Patent Publication Number: US-8970388-B2

Title: Battery life indication techniques for an electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 13/051,669, filed Mar. 18, 2011. 
    
    
     TECHNICAL FIELD 
     Embodiments of the subject matter described herein relate generally to power control, management, and monitoring for electronic devices, such as fluid infusion pumps, analyte sensor devices, mobile phones, and the like. More particularly, embodiments of the subject matter relate to power management and battery life indication schemes for a portable electronic device having a primary battery and a secondary battery. 
     BACKGROUND 
     The prior art is replete with various types of electronic devices. For example, portable medical devices are useful for patients that have conditions that must be monitored on a continuous or frequent basis. In this regard, diabetics are usually required to modify and monitor their daily lifestyle to keep their blood glucose (BG) in balance. Some diabetics use portable insulin pump systems that are designed to deliver accurate and measured doses of insulin via infusion sets (an infusion set delivers the insulin through a small diameter tube that terminates at, e.g., a cannula inserted under the patient&#39;s skin). Portable insulin pumps are usually powered by either an alkaline battery, a lithium-ion battery, or a rechargeable battery. 
     One drawback with battery operated devices is the inability to utilize all of the energy stored in the battery due to the natural voltage decay associated with energy depletion. This particular problem is most prevalent with alkaline batteries, which tend to suffer a drop in voltage after a relatively short period of time even though an adequate amount of stored energy remains. Lithium and nickel-metal hydride (NiMH) batteries tend to maintain a more stable voltage over time, which generally allows for a higher percentage of the stored energy to be utilized, relative to the amount of stored energy typically utilized with alkaline batteries. Although lithium and NiMH batteries maintain a very stable voltage over time, they suffer from a sharp voltage drop at the end of life. Predicting when this drop will occur is very difficult and often requires a great deal of testing and characterization to allow for a sufficient user warning before the actual end of the battery life. 
     The remaining amount of battery life is often displayed on an electronic device in the form of a graphical icon, an indicator, a graph, or the like. Conventional battery life indicators used with consumer devices (e.g., mobile phones, digital media players, and video game devices) can be inaccurate and imprecise. Moreover, conventional battery life indicators may not use a proportional time scale for purposes of representing the remaining amount of battery life. For example, if the total lifespan of a replaceable battery is ten days for a given electronic device, a conventional battery life indicator might indicate full battery capacity for eight days, and thereafter indicate a quick decrease in battery capacity. Thus, it would be desirable to have a battery life indicator that accurately and proportionately indicates the remaining amount of battery life relative to actual runtime of the battery. 
     BRIEF SUMMARY 
     An exemplary embodiment of a power management method for an electronic device having a primary battery and a secondary battery is provided. The method involves operating the electronic device in different power phases: a first power phase during which the primary battery provides energy to support all functions of the electronic device; a second power phase during which the primary battery provides energy to support basic functions of the electronic device, and during which the secondary battery provides energy to support high power functions of the electronic device; and a third power phase during which the secondary battery provides energy to support all functions of the electronic device. 
     Also provided is an exemplary embodiment of a power management method for an electronic device having a primary battery, a secondary battery, a voltage converter to convert an output voltage of the primary battery to a main supply voltage for the electronic device, a first voltage rail to provide operating voltage for basic functions of the electronic device, a second voltage rail to provide operating voltage for high power functions of the electronic device, and a power distribution system. The method monitors the main supply voltage during operation of the electronic device and arranges the power distribution system in an appropriate manner. The method initially operates the power distribution system in a first power phase such that the primary battery provides voltage for the first voltage rail and the second voltage rail. The method transitions the power distribution system from the first power phase to a second power phase such that the primary battery provides voltage for the first voltage rail, and such that the secondary battery provides voltage for the second voltage rail. Transitioning from the first power phase to the second power phase is triggered when the main supply voltage falls below a threshold value while monitored during the first power phase. The method also transitions the power distribution system from the second power phase to a third power phase such that the secondary battery provides voltage for the first voltage rail and the second voltage rail. Transitioning from the second power phase to the third power phase is triggered when the main supply voltage falls below the threshold value while monitored during the second power phase. 
     An exemplary embodiment of a power distribution system for a portable electronic device is also provided. The power distribution system includes: a first voltage rail to provide operating voltage for basic functions of the electronic device; a second voltage rail to provide operating voltage for high power functions of the electronic device; a primary battery coupled in a selectable manner to the first voltage rail and the second voltage rail; a secondary battery coupled in a selectable manner to the first voltage rail and the second voltage rail; a selection architecture coupled to the first voltage rail, the second voltage rail, the primary battery, and the secondary battery; and a control module to regulate operation of the selection architecture in accordance with different power phases. 
     An exemplary embodiment of a method of controlling a battery life indicator for a primary battery of an electronic device is also presented. The method involves: monitoring a battery voltage of the primary battery; obtaining at least one operating parameter of the electronic device other than the battery voltage of the primary battery; and generating the battery life indicator with characteristics that represent remaining battery life of the primary battery, wherein the characteristics are dictated by the monitored battery voltage and the obtained at least one operating parameter. 
     Also provided is an exemplary embodiment of a method of controlling a battery life indicator for an electronic device having a primary battery and a secondary battery. The electronic device operates in either a first power phase during which only the primary battery supports functions of the electronic device, a second power phase during which both the primary battery and the secondary battery support functions of the electronic device, or a third power phase during which only the secondary battery supports functions of the electronic device. The method involves: determining whether the electronic device is operating in the first power phase, the second power phase, or the third power phase, resulting in a determined power phase; obtaining a runtime measurement for the primary battery; and generating the battery life indicator with characteristics that represent remaining battery life of the primary battery, wherein the characteristics are controlled by the determined power phase and the obtained runtime measurement. 
     An exemplary embodiment of a battery monitor system for an electronic device having a primary battery and a secondary battery is also presented. The battery monitor system includes: a voltage monitor that monitors a battery voltage of the primary battery; a control module to operate the electronic device in a designated power phase corresponding to either a first power phase, a second power phase, or a third power phase; a runtime counter to maintain a runtime measurement for the primary battery; and a battery life indicator controller coupled to the voltage monitor, the control module, and the runtime counter to generate a battery life indicator for the electronic device that indicates an amount of remaining battery life of the primary battery. The amount of remaining battery life is governed by at least two of: the battery voltage of the primary battery; the designated power phase; and the runtime measurement. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the subject matter may be derived by referring to the detailed description and claims when considered in conjunction with the following figures, wherein like reference numbers refer to similar elements throughout the figures. 
         FIG. 1  illustrates voltage level versus time provided by different types of batteries; 
         FIG. 2  is a plan view of an exemplary embodiment of a fluid infusion device; 
         FIG. 3  is a schematic block diagram representation of an exemplary embodiment of a fluid infusion device; 
         FIG. 4  is a schematic representation of an exemplary embodiment of a power distribution system suitable for use with an electronic device such as the fluid infusion device shown in  FIG. 3 ; 
         FIG. 5  is a flow chart that illustrates an exemplary embodiment of a phased power management process associated with the operation of an electronic device; 
         FIG. 6  is a flow chart that illustrates an exemplary embodiment of a battery life indicator process associated with the operation of an electronic device; and 
         FIG. 7  is a flow chart that illustrates a particular embodiment of a battery life indicator process associated with the operation of an electronic device. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely illustrative in nature and is not intended to limit the embodiments of the subject matter or the application and uses of such embodiments. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Any implementation described herein as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     Techniques and technologies may be described herein in terms of functional and/or logical block components, and with reference to symbolic representations of operations, processing tasks, and functions that may be performed by various computing components or devices. It should be appreciated that the various block components shown in the figures may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of a system or a component may employ various integrated circuit components, e.g., memory elements, digital signal processing elements, logic elements, look-up tables, or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. 
     The subject matter described here relates to battery systems, power management, displayed battery life indicators, and related processes that may be carried out by an electronic device. The electronic device will typically be a portable or mobile device, although portability is not a requirement. In practice, a portable electronic device may be a personal medical device (e.g., a fluid infusion device such as an insulin pump, a glucose sensor, a transmitter, a pacemaker, or any type of medical monitor), a mobile phone, a handheld computer, a digital media player, a video game device, an electronic book reader, or the like. Indeed, the subject matter presented here applies to any electronic device that is powered or can be powered by a removable primary battery and a secondary battery. 
     Although certain exemplary embodiments are described below in the context of a fluid infusion device, the concepts and methodologies need not be limited to that particular application. Moreover, for the sake of brevity, conventional techniques and technologies related to infusion system operation, insulin pump and/or infusion set operation, blood glucose sensing and monitoring, and other functional aspects of the systems (and the individual operating components of the systems) may not be described in detail here. Examples of infusion pumps and/or related pump drive systems used to administer insulin and other medications may be of the type described in, but not limited to, U.S. Pat. Nos. 4,562,751; 4,678,408; 4,685,903; 5,080,653; 5,505,709; 5,097,122; 6,485,465; 6,554,798; 6,558,351; 6,659,980; 6,752,787; 6,817,990; 6,932,584; and 7,621,893; which are herein incorporated by reference. 
     Many portable electronic devices are powered by one or more batteries. The standard AA battery is commonly used in a wide variety of electronic devices, including portable medical devices. The nominal voltage of a AA battery is typically within the range of about 1.25 to 1.65 volts, depending upon the chemistry type of the AA battery. Electronic devices are often powered by alkaline, nickel-cadmium (NiCad), lithium, or lithium-ion batteries. Different types of batteries exhibit different voltage characteristics over time. In this regard,  FIG. 1  illustrates voltage level versus time provided by different types of batteries. 
     The plot  10  in  FIG. 1  represents a typical voltage curve for a replaceable alkaline battery. The alkaline battery begins its life at a relatively high voltage, e.g., approximately 1.55 volts for a AA size battery, but its initial voltage drops after a short amount of time. Thereafter, its voltage decreases somewhat gradually over time. In contrast, a lithium battery is capable of providing a much higher initial voltage and sustaining relatively high voltage for a long period of time. However, as illustrated by the plot  14  in  FIG. 1 , a lithium battery typically experiences a sharp voltage drop at or near its end of life. This rapid drop in voltage is represented by the “knee” characteristic of the plot  14 . If a lithium battery is being used in a portable electronic device, a user of the portable electronic device may have only a short amount of time after receiving a low battery message before the portable electronic device loses power. A rechargeable battery can be a good economic solution for an owner of a portable electronic device. Rather than buying new replaceable batteries, the user may utilize household current to charge a rechargeable battery after the battery has expended its energy. Many portable electronic devices cannot utilize rechargeable batteries because the initial voltage supplied by rechargeable batteries is too low to satisfy the operating requirements of those devices. The rechargeable battery has characteristics similar to the alkaline battery in terms of how long it can power a device, but as illustrated by the plot  16  in  FIG. 1 , the initial voltage supplied by the rechargeable battery is lower than the initial voltage supplied by the alkaline battery. 
     The electronic device described below employs a primary battery (which is a replaceable battery in the exemplary embodiment) and a secondary battery (which is a “permanent” or non-replaceable rechargeable battery in the exemplary embodiment). The electronic device carries out a power management scheme that enables the electronic device to utilize most of the stored energy in the primary battery before it needs to be replaced. The power management scheme allows the electronic device to efficiently and interchangeably use alkaline, lithium, and other battery types as the primary battery. In practice, the power management scheme could also leverage some of the features described in U.S. Pat. No. 7,737,581, the relevant content of which is incorporated by reference herein. 
     As mentioned above, a portable medical device such as a fluid infusion device could leverage the power management and battery life indication techniques presented here. In this regard,  FIG. 2  is a plan view of an exemplary embodiment of a fluid infusion device  100 .  FIG. 2  also shows an infusion set  102  coupled to the fluid infusion device  100 . The fluid infusion device  100  is designed to be carried or worn by the patient. The fluid infusion device  100  may leverage a number of conventional features, components, elements, and characteristics of existing fluid infusion devices. For example, the fluid infusion device  100  may incorporate some of the features, components, elements, and/or characteristics described in U.S. Pat. Nos. 6,485,465 and 7,621,893, the relevant content of which is incorporated by reference herein. 
     This embodiment shown in  FIG. 2  includes a user interface  104  having several buttons that can be activated by the user. These buttons can be used to administer a bolus of insulin, to change therapy settings, to change user preferences, to select display features, and the like. Although not required, the illustrated embodiment of the fluid infusion device  100  includes a display element  106 . The display element  106  can be used to present various types of information or data to the user, such as, without limitation: the current glucose level of the patient; the time; a graph or chart of the patient&#39;s glucose level versus time; device status indicators, including a battery life indicator  107 ; etc. In some embodiments, the display element  106  is realized as a touch screen display element and, therefore, the display element  106  also serves as a user interface component. 
     The fluid infusion device  100  accommodates a fluid reservoir (hidden from view in  FIG. 2 ) for the fluid to be delivered to the user. Activation of an internal motor results in actuation of the fluid reservoir, which in turn delivers the fluid. A length of tubing  108  is the flow path that couples the fluid reservoir to the infusion set  102 . The tubing  108  extends from the fluid infusion device  100  to the infusion set  102 , which provides a fluid pathway with the body of the user. A removable cap or fitting  110  is suitably sized and configured to accommodate replacement of fluid reservoirs (which are typically disposable) as needed. In this regard, the fitting  110  is designed to accommodate the fluid path from the fluid reservoir to the tubing  108 . 
     As mentioned previously, the fluid infusion device  100  is suitably configured to support a number of power and battery related techniques, processes, and methodologies. In practice, the fluid infusion device  100  includes one or more electronics modules, processing logic, software applications, and/or other features that are used to carry out the various operating processes described here. In this regard,  FIG. 3  is a schematic block diagram representation of an exemplary embodiment of the fluid infusion device  100 .  FIG. 3  depicts some previously-described elements of the fluid infusion device  100  as functional blocks or modules, namely, the display element  106 ; the user interface  104 ; and the battery life indicator  107 .  FIG. 3  also depicts a fluid reservoir  111  and the infusion set  102  in block format. This particular embodiment of the fluid infusion device  100  also includes, without limitation: one or more electronics, processor, and control modules  120 ; a suitable amount of memory  122 ; a backlight element  124 , which may be integrated with the display element  106 ; an audio transducer element  126 ; a power distribution system  128 ; a voltage monitor  130  (which in certain embodiments may be realized as a voltage supervisor); a battery runtime counter  132 ; a motor  134  to actuate the fluid reservoir  111 ; and other infusion pump hardware, software, and applications  136 . The elements of the fluid infusion device  100  may be coupled together via an interconnection architecture  138  or arrangement that facilitates transfer of data, commands, power, etc. 
     The module(s)  120  may represent any number of electronics modules, processor modules, logical elements, controllers, and/or control modules of the fluid infusion device  100 . The module(s)  120  may include or be implemented with a general purpose processor, a plurality of cooperating processor devices, a content addressable memory, a digital signal processor, an application specific integrated circuit, a field programmable gate array, any suitable programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination designed to perform the functions described here. A processor device may be realized as a microprocessor, a controller, a microcontroller, or a state machine. Moreover, a processor device may be implemented as a combination of computing devices, e.g., a combination of a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other such configuration. 
     As described in more detail below, the module(s)  120  may be responsible for operating the fluid infusion device  100  in various power phases or modes to take better advantage of stored battery energy. In this regard, the module(s)  120  may be used to monitor and/or measure operating parameters of the fluid infusion device  100  (such as voltage levels), and regulate operation of switches, multiplexers, voltage converters, a battery charger, and the like. The module(s)  120  may also be responsible for controlling and generating the battery life indicator  107  in accordance with the methodologies described below. Moreover, a functional or logical module/component of the fluid infusion device  100  might be realized by, implemented with, and/or controlled by processing logic maintained by or included with the module(s)  120 . For example, the display element  106 , the user interface  104 , the motor  134 , and/or the infusion pump hardware, software, and applications  136  (or portions thereof) may be implemented in or controlled by the module(s)  120 . 
     The memory  122  may be realized as RAM memory, flash memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. In this regard, the memory  122  can be coupled to the module(s)  120  such that the module(s)  120  can read information from, and write information to, the memory  122 . In the alternative, the memory  122  may be integral to the module(s)  120 . As an example, a processor and the memory  122  may reside in an ASIC. In practice, a functional or logical module/component of the fluid infusion device  100  might be realized using program code that is maintained in the memory  122 . Moreover, the memory  122  can be used to store data utilized to support the operation of the fluid infusion device  100 , including, without limitation, voltage measurements, operating status data, battery voltage thresholds, and the like (as will become apparent from the following description). 
     The user interface  104  may include a variety of items such as, without limitation: a keypad, keys, buttons, a keyboard, switches, knobs (which may be rotary or push/rotary), a touchpad, a microphone suitably adapted to receive voice commands, a joystick, a pointing device, an alphanumeric character entry device or touch element, a trackball, a motion sensor, a lever, a slider bar, a virtual writing tablet, or any device, component, or function that enables the user to select options, input information, or otherwise control the operation of the fluid infusion device  100 . In this context, the user interface  104  may cooperate with or include a touch screen display element  106 . The user interface  104  allows a user to control the delivery of fluid via the infusion set  102 . 
     The display element  106  represents the primary graphical interface of the fluid infusion device  100 . The display element  106  may leverage known plasma, liquid crystal display (LCD), thin film transistor (TFT), and/or other display technologies. The actual size, resolution, and operating specifications of the display element  106  can be selected to suit the needs of the particular application. Notably, the display element  106  may include or be realized as a touch screen display element that can accommodate touch screen techniques and technologies. In practice, the display element  106  may be driven by a suitable display driver to enable the fluid infusion device  100  to display physiological patient data, status information, clock information, alarms, alerts, and/or other information and data received or processed by the fluid infusion device  100 . For example, the display element  106  could be used to display a graphical representation of the battery life indicator  107 , as shown in  FIG. 2 . 
     The fluid infusion device  100  may include the backlight element  124  integrated with or cooperating with the display element  106 . The backlight element  124  is illuminated when needed (or when commanded to do so) to enhance the readability of the contents rendered on the display element  106 . As explained in more detail below, operation of the backlight element  124  may be considered to be a high power function of the fluid infusion device  100  because activation of the backlight element  124  typically requires a high amount of electrical current, which consumes a relatively high amount of energy. Consequently, the backlight element  124  is coupled to a high power voltage rail of the fluid infusion device  100  (the voltage rail is not shown in  FIG. 3 ). 
     The fluid infusion device  100  may also include one or more audio transducer elements  126  to generate sound as needed or desired. In practice, the audio transducer element  126  requires a relatively high amount of energy to be driven properly (in certain embodiments, the audio transducer element  126  may be realized as a piezoelectric transducer, a speaker, or the like). Accordingly, operation of the audio transducer element  126  may be considered to be a high power function of the fluid infusion device  100  because activation of the audio transducer element  126  typically requires a high amount of electrical current, which consumes a relatively high amount of energy. Consequently, the audio transducer element  126  is also coupled to the high power voltage rail of the fluid infusion device  100 . 
     The power distribution system  128  is responsible for various power management and battery selection processes carried out by the fluid infusion device  100 . It should be appreciated that a module  120 , the voltage monitor  130 , the battery runtime counter  132 , and/or some of the other infusion pump hardware, software, and applications  136  may be considered to be a part of the power distribution system  128 . During operation of the fluid infusion device  100 , the power distribution system  128  is controlled and arranged to transition between different power phases (the different power phases are associated with primary battery operation and/or secondary battery operation). An exemplary embodiment of the power distribution system  128  is described in more detail below with reference to  FIG. 4 . 
     The voltage monitor  130  is suitably configured to monitor one or more voltage levels of the fluid infusion device  100 . In this regard, the voltage monitor  130  may be coupled to one or more voltage rails, voltage buses, electrical nodes, or the like for purposes of detecting and measuring the respective voltage. Alternatively (or additionally), the voltage monitor  130  could be incorporated into a power supply, a voltage converter, a device driver, or the like. For example, and without limitation, the voltage monitor  130  could monitor the primary battery voltage, the secondary battery voltage, the output of a voltage converter that converts the primary battery voltage, the output of a voltage converter that converts the secondary battery voltage, a main supply voltage rail, a high power voltage rail, a low power voltage rail, or the like. When monitoring the primary battery for generation of the battery life indicator  107 , the voltage monitor  130  may measure the primary battery voltage in a loaded state or in a virtually unloaded state (where loads that are not necessary for voltage measurement are disconnected from the primary battery). Although this description refers to a single voltage monitor  130 , an embodiment of the fluid infusion device  100  may utilize a plurality of voltage monitors  130  if so desired. 
     The battery runtime counter  132  keeps track of a runtime measurement for the primary battery (and, in certain embodiments, the secondary battery). This enables the fluid infusion device  100  to generate the battery life indicator  107  in a manner that is influenced by the runtime measurement. In practice, the battery runtime counter  132  may be realized as a timer that is reset whenever a primary battery is installed. The battery runtime counter  132  may keep track of the runtime in any desired unit or units of time, e.g., minutes, hours, days, or weeks. Alternatively, the battery runtime counter  132  could measure the runtime of the battery using any arbitrary reference system or unit of measurement. 
     An exemplary implementation of the battery life indicator  107  is shown in  FIG. 2 . For this embodiment, the battery life indicator  107  is realized as a dynamic graphical icon that is rendered on the display element  106 . The illustrated embodiment of the battery life indicator  107  includes multiple segments (four segments for this example). Moreover, each segment of the battery life indicator  107  is intended to represent a proportional amount of remaining battery life. Thus, if all four segments are displayed, then the battery could have up to 100% of its total life remaining. In contrast, only one displayed segment might indicate a low battery condition, a limited amount of remaining runtime, or a relatively low percentage of battery life remaining. 
     It should be appreciated that other embodiments may utilize more or less than four icon segments. Yet other embodiments could employ a different scheme to represent the remaining battery life of the battery using the battery life indicator  107 . For example, an embodiment of the battery life indicator  107  could be rendered in a continuous or virtually continuous manner that does not rely on distinct segments per se. As another example, an embodiment of the battery life indicator  107  could use alphanumeric characters that indicate the amount of remaining runtime and/or a percentage of remaining battery life. Yet other embodiments of the battery life indicator  107  could implement other graphical schemes or icons to represent the remaining battery life. 
     The motor  134  represents the fluid delivery or drive motor of the fluid infusion device  100 . The motor  134  is controlled and activated to actuate the fluid reservoir  111  to deliver fluid via the infusion set  102 . The motor  134  may also be controlled and activated to rewind the actuator of the fluid reservoir  111  to accommodate removal and replacement of the fluid reservoir  111 . As explained in more detail below, operation of the motor  134  may be considered to be a high power function of the fluid infusion device  100  because activation of the motor  134  typically requires a high amount of electrical current, which consumes a relatively high amount of energy. Consequently, the motor  134  is coupled to a high power voltage rail of the fluid infusion device  100  (the voltage rail is not shown in  FIG. 3 ). 
     The infusion pump hardware, software, and applications  136  are utilized to carry out other fluid infusion features, operations, and functionality that may not be the focus of this description. Thus, the infusion pump hardware, software, and applications  136  may include or cooperate with the infusion set  102  and/or the fluid reservoir  111  (as described above). It should be appreciated that the infusion pump hardware, software, and applications  136  may leverage known techniques to carry out conventional infusion pump functions and operations, and such known aspects will not be described in detail here. 
     As mentioned previously, the fluid infusion device  100  obtains its operating power from a primary battery and a secondary battery, which may be used independently or in conjunction with one another. The power distribution system  128  is controlled and manipulated in an appropriate manner such that the primary battery and the secondary battery support designated functions and operations of the fluid infusion device during specified power phases. In this regard,  FIG. 4  is a schematic representation of an exemplary embodiment of the power distribution system  128 . It should be appreciated that  FIG. 4  depicts only one possible implementation of the power distribution system  128 . Other embodiments of the host electronic device may utilize a power distribution system having a different architecture and topology than that shown in  FIG. 4 . 
     The illustrated embodiment of the power distribution system  128  includes or cooperates with a primary battery  202  and a secondary battery  204 . The primary battery  202  will typically be a replaceable battery, such as an alkaline or a lithium AA size battery, while the secondary battery  204  will typically be a rechargeable battery. In practice, the secondary battery  204  may be considered to be a backup battery. Moreover, in certain embodiments the secondary battery  204  is internal to the fluid infusion device  100 , and it is not accessible to the user. In other words, the secondary battery  204  may be a “permanent” and non-replaceable battery. 
     The power distribution system  128  includes a plurality of voltage rails, each of which is coupled to various elements, devices, modules, and features of the fluid infusion device  100 . For the sake of simplicity,  FIG. 4  depicts only two voltage rails: a voltage rail  206  to provide operating voltage for basic functions of the fluid infusion device  100 ; and another voltage rail  208  to provide operating voltage for high power functions of the fluid infusion device  100 . As used here, basic functions represent relatively low power and/or relatively low current functions of the fluid infusion device  100 , e.g., functions that might require less than about 50 mA of current. In contrast, high power functions represent relatively high power and/or relatively high current functions, e.g., functions that might require more than about 50 mA of current. Depending upon the specific requirements and features of the fluid infusion device  100 , the power distribution system  128  may include one or more additional voltage rails, which may be designated as low power rails, high power rails, basic function rails, or as otherwise needed. Moreover, additional elements can be included in the power distribution system  128  to result in any alternate configuration needed to cooperate with additional voltage rails. 
     The illustrated embodiment of the power distribution system  128  also generally includes, without limitation: a voltage converter  210  associated with the primary battery  202 ; a voltage converter  212  associated with the secondary battery  204 ; a charger  214  for the secondary battery  204 ; a voltage multiplexer  220  for the voltage rail  206 ; and a voltage multiplexer  222  for the voltage rail  208 . For ease of description,  FIG. 4  also depicts the voltage monitor  130  even though it need not be considered to be a part of the power distribution system  128 . For simplicity,  FIG. 4  does not include reference (e.g., ground) voltage terminals, nodes, or connections for the elements and components of the power distribution system  128 . 
     The primary battery  202  is coupled to both the input of the voltage converter  210  and the input of the charger  214 . The output of the charger  214  is coupled to the secondary battery  204  to accommodate charging of the secondary battery  204  as needed. The secondary battery  204  is coupled to the input of the voltage converter  212 . The output of the voltage converter  210  corresponds to a main voltage rail  228  of the fluid infusion device  100  (the main voltage rail  228  provides the main supply voltage for the fluid infusion device  100 ). The main voltage rail  228  is coupled to an input  230  of the voltage multiplexer  220  and to an input  232  of the voltage multiplexer  222 . The output of the voltage converter  212  corresponds to a backup voltage rail  234  of the fluid infusion device  100 . The backup voltage rail  234  is coupled to an input  236  of the voltage multiplexer  220 . Accordingly, in the illustrated embodiment the voltage multiplexer  220  is coupled to the primary battery  202  via the voltage converter  210 , and to the secondary battery  204  via the voltage converter  212 . 
     In the illustrated embodiment, the secondary battery  204  is directly coupled to an input  239  of the voltage multiplexer  222 . In alternate embodiments, however, the output of the voltage converter  212  may be coupled to an input  238  of the voltage multiplexer  222  (represented by the dashed arrow in  FIG. 4 ). Accordingly, in the illustrated embodiment the voltage multiplexer  222  is coupled to the primary battery  202  via the voltage converter  210 , and to the secondary battery  204  via a direct connection. The output  240  of the voltage multiplexer  220  is coupled to the “basic functions” voltage rail  206 , and the output  242  of the voltage multiplexer  222  is coupled to the “high power functions” voltage rail  208 . The voltage monitor  130  may be coupled to one or more voltage rails, nodes, and/or terminals of the power distribution system  128  as needed for voltage monitoring, measurement, and detection. For example, the voltage monitor  130  might be coupled to monitor the a voltage of the primary battery, a voltage of the secondary battery, an output voltage of the voltage converter  210 , an output voltage of the voltage converter  212 , etc. In certain implementations, the voltage monitor  130  is used to monitor the voltage present at the main voltage rail  228 , as depicted in  FIG. 4 . 
     In certain embodiments, the primary battery  202  is a replaceable battery, such as a standard AA battery (alkaline, lithium, or the like). For such an implementation, the nominal voltage of the primary battery  202  will be about 1.5 volts. For this example, the secondary battery  204  is a rechargeable battery, such as a rechargeable lithium-ion battery. Although not always required, the secondary battery  204  may have a nominal voltage of about 3.7 volts. In practice, the primary battery  202  represents the main power supply of the fluid infusion device  100 , and the secondary battery  204  represents the backup power supply of the fluid infusion device  100 , as will be explained in more detail below. 
     The operation of the charger  214  may be controlled or regulated by one or more of the electronics, processor, and control module(s)  120  described above with reference to  FIG. 3 . In this regard, operation of the charger  214  is controlled to recharge the secondary battery  204  with the primary battery  202  as needed or desired. In other words, the energy of the primary battery  202  can be used to charge the secondary battery  204  (assuming that the primary battery  202  has sufficient energy to do so). To recharge the secondary battery  204 , the charger  214  is turned on or is otherwise controlled into its active state so that energy from the primary battery  202  can be used to recharge the secondary battery  204 . 
     The voltage converter  210  (which need not be included in all embodiments) converts the battery voltage of the primary battery  202  to a desired DC voltage level that is suitable for use as the main supply voltage on the main voltage rail  228 . Depending on the nominal battery voltage and the specification for the main supply voltage, the voltage converter  210  may function to increase or decrease the battery voltage of the primary battery  202 . For the exemplary embodiment described here, the voltage converter  210  boosts the nominal output voltage of the primary battery  202  (1.5 volts DC for this example) to the main supply voltage for the fluid infusion device  100  (which is about 3.26 volts DC for this example). The illustrated embodiment assumes that the main supply voltage serves as a common input to both voltage multiplexers  220 ,  222 . If different voltages need to be routed to the different voltage rails  206 ,  208 , then the voltage converter  210  (or more than one voltage converter) could be suitably configured to provide two or more supply voltages. 
     Similarly, the voltage converter  212  (which need not be included in all embodiments) converts the battery voltage of the secondary battery  204  to a desired DC voltage level that is suitable for use as the backup main supply voltage on the backup voltage rail  234 . Depending on the nominal voltage of the secondary battery  204  and the specification for the backup main supply voltage, the voltage converter  212  may function to increase or decrease the battery voltage of the secondary battery  204 . For the exemplary embodiment described here, the voltage converter  212  converts the nominal output voltage of the secondary battery  204  (3.7 volts DC for this example) to the backup main supply voltage for the fluid infusion device  100  (which is about 3.13 volts DC for this example). The illustrated embodiment assumes that the backup main supply voltage serves as one input to the voltage multiplexer  220 , while the unconverted output of the secondary battery  204  serves as one input to the voltage multiplexer  222 . In such an embodiment, the voltage converter  212  may be used to reduce the voltage of the secondary battery  204  before providing the reduced voltage to the input  236  of the voltage multiplexer  220  (for use with the “basic functions” voltage rail  206 ), while the unconverted output of the secondary battery  204  is directly used with the “high power functions” voltage rail  208 . Of course, if additional voltages need to be routed to the different voltage rails  206 ,  208  and/or to other voltage rails, then the voltage converter  212  (or more than one voltage converter) could be suitably configured to provide two or more supply voltages. 
     In practice, the voltage output of the secondary battery  204  can be applied to the voltage rail  208  because some or all of the high power functions include or cooperate with respective power supplies, drivers, or voltage converters that are able to boost or reduce the voltage of the secondary battery  204  as needed. Accordingly, the architecture need not stage power supplies or voltage converters in series between the secondary battery  204  and the high power voltage rail  208 . In contrast, the system is preferably designed such that the various basic functions can be driven with a common supply voltage present at the basic functions voltage rail  206 . 
     The voltage multiplexer  220  is controlled to select one of its two input voltages as its output voltage for the voltage rail  206 . Thus, in one operating state, the DC voltage present at the input  230  of the voltage multiplexer  220  corresponds to the DC voltage of the voltage rail  206 . In the other operating state, the DC voltage present at the input  236  of the voltage multiplexer  220  corresponds to the DC voltage of the voltage rail  206 . Similarly, the voltage multiplexer  222  is controlled to select one of its two input voltages as its output voltage for the voltage rail  208 . Thus, in a first operating state, the DC voltage present at the input  239  of the voltage multiplexer  222  corresponds to the DC voltage of the voltage rail  208 . In a second operating state, the DC voltage present at the input  232  of the voltage multiplexer  222  corresponds to the DC voltage of the voltage rail  208 . Accordingly, the control and operation of the voltage multiplexers  220 ,  222  allows the primary battery  202  and the secondary battery  204  to be coupled in a selectable manner to the voltage rails  206 ,  208  as needed. In this context, the voltage multiplexers  220 ,  222  (individually and collectively) represent a selection architecture of the power distribution system  128 , where the selection architecture is coupled to the voltage rail  206 , the voltage rail  208 , the primary battery  202 , and the secondary battery  204 . As explained above, the voltage converters  210 ,  212  may (but need not) appear as intervening elements coupled between the batteries  202 ,  204  and the voltage multiplexers  220 ,  222 . 
     The voltage rail  206  provides the operating voltage for certain functions or elements of the fluid infusion device  100  (e.g., basic or low power functions). Such basic functions may include, without limitation: the electronics, processor, and control module(s)  120 ; a wireless transceiver; a display driver; sensors; flash memory; keypad lighting; light emitting diodes; etc. In contrast, the voltage rail  208  provides the operating voltage for other functions or elements of the fluid infusion device  100  (e.g., high power functions). Such high power functions may include, without limitation: operating the fluid delivery or drive motor  134 ; operating the display backlight element  124 ; operating the audio transducer element  126 ; etc. In this regard, the motor  134 , the backlight element  124 , and the audio transducer element  126  are coupled to the voltage rail  208  to obtain operating voltage (which may be supplied by the primary battery  202  or the secondary battery  204  depending upon the power phase of the fluid infusion device  100 ). 
     During operation of the fluid infusion device  100 , one or more of the electronics, processor, and control modules  120  (see  FIG. 3 ) regulates the operation of the power distribution system  128  in accordance with a plurality of different power phases that are intended to take better advantage of the energy capacity of the primary battery  202 . The exemplary embodiment described here employs at least three distinct power phases (although more or less than three could be implemented in practice). During a first power phase, the primary battery  202  is coupled to the voltage rail  206  and to the voltage rail  208  to provide energy for the basic functions and the high power functions. During a second power phase, the primary battery  202  is coupled to the voltage rail  206  to provide energy for the basic functions, and the secondary battery  204  is coupled to the voltage rail  208  to provide energy for the high power functions. During the third power phase, the secondary battery  204  is coupled to the voltage rail  206  and to the voltage rail  208  to provide energy for the basic functions and the high power functions. 
       FIG. 5  is a flow chart that illustrates an exemplary embodiment of a phased power management process  500  associated with the operation of an electronic device, such as the fluid infusion device  100 . The various tasks performed in connection with the process  500  (and other processes described herein) may be performed by software, hardware, firmware, or any combination thereof. For illustrative purposes, the following description of a given process may refer to elements mentioned above in connection with  FIGS. 2-4 . In practice, portions of a described process may be performed by different elements of the described system, e.g., a battery, a voltage multiplexer, a controller, processor, or electronics module, or the like. It should be appreciated that a described process may include any number of additional or alternative tasks, the tasks shown in the figures need not be performed in the illustrated order, and a described process may be incorporated into a more comprehensive procedure or process having additional functionality not described in detail herein. Moreover, one or more of the tasks shown in the figures could be omitted from an embodiment of a described process as long as the intended overall functionality remains intact. 
     The phased power management process  500  may be executed by an electronic device to increase the amount of energy that is extracted from its primary battery before replacement. This embodiment of the process  500  begins by detecting the installation of a new or replacement primary battery (task  502 ). Task  502  may involve the monitoring of the primary battery voltage to detect a condition that is indicative of the removal and/or replacement of a primary battery. For example, if a minimum voltage (e.g., 500 mV) is detected at the primary battery output, then the process  500  assumes that a primary battery is present. Accordingly, if the detected primary battery voltage falls below this threshold for a sufficient duration of time, then task  502  assumes that the primary battery has been removed. Thereafter, detection of a primary battery voltage above the threshold will signify that the primary battery has been replaced. 
     Although a “new” primary battery will typically be unused, the process  500  also contemplates the installation of a primary battery that has at least some of its energy depleted. In response to the installation of a primary battery, the power distribution system is arranged and configured to initially operate the device in the first power phase (task  504 ). During the first power phase, the primary battery provides the energy to support all of the functions of the device, including the basic functions and the high power functions (task  506 ). Moreover, the secondary battery is charged with the primary battery (as needed and if possible to do so) while the device is operating in the first power phase (task  508 ). This example assumes that the primary battery is able to support all of the functions for at least an initial period of time and, therefore, that the device is actually operated in the first power phase. During this period of time, the power distribution system is arranged such that the primary battery provides voltage for the “basic functions” voltage rail and the “high power functions” voltage rail. Accordingly, the secondary battery is disconnected from the two voltage rails for operation in the first power phase. 
     In certain embodiments, the main supply voltage (present at the main voltage rail) is monitored during operation of the electronic device, and the detected main supply voltage controls or otherwise influences the transition from one phase to another phase. In this regard, the power distribution system remains arranged in accordance with the first power phase when the main supply voltage is stable and greater than or equal to a stated threshold value. In practice, this threshold value may be selected based on the operating voltage and electrical current requirements and specifications of the components, devices, and elements coupled to the voltage rails. Thus, if the present state of the primary battery can provide sufficient energy to maintain the main power rail at a minimum voltage level required for the high power functions (given the electrical loading conditions at that time), then the process  500  assumes that it is safe to continue operating the device in the first power phase. For the example described here, the threshold value for the main supply voltage is within the range of about 3.050 to 3.100 volts, and is preferably about 3.075 volts. It should be appreciated that the nominal threshold value will be influenced by the specifications and nominal output voltage of the primary battery and/or the nominal output voltage of the voltage converter for the primary battery. For example, the exemplary threshold voltage range given above assumes that the nominal and expected output voltage of the voltage converter  210  is about 3.260 volts (see  FIG. 4 ). 
     If the high power functions of the device are supported by the primary battery (query task  510 ), then the power distribution system will remain arranged in accordance with the first power phase. Referring again to  FIG. 4 , for the first power phase the voltage multiplexer  220  is controlled such that the voltage from the voltage converter  210  appears at the voltage rail  206 , and the voltage multiplexer  222  is controlled such that the voltage from the voltage converter  210  also appears at the voltage rail  208 . During the first power phase, the charger  214  may also be controlled as needed to charge the secondary battery  204  with the primary battery  202 . 
     If the high power functions of the device are no longer supported by the primary battery (query task  510 ), then the process  500  may check whether the basic functions of the device are supported by the primary battery (query task  512 ). If the basic functions can be supported by the primary battery, then the power distribution system transitions from the first power phase to the second power phase. If the basic functions cannot be supported by the primary battery, then the power distribution system transitions from the first power phase to the third power phase, and the process  500  may proceed to a task  524  (described below). 
     The monitored main supply voltage may be analyzed to determine whether or not the basic functions can be supported by the primary battery. For this example, transitioning the power distribution system from the first power phase to the second power phase is triggered when the main supply voltage falls below the threshold value (while it is being monitored in the first power phase). Thus, the power distribution system can be arranged for operation in accordance with the second power phase (task  514 ) in response to a determination that the primary battery can no longer support the high power functions. If, after transitioning to the second power phase, the current state of the primary battery can provide sufficient energy to maintain the main power rail at the minimum voltage level, then the process  500  assumes that it is safe to continue operating the device in the second power phase. 
     During operation in the second power phase, the primary battery provides the energy to support the basic functions of device (task  516 ), while the secondary battery provides the energy to support the high power functions of the device (task  518 ). In addition, the secondary battery is recharged with the primary battery (as needed and if possible to do so) while the device is operating in the second power phase (task  520 ). For operation in the second power phase, the power distribution system is arranged such that the primary battery provides voltage for the basic functions voltage rail, and such that the secondary battery provides voltage for the high power functions voltage rail. 
     Referring again to  FIG. 4 , for the second power phase the voltage multiplexer  220  is controlled such that the voltage from the voltage converter  210  appears at the voltage rail  206 , and the voltage multiplexer  222  is controlled such that the voltage from the secondary battery  204  appears at the voltage rail  208 . This action also disconnects the primary battery  202  from the voltage rail  208 . While operating in the second power phase, the charger  214  may also be controlled to as needed to charge the secondary battery  204  with the primary battery  202 . Notably, the transition to the second power phase changes the load of the primary battery  202 . Consequently, under normal conditions the monitored main supply voltage will increase to a level that is greater than the designated voltage threshold. 
     If the basic functions of the device are supported by the primary battery (query task  522 ), then the power distribution system will remain arranged in accordance with the second power phase. If, however, the basic functions of the device are no longer supported by the primary battery, then the power distribution system transitions from the second power phase to the third power phase. As mentioned above, if the monitored main supply voltage falls below the threshold voltage value while operating in the second power phase, then the process  500  assumes that the primary battery can no longer support even the basic functions. Consequently, the power distribution system is transitioned and arranged for operation in the third power phase (task  524 ). For this embodiment, transitioning the power distribution system from the second power phase to the third power phase is triggered when the main supply voltage falls below the threshold value (while it is being monitored in the second power phase). 
     During operation in the third power phase, the secondary battery provides the energy to support all functions of the device (task  526 ), including the basic functions and the high power functions. In other words, the electronic device does not rely on the primary battery for any of its operating functions. However, the primary battery may still be used to recharge the secondary battery (task  528 ) as needed and if possible to do so. Thus, any residual energy left in the primary battery could be used to charge the secondary battery. 
     In certain embodiments, the process  500  generates a low battery warning at the electronic device (task  530 ) in response to the transition from the second power phase to the third power phase. The low battery warning may be associated with an audible alert, a displayed message, an activated graphical icon, or the like. The low battery warning is intended to notify the user of the low battery condition and to remind the user to replace the primary battery with a fresh battery as soon as possible to avoid any device downtime. 
     For operation in the third power phase, the power distribution system is arranged such that the secondary battery provides voltage for both of the voltage rails. Referring again to  FIG. 4 , for the third power phase the voltage multiplexer  220  is controlled such that the voltage from the voltage converter  212  appears at the voltage rail  206 , and the voltage multiplexer  222  is controlled such that the voltage from the secondary battery  204  appears at the voltage rail  208 . This action effectively disconnects the primary battery  202  from both voltage rails  206 ,  208  during the third power phase. During the third power phase, the charger  214  may also be controlled as needed to charge the secondary battery  204  with the primary battery  202 . 
     The third power phase may be maintained for a predetermined period of time that is based on the expected energy capacity of the secondary battery, assuming that the secondary battery by itself is responsible for the operation of the device. For example, the third power phase may timeout after a specified number of minutes or hours, e.g., ten hours. Thereafter, it may not be possible to support all of the normal operations of the device. Accordingly, the user will have the opportunity to replace the primary battery during the third power phase. 
     Notably, the phased power management technique described above enables the electronic device to prolong the useful life of the primary battery regardless of the specific type (chemistry) of battery used. Theoretically, up to 90% of the total energy of a new primary battery can be utilized if this power management scheme is implemented. Moreover, the power management scheme need not have advance knowledge of the installed battery type, and the electronic device need not rely on any empirical characterizations of different battery types. 
     In addition to the phased power management scheme described above, the fluid infusion device  100  may employ an intelligent methodology for monitoring and indicating the remaining life of the primary battery. In contrast to traditional approaches that rely solely on the battery voltage level or a coulomb counter, the battery life indicator of the fluid infusion device  100  is generated using a combination of operating parameters, and in a manner that results in an accurate and time proportional indication of remaining battery life. 
       FIG. 6  is a flow chart that illustrates an exemplary embodiment of a battery life indicator process  600  associated with the operation of an electronic device, such as the fluid infusion device  100 . Referring again to  FIG. 3 , a battery monitor system for the fluid infusion device  100  could be implemented with one or more of the electronics, processor, and control modules  120 , which may cooperate with the voltage monitor  130 , the battery runtime counter  132 , and the power distribution system  128  for purposes of generating the battery life indicator  107 . 
     This embodiment of the process  600  begins by detecting the installation of a new or replacement primary battery (task  602 ). Although a “new” primary battery will typically be unused, the process  600  also contemplates the installation of a primary battery that has at least some of its energy depleted. In response to the installation of a primary battery, the process  600  initializes and starts the runtime counter for the primary battery (task  604 ). In certain embodiments, task  604  is associated with the resetting or zeroing of the runtime counter, which may keep track of runtime in any desired unit (or units) of time, such as minutes, hours, or days. The process  600  monitors and measures a battery voltage, V B , of the primary battery in an ongoing manner (task  606 ). The exemplary embodiment described here uses the voltage monitor to measure an “unloaded” battery voltage at a time when loading of the primary battery is at a minimum. In this regard, the unloaded primary battery condition might represent a state where the primary battery is loaded with only those components that are necessary to obtain the battery voltage reading (e.g., one or more of the modules  120 , the voltage monitor  130 , the memory  122 , etc.). The measured battery voltage may be recorded or otherwise saved as appropriate. 
     In contrast to traditional approaches that use only the battery voltage as the metric for calculating remaining battery life, the technique described here also obtains at least one other operating parameter of the fluid infusion device (i.e., operating parameter(s) other than the battery voltage of the primary battery) and generates the battery life indicator based on the monitored battery voltage and the obtained operating parameter(s). The additional operating parameters considered by the process  600  may include, without limitation, a runtime measurement for the primary battery, and the power phase in which the device is currently operating (for the embodiment described above, the device operates in either a first power phase, a second power phase, or a third power phase). For this particular example, it is assumed that the indicating characteristics of the battery life indicator are controlled, governed, determined, or otherwise influenced by the power phase, the runtime measurement, and the monitored battery voltage of the primary battery. In alternate implementations, however, the characteristics of the battery life indicator might be controlled by: the power phase and the runtime measurement only; the power phase and the monitored battery voltage only; or the runtime measurement and the monitored battery voltage only. In other words, the amount of remaining battery life conveyed by the battery life indicator is governed by at least two of: the monitored battery voltage; the designated power phase; and the runtime measurement. 
     Assuming that the power phase of the device will be considered, the process  600  determines or otherwise obtains the power phase of the electronic device (task  608 ). For this example, therefore, task  608  determines whether the electronic device is operating in the first power phase, the second power phase, or the third power phase. The determined power phase may be recorded or otherwise saved as appropriate. The process  600  also obtains the runtime measurement of the primary battery (task  610 ) and records or saves the runtime measurement. 
     Referring again to  FIG. 2 , the illustrated embodiment of the battery life indicator  107  includes four segments that represent the remaining battery life of the primary battery. Alternatively, the battery life indicator  107  may be displayed, generated, annunciated, or otherwise presented to the user with appropriate characteristics that represent the remaining battery life. In other words, the use of a battery icon having four graphically distinct segments represents merely one of many possible embodiments for the battery life indicator  107 . For a segmented battery life indicator such as that depicted in  FIG. 2 , the process  600  calculates the number of indicator segments to be displayed, illuminated, or otherwise rendered (task  612 ). Again, this particular embodiment calculates the number of segments based on the monitored battery voltage, the runtime measurement, and the power phase. Next, the process  600  generates and displays the battery life indicator with the calculated number of segments (task  614 ). 
     The amount of remaining battery life represented by one, two, three, four, or no icon segments may be designated or configured as appropriate for the particular embodiment. For this particular example, four segments indicates that about 67% to about 100% of the battery life remains, three segments indicates that about 33% to about 67% of the battery life remains, and two segments indicates that less than about 33% of the battery life remains. Thus, each of the “top” three segments approximately represents about one-third of the total battery life. Notably, only one segment displayed indicates a low battery condition corresponding to a maximum remaining runtime of about ten hours (or about 2% of remaining battery life). In other words, about ten hours of battery life remains when the battery life indicator  107  transitions from two segments to only one segment. For this particular embodiment, no segments displayed indicates an “end of battery life” condition corresponding to a maximum remaining runtime of about thirty minutes. Accordingly, only about thirty minutes of batter life remains when the battery life indicator  107  transitions from one segment to no segments. 
     If the primary battery is removed (query task  616 ), then the process  600  may begin again at task  602 . If not, then most of the process  600  is repeated in an ongoing manner to update the battery life indicator in a continuous manner. 
     As mentioned in the context of the process  600 , the number of battery life indicator segments may be determined based on two or more of: the monitored battery voltage, the runtime measurement, and the power phase of the device. In this regard,  FIG. 7  is a flow chart that illustrates one particular embodiment of a battery life indicator process  700  associated with the operation of an electronic device such as the fluid infusion device  100 . In practice, the process  700  may be incorporated into the process  600 , and some aspects of the process  700  may be shared with the process  600 . 
     The process  700  may be initiated whenever the battery voltage of the primary battery, V B , is measured (task  702 ). For the exemplary embodiment described here, V B  represents the voltage of the primary battery in an “unloaded” state, as explained in more detail above. In practice, task  702  may be performed periodically, in accordance with a predetermined schedule, or in accordance with the management of other processes, applications, and operations supported by the device. For example, it may be desirable to measure V B  once a minute. In addition to task  702 , the process  700  may perform an initial check to determine whether the operating state of the primary battery satisfies certain baseline criteria (query task  704 ). This embodiment checks whether the remaining runtime of the primary battery satisfies a threshold time period, such as thirty minutes. The threshold time period indicates that the primary battery is near its end of life. In practice, the determination made at query task  704  may be based on another process that is performed independently of the process  700 , or it may be based on the current status of a variable maintained by the device. As another example, query task  704  might simply check whether the measured value of V B  exceeds a minimum baseline voltage threshold. 
     If query task  704  determines that the primary battery does not have a sufficient amount of available runtime remaining, then the battery life indicator is generated such that no indicator segments are displayed (task  706 ). If query task  704  determines that the primary battery has at least a minimum amount of runtime remaining, then the process  700  checks whether the electronic device is currently operating in the third power phase (query task  708 ). If so, then the battery life indicator is generated such that only one indicator segment is displayed (task  710 ). 
     If the electronic device is not operating in the third power phase, then the process  700  continues by checking whether the monitored battery voltage (V B ) is greater than an upper threshold voltage value, V T     —     U  (query task  712 ). Notably, the same upper threshold voltage value is used for all primary battery types and chemistries, e.g., alkaline, lithium, or the like. In practice, V T     —     U  is selected in accordance with the expected nominal battery voltage, the operating requirements of the electronic device, and/or other operating parameters. More specifically, this threshold is selected after characterizing different battery types (AA size) and determining an accurate measure of full capacity or near-full capacity (i.e., at or near 100% life remaining). For the non-limiting example presented here, V T     —     U =1.3 volts DC. If the currently measured value of V B  is less than or equal to V T     —     U  (the “NO” branch of query task  712 ), then the process  700  checks whether V B  is greater than a lower threshold voltage value, V T     —     L  (query task  714 ). The same lower threshold voltage value may be used for all primary battery types and chemistries. In practice, V T     —     L  is selected in accordance with the expected nominal battery voltage, the operating requirements of the electronic device, and/or other operating parameters. More specifically, this lower threshold is selected after characterizing different battery types and determining a voltage that generally indicates some decay or a typical amount of energy consumption. For the non-limiting example presented here, V T     —     L =1.2 volts DC. If the currently measured value of V B  is less than or equal to V T     —     L  (the “NO” branch of query task  714 ), then the battery life indicator is generated such that only two indicator segments are displayed (task  716 ). Note that the upper and lower threshold values apply to different battery chemistries such that the process  700  can be universally executed without regard to the specific battery type that is currently installed. 
     Referring back to query task  714 , if the currently measured value of V B  is greater than V T     —     L  (the “YES” branch of query task  714 ), then the process  700  checks whether the runtime measurement (t) is greater than an upper threshold time value, t T     —     U  (query task  718 ). For this embodiment, the same upper threshold time value is used for all primary battery types and chemistries, e.g., alkaline, lithium, or the like. In practice, t T     —     U  is selected in accordance with the expected lifespan of a new primary battery, considering the variations associated with different battery types. The value of t T     —     U  may also be selected based on the number of segments in the battery life indicator and the desired manner in which the display of the segments is regulated. For the non-limiting example presented here, t T     —     U =14 days. If the currently obtained value of t is greater than t T     —     U  (the “YES” branch of query task  718 ), then the battery life indicator is generated such that only two indicator segments are displayed (task  716 ). If, however, the currently obtained value of t is less than or equal to t T     —     U  (the “NO” branch of query task  718 ), then the battery life indicator is generated such that only three indicator segments are displayed (task  720 ). 
     Referring back to query task  712 , if the currently measured value of V B  is greater than V T     —     U  (the “YES” branch of query task  712 ), then the process  700  continues by checking whether the runtime measurement (t) is greater than a lower threshold time value, t T     —     L  (query task  722 ). For this embodiment, the same lower threshold time value is used for all primary battery types and chemistries, e.g., alkaline, lithium, or the like. In practice, t T     —     L  is selected in accordance with the expected lifespan of a new primary battery, considering the variations associated with different battery types. The value of t T     —     L  may also be selected based on the number of segments in the battery life indicator and the desired manner in which the display of the segments is regulated. For the non-limiting example presented here, t T     —     L =4 days. If the currently obtained value of t is greater than t T     —     L  (the “YES” branch of query task  722 ), then the process  700  leads to query task  718  and continues as described above. If, however, the currently obtained value of t is less than or equal to t T     —     L  (the “NO” branch of query task  722 ), then the process  700  checks whether the device is currently operating in the first power phase (query task  724 ). 
     If the device is not operating in the first power phase (the “NO” branch of query task  724 ), then the battery life indicator is generated such that only three indicator segments are displayed (task  720 ). If, however, the device is operating in the first power phase (the “YES” branch of query task  724 ), then the battery life indicator is generated such that all four indicator segments are displayed (task  726 ). 
     The conditions and criteria associated with the exemplary process  700  may be summarized in the following manner. No segments are rendered if the remaining runtime of the primary battery is less than a designated time, or if the device otherwise indicates that the primary battery has failed, is completely or virtually void of charge, or the like. One (and only one) segment is rendered when the device is operating in the third power phase. Two (and only two) segments are rendered under three different scenarios: (a) when the electronic device is not operating in the third power phase, and V B ≦V T     —     L ; (b) when the electronic device is not operating in the third power phase, and V T     —     L &lt;V B ≦V T     —     U , and t&gt;t T     —     U ; or (c) when the electronic device is not operating in the third power phase, and V B &gt;V T     —     U , and t&gt;t T     —     U . Three (and only three) segments are rendered under three different scenarios: (d) when the electronic device is not operating in the third power phase, and V T     —     L &lt;V B ≦V T     —     U , and t≦t T     —     U ; (e) when the electronic device is not operating in the third power phase, and V B &gt;V T     —     U , and t T     —     L &lt;t≦t T     —     U ; or (f) when the electronic device is operating in the second power phase, and V B &gt;V T     —     U , and t≦t T     —     L . Finally, all four segments are rendered when the electronic device is operating in the first power phase, and V B &gt;V T     —     U , and t≦t T     —     L . 
     Under typical and normal operating conditions, the battery life indication techniques described here result in predictable, accurate, and temporally proportional behavior. For example, if the normally expected lifespan of a fully charged primary battery is forty days, then each displayed indicator segment will roughly correspond to ten remaining days of battery life. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or embodiments described herein are not intended to limit the scope, applicability, or configuration of the claimed subject matter in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope defined by the claims, which includes known equivalents and foreseeable equivalents at the time of filing this patent application.