Patent Publication Number: US-9847661-B2

Title: Extended battery cycle life through smart charging of rechargeable batteries

Description:
PRIORITY APPLICATION 
     This application claims priority under 35 U.S.C. §119(e) to U.S. patent application Ser. No. 14/479,679, titled “Battery Cycle Life Through Smart Overnight Charging”, filed on Sep. 8, 2014, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates in general to method for charging a rechargeable battery within a user equipment. More particularly, the present disclosure relates to charging a rechargeable battery within a user equipment in order to improve the battery&#39;s cycle life by providing a decreased charge rate during a period of time when the user equipment is being charged and has a high probability of not being used actively by the user. 
     BACKGROUND 
     Batteries, and in particular rechargeable batteries, have a finite life due to the occurrence of unwanted chemical or physical changes to, or the loss of, the active materials of which they are made. Without the unwanted chemical or physical changes, rechargeable batteries could last indefinitely over an infinite number of charge cycles, wherein the charge cycle is defined as the complete charging and complete discharging of the rechargeable battery. The unwanted chemical or physical changes to the active materials within a rechargeable battery are usually irreversible and affect the electrical performance of the rechargeable battery or cell over time. 
     Battery cycle life is defined as the number of complete charge-discharge cycles a battery can perform before its full charge capacity falls below 80% of its initial full charge capacity. A battery&#39;s capacity is usually rated in milliamp hours (mAh). Two key factors that affect a battery&#39;s cycle life are change rate and a number N of charge-discharge cycles completed. 
     A battery cycle life of 300 to 1200 cycles is typical depending on various factors including how fast the battery is recharged. The aging process of the battery results in a gradual reduction in the full charge capacity over time. That is when a cell reaches its specific lifetime it does not stop working suddenly. Instead, the aging process continues at a rate wherein a cell or battery whose capacity had fallen to 80% after 500 cycles will probably continue working to 1000 cycles, but its effective capacity will continue to fall. Thus, there is no need to fear sudden death when a rechargeable cell reaches the end of its specified battery life. 
     Mobile communication devices, such as mobile phones, tablet pads, personal digital assistants (PDAs), laptop computers and the like (hereinafter user equipment (UE)) often use lithium-ion batteries. It is the nature of lithium-ion batteries and other rechargeable batteries such as nickel-metal hydride, lithium polymer, and NiCad batteries (hereinafter referred to as a “rechargeable batteries” or “batteries”) after many charge-discharge cycles of the batteries, to lose their ability to recharge to their original capacity. In other words, after many charge cycles of the battery, the battery stores or holds a lower maximum mAh. 
     From a user&#39;s perspective, this means that a UE having a rechargeable battery that originally operated for 18 to 20 hours between requiring a battery charge will, over time, only operate for about 14 to 16 hours before being fully discharged and requiring a battery recharge. 
     Presently, UEs having rechargeable batteries are designed to charge their rechargeable batteries as quickly as possible. For example, many manufacturers would like the rechargeable batteries of a UE to charge within about 1 to 2 hours. Ideally, many manufacturers want the charge time to be as short as possible so that the user waits a minimal amount of time before being able to use his fully charged UE again. 
     It has been found that charging a rechargeable battery at the maximum charge rate minimizes the number of charge cycles in a battery&#39;s cycle life. Alternatively, it is known that one way to increase the number of charge cycles in the cycle life of a rechargeable battery is to charge the rechargeable battery at a slower rate over a longer period of time. 
     What is needed is a system and method for recharging a battery in a UE and at a reduced charge rate in order to increase the number of charge cycles in the cycle life of the UE&#39;s rechargeable battery. Furthermore, what is needed is a system and method for recharging the battery in a UE at a decreased charge rate during a time period when the user is unlikely to be actively using the UE and to recharge the battery of the UE and alternatively at a maximum charge rate when the user is most inconvenienced by having to wait an extended period of time for the rechargeable battery of the UE to be recharged. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding, reference is now made to the following description taken in conjunction with the accompanying Drawings in which: 
         FIG. 1  provides a chart indicating the additional number of charge cycles available in the cycle life of different batteries charged at different decreased charge rate percentages of a maximum charge rate; 
         FIG. 2  illustrates a block diagram of a UE incorporating an embodiment of a UE that improves battery cycle life; and 
         FIG. 3  is a flowchart of a method that increased the number of charge cycles in the cycle life of a UE&#39;s battery when an alarm application is used. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, wherein like reference numbers are used herein to designate like elements throughout, the various views and embodiments of the system and method for improved battery cycle life through smart overnight charging are illustrated and described, and other possible embodiments are described. The figures are not necessarily drawn to scale, and in some instances the drawings have been exaggerated and/or simplified in places for illustrative purposes only. One of ordinary skill in the art will appreciate the many possible applications and variations based on the following examples of possible embodiments. 
     It would be advantageous to increase the number of charge cycles in the cycle life of a battery without requiring the user to wait extended periods of time, due to a decreased battery charging rate, when the user needs the rechargeable battery recharged quickly. In order to achieve this, it would be advantageous to charge the UE&#39;s rechargeable battery more slowly when the UE determines that the user will most likely not need a fully charged battery in less than about 1½ hours (e.g., 1 to 2 hours). 
     Various embodiments determine whether the user of the UE will most likely need a fully charged battery in less than or greater than about 1½ hours from a time that UE is connected to an external charging device. Embodiments check whether an alarm clock application, which is processed by a processor within the UE, has been set to alarm within about 1½ hours, along with a few other criteria in order to determine whether the battery of the UE can be charged at a slower rate or needs to be charged at a maximum charge rate. 
       FIG. 1  provides a chart showing the charge rate of various rechargeable batteries (battery  1 -battery  9 ). Here the maximum charge rate for each battery is designated as C. For this chart, the maximum charge rate C is the charge rate at which the rechargeable battery can be charged from 0 mAh to full capacity mAh in one hour. Thus, charging a same battery at 0.5 C would take two hours. The center column of  FIG. 1 , titled Cycle life of 500 Cycles indicates the charge rate of each battery resulting in a cycle life of 500 cycles. For example, battery  1  is charged at 0.7 C and then completely discharged in a cyclic manner until battery  1  could only be charged to 80% of its original maximum mAh charge. Using this method it was found that battery  1  had a cycle life of 500 cycles when charged at 0.7 C. As shown in the right hand column, cycle life of 800 cycles, when another battery  1  was charged at 0.3 C and then discharged cyclically, it was found that battery  1  had a cycle life of 800 cycles. Similarly, for batteries  2 - 9  shown in  FIG. 1 , each battery when charged at a decreased charge rate, had an increased cycle life when compared to the same battery charged at a higher charge rate. 
     Many UE users charge their UE overnight while they are sleeping, which also happens to be during a time when the amount of time required to recharge the phone is relatively unimportant to the user and is greater than 1 to 2 hours. That is, it is unlikely that the user will actively use the phone while they are sleeping. In this situation, where a user generally sleeps for more than about 1½ hours at night and is only concerned that the phone is fully charged when he or she wakes up, embodiments can be set to charge the battery at a decreased charge rate in order to increase the number of cycles in the cycle life of the UE&#39;s battery. In various embodiments, the decreased charge rate can be set to a fixed decreased charge rate that is fixed at between 1 and 99% of the maximum charge rate that a charging circuit in the UE can charge the battery. Alternatively, in other embodiments, the fixed decreased charge rate may be a charge rate that is between 1 and 99% of a maximum charge rate the UE&#39;s charging circuit can charge the battery based on an amount of power provided to the UE from an external charger, such as a power adapter that converts AC voltage to a to a DC supply voltage, an external powerpack or external rechargeable phone charger device. 
     In one embodiment, for example, when a user sets the alarm clock application on their mobile terminal or UE for 6 AM, and the processor within the UE senses, via a charging circuit within the UE that the charging circuit is being connected to an external power source at 9 PM in the evening, the UEs processor can be configured to signal and adjust the charging rate of the UE&#39;s charging circuit to charge the battery at a decreased charging rate, wherein the decreased charging rate is less than the maximum charge rate of the UE&#39;s charging circuit. 
     In other embodiments, the decrease charge rate can be selected from one of a plurality of decreased charge rates that are each lower than the maximum charge rate. Each one of the plurality of decreased charge rates can be selected based on the amount of time in the future from the present time that the alarm clock application will sound the alarm (the delta time) and wake user. Here, a selected one of the plurality of decreased charge rates is selected to coincide with or be less than the delta time until the alarm clock application sounds the alarm to wake the user. In some embodiments, the expected idle time of the UE is, for example the measure of time between when the user connects the UE to an external charger in the evening and the time that the user has set the alarm application to sound or alarm (i.e., the delta time). 
     In other embodiments, the UE, via the internal charging circuit and the processor, detects that the UE has been connected to a charging device for an overnight charge based on alarm being set for an AM hour (e.g., between 4 AM and 10 AM) and that the user connected the UE to the external charger in the evening (e.g., between 6 PM and 1 AM). If these two criteria are sent by the charging application running on the processor, the processor sets or signals the internal charging circuit of the UE to charge the battery at a decreased charge rate, otherwise the processor will signal the internal charging circuit to charge the battery at a maximum or normal charge rate such that the battery will charge within about 1½ hours. 
     In some embodiments the UE comprises components that can perform basic logic functions to determine whether the UE is connected to an external charging device that is providing power to the internal charging circuit and determine whether the alarm application is set for more than, for example, 1½ to 3 hours in the future. In this embodiment, if the alarm is set for less than three hours in the future, the battery will be charged at the maximum or higher charge rate. Conversely, if the alarm is set for a delta time of more than three hours into the future, the charge rate can be set to a decreased charge rate and the battery will also be completely charged at or by a time prior to the alarm time. 
     Referring to  FIG. 2  a block diagram of a UE embodiment is depicted. The UE  200  can be any mobile communication or mobile terminal device such as a mobile phone, a mobile terminal, a smartphone, a tablet pad, a personal digital assistant (PDA), a laptop computer, or any portable rechargeable device that has a programmable alarm clock function. The UE  200  has one or more processors  202  that uses various applications, operations and circuits within the UE  200 . For example, UE  200  has a memory  204  that may have various applications with instructions for the processor  202  use. Here the memory  204  includes a battery charge application  206  and an alarm clock application  208 . The processor  202  is also connected to a user interface  210 . The user interface  210  may include a touchable display screen and buttons for a user to interface with the UE  200  and set and operate various applications, controls, settings and functions available to the user via applications stored in memory  204  and/or other electronics in the UE. For example, a user may select and run the alarm application  208  on the user interface  210 . While in the alarm clock application  208 , the user may set an alarm time for when the alarm clock is to sound. The user may set the alarm to be operational in the evening prior to going to sleep such that the alarm time is set to sound or alarm in the morning to wake the user up. Alternatively, the user may set the alarm clock to alarm every day or on only selected days. Prior to going to sleep the user may connect an external charger  212  to a connector  214  on the UE  200 . The external charger  212  may also be connected to a power source  216 , such as a wall socket or a rechargeable battery pack used for recharging mobile communication devices or other devices having lithium-ion or other types of rechargeable batteries therein. 
     Furthermore, the UE  200  includes a rechargeable battery  218  (herein also referred to as “a battery”) that is connected to a charging circuit  220  and a fuel gauge circuit  222 . The charging circuit  220  is connected to the connector  214  or is adapted to be connected to the external charger  212 . The fuel gauge circuit  222  monitors the power level of the battery and provides information to the processor  202 . The charging circuit  220  is configured to be able to charge the battery at a maximum charging rate based on the amount of power provided to the charging circuit from the external charger  212 . Additionally, the charging circuit  220  can be instructed by the processor, via a decreased charge rate signal, to charge the battery at a decreased charge rate. The decrease charge rate is a rate that is less than the maximum charge rate. In some embodiments, the charging circuit  220  is configured to provide a plurality of decreased charge rates that will charge the battery  218  from, for example, a discharged state to a charged state in different amounts of time, wherein the maximum charge rate will charge a discharged battery  218  in a least amount of time. 
     The UE also comprises a light sensor  224  that is adapted to sense or measure an amount of ambient light outside of the UE. In some embodiments, the light sensor is an integral part of a camera incorporated into the UE. The light sensor  224  senses the amount of ambient light or lumens about the UE and provides a signal indicative of the amount of lumens sensed to the processor. 
     The UE may also comprise a motion sensing circuit  226  that is configured to sense, among other things, whether the UE is stationary, moving and/or, in some embodiments, accelerating in one or more directions. The motion sensing circuit  226  is also configured to provide a signal to the processor indicative of whether the UE is stationary, moving, and or accelerating in one or more directions. 
     Embodiments of the UE  200  may also include a microphone circuit  228  that can sense sound levels that are about, near or proximate to the UE. The microphone circuit  228  provides a sound signal to the processor  202  and/or related circuitry that is indicative of, among other things, the sound level in decibels (dB) that the microphone circuit  228  receives from the environment near, about or proximate to the UE  200 . 
     Some embodiments have a charging circuit  220  that is configured to charge the battery  218  at a maximum charge rate or a decreased charge rate. The decreased charge rate is a charge rate that is lower than the maximum charge rate. The charging circuit  220  has an input or connector  214  adapted for connection to an external power supply, rechargeable battery pack or charger  212 . The charging circuit  220  provides a signal to the processor indicative of whether the charging circuit  220  is connected to the external charger  212 . When an external charger  212  is connected to the charging circuit  220  and providing power, the charging circuit may initially charge the battery  218  at a maximum charge rate. 
     The processor  202  follows instructions of the battery charging application  206  to check a variety of variables. The charging circuit will check to see if the alarm clock application  208  indicates that an alarm has been set. If no alarm has been set, then the processor  202  will direct or allow the charging circuit  220  to continue charging the battery  218  at a maximum charge rate. By charging the battery at a maximum charge rate, the battery should be fully charged, as determined by the fuel gauge circuit  222 , in a minimum charge time of about 1 to 2 hours. Alternatively, if an alarm has been set, the processor determines, in accordance with the battery charging application  206 , whether the alarm time is more than the minimum charge time in the future. In other words, when the UE is connected to an external power source, the processor determines whether the amount of time between the present time and the time that the alarm is set for (the delta time) is greater than the minimum charge time of the discharged battery  218  when being charged at the maximum charge rate provided by the charging circuit  220 . In some embodiments, the fuel gauge circuit  222  will provide the processor  202  an indication of how much “fuel” charge (mAh) is present in the battery  218  via a fuel signal. The processor  202  can calculate the minimum charge time for the battery based on the battery&#39;s present charge and the maximum charge rate that the charging circuit  220  can provide to the battery. When the calculated or determined minimum charge time of a partially charged battery is greater than or equal to the delta time, then than the processor  202  will instruct the charging circuit  220  to charge the battery at the maximum charge rate. 
     Conversely, when the calculated or determined minimum charge time is less than the delta time, then the microprocessor  202  will signal the charging circuit to charge at a decreased charging rate. The decreased charging rate will increase the number of charge cycles in the cycle life of the rechargeable battery  218 . In various embodiments, the decreased charging rate is set to a predetermined decreased charging rate that will charge the battery  218  to a full charge with in the amount of time between the present time and the alarm time. 
     In various embodiments other criteria is also checked by the processor  202  in order to increase the probability that the UE in a situation where it won&#39;t be disturbed between the present time and the alarm time. For example, in some embodiments processor  202  also monitors the motion sensing circuit  226  to determine whether the motion sensing circuit  226  senses no movement of the UE  200  for a predetermined period of non-motion time. This assumes that the UE not moving for a predetermined amount of non-motion time is an indication that the user may have gone to bed and/or will not be disturbing the phone until the alarm sounds. After it is determined that the UE has not moved for the predetermined period of non-motion time, the processor may provide a decreased charge rate signal to the charging circuit. 
     In other embodiments, the probability that the UE will not be disturbed between the present time the alarm time can be increased further by the processor  202  also monitoring the light sensor  224  in order to determine whether the ambient light about the UE and received by the light sensor  224  is below predetermined luminance level for at least a low lumen time. When the ambient light about the UE is below the predetermined lumen level for the predetermined low lumen time, it is considered another indication that the UE is in a darkened room, such as a bedroom, that the user is in bed and/or will be sleeping until the alarm time. The low ambience time may be a time period of between about 1 and about 90 minutes. After it is determined that the light received by the light sensor is below the predetermined luminance level for the predetermined low ambience time, the processor may provide a decreased charge rate signal to the charging circuit. 
     In additional embodiments, another criteria that may be used to help determine whether the UE  200  will not be disturbed between the present time and the alarm time is by the processor  202  also monitoring the microphone  228  in order to determine whether sound about the UE is below a predetermined decibel level for a predetermined length of quiet time while monitoring the microphone. The length of quiet time may be from 1 to about 90 minutes. After it is determined that the decibel level has stayed below the predetermined decibel level for the quiet time period, it may be assumed that the user has stopped talking or listening to a sound device, is not in an active location and has decided to go to sleep and as such, the processor may provide a decreased charge rate signal to the charging circuit. 
     Depending on the embodiment, if any one of the one or more various criteria of non-motion, low ambient light, and/or low decibel level are not met for their predetermined amounts of time, the processor will not provide a decreased or reduced charge rate signal to the charging circuit and the charging circuit will charge the battery at the maximum charging rate regardless of the amount of time remaining between the present time and the alarm time. 
       FIG. 3  provides a flowchart of a method of charging a battery in a UE. At step  300  the charging circuit is constantly monitoring whether it is connected to an external charger that is providing power for charging the UE&#39;s battery. In various embodiments, the processor within the UE is in electronic communication with the charging circuit in order to determine whether a power source is connected to the charging circuit of the UE. When it is determined that the charging circuit is connected to an external power source, such as a power converter, a rechargeable external powerpack, a power output from an electronic device such as a USB output, or other adaptable power source, at step  302  the charging circuit begins to charge the rechargeable battery of the UE at a maximum charging rate. It is understood that the maximum charging rate can be partially dependent on the amount of power being provided from the external power source. In various embodiments, charging the maximum charging rate will charge the battery in a minimum charge time. In various embodiments the minimum charge time can be between one and two hours. In other embodiments the minimum charge time is a calculated minimum charge time based on a measured amount of existing charge in the battery. 
     At step  304 , the processor determines whether an alarm clock application is running and whether an alarm clock time has been set to alarm or sound in the future. If no alarm time has been set, then at step  306  the charging circuit continues to charge at the maximum charging rate. The charging circuit will continue to charge the battery at the maximum charging rate until the battery is fully charged or the user disconnects the external charger from the UE. Thus, the method may loop back to step  300  to determine whether or not the charging circuit is still connected to the external charger. 
     If at step  304  it is determined that the alarm clock application is set to alarm at an alarm time in the future, then at step  308  the processor determines the amount of time between the present time and the alarm time (the delta time) in accordance with the battery charge application. At step  310 , the processor determines whether the delta time is greater than the minimum charge time. As discussed above, if the delta time is greater than the minimum charge time then, in some embodiments, the battery can be charged at a reduced charge rate in order to increase the number of battery charge cycles in the battery cycle life. Conversely, if the delta time is not greater than the minimum charge time then the battery will be charged that the maximum charge rate  306 . 
     Again if the delta time is greater than the minimum charge time then at steps  312 ,  314  and  316  the processor will determine whether the UE is being subjected to any motion  312 , noise above a predetermined decibel level  314  and/or ambient light above a predetermined brightness or lumen level during a predetermined time period from when the external charger was connected to the charging circuit of the UE. Some embodiments check for all three (motion, noise and light) criteria other embodiments check for specific ones of the three criteria depending on the time of day that the external charger is connected to the charging circuit and the delta time between the present time and the alarm set time. For example, if the UE is connected to an external charger in the early afternoon and the alarm set time is set for an early morning alarm time, it might not be prudent to check for the amount of ambient light about the UE since the UE was plugged in or connected to an external charger in the early afternoon. 
     Thus at steps  312 ,  314  and  316 , if motion  312  is being sensed in the embodiment and motion is detected during the predetermined time period after the charging circuit senses that it has been connected to an external connector, or if a noise above a predetermined noise level is sensed  314  during the predetermined time period, or if the ambient light is being sensed and it is determined to be above a predetermined light lumen level for the predetermined time period, then the method moves to step  306  and charges the battery at the maximum charge rate. Alternatively, when the motion  312 , the noise level  314 , and/or the ambient light about the UE is sensed to be below a predetermined levels for the predetermined time period(s), then the processor at step  318  will provide a reduced charge rate signal to the charging circuit instructing the charging circuit to charge the battery at a reduced charge rate of between 1% and 99% of the maximum charge rate. 
     In some embodiments, while the battery is being charged at a reduced charge rate the processor may continue or loop back in the method to check the motion, noise and/or light criteria on a periodic basis to determine whether it has changed. If one or more of the criteria has changed such that motion is being sensed, an increased noise level is being sensed, and/or light above a certain lumen level is being sensed, various embodiments of the invention can switch to the maximum charge rate to help ensure that the battery will be charged quickly because the user may be getting ready to use the UE again or because the UE has initially incorrectly determined that the UE&#39;s delta time period will be longer than the minimum charge time. 
     In various embodiments, the charging circuit can be set to reduce the charging rate so that the battery can be charged at a selectable or variable decreased charge rate that will fully charge the battery within the delta time period. By selecting a decreased charge rate that will charge the battery within the delta time period, the number of charge cycles within the battery lifetime is increased. The more often that the rechargeable battery is charged at a charge rate that is lower than the maximum charge rate, the more of an increase in the charge-discharge cycles of the battery cycle life and longer the battery will maintain a charge capacity of greater than 80% of the original battery charge capacity when compared to always charging the battery at a maximum charge rate. 
     Since many UE users charge their mobile terminals or mobile communication devices overnight when the charge time for the UE&#39;s battery is not important to the user (as long as the battery is completely charged by the time the user wakes up in the morning) then detecting that the battery has been connected to a charger for an overnight charge (i.e., the alarm clock function has been set for the morning), and setting the charge rate to a lowest acceptable charge rate that will enable the rechargeable battery to be fully charged by the time the alarm clock alarms and wakes the user is perfectly acceptable to the user. Since overnight charges can often enable a decreased charge rate of less than about 0.5 C of the maximum charge rate then the user may see the cycle life of their UE&#39;s battery increase from about 400 charge-discharge cycles to about 800 or about a 200% or higher charge cycle increase for the battery cycle life. Embodiments can enable the second and third year battery life of a UE to be greatly improved. In addition, embodiments also charge the battery as fast as possible during the day, while the UE is being charged in a moving automobile, in a noisy well lit office or in other places where the user probably would like the battery to be charged as quickly as possible (e.g., charged within one to two hours). 
     It will be appreciated by those skilled in the art having the benefit of this disclosure that this system and method to improve battery cycle life through smart overnight charging provides a provides a rechargeable user equipment having a charging circuit configured to charge a battery at a maximum charge rate or a decrease charge rate. The charging circuit comprises an input adapted for connection to an external charging device. Embodiments have a motion sensing circuit that senses non-movement of the rechargeable user equipment. Embodiments may also have an audio sensing circuit that senses the sound level about the rechargeable user equipment and a light sensing circuit that senses a lighting level about the UE. The processor is connected to charging circuit, the motion sensing circuit, and the audio sensing circuit is configured, via a charging application stored in memory of the UE, to determine whether an alarm has been set to alarm at a particular alarm time. The processor can further determine whether the charging circuit is receiving power from the external charger. If the processor is receiving power from the external charger, then the processor may determine whether the motion sensing circuit is (1) sensing non-movement of the UE for a predetermined continuous non-movement time, (2) sensing that the sound level about the UE has remained below a predetermined decibel level for a continuous predetermined quiet time, and/or (3) sensing that the ambient light about the UE has remained below a predetermined lumen level for a predetermined low lumen time, then the processor will signal the charging circuit to charge the battery at a decreased charging rate, otherwise the process will signal the charging circuit to charge the battery at a maximum charge rate. Accordingly, embodiments can increase the cycle life of a UE&#39;s battery from 300 cycles to over 800 cycles (more than 200%) when the alarm clock is used regularly and the mobile device is being charged overnight. It should be understood that the drawings and detailed description herein are to be regarded in an illustrative rather than a restrictive manner, and are not intended to be limiting to the particular forms and examples disclosed. On the contrary, included are any further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments apparent to those of ordinary skill in the art, without departing from the concepts and scope hereof, as defined by the following claims. Thus, it is intended that the following claims be interpreted to embrace all such further modifications, changes, rearrangements, substitutions, alternatives, design choices, and embodiments.