Patent Publication Number: US-2011068742-A1

Title: Audio device that interfaces with a battery charger

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part application of co-pending patent application Ser. No. 12/605,482, filed Oct. 26, 2009, which is a continuation of patent application Ser. No. 10/926,744, filed on Aug. 26, 2004, now U.S. Pat. No. 7,609,027, which is a continuation-in-part of patent application Ser. No. 10/291,868, filed Nov. 8, 2002, now U.S. Pat. No. 6,982,541, which claims the benefit of Provisional Patent Application Ser. No. 60/379,068, filed May 9, 2002 and Provisional Patent Application Ser. No. 60/344,431, filed on Nov. 9, 2001. patent application Ser. No. 10/926,744 also claims the benefit of Provisional Patent Application Ser. No. 60/523,541, filed Nov. 19, 2003, and Provisional Patent Application Ser. No. 60/540,313, filed Jan. 28, 2004. The entire contents of all of the above applications are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The invention relates to audio devices that are operable with rechargeable batteries. 
     Audio devices that output audio signals, such as radios, compact disc players, mp3 players, and the like, use a power supply to provide power for an audio circuit capable of outputting the audio signals. Some audio devices connect to a fixed AC power supply, such as a 120 Volt, 60 Hz outlet in a building. Other audio devices use a battery power supply and in some cases rechargeable batteries to power an audio circuit. 
     Rechargeable power tool batteries are frequently available on a construction and other jobsite. These power tool batteries can be interchangeably used by different types of power tools including, for example, drills and screwdrivers. Audio devices (e.g., jobsite radios) have been developed that can also be powered by these rechargeable power tool batteries. 
     SUMMARY 
     In one embodiment, the invention provides an audio system including a battery charger housing and an audio device housing that are selectively engagable. The battery charger housing includes a charger control circuit and a first rechargeable battery receptacle having a first battery position. The charger control circuit is electrically coupled to the first rechargeable battery receptacle and is operable to charge a battery in the first battery position within the first rechargeable battery receptacle. 
     The audio device housing includes an audio circuit and a second rechargeable battery receptacle. The audio circuit is electrically coupled to the second rechargeable battery receptacle and is operable to generate sound using at least one audio generator. A pass-through circuit is electrically coupled to the audio circuit and to the first battery position. The pass-through circuit is operable to receive power from an external source, provide the power to the charger control circuit, and provide the power to the audio circuit. 
     In another embodiment, the invention provides an audio system including a battery charger housing and an audio device housing that are selectively engageable. The battery charger housing includes a battery charger housing having a charger control circuit and a first battery receptacle operable to receive a first removable battery. The charger control circuit is electrically coupled to the first battery receptacle to charge the first battery when in a first battery position within the first battery receptacle. 
     The audio device housing includes an audio circuit and a second battery receptacle. The audio circuit is electrically coupled to the second battery receptacle and is operable to generate sound using at least one audio generator. The audio circuit is also operable to at least one of combine and selectively apply power received from a second removable battery within the second battery receptacle and power received from an external power source to the at least one audio generator. 
     In another embodiment, the invention provides an audio system including a battery charger housing and an audio device housing. The battery charger housing includes a charger control circuit and a first battery receptacle. The charger control circuit is coupled to a first electrical connection in the first battery receptacle and is operable to charge a first removable battery in the first battery position. 
     The audio device housing is engageable with the battery charger housing and includes an audio circuit and a second battery receptacle. The audio circuit is electrically coupled to the second battery receptacle and operable to generate sound using at least one audio generator. The audio circuit is operable to selectively couple the at least one audio generator to the second battery receptacle and an input configured to receive power from an external source. When the battery charger housing is engaged with the audio device housing and the power is received at the input from the external source, the charger control circuit and the audio circuit share the power received from the external source. 
     In another embodiment, the invention includes a method of charging a battery and generating audio. The method includes operating an audio housing in a first mode, and at least one of a second mode and a third mode. The first mode includes coupling a battery charger housing to the audio housing. The battery charger housing includes a first battery receptacle and a charging circuit and the audio housing includes an audio generating circuit and a second battery receptacle. The first mode also includes coupling the battery charger housing to an external power source using a cord such that an electrical connection is formed between the external power source, the charging circuit, and the audio generating circuit. The first mode further includes charging a first battery in a first position in the first battery receptacle and generating audio using the audio generating circuit powered by the external power source. 
     The second mode includes disconnecting at least one of the cord from the battery charger housing and the battery charger housing from the audio housing and generating audio using the audio generating circuit powered by a second battery in the second battery receptacle. 
     The third mode includes disconnecting at least one of the cord from the battery charger housing and the battery charger housing from the audio housing; coupling the external power source or a different external power source to the audio housing; and generating audio using the audio generating circuit powered by the external power source or the different external power source. 
     In some embodiments, the method includes operating the audio housing in a fourth mode. The fourth mode includes placing the first battery in a second position within the first battery receptacle, and generating audio using the audio generating circuit powered by the first battery in the second position. 
     In some embodiments of the method, the audio housing includes one of a fixed cord and a selectively removable cord, and the battery charger housing includes one of a fixed cord and a selectively removable cord. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 2  is a schematic diagram of an audio circuit according to embodiments of the invention. 
         FIGS. 3-6  illustrate an audio housing, battery charger housing, and cords according to embodiments of the invention. 
         FIG. 7  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIGS. 8-11  illustrate an audio housing, battery charger housing, and cords according to embodiments of the invention. 
         FIG. 12  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 13  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 14  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 15  is a schematic diagram of an audio device according to embodiments of the invention. 
       FIGS.  16  and  17 A-B illustrate an audio housing, battery charger housing, and cords according to embodiments of the invention. 
         FIGS. 18A-B  are a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 19  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 20  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 21  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 22  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 23  is a schematic diagram of an audio device according to embodiments of the invention. 
         FIG. 24  depicts a first mode of operating an audio system according to embodiments of the invention. 
         FIG. 25  depicts a second mode of operating an audio system according to embodiments of the invention. 
         FIG. 26  depicts a third mode of operating an audio system according to embodiments of the invention. 
         FIG. 27  depicts a fourth mode of operating an audio system according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
     Although audio devices (e.g., jobsite radios) have been developed that are powered by rechargeable power tool batteries, the batteries eventually lose their charge and the audio device will not function until a new battery is inserted or the audio device is connected to an external power source. As is explained in more detail below, embodiments of the invention provide unique and improved systems and methods of selectively attaching a battery charger housing with an audio device. 
       FIG. 1  depicts an audio system  100  according to one embodiment of the invention. The audio system  100  includes a battery charger housing  102  and an audio housing  104 . The audio housing  104  includes an audio circuit  106  and speakers  108  for generating and outputting sound, such as music or audio books. The audio housing  104  also includes selector  158  and user input  170 , which will be described in greater detail below. The audio circuit  106  receives power from at least one of two sources: 1) a rechargeable battery  110  coupled to the audio housing  104  and 2) an external power source coupled to the battery charger housing  102  via cord  113 . An AC/DC converter  117  is provided between the audio circuit  106  and socket  116 . The AC/DC converter  117  converts alternating current received from an external power source via socket  116  and outputs direct current to the audio circuit  106 . An exemplary external power source is a 120 volt, 60 hertz wall outlet typically found in homes and businesses. Other external power sources, including those with different voltage types and ratings such as a 12-volt DC car battery, may also be used. 
     The battery charger housing  102  is electrically coupled to the audio housing  104  via a plug  114  and socket  116  connection. In some embodiments, the plug  114  is part of the audio housing  104  and the socket  116  is part of the battery charger housing  102 . The battery charger housing  102  receives power from the external power source via cord  113  and uses the power to charge a battery  118 . The cord  113  with plug  112  is coupled to the battery charger housing  102  by plug  120  and socket  122  (i.e., a male-female connection). In some embodiments, the plug  120  is part of the battery charger housing  102  and the socket  122  is part of cord  113 . In some embodiments, connection techniques other than the depicted plug and socket connection are used to couple the audio housing  104  and battery charger housing  102 . 
     The battery charger housing  102  includes an AC/DC converter  124 , a charger control circuit  126 , and a battery receptacle  128 . The battery receptacle  128  receives and is electrically coupled to the battery  118 . Alternating current from the external source is received by the AC/DC converter  124 , which converts the alternating current and outputs direct current to the charger control circuit  126 . The charger control circuit  126  outputs DC voltage and charges battery  118 . 
     Thus, the external power source provides power to both charge the battery  118  and power the audio circuit  106 . The electrical connections within the audio and battery housing, including the socket  122 , plug  114 , and socket  116 , that enable external power to reach the audio circuit  106 , and AC/DC converters  117  and  124  may be referred to as a pass-through circuit. Unlike the battery  110 , the battery  118  does not provide power to the audio circuit  106 . In other embodiments, however, additional electrical connections are provided such that battery  118  provides power to the audio circuit  106 . Batteries  110  and  118  can be lithium-based, nickel-based, or any other rechargeable battery chemistry suitable to power audio system  100 . 
     The battery charger housing  102  is removable from the audio housing  104  and each is usable independent of the other. In other words, when separated, the battery charger housing  102  still functions to charge the battery  118  and the audio housing  104  still functions to generate audio. When separated, the audio housing  104  can receive power from either the battery  110  or by an external power source providing power via socket  116 . An additional cord  130  includes plugs  132  and  134  and is similar to cord  113 . When the battery charger housing  102  is separated from the audio housing  104 , plug  134  can be coupled to the socket  116  and provide power to the audio circuit  106  by connecting plug  132  to the external power source. Cords  130  and  113  are interchangeable between the audio housing  104  and the battery charger housing  102 . 
       FIG. 2  depicts the audio circuit  106  according to one embodiment of the invention. Power provided by the external power source via socket  116  is supplied along power line  150 . Power provided by battery  110  is supplied along power line  152 . A switch  154 , controlled by power control  156 , is configured to selectively couple either power line  150  or power line  152  to power control  156 , which outputs DC voltage V in . When power control  156  is coupled to power lines  150  or  152 , the DC voltage is passed-through or modified (stepped-up or stepped-down) to V in . V in  is a direct current voltage appropriate for the components of the audio circuit  106 . For instance, V in  can be 5V or 3.3V. In other embodiments, some of the components of audio circuit  106  require different voltage inputs. For instance, V in  is 5V for some components (e.g., the microcontroller  160 ) but 3.3V for other components (e.g., output selector  164 ). In some embodiments, DC voltage of the battery  110  is supplied to the audio circuit  106  and no AC/DC conversion hardware is provided within the audio circuit. In some embodiments, the AC/DC converter  117  is located within the audio circuit  106 . Thus, the power control  156  selectively applies DC power from power lines  150  or  152  to the components of audio circuit  106 . 
     In some embodiments, the power control  156  controls the switch  154  to supply power from the power line  150  when the power control  156  detects that the socket  116  is coupled to an external power supply and to provide power from the battery  110  when no external power supply is available. Is some embodiments, the power control  156  controls the switch  154  based on input from selector  158 . The selector  158  is a pushbutton, sliding actuator, or other similarly functioning device, that enables a user to selectively choose between the battery  110  power or the external power provided through socket  116 . In some embodiments, the audio circuit  106  does not include a switch  154 . Rather, the power control  156  receives power from both power lines  150  and  152  and combines the power input by both to output V in . In these embodiments, the battery  110  is not charged by the external source. In other embodiments, the battery  110  is charged by the external source while inserted in the battery receptacle  111 . 
     The exemplary audio circuit  106  of  FIG. 2  also includes a microcontroller  160 , display  162 , output selector  164 , amplifier  166 , and several audio generators  168   a - f . The microcontroller  160  includes software, hardware, or a combination thereof to control the display  162 , output selector  164 , and audio generators  168   a - f . In one embodiment, the microcontroller controls the display  162  to display the current audio generator  168   a - f  selection and other status information. For instance, if the audio circuit  106  is set to AM radio station  1000 , the display may show “AM 1000.” Other appropriate status information may be displayed as is apparent to one of ordinary skill in the art. 
     The microcontroller  160  receives input from user input  170 . User input  170  can include an audio generator selector such as one or more push buttons to control which audio generator  168   a - f  is currently active. Additional user input  170  can include selectors to control the operation of particular audio generators, such as, for instance, controls for playing, stopping, fast forwarding, or rewinding a compact disc, tape, or other media. Other appropriate controls for audio generators  168   a - f  may be included as is apparent to one of ordinary skill in the art. 
     Upon receipt of input from user input  170 , the microcontroller  160  enables one of the audio generators  168   a - f  and controls the output selector  164  to connect the output from the selected audio generator  168   a - f  to the input of amplifier  166 . The amplifier  166  amplifies the audio signals received from the selected audio generator by an amount specified by a user via user input  170  and microcontroller  160 . The amplifier  166  outputs the amplified audio signal to speakers  108 . 
     Audio circuit  106  is merely an exemplary audio circuit used in some embodiments of the invention. In some embodiments, other audio circuits are used to generate audio signals for speakers  108 . 
       FIGS. 3-6  depict an exemplary audio housing  104 , battery charger housing  102 , and cord  113 . The battery charger housing  102  can be mechanically coupled to the audio housing  104  so as to provide a secure and stable joining of the two housings. The battery charger housing  102 , shown without the battery  118 , includes a T-shaped slot  172  to engage a T-shaped protrusion  171  on the audio housing  104 . The battery charger housing  102  is slid into a locked position by engaging the T-shaped slot with the T-shaped protrusion. The locked position may be achieved by a friction-fitting of a closely paired T-shaped slot and protrusion, by a locking tab, or by another suitable engagement technique. In some instances, the plug  114  and socket  116  secure the battery charger housing  102  to the audio housing  104  without relying on additional mechanical coupling techniques. 
       FIGS. 4A-B  depict two views of an exemplary cord  113 . Cord  113  includes plug  120  for engaging the socket  122  or, if the battery charger housing  102  is not connected to the audio housing  104 , for engaging the socket  116  (not shown in  FIGS. 3-6 ). 
       FIG. 5  depicts battery charger housing  102  engaged with the audio housing  104 . The cord  113  is connected to the battery charger housing  102 .  FIG. 6  depicts the battery charger housing  102  with socket  122 , which connects to cord  113  via plug  120 . 
       FIG. 7  depicts an audio system  200  according to another embodiment of the invention. The audio system  200  is similar to the audio system  100 . However, a cord  201  is fixed to the battery charger housing  202 , in contrast to the removable cord  113 . Also, a cord  203  is fixed to the audio housing  204 , in contrast to the removable cord  130 . In some embodiments, when the battery charger housing  202  is coupled to the audio housing  204  via plug  114  and socket  116 , the fixed cord  203  is hidden from view. 
     For instance, a cord wrap device  206  can be included on the audio housing  204 , as depicted in  FIG. 8 . Before attaching the battery charger housing  202  to the audio housing  204  by sliding the T-shaped slot  172  onto the T-shaped protrusion  208 , the cord  203  can be wrapped around the cord wrap device  206 . Upon securing the battery charger housing  202  to the audio housing  204 , the cord  203  is hidden from view. In this situation, when the battery charger housing  202  is connected to the audio housing  204 , the cord  201  can be used to supply power to both the AC/DC converter  123  and the audio circuit  106 . However, when the battery charger housing  202  is removed from the audio housing  204 , the cord  203  can be used to couple the audio housing  204  to an external power source and the cord  201  can be used to couple the battery charger housing  202  to an external power source. In other words, the audio housing  204  and battery charger housing  202  can be used together or independently.  FIG. 9  depicts the plug ends of the fixed cords  201  and  203 .  FIG. 10  depicts the audio housing  204  and battery charger housing  202  coupled. The fixed cord  201  is visible, while the fixed cord  203  is wrapped around cord wrap device  206  and hidden from view.  FIG. 11  depicts the battery charger  202  with fixed cord  201 . 
       FIG. 12  depicts an audio system  210  according to another embodiment of the invention. The audio system  210  is similar to the audio system  200 , except that only one fixed cord  213  is provided. The battery charger housing  212  has no separate cord, but rather, receives power through socket  116  and plug  114 . The fixed cord  213  is fed through a slot  209  (see  FIG. 8 ) of the audio housing  204  such that fixed cord  213  can be plugged into a wall outlet even when the battery charger housing  202  is coupled to the audio housing  204 . 
       FIG. 13  depicts an audio system  220  according to another embodiment of the invention. The audio system  220  is similar to the audio system  200 , except that the audio system  220  includes a removable cord  223  for battery charger housing  222  and a fixed cord  225  for the audio housing  224 . The fixed cord  225  is intended for use when the battery charger housing  222  is separated from the audio housing  224 . When the battery charger housing  222  is attached to the audio housing  224 , the fixed cord  225  is hidden from view using a cord wrap device and cord  223  is connected to the external power source. 
       FIG. 14  depicts an audio system  230  according to another embodiment of the invention. The audio system  230  is similar to the audio system  200 , except that the audio system  230  includes a removable cord  235  for plugging into the audio housing  234  when the battery charger housing  232  is not coupled to the audio housing  234 . Additionally, the battery charger housing  232  includes a fixed cord  233 . Thus, the battery charger housing  232  can charge a battery when the battery charger housing  232  is separated from the audio housing  234 . In some embodiments, the audio housing  234  and audio housing  104  include a cord wrap device similar to cord wrap device  206  of  FIG. 8 . 
       FIG. 15  depicts an audio system  240  according to another embodiment of the invention. The audio system  240  is similar to the audio system  200  except that the audio housing  244  and battery charger housing  242  each have respective fixed cords  243  and  241 , and the battery charger housing  242  and audio housing  244  are not electrically coupled by a socket and plug combination on the housings. In some embodiments, the cords  241  and  243  are similar to cords  201  and  203  of  FIG. 9 . In other embodiments, the cords  241  and  243  have an interlocking arrangement as depicted in  FIGS. 17A-B . In the interlocking arrangement, the cord  241  may engage a wall outlet, and the cord  243  may engage the back of the cord  241  via slots  245 , or vice versa. Thus, only one wall outlet socket is needed for two cords in the interlocking arrangement. In some embodiments, only one cord (e.g., cord  241 ) has an interlocking capable back, while the other cord (e.g., cord  243 ) is similar to cord  201  or  203  of  FIG. 9 . As depicted in  FIG. 16 , the audio housing  244  includes a slot  249  through which the cord  243  can be fed even when the battery charger housing  242  is coupled to the audio housing  244 . 
       FIG. 18A  depicts an audio system  250  with a battery charger housing  252  and an audio housing  254  according to another embodiment of the invention. The audio system  250  includes a removable cord similar to the audio system  100  depicted in  FIG. 1 . However, the audio system  250  includes a two-position battery receptacle  251 , a plug  253 , a socket  257  for receiving plug  253 , and battery sockets  256  and  258 . In a first position, a battery connector  255  of the battery  118  is inserted into the battery socket  258 . When the battery  118  is placed in battery receptacle  251  in the first position as depicted in  FIG. 18A , the audio system  250  functions the same as the audio system  100 . In other words, the battery  118  can be charged, but does not provide power to the audio circuit  106 . In contrast to the audio system  100 , the battery  118  can be placed in a second position. In the second position, the battery connector  255  is placed within a battery socket  256 . In the second position, the battery  118  provides power to the audio circuit  106 , but is not charged. The audio circuit  106  can either select one of the batteries  118  or  110  to provide power or combine the power from both batteries  118  and  110  for simultaneous use. 
     In some embodiments, a two-position battery receptacle  260  is provided as shown in  FIG. 18B . Battery receptacle  260  includes one battery socket  262  that enables switching positions simply by rotating the battery  118 . For instance, in one embodiment, rotating the battery  118  by 90 degrees breaks the electrical connection to the charger control circuit  126  and electrically connects the battery  118  to the audio circuit  106  shown in  FIG. 18A . The effect of rotating the battery  118  is similar in function to switching the battery  118  from the first position and second position of battery receptacle  251 . Rotating the battery  118  back 90 degrees will switch the battery  118  from the second to the first position. In one embodiment, four electrical contacts are provided in the battery socket  262 . Two of the electrical contacts of the battery socket  262  align with two electrical contacts of the battery  118  in the first position  264 . The other two electrical contacts of the battery socket  262  align with the two electrical contacts of the battery  118  in the second position  266 . The dashed boxes  268  and  269  indicate the approximate location of the battery  118  in the first and second positions, respectively. Various degrees of rotation can be used to switch between the first and second positions in other embodiments. 
     In some embodiments of the audio system  250  with a two-position battery receptacle  251  or  260 , the battery  110  and battery receptacle  111  are not provided. Any of the cord arrangements (i.e., fixed cords, removable cords, or a combination thereof) described in relation to audio systems  200 ,  210 ,  220 ,  230 , and  240  may be implemented on audio system  250 . In some embodiments of audio housings  104 ,  204 ,  214 ,  224 ,  234 ,  244 , and  254 , multiple battery receptacles are provided and the power control  156  operates to select one or a combination of the batteries to supply power to the components of the audio circuit  106 . In some embodiments of the audio systems  100 ,  200 ,  210 ,  220 ,  230 ,  240 , and  250 , the external power source is a DC source, such as a 12 volt car battery, and the AC/DC converters of the audio systems are bypassed. 
       FIG. 19  depicts an audio system  270  according to another embodiment of the invention. The audio system  270  is similar to the audio system  230  except that a single integrated audio and battery charger housing  272  is implemented in place of two independent housings. Thus, only a single cord  274  is attached to the audio and battery charger housing  272 . In the embodiment shown, the cord  274  is fixed to the audio and battery charger housing  272 ; however, the cord  274  is removable in other embodiments. Furthermore, in some embodiments, a separate cord (not shown) is coupled to the audio circuit  106  via AC/DC converter  117  and the cord  274  is coupled to the charger control circuit via the AC/DC converter  124 . Thus, the audio circuit  106  and charger control circuit  126  each have separate connections to one or more external power sources. 
       FIG. 20  depicts an audio system  300  according to another embodiment of the invention. The audio system  300  includes a transformer box  302   a  and an audio housing  304 . Within the audio housing  304  is a battery receptacle  306  that receives the rechargeable battery  110 , the audio circuit  106 , the selector  158 , the user input  170 , and the speakers  108 . 
     The transformer box  302   a  couples the audio circuit  106  and the battery  110  to an external power source via a wall outlet. Within the transformer box is an AC/DC converter  310   a  to connect to the audio circuit  106 , and also a battery charger circuit and AC/DC converter  312   a  to connect to the battery  110 . The transformer box  302   a  includes two prong sets  313  and  314  for engaging two outlets of an AC power outlet fixture (not shown). 
     In some embodiments, the transformer box  302   a  is attached to the audio housing  304  at connector  308   a  by a fixed cord. In other embodiments, the transformer box  302   a  is removably attached to the audio housing  304  at connector  308   a  by a removable cord. 
     Alternative transformer boxes  302   b - d  are also shown in  FIG. 20 . Transformer box  302   b  is similar to transformer box  302   a  except that only a single prong set  314  is provided. The single prong set  314  engages one outlet of an AC power outlet fixture (not shown). The battery charger circuit and AC/DC converter  312   b , AC/DC converter  310   b , and connector  308   b  function similarly to their counterparts of transformer box  302   a.    
     Transformer box  302   c  is connected to a DC voltage source  316  by a single connector  318 . Since the transformer box  302   c  receives DC voltage, no AC/DC conversion is necessary. Thus, the AC/DC converter components of the transformer boxes  302   a  and  302   b  are not included in transformer boxes  302   c . The transformer box  302   c  passes the DC voltage to the audio circuit  106  through connector  308   c  and to the battery charger circuit  312   c . The battery charger circuit  312   c  is then coupled to the battery  110  via connector  308   c . In some embodiments, the DC voltage source  316  is a car battery and the connector  318  is a plug adapted to fit into a DC car outlet (commonly referred to as a cigarette lighter receptacle). 
     Similar to transformer box  302   c , transformer box  302   d  receives DC voltage and, therefore, does not include AC/DC conversion circuitry. In contrast to transformer box  302   c , transformer box  302   d  includes two connectors  320  and  322  for connecting to the DC voltage source  316  separately. For instance, the two connectors  320  and  322  may connect to two different DC car outlets. Through connectors  322  and  308   d , the transformer box  302   d  connects the DC voltage source  316  to the audio circuit  106 . The connector  320  connects the DC voltage source  316  to the battery charger circuit  312   d , which provides power to the battery  110  via connector  308   d.    
       FIG. 21  depicts an audio system  330  with transformer box  332   a  and audio housing  334 . The audio system  330  is similar to audio system  300  except that the battery charger circuit  336  is within the audio housing  334 , not a transformer box. The audio system  330  can receive power via transformer box  332   a ,  332   b ,  332   c , or  332   d . The transformer box  332   a  includes two prong sets  342   a  and  342   b  to couple AC/DC converters  338   a  and  340   a  to the battery charger circuit  336  and audio circuit  106 , respectively. The transformer box  332   b  includes a single prong set  344  coupled to both the AC/DC converter  338   b  and AC/DC converter  340   b . When the single prong set  344  is connected to an external power source, the AC/DC converter  338   b  provides DC power to the battery charger circuit  336  and the AC/DC converter  340   b  provides DC power to the audio circuit  106 . The transformer boxes  332   c  and  332   d  are essentially DC pass-through circuits that connect to the DC voltage source  316 , to provide power to the audio circuit  106  and battery charger circuit  336 . 
       FIG. 22  depicts an audio system  350  with transformer box  352   a  and audio housing  354 . The transformer box  352   a  includes an AC/DC converter  356   a . The AC power provided along prong set  357  is received by the AC/DC converter  356   a  and output as DC power to the battery charger circuit  336 . The AC power provided along prong set  358  is forwarded directly to the audio circuit  106 , which includes an AC/DC converter. Alternatively, a single prong set transformer box  352   b  with prong set  359  and AC/DC converter  356   b  may be used in place of transformer box  352   a.    
       FIG. 23  depicts an audio system  360  with transformer box  362   a  and audio housing  364 . The audio housing  364  is similar to audio housing  354  except that audio housing  364  includes an AC/DC converter  365  and the audio circuit  106  does not include an AC/DC converter. The transformer box  362   a  includes an AC/DC converter  366   a  and two prong sets  367  and  368 . The AC power provided along prong set  367  is provided directly to AC/DC converter  365  within the audio housing  364 . The AC power provided along prong set  368  is converted to DC power by AC/DC converter  366   a  and output to the audio circuit  106 . Alternatively, a single prong set transformer box  362   b  with prong set  369  and AC/DC converter  366   b  may be used in place of transformer box  362   a.    
     In some embodiments, the audio housings  304 ,  334 ,  354 , and  364  include a second battery receptacle (not shown) similar to the battery receptacle  111  of audio system  100 . The second battery receptacle is operable to receive the battery  118 . The second battery receptacle is electrically connected to the audio circuit  106  and includes electrical contacts. Thus, the second battery receptacle is operable to connect the battery  118  to the audio circuit  106  to provide DC power to the audio circuit  106 . The power control  156  selectively couples the second battery to the components of audio circuit  106  as described above with respect to other embodiments. 
     In some embodiments, the battery receptacle  306  is a two-position receptacle similar to battery receptacle  251  and  260  of  FIGS. 18A-B . That is, the battery  118  is operable to receive power from a charging circuit in the first position and operable to power the audio circuit when in the second position. In other embodiments, the battery receptacle  306  includes a two-position receptacle whereby the battery  110  switches between a first and second position by rotation as described above. 
       FIGS. 24-27  depict four modes of operating one or more of the above described audio systems. For illustration, the modes will be discussed in relation to audio system  250  of  FIGS. 18A-B . However, the modes of operation are also applicable to other audio systems described above. 
       FIG. 24  depicts a first mode  400  of operating the audio system  250 . In step  402 , the battery charger housing  252  is coupled to the audio housing  254 , for instance, by connecting plugs  114  and  253  with sockets  116  and  257 . In step  404 , the cord  113  is coupled to the battery charger housing  252  using plug  122  and to an external power source using plug  112 . Once the connections are made, in step  406 , the battery  118  within battery receptacle  251  is charged using the charger control circuit  126 . In step  408 , the audio circuit  106  and speakers  108  generate audio. The external power source provides power for charging the battery  118  in step  406  and generating audio in step  408 . In some embodiments, steps  406  and  408  occur simultaneously. In other embodiments, steps  406  and  408  occur consecutively, simultaneously, and/or a combination thereof, depending on the status of the selector  158  and user input  170 . Similarly, the order of steps  402  and  404  is alterable such that step  404  may occur before or simultaneously with step  402 . 
       FIG. 25  depicts a second mode  420  of operating the audio system  250 . In step  422 , the battery charger housing  252  is disconnected from the audio housing  254  or the cord  113  is disconnected from the battery charger housing  252 . Thus, in either instance, the audio housing  254  is no longer coupled to the external power source. In step  424 , the audio circuit  106  and speakers  108  generate audio using power from battery  110  in the battery receptacle  111 . 
       FIG. 26  depicts a third mode  430  of operating the audio system  250 . In step  432 , the battery charger housing  252  is disconnected from the audio housing  254 . In step  434 , the audio housing  254  is coupled to the external power source or to a different external power source (e.g., if the audio system  250  is transported to a different location) by coupling cord  113  to socket  116 . In step  436 , the audio circuit  106  and speakers  108  generate audio using power from the external power source or the different external power source. The particular implementation of steps  432  and  434  may vary depending on the audio system in operation. For instance, in audio system  200 , either the battery charger housing  202  is removed or the plug  201  is disconnected in step  432 . In step  434 , the cord  203  is coupled to the external power source or a different external power source. Regardless of the audio system, the result of step  432  and  434  is that the audio housing will no longer receive power through a battery charger housing and pass through circuit. Rather, a connection between an external power source and the audio housing will exist via a cord connected to the audio housing. 
       FIG. 27  depicts a fourth mode  440  of operating the audio system  250 . In step  442 , the battery  118  is switched from the first position  258  to the second position  256 . In step  444 , the audio circuit  106  and speakers  108  generate audio using power from battery  118  in the second position  256  of battery receptacle  251 . The fourth mode applies to those audio systems that include two-position battery receptacles, such as the two-position battery receptacles depicted in  FIGS. 18A and 18B . 
     In some embodiments, the battery chargers described above are operable to charge any of a plurality of different types of batteries or battery packs. For example, the battery chargers are capable of charging battery packs having any number of different voltage ratings, capacity ratings, configurations, shapes, and sizes. Such battery packs include those that are attachable to and detachable from electrical devices such as power tools, test and measurement equipment, vacuum cleaners, outdoor power equipment, and vehicles. Power tools include, for example, drills, circular saws, jig saws, band saws, reciprocating saws, screw drivers, angle grinders, straight grinders, hammers, impact wrenches, angle drills, inspection cameras, and the like. Test and measurement equipment includes digital multimeters, clamp meters, fork meters, wall scanners, IR temperature guns, and the like. Vacuum cleaners include stick vacuums, hand vacuums, upright vacuums, carpet cleaners, hard-surface cleaners, canister vacuums, broom vacuums, and the like. Outdoor power equipment includes blowers, chain saws, edgers, hedge trimmers, lawn mowers, trimmers, and the like. 
     In some embodiments, the battery charger housings  102 ,  202 ,  212 ,  222 ,  232 ,  242 , and  252  are also able to be coupled to non-audio generating devices. For example, in some embodiments, the battery chargers  102 ,  202 ,  212 ,  222 ,  232 ,  242 , and  252  are attachable to and detachable from the electrical devices listed above including power tools, test and measurement equipment, vacuum cleaners, outdoor power equipment, and vehicles. 
     Thus, the invention provides, among other things, audio devices powerable by rechargeable batteries or an external power source. Additionally, the audio devices include a separate battery charging housing or separate battery charging circuit. A separately attachable battery charger presents a user with options for using the audio device alone, battery charger alone, or attaching the audio device and battery charger together for simultaneous use. Thus, if only one of the two devices is desired, a user can carry the single device, which weighs less than the combination of the two devices. As the battery charger and audio device have independent circuits, upon a malfunction of one component (e.g., the battery charger), a replacement component can be purchased without the need for replacing the entire system, which reduces waste and replacement costs. 
     Additionally, many embodiments provide multiple battery receptacles allowing the charging of one battery while another battery provides power or is stored in a position to provide power upon disconnection of the audio device from an external power source. Thus, in some embodiments, multiple batteries and a battery charger can be secured to the audio device for ease of transport of the audio device, battery charger, and batteries. Moreover, the battery charger is modular and, with battery charger attachments incorporated onto multiple devices (e.g., radio, vacuum, or lawn care products), the user is provided multiple product options for attaching to the battery charger. Various additional features and advantages of the invention are set forth in the following claims.