Abstract:
An overall standard sized battery having a physical characteristic for differentiation between rechargeable and non-rechargeable types, and a corresponding feature in the battery cavity of an electronic device, such that the electronic device can discern this physical characteristic. A mechanical modification may be made to the standard size rechargeable batteries. This is detected by the electronic product, and enables the product to easily distinguish between standard primary batteries and rechargeable batteries having the same overall standard size dimensions. The product is configured to safely recharge only secondary batteries. Possible mechanical modifications to the battery include: the size and/or shape of the positive tip or the negative end of the battery; the cross-sectional shape of the barrel of the battery; an added notch or projection on the battery; and extension or shortening the length of the battery. Detection methods may be mechanical, optical, electrical or magnetic.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of batteries, especially batteries with distinctive features for distinguishing between primary and secondary batteries. 
       BACKGROUND OF THE INVENTION 
       [0002]    Standard size batteries according to the various ANSI C18 standards, are available with different battery chemistries. Some are secondary (rechargeable) batteries such as Nickel-Cadmium (Ni—Cd) or Nickel Metal Hydride (NiMH). Others are primary (non-rechargeable) batteries, such as Alkaline and Lithium Iron Disulphide (LiFeS 2 ). It is potentially dangerous to attempt to charge such primary cells, as they may heat up excessively or even explode when an excessive current is forced through them. 
         [0003]    Portable electronic products can use both type of batteries. In order to recharge the secondary batteries, the user sometimes needs to take them out of the product and put them in a separate charger. This limitation leads to inconvenience in usage of electronic devices. Many mobile devices today have a connection to an external wall charger, or have their own built-in charger for connection to a wall source, such that the internal battery can be charged in situ. Such devices sometimes include battery chemistry detection circuits, such as those described in co-pending International Patent Application No. PCT/IL2007/001532 for “Charging Methods for Battery Powered Devices”, herewith incorporate by reference in its entirety. Use of such circuits enables the device to determine whether the installed battery is a secondary battery and can be safely charged, or whether it is a primary battery which would be unsafe to charge. However, such circuits are not common on low cost, popular electronic devices, because of the expense of providing the circuitry, which, to be fully effective, generally needs to be microprocessor controlled. 
         [0004]    It would therefore be useful to provide a method and system whereby the nature of the battery chemistry would be simply indicated by the battery itself, without the need for complex electronic circuitry in the device, yet without diverging from the standard ANSI overall sizes of such batteries. 
         [0005]    Although the term battery, according to strict technical nomenclature, comprises a number of cells, throughout this application, the term is to be understood to be interpreted and is thuswise claimed according to its popular usage, whereby a single cell is also called “a battery”. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention seeks to provide new forms of batteries, having the overall standard sizes of batteries in common use, but having an additional physical characteristic for differentiation between rechargeable and non-rechargeable types. A corresponding feature is provided in the electronic device such that the electronic device can discern this physical characteristic, and enable or disable its battery charging ability accordingly. 
         [0007]    According to a first preferred embodiment, a small mechanical modification is made to the standard size rechargeable batteries. This is detected by the electronic product when the battery is inserted into its cavity, and enables the product to easily distinguish between standard size primary batteries and rechargeable batteries having the same overall standard size dimensions. The product can then be configured to safely recharge only batteries which are detected as secondary. 
         [0008]    According to different preferred variations of this invention, the physical modifications can be mechanical modifications, and various detection methods of these mechanical modifications can be provided, whether mechanical, optical, magnetic or electrical. It is to be understood that the term mechanical modification is meant to include any physical modification to the battery which manifests itself externally as a modified mechanical part of the battery, even if detection of that mechanical modification is not performed mechanically. Thus, an electrically conductive or optically reflective region of the batteries&#39; outer surface is also termed a mechanical modification in this application, even though detection of that modification may preferably be performed electrically or optically. 
         [0009]    Possible preferred mechanical modifications may include, though are not limited to:
   (i) Change in the size and/or shape of the positive tip of the battery   (ii) Providing the barrel of the battery with a different shape such as a triangular or rectangular prismatic shape.   (iii) Addition of a notch or a projection somewhere on the battery body.   (iv) Extension or shortening of the length of the battery by a small amount   (iv) Change in the size and/or shape of the negative end of the battery.   (v) Change in the electrical or optical surface properties of the battery outer cover.   
 
         [0016]    Possible detection methods may include, though are not limited to:
   (i) Mechanically operated Micro-switch   (ii) Optoelectronic-switch   (iii) Magnetic proximity switch   (iv) Electrical continuity or voltage test   
 
         [0021]    It is important that the device in which the detection apparatus for the modified batteries of the present invention is fitted will continue to operate with standard batteries, unmodified according to the present invention. This is essential to provide for general acceptance of the batteries of the present invention. The details of the various embodiments of the present invention device must be such that the device will work normally with an unmodified battery, while the modified battery according to the present invention will activate the charge enabling or disabling facility of the device, thus fulfilling its intended function but without detracting from its normal historic mode of operation. Conversely, the modified battery itself must be such that it will operate normally in a device which is not fitted with the detection apparatus of the present invention. Both aspects of the invention, modified battery and detection equipped device must therefore be completely transparent for normal operation, to the special characteristics of the present invention. 
         [0022]    The present invention thus enables a simple, low cost method of distinguishing between primary and secondary standard sized batteries. It enables accurate and safe electro-mechanical, electro-optical, magnetic or optical detection of batteries that are can be safely recharged, without the need for complex electronic detection circuits. This ability to safely detect a rechargeable battery can improve the convenience of new electronic products by enabling the user to recharge his batteries while they are in the product, and still keep the benefit of also using primary batteries in the product when needed. Although the present invention has been described in this application as applicable for use in electronic devices, it is to be understood that it is equally useful for application in battery chargers as stand-alone instruments. 
         [0023]    There is thus provided in accordance with a preferred embodiment of the present invention, a system for providing battery power to an electronic device having a battery cavity, the system comprising:
   (i) a battery having at least one physical characteristic other than its chemistry for differentiation between rechargeable and non-rechargeable types, and   (ii) a corresponding feature of the battery cavity adapted to differentiate between the battery types by means of the physical characteristic.   
 
         [0026]    In the above described system, the physical characteristic may preferably be the external shape of the battery. In this case, the external shape may preferentially be an essentially rectangular barrel, and the corresponding feature of the battery cavity may be either a micro-switch or an opto-electric circuit activated by the essentially rectangular barrel. Alternatively and preferably, the battery may have a generally cylindrical body, and the external shape may be a projection from the generally cylindrical barrel, and the corresponding feature of the battery cavity may then be a micro-switch or an opto-electrical circuit activated by the projection. In all of these systems, the electronic device preferably comprises charging circuits which are applied to the battery only when the corresponding feature discerns that the physical characteristics are those associated with a rechargeable battery. 
         [0027]    In accordance with still another preferred embodiment of the present invention, the physical characteristic may preferably be the size of the positive contact of the battery. In such a case, the corresponding feature of the battery cavity may preferably be a two-part contact adapted to provide an enabling signal to provide recharging current only to a battery having a positive contact of at least a predetermined diameter. Alternatively and preferably, the corresponding feature of the battery cavity may be a two-part contact adapted to provide an enabling signal to provide recharging current only to a battery having a positive contact of less than a predetermined diameter. 
         [0028]    There is further provided in accordance with still another preferred embodiment of the present invention, a system as described above, and wherein the physical characteristic is either one of the size or shape of the negative contact of the battery. The corresponding feature of the battery cavity is then preferably a two-part contact adapted to provide an enabling signal to provide recharging current only to a battery having a negative contact of less than a predetermined diameter. 
         [0029]    There is even further provided in accordance with another preferred embodiment of the present invention, a system as described above, and wherein the physical characteristic is a partial coverage of the negative base of the battery by an insulating layer. The corresponding feature of the battery cavity is then preferably a negative contact adapted to provide an enabling signal to provide recharging current only to a battery having the partial coverage of the negative base of the battery by an insulating layer. 
         [0030]    Furthermore, in accordance with yet another preferred embodiment of the present invention, in the above described system, the physical characteristic may preferably be the length of the battery. In this case, the length may preferably be different from that of a standard battery, and the corresponding feature in the electronic device is either a micro-switch or an opto-electric circuit activated by a battery of the different length. 
         [0031]    There is also provided in accordance with a further preferred embodiment of the present invention, a system wherein the physical characteristic is the presence of a magnetized material mounted in or on the battery. The corresponding feature of the battery cavity is then preferably a magnetic field detection element adapted to provide an enabling signal to provide recharging current only to a battery having the magnetized material associated with it. 
         [0032]    In accordance with yet another preferred embodiment of the present invention, 
         [0000]    the physical characteristic may be a region of electrical conductivity on the generally insulating outer surface of the battery, and the corresponding feature of the battery cavity may then be a pair of electrical contacts which are connected and thus provide an enabling signal to provide recharging current only by a battery having the region of electrical conductivity on its generally insulating outer surface. 
         [0033]    In any of the above described systems using an opto-electric detection circuit, the circuit preferably may comprise an emitter and a photodetector, and the circuit is closed when a battery having a predetermined reflective part of its surface is inserted into the cavity, such that light from the emitter is reflected into the photodetector. Alternatively and preferably, the opto-electric circuit may be closed when a battery having a predetermined modified shape is inserted into the cavity, such that light from the emitter may be transmitted into the photodetector. 
         [0034]    There is further provided in accordance with yet another preferred embodiment of the present invention, a method of preventing the charging of a primary battery, comprising:
   (i) providing a battery having at least one physical characteristic other than its chemistry for differentiation between primary and secondary batteries,   (ii) providing a battery charger having a charging circuit and a battery cavity for receiving a battery to be charged, and   (iii) equipping the battery cavity with a feature adapted to differentiate between primary and secondary batteries by means of the physical characteristic.   
 
         [0038]    In the above described method, the physical characteristic may preferably be the external shape of the battery, and the battery cavity may preferably detect the physical characteristic of the battery by means of a mechanical, electrical, optical or magnetic detection procedure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
           [0040]      FIGS. 1A-1B  illustrate schematically, according to a first preferred embodiment of the present invention, a standard prior art battery, adapted by use of a modified positive tip to differentiate a secondary battery from a primary battery; 
           [0041]      FIGS. 2A-2C  illustrate schematically a preferred embodiment of the corresponding positive current contact in the battery cavity of an electronic device constructed to make use of the modified feature of the batteries of  FIGS. 1A and 1B ; 
           [0042]      FIGS. 3A-3B  illustrate schematically, according to another preferred embodiment of the present invention, a scheme similar to that of  FIGS. 1A to 2C , but using a modified negative end of the battery; 
           [0043]      FIGS. 4A to 4C  illustrate schematically, according to another preferred embodiment of the present invention, a scheme whereby a modified battery cross sectional shape is used to differentiate between rechargeable and primary batteries; 
           [0044]      FIGS. 5A-5C  and  6 A- 6 E illustrate schematically, according to more preferred embodiments of the present invention, schemes whereby a modified battery length is used to differentiate between rechargeable and primary batteries.  FIGS. 5A-5E  illustrate how a battery of slightly increased length is used, while  FIGS. 6A-6E  illustrate how a battery of standard length is used; 
           [0045]      FIGS. 7A-7E  illustrate schematically a further preferred embodiment of the present invention, in which the electrical conductivity of the outer surface of the battery is used for distinguishing a modified battery from a standard battery; 
           [0046]      FIGS. 8A-8E  illustrate schematically a further preferred embodiment of the present invention, in which electrical continuity is used for distinguishing a modified battery from a standard battery; 
           [0047]      FIGS. 9A-9E  illustrate schematically a further preferred embodiment of the present invention, in which opto-electronic detection is used for distinguishing a modified rechargeable battery from a standard battery; 
           [0048]      FIGS. 10A-10E  illustrate schematically a further preferred embodiment of the present invention, in which a transmissive opto-electronic detection method is used for distinguishing a modified rechargeable battery from a standard battery; and 
           [0049]      FIGS. 11A-11C  illustrate schematically a further preferred embodiment of the present invention, in which magnetic detection is used to determine the presence of a modified battery. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0050]    Reference is now made to  FIGS. 1A and 1B  which illustrate schematically, according to a first preferred embodiment of the present invention, a standard prior art battery, adapted by use of a modified positive tip to differentiate a secondary battery from a primary battery.  FIG. 1A  shows a completely standard battery  10 , with its positive contact  11 . According to this preferred embodiment, as shown in  FIG. 1B , the rechargeable battery  12  is manufactured to be of the same overall dimensions as the conventional battery of the same size, such that it will fit correctly in the cavity of the device, but having a modified positive contact  14  of larger diameter than that of the standard battery of  FIG. 1A . This, and the other preferred embodiments shown in this application, use an AA or an AAA battery as examples for the implementation of the invention. It is to be understood though that the invention is not intended to be limited to such batteries, but is applicable to any standard size and shape of battery in common use. 
         [0051]    Reference is now made to  FIGS. 2A-2C , which illustrate schematically a preferred embodiment of the corresponding positive current contact  20  in the battery cavity of an electronic device constructed to make use of the modified feature of the batteries of  FIGS. 1A and 1B . The modified positive cavity contact has two-parts—an outer contact  22  and an inner contact  24 , connected to the device&#39;s power circuitry through leads  1  and  2  respectively. As shown in  FIG. 2B , the standard sized positive tip  11  of a conventional cell  10  can make contact only with the inner cavity contact  24 , connected by lead  2  to the device&#39;s power circuitry. On the other hand, when a rechargeable battery  12 , modified with a larger diameter positive contact tip  14  is inserted into the cavity, the larger positive tip can make contact with the outer contact  22  of the cavity. Thus, contact  22  and its associated lead  1  can only make contact with the larger diameter positive tip of a rechargeable battery, but not with the positive tip of a standard, non-rechargeable battery. The recharging circuits of the electronic device can be arranged such that they only feed the outer part  22  of the modified positive contact through lead  1 , such that only a rechargeable battery of the present invention can be charged when inserted into the device. 
         [0052]    Alternatively and preferably, the outer part  22  of the contact can be used simply to detect when a voltage is present, this indicating the presence of a rechargeable battery with a large positive tip  14 . The presence of this voltage on lead  1  is then used to enable the device&#39;s charging circuit, which can then charge the battery. 
         [0053]    Power for regular operation of the device is supplied from the battery through lead  2 , attached to the inner part  24  of the modified positive contact, such that either a non-rechargeable or a rechargeable modified battery, when inserted into the battery cavity of the device, will power the device correctly through this inner contact. 
         [0054]    Although this preferred embodiment has been shown with the positive tip of the modified battery enlarged in comparison with that of the conventionally sized tip, it is to be understood that the invention could also be adapted to operate if the positive tip of the modified secondary battery were reduced in diameter compared to the standard diameter tip of a regular battery. In this case, however, the invention would operate only by means of a voltage enablement scheme, such as the provision of charging current to the inner contact, only if there is no voltage present on the outer contact. This combination would indicate that there is a modified rechargeable battery with a small diameter tip in the cavity, while a standard sized tip would provide voltage to both parts of the cavity contact, and would thus disable charging. 
         [0055]    These embodiments thus fulfill the dual requirements of differentiating between chargeable and primary cells, and of providing transparent operation of the device regardless of which type of battery is used in the cavity. 
         [0056]    Reference is now made to  FIGS. 3A and 3B  which illustrate schematically, according to another preferred embodiment of the present invention, a scheme similar to that of  FIGS. 1A to 2C , but using a modified negative end of the battery instead. According to this embodiment, as shown in  FIG. 3A , the negative end  32  of the rechargeable battery  30  can be modified by decreasing the diameter of the electrical contact area on the end of the battery, such that it has a shape approaching that of the positive tip. The electronic device can then be provided with a modified two-part contact structure, similar to that shown in  FIGS. 2A-2C  above, preferably with a mechanism such as spring loading to ensure that the battery can be inserted and that the contacts sit firmly against the negative end plate. The operation of the negative contact embodiment of  FIGS. 3A and 3B  is unlike the positive tip contact embodiment of  FIGS. 1A to 2C , in that the outer part of the contact would be used only for detection of the absence or presence of a negative voltage relative to the positive terminal. It is only the inner contact part which makes the current contact with the negative end of the battery. The presence of a voltage (negative) on the outer contact is indicative of a standard battery, which, since it may be a primary battery, is operative to disable the circuits for providing charging current to the inner part of the contact. On the other hand, the absence of a voltage on the outer contact indicates that a modified rechargeable battery  30  with a reduced diameter negative contact end  32  is fitted in the cavity, thus enabling charging of the battery. This embodiment thus mandates the use of sensing circuits to enable the charging function. Alternatively and preferably, as described in the embodiments hereinbelow, a mechanical or opto-electronic method can be used to detect the presence of the reduced diameter at the negative end of the cell, and a charge enabling signal generated therefrom. 
         [0057]    Reference is now made to  FIG. 3B , which illustrates schematically, an alternative preferred method by which the modified negative end of a rechargeable battery  34  can be implemented, according to a further preferred embodiment of the present invention. In this modified battery  34 , the insulating covering applied to the cylindrical surface of the battery is extended such that it also insulates the outer diametrical annulus  36  of the negative end of the battery. The battery is then different from a regular sized battery only by the extent of the insulating cover applied to the battery. It is important that the extent of the added end insulation is not so much that it interferes with the contact between the central part of the end plate  38  and the standard spiral spring used in many current devices, If the end insulation covers an annulus of too large a width, no contact will be made, and the modified rechargeable battery of the present invention will not be useable in such devices. The modified rechargeable battery may not readily operate in current devices which use a spring metallic contact tongue, and full benefit may require slight adaptation of the negative contacts of devices which are to make use of this embodiment. 
         [0058]    The advantage of the above described options using modified battery contacts, whether positive tip or negative end, is the backward compatibility generally provided, i.e. that the modified rechargeable batteries can still generally be used in most existing products, and that standard batteries can be used in new devices having modified contacts, but with the added value of enabling the simple and low cost detection of rechargeable batteries in the new devices. 
         [0059]    Reference is now made to  FIGS. 4A to 4C , which illustrate schematically, according to another preferred embodiment of the present invention, a scheme whereby a modified battery cross sectional shape is used to differentiate between rechargeable and primary batteries. According to these preferred embodiments, the modified rechargeable battery is provided with a distinctively shaped barrel, different from the cylindrical barrel of a standard, prior art battery. A rectangular shaped barrel is a particularly preferred shape. 
         [0060]      FIG. 4A  shows schematically, one manner in which the battery cavity  40  of the device can be modified, preferably by the addition of a microswitch  42 , whose tongue  44  is activated by the shape of the modified rechargeable battery to enable the recharging current to be applied to the battery.  FIG. 4B  shows a standard cylindrical barrel battery  46  inserted into the cavity, where because of its cross sectional shape, it will not activate the microswitch  42 , such that no charging is enabled to the battery. 
         [0061]      FIG. 4C  shows schematically the insertion into the cavity of a modified rechargeable battery  47  according to this preferred embodiment, the battery having a rectangular cross section  48 , which depresses the microswitch tongue  44 , activating the microswitch and enabling charging current to be applied to the battery. 
         [0062]    Although a mechanically operated microswitch is a particularly simple implementation of the modified cross sectional shape embodiment of this invention, it is to be understood that such a modified shape could also be detected using an optical detection scheme, or an electrical contact scheme, or a magnetic proximity scheme, as is known in the art, without detracting from the novelty of this embodiment. 
         [0063]    An advantage of this shape option is that any existing standard-shaped rechargeable battery can be readily converted to the new format of this embodiment by use of a prismatic cover added to the standard battery. 
         [0064]    As an alternative to the provision of a completely distinctive shape, the modified rechargeable battery can be provided with a projection at a predetermined position, preferably along the length of the battery, and this projection is detected by the microswitch or other detection mechanism in the battery cavity. 
         [0065]    Reference is now made to  FIGS. 5A to 5C  and  6 A to  6 E, which illustrate schematically, according to more preferred embodiments of the present invention, schemes whereby a modified battery length is used to differentiate between rechargeable and primary batteries.  FIGS. 5A to 5E  illustrate an embodiment in which a battery of slightly increased length is used, while  FIGS. 6A to 6E  illustrate an embodiment in which a battery of standard length is used. According to either of these preferred embodiments, a micro-switch or an opto-electronic switch or any other suitable detection device as suggested hereinabove, is provided in the device battery cavity to detect this amended length, whether it is an increased length or a decreased length. 
         [0066]    In the preferred embodiments of  FIGS. 5A-5E , since the modified rechargeable battery is lengthened over that of a standard battery, a special battery cavity is required in the electronic device.  FIG. 5A  schematically shows a standard sized battery  50 , as compared to the modified battery  51  of  FIG. 5B , which is slightly longer.  FIG. 5C  shows a schematic drawing of a modified battery cavity  52 , to detect the longer modified battery of  FIG. 5B . The cavity preferably has a microswitch  53  or equivalently functioning position measuring device, and an appropriately positioned negative contact  54 , preferably constructed of a springy tongue as is commonly used in regular battery cavities.  FIG. 5D  now shows the standard length, unmodified, primary battery of  FIG. 5A  inserted into the cavity. The battery makes good contact with the negative contact  54  of the cavity, but is not long enough to depress the microswitch  53 , or otherwise to activate the length sensor used instead of the microswitch.  FIG. 5E  now shows the modified length rechargeable battery  51  of  FIG. 5B  inserted into the cavity. As in  FIG. 5D , the battery makes good contact with the negative contact  54  of the cavity, and depresses it sufficiently to activate the microswitch  53  or other length sensor, and thus to enable application of charging current to the cavity. 
         [0067]    In order that this changed length embodiment be backward compatible with standard battery sizes, the length change is preferably made by reduction of the length of the body of the battery barrel, but without changing the overall length of the battery from negative end to positive tip, such as is illustrated in  FIGS. 6A-6E .  FIG. 6A  schematically shows a standard sized battery  60 , as compared to the modified battery  61  of  FIG. 6B , which has a shorter body but the same overall length, such that it can be used in existing, conventional length battery cavities.  FIG. 6C  shows a schematic drawing of a modified battery cavity  62 , to detect the modified battery of  FIG. 6B . The cavity preferably has a microswitch  63  or equivalently functioning position measuring device, positioned such that the conventional form battery  60  of  FIG. 6A  will actuate the microswitch, or alternative sensor when it is inserted into the cavity, as shown in  FIG. 6D . This actuation is operative to disable the charging function to the cavity, thus preventing the primary battery from being charged, On the other hand, when a modified rechargeable battery  61  of the present invention, is inserted into the cavity, as in  FIG. 6E , the shortened barrel does not actuate the microswitch  63 , and charging is thus not disabled. 
         [0068]    The length detection scheme shown in  FIGS. 6A to 6E  could also be used on the above mentioned embodiment of  FIG. 3A , showing the reduced diameter negative contact end of the modified battery, since such a reduced diameter negative contact region can also be distinguished by the reduced barrel length at the outer diameter of the negative end of the battery. 
         [0069]    It is to be understood that although the non-standard length embodiments have been shown with the apparent increase in length at the negative end of the battery, this is purely for ease of explanation of the operation of the embodiment, and it is equally operative with the increased length “as if” at the positive end. 
         [0070]    The previous embodiments of the present invention have been related to physical changes in the dimensions of the modified rechargeable cell. However, it is also possible, according to further preferred embodiments of the present invention, to differentiate between different batteries by means of physical properties of the batteries other than dimensions, such as electrical properties, optical properties or magnetic properties. 
         [0071]    Reference is now made to  FIGS. 7A to 7E , which illustrate schematically, a further preferred embodiment of the present invention, in which the electrical conductivity of the outer surface of the battery is used for distinguishing a modified battery from a standard battery.  FIG. 7A  schematically shows a standard sized battery  70 , as compared to the modified rechargeable battery  71  of  FIG. 7B , which has the same dimensions, such that it can be used in existing, conventional length battery cavities. The battery of  FIG. 7B  is modified by the existence of an electrically conductive region  73  over part of its surface. In the preferred embodiment shown, the conductive region is shown at the central region of the barrel. The rest of the surface of the barrel is insulating.  FIG. 7C  shows a schematic drawing of a modified battery cavity  72 , to detect the modified battery of  FIG. 7B . The cavity preferably has a pair of electrical contacts  75  disposed such that when the battery of  FIG. 7B  is inserted, as shown in  FIG. 7E , there is electrical continuity between the two contacts. This electrical continuity can be used to activate the charging enabling circuitry  76 . If a standard battery  70  is inserted into the cavity, as shown in  FIG. 7D , the conventional surface insulation prevents charging from being activated. In order to avoid interference with the normal current flow of the battery, the conductive layer  73  is preferably printed onto the battery insulation, and is not simply a region in which the insulation ahs been removed. 
         [0072]    Reference is now made to  FIGS. 8A to 8E , which illustrate schematically, a further preferred embodiment of the present invention, in which electrical continuity is used for distinguishing a modified battery from a standard battery.  FIG. 8A  schematically shows a standard sized battery  80 , as compared to the modified rechargeable battery  81  of  FIG. 8B , which has the same dimensions, such that it can be used in existing, conventional length battery cavities. The battery of  FIG. 8B  is modified by the extension of the positive contact region of the battery by means of an electrically conductive layer preferably over part or over the entire top end of the battery  83 .  FIG. 8C  shows a schematic drawing of a modified battery cavity  82 , to detect the modified battery of  FIG. 8B . The cavity preferably has an electrical contact  85  disposed such that when the modified secondary battery  81  of  FIG. 8B  is inserted, as shown in  FIG. 8E , the contact acquires the same positive voltage as that of the positive battery contact of the cavity. This lack of differential voltage can be used, after inversion, to activate the charging enabling circuitry  86 . On the other hand, if a standard battery  80  is inserted into the cavity, as shown in  FIG. 8D , there is a voltage difference between the positive lead of the cavity and the contact  85 , and this voltage difference can be used to hold-off the charging circuits, such that the conventional battery  80  will not be charged. 
         [0073]    In those various embodiments of the rechargeable battery of the present invention which utilize amended mechanical shapes, opto-electronic detection can alternatively be used to detect the presence or absence of the amended mechanical shape of the battery, instead of the above-described mechanical microswitch detection. This can be operative either by detecting the blocking or passage of light passing between an opto-transmitter and detector, due to the presence or absence of the mechanical amendment to the battery shape, or by detecting whether light is reflected or not from the presence or absence of the mechanical amendment. Such an opto-electronic detection scheme can be applied whether to an amended barrel shape, to a mechanical projection, to an increased or decreased length, or even to a modified positive or negative battery tip. 
         [0074]    Reference is now made to  FIGS. 9A to 9E , which illustrate schematically, a further preferred embodiment of the present invention, in which opto-electronic detection is used for distinguishing a modified rechargeable battery from a standard battery.  FIG. 9A  schematically shows a standard sized battery  90 , as compared to the modified rechargeable battery  91  of  FIG. 9B , which has the same dimensions, such that it can be used in existing, conventional length battery cavities. The battery of  FIG. 9B  is modified by the existence of an optically high reflectivity region  93  over part of its surface. In the preferred embodiment shown, the reflective region  93  is shown at the central region of the barrel. The rest of the surface of the barrel is generally optically absorptive.  FIG. 9C  shows a schematic drawing of a modified battery cavity  92 , to detect the modified battery  91  of  FIG. 9B . The cavity preferably has an optical emitter  95 , such as a small LED, directed such that it emits a beam in the direction of a battery inserted in the cavity. A photodetector  97  is disposed such that when the modified secondary battery  91  of  FIG. 9B  is inserted into the cavity, as shown in  FIG. 9E , the light emitted from the source  95  is reflected by the reflective region of the modified battery  91 , into the photodetector  97 . The signal from the photodetector  97  can be used to enable the charging circuits of the electronic device. On the other hand, if a standard battery  90  is inserted into the cavity, as shown in  FIG. 9D , the light from the source  95  is diffusely scattered by the battery surface, and no signal is generated by the photodetector  97 , such that charging is not enabled. 
         [0075]    The embodiment of  FIGS. 9A to 9E  describes a reflective optical method of differentiating between batteries. However, light can also be used in a transmissive mode to perform this discrimination. 
         [0076]    Reference is now made to  FIGS. 10A to 10E , which illustrate schematically, a further preferred embodiment of the present invention, in which a transmissive opto-electronic detection method is used for distinguishing a modified rechargeable battery from a standard battery.  FIG. 10A  schematically shows a standard sized battery  100 , as compared to the modified rechargeable battery  101  of  FIG. 10B , which has the same dimensions, such that it can be used in existing, conventional length battery cavities. The battery of  FIG. 10B  is modified by the existence of a reduced diameter barrel  103  at the negative end of the battery, similar to that shown in the embodiment of  FIG. 3A .  FIG. 10C  shows a schematic drawing of a modified battery cavity  102 , to detect the modified battery  101  of  FIG. 10B . The cavity preferably has an optical emitter  105 , such as a small LED, directed such that it emits a beam in the direction of a battery inserted in the cavity. A photodetector  107  is disposed such that, unless blocked, it receives the light emitted by the LED  105 . As shown in  FIG. 10D , if a standard battery  100  is inserted into the cavity, the light from the source  105  is blocked by the end of the battery, and no signal is generated by the photodetector  97 , such that charging is not enabled. On the other hand, when the modified secondary battery  101  of  FIG. 10B  is inserted into the cavity, as shown in  FIG. 10E , the light emitted from the source  105  is not blocked by the battery because of the modified shape of the negative end, and the signal from the photodetector  107  can be used to enable the charging circuits of the electronic device. Instead of a modified barrel end, any other mechanical feature which allows transmission of the light could also be used, such as a groove in the surface, or the like. 
         [0077]    Reference is now made to  FIGS. 11A to 11C , which illustrate schematically a further preferred embodiment of the present invention, in which magnetic detection is used to determine the presence of a modified battery.  FIG. 11A  shows schematically a modified rechargeable battery  110  according to this preferred embodiment, with a small particle of magnetized material  113  mounted on or in the modified battery. The battery cavity  112  shown in  FIG. 11C  has a magnetic detection unit  115  installed, the output from which is used to enable or disable the charging functionality of the cavity. The magnetic field detector could preferably be a reed switch or a Hall probe or another suitable element sensitive to the presence of a magnetic field. In the embodiment shown in  FIG. 11B , a reed switch is depicted, whose contacts close in the vicinity of a magnetic field.  FIG. 11C  shows the insertion of the modified battery  110  into the cavity  112 , thus actuating the magnetic switch  115  by closing its contacts, which can be connected to the charging control to enable the charging circuits in the electronic device to operate. A conventional battery without the magnet would not affect the reed switch, and so could not be charged. Since the magnetic field passes through the casing of the battery, this embodiment of the present invention can also be implemented with the magnetized material mounted within the body of the battery, rather than being an external physical appurtenance, as with the previously described embodiments of this application. This can be achieved during manufacture by mounting a tiny magnet within the battery in a predetermined location, and arranging that the position of the magnetic field detector in the battery cavity is such that it is sensitive to the presence of the magnetic field from the battery. 
         [0078]    All of the above referenced embodiments have been described in terms of the rechargeable battery being modified, and the standard form being used for the primary battery. This would appear to be the more logical choice since primary batteries are the more basic and have more widespread use. However, it is to be understood that the present invention is not meant to be limited to this arrangement, but is equally applicable to embodiments wherein the rechargeable battery is the standard battery, and the primary battery is the modified battery. 
         [0079]    It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.