Resistance measurement for battery cells

• US 9,140,760 B2
• Filed: 02/15/2013
• Issued: 09/22/2015
• Est. Priority Date: 02/15/2012
• Status: Active Grant

• Current Assignee: Flextronics International Limited
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Covasala, Alexander
• Primary Examiner(s): Nguyen, Tung X
• Assistant Examiner(s): ALLGOOD, ALESA M
• Application Number:
  US13/768,951
• Publication Number:
  US 20130241568A1
• Time in Patent Office: 949 Days
• Field of Search: 324/429, 324/421, 324/525, 324/691, 324/430, 324/426
• US Class Current: 1/1
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G01R 31/64 Testing of capacitors

Abstract

A power supply is disclosed that is configured for installation in a motor vehicle. The power supply comprises an energy source and a system for accurately measuring the internal resistance of the energy source during the operation of the power supply, without a distortion that would normally result from discharge of the energy storage device.

Claims

1. A resistance measuring device for the load-independent measurement of the internal resistance (Ri) of an energy storage device, in particular in an electrical system of a motor vehicle, comprises:

an energy storage device coupled with an electrical system of a motor vehicle such that the energy storage device provides power to the electrical system along a power path from the energy storage device through the electrical system;

a measuring circuit coupled in parallel with the energy storage device outside of the power path and comprising a component, a switch and a current measuring resistor coupled together in series, wherein the measuring circuit is configured to generate a current pulse by switchably electrically coupling the current measuring resistor to the component via closing the switch; and

a measuring device coupled to positive and negative poles of the energy storage device and configured to measure a voltage drop (Δ

U) of the energy storage device between the positive pole and the negative pole and to measure a current difference (Δ

i) across the current measuring resistor, wherein the component comprises a passive energy storage element, in particular as a capacitor.

2. The resistance measuring device of claim 1, wherein the capacitor comprises an electrolytic capacitor.

3. The resistance measuring device of claim 1, wherein the length of the current pulse generated coupling the current measuring resistor to the component is determined from the total resistance of a circuit comprising the energy storage device, the component, the switch, and the current measuring resistor, and the capacitance of the component.

4. The resistance measuring device of claim 1, wherein the switch comprises a MOSFET.

5. The resistance measuring device of claim 1, wherein the measuring device further comprises a microprocessor configured to determine the internal resistance (Ri) of the energy storage device.

6. The resistance measuring device of claim 1, wherein the switch is positioned between the component and the current measuring resistor.

7. The resistance measuring device of claim 1, wherein the measurement of Ri is carried out independently of a load produced by the electrical system of the motor vehicle.

8. The resistance measuring device of claim 1, further comprising a discharge resistor coupled in parallel with the component.

9. A motor vehicle comprising:

an electrical system;

an energy storage device coupled with the electrical system such that the energy storage device provides power to the electrical system along a power path from the energy storage device through the electrical system; and

a measuring circuit coupled in parallel with the energy storage device outside of the power path, wherein the measuring circuit comprises a capacitor, a switch and a current measuring resistor coupled together in series and a discharge resistor coupled in parallel with the capacitor, wherein the measuring circuit is configured to generate a current pulse by switchably electrically coupling the current measuring resistor to the capacitor via closing the switch; and

a measuring device directly coupled to positive and negative poles of the energy storage device and configured to measure a voltage drop (Δ

U) of the energy storage device between the positive pole and the negative pole and to measure a current difference (Δ

i) across the current measuring resistor.

10. A power supply according to claim 9, wherein the energy storage device comprises at least one supercap capacitor.