Abstract:
A power system having an extended life and a system and method for extending the life of a battery powered device. In one embodiment, the method comprises providing a plurality of power sources and an alternate energy source. The method also comprises measuring the voltage of the power sources and the alternate energy source. The method further comprises selecting a power source to provide voltage to the device, wherein the selected power source provides voltage to the device. In addition, the method comprises optionally charging any power source that is providing voltage to the device. Moreover, the method is repeated after a variable delay. Further embodiments include switching to providing the voltage to the device from a power source while charging another power source.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This non-provisional application claims the benefit of U.S. Provisional Application No. 60/473,554, filed May 27, 2003, which is hereby incorporated by reference in its entirety. 
     
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    1. Field of the Invention  
           [0004]    This invention relates to the field of power systems and more specifically to the field of extending the life of battery powered systems.  
           [0005]    2. Background of the Invention  
           [0006]    There has been an increasing need to extend the uptime for battery powered devices while also extending the life of the devices. Traditional battery powered devices are only operable for a finite time as traditional batteries have a limited useful life. In addition, the devices are typically inoperable or unusable when their batteries are being charged. When the batteries are sufficiently charged, the device again becomes available. Besides the device downtime involved, further drawbacks include battery memory and reduction in battery life.  
           [0007]    For instance, in the field of sensor networks, access to a power grid is typically unavailable. Therefore, the devices are typically independent. A typical drawback is trading off device/network lifetime versus the ability for the devices to transfer data between nodes. Traditional charging schemes either allow the device to run and communicate or allow the device to charge the battery.  
           [0008]    Battery powered devices recharged by alternate energy sources have been developed to extend battery life. However, such alternate energy sources typically do not provide enough energy to support full device operation while storing energy for later use. Additional drawbacks include the effects of battery memory because of prematurely discharging the battery before it finishes charging.  
           [0009]    Because battery life and uptime can be quality measures of battery powered devices, there is a need for maximizing the lifetime and uptime of an individual independently powered device. Additional needs include increasing the lifetime and uptime of individual powered devices that consume large amounts of power. Further needs include operating an independently powered device while at the same time charging its batteries. In addition, needs include maximizing use of alternate energy sources.  
         BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS  
         [0010]    These and other needs in the art are addressed in one embodiment by a system for extending a device life. The system includes a plurality of power sources, wherein each power source is disposed to be charged when one of the power sources is providing voltage to the device. The system further includes an alternate energy source, wherein the alternate energy source is disposed to charge power sources that are not providing voltage to the device. Moreover, the system includes a processing device.  
           [0011]    An additional embodiment of the present invention includes a method for extending a device life. The method comprises providing a plurality of power sources and an alternate energy source. In addition, the method comprises measuring the voltage of the power sources and the alternate energy source. Moreover, the method comprises selecting a power source to provide voltage to the device, wherein the selected power source provides voltage to the device. The method further comprises optionally charging any power source that is not providing voltage to the device. The method is repeated after a variable delay.  
           [0012]    In addition, the present invention includes an embodiment comprising a method for extending a device life wherein the method includes providing a plurality of power sources and an alternate energy source, wherein the plurality of power sources are capable of being charged. The method also comprises measuring the voltage of the plurality of power sources and the alternate energy source. The method further comprises comparing the voltage of a first power source to a first power source minimum threshold voltage, wherein the plurality of power sources includes the first power source. The method also comprises optionally comparing the voltage of at least one other power source to at least one power source minimum threshold voltage and optionally selecting a low power mode for the device. In addition, the method comprises optionally comparing the voltages of the alternate energy source to an alternate energy minimum threshold voltage.  
           [0013]    It will therefore be seen that a technical advantage of the present invention includes an independently powered device (such as a battery powered device) that has an increased lifetime and uptime, thereby eliminating problems encountered by using conventional battery powered devices. For instance, problems encountered with downtime of the device when charging the battery are overcome as one battery can provide voltage while the other batteries are being charged. In addition, problems with reduction in battery life and battery memory are also overcome as the present invention allows one battery to be fully discharged before it is charged.  
           [0014]    The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:  
         [0016]    [0016]FIG. 1 illustrates a power system hardware block diagram;  
         [0017]    [0017]FIG. 2 illustrates a schematic block diagram of an algorithm operating in the system of FIG. 1; and  
         [0018]    [0018]FIG. 3 illustrates a power system hardware block diagram having sensor and communication modules. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    [0019]FIG. 1 illustrates a hardware block diagram of a power system  1  having an alternate energy source  5 , a first battery  10 , a second battery  15 , and a processing device  20 . Alternate energy source  5  can be any suitable source of alternate energy. For instance, solar cells, wind turbines, hydroelectric power, conversion of mechanical stress to electricity by the Piezoelectric effect, and the like can be used as alternate energy source  5 . Alternative embodiments include using more than one type of alternate energy for alternate energy source  5 . It is to be understood that one skilled in the art would select an alternate energy source that is suitable for the application.  
         [0020]    For illustration purposes, power system  1  is shown having two batteries (first and second batteries  10 ,  15 ). Power system  1  is not limited to two batteries but can have more than two batteries. Power system  1  can have any type of battery that is chargeable. Chargeable batteries are well known, and examples of suitable types of chargeable batteries include AA NiMH, NiCd, lithium ion, lithium polymer, and the like. It is to be understood that one skilled in the art would select batteries that are suitable for the application. The batteries of power system  1  can be the same or different types of batteries, preferably the same. For instance, first battery  10  and second battery  15  can be the same type of battery or different types of batteries. It is to be understood that the present invention is not limited to batteries but can include any rechargeable power source. Examples of such power sources can include miniature fuel cells and capacitors.  
         [0021]    Processing devices are well known in the art, and processing device  20  can be any suitable type of processing device. One skilled in the art can select a suitable processing device for the application. Examples of processing devices include microcontrollers, programmable logic devices, field programmable gate arrays, general purpose processors (GPP), and the like. Preferably, the processing device is a microcontroller. Examples of microcontrollers include a 16-bit MPS430 microcontroller, AT91 ARM Thumb, Z World Rabbit Microprocessor, and the like. In alternative embodiments (not illustrated), power system  1  has more than one processing device.  
         [0022]    Hardware for power system  1  can also include control system  25 . Control system  25  can include charge circuitry and power control hardware. Charge circuitry and power control hardware are well known in the art, and the control system  25  of the present invention can be any suitable type of such hardware. Preferably, control system  25  can include any type of circuitry sufficient for receiving signals from processing device  20  and for allowing alternate energy source  5  to charge the batteries of power system  1 .  
         [0023]    Power system  1  can further include hardware  30 , which can include hardware such as charge pumps, voltage regulators, and power control hardware. Charge pumps, voltage regulators, and power control hardware are well known in the art, and the hardware  30  of the present invention can be any suitable type of such hardware. Preferably, hardware  30  can be any type of such hardware sufficient for receiving signals from processing device  20  and for providing charge from a battery to system power  33 .  
         [0024]    Power system  1  can also have at least one analog-to-digital (A/D) converter  35 . Analog-to-digital converters are well known in the art, and the A/D converter  35  of the present invention can be any suitable type of A/D converter. Preferably, A/D converters  35  are suitable for converting voltage signals from the batteries and alternate energy source  5 . In alternative embodiments (not illustrated), the A/D converter  35  is part of processing device  20 . In other alternative embodiments (not illustrated), A/D converter  35  is part of hardware  30 .  
         [0025]    [0025]FIG. 2 illustrates a schematic block diagram of an algorithm  37 , which can be operated in the system of FIG. 1. Algorithm  37  is programming language independent and can be run on any software. Preferably, the software is programmable for processing device  20 . In a first step  40 , power system  1  is initialized. When initializing the system, preference can be given to one of the batteries over the other battery or batteries. For illustration purposes and without limitation, preference is given to first battery  10 . During initialization, the system also allows first battery  10  to provide power to system power  33  via hardware  30 . Also during initialization, processing device  20  can initialize the software methods, variables, memory, and the like.  
         [0026]    The voltages of first and second batteries  10 ,  15  and alternate energy source  5  are read in the next step  45 . When such readings are in analog, A/D converters  35  convert the readings to digital for processing device  20 . Processing device  20  saves the voltage readings in step  50 .  
         [0027]    In analyzation step  55 , processing device  20  analyzes the voltage readings and also may compare the voltage readings to saved reference voltage data and/or historical reference voltages. The reference voltage data can be input data to use as reference comparisons for the voltage readings, and the historical reference voltages can be saved voltages from past readings. Step  60  involves processing device  20  modifying parameters of power system  1  based upon the results of analyzation step  55 . The modifications can be based upon comparisons based on the reference voltages and/or the historical voltages. Parameters can include the length of a variable delay, voltage to be output from power system  1 , which battery is providing voltage to be output from power system  1  to system power  33 , which battery is being charged, and any parameters associated with the specific alternate energy source used. Modifying voltage output from power system  1  includes modifying the voltage output from alternate energy source  5 , first battery  10 , and/or second battery  15 . It is to be understood that modifying the parameters is not required but is optional based upon analysis by processing device  20 . The variable delay is the time length for the next iteration of algorithm  37 , and it can be any desired length. Preferably, the variable delay is selected based upon the application, reference voltages and/or historical voltages, the power mode of system power  33 , and the like. The variable delay for algorithm  37  can be set with varying lengths depending on the application.  
         [0028]    Step  65  is a decision step in which the voltage of first battery  10  is compared by processing device  20  to a minimum threshold voltage for first battery  10 . The minimum threshold voltage for first battery  10  can be any desired voltage. Preferably, the minimum threshold voltage for first battery  10  is a voltage that below which is not sufficient for hardware  30  to use first battery  10 , below which first battery  10  can cease to be charged and/or below which first battery  10  can be insufficient for system power  33 . If the voltage of first battery  10  is not less than its minimum threshold voltage, power is supplied to system power  33  from first battery  10  at step  70 . The power can be supplied to system power  33  from first battery  10  via hardware  30 . System power  33  can be the power supplied to operate power system  1  or a device and/or application that is powered by power system  1 . Step  75  is a decision step in which the voltage of alternate energy source  5  is compared by processing device  20  to a minimum threshold voltage for alternate energy source  5 . If the voltage of alternate energy source  5  is greater than its minimum threshold voltage, second battery  15  can be charged in step  80 . Step  80  involves processing device  20  indicating to control system  25  to charge second battery  15  from alternate energy source  5 . If the voltage of alternate energy source  5  is not greater than its minimum threshold voltage, the battery charger can be disabled in step  85 . Step  85  involves processing device  20  indicating to control system  25  to not charge second battery  15  from alternate energy source  5 .  
         [0029]    If the voltage of first battery  10  is determined to be less than its minimum threshold voltage in step  65 , processing device  20  in decision step  90  can compare the voltage of second battery  15  to a minimum threshold voltage for second battery  15 . If the voltage of second battery  15  is not less than its minimum threshold voltage, power can be supplied to system power  33  from second battery  15  in step  95 . In step  95 , processing device  20  indicates to hardware  30  to supply power to system power  33  from second battery  15 . Step  100  is a decision step in which the voltage of alternate energy source  5  is compared by processing device  20  to a minimum threshold voltage for alternate energy source  5 . If the voltage of alternate energy source  5  is greater than its minimum threshold voltage, first battery  10  can be charged in step  105 . Step  105  involves processing device  20  indicating to control system  25  to charge first battery  10  from alternate energy source  5 . If the voltage of alternate energy source  0 . 5  is not greater than its minimum threshold voltage, the battery charger can be disabled in step  110 . Step  110  involves processing device  20  indicating to control system  25  to not charge first battery  10  from alternate energy source  5 .  
         [0030]    If in step  90  processing device  20  determines that the voltage of second battery  15  is less than its minimum threshold voltage, processing device  20  can switch power system  1  into low power mode in step  115 . Low power mode includes not sending voltage to system power  33 . In some embodiments, low power mode can include processing device  20  receiving sufficient power to control power system  1 . Low power mode may include not sending voltage to parts of system power  33  that are not involved in power system  1 . In alternative embodiments, voltage is not supplied to processing device  20 . For instance, in such alternative embodiments, processing device  20  may not support the voltage in low power mode. After power system  1  is in low power mode, in step  120  the voltage of alternate energy source  5  can be compared by processing device  20  to its minimum threshold voltage. If the voltage of alternate energy source  5  is not greater than its minimum threshold voltage, the battery charger can be disabled in step  130 . Step  130  involves processing device  20  indicating to control system  25  to not charge first battery  10  and second battery  15  from alternate energy source  5 . If the voltage of alternate energy source  5  is greater than its minimum threshold voltage, first and second batteries  10  and  15  are charged in step  125 . Step  125  involves processing device  20  indicating to control system  25  to charge first battery  10  and second battery  15  from alternate energy source  5 .  
         [0031]    Algorithm  37  can have any desired number of iterations with the variable delay determining when the next iteration begins. It is to be understood that when a next iteration begins, such next iteration preferably begins at step  45 . As described above, power system  1  and algorithm  37  allow voltage to be supplied to system power  33  and at the same time allow for charging of a battery. In addition, the energy collected by alternate energy source  5  can be maximized. After algorithm  37  has been followed for an iteration, the time remaining during the variable delay until the next iteration begins allows such voltage to be supplied and also allows for the charging of a battery. The variable delays can be the same or can have varying lengths.  
         [0032]    In alternative embodiments, processing device  20  can stop iteration  37  and not supply any voltage from the batteries to system power  33 . For instance, the application for which system power  33  is applied may not need to be active at nighttime. In such an application, processing device  20  can determine from historical data in step  55  that it is nighttime (e.g., historical voltage data for alternate energy source  5  when the source is a solar source). Upon such a determination, processing device  20  can indicate to power system  1  to not supply any voltage to system power  33  and to not run any further iterations for a given variable delay (e.g., a variable delay that will last until dawn). Preferably, processing device  20  can receive sufficient power to control power system  1 .  
         [0033]    It is to be understood that algorithm  37  is not limited to alternate energy source  5 , first battery  10 , and second battery  15  but can be extended to be used with embodiments having more than two batteries and/or more than one alternate energy source. In such embodiments, algorithm  37  can be extended to incorporate the additional batteries and/or alternate energy sources. In addition, extra hardware such as additional charge circuitry and power control and/or charge pumps, voltage regulators, and power control can be added to power system  1  as well. For instance, in an embodiment (not illustrated) wherein power system  1  has a third battery, steps  80 ,  105 , and  125  can also include charging the third battery. In such an embodiment, algorithm  37  can also have additional steps between step  90  and step  115 , with such steps being similar to steps  65 ,  70 ,  75 ,  80  and  85  or steps  90 ,  95 ,  100 ,  105 , and  110 , but processed in regards to the third battery. For further instance, in an embodiment (not illustrated) wherein power system  1  has a second alternate energy source, algorithm  37  can have steps  75 ′,  100 ′, and  120 ′. In such a further instance, if the voltage of the first alternate energy source is determined to not be greater than its minimum threshold voltage, the voltage of the second alternate energy source can be compared to its minimum threshold voltage in steps  75 ′,  100 ′, or  120 ′. The second alternate energy source can charge a battery or batteries in steps  80 ,  105 , or  125  if it has a voltage greater than its minimum threshold voltage, or if not then the chargers are disabled in steps  85 ,  110 , or  130 .  
         [0034]    Power system  1  can be used for any desired application or device in which chargeable power sources and/or batteries are used. Examples of applications include cell phones, wireless sensor networks, seismic detection, cure-rate monitoring, contaminant and flow monitoring, tracking and routing of personnel and machinery, seismic monitoring of civil structures, and the like. Algorithm  37  enables power system  1  and any device or application powered by it to have an extended life and uptime. As one power source is supplying power to system power  33 , the other power source or sources are being charged by the alternate energy source. A power source selected by algorithm  37  can have reduced problems such as battery memory by its providing power to system power  33  until it is below its minimum threshold voltage.  
         [0035]    Power system  1  is not limited to the hardware as illustrated in FIG. 1 but can have additional hardware as desired for an application. For instance, sensor modules, communication modules, and the like can be included. FIG. 3 illustrates an embodiment of power system  1  having some of such additional hardware. FIG. 3 comprises substantially all of the elements of the above-discussed embodiments as illustrated in FIG. 1 and alternative embodiments thereof, with the additional elements discussed below. As illustrated in FIG. 3, power system  1  has a sensor module  135 , a communications module  140 , a data storage module  145 , expansion ports  150  and  155 , and a GPS module 160 . For instance, a communications node having the hardware of FIG. 3 can have its longevity extended indefinitely.  
         [0036]    It is to be understood that the present invention is not limited to batteries supplying voltage to power system  33 . Additional alternative embodiments include alternate energy source  5  also supplying voltage to system power  33 .  
         [0037]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.