METHOD AND APPARATUS FOR DETERMINING BATTERY PERFORMANCE AT ONE TEMPERATURE WHEN BATTERY IS AT ANOTHER TEMPERATURE

• US 3,876,931 A
• Filed: 12/26/1973
• Issued: 04/08/1975
• Est. Priority Date: 01/14/1972
• Status: Expired due to Term

• Current Assignee: James B. Godshalk
• Original Assignee: James B. Godshalk
• Inventors: Godshalk, James B.
• Primary Examiner(s): Corcoran, Robert J.
• Application Number:
  US05/428,016
• Time in Patent Office: 468 Days
• Field of Search: 324/29.5 340/249 320/48
• US Class Current: 324/429
• CPC Class Codes: G01R 31/005 Testing of electric installations on transport means
• CPC Class Codes: G01R 31/374 with means for correcting the measurement for temperature or ageing
• CPC Class Codes: G01R 31/379 for lead-acid batteries
• 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: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Lead-acid storage batteries of various load ratings are tested with at least service station accuracy by discharging the battery at a known temperature and a single predetermined load, irrespective of the actual load rating of the battery, to provide an electrical quantity representative of the terminal voltage of the battery at that temperature and load, and converting that electrical quantity into an observable indication representing the terminal voltage which the battery would exhibit if discharged at its rated load at a predetermined different temperature. The invention is especially useful for testing automotive batteries and has the advantage of not requiring the capability of matching an actual load to the rating of the particular battery under test.

Claims

1. The method for testing a lead-acid storage battery, with accuracies at least adequate for automotive service station battery testing purposes, to provide an observable indication of whether the battery is capable of delivering a stated cranking current at a predetermined temperature when the battery is in fact at a different temperature, comprising discharging the battery through a known load resistor at a current different than the stated cranking current for a short period of time;

deriving from the battery while it is still being so discharged a first electrical quantity representative of the actual terminal voltage of the battery at the end of said period of time;

sensing the actual temperature of the battery;

developing a second electrical quantity representative of the difference between said actual temperature and said predetermined temperature;

developing a third electrical quantity representative of the difference between said stated cranking current and said current obtained by discharging the battery through said known load resistor; and

converting said first electrical quantity into an observable indication which differs from that which would accurately indicate the terminal voltage of the battery by amounts representative of the algebraic combination of said second and third electrical quantities.

2. In an apparatus for testing a lead-acid storage battery to determine, with accuracies at least adequate for automotive services station battery testing purposes, whether the battery is capable of delivering a stated cranking current at a predetermined temperature when the battery is in fact at a different temperature, the combination of discharge circuit means comprising means for discharging the battery for a short period of time at a known rate different from the stated cranking current;

and test circuit means connectable to the battery and comprising means for deriving from the battery a first electrical quantity representative of the actual terminal voltage of the battery while still being discharged at said known rate at the end of said short period of time, thermally responsive means for sensing the actual temperature of the battery, electro-responsive indicating means connected to said first electrical quantity to provide an observable indication of battery condition, and calibrating means connected to said indicating means and comprising first means for modifying the indication displayed by said indicating means in response to said thermally responsive means, and second means for further modifying said indication in accordance with the difference between said known discharge rate and the stated cranking current.

3. The combination defined in claim 2, wherein said second means of said calibrating means comprises adjustable resistance means, and manually operable means for selectively adjusting said resistance means in accordance with the cranking ampere rating of the battery to be tested.

4. The combination defined in claim 3, wherein said adjustable resistance means comprises a plurality of resistors of different resistance values corresponding to known cranking ampere ratings of batteries to be tested;

and said manually operable means comprises a selector switch and cooperating indicia representative of said cranking ampere ratings.

5. The combination defined in claim 3, wherein said adjustable resistance means comprises a potentiometer having a plurality of taps, and a plurality of resistors of different resistance values corresponding to known cranking ampere ratings of batteries to be tested, said resistors each being connected between a different pair of said taps;

said manually operable means comprising means for adjusting said potentiometer, and cooperating indicia representative of said cranking ampere ratings.

6. The combination defined in claim 2, wherein said indicating means is a voltmeter;

said first means of said calibrating means comprises a thermally responsive resistor connected in parallel with said voltmeter; and

said second means of said calibrating means comprises adjustable resistance means connected in series with said voltmeter.

7. The combination defined in claim 6, wherein said first means of said calibrating means comprises a plurality of resistors, and means including a selector switch for connecting selected ones of said resistors in series with said thermally responsive resistor;

and said second means of said calibrating means comprises adjustable resistance means, and manually operable means for adjusting said adjustable resistance means in accordance with the cranking ampere ratings of batteries to be tested;

said selector switch being ganged with said manually operable means to select resistors of decreasing value as said manually operable means is operated to adjust said adjustable resistance means to values for batteries of lower cranking ampere ratings.

8. In an apparatus for testing lead-acid storage batteries, the combination of temperature responsive means for sensing the temperature of the battery;

first means for deriving from the battery an electrical quantity representative of the terminal voltage of the battery at a known load;

second means for generating a first calibration signal representative of the difference between a predetermined temperature and the temperature sensed by said temperature responsive means;

third means for generating a second calibration signal representative of the difference between a predetermined load and said known load; and

fourth means connected to said first, second and third means for combining said first and second calibration signals and modifying said electrical quantity in accordance with the combined signal to generate a simulated indication of the performance of the battery if discharged through said predetermined load at said predetermined temperature.