Patent Publication Number: US-10326292-B2

Title: Battery charger operating method and method usable with plural different power supplies

Description:
This Application is a division of U.S. patent application Ser. No. 15/053,539 filed Feb. 25, 2016 entitled “USB CONNECTOR USABLE WITH A BATTERY CHARGER AND OTHERWISE,” and is also a division of U.S. patent application Ser. No. 15/053,606 filed Feb. 25, 2016 entitled “BATTERY CHARGER USABLE WITH PLURAL DIFFERENT POWER SUPPLIES,” both of which claim the benefit of U.S. Provisional Application Ser. No. 62/249,606 filed Nov. 2, 2015 entitled “BATTERY CHARGER USABLE WITH PLURAL DIFFERENT POWER SUPPLIES,” and of U.S. Provisional Application Ser. No. 62/132,037 filed Mar. 12, 2015 entitled “BATTERY CHARGER USABLE WITH PLURAL DIFFERENT POWER SUPPLIES,” each of which is hereby incorporated herein by reference in its entirety. 
    
    
     In one aspect, the invention relates to a method for charging one or more batteries. The invention also relates to a method for operating a battery charger. 
     In another aspect, the invention may relate to a connector arrangement usable with the battery charger and otherwise. In yet another aspect, the present invention may relate to a battery charger and, in particular, to a battery charger usable with plural different power supplies. 
     As the size and power requirements of electronic circuitry has shrunk and the energy storage capacity of batteries per unit volume has increased, more and more types of electronic devices shrink in size and become more portable, thus lending themselves to charging from lower power capacity power supply devices as well as from conventional power supplies. Typically power supplies have distinctive connectors, or a variety of relatively standardized power connectors, e.g., coaxial contact connectors of different voltages, currents, polarity and diameters, and so are not interchangeable with each other. 
     Also, as more electronic devices transmit and receive data via connecting cables, and to and from external memory devices, e.g., external drives and “thumb” or flash drives, a standardized interface called a universal serial bus (USB) interface has become the standard for interconnection with and between electronic devices. The USB interface includes a pair of male and female mating connectors that have power pins for +5 volts DC and ground or return, and two pins for data transmission. 
     While the current available from the +5 Volt DC (herein VDC) USB connector power supply pin can vary greatly, e.g., from a standard level of one hundred milliamperes, e.g., from a device such as a laptop computer, but possibly to a greater current, e.g., up to about 1.8 or about 2.4 amperes from a power supply, it is usually able to provide a level of current that is sufficient for recharging a rechargeable battery, even if at a less than optimum or less than maximum charge rate. The longer charging time is often an acceptable penalty in exchange for the convenience of using an available USB port to recharge a device. 
     In another aspect, conventional USB connectors, such as those usable with battery charging, can be damaged relatively easily if not properly aligned and/or oriented when being connected, e.g., mated with a compatible connector, and also may be subject to being dislodged or de-mated unintentionally. 
     Applicant believes there may be a need for a battery charger and for a method for operating a battery charger that addresses some or all of the foregoing battery charger related aspects. In addition, Applicant also believes there may be a need for a connector that addresses some or all of the foregoing connector related aspects. 
     Accordingly, a battery charger may comprise: a housing having at least one cradle; a connector port for receiving at different times electrical plug connectors having different contact configurations; electrical receptacles in the connector port for receiving at different times electrical plug connectors associated with different electrical power supplies; a first electrical receptacle having a different contact configuration than a second electrical receptacle; the electrical receptacles being closely adjacent such that an electrical connector inserted into one of the electrical receptacles physically prevents an electrical connector from being inserted into the other electrical receptacle; and an electrical circuit coupling electrical power received at the electrical receptacles to the at least one cradle. 
     In another aspect, an electrical connector may comprise: an elongated connector body with an electrical connector frame at one end thereof; the connector body having a longitudinal alignment feature, a guide feature defining an orientation, and a retaining feature. 
     An electrical connector may comprise: an electrical connector frame supported on a base; an alignment and retaining structure including first and second opposing guide members configured for an elongated connector body to be placed therebetween to mate with the electrical connector frame; the first guide member configured to align a complementary feature of the connector body and to receive a guide feature on the connector body that defines an orientation; and at least one of the first and second guide members having a retaining feature configured to engage the connector body for retaining the elongated connector body between the first and second guide members with the connector body mated with the electrical connector frame. 
     In yet another aspect, a method for charging a battery may comprise:
         a) determining whether a battery is present;   b) setting an initial charge current level;   c) repetitively interrupting charging of the battery at a predetermined timing to define a periodic cycle, and for each periodic cycle:
           measuring an open circuit voltage of the battery when charging of the battery is interrupted,   determining from the measured open circuit voltage a level of charging current;   applying charging current to the battery; and   
           d) repeating the periodic cycle at least until the open circuit voltage is at a voltage indicative of the battery being fully charged or until the battery is disconnected.       

     According to another aspect, a method for charging a rechargeable battery may comprise:
         a) determining whether a battery is present;   b) setting an initial charge current level;   c) determining the current available from an external power supply including:
           i) measuring a voltage provided by the external power supply;   ii) determining whether the external power supply voltage is less than a predetermined voltage and, if so:   iii) decreasing the current drawn from the external power supply;   
           d) repeating the foregoing steps of i) measuring, ii) determining and iii) decreasing until the external power supply voltage is not less than the predetermined voltage.       

     According to a further aspect, a method for charging a rechargeable battery may comprise:
         a) determining whether a battery is present;   b) setting an initial charge current level;   c) determining the current available from an external power supply including:
           i) measuring a voltage provided by the external power supply;   ii) determining whether the external power supply voltage is less than a predetermined voltage and, if so:   iii) decreasing the current drawn from the external power supply;   
           d) repeating the foregoing steps of i) measuring, ii) determining and iii) decreasing until the external power supply voltage is not less than the predetermined voltage; and   e) repetitively interrupting charging of the battery at a predetermined timing to define a periodic cycle, and for each periodic cycle:
           i) measuring an open circuit voltage of the battery when charging of the battery is interrupted,   ii) determining from the measured open circuit voltage a level of charging current;   iii) applying charging current to the battery; and   
           f) repeating the periodic cycle at least until the open circuit voltage is at a voltage indicative of the battery being fully charged or until the battery is disconnected.       

     In summarizing the arrangements described and/or claimed herein, a selection of concepts and/or elements and/or steps that are described in the detailed description herein may be made or simplified. Any summary is not intended to identify key features, elements and/or steps, or essential features, elements and/or steps, relating to the claimed subject matter, and so are not intended to be limiting and should not be construed to be limiting of or defining of the scope and breadth of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The detailed description of the preferred embodiment(s) will be more easily and better understood when read in conjunction with the FIGURES of the Drawing which include: 
         FIGS. 1A, 1B and 1C  are three different perspective views of an example embodiment of a battery charger having a rechargeable electronic device and a rechargeable battery in respective cradles thereof; 
         FIGS. 2A and 2B  are front views of the example embodiment of a battery charger of  FIG. 1  with and without the rechargeable electronic device light and the rechargeable battery in the respective cradles thereof; 
         FIG. 3  is a side cross-sectional view of the example embodiment of a battery charger of  FIGS. 1 and 2  with a rechargeable electronic device in one cradle thereof and a rechargeable battery in another cradle thereof; 
         FIG. 4A  is a view of the bottom end of example embodiment of the battery charger of  FIGS. 1-3  and  FIG. 4B  which is an enlargement of a portion of  FIG. 4A  showing a connector port thereof; 
         FIGS. 5A and 5B  are respective views of the connector port on the bottom end of the example embodiment of a battery charger with each of two different plug connectors inserted therein; 
         FIGS. 6A, 6B and 6C  are a perspective view and two different side views, respectively, of the connector port on the bottom end of the example embodiment of a battery charger including an example embodiment of a connector alignment arrangement; 
         FIGS. 7A, 7B and 7C  are respective perspective views of an example embodiment of an alternative connector, and of the alternative connector partially inserted and fully inserted in the connector port of the example embodiment of a battery charger including an example embodiment of an alignment and retaining arrangement, and  FIG. 7D  is a cross-sectional view of the example connector in a mated configuration; 
         FIG. 8  includes two perspective views and four orthogonal views of the example embodiment of alternative connector of  FIG. 7  including an example embodiment of an alignment and retaining arrangement; 
         FIG. 9  is an electrical schematic diagram of an example embodiment of an electrical circuit suitable for use with the example embodiment of a battery charger of  FIGS. 1-6C , and  FIG. 9A  is an alternative example embodiment of the example electrical circuit of  FIG. 9 ; 
         FIGS. 10 and 10A  are schematic flow diagrams illustrating an example of the operation of the example embodiment of a battery charger and electrical circuit of  FIGS. 1-9A ; and 
         FIGS. 11A, 11B and 11C  are together a single schematic flow diagram illustrating an alternative example of the operation of the example embodiment of a battery charger and electrical circuit of  FIGS. 1-9A . 
     
    
    
     In the Drawing, where an element or feature is shown in more than one drawing figure, the same alphanumeric designation may be used to designate such element or feature in each figure, and where a closely related or modified element is shown in a figure, the same alphanumerical designation primed or the like may be used to designate the modified element or feature. Similarly, similar elements or features may be designated by like alphanumeric designations in different figures of the Drawing. and with similar nomenclature in the specification. As is common, the various features of the drawing are not to scale, the dimensions of the various features may be arbitrarily expanded or reduced for clarity, and any value stated in any Figure is given by way of example only. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
       FIGS. 1A, 1B and 1C  are three different perspective views of an example embodiment of a battery charger  100  having a rechargeable electronic device  180  and a rechargeable battery  190  in respective cradles  110 ,  120  thereof; and  FIGS. 2A and 2B  are front views of the example embodiment of a battery charger  100  of  FIG. 1  with and without the rechargeable electronic device  180 , e.g., a flashlight  180 , and the rechargeable battery  190  in the respective cradles  110 ,  120  thereof.  FIG. 3  is a side cross-sectional view of the example embodiment of a battery charger  100  of  FIGS. 1 and 2  with a rechargeable electronic device  180  in one cradle  110  thereof and a rechargeable battery  190  in another cradle  120  thereof. 
     The example embodiment  100  illustrated is a Streamlight STRION Piggyback Battery Charger  100  that has two receptacles  110 ,  120  or cradles  110 ,  120 —one  110  for charging a battery or battery pack within a flashlight  180  that is placed into the receptacle  110  and a second  120  for charging a battery  190  or battery pack  190  apart from a flashlight  180 , e.g., typically the battery packs  190  are of the same type with each being a replacement for the other. Charger  100  receives electrical power from either of two different electrical power supplies via connector port  150 :
         A 12/18/24 volt DC power source that connects, e.g., to a DC vehicle system or to another source that connects to AC power mains, and   A USB power source, sometimes connected to a power “cube” or “block” that provides, e.g., +5 volts DC, or to a device, e.g., a personal computer, that provides, e.g., +5 VDC, at a USB port.       

     Charger  100  has a generally rectangular base  130  or housing  130  from which a pair of spring-biased arms  112  extend to define a first cradle  110  having electrical contacts  116 . When placed into the first cradle  110 , an electronic device, e.g., flashlight  180 , is retained therein by the spring-biased arms  112  and electrically connects to the circuitry  200  of the charger  100  to receive charging current via corresponding electrical contacts  116 . A second or auxiliary cradle  120  is defined, e.g., along one side of the rectangular housing  130  to receive a battery  190 , e.g., a battery  190  or battery pack  190  apart from a flashlight, such as an auxiliary battery or a spare battery, which is retained therein to electrically connect to the circuitry  200  of the charger  100  to receive charging current via corresponding electrical contacts  116 . The charger electrical circuitry  200  is contained and supported within the charger base  130 . 
     First and second electrical receptacles  152 ,  154 , e.g., electrical connectors  152 ,  154 , are provided in a charger connector port  150 , e.g., an opening  150  in the charger base  130 , e.g., on the bottom side thereof, for receiving connectors of electrical cables from two or more different electrical power supplies. Preferably, one opening or port  150  in the charger base  130  provides access to plural electrical connectors  162 ,  164 , e.g., two electrical connectors  152 ,  154 , and the one opening  150  is configured so that the external outlines of the plural, e.g., two, different electrical power supply connectors  162 ,  164  cannot be connected to the charger base  130  at the same time. In other words, when either one of the plural, e.g., two, cable connectors  162 ,  164  is plugged into its corresponding connector  152 ,  154  in the port  150  of the charger base  130  it overlaps in part the other connector or connectors  152 ,  154  thereof so that the plugged in connector  162 ,  164  mechanically interferes with and prevents another cable connector  162 ,  164  from being plugged into its corresponding connector  152 ,  154  in the connector port  150 . 
     An example of such connector opening or port  150  having first and second electrical receptacles  152 ,  154  for receiving at different times first and second electrical connectors  162 ,  164 , e.g., an AC or DC power supply connector  162  and a USB connector  164 , is described below in relation to  FIGS. 4 and 5 . Power source  160  typically includes one of electrical connectors  162 ,  164  that connect via a respective electrical cable  166  to a respective power source  168 , which in the Figure represent any one of several external power sources  168 , including a USB power source  168 . 
     Charger housing or base  130  includes a housing body  132  having an opening on the underside thereof that is covered by a housing base  134 . A pair of arm supports  136  extend from the face of charger housing body  132  and provide respective pivotable joints at which spring arms  112  are pivotably attached  137 , e.g., by a pivot pin  137 , to arm supports  136  of housing body  132 . Spring arms  112  are biased by respective springs to pivot towards each other and have respective opposing sloped surfaces at the ends thereof distal the pivot pins  137  to facilitate flashlight  180  being placed into cradle  110  with a snap-in motion. That is, when flashlight  180  is pressed against the sloped surfaces of spring arms  112 , spring arms  112  move away from each other against the spring bias to allow flashlight  180  to move into cradle  110  whereupon spring-biased arms  112  move closer to each other to retain flashlight  180  in cradle  110  (as illustrated by double-ended arrows). Thus, an electrical device  180  may conveniently be quickly snapped into cradle  110  and snapped out of cradle  110 . 
     Preferably, flashlight  180  is guided to a predetermined position in cradle  110  whereat charging contacts of flashlight  180  make electrical connection to electrical charging contacts  116  within cradle  110 . Cradle  110  preferably has a triangular guide member  114 , e.g., a triangular recess  114 , that corresponds to a corresponding triangular guide member, e.g., a triangular raised feature, of flashlight  180 . When the corresponding guide members of cradle  110  and flashlight  180  engage each other, the electrical charging contacts  189  of flashlight  180  are in electrical contact with electrical charging contacts  116  of charger  100 , as illustrated in  FIGS. 2B and 3 . 
     An optional auxiliary or “piggyback” secondary housing  140  may be attached to charger housing  130  in which position it is electrically connected to the circuitry of charger  100  for charging a rechargeable battery  190  which may be placed into cradle  120  of housing  140 . Connection end  142  of housing  140  includes electrical contacts for making electrical connection to electrical contacts of rechargeable battery  190 . An example of a suitable contact arrangement may be found in, e.g., U.S. Pat. No. 6,652,115 entitled “BATTERY CHARGER STRUCTURE AND RECHARGEABLE FLASHLIGHT SYSTEM USING THE SAME” issued Nov. 25, 2003, which is assigned to Streamlight, Inc., the assignee of the present Application, and which is hereby incorporated herein by reference in its entirety. 
     An indicator light  138 , e.g., a light emitting diode (LED)  138 , on charger housing  130  provides a visual indication of the status of the charging being provided via cradle  110  when an electronic device  180  is disposed therein. Similarly, an indicator light  148 , e.g., a light emitting diode  148 , on secondary charger housing  140  provides a visual indication of the status of the charging being provided via cradle  120  when a rechargeable battery  190  is disposed therein. Either or both of indicators  138 ,  148  may be a light emitting diode or may include an optical light pipe coupled to light emitting diodes within charger base  130  and secondary housing  140 , respectively. 
     Example electronic device  180  may be a flashlight  180  having a device housing  182  with a light head  184  at a forward end thereof and a barrel  186  toward a rearward end thereof, with an actuator  188  at the rearward end thereof for controlling operation of flashlight  180 . Light head  184  includes a light source, e.g., a light emitting diode  184 L and a reflector  185 R that forms the light from LED  184 L into a desired beam shape which exits via lens  185 . A rechargeable battery  190  may be disposed within barrel  186  and actuator  188  may actuate an electrical switch within flashlight housing  182  for controlling the operation of flashlight  180 . 
     As illustrated in  FIG. 3 , housing base  134  is retained to the underside of housing body  132  by one or more threaded or other fasteners and an electronic circuit board  200  is disposed in housing  130 . Charging contacts  116  are spring biased by respective springs, e.g., helical springs, surrounding the respective bases thereof so as to be urged outward toward the position in the first cradle  110  whereat the corresponding charging contacts  189  of flashlight  180  are positioned when flashlight  180  is seated in cradle  110 . Contacts  116  are connected to the circuitry of circuit board  200  by respective electrical wires  202  for conducting charging current to electronic device  180 , e.g., flashlight  180 , via contacts  116  and for sensing the voltage of the battery  190  therein, as described below. Piggyback or secondary charger housing  140  may attach to charger housing  130  by its base serving in place of the base  134  of housing  140  and being fastened thereto by one or more fasteners, e.g., self-tapping screws. Secondary charger housing  140  may connect electrically by plural electrical conductors, e.g., wires, connected between an electronic circuit board mounted in secondary housing  140  and the electronic circuit board  200  mounted in housing  130 . 
     Device  180  is seen to have two coaxial helical springs extending rearward from the forward or light head  184  end thereof for making electrical connection to a central contact and to a surrounding annular contact at the forward end of battery  190 . Actuator  188  is seen to have a central region that actuates a switch  188 S via a spring and plunger that are contained within the tail cap  186 T that is on the end of barrel  186  of housing  182  of flashlight  180 . Switch  188 S may be connected by barrel  186  providing one electrical conductor and by battery  190  providing a second electrical conductor via a spring of switch  188 S and an electrical contact at the rearward end of battery  190 . 
       FIG. 4A  is a view of the bottom end of example embodiment of a battery charger  100  of  FIGS. 1-3  and  FIG. 4B  is an enlargement of a portion of  FIG. 4A  showing a connector port  150  thereof; and  FIGS. 5A and 5B  are respective views of the connector port  150  on the bottom end of the example embodiment of a battery charger  100  with each of two different plug connectors  162 ,  164  inserted therein. 
     Connector  152  is, e.g., a connector having two receptacle contacts  152 C for receiving a two prong plug  162  associated with a DC power source, e.g., such as ones available from Streamlight, Inc., located in Eagleville, Pa., that provide a DC voltage in the range of about 10 to 24 VDC. These connectors  152 ,  162  are keyed by a rectangular recess on connector  152  that corresponds with a rectangular projection of connector  162  so that the two connectors  152 ,  162  can mate in only one orientation so as to provide proper polarity DC voltage to charger  100 , e.g., to circuit board  200  thereof. Preferably a shroud or frame surrounds the contacts of connectors  152 ,  154  so as to reduce the likelihood of their inadvertently coming in to electrical contact with other than the recessed receptacle contacts  152 C of connector  152 . 
     Connector  154  is, e.g., a USB connector, having four contacts  154 C for receiving a USB plug  164  associated with a USB DC power source, e.g., such as ones available from Streamlight, Inc., of Eagleville, Pa., as well as from many other sources. USB power sources provide a DC voltage of about 5.0 VDC on two of the connections and can provide signals and/or data on the remaining connections. These connectors  154 ,  164  are keyed by a shaped rectangular frame on connector  154  that corresponds with a shaped rectangular frame of connector  164  so that the connectors  154 ,  164  can mate in only one orientation so as to provide proper polarity DC voltage to charger  100 , e.g., to circuit board  200  thereof. The respective frames surround the contacts of connectors  154 ,  164  so as to reduce the likelihood of their inadvertently coming in to electrical contact other than with the mating contacts of another USB connector  154 ,  164 . Typically, connector  154  is a female USB connector and connector  164  is a male USB connector. 
     Connector port  150  is shaped so that the respective shells of connectors  162 ,  164  physically block the other connector  164 ,  162  from being connected to connector port when one of connectors  162 ,  164  is connected thereto. Connector  162  has a shell whose outline  163  is indicated by a dashed rectangle surrounding connector  152  and connector  164  has a shell whose outline  165  is indicated by a dashed rectangle surrounding connector  154  to illustrate that the respective shells  163 ,  165  physically interfere to prevent both being connected to charger  100  at the same time. Specifically, the shell  163  of connector  162  blocks the shell  165  of connector  164  and so prevents connector  164  from being mated with connector  154 , and the shell  165  of connector  164  blocks the shell  163  of connector  162  and so prevents connector  162  from being mated with connector  152 . 
       FIGS. 6A, 6B and 6C  are a perspective view and two different side views, respectively, of the connector port  150  on the bottom end of the example embodiment of a battery charger  100  including an example embodiment of a connector alignment arrangement  156 . USB connector  164  is illustrated as being plugged in to USB connector  154  of connector port  150 . Many USB connectors can easily be attempted to be connected with the USB plug  164  when misaligned from the USB receptacle  154  which can damage either or both connectors. Alignment arrangement  156  includes a plurality of guides  156  that extend outwardly from housing  130  around USB connector  154  to define a guide path to decrease any misalignment of USB plug  164  before it comes into mating position with USB connector  154 , thereby to reduce the risk of damage. 
     The plurality of guides  156  provided extend outwardly from housing  130 , e.g., substantially perpendicularly to the surface of housing  130  around USB connector  154  so as to be adjacent to USB plug  164  when USB plug  164  is plugged into USB connector  154  or is being plugged into connector  154 . Guides  156  preferably are spaced apart a distance that is slightly greater than the transverse dimensions of connector  164  so that the body of connector  164  is constrained by the spacing between guides  156  to be substantially aligned with connector  154  as the two are moved closer together for mating. 
     In the illustrated example arrangement, e.g., three guides  156  are provided, one guide  156  adjacent a narrow side of connectors  152 ,  164  and two opposing guides  156  adjacent the two wider sides of connector  154 ,  164 . The latter two guides may be, and preferably are, U-shaped when viewed on end, e.g., for increasing their resistance to breakage. The function of a guide  156  at the other narrow side of connector  152 ,  164  in this example embodiment is provided by the body of connector  152  which extends outwardly form housing  130 , however, it could be provided by another guide  156 . 
       FIGS. 7A, 7B and 7C  are respective perspective views of an example embodiment of an alternative connector  164 ,  300  and of the alternative connector  164 ,  300  partially inserted and fully inserted in the connector port  150 ,  156  of the example embodiment of a battery charger  100  including an example embodiment of an alignment and retaining arrangement  156 , and  FIG. 7D  is a cross-sectional view of the example connector  300  in a mated configuration; and  FIG. 8  includes two perspective views and four orthogonal views of the example embodiment of an alternative connector  164 ,  300  of  FIG. 7  including an example embodiment of an alignment and retaining arrangement  156 . 
     Connector  164 ,  300  includes a connector body  310  that is, e.g., molded over the electrical elements of a connector, e.g., a USB connector frame  164 P, to which is connected an electrical cable  166  over which body  310  is preferably also over-molded. The rear end of body  310 , i.e. the end distal connector frame  164 P, tapers narrower and has a plurality of recesses  312  for reducing the strain between cable  166  and body  310  where cable  166  enters body  310 . Strain relief  312  reduces the strain and thus renders the exterior surface of cable  166  less likely to separate from the molded material of body  310 . Connector body  310  preferably also has one or more gripping features  314 ,  316 , e.g., ridges, bumps and/or recesses  314 ,  316 , on opposing faces thereof to facilitate insertion and removal of connector  300  from its mating connector. 
     The forward end of connector body  310 , i.e. the end proximal connector frame  164 P, preferably has one or more features  320 ,  330 ,  340  for facilitating the alignment of connector  300  for insertion into its mating connector, e.g., a connector  154 . In particular, features  320 ,  330 ,  340  cooperate with guides  156 ,  400  and corresponding features thereof to require the substantial alignment of connector  300  for insertion into its mating connector, e.g., a connector  154 , of base  130 B to prevent connector frame  164 P from entering its mating connector, e.g., a connector  154 , if in reversed orientation, and to retain connector  300  in position with connector frame  164 P mated with its mating connector, e.g., a connector  154 . 
     Accordingly, connector  300  preferably has at least one alignment feature  320 , e.g., an alignment rib  320 , and guides  156 ,  400  preferably have at least one corresponding alignment feature  420 , e.g., an alignment groove  420 , for substantially aligning the respective longitudinal axes of connector  300  and its mating connector, e.g., a connector  154 , at least in one axis, for proper mating. 
     Connector  300  preferably includes at least one raised guide  330  for allowing connector  300  to enter guides  400 , which includes opposing guides  156  which extend from base  130 B and are spaced apart by a distance that is slightly greater than the dimension of connector body  310 , but less than the combined dimension of connector body  310  and raised guide  330  thereon, only if in the proper orientation wherein raised guide  330  becomes disposed in alignment groove  420  upon mating and so cannot be inserted in an inverted orientation. 
     Connector  300  preferably also includes one or more retaining features  340 , e.g., transverse retaining ribs  340 , complementary to one or more corresponding retaining features, e.g., transverse retaining grooves  440 , of guides  156 ,  400  so that retaining ribs  340  become disposed in retaining grooves  440  when connector  300  is fully mated with its mating connector, for retaining connector  300  in mating connection with its mating connector, e.g., a connector  154 . One or more retaining features  340  may be provided on one or more surfaces of connector body  310 , and alternatively, the ribs  340  could be provided on guides  400  and the grooves  440  could be provided on connector  300 . 
     Guides or guide members  156 ,  400  of this example embodiment are preferably “C-shaped” when viewed from the end. Guides  156 ,  400  provide two opposing broad inward facing surfaces that are adjacent to and guide the two opposing broad outer surfaces of connector body  310  and are of sufficient thickness to provide strength and to provide groove  420  and recesses  440  on at least one of the inward facing surfaces thereof. The remote ends of the C-shaped guides  156 ,  400  bend around and are adjacent to the two opposing narrow sides of connector body  310  and guide the two opposing narrow sides of connector body  310  during mating and de-mating of connector  164 ,  300  and, e.g., its mating connector  154 . 
     In one example embodiment of a connector  300 , the over-molded plug housing  310  including raised guide  330  and alignment rib  320  is a slip-fit into guide  400  with the engagement of retaining rib  340  and retaining groove  440  being more of an interference or snap-fit with guide  400 . The slip-fit tolerance is selected to be close enough to guide the connector  300  and prevent accidental damage thereto while allowing proper insertion depth for the proper mating of connectors  164 ,  154 . The position of the retaining rib or ribs  340  relative to retaining grooves  440  determines the insertion depth for a given connector types, and will be different for different connector types, and so the dimensions and tolerances selected must relate to or comply with the particular connector and/or connector standard chosen for the application. 
     For example: where the charger  100  employs a Micro-B type USB connector configuration, connector body  310  and guide  400  will be configured and sized to be compatible with the published Micro-USB cable and connector standards. In the illustrated example embodiment, connector  300  is a Micro-B USB connector and an optional raised letter “B” representative thereof may be provided on connector body  310 , e.g., in recess  314  thereof where it provides further indication of the orientation of connector body  310 . The present arrangement is configurable to be compatible with mini-USB and micro-USB connectors, type A and type B USB connectors, and with USB 1.x, 2.x and 3.x standards, as well as with other non-USB connectors, of both standard and proprietary types, and the term “USB” is intended to include any and all of the foregoing USB connector types, as well as future USB connector types. 
       FIG. 9  is an electrical schematic diagram of an example embodiment of an electrical circuit  200  suitable for use with the example embodiment of a battery charger  100  of  FIGS. 1-8 , and  FIG. 9A  is an alternative example embodiment of the example electrical circuit of  FIG. 9 . Therein, charger input connectors  152 ,  154  for receiving electrical power from either of the two power supplies  168  are shown at the upper left and the two pairs of output charging contacts, identified as C+ and C− to indicate DC polarity, for providing electrical charging power to the two receptacles or cradles  110 ,  120  are shown at the far right. 
     A DC converter  210  including regulator integrated circuit U 1  and its associated components shown in the left half of the schematic diagram provide, e.g., a buck PWM (pulse width modulated) voltage regulator that converts the input voltage at connector  152  from the 12/18/24 VDC voltage of power supply  168  (identified as VDD) down to about 5.1 VDC (nominally 5.12 VDC) at the cathode of D 3 , also designated as VDD, which powers the battery charging via output charging contacts C+ and C− when the 12/18/24 VDC power supply  168  is connected via connectors  152 ,  162  and is electrically powered. 
     The +5 VDC provided via the USB connection  154  is directly connected as VDD to power the battery charging via output charging contacts C+ and C− when the charging power from power supply  168  is provided via the USB connectors  154 ,  164 . Because mechanical interference between connectors  162  and  164  prevents both of connectors  162  and  164  from being mated to charger port  150  at the same time, thereby to prevent electrical power from being applied via both power supply input connectors  152 ,  154  at the same time, no diode or other isolation thereof is needed to prevent a connection being made between two external power supplies  168  through the circuitry of charger  100 . 
     Microprocessor or microcontroller  220 , U 2  controls operation of the charging circuitry  200  of charger  100 . The type of power supply  168  that is connected  152 ,  154  is detected by microprocessor U 2  and predetermined maximum current levels that can be drawn from that type of power supply  168  are then set accordingly. In the case of a USB power supply  168 , signals on pins D− and D+ may be utilized to indicate the type of USB power supply, e.g., a USB “cube,” and the maximum current that will be drawn therefrom may be set accordingly to a predetermined level. 
     In the event that the +5 VDC voltage supplied by the USB power supply  168  were to be below a predetermined minimum voltage, e.g., about 4.52 volts (nominal value), the maximum current that will be drawn by charger  100  may be and preferably is reduced by microprocessor  220 , U 2  in increments of current until the number of increments of reduced current is sufficient to reduce the maximum current drawn to a sufficiently lower current so that the voltage supplied by the USB-power source  168  increases to a level greater than the predetermined minimum voltage, e.g., greater than about 4.52 volts, but not to reduce the current below what is needed to provide some charging for a flashlight  180  and/or battery  190 , e.g., about 50 milliamperes. Preferably this feature operates based only on the measured voltage received from a USB power source  168  independently of the power rating and power dissipation of the USB power supply  168  which is need not be measured nor calculated, and preferably is not measured nor calculated. 
     Two independent linear charge current regulators  230 ,  240  are provided respectively by FET transistors Q 2  and Q 4  under control of microprocessor  220 , U 2  for providing respective predetermined constant charging currents to a flashlight  180  in the first receptacle  110  and/or to a battery  190  in the second receptacle  120 , i.e. at their respective charging contacts C+ and C−. Charging current may be supplied to both sets of output charging contacts C+ and C− simultaneously or to one set of output charging contacts C+ and C− when only a flashlight  180  or a battery  190  is present in its respective receptacle  110 ,  120  or when the charging current to one set of charging contacts is reduced, e.g., to zero, when the battery  190  (in flashlight  180  in cradle  110  or a battery  190  in cradle  120 ) connected thereto is fully charged. 
     In each instance, the magnitude of the charging currents provided at the respective output charging contacts C+ and C− is determined and controlled by operation of microprocessor or microcontroller U 2 ,  220  and its associated components shown in the right half of circuit  200  in the schematic diagram. FET Q 6  may prevent discharge of a flashlight battery  190  in the first cradle  110  and of a separate battery  190  in the second cradle  120  from discharging into the charger circuitry  200  when input power from a power supply  168  is not present, e.g., when the power supply  168  is disconnected. FETs Q 2  and Q 4  serve to prevent overcharge of the battery in the corresponding cradle  110 ,  120  due to conduction by the inherent body diode of a FET. 
     A primary charge control circuit  230  for the primary cradle  110  includes resistor R 11  for sensing the charging current flowing via Q 2  and (upper) charging contacts C+ and C− (e.g., contacts  116 , all at the upper right of the diagram) into a battery  190  in a flashlight  180  connected between those charging contacts C+ and C−,  116 , wherein feedback from current sensing resistor R 11  is applied to the non-inverting (+) input of an operational amplifier (e.g., upper triangular symbol) of microprocessor U 2 ,  220 , thereby to linearly control transistor Q 2 . If the feedback signal from resistor R 11  exceeds the reference signal, then the conduction of FET Q 2  is reduced to reduce the charging current and if the feedback signal is less than the reference signal, then the conduction of FET Q 2  is increased to increase the charging current, thereby to supply a substantially constant current to battery  190 . 
     The voltage of a battery  190  in a flashlight  180 , e.g., the open circuit voltage thereof, connected between those (upper) charging contacts C+ and C− ( 116 ) is measured by microprocessor U 2  via resistor divider R 9  and R 10  when transistor Q 3  is turned on. 
     The predetermined value of substantially constant charging current is controlled by controlling the “reference” level which is applied to the inverting (−) input of the upper operational amplifier via a low pass filter network including resistors R 14 , R 15  and R 16  and capacitor C 6 . The output from microprocessor U 2 ,  220  to the lowpass filter may be an analog signal or a digital signal, e.g., a PWM signal, and the output of the low-pass filter provides a filtered analog reference signal to the inverting (−) input of the upper operational amplifier of microprocessor U 2 ,  220  to control the magnitude of the battery charging current provided to primary cradle  110 . 
     A secondary charge control circuit  240  for the secondary cradle  120  includes resistor R 21  for sensing the charging current flowing via Q 4  and (lower) charging contacts C+ and C− (all at the lower right of the diagram) into a battery  190  connected between those charging contacts C+ and C−, wherein feedback from current sensing resistor R 21  is applied to the non-inverting (+) input of an operational amplifier (e.g., lower triangular symbol) of microprocessor U 2 ,  220  thereby to linearly control transistor Q 4 . If the feedback signal from resistor R 21  exceeds the reference signal, then the conduction of FET Q 4  is reduced to reduce the charging current and if the feedback signal is less than the reference signal, then the conduction of FET Q 4  is increased to increase the charging current, thereby to supply a substantially constant current to battery  190 . The secondary or “piggyback” charger  120  and its circuitry  240  are an optional feature of charger  100 , and are configured to be added to and removed from housing  130  of charger  100 . 
     The voltage of a battery  190  connected between those (lower) charging contacts C+ and C− is measured by microprocessor U 2 ,  220  via resistor divider R 19  and R 20 , when transistor Q 5  is turned on. 
     The predetermined value of charging current is controlled by controlling the “reference” level which is applied to the inverting (−) input of the lower operational amplifier via low pass filter network including resistors R 24 , R 25  and R 26  and capacitor C 7 . The output from microprocessor U 2 ,  220  to the lowpass filter may be an analog signal or a digital signal, e.g., a PWM signal, and the output of the low-pass filter provides a filtered analog reference signal to the inverting (−) input of the lower operational amplifier of microprocessor U 2 ,  220  to control the magnitude of the battery charging current provided to cradle  120 . 
     Each of the primary and secondary charging circuits  230 ,  240  operates in the same manner, however, each provides a level of charging current to a battery in cradle  110  and  120 , respectively, that is determined independently of the other based upon the terminal voltage, e.g., an open-circuit terminal voltage, of the particular battery  190  it is charging. The charging current may be reduced from those levels if the current available from the external power supply  168  is insufficient to charge both batteries  190  in both cradles  110 ,  120  at their respective predetermined substantially constant current levels at the same time. 
     Because during charging there is a significant voltage difference between the voltage at charging contacts C+ and C− and the terminal voltage of the battery (cells)  190  of the flashlight  180  or of battery pack  190  being charged, e.g., due to contact resistance (e.g., between contacts  116  and  189 ) and wiring resistance and/or due to series elements within the flashlight  180  or battery pack  190 , e.g., a diode in parallel with a resistor, the battery terminal voltage cannot be measured with sufficient accuracy at charging contacts C+ and C− when the battery  190  is being charged. Therefore, charging is interrupted periodically (e.g., charge current is essentially zero) so that the battery  190  open circuit voltage may be measured. 
     Each charging circuit  230 ,  240  operates on a predetermined repeating cycle wherein charging current is provided for a very large portion of the cycle, and is interrupted for a much shorter time during which the open circuit voltage of battery  190  is measured and a predetermined level of charging current, e.g., a substantially constant charging current, is set for the next period of charging based upon the measured open circuit battery voltage. In one example embodiment in which each cycle of charging is about 2.10 seconds in duration, charging is interrupted for about 25 milliseconds, e.g., about 1% of the cycle, during which the open circuit voltage of the battery is measured followed by an about 2.07 second charging time, e.g., about 99% of the cycle, at the current determined by the open circuit voltage measured immediately prior thereto. The cycling of the respective charging circuit cycles of circuits  230 ,  240  for electronic device cradle  110  and battery cradle  120  could be concurrent, i.e. in unison, or their respective repeating cycles could be offset from each other in time, e.g., by about half the cycle time, e.g., by about 1.05 seconds in the example cycle. 
     An example of typical values of battery open circuit voltage V OC  and corresponding typical charging current levels for an example Lithium-Ion battery is presented in Table I following: 
     
       
         
           
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 BATTERY CHARGE CURRENT &amp; BATTERY VOLTAGE (4) 
               
            
           
           
               
               
               
            
               
                 If Battery V OC  Is: 
                 Then I CHARGE  Should be: 
                 Notes: 
               
               
                   
               
               
                 &lt;4.0 VDC 
                 750 milliamperes 
                 (1), (2) 
               
               
                 &gt;4.0 VDC 
                 500 milliamperes 
                 (1) 
               
               
                 &gt;4.1 VDC 
                 200 milliamperes 
                 (1) 
               
               
                 &gt;4.2 VDC 
                  0 milliamperes 
                 (1), (3) 
               
               
                   
               
               
                 Notes: 
               
               
                 (1) If temperature is within limits for charging. 
               
               
                 (2) May begin charging gently if battery state of charge is very low or temperature is too high or too low. 
               
               
                 (3) Lithium battery charging is cut off; other battery types may be trickle charged. 
               
               
                 (4) Values are examples and will be different for different batteries, e.g., batteries of different capacity and/or from different manufacturers. 
               
            
           
         
       
     
     A thermistor, e.g., thermistor TR 1 , may be provided in the case or housing  132  of the charger base  130  to sense the ambient temperature thereof; the thermistor TR 1  is not attached to a power transistor or to a power supply or to a heat sink for measuring the temperature or power dissipation thereof. Thermistor TR 1  and resistor R 18  form a voltage divider that supplies a temperature dependent voltage signal to microprocessor U 2 ,  220  from which microprocessor U 2 ,  220  preferably determines the ambient temperature of charger  100 , e.g., for the purpose of controlling the charging current applied to a battery being charged in cradle  110  and/or  120  responsive to ambient temperature. Thermistor TR 1  is preferably used to prevent a battery  190  from (a) being charged if the battery is too “hot” (e.g., above 122° F.) or being charged at a high charge current if the battery is “cold” (e.g., below 20° F.), as approximated by the likelihood that the ambient temperature of the charger base  130  is indicative of the temperature of the battery  190  or would be after a period of time. It is noted that the temperatures referred to as “hot” and “cold” may differ for different embodiments and different sizes and types of batteries. 
     Charger  100  preferably applies charging current only at predetermined fixed levels to charge a battery and need not control, and preferably does not control, the voltage applied to the battery or apply a fixed or predetermined voltage thereto, i.e. it does not provide, and preferably does not provide, a constant voltage to the battery. Preferably, data stored, e.g., in microprocessor  220 , U 2  or in a memory associated therewith, defines predetermined substantially constant current levels for charging current to be applied to charge battery  190  as a function of open circuit battery voltage, and charger  100  preferably does not need and does not have a table of values that relate a voltage to be applied to the battery  190  to the battery open circuit voltage and/or to an “optimum” battery voltage, and so does not need to and preferably does not measure the voltage applied to battery  190  while battery  190  is receiving charging current. Charger  100  need not and preferably does not measure or calculate the power dissipation of any power supply  168  and need not and preferably does not measure or calculate the power dissipation of any power transistor. 
     Electrical circuit  200 ′ of  FIG. 9A  is substantially the same as electrical circuit  200  of  FIG. 9  with certain changes thereto. For example, plural transient voltage suppression devices TVS are included with TVS 1  connected across resistor R 4 , TVS 2  connected across capacitor C 4 , TVS 3  connected across resistor R 6 , TVS 4  connected across indicator LED 2 , TVS 5  connected across indicator LED 1  which is reconfigured relative to its drive from processor  220 , TVS 6  is connected between the C+ and C− terminals  116  of cradle  110 , and TVS 7  is connected between the C+ and C− terminals of cradle  120 . In addition, capacitor C 9  is connected across the gate-source terminals of FET Q 2  and capacitor C 10  is connected across the gate-source terminals of FET Q 4 . Resistor R 28  also assists in suppressing transients. 
     Each charging circuit  230 ,  240  of circuit  200  and of circuit  200 ′ preferably operates on a predetermined repeating cycle wherein charging current is provided for a very large portion of the cycle, and is interrupted for a much shorter time during which the open circuit voltage of battery  190  is measured and a predetermined level of charging current, e.g., a substantially constant charging current, is set for the next period of charging based upon the measured open circuit battery voltage. In one example embodiment, each cycle of charging is about 2.10 seconds in duration and charging is interrupted for about 25 milliseconds, e.g., about 1% of the cycle, during which the open circuit voltage V OC  of the battery is measured followed by an about 2.07 second charging time, e.g., about 99% of the cycle, at the constant current determined by processor  220  based upon the open circuit voltage V OC  measured immediately prior thereto. 
     While the cycling of the respective charging circuit cycles of circuits  230 ,  240  for electronic device cradle  110  and battery cradle  120  could be concurrent, i.e. in unison, or their respective repeating cycles could be offset from each other in time, e.g., by about half the cycle time, e.g., by about one second in the example cycles described. Preferably, batteries in both cradles are charged concurrently with priority being given to the battery in cradle  110 , which is thought to be more likely to be quickly put back into use, although alternative charging priority may be provided, e.g., preferentially charge the battery in cradle  120 , or share the available charging relatively evenly between the batteries in cradle  110  and in cradle  120 . 
     An example of typical values of battery open circuit voltage V OC  and corresponding typical charging current levels for an example Lithium-Ion battery is presented in Table II following: 
     
       
         
           
               
             
               
                 TABLE II 
               
             
            
               
                   
               
               
                 BATTERY CHARGE CURRENT &amp; BATTERY VOLTAGE (4) 
               
            
           
           
               
               
               
            
               
                 If Battery V OC  Is: 
                 Then I CHARGE  Should be: 
                 Notes: 
               
               
                   
               
               
                  &lt;4.2 VDC 
                 750 milliamperes 
                 (1), (2) 
               
               
                 then: 
                  0 milliamperes for time T D   
                   
               
               
                  &lt;4.2 VDC 
                 100 milliamperes 
                 (1) 
               
               
                  ≥4.2 VDC 
                  0 milliamperes 
                 (3) 
               
               
                 &lt;4.05 VDC 
                 If Voc decreases, repeat cycle 
               
               
                   
               
               
                 Notes: 
               
               
                 (1) If temperature is within limits for charging, e.g., 50° F. to 101° F.. 
               
               
                 (2) May begin charging gently if battery state of charge is very low, e.g., V OC  is low, or temperature is either too high or too low, e.g., at a temperature less than about 40° F. or higher than about 100° F. 
               
               
                 (3) Lithium battery charging is cut off; other battery types may be trickle charged. 
               
               
                 (4) Values are examples and will be different for different batteries, e.g., batteries of different capacity, different chemistry, and/or from different manufacturers, and/or at different temperatures (above about 113° F. the charging cut off voltage is about 4.1 VDC). 
               
            
           
         
       
     
     Because it is desirable to charge or recharge the battery in the shortest time allowable, a constant charging current that is close to a maximum allowable safe charging current may be applied, and so the terminal voltage of the battery being so charged may increase slightly above the voltage representative of being fully charged. When the battery is rapidly charged, e.g., at 500 milliamperes or at 750 milliamperes, its terminal voltage V OC  changes and so a “relaxation” time TD may be provided before charging is resumed, e.g., before topping off the charge. The time TD may be a predetermined time, e.g., about 4 minutes or longer, and in a typical example about 4.25 minutes, or may be a function of a predetermined parameter, e.g., of a temperature or a current at which charging was done, which may be measured within charger  100 , or may be related to the temperature of the battery being charged. The foregoing does not require that battery temperature or any other parameter be monitored or compensated for, however, it does not preclude such monitoring and/or compensating of temperature or another parameter. 
     Optionally, but preferably, charger  100  detects which of the possible external charging sources  168  is connected to and supplying charging current to charger  100 . External charging power source  168  may be a 12-18 volt or a 12-24 volt source such as may be provided from typical AC power mains or from a vehicle power system, such as battery charger power sources supplied by Streamlight, Inc. of Eagleville, Pa., for various wall and vehicle mountable chargers, or external charging power source  168  may be a USB compatible power source. With such power sources, charging currents of about 750 milliamperes may provided to one battery and/or about 1000 milliamperes (about one ampere) total may be provided to both batteries (both cradles  110 ,  120 ). 
     When charging power is provided from a detected USB external power source, e.g., a laptop computer or smart phone or a typical USB power cube, the maximum current that can be drawn therefrom is limited, e.g., to about 500 milliamperes. In that instance, where only a single battery is present to be charged, e.g., a battery only in cradle  110  or a battery only in cradle  120 , but not in both, will be charged using the full available current, e.g., about 500 milliamperes, available from the USB external source  168 ; however, if a battery is also in cradle  120 , e.g., there are batteries in both of cradles  110  and  120 , then the maximum charging current to the battery in cradle  110  is reduced, e.g., to about 400 milliamperes, and the remainder, e.g., about 100 milliamperes, will be utilized to charge the battery in cradle  120 , although other apportionments of the available charging current may be utilized. 
     If, however, the external USB power source  168  is a Streamlight AC/5V USB power cube adapter that will be made available with the charger  100  described herein, the maximum available current that can be drawn is about 1 ampere (about 1000 milliamperes). Preferably, the Streamlight AC/5V USB power cube adapter has the data+ and data− terminals of its USB connector connected together by a very low resistance, e.g., zero ohms, thereby making its presence easily detectable by processor  220  of circuit  200 ,  200 ′ of charger  100 . Thus, if the battery in cradle  110  is being charged at a constant current of about 750 milliamperes, the remaining about 250 milliamperes of available current may be utilized to charge a battery in cradle  120 , assuming that temperature and battery open circuit voltage V OC  are within the limits permitting such high current charging, thereby giving priority to the battery in cradle  110  as is preferred in the present example. 
     Indicator lights LED 1  and LED 2  relating to cradles  110  and  120 , respectively, may be, and preferably are, each energized in different manners so as to convey information about the charging of the battery in each respective cradle  110 ,  120 . For example, the LED indicator may be pulsed, e.g., at once per second, to indicate that the battery being charged is substantially at or near full charge and is in the predetermined time period TD, and the LED indicator may be blinked on and off at a fast rate, e.g., easily observable as being faster than once per second, to indicate an error, e.g., when charging has ceased due to too high or too low a temperature. 
     When the temperature is either high or low, e.g., less than about 41° F., charge current preferably is limited, e.g., to about 200 milliamperes, and when temperature is less than about 50° F. or higher than about 101° F., charge current preferably may be limited, e.g., to about 490 milliamperes; no charging will be done at temperatures that are too high or too low, e.g., below about 20° F. and above about 122° F. At a temperature above about 113° F., the charging termination voltage is reduced, e.g., from about 4.2 VDC to about 4.1 VDC. 
       FIGS. 10 and 10A  are schematic flow diagrams illustrating an example of the operation  1100  of the example embodiment of a battery charger  100  and electrical circuit  200  of  FIGS. 1-9A . In general,  FIG. 10  is an overall flow diagram presented to describe the major functions  1100  of battery charger  100  in a general manner with the following  FIG. 10A  providing further details and/or alternatives for the major functions  1100  of  FIG. 10 . It is noted that the functions may be performed in a sequence different from the example sequence illustrated unless specifically stated that a particular order or sequence must be followed. It is further noted that some functions described may be removed and/or other functions may be added, as may be expeditious in any particular instance. 
     Operation or process  1100  is first initialized  1110  upon application of electrical power to the charger  100  so that its operation commences from a known predetermined condition, and then checks  1300  to see if a battery is present, e.g., to detect  1300  if a battery  190  (e.g., in a flashlight  180 ) is connected in cradle  110  (battery #1), or if a battery  190  is connected in cradle  120  (battery #2), or both cradles  110  and  120 . 
     At some point in process  1100  after a battery is detected  1300 , process  1200  commences to detect and identify  1200  the type of power supply  168  that is connected to charger  100  and supplying electrical power thereto. Based upon the type of power supply detected, e.g., upon the level of current that is know to be available from such type of power supply, a maximum current level Imax is established (set)  1250 . Process  1200  may be performed at any one of several times, e.g., after a battery is detected  1300  or after charging current is initialized  1400 , wherein the latter is currently thought to be preferred. 
     If the identified power supply  168  is a 12/18/24 VDC power supply  168  connected via connector  152 , then the known level of current that can be drawn therefrom may be relatively high, e.g., 1.8-2.5 amperes, however, if the identified power supply  168  is a USB power supply  168  connected via connector  154 , then the current that can be drawn may vary over a wide range, e.g., 100 milliamperes to 2.4 amperes, depending upon the nature of the source. Power drawn from the USB port of an electronic device, e.g., a portable computer, may be limited to a low value, e.g., 100 milliamperes, while up to 2.4 amperes may be drawn for a USB wall cube that plugs into a 110-240 VAC wall outlet. 
     Thereafter, process  1100  proceeds to initialize  1400  the charging current that is applied to battery #1 and/or battery #2, as may been detected  1300 . Charge current initialization  1400  is illustrated as separate functions  1400 - 1  and  1400 - 2  because the current level must be set for each of the current controlled constant current charging circuits  230 ,  240 , however, the value to which the charging currents are initially set  1400  may be established by the initialization  1110  of process  100 . Typically, and preferably, the initial charging current is initially set  1400  to a relatively low value at which it is safe to charge a battery irrespective of temperature and the battery&#39;s state of charge, which might be thought of as a safe charging mode. 
     While the initial charging  1400  usually, and preferably, is the same for both battery cradles  110 ,  120 , subsequent charging  1500  for each battery, labeled as  1500 - 1 ,  1500 - 2  is likely to be at different current levels depending upon the respective states of charge of the two batteries when batteries are present in both cradles  110 ,  120 , and upon the sequence in which charger  100  is programmed to charge batteries  180 - 190  and  190  when batteries are present in both cradles  110 ,  120 . Thus, due to similarity, only one of each of the charging regimes  1400 ,  1500  need be described. 
     As to the sequencing, e.g., priority of charging, for the battery  190  of a flashlight  180  in cradle  110  and for a battery  190  in cradle  120 , in one preferred embodiment the charging of flashlight  180  is given preference because it is thought that if both a flashlight  180  and a spare battery  190  are present  1300  in battery charger  100 , then it is probably more likely that a user will first remove flashlight  180  for use (desiring that it be substantially if not fully charged) before removing a spare battery  190  for use. In any event, it is preferred that if a flashlight  180  is present  1300 , but not a battery  190 , or if a battery  190  is present  1300 , but not a flashlight  180 , then whichever one is present is given charging priority, at least for as long as it is the only one present in charger  100 . 
     Alternatively, the one of flashlight  180  and battery  190  that is closest to being fully charged, e.g., as determined from its open circuit voltage, could be given priority in charging, or an extra battery  190  could be given priority over a flashlight  180 , or both could be given the same priority. When both are given the same priority, charging both simultaneously at a reduced charge current level or charging both contemporaneously at a relatively higher current level on alternating repetitions of the relatively short about 2 second charging time of the repeating cycles described herein typically might lengthen the time necessary for either or both to reach full charge. 
     Returning to operation  1100 , each battery is charged under the same charging process  1500  although the particular levels of current applied at any time will be separately determined based upon the parameters of each particular battery, e.g., as determined by its open circuit voltage. Each process  1500  ( 1500 - 1 ,  1500 - 2 ) begins by counting time to determine  1515  whether the predetermined charging time has been reached. If not  1515 N, it continues counting time  1515 . When the predetermined cycle time, e.g., 2 seconds, has been reached  1515 Y, charging is interrupted  1520  for a short interval sufficient to measure  1525  the open circuit voltage Voc of the battery which is then receiving no charging current. Therein, measuring  1525  Voc also includes determining  1530  whether a battery is still present and if not  1530 N, returning to battery detection process  1300 . If a battery is present  1530 Y, then the charging  1535 - 1580  of that battery commences and/or continues. 
     Charging  1500  includes repetitively measuring the open circuit battery voltage Voc in each repeating cycle and setting a level of charge current for the next cycle that is determined  1535 - 1580  based upon the measured open circuit battery voltage Voc of the battery immediately preceding that cycle. Recall that the charging current was initially set to a relatively low level that is deemed to be safe. If Voc is determined  1535  to not be greater than a voltage Vsafe which is a minimum battery voltage at which charging at a relatively high current is safe, then  1535 N returns to process  1400  where the battery is charged at the safe relatively low current. 
     If Voc is determined  1535  to be greater than a relatively low voltage Vsafe indicating that charging of the battery can begin in earnest, then  1535 Y is followed and if the measured battery voltage Voc is determined  1540  to be less than a first predetermined voltage, then  1540 N is followed and the charging current is set  1545  to a relatively high value Ichg=Imax/N, wherein Imax/N is the lower of the maximum current that can safely be applied to charge the battery  180 ,  190  and the maximum current that may be drawn from power supply  168  divided by the number N of batteries to be charged simultaneously or contemporaneously. Having established (set)  1545  the predetermined level of charging current to be applied, charging resumes  1550  applying that predetermined level of charging current to the battery for the present repetitive charging cycle. 
     Thus begins a series of determinations  1540 ,  1560 ,  1570 , . . .  1580  wherein the last measured  1525  battery voltage Voc is compared to a set of different predetermined voltages to determine  1540 ,  1560 ,  1570 , . . .  1580  the level of charging current that is to be applied  1550  to charge the battery for the immediately following charging interval. Depending upon the last measured  1525  value of battery open circuit voltage Voc, a predetermined level of charge current is selected (set)  1545 ,  1565 ,  1575 , . . .  1585  and is applied  1550  to charge the battery for the immediately following charging interval. 
     The determinations  1540 ,  1560 ,  1570 , . . .  1580  occur by following the Y paths from each until a negative determination  1540 ,  1560 ,  1570 , . . .  1580  is made and the N path from that comparison  1540 ,  1560 ,  1570 , . . .  1580  is followed to set  1545 ,  1565 ,  1575 , . . .  1585  the charge current level. In this description and the Figures to which it relates, an ellipses (“ . . . ”) is used to indicate that a greater or lesser number of steps, e.g., comparisons  1540 ,  1560 ,  1570 , . . .  1580  and current settings  1545 ,  1565 ,  1575 , . . .  1585 , could be employed. 
     If all of comparisons  1540 ,  1560 ,  1570 , . . .  1580  are negative, one of their possible N paths is followed, and battery charging continues  1550  at the last set  1545 ,  1565 ,  1575 , . . .  1585  level of charging current. If the battery open circuit voltage Voc is determined  1580  to be equal to or greater than a predetermined voltage Vfc that is indicative that the battery is fully charged, then  1580 Y is followed and the charging is terminated  1590 , i.e. the charging current is set  1590  to zero current. 
     At this point, the charging cycling  1500  continues to repeat at the predetermined repetitive cycle time, e.g., at the about 2.1 seconds. If the flashlight  180  and/or battery  180 , as the case may be, continues to present an open circuit voltage Voc that equals or exceeds the full charge voltage Vfc, charging current remains set  1585  at zero, and should the open circuit voltage Voc decrease to below the full charge voltage Vfc, charging current will be set  1545 ,  1565 ,  1575 , . . .  1585  in accordance with the then presented open circuit voltage Voc. 
     The foregoing processes  1400 ,  1500  repeat until one or both of the flashlight  180  and/or battery  190  are removed from the respective cradle  110 ,  120  of battery charger  100  whereat the affected charging cycle  1400 ,  1500  return to detection  1300  and the unaffected charging cycle  1400 ,  1500  continues as described. 
       FIGS. 11A, 11B and 11C  are together a single schematic flow diagram illustrating an example of an alternative operation  2000  of the example embodiment of a battery charger  100  and electrical circuit  200  of  FIGS. 1-9A . It is noted that the functions of operation  2000  or process  2000  may be performed in a sequence different from the example sequence illustrated unless specifically stated that a particular order or sequence must be followed. It is further noted that some functions described may be removed and/or other functions may be added, as may be expeditious in any particular instance. Process  2000  begins with the initialization  2005  of the charger electronic circuitry  200  so that process  2000  commences from a known state, e.g., upon initially being powered on and after a power interruption or outage. 
     It is noted that process  2000  repeats periodically so that the status of charger  100 , the charging of battery #1 in cradle  110 , the charging of battery #2 in cradle  120 , the parameters thereof established for safe charging and or other safety and other reasons, are all repetitively monitored and adjusted so the batteries #1 and #2 may be rapidly and efficiently charged under whatever conditions are detected. Typically, process  2000  is repeated many times during each cycle of battery charging and voltage Voc measuring, e.g., 32 times per each cycle of 1.1 or 2.1 seconds in the examples herein. 
     First, the presence of a rail voltage is checked  2010 ,  2015  to begin verifying that input power is being received  2010  from an external source  168  of charging power and whether the rail voltage is within a predetermined acceptable range of voltages  2015 , e.g., either by testing  2015  whether it is outside of that range (as illustrated) or whether it is within that range. If the rail voltage Vrail is outside the predetermined range, then  2015 —Y (“Y” indicates “yes” and “N” indicates “no”) is followed and a Verror count is incremented  2020  or a Verror flag is set  2020  thereby to indicate an out of range condition. If the rail voltage Vrail is within the predetermined range, then  2015 —N is followed and the Verror flag or count is cleared  2025  thereby to indicate an in-range value of the Vrail input voltage. 
     The Vrail error flag or count is tested  2030  and if the error flag or count is set, then  2030 —Y is followed directly to step  2060 . If the Verror flag or count is not set, then  2030 —N is followed and the temperature is checked  2040  to determine, e.g., whether it is safe to charge the battery and if so, at what constant current level. Temperature is checked  2040 ,  2045  to begin verifying whether the temperature is within a predetermined acceptable range of temperature  2045 , e.g., either by testing  2045  whether it is outside of that range (as illustrated) or whether it is within that range. If the temperature is outside the predetermined range, then  2045 —Y is followed and a Terror count is incremented  2050  or a Terror flag is set  2050  thereby to indicate an out of range condition. If the temperature is within the predetermined range, then  2045 —N is followed and the Terror flag or count is cleared  2055  thereby to indicate an in-range or acceptable temperature. 
     If a Verror or Terror flag is set  2060 , then battery charging should not be commenced or continued and  2060 —Y is followed to stop charging  2065  and to blink an indicator light  2065 , e.g., if a battery is detected as being present in a cradle  110 ,  120 , and to return to step  2010 . If a Verror or Terror flag is not set  2060 , then battery charging should be commenced or continued and  2060 —N is followed to determine  2070  the maximum level of constant current charging allowable and the charge completion voltage Voc based upon the last determined temperature  2040 . 
     If a battery #1 flag is set  2075 , e.g., a battery has been detected as being present in cradle  110 ,  2075 —Y is followed to go to step  2150 . Detection of the presence of a battery may employ any one of several tests, e.g., signaling the charge current circuit  230  or  240  to apply a short duration pulse of charging current while monitoring the charging current feedback, e.g., via resistor R 11  or R 21 , to determine whether such current actually flows because current will only flow if a battery is connected to terminals  116  of cradle  110  or to those of cradle  120 . 
     If a battery #1 flag is not set  2075 , e.g., a battery was not detected as being present in cradle  110 ,  2075 —N is followed to indicate  2080  that the battery is not charging and to check  2080  the battery voltage Voc. If the battery voltage Voc indicates  2085  that charging is complete, then  2085 —Y is followed and the battery detected and charge complete counts are incremented  2090  and process  2000  proceeds to  2110 . If the battery voltage Voc indicates  2085  that charging is not complete, e.g., the battery is not fully charged, then  2085 —N is followed and the charge complete count is cleared  2095 , a pulse of charging current is applied  2095  and the battery detected count is incremented  2095 . 
     If the charging current is regulating to a constant current  2100 , then a battery is present and being charged and  2100 —Y is followed to  2110 . If the charging current is not regulating  2100 , then  2100 —N is followed to clear  2105  the battery detected count. If the detected count is not at or above a predetermined count  2110 , e.g., the detect count is not great enough  2110 , then  2110 —N is followed to step  2150 . If the detected count is at or above a predetermined count  2110 , e.g., the detect count is great enough  2110 , then  2110 —Y is followed to determine  2115  if the complete count is enough. If the complete count is enough  2115 , then  2115 —Y is followed, the charge complete flag is set  2120 , and process  2000  proceeds to step  2125 . If the complete count is not enough  2115 , then the battery should continue charging and so  2115 —N is followed, the detect flag is set  2125 , the charging indicator light is energized to indicate  2125  that the battery is charging, and process  2000  proceeds to step  2150 . Thus far in example process  2000 , at least the initial setting up of the charging of a battery in cradle  110  for which charging priority is desired to be given is established. 
     Step  2150  determines whether charger  100  is in a “piggyback” configuration, e.g., whether or not an auxiliary cradle  120  is present in addition to the primary cradle  110  included in housing  110 . If an auxiliary cradle  120  is not present, then  2150 —N is followed to proceed to step  2210 . If auxiliary cradle  120  is present, then  2150 —Y is followed to determine  2155  whether a battery is present in cradle  120 , e.g., as indicated by a battery #2 detected flag being set  2155 . If yes, then  2155 —Y is followed to proceed to step  2210 . If a battery is not detected  2155  in cradle  120 , then  2155 —N is followed to step  2160 . 
     Steps  2155  through  2205  relating to battery #2, e.g., the battery in cradle  120 , are exactly parallel to and substantially the same as steps  2075  through  2125 , and so will not be separately described herein. Steps  2155  through  2205  are described by the description of steps  2075  through  2125  if  80  is added to the item numbers set forth in the description of steps  2075  through  2125 , respectively. 
     If neither battery flag is set  2210 , then no battery is present and  2210 —N is followed to step  2215  to set an input source flag to “0” to force a redetermination of the charging current level at step  2300 . Step  2215  proceeds to step  2010 . If either battery flag is set, then  2210 —Y proceeds to step  2220  to control the charging of battery #1, e.g., the battery in cradle  110 . 
     Control of the charging of battery #1 proceeds as follows: First, completeness of charging is determined  2220 , e.g., by testing the battery voltage Voc against a predetermined charging termination voltage, e.g., 4.2 VDC. Steps  2220 - 2235  can check whether the battery is currently being “topped off,” because after charging is complete, the battery could be in the relaxation time, in topping off, or has completed topping off after which the battery voltage is monitored to determine whether the battery voltage Voc has dropped below a predetermined threshold voltage, e.g., 4.05 VDC, indicating that charging should be resumed or the battery has been removed. If the charging of battery #1 is not complete  2220 , then  2220 —N is followed to step  2245  for beginning a parallel and substantially the same charging control process for battery #2. If the charging of battery #1 is complete  2220 , then  2220 —Y is followed to step  2225  for energizing the charging indicator light to indicate that charging of battery #1 in cradle  110  is complete, e.g., flashing at a once per second rate. If complete, the battery voltage Voc is monitored  2230  to determine if “topping off” the charge  2230  is being performed. Topping off is done after a period of time commencing at the indication of completion of charging and ending at a later time, e.g., either based upon a predetermined time, by a temperature, or by a combination thereof. Topping off may comprise charging at a lower constant current, e.g., at about 100 milliamperes. If topping off  2230  is yes, then  2230 —Y is followed to step  2245 . If topping off  2230  is no, then  2230 —N is followed to determine  2235  whether the battery voltage Voc is less than the voltage indicating that restarting charging should occur, e.g., the charge restart voltage of about 4.05 VDC. If it is not, then  2235 —N is followed to step  2245 . If it is, then  2235 —Y is followed to increment  2240  the undetected count and set  2240  an undetected flag, and proceed to step  2245 . 
     Steps  2245  through  2265  relating to battery #2, e.g., the battery in cradle  120 , are exactly parallel to and substantially the same as steps  2220  through  2240  and so will not be separately described herein. Steps  2245  through  2265  are described by the description of steps  2220  through  2240  if  25  is added to the item numbers set forth in the description of steps  2220  through  2240 , respectively. The completion of steps  2245 - 2265  and of steps  2220 - 2240  both lead the process  2000  to step  2300 . Steps  2245 —N,  2255 —Y,  2260 —N, and  2265  lead the process  2000  to step  2300 . 
     Step  2300  determines  2300  whether the input source flag is determined yet, e.g., what type of source is present. If zero, then the type of source is not determined and  2300 —Y is followed to determine the source  2305  that is present, e.g., the type of external source of charging power  168  that is connected, e.g., a Streamlight USB source being indicated by a very low or zero resistance between its data+ and data− terminals, and to set  2305  the maximum current that will be drawn from that source. Once the type of source  168  is determined, the value of the input source flag is set to a value corresponding to the current level that is available from the determined type of source. If the input source  168  is already determined, then  2300 —N is followed to step  2310  as also follows step  2305 . 
     Charging status for battery #1 is determined  2310 . If battery #1 is present and if the predetermined charging time between battery voltage measurements has been fulfilled and if battery #1 is charging, then  2310 —Y is followed to measure  2315  the battery open circuit voltage Voc. This step  2315  includes interrupting  2315  the charging current to battery #1 and measuring the open circuit voltage Voc at the charger terminals  116 , checking (verifying)  2315  that battery #1 is still present in cradle  110 , reducing  2315  the maximum allowable battery charging current setting if the voltage Voc of battery #1 is below a predetermined threshold considered to indicate that battery is substantially discharged, e.g., “dead,” and resuming  2315  constant current charging of battery #1 if the charging thereof is not complete, e.g., as indicated by its open circuit voltage Voc being below the charge termination voltage. If test  2310  is negative, then  2310 —N is followed to step  2320 . At the completion of step  2315  which follows from step  2310 —Y, the process  2000  proceeds to step  2350 . 
     Charging status for battery #2 is determined  2320 . Steps  2320  and  2325  are parallel to and substantially the same as steps  2310  and  2315  for battery #1 and will not be separately described, except to state that steps  2320 - 2325  pertain to battery #2, e.g., a battery in cradle  120 . Step  2325  also leads to step  2350 , as do steps  2310 - 2315 , and step  2320 —N goes to step  2330 . Step  2320 —N goes to step  2330 . At the completion of step  2325  which follows from step  2320 —Y, the process  2000  proceeds to step  2350 . 
     Charging of battery #1 is resumed  2330 - 2335 . If battery #1 is detected  2330  and its charging is not complete, then  2330 —Y is followed to resume charging  2335  of battery #1. Resuming charging  2335  includes measuring  2335  the constant current charging current, checking  2335  that battery #1 is still present, setting  2335  a target value for the constant current charging of battery #1 based upon, e.g., temperature, its state of charge, e.g., as indicated by its voltage Voc, and the type of input source present, e.g., the type of external charging current power source  168 , and reducing  2335  the charging current if it is above the newly set target value. If test  2330  is negative, then  2330 —N is followed to step  2340  and at the completion of step  2335  the process  2000  also proceeds to step  2340 . 
     Charging of battery #2 is resumed  2340 - 2345 . Steps  2340  and  2345  are parallel to and substantially the same as steps  2330  and  2335  for battery #1 and will not be separately described, except to state that steps  2340 - 2345  pertain to battery #2, e.g., a battery in cradle  120 . Both lead to step  2350 , and preferably after the constant charging currents for batteries #1 and #2 have been set and applied. 
     The particular external charging current power source  168  that is connected to charger  100 , from which the electrical power from which the constant currents that charge batteries #1 and #2 are drawn, is tested to determine  2350  whether it has sufficient capacity to supply those charging currents. Testing step  2350  is preferably performed by measuring the input voltage to charger  100 , e.g., at input connectors  152  or  154 , but particularly at input connector  154  to which a USB power source  168  can be connected. The external power source  168  provided by Streamlight, Inc. with the portable light described herein, as well as with previous lights, can typically provide electrical power that is more than sufficient to charge the light described herein. 
     USB power sources  168 , e.g., USB power cubes (other than the Streamlight AC/5V USB adapter), typically have a much more limited capacity to provide charging power at +5 VDC to charger  100 , e.g., many provide only about 500 milliamperes at +5 VDC, and so when current beyond that capacity is drawn, the voltage at connector  154  tends to decrease, or experience “droop,” to a lower voltage. If the detected  2350  voltage “droops” below a predetermined voltage, e.g., about 4.52 volts, then  2350 —Y is followed and the battery charging currents are reduced  2355 . For example, the maximum charging current to battery #1 will be reduced  2355 , e.g., in increments from as much as about 750 milliamperes, to a lower level so that the total charging current to batteries #1 and #2 is similarly reduced, thereby reducing the current drawn from external power source  168 . In a preferred arrangement wherein the charging of the battery #1 in cradle  110  is given priority regarding charging, the charging current to battery #2 is reduced, thereby to reduce the current drawn from external power source  168 , before the charging current to battery #1 is reduced. 
     Reducing the current drawn from external power source  168  allows the voltage provided thereby to recover, e.g., to droop less, until the voltage from external power source  168  returns to an acceptable level, e.g., above about 4.52 volts. In a preferred example, the charging currents to battery #1 and to battery #2 are both reduced  2355  sufficiently for the voltage provided by external power source  168  to recover. Process  2000  then returns to step  2010  and begins another in its sequence of repetitive cycles. An advantage of the foregoing arrangement is that the current draw is automatically reduced to a level that does not draw excessive current from the external power source  168  without having to know a priori or determine the actual current supplying capacity of source  168 , which is seen to increase flexibility to operate charger  100  with a wide variety of different capacity USB power sources. 
     It is noted that voltage droop is not expected when the external source  168  is one of the 12, 18 or 24 VDC sources which is configured to provide sufficient power for charging such portable lights  110  with the maximum charge currents as described herein. Likewise, voltage droop is not expected when external source  168  is the Streamlight AC/5V USB cube which is also configured to supply sufficient power to charge the battery or batteries as the maximum charge currents described. However, for other USB power sources, e.g., a USB connector of a laptop computer or a smart phone charger, if the source is unable to supply the nominal 500 milliampere that the charger is programmed to draw, then the voltage provided by the USB source  168  will droop and the charging current will be reduced. Because in the example described, charging of the battery in cradle  110  is presumed to be given priority in charging, then any charging current being provided to a battery in auxiliary cradle  120  will be reduced before the charging current to the battery in cradle  110  will be reduced. If the charging current to cradle  120  has already been reduced to a predetermined minimum charging current, e.g., about 75 milliamperes, and voltage droop is still detected, then the charging current to cradle  110  will be reduced in increments towards a minimum nominal value, e.g., about 100 milliamperes. The 400 milliampere charging current example above for cradle  110  with a 100 milliampere charging current for cradle  120  is just an example, e.g., at the end of or in a sequence of incremental reductions controlled by process  2000 . This preferred arrangement, may be varied, e.g., as different priority for charging may be desired as between the batteries in cradles  110  and  120 . 
     If the source  168  voltage is not droopy  2350 , then  2350 —N is followed and the charging currents to batteries #1 and #2 is incremented  2360  upward over a number of repetitive cycles of process  2000  until the target current (see  2335 ,  2345 ) is reached. Process  2000  then returns to step  2010  and begins another in its sequence of repetitive cycles. 
     In a typical embodiment, housings  130  and  140 , and parts thereof such as spring arms  112 , may be of any suitable metal, e.g., a cast, machined or stamped aluminum, or a suitable plastic material, e.g., preferably a molded plastic such as a nylon, engineered nylon, ABS plastic, polycarbonate, polyethylene, or other resin, with or without a reinforcing material such as a fiberglass, carbon fiber, or the like, or any other suitable plastic or other moldable material. Reinforcing materials may provide improved strength, impact resistance, dimensional stability and/or consistency, high temperature stability, and the like. 
     A battery charger  100  may comprise: a housing  110  having at least one cradle  110 ,  120  including electrical contacts for receiving a rechargeable battery  180 ,  190 ; a connector port  150  on the housing  130  for receiving at different times at least two electrical plug connectors  162 ,  164 ,  300  having different electrical contact configurations; first and second electrical receptacles  152 ,  162  disposed in the connector port  150  of the housing  130  for receiving at different times respective first and second electrical plug connectors  162 ,  164 ,  300  that are respectively associated with first and second electrical power supplies  168 ; the first electrical receptacle  152 ,  154  having a contact configuration that may be different from the contact configuration of the second electrical receptacle  154 ,  152 ; the first and second electrical receptacles  152 ,  154  being closely adjacent each other such that an electrical plug connector  152 ,  154  inserted into one of the first and second electrical receptacles  152 ,  154  physically interferes with and prevents an electrical plug connector  154 ,  152  from being plugged into the other of the first and second electrical receptacles  152 ,  154 ; and an electrical circuit  200  disposed in the housing for coupling electrical power received at the first and second electrical receptacles  152 ,  154  to the electrical contacts of the at least one cradle  110 .  120  of the housing. The connector port  150  may define an opening that includes a substantial part of an outline of a first electrical plug connector  162 ,  164  and a substantial part of an outline of a second electrical plug connector  164 ,  162 , wherein parts of the outlines of the first and second electrical plug connectors  162 ,  164  overlap within the opening of the connector port  150 . One of the first and second electrical receptacles  152 ,  154  may include a USB connector. The at least one cradle  110 ,  120  of the housing  130  may include: a pair of spring biased arms  112  for retaining an electronic device  180  including the rechargeable battery  190  therein, and optionally may include a second cradle  120  for receiving a second rechargeable battery  190  therein. The at least one cradle  110 ,  120  of the housing  130  may include: a guide member  114  for locating an electronic device  180  including a rechargeable battery  190  therein and a pair of spring biased arms  112  for retaining the electronic device  180  therein. The rechargeable battery  190  may be included in an electronic device  180  that is configured to be retained in the at least one cradle  110 ,  120  of the housing  130 . The at least one cradle  110 ,  120  of the housing  130  may include first and second cradles  110 ,  120 , the first cradle  110  being configured to receive an electronic device  180  including a rechargeable battery  190  therein and the second cradle  120  being configured to receive a rechargeable battery  190  therein. The electrical circuit  20  may include a DC converter  210  having an input coupled to one of the first and second receptacles  152 ,  154  and an output coupled to the electrical contacts of the at least one cradle  110 ,  120 . The DC converter  210  may be coupled to the electrical contacts of the at least one cradle  110 ,  120  by a circuit  220 ,  230 ,  240  providing a constant current to charge a battery  180 ,  190  connected to the electrical contacts of the at least one cradle  110 ,  120 . The constant current provided to a rechargeable battery  180 ,  190  connected to the electrical contacts of the at least one cradle  110 ,  120  may have a magnitude determined as a function of the open circuit voltage of the rechargeable battery  180 ,  190 . One or more guides  156 ,  400  may extend from the housing  130  adjacent at least one of the first and second electrical receptacles  152 ,  154  for aligning a mating connector  162 ,  164 ,  300  with respect to the at least one of the first and second electrical receptacles  152 ,  154 . The one or more guides  156 ,  400  extending from the housing  130  may have a groove  420 : for aligning a rib  320  of a mating connector  300  with respect to the at least one of the first and second electrical receptacles  152 ,  154 , or for receiving a raised guide  330  of a mating connector  300  for defining a single physical orientation for mating the mating connector  300 , or for aligning a rib  320  of a mating connector  300  with respect to the at least one of the first and second electrical receptacles  152 ,  154  and for receiving a raised guide  330  of a mating connector  300  for defining a single physical orientation for mating the mating connector  300 . The battery charger  100  may be in combination with an electronic device  180  including a rechargeable battery  190  therein that is rechargeable in the at least one cradle  110 ,  120  of the battery charger  100 . The at least one cradle  110 ,  120  of the housing  130  may include: one or more electrical contacts configured for making electrical connection to a rechargeable battery  190 ; or one or more electrical contacts configured for making electrical connection to an electronic device  180  including a rechargeable battery  190 ; or one or more electrical contacts configured for making electrical connection to a rechargeable battery  190  and one or more electrical contacts configured for making electrical connection to an electronic device  180  including a rechargeable battery  190 . A first of the at least two electrical plug connectors  162 ,  164 ,  300  may be of a male or female gender; or a second of the at least two electrical plug connectors  162 ,  164 ,  300  may be of a male or female gender; or the first electrical receptacle  152 ,  162  may be of a male or female gender; or the second electrical receptacle  152 ,  162  may be of a male or female gender; or any compatible mate-able combination thereof. The battery charger  100  may be in combination with a power supply  168  having an electrical plug connector  162 ,  164 ,  300  that is insertable into one of the first and second electrical receptacles of the battery charger  100 . The housing may include a sensor responsive to the temperature thereof and coupled to the electrical circuit. The electrical circuit  200  may be configured to charge a rechargeable battery  180 ,  190  disposed in the at least one cradle  110 ,  120  by: a) setting  1400 ,  2070  an initial charge current level that is substantially lower than a charge current that the battery  180 ,  190  can accept; b) repetitively interrupting  1520 ,  2310 ,  2320  charging  1500 ,  1520 ,  2315 ,  2325  of the battery  180 ,  190  at a predetermined timing to define a periodic cycle, and for each periodic cycle: measuring  1525 ,  2315 ,  2325  an open circuit voltage of the battery  180 ,  190  when charging of the battery  180 ,  190  is interrupted, determining  1540 - 1580 ,  2335 ,  2345  from the measured open circuit voltage of the battery  180 ,  190  a corresponding predetermined level of charging current to be applied to the battery  180 ,  190 ; applying charging current  1550 ,  2315 ,  2325 ,  2335 ,  2345  to the battery  180 ,  190  at the predetermined level of charging current; and c) repeating  1550 - 1515 ,  2355 - 2010 ,  2360 - 2010  the periodic cycle at least until the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged or until the battery is disconnected from the at least one cradle. One of the first and second electrical receptacles  152 ,  154  may include a connector guide  400 ,  156  and wherein an electrical connector  164 ,  300  configured to mate therewith may comprise: an elongated connector body  310  defining a longitudinal direction and having an electrical cable  166  extending from the connector body  310 ; an electrical connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal alignment feature  320  on the elongated connector body  310  configured for aligning the elongated connector body  310  with the connector guide  400 ,  156 ; a guide feature  330  on the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and a retaining feature  340  on the elongated connector body  310  configured for retaining the elongated connector body  310  in the connector guide  400 ,  156 , whereby the elongated connector body  310  when inserted into the connector guide  400 ,  156  is aligned with the connector guide  400 ,  156  by the longitudinal alignment feature  320 , is in the unique orientation defined by the guide feature  330  and is retained in the connector guide  400 ,  156  by the retaining feature  340 . 
     A connector  164 ,  300  may comprise: an elongated connector body  310  defining a longitudinal direction and having an electrical cable  166  extending from the connector body  310 ; an electrical connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal alignment feature  320  on the elongated connector body  310  configured for aligning the elongated connector body  310  with a connector guide  156 ,  400 ; a guide feature  330  on the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and a retaining feature  340  on the elongated connector body  310  configured for retaining the elongated connector body  310  in the connector guide  165 ,  400 , whereby the elongated connector body  310  when inserted into the connector guide  156 ,  400  may be aligned with the connector guide  156 ,  400  by the longitudinal alignment feature  320 , may be in the unique orientation defined by the guide feature  330  and may be retained in the connector guide by the retaining feature  340 . The longitudinal alignment feature  320  may include a raised longitudinal rib  320 ; or the guide feature  330  may include a raised guide member  330 ; or the longitudinal alignment feature  320  may include a raised longitudinal rib  320  and the guide feature  330  may include a raised guide member  330 ; or the retaining feature  340  may include at least one raised transverse rib  340 ; or the longitudinal alignment feature  320  may include a raised longitudinal rib  320  and the retaining feature  340  may include at least one raised transverse rib  340 ; or the guide feature  330  may include a raised guide member  330  and the retaining feature  340  may include at least one raised transverse rib  340 ; or the longitudinal alignment feature  320  may include a raised longitudinal rib  320  and the guide feature  330  may include a raised guide member  330  and the retaining feature  340  may include at least one raised transverse rib  340 . The connector  164 ,  300  may be in combination with a connector guide  156 ,  400 , the connector guide  400  may comprise: one or more guide members  400 ,  156  extending outwardly from a base  130 ,  130 B adjacent a mating connector  152 ,  154  for the electrical connector frame  164 P; the one or more guide members  400 ,  156  configured to be adjacent to the elongated connector body  310  to align the elongated connector body  310  and the mating connector  152 ,  154  when the electrical connector frame  164 P mates with the mating connector  152 ,  154 . The one or more guide members  400 ,  156  may have: a longitudinal alignment guide  420  complementary to the longitudinal alignment feature  320  of the elongated connector body  310 ; the longitudinal alignment guide  420  being configured to receive the guide feature  320  on the elongated connector body  310  when the elongated connector body  310  is in the defined unique orientation; a complementary retaining feature  440  configured to receive the retaining feature  340  on the elongated connector body  310  for retaining the elongated connector body  310  in the connector guide  156 ,  400  and mated to the mating connector  152 ,  154 . The longitudinal alignment feature  320  on the elongated connector body  310  may include a raised alignment rib  320  configured for aligning with a groove  420  on an inward facing surface of the one or more guide members  156  of the connector guide  156 ,  400 ; the guide feature  330  on the elongated connector body  310  may include a raised guide  330  defining a unique orientation of the elongated connector body  310  and engages the groove  320  on an inward facing surface of the one or more guide members  156 ,  400 ; and the retaining feature  340  on the elongated connector body  310  may be a raised rib  340  or a recess  340  that engages a complementary recess  340  or raised rib  340  on an inward facing surface of the one or more guide members  156 ,  400 . The connector body  310  may be a slip fit with the connector guide  156 ,  400  and the retaining feature  340  may be an interference fit or a snap fit with the connector guide  156 ,  400 . The connector body  310  may be a slip fit with the connector guide  400 ,  156  and the retaining feature  340  may be an interference fit or a snap fit with the connector guide  400 ,  156 . The connector frame  164 P may include a USB connector frame  164 P. The electrical connector  300 ,  400  may be configured to connect an external electrical power supply  168  to a charger housing  100 , and the charger housing  100 ,  130  may include an electronic circuit  200  for determining the level of current available from the external power supply  168  via the electrical connector  300 ,  400 ,  152 ,  154  including: measuring  1200 ,  2350  a voltage provided by the external power supply  168 ; determining  1200 ,  2350  whether the voltage provided by the external power supply  168  is less than a predetermined voltage and, if so: decreasing  1250 ,  2355  the current drawn from the external power supply  168  by a predetermined amount; repeating the foregoing steps of measuring  1200 ,  2350 , determining  1200 ,  2350  and decreasing  1250 ,  2355  until the voltage provided by the external power supply  168  is not less than the predetermined voltage. The electrical connector  300 ,  400  may be configured to connect a first external power supply  168  to a first electrical connector  152 ,  154  of a charger housing  130 : the charger housing  130  including a second electrical connector  154 ,  152  configured for receiving electrical power from a second external electrical power supply  168 , wherein the first electrical connector  152  and the second electrical connector  154  are closely adjacent each other such that an external electrical connector  162 ,  164 ,  300 ,  400  mated with the first electrical connector  152  or with the second electrical connector  154  physically interferes with and prevents an external electrical connector from being mated with the other of the first electrical connector  152  and the second electrical connector  154 . 
     An electrical connector  154 ,  400  may comprise: an electrical connector frame  154  supported on a base  130 ,  130 B and defining a longitudinal direction extending from the base  130 ,  130 B; an alignment and retaining structure  400  including first and second opposing guide members  156  extending from the base  130 ,  130 B in the longitudinal direction, the first and second opposing guide members  156  each having an inward facing surface that faces the other guide member  156 , wherein the first and second guide members  156  are located spaced apart by a distance configured for an elongated connector body  310  to be placed therebetween with an electrical connector frame  164 P of the elongated connector body  310  positioned to mate with the electrical connector frame  154  supported on the base  130 ,  130 B; the first guide member  156  having on the inward facing surface thereof a longitudinal alignment feature  420  configured to align a complementary longitudinal alignment feature  320  of the connector body  310  with the electrical connector frame  154  supported on the base  130 ,  130 B, wherein the longitudinal alignment feature  420  of the first guide member  156  is configured to receive a guide feature  330  on the elongated connector body  310  that defines a unique orientation of the elongated connector body  310 ; and at least one of the first and second guide members  156  having on the inward facing surface thereof a retaining feature  440  configured to engage a complementary retaining feature  340  of the elongated connector body  310  for retaining the elongated connector body  310  between the first and second guide members  156  with the electrical connector frame  164 P of the elongated connector body  310  mated with the electrical connector frame  154  supported by the base  130 ,  130 B, whereby the elongated connector body  310  when inserted to mate with the electrical connector frame  154  supported by the base  130 ,  130 B is aligned therewith by the complementary longitudinal alignment features  320 ,  420 , is in the unique orientation defined by the guide feature  330  and is retained between the first and second guide members  156  by the complementary retaining features  340 ,  440 . The longitudinal alignment feature  420  of the first guide member  156  may include a longitudinal groove  420 ; or the retaining feature  440  of the at least one of the first and second guide members  156  may include a transverse rib or groove  440 ; or the longitudinal alignment feature  420  of the first guide member  156  may include a longitudinal groove  420  and the retaining feature  440  of the at least one of the first and second guide members  156  may include a transverse rib or groove  440 . The electrical connector  154 ,  400  in combination with a mating electrical connector  164 ,  300  which may comprise: an elongated connector body  310  in the longitudinal direction and having an electrical cable  166  extending from the connector body  310 ; an electrical connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal alignment feature  420  on the elongated connector body  310  configured for aligning the elongated connector body  310  with the alignment feature  420  of the first guide member  156 ; a guide feature  330  on the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and a retaining feature  340  on the elongated connector body  310  configured for engaging the at least one of the first and second guide members  156  for retaining the elongated connector body  310  in the first and second guide members  156 , whereby the elongated connector body  310  when inserted between the first and second guide members  156  so that when the respective electrical connector frames  154 ,  164 P thereof are mated the connector body  310  is aligned by the respective longitudinal alignment features  320 ,  420 , is in the unique orientation defined by the guide feature  320  and is retained between the first and second connector guide members  156  by the respective retaining features  340 ,  440 . The longitudinal alignment feature  420  of the first guide member  156  may be configured to receive the guide feature  330  on the elongated connector body  310  when the elongated connector body  310  is in the defined unique orientation. The longitudinal alignment feature  320  on the elongated connector body  310  may include a raised alignment rib  320  configured for aligning with a groove  420  on the inward facing surface of the first and second guide members  156 ; the guide feature  330  on the elongated connector body  310  may include a raised guide  330  on the alignment rib  320  defining a unique orientation of the elongated connector body  310  and may engage the groove  420  on the inward facing surface of the first and second guide members  156 ; and the retaining feature  340  on the elongated connector body  310  may be a raised rib  340  or a recess  340  that engages a complementary recess  440  or raised rib  440  on the inward facing surface of the first and second guide members  156 . The elongated connector body  310  may be a slip fit with the first and second guide members  156  and the retaining feature  340  thereof may be an interference fit or a snap fit with the retaining feature  440  of the at least one of the first and second guide members  156 . The electrical connector frame  154 ,  164 P may include a USB connector frame. The base  130 ,  130 B may include a charger housing  130  and the electrical connector frame  154  of the electrical connector  154  may be configured for receiving electrical power from an external electrical power supply  168 , the charger housing  130  may include an electronic circuit  200  for determining the level of current available from the external power supply  168  via the electrical connector  154 ,  164 ,  300  including: measuring  1200 ,  2350  a voltage provided by the external power supply  168 ; determining  1200 ,  2350  whether the voltage provided by the external power supply  168  is less than a predetermined voltage and, if so: decreasing  1250 ,  2355  the current drawn from the external power supply  168  by a predetermined amount; repeating the foregoing steps of measuring  1200 ,  2350 , determining  1200 ,  2350  and decreasing  1250 ,  2355  until the voltage provided by the external power supply  168  is not less than the predetermined voltage. The base  130 ,  130 B may include a charger housing  130  and the electrical connector frame  154  of the electrical connector  154  may be configured for receiving electrical power from a first external electrical power supply  168 , the charger housing  130  may include a second electrical connector  152  configured for receiving electrical power from a second external electrical power supply  168 , wherein the electrical connector  154  and the second electrical connector  152  are closely adjacent each other such that an external electrical connector  164 ,  162  mated with the electrical connector  154  or with the second electrical connector  152  physically interferes with and prevents an external electrical connector  162 ,  164  from being mated with the other of the electrical connector  154  and the second electrical connector  152 . 
     An electrical connector  164 ,  300  may comprise: a substantially rectangular elongated connector body  310  defining a longitudinal direction and having an electrical cable  166  extending from the elongated connector body  310 ; a USB connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal raised rib  320  on the elongated connector body  310  configured for aligning the elongated connector body  310  with a connector guide  400 ,  156  for a mating USB connector  154 ; a raised guide feature  330  on the raised rib  320  of the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and at least one transverse rib  340  or transverse groove  340  on the elongated connector body  310  configured to engage the connector guide  400 ,  156  for retaining the elongated connector body  310  in the connector guide  400 ,  156 , whereby the elongated connector body  310  when inserted into the connector guide  400 ,  156  for the mating USB connector  154  is aligned with the connector guide  400 ,  156  and the mating USB connector  154  by the longitudinal raised rib  320 , is in the unique orientation defined by the raised guide feature  330  and is retained in the connector guide  400 ,  156  by the transverse rib  340  or transverse groove  340 . The retaining feature  340  may include at least one raised transverse rib  340  and/or at least one transverse groove  340 . 
     A pair of mating electrical connectors  154 ,  400 ,  164 ,  300  may comprise: a first electrical connector  164 ,  300  including: a substantially rectangular elongated connector body  310  defining a first longitudinal direction and having an electrical cable  166  extending from the elongated connector body  310 ; a first USB connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal raised rib  320  on the elongated connector body  310  configured for aligning the elongated connector body  310  with a connector guide  400 ,  156  for a mating USB connector  154 ; a raised guide feature  330  on the raised rib  320  of the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and at least one transverse rib  340  or transverse groove  340  on the elongated connector body  310  configured to engage the connector guide  400 ,  156  for retaining the elongated connector body  310  in the connector guide  400 ,  156 ; and a second electrical connector  154 ,  400  including: a second USB electrical connector frame  154  supported on a base  130 ,  130 B and defining a second longitudinal direction extending from the base  130 ,  130 B; an alignment and retaining structure  400  including first and second opposing guide members  156  extending from the base  130 ,  130 B in the second longitudinal direction, the first and second opposing guide members  156  each having an inward facing surface that faces the other guide member  156 , wherein the first and second guide members  156  are located spaced apart by a distance configured for the elongated connector body  310  to be placed therebetween with the first USB electrical connector frame  164 P of the elongated connector body  310  positioned to mate with the second USB electrical connector frame  154  supported on the base  130 ,  130 B, whereby the first and second longitudinal directions are substantially aligned; the first guide member  156  having on the inward facing surface thereof a longitudinal groove  420  configured to align the complementary longitudinal raised rib  320  of the connector body  310  with the electrical connector frame  154  supported on the base  130 ,  130 B, wherein the longitudinal groove  420  of the first guide member  156  is configured to receive the guide feature  330  on the elongated connector body  310  that defines a unique orientation of the elongated connector body  310 ; and at least one of the first and second guide members  156  having on the inward facing surface thereof a transverse rib  440  or transverse groove  440  configured to engage a complementary transverse groove  340  or transverse rib  340  of the elongated connector body  310  for retaining the elongated connector body  310  between the first and second guide members  156  with the first USB electrical connector frame  164 P of the elongated connector body  310  mated with the second USB electrical connector frame  154  supported by the base  130 ,  130 B, whereby the first USB electrical connector frame  164 P of the elongated connector body  310  when inserted to mate with the second USB electrical connector frame  154  supported by the base  130 ,  130 B is aligned therewith by the complementary longitudinal raised rib  320  and longitudinal groove  420 , is in the unique orientation defined by the guide feature  330  and is retained between the first and second guide members  156  by the complementary transverse rib  340 ,  440  and transverse groove  340 ,  440 , with the first and second longitudinal directions substantially aligned. 
     A method  1100 ,  2000  for charging at least one rechargeable battery  180 ,  190  connected to a battery charger  100  may comprise: a) determining  1300 ,  2075 ,  2155  whether a battery  180 ,  190  is present; b) setting  1400 ,  2070  an initial charge current level that is substantially lower than a charge current that the battery  180 ,  190  can accept; c) repetitively interrupting  1500 ,  1520 ,  2315 ,  2325  charging of the battery  180 ,  190  at a predetermined timing to define a periodic cycle, and for each periodic cycle: measuring  1525 ,  2315 ,  2325  an open circuit voltage of the battery  180 ,  190  when charging of the battery  180 ,  190  is interrupted  1500 ,  1520 ,  2315 ,  2325 , determining  1540 - 1590 ,  2335 ,  2345  from the measured open circuit voltage of the battery  180 ,  190  a corresponding predetermined level of charging current to be applied to the battery  180 ,  190 ; applying charging current  1550 ,  2315 - 2345  to the battery  180 ,  190  at the predetermined level of charging current; and d) repeating the periodic cycle  1500 ,  2000  at least until the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery being fully charged  1580 ,  2085 ,  2165  or until the battery is disconnected  1530 ,  2315 ,  2325  from the battery charger  100 . A method  1100 ,  2000  may further comprise determining  1200 ,  2350 - 2355  the level of current available from an external power supply  168  including: e) measuring  1200 ,  2350  a voltage provided by the external power supply; f) determining  1200 ,  2350  whether the voltage provided by the external power supply  168  is less than a predetermined voltage and, if so: g) decreasing  1250 ,  2355  the current drawn from the external power supply  168  by a predetermined amount; h) repeating  1200 ,  2000  the foregoing steps of e) measuring  1200 ,  2350 , f) determining  1200 ,  2350  and g) decreasing  1250 ,  2355  until the voltage provided by the external power supply  168  is not less than the predetermined voltage. The method  1100 ,  2000  may further comprise setting  1250 ,  1545 ,  2360  a maximum charge current for the battery  180 ,  190  that is equal to or less than the level of current drawn from the external power supply  168  when the voltage provided by the external power supply  168  is not less than the predetermined voltage. In the method  1100 ,  2000 , the initial charge current level may be at a level of current that is safe for applying to a battery  180 ,  190  irrespective of its temperature, or irrespective of its state of charge, or irrespective of its temperature and its state of charge. In the method  1100 ,  2000  the predetermined level of charging current to be applied to the battery  180 ,  190  may be substantially zero  1580 ,  1590 ,  2230 ,  2255  when the measured  1525  open circuit voltage of the battery  180 ,  190  is greater than or equal to a voltage indicative of full charge for the battery  180 ,  190 . The method  1100 ,  2000  may further comprise: reducing  1590 ,  2230 ,  2255  the charging current applied to the battery  180 ,  190  substantially to zero for a period of time after the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged; or reducing  1590 ,  2230 ,  2255  the charging current applied to the battery substantially to zero for a predetermined period of time after the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged. The method  1100 ,  2000  may further comprise: applying  2230 ,  2255  charging current to the battery  180 ,  190  after the predetermined period of time or after the predetermined period of time at least until the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery being fully charged, thereby to top off the battery charge. The method  1100 ,  2000  with battery charger  100  in combination with an external source of electrical power  168  may further comprise: receiving electrical power from the external source of electrical power  168  via a first electrical connector  152 ,  154 . The method  1100 ,  2000  may further comprise: employing a second electrical connector  152 ,  154  for receiving electrical power from a second external source of electrical power  168 , wherein the first and second electrical connectors  152 ,  154  are closely adjacent each other such that an external electrical connector  162 ,  164 ,  300  inserted into one of the first and second electrical connectors  152 ,  154  physically interferes with and prevents an external electrical connector  162 ,  164 ,  300  from being plugged into the other of the first and second electrical connectors  152 ,  154 . The first electrical connector  154  may include a connector guide  400 ,  156  and an electrical connector  164 ,  300  configured to mate therewith may comprise: an elongated connector body  310  defining a longitudinal direction and having an electrical cable  166  extending from the connector body  310 ; an electrical connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal alignment feature  320  on the elongated connector body  310  configured for aligning the elongated connector body  310  with the connector guide  400 ,  156 ; a guide feature  330  on the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and a retaining feature  340  on the elongated connector body  310  configured for retaining the elongated connector body  310  in the connector guide  400 ,  156 , whereby the elongated connector body  310  when inserted into the connector guide  400 ,  156  is aligned with the connector guide  400 ,  156  by the longitudinal alignment feature  320 , is in the unique orientation defined by the guide feature  330  and is retained in the connector guide  400 ,  156  by the retaining feature  340 . 
     A method  1100 ,  2000  for charging at least one rechargeable battery  180 ,  190  connected to a battery charger  100  may comprise: a) determining  1200 ,  2075 ,  2155  whether a battery is present; b) setting  1400 ,  2070  an initial charge current level that is substantially lower than a charge current that the battery  180 ,  190  can accept; c) determining  1200 ,  2305 ,  2355  the level of current available from an external power supply  168  including: i) measuring  1200 ,  2350  a voltage provided by the external power supply  168 ; ii) determining  1200 ,  2350  whether the voltage provided by the external power supply  168  is less than a predetermined voltage and, if so: iii) decreasing  1250 ,  2355  the current drawn from the external power supply  168  by a predetermined amount; d) repeating  1200 ,  2000  the foregoing steps of i) measuring  1200 ,  2350 , determining  1200 ,  2350  and iii) decreasing  1250 ,  2355  until the voltage provided by the external power supply  168  is not less than the predetermined voltage. The method  1100 ,  2000  may further comprise setting  1250 ,  1545 ,  2360  a maximum charge current for the battery  180 ,  190  that is equal to or less than the level of current drawn from the external power supply  168  when the voltage provided by the external power supply  168  is not less than the predetermined voltage. The initial charge current level may be at a level of current that is safe for applying to a battery  180 ,  190  irrespective of its temperature, or irrespective of its state of charge, or irrespective of its temperature and its state of charge. The method  1100 ,  2000  may further comprise: e) repetitively interrupting  1500 ,  1520 ,  2315 ,  2325  charging of the battery  180 ,  190  at a predetermined timing to define a periodic cycle, and for each periodic cycle: measuring  1525 ,  2315 ,  2325  an open circuit voltage of the battery  180 ,  190  when charging of the battery  180 ,  190  is interrupted  1520 ,  2315 ,  2325 , determining  1540 - 1590 ,  2335 ,  2345  from the measured open circuit voltage of the battery  180 ,  190  a corresponding predetermined level of charging current to be applied to the battery  180 ,  190 ; applying charging current  1550 ,  2315 - 2345  to the battery  180 ,  190  at the predetermined level of charging current; and f) repeating the periodic cycle  1500 ,  2000  at least until the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged or until the battery  180 ,  190  is disconnected from the battery charger  100 . The predetermined level of charging current to be applied to the battery  180 ,  190  may be substantially zero when the measured open circuit voltage of the battery  180 ,  190  is greater than or equal to a voltage indicative of full charge for the battery  180 ,  190 . The method  1100 ,  2000  may further comprise: reducing  1590 ,  2230 ,  2255  the charging current applied to the battery  180 ,  190  substantially to zero for a period of time after the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged; or reducing  1590 ,  2230 ,  2255  the charging current applied to the battery  180 ,  190  substantially to zero for a predetermined period of time after the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged. The method further comprises: applying  2230 ,  2255  charging current to the battery  180 ,  190  after the predetermined period of time or after the predetermined period of time at least until the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery  180 ,  190  being fully charged, thereby to top off the battery charge. The method  1100 ,  2000  with battery charger  100  in combination with an external source of electrical power  168  may further comprise: receiving electrical power from the external source of electrical power  168  via a first electrical connector  152 ,  154 . The method  1100 ,  2000  may further comprise: employing a second electrical connector  152 ,  154  for receiving electrical power from a second external source of electrical power  168 , wherein the first and second electrical connectors  152 ,  154  are closely adjacent each other such that an external electrical connector  162 ,  164 ,  300  inserted into one of the first and second electrical connectors  152 ,  154  physically interferes with and prevents an external electrical connector  162 ,  164 ,  300  from being plugged into the other of the first and second electrical connectors  152 ,  154 . The first electrical connector may include a connector guide  400 ,  16  and an electrical connector  162 ,  164 ,  300  configured to mate therewith may comprise: an elongated connector body  310  defining a longitudinal direction and having an electrical cable  166  extending from the connector body  310 ; an electrical connector frame  164 P at one end of the elongated connector body  310 ; a longitudinal alignment feature  320  on the elongated connector body  310  configured for aligning the elongated connector body  310  with the connector guide  400 ,  156 ; a guide feature  330  on the elongated connector body  310  defining a unique orientation of the elongated connector body  310 ; and a retaining feature  340  on the elongated connector body  310  configured for retaining the elongated connector body  310  in the connector guide  400 ,  156 , whereby the elongated connector body  310  when inserted into the connector guide  400 ,  156  is aligned with the connector guide  400 ,  156  by the longitudinal alignment feature  320 , is in the unique orientation defined by the guide feature  320  and is retained in the connector guide  400 ,  156  by the retaining feature  340 . 
     A method  1100 ,  2000  for charging at least one rechargeable battery  180 ,  190  connected to a battery charger  100  may comprise: a) determining  1300 ,  2075 ,  2155  whether a battery  180 ,  190  is present; b) setting  1400 ,  2070  an initial charge current level that is substantially lower than a charge current that the battery  180 ,  190  can accept; 
     c) determining  1200 ,  2305 ,  2355  the level of current available from an external power supply  168  including: i) measuring  1200 ,  2350  a voltage provided by the external power supply  168 ; ii) determining  1200 ,  2350  whether the voltage provided by the external power supply  168  is less than a predetermined voltage and, if so: iii) decreasing  1250 ,  2355  the current drawn from the external power supply  168  by a predetermined amount; d) repeating  1200 ,  2000  the foregoing steps of i) measuring  1200 ,  2350 , ii) determining  1200 ,  2350  and iii) decreasing  1250 ,  2355  until the voltage provided by the external power supply  168  is not less than the predetermined voltage; and e) repetitively interrupting  1500 ,  1520 ,  2315 ,  2325  charging of the battery  180 ,  190  at a predetermined timing to define a periodic cycle, and for each periodic cycle: i) measuring  1525 ,  2315 ,  2325  an open circuit voltage of the battery  180 ,  190  when charging of the battery  180 ,  190  is interrupted  1500 ,  1520 ,  2315 ,  2325 , ii) determining  1540 - 1590 ,  2335 ,  2345  from the measured open circuit voltage of the battery  180 ,  190  a corresponding predetermined level of charging current to be applied to the battery  180 ,  190 ; iii) applying charging current  1550 ,  2315 - 2345  to the battery  180 ,  190  at the predetermined level of charging current; and f) repeating the periodic cycle  1500 ,  2000  at least until the open circuit voltage of the battery  180 ,  190  is at a predetermined voltage indicative of the battery being fully charged  1580 ,  2085 ,  2165  or until the battery is disconnected  1530 ,  2315 ,  2325  from the battery charger  100 . 
     As used herein, the term “about” means that dimensions, sizes, formulations, parameters, shapes and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, a dimension, size, formulation, parameter, shape or other quantity or characteristic is “about” or “approximate” whether or not expressly stated to be such. It is noted that embodiments of very different sizes, shapes and dimensions may employ the described arrangements. 
     As used herein, the terms “electrical receptacle connector” and “electrical receptacle” and “receptacle” refers to an electrical connector and/or contacts, whether of the male or female type or of mixed types, that is associated with charger base or housing, e.g., typically disposed in a connector port thereof for receiving an electrical plug; and the terms “electrical plug connector” and “electrical plug” and “plug” refers to an electrical connector, whether of the male or female type or of mixed types, that is associated with an electrical power supply, e.g., with a housing thereof and/or a cable thereof. 
     Although terms such as “up,” “down,” “left,” “right,” “up,” “down,” “front,” “rear,” “side,” “end,” “top,” “bottom,” “forward,” “backward,” “under” and/or “over,” “vertical,” “horizontal,” and the like may be used herein as a convenience in describing one or more embodiments and/or uses of the present arrangement, the articles described may be positioned in any desired orientation and/or may be utilized in any desired position and/or orientation. Such terms of position and/or orientation should be understood as being for convenience only, and not as limiting of the invention as claimed. 
     The term battery is used herein to refer to an electro-chemical device comprising one or more electro-chemical cells and/or fuel cells, and so a battery may include a single cell or plural cells, whether as individual units or as a packaged unit. A battery is one example of a type of an electrical power source suitable for a portable or other device. Such devices could include power sources including, but not limited to, fuel cells, super capacitors, solar cells, and the like. Any of the foregoing may be intended for a single use or for being rechargeable or for both. The term battery  190  may be used to describe a battery  190  that is disposed in a flashlight  180  (as may be placed into a flashlight cradle, e.g., cradle  110 ), or a battery  190  not in a flashlight (as may be placed into a secondary cradle, e.g., cradle  120 ). 
     Various embodiments of a battery may have one or more battery cells, e.g., one, two, three, four, or five or more battery cells, as may be deemed suitable for any particular device. A battery may employ various types and kinds of battery chemistry types, e.g., a carbon-zinc, alkaline, lead acid, nickel-cadmium (Ni—Cd), nickel-metal-hydride (NiMH) or lithium-ion (Li-Ion) battery type, of a suitable number of cells and cell capacity for providing a desired operating time and/or lifetime for a particular device, and may be intended for a single use or for being rechargeable or for both. Examples may include a two cell lead acid battery typically producing about 4 volts, a three cell Ni—Cd battery typically producing about 3.6 volts, a four cell NiMH battery typically producing about 4.8 volts, a Lithium-Ion battery typically producing about 2.5 to 4.2 volts, it being noted that the voltages produced thereby will be higher when approaching full charge and will be lower when not fully charged and in discharge, particularly when providing higher current and when reaching a low level of remaining charge, e.g., becoming discharged. 
     The term DC converter is used herein to refer to any electronic circuit that receives at an input electrical power at one voltage and current level and provides at an output DC electrical power at a different voltage and/or current level. Examples may include a DC-DC converter, an AC-DC converter, a boost converter, a buck converter, a buck-boost converter, a single-ended primary-inductor converter (SEPIC), a series regulating element, a current level regulator, and the like. The input and output thereof may be DC coupled and/or AC coupled, e.g., as by a transformer and/or capacitor. A DC converter may or may not include circuitry for regulating a voltage and/or a current level, e.g., at an output thereof, and may have one or more outputs providing electrical power at different voltage and/or current levels and/or in different forms, e.g., AC or DC. 
     While the present invention has been described in terms of the foregoing example embodiments, variations within the scope and spirit of the present invention as defined by the claims following will be apparent to those skilled in the art. For example, while charger  100  is shown as having a cradle  110  configured to receive an electronic device, e.g., a flashlight, including a rechargeable battery and a cradle  120  (which can be optional) configured to receive a rechargeable battery, either cradle  110  or cradle  120  or both of cradles  110  and  120  can be configured to receive an electronic device, or to receive a rechargeable battery. 
     Further, either cradle  110  or cradle  120  or both of cradles  110  and  120  can be configured to receive an electronic device and a rechargeable battery one at a time, e.g., with suitable electrical contacts and/or positioning guides provided for cradle  110  and/or cradle  120 . In other words, an electronic device can be placed into cradle  110  for recharging the battery therein or a battery apart from an electronic device can be placed into cradle  110  for recharging, cradle  110  being configured to have electrical contacts for making electrical connection to the electronic device and for making electrical contacts to the battery. In addition, cradle  120 , if provided, may be similarly configured with electrical contacts for making electrical connection to an electronic device and to a battery. 
     Regarding connector port  150 , while two different generally rectangular receptacles for receiving power supply plugs are illustrated, the different receptacles could be rectangular, square, trapezoidal, circular, oval, triangular, or any other shape. The mating plugs and receptacles may have complementary male pins, female pins, or a combination thereof, and may be of similar shape or of dissimilar shape. 
     Further, where a particular type of connector is shown, e.g., a USB connector, another type of connector could be provided The term USB connector is considered to encompass both plugs and receptacles, type A and B USB connectors, versions 1.x, 2.x and 3.x, and all other varieties thereof. Similarly, the relative positions of male and female connectors, e.g., receptacles and plugs, can be interchanged unless specifically stated otherwise, and further, a plug may be of either the male gender or the female gender and a receptacle may be of either the male gender or the female gender. 
     While the example electronic device  180  has an electrical switch  188 S in the tail cap  186 T thereof, the electrical switch could be located internally forward of battery  190  and actuator  188  could move battery  190  forward so that the forward end thereof actuates an electrical switch associated, e.g., with circuit board thereof, or a switch and/or actuator could be provided on another location on light  180 . 
     Raised and recess features intended to engage may be interchanged, e.g., a raised feature may be provided where a recess feature is shown herein and a corresponding recess feature may be provided where a corresponding raised feature is shown. Alternatively, raised and recessed features may both be utilized, e.g., as for retaining features  340  of connector  300  and the complementary retaining features  440  of guides  156 ,  400 . 
     While certain features may be described as a raised feature, e.g., a ridge, boss, flange, projection or other raised feature, such feature may be positively formed or may be what remains after a recessed feature, e.g., a groove, slot, hole, indentation, recess or other recessed feature, is made. Similarly, while certain features may be described as a recessed feature, e.g., a groove, slot, hole, indentation, recess or other recessed feature, such feature may be positively formed or may be what remains after a raised feature, e.g., a ridge, boss, flange, projection or other raised feature, is made. 
     While connector body  310  is substantially rectangular as illustrated, with various features  312 ,  320 ,  330 ,  340  added thereto, other shapes could also be employed, e.g., substantially cylindrical with a circular, elliptical or oval cross-section, triangular, hexagonal, and so forth. 
     Each of the U.S. Provisional Applications, U.S. Patent Applications, and/or U.S. Patents, identified herein is hereby incorporated herein by reference in its entirety, for any purpose and for all purposes irrespective of how it may be referred to or described herein. 
     Finally, numerical values stated are typical or example values, are not limiting values, and do not preclude substantially larger and/or substantially smaller values. Values in any given embodiment may be substantially larger and/or may be substantially smaller than the example or typical values stated.