Circuit and Method for Battery Leakage Detection

Patent metadata

Field	Value
Publication number	US-2016200209-A1
Application number	US-201514595478-A
Country	US
Kind code	A1
Filing date	Jan 13, 2015
Priority date	Jan 13, 2015
Publication date	Jul 14, 2016
Grant date	—

Abstract

A battery management system includes a switching element configured to selectively couple a resistive network in parallel with a capacitor that couples a voltage bus and a ground reference. A controller is programmed to, in response to activating the switching element for a predetermined time, output a diagnostic according to a leakage resistance that is based on a time associated with a predetermined change in a voltage across the capacitor. A time constant is derived from the voltage response and the leakage resistance is derived from the time constant.

First claim

1 . A vehicle comprising:
a capacitor connected between a voltage bus and a chassis of the vehicle; and at least one controller programmed to, in response to activating a switching element to couple a resistive network in parallel with the capacitor for a predetermined time, output a diagnostic according to a leakage resistance estimate that is based on a time associated with a predetermined change in a voltage across the capacitor.

2 . The vehicle of claim 1 wherein the predetermined change is defined by a product of (1−1/e), where e is Euler's number, and a magnitude of a difference between an initial voltage across the capacitor and a final voltage across the capacitor.

3 . The vehicle of claim 2 wherein the initial voltage is the voltage at a time immediately after activating the switching element.

4 . The vehicle of claim 2 wherein the final voltage is the voltage at the predetermined time, and wherein the predetermined time is such that a rate of change of the voltage with respect to time is approximately zero at the predetermined time.

5 . The vehicle of claim 1 wherein the leakage resistance estimate is further based on a capacitance of the capacitor.

6 . The vehicle of claim 1 wherein the resistive network includes a current limiting resistor and a voltage measurement resistor connected in series, and wherein the voltage across the capacitor is proportional to a voltage across the voltage measurement resistor.

7 . The vehicle of claim 1 wherein the leakage resistance estimate is a parallel combination of a first leakage resistance between a positive terminal of the voltage bus and the chassis of the vehicle and a second leakage resistance between a negative terminal of the voltage bus and the chassis of the vehicle.

8 . The vehicle of claim 1 wherein the at least one controller is further programmed to output the diagnostic when the leakage resistance estimate is less than a predetermined resistance.

9 . A battery management system comprising:
a switching element configured to selectively couple a resistive network in parallel with a capacitor that couples a voltage bus and a ground reference; and at least one controller programmed to, in response to the selective coupling exceeding a predetermined time, output a diagnostic according to a leakage resistance estimate that is based on a time associated with a predetermined change in a voltage across the capacitor.

10 . The battery management system of claim 9 wherein the resistive network includes a current limiting resistor and a voltage measurement resistor connected in series, wherein the voltage across the capacitor is proportional to a voltage across the voltage measurement resistor.

11 . The battery management system of claim 9 wherein the predetermined change is defined by a product of (1−1/e), where e is Euler's number, and a magnitude of a difference between an initial voltage across the capacitor and a final voltage across the capacitor.

12 . The battery management system of claim 11 wherein the initial voltage is the voltage at a time immediately after the coupling.

13 . The battery management system of claim 11 wherein the final voltage is the voltage at the predetermined time, and wherein the predetermined time is such that a rate of change of the voltage with respect to time is approximately zero at the predetermined time.

14 . The battery management system of claim 9 wherein the leakage resistance estimate is further based on a capacitance of the capacitor.

15 . The battery management system of claim 9 wherein the at least one controller is further programmed to activate the switching element in response to a signal indicative of an end of an ignition cycle.

16 . The battery management system of claim 9 wherein the leakage resistance estimate is based on a parallel combination of a first leakage resistance between a positive terminal of the voltage bus and the ground reference and a second leakage resistance between a negative terminal of the voltage bus and the ground reference.

17 . The battery management system of claim 9 wherein the at least one controller is further programmed to output the diagnostic when the leakage resistance estimate is less than a predetermined resistance.

18 . A method comprising:
coupling, by a controller, a resistor network in parallel with a capacitor that couples a voltage bus and a chassis of a vehicle for a predetermined time; and outputting, by the controller, a leakage resistance value based on a time for a voltage across the capacitor to change by a predetermined amount.

19 . The method of claim 18 wherein the predetermined amount is defined by a product of (1−1/e), where e is Euler's number, and a magnitude of a difference between an initial voltage and a final voltage.

20 . The method of claim 19 wherein the final voltage is less than the initial voltage.

Assignees

• Ford Global Tech Llc

Inventors

• Tabatowski-Bush Benjamin A
• Bilezikjian John Peter

Classifications

• B60L2240/549

  Current · CPC title

• Y02T10/7072

  Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors · CPC title

• Y02T10/70

  Energy storage systems for electromobility, e.g. batteries · CPC title

• G01R31/382

  Arrangements for monitoring battery or accumulator variables, e.g. SoC · CPC title

• G01R27/14

  Measuring resistance by measuring current or voltage obtained from a reference source (G01R27/16, G01R27/20, G01R27/22 take precedence) · CPC title