Patent Publication Number: US-2023155404-A1

Title: Mechanical Foolproof Design of Battery Charger and Rechargeable Battery

Description:
FIELD OF THE INVENTION 
     The present invention relates to a rechargeable battery and a battery charger both configured with respective mechanical features for enabling the battery charger to distinguish the rechargeable battery, which is of a preselected type, against a battery of an unaccepted type such that the battery charger recharges the preselected-type battery but does not recharge the unaccepted-type battery. 
     BACKGROUND 
     There are many different kinds of rechargeable batteries and different types of battery chargers in the global market. However, different kinds of rechargeable batteries employ different materials and chemical mechanisms in discharging and recharging. Under different chemical mechanisms and materials, different recharging arrangements and operation parameters should be used by battery chargers in order to ensure that respective chemical systems used in batteries are fully and safely charged. If, however, a rechargeable battery functioned under a certain chemical system is charged by a battery charger not matched to the chemical system used in the battery, the battery may be not fully charged or may be over-charged. Both cases create application problems or safety problems. 
     It is desirable if the battery charger used for recharging a certain rechargeable battery is capable of distinguishing the type of chemical system used in this battery. In the art, e.g., in CN 107994632A, an electronic circuitry is usually employed in the battery charger to identify the type of chemical system used in a battery under consideration for recharging. A major drawback of this approach is that a cost of the battery charger is inevitably increased. The increased cost is not desirable if, e.g., the battery charger is a disposable one bundled with a plurality of rechargeable batteries sold to a customer, where the battery charger is dedicated for recharging the plurality of rechargeable batteries. There is a need in the art for a cost-effective technique used in a battery charger for distinguishing a battery of a preselected, permitted type against unaccepted-type batteries. 
     SUMMARY OF THE INVENTION 
     The present invention is concerned with a co-design of rechargeable battery and a battery charger where the rechargeable battery belongs to a battery type intended to be recharged by the battery charger, and the battery charger is configured to avoid recharging batteries not of this battery type. 
     In a first aspect of the present invention, the battery charger is provided. The battery charger comprises one or more slots. An individual slot is used for recharging a preselected-type battery after the preselected-type battery is accommodated into the individual slot. The preselected-type battery has a lateral surface and a front-end surface. An edge formed between the lateral and front-end surfaces is a beveled edge. An unaccepted-type battery is defined as the preselected-type battery with the lateral and front-end surfaces extended such that the beveled edge is replaced by a line edge. 
     The individual slot comprises a cap and a positive charging terminal. The cap is formed with an interior channel used for receiving a front-end portion of the preselected-type battery. The cap comprises a stopping member. Advantageously, the stopping member gradually narrows the channel along a battery-insertion direction for stopping the preselected-type battery and the unaccepted-type battery from further advancement into the channel while the beveled edge enables the preselected-type battery to go deeper into the channel than the unaccepted-type battery does, thereby enabling the battery charger to distinguish the preselected-type battery from the unaccepted-type battery. The positive charging terminal is used for providing an external voltage to a positive electrode of the preselected-type battery to recharge the preselected-type battery. The positive charging terminal is positioned in the channel to barely touch the positive electrode when the preselected-type battery is stopped by the stopping member. It follows that while the preselected-type battery is allowed to be recharged, the positive charging terminal is disconnected from the unaccepted-type battery when the unaccepted-type battery is inserted into the channel, thereby achieving a desirable result of avoiding the battery charger from accidentally recharging the unaccepted-type battery. In addition to this advantage, in case the preselected-type battery is put into the individual slot in a wrong orientation such that a back-end portion of the preselected-type battery is inserted into the channel, the stopping member blocks a negative electrode of the preselected-type battery from contacting the positive charging terminal, enhancing safety in using the battery charger. 
     In certain embodiments, the stopping member is shaped to complement the beveled edge such that the stopping member seamlessly receives the beveled edge when the preselected-type battery is inserted into the channel. As a result, a mismatch between the stopping member and the line edge causes the stopping member to block the unaccepted-type battery from reaching deeper into the channel than the preselected-type battery when the unaccepted-type battery is inserted into channel. It causes the positive charging terminal to be disconnected from the unaccepted-type battery to thereby avoid the battery charger from accidentally recharging the unaccepted-type battery. 
     In certain embodiments, the cap further comprises an interior wall defining the interior channel, and the stopping member is a portion of the interior wall. 
     In certain embodiments, the cap further comprises an interior wall defining the interior channel, and a portion of the interior wall is shaped to complement the front-end surface such that the preselected-type battery is mated to the cap when the preselected-type battery is inserted into the channel. 
     In certain embodiments, the cap further comprises an interior wall defining the interior channel, and the stopping member is a flange protruding from the interior wall. 
     In certain embodiments, the cap further comprises an interior wall defining the interior channel, and the stopping member is a plurality of protrusions protruding from the interior wall. 
     In certain embodiments, the stopping member is shaped to complement a first beveled edge formed with a V-bevel. 
     In certain embodiments, the stopping member is shaped to complement a second beveled edge formed with a compound V-bevel. 
     In certain embodiments, the stopping member is shaped to complement a third beveled edge formed with a J-bevel. 
     In certain embodiments, the stopping member is shaped to complement a fourth beveled edge formed with a compound J-bevel. 
     In certain embodiments, the stopping member is shaped to complement a fifth beveled edge formed with a convex bevel. 
     In certain embodiments, the stopping member is shaped to complement a sixth beveled edge formed with a compound convex bevel. 
     In a second aspect of the present invention, an electrical-power supplying product is provided. 
     The electrical-power supplying product comprises one or more batteries of a preselected type. An individual preselected-type battery comprises a lateral surface and a front-end surface. An edge formed between the lateral and front-end surfaces is a beveled edge. The electrical-power supplying product further comprises a battery charger for recharging the one or more preselected-type batteries. The last-mentioned battery charger is any of the embodiments of the battery charger as disclosed in the first aspect of the present invention. 
     In certain embodiments, the beveled edge of the individual preselected-type battery is a first beveled edge formed with a V-bevel. Optionally, the stopping member of the cap of the individual slot is shaped to complement the first beveled edge. 
     In certain embodiments, the beveled edge of the individual preselected-type battery is a second beveled edge formed with a compound V-bevel. Optionally, the stopping member of the cap of the individual slot is shaped to complement the second beveled edge. 
     In certain embodiments, the beveled edge of the individual preselected-type battery is a third beveled edge formed with a J-bevel. Optionally, the stopping member of the cap of the individual slot is shaped to complement the third beveled edge. 
     In certain embodiments, the beveled edge of the individual preselected-type battery is a fourth beveled edge formed with a compound J-bevel. Optionally, the stopping member of the cap of the individual slot is shaped to complement the fourth beveled edge. 
     In certain embodiments, the beveled edge of the individual preselected-type battery is a fifth beveled edge formed with a convex bevel. Optionally, the stopping member of the cap of the individual slot is shaped to complement the fifth beveled edge. 
     In certain embodiments, the beveled edge of the individual preselected-type battery is a sixth beveled edge formed with a compound convex bevel. Optionally, the stopping member of the cap of the individual slot is shaped to complement the sixth beveled edge. 
     In certain embodiments, the cap of the individual slot further comprises an interior wall defining the interior channel. A portion of the interior wall is shaped to complement the front-end surface of the individual preselected-type battery such that when a respective preselected-type battery is inserted into the channel of the cap of the individual slot, the respective preselected-type battery is mated to the cap of the individual slot. 
     In certain embodiments, the stopping member of the cap of the individual slot is shaped to complement and fully cover the beveled edge. In addition, the beveled edge of the individual preselected-type battery has a height selected to be greater than a height of a positive electrode of the individual preselected-type battery for additionally allowing foolproof use of the battery charger by an end user. 
     In certain embodiments, the individual preselected-type battery further comprises: a rechargeable raw cell having a cylindrical shape; and a circuit board including an electronic circuit electrically connected to the raw cell for providing electrical protection to the individual preselected-type battery. 
     In certain embodiments, the electronic circuit is configured to provide a voltage step-down function during discharge of the raw cell. 
     In certain embodiments, the electronic circuit is further configured to provide over-charge or over-discharge protection to the raw cell. 
     In certain embodiments, the electronic circuit includes a light-emitting diode (LED) for signaling that the raw cell is under recharging. 
     In certain embodiments, the individual preselected-type battery further comprises a plastic cover for providing protection to the electronic circuit, the plastic cover being formed with the beveled edge. 
     In certain embodiments, the individual preselected-type battery further comprises: a metal electrode cap electrically connected to the circuit board for forming a positive electrode of the individual preselected-type battery; and a metal support ring between the raw cell and the circuit board for securely fixing the circuit board and the metal electrode cap at desired locations inside the individual preselected-type battery. 
     In certain embodiments, the circuit board is integrated with a wire and a metal pad for connecting the electronic circuit to a positive terminal of the raw cell, and the electronic circuit is electrically connected to a negative terminal of the raw cell through the metal support ring. 
     In certain embodiments, the electronic circuit includes a LED for signaling that the raw cell is under recharging, and the metal support ring is formed with one or more openings for allowing LED light generated from the electronic circuit to leave the individual preselected-type battery. Optionally, the individual preselected-type battery further comprises a plastic cover for providing protection to the electronic circuit, the plastic cover being transparent or semi-transparent for allowing LED light to leave the individual preselected-type battery. 
     In certain embodiments, the individual preselected-type battery further comprises an insulation tap ring partially covering the metal electrode cap for avoiding splashing water from going inside the individual preselected-type battery. 
     In certain embodiments, the individual preselected-type battery further comprises a plastic cover for providing protection to the electronic circuit, the plastic cover being formed with the beveled edge. In addition, the metal support ring includes one or more slot features for locking with the plastic cover, and the plastic cover includes one or more locking features for locking with the metal support ring. 
     In certain embodiments, the individual preselected-type battery further comprises a plastic label formed by a shrinkable sleeve for laterally covering the individual preselected-type battery. 
     In a third aspect of the present invention, a rechargeable battery is provided. 
     The battery comprises a lateral surface and a front-end surface. An edge formed between the lateral and front-end surfaces is a beveled edge. The beveled edge is recognizable as the preselected-type battery by the battery charger disclosed in the first aspect of the present invention, enabling the battery charger to recharge the battery. 
     In certain embodiments, the battery further comprises: a rechargeable raw cell having a cylindrical shape; and a circuit board including an electronic circuit electrically connected to the raw cell for providing electrical protection to the battery. 
     In certain embodiments, the electronic circuit is configured to provide a voltage step-down function during discharge of the raw cell. 
     In certain embodiments, the electronic circuit is further configured to provide over-charge or over-discharge protection to the raw cell. 
     In certain embodiments, the electronic circuit includes a LED for signaling that the raw cell is under recharging. 
     In certain embodiments, the battery further comprises a plastic cover for providing protection to the electronic circuit, the plastic cover being formed with the beveled edge. 
     In certain embodiments, the battery further comprises: a metal electrode cap electrically connected to the circuit board for forming a positive electrode of the battery; and a metal support ring between the raw cell and the circuit board for securely fixing the circuit board and the metal electrode cap at desired locations inside the battery. 
     In certain embodiments, the circuit board is integrated with a wire and a metal pad for connecting the electronic circuit to a positive terminal of the raw cell, and the electronic circuit is electrically connected to a negative terminal of the raw cell through the metal support ring. 
     In certain embodiments, the electronic circuit includes a LED for signaling that the raw cell is under recharging, and the metal support ring is formed with one or more openings for allowing LED light generated from the electronic circuit to leave the battery. Optionally, the battery further comprises a plastic cover for providing protection to the electronic circuit, the plastic cover being transparent or semi-transparent for allowing LED light to leave the battery. 
     In certain embodiments, the battery further comprises an insulation tap ring partially covering the metal electrode cap for avoiding splashing water from going inside the battery. 
     In certain embodiments, the battery further comprises a plastic cover for providing protection to the electronic circuit, the plastic cover being formed with the beveled edge. In addition, the metal support ring includes one or more slot features for locking with the plastic cover, and the plastic cover includes one or more locking features for locking with the metal support ring. 
     In certain embodiments, the battery further comprises a plastic label formed by a shrinkable sleeve for laterally covering the battery. 
     Other aspects of the present disclosure are disclosed as illustrated by the embodiments hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts, for illustrative purposes, a typical cylindrically-shaped battery shown in a first perspective view viewed from the top and a second perspective view viewed from the bottom. 
         FIG.  2    depicts a preselected-type battery comprising a mechanical feature, which is a beveled edge, recognizable by a battery charger such that the battery charger is activated to recharge the preselected-type battery. 
         FIG.  3    depicts an unaccepted-type battery not having the aforementioned mechanical feature such that the battery charger is not activated to recharge the unaccepted-type battery. 
         FIG.  4    depicts, in accordance with an exemplary embodiment of the present invention, a battery charger for recognizing and thereby recharging the preselected-type battery while disallowing the unaccepted-type battery to be recharged by the battery charger. 
         FIG.  5    depicts an enlarged view of the battery charger around a cap installed in a slot of the battery charger, where the cap is installed with a mechanical arrangement, which is a stopping member, for distinguishing the preselected-type battery against the unaccepted-type battery. 
         FIG.  6    depicts a first variant of the stopping member usable in the battery charger. 
         FIG.  7    depicts a second variant of the stopping member usable in the battery charger. 
         FIG.  8    depicts different shapes usable to form the beveled edge as used in designing the preselected-type battery and the battery charger. 
         FIG.  9    depicts a rechargeable battery as one implementation of the preselected-type battery, where the rechargeable battery incorporates an electronic circuit and a rechargeable electric cell of standard cylindrical shape. 
         FIG.  10    depicts various views of a metal support ring for illustrating internal features thereof, where the metal support ring is used in the rechargeable battery of  FIG.  9   . 
         FIG.  11    depicts veracious views of a plastic cover for illustrating internal features thereof, where the plastic cover is used in the rechargeable battery of  FIG.  9   . 
         FIG.  12    plots cross-section diagrams depicting examples of the stopping member for illustrating three different configurations of the stopping member. 
     
    
    
     Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale. 
     DETAILED DESCRIPTION 
     As used herein, the term “avoid” or “avoiding” refers to any method to partially or completely preclude, avert, obviate, forestall, stop, hinder or delay the consequence or phenomenon following the term “avoid” or “avoiding” from happening. The term “avoid” or “avoiding” does not mean that it is necessarily absolute, but rather effective for providing some degree of avoidance or prevention or amelioration of consequence or phenomenon following the term “avoid” or “avoiding”. 
     The following terms are used herein in the specification and appended claims. “An edge” of an object is a line or an elongated strip joining two non-parallel surfaces of the object. The edge may have a negligible width or a noticeable width. “A line edge” is an edge having a negligible width. In practice, a line edge formed by bending a metal sheet is usually a curvature having a small radius (e.g., ˜0.2 mm). For the purpose of determining a line edge, the aforementioned negligible width may be upper-bounded by 0.8 mm, assuming a 0.5 mm radius of curvature and an angle of 90° between the two non-parallel surfaces. “A beveled edge” is an edge formed by two non-parallel surfaces of an object and realized as an elongated strip having a strip surface, where the strip surface is distinguishable from, and is comparatively smaller than, the two non-parallel surfaces. Note that the strip surface, i.e. the beveled edge itself, forms a transition between the two non-parallel surfaces. Usually, the strip surface does not make a right angle with any one of the two non-parallel surfaces. In one common form, the beveled edge has a flat strip surface and is realized as a chamfered edge from a carpenter&#39;s viewpoint. 
     Technical terms used herein for describing various parts of a battery are illustrated in this paragraph with the aid of  FIG.  1   , which depicts a typical battery  100  shown in a first perspective view viewed from the top and a second perspective view viewed from the bottom. The battery  100  has “a positive electrode”  141 , “a negative electrode”  142 , and “an elongated body”  115 . The elongated body  115  is usually substantially-cylindrical in shape. The elongated body  115  has “a front end”  123  and “a back end”  133 , where the positive electrode  141  resides on the front end  123  and the negative electrode  142  resides on the back end  133 . Furthermore, the front end  123  includes the positive electrode  141 , and the back end  133  includes the negative electrode  142 . “A front-end surface”  120  is a surface of the front end  123 . “A back-end surface”  130  is a surface of the back end  133 . Note that the front-end surface  120  includes a surface of the positive electrode  141 , and the back-end surface  130  includes a surface of the negative electrode  142 . Denote “a front-end portion”  125  of the battery  100  as a portion of the elongated body  115  adjacent to, and including, the front end  123 . Denote “a back-end portion”  135  of the battery  100  as a portion of the elongated body  115  adjacent to, and including, the back end  133 . Between the front end  123  and the back end  133  there is “a lateral surface”  110  on the elongated body  115 . An edge  121  is formed between the lateral surface  110  and the front end  123 . Typically, the edge  121  is a line edge, which has a negligible width so that the edge  121  forms a sharp corner in the front-end portion  125 . However, the present invention is not limited only to the case that the edge  121  is a line edge; the edge  121  may have a non-negligible width. 
     The present invention provides a co-design of a rechargeable battery and a battery charger where the rechargeable battery belongs to a battery type intended to be recharged by the battery charger, and the battery charger avoids itself from recharging batteries not of this battery type. Denote the battery type intended to be recharged by the battery charger as “a preselected type”. Hence, the aforementioned rechargeable battery is “a battery of a preselected type” or “a preselected-type battery.” Denote a battery that the battery charger avoids to recharge as “a battery of an unaccepted type” or “an unaccepted-type battery.” 
     The Inventors notice that in reducing a cost of manufacturing the battery charger while enabling the battery charger to distinguish different types of rechargeable batteries and recharge only batteries of a preselected type, a mechanical arrangement is more preferable than an electronic means in checking if a battery received by the battery charger is a preselected-type battery. Furthermore, the mechanical arrangement is required to be simple and foolproof because an end user actually handles the operational procedure of using the battery charger to recharge batteries. 
     Exemplarily,  FIG.  2    depicts a preselected-type battery  200  comprising a mechanical feature recognizable by a battery charger for triggering or activating the battery charger to recharge the preselected-type battery  200 . For comparison,  FIG.  3    depicts an unaccepted-type battery  300 , which does not have the aforementioned mechanical feature such that the battery charger is not activated to recharge the unaccepted-type battery  300 . 
     The preselected-type battery  200  comprises a lateral surface  210 , a front-end surface  220 , and an edge  221  formed between the lateral surface  210  and the front-end surface  220 . Specifically, the edge  221  is formed as a beveled edge  221 . As will be explained later, the beveled edge  221  is advantageously used as the aforementioned mechanical feature for enabling the battery charger to distinguish the preselected-type battery from the unaccepted-type battery  300 . For the purpose of forthcoming illustration of the disclosed battery charger, it is mentioned that generally the preselected-type battery  200  further comprises a positive electrode  241 , a negative electrode  242 , an elongated body  215 , a front end  223 , a back end  233 , a front-end surface  220 , a back-end surface  230 , a front-end portion  225  and a back-end portion  235 . The elongated body  215  has a major axis  290 . 
     The unaccepted-type battery  300  is defined as the preselected-type battery  200  with the lateral surface  210  and front-end surface  220  extended such that the beveled edge  221  is replaced by a line edge. Particularly, the lateral surface  210  is extended along a direction of the major axis  290  to meet the front-end surface  220  that is extended along a radial direction perpendicular to the major axis  290 . That is, in the unaccepted-type battery  300 , an edge  321  formed by a lateral surface  310  and a front-end surface  320  is a line edge  321  while the preselected-type battery  200  and the unaccepted-type battery  300  are kept the same in height and width. A height  285  of the preselected-type battery  200  is a distance between the front end  223  (or the positive electrode  241 ) and the back end  233  of the preselected-type battery  200 . A height  385  of the unaccepted-type battery  300  is a distance between a front end  323  (or a positive electrode  341 ) and a back end  333  of the unaccepted-type battery  300 . A width  286  of the preselected-type battery  200  is a width of the elongated body  215  of the preselected-type battery  200 . A width  386  of the unaccepted-type battery  300  is a width of an elongated body  315  of the unaccepted-type battery  300 . Note that the unaccepted-type battery  300  resembles a commercially-available cylindrically-shaped battery compliant to published standards put forth by International Electrotechnical Commission, such as an AA-size battery. 
       FIG.  4    depicts an exemplary battery charger  400  for recognizing the beveled edge  221  of the preselected-type battery  200  and hence recharging the preselected-type battery  200  while disallowing the unaccepted-type battery  300  from being recharged by the battery charger  400 . 
     The battery charger  400  comprises one or more slots  410 - 413 . Although  FIG.  4    depicts that four slots are used in the battery charger  400  as a particular case for illustration, the present invention is not limited only to this number of slots in implementing the battery charger  400 ; the battery charger  400  may be installed with any positive number of slot(s). An individual slot (i.e. any one of the slots  410 - 413 ) is used for recharging the preselected-type battery  200  after the preselected-type battery  200  is accommodated into the individual slot. The individual slot is installed with a cap for receiving a front-end portion of a battery that is inserted to the individual slot. The slots  410 - 413  are installed with respective caps  420 - 423 , respectively. In implementation of the battery charger  400 , the respective caps  420 - 423  may be realized as physically separate components, or more commonly, may collectively be manufactured as one integrated unit composed of the respective caps  420 - 423 . 
     Without loss of generality, consider the slot  410  as a representative slot for illustrating operating principles of the battery charger  400 .  FIG.  5    depicts an enlarged view of the battery charger  400  around the cap  420  of the slot  410 . The cap  420  is formed with an interior channel  520  used for receiving the front-end portion  225  of the preselected-type battery  200 . The preselected-type battery  200 , or any other battery such as the unaccepted-type battery  300 , is inserted into the channel  520  along a battery-insertion direction  590 . The cap  420  comprises a stopping member  530 . Particularly, the stopping member  530  gradually narrows the channel  520  along the battery-insertion direction  590  for stopping the preselected-type battery  200  and the unaccepted-type battery  300  from further advancement into the channel  520 . In practice, the stopping member  530  is also used for stopping any battery received by the slot  410  where the battery is similar to the preselected-type battery  200  in size. As a particular advantage of gradually narrowing the channel  520  along the battery-insertion direction  590 , the beveled edge  221  enables the preselected-type battery  200  to go deeper into the channel  520  than the unaccepted-type battery  300 , thereby enabling the battery charger  400  to distinguish the preselected-type battery  200  from the unaccepted-type battery  300 . Note that by “gradually narrowing the channel  520 ,” abrupt narrowing the channel  520  by a step change at a certain location of the channel  520  is excluded. The presence of the step change may block both the preselected- and unaccepted-type batteries  200 ,  300  at the aforementioned certain location of the channel  520 . The slot  410  is further installed with a positive charging terminal  510  for providing an external voltage to the positive electrode  241  of the preselected-type battery  200  in order to recharge the preselected-type battery  200 . (The external voltage is usually a positive voltage with respect to a reference voltage at the negative electrode  242  of the preselected-type battery  200 .) In particular, the positive charging terminal  510  is positioned in the channel  520  to barely touch the positive electrode  241  when the preselected-type battery  200  is stopped by the stopping member  530  during the preselected-type battery  200  advancing into the channel  520 . As used herein, “barely touch” means “only just touch”. The combination of this positional arrangement of the positive charging terminal  510  and the different depths of penetration into the channel  520  by the preselected- and unaccepted-type batteries  200 ,  300  gives rise to the following advantage. While the preselected-type battery  200  is allowed to be recharged by connecting to the positive charging terminal  510 , the positive charging terminal  510  is disconnected from the unaccepted-type battery  300  when the unaccepted-type battery  300  is inserted into the channel  520 , thereby avoiding the battery charger  400  from accidentally recharging the unaccepted-type battery  300 . 
     As one form of gradually narrowing the channel  520  along the battery-insertion direction  590 , the stopping member  530  is shaped to complement the beveled edge  221  (as shown in  FIG.  2   ) such that the stopping member  530  seamlessly receives the beveled edge  221  when the preselected-type battery  200  is inserted into the channel  520 . By shaping the stopping member  530  to complement the beveled edge  221 , it is meant that a first surface of the stopping member  530  intended to contact a second surface of the beveled edge  221  has a surface profile complementary to a surface profile of the second surface such that when the beveled edge  221  is received and contacted by the stopping member  530 , an empty space formed between the first and second surfaces is substantially vanished. The stopping member  530  may be further configured to fully, or partially, cover the beveled edge  221  when the preselected-type battery  200  is stopped by the stopping member  530 . Furthermore, positioning the positive charging terminal  510  to barely touch the positive electrode  241  upon the preselected-type battery  200  being stopped by the stopping member  530  is achievable by judiciously setting a distance  535  measured along a major axis  430  of the slot  410  between the positive charging terminal  510  and the stopping member  530 . The distance  535  is required to be the same as a corresponding distance  281  between the positive electrode  241  and the beveled edge  221  of the preselected-type battery  200  (see  FIG.  2   ). Note that the corresponding distance  281  is measured along the major axis  290  of the elongated body  215 . As a result of the above-mentioned arrangement on shaping the stopping member  530  and positioning the positive charging terminal  510 , a mismatch between the stopping member  530  and the line edge  321  of the unaccepted-type battery  300  causes the stopping member  530  to block the unaccepted-type battery  300  from reaching deeper into the channel  520  than the preselected-type battery  200  does when the unaccepted-type battery  300  is inserted into channel  520 . It causes the positive charging terminal  510  to be disconnected from the unaccepted-type battery  300 , thereby avoiding the battery charger  400  from accidentally recharging the unaccepted-type battery  300 . 
       FIG.  12    plots cross-section diagrams depicting examples of the stopping member  530  for illustrating the three different configurations of the stopping member  530  as disclosed above. A first stopping member  1230   a  depicts an exemplary general configuration of the stopping member  503  that gradually narrows along the battery-insertion direction  590 . A second stopping member  1230   b  is shaped to complement and fully cover the beveled edge  221 . A third stopping member  1230   c  is shaped to complement the beveled edge  221  as well, but the third stopping member  1230   c  only partially covers the beveled edge  221 . 
     As a demonstration, the two slots  422 ,  423  as shown in  FIG.  4    are inserted with the unaccepted-type battery  300  and the preselected-type battery  200 , respectively. It is apparent that the preselected-type battery  200  advances deeper into the interior channel of the slot  423  than the unaccepted-type battery  300  goes into the interior channel of the slot  422  because the line edge  321  of the unaccepted-type battery  300  is blocked by the stopping member of the slot  422  whereas the beveled edge  221  of the preselected-type battery  200  is well received by the stopping member of the slot  423 . The positive electrode  241  of the preselected-type battery  200  is able to contact the positive charging terminal of the slot  423 , allowing the battery charger  400  to recharge the preselected-type battery  200 . On the other hand, the positive electrode  341  of the unaccepted-type battery  300  is unable to contact the positive charging terminal of the slot  422 , preventing the battery charger  400  from recharging the unaccepted-type battery  300 . 
     In addition to this advantage, the battery charger  400  provides another advantage of enhancing safety in using the battery charger  400  in case an end user incorrectly puts the preselected-type battery  200  into the slot  410  in a wrong orientation such that the back-end portion  235  is inserted into the channel  520 . In this case, the stopping member  530  blocks the negative electrode  242  from contacting the positive charging terminal  510 . 
     As shown in  FIG.  5   , the cap  420  further comprises an interior wall  521  where the interior wall  521  defines the interior channel  520 . 
       FIG.  5    additionally depicts certain embodiments of forming the stopping member  530  in the cap  420 . Preferably, the stopping member  530  is a surface formed by a first portion  541  of the interior wall  521 . Furthermore, it is preferable that a second portion  542  of the interior wall  521  is shaped to complement the front-end surface  220  of the preselected-type battery  200 . As a result, the preselected-type battery  200  is mated to the cap  420  when the preselected-type battery  200  is inserted into the channel  520 . In general, shaping the interior wall  521  to the front-end portion  225  of the preselected-type battery  200  has the advantages that the stopping member  530  is simultaneously formed with the cap  420  in manufacturing the battery charger  400  and that the positive charging terminal  510  can be simply put on the interior wall  521  during assembling the battery charger  400 . 
       FIGS.  6  and  7    illustrate other embodiments of forming the stopping member  530  by depicting respective caps in cross-sectional top view and cross-sectional side view.  FIG.  6    depicts the cap  420  installed with a first variant of stopping member  530   a . The stopping member  530   a  is realized as a flange protruding from the interior wall  521 .  FIG.  7    depicts the cap  420  installed with a second variant of stopping member  530   b . The stopping member  530   b  is formed as a plurality of protrusions protruding from the interior wall  521 . Other variants of the stopping member  530  are also possible, and can be designed by those skilled in the art according to the teaching disclosed herein. 
     Various embodiments of the beveled edge  221  can be adopted in designing the preselected-type battery  200  as well as in designing the stopping member  530  of the battery charger  400 .  FIG.  8    depicts various shapes that can be used to form the beveled edge  221 . In its simplest form, the beveled edge  221  may be a first beveled edge  221   a  formed with a V-bevel. Instead of forming the beveled edge  221  with one slope as in the V-bevel, it is possible to form the beveled edge  221  with multiple slopes. In this configuration, the beveled edge  221  may be a second beveled edge  221   b  formed with a compound V-bevel. Apart from V-bevel, a J-bevel may also be used. The beveled edge  221  may be a third beveled edge  221   c  formed with a J-bevel. The beveled edge  221  may also be a fourth beveled edge  221   d  formed with a compound J-bevel. Note that the J-bevel has a concave shape. Correspondingly, there is a convex bevel. The beveled edge  221  may be a fifth beveled edge  221   e  formed with a convex bevel. The beveled edge  221  may also be a sixth beveled edge  221   f  formed with a compound convex bevel. Similarly, the stopping member  530  of the battery charger  400  may be shaped to complement the first beveled edge  221   a , the second beveled edge  221   b , the third beveled edge  221   c , the fourth beveled edge  221   d , the fifth beveled edge  221   e , or the sixth beveled edge  221   f.    
     One parameter involved in the co-design of the preselected-type battery  200  and the battery charger  400  is a height  282  of the beveled edge  221 . If the stopping member  530  is shaped to complement and fully cover the beveled edge  221 , the beveled-edge height  282  is roughly a distance between the positive charging terminal  510  of the battery charger  400  and the positive electrode  341  of the unaccepted-type battery  300 . Hence, the beveled-edge height  282  characterizes an allowable displacement measured along the major axis  430  in positioning the positive charging terminal  510  in the interior channel  520  with respect to the stopping member  530 . This allowable displacement is related to manufacturing tolerance and long-term reliability of the battery charger  400 . The beveled-edge height  282  may be set from 1 mm to 4 mm in general, more preferably from 2 mm to 4 mm, and even more preferably from 3 mm to 4 mm. Preferably, the beveled-edge height  282  is selected to be greater than a height  283  of the positive electrode  241  for additionally allowing foolproof use of the battery charger  400  by an end user, under the condition that the stopping member  530  is shaped to complement and fully cover the beveled edge  221 . Note that the beveled-edge height  282  and the positive-electrode height  283  are measured along the major axis  290  of the elongated body  215 . 
     The disclosed battery charger  400  offers various advantages such as reducing a manufacturing cost, being simple to use and being foolproof. By using the stopping member  530  to avoid the unaccepted-type battery  300  from being recharged while allowing the preselected-type battery  200  to be recharged, an electronic means for detecting the type of battery inserted into the slot  410  is not required, allowing the manufacturing cost of the battery charger  400  to be reduced. In operating the battery charger  400 , an end user is only required to insert a battery into a slot of the battery charger  400  in an ordinary way. Whether or not the battery is of the preselected type is determined entirely by the battery charger  400 , and the battery charger  400  may be programmed or configured to automatically initiate a recharging process after the battery is determined to be of the preselected type, offering convenience to the end user. The battery charger  400  is foolproof in that the battery charger  400  automatically determines whether the battery that is inserted is of the preselected type or of the unaccepted type without a need for the end user&#39;s additional involvement in the determination. 
     Those skilled in the art will notice that additional components are required to be implemented in the battery charger  400  for making the battery charger  400  functional, and that determination of these additional components is within the common knowledge of those skilled in the art. These additional components may be: a negative charging terminal for maintaining a negative voltage (with respect to the external voltage provided by the positive charging terminal  510 ) at the negative electrode  242  of the preselected-type battery  200 ; a clamping mechanism for securely holding the preselected-type battery  200  between the positive charging terminal  510  and the negative charging terminal; a charging circuit for providing a charging current to the preselected-type battery  200 ; an overcurrent protection circuit for preventing excessive current to be supplied to the preselected-type battery  200 ; a casing for enabling the end user to easily grasp the battery charger  400 ; any feature related to safety in using the battery charger  400 ; etc. 
     Note that in the presence of the beveled edge  221 , the preselected-type battery  200  has a shape deviated from a conventional design of a cylindrically-shaped battery. Despite this, the unconventional shape does not necessarily require a substantial re-design of an internal structure of a standard cylindrical battery to form the preselected-type battery  200  if the preselected-type battery  200  is formed with not only one or more electric cells of standard cylindrical shape but also an electronic circuit for performing certain functions in battery management and output-current management. Advantageously, electric cells of standard cylindrical shape as manufactured in bulk quantity for conventional cylindrically-shaped batteries are reusable in the preselected-type battery  200 . 
     One reason for including electronic circuits in practical rechargeable batteries is that a lithium-ion (Li-ion) cell provides a voltage of ˜3.6V but a standard cylindrically-shaped battery (e.g., AA or AAA battery) offers a nominal voltage of 1.5V. In a rechargeable battery, an electronic circuit is therefore required for stepping down the voltage from 3.6V to 1.5V and cutting off an external voltage from electrical cells housed in the battery in case overcharging happens. 
       FIG.  9    depicts a rechargeable battery  900  incorporating an electronic circuit and a rechargeable electric cell of cylindrical shape, where the battery  900  represents certain embodiments of the preselected-type battery  200  and forms one implementation of the preselected-type battery  200 . The battery  900  comprises: a raw cell  910  that is rechargeable; a circuit board  940  including an electronic circuit  943 ; a metal support ring  950  between the raw cell  910  and the circuit board  940 ; a metal electrode cap  930  atop the circuit board  940 ; an insulation tap ring  960  resting on the metal electrode cap  930 ; a plastic cover  920  partially covering the insulation tap ring  960  and the metal electrode cap  930 ; and a plastic label  952  for laterally covering the battery  900 . Note that the plastic cover  920  is formed with a beveled edge  928 , a main feature for enabling the battery charger  400  to recognize that the battery  900  is of the preselected type. 
     The raw cell  910  has a cylindrical shape and is used for providing electrical power though discharging and for storing electrical energy during recharging. The raw cell  910  has a positive terminal  911  and a negative terminal  912 . The positive terminal  911  is located at a center of a top side of the raw cell  910  whereas the negative terminal  912  covers not only a bottom side of the raw cell  910  but also a lateral side thereof. In one embodiment, the raw cell  910  is secondary Li-ion chemistry cell providing a nominal voltage of 3.2V between the positive and negative terminals  911 ,  912 . In general, the provided voltage depends on chemical compositions of the raw cell  910 . 
     The electronic circuit  943  installed in the circuit board  940  is used to provide electrical protection to the battery  900 . Particularly, the electronic circuit  943  is electrically connected to the raw cell  910 . The electronic circuit  943  may provide over-charge or over-discharge protection to the raw cell  910 . The electronic circuit  943  may also provide a voltage step-down function from 3.2V to 1.5V during discharge of the raw cell  910 . Optionally, the electronic circuit  943  includes a LED for signaling that the raw cell  910  is under recharging. The circuit board  940  may be integrated with a wire  941  and a metal pad  942  for connecting the electronic circuit  943  to the positive terminal  911  of the raw cell  910 . In practical implementation, the wire  941  and the metal pad  942  may be different objects joined together by, e.g., soldering or welding, or may be collectively formed as a single piece of metal strip. Preferably and conveniently, the electronic circuit  943  is electrically connected to the negative terminal  912  through the metal support ring  950 . 
     The metal electrode cap  930  forms a positive electrode of the battery  900  and is electrically connected to the circuit board  940 . Preferably, the metal electrode cap  930  has a flat bottom surface for conveniently mounting the metal electrode cap  930  to the circuit board  940  during assembling the battery  900 . 
     The metal support ring  950  provides a platform for securely fixing the circuit board  940  and the metal electrode cap  930  at desired locations inside the battery  900 . The metal support ring  950  also provides an electrical connection between the negative terminal  912  of the raw cell  910  and the circuit board  943 . Optionally, the metal support ring  950  is formed with one or more openings  951  for allowing LED light generated from the electronic circuit  943  to leave the battery  900 . 
     The plastic cover  920  provides protection to the electronic circuit  943 . Optionally, the plastic cover  920  is transparent or semi-transparent for allowing LED light to leave the battery  900 . 
     The insulation tap ring  960  partially covering the metal electrode cap  930  provides a top cover to the battery  900  for avoiding splashing water from going inside the battery  900  through the top side. 
     The plastic label  952  for laterally covering the battery  900  may be formed by a shrinkable sleeve. 
       FIG.  10    depicts various views of the metal support ring  950  for illustrating internal features thereof. Preferably, the metal support ring  950  includes one or more slot features  956  for locking with the plastic cover  920 . In one embodiment, there is a pair of slot features  956  as shown in  FIG.  10   . Preferably, the metal support ring  950  has a flat bottom surface  955  for allowing the metal support ring  950  to be soldered to the top of the raw cell  910 . It is also preferable that the metal support ring  950  has a flat top surface  957  for facilitating the metal support ring  950  to be soldered or welded to the circuit board  940 . 
       FIG.  11    depicts various views of the plastic cover  920  for illustrating internal features thereof. Preferably, the plastic cover  920  includes one or more locking features  921  for locking with the metal support ring  950 . In one embodiment, there is a pair of locking features  921  as shown in  FIG.  11   . Preferably, the plastic cover  920  further includes one or more ribs  922  at an inner surface of the plastic cover  920  for controlling positions of components held inside the plastic cover  920 . Optionally, the plastic cover  920  further includes an upper step  923  for providing a space to add a sealing glue thereon. In certain embodiments, the plastic cover  920  further includes a bottom step  924  for covering a bottom edge of the metal support ring  950 . 
     Based on the preselected-type battery  200  and the battery charger  400  as disclosed above, an electrical-power supplying product may be formed. The product comprises one or more batteries of a preselected type, and any of the above-disclosed embodiments of the battery charger  400  for recharging the one or more preselected-type batteries. Each aforesaid preselected-type battery is an embodiment of the preselected-type battery  200  as disclosed above. The product may be formed as a package containing articles, where the articles include the battery charger  400  and the one or more batteries of the preselected type. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.