Patent Publication Number: US-2023146458-A1

Title: Power Management For Removable Batteries

Description:
BACKGROUND 
     Portable electronic devices are generally powered by on-board batteries. Such batteries have limited capacities, and therefore provide the electronic devices with a finite amount of power which limits the operating time of the device. When such batteries are exhausted, they must either be replaced with fresh batteries or be connected to a power source to charge. If batteries are removed from the device to be replaced, the device typically powers down. Some electronic devices may have charging circuitry that enables batteries to be charged without the need to shut down the device. However, the electronic device ceases to be portable when connected to a power source to charge its batteries using the charging circuitry. In either case, the use of a portable electronic device is interrupted whenever its batteries run low. Interruption for charging at a power source can be particularly disruptive in the case of smart glasses with prescription lenses since the wearer may be reliant on the lenses. 
     Typically, batteries powering an electronic device should be maintained at roughly equal levels of charge. An uneven charge between batteries may result in an inrush of current when a relatively fresh battery is connected in parallel to a relatively depleted battery. Such an inrush of current may damage the circuitry of the electronic device. Moreover, powering an electronic device using batteries having different charge levels may be inefficient. For instance, the battery having a higher charge level may be depleted more quickly than the battery having a lower charge level. Additionally, the battery having a lower charge level may have a higher resistance than the battery with the higher charge level, which may cause the battery with the lower charge level to overheat or otherwise become damaged. Further, inrush current may trigger overcurrent protection in the hardware, which may interrupt the intended operation of the device. To avoid these issues, typically all batteries are replaced at the same time to assure similar charge levels between all of the batteries. In situations where rechargeable batteries are used, a user may have to wait until a full set of batteries are completely charged to be certain that each battery in the set carries an equal charge. The requirement for equally charged batteries can thus extend interruptions to the use of portable electronic devices. 
     BRIEF SUMMARY 
     Aspects of this disclosure are directed to power management systems for electronic devices. The power management system may allow for a battery of an electronic device to be replaced while the electronic device remains powered by another battery. The power management system may also be configured to manage batteries having different levels of charge. 
     In one aspect, a power delivery system may comprise a battery connection, and a soft-start circuit connected to the battery connection and a main power bus. The soft-start circuit may be configured to provide increasing levels of power to the main power bus when a battery having a voltage level higher than a voltage level on the main power bus is connected to the battery connection, and prevent power delivery to the main power bus from the battery when the voltage level of the battery is less than the voltage level on the main power bus. 
     In some arrangements according to any of the foregoing, the battery connection may be a first battery connection, the soft-start circuit is a first soft-start circuit, and the battery is a first battery, and the system may further comprise a second battery connection, and a second soft-start circuit connected to the battery connection and the main power bus. The second soft-start circuit may be configured to provide increasing levels of power to the main power bus from the second battery connection when a second battery having a voltage level higher than a voltage level on the main power bus is connected to the second battery connection, and stop power delivery from the second battery to the main power bus when the voltage level of the second battery is less than the voltage level on the main power bus. 
     In some arrangements according to any of the foregoing, the soft start circuit may include an output transistor, and the provision of power to the power bus is through the output transistor. 
     In some arrangements according to any of the foregoing, the output transistor may be a field effect transistor, and a voltage at a gate of the output transistor is a function of a voltage at the battery connection and a voltage at the power bus. 
     In some arrangements according to any of the foregoing, the soft start circuit may further comprise an operational amplifier and a governance transistor, wherein the battery connection is wired to a first input of the operational amplifier, the power bus is wired to a second input of the operational amplifier, the output of the operational amplifier is wired to a gate of the governance transistor, and a drain of the governance transistor is wired to the gate of the output transistor. 
     In some arrangements according to any of the foregoing, the gate of the output transistor and the first input of the operational amplifier may be wired in parallel to the respective battery connection. 
     In some arrangements according to any of the foregoing, the output transistor may be an n-channel transistor and the governance transistor is a p-channel transistor. 
     In some arrangements according to any of the foregoing, an electronic system may comprise any of the foregoing power management systems and a charging pod for charging batteries connectable to the battery connections. 
     In some arrangements according to any of the foregoing, a wearable smart glasses device may comprise any of the foregoing power management systems. 
     In some arrangements according to any of the foregoing, the smart glasses may include two temple tips, each of the two temple tips including one or more batteries. 
     In some arrangements according to any of the foregoing, the temple tips may each be independently removable from the electronic device. 
     In some arrangements according to any of the foregoing, an electronic system may comprise any of the foregoing smart glasses devices and a charging pod including a wireless charging coil configured to receive one or more of the two temple tips and charge the one or more batteries. 
     In another aspect, an electronic device may comprise a first electrical connection, a second electrical connection, wherein each of the first electrical connection and the second electrical connection includes a battery connection, and an integrated circuit having stored thereon software instructions that, when executed, will cause the integrated circuit to restrict current draw from a battery connected to the first electrical connection or second electrical connection if the voltage of the battery exceeds a threshold voltage. 
     In another aspect, a power delivery system may comprise a first electrical connection, a second electrical connection, wherein each of the first electrical connection and the second electrical connection includes a battery connection, and an integrated circuit having stored thereon software instructions that, when executed, will cause the integrated circuit to restrict current draw from a battery connected to the first electrical connection or second electrical connection if the voltage of the battery exceeds a threshold voltage while allowing an electronic device comprising the power delivery system to be maintained powered by one or more batteries connected to the other electrical connection. 
     In some arrangements according to any of the foregoing, the device may further comprise two soft start switches controlled by the integrated circuit, each soft start switch associated with a respective one of the battery connections so as to be able to limit current draw from the respective one of the battery connections. 
     In some arrangements according to any of the foregoing, the device may further comprise a gas gauge associated with each of the battery connections and the governance of the current drawn from the battery connections may include monitoring the gas gauges. 
     In some arrangements according to any of the foregoing, the power delivery system may further comprise a gas gauge associated with each of the battery connections and the integrated circuit may be configured to monitor the gas gauges for a governance of a current draw from batteries connected to the first and second electrical connections. 
     In some arrangements according to any of the foregoing, the integrated circuit may be configured to send an error message to an output device if a battery having a voltage below a predefined threshold is connected within either of the battery connections. 
     In some arrangements according to any of the foregoing, the instructions, when executed, may further cause the integrated circuit to decrease the restriction of current draw as time elapses after connection of a battery carrying a voltage exceeding the threshold. 
     In some arrangements according to any of the foregoing, the instructions, when executed, may further cause the integrated circuit to decrease the restriction of current draw gradually. 
     In some arrangements according to any of the foregoing, the threshold may be a predefined threshold. 
     In some arrangements according to any of the foregoing, the battery may be a first battery and the threshold is a voltage of a second battery connected to the second battery connection. 
     In some arrangements according to any of the foregoing, the restriction of current draw may be directly related to a difference between the voltage of the first battery and the threshold. 
     In another aspect, a power delivery system according to any one of the foregoing arrangements may comprise at least one additional battery connection and at least one additional soft-start circuit connected to the at least one additional battery connection and the main power bus. The at least one additional soft-start circuit may be configured to provide increasing levels of power to the main power bus when a battery having a voltage level higher than a voltage level on the main power bus is connected to the at least one additional battery connection. The at least one additional soft-start circuit may also be configured to prevent power delivery to the main power bus from the battery connected to the at least one additional battery connection when the voltage level of this battery is less than the voltage level on the main power bus. 
     In some arrangements according to any of the foregoing, the restriction of current draw may be based on a difference between the voltage of a first battery connected to the first electrical connection and a threshold voltage for a second battery connected to the second battery connection. 
     In another aspect, an electronic device may comprise a power delivery system according to any of the foregoing arrangements. 
     In some arrangements according to any of the foregoing, the electronic device may be a wearable smart glasses device. 
     In some arrangements according to any of the foregoing, the electronic device may comprise two temples for wearing the electronic device on a head of a user, and each temple may comprise a temple tip including one or more batteries. 
     In some arrangements according to any of the foregoing, the temple tips may each be independently removable from the electronic device. 
     In another aspect, an electronic system may comprise an electronic device according to any of the foregoing arrangements, and a charging pod for charging one or more batteries that are connectable to a battery connection of the electronic device. 
     In some arrangements according to any of the foregoing, the charging pod may include a wireless charging coil. 
     In some arrangements according to any of the foregoing, the charging pod may be configured to charge one or more batteries of a temple tip of the electronic device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic representation of an electronic device connected to a power delivery system according to an aspect of the disclosure. 
         FIG.  2    is a diagram of a soft-start circuit according to an aspect of the disclosure. 
         FIG.  3    is a schematic representation of an electronic device connected to a power delivery system according to an aspect of the disclosure. 
         FIG.  4    is a flowchart of logic according to an aspect of the disclosure. 
         FIG.  5 A  is a perspective view of an example hardware implementation of aspects of the disclosure. 
         FIG.  5 B  illustrates a charging accessory usable with aspects of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     The present disclosure is directed to a power delivery system that allows for safe replacement of a battery of an electronic device to be replaced Each battery may simultaneously provide power to the electronic device through the power delivery system. When a battery is depleted or otherwise has a low charge level, the battery may be removed from the electronic device and replaced with a battery having more charge, such as a freshly charged battery. As the power delivery system provides power to the electronic device from multiple batteries connected in parallel when one of the batteries is removed the power delivery system may continue to provide power from the remaining batteries to the electronic device. 
     The present disclosure avoids the need for equally charged batteries for safe operation of a battery powered device. According to some aspects, this may be accomplished by configuring the device to soft-start a battery upon connection to the device, when the battery being connected has relatively more charge than the one or more other batteries powering the device. The device may also be configured to stop drawing from a battery that has a relatively low charge relative to the one or more other batteries, so as to draw only from the batteries having greater charge until the batteries are at a relatively equal charge. The above described functionality may enable a battery to be replaced while the electronic device remains powered by another battery. In this regard, the power delivery system of the electronic device may include two or more batteries connected in parallel. 
     A power management subsystem may be configured to balance the current drawn from the batteries when powering an electronic device. The power management subsystem may inhibit the current draw from a battery having a relatively greater charge. The inhibition may be a function of a difference in charge between two batteries. The power management subsystem may be, for example, a programmable integrated circuit (PIC). In one exemplary embodiment, instructions stored on the PCI may, when executed, cause the integrated circuit to restrict current draw from a battery connected to the first electrical connection or second electrical connection if the voltage of the battery exceeds a threshold voltage. This may for example include instructions to monitor gas gauges of the batteries and adjust current drawn therefrom. Alternatively, the power management subsystem may be a hardware circuit at each battery connection that is constructed to open or close a field effect transistor to varying degrees depending on the proportion of the voltage across the battery to the voltage at a power bus for the other systems of the device. 
     As used herein the term “electronic device” may include any device capable of being at least partially powered by one or more batteries. For example, an electronic device may be a tablet computer, laptop computer, mobile phone, earphones, wearable devices, such as smart watches, fitness trackers, health monitors, smart fashion, etc. As further described herein, the electronic device may be a pair of smart glasses. The smart glasses may include a battery slot at each temple tip. The battery slots may be connected in parallel to the electronics of the device such that the device may continue to operate when one battery is removed. The device may be provided with a battery charging pod and at least one spare battery so that the device may operate indefinitely. The charging pod may be capable of charging the batteries wirelessly, such as by the inclusion of at least one charging coil for inductive charging. 
     Example Systems 
       FIG.  1    illustrates an electronic device  20  connected to a power delivery system  10 . The electronic device is connected to a first soft-start circuit  100  and second soft-start circuit  200  via a power bus  30 . As described herein, each soft-start circuit may include a power source, such as one or more batteries that deliver power to the electronic device through the power bus  30 . Although not shown, electronic device  20  may include any number of components, circuits, or subsystems, any of which may be independent of one another or grouped within systems or subsystems themselves. 
     As further shown in  FIG.  1   , the power bus  30  may receive power through a power management subsystem  15  of power delivery system  10 , provided collectively by the first soft-start circuit  100  and a second soft-start circuit  200 . Although  FIG.  1    illustrates only two soft-start circuits, any number of soft-start circuits may be included in the power delivery system  10 . The power management subsystem  10  is illustrated as including two soft-start circuits  100 ,  200  by way of example only. In this regard, the power management subsystem may include any number of soft-start circuits. Each soft-start circuit may be similar to first soft-start circuit  100 , described in detail below, and may each be connected to a common power bus. 
       FIG.  2    illustrates first soft-start circuit  100 . Second soft-start circuit  200  is generally alike to first soft-start circuit  100 . That is, the illustration and the following description of the first soft-start circuit  100  may apply to the second soft-start circuit  200 . In some instances, power delivery system  10  may be designed such that second soft-start circuit  200  differs from first soft-start circuit  100  in some ways, such as with more or fewer components. Likewise, where a device includes more than two soft-start circuits, each additional soft-start circuit may be compared with first soft-start circuit  100 , without necessarily being identical to soft-start circuit  100 . 
     As shown in  FIG.  2   , first soft-start circuit  100  includes a battery connection  110  at which a (first) battery  112  may be connected. Battery  112 , though illustrated in  FIG.  2    as being integrated into the soft-start circuit  100 , may be removable from the first soft-start circuit  100 . Moreover, although only a single battery  112  is shown, any number of batteries, such as a battery pack containing multiple batteries, may be connected to the battery connection  110 . 
     First soft-start circuit  100  is configured to compare the voltage of the battery  112  to the voltage on power bus  30 . In this regard, the first soft-start circuit  100  measures the voltage on power bus  30  to the voltage of the battery  112 . The first soft-start circuit  100  may measure the voltage on the bus measuring line  150  to determine the voltage of the power bus  30 . The first soft-start circuit may control the power output by the battery  112  onto power out line  151  dependent on the outcome of the comparison. 
     In the example illustrated in  FIG.  2   , first soft-start circuit  100  will effectively disconnect battery  112  from power bus  30  when the voltage on power bus  30  exceeds the voltage of battery  112 . By disconnecting batteries holding relatively low charge, soft-start circuits  100 ,  200  will protect those batteries and the efficiency of the system, as current will be prevented from flowing from power bus  30  to a battery of lower voltage. In some arrangements, the soft-start circuits  100 ,  200  may be implemented with a tolerance allowing a battery to remain connected until a difference or ratio between the power bus  30  voltage and the battery voltage reaches a minimum threshold. Such tolerance may be provided by, for example, modifying comparison lines  154 ,  155 , described below, or by adding a Schmitt Trigger circuit to the soft-start circuits  100 ,  200 . 
     The first soft-start circuit  100  will restrict power from battery  112  to power bus  30  when the voltage of battery  112  exceeds the voltage on power bus  30 . When the voltage of battery  112  exceeds the voltage on power bus  30 , the degree to which first soft-start circuit  100  restricts connection between battery  112  and power bus  30  will increase as the difference between the voltages increases. That is to say, the amount of power output by the battery  112  onto the power bus  30  may be prevented or limited when the voltage of the battery  112  is larger than the voltage on the power bus  30 . Soft-start circuits  100 ,  200  according to the illustrated example will therefore protect depleted batteries and the efficiency of the device by preventing unintended rushes or redirection of current as batteries with a higher charge are connected. By restricting output from batteries carrying a higher voltage than power bus  30 , soft-start circuits  100 ,  200  will also protect main system  20  from inrush current when a freshly charged battery is connected. Since the restriction of the connection has a direct relationship with the amount that the voltage of a battery exceeds the voltage on power bus  30 , the restriction will decrease over time, as further described herein. 
     The first soft-start circuit  100  will provide an unobstructed connection between battery  112  and power bus  30  when the voltage of battery  112  equals the voltage on power bus  30 . The soft-start circuits  100 ,  200  may be modified from the numerical ratios stated herein and the arrangement illustrated in  FIG.  2    to allow unobstructed connection between battery  112  and power bus  30  when the voltage of battery  112  differs slightly from voltage on power bus  30  as well. The amount of difference tolerable for unobstructed connection depends, at least in part, on the chemistry and type of battery  112 . Any plural number of soft-start circuits according to the following description of first soft-start circuit  100  may therefore be connected to a common power bus  30  to enable batteries at various levels of charge to be safely connected or disconnected from respective soft-start circuits without interrupting operation of main system  20 . 
     To accomplish the above described comparison between the voltage of battery  112  and the voltage on the power bus  30 , positive comparison line  154  and negative comparison line  155  are connected to a positive input  121  and a negative input  123 , respectively, of an operation amplifier (op-amp)  114  of the first soft-start circuit  100 . The positive power supply terminal  115  of op-amp  114  is connected to power bus  30 , while the negative power supply terminal  117  of op-amp  114  goes to ground  119 . As such, op-amp  114  is powered by power bus  30 . Although a number of grounds are shown in  FIG.  2   , for clarity only ground  119  is labeled. 
     Positive comparison line  154  is connected to a voltage divider formed between battery out line  152  and battery ground line  153 . As shown in  FIG.  2   , battery out line  152  is connected to battery connection  110  and battery ground line  153  is connected to ground. The voltage divider is formed by resistor  120  and resistor  122 . The resistors may be sized such that the voltage between resistor  120  and resistor  122  is within the operating parameters of the op-amp  114 . For instance, resistor  120  may be 10 kiloohm (K) and resistor  122  may be 1 K. Resistors  120  and resistor  122  are arranged in series to act as a voltage divider between battery out line  152  and battery ground line  153 . 
     Positive comparison line  154  is connected between resistors  120 ,  122 , and thus carries a fraction of the voltage of battery  112 . Capacitor  124 , for which a suitable capacitance may be 1 microfarad (μF), is arranged in parallel with resistor  122  to act as a filter. Voltage on positive comparison line  154  and into positive input  121  will therefore be generally proportional to voltage across battery  112 . 
     Similarly, negative comparison line  155  is connected to bus measuring line  150  to carry a fraction of the voltage on the bus measuring line  150 . Resistor  126  and resistor  128 , for which suitable resistances are 10.1 K and 1 K, respectively, are arranged in series between bus measuring line  150  and ground to act as a voltage divider. Negative comparison line  155  is connected between resistors  126 ,  128 , and thus carries a fraction of the voltage of power bus  30 . Capacitor  130 , for which a suitable value is 1 μF, is arranged in parallel with resistor  128  to act as a filter. The voltage on negative comparison line  155  and into negative input  123  will therefore be generally proportional to the voltage on power bus  30 . 
     The positive input  121  and negative input  123  to op-amp  114  are therefore proportional to the voltages of battery  112  and power bus  30 , respectively. As such, the output from op-amp  114  will vary as the relationship between the voltages of battery  112  and power bus  30  varies. 
     Op-amp  114  outputs on op-amp output line  156  to a gate of a governance transistor  116 , which is a normally off transistor that will turn on as voltage at its gate increases beyond voltage at its source. In the illustrated example, governance transistor  116  is an enhancement type N-channel metal oxide semiconductor field effect transistor (MOSFET). The source of governance transistor  116  is connected to ground, so the drain-source conductivity of governance transistor  116  will largely depend on the output of op-amp  114 . 
     A governing line  157  connects the drain of governance transistor  116  to the gate of an output transistor  118 , which is a normally off transistor that will turn on as the voltage at its gate falls below the voltage at its source. In the illustrated example, output transistor  118  is an enhancement type P-channel MOSFET. Battery out line  152  is connected to the source of output transistor  118  and, through a resistor  132 , to governing line  157 . Voltage on governing line  157  is thus proportional to the voltage of battery  112  at a magnitude depending on the degree to which governance transistor is turned on, which in turn depends on the relationship between the voltages of battery  112  and power bus  30 . Power out line  151  connects the drain of output transistor  118  to power bus  30 . Thus, the connection between battery  112  and power bus  30  is throttled by output transistor  118  by an amount depending on the relationship between the voltages of battery  112  and power bus  30 . Specifically, output transistor  118  will be completely off when the voltage on power bus  30  exceeds the voltage of battery  112 , output transistor  118  will be completely on when the voltage on power bus  30  equals the voltage of battery  112 , and when the voltage of battery  112  exceeds the voltage on power bus  30 , output transistor  118  will be partially on to a degree that is inversely proportional to the difference between voltages. 
     As shown, first soft-start circuit  100  includes resistors and capacitors. Numerical values for suitable resistances and capacitances of these elements are set forth herein. Such values are suitable at least for a battery  112  with capacity for, for example, equal to or about 3.8 volts at maximum charge. Such values are merely examples and may differ in other arrangements according to the present disclosure. For example, the values may be increased or decreased in proportion with one another. For that reason, the disclosed values also indicate suitable ratios between the resistances and capacitances of the elements of first soft-start circuit  100 . Individual values may also be varied without entirely altering the function of first soft-start circuit  100 . For each resistance or capacitance described herein, values greater or less than the stated value by 10% of the stated value are also within the scope of the disclosure. All ratios between values resulting from such variation of individual values are also contemplated. 
     Resistor  132  and resistor  136 , for which suitable resistances are 100 K and 10 K, respectively, are arranged in series between battery out line  152  and governance transistor  116  to act as a voltage divider. Governing line  157  is connected between resistors  132 ,  136 , and thus carries a fraction of the voltage of battery out line. Capacitor  134 , for which a suitable capacitance is 0.01 μF, is arranged in parallel with resistor  132  to act as a filter. Capacitor  138 , for which a suitable capacitance is 0.47 μF, is also connected in parallel with resistor  136  and across the drain and source of governance transistor  116 , to act as another filter. 
       FIG.  3    illustrates another electronic device  320  connected to a power delivery system  310 . As illustrated, the electronic device is connected to the power delivery system via power bus  330 . Power is supplied to bus  330  by a power management subsystem  315  including a programmable integrated circuit (PIC)  318 , first soft start switch  342 , and second soft start switch  352 . The first soft start switch  342  is controllable by PIC  318  to throttle power drawn from a removable first battery  340 , and second soft start switch  352  is controllable by PIC  318  to throttle power drawn from a removable second battery  350 . The power delivery system is illustrated with two soft-start switches  342 ,  352  and two batteries  340 ,  350  by way of example only, and alternative arrangements may have any plural number of soft-start switches and batteries generally like those described here. 
     First battery  340  includes a first cell  344  and a first gas gauge  346 , and second battery  350  includes a second cell  354  and a second gas gauge  356 . Gas gauges  346 ,  356  measure charge held by their respective cells  344 ,  354 , such as through temperature measurements. PIC  318  may monitor gas gauges  346 ,  356 , and thereby the charge held by cells  344 ,  354 . 
     PIC  318  may include a processor and a non-transitory computer readable memory medium carrying instructions that, when executed, cause PIC  318  to read gas gauges  346 ,  356  and control soft-start switches  342 ,  352  to prevent unintended current rushes or redirections as batteries  340 ,  350  are connected or disconnected, without interruption to the operation of main system  320  as long as at least one battery  340 ,  350  carrying sufficient charge remains connected, in a manner similar to that described above with regard to soft-start circuits  100 ,  200 . 
     In one example, PIC  318  may be programmed to control soft-start switches  342 ,  352  to disconnect a battery  340 ,  350  carrying a cell  344 ,  354  with a lower voltage than a voltage on bus  330 , as estimated from measurements through gas gauges  346 ,  356 . PIC  318  may be programmed to control soft start switches  342 ,  352  to, upon connection of a battery  340 ,  350  carrying a cell  344 ,  354  with a greater voltage than a voltage on bus  330  as estimated from measurements through gas gauges  346 ,  354 , initially restrict a connection between the cell carrying the higher voltage and the bus  330 . PIC  318  may further be programmed to decrease such restriction over time, thus soft-starting the newly connected battery. 
     In another example, the memory medium of PIC  318  may carry instructions that, when executed, cause PIC  318  to execute a power management logic illustrated by the flowchart of  FIG.  4   . The logic  410  may be followed independently with regard to each connection point where a battery, such as batteries  340 ,  350 , may be attached. PIC  318  may begin at step  414  by checking, continuously or at intervals, whether a battery is attached to a given battery connection point. When a battery, such as first battery  340 , is detected as connected, PIC  318  will read the gas gauge at step  418 , such as first gas gauge  346 . 
     After acquiring the measurement from the gas gauge, PIC  318  will determine whether the battery cell, such as first battery cell  344 , is healthy by comparing the gas gauge measurement to a predetermined threshold at step  422 . A measurement exceeding the predetermined threshold will indicate that the cell carries a certain minimum amount of charge to be considered “healthy,” while a measurement below the predetermined threshold will reveal the battery cell to be “unhealthy.” In the illustrated example, if the cell is found unhealthy, PIC  318  may send a warning message at step  426  to a user through an output system or user interface of the electronic device. However, in other arrangements, no warning message is sent. 
     If the cell is determined to be healthy, PIC  318  will prevent an inrush current by activating the respective soft-start switch at step  430  to restrict connection between the cell and bus  330  by a gradually decreasing amount. 
     The cell, whether healthy or unhealthy, may then remain connected to bus  330  until the battery holding the cell is detached. The PIC  318  may monitor for detachment of the cell at step  434 . After the battery is detached, PIC  318  may return to monitoring the battery connection point at step  414  for connection of a battery. 
       FIG.  5 A  illustrates an example of an electronic device  500  wherein any of the foregoing power delivery systems may be implemented. In the illustrated example, device  500  is a pair of smart glasses. In the illustrated example, the device may include any operating hardware typical of smart glasses, such as user interface systems, a projector, a microphone, a speaker, a camera, a radio, wireless communication systems, or any combination of the foregoing. 
     Smart glasses  500  include a left temple  510  and a right temple  520 , which end, respectively, in a left temple tip  515  and a right temple tip  525 . Battery connections or connection points according to the above described power delivery systems  10 ,  310  and power management subsystems  15 ,  315  may be located anywhere in the smart glasses  510 , with, in some examples, each of the temple tips  515 ,  525  including one connection or connection point. The soft-start circuits  100 ,  200  or soft-start switches  342 ,  352  may also each be included in a respective one of the temple tips  515 ,  525 , or elsewhere within a respective one of the temples  510 ,  520 , or anywhere else in the smart glasses  500 . 
     Batteries may be removably connected to the connections or connection points within temple tips  515 ,  525 . In addition or in the alternative, temple tips  515 ,  525  may be removably connected to the respective temples  510 ,  520 . Thus, in various examples, when a battery needs to be replaced, a user may replace the battery itself, or may remove the temple tip  515 ,  525  containing the battery and replace it with a charged temple tip. 
       FIG.  5 B  illustrates a charging pod  555  that may be used with smart glasses  500  or any other implementation of the above described power delivery system  10 ,  310  and power management subsystems  15 ,  315 . Charging pod  550  according to the illustrated arrangement includes two charging slots  555  for receiving and charging a  112  or a battery  340 ,  350  (referred to generically as “batteries” below) according to the foregoing arrangements  10 ,  310 . However, in alternative examples, charging pod  550  may have only one charging slot  555 , or any other natural number quantity of charging slots  555 . Charging pod  550  may be configured to receive power from any suitable power source, such as a typical plug for a wall outlet, or any variety of USB or similar electronic connection. 
     Charging slots  555  may be any type of apparatus used for charging batteries. In some examples, charging slots  555  are inductive charging coils capable of wirelessly charging the batteries. However, in other examples, charging slots  555  may include electrical contacts for conductively charging the batteries. According to the above described alternative arrangements of the temple tips  515 ,  525 , the charging slots  555  may be configured to receive and charge the batteries alone, or the charging slots  555  may be configured to receive one of the temple tips  515 ,  525 , and to charge the battery contained within or connected to a received temple tip. 
     Charging pod  550  may be part of a system including electronic device  500 , or any device including power delivery systems  10 ,  310  according to the present disclosure, and at least one rechargeable battery. The system may include, for example, two, three, four, or more batteries. Since the above described power delivery systems  10 ,  310 , enable uninterrupted operation of electronic device  500  as batteries are individually connected or disconnected, as long as one charged battery, or a sufficient minimum number of charged batteries, remains connected to device  500 , inclusion of plural batteries in the system enables device  500  to operate indefinitely. Where multiple batteries are provided, one battery may power device  500  while another is charged in pod  550 . A charged battery may be connected to device  500  before disconnecting a relatively depleted battery from device  500  and charging the depleted battery with pod  550 . Thus, shutdown of device  500  is not necessary. 
     Although the concept herein has been described with reference to particular examples, it is to be understood that these examples are merely illustrative of the principles and applications of the present concept. It is therefore to be understood that numerous modifications may be made to the illustrative examples and that other arrangements may be devised without departing from the spirit and scope of the present concept as defined by the appended claims.