Battery tester using internal resistance to measure a condition of a battery

• US 6,384,608 B1
• Filed: 03/13/2001
• Issued: 05/07/2002
• Est. Priority Date: 03/13/2001
• Status: Expired due to Fees

• Current Assignee: SPX Development Corporation
• Original Assignee: Actron Manufacturing Incorporated (SPX Corporation)
• Inventors: Namaky, Hamid
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/805,269
• Time in Patent Office: 420 Days
• Field of Search: 324/425, 324/426, 324/429, 324/430, 324/433, 320/132, 320/DIG.21
• US Class Current: 324/430
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

A method of measuring a condition of a battery is disclosed comprising the steps of: inducing an AC signal across the terminals of the battery by applying an AC current load thereto; measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery'"'"'s internal resistance; applying the first voltage potential signal across a voltage divider network calibrated in accordance with a predetermined battery rating scale to render a multiplicity of second voltage potential signals at a corresponding multiplicity of taps along the voltage divider network, values of the second voltage potential signals being representative of the calibrated battery rating scale; and sequentially selecting the second voltage potential signals along the taps for comparison with a threshold voltage potential signal to determine a measure of the condition of the battery. An electronic battery tester is also disclosed including a voltage divider network coupled across the first voltage potential signal and calibrated in accordance with a predetermined battery rating scale to create from the first voltage potential signal a multiplicity of second voltage potential signals at a corresponding multiplicity of taps along the voltage divider network, and a rotary switch for selecting the second voltage potential signal of the multiplicity of second voltage potential signals along the taps based on a predetermined battery rating of the battery under test for comparison with a threshold voltage potential signal to determine a condition of the battery.

Claims

1. Method of measuring a condition of a battery using a measure of the internal resistance thereof comprising the steps of:

inducing an AC signal across the terminals of the battery by applying an AC current load thereto;

measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery'"'"'s internal resistance;

applying the first voltage potential signal across a voltage divider network calibrated in accordance with a predetermined battery rating scale to render a multiplicity of second voltage potential signals at a corresponding multiplicity of taps along the voltage divider network, values of said second voltage potential signals being representative of the calibrated battery rating scale; and

sequentially selecting the second voltage potential signals along the taps for comparison with a threshold voltage potential signal to determine a measure of the condition of the battery.

2. The method of claim 1 wherein the voltage divider network is calibrated in accordance with the battery manufacture'"'"'s “

cold cranking amperes”

(CCAs) rating which corresponds with an original internal resistance of the battery; and

wherein the selected second voltage potential signals are compared with a threshold voltage potential signal representative of an internal resistance measurement corresponding to a battery of a predetermined CCA rating.

3. The method of claim 2 wherein the threshold voltage potential signal used for comparison is representative of an internal resistance measurement corresponding to a battery of the highest CCA rating of the scale of CCA ratings.

4. The method of claim 1 wherein the step of sequentially selecting includes the steps of:

connecting the multiplicity of taps of the voltage divider network to corresponding throw positions of a single pole multiple throw rotary switch;

rotating the switch sequentially through its throw positions to render the second voltage potential signals at the pole position;

comparing the second voltage potential signal at the pole position of the rotary switch with the threshold voltage potential signal in a comparator circuit; and

driving an indicator by the comparator circuit based on the result of said comparison.

5. The method of claim 4 including the steps of:

marking the throw positions of the rotary switch with indicia of battery ratings corresponding to the battery rating scale of the calibration;

driving said indicator in first and second states based on the comparison results of the selected second voltage potential signal and the threshold voltage potential signal; and

determining the measure of the battery condition based on the observation of the state of the indicator and the indicia of the throw position of the rotary switch.

6. The method of claim 5 including the steps of:

driving said indicator from the first state to the second state when the switch is rotated to a throw position in which the corresponding second voltage potential signal exceeds the threshold voltage potential signal; and

determining the measure of the battery condition based on the observation of the indicator being switched to the second state and the indicia of the throw position of the rotary switch rendering said change in indicator state.

7. The method of claim 5 wherein the rotary switch is manually rotated sequentially through its throw positions.

8. The method of claim 5 wherein the state of the indicator is visually observed.

9. The method of claim 5 wherein the indicia of the throw position rendering the change in indicator state is visually observed.

10. The method of claim 1 wherein the measure of the condition of the battery is representative of the amount of power the battery is capable of delivering.

11. An electronic battery tester comprising:

a first circuit for applying an AC current load to the battery under test to induce an AC signal across the terminals of the battery;

a second circuit for measuring the induced AC signal and converting it to a first voltage potential signal which is a measure of the battery'"'"'s internal resistance;

a voltage divider network coupled across the first voltage potential signal, said voltage divider network calibrated in accordance with a predetermined battery rating scale to create from the first voltage potential signal a multiplicity of second voltage potential signals at a corresponding multiplicity of taps along the voltage divider network, values of said second voltage potential signals being representative of the calibrated battery rating scale; and

means for selecting the second voltage potential signal of the multiplicity of second voltage potential signals along the taps based on a predetermined battery rating of the battery under test for comparison with a threshold voltage potential signal to determine a condition of the battery.

12. The batter tester of claim 11 wherein the voltage divider network is calibrated in accordance with the battery manufacture'"'"'s “

cold cranking amperes”

(CCAs) rating which corresponds with an original internal resistance of the battery; and

including a third circuit for generating the threshold voltage potential signal representative of an internal resistance measurement corresponding to a battery of a predetermined CCA rating.

13. The battery tester of claim 12 wherein the threshold voltage potential signal is generated as being representative of an internal resistance measurement corresponding to a battery of the highest CCA rating of the scale of CCA ratings.

14. The battery tester of claim 11 wherein the selecting means includes:

a single pole multiple throw rotary switch wherein the multiplicity of taps of the voltage divider network are connected to corresponding throw positions of the single pole multiple throw rotary switch;

a comparator circuit wherein the pole position of the rotary switch is connected to one input thereof and the threshold voltage potential signal is connected to another input thereof, the second voltage potential signal at the pole position of the rotary switch and the threshold voltage potential signal being compared in the comparator circuit; and

an indicator driven by the comparator circuit based on the result of said comparison to indicate the condition of the battery.

15. The battery tester of claim 14 wherein the throw positions of the rotary switch are marked with indicia of battery ratings corresponding to the battery rating scale of the calibration.

16. The battery tester of claim 14 wherein the indicator is driven by the comparator circuit into pass and replace states based on the comparison results of the second voltage potential signal selected by the rotary switch and the threshold voltage potential signal to indicate the condition of the battery.

17. The battery tester of claim 11 wherein the voltage divider network is calibrated in equal increments of the industry standard battery rating scale.

18. The batter tester of claim 11 wherein the voltage divider network is calibrated in accordance with the battery manufacture'"'"'s “

cold cranking amperes”

(CCAs) rating which corresponds with an original internal resistance of the battery and divided into equal increments representative of CCA increments.

19. The battery tester of claim 18 wherein the voltage divider network is calibrated over a range of hundreds of CCAs.

20. The battery tester of claim 11 wherein the voltage divider network comprises a resistance divider network.