Patent Publication Number: US-8120268-B2

Title: Lighting device and method of control based on chemistry composition of power source

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Nos. 61/023,577 and 61/023,632, both filed on Jan. 25, 2008, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to lighting devices and, more particularly, relates to a lighting device that has one or more batteries as the power source. 
     Portable lighting devices, such as flashlights and head worn lights, generally employ a light source, such as an incandescent lamp or one or more light emitting diodes (LEDs), a reflector or other optics, and a power source typically employing one or more electrochemical cell batteries. Some portable lighting devices are adapted to be worn on the head of a user, commonly referred to as a headlamp, whereas other lighting devices may be structurally mounted to a supporting structure. 
     It would be desirable to provide for a portable lighting device that provides for enhanced light illumination and enhanced features for use in the field. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, a lighting device is provided that detects chemistry composition of a power source and controls operation of the lighting device based upon the determined chemistry composition. The lighting device includes a light source and a power source for supplying power to the light source, wherein the power source includes a chemistry composition. The lighting device also includes a chemistry detection device that determines the chemistry composition of the power source. The lighting device further includes control circuitry for controlling operation of the lighting device based upon the determined chemistry composition. 
     According to another aspect of the present invention, the chemistry detection device determines the chemistry composition of the power source based upon at least an internal resistance and the operating voltage of the power source. According to further aspect of the present invention, the control circuitry controls electrical power supplied to the light source to supply a first high power current to the light source when a high capacity chemistry composition is determined and supplies a second lower power current to the light source when a lower capacity chemistry composition is determined. 
     According to yet another aspect of the present invention, a method of controlling a lighting device based upon the chemistry composition of a power source is provided. The method includes the steps of providing a power source including a chemistry composition to supply power to a lighting device. The method also includes the steps of determining an internal resistance of the power source, and determining the chemistry composition of the power source based upon the internal resistance and operating voltage of the power source. The method further includes the step of controlling operation of the lighting device as a function of the determined chemistry composition. 
     According to a further aspect of the present invention, a method of controlling a lighting device based upon the electrochemical composition of a power source is provided. The method includes the steps of providing a power source comprising an electrochemical composition to supply power to a light source of a lighting device, and determining the electrochemical composition of the power source. The method also includes the step of a controlling operation of the light source as a function of the determined electrochemical composition, wherein a first power is supplied to the light source when a first capacity electrochemical composition is determined, and a second power is supplied to the light source when a second capacity electrochemical composition is determined. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a front perspective view of a lighting device, according to one embodiment of the present invention; 
         FIG. 2  is a front perspective view of the lighting device shown in  FIG. 1 ; 
         FIG. 3  is an enlarged front perspective view of the lighting device shown in  FIG. 1 ; 
         FIG. 4  is a bottom view of the lighting device shown in  FIG. 3 ; 
         FIG. 5  is a front view of the lighting device shown in  FIG. 3 ; 
         FIG. 6  is a rear view of the lighting device shown in  FIG. 3 ; 
         FIG. 7  is an exploded view of the light body of the lighting device shown in  FIG. 3 ; 
         FIG. 8  is a cross-sectional view of the lighting device taken through lines VIII-VIII of  FIG. 5 ; 
         FIG. 9  is an enlarged cross-sectional view of section IX taken from  FIG. 8  further showing the optics pack; 
         FIG. 10  is a block/circuit diagram illustrating control circuitry for controlling operation of the lighting device, according to one embodiment; 
         FIGS. 11A and 11B  are a circuit diagram showing implementation of the control circuitry, according to a first embodiment; 
         FIG. 12  is a circuit diagram illustrating implementation of the control circuitry, according to an alternate second embodiment; 
         FIG. 13  is a circuit diagram illustrating implementation of the control circuitry, according to a third embodiment; 
         FIG. 14  is a flow diagram illustrating a routine for controlling the non-colored white LED, according to one embodiment; 
         FIG. 15  is a flow diagram illustrating a control routine for controlling the colored LED, according to one embodiment; 
         FIG. 16  is a flow diagram illustrating a routine for controlling light illumination intensity with the light control circuitry, according to one embodiment; 
         FIG. 17  is a flow diagram illustrating a routine for determining chemistry composition of a power source and controlling the lighting device based on the chemistry composition, according to one embodiment; 
         FIG. 18  is a schematic diagram of a three-position toggle switch, according to a second switch embodiment; 
         FIG. 19  is an exploded assembly view of the three-position toggle switch shown in  FIG. 18  according to the second switch embodiment; 
         FIGS. 20A-20D  are cross-sectional views taken through the three-position toggle switch shown in  FIG. 18  that show the switch in various positions for controlling the light sources of the lighting device; 
         FIG. 21  is a chart illustrating one example of a state of charge with respect to a voltage potential and an internal resistance of a battery cell with different electrochemical compositions; 
         FIG. 22  is a circuit diagram generally illustrating test circuitry for detecting the chemistry composition of a battery cell, according to one embodiment; 
         FIG. 23  is a flow diagram illustrating a routine for determining chemistry composition of a power source and controlling the lighting device based on the chemistry composition, according to another embodiment; 
         FIG. 24  is a circuit diagram generally illustrating test circuitry for detecting the chemistry composition of multiple battery cells, according to another embodiment; 
         FIGS. 25A-25B  is a flow diagram illustrating a routine for determining chemistry composition of a power source and controlling the lighting device based on the chemistry composition, according to another embodiment; and 
         FIG. 26  is a graph illustrating changes in voltage realized for three battery types during the detection test, according to one example. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to a lighting device and method of operating thereof. Accordingly, the apparatus components and method steps have been represented, where appropriate, by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Further, like reference characters in the description and drawings represent like elements. 
     In this document, relational terms, such as first and second, top and bottom, and the like, may be used to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises” does not, without more constraints, preclude the existence of additional elements in the process, method, article, or apparatus that comprises the element. 
     Referring now to  FIGS. 1-6 , a portable lighting device  10  is generally illustrated to provide a user with lighting, according to one embodiment of the present invention. The lighting device  10  generally includes a light body  12 . The light body  12  generally includes a housing that contains the various electrical and optical components of the lighting device  10 . In the disclosed embodiment, the light body  12  has four light sources, namely three forward facing light emitting diodes (LEDs)  14 ,  16  and  18 , and one side facing LED  20 . In the disclosed embodiment, the central forward facing light source  14  is implemented as a white LED, also referred to as a non-colored LED, adapted to emit a forward projecting visible beam of non-colored (white) light illumination generally in the visible light spectrum having a wavelength in the range of about 420 nanometers to 680 nanometers, according to one embodiment. Light source  16  is implemented as an infrared (IR) LED for emitting a forward projecting beam of infrared (IR) illumination in the visible or invisible IR spectrum. The IR illumination may be in the invisible IR spectrum having a wavelength generally in the range of about 680 nanometers to 1.2 micrometers, according to one embodiment. The invisible IR is generally invisible to the naked eye, but may be viewable by a person with the use of night vision equipment (e.g., night vision goggles). Light source  18  is implemented as a colored LED for emitting a forward projecting beam of visible colored light in a colored illumination beam. According to one embodiment, the colored light LED  18  is a blue LED that illuminates visible blue light generally in the visible blue light spectrum having a wavelength in the range of about 400 to 500 nanometers, according to one embodiment. 
     According to one embodiment, the side facing light source  20  is employed as another light source that may include white light, colored light or IR. The light source  20  may operate intermittently to provide a blinking signal, according to one embodiment. 
     The light body  12  is further configured with a plurality of user actuatable control switches for controlling activation and illumination of the light sources  14 ,  16 ,  18  and  20 . A first push-button switch  24  is located on the top gripping portion of the light body  12  and is actuatable by a user depressing the push-button switch  24 . Switch  24  controls activation and illumination intensity of the visible white light source  14 . Switch  24  is depressible to turn white light source  14  on and off and may be further actuatable to control the intensity (brightness) of the visible white light illumination beam as described herein. According to one embodiment, switch  24  may be actuated repeatedly to turn on and off the light source  14  and to sequentially change intensity of the white light emitted by light source  14  among a plurality of brightness settings, including high, medium and low intensity settings. According to another embodiment, switch  24  may be further actuated by continuous depression to adjust the white light intensity at more incremental settings by ramping the white light intensity up and down. 
     A second push-button switch  26  is located on the bottom handle portion of the light body  12 . The second push-button switch  26  is likewise actuatable by a user to control illumination of the visible colored (blue) light source  18 . Switch  26  may be depressed to activate light source  18  to turn the blue light source  18  on and off and may further be actuatable to control the illumination intensity (brightness) of colored light source  18 . According to one embodiment, switch  26  may be actuated repeatedly to turn the colored light source  18  on and off and to sequentially change intensity of the colored light emitted by light source  18  among a plurality of brightness settings, including high, medium and low intensity settings. According to another embodiment, switch  26  may be further actuated by continuous depression to adjust the colored light intensity at more incremental settings by ramping the colored light intensity up and down. 
     The light body  12  further includes a three-position toggle switch  22  shown located on a lateral side of the light body  12 . According to one embodiment, the toggle switch  22  is a three-position contact switch with three states configured to limit lighting operation to one light source at a time, and to prevent activation of other light sources. Specifically, the three-position switch  22  has a first side light position that activates the lateral side facing light source  20 , a second “IR” position that activates the forward facing IR light source  16 , and a third “off” position that keeps the first and second light sources off and enables operation of either the colored or non-colored visible light sources  14  and  18 . In the third “off” position, the three-position switch  22  enables operation of either the visible white or colored light sources  14  or  18  when the corresponding switch  24  or  26  is actuated, and prevents activation of the IR light source  16  and other light source  20 . In the second IR position, the three-position switch  22  activates the forward facing IR LED  16  and prevents other light sources from being activated. In the first side light position, the three-position switch  22  activates the side facing light source  20 . In this first switch position, no other light sources may be activated. Thus, the three-position switch  22  controls which light sources may be activated and which light sources are deactivated, and prevents simultaneous activation of two or more of the light source  20 , IR light source  16  and visible light sources  14  or  18 . 
     Referring to  FIGS. 7 and 8 , the assembly of the light body  12  is further illustrated having a housing generally including a main housing body  30  with upper and lower grips  31  and  33  adhered, overmolded, or otherwise attached thereto, a front housing body  56 , and a rear end cap  60 . Disposed within main body housing  30  is a generally cylindrical battery compartment  32  for receiving one or more batteries  58  as the power source. In the disclosed embodiment, a single cell battery  58  is employed to provide a power source voltage of about 1.5 volts. The battery  58  serves as a power source for providing electrical power to power the light sources and control circuitry. While a single 1.5 volt battery is shown and described herein as the power source, it should be appreciated that single or plural batteries in various sizes, shapes, power and voltage configurations may be employed to provide electrical power as the power source. 
     The rear end cap  60  threadingly engages the rear end of main housing body  30  and serves as a removable cover that may be twisted on and off to allow replacement of the battery  58 . The end cap  60  generally includes electrical contacts  61  and  63  that are disposed in the interior of end cap  60  to provide contact with battery  58  and electrical current paths. Contact  61  has a spring  67  as should be evident to those in the art to spring bias the battery  58  into contact with electrical contacts  35  and  61  at opposite end terminals of the battery  58 . Additionally, the end cap  60  is connected to an end loop of a tether  62  which, in turn, is connected to the main body  30  of light body  12 . The tether  62  may be flexible such that it bends and may slide within a holder on the main body  30 . The tether  62  serves to retain the end cap  60  attached to the light body  12  during removal of the end cap  60  from housing body  30  to allow for insertion and removal of a battery  58  without misplacing the end cap  60 . It should be appreciated that a gasket may be disposed between end cap  60  and housing body  30  to facilitate a watertight closure. 
     The light body  12  further includes one or more circuit boards which may be implemented as LED printed circuit boards having circuit components including one or more LEDs, switches and electrical circuit traces and contacts formed thereon for providing control circuitry and electrical circuit connections. In the embodiment shown, three circuit boards  40 ,  42  and  44  are shown disposed within the main housing body  30 . The first circuit board  40  is shown having circuit contacts of switch  24  connected thereto. Additionally, IR light source  16  is connected to the first circuit board  40  at the forward end. Electrical circuit traces are provided on the first circuit board  40  to allow switch  24  and control circuitry to control activation of IR light source  16 . According to one embodiment, the IR LED  16  may include Part No. GB-IR224B31C-015, commercially available from Globe Technology Component. 
     Additionally, the side facing light source  20  is also shown connected to the first circuit board  40 . The electrical circuitry provided on the circuit board  40  also allows activation of the light source  20 . The light source  20  extends through an opening in the side of the main housing body  30  aligned behind optical lens  23  and protective cover  21 . Illumination of the light source  20  provides a spot indicator at lens cover  21  that is viewable at the side. 
     The second circuit board  42  has circuit contacts of switch  26  connected thereto. Additionally, colored light source  18  is connected to circuit board  42  at the forward end. Circuit board  42  likewise has electrical circuitry, such as circuit traces, coupling switch  26  and control circuitry to colored light source  18  to allow control thereof. The first and second circuit boards  40  and  42  are generally shown arranged parallel to one another and disposed on opposite upper and lower outer sides of the battery compartment  32 . According to one embodiment, the colored blue LED  18  may include Part No. GB-333B473C-032, commercially available from Globe Technology Component. 
     The third circuit board  44  is located at the forward end of housing body  30  and is arranged orthogonal to first and second circuit boards  40  and  42 . The main white LED  14  is mounted to the front facing side of circuit board  44 . The circuit board  44  likewise has electrical circuitry, such as circuit traces, provided thereon to supply power to the white LED  14  and allow activation of the white LED  14 . According to one embodiment, the main white LED  14  may include Luxeon® Rebel having Part No. LXML-PWC1-0100, commercially available from Philips Lumiled. 
     The white LED  14  generally provides a higher light intensity output than the other light sources  16 ,  18  and  20 . According to one embodiment, the white LED  14  may typically be driven at a current of approximately 120 milliamps to achieve about 40 lumens of light illumination, whereas the colored LED  18  and side light LED  20  may typically be driven at approximately 30 milliamps to achieve approximately 10 lumens of light illumination for each light source, and the IR LED  16  may be driven at approximately 30 milliamps to achieve about 0.02 watts of optical power. It should be appreciated that the white LED  14  thereby serves as the main light source for providing the greatest amount of illumination. However, it should be appreciated that the amount of illumination achieved with each of the lighting sources  14 ,  16 ,  18  and  20  may be varied according to other embodiments. 
     Disposed adjacent to the backside of circuit board  44  is the three-position toggle switch  36 . Switch  36  generally includes PCB IR switch box  36 A assembled to an electronics frame  36 B. The toggle switch  36  has a toggle arm or pin  36 C that extends from switch box  36 A through a switch opening in the main housing body  30  and is assembled to an actuator member  37 . Actuator member  37 , in turn, fits within and engages an overlaying rubber boot  38  that flexes when switch  36  is actuated and provides a water tight seal to close the switch opening in the main housing body  30 . A fascia cover  39  lays over the top perimeter of the rubber boot  38 . In one embodiment, the three-position switch  36  is actuated by applying lateral force to slide toggle member  37  and pin  36 C into one of three contact positions. According to another embodiment, the three-position switch  36  is actuated by first depressing the toggle member  37  by pushing downward on boot  38  and actuator member  37  and then applying lateral force to slide or rotate the switch  36  into one of three contact positions. 
     Disposed in front of the forward facing light sources  14 ,  16  and  18 , are optical lenses for focusing each of the corresponding forward directed light beams in a desired beam pattern. A total internal reflectance (TIR) optical lens  50  is disposed in front of the main white LED  14 . The TIR lens  50  may be made of a thermoplastic and transparent plastic, also referred to as acrylic glass. One example of a suitable acrylic glass is polymethyl methacrylate (PMMA). In an exemplary embodiment, the TIR lens  50  may include a TIR Rebel lens with an O-ring that may be injection molded. Lens  50  is shown in  FIGS. 8 and 9  disposed in the front housing body  56  by way of a collar  53  trapped within channel  57 . Thus, the optical lens  50  is disposed in front of the white LED  14  and is spaced therefrom by a distance. The TIR lens  50  is generally conical or frustoconical (in the shape of a frustum of a cone) with a recess provided at the vertex end for receiving the LED  14 . TIR lens  50  internally reflects and collimates light and transmits the light into a desired collimated beam pattern. In one exemplary embodiment, the TIR lens  50  has a maximum diameter of twelve millimeters (12 mm) and achieves an efficiency of at least eighty-eight (88) percent. In a specific embodiment, fifty (50) percent of light generated by LED  14  is transmitted by TIR lens  50  within a window of ±thirteen (13) degrees. 
     The white LED  14  is generally configured as an LED package that includes a powered LED component  14 A and a primary optical lens  14 B. The primary optical lens  14 B may include a silicone lens that provides an optical path for light generated by LED component  14 A to pass forward in a desired beam pattern. Disposed between the primary optical lens  14 B and the optical lens  50 , also referred to herein as a secondary optical lens, is a light transparent medium, in the form of a gel  55 . The light transparent gel  55  is disposed between the primary optic lens  14 B and the secondary optical lens  50  to enhance or optimize the efficiency of the light transmission between the two lenses  14 B and  50 . The light transparent gel  55  may include a transparent silicone, according to one embodiment. According to one example, the silicone may be a silicone adhesive, such as Part No. OE-6450, commercially available from Dow Corning. In this example, the silicone adhesive may have a thickness of about 1 millimeter and may not be hardened such that it does not set and remains in a gel state. The transparent gel  55  may be applied as a gel encapsulant for the LED package. It should be appreciated that the LED component  14 A and its primary optic lens  14 B together with the secondary optic lens  50  and the light transparent gel  55  provides for an optics package for the lighting device  10 . According to a further embodiment, a light transparent gel may be disposed between the LED component  14 A and primary optics lens  14 B to enhance light transmission therebetween. 
     According to one example, the primary optical lens  14 B has an index of refraction of approximately 1.6, the secondary optical lens  50  has an index of refraction of about 1.5, and any unoccupied area filled with air has an index of refraction of about 1.0. The light transparent gel has an index of refraction that substantially matches the index of refraction of at least one of the primary optical lens  14 B and the secondary optical lens  50 . According to an exemplary embodiment, the light transparent gel  55  has an index of refraction of about 1.54. More generally, the light transparent gel  50  has an index of refraction generally greater than 1.0, such as 1.1 or greater and has an index of refraction generally between the index of refraction of the primary and secondary optic lenses  14 B and  50 . According to one embodiment, the light transparent gel  55  has an index of refraction between 1.0 and 2.0. 
     By enhancing the index of refraction in the region between the primary optical lens  14 B and the secondary optical lens  50 , losses that would otherwise occur at the interface between each of the primary and secondary optical lenses  14 B and  50  and an otherwise open air gap are eliminated such that the light illumination is more efficiently transmitted from the primary optical lens  14 B to the secondary optical lens  50 . The light transparent gel  55  reduces variations in index of refraction from the primary optical lens  14 B to the secondary optical lens  50  so as to reduce interface loses that would otherwise occur due to larger index of refraction mismatches. 
     The light transparent gel  55  may be injected as a fluidous gel to completely fill the void region between the primary lens  14 B and secondary lens  50  to substantially eliminate open air gaps so as to maintain a substantially matched index of refraction at the interface regions of the primary and secondary optical lenses  14 B and  50 . The light transparent gel  55  may be applied as a gel, such as a liquid that flows into the region between the primary optical lens  14 B and the secondary optical lens  50 . Subsequently, the light transparent gel  55  may be at least partially cured, according to one embodiment. The use of a light transparent gel  55  enables the air gap to be substantially filled in such that the gel  55  is conformal to the surface contour of the primary and secondary optical lenses  14 B and  50 . Additionally, it should be appreciated that the light transparent gel  55  may include a colored die that may provide color to the light illumination. 
     Disposed in front of IR light source  16  is an IR optical lens  52 . The infrared lens may include Part No. 0.1*, commercially available from Fresnel Technologies, Inc. The IR lens  52  may include a fresnel lens for collimating the infrared radiation into a desired beam pattern. Similarly, disposed in front of the colored blue light source  18  is a blue optical lens  54 . The blue colored optical lens  54  may include a fresnel lens having Part No. 0.1*, commercially available from Fresnel Technologies, Inc. The blue optical lens  54  may include a fresnel lens for collimating the colored blue light into a desired beam pattern. According to various embodiments, the optical lenses  52  and  54  may be conical TIR lenses, fresnel lenses or other optics. It should further be appreciated that a light transparent gel  55  may also be disposed between LED  16  and optical lens  52 , as well as between LED  18  and optical lens  54 , according to further embodiments to further enhance the light transmission therebetween. Lenses  50 ,  52  and  54  are generally positioned in corresponding openings provided in the front facing portion of front housing body  56 . 
     Additionally, a thermally conductive member  48  generally receives the TIR lens  50  and abuts the inner surface of the front housing body  56 . Thermally conductive member  48  is made of a thermally conductive material that acts as a heat sink to dissipate thermal energy (heat) away from the white LED  14 . Heat sink  48  also dissipates thermal energy away from LEDs  16  and  18 . By dissipating thermal energy away from the light sources  14 ,  16  and  18 , enhanced performance of the lighting sources may be realized. 
     The housing of light body  12  which generally includes the main housing body  30  with upper and lower grips  31  and  33 , the front housing body  56 , and the rear end cap  60  is generally made up of an impact resistant material capable of withstanding adverse use in the field. According to one embodiment, the housing may be made up of a thermoplastic such as acrylonitride-butadiene-styrene (ABS). According to a second embodiment, the material may be made up of a nylon-ABS blend, which offers a good combination of stiffness and toughness. Examples of a nylon-ABS blend include Nylon 66/6 which is a copolymer offering dimensional stability and good impact resistance. Examples of a nylon-ABS blend include Lumid® Hi-5006 A, commercially available from LG Chemical Ltd., Excelloy AK15 (DRIE), commercially available from Techno Polymer America, Inc., and Toyolac® SX01, commercially available from Toray Resin Company. According to other embodiments, the housing of light body  12  may be made of a nylon, such as an impact modified and/or glass filled nylon, with the elastomer blended into the nylon for optimal toughness. A further embodiment of the housing material may include a polycarbonate. 
     The components of the housing and other components connected thereto may be held in place with an adhesive, according to one embodiment. The adhesive may include adhesives from the following families: cyanoacrylites, epoxies and urethanes. It should be appreciated that the aforementioned adhesives are commercially available under the brand name Loctite® from Henkel Corporation. According to another embodiment, the components of the housing and other components connected thereto may be held together via ultrasonic welding. 
     The lighting device  10  may be employed as a portable handheld lighting device, according to one embodiment. According to other embodiments, the lighting device  10  may be connected to a supporting structure, such as an article of clothing (e.g., hat). To accommodate mounting to a support structure, the lighting device may include a connecting structure (not shown). 
     The lighting device  10  includes control circuitry  100  for controlling operation of the light sources  14 ,  16 ,  18  and  20 . The control circuitry  100  is generally illustrated in  FIG. 10 , and specific control circuitry is further illustrated in  FIGS. 11A-13  according to various disclosed embodiments. As seen in  FIG. 10 , the control circuitry  100  includes a microprocessor  110  coupled to memory  112 . The microprocessor  112  may include any signal processing device capable of processing switch inputs, executing routines, and generating control signals as described herein. Memory  112  may include volatile and nonvolatile memory devices, such as electronically erasable programmable read-only memory (EEPROM), flash memory, or other known memory devices. Stored within memory  112  are a plurality of routines including a visible white light control routine  200  for controlling activation and intensity of the visible white light source  14 , a colored light control routine  230  for controlling activation and intensity of the colored light source  18 , a battery chemistry detection and control routine  400  for detecting the type of electrochemical cell battery employed and controlling the lighting device  10  based on the detected type of cell employed, and a ramping light intensity control routine  300  for controlling illumination intensity of either of the white and colored light sources  14  and  18  in a cyclical ramping mode, according to one embodiment. 
     The control circuitry  100  further includes boost control circuitry for supplying a substantially constant current or substantially constant voltage to one or more of the light sources  14 ,  16 ,  18  and  20 , which are shown as light emitting diodes, and are generally connected to the three-position switch  22 . In certain disclosed embodiments, the boost circuitry includes a first DC/DC converter boost control circuit  114  generally coupled to the LEDs  14 ,  16 ,  18  and  20  for controlling power supplied to the LEDs. In certain embodiments, the boost control circuit  100  further includes second DC/DC converter boost control circuitry  116  that controls power supplied to the microprocessor  110 . In such embodiments, the first boost control circuitry  114  may be turned off such that no power is supplied to the light sources when all light sources of the lighting device  10  are turned off, whereas power may be supplied periodically or continuously to the microprocessor  110  by way of the second boost circuit  116 . The first and second boost circuits  14  and  16  receive power from the battery  58  at a voltage potential V BAT . In the disclosed single battery cell embodiment, V BAT  is about 1.5 volts. However, V BAT  may drop to about 1.0 volts or less as the battery is depleted and still operate the light. Additionally, the voltage V BAT  is supplied to the microprocessor  110 . The microprocessor  110  also receives inputs from each of the visible white light switch  24  and the colored light switch  26 . 
     The microprocessor  110  processes the inputs from switches  24  and  26  and executes routines  200 ,  230 ,  300  and  400  stored in memory  112  and controls the activation and intensity of the visible white and blue light sources  14  and  18 , whenever the three-position switch  22  is in the off position. The first boost control circuit  114  supplies a boost rail voltage of 3.8 volts that serves to power LEDs  14 ,  16 ,  18  and  20 . According to one embodiment, the microprocessor  110  provides a pulse width modulated (PWM) output signal to each of the transistors (e.g., MOSFETs)  120  and  122  to control current flow through LEDs  14  and  18 , and thus the activation and intensity of the visible light emitted by the visible light sources  14  and  18 . Alternately, the microprocessor  110  could provide a pulse width modulated (PWM) output signal to the first DC/DC converter boost circuit  114  shutdown input to control the intensity of the light emitted by the visible light sources  14  and  18 , while MOSFETs  120  and  122  are used to control which light sources  14  and/or  18  are receiving power. Thus, when the microprocessor  110  outputs a signal on either of MOSFETs (transistors)  120  and  122 , and the three-position switch  22  is in the “off” position, power is supplied to the corresponding light source  14  or  18  at a light intensity determined by the microprocessor  110 , which generally is in response to activation of the respective user input actuation of switches  24  or  26 . The microprocessor generated outputs for controlling light intensity for a light source may be output at a predetermined number of levels, such as a high, medium and low intensity, or may be continuously ramped up and down, according to two disclosed embodiments. 
     When the three-position switch  22  is actuated into the “IR” position, electrical current is supplied through the IR light source  16  and a resistor R and to ground to operate light source  16 , and no other light sources are operable in that position of switch  22 . When switch  22  is actuated into the “side” position, electrical current is supplied through the side LED  20  and resistor R and to ground to operate the light source  20 , and no other light sources are operable in that position. Thus, the three-position switch  22  thereby ensures that the side light mode, IR mode and visible light modes cannot operate at the same time. 
     Referring to  FIGS. 11A and 11B , one example of the boost control circuitry  100  is illustrated providing a substantially constant current to the lighting sources according to a first boost circuit embodiment. The control circuitry  100  is shown having a microprocessor  110  providing output control signals to transistors  120  and  122  to control activation and light intensity of the main white LED  14  and colored LED  18 . Transistor  124  is used to control the blinking of the side LED  20 . The IR LED  16  is controlled in response to switch  22  actuated into the IR position to complete the rail voltage to ground connection through IR LED  16 . The position of switch  22  is detected by microprocessor  110  sensing that switch  22  is not in either of the off or IR positions. The microprocessor  110  is connected to a resistor network  140  on pin RC 0  that also connects to the V ref  input of the main boost circuit  114  at pin  6 . The main boost circuit  114  thereby provides one or more output levels based on the state of the microprocessor  110  output on pin RC 0 . This allows the microcontroller  110  to control the output level of the main boost circuit  114  by means of software routines. This output level may be changed based on the detected battery chemistry presented to the microprocessor  110  at pin  3  labeled RA 4 . 
     The battery voltage V BAT , supplied at 1.5 volts according to one embodiment, is supplied to inductors L 1  and L 2 . Inductor L 2  is a mutually coupled inductor which supplies a substantially constant current through diode D 4  on the rail that powers light sources  14 ,  16 ,  18  and  20 . Inductor L 2  with first boost circuit  114  thereby provides electrical energy at a substantially constant current to the rail. A transistor Q 1  serves as a main power switch for the first boost circuit  114 . It should be appreciated that resistors R 11 , R 13 , R 15  and R 21  and capacitor C 11  provide a voltage divider to monitor for over voltage which is sensed at pin  5  of the main boost converter  114 . 
     The second boost circuitry  116  is generally coupled to inductor L 1  which steps up the battery supplied voltage from 1.5 volts to about 3.0 or 3.3 volts to serve as voltage V DD . The second boost circuit  116  serves as a boost for the voltage V DD  and provides stable operating voltage and/or power to the microprocessor  110 . 
     The three-position switch  22  allows for switching amongst the visible, IR and side light positions. The three-position switch  22  also serves as a return path to ground for electrical current for both the visible white and blue LEDs  14  and  18 . The IR LED  16  also passes current to ground when switch  22  is in the IR position. 
     Referring to  FIG. 12 , an alternate second control circuit  100  is shown providing a substantially constant voltage to the light sources  14 ,  16 ,  18  and  20 . In this second embodiment, a single boost circuit configuration is employed. The control circuitry  100  generally illustrated in  FIG. 12  includes microprocessor  10  having outputs coupled to transistors  120 ,  122 ,  124  for controlling white light LED  14 , colored LED  18  and side LED  20 , respectively. The microprocessor  10  receives as inputs signals from switches  24  and  26  on lines RB 0  and RB 1  which are generated in response to user activation. 
     Control circuitry  100  includes a single boost circuit  116  in  FIG. 12  for providing a rail voltage of 3.8 volts that serves as a substantially constant voltage supply of 3.8 volts for powering light sources  14 ,  16 ,  18  and  20 . Additionally, the boosted 3.8 volts is used to power the microprocessor  110 . The single boost circuitry  116  generally includes an inductor L coupled to the battery which supplies the voltage of about 1.5 volts. The voltage of 1.5 volts is stepped up by inductor L to 3.8 volts and serves as the rail voltage. Coupled between the rail supplying 3.8 volts and each of the light sources  14 ,  16 ,  18  and  20  are resistors R that serve as current limiting resistors. With the three-position switch  22  in the IR position, current flows from the rail of 3.8 volts through IR LED  16  and then to ground through the three-position switch  22 , which is shown having four terminals, with one terminal connected to ground. With the three-position switch  22  in the side light position, current flows from the rail voltage of 3.8 volts through the side LED  20  as controlled by transistor  124  to ground through the switch  22 . With the three-position switch  22  in the off position, current may flow through either LED  14  or LED  18  from the 3.8 volt rail to ground as controlled by transistors  120  and  122 . 
     Thus, the second embodiment of the control circuitry  100  allows for the use of a single boost circuit to supply a substantially constant rail voltage for supplying electrical power to the light sources  14 ,  16 ,  18  and  20 . In order to make efficient use of the battery power source  58 , it should be appreciated that the boost circuit and other control circuitry may be periodically powered on and off to operate in a wake up mode so that electrical current is not continually transmitted through circuitry to drain the battery power source  58 . 
     Referring to  FIG. 13 , the control circuitry  100  is shown according to a third embodiment employing first and second boost circuitry  114  and  116 . The control circuitry  100  shown in  FIG. 13  employs microprocessor  110 , and first and second boost circuits  114  and  116  to provide for another double boost circuit embodiment. In this embodiment, the first boost circuit  114  serves as a current regulator to provide a substantially constant current to the white LED  14 , using pulsed frequency modulation (PFM). Thus, the boost circuitry  114  provides current regulation which is generally achieved by the use of inductor L 2  to power the highest intensity LED  14 . With the three-position switch  22  in the off position, the white LED  14  is activated by switch  24  and transistor Q 3  is used to turn off the white LED  14 . 
     The pulsed frequency modulation (PFM) provided by the first boost circuitry  114  is used to control activation and intensity of the white LED  14 . Thus, by pulsing the frequency modulation of the signal, the intensity of the white LED  14  may be adjusted to achieve a desired brightness in response to activation of the corresponding user actuatable switch  24 . While pulsed frequency modulation is disclosed in this embodiment, it should be appreciated that other forms of intensity control, such as pulse width modulation (PWM) may be employed to control intensity of one or more of the lighting sources  14 ,  16 ,  18  and  20 . 
     The second boost circuit  116  is shown coupled to the battery voltage of 1.5 volts and inductor L 1  to provide a 3.6 voltage rail which is supplied to LEDs  16 ,  18  and  20 . The second boost circuit  116  regulates the current provided to the colored LED  18 , side LED  20  and IR LED  16 . Thus, the second boost circuit  116  provides a rail voltage of 3.6 volts and regulates the current provided to the three LEDs  16 ,  18  and  20  connected to the rail voltage. The three-position switch  22  is shown providing an IR position for controlling activation of the IR LED  16  by allowing current to flow from the 3.6 volt rail through resistor R 3  and LED  16  to ground. In the side light position of three-position switch  22 , current flows from the 3.6 volt rail through resistor R 2 , ILED  20 , and transistor Q 2  to ground. With the three-position switch  22  in the off position, the blue LED  18  may be controlled by way of transistor Q 1 . The control circuitry  100  is shown powered by a battery supplying 1.5 volts, however, it should be appreciated that control circuitry  100  can operate at various other voltage potentials, such as 3.0 volts supplied by two battery cells connected in series. 
     Referring to  FIG. 14 , the white light control routine  200  is illustrated for controlling the operation of the visible white light source  14  to activate and deactivate the light source  14  and to further provide three available light intensities. Routine  200  begins at step  202  and proceeds to set the white LED to the off state. Next, in decision step  206 , routine  200  determines if the three-position switch  22  is set to the off position and, if not, prevents activation of the visible white light source and returns to step  204 . If the three-position switch is set to the off position, routine  200  proceeds to step  208  to determine if the white LED switch  24  is depressed and, if so, turns the white LED on at a high intensity level in step  210 , preferably setting the white LED at the highest intensity level. Accordingly, the white LED, when turned on, is turned on at the highest intensity setting. 
     With the white LED set to the high intensity level, routine  200  proceeds to decision step  212  to determine if the white LED switch has been depressed within three seconds of turning the white LED on high and, if so, proceeds to step  216  to set the white LED to the next lowest intensity setting which, in one embodiment, is the medium intensity setting. If the white LED switch has not been depressed within the three second time period, routine  200  proceeds to decision step  214  to determine if the white LED switch is depressed after the three second time period and, if so, returns to step  204  to turn the white LED off. However, if the white LED switch is not depressed after three seconds, the white LED remains in the high intensity state. 
     With the white LED set to the medium intensity setting, routine  200  proceeds to step  218  to determine if the white LED switch is depressed within a three second time period of setting the white LED to the medium setting and, if so, sets the white LED to the next lowest intensity setting in step  222  which, in this embodiment, is the lowest intensity setting. If the white LED switch has not been depressed within the three second time period, routine  200  proceeds to step  220  to determine if the white LED switch is depressed after the three second time period and, if so, returns to step  204  to turn the white LED off. Otherwise, the white LED remains on at the medium intensity setting. 
     With the white LED set to the low intensity setting, routine  200  proceeds to step  224  to determine if the white LED switch has been depressed within a three second time period and, if so, returns to step  210  to turn the white LED on the high intensity setting. If the white LED switch has not been depressed within three seconds, routine  200  proceeds to step  226  to determine if the white LED switch has been depressed after three seconds and, if so, turns the white LED off in step  204 . Otherwise, the white LED remains on at the low intensity setting. 
     Accordingly, the intensity of the white LED is selectively changed when the LED switch is depressed within three seconds for each switch depression to switch the white LED sequentially from high to medium to low intensity settings, and to repeat the sequence. It should be appreciated that the intensity of the white LED light source may be changed using pulse width modulation (PWM) light control, according to one embodiment. According to another embodiment, the intensity of the white LED may be controlled using pulsed frequency modulation (PFM). 
     Referring to  FIG. 15 , the colored light control routine  230  for controlling activation and further controlling intensity of the visible colored light source  14  is illustrated. Routine  230  begins at step  232  and proceeds to step  234  to set the colored LED to the off state. Next, in decision step  236 , routine  230  determines if the three-position switch  22  is set to the off position and, if not, prevents activation of the visible colored light source and returns to step  234 . If the three-position switch is set to the “off” position, routine  230  proceeds to step  238  to determine if the colored LED switch  24  is depressed and, if so, turns the colored LED on at a low intensity level in step  240 , preferably setting the colored LED at the lowest intensity level. Accordingly, the colored LED, when turned on, is turned on to the lowest intensity setting. With the colored LED set to the low intensity level, routine  230  proceeds to decision step  242  to determine if the colored LED switch has been depressed within three seconds of turning the colored LED on low and, if so, proceeds to step  246  to set the colored LED to the next highest intensity setting, which in one embodiment is the medium intensity setting. If the colored LED switch has not been depressed within the three second time period, routine  230  proceeds to decision step  244  to determine if the colored LED switch is depressed after the three second time period and, if so, returns to step  234  to turn the colored LED off. However, if the colored LED switch is not depressed after three seconds, the colored LED remains on at the low intensity setting. 
     With the colored LED set to the medium intensity setting, routine  230  proceeds to step  248  to determine if the colored LED switch is depressed within a three second time period of setting the colored LED to the medium setting and, if so, proceeds to step  252  to set the colored LED to the next highest intensity setting, which in this embodiment is the highest intensity setting. If the colored LED switch has not been depressed within the three second time window, routine  230  proceeds to step  50  to determine if the colored LED switch is depressed after the three second time period and, if so, returns to step  234  to turn the colored LED off. Otherwise, the colored LED switch remains on at the medium intensity setting. 
     With the colored LED set to the high intensity setting, routine  230  proceeds to step  254  to determine if the colored LED switch has been depressed within a three second time period and, if so, returns to step  240  to adjust the colored LED setting to the low intensity setting. If the colored LED switch has not been depressed within three seconds, routine  200  proceeds to step  256  to determine if the colored LED switch has been depressed after three seconds and, if so, turns the colored LED off in step  234 . Otherwise, the colored LED remains on at the high intensity setting. 
     Accordingly, the intensity of the colored LED may be selectively changed if the LED switch is depressed within three seconds for each switch depression to switch the colored LED sequentially from low to medium to high intensity settings and to repeat the sequence. It should be appreciated that the intensity of the colored LED light source may be changed using pulse width modulation (PWM) light control, according to one embodiment. According to another embodiment, the intensity of the colored LED may be controlled using pulsed frequency modulation (PFM). 
     The visible white light source  14  and colored light source  18  of lighting device  10  may be actuated and controlled in light intensity to provide desired intensity visible white and colored light beams. The lighting device  10  advantageously turns the visible white light source  14  on at a high intensity setting, whereas the colored light source  18  is turned on at a low intensity setting. This advantageously provides a user in the field with the ability to immediately realize bright white lighting from the white light source  14  on the one hand, whereas, on the other hand, the colored light may be used as a low profile light that turns on at low intensity and is less likely to be seen by an unwanted viewer in the field, particularly for a hunting application. While the light levels of intensity disclosed in the aforementioned embodiment include high, medium and low intensity settings, it should be appreciated that the visible white and colored light sources may be adjusted in different intensity levels, and may include a substantially continuous or ramped change in the level of light intensity, such as is discussed in the following embodiment. 
     Referring to  FIG. 16 , a routine  300  is illustrated for providing user selectable light illumination intensity control of either one of the visible white light source  14  and colored light source  18 . The light control routine  300  essentially processes the output signals of switches  24  and  26  and provides a controlled pulse width modulation signal to increase and decrease the intensity of the corresponding light beam generated by the corresponding light source. The pulse width modulation signal is supplied as an input to power the corresponding LED and has a duty cycle that is controlled to change the intensity of the light beam. To increase intensity of the light beam, the duty cycle of the pulse width modulated signal is increased, whereas to decrease intensity of the light beam the duty cycle of the pulse width modulation signal is decreased. 
     According to one embodiment, the microprocessor may employ an eight-bit PIC 16F616 having 256 output states to set the duty cycle of the pulse width modulated signal which, in this embodiment, allows the pulse width modulated signal to be adjusted incrementally in 1/256 th  increments. At the maximum beam setting, the power supplied to the corresponding LED is continuous, with no duty cycle, whereas at the minimum light beam intensity, the duty cycle is set at about 12.5 percent, according to one example. When one of switches  24  and  26  is continuously depressed and the visible light is available, the duty cycle of the pulse width modulated signal supplied to the corresponding light source  14  or  18  is continuously increased and decreased to incrementally increase and decrease the light illumination intensity in a repeated ramp cycle, until the user no longer depresses the corresponding switch  24  or  26 . Additionally, when the light source  14  or  18  approaches the maximum light intensity, the LED flashes and then begins to decrease in intensity and, when approaching the minimum light source, the LED flashes and then begins to increase in intensity. Thus, the light illumination intensity of the LED  14  or  18  cycles up and down repeatedly as the user continuously depresses and holds the corresponding switch  24  or  26  in the closed contact “on” position. 
     The light control routine  300 , shown in  FIG. 16  may be implemented as software executed by a controller, specifically the microprocessor. The light control routine  300  begins at step  302 , proceeds to step  304  and, if the user selectable switch is engaged such that the electrical switch contact is closed, then proceeds to step  306  to set the light source on the maximum brightness. Next, method  300  proceeds to determine if the switch has been released such that the contact is open in decision step  308  and, if so, maintains the maximum brightness setting of the light source. Thereafter, in decision step  312 , method  300  determines whether the switch has been pressed and, if so, turns the light source off in step  314 . When the light source  14  or  18  is turned off, method  300  may enter a sleep mode in which no or very little power consumption is required by the control circuitry. If the switch  24  or  26  has not been pressed, the maximum brightness of the light source is maintained. 
     If the switch  24  or  26  has not been released as determined in step  308 , method  300  proceeds to wait for a time delay of approximately 0.25 seconds in step  316 , which provides a sufficient time to distinguish between an initial switch depression to turn the light on and off, and further desire to adjust brightness of the light source  14  or  18 . Following the 0.25 second time delay, method  300  proceeds to decision step  320  to determine whether the switch has been released. If the switch is released, method  300  no longer reduces the brightness and maintains the brightness at the set level in step  322 . With the brightness set at the set level, method  300  monitors the switch  24  or  26  to determine if the switch  24  or  26  has been depressed in decision step  324 , and, if so, turns the light source  14  or  18  off in step  326 . Otherwise, the brightness remains at the set level. 
     The light source  14  or  18  will continue to be incrementally decreased in brightness in step  318  with the switch continuously depressed, until a minimum brightness is reached. The reduction in brightness of the light source  14  or  18  may include an incremental decrease in brightness of the light source  14  or  18  by changing the duty cycle of the pulse width modulated signal, according to one embodiment. If decision step  320  determines that the switch  24  or  26  has been released, method  300  proceeds to step  328  to continue to reduce the brightness. In decision step  330 , method  300  determines whether the minimum brightness has been reached, and, if not, continues to reduce the brightness of the light source  14  or  18 . If the minimum brightness has been reached, method  300  proceeds to step  332  to cause the light source  14  or  18  to flash at the minimum brightness, thus providing the user with an indication that the minimum brightness level has been reached. 
     Once the minimum brightness has been reached and the light source  14  or  18  flashes at step  332 , the light intensity begins to ramp up to increase the brightness as long as the corresponding switch  24  or  26  remains depressed. In decision step  334 , method  300  will monitor whether the switch  24  or  26  has been released or not. If the switch  24  or  26  has not been released, the brightness continues to increase in step  336  until either the switch  24  or  26  is released or the maximum brightness level is reached. At decision step  344 , routine  300  determines if the maximum brightness has been reached and, if not, returns to step  334  to determine if the switch  24  or  26  has been released. If the switch  24  or  26  is released, the brightness level remains at the set level in step  338 . Thereafter, method  300  proceeds to monitor whether the switch  24  or  26  has been depressed in step  340 , and, if so, turns the light source  14  or  18  off in step  342 . 
     If the switch  24  or  26  has not been released and the brightness is increasing and in decision step  344  it is determined that the maximum brightness has been reached, then routine  300  flashes the light source  14  or  18  at the maximum brightness in step  346 . It should be appreciated that the light source  14  or  18  is flashed at both maximum and minimum brightness levels to provide a user with an indication of reaching the extreme illumination intensity settings. The flash may be achieved by turning the light source  14  or  18  off and on one or more times. Following flash of the light source  14  or  18  in step  346 , routine  300  returns to step  320  to determine if the corresponding switch  24  or  26  has been released and, if not, starts to repeat step  328  to reduce brightness of the light source  14  or  18 . Accordingly, the light illumination intensity repeatedly cycles up and down when the switch  24  or  26  is continuously held in the closed contact position. 
     Accordingly, the light control routine  300  advantageously allows for a user to control the lighting device  10  by activating the corresponding switch  24  or  26  to turn the respective light source  14  or  18  on and off and to further adjust the intensity of the light illumination for both the visible white and colored light sources  14  and  18 . By simply depressing the corresponding switches  24  or  26 , the control circuitry is able to cyclically increase and decrease the light illumination intensity for the corresponding light source  14  or  18 , respectively, thus offering the user the ability to select the desired intensity level of the light beam provided thereby. 
     Battery Detection and Control of Lighting Device 
     The lighting device  10  employs an electrochemical cell battery  58  as the power source for supplying electrical power to the one or more light sources  14 ,  16 ,  18  and  20 , in addition to powering the control circuitry. The lighting device  10  may be powered by one of a number of different types of electrochemical cell batteries. For example, a single AA-size alkaline electrochemical cell battery having an electrochemistry that includes an alkaline electrolyte and electrodes generally made up of zinc and manganese dioxide (Zn/MnO 2 ) as the active electrochemical materials, according to one embodiment may be employed. According to another embodiment, a lithium AA-size LiFeS 2  electrochemical cell may be employed as the power source. According to a further embodiment, a nickel metal hydride (NiMH) electrochemical cell may be employed as the power source. Different types of batteries cells employing different chemical compositions provide different power capabilities. The lighting device  10  of the present invention advantageously determines the type of electrochemical cell battery  58  and provides optimal control to control the lighting device  10  based on the determined electrochemical cell composition. Specifically, the control circuitry may control the electrical power supplied to one or more lighting sources when a higher capacity battery chemistry composition of the power source is determined, and may provide a lesser power supplied to the one or more lighting sources when a lesser capacity battery chemistry composition of the power source is determined. 
     According to one embodiment, the control circuitry may provide enhanced operation of the lighting device  10  to achieve a desired minimum operating time for a given application. For example, given a requirement to provide a minimum of six hours of operation for a given lighting source, the lighting device  10  may control electrical power supplied to the corresponding light source to achieve the minimum operating time of six hours while providing an optimum or maximum light illumination during that six hour time period. For example, if an alkaline battery power source supplies enough power to achieve light illumination of nineteen lumens with a light source for six hours, whereas a lithium battery cell is capable of providing greater than nineteen lumens for six hours, then the power supplied to the lithium powered light source may be increased to a higher illumination setting to provide greater than nineteen lumens as long as the light operates for at least the minimum time period of six hours. In this case, the control circuitry will drive a lithium (Li) powered light source at a higher current to achieve greater light illumination, as compared to when an alkaline electrochemical cell is employed as the power source. 
     The battery power source  58  can have a variety of electrochemical compositions, wherein the electrochemical composition can be determined in order to control one or more of the lighting devices  14 ,  16 ,  18 ,  20 , according to one embodiment. Typically, each of the lighting devices  14 ,  16 ,  18  and  20  has a load that is in electrical communication with the power source, when switched on, such as the visible white LED  14  being in electrical communication with the battery power source  58 . The processor  112  can determine the electrochemical composition of certain battery power sources, according to the disclosed embodiments. 
     The processor  112  can determine the electrochemical composition of the battery power source  58  by executing software routine  400  shown in  FIG. 17  and by receiving data to determine a voltage potential of the battery power source  58  under at least one operating condition of the lighting device  10  with respect to a load. The load may be a known load, such as a resistor or one of the light sources. According to one embodiment, the processor  112  can determine open circuit voltage, closed circuit voltage, and an electrical current supplied by the battery power source  58  to the load, and detect the electrochemical composition of the battery power source  58  based upon the determined voltage potential under the operating condition and the determined electrical current. 
     According to one embodiment, the processor  112  determines an open circuit voltage (V oc ) and a closed circuit voltage (V cc ) under known load conditions. The known load condition may include a test load resistance R LOAD  having a known resistance value that has applied for a time period, such as 100 milliseconds, sufficient to acquire the open circuit voltage, closed circuit voltage and current, according to one embodiment. The open circuit voltage (V oc ) and the closed circuit voltage (V cc ) can be subtracted and divided by the determined electrical current provided to the load in order to determine the internal resistance (R INTERNAL ) of the battery power source  58 , according to one embodiment. Based upon the internal resistance (R INTERNAL ) of the battery power source  58 , the electrochemical composition of the battery power source  58  can then be determined. Thus, the internal resistance (R INTERNAL ) of the battery power source  58  can be represented by the following equation: 
     
       
         
           
             
               
                 ( 
                 
                   
                     V 
                     oc 
                   
                   - 
                   
                     V 
                     cc 
                   
                 
                 ) 
               
               I 
             
             = 
             
               R 
               INTERNAL 
             
           
         
       
     
     According to another embodiment, the processor  12  determines the internal resistance (R INTERNAL ) of the battery power source  58  based on the open circuit voltage, closed circuit voltage, and the known load resistance R LOAD , as set forth in the following equation: 
     
       
         
           
             
               R 
               INTERNAL 
             
             = 
             
               
                 
                   ( 
                   
                     
                       V 
                       oc 
                     
                     - 
                     
                       V 
                       cc 
                     
                   
                   ) 
                 
                 × 
                 
                   R 
                   LOAD 
                 
               
               
                 V 
                 cc 
               
             
           
         
       
     
     In this embodiment, the electrical current need not be determined by the processor. Instead, the internal resistance of the battery power source  58  is determined by the difference between the open circuit voltage and the closed circuit voltage multiplied by the known load resistance R LOAD  divided by the closed circuit voltage V cc . It should be appreciated that the above determinations of internal resistance generally apply to determining the internal resistance of a single cell battery. However, it should be appreciated that the internal resistance of multiple cells, such as two battery cells, may be determined. It should be appreciated that other suitable determinations for the internal resistance can be employed, according to other embodiments. 
     The processor  112  can then use the internal resistance (R INTERNAL ), the magnitude of the voltage (e.g., the open circuit voltage (V oc ) and the closed circuit voltage (V cc ), temperature data (e.g., data received from a temperature monitoring device, if available), stored hierarchical correction data, a lookup table of known internal resistance (R INTERNAL ) values for different electrochemical compositions, or a combination thereof, to determine the electrochemical composition of the battery power source  58 . Correction data may include correction values, such as multiplier factors to compensate for parameters that may affect the determination of the internal resistance and determination of the chemistry composition. The lookup table may be predetermined, according to one embodiment, or may be dynamically adjusted and updated. Typically, the lookup table data is stored in a memory device. Additionally, the determined open circuit voltage (V oc ) can be used as a cross-reference with the internal resistance (R INTERNAL ) of the processor  112  to determine the electrochemical composition of the battery power source  58 . The controller  112  can then control one or more operating parameters of one or more of the lighting devices  14 ,  16 ,  18  and  20  based upon the determined electrochemical composition of the battery power source  58 . 
     By way of explanation and not limitation, the determined electrochemical composition of the battery power source  58  can be used to determine the state of charge of the battery power source  58 , as described in greater detail herein. Additionally or alternatively, the determined electrochemical composition of the battery power source  58  can be used to alter the electrical current supplied to one or more of the lighting sources  14 ,  16 ,  18  and  20  in conjunction with the temperature data received by the processor  112  from the temperature monitoring device (if available). Thus, the heat emitted by the lighting sources  14 ,  16 ,  18  and  20  can be monitored by a temperature monitoring device, and the electrical current supplied to the lighting sources  14 ,  16 ,  18  and  20  can be controlled according to a desired lighting operating temperature with respect to the electrochemical composition of the battery power source  58 . 
     According to one embodiment, the processor  112  determines the electrochemical composition of the battery power source  58  at time intervals, such as, but not limited to, detecting the electrochemical composition every five (5) minutes. By detecting the electrochemical composition of the battery power source  58  at predetermined time intervals, the power consumption of the processor  112  and processing load of the processor  112  for the electrochemical composition determination is limited when compared to continuously determining the electrochemical composition of the battery power source  58 . Further, by determining the electrochemical composition of the battery power source  58  at predetermined time intervals, the processor  112  can confirm or correct the previous electrochemical composition determination and/or determine the electrochemical composition of the newly connected battery power source  58 . While time intervals may be used to determine the electrochemical composition of the battery power source  58 , it should be appreciated that other events may trigger the determination of battery cell chemistry including light activation or use, temperature, lumen output, switching of modes, and other events, according to other embodiments. 
     According to one embodiment, a method of determining the electrochemical composition of the battery power source  58  is generally shown in  FIG. 17  at reference identifier  400 . The method  400  starts at step  402 , and proceeds to step  404 , wherein an open circuit voltage is determined. At step  406 , a closed circuit voltage is determined. Typically, the closed circuit voltage can be determined with respect to a known load. The method  400  then proceeds to step  408 , wherein the internal resistance (R INTERNAL ) of the battery source  58  is determined based upon the open circuit voltage, the closed circuit voltage, and an operating electrical current. At step  410 , the electrochemical composition of the battery power source  50  is determined based upon the internal resistance (R INTERNAL ) and the open and close circuit voltages. 
     Once the electrochemical composition of the battery power source  50  is determined, method  400  advantageously employs the determined electrochemical composition to control one or more light sources  14 ,  16 ,  18  and  20  of the lighting device  10 . Proceeding to step  412 , method  400  determines if the battery cell is a lithium battery cell according to the disclosed embodiment. If the battery cell is determined to be a lithium battery cell, method  400  proceeds to step  414  to supply a first higher power to one or more of the light sources so as to provide a higher lighting intensity from the actuated light source. Whereas, if the battery cell is determined not to be a lithium cell, method  400  proceeds to step  416  to supply a second lower power to the one or more lighting devices so as to operate the selected lighting device at a lower light intensity. In this example, the battery cell that is determined not to be a lithium cell may be assumed to be an alkaline battery cell or other cell generally having a more limited power capability as compared to a lithium battery. 
     While the method  400  of detecting a battery chemistry composition and controlling the lighting device controls the lighting device based on detection of either a lithium or a non-lithium battery cell according to one embodiment, it should be appreciated that the method  400  may further determine other types of electrochemical cell batteries including, but not limited to, carbon-zinc alkaline cells, lithium cells, lithium ion cells, and nickel metal hydroxide electrochemical cells, according to other embodiments. The routine  400  thereby ensures that the lighting device  10  is sufficiently operated at a light illumination that achieves the required minimum time period of operation with optimum light illumination. The method  400  may controls various features and operating characteristics of the lighting device  10 , and may further provide an indication of the available electrical charge, based on the determined electrochemical composition, according to further embodiments. 
     According to one example, the white LED  14  may be controlled to achieve 6 hours of continuous operation by driving the white LED  14  at an electrical current of approximately 60 milliamps to achieve 20 lumens of light illumination when the power source is a single AA-size alkaline electrochemical cell battery. The white LED  14  may be controlled to be driven at a higher current of 120 milliamps to achieve 40 lumens of light illumination for 6 continuous hours when the power source is a single AA-size lithium battery cell. While an example of 6 hours of operation time is being described herein, it should be appreciated that the minimum required operating time may include any designated time period. 
     Additionally, the lighting device  10  may be controlled to provide a minimum amount of lesser illumination light sufficient to allow a user to change out the battery when the battery approaches depletion of sufficient stored energy and nears the end of its life. Specifically, it may be desirable to provide for a time period, such as half an hour, of reduced lighting intensity to ensure extended availability of at least some lighting while providing sufficient time for the user to change out the battery. If a fuel gauge device is employed, the fuel gauge may warn the user of the need to change the battery, and the lighting device  10  may be controlled based upon the determined chemistry detection to optimize availability of the light source for a minimum required time period. 
     As illustrated in  FIG. 21 , the percentage depth of discharge, voltage potential, and the internal resistance (R INTERNAL ) of a power source differs based upon the electrochemistry composition of the power source. Typically, the voltage potential of the power source changes based upon the percentage depth of discharge at one rate of change, and the internal resistance (R INTERNAL ) of the power source alters based upon the percentage of discharge at a second rate of change. Thus, by comparing the voltage potential and the internal resistance (R INTERNAL ) when the electrochemistry composition of the power source is determined, the percent depth of discharge can then be determined. 
     Referring to  FIG. 22 , electrochemistry composition test circuitry  490  is illustrated for detecting chemistry composition of a battery cell  58 , according to one embodiment. It should be appreciated that the test circuitry  490  may be built into the lighting device and may be included as part of the control circuitry. Alternately, the test circuitry  490  may be a separate circuit. Test circuitry  490  employs the microprocessor  110  powered by a voltage supply of five volts (+5 v), according to one example. It should be appreciated that a voltage boost circuit may be employed to boost a voltage of the battery cell  58  to five volts to power the microprocessor  110 . The test circuitry includes a known load resistance R LOAD  connectable via a switch, shown as a field effect transistor (FET) Q, in parallel with the battery cell  58 . According to one embodiment, the load resistance R LOAD  has a known value of 2.2 ohms. Connected in series with the load resistance R LOAD  is the transistor Q for switching the load resistance R LOAD  in or out of a closed circuit with the battery cell  58 . Switch Q may be implemented as an FET transistor controlled by an output of the microprocessor  110 . Transistor Q may be controlled by the microprocessor  110  to apply the load resistance R LOAD  across the battery cell  58  to allow for measurement of the closed circuit voltage and current, and may be opened to allow for measurement of the open circuit voltage of the battery cell  58 . Voltage measurements may be taken from the positive (+) terminal of battery cell  58  by an RC circuit coupled to the microprocessor  110 . 
     It should be appreciated that according to the illustrated test circuit  490 , a switch SW may be actuated by depression to initiate the chemistry composition test, according to one embodiment. However, it should be appreciated that the test circuitry  490  may be implemented automatically by the microprocessor  110  based on time intervals, or other triggering events such as activating one or more light sources or changing (replacing) one or more batteries. Further, three LEDs are shown connected to the microprocessor  110 , The three LEDs may include light sources of the lighting device, or may include additional lighting indicators that may be used to indicate the determined type of battery cell chemistry composition. For example, a first LED may be employed to indicate detection of a lithium battery cell, a second LED may be employed to indicate detection of a nickel metal hydride battery cell, and a third LED may be used to indicate detection of an alkaline battery cell. 
     Referring to  FIG. 23 , a method of determining the electrochemical composition of a battery power source  58  is generally illustrated at reference identifier  500 , according to another embodiment. The method  500  starts at step  502 , and proceeds to step  504  to apply a known load resistance R LOAD  of about 2.2 ohms, according to one example, to the battery cell  58  for a test time period of about 100 milliseconds, according to one example. During the chemistry detection test, method  500  determines an open circuit voltage V oc  in step  506  and a closed circuit voltage V cc  in step  508 . The open circuit voltage V oc  is determined with the load not applied to the battery cell such that the battery circuit is open-circuited and no current flows in or out of the battery cell, whereas the closed circuit voltage V cc  is determined when the known load resistance R LOAD  is applied across the battery cell terminals such that current flows across the load resistance R LOAD . The method  500  then proceeds to step  510 , wherein the internal resistance (R INTERNAL ) of the battery cell  58  is determined based upon the open circuit voltage V oc  and closed circuit voltage V cc . According to one embodiment, current may also be used to determine the internal resistance of the battery cell. The internal resistance value is determined as a decimal equivalent value, according to the disclosed embodiment, which is determined based on a multiplication factor, such as 1/1000 th  of the actual resistance. It should be appreciated that the internal resistance may be determined as an actual ohmic value, according to another embodiment. 
     The battery chemistry detection method  500  then proceeds to decision step  512  to compare the open circuit voltage V oc  to a voltage threshold of about 1.65 volts, according to one embodiment. If the open circuit voltage V oc  is greater than the voltage threshold of 1.65 volts, method  500  determines that the battery cell is a lithium cell in step  514 , and proceeds to supply a first higher power to a light source, when activated, in step  516  since the lithium battery cell in the given example has the highest battery capacity. 
     If the open circuit voltage V oc  is not greater than 1.65 volts, method  500  proceeds to decision step  518  to determine if the internal resistance value is less than a low first value of 89. If the internal resistance value is less than the value of 89, method  500  determines that the battery cell is a nickel metal hydride (NiMH) in step  520 . When the battery cell is determined to be a nickel metal hydride cell, method  500  supplies a second medium power to the light source(s), when activated, in step  522 . Accordingly, a nickel metal hydride battery in this example is considered a medium power battery and the power supplied to the light source(s) is controlled to provide a medium power supply that is less than the high power supply and greater than a low power supply. 
     If the internal resistance R INTERNAL  value is equal to or greater than the low first value of 89, method  500  proceeds to decision step  524  to determine if the internal resistance R INTERNAL  value is in a range between the low first value of 89 and a high second value of 150. If the internal resistance value is between the low value of 89 and the high value of 150, method  500  determines that the battery cell is a lithium cell in step  526 , and then proceeds to supply the first higher power to the light source(s), when activated, in step  516 . It should be appreciated that the battery cell may be determined to be a lithium battery cell which has a voltage less than or equal to 1.65 volts and has an internal resistance value between low value 89 and high value 150 when the lithium battery cell has been partially discharged, as opposed to a fully charged lithium battery cell. 
     If the internal resistance R INTERNAL  value is greater than or equal to the second high value 150 in decision step  524 , method  500  proceeds to step  528  to determine that the battery cell is an alkaline battery cell. When the battery cell is determined to be an alkaline battery cell, method  500  supplies a third lower power to the light source(s), when activated, in step  530 . Accordingly, a high internal resistance value is used to determine that an alkaline battery cell is present such that a light source may be adjusted to receive only a lower power so that the light source may be operated sufficiently long in duration. Once the light source has been supplied power at the appropriate power level according to the determined battery cell composition, routine  500  ends at step  532 . It should be appreciated that method  500  may be repeated at select intervals or based on any of the number of triggering events, such as replacement of the batteries, actuation of a light source, and other events. 
     It should further be appreciated that the internal resistance value and chemistry composition of multiple cells employed in the lighting device  10  may be determined, according to further embodiments. In one embodiment, multiple battery cells connected in series may be tested to determine the internal resistance R INTERNAL  of each battery cell and the electrochemical composition of each battery cell, as shown by the circuit  550  in  FIG. 24 . In this embodiment, a plurality of battery cells  58 , labeled BAT  1 -BAT n are shown connected in series, such that the positive terminal of one battery electrically contacts the negative terminal of an adjoining connected battery. Each battery cell  58  generates a voltage potential and, in a series connection, the voltage potentials are summed together. The chemistry detection circuit  550  is shown including the microprocessor  110  having a plurality of voltage sensing lines for sensing voltages V 1 -V n  which measure the voltage potential at the positive terminals of each of the plurality of batteries BAT  1 -BAT n, respectively. The sensed voltage of BAT  1  is voltage V 1 , the sensed voltage of BAT  2  is the difference between voltages V 2  and V 1 , etc. 
     The battery chemistry detection circuit  550  includes three switches, shown as FET transistors Q 1 -Q n  each having a control line for receiving a control signal from microprocessor  110 . Transistor Q 1  switches the known load resistance R LOAD  into a closed circuit connection with the first battery BAT  1  in response to a control signal from the microprocessor  110 . Transistor Q 2  switches the load resistance R LOAD  into a closed circuit connection with batteries BAT  1  and BAT  2 . Transistor Q n  switches the load resistance R LOAD  into connection with batteries BAT  1 -BAT n. 
     When transistor Q 1  is closed, the load resistance R LOAD  is applied across the first battery BAT  1 , such that current flows through the first battery and the load resistance R LOAD . During a test procedure, the open circuit voltage for voltage potential V 1  is measured when the load resistance R LOAD  is not applied across the battery BAT  1 , and the closed circuit voltage V cc  is measured while the load resistance R LOAD  is applied across battery BAT  1 . When transistor Q 2  is closed, the open and closed circuit voltages of the voltage potentials V 1  and V 2  are measured during the test procedure. Similarly, when transistor Q n  is closed, the open and closed circuit voltages of voltage potentials V 1 -V n  are measured during the test procedure. 
     It should be appreciated that the open circuit voltage of the first battery BAT  1  is determined by sensing voltage V 1 , whereas the open circuit voltage of the second battery BAT  2  is determined by subtracting the voltage V 1  from voltage V 2 , and the open circuit voltage of BAT n is determined by subtracting voltage V n-1  from voltage V n . The closed circuit voltages are also similarly measured. The internal resistance of each battery may be determined according to the following equations: 
     
       
         
           
             
               
                 R 
                 
                   INTERNAL 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
               = 
               
                 
                   
                     
                       V 
                       
                         oc 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                     - 
                     
                       V 
                       
                         cc 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   
                     V 
                     
                       cc 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                 
                 · 
                 
                   R 
                   LOAD 
                 
               
             
             ; 
           
         
       
       
         
           and 
         
       
       
         
           
             
               
                 R 
                 
                   INTERNAL 
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                   1 
                 
               
               + 
               
                 R 
                 
                   INTERNAL 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
             
             = 
             
               
                 
                   
                     V 
                     
                       
                         oc 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       + 
                       1 
                     
                   
                   - 
                   
                     V 
                     
                       
                         cc 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       + 
                       1 
                     
                   
                 
                 
                   V 
                   
                     
                       cc 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                     + 
                     1 
                   
                 
               
               · 
               
                 
                   R 
                   LOAD 
                 
                 . 
               
             
           
         
       
     
     V oc1  represents the open circuit voltage of battery BAT  1 , and V cc1  represents the closed circuit voltage of battery BAT  1 . V oc2  represents the open circuit voltage of battery BAT  2 , and V cc2  represents the closed circuit voltage of battery BAT  2 . The internal resistance R INTERNAL1  is the internal resistance of the first battery BAT  1 . The internal resistance R INTERNAL2  is the internal resistance of the second battery BAT  2 . It should be appreciated that the internal resistance of further batteries up to BAT n may likewise be determined. 
     It should further be appreciated that the battery chemistry detection circuit  550  may detect different types of batteries, such as alkaline, nickel metal hydride and lithium battery cells used in various combinations. While one example of a battery chemistry detection circuit  550  has been illustrated for detecting chemistry of a plurality of battery cells in a series connection, it should be appreciated that other configurations of circuit  550  may be employed to detect other arrangements of batteries, such as a plurality of batteries connected in parallel and/or series, in various battery cell numbers and combinations. 
     Referring to  FIGS. 25A-25B , a method of determining the electrochemical composition of a battery power source is generally illustrated at reference identifier  600 , according to another embodiment. In this embodiment, the method  600  determines a recovery time period for the battery under test to return to a predetermined percentage of its voltage, and further determines the electrochemical composition of the battery based on the determined recovery time. It should also be appreciated that method  600  determines the electrochemical composition of the battery as a function of the determined recovery time, in combination with one or more of the internal resistance, the open circuit voltage (V oc ), and the closed circuit voltage (V cc ). 
     With particular reference to  FIG. 26 , the output voltages of three different batteries having different electrochemical compositions are illustrated during a test procedure to detect battery chemistry. Included in the test is a lithium battery cell having a voltage shown by line  650 , an alkaline battery cell having a voltage shown by line  652  and a nickel metal hydride battery cell having a voltage shown by line  654 . Each of the batteries were subjected to a load resistance R LOAD  of about 0.1 ohms for a time period of about 11 milliseconds. Prior to application of the load, the battery cells each had a substantially constant voltage, and during application of the load resistance, the output voltage drops significantly as shown during the time period from 0.000 to 0.011 seconds. At time period 0.011 seconds, the load resistance is no longer applied and the voltage of each of the battery cells recovers over a period of time. The period of time that it takes each battery cell to recover to percentage threshold of 98.5 percent of the voltage prior to applying the load is referred herein as the recovery time. It should be appreciated that in the example shown, a battery cell that recovers to 98.5 percent of the preload voltage in less than 1 millisecond is determined to be a nickel metal hydride battery, whereas the lithium and alkaline battery cells have a longer recovery time, according to the present embodiment of the chemistry detection test process. 
     Returning to  FIGS. 25A-25B , method  600  starts at step  602 , and proceeds to step  604  to apply a known load resistance R LOAD  of about 0.1 ohm, according to one example, to the battery cell for a test period of about 11 milliseconds, according to one example. It should be appreciated that the test period may include other time periods, and that the load resistance R LOAD  may have other values. During the chemistry detection test, method  600  determines an open circuit voltage V oc  in step  606  and a closed circuit voltage V cc  in step  608 . The open circuit voltage V oc  is determined with the load resistance not applied to the battery cell such that the battery circuit is open-circuited and no current flows in or out of the battery cell, whereas the closed circuit voltage V cc  is determined when the known load resistance R LOAD  is applied across the battery cell terminals such that current flows across load resistance R LOAD . The method  600  then proceeds to step  610 , wherein the internal resistance R INTERNAL  of the battery cell is determined based upon the open circuit voltage V oc  and closed circuit voltage V cc . In the example shown in block  610 , the internal resistance R INTERNAL  is shown as the difference between the open circuit voltage V oc  and the closed circuit voltage V cc  multiplied by the resistance load R LOAD  multiplied by a multiplication factor of 1000 and divided by the closed circuit voltage V cc . The internal resistance value R INTERNAL  may be determined as a decimal equivalent value, based on a multiplication factor such as 1000, or may include the actual ohmic value of resistance. 
     Routine  600  then proceeds to step  612  to determine the recovery time of the battery to reach 98.5 percent of the output voltage prior to application of the load. The recovery time is monitored from the time that the load resistance R LOAD  is no longer applied to the battery until the voltage of the battery rises to about 98.5 percent of the voltage prior to applying the load. While a recovery time based on 98.5 percent is disclosed according to the present embodiment, it should be appreciated that the recovery time may be based on other percentage values or voltage levels. 
     The battery chemistry detection method  600  then proceeds to decision step  614  to compare the open circuit voltage V oc  to a voltage threshold of about 1.65 volts, according to one embodiment. If the open circuit voltage V oc  is greater than the voltage threshold of 1.65 volts, method  600  determines that the battery cell is a lithium cell in step  616 , and proceeds to supply a first higher power to a light source, when activated, in step  618 , since the lithium battery cell in the given example has the highest battery capacity. Method  600  then ends at step  638 . 
     If the open circuit voltage V oc  is not greater than 1.65 volts, method  600  proceeds to decision step  620  to determine if the determined recovery time is less than 1 millisecond. If the recovery time is determined to be less than 1 millisecond, routine  600  proceeds to determine that the battery cell is a nickel metal hydride (NiMH) cell in step  622 . When the battery cell is determined to be a nickel metal hydride cell, method  600  supplies a second medium power to a light source, when activated, in step  624 , and then ends at step  638 . Accordingly, a nickel metal hydride battery cell in this example is considered a medium power battery cell and the power supplied to the light source(s) is controlled to supply a medium power supply that is less than the high power supply and greater than a lower power supply, according to disclosed embodiment. Since any fresh lithium cell would have been detected in step  614 , step  620  is able to detect a nickel metal hydride battery cell based on the recovery time. 
     If the recovery time is not less than 1 millisecond, method  600  proceeds to decision step  626  to determine if the closed circuit voltage V cc  is less than 0.9 volts. If the closed circuit voltage V cc  is less than 0.9 volts, method  600  determines that the battery cell is an alkaline battery cell in step  628 . When the cell is determined to be an alkaline battery cell, method  600  supplies a third lower power to a light source, when activated, in step  630 , and then ends at step  638 . Accordingly, a low closed circuit voltage below 0.9 volts is used to determine than an alkaline battery cell is present such that a light source may be adjusted to receive only a lower power so that the light source may be operated sufficiently long in duration. 
     If the closed circuit voltage is not less than 0.9 volts, method  600  proceeds to decision step  632  to determine if the open circuit voltage V oc  is greater than 1.60 volts. If the open circuit voltage is greater than 1.60 volts, method  600  proceeds to step  628  to determine that the cell is an alkaline battery cell, and then supplies the third lower power to the light source in step  630 . Accordingly, an open circuit voltage V oc  greater than 1.60 volts at the step  632  of method  600  is indicative of a fresh high capacity alkaline battery cell. 
     If the open circuit voltage V oc  is not less than 0.9 volts and not greater than 1.60 volts, method  600  proceeds to decision step  634  to determine if the internal resistance R INTERNAL  count is less than a value of 50. If the internal resistance value is less than a value of 50, method  600  determines that the battery cell is a nickel metal hydride battery cell in step  622 , and then proceeds to supply the second medium power to the light source in step  624 . Accordingly, the internal resistance count may be employed to determine the presence of a nickel metal hydride battery cell. 
     If the internal resistance count is not less than 50, method  600  proceeds to decision step  636  to determine if the open circuit voltage V oc  is greater than 1.5 volts. If the open circuit voltage V oc  is greater than 1.5 volts, method  600  proceeds to step  616  to determine that the cell is a lithium battery cell and then supplies the first higher power to the light source in step  618 . Otherwise, if the open circuit voltage V oc  is not greater than 1.5 volts, method  600  proceeds to step  628  to determine the cell is an alkaline battery cell and then supplies the third lower power to the light source in step  630  before ending at step  638 . Accordingly, step  636  is able to distinguish between a lithium battery cell and an alkaline battery cell based on the open circuit voltage V oc . 
     While chemistry detection and control method  600  advantageously determines the chemistry composition of a battery cell based on internal resistance, recovery time, open circuit voltage and closed circuit voltage, it should be appreciated that the method  600  may look to one or more or any combination of these characteristics to determine the chemistry composition of the battery cell. It should further be appreciated that the method  600  may control any of a number of devices, including lighting devices, cameras, cell phones and other electrically powered devices based on the determined chemistry composition. Further, it should be appreciated that a stand alone battery chemistry detection device may be employed to determine the chemistry of the battery cell, which device may then be useful to provide an indication of the battery cell type and/or to control operation of an electronic device. 
     Referring to  FIGS. 18 and 19 , a three-position toggle switch  22 ′ is illustrated according to a second embodiment of the present invention. The three-position switch  22 ′ shown in the second embodiment employs a toggle switch that is required to be pushed and rotated into one of three contact positions. By requiring double action of pushing and sliding/rotation, the switch  22 ′ allows for controlled operation between the side light mode, IR mode and visible light modes while preventing accidental unintended movement of the switch  22 ′ to an unintended position. This advantageously allows for the lighting device  10  to be activated in the side light or IR modes which are typically desirable in stealth conditions and prevents accidental activation of a visible light source due to accidental or unintended activation of the switch  22 ′. 
     As seen in  FIGS. 18 and 19 , the three-position switch  22 ′ includes a toggle switch box  36 A having a pin  36 C extending therefrom and assembly  36 B. In addition, switch  22  includes bracket  36 D, and a rotating arm  36  having an opening for receiving pin  36 C and having prongs  36 G for engaging a tooth  36 H in the off position or for engaging channels  36 I or  36 J in the side light or IR switch positions. 
     As seen in  FIGS. 20A-20D , the three-position switch  22  is actuatable by a user to achieve a desired lighting operation. In the off position of switch  22 ′, arm  36 E has prongs  36 G engaged with tooth  364  of bracket  36 F when pin  36 C of the toggle switch  22 ′ is in the central position as shown in  FIG. 20A . In order to actuate switch  22 ′ to the side light position, actuator member  37  is depressed as shown in  FIG. 20B  which pushes bracket  36 F and its tooth  36 H away from and out of engagement with prongs  36 G of arms  36 E. With the actuation member  37  depressed, the switch  22 ′ may be slid or rotated to the side light position as shown in  FIG. 20C  and actuation member  37  may then be released as shown in  FIG. 20D  such that the bracket  36 F returns to trap the prongs  36 G of arm  36 E into the locked position in the side light mode. In this position, toggle pin  36  may not be easily rotated as it requires first a push and then a rotation movement. To place switch  22 ′ in the IR mode, the actuator member  37  is depressed and rotated in the opposite direction to lock the prongs  36 G into engagement with the other slot of bracket  36 F. The three-position switch  22 ′ thereby provides for user controlled reliable switching between the various lighting modes while inhibiting accidental switching to unintended lighting modes. 
     It should be appreciated that the lighting device  10  may be useful in various applications. For example, the light body  12  may be connected to a mount assembly that enables the lighting device  10  to be employed on an article of clothing, such as a headband, a baseball cap or visor, or anywhere else. 
     While the invention has been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and changes therein may be affected by those skilled in the art without departing from the spirit of the invention. Accordingly, it is our intent to be limited only by the scope of the appending claims and not by way of the details and instrumentalities describing the embodiments shown herein.