the first time interval and the previous measurement result in the first multiple measurements of the intermediate voltage is small during the steady state period (i.e., less than the first threshold voltage).

[0034] Therefore, in this case, it can be concluded that the first stable value of the intermediate voltage is equal to the measured result of the intermediate voltage at the upper limit of the first time interval.

[0035] The first extrapolation function can be defined by the following formula: Where E is the voltage constant, τ is the time constant, and V0 is the value of the intermediate voltage at the beginning of step (d).

[0036] At t = 0 s, the value of the intermediate voltage is equal to V0.

[0037] As t increases, the term It approaches 1, and the value of the intermediate voltage then approaches the first stable value, where: E + V0.

[0038] We can assume that when t is large enough (i.e., when...) When the voltage is sufficiently close to 1, the intermediate voltage will change from a transient state to a steady state. The value of t during this transition is defined by the first threshold voltage.

[0039] The extrapolation in step (e1) may include the following sub-steps: (e1-a) determines the time constant τ through a convergent loop; and (e1-b) Derive the voltage constant E.

[0040] The results of the first multiple measurements yielded a set of two equations for the intermediate voltage at two different times.

[0041] By solving these two equations simultaneously, a single equation with the time constant τ as the unknown is obtained.

[0042] Step (e1-a) can be performed using the solver of the equation.

[0043] The solver can be a convergent loop that checks the value of the time constant τ in the equation until it converges to an exact value.

[0044] The solver can be a convergent loop that checks the value of the time constant τ in the equation until it converges to a value with an error of less than 0.01.

[0045] For example, a convergence loop can be an alternation of positive and negative increments of the time constant τ, where the increments are adjusted at each iteration.

[0046] The increment can be between 0.01 s and 1 s.

[0047] If the difference between the measurement result of the intermediate voltage at the upper limit of the second time interval and the previous measurement result of the second multiple measurements of the intermediate voltage is greater than the second threshold voltage, then step (h) includes the following sub-steps: (h1) Perform a second extrapolation on the second multiple measurement result of the intermediate voltage using a second extrapolation function. In the second case, the second extrapolation function is an increasing exponential function representing the charging of the first and second structural capacitors of the vehicle, and in the first case, the second extrapolation function is a decreasing exponential function representing the discharging of the first and second structural capacitors of the vehicle. (h2) The second stable value of the intermediate voltage is derived by calculation; Otherwise, the second stable value of the intermediate voltage is equal to the measurement result of the intermediate voltage at the upper limit of the second time interval.

[0048] The variant and the first multiple measurement results of the intermediate voltage presented in step (e) can be transposed to the second multiple measurement results of the intermediate voltage in step (h).

[0049] The second extrapolation function can be defined by the following formula: Where E' is the voltage constant, τ' is the time constant, and V0' is the value of the intermediate voltage at the beginning of step (g).

[0050] At t = 0 s, the value of the intermediate voltage is equal to V0'.

[0051] As t increases, the term It approaches 1, and the value of the intermediate voltage then approaches the second stable value, where: E' + V0'.

[0052] We can assume that when t is large enough (i.e., when...) When the voltage is sufficiently close to 1, the intermediate voltage will change from a transient state to a steady state. The value of t during this transition is defined by the first threshold voltage.

[0053] The extrapolation in step (h1) may include the following sub-steps: (h1-a) determines the time constant τ' through a convergent loop; and (h1-b) Derive the voltage constant E'.

[0054] The second set of measurements yielded a set of two equations for the intermediate voltage at the two time points.

[0055] By solving these two equations simultaneously, a single equation with the time constant τ as the unknown is obtained.

[0056] Step (h1-a) can be performed using the solver of the equation.

[0057] The solver can be a convergent loop that checks the value of the time constant τ in the equation until it converges to an exact value.

[0058] The solver can be a convergent loop that checks the value of the time constant τ in the equation until it converges to a value with an error of less than 0.01.

[0059] For example, a convergence loop can be an alternation of positive and negative increments of the time constant τ, where the increments are adjusted at each iteration.

[0060] The increment can be between 0.01 s and 1 s.

[0061] The first threshold voltage and / or the second threshold voltage can be between 1 mV and 20 mV.

[0062] This document also relates to a computer including a processor and a memory, the processor being able to access the memory to read steps stored in the memory, the computer being characterized in that it is configured to perform each step of a method of the type described above.

[0063] This document also relates to a motor vehicle equipped with a battery and a computer of the type described above. Attached Figure Description

[0064] Other features, details, and advantages will become apparent by reading the following detailed description and studying the accompanying drawings, in which: [ Figure 1 [This is a schematic diagram of a circuit for measuring the leakage current of a battery, based on existing technology.] [ Figure 2 This document illustrates different steps in a method for measuring the leakage current of a battery according to embodiments thereof. [ Figure 3 [This is based on] Figure 2 The method step (a) is a schematic diagram of the circuit used to measure the leakage current of the battery. [ Figure 4This is based on the second situation. Figure 2 The schematic diagram of the circuit used to measure the leakage current of the battery is shown in step (c) of the method. [ Figure 5 This is based on the second case, when SW2 is closed. Figure 2 The graph showing the change in intermediate voltage in step (d) of the method. [ Figure 6 This is based on the second situation. Figure 2 The method step (f) includes a schematic diagram of the circuit used to measure the leakage current of the battery, and [ Figure 7 This is based on the second scenario, when SW2 is disconnected. Figure 2 The method step (g) is a graph showing the change in intermediate voltage. Detailed Implementation

[0065] Figure 2 Different steps of a method for measuring the leakage current of a battery according to one embodiment of this document are shown.

[0066] The circuit used to measure leakage current is Figure 3 The circuit shown includes: - The traction battery BAT for motor vehicles, which includes a high-potential BAT+ and a low-potential BAT-. - Voltage divider bridge P1, which includes a first resistor R1 and a second resistor R2 electrically connected to each other at the midpoint defining an intermediate potential Vmid. The first resistor R1 is electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery, and the second resistor R2 is electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery. - A third resistor R3, which can be electrically connected or not electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery via a switching device SW1, and - A fourth resistor R4, which can be electrically connected or not electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery via the switch SW2 of the switching device, the intermediate potential Vmid being intended to be electrically connected to the vehicle's ground terminal GND.

[0067] The vehicle is limited to: - First, a first structural capacitor CyP and a first parasitic resistor RIP are connected in parallel between the intermediate potential Vmid and the high potential BAT+, and - Secondly, a second structural capacitor CyM and a second parasitic resistor RIM are connected in parallel between the intermediate potential Vmid and the low potential BAT-.

[0068] The circuit further includes: - A first additional voltage divider bridge, comprising a second resistor R2 and a measuring resistor RMEAS electrically connected to each other at a first additional midpoint defining the measuring potential VISO_MEAS. The difference between the measuring potential VISO_MEAS and the low potential BAT- of the battery is the measuring voltage VISO_MEAS, which is a fraction of the intermediate voltage Vmid. - A second additional voltage divider bridge, comprising a fourth resistor R4 and a diagnostic resistor RDIAG electrically connected to each other at a first additional midpoint defining the diagnostic potential VISO_DIAG. The difference between the measured potential VISO_DIAG and the low potential BAT- of the battery is the diagnostic voltage VISO_DIAG, which is used to check the correct operation of switches SW1 and SW2.

[0069] In the following text, the measurement of intermediate voltages Vinit, Vmid1, and Vmid2 is understood to refer to the derivation of the intermediate voltage measurement results by measuring voltage VISO_MEAS.

[0070] In step (a) of the method, a switching device is used such that the third resistor R3 is not electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery BAT, and the fourth resistor R4 is not electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery BAT. In other words, switches SW1 and SW2 are open.

[0071] In step (b) of the method, the initial value of the intermediate voltage Vinit is measured. If the initial value of the intermediate voltage Vinit is less than or equal to half of the difference between the high potential BAT+ and the low potential BAT- of the battery BAT, the subsequent steps of the method are performed according to the first case; otherwise, the subsequent steps of the method are performed according to the second case.

[0072] Here, the initial value of the intermediate voltage measured is Vinit = 350 V.

[0073] When VBAT = 600 V, Vinit > VBAT / 2, and the method continues according to the second case.

[0074] In the first case, a switching device is used such that the third resistor R3 is electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery BAT, and the fourth resistor R4 is not electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery BAT. In other words, in the first case, SW1 is closed.

[0075] In the second case, a switching device is used such that the third resistor R3 is not electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery BAT, and the fourth resistor R4 is electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery BAT. In other words, in the second case, SW2 is closed, and the circuit is in... Figure 4 The configuration shown.

[0076] In step (d) of the method, a first multiple measurement Vmid1 is performed on the difference between the intermediate potential Vmid and the high-voltage grounding terminal GND of the vehicle.

[0077] In this configuration, this difference corresponds to the intermediate voltage Vmid1.

[0078] Now for reference Figure 5 The figure is a curve showing the change of the intermediate voltage Vmid1 over time. The first multiple measurements of the intermediate voltage Vmid1 include the measurement result V0 at t0 = 0 s, the measurement result V2.5 at t2.5 = 2.5 s, the measurement result V4.3 at t4.3 = 4.3 s, and the measurement result V5 at t5 = 5 s within the first time interval having a lower limit t0 and an upper limit t5.

[0079] In step (e) of the method, a first stable value Vstab1 of the intermediate voltage Vmid1 is derived from the first multiple measurement results.

[0080] It can be observed that the measured value is in the transient state of Vmid1; in particular, it can be observed that when Vseuil1 = 0.01 V, V5 – V4.3 > Vseuil1.

[0081] In this case, step (e) includes sub-steps (e1) and (e2).

[0082] In substep (e1), a first extrapolation is performed on the second multiple measurement result Vmid1 of the intermediate voltage using an increasing exponential function representing the discharge of the vehicle's first and second structural capacitors CyP and CyM. The intermediate voltage Vmid1 is defined by the following load function: [Mathematical Expression 1] Where E is the voltage constant and τ is the time constant.

[0083] The sub-step (e1) itself includes multiple sub-steps (e1-a) and (e1-b).

[0084] In sub-step (e1-a), the time constant τ is determined by a convergence loop.

[0085] For example, take the first system of two equations, which includes equations V5 and V2.5.

[0086] Then, the following equation is obtained: [Mathematical Expression 2] [Mathematical Expression 3] Combining these two equations, we get: [Mathematical Expression 4] Next, the equation is solved using a solver. The solver will first verify the initial value of the time constant τ, and then generate positive and / or negative increments of τ to converge to an approximate value of τ.

[0087] Here, V5 = 0.577 V, V2.5 = 0.754 V and V0 = 1.483 V were measured.

[0088] The accuracy of an approximation of τ can be defined by requiring that the terms on both sides of the equation be equal within positive or negative voltage uncertainties, or by applying a minimum increment.

[0089] With a minimum increment of 0.01 s, we obtain τ = 5.03 s.

[0090] In sub-step (e1-b) of this method, the voltage constant E is then derived using the following formula: [Mathematical Expression 5] Then, we get E = -0.9641 V.

[0091] Then, in step (e2), the first stable value of the intermediate voltage Vstab1 is derived from Vstab1 = E + V0 = 0.518 V.

[0092] Next, in step (f) of the method, the switches closed in step (c) are disconnected, namely SW1 in the first case and SW2 in the second case. Therefore, the third resistor R3 is not electrically connected between the intermediate potential Vmid and the high potential BAT+ of the battery BAT, and the fourth resistor R4 is not electrically connected between the intermediate potential Vmid and the low potential BAT- of the battery BAT.

[0093] get Figure 6 The second electrical configuration shown.

[0094] Similar to step (d), in step (g) of the method, a second multiple measurement Vmid2 is performed on the intermediate voltage in the second configuration.

[0095] Now for reference Figure 7 The figure is a curve showing the change of the intermediate voltage Vmid2 over time. The second multiple measurements of the intermediate voltage Vmid2 include the measurement results V0' at t0' = 0 s, V2' at t2' = 2 s, V5' at t5' = 5 s, and V7' at t7' = 7 s within a second time interval with a lower limit t0 and an upper limit t7.

[0096] It can be observed that the measured value is in the transient state of Vmid2; in particular, it can be observed that when Vseuil2 = 0.01 V, V7' – V5' > Vseuil2.

[0097] In this case, step (h) includes sub-steps (h1) and (h2).

[0098] In substep (h1), a second extrapolation is performed on the second multiple measurement result Vmid2 of the intermediate voltage using an increasing exponential function representing the charging of the vehicle's first and second structural capacitors CyP and CyM. The intermediate voltage Vmid2 is defined by the following load function: [Mathematical Expression 6] Where E' is the voltage constant and τ' is the time constant.

[0099] The sub-step (h1) itself includes multiple sub-steps (h1-a) and (h1-b).

[0100] In sub-step (h1-a), the time constant τ' is determined by a convergent loop.

[0101] For example, consider the second system of two equations, which includes equations V5' and V7'.

[0102] Then, the following equation is obtained: [Mathematical Expression 7] [Mathematical Expression 8] Combining these two equations, we get: [Mathematical Expression 9] Similarly, the solver used in step (e1-a) is used to solve the equation.

[0103] Here, V7' = 1.245 V, V5' = 1.129 V and V0' = 0.521 V were measured.

[0104] Of course, measurement results other than those selected from the first multiple measurement results and the second multiple measurement results from the first equation set and the second equation set, respectively, can also be used.

[0105] In this case, with a minimum increment of 0.01 s, we obtain τ' = 5.03 s.

[0106] In sub-step (h1-b) of this method, the voltage constant E' is then derived using the following formula: [Mathematical Expression 10] Then, we get E' = 0.9641 V.

[0107] Then, in step (h2), the second stable value of the intermediate voltage Vstab2 is derived by means of Vstab2 = E' + V0' = 1.485 V.

[0108] In step (i) of the method, the values ​​of the first parasitic resistor RIP and the second parasitic resistor RIM are derived by calculation using the first stable value Vstab1 and the second stable value Vstab2 of the intermediate voltage.

[0109] In step (j) of the method, the leakage current at the terminals of the first parasitic resistor RIP and the second parasitic resistor RIM is derived by calculation.

Claims

1. A method for measuring the leakage current of a battery (BAT) of an electric circuit comprising: - the battery (BAT), which is a traction battery (BAT) of a motor vehicle and has a high potential (BAT+) and a low potential (BAT-), - a voltage divider bridge comprising a first resistor (R1) and a second resistor (R2) electrically connected to each other at a midpoint defining an intermediate potential (Vmid), the first resistor (R1) being electrically connected between the intermediate potential (Vmid) and the high potential (BAT+) of the battery (BAT), the second resistor (R2) being electrically connected between the intermediate potential (Vmid) and the low potential (BAT-) of the battery (BAT), - a third resistor (R3) which can be electrically connected or not electrically connected between the intermediate potential (Vmid) and the high potential (BAT+) of the battery (BAT) by means of a switching device (SW1, SW2), - a fourth resistor (R4) which can be electrically connected or not electrically connected between the intermediate potential (Vmid) and the low potential (BAT-) of the battery (BAT) by means of said switching device (SW1, SW2), the intermediate potential (Vmid) being intended to be electrically connected to a high-voltage ground terminal (GND) of the vehicle, the vehicle defining a first configuration capacitor (CyP) and a first parasitic resistor (RIP) connected in parallel to each other between the intermediate potential (Vmid) and the high potential (BAT+), the vehicle defining a second configuration capacitor (CyM) and a second parasitic resistor (RIM) connected in parallel to each other between the intermediate potential (Vmid) and the low potential (BAT-), the method comprising the following successive steps: (a) using the switching device (SW1, SW2), so that the third resistor (R3) is not electrically connected between the intermediate potential (Vmid) and the high potential (BAT+) of the battery (BAT), and so that the fourth resistor (R4) is not electrically connected between the intermediate potential (Vmid) and the low potential (BAT-) of the battery (BAT); (b) measuring an initial value (Vinit) of the intermediate voltage corresponding to the potential difference between the intermediate potential (Vmid) and the high-voltage ground terminal (GND) of the vehicle, if the initial value (Vinit) of the intermediate voltage is less than or equal to half the difference between the high potential (BAT+) and the low potential (BAT-) of the battery (BAT), the subsequent steps of the method are carried out according to a first case, otherwise, the subsequent steps of the method are carried out according to a second case; (c) in the first case, using the switching device (SW1, SW2), so that the third resistor (R3) is electrically connected between the intermediate potential (Vmid) and the high potential (BAT+) of the battery (BAT), and so that the fourth resistor (R4) is not electrically connected between the intermediate potential (Vmid) and the low potential (BAT-) of the battery (BAT); In this second case, using the switching means (SW1, SW2) such that the third resistor (R3) is not electrically connected between the intermediate potential (Vmid) and the high potential (BAT+) of the battery (BAT) and such that the fourth resistor (R4) is electrically connected between the intermediate potential (Vmid) and the low potential (BAT-) of the battery (BAT); (d) performing a first plurality of measurements (Vmid1) of a difference between the intermediate potential (Vmid) and a high voltage ground (GND) of the vehicle, said difference corresponding to an intermediate voltage, said first plurality of measurements (Vmid1) being spaced in time within a first time interval and comprising a measurement of the intermediate voltage at an upper limit of the first time interval; (e) deriving a first stable value (Vstab1) of the intermediate voltage from the first plurality of measurements (Vmid1); (f) using the switching means (SW1, SW2) such that the third resistor (R3) is not electrically connected between the intermediate potential (Vmid) and the high potential (BAT+) of the battery (BAT) and such that the fourth resistor (R4) is not electrically connected between the intermediate potential (Vmid) and the low potential (BAT-) of the battery (BAT) by the switching means (SW1, SW2); (g) performing a second plurality of measurements (Vmid2) of the intermediate voltage, said second plurality of measurements (Vmid2) being spaced in time within a second time interval and comprising a measurement of the intermediate voltage at an upper limit of the second time interval; (h) deriving a second stable value (Vstab2) of the intermediate voltage from the second plurality of measurements (Vmid2); (i) deriving values of the first parasitic resistor (RIP) and of the second parasitic resistor (RIM) by calculation using said first stable value and said second stable value of the intermediate voltage; and (j) deriving a leakage current at the terminals of the first parasitic resistor (RIP) and of the second parasitic resistor (RIM) by calculation.

2. The method of the preceding claim, wherein, If the difference between the measurement of the intermediate voltage at the upper limit of the first time interval and the preceding one of the first plurality of measurements (Vmid1) of the intermediate voltage is greater than a first threshold voltage, step (e) comprises the following sub-steps: (e1) performing a first extrapolation of the first plurality of measurements (Vmid1) of the intermediate voltage using a first extrapolation function, which, in the second case, is a decreasing exponential function representative of the discharge of the first and second configuration capacitors (CyP, CyM) of the vehicle and which, in the first case, is an increasing exponential function representative of the charge of the first and second configuration capacitors (CyP, CyM) of the vehicle; (e2) deriving the first stable value (Vstab1) of the intermediate voltage by calculation; Otherwise, the first stable value (Vstab1) of the intermediate voltage is equal to the measurement of the intermediate voltage at the upper limit of the first time interval.

3. The method of the preceding claim, wherein, The first extrapolation function is defined by the following formula: where E is a voltage constant, τ is a time constant, and V0 is the value of the intermediate voltage at the beginning of step (d).

4. The method of the preceding claim, wherein, The extrapolation in step (el) comprises the following sub-steps: (el-a) determining the time constant τ by a convergence loop; and (el-b) deriving the voltage constant E.

5. The method of one of the preceding claims, wherein, If the difference between the measurement of the intermediate voltage at the upper limit of the second time interval and the preceding one of the second plurality of measurements of the intermediate voltage (Vmid2) is greater than a second threshold voltage, then step (h) comprises the following sub-steps: (h1) performing a second extrapolation on the second plurality of measurements of the intermediate voltage (Vmid2) using a second extrapolation function, which, in the second case, is an increasing exponential function representative of the charging of the first and second construction capacitors (CyP, CyM) of the vehicle, and, in the first case, is a decreasing exponential function representative of the discharging of the first and second construction capacitors (CyP, CyM) of the vehicle; (h2) deriving the second stable value of the intermediate voltage (Vstab2) by calculation; Otherwise, the second stable value of the intermediate voltage (Vstab2) is equal to the measurement of the intermediate voltage at the upper limit of the second time interval.

6. The method of the preceding claim, wherein, The second extrapolation function is defined by the following formula: where E' is a voltage constant, τ' is a time constant, and V0' is the value of the intermediate voltage at the beginning of step (g).

7. The method of the preceding claim, wherein, The extrapolation in step (h1) comprises the following sub-steps: (h1-a) determining the time constant τ' by a convergence loop; and (h1-b) deriving the voltage constant E'.

8. The method of one of claims 2 to 7, wherein The first and / or second threshold voltage (Vseuil1, Vseuil2) is between 1 mV and 20 mV.

9. A computer comprising a processor and a memory, the processor being able to access the memory to read the steps stored in the memory, the computer being characterized in that it is configured to perform each of the steps of the method according to one of the preceding claims.

10. A motor vehicle equipped with a battery (BAT) and a computer according to the preceding claim.

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