Method and apparatus for determining battery performance at one temperature when battery is at another temperature

Claim 3

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.

Claim 4

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.

Claim 5

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.

Claim 6

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.

Claim 7

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.

Claim 8

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.

Claim 9

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.

Claim 10

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.

Claim 11

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.