Abstract:
A power tool battery, battery charger, and a method of operating the same. The battery and the charger can be lockingly engageable with each other. The battery can be electrically coupled to a charging circuit of the charger for charging the battery. One of the battery and the charger can include a protrusion and the other of the battery and charger can include a recess for receiving the protrusion. The method can include inserting the battery into the charger along an insertion axis and charging the battery. The method can further include rotating the battery about the insertion axis to secure the battery with the charger while continuing to charge the battery.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 11/435,640, filed May 17, 2006, which claims priority under 35 U.S.C. §119 to Provisional Patent Application No. 60/682,192 filed on May 17, 2005, the entire contents of both of which are hereby incorporated by reference. 
     The present application also incorporates by reference the entire contents of U.S. patent application Ser. No. 11/435,596, filed May 17, 2006. 
    
    
     BACKGROUND 
     The present invention relates generally to power tools, and more particularly to rotary power tools, such as drills and screwdrivers. 
     Power tools, such as rotary power tools, are used to work on or cut a variety of workpieces, such as metal, wood, drywall, etc. Such tools typically include a housing, a motor supported by the housing and connectable to a power source, and a spindle rotatably supported by the housing and selectively driven by the motor. A tool holder, such as a chuck, is mounted on the forward end of the spindle, and a tool element, such as, for example, a drill bit, is mounted in the chuck for rotation with the chuck and with the spindle to operate on a workpiece. 
     SUMMARY 
     In some embodiments, the invention provides a method of operating a power tool. The power tool can include a housing supporting a motor, a switch assembly, and a fuel gauge. The method can include the acts of activating the switch assembly to electrically connect the motor and a battery, recording a state of charge of the battery, displaying the state of charge of the battery on the fuel gauge before electrically connecting the motor and the battery, and stopping the display of the state of charge before deactivating the switch assembly. 
     In other embodiments, the invention provides a method of operating a power tool including a housing supporting a motor and a fuel gauge. The method can include the acts of connecting a battery to the housing, the battery having an at rest state of charge, displaying the at rest state of charge of the battery on the fuel gauge, and activating the motor and continuing to display the at rest state of charge of the battery on the fuel gauge. 
     The invention also provides a power tool including a movable spindle for supporting a tool element, and a housing supporting a motor and a drive mechanism driven by the motor. The drive mechanism can be operably connected to the spindle for causing movement of the spindle relative to the housing. The housing can have a forward end supporting the spindle and a rearward end. The power tool can also include a battery connectable to the rearward end, and a fuel gauge supported on the housing for displaying an at rest state of charge of the battery. 
     In some embodiments, the invention provides a method of operating a battery charger. The battery charger can include a body defining an aperture and a charging circuit extending through the body. The method can include the acts of inserting a battery into the aperture along an insertion axis, electrically connecting the battery to the charging circuit to charge the battery and pivoting the battery about the axis relative to the battery charger to secure the battery in the battery charger. 
     In other embodiments, the invention provides a method of operating a battery charger. The battery charger can include a body and a charging circuit. One of the charger and the battery can include an outwardly extending protrusion, and the other of the charger and the battery can define a recess for receiving the outwardly extending protrusion. The method can include the acts of electrically connecting the battery and the charging circuit to charge the battery before engaging the protrusion in the recess to secure the battery to the body of the charger. 
     In other embodiments, the invention provides a method of operating a battery charger. The battery charger can include a body and a charging circuit extending through the body. The method can include the acts of electrically connecting the battery to the charging circuit to charge the battery, and moving the battery with respect to the battery charger to secure the battery to the body while continuing to charge the battery. 
     The invention also provides a combination of a battery and a battery charger. The battery can include a casing and a battery cell supported in the casing. The battery charger can include a body and a charging circuit. One of the charger and the battery can include an outwardly extending protrusion, and the other of the charger and the battery can define a recess for receiving the outwardly extending protrusion. The battery can be movable relative to the body of the charger between a locked position, in which the protrusion can lockingly engage the recess, and an unlocked position, in which the protrusion can removably engage the recess. The battery cell can be electrically connectable to the charging circuit of the battery charger when the battery is in the locked position and the unlocked position. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     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 embodiment 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. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a power tool according to an embodiment of the invention. 
         FIG. 2  is a left side view of the power tool shown in  FIG. 1 . 
         FIG. 3  is a top view of the power tool shown in  FIG. 1 . 
         FIG. 4  is a right side view of the power tool shown in  FIG. 1 . 
         FIG. 5  is a section view of the power tool taken along line  5 - 5  of  FIG. 3 . 
         FIG. 6  is a perspective view of a battery according to an embodiment of the invention. 
         FIG. 7  is an exploded view of the battery shown in  FIG. 6 . 
         FIG. 8  is a front view of the battery shown in  FIG. 6 . 
         FIG. 9A  is a section view of the battery taken along line A-A of  FIG. 8 . 
         FIG. 9B  is a section view of the battery taken along line B-B of  FIG. 8 . 
         FIG. 9C  is a section view of the battery taken along line C-C of  FIG. 8 . 
         FIG. 9D  is a detail view of the electrical connection between the battery and the charger shown in  FIG. 9C . 
         FIG. 10  is a perspective view of a retainer clip. 
         FIG. 11A  is a first perspective view of a charger according to an embodiment of the invention. 
         FIG. 11B  is a second perspective view of the charger shown in  FIG. 11A . 
         FIG. 12  is an exploded view of a battery and the charger shown in  FIG. 11A . 
         FIG. 13  is a top view of the charger shown in  FIG. 11A . 
         FIG. 14  is a bottom view of the charger shown in  FIG. 11A . 
         FIG. 15A  is a first perspective view of the charger shown in  FIG. 11A  supporting a battery for charging. 
         FIG. 15B  is a second perspective view of the charger shown in  FIG. 11A  supporting a battery for charging. 
         FIG. 16  is a top view of the charger and inserted battery shown in  FIG. 15A . 
         FIG. 17  is a first cross-sectional view of the charger and battery assembly shown in  FIGS. 15A-16 . 
         FIG. 18  is a second cross-sectional view of the charger and battery assembly shown in  FIGS. 15A-16 . 
         FIG. 19  is a third cross-sectional view of the charger and battery assembly shown in  FIGS. 15A-16 . 
         FIG. 20  is a fourth cross-sectional view of the charger and battery assembly shown in  FIGS. 15A-16 . 
         FIG. 21  is a schematic illustration of the power tool shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-5  illustrate a hand-held, battery-operated power tool  10 , such as, for example, a screwdriver, a drill, or another rotary tool. The power tool  10  is operable to receive power from a battery, such as the battery  200  shown in  FIGS. 6-9C . In other embodiments, the power tool  10  can be another hand-held power tool, such as, for example, a reciprocating saw, a hammer drill, a router, a circular saw, a grinder, a sander, etc. 
     The power tool  10  includes a housing assembly  12  having a body  14  and a main operator&#39;s handle portion or hand grip  16  connected to a rearward portion  18  of the body  14 . 
     The body  14  defines a longitudinal body axis  22  and houses a drive mechanism  26 , a motor  28 , and a spindle  30  supported by a forward end  31  of the body  14 . Together, the drive mechanism  26 , the motor  28 , and the spindle  30  are operable to rotate a tool element (not shown) generally about a tool axis for working on a workpiece (also not shown). In other embodiments, the drive mechanism  26 , the motor  28 , and the spindle  30  can also or alternatively reciprocate the tool element along the tool axis for working on a workpiece. 
     In the illustrated embodiment of  FIGS. 1-5 , the spindle  30  is a tool-less spindle, which can accept and lockingly engage the tool element. The tool element is secured to the spindle  30  by a ball-detent arrangement and requires no tools for tool element insertion or removal. In other embodiments, a chuck, collets, a blade clamp, adapters, or other conventional connecting structure may be used to secure a tool element to the spindle  30 . 
     As shown in  FIGS. 1-5 , the hand grip  16  is pivotably connected to the rearward portion  18  of the body  14  rearwardly of the motor  28 . The hand grip  16  defines a grip axis  32  and is supported for pivoting movement relative to the body  14  about a pivot axis  34 . In the illustrated embodiment, the pivot axis  34  is substantially perpendicular to both the body axis  22  and the grip axis  32 . 
     In other embodiments (not shown), the orientation of the axes  22 ,  32 , and  34  may be different, such as, for example, generally parallel or skew. Also, the hand grip  16  may be movable in other manners, such as, for example, slidably, rotatably, or pivotably about two axes (i.e., about the pivot axis  34  and about an axis parallel to the body axis  22  and/or to the grip axis  32 ). 
     In some embodiments, the body  14  is formed of two body halves  14   a ,  14   b  (see  FIG. 3 ). Similarly, the hand grip  16  is formed of two grip halves  16   a ,  16   b  (also shown in  FIG. 3 ). In these embodiments, a first end  40  of the hand grip  16  sandwiches the rearward portion  18  of the body  14 . A pivot pin  42 , defining the pivot axis  34 , extends through the first end  40  of the hand grip  16  and through the rearward portion  18  of the body  14  to pivotally connect the hand grip  16  to the body  14 . 
     The hand grip  16  is movable relative to the body  14  between a first position (shown in  FIG. 1 ), in which the body axis  22  and the grip axis  32  are generally aligned and are substantially parallel, and a second position (shown in  FIG. 2 ), in which the grip axis  32  is misaligned with the body axis  22 . In the second position, the hand grip  16  is positioned so that the grip axis  32  and the body axis  22  define an angle a of between about 90 degrees and about 135 degrees. The hand grip  16  may also be movable to one or more positions between the first and second positions. 
     Also, the hand grip  16  is pivotable relative to the body  14  to change the length of the power tool  10 , measured from a forward end  31  of the body  14  to a rearward end  44  of the hand grip  16 . In the position shown in  FIG. 1 , the power tool  10  has a first length measured between the forward end  31  of the body  14  and the rearward end  44  of the hand grip  16 . In the position shown in  FIG. 2 , the power tool  10  has a second shorter length measured between the forward end  31  of the body  14  and the rearward end  44  of the hand grip  16 . 
     With respect to the illustrated embodiment of  FIGS. 1-5 , the motor  28  is an electric motor that is connectable to a power source, such as the battery  200 , by an electrical circuit  310  (shown schematically in  FIG. 21 ). The battery  200  is removably supported in a battery chamber  56  extending through the rearward end  44  of the hand grip  16  and is slidably attached to the hand grip  16  in a direction generally parallel to the grip axis  32 . In other embodiments, the hand grip  16  can support two or more batteries  200  in a battery chamber  56 , or alternatively, the battery(ies)  200  can be slidably connected to an outer engagement surface of the hand grip  16 . 
     The power tool  10  includes an on/off switch assembly  74  which is operable to connect the motor  28  to the power source. In the illustrated embodiment of  FIGS. 1-5 , the switch assembly  74  includes a direction switch  76  (shown in  FIG. 21 ) having a trigger  77  supported on a side surface  78  of the body  14  for operation by the thumb or finger of either a right-handed or a left-handed operator. In the illustrated embodiment, the trigger  77  is positioned toward the rear of the body  14 , near the hand grip  16 . As shown in  FIGS. 1-5 , at least a portion of the switch assembly  74 , such as the trigger  77 , is movable with the body  14  relative to the hand grip  16  during pivoting movement of the hand grip  16 . 
     In other embodiments (not shown), the power and direction of rotation of the motor  28  may be controlled by other elements and structure. In one such alternate embodiment, a single trigger can be actuated to cause the motor shaft  58  to rotate relative to the body  14 . The direction of rotation of the motor shaft  58  can be controlled by a separate direction switch, which may be operable between a “forward” position and a “reverse” position, and may additionally be provided with a lockout feature to prevent actuation of the trigger and energization of the motor  28 . 
     In some embodiments, the power tool  10  can include a speed control mechanism  82 , which is operable to adjust the rotational speed of a tool element supported by the power tool  10  and/or the rotational speed of the spindle  30  between two or more different rotational speeds (e.g., a high speed, a low speed, and intermediate speeds). As shown in  FIGS. 1-5 , the speed control mechanism  82  can be supported on an upper surface  84  of the body  14  and can be operable to move the drive mechanism  26  between a first configuration, in which elements of the drive mechanism  26  are oriented to rotate a tool element and/or the spindle  30  about the tool axis at a first rotational speed, and a second configuration, in which elements of the drive mechanism  26  are oriented to rotate a tool element about the tool axis at a second, different rotational speed. In other embodiments, the speed control mechanism  82  may be operable to control the power supplied by the power source (e.g., the battery  200 ) to the motor  28  to rotate the motor shaft  58  at a first rotational speed and a second, different rotational speed. 
     As shown in  FIGS. 1-5 , the power tool  10  also includes a locking assembly  110  for locking the hand grip  16  in a position relative to the body  14 . The locking assembly  110  is operable between a locked position, in which the hand grip  16  is fixed in a position relative to the body  14 , and an unlocked position, in which the position of the hand grip  16  relative to the body  14  is adjustable. In some embodiments, the locking assembly  110  may be substantially similar to that disclosed in U.S. patent application Ser. No. 09/704,914, filed Nov. 2, 2000 and/or U.S. patent application Ser. No. 10/796,365, filed Mar. 9, 2004, the entire contents of each of which is hereby incorporated by reference. 
     In the illustrated embodiment, the locking assembly  110  includes a detent arrangement between the hand grip  16  and the body  14  to provide a positive engagement between the hand grip  16  and the body  14 . The locking assembly  110  includes a locking member  112 , a portion of which is selectively engageable in a first recess, to fix the hand grip  16  in the first position relative to the body  14 , and a second recess, to fix the hand grip  16  in the second position relative to the body  14 . The locking assembly  110  can also include additional recesses in which the locking member  112  can be engageable to fix the hand grip  16  in additional positions relative to the body  14 . 
     The locking assembly  110  can also include an actuator  114  for moving the locking member  112  between the locked and unlocked positions. In the illustrated embodiment of  FIGS. 1-5 , the actuator  114  is positioned on an upper surface  84  of the body  14  for operation by the thumb or finger of either a right-handed or a left-handed operator. A portion of the actuator  114  extends through the housing  12  and is selectively engageable with the locking member  112  to move the locking member  112  between the locked and unlocked positions. In some embodiments, the locking assembly  110  can include a biasing member, such as a spring, for biasing the locking member  112  toward the locked position, or alternatively, for biasing the locking member  112  toward the unlocked position. 
     To move the hand grip  16  relative to the body  14 , the actuator  114  is operated to move the locking projection  114  out of engagement with the recesses. The hand grip  16  is then moved relative to the body  14  to a position corresponding to engagement of the locking projection  114  with one of the recesses. When the hand grip  16  is in the desired position, the locking projection  114  is moved (e.g., by a spring) into the corresponding recess. 
     In other embodiments (not shown), the locking assembly  110  may include a different locking arrangement, such as a frictional engagement between the hand grip  16  and the body  14 . In such an embodiment, the locking assembly  110  may also include a positive engagement arrangement, such as inter-engaging teeth formed on the body  14  and the hand grip  16  which are engaged when the locking assembly  110  is in the locked condition. 
     The locking assembly  110  may also include a pivoting lockout, which prevents the hand grip  16  from being pivoted about the pivot axis  34  relative to the body  14  when the motor  28  is in operation and/or when the switch assembly  74  is activated. 
     The power tool  10  can also include a fuel gauge  118  for displaying a state of charge of the battery  200  supported in the battery chamber  56 . As shown in  FIGS. 1 and 2 , the fuel gauge  118  can include a display  120  positioned on a side of the hand grip  16 . In some embodiments, such as the illustrated embodiment of  FIGS. 1 and 2 , the display  120  can include a series of indicator lights  122  (e.g., light-emitting diodes) arranged to form a scale. In these embodiments a number of indicator lights  122  can be illuminated when the battery state of charge is high and one or no lights can be illuminated to show that the battery state of charge is low. In other embodiments, one light can flash to show that the battery state of charge is low. In further embodiments, the display  120  can include other display screens and/or indicator lights having other relative orientations and positions and can include indicator lights of different colors (e.g., green, blue, yellow, orange, and red) for displaying the state of charge of the battery  200 . In still further embodiments, the display  120  can be used to inform the user of other conditions, such as, for example, abnormal (high or low) battery temperature, an electrical fault within the electrical circuit  310 , or other information pertaining to the battery  200  or tool  10 . 
     In some embodiments, such as the embodiment shown in  FIG. 21 , the electrical circuit  310  includes a controller  320 . The controller  320  can perform various functions within the tool  10 , such as, for example, measuring various battery conditions (e.g., state of charge of battery cell  208 ), controlling various components included in the circuit  310  (e.g., the fuel gauge  118 ), controlling operation of the power tool  10 , and gathering and storing data pertaining to tool operation, battery conditions, and component operation within the circuit  310 . In other embodiments, the controller  320  and/or electrical circuit  310  can include similar components and/or perform similar functions as the battery controllers and electrical circuits shown and described in U.S. patent application Ser. No. 10/720,027, filed Nov. 20, 2003 and U.S. patent application Ser. No. 11/138,070, filed May 24, 2005, the entire contents of each of which is hereby incorporated by reference. 
     In some embodiments, the controller  320  is programmed to measure state of charge in response to the activation of the trigger  77 , as discussed below. In these embodiments, the battery state of charge data is measured prior to activation of the motor  28 ; that is, before the battery state of charge is effected by the current draw being supplied to the motor  28 . This measurement of the battery state of charge represents an at rest state of charge of the battery  200 . In these embodiments, only the at rest state of charge measurements are displayed on the fuel gauge  118 . In some embodiments, the state of charge data is displayed for a predetermined time after the trigger  77  is actuated. In one embodiment, the predetermined time is approximately two (2) seconds. In other embodiments, the predetermined time can be greater than two (2) seconds. In further embodiments, the predetermined time can be less than two (2) seconds. After the predetermined time is exceeded, the display  120  can be cleared. In one embodiment, the display  120  is cleared when the predetermined time expires regardless whether the trigger  77  is still actuated. In some embodiments, the display  120  is cleared when the predetermined time expires regardless of the trigger  77  activity. In still further embodiments, the display  120  is cleared prior to expiration of the predetermined time (e.g., approximately two (2) seconds) when the trigger  77  is released. 
     The circuit  310  also includes the direction switch  76  which controls and/or selects the rotational direction of the motor shaft  58 . The circuit  310  also includes an on/off switch  330 , a brake  335 , a mechanical torque clutch  340  and a temperature sensing device or thermistor  350 . In some embodiments, the on/off switch  330  and the brake  335  can include a field effect transistor, such as a MOSFET. 
     The on/off switch  330  is controlled by the controller  320  and activated by the controller  320  under various conditions. For example, the controller  320  activates the on/off switch  330  to a conducting state for power to be delivered to the motor  28  in response to activation of the trigger  77 . The controller  320  can also activate the switch  330  to a non-conducting state to interrupt current being supplied to the motor  28  when the state of charge of the battery  200  reaches a cut-off threshold or when an overload condition is sensed by the controller  320 . In some embodiments, an overload condition can occur when the temperature of the battery  200  as sensed by the controller  320  via the thermistor  350  reaches a high temperature threshold or when the current being supplied to the motor  320  reaches a high current threshold. In these embodiments, the controller  320  can indicate to a user that an overload condition has occurred via the display  120 , such as flashing one or more lights  122 . 
     The brake  335  is controlled by the controller  320  and activated by the controller  320  when the torque of the motor  28  exceeds the torque setting of the tool  10  as sensed by controller  320  via the clutch  340 . 
     As shown in  FIGS. 1-10 , the battery  200  of the illustrated embodiment is substantially cylindrically shaped and has a substantially circular cross-section. In other embodiments, the battery  200  can have any other shape and/or cross-sectional shape, including without limitation rectangular, oval, polygonal, irregular, etc. 
     In the illustrated embodiment of  FIGS. 1-10 , the battery  200  includes a battery sleeve or casing  204  and a battery cell  208  supported in the battery casing  204 . The battery  200  can also include a cap  206 , which can be secured to a second end  205  of the battery casing  204  to substantially enclose the battery cell  208 . In other embodiments, the battery  200  can include two or more battery cells  208  arranged in various combinations of serial and parallel cell arrangements. 
     In the illustrated embodiment of  FIGS. 1-10 , the battery  200  includes a single battery cell  208  having a nominal voltage rating of approximately 4.0 volts (V) and a capacity of approximately 3.0 Ampere-hours (Ah). In this embodiment, the battery cell  208  also has a Lithium-based chemistry, such as, for example a Li-ion chemistry. The Lithium-based chemistry can include various Li-ion chemistries, such as, for example, Lithium Cobalt, Lithium Manganese (“Li—Mn”) Spinel, or Li—Mn Nickel. 
     As shown in  FIGS. 6-9D , contact recesses  216   a ,  216   b  extend radially through a first end  203  of the casing  204 . In the illustrated embodiment, the contact recesses  216   a ,  216   b  are generally L-shaped. In other embodiments, one or both of the contact recesses  216   a ,  216   b  can have other shapes and can be positioned in other locations along the battery casing  204 . 
     The battery  200  also includes a first (e.g., a negative) battery terminal  202   a  and second (e.g., a positive) battery terminal  202   b , portions of which are accessible through the contact recesses  216   a ,  216   b  to electrically connect the battery cell  208  to the corresponding electrical terminals (not shown) of the power tool  10 , or alternatively, to the electrical terminals (not shown) of a battery charger. In some embodiments, the battery terminals  202   a  and  202   b  can also or alternatively at least partially physically connect the battery  200  to the hand grip  16  of the power tool  10 . 
     As shown in  FIGS. 6-9D , the battery terminals  202   a ,  202   b  are equally spaced circumferentially (e.g., approximately 180 degrees apart) around a front end of the battery cell  208 . In other embodiments, the battery terminals  202   a ,  202   b  can have other orientations and locations, depending in part on the location and orientation of the contact recesses  216   a ,  216   b.    
     In the illustrated embodiment, when a battery  200  is inserted into the battery chamber  56  of a power tool  10 , the battery  200  can be pivoted about the battery axis  201 , which can be coincident with the grip axis  32  so that the first battery terminal  202   a  of the battery  200  wipes across the electrical terminal of the power tool, cleaning the battery terminal  202   a  of the battery  200  and the corresponding power tool terminal before an electrical connection is established between the battery  200  and the power tool  10 . 
     Similarly, the second battery terminal  202   b  of the battery  200  can be wiped across the electrical terminal of the power tool, cleaning the electrical connector  202   b  of the battery  200  and the corresponding power tool terminal. In this manner, the first and second battery terminals  202   a ,  202   b  of the battery  200  and the first and second terminals of the power tool are cleaned each time a battery  200  is electrically connected to the power tool  10  and/or each time a battery  200  is disconnected from the power tool  10 . 
     In the illustrated embodiment of  FIGS. 6-9D , a retainer clip  210  is supported in the battery casing  204  and is operable to position and retain the battery terminals  202   a ,  202   b  and the battery cell  208  in their respective locations and orientations within the battery casing  204 . In the illustrated embodiment, the retainer clip  210  includes a radially outwardly extending projection  211 , which is engageable in a recess (not shown) in the battery casing  204  to orient the retainer clip  210  in a predetermined orientation in the battery casing  204 . 
     As shown in  FIG. 10 , the retainer clip  210  can also include two recesses  212 ,  213  for receiving portions of the battery terminals  202   a ,  202   b , respectively. Thus, when assembled with the retainer clip  210 , the battery terminals  202   a ,  202   b  are fixed in a predetermined circumferential orientation with respect to the battery casing  204 . 
     In the illustrated embodiment of  FIGS. 6-9D , an insulator  214  (e.g., a foam insert) is located between a front end of the battery cell  208  and the cap  206 . In this embodiment, the cap  206  is positioned over the insulator  214  and secured to the battery casing  204  by a pair of cap-retaining barbs  215 , which extend radially outwardly from the casing  204 . In other embodiments, the cap  206  can be connected to the casing  204  via screws, bolts, nails, rivets, pins, posts, clips, clamps, and/or other conventional fasteners, inter-engaging elements on the cap  206  and the casing  204  (e.g., tabs, flanges, or other extensions inserted within slots, grooves, or other apertures, etc.), by adhesive or cohesive bonding material, or in any other suitable manner. 
     In some embodiments, the battery  200  includes a locking arrangement  220  for locking the battery  200  in the battery chamber  56  of the power tool  10 . In the illustrated embodiment of  FIGS. 6-9D , the locking arrangement  220  includes first and second lugs  222   a ,  222   b , which extend radially outwardly from the casing  204  of the battery  200 . 
     As shown in  FIGS. 6-8 , the first and second lugs  222   a ,  222   b  each have generally rectangular cross-sectional shapes, and the first lug  222   a  is larger in size than the second lug  222   b . In other embodiments, the first and second lugs  222   a ,  222   b  can have any other shape and/or cross-sectional shape, including without limitation round, oval, polygonal, irregular, etc. 
     Corresponding slots extend axially along the sides of the battery chamber  56  of the power tool  10 . One of these slots is sized and shaped to receive the first lug  222   a  and the other slot is sized and shaped to receive the second lug  222   b , thereby ensuring that the battery  200  can only be inserted into the power tool  10  in a single desired orientation (i.e., with the battery terminals  202   a ,  202   b  of the battery  200  aligned with and electrically connected to corresponding terminals of the power tool  10 ). 
     In some such embodiments, the slots extend axially along the inner wall of the battery chamber  56  of the power tool  10  and include lower ends which extend circumferentially around at least a portion of the inner wall of the battery chamber  56 . In these embodiments, the slots are substantially L-shaped. In this manner, after the battery  200  is inserted axially into the battery chamber  56  of the power tool  10 , the battery  200  can be pivoted about the battery axis  201  and relative to the housing  12  to lockingly engage the lugs  222   a ,  222   b  in the respective L-shaped receiving slots to lockingly connect the battery  200  to the power tool  10 . In other embodiments (not shown), the locking arrangement  220  may include a single lug and a single receiving slot. 
     As shown in  FIGS. 6-9D , the battery  200  can also include axially extending projections  224  located on the front end of the battery  200  opposite the cap  206 . The projections  224  can be engageable with a complementary part(s) in the battery chamber  56  to provide tactile and/or audible feedback to the operator upon rotation of the battery  200  relative to the hand grip  16 . In other embodiments, the battery  200  can have a single projection  224  or more than two projections  224 , which can be placed on the battery casing  204  at various locations for engagement with the battery chamber  56 . In other embodiments, the projections  224  can be engageable with a complementary part(s) in a battery charger  400  to provide tactile and/or audible feedback to the operator upon rotation of the battery  200  relative to the battery charger  400 . 
     As shown in  FIGS. 11A-20 , the battery  200  is engageable in a battery charger  400 , which is operable to charge one or more battery(ies)  200 . In some embodiments, AC current from an electrical source (e.g., a land-based power network) can be provided through a charging circuit  401  to a battery  200  supported on the charger  400 . In some embodiments, the charging circuit  401  may convert AC power to DC power. In other embodiments, the battery charger  400  can provide power to the battery  200  from an unconventional power source including supplementary batteries and various AC and DC sources. In some such embodiments, the charging circuit  401  can include AC/DC converting components and can also or alternatively provide current and/or voltage limiting functions, signal conditioning, and the like. 
     The charging circuit  401  can include similar components and implement similar charging algorithms as the charging circuits shown and described in U.S. patent application Ser. No. 10/719,680, filed Nov. 20, 2003, U.S. patent application Ser. No. 11/139,020, filed May 24, 2005, and U.S. patent application Ser. No. 11/266,007, filed Nov. 2, 2005, the entire contents of each of which is hereby incorporated by reference. 
     In the illustrated embodiment of  FIGS. 11A-20 , the charger  400  includes a charger casing or body  402  having an upper portion  402   a  and a lower portion  402   b . As shown in  FIGS. 11A-20 , the casing  402  can define a battery chamber  403  and can include an opening  404  for receiving batteries  200 . In the illustrated embodiment, the opening  404  is located generally toward the front end  406  of the charger  400 . A rear portion  408  of the charger  400  is provided with an electrical input receptacle  410  for receiving a cord or plug. 
     As best shown in  FIGS. 11A and 11B , first and second receiving slots  418   a ,  418   b  extend through the charger casing  402  on opposite sides of the opening  404  and are sized to engage portions of the battery  200  to retain the battery  200  in the charger  400  and to orient the battery  200  with respect to the charger  400 . In some embodiments, the receiving slots  418   a ,  418   b  are similar in size, shape, and relative orientation to the receiving slots in the battery chamber  56  of the power tool  10 . 
     In some embodiments, the receiving slots  418   a ,  418   b  can be differently sized so that the battery  200  can only be inserted into the battery chamber  403  in a required orientation (i.e., with the battery terminals  202   a ,  202   b  engaging respective terminals  420   a ,  420   b  of the battery charger  400 ). 
     In the illustrated embodiment of  FIGS. 11A-20 , the receiving slots  418   a ,  418   b  are generally L-shaped. In this manner, after a battery  200  is inserted axially through the opening  404  and into the battery chamber  403 , the battery  400  can be pivoted about the battery axis  201  and relative to the casing  402  from an unlocked position, in which the battery  200  is movable axially out of the opening  404 , toward a locked position, in which the engagement between the lugs  222   a ,  222   b  and the receiving slots  418   a ,  418   b  prevents the battery  200  from being moved axially out of the battery chamber  403 . 
     As shown in  FIGS. 12 ,  13 , and  15 A- 16 , the charger  400  can include an indicator  419  located on an outer surface of the casing  402  and the battery  200  can include a similar indicator  223 . In this manner, when the indicator  419  of the charger  400  and the indicator  223  of the battery  200  are misaligned, the operator will be able to confirm that the battery  200  is in the unlocked position. Similarly, when the indicator  419  of the charger  400  and the indicator  223  of the battery  200  are aligned, the operator will be able to confirm that the battery  200  is in the locked position. 
     In embodiments of the charger  400 , such as the illustrated embodiment of  FIGS. 11A-20 , having L-shaped receiving slots  418   a ,  418   b , the terminals  420   a ,  420   b  of the battery charger  400  can extend circumferentially around at least a portion of the battery chamber  403  so that the battery terminals  202   a ,  202   b  can be electrically connected to respective terminals  420   a ,  420   b  of the battery charger  400  when the battery  200  is in the locked and unlocked positions. 
     In some such embodiments, the charger  400  is operable to charge the battery  200  while the battery  200  is in either the locked position or the unlocked position. This can be a point of convenience for operators, some of whom may wish to quickly insert the battery  200  for charging without having to pivot the battery  200  toward a locked position. Alternatively, in applications in which the charger  400  is mounted on a wall or another vertical surface (i.e., so that the battery chamber  403  opens in a direction substantially parallel to the ground), operators can insert the battery  200  into the battery chamber  403  and pivot the battery  200  toward the locked position so that the battery  200  can be charged and so that the battery  200  does not fall out of the charger  400  during charging. 
     As shown in  FIG. 14 , the charger  400  can include mounting receptacles  428  for mounting the charger  400  on a wall or other inclined surface, or alternatively, for securing the charger  400  to a work cart, a horizontal surface, a work table or bench, and the like. In some embodiments, such as the illustrated embodiment of  FIG. 14 , the charger  400  can also include feet  430  for supporting the charger  400 . 
     As shown in  FIG. 13 , the charger  400  can also include detents  422  for engagement with the projections  224  on the battery  200  to provide tactile and/or audible feedback to the operator to indicate to the operator that the operator has moved the battery  200  to the locked position, or alternatively, to the unlocked position. In the illustrated embodiment of  FIGS. 11A-20 , the detents  422  are elastically deformable and extend horizontally across the lower end of the battery chamber  403 . In other embodiments, the detents  422  can have other relative orientations and positions. For example, in some embodiments, the detents  422  can extend circumferentially around the side walls of the battery chamber  403  for engagement with corresponding battery projections  224  located on the sides of the battery  200 . 
     A charge indicator  412  (e.g., a light-emitting diode (LED) or another light) can be supported on the upper charger casing  402   a  for displaying charge data to an operator (e.g., charge time remaining, charging in progress, charging complete, etc.). In other embodiments, the charger  400  can also or alternatively include other indicators or displays. 
     Operation of the power tool will be discussed with respect to  FIGS. 1 ,  2  and  21 . 
     For operation, an operator grasps the hand grip  16  with a first hand and grasps the body  14  with a second hand and pivots the hand grip  16  about the pivot axis  34  from the first position (shown in  FIG. 1 ) toward the second position (shown in  FIG. 2 ). 
     If the locking assembly  110  is in the locked position, the operator can move the actuator  114  with respect to the housing  12  to move the locking member  112  from the locked position toward the unlocked position before and/or during pivoting of the body  14  and hand grip  16 . When a desired orientation between the body  14  and the hand grip  16  is achieved, the operator can insert a tool into the spindle  30 . 
     The operator can also insert the battery  200  into the battery chamber  56  to provide power to the power tool  10 . The operator can then move the trigger  77  toward an operational position, in turn engaging the direction switch  76 . When the trigger  77  is activated, power is supplied to the electrical circuit  310  from the battery  200  and the controller  320  wakes from a low power state. The controller  320  in turn takes a state of charge reading from the battery  200 , stores the reading in the controller&#39;s internal memory (not shown) and activates the fuel gauge  118  to display the current at rest state of charge of the battery  200 . 
     Once the at rest battery state of charge has been measured, the controller  320  switches the normally non-conducting on/off switch  330  into the conducting state such that current is supplied from the battery cell  208  to the motor  28  as determined by the directional switch  76 , causing the motor  28  to rotate the spindle  30  and the tool element. The controller  320  continues to display the state of charge reading via the fuel gauge  118  until the predetermined time period expires. 
     The operator can then move the hand grip  16  from the second position back to the first position, or alternatively, to an intermediate position (not shown) to orient the power tool  10  to operate in a confined workspace and/or to perform a different operation. Alternatively or in addition, an operator may pivot the hand grip  16  about the pivot axis  34  and relative to the body  14  with a flick of the wrist and/or by grasping one of the hand grip  16  and the body  14  with one hand and pressing the other of the hand grip  16  and the body  14  against his body. 
     In one embodiment, once the trigger  77  is released, the on/off switch  330  is positioned in the non-conducting state and the controller  320  beings to count down the waiting period. In this embodiment, if the user activates the trigger  77  prior to the expiration of the waiting period, the controller  320  approximates the battery&#39;s current state of charge based on the previous state of charge reading and the time duration that the motor  28  was running and displays that approximation. In some constructions, if the time duration that the motor  28  was running is longer than a predetermined time period, the controller  320  does not calculate or approximate a current state of charge reading of the battery and does not display any battery state of charge reading on the fuel gauge  118 . 
     If the user activates the trigger subsequent to the expiration of the waiting period, the controller  320  takes another at rest battery state of charge reading prior to activation of the on/off switch  330  and power being supplied to the motor  28 , as discussed above. 
     After operating the power tool  10  and the battery  200 , the operator can remove the battery  200  from the power tool  10  and insert the battery  200  into the charger  400  to recharge the battery  200 . In some embodiments, the operator can insert the battery  200  axially into the battery chamber  403  of the battery charger  400  to initiate battery charging. Alternatively or in addition, the operator can pivot the battery  200  toward a locked position so that the battery  200  is lockingly secured to the battery charger  400  during charging. 
     After charging is completed (e.g., after a predetermined charging time or when charging complete data is displayed on the indicator  412  of the charger  400 ), the operator can remove the battery  200  from the charger  400  and insert the newly charged battery  200  into the battery chamber  56  of the power tool  200 . To confirm that the battery  200  is fully charged, the operator can depress the trigger  77 , causing the state of charge data to be shown on the display  120 . 
     One or more of the above-identified and other independent features and independent advantages are set forth in the following claims.