Patent Publication Number: US-2021193979-A1

Title: Retrofit battery module

Description:
RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 62/950,634, filed on Dec. 19, 2019, which is herein incorporated by reference in its entirety. 
    
    
     FIELD 
     The technology disclosed herein relates generally to door locks, specifically to a retrofit device configured to provide electric power and/or smart connectivity to existing electronic locks. 
     BACKGROUND 
     Locks are conventionally used to secure access points (e.g., doors, windows, etc.) from unauthorized entry. The earliest locks were purely mechanical. These locks used a key to physically manipulate the relative positions of one or more internal components to lock or unlock an access point. As technology matured, locks began incorporating electronic elements to improve security and ease of use. Some locks replaced physical keys with alternate credentials such as passwords, magnetic tokens, or biometrics, which when presented and validated would lock or unlock the access point. Some of these locks manipulate the internal lock components via electronic actuators such as motors, solenoids, etc. Such locks may also include sensors to track the relative positions of internal components. Recent technological advances have further improved electronic locks by connecting them to mobile devices and the cloud via wired and wireless signals. Doing so has further increased the safety, ease of use, and experience associated with locks. 
     SUMMARY 
     According to one aspect, a smart retrofit battery pack for a preexisting electronic lock is provided. The pack includes a housing electrically couplable to the electronic lock. A plurality of rechargeable battery modules is also included. Each of the plurality of rechargeable battery modules is removably electrically coupled to the housing. A wireless communication module is integral to the housing capable of interfacing with the preexisting electronic lock and at least one external wireless device. 
     According to another aspect, a retrofit battery pack, a retrofit battery pack for a preexisting electronic lock is provided. The pack includes a housing electrically couplable to the electronic lock. A plurality of rechargeable battery modules is also included. Each of the plurality of rechargeable battery modules is removably electrically coupled to the housing. When at least one of the plurality of rechargeable battery modules is removed from the housing, the remaining one or ones of the plurality of rechargeable battery modules is configured to provide power to the housing and the housing thereby is configured to provide power to the preexisting electronic lock. 
     It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
         FIG. 1A  is a front, top, right side perspective view of an exemplary electronic lock mounted to an interior side of a door; 
         FIG. 1B  is a front, top, right side perspective view of the exemplary electronic lock mounted to an exterior side of a door; 
         FIG. 1C  is an exploded perspective view of the exemplary electronic lock and the smart retrofit rechargeable battery pack with connectivity bridge; 
         FIG. 1D  is an exploded perspective view of the exemplary electronic lock and the smart retrofit rechargeable battery pack with connectivity bridge; 
         FIG. 1E  is a section view taken along line  1 D- 1 D of  FIG. 1D  showing the smart retrofit rechargeable battery pack with connectivity bridge installed in the exemplary electronic lock and schematically showing wireless connectivity; 
         FIG. 1F  is a section view taken along line  1 D- 1 D of  FIG. 1D  showing the smart retrofit rechargeable battery pack with connectivity bridge installed in the exemplary electronic lock and schematically showing a different embodiment of wireless connectivity. 
         FIG. 2  is a perspective view of the smart retrofit rechargeable battery pack with connectivity bridge according to one embodiment; 
         FIG. 3A  is a rear, top, left side perspective view of  FIG. 2  with a single rechargeable battery module installed according to one embodiment; 
         FIG. 3B  is a rear, top, left side exploded perspective view of  FIG. 3A ; 
         FIG. 4A  is a rear, top, left side perspective view of  FIG. 2  with two rechargeable battery modules installed; 
         FIG. 4B  is a rear, top, left side exploded perspective view of  FIG. 4A ; 
         FIG. 5  is a rear, top, left side perspective view of a smart retrofit rechargeable battery pack with ribbon connector; 
         FIG. 6  is a front, top, right side perspective view of a retrofit rechargeable battery pack according to one embodiment; 
         FIG. 7A  is a rear, top, left side perspective view of  FIG. 6  with a single rechargeable battery module installed; 
         FIG. 7B  is a rear, top, left side exploded perspective view of  FIG. 7A ; 
         FIG. 8A  is a rear, top, left side perspective view of  FIG. 6  with two rechargeable battery modules installed; and 
         FIG. 8B  is a rear, top, left side exploded perspective view of  FIG. 8A ; 
     
    
    
     DETAILED DESCRIPTION 
     Electronic locks exist to secure access points. Such locks are actuated when a user presents a valid credential or token (e.g., passcode, magnetic card, biometric, RFID tag, etc.). A power source is required for both the processing required to validate a credential and the actuation that allows or disallows access. This power source may be internal, as is the case with a battery, or external, as is the case with a wired connection to wall power. Traditionally, battery enabled locks use alkaline batteries which can be expensive, drain rapidly, and are inconvenient to dispose of. During periods when these batteries are dead or being replaced, the lock is not powered, which can prevent users from gaining access as needed. Directly powering these locks can be beneficial, but the installing the necessary wiring requires significant labor and cost, which can be prohibitive for consumers and businesses. 
     Some electronic locks are self-contained in that they are not configured to communicate with external wireless devices, such as mobile phones, or networks, such as the internet. Other electronic locks are configured to communicate with such external wireless devices or networks by use of a wireless communications module connected to the electronic lock. The communication pathways enabled by these modules enables users to interact with the lock. For example, they may allow users to monitor and/or change the lock status (e.g., lock or unlock the lock). 
     The inventors have recognized the benefits of an easy to install apparatus that is backwards compatible with electronic door locks and provides for a rechargeable power source and/or wireless communication. 
     Such an apparatus may be configured to removably fit an existing internal cavity within an electronic lock (e.g., the battery cavity, a space behind a decorative escutcheon or rosette, etc.) or an existing mortise within the door the lock is mounted to. Alternate embodiments may be configured to be affixed to an exterior surface proximate to the lock, door, or access point. 
     This apparatus may provide power to itself and the lock via one or more internal power sources eliminating the need to use alkaline batteries and/or route electric wiring to the electronic lock from an external power source. The power source may include one or more battery modules (or other power storage components) which may be rechargeable and provide additional benefits such as improved battery life per a given volume due to the higher energy density rechargeable battery modules typically have compared to alkaline batteries. In some embodiments, the power source may also provide power to additional components and/or sensors on or near the electronic lock including, but not limited to microphones, cameras, accelerometers, and photoresistors. Such a system may enable continued operation when one or more of the battery modules is not providing power. That is, when one or more of the battery modules is removed, dead, and/or recharging, one or more of the remaining installed battery modules may provide requisite power to the electronic lock. Alternate embodiments may take power from external sources such as wall power or photovoltaic cells in communication with the apparatus and/or lock. 
     Some embodiments may provide a retrofit capability that allows wireless communication between the electronic lock and an external wireless device (e.g., mobile phone, wireless bridge, internet router, etc.) allowing authorized users to locally or remotely monitor the lock, manipulate the lock status (e.g., lock or unlock), track and view lock or user activity, track and view battery life, and more. A combined retrofit battery pack with a wireless communications module coupled thereto may be termed herein as a smart retrofit battery pack. As used herein a mobile device includes, but is not limited to, a cell phone, such as Apple&#39;s iPhone™, other portable electronic devices, such as Apple&#39;s iPod Touches™, Apple&#39;s iPads™, and mobile devices based on Google&#39;s Android™ operating system, and any other portable electronic device that includes software, firmware, hardware, or a combination thereof that is capable of at least receiving the signal, decoding if needed, exchanging information with a server to verify information. Typical components of mobile device may include but are not limited to persistent memories like flash ROM, random access memory like SRAM, a camera, a battery, LCD driver, a display, a cellular antenna, a speaker, a Bluetooth™ circuit, and Wi-Fi circuitry, where the persistent memory may contain programs, applications, and/or an operating system for the mobile device. A mobile device can be a key fob. A key fob, which can be a type of security token, is a small hardware device with built in authentication mechanisms. It is used to manage and secure access to network services, data, provides access, communicates with door systems to open and close doors and the like. 
     In one embodiment, the apparatus includes a housing for interfacing one or more rechargeable battery modules and a wireless communications module to the electronic lock. Such a housing may provide for increased fire rating, such as the housings described in co-pending U.S. patent application Ser. Nos. 16/009,454 and 16/517,848, each incorporated herein by reference in its entirety. 
     In one embodiment, the apparatus housing may be configured to include a wireless communications module. The relatively larger size of an apparatus configured to hold a wireless communications module and a power source may provide additional benefits over a module solely configured to hold a wireless communications module. For example, the increased size may allow the use of a relatively larger and/or more powerful module. The size may also allow for a more strategic positioning of the module within the apparatus and the electronic lock. Combined, these features may improve the wireless communication signal. 
     In one embodiment, the apparatus housing may include one or more additional features such as a microphone to detect a knock on the door. Alternatively the housing may include an accelerometer used for this purpose. Further embodiments may utilize both in combination. In this respect, the knock on the door may be detected and the wireless communication module may thereafter send a signal to the external wireless device alerting a user that someone is at the door. Other embodiments may use alternative sensors to detect the presence of a person at the door including cameras, proximity sensors including infrared proximity sensors, or motion detectors including passive infrared, microwave, and ultrasonic motion detectors. 
     In one embodiment, an additional feature such as tamper detection may be included. In this regard, a microphone and/or accelerometer may be used to detect vibrations or noises that may be mapped to a signal indicative of someone tampering with the lock, for example someone attempting to pick the lock, jimmy the latch, or otherwise simply force the door open. 
     In one embodiment, other sensors or detectors may be included, such as dawn/dusk sensors, occupancy sensors, proximity sensors, temperature sensors, and/or door open/close sensors. Such sensors may provide added functionality, such as turning lights on or off depending on time of day and/or occupancy and/or proximity, alerting the status of the lock based on the time of day and/or occupancy, alerting the status of the door based on detecting whether the door is opened or closed, and otherwise interfacing with other systems in a home such as sensing outdoor and/or indoor temperature and communicating with a dwelling heating/cooling system to adjust the interior temperature accordingly. 
     In one embodiment, the communication module may act as a hub for a local door network. In this regard, any of the above noted or other sensors may be remote from the lock but may communicate with the module over a relatively short distance communication protocol such as Bluetooth™, Wi-Fi, ZigBee™, z-wave, etc. and the communication module may then relay any detected characteristic to a home network, the internet, or to any other external wireless device. 
     Turning now to the figures, according to one embodiment illustrated in  FIGS. 1A and 1B  an electronic door lock  100  includes a first lock housing  110  mounted to a first side  122  (e.g., interior) of a door  120  and a second lock housing  112  mounted to a second side  124  (e.g., exterior) of door  120 . It should be appreciated that electronic door lock  100  may be a pre-existing and/or pre-installed door lock. The upper exterior of first body portion  110  includes a removable face plate  130 . Protruding outwardly from the lower portions of each the first and second housings  110  and  112  are a first handle  110   a  (e.g., interior) and a second handle  112   a  (e.g., exterior). These handles can be of a variety of form factors (e.g., handle, knob, lever, etc.) as the present disclosure is not limited in this respect. Handles  110   a  and  112   a  are operatively attached to latch  114  through a series of internal lock components as would be familiar to those of skill in the art. When the electronic door lock  100  is in an unlocked state, rotating either the first or second handle  110   a  or  112   a  causes latch  114  to retract allowing door  120  to be opened. When the electronic door lock  100  is in a locked state, components internal to the lock in a way familiar to those of skill in the art prevent the user from rotating one or both of the handles  110  and  112 , preventing latch  114  from retreating, preventing door  120  from being opened. The door is transitioned from a locked to unlocked state by either rotating lock button  116  of the first handle  110   a , entering the correct passcode on keypad  118  of the second lock housing  112 , or manually twisting a key in the keyway  119  on the second door handle  112   a . The lock embodied in  FIGS. 1A and 1B  is an electronic door lock with keypad and lever handle, however it should be appreciated that the disclosure is not limited to any specific type of lock. 
       FIG. 1C  shows an exploded view of electronic door lock  100  including one embodiment of a smart retrofit battery pack  200 . Interior mounting plate  117  is used to attach the first lock housing  110  and all components contained therein/thereon to door  120 . Mounting plate  117  contains multiple through holes and embossed features that facilitate properly alignment and installation on door  120 . Specifically, mounting plate  117  contains through hole  117   a  which, when properly mounted, is concentric with door bore hole  121 . Through these holes, and a corresponding hole on the mounting plate used to attached second door housing  112  to door  120  (not pictured), handles  110   a  and  112   a  are operatively connected by a series of internal components including cylinder  111 , spindle  115 , and driver  115   a . In an unlocked state, rotating either handle  110   a  or  112   a  rotates spindle  115 , which has a square cross section. This square cross section enables the rotational motion of the spindle to be transferred to cam drive units internal to the latch assembly. Rotating these cam drive units results in the linear motion of a transmission plate, which in turn pulls latch  114 , enabling the door to open. When in a locked state, driver  115   a  prevents the rotation of spindle  115 , thereby preventing latch  114  from being pulled as previously described. 
       FIG. 1D  shows electronic door lock  100  with faceplate  130  removed, exposing interior cavity  140  located within first body portion  110 . Additionally,  FIG. 1D  shows one embodiment of a smart retrofit battery pack  200  as it would be installed in interior cavity  140 . Interior cavity  140  contains multiple components including, but not limited to, battery chassis  142 , PCB  148  spanning the area behind and coplanar with the rear face of battery chassis  142 , and connection port  146  mounted to a tab on the upper right hand corner of PCB  148 . Battery chassis  142  comprises a plurality of slots  143  which secure individual batteries, each comprising a positive terminal  144   a  and negative terminal  144   b  at opposite ends of the slots&#39; lengths. In some embodiments, the positioning of the positive and negative terminals is alternated in adjacent slots. These terminals are configured to electrically connect batteries installed within battery chassis  142  to smart retrofit battery pack  200  and electronic door lock  100  for the purpose of distributing electrical power. Connection port  146  enables compatible modules to connect to and communicate with PCB  148  and other electronic components internal to door lock  100 . 
       FIG. 1E  shows a section view of electronic door lock  100  with smart retrofit battery pack  200  installed taken along line  1 D- 1 D of  FIG. 1E . In this embodiment, smart retrofit battery pack  200  comprises of a main housing  210 , a rechargeable battery module  250 , contact pads  220 , a wireless antenna  260 , and connector  230 . 
     As shown, main housing  210  is configured to nest with interior cavity  140  of electronic door lock  100  without interfering with normal installation of face plate  130 . 
     Battery module  250  may be used to power any components constituting smart retrofit battery pack  200 . For example, battery module  250  may provide power to antenna  260 , or any other wireless device configured to communicate with external electronic devices. Additionally, battery module  250  may be used to power LED indicators  256 ,  257   a ,  257   b , or any other components requiring electrical power to operate. In embodiments containing multiple battery modules, each individual battery module may be used to power all desired components such that there is no down time when one or more battery modules are unable to provide power (e.g., dead, removed for charging, etc.). 
     Battery module  250  is electronically connected to contact pads  260 , which are electrically connected with positive and negative terminals  144   a  and  144   b  when smart retrofit battery pack  200  is installed in electronic door lock  100 . Through this connection, the smart retrofit battery pack  200  is able to provide power (e.g., electric voltage and current) to electronic door lock  100 . This power drives, among others, the lock components internal to door lock  100 , allowing it to be locked and unlocked. In some embodiments, this battery pack could additionally be used to power sensors internal and external to the electronic lock  100  such as microphones, cameras, photoresistors, accelerometers, reed switches, etc. In embodiments containing multiple battery modules, each individual battery module may be used to power all desired components such that there is no down time when one or more battery modules are unable to provide power (e.g., dead, removed for charging, etc.). In some embodiments, battery module  250  may be contain 2000 to 3000 mAh with a cell voltage of 1.2V to 1.5V corresponding to the typical energy capacity and voltage of a AA alkaline battery. In other embodiments, battery module  250  may contain a larger energy capacity such as 3600 mAh to increase battery life over standard AA alkaline batteries. It should be noted that battery life is a function of usage and environment as well as energy capacity, here measured in mAh. As such, some usage patterns and environmental factors (e.g., extreme cold or hot weather) may result in higher or lower battery life when compared to standard AA alkaline batteries. 
     In the embodiment shown in  FIG. 1E , wireless antenna  260  is shown to be located in the upper, exterior facing portion of smart retrofit battery pack  200 . This may be a preferred location in that it provides better signal strength or simplifies internal wire routing. This wireless antenna may be powered via battery module  250  and is in communication with PCB  148  via an electronic connection between connector  230  and connection port  146 . Wireless antenna  260  is shown to wirelessly communicate with one or more external devices. In one possible wireless communication pathway, shown by Path A, wireless antenna  260  is connected to the internet  262 , from which one or more authorized connected devices  263  can communicate with the lock  100 . In some embodiments, this internet connection may require an external wireless bridge which may be located in the consumers home. In an alternate embodiment, shown by Path B, wireless antenna  260  communicates locally with an authorized connected device  263 . In some embodiments, both communication paths are possible. Any wireless communication protocol may be used for this communication including Bluetooth, Wi-Fi, ZigBee, z-wave, etc. Through either or both paths, authorized users are able to remotely send commands to and receive data from lock  100 . 
       FIG. 1F  is a schematic view showing one embodiment of electronic door lock  100  including a microphone  162  and auxiliary sensor  160  interfacing with smart retrofit battery pack  200 . 
     In some embodiments, auxiliary sensor  160  is installed on the door is to sense one or more conditions, such as detecting door open/close status, knocking or tampering, temperature, proximity, occupancy, ambient lighting, time of day (night/day), images. Such sensor(s) may include an accelerometer, reed switch, or hall effect sensor for sensing door open/close status. In other embodiments, the proximity sensor may be used to detect motion correlating to the arrival of a guest at the door. In further embodiments, the sensor may be a camera to detect images, a light sensor to detect ambient lighting and/or nighttime/daytimes, a temperature sensor to detect interior and/or exterior temperature, or any other sensor suitable for fulfilling a desired application. Auxiliary sensor  160  may be configured to relay data to antenna  260  in smart retrofit battery pack  200  via any of the suitable local wireless communication protocols, such as those detailed above. 
     Included on the exterior lock housing is a microphone,  162 , which may be used to detect knocking or tampering in some embodiments. It should be appreciated that one of more of these sensors may be used to senses more than one condition. For example, a proximity sensor may be used to detect both proximity of a person as well as whether the dwelling is occupied. Similarly, a camera, which may be an infrared camera, may be used to detect occupancy as well as temperature. While shown on the exterior of the door, it should be appreciated that the one or more sensor(s) may be housed in an interior cavity of the door, in an interior cavity of electronic door lock  100 , or some other location proximate to electronic door lock  100 . While only one sensor is shown, the disclosure is not limited in this respect and any number of sensors may be used and situated in any suitable location. Microphone  162  may send data to smart retrofit battery pack  200  via a similar wireless communication protocol or via a direct wired connection to PCB  148   
     Once smart retrofit battery pack  200  receives signals from the microphone  162  and/or auxiliary sensor  160 , it may relay the data or a predetermined signal to an external wireless device  263 . External wireless device  263  may also be configured to communicate directly with any of the external components for the purposes of triggering an action (e.g., lock or unlock the door), checking the status of any of the components (e.g., checking lock/unlock status), etc. While an abridged and direct line of communication between antenna  260  and external wireless device  263  is shown in  FIG. 1F , it should be appreciated that this signal pathway may have one or more intermediaries such as those outlined in Path A of  FIG. 1D  as the disclosure is not limiting in this respect. 
     In some embodiments, an electronic lock  100  with smart retrofit battery pack  200  installed may serve as the central hub of a network of connected smart locks. For example, the electronic lock  100  with smart retrofit battery pack  200  shown in  FIG. 1F  may serve as an intermediary connecting one or more additional electronic locks with limited wireless communication capabilities (e.g., Bluetooth only) to a network they would otherwise be unable to access (e.g., Wi-Fi). This central hub configuration enables the additional electronic locks to have relatively cheaper, smaller wireless communication antennas which may require a lower amount of power to operate. 
       FIG. 2  shows one embodiment of a smart retrofit battery pack  200 . This pack includes a main housing  210  which is configured to nest within interior cavity  140  without interfering with normal installation and removal of face plate  130  as shown in  FIG. 1D . To facilitate this nesting, one embodiment of smart retrofit battery pack  200  may include ridges  212  as shown which may be configured to mate with the individual slots  143  of battery chassis  142 . Additionally, these ridges may help align pack  200  during installation and maximize space utilization allowing for larger battery modules  250 ,  251   a ,  251   b  to be used. Of course, it should be appreciated that the ridges need not be included in the housing. In some embodiments, one or more additional channels  213  are included to prevent interference with existing features located within cavity  140 . It should be appreciated that the present disclosure is not limited with respect to what geometric features (e.g., chamfers, filets, extrusions, slots, etc.) are or are not included in the housing design. Any such features may be included in any suitable quantities or excluded to facilitate the nesting of pack  200  within an existing cavity. 
     In one embodiment, smart retrofit battery pack  200  may include its own faceplate or other exterior surface intended to replace faceplate  130 . In some embodiments, this surface may include additional functional components such as photovoltaic cells for recharging batteries, sensors (e.g., microphones, accelerometers, sensors for detecting light such as photoresistors, etc.), or lights. 
     The embodiment of a smart retrofit battery pack  200  shown in  FIG. 2  includes contact pads  220  arranged to form electrical connections with positive and negative terminals  144   a  and  144   b  of battery chassis  142  when the module is installed. While not visible in  FIG. 2 , corresponding conductive pads may be located on the underside of housing  210  such that each terminal in battery chassis  142  is in direct contact with a contact pad  220 . Once the module is installed, the electrical connection formed between the contact pads  220  and positive and negative terminals  144   a  and  144   b  enables the transmission of electricity (e.g. current and/or voltage) from smart retrofit battery pack  200  to electronic door lock  100 . The electric power delivered would be used to drive internal components, for example, to lock or unlock the door, power sensors, for example, microphones and/or accelerometers, and more. 
     It should be appreciated that the battery chassis of the door lock may be removable from some pre-existing door locks. In such cases, the retrofit battery module may be configured geometrically differently to fit with the door lock. In such instances, an alternative means of providing electronic power from the smart retrofit battery pack  200  to the existing electronic door lock  100  and any additional sensors and/or components would need to be provided. For example, in an embodiment where the battery chassis was electronically connected to the electronic door lock via a plug connector, the retrofit battery pack configured to replace the battery chassis may be configured to include the same connector as the chassis such that it could directly plug into the door lock. 
       FIG. 3A  shows the exterior facing side of smart retrofit battery pack  200 . The lower portion of the pack contains a chamber  240  which houses removable rechargeable battery module  250 . In one embodiment, battery module  250  is configured with Li-Ion cells, but it should be understood any suitable rechargeable battery technology may be used (e.g., Nickel-Cadmium, Nickel-Metal Hydride, Lithium Ion Polymer, etc.). LED power indicator  256  is located on the battery pack  200  above battery module  250 . This indicator may be configured to communicate to the user how much power remains in the battery. LED  256  may illuminate one or more colors. While a single LED is shown in this embodiment, any suitable means of conveying battery status to the user may be used in alternate embodiments including but not limited to a plurality of LED lights, an LCD display, or a dot matrix display. Non-visual means to convey battery status can be used independent of or in concert with a visual means such as LED  256 . On smart retrofit battery packs with connectivity options, push notifications may be sent via wireless connection to external devices. 
       FIG. 3B  shows the smart retrofit battery pack  200  with rechargeable battery module  250  removed, revealing battery chamber  240 . Battery charging port  252  and contact terminals  254  are shown disposed on the battery module  250 . Charging port  252  is configured to receive an external charger from which electric power can be delivered. Charging port  252  may be configured as a micro USB, mini USB, or other commercially available connector port. Contact terminals  254  contact with corresponding terminals (not shown) located within the chamber  240  allowing power to be transmitted from the rechargeable battery module  250  to smart retrofit battery pack  200 . In a single battery embodiment, one or more internal components (e.g., a non-removable internal rechargeable battery, a sufficiently sized capacitor, or a sufficiently sized super capacitor) may provide power to the electronic lock while battery module  250  is removed for charging. Additionally, one or more spare battery modules may be provided in a kit such that an alternate may be installed when the battery module  250  is removed for charging. 
       FIGS. 4A and 4B  show an alternate embodiment of smart retrofit battery pack  201  which contains two removable battery modules. The design and functionality of this embodiment is similar to that of the aforementioned single battery module smart retrofit battery pack  200 , and thus not all details will be described with respect to this embodiment. Each battery module,  251   a  and  251   b , includes a charging port,  253   a  and  253   b , and contact terminals,  255   a  and  255   b . Each battery module is installed in a chamber,  241   a ,  241   b , located in the lower portion of the smart retrofit battery module. LED indicators  257   a  and  257   b  are located above each chamber. These display the battery status to the user. Any suitable alternative to this configuration such as those listed above can be used in place of the LEDs shown. In one embodiment, in a two battery module configuration, each battery module may individually power the lock. In this way, one battery module may be removed for charging while the second remains installed powering the lock. This would enable continuous operation with no power interruption. Additionally, any of the aforementioned internal components enabling power when both battery modules are removed may also be used. 
     The embodiments of a smart retrofit battery pack,  200  and  201 , shown in  FIGS. 2C-4B  depict a single housing comprising connector  230 .  FIG. 5  shows an alternate embodiments of a smart retrofit battery pack  202  configured with connector  230  at the proximal end of a ribbon cable  232  connected to the smart retrofit battery pack. While  FIG. 5  depicts a ribbon cable  232 , it should be appreciated that any suitable multi conductor connector familiar to one of skill in the art may be used. While  FIG. 5  depicts the smart retrofit battery pack  202  with a single battery module  240 , it should be understood that any number of battery modules may be used. This embodiment may also be configured with the wireless communication module  260  adjacent to the battery module(s) to reduce the footprint size of smart retrofit battery pack  230 . This may enable compatibility with a plurality of different existing electronic locks. 
       FIG. 6  shows an alternate embodiment of a retrofit battery pack  300  without components for wireless communication. This pack comprises a main housing  310  which is configured to nest within interior cavity  140  without interfering with normal installation and removal of face plate  130  as shown in  FIG. 1D . To facilitate this nesting, one embodiment of retrofit battery pack  300  may include ridges  312  as shown which may be configured to mate with the individual slots  143  of battery chassis  142 . Additionally, these ridges may help align pack  300  during installation and maximize space utilization allowing for larger battery modules  350 ,  351   a ,  351   b  to be used. Of course, it should be appreciated that the ridges  312  need not be included in the housing. It should also be appreciated that the present disclosure is not limited with respect to what geometric features (e.g., chamfers, filets, extrusions, slots, etc.) are or are not included in the housing design. Any such features may be included in any suitable quantities or excluded to facilitate the neat nesting of retrofit battery pack  300  within an existing cavity. 
     In one embodiment, retrofit battery pack  300  may include its own faceplate or other exterior surface intended replace faceplate  130 . In some embodiments, this surface may include additional functional components such as photovoltaic cells for recharging batteries, sensors (e.g., microphones, accelerometers, sensors for detecting light such as photoresistors, etc.), or lights. 
     The embodiment of a retrofit battery pack  300  shown in  FIG. 6  includes contact pads  320  arranged to form electrical connections with positive and negative terminals  144   a  and  144   b  of battery chassis  142  when the module is installed. While not visible in  FIG. 6 , corresponding conductive pads may be located on the underside of housing  310  such that each terminal in battery chassis  142  is in direct contact with a contact pad  320 . Once the module is installed, the electrical connection formed between the contact pads  320  and positive and negative terminals  144   a  and  144   b  enables the transmission of electricity (e.g. current and/or voltage) from battery pack  300  to electronic door lock  100 . The electric power delivered would be used to drive internal components, for example, to lock or unlock the door, power sensors, for example, microphones and/or accelerometers, and more. 
     It should be appreciated that the battery chassis of the door lock may be removable from some pre-existing door locks. In such cases, the retrofit battery pack  300  may be configured geometrically different yet configured to fit with the door lock. 
       FIG. 7A  shows the exterior facing side of retrofit battery pack  300 . The lower portion of the pack contains a chamber  340  which houses removable rechargeable battery module  350 . In one embodiment, battery module  350  is configured to be a Li-Ion battery, but it should be understood any suitable rechargeable battery technology may be used (e.g., Nickel-Cadmium, Nickel-Metal Hydride, Lithium Ion Polymer, etc.). LED power indicator  356  is located on retrofit battery pack  300  above battery  350  when installed. This indicator may be used to communicate to the user how much power remains in the battery. LED  356  may illuminate one or more colors. While a single LED is shown in this embodiment, any suitable means of conveying battery status to the user may be used in alternate embodiments including but not limited to a plurality of LED lights, an LCD display, or a dot matrix display. Non-visual means to convey battery status can be used independent of or in concert with a visual means such as LED  356 . 
       FIG. 7B  shows the retrofit battery pack  300  with rechargeable battery module  350  removed, revealing battery chamber  340 . Battery charging port  352  and contact terminals  354  are shown disposed on battery module  350 . Charging port  352  is configured to receive the an external charger from which electric power may be delivered. Charging port  353  may be configured as a micro USB, mini USB, or other commercially available connector port. Contact terminals  354  contact with corresponding terminals (not shown) located within the chamber  340  allowing power to be transmitted from rechargeable battery module  350  to retrofit battery pack  300 . In a single battery embodiment, one or more internal components (e.g., a non-removable internal rechargeable battery, a sufficiently sized capacitor, or a sufficiently sized super capacitor) may provide power to the electronic lock while battery module  350  is removed for charging. Additionally, one or more spare battery modules may be provided in a kit such that an alternate may be installed when battery module  350  is removed for charging. 
       FIGS. 8A and 8B  show an alternate embodiment of retrofit battery pack  301  which contains two removable battery modules. The design and functionality of this embodiment is similar to that of the aforementioned single battery retrofit battery pack  300 , and thus not all details will be described with respect to this embodiment. Each battery module,  351   a  and  351   b , includes a charging port,  353   a  and  353   b , and contact terminals,  355   a  and  355   b . Each battery module is installed in a chamber,  341   a ,  341   b , located in retrofit battery pack  300 . LED indicators  357   a  and  357   b  are located above each battery module. These display the battery status to the user. Any suitable alternative to this configuration such as those listed above can be used in place of the LEDs shown. In one embodiment, in a two battery module configuration, each battery module may individually power the lock. In this way, one battery module may be removed for charging while the second remained installed powering the lock. This would enable continuous operation with no down time. Additionally, any of the aforementioned internal components enabling power when both battery modules are removed may also be used. 
     While the embodiments shown in  FIGS. 3A through 8B  contain one or two battery modules, it should be understood that any desirable number of battery modules may be used. Additionally, any suitable number of cells may be located within each of the one or two battery modules shown in  FIGS. 3A through 8B . In all embodiments, the battery modules are shown as being rectangular. The design is not limited in this respect, and the battery modules may be on any suitable shape and/or configuration. 
     Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope disclosed herein. Accordingly, the foregoing description and drawings are by way of example only.