BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to monitoring a state of batteries within a multi-battery power supply, and more particularly relates to a multi-battery charge/discharge circuit, multi-battery power supply, and battery-supported electronic device, which are capable of selectively testing for a physical and electrical presence of each battery wired in parallel within the circuit, supply and device, without disconnecting the battery under test from its battery discharge path (when present in-circuit). 
         [0003]    2. Description of the Related Art 
         [0004]    Various battery systems are known, many rechargeable. Rechargeable battery systems or power supplies have numerous uses, being found in or used with many known electronic devices and systems, particularly portable or hand-held standalones. Some devices and systems require “uninterruptible” power supplies to assure operation of a supply-supported device, if necessary, without fail. As used herein, the term battery shall be used to describe an individual battery cell, or a multiple-cell battery unit, wherein the cells are typically arranged in a serial combination to form the battery unit, or battery. The term electronic device shall be used broadly herein to include known electronic devices and systems that include battery charge/discharge circuitry for maintaining a plurality of batteries in a ready-charge state. For example, a security or fire alarm device or system is an example of an electronic device. The term alarm system, as used herein, is used to describe any known alarm-based system or device, such as a fire or smoke detection system or device, a security system, a CO or CO 2  level detection system or device, etc. 
         [0005]    Conventional battery charge/discharge circuitry includes a charge path terminal (to sink current), a discharge path terminal (to source current) and control circuitry to control battery charge/discharge operation. Such conventional circuitry, however, is unable to detect whether one of an aggregate set of batteries, fixed in place physically and maintained by the charge/discharge circuitry, is missing electrically and physically from the circuit. The legacy charge control circuitry “sees” (or electrically detects) the aggregate current source, or aggregate voltage potential at the discharge terminal, but does not “see” or readily detect, nor can verify that individual batteries are present or not present in-circuit. For that matter, conventional charge/discharge circuits require a hands-on physical removal of a battery from its receptacle to test its health, i.e., in a separate battery tester. Human error sometimes leads to a failure to replace a dead or failing battery after out-of-holder testing, or worse, we sometimes fail to re-insert a dead battery in the dead battery&#39;s holder in instances where there is no replacement battery readily available. 
         [0006]    What is needed is a rechargeable battery circuit, multi-battery rechargeable power supply, and electronic device that includes the circuitry and/or power supply that are able to selectively test for a battery&#39;s present or missing state without disconnecting the battery from its in-circuit battery discharge path (if present), and communicating the testing result. The term “missing” as used herein is meant to describe a condition where a battery is not physically and electrically present in the circuit at its receptacle, i.e., not in-circuit. 
       SUMMARY OF THE INVENTION 
       [0007]    To that end, the inventions set forth and described herein include circuitry to monitor batteries arranged in a parallel battery configuration for charge/discharge circuit operation. The inventive circuitry may selectively test for each battery&#39;s presence in a battery holder or receptacle included for holding each battery in-circuit, when present. The circuitry includes a circuit discharge path and terminal, and a circuit charge path and terminal, to accommodate normal charge/discharge operation of the parallel batteries in-circuit. The discharge path is electrically connected to each battery receptacle so that the plurality of batteries can supply charge, if called upon to do so, during normal circuit operation. The circuit charge path supplies current to charge the batteries during normal circuit operation. 
         [0008]    To test for a battery&#39;s in-circuit physical and electrical presence, the inventive circuit selectively tests each receptacle (for battery presence therein) without the need to disconnect the battery from the circuit discharge path connection (if present). As such, circuit discharge operation need never be interrupted while testing for individual battery presence in-circuit. The inventive circuitry generates a signal for communicating the missing battery state. The “missing battery” signal may drive an LED, audible alarm, or other element to communicate the missing battery state locally, or may be transmitted to a distant device, system or network. The inventive circuitry may operate to enable existing or legacy control circuitry comprising an electronic device or system to notice individual missing batteries where the legacy control circuitry is functionally constructed to detect only missing circuit charge path states. 
         [0009]    Another embodiment of the invention includes a rechargeable multi-battery power supply for maintaining a plurality of batteries electrically connected in circuit via a plurality of battery receptacles in a ready charge state. The supply includes electrical or electronic elements for selectively testing each battery receptacle to determine whether there is a battery present (electrically present) therein. The power supply includes power supply control circuitry for controlling normal charge/discharge operation of the batteries, and a charge/discharge circuit electrically connected to the control circuitry. The charge/discharge circuit is connected to the control circuitry at circuit discharge and circuit charge path terminals. The battery charging cycle may be periodic or continuous, interrupted only if the batteries are called upon to operate as charge suppliers. The power supply or system receives and is responsive to a battery selection signal, which selects a particular battery, or battery receptacle to be tested for battery presence therein. The power supply generates and provides a signal to communicate the battery test results, for example, to control an LED or device arranged to monitor the state of power supply operation. Normal battery discharge operation never need be interrupted. 
         [0010]    The invention may further comprise an electronic system or device, such as a security alarm system, which includes charge/discharge circuitry or a power supply modeled in accord with the inventive principles set forth. The electronic device or system circuitry is able to selectively interrogate each battery receptacle included and electrically connected to the device or system to determine whether a battery is present therein. The selective testing may be conducted during normal battery charge/discharge operation without having to physically remove the battery (if present) from its discharge circuit path. The signals generated by the selective tests are constructed to complement legacy battery check systems that may normally check only for circuit charge path presence, but not for individual battery presence. A “missing” or “present” state corresponding to a missing battery determination is coded in a signal that is used to communicate the missing battery or fault state to a user, electronic device or controller. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of embodiments of the inventions, with reference to the drawings, in which: 
           [0012]      FIG. 1  is a circuit diagram that depicts one embodiment of a charge/discharge circuit of the present invention; 
           [0013]      FIG. 2  is an example of an electronic device including a charge/discharge of the invention; and 
           [0014]      FIG. 3  is a schematic block diagram of an electronic system into which an inventive charge/discharge circuit with missing battery detection ability is included 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    The inventive charge/discharge circuit, power supply and electronic device set forth and described herein maintain in a ready-charge state a set of rechargeable batteries in a parallel electrical configuration, and provides for selective testing of each individual battery&#39;s in-circuit presence without electrically disconnecting the battery from its discharge path, or interrupting normal battery supply operation (discharging operation). The figures and descriptions, however, are intended only as examples, are not exclusive, and should not be interpreted to limit the scope of the invention in any way. 
         [0016]      FIG. 1  is a schematic circuit diagram of a first embodiment of a battery charge/discharge circuit  100  of the invention. Charge/discharge circuit  100  is constructed and arranged for maintaining two (2) batteries, B 1 , B 2 , in a ready-charge state. The skilled artisan should understand that the inventive charge/discharge circuit may operate upon any number of batteries, or battery receptacles, and is not limited to the two-battery configuration depicted in  FIG. 1 . Charge/discharge circuit  100  includes a battery plus terminal  120  (for battery discharge or sourcing operation), and a battery minus terminal  130  (for battery charging). Battery plus terminal  120  connects to a positive battery receptacle terminal  111  of each battery receptacle wired in-circuit in the parallel circuit configuration. The positive battery receptacle terminals are required to physically hold each battery in place in the circuit, and to electrically connect to anode electrodes of batteries B 1 , B 2  when physically present in a receptacle. 
         [0017]    Each positive battery receptacle terminal  111  electrically connects to first ends of resistors R 1  and R 2 , respectively, in the embodiment shown. The other or second ends of each of resistors R 1  and R 2  are electrically connected to one of respective blocks of comparators, one of respective cathode ends of diodes D 1  and D 2 , one of each respective switch or pole SW 1  and SW 2 , and to one of respective negative battery receptacle terminals  112 . The electrical point so defined may be referred to hereinafter as a “compare” node. The switch common and the anode ends of diodes D 1  and D 2  are electrically connected to battery minus terminal  130 , the charging path with the circuit so constructed. The skilled artisan should note that the circuit conventions may be reversed, without deviating from the scope and spirit of the invention. During selective testing operation, a signal is asserted at switch SW 1  or switch SW 2 , respectively. The switching opens the respective or corresponding switch to switch the diode associated with the battery, or battery receptacle under test, in-circuit. A change in voltage potential or current draw at the respective comparators (i.e., a compare node) provides a comparator output indicative of the battery&#39;s missing state, present state, sourcing state and test state. 
         [0018]    That is, at switching, if the discharge path is drawing current from the battery (sourcing), the battery voltage at the respective comparators swings below ground, and the battery is present in-circuit in the receptacle. Sourcing is assumed to be a battery test, even though it could very well be a result of a loss of AC power. And if current is not sourced through the discharge path, the comparator is pulled high indicating that the battery is not present. That is, where a battery is not present in its receptacle, charge/discharge circuit  100  attempts to charge the switched battery (battery receptacle) through the charge path terminal such that the voltage potential at the compare node rises. The respective comparators included in the  FIG. 1  embodiment generate two (2) output signals associated with each battery or battery receptacle&#39;s to communicate a battery&#39;s missing or sourcing state. Communicating the two signals may be implemented with any available or known circuitry able to sufficiently identify that one or more batteries are missing, such as by transmitting a signal to a remote monitoring device, or using a signal to drive an LED or like device. 
         [0019]      FIG. 2  is an electronic alarm device  200 , within which a battery charge/discharge circuit that includes missing battery detection and discrimination ability is included. Device  200  includes alarm panel, P 1 , for controlling alarm device operation in coordination with a microprocessor, IC 1 . Alarm panel P 1  is electrically connected to a panel plus terminal  220  (discharge), and a panel minus terminal  230  (charge). Panel plus terminal  220  also electrically connects to battery receptacle terminals  211  of each of two battery receptacles. The battery receptacles are wired in parallel to hold and make electrical contact with anode and cathode electrodes of two batteries B 1 , B 2 , when physically present in the respective receptacles. Like the  FIG. 1  embodiment, the  FIG. 2  circuit embodiment as shown is constructed to hold and maintain two (2) batteries. The reader should note, however, that the embodiments are presented for exemplary purposes only. The invention is not limited functionally in any way to circuits, power supplies and/or electronic devices comprising only two (2) batteries, but may implemented to operate with any number of batteries wired in parallel for charge/discharge operation., e.g., four (4) or six (6) batteries. 
         [0020]    The panel plus terminal  220  connects to the battery receptacle terminals  211  through a voltage regulator, REG 1 , which regulator is provided with a diode D 3  connected across it such that the diode&#39;s cathode end connects to receptacle terminals  211 . The cathode end of diode D 3  connects to panel plus terminal  220 , and a low battery input of microprocessor IC 1 . The regulator REG 1  is controlled in accord with a control signal, PWM, which is filtered in filter F 1 . A diode D 4  is connected at its anode end to panel plus terminal  220 , and at its cathode end to a power supply PS 1 . Cathode ends of batteries B 1 , B 2 , when present in-circuit, electrically connect to receptacle minus terminals  212 , which further connect to one of respective cathode ends of diodes D 1  and D 2 , one of each respective FET switches SW 1  and SW 2 , and to one of respective ports C 1 , C 2 , of a missing battery and current sourcing detection circuit  250 . 
         [0021]    The other sides of FET switches SW 1 , SW 2 , are connected to panel minus terminal  230 , and the anode ends of diodes D 1 , D 2 . Individual wires are shown connecting microprocessor IC 1  to the switching control terminals of the FET switches, as well as an individual wire provided between the panel P 1  and microprocessor IC 1 . As shown in the figure, the microprocessor IC 1  also includes two (2) LEDs, LED 1 , LED 2 , for communicating a missing battery condition depending on the state of inputs C 1 , C 2 . An actuation switch ACT 1  is included to allow for operator pushbutton control of battery testing. 
         [0022]    Functionally, switching off one of FET switches SW 1 , SW 2 , opens the electrical path through the FET, and switches respective diodes D 1 , D 2 , in-circuit. A change in voltage potential or current draw at the respective ports C 1 , C 2  (at respective compare nodes), of missing battery and current sourcing detection circuit  250 , generates an output signal indicative of whether the respective battery associated with the switched FET is missing or present. If a battery is sourcing current, it must be present in-circuit. That is, if at FET switching the discharge path is drawing current from the battery (sourcing), the battery voltage at the respective inputs C 1 , C 2  at circuit  250  swings below ground. This indicates that the battery is present in-circuit at the receptacle. Sourcing is assumed to be a battery test, even though it could very well be a result of a loss of AC power. 
         [0023]    And if current is not sourced through the discharge path, voltages at C 1 , C 2  swing high indicating that the battery is not present. That is, where a battery is not present, the circuit attempts to charge the switched battery (battery receptacle) through the charge path terminal regardless of whether the positive discharge path terminal is drawing current or not. In consequence, the voltage potential at C 1 , C 2 , and diode cathode voltage rises. The signals generated by switching at C 1 , C 2 , generate at least four (4) output signals, which are provided to microprocessor IC 1 . The four signals are associated with each of the two battery&#39;s “missing” and “sourcing” states. Communicating the states may be implemented with any available or known circuitry to generate a signal sufficient identify that a battery is missing. For example, LEDs LED 1 , LED 2 , may be used to communicate a missing or present state of batteries B 1 , B 2 , in accord with the outputs of circuit  250 . 
         [0024]      FIG. 3  is a schematic block diagram of an electronic system or device  400 , into which an inventive charge/discharge circuit or rechargeable power supply  401  is included. Rechargeable power supply  401  supports normal charge/discharge operation of a number of batteries arranged therein in parallel. Power supply operation is controlled by an electronic device portion  403  of electronic device  400 . The power supply or circuitry  401  includes a discharge path  404 , electrically connected to the device portion  403 , so the device portion  403  can receive current from the batteries during battery discharging operation. A charge path  408  connects the power supply circuitry  401  to the device portion, and a line  407  is included to show a path for control signal exchange, battery presence detection signals, and like signals generated during operation. Such signals must be exchanged or communicated between the supply circuitry and the device portion  403 . The device portion may include an alarm portion  409 , in the embodiment shown. 
         [0025]    The alarm portion  409  may be driven by the device portion to communicate the state of testing, or communicate a fault condition indicating that at least one battery is missing from its intended in-circuit position. That is, when one or more of the individual battery positions (at a receptacle included to contain in-circuit batteries) is selectively tested via system  400 , the electrical connection of the battery receptacle (and the battery, if present) to the discharge path  404  is not interrupted. There is no need to physically inspect for missing batteries. If a battery is missing, the fault is communicated via alarm portion  409 . To that end, alarm portion  409  may embody any known signal communication device, such as a video monitor, alarm signal sound generator, alarm signal light generator, silent alarm signal, telephone system, electronic computer based network, and like known devices, etc. 
         [0026]    With each switch in its closed or thrown position, each respective diode is bypassed to the charge terminal (out of circuit). When a switch pole is controlled to be in its open position, the pole&#39;s respective diode is switched into the particular battery or battery receptacle charge path (diode is in-circuit). As such, the respective diode cathode voltage is the same voltage at the battery&#39;s respective compare circuit input. The switching isolates the charge path for the battery under test, requiring charge to the battery to pass through the diode, without interrupting normal operation. At the time diode D 2  is switched in-circuit, a signal is generated by compare circuit  430  and provided to controller  405  of device portion  403  to convey a fault condition, where the battery is missing. The battery select signal is preferably asserted under test only for the time necessary to detect a battery&#39;s presence, and communicate it. 
         [0027]    It will be recognized that there are many variations on the embodiments shown and described may be possible without departing from the scope and spirit of the invention. Consequently, the examples listed above are illustrative, and not meant to be exhaustive.
The invention includes a circuit to monitor batteries arranged in a parallel battery configuration for charge/discharge battery circuit operation. The circuit selectively tests for each battery's presence in a battery holder or receptacle without interrupting circuit discharging operation, e.g., physical removal, and communicates a fault condition if the battery is determined to be missing. The inventive circuit enables existing or legacy control circuitry operating with the circuit to detect individual missing batteries where the legacy control circuitry is constructed to detect only missing circuit charge paths states.