EP0102428B1

EP0102428B1 - Method and system for testing and sorting batteries

Info

Publication number: EP0102428B1
Application number: EP82304662A
Authority: EP
Inventors: Sheldon A. Buckler; Jeffrey B. Burns; Alfredo G. Kniazzeh; Paul A. Plesse; David J. Sullivan
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1982-09-02
Filing date: 1982-09-06
Publication date: 1987-03-11
Also published as: JPH0366625B2; EP0102428A1; JPS5961785A; CA1187939A; DE3275634D1

Description

This invention relates to battery testing and sorting. More particularly, it concerns a method for testing individual batteries for anticipated shelf-life and culling those individual batteries which are not acceptable.
In the merchandising of most battery powered appliances and the like, it is accepted practice to separately package and retail the batteries required for use of the appliance. Among the reasons for this practice are a different manufacturing origin of the appliance and the batteries, different storing, shipping and handling requirements of the appliance and battery, and possible damage to the appliance by defective batteries. Most germane to these reasons and others for separate merchandising of batteries is that the electric charge stored by substantially all batteries deteriorates in time, without use, so that the batteries exhibit a shelf-life of limited duration whereas the appliance with which they are used will last indefinitely without use if proper storage conditions are met.
An exception to the practice of separately merchandising batteries and related goods is exemplified by the merchandising of photographic film for use in electrically powered cameras. Film packs for use in instant cameras of the type available from Polaroid Corporation, Cambridge, Massachusetts under the trade designation "POLAROID SX-70 LAND FILM", for example, include a sheet-like battery arranged to be engaged by camera supported contacts upon insertion of the film pack into the camera, thus assuring that the camera powering battery is replaced after exposure and motorized processing of the limited number of film units supplied for each film pack.
The sheet-like batteries used in such film packs employ materials selected to require storage conditions which correspond ideally with those of the photographic film units included in the film pack. Also, the construction of such batteries has been developed to a point where the open circuit voltage decay rate is exeptionally low. In this latter respect, the disclosure of US-A-4 028 479 is illustrative in that it describes such a battery and includes graphs showing the results of periodically testing open-circuit and closed-circuit voltages of batteries over an extended period of storage time. In spite of the complementary storage condition requirements and construction of this type of battery, however, the shelf-life characteristics of a given battery are difficult to discern at the time of battery production and often will have a longevity falling below that of the corresponding shelf-life of the film units with which they are packaged.
To minimize film wastage as a result of abnormally short battery shelf-life, current procedures used in the manufacture and testing of such batteries involve a batch or production run sampling technique by which the anticipated shelf-life of each batch or run of batteries is ascertained before any of the individual batteries in such a batch or run are assembled and packaged with film units in a film pack. Specifically, a sampling of batteries manufactured in each production run or batch is tested immediately upon completion for the voltage of the stored electrical charge, and the voltage of the sample is recorded. Samples are then stored for a period of time, retested for voltage charge, the retested voltage compared with the original test voltage and the voltage decay rate computed to provide a measure of shelf-life. If the shelf-life of the sampling of any batch indicates a shelf-life shorter than is acceptable, the entire batch or production run corresponding to the sampling is discarded to ensure that only those batches or production runs of batteries exhibiting an acceptable shelf-life will be used.
While the present procedures have demonstrated statistical soundness, it has been found that the shelf-life of individual batteries in a given batch or production run may vary considerably. As a result, many of the batteries discarded as a result of the batch or production run sampling technique are found to exhibit an acceptable shelf-life. Accordingly, current procedures are in need of improvement from the standpoint of reducing battery wastage.
An example of sorting individual devices in accordance with recorded test data is found in US-A-3 583 561; this discloses the testing of a wafer of semiconductor devices to determine the testing of a wafer of semiconductor devices to determine the quality of each device, the test data with respect to each device being photographically recorded in positions on a record medium related to the positions of the devices on the wafer. This is followed by the subsequent synchronised reading of the recorded data and sorting of the devices separated from the wafer.
US-A-4081 743 discloses a cell discharge voltage monitor circuit for cell capacity grading. The cells are individually sorted in accordance with the time for discharging a charged cell to a predetermined cell voltage indicative of total discharge of the capacity of the cell.
The present invention consists in a method of testing and sorting a production run of electric batteries in which individual batteries of the production run are tested and in which after a period of storage the same batteries are retested to enable a voltage decay rate to be obtained, characterised by the steps of:

(a) testing each battery of the production run to obtain a first voltage value for each battery;
(b) forming on each such battery machine-readable indicia corresponding to the first voltage value and to the time of testing;
(c) after the said period of storage, retesting each of the individual batteries to obtain a second voltage value for each battery;
(d) machine-reading the voltage and time indicia and computing, in accordance with the elapsed period of time and the difference between the first and second voltage values of each battery, the rate of voltage decay for each battery; and
(e) sorting the batteries in accordance with the computed rate of decay to separate those individual batteries of the production run having a rate of voltage decay exceeding an acceptable value from those batteries of the same production run having a rate of voltage decay equal to or lower than the acceptable value.

If desired, a preliminary sorting operation may be carried out after the first voltage value has been obtained, to separate those individual batteries having a first voltage value outside an acceptable range of first values from those batteries for which the first voltage value lies within the acceptable range.
Preferably, the machine-readable indicia are formed on the battery by a non-contact printer, for example an ink jet printer. A method for controlling a row of ink jets to produce printed bars on a recording surface is disclosed in US-A-3 787 881.
The invention also comprises a system for sorting a production run of electric batteries. The invention is particularly advantageous in the production of batteries designed to be packaged and merchandised with related goods of predictable shelf-life, although it can be used with batteries of other kinds.
In order that the invention may be better understood, an example of a method and system embodying the invention will now be described with reference to the accompanying drawings, in which:-

Figure 1 is a schematic view illustrating the system of the present invention;
Figure 2 is a plan view of a battery for which the sorting method and system of the present invention is particularly intended; and
Figure 3 is a perspective view illustrating in schematic form the organization of a battery testing station incorporated in the system of the present invention.

Although it will be apparent from the detailed description to follow that the testing system and method of the present invention is applicable broadly to all type of batteries, the embodiment to be described is particularly intended for production run testing and sorting of sheet like batteries typified by the disclosure of the aforementioned US Patent No. 4,028,479. An example of such a battery is illustrated most clearly in Figure 2 and is generally designated in the drawings by the reference numeral 10. A most salient feature of the battery 10 from the standpoint of accommodation to the system and method of the present invention, is that in addition to its flat rectangular sheet-like configuration, the terminals 12 and 14 thereof are presented through openings 16 and 18 in an exterior paper or cardboard layer 20. The outer surface 22 of the layer 20, coupled with the uniformly rectangular peripheral configuration or shape of the battery and of the layer 20, facilitates the reception of printed indicia 24 to be described in more detail below, in a precisely registered position relative to the terminals 12 and 14 and to the peripheral edges of the battery.
The batteries 10 are mass produced in batches or runs of several hundred or more individual batteries. The manufacture or assembly of each battery is completed by application of the cardboard layer 20 to the internal cell structure and by a peripheral heat sealing or bonding of the layer 20 to an insulative layer or covering (not shown) on the opposite side of the battery from the layer 20. In accordance with the present invention and as shown in Fig. 1, each battery 10 is passed upon manufacturing completion by an appropriate dispenser or conveyor (not shown) to a first testing station 26. At the station 26, a value of the open circuit voltage of each battery is obtained. As shown in Fig. 3, this voltage is detected by a meter 28 having a pair of contact probes or brushes 30 and 32 adapted to engage both terminals 12 and 14 of each battery. The meter 28 may be any of several known types of volt meters capable of generating a signal corresponding to the open circuit voltage across the probes 30 and 32.
Located at the first station with the meter 28 is a recording device or printer 34. The printer 34 is responsive to and controlled by the meter 28 and is operative to form the printed indicia 24 directly on the outer surface 22 of the cardboard battery layer 20. As shown in Fig. 1, the printer 34 is preferably spaced from the battery 10 and is a non-contact printer, for example, an inkjet printer which essentially exerts no force, or quite negligible force, on the battery since only the ink contacts the battery surface. The non-contact printing eliminates the possibility of battery damage due to printing and also may easily accommodate a wide variety of battery configurations such as, for example, cylindrical. While other non-contact printers such as, for example, a laser type will also be applicable, the ink jet printer is relatively maintenance-free and provides excellent indicia.
As most clearly illustrated in Fig. 2, the indicia is preferably provided as a bar/half bar code in the form of a series of variable height lines representing a binary or other type encoding capable of representing the precise voltage detected by the meter 28 in a form which may be sensed or read by machine. Other forms of indicia may also be utilized, and while encoded indicia rather than alphanumerical is preferred for reliability, the latter could also be employed. Hence, the meter 28 and printer 34 provide testing and marking means for providing a first value of battery energy and for placing the measured value on each battery in machine readable form. Further, as noted below, these means also preferably determine and record the time of measurement as well as other manufacturing information. Consequently, the indicia 24 include machine readable information representative of the time at which the voltage for a particular battery 10 was measured by the meter 28. As will be appreciated by those skilled in the art, an encoded indicia of the type illustrated may include information relative to month, day of the month, hour and minute of each day.
After passing the first testing station 26, the batteries 10 may be advanced to a first sorting station 36 operated under the control of the first testing station 26 to cull those batteries for which the initial voltage detected at the station 26 was below a predetermined acceptable limit. Each acceptable battery passing the station 36 is retained and passed to a storage station 38.
In practice, the storage station 38 may take a variety of specific forms such as a plurality of magazine-like receptacles for warehouse storage, or in-line storage bins in which the batteries 10 may be stored for a period of time, or delay period, determined in accordance with such factors as the anticipated voltage decay rate of the batteries as well as the sensitivity of the metering equipment used in the system for detecting the open circuit voltage for each battery. In other words, it is necessary only that the batteries remain at the storage station 38 for a period of time adequate to undergo a discernible voltage decay from the voltage detected at the first testing station 26. However, since the purpose is to extrapolate or predict from a measured decay the subsequent time, many months or years later, at which the battery energy will fall below a given value, a reasonable decay period of several weeks is preferred.
After storage, the batteries are again tested by passing them to a second testing station 40. As suggested by the legend in Fig. 1 of the drawings, at the station 40 the open circuit voltage of each battery 10 is again detected, the voltage recorded at the first testing station and represented by the indicia 24 on each battery 10 is read, the two voltage readings are compared and the voltage decay rate for each battery computed. Hence the station 40 provides testing and reading means for providing or obtaining a second value for each battery after the time interval, for reading the previously printed indicia.
As above-indicated, the indicia 24 carries information as to the time at which the first voltage reading was taken at the station 26. The availability of this information on each battery 10 at the second testing station 40 provides data by which the voltage decay rate for each battery may be directly computed. Station 40 reads the original voltage value and original test time and compares the two voltage values and also the first and second test times to determine the specific length of time the batteries 10 were retained between tests, and computes the rate or decay of the battery under test.
After passing the second sorting station 40, the batteries are passed through a second sorting station 42, which is responsive to and controlled by the test station 40 and operative to reject those individual batteries 10 for which the computed decay rate is in excess of a pre-established or acceptable decay rate. Thus, only those batteries which pass from the sorting station 42 to a packaging station (not shown) will have a tested decay rate corresponding to an acceptable battery shelf-life.

Claims

1. A method of testing and sorting a production run of electric batteries in which individual batteries of the production run are tested and in which after a period of storage the same batteries are retested to enable a voltage decay rate to be obtained, characterised by the steps of:

(a) testing (28) each battery of the production run to obtain a first voltage value for each battery (10);

(b) forming (34) on each such battery machine-readable indicia (24) corresponding to the first voltage value and to the time of testing;

(c) after the said period of storage, retesting (40) each of the individual batteries to obtain a second voltage value for each battery;

(d) machine-reading (40) the voltage and time indicia and computing, in accordance with the elapsed period of time and the difference between the first and second voltage values of each battery, the rate of voltage decay for each battery; and

(e) sorting (42) the batteries in accordance with the computed rate of decay to separate those individual batteries of the production run having a rate of voltage decay exceeding an acceptable value from those batteries of the same production run having a rate of voltage decay equal to or lower than the acceptable value.

2. A method in accordance with claim 1, further comprising assembling and packaging acceptable batteries with related goods to be merchandised with the individual batteries of such a production run.

3. A method in accordance with claim 1 or 2, wherein the batteries are sheet-like, rectangular electric batteries (Figure 2) having terminals (12, 14) presented through apertures in the exterior layer (20) receptive to placement of indicia by printing, and wherein each battery is tested by passing contact members (30, 32) through the apertures in the exterior layer and machine-readable indicia are placed on the exterior layer of each such battery corresponding to the first voltage value and the time of testing.

4. A method according to any one of claims 1 to 3, further comprising the step (36) of sorting the batteries after completion of step (a) in accordance with the first voltage value to separate those individual batteries having a first voltage value above or below an acceptable range of first values from those batteries having a first voltage value within the acceptable range.

5. A method according to any one of the preceding claims, wherein the step of forming machine-readable indicia includes forming the indicia by a non-contact printer or with only negligible force applied to the battery.

6. A method according to claim 5, wherein the step of forming the machine-readable indicia is provided by directing ink to the battery to form the indicxia by means of an ink jet printer.

7. A system for sorting a production run of electric batteries, comprising testing means for obtaining a first voltage value for individual batteries (10) of the production run and for obtaining a second voltage value for the same batteries (10) after a period of storage to enable a voltage decay rate to be derived, characterised in that the testing means obtains the said voltage values for each battery (10) of the production run and in that the system includes:

marking means (34) for placing machine-readable indicia (24) on each battery (10) of the production run corresponding to the first voltage value and to the time of obtaining the said first value;

reading means (40) operative when the second voltage value has been obtained after the storage period for machine-reading the voltage and time indicia from each tested battery (10);

means for computing, in accordance with the elapsed period of time and the difference between the said first and second voltage values of each battery (10), the rate of voltage decay for each battery (10); and

means (42) for sorting the batteries (10) individually in accordance with the computed rate of decay to separate those individual batteries (10) of the production run having a rate of voltage decay exceeding an acceptable value from those batteries (10) of the same production run having a rate of voltage decay equal to or lower than the acceptable value.

8. A system according to claim 7, wherein the marking means is a non-contact printer (34) spaced from the batteries (10).

9. A system according to claim 7 or 8, further including preliminary means (36), responsive to the first voltage value, for effecting a preliminary sorting of the batteries (10) in accordance with the obtained first voltage value.

10. A system according to claim 7, 8 or 9, wherein the testing means (28) for obtaining the first voltage value and the marking means (34) are juxtaposed at a single station (26).

11. A system according to any one of claims 7 to 10, wherein the testing means for obtaining the second voltage value and the reading means (40) are juxtaposed at a single station (40).

12. A system according to any one of claims 7 to 11, comprising means for individually packaging batteries (10) having an acceptable rate of voltage decay with related goods to be merchandised.