MXPA97005573A - Condition tester for a battery - Google Patents

Abstract

A tester (10) for determining the condition of an electrochemical power source, e.g. a battery or main cell (30), is disclosed. The tester may comprise an electrolytic (coulometric) cell (20) connected in series to an auxiliary cell (25). The auxiliary cell (25) is a miniature electrochemical power cell. The electrolytic (coulometric) cell (20) may have no electromotice force of its own and may comprise an anode (47) and cathode (43) of the same material, desirably silver, with an electrolyte (45) contacting at least a portion of both the anode (47) and cathode (43). The tester (10) may be permanently connected in parallel to a main cell (30) being tested and is thin enough to be integratable into a label (58) for the main cell (30). As the main cell (30) discharges, the electrolytic cell anode (47) clears proportionally to the discharge of one of the electrodes of the main cell to provide a continuous visually discernible indication of the state of charge of the main cell (30).

Description

CONDITION TESTER FOR A BATTERY DESCRIPTION OF THE INVENTION This invention relates to a condition tester for determining the condition of a battery. More specifically, the invention relates to the condition of load testers (coulometric). Primary electrochemical cells are known which include devices for visually indicating the condition or condition of the cell. Known devices include chemical indicators that react with materials within the battery, chemical indicators located externally to the battery, elements embedded within an electrode and which become visible during discharge, and ter-chromic materials in thermal contact with a resist element. which is adapted to be connected through the battery. The coulometric devices can keep track of the coulombs of electric charge that pass through the electronic equipment with which these may be associated. Examples of coulometric devices that use an electrochemically induced change in the length of a mercury column to give visual indication of the amount of spent charge are described in U.S. Patent Nos. 3,045,178 REF: 25229 and 3,343,083. The coulometric devices have not been successfully applied to primary batteries. The present invention relates to a thin film electrolytic cell which functions as a coutro etro and gives a continuous visual indication of the state of charge of a main cell or battery being tested. The invention will be better understood with reference to the drawings, in which: Figure 1 is a circuit diagram showing the connection of the tester assembly of the invention to the main cell being tested.

Figure 2 is a perspective, sectional view of the tester assembly referred to in Figure 1.

Figure 2A shows a battery having a permanently connected tester, with the tester in a partial cross-sectional view enlarged.

Figure 3 is a circuit diagram showing an alternative mode, by which the coulometric cell is connected through a shunt resistor on the anode side of the main cell being tested.

Figure 3A is a partial perspective view showing the shunt resistor of Figure 3, which forms a portion of the anode side of a main cell being tested.

Figure 4 is a circuit diagram showing another embodiment, by which the coulometric cell is connected to a shunt resistor on the cathode side of the main cell.

Figure 4A is a partial exploded view of a mode showing the shunt resistor of Figure 4, which forms a portion of the cathode side of the main cell being tested.

Figure 5 is a plan view of an alternative embodiment of the coulometric cell.

Figure 6 is a cross-sectional view of the coulometric cell of Figure 5, taken through line 6-6.

The invention is directed to a condition indicator (tester) which is electrically connected to and visually displays the condition of an electrochemical energy source, for example, a battery. The condition indicator comprises a coulometric cell which is an electrolytic cell comprising an anode, a cathode, and an electrolyte in contact with at least one portion of the anode and the cathode. The electrolytic cell essentially does not have electromotive force (e .f.) By itself, and its anode and cathode are desirably of the same material, preferably silver. The condition indicator is thin and can be integrated into the label for a battery being tested. The condition indicator preferably comprises an auxiliary cell electrically connected in series to the electrolytic cell. The auxiliary cell is a power generating cell different from the power source that is tested, and is electrically connected either positive to positive or negative to negative with the power source, for example, the battery being tested. This produces a low net voltage available to drive the electrolytic cell. As the electrochemical energy source is discharged, the auxiliary cell is discharged in proportional amount. Electrolysis occurs in the electrolytic cell, coul- bly equal to the coulombic discharge of the auxiliary cell. In this way, the electrolytic cell is also discharged proportionally to the main cell. During electrolysis at least one of the anode and cathode of the electrolytic cell is visible, and a change in the visible electrode occurs. The amount of change, eg, depletion, at the visible electrode, usually the anode, provides a visual indication of the state of charge (the remaining percentage capacity) of the electrochemical energy source being tested. In other aspects, the invention is directed to the portion of the electrolytic cell of the condition indicator, connected through a shunt resistor located either on the anode side or the cathode side of a battery being tested. In such cases, the auxiliary cell can be eliminated, although its inclusion is nonetheless preferred - to increase the control over the operation of the electrolytic cell. In a specific embodiment (Figure 2) the tester 10 (condition indicator) of the invention comprises a coulometric cell 20 connected in series with an auxiliary cell 25. The tester 10 as a whole can be connected in parallel to the main cell 30 that is tested. The coulometric cell 20, best illustrated in Figure 2, is a miniature electrolytic cell that essentially has no electromotive force (e.m.f.) per se, that is, less than about 100 millivolts and preferably zero volts. The electrolysis that results in the depletion of one of the electrodes in the coulometric cell 20 occurs when the current passes through it. The auxiliary cell 25 is a miniature electrochemical cell which helps to control the operation of the coulometric cell 20. The tester 10 can be connected in parallel to the main cell 30 being tested. Preferably, the auxiliary cell 25 is connected to the main cell, so that the anode 77 of the auxiliary cell is electrically connected to the anode 115 of the main cell or the cathode 83 of the auxiliary cell is electrically connected to the cathode 145 of the cell principal. Such a connection results in a very low net voltage, available to drive the coulometric cell during charge discharge of the main cell. Also, the coulometric cell 20 is connected to the main cell 30, so that the anode of the coulometric cell is electrically connected to the positive terminal of the main cell, or the cathode of the coulometric cell is electrically connected to the negative terminal of the cell. the main cell. In addition, the open cell voltage (OCV) of the auxiliary cell 25 is substantially similar, for example, within about 100 millivolts, to the open cell voltage of the main cell 30. This prevents the discharge of the coulometric cell 20 before that the load 38 be connected to the main cell 30. In the preferred embodiment, the voltage across the coulometric cell 20 is very low, so that it does not noticeably alter the voltage capacity profile of the auxiliary cell. The electrochemistry of the auxiliary cell 25 and thus the voltage-capacity profile of the auxiliary cell, is preferably similar to that of the main cell. This ensures that the auxiliary cell 25 is discharged in a proportionally linear manner to that of the main cell 30. The coulometric cell which is in series with the auxiliary cell is discharged in a proportionally linear fashion to the auxiliary cell 25, and thus also to the main cell 30. In the preferred circuit arrangement, described in Figure 1, the auxiliary cell anode 77 is electrically connected to} , cathode 43 of the coulometric cell, the cathode 83 of the auxiliary cell is connected to the cathode 145 of the main cell, and the anode 47 of the coulometric cell is connected to the anode 115 of the main cell. (The anode either of the auxiliary cell 25 or of the coulometric cell 20 is defined as the electrode that is oxidized, and in this way releases electrons). The tester 10 comprising a coulometric cell 20 and the auxiliary cell 25, are shown in Figure 2 in an array consistent with the circuit diagram of Figure 1. The tester 10 can be permanently connected to a main cell 30 (Figure 2A ), such as a conventional alkaline cell, for example, by integrating it into the label for the main cell. The voltage of the tester follows that of the main cell, because the capacity of the tester is much lower and its resistance is much higher. Therefore, for electrochemically equivalent auxiliary main-cell cell combinations that have identical capacity / voltage characteristics, as the main cell is discharged, the ratio of current flow through the main cell to the current flow through the auxiliary cell, remains at almost constant value. This will be independent of the load on the main cell. Thus, at any time during the discharge of the main cell, the percent depletion of one of the anode or cathode of the auxiliary cell will be approximately the same as the percent depletion of one of the anode or cathode of the cell principal. (If the quantity of active material of the anode or active material of the cathode in the main cell or in the auxiliary cell is in excess, the comparison of the percentage depletion between the two cells should be made using the electrode containing the active material not in The excess electrode can be referred to herein as the control electrode). If the tester 10 is constructed so that the load capacity of the coulometric anode 47 is equal to that of the control electrode of the auxiliary cell, then at any time during the discharge of the auxiliary cell, the percent depletion of the anode of the cell coulometric 20 will be controlled and will be approximately the same as the percentage depletion of the control electrode of the auxiliary cell. In this way, the percent depletion (clearance) of the anode of the coulortretic cell 20 reflects the percent depletion of a control electrode in the main cell. This can be used to provide a continuous visual indication of the condition (state of charge) of the main cell. The percent of active material that remains in the coulometric cell can be visually discernible at any time during the life of the main cell. For example, if the coulo-electric anode is being depleted, the anode may be visually discernible and a graphical scale placed next to that anode may indicate the percent of charge remaining in the main cell and / or if the main cell needs to be replaced . During electrolysis, as the anode material is depleted, it is typically deposited on the cathode resulting in an enlargement of the cathode. In such a case, the cathode can be made visually discernible and a graphic scale placed next to it indicates the percentage charge remaining in the main cell. The tester 10 can be connected in parallel with the main cell 30 being tested, for example, as illustrated in the circuit diagram of Figure 1. In Figure 1, the main cell 30 is shown schematically with the negative terminal. 115 and the positive terminal 145. In use, when the main cell 30 is connected to a load 38 and discharged, the current iL flows through the load 38, the current iM flows through the main cell, and the current it flows through the tester 10, such that iL = iM + it. The resistance of the auxiliary cell 25 is desirably much greater than the internal resistance of the main cell 30, and the resistance of the coulometric cell 20 in turn is much greater than the resistance of the auxiliary cell 25. For example, in the configuration of circuit of Figure 1, if the main cell is a conventional AA size alkaline cell, having an internal resistance of about 0.1 ohm during normal operation, the strength of the auxiliary cell 25 may desirably be between about 500 and 2000 ohms , and the resistance of the coulometric cell 20 may desirably be between about 4,000 and 8,000 ohms. The auxiliary cell voltage will be slightly greater than the main cell voltage for any given load on the main cell. This small difference in voltage results in a small net voltage available to drive the auxiliary cell 25 during the discharge of the load from the main cell. For example, at a typical load of between 70 ohm and 1 ohm for a main cell of 1.5 volts, AA, conventional, the net voltage that drives the auxiliary cell 25 is between 0.05 and 0.1 volt, and the current flow through the coulometric cell 20 can typically be between approximately 0.05 x 10 ~ 6 amp and 5 x 10"6 amp.

In the preferred embodiment of the tester 10 (Figure 2), the auxiliary cell 25 is a flat, miniature electrochemical energy source, which at least partially powers the coulometric cell 20. The main cell 30 may be a primary or secondary battery, and typically it can be a conventional alkaline cell. The tester 10 is a flat assembly of thickness less than about 2.5 mm (100 mils), preferably between about 0.05 and 2.5 mm (2 and 100 mils), more preferably between about 0.05 and 0.4 mm (2 and 15). thousandths of an inch). The tester 10 can be integrated into the label for the main cell 30, for example, by coupling it to the internal surface of the label. The coulometric cell 20 contains an anode 47 and a cathode 43, advantageously composed of the same material. The auxiliary cell 25 is discharged in a linear manner proportional to the discharge of the main cell 30, independently of the load 38. For example, the auxiliary cell 25 can be calibrated so that during the discharge of the main cell 30 the percentage discharge already either the anode or the cathode of the auxiliary cell 25, will be the same as or at least a linear function of the discharge percent of a control electrode of the main cell 30. The coulometric cell 10 (Figure 2) is an electrolytic cell in miniature containing a cathode material 43 and an anode material 47, which are desirably separated from one another, and which may lie in the same plane. The coulometric cell 10 has a thickness of less than 2.5 mm (100 mils), preferably, a thickness between 0.05 and 2.5 mm (2 and 100 mils), more preferably a thickness between about 0.05 and 0.4 mm (2 yrs. 15 mils). The cathode 43 and anode 47 are desirably of the same metal, which can be easily plated electrochemically, and stripped of electrons (having a relatively high current density at a low drive voltage) when in contact with an electrolyte containing the ion of that metal. The cathode 43 and the anode 47 are thin coatings deposited on the substrates 42 and 48, respectively. It is desirable that the metal used for the cathode 42 and 48 is not reactive in the ambient atmosphere, or subject to corrosion. As a practical measure, silver is preferred for cathode 43 and anode 47, due to its high electrochemical activity, and is noble and non-reactive with environmental oxygen and moisture. The substrate 48 of the anode is conductive and preferably carbon, and the substrate 42 of the cathode is preferably also conductive. (It is possible to use a non-conductive material for the substrate 42 of the cathode, but a conductive substrate is preferred, and will be described herein). An anode substrate 48, conductive, is required in order that the electrically insulated metal islands are not left behind as the anode 47 is electrically stripped of electrons (cleared) from one end to the other. A further requirement is that the anode substrate 48 be of a color that provides high contrast to the color of the anode 47, thus giving highly discernible visual indication of the anode clearance 47. A preferred arrangement of the cathode 43 and the anode 47 one relative to the another and the underlying conductive substrate, is shown in Figure 2. A space 44 separates the cathode 43 from the anode 47 and also separates the underlying conductive substrates 42 from the 48, as can best be seen in Figure 2. Also, there may be a insulating material film 35 under conductive substrates 42 and 48. Conductive substrate 42 (Figure 2) may extend beyond the edge 43 (b) of the superimposed cathode material, to form extended substrate portions 42 (a). Similarly, the conductive substrate 48 may extend beyond the edge 47 (b) of the superposed anode material, to form the extended substrate portion 48 (a). An adhesive is applied to the surface of the extended portions 42 (a) and 48 (a), thereby forming an adhesive limit 55 around the periphery of the conductive substrates 42 and 48. If the cathode substrate 42 is not conductive, then the cathode edge 43 (b) it can extend and continue outward from the adhesive limit 55, in order to serve as an electrical contact at the end 42 (b). The adhesive limit 55 defines a window space 53 on the cathode 43 and the anode 47. A clear electrolyte cap 45 is applied in the window space 53, so that it covers the cathode 43 and the anode 47. The end 48 (b) of the extended substrate portion 48 (a) projects from the anode side of the cell 20. Similarly, the end 42 (b) of the extended substrate portion. 42 (a) is projected from the cathode side of cell 20. A piece of aluminum foil 65 is coupled to end portion 48 (b), using conductive adhesive 62 placed therebetween. The blade 65 serves to carry current from the substrate 48 to the negative terminal 115 of the battery (Figure 2A). The end portion 42 (b) is covered on its top surface with conductive adhesive 61. A transparent barrier film 52 is applied over the window 53 with the edges of the film in contact with the adhesive limit 55. Thus, the film The barrier film 52 is a protective film that covers and seals the electrolyte 45. The barrier film 52 is held in place by the adhesive limit 55. The coulometric cell 20 can be secured to the housing or case of the main cell 30, with a pressure sensitive adhesive 32, applied below the tester, under the insulating film 35. The auxiliary cell 25 (Figure 2) is desirably a flat, energy cell designed to have a similar open cell voltage, as the main cell 30. In addition, it is desirable that the auxiliary cell 25 display capacity / voltage characteristics (open circuit versus percentage capacity profile) similar to that of the primary cell. incipal 30. Auxiliary cell 25 has a thickness less than 2.5 mm (100 mils), preferably a thickness between about 0.05 and 2.5 mm (2 and 100 mils), more preferably a thickness between about 0.05 and 0. 4 mm (2 and 15 mils). The auxiliary cell 25 contains a coating of active material 77 of the anode, a coating of active material 83 of the cathode, and the electrolyte layer 73 therebetween. The cathode material 83 is preferably a coating of manganese dioxide applied to a conductive substrate containing a plastic film 81 filled with carbon. The active material 83 of the cathode is preferably manganese dioxide, because it is the same cathode active material used in the main alkaline cell 30. This helps to ensure that the auxiliary cell 25 and the main cell 30 have similar capacity characteristics. voltage. The amount of active material in the cathode 83 must be such that it has the same coulombic capacity as the coulometric anode 47. The opposite side of the film 81 filled with carbon is covered with conductive aluminum foil 82. The aluminum foil 82 it serves as a vapor barrier to seal the auxiliary cell 25 of the environment, and can also serve as a current collector for the cathode 83. The film 81 filled with carbon protects the sheet 82 from corrosion by the electrolyte 73, while which at the same time electrically contacts the cathode 83 to the sheet 82. An insulating film 85 is applied around the boundary of the exposed edges of the cathode layer 83. A separator 72 saturated with the electrolyte 73 is applied over the active layer 83 of the cathode, within the space joined by the insulating boundary 85. The active material 77 of the anode makes contact with the separator 72. The active material 77 of the anode may be a rec Zinc coating applied under a conductive substrate of plastic film 76 filled with carbon. The amount of active material 77 of the anode is preferably such that its coulombic capacity is considerably greater than that of the cathode 83. The opposite side of the film 76 filled with carbon is covered with a layer of conductive aluminum foil 78. A portion of the sheet 78 is left uncoated with active material from the anode. This portion forms the tab 79 of the anode which projects from the auxiliary cell. The tab 79 of the anode is composed of a projecting portion 78 (a) of aluminum sheet 78 and a projecting portion 76 (a) of the underlying conductive layer 76. The active material 77 of the anode makes contact with the separator 72 filled with the electrolyte. A conductive adhesive 92 is applied to the underside of the cell 25, in contact with the exposed surface of the sheet 82. The auxiliary cell 25 is secured to the main cell 30 through the conductive adhesive 92, which secures the cell 30 to the housing of the main cell.

The coulometric cell 20 (Figure 2) is electrically connected to the auxiliary cell 30 by application of the anode tab 79, so that the underlying conductive layer 76 (a) of the anode tab contacts the conductive adhesive 61 on the tongue 42 (b). This electrically connects the anode active material 77, auxiliary, with the cathode 43 of the coulometric cell 20, consistent with the circuit diagram of Figure 1. The connections of the main cell 30, typically a conventional alkaline cell, are illustrated with reference to Figures 2 and 2A. The active material 83 of the auxiliary cathode is electrically connected to the positive terminal 145 of the main cell 30, through the conductive adhesive 92 (Figure 2) which connects the auxiliary cathode 83 to the housing of the main cell, as shown in Figure 2A. The leaf tab 65 is pressed in permanent contact with the negative end cap 110 of the main cell (Figure 2A) so that the conductive adhesive 62 makes contact with the end cap 110. Such connection places the anode 47 of the coulometric cell 20 in electrical contact with the negative terminal 115 of the main cell 30. The tester 10 may be integrated on the inner surface of a film label 58 for the main cell, as illustrated in Figure 2A. Label 58 may desirably be a heat shrinkable film, such as polyvinyl chloride or polypropylene. The tester 10 can be formed on one side of the label by sequential printing or lamination of each of the coatings comprising the coulometric cell 20 and the auxiliary cell 25. A layer of heat-sensitive pressure sensitive adhesive can to be applied to the internal surface of the label, and the label with the integrated tester can be applied to the main cell 30 by wrapping it around the cell housing. The ends of the label can then be heat shrunk onto the upper and lower shoulders 152 and 154, respectively, in a conventional manner by holding the edges of the label at sufficient heat to cause shrinkage. In operation, whenever the main cell 30 is discharged, the auxiliary cell 25 is discharged, which in turn causes the coulometric cell 20 to operate. Specifically, in the embodiment shown in Figures 1 and 2, as the main cell 30 is discharged, the active material 47 of the coulometric anode becomes plated on the cathode 43. In the plating process the active material 47 of the anode gradually disappears of the portion of the active layer of the anode, closest to the layer 43 of the cathode, namely, from the end 47 (a) (Figure 2). This provides a visually discernible fuel metering effect. The amount of coulometric anode remaining in cell 20 at any time during the life of main cell 30, is easily visible through transparent electrolyte 45. A graphic scale adjacent to the coulometric anode 47 can be placed. A graphic scale can be calibrated to indicate the degree to which the coulometric anode 47 has been exhausted and consequently if the main cell needs to be replaced. The tester 10 comprising the coulometric cell 20 and the auxiliary cell 25 has a high resistance, so that the current passing through it on the discharge is very small. The tester 10 shows essentially the same voltage profile versus percentage capacity as the main cell. The current ratio, it (which passes through the tester 10) to the current iM (which passes through the main cell 30) is approximately the same regardless of the resistance load on the main cell. Thus, for any given load on the main cell, the auxiliary cathode 83 is discharged approximately to the same degree as the cathode of the main cell, and in turn causes the coulometric anode 47 to clear to that same degree. Consequently, at any time during the life of the main cell, the percentage of cathode discharge from the main cell will be approximately the same as the percentage of auxiliary cathode 83 discharge, which in turn will be approximately the same as the percentage of the coulometric anode 47 that has been cleared. This makes it possible to easily determine the degree of discharge of the main cell, by visual inspection through the window 53, of the amount of anode 47 that remains in the coulometric cell 20. A calibrated graphic scale, which can be provided adjacent to the coulometric anode 47, it makes it easier to determine when the anode 47 has been sufficiently depleted, indicating that the main cell 30 must be replaced. The following materials can be used to build the tester 10: the anode substrate 48 of the coulometric cell can be composed of an insulating plastic such as the KAPTON polyimide insulating film (EI Dupont Company) coated with the carbon 48 conductive composition ( to) . A suitable carbon coating 48 (a) is an epoxy ink filled with carbon, available under the trademark ink 113-26 from Creative Materials Inc. (CMI). Alternatively, the anode substrate 48 may be composed of an insulating plastic film such as the ACLAR (polychlorotrifluoroethylene) film, from Allied Signal Company or the KALODEX (polyethylene naphthalate) film from ICI Americas, coated with an electronically conductive film, such as Indium-tin oxide (ITO) or conductive carbon coating. Alternatively, the anode substrate 48 can be formed of a conductive, carbon-filled plastic, such as the carbon-filled fluorocarbon polymer film, available as a carbon-filled film X17611 from W.L. Gore Company. The substrate 48 of the anode desirably has a thickness between about 12.7 microns and 25.4 microns (0.5 and 1 mils). The anode 47 of the coulometric cell may be composed of a silver coating (with thickness between approximately 500 and 1,000 angstroms) deposited on the upper part of the anode substrate 48, by sputtering or by electron beam evaporation. The cathode substrate 42 of the coulometric cell can be formed of the same material and of the same thickness as the anode substrate 48, described above, or alternatively, it can simply be an insulating plastic film such as the ACLAR or KALODEX film. The layer 43 of the cathode of the coulometric cell can be composed of a silver coating (with a thickness of between 500 and 1,000 angstroms) deposited on the upper part of the cathode substrate 42, by sputtering or by electron beam evaporation. Coulometric electrolyte 45 (Figure 2) can be prepared first by forming an electrolyte solution of a coating composed of a mixture of silver trifluoromethanesulfinylimide (AgTFSI) in a 1: 1 by volume mixture of ethylene carbonate and 3-methylsulfolane as solvent, and then gelling the solution with poly (vinylidene fluoride). The electrolyte 45 can be prepared by mixing 8 parts by weight of the electrolyte solution with 3 parts by weight of the poly (vinylidene fluoride). The mixture is extruded at a temperature of about 140 ° C to the desired thickness, preferably between about 0.025 mm and 0.10 mm (1 and 4 mils) and applied over the coulometric anode 47 and the cathode 43. The frame or coulometric adhesive structure 55 (Figure 2) can be selected from a wide range of pressure sensitive adhesives. A desirable adhesive is a conventional adhesive based on butyl rubber such as the polyisobutylene / isoprene copolymer adhesive available as Butyl rubber adhesive 065 from EXXON Company. Adhesive structure 55 desirably has a thickness between about 0.025 mm and 0.625 mm (1 and 2.5 mils). The transparent coulometric barrier 52 may be desirably composed of ACLAR (polychlorotrifluoroethylene) (Allied Signal Company) film of thickness between about 0.015 and 0.025 mm (0.6 and 1 mils). The conductive adhesive 65 may desirably be a conductive adhesive filled with carbon, such as that available under the trade designation ARCLAD adhesive of the driver transfer type, from Adhesives Research Company. The adhesive coating 62 may desirably be 0.012 mm (0.5 mils) thick. The liner or backing 65 of the sheet may desirably be an aluminum sheet of between about 0.006 and 0.012 mm (0.25 and 0.5 mils) thick. The conductive substrate 81 of the cathode of the auxiliary cell can be composed of the polymeric poly (vinyl acetate) film filled with conductive carbon / poly (vinyl chloride) (conductive plastic film Rexham Graphics, No. 2664-01). As described above, the conductive layer 81 is laminated to a layer 82 of the aluminum foil. The conductive polymeric film can be desirably 0.025 mm (1 mil) thick, and the aluminum foil between about 0.006 and 0.012 mm (0.25 and 0.5 mils) thick. The cathode 83 of the auxiliary cell is desirably composed of a printed coating containing X% electrolyte manganese dioxide (EMD), (90-X)% graphite, and 10% polyvinyl chloride binder. The active layer 83 of the cathode can be prepared by dispersing 3 parts by weight of the mixture of EMD and graphite, in 7 parts by weight of 0.75% aqueous Carbopol 940 (BF Goodrich Company) which is a copolymer of acrylic acid crosslinked, and adjusting the mixture to a pH of 10 with potassium hydroxide, and then adding HALOFLEX 320 (ICI Americas - US Resins Division) PVC latex in sufficient quantity comprising 10% by weight of the final, dry cathode material. The mixture was then coated as a wet film of 2.5 microns to 12.7 microns (0.2 to 0.5 mils) thick on the polymeric layer 81 filled with carbon, and then dried in air to form the active layer 83 of the dry cathode. The separator 72 of the auxiliary cell may be a porous membrane of nitrocellulose or cellophane of thickness of about 0.025 mm (1 mil) containing about 2-8 microliters of an electrolyte solution 73 composed of about 24 to 32 wt.% ZnCl aqueous adjusted to a pH of 4, by the addition of ZnO. The substrate 76 of the anode of the auxiliary cell may be composed of the polymeric poly (vinyl acetate) film filled with conductive carbon / poly (vinyl chloride) (Rexham Graphics conductive plastic film No. 2664-01). The substrate 76 is laminated to a layer 78 of aluminum foil. The conductive polymeric film may desirably be 0.025 mm (1 mil) thick and the aluminum foil between about 0.006 and 0.012 mm (0.25 and 0.5 mils) thick. The anode layer 77 of the auxiliary cell can be a coating composed of 90% zinc powder and 10% styrene-butadiene copolymer binder (SBR). The layer 77 of the anode can be prepared firstly by the dispersion of 6.5 parts by weight of zinc powder (particle size of 5 to 7 microns) in 3.5 parts by weight of copolymer gel of acrylic acid crosslinked with aqueous Carbopol 940 at 1.25% (adjusted to a pH of 12 with potassium hydroxide). A styrene-butadiene rubber latex is then added (latex ROVENE 5550 SBR from Rohm & amp;; Haas Company) in sufficient quantity to produce 1 part by weight of styrene-butadiene by 9 parts of zinc in the final dry film. The mixture is then coated with a wet film of 12.7 microns to 38.1 microns (0.5 to 1 mils) thick on the polymeric layer 76 filled with carbon and then air dried. The contact adhesive 61 and 92 of the auxiliary cell can be selected from a variety of conductive adhesives. A suitable adhesive 61 or 92 may be a conductive carbon-filled transfer adhesive, available as an ARCLAD adhesive from Adhesives Research Company. Such an adhesive can be coated to a thickness of about 0.012 mm (0.5 mils) on a layer 82 of an aluminum foil layer forming the adhesive layer 92. The same adhesive composition can be coated to a thickness of about 0.012 mm (0.5 mils) forming the adhesive layer 61 on the end 42 (b) of the coulometric cathode substrate. The insulator 85 of the auxiliary cell can be suitably formed of a heat-sealable film of polyvinyl acetate / polyvinyl chloride. Alternatively, it may be comprised of a pressure sensitive adhesive of butyl rubber, such as Butyl rubber 065 from Exxon Company. Insulator 85 is advantageously between about 0.025 and 0.05 mm (1 and 2 mils) thick. The coulometric backing adhesive 32 can be selected from a wide variety of pressure sensitive adhesives. Desirably, the adhesive 32 is comprised of a butyl rubber pressure sensitive adhesive, such as Butyl 065 rubber from Exxon Company. An alternative embodiment of the coulometric cell is shown as a coulometric cell 120 in Figures 5 and 6. The coulometric cell 120 can be replaced by cell 20 in Figure 2. Coulometric cell 120 differs from cell 20 in that it has a transparent conductive substrate 148 for the anode 47. The anode 47 is deposited on the transparent conductive substrate 148, and in this way the transparent conductive substrate 148 lies between the transparent barrier layer 72 and the anode 47 (Figure 6). The cathode 43 is deposited directly under the barrier layer 52, without the need for any substrate 148 between them. As they are manufactured in this way, the transparent barrier 52, the transparent substrate 148, the anode 47 and the cathode 43 together comprise a simple discrete sub-assembly 165, when the coulometer 120 is mounted. The coulometer 120 is mounted by applying an adhesive border or edge 55 (Figure 6) around a barrier layer 134. The adhesive border or edge 55 defines a window area that can be filled with the electrolyte 45. The coulometer 120 it can then be assembled by applying sub-assembly 165 in contact with the edge or adhesive edge 55, as shown in Figure 6. The anode end 47 (b) and the cathode end 43 (b) extend beyond the adhesive edge 55, to serve as electrical contacts. The coulometer 120 is applied to the cell with the insulating layer 134 closer to the housing of the cell. In this embodiment, the anode 47 (Figure 5) is observable through the superimposed transparent barrier 52, and the transparent conductive layer 148, and therefore the electrolyte 45 need not be clear as in the embodiment of Figure 2, but rather, it can be colored to provide contrast as the anode 47 becomes exhausted. If the electrolyte 45 is lighter than the underlying barrier layer, it must be colored to provide the necessary contrast. Preferred materials for the transparent conductive substrate 148 include indium tin oxide and other transparent semiconductors which are easily deposited by thin film deposition techniques such as sputtering or electronic deposition. Preferred materials for the barrier film 52 include poly (ethylene naphthalate) and other chemically inert transparent films, which are stable at the high temperatures encountered during thin film depositions. The insulating layer 134 can be of Aclar or Kalodex material, which is a subcoated contact adhesive, for example the adhesive 32 described above, to ensure the attachment of the layer 134 to the housing of the main cell 30. The coulometer can be connected to the auxiliary cell 25 and the main cell 30, in a manner analogous to that described with reference to Figure 2. In an alternative embodiment, the auxiliary cell can be eliminated, and the coulometric cell 20 or 120 can be directly connected to the main cell 30. This can be achieved by placing a shunt resistor inside the main cell being tested. In such a case, the shunt resistor, shown as resistor 122, can be placed on the anode side of the main cell 30, consistent with the circuit diagram of Figure 3. Alternatively, the shunt resistor, shown as resistor 112, can be placed on the cathode side of the main cell 30, consistent with the circuit diagram of Figure 4. The shunt resistor 112 or 122 can be adjusted to appropriate values, desirably between about 1 and 10 milliohms, to ensure that the percent depletion rate of the anode 47 of the coulometric cell is approximately the same as the rate or percent depletion rate of the control anode or the cathode of the main cell 30, independent of the load 38 on the main cell. (The electrode of the main cell not in excess can be considered the control electrode). Thus, as in the preceding modes, the remaining amount of the anode 47 in the coulometric cell provides a continuous visual indication of the state of charge of the main cell 30. The shunt resistor 122 can be placed on the anode side of the cell 30 (Figure 3) by adding the resistor 122 in series between the anode 77 of the main cell and the negative terminal 115. This can be achieved by coupling a metal resistance disk 122 in series between the current collector 118 and the end cap 110 as shown in Figure 3A. (The elongated metal members called current collectors, which connect the end cap of the anode with the anode active material in the cell, are commonly used in conventional cells). The current collector 118 may be coupled to one side of the disk 122, and the other side of the disk 122 may be coupled to the end cap 110 (FIG. 3A). In order to connect the coulometric cell 20 through the resistor disc 122, the current collector 118 is passed through an additional disk 125 composed of a conductive surface 134 sandwiched between two insulating layers 130 and 132, so that the current collector 118 makes electrical contact to the conductive surface 134. The insulating layers 130 and 132 protect the conductive layer 134, and prevent electrical shorting between the housing or can of the battery and the end cap 110. The conductive layer 134 can be formed by the deposition of a conductive material such as silver on the insulating disk 132. The disk 132 can be selected from a wide range of chemically resistant plastics, preferably nylon. A conductive tab 136 may be provided and is comprised of a portion of conductive layer 134 on the disc 132 extending from one edge of the disc. The coulometric cell 20 can thus be connected through the resistor disc 122 by the electrical connection of the coulometric anode 47 to the negative end cap 110 of the main cell, and by the electrical connection of the coulometric cathode 43 to the conductive tongue 136. The resistance disk 122 can be advantageously formed of a semiconductor material, preferably with conductivity in the range of 10 to 50 ohm_1 / cm. Suitable intrinsic semiconductors can include silicon, germanium, sulfides such as ZnS or FeS2, or oxides such as Sn02-The conductive layer 134 can be conductive material such as silver and the insulating disks 130 and 132 can be chemically resistant insulating plastic, such like nylon. Alternatively, a shunt resistor, represented as the resistor 112, may be placed within the main cell 30 on the cathode side thereof, consistent with the circuit diagram described in Figure 4. This may be carried out in a manner practice by adding the additional resistor 112 between the positive terminal 145 and the cathode of the main cell as shown in Figure 4A. This can be done first by increasing the depth of the positive terminal 145, by the addition of semiconductor material such as those listed above, between the positive terminal 145 and the housing 144 of the main cell. The coulometric anode 47 is then brought into contact with the housing 144, and the coulometric cathode 43 is brought into contact with the positive terminal 145. In the embodiments described above (Figures 3A and 4A) the shunt resistor 122 or 112 desirably has a resistance of less than about 10 percent of the internal resistance of the main cell being tested. Thus, if the main cell is a conventional alkaline cell having an internal resistance of about 0.1 ohm, the shunt resistor may desirably have a resistance of less than about 0.01 ohm. A higher bypass resistance is possible for the acceptable operation of the coulometric cell, but such higher bypass resistance tends to interfere too much with the proper operation of the main cell. Although the embodiments (Figures 3A and 4A) can be employed without an auxiliary cell, the use of an auxiliary cell is advantageous because it results in a more stable and reliable coulometric cell. During the discharge of the main cell, the voltage drop across the shunt resistor varies according to the load resistance 38, and may typically be in the range of about 1 to 10 millivolts for the load resistance between about 1 and 10 ohms. . Therefore, to be used with such a shunt resistor, the coulometric cell must have a high electrochemical activity to be able to operate at such small voltages. Silver electrolytes such as aqueous avocado perchlorate have sufficiently high electrochemical activity and are desirable. The following is an example of work of the tester described with reference to Figure 2: Example 1 Work testers of the type described in the preferred embodiment (Figure 2) are constructed and used to indicate the state of charge of the AA alkaline cells discharged through various loads. The coulometric cells as described with reference to Figure 2, are prepared with the following components: The coulometric anode and cathode are prepared by sputtering 1000 angstroms of silver onto conductive carbon-coated substrates (from Creative Materials Inc. ) consisting of a KAPTON 25 micron (1 mil) thick polyimide film with carbon / binder coating of 2.5 microns (0.1 mil) in thickness. The cathode substrates are approximately 11.9 mm (0.47 inches) long by 5 mm (0.20 inches) wide, and the anode substrates are approximately 21.8 mm (0.86 inches) long by 5 mm (0.20 inches) wide . The cathodes are approximately 4 mm (0.16 inches) in length by 5 mm (0.20 inches) in width and the anodes are approximately 10 mm (0.40 inches) in length by 5 mm (0.20 inches) in width, giving the anodes a capacity of approximately 14 x 10"6 Amp» hour The cathode is separated from the anode by an empty space of approximately 1.2 mm (0.05 inches) inside a window of pressure sensitive adhesive of butyl rubber of 63.5 microns (2.5 mils) of thickness having an interior space of approximately 16.7 mm (0.66 inches) in length by 7.6 mm (0.30 inches) in width.The anode and cathode are connected by a transparent electrolyte of 50.8 microns (2 mils) in thickness and approximately 15.5 mm (0.61 inches) in length by approximately 6.3 mm (0.25 inches) in width, consisting of AgTFSI 0.35 M (silver trifluoromethanesulfonylimide) in solvent, and prepared as previously described for the preferred embodiment. A transparent barrier film of ACLAR 33C of 25 microns (1. mil) in thickness and approximately 26.9 mm (1.06 in) in length by 15.2 mm (0.60 in) in width, is used to seal the coulometers. The finished coulometers are between approximately 0.15 and 0.18 mm (6 and 7 mils) thick, and have AC resistances measured at 1 ilohertz of approximately 4 k-ohm. Auxiliary cells of the type described with reference to Figure 2 are prepared with the following components. The cathode of the auxiliary cell is prepared by coating a layer of manganese dioxide containing the electrolytic manganese dioxide (EMD) on a conductive substrate composed of plastic film filled with carbon, Rexham Graphics No. 2664-01 as previously described. The manganese dioxide coating is applied as a wet film of 12.7 microns (0.5 mils) thick having a dry composition which is 72% EMD and 18% graphite. The manganese dioxide layer has an area of approximately 1,161 mm2 (0.018 inch2), in order to give the capacity of approximately 14 x 10 ~ 6 Amp per hour. The anode of the auxiliary cell is prepared by applying a zinc coating on the carbon-filled plastic substrate, conductor, Rexham Graphics No. 2664-01, as described in the preceding description. The anode with dry zinc has a thickness of approximately 25 microns (1 mil) and an area of approximately 4.516 mm2 (0.070 inches2) to give a capacity several times greater than that of the cathode. The separator is prepared using a cellophane material Courtaulds 350 POO of microns (1 mil) thick containing approximately 6 x 10"6 liters of pH 4 electrolyte (ZnCl2 at 28%). The adhesive 85 is a 50 mil (2 mils) thick butyl rubber pressure sensitive adhesive (Exxon Butyl 065 rubber adhesive) used to seal the auxiliary cell. The finished auxiliary cells are approximately 0.20 mm (8 mils) thick and had AC resistance measured at 1 kHz of approximately 2 k-ohm. The finished testers in this example have thicknesses between approximately 0.15 and 0.20 mm (6 and 8 mils). The coulometer and the auxiliary cells are brought into contact with each other in a side by side arrangement as in Figure 2 and with new AA alkaline batteries (Figure 2A) using the ARCLAD conductive adhesive of 12. 7 microns (0.5 mils) thick (61 and 92) as previously described. AA batteries are discharged from 1. 5 to 0.8 volts through the load resistors either 1 ohm, 4 ohm, 36 ohm or 75 ohm, either continuously or intermittently. During the discharge, in each case the voltage across the coulometric cell is small. For example, for a 4 ohm load, the voltage across the coulometric cell is between about 40 and 100 millivolts, and the current through the coulometric cell is about 2 x 10"6 amps. the coulometric anode is cleared in a manner similar to a meter, to visually reveal the underlying black conductive substrate (48), with the clearance beginning with the end 47 (a) closest to the cathode, and proceeding to the opposite end of the cathode The amount of clearing correlates proportionally linearly with the degree of discharge of the AA cell.Thus the tester serves as an effective state of charge indicator for the main cell.The coulometric cell modalities described herein they can be used advantageously to test the condition of conventional Zn / Mn02 alkaline cells which can typically operate with load resistance between approximately 1 and 1000 ohm The application of the invention, however, is not intended to be limited to alkaline cells, but rather to be used effectively to test the condition of any dry cell. Although the present invention has been described with reference to specific embodiments and specific construction materials, it will be appreciated that other embodiments and materials are possible without departing from the concept of the invention. Therefore, it is not intended that the invention be limited to the specific embodiments described herein, but rather the scope of the invention is defined by the claims and equivalents thereof.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following:

Claims (20)

1. The combination of a battery and an indicator for the condition of the battery, wherein the battery comprises a housing, a negative terminal and a positive terminal; characterized in that the condition indicator comprises an electrolytic cell which essentially has no electromotive force per se, the electrolytic cell comprises an anode, a cathode, and an electrolyte, and said condition indicator is permanently electrically connected to the battery; wherein at least one of the anode and cathode of the electrolytic cell is visible and wherein, during the discharge of the battery, the reaction begins in a first region of the visible electrode, and continues from it to a remote region thereof.

2. The combination according to claim 1, characterized in that the condition indicator further comprises an auxiliary cell electrically connected in series to the electrolytic cell, wherein the auxiliary cell is an electrochemical cell different from the battery, the auxiliary cell comprising an anode , a cathode, and an electrolyte that contacts at least a portion of the anode and cathode of the auxiliary cell, wherein the battery is electrically connected to the auxiliary cell either with the positive terminal of the battery that is electrically connected to the cathode of the auxiliary cell, or the negative terminal of the battery that is electrically connected to the anode of the auxiliary cell.

3. The combination according to claim 1, characterized in that the anode and the cathode of the electrolytic cell comprise the same electrochemically active material.

4. The combination according to claim 1, characterized in that the anode and the cathode of the electrolytic cell are laterally separated, so that no portion of the anode of the electrolytic cell overlaps any portion of the cathode of the electrolytic cell.

5. The combination according to claim 1, characterized in that the anode and the cathode of the electrolytic cell comprise both silver.

6. The combination according to claim 1, characterized in that the condition indicator of the cell has a thickness of less than about 2.5 mm (100 mils).

7. The combination according to claim 1, characterized in that the indicator of the condition of the cell has a thickness between approximately 0.05 and 0.4 mm (2 and 15 mils).

8. The combination according to claim 2, characterized in that the cathode of the auxiliary cell is electrically connected to the positive terminal of the battery, and the anode of the auxiliary cell is electrically connected to the cathode of the electrolytic cell, and the anode of the Electrolytic cell is electrically connected to the negative terminal of the battery.

9. The combination according to claim 2, characterized in that the anode of the auxiliary cell is electrically connected to the negative terminal of the battery, and the cathode of the auxiliary cell is electrically connected to the anode of the electrolytic cell, and the cathode of the Electrolytic cell is electrically connected to the positive terminal of the battery.

10. The combination according to claim 1, characterized in that the condition indicator is integrated into a label for the battery.

11. An indicator of the condition for an electrochemical cell, characterized in that the indicator of the condition has a thickness of less than 2.5 mm (100 mils), and comprises an electrolytic cell that has essentially no electromotive force by itself, the electrolytic cell comprises a anode, a cathode, and an electrolyte, the electrolyte being electrically in contact with at least a portion of the anode and the cathode, wherein at least a portion of one of the anode and the cathode is visible, and wherein during electrolysis in the electrolytic cell, the reaction begins in a first region of the visible electrode, and continues from it to remote regions thereof.

12. The indicator of the condition according to claim 11, characterized in that the anode and the cathode are laterally separated one from the other, so that no portion of the anode overlaps the cathode, and where during the electrolysis in the electrolytic cell the clearing occurs of the anode from the end of it, closer to the cathode.

13. The indicator of the condition according to claim 11, characterized in that the condition indicator has a thickness between 0.05 and 0.4 mm (2 and 15 mils).

14. The indicator of the condition according to claim 11, characterized in that the anode and the cathode comprise the same electrochemically active material.

15. The indicator of the condition according to claim 11, characterized in that the anode and the cathode comprise both silver.

16. The indicator of the condition according to claim 11, characterized in that the electrolytic cell further comprises a conductive substrate in contact with one side of the anode.

17. The indicator of the condition according to claim 12, characterized in that the electrolytic cell further comprises a protective film on the electrolyte, at least a portion of the anode is visible through said protective film and electrolyte.

18. The indicator of the condition according to claim 11, characterized in that the electrolytic cell further comprises a transparent conductive substrate in contact with one side of the anode, wherein at least a portion of the anode is visible through the transparent conductive substrate.

19. The indicator of the condition according to claim 18, characterized in that the transparent conductive substrate comprises indium-tin oxide.

20. The condition indicator according to claim 15, characterized in that the electrolyte comprises silver trifluoromethanesulfonylimide.