Abstract:
A battery management system can have a portable electronic device for providing electrical therapy to the body of a patient responsive to the occurrence of a treatable condition. The portable device can have a rechargeable battery, memory, data processor for determining available operating time for the portable device prior to recharging, and a display panel, or alarm, to inform the patient of, inter alia, available operating time. The portable device data processor can obtain and record data regarding the patient, the battery, and the portable device operational status. The battery management system can also include a rechargeable “smart battery,” of known design, which has an integral processor and memory capable of monitoring and updating the status and condition of the battery. The portable electronic device can communicate with and update the operational characteristics stored by the smart battery. The smart battery can be recharged using an appropriate conventional recharger. The portable electronic device can include battery maintenance capabilities to perform tests on the smart battery to independently evaluate the condition thereof. The portable electronic device can also have a battery status monitoring circuit which can monitor the battery condition independently of the smart battery internal monitoring system. The portable electronic device can further include a converter-defibrillator.

Description:
RELATED PATENT APPLICATIONS 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 08/995,713, filed Dec. 22, 1997, now U.S. Pat. No. 5,929,601 which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to portable electronic devices which utilize batteries. More particularly, the present invention relates to portable medical devices. Still more particularly, the present invention relates to methods and apparatus for the maintenance and management of the batteries of such portable medical devices. 
     2. Description of the Prior Art 
     Battery management is a concern in any portable electronic device, but is a primary concern in portable medical devices. The need for more comprehensive battery maintenance in portable and implantable medical devices has been noted, for example, in U.S. Pat. No. 4,080,558 to Sullivan, U.S. Pat. No. 5,411,537 to Munshi, et. al., U.S. Pat. No. 5,483,165 to Cameron, et. al., and U.S. Pat. No. 5,470,343 to Fincke, et. al. 
     A defibrillator is a device capable of delivering a preset amount of electrical energy to a patient&#39;s heart for the purpose of terminating an arrhythmia. For portable defibrillators, batteries are used to provide the electrical energy delivered. Historically, portable defibrillator maintenance has been problematic due to insufficient means to ensure comprehensive management of the batteries. As portable medical devices are intended for relatively long-term monitoring and, in the case of portable defibrillators, intended for therapeutic shock delivery for patients at risk from sudden cardiac death due to tachyarrhythmias, a comprehensive battery management program is essential. 
     Historically portable defibrillator design has been concerned with ensuring that the devices function properly when needed. Problems may arise if the batteries of the defibrillators are at less than full capacity or are worn out or are accidentally taken off their chargers so that the batteries are nonfunctional. 
     Therefore, there is a need in the portable electronic device industry, and, in particular, in the portable medical electronic device industry to implement a comprehensive way of informing the patient, as precisely as possible, of the status of that patient&#39;s device, and particularly the status of the device battery. This status should include not only the current conditions of the device battery but also other information, such as an indication of how much time remained in which the device would be operable. 
     SUMMARY OF THE INVENTION 
     The present invention is preferably utilized in connection with a patient-worn energy delivery system for imparting electrical therapy to the body of a patient responsive to an occurrence of a treatable condition. The present invention is designed to constantly monitor and comprehensively inform the patient of the condition of the device, and particularly the condition of the device battery. 
     The system includes a monitor-defibrillator worn by the patient. The monitor-defibrillator monitors the patient&#39;s ECG to detect life threatening arrhythmias and delivers a cardioverting or defibrillating shock if needed. The monitor-defibrillator records system operational information and ECG signal data. Periodically the patient is required to off-load this information to a patient base station. This is accomplished when the monitor-defibrillator is connected to a patient base station at the time battery charging is initiated. Thus, the patient base station is coupled with the monitor-defibrillator for periodic battery charging, device maintenance and the offloading of data. When a monitor-defibrillator is inserted into the monitor interface connector, the patient base station retrieves battery status from the monitor. The patient base station analyzes this information and may schedule maintenance operations or patient notifications if certain conditions are met. 
     The primary functions performed by the patient base station are providing data communication interfaces to the various components of the system, battery pack charging and maintenance, monitor-defibrillator maintenance, monitor-defibrillator data retrieval and storage, facilitating monitor-defibrillator initialization via the physician programming console and providing visual and audible feedback for patient interactions. 
     The patient base station provides means to simulate the operation of various monitor-defibrillator and electrode harness hardware functions. These enable the patient base station to verify that the monitor-defibrillator and the electrode harness hardware is functioning properly. 
     A physician programming console is also utilized, which is an IBM PC-AT compatible computer. The physician programming console facilitates programming of the patient base station and the monitor-defibrillator. Also included is an electrode harness, worn by the patient on the chest, which contains electrodes for sensing ECG signals from the heart and large surface area electrodes for delivering therapy pulses to the heart in the event of the occurrence of a treatable arrhythmia. 
     The monitor-defibrillator indicates the future time or activity level remaining at which the device could operate. The apparatus considers the rates of discharge and the rates of use and the amount of energy taken out of the battery. The device also monitors the number of charge cycles on the battery, the date when the battery was installed and other pertinent information such as battery pack expiration parameters. 
     The monitor-defibrillator itself includes circuitry to monitor the capacity of the battery. Thus, if the monitor-defibrillator undergoes some kind of abnormality, for example, some component begins drawing more current than the normal average current of the device, the circuit will detect the abnormality and the current will trip a comparator. The comparator alerts the computer and the remaining run time of the battery pack will be adjusted accordingly and can be displayed to the patient. 
     The patient base station also periodically performs a capacity check on the monitor-defibrillator when the monitor-defibrillator is coupled to the patient base station during charging and maintenance operations. This is a more comprehensive check than the one performed internal to the monitor-defibrillator. The patient base station can discharge the battery fully, charge it up fully and then discharge the battery. The current that&#39;s being discharged is precise, thus, over a period of time the processor could calculate whether the actual capacity of the battery is meeting the specifications. Factors such as the amount of charge and the rate of discharge are considered. 
     Having the capability to perform the monitoring functions on the monitor-defibrillator rather than solely at some remote base station is beneficial because the battery is necessarily contained in the monitor-defibrillator or attached to it via an electrical connector. Thus, if the patient has traveled away from the base station, that patient would have to return to the base station to be certain that sufficient capacity remained in the battery. 
     Alternatively, the monitor-defibrillator could itself be designed with additional functionality to perform all of the heretofore mentioned functions of the patient base station except, preferably, for the battery recharging function. In such a system, the battery can be a “smart” battery which has an internal memory/processor that can monitor and store information regarding the status of the battery. In this system, a dedicated battery recharger, also having a processor which communicates with the memory/processor in the smart battery can be utilized which does not require the functional capability of a patient base station. The smart battery memory/processor also communicates with the monitor-defibrillator when it is connected thereto. 
     Furthermore, although the smart battery can have the capability to monitor and determine operational characteristics thereof, it can be desirable that the monitor-defibrillator also independently, and more precisely, monitor the condition of the smart battery, particularly, for example, during a rapid drain condition as when electrical energy is being delivered to a patient when treatment is required. It is very important for the monitor-defibrillator to very precisely monitor the battery condition to ensure that a sufficient energy supply remains in the battery. Typically, the smart battery only monitors the data storage/processor circuitry of the monitor-defibrillator and not the converter. Thus, the monitor-defibrillator uses this added information to update the memory/processor in the smart battery. 
     These and other objects and advantages of the invention will become apparent from the following description of certain present preferred embodiments taken in conjunction with the appended claims and the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a patient base station block diagram showing the patient base station, physician&#39;s programming console and the monitor-defibrillator connected to either the patient base station or the electrode harness. 
     FIG. 2 is a block diagram showing the patient base station computer, real-time clock, counter timer, analog/digital converter and backup battery, and monitor-defibrillator battery connection. 
     FIG. 3 is a block diagram for the battery load test function. 
     FIG. 4 is a diagrammatic perspective view of the monitor-defibrillator and patient base station. 
     FIG. 5 is a block diagram for the patient base station patient interface module. 
     FIG. 6 is a simplified diagrammatic perspective view of an alternative embodiment of a monitor defibrillator, battery pack and battery recharger. 
     FIG. 7 is a simplified diagram illustrating a presently preferred alternative embodiment of a monitor-defibrillator. 
     FIG. 8 is a flow diagram illustrating a presently preferred initialization method. 
     FIG. 9 is a flow diagram illustrating a presently preferred battery operation method. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An apparatus is provided for monitoring and supporting the monitor-defibrillator electronics and the rechargeable battery pack provided therein. The system  10  of the present invention is shown schematically in FIG.  1 . As can be seen from FIG. 1, the present system  10  involves a number of interrelated components. A monitor-defibrillator  12  is included which is operatively connectable via an interface module  26 , to either a patient base station  30  or an electrode harness  66  having two groups of electrodes  14 ,  16 . A group of delivering electrodes  14  is provided for delivering a cardioverting or defibrillating shock when necessary to a patient. Another group of electrodes  16  performs sensing operations in which the physiological condition of a patient may be monitored. The delivering electrodes  14  are operatively connected to a converter-defibrillator  19  located within the monitor-defibrillator  12 . The electrode harness  66  also includes a patient display  24  with the capability of displaying visual messages, enunciating audio messages and activating audio alarms. The patient display  24  also includes various buttons for providing the patient with a means of input to the device. The operation of the electrode harness/monitor-defibrillator are more particularly described in co-pending application Ser. No. 08/651,274, assigned to the present assignee and hereby incorporated by reference herein. 
     The battery pack  18  is responsible for providing the necessary power to operate the converter-defibrillator circuitry for delivering the cardioverting or defibrillating shock. Therefore, it is important that the energy capacity of battery  18  be ensured. The monitor-defibrillator  12  preferably utilizes a high-energy-density nickel-cadmium battery. Preferably, the battery is comprised of five 1.2 volt cells connected in series to yield six volts. 
     The monitor-defibrillator  12  also includes battery control circuitry  20  which can activate the battery  18  to deliver its charge to the converter-defibrillator  19  and subsequently to the delivery electrodes  14  when necessary. The battery control circuitry  20  is responsive to certain data conditions of the patient. For this reason, the battery control  20  is operatively connected to data storage/processor  22 , also located within the monitor-defibrillator  12 . The data storage/processor  22  receives data from the sensing electrodes  16 . The data storage/processor  22  in the monitor-defibrillator preferably utilizes non-volatile memory. The data storage/processor  22  stores programmable system operational parameters, system operating status information, digitized ECG episodes and the results of hardware diagnostic tests. This data, through subsequent analysis, provides the means to allow reconstruction of ECG events and analysis of device performance. 
     The monitor-defibrillator  12  is able to perform various system and battery checks. Energy usage of the monitor-defibrillator  12  is monitored in real time to determine the useful energy remaining of the battery  18  per charge. The patient display  24  located on the electrode harness  66  indicates the operating time remaining for the battery  18 . The patient may access this function at any time by pressing a button on the patient display  24 . The run-time parameter is available to an external host via the communications interface located in the interface module  26 . A low battery condition as determined by the monitor-defibrillator  12  is recorded in non-volatile memory of the data storage/processor  22 . The patient is also alerted to a low battery condition by the patient display  24 . 
     The monitor-defibrillator  12  monitors the battery current consumption and, if required, makes an appropriate adjustment to the battery run-time parameter based on sampling the real-time monitor-defibrillator current consumption. The current is monitored by an analog circuit in the monitor-defibrillator  12  and is input into a comparator at a trip level of current. The voltage is monitored but is not sent to the comparator. The trip level is a level of current that is based on a precalculated worst case (i.e., maximum) average current developed for the device. For the particular hardware used with the present invention, the amount of typical maximum run current (i.e., the trip level current) is 74 milliamps. If the measured current exceeds the trip level, the comparator trips and the analog to digital converter in the data storage/processor  22  is commanded to read the analog representation of the current that is being drawn by the monitor-defibrillator  12 . The monitor-defibrillator  12  measures the time period of excessive current draw and the amount of current above the trip level. Based on the measured readings, time is deducted from the battery runtime parameter by the monitor-defibrillator. The updated runtime remaining may be accessed by the patient at any time, as discussed above. 
     As long as the actual, measured current of the monitor-defibrillator  12  is less than the trip level current, the data storage/processor  22  presumes that the actual current is the same as the trip current when deducting time from the battery runtime parameter. Thus, although the typical maximum run current is provided as 74 mils, the battery  18  is nearly always providing a current below 74 milliamps. 
     The patient has the capability to access buttons on the patient display  24  that when activated will cause the remaining run time to be indicated. If a patient is very active so as to cause one of the sensing electrodes  16  to have fallen off or otherwise become disconnected from the patient, an alarm is sounded. The activation of this alarm also utilizes energy which will be subtracted from the run time. 
     The current measuring capability of the monitor-defibrillator  12  does not include current drawn by the converter-defibrillator  19 . The monitor-defibrillator  12  tracks the periods when the converter-defibrillator  19  is actively drawing current from the battery  18  and makes adjustments to the battery run time to compensate for the energy loss. 
     The monitor-defibrillator  12  also makes adjustments for depletion of battery  18  capacity during periods when the device is not being used. When not in use (such as when stored on a shelf or taken by the patient on a day&#39;s outing as a spare device) the monitor-defibrillator  12  will automatically power itself up at specified intervals and make adjustments to the battery run time to compensate for energy losses due to self-discharge of the battery and current draw of monitor-defibrillator  12  components when powered down. 
     The monitor-defibrillator  12  will utilize measures intended to reduce depletion of battery  18  capacity in order to maximize available energy if a treatment pulse is required. The monitor-defibrillator  12  will be optimized to execute its monitoring functions as rapidly as possible and then enter a low power operating mode until the monitoring functions must again be executed. The monitor-defibrillator can be kept in a low power operating mode when not performing necessary system operating functions. Additionally, when possible, high current devices will be powered down after completing their required tasks. An example would be the analog to digital converter. By scheduling analog to digital conversion readings at the beginning of monitoring functions, the analog to digital converter can be powered down sooner than if analog to digital readings are interspersed throughout the monitoring functions. 
     If the run time parameter indicates that the depletion of battery  18  capacity has reached the level at which the battery  18  should be recharged utilizing the patient base station  30 , then the patient display  24  will provide notification. The notification will consist of visual and/or audio indicators. The notification will require acknowledgment by the patient before it will be discontinued. The notification will be repeated at predetermined intervals, for example, every 15 minutes, until the battery  18  is recharged by the patient base station  30 . The monitor-defibrillator  12  can also determine the available device operating time (prior to recharging the battery), taking into account at least: (1) adjustments for abnormally high current draw of the device including adjustments for converter operation or operation of other high current draw devices as well as adjustments for excessive current draw from a defective component; (2) adjustments for normal current draw during an elapsed time period; (3) adjustments for device fault conditions such as failure of a battery load test or a problem with operation of the converter; and (4) adjustments for depletion of battery capacity during periods of non-use. The patient display  24  or alarms can be used to notify the patient of the available device operating time. 
     The monitor-defibrillator  12  will also utilize an analog to digital converter located in the data storage/processor  22  to supervise the battery  18  voltage during operation of the converter-defibrillator  19 . The converter-defibrillator  19  may be operated in either a fast charge mode or a slow charge mode. The fast charge mode minimizes the time to charge the converter-defibrillator  19  but at a maximized current draw from the battery  18 . The slow charge mode minimizes the capacitor charging current but with an increased time to charge the converter-defibrillator  19 . The converter-defibrillator  19  is normally operated in fast charge mode. 
     If the battery  18  voltage falls below a level at which the monitor-defibrillator  12  can reliably operate the converter-defibrillator  19 , then the monitor-defibrillator  12  will switch the converter-defibrillator  19  to a slow charge mode. This will permit the battery  18  voltage level to recover to a level at which the monitor-defibrillator  12  can again reliably operate the converter-defibrillator  19 . Use of the slow charge mode permits the converter to be operated and a therapy pulse delivered to the patient when the battery  18  capacity is low. 
     If during operation of the converter-defibrillator  19  in the slow charge mode the battery  18  voltage falls below a level at which the monitor-defibrillator  12  can reliably operate the converter-defibrillator  19 , then the monitor-defibrillator  12  will deactivate the converter and evaluate the energy capability stored in the converter. If the energy stored in the converter is sufficient to deliver at least a minimal energy pulse, such as, for example, 30 joules, then the treatment cycle will continue with delivery of the available energy. If there is not enough energy stored in the converter to deliver a minimal energy pulse, then the converter will be discharged. In addition, notification will be given using the patient display  24  that the device is disabled and medical assistance should be provided to the patient. 
     If the monitor-defibrillator  12  determines that the battery  18  capacity has fallen below a level at which the system performance data is in danger of being corrupted then the monitor-defibrillator  12  will remove operating power. The removal of operating power will reserve the remaining battery  18  capacity for maintenance of the data storage/processor  22 . The integrity of the data storage is essential to evaluating the proper operation of the device. Since this low level of battery  18  capacity is inadequate for reliable operation of the monitor-defibrillator, the best possible use of the remaining battery  18  capacity is to preserve the operational history of the device stored in the data storage/processor  22 . When this state has been reached, the monitor-defibrillator will refuse to power up until connected to the patient base station  30 . If required, the patient base station  30  will provide additional energy to the monitor-defibrillator  12  to insure proper functioning during this power up sequence. The patient base station will then retrieve the operational history from the monitor-defibrillator  12  and recharge the battery  18 . 
     The analog to digital converter located in the data storage/processor  22  is powered up each interim cycle to sample the analog inputs. This interim cycle is preferably every 5 milliseconds, which generally corresponds to the ECG sampling rate. After sampling the analog inputs, the analog to digital converter is powered down to conserve battery power. There are entire portions of the monitor-defibrillator  12  that periodically go into a low current sleep mode. 
     On a routine basis the patient is required to couple the monitor-defibrillator  12  with the patient base station  30  (see FIG.  4 ). When the monitor-defibrillator  12  is removed from the electrode harness  66  and inserted in the receptacle  31  of the patient base station, connection is made between the monitor-defibrillator interface  26  and a monitor-defibrillator interface  32  located within the patient base station  30 . The patient base station monitor-defibrillator interface  32  is thus operatively connected to the data storage/processor  22  of the monitor-defibrillator  12 . In this way, the monitor-defibrillator interface  32  can download information from the memory of the data storage/processor circuitry  22 ; i.e., information, that was received from both the sensing electrodes  16  regarding the patient&#39;s physiological data, and also from the battery control circuitry  20  regarding the operating history of the monitor-defibrillator  12 . 
     The monitor-defibrillator interface  32  of the patient base station  30  is also operatively connected to the battery  18 . In this way, the patient base station  30  can perform comprehensive tests as to the operating parameters of the battery  18 . Further, charging of the battery  18  can also be performed through the monitor-defibrillator interface  32 . The battery  18  of each monitor-defibrillator  12  requires periodic charging. Thus, monitor-defibrillators  12  that are not in use are to be stored on a patient base station charging port (i.e., coupled to the monitor-defibrillator interface  32 ), where they undergo charging and maintenance operations. The patient base station  30  provides battery status information to the patient by way of a visual display including indicator lights as well as by audio alarms provided by the patient interface  46 . 
     The power required to charge the battery  18  of the monitor-defibrillator  12  is supplied by either an internal or an external power supply. As shown in FIG. 1, an internal power supply  38  may be used which is operatively connected to the charger interface module  34 . A switch mode type power supply  38  is preferred. However, a linear type power supply  38  could also be utilized. If a linear type power supply  38  is used, a heat sink and a fan would be needed in the patient base station  30 . Use of a switch mode type power supply  38  would eliminate the fan, reduce the size of the heat sinks and would reduce the size of the system package and is thus preferred. 
     The power supply  38  utilizes a power entry module  36 . The power entry module  36  provides a standard IEC 320 type power entry connector. The power entry module  36  functions over a full range of standard household international voltages and frequencies. The power entry module  36  shall preferably use a standard international “1/0” icon for power status indication. 
     The monitor-defibrillator interface  32  is operatively connected to the charger interface module  34  within the patient base station  30 . The charger interface module  34  provides a standard PC-AT compatible ISA type interface and provides all the necessary bus signals for computer control of the various charger interface module functions. In this way, data received by the monitor-defibrillator interface  32  from the data storage/processor  22  of the monitor-defibrillator  12  is provided to a computer  40 . In this way, communication is then established for transfer of operational data to the patient base station mass data storage area  42 . This data is a record of device performance and any ECG data that may have been stored within the monitor-defibrillator  12  during patient monitoring. 
     Thus, the patient base station initiates data retrieval operations from the monitor-defibrillator  12  if operational or ECG data is stored within the internal memory included in the data storage/processor  22  of the monitor-defibrillator  12 . As part of normal maintenance of the monitor-defibrillator  12 , this data is transferred to the patient base station  30  for long-term data storage  42 . The patient base station  30  may store retrieved data on a removable floppy disk, removable or fixed hard disk or other removable media. In the preferred embodiment, the data is stored on a fixed hard disk. At the successful completion of data transfer, the computer  40  of the patient base station  30  issues a clear memory command via the monitor-defibrillator interface  32  to the monitor-defibrillator  12 . This command erases the temporary memory in the data storage/processor  22  in the monitor-defibrillator  12 . In the embodiment utilizing rotating media, the patient base station notifies the patient when the removable media requires replacement due to inadequate storage area remaining. 
     The computer  40  utilized by the patient base station  30  incorporates an imbedded, PC-AT-compatible computer architecture. The computer  40  preferably utilizes an Intel™ 80×86 type central processing unit, with a performance no less than that of a 25 MHz 80386SX Intel™ processor. The computer  40  preferably includes two standard PC-AT type serial ports. A modem interface port  44  should also be available for connecting the computer  40  to a telephone modem (not shown). The modem interface  44  is designed to interface to a telephone modem with no less than 14.4 kpbs data rate capability. The modem preferably interfaces to the single board computer  40  via one of its serial ports. 
     A physician&#39;s programming console (“PPC”) interface  48  provides a communication link from the patient base station (“PBS”)  30  to a physician&#39;s programming console  70 . The physician&#39;s programming console interface  48  contains an ethernet communications module  52  for providing a standard 10 Mbps data link to the physician&#39;s programming console  70 . This module  52  preferably interfaces to the single board computer  40  via an expansion bus  54 . Data transfers between the patient base station  30  and the physician&#39;s programming console  70  are handled via the ethernet port  52 . This allows the significant amount of data generated by the monitor-defibrillator  12  to be offloaded in a reasonable time at the physician&#39;s office during the patient&#39;s periodic visits. The external panel connection for the high speed physician&#39;s programming console  70  data link can use a standard BNC type female connector. A serial communications port  50  is also part of the physician programming console interface  48  and is provided for connection of the computer  40  to the physician&#39;s programming console  70 . Data transfer from the patient base station  30  to the physician&#39;s programming console  70  can also occur via high speed modem interface  44  from the patient&#39;s home. 
     The computer  40  is operatively connected to an ISA type expansion bus  54 . The expansion bus  54  is designed to be capable of supporting up to four 16 bit expansion modules or cards. The computer  40  utilizes the expansion bus  54  to facilitate communications, control and status transfers to and from the charger interface module  34  and ethernet communication module  52  of the physicians programming console interface  48 . The expansion bus  54  also provides power to the computer  40  and the ethernet communication module  52  from the charger interface module  34 . 
     The operating system and applications software for the patient base station  30  may be stored on rotating media in the mass data storage area  42 . However, the preferred embodiment embeds this software in non-volatile read only memory, such as EEPROM or FLASH memory. These embodiments allow the device to operate without need of rotating media. Additional non-volatile memory is provided to store certain manufacturing information and device-specific data. These memory locations are written to only during the initial manufacturing processes and are then write inhibited by hardware means. As shown in FIG. 2, a real time clock may be implemented in conjunction with the computer  40  to maintain date and time of day information. The clock has backup power  62  provided to maintain operation if power is removed from the patient base station. A counter-timer  72  is provided to coordinate time critical operations. An analog to digital converter  64  is also provided. 
     The patient base station computer  40  controls battery charging, both rapid charging and float charging once the fill charge point is reached. The computer  40  also controls discharging of the battery  18 , as required. A battery capacity test is periodically performed to verify the stored energy capacity of the monitor-defibrillator battery pack  18 . The system processor  40  controls all battery capacity measurement operations by discharging the battery  18  to a defined starting level, rapid-charging the battery  18  to full potential, implementing a timed discharge cycle to deplete the battery  18  and calculating the actual energy capacity. This process can determine if a bad cell is present in the battery pack, or the measured battery capacity is less than a defined acceptable limit. 
     The patient interface module  46 , as shown in FIG. 5, can have a visual display  47 , battery status LED indicators  51 , acknowledge push button  57  and ambient light sensor  49 . The patient interface module  46  can be operatively associated with the charger interface module  34  and the analog to digital converter  64 . The analog to digital converter  64  with an analog multiplexer is preferably provided within the patient base station  30 . This analog to digital converter  64  allows the single board computer  40  (FIG. 1) to monitor the charging current of the charger/discharger  34 , discharging current of the charger/discharger  34 , the battery voltage present at the monitor-defibrillator interface  32 , the ambient light sensor  49  of the patient interface module  46  and the ambient temperature within the patient base station  30  enclosure via a temperature sensor  55  (shown in FIG.  2 ). 
     Referring again to FIG. 1, the patient interface  46  in the patient base station  30  indicates the status of the monitor-defibrillator battery  18  during the battery capacity test cycle. The patient interface  46  preferably incorporates a front panel mounted vacuum fluorescent (VF) type display  47  (shown in FIG.  4 ). This display  47  may be a character type with standard 5 mm, 5×7 dot characters. The PBS display  47  is preferably arranged in one of the following configurations: a 2 line by 40 character or a 4 line by 20 character. The PBS display  47  is controlled by the single board computer  40  via the charger interface module  34  through a parallel data interface. As an alternative, a graphics type LCD may be used for the PBS display  47 . If an LCD display is used, the patient base station may include an ambient light sensor  49  to control the LCD backlight for improved readability. 
     In addition, the patient base station  30  tracks battery  18  usage and notifies the patient when replacement of the battery  18  is required. If the battery  18  expiration parameters have been exceeded (the expiration date or the number of charge cycles), the battery  18  can still be used by the monitor-defibrillator  12 , but the patient will be notified to replace the monitor-defibrillator  12  as soon as possible. The number of charging cycles performed on the battery  18  is recorded in the monitor-defibrillator memory of the data storage/processor  22 . Also, the date the battery  18  was installed in the monitor-defibrillator  12 , the type of cell used in the battery  18 , and the expiration date of the battery  18  as well as any other pertinent information is stored in monitor-defibrillator data storage/processor  22 . 
     The communications interface created when the patient base station  30  and attached monitor-defibrillator  12  is connected to the physician&#39;s programming console  70  is utilized during the initial configuration programming of the monitor-defibrillator  12 . Preferably, the following information is configured: name, address, telephone number, hospital, attending physician, medications; monitor-defibrillator detection and treatment parameters such as heart rate threshold or rate cutoff, defibrillation energy to be delivered in therapy pulses; and monitor-defibrillator manufacturing data such as device serial numbers, monitor-defibrillator battery pack. and expiration date, electrode harness(s) and expiration date(s). 
     A data communications protocol facilitates the transfer of digital information between the patient base station  30  and the physician&#39;s programming console  70 . This protocol consists of transferring data in blocks or frames. To ensure the integrity of transmitted and received data, the protocol implements error checking techniques. 
     The patient base station  30  to physician&#39;s programming console  70  communications protocol consists of transferring data in frames. Communication frames are transferred via the serial communication port  50 . Serial communication port  50  hardware control lines are utilized to provide handshaking between the patient base station  30  and the physician&#39;s programming console  70  that will delimit the frame boundaries. Each communication cycle consists of a command frame sent from the physician&#39;s programming console  70  to the patient base station  30 , followed by a response frame sent from the patient base station  30  to the physician&#39;s programming console  70 . Each command frame will contain a command code followed by any relevant data, followed by an error checking code such as a CRC code. 
     If the command is successfully processed by the patient base station  30 , the patient base station  30  will return a response frame that contains an ACK code, followed by the original received command code, followed by any relevant data, followed by an error checking code such as a CRC code. 
     If the command is not successfully processed by the patient base station  30 , the patient base station  30  will return a response frame that contains a NAK code, followed by the original received command code, followed by any relevant data, followed by an error checking code such as a CRC code. 
     If a command frame is received by the patient base station  30  that contains an invalid error checking code, the patient base station  30  will ignore the communication frame. The physician&#39;s programming console  70  will be responsible for monitoring the patient base station  30  response. If the patient base station  30  does not respond to a command frame the physician&#39;s programming console  70  can elect to resend the frame. 
     If a response frame is received by the physician&#39;s programming console  70  that contains an invalid error checking code, the physician&#39;s programming console  70  can elect to resend the frame. 
     Another data communications protocol facilitates the transfer of digital information between the monitor-defibrillator  12  and the patient base station  30 . The protocol consists of transferring data in blocks or frames. 
     The patient base station (“PBS”)  30  to monitor- defibrillator (“M-D”)  12  communications protocol consists of transferring data in frames. Communication frames are transferred via the PBS/M-D interface  32 . PBS/M-D interface  32  hardware control lines are utilized to provide handshaking between the patient base station  30  and the monitor-defibrillator  12  that will delimit communication frame boundaries. Each communication cycle consists of a command frame sent from the patient base station  30  to the monitor-defibrillator  12 , followed by a response frame sent from the monitor-defibrillator  12  to the patient base station  30 . Each command frame will contain a command code followed by any relevant data, followed by an error checking code such as a CRC code. 
     If the command is successfully processed by the monitor-defibrillator  12 , the monitor-defibrillator  12  will return a response frame that contains an ACK code, followed by the original received command code, followed by any relevant data, followed by an error checking code such as a CRC code. 
     If the command is not successfully processed by the monitor-defibrillator  12 , the monitor-defibrillator  12  will return a response frame that contains a NAK code, followed by the original received command code, followed by any relevant data, followed by an error checking code such as a CRC code. The patient base station  30  will determine and execute a response appropriate for the failed monitor-defibrillator  12  command process. 
     If a command frame is received by the monitor-defibrillator  12  that contains an invalid error checking code, the monitor-defibrillator  12  will return a response frame that contains a code indicating that the command was not properly received and should be resent. The patient base station  30  can elect to resend the command frame. 
     If a response frame is received by the patient base station  30  that contains an invalid error checking code, the patient base station  30  can elect to resend the frame or initiate monitor-defibrillator  12  fault condition processing. 
     The patient base station  30  offers a collection of commands that the physician&#39;s programming console  70  can utilize during communications with the patient base station  30 . The command set provides a means to initiate various patient base station  30  and monitor-defibrillator  12  diagnostic, configuration, and data retrieval procedures. 
     The physician&#39;s programming console  70  can gain access to various monitor-defibrillator  12  information and operational features by issuing commands to the patient base station  30  via the serial communications port  50 . Upon receipt of these commands, the patient base station  30  will issue the appropriate commands to the monitor-defibrillator  12  via the PBS/ M-D interface  32 , that will carry out the desired operation. The patient base station  30  will return to the physician&#39;s programming console  70  the monitor-defibrillator  12  response to the operation. 
     A digital output from the monitor-defibrillator data storage/processor is provided to control the activation of the battery test load. Activation of the load places a high current demand on the monitor-defibrillator battery  18 . This determines if the monitor-defibrillator battery pack contains any defective cells. The monitor-defibrillator  12  can determine the available device operation time (prior to recharging the battery) utilizing adjustments for abnormally high current draw, normal current draw, device fault conditions, and depletion of battery capacity during periods when the device is not in use. 
     Upon command from the patient base station or the monitor-defibrillator display, the monitor-defibrillator  12  performs a battery load test. The monitor-defibrillator  12  returns a pass-fail indication to the patient base station or the display. Load tests are most often performed with the display as the host. If the battery  18  fails the load test, the battery voltage measurement prior to the load test and at the point of failure are stored in the monitor-defibrillator non-volatile memory. 
     Referring to FIG. 3, the patient base station  30  provides circuitry in the charger interface module  34 , that can charge or discharge the monitor-defibrillator  12  battery pack  18 . The charger interface module  34  connects to the monitor-defibrillator  12  battery pack  18  via the PBS/M-D interface  32 . Prior to battery pack  18  maintenance operations, the patient base station  30  will retrieve battery pack  18  identification information from the monitor-defibrillator  12  via the PBS/M-D interface  32 . 
     Two charging modes are provided; rapid charging and float charging. During the rapid charge cycle the charger interface module  34  supplies charging current at the one hour charge rate of the battery pack  18 . During float charge operations, the charger interface module  34  supplies charging current at the continuous maintenance rate of the battery pack  18 . 
     The rapid and float charge current rates supplied by the charger interface module  34  are adjustable by the patient base station computer  40 . The patient base station computer  40  will configure the charger interface module  34  to supply a charge current rate that is appropriate for the connected battery pack  18 . 
     During the discharge cycle, the charger interface module  34  provides a resistive load to the battery pack  18  that discharges the battery pack  18  at the one hour discharge rate of the battery pack  18 . The discharge resistive load applied by the charger interface module  34  is adjustable by the patient base station computer  40 . The patient base station computer  40  will configure the charger interface module  34  to apply a resistive load that causes a one hour current drain rate that is appropriate for the connected battery pack  18 . 
     The battery charger interface module  34  can be controlled by the patient base station computer  40  or by the monitor-defibrillator  12  via the PBS/M-D interface  32 . Monitor-defibrillator  12  control of the charger interface module  34  is accomplished by activating I/O control lines located in the PBS/M-D interface  32 . These I/O lines will configure the charger interface module  34  for the desired charge/discharge operation. Alternately, the patient base station computer  40  can control the I/O lines and configure the charger interface module  34  for the desired charge/discharge operation. Under normal operation the monitor-defibrillator  12  controls the configuration of the charger interface module  34 . The patient base station  30  configuration of the charger interface module  34  is a redundant feature that can be utilized if certain monitor-defibrillator  12  fault conditions exist such as a totally discharged monitor-defibrillator  12  battery pack  18 . 
     Battery pack  18  charge and discharge cycles are initiated by the patient base station computer  40 . When a monitor-defibrillator  12  is connected to the patient base station  30 , the patient base station  30  retrieves monitor-defibrillator  12  battery operational status data from the data storage/processor  22  via PBS/M-D interface  32 . The retrieved battery operational status data includes information such as the remaining battery capacity, fault condition flags, expiration parameters, battery maintenance parameters, and battery identification information. The patient base station  30  analyzes the retrieved battery data to determine the appropriate battery pack  18  maintenance procedure. 
     If the patient base station  30  determines that a rapid charge cycle is required, a command to initiate a rapid charge cycle will be sent to the monitor-defibrillator  12  via the PBS/M-D interface  32 . Upon receipt of this command, the monitor-defibrillator  12  will configure the charger interface module  34  for rapid charge operation by activating I/O control lines located in the PBS/M-D interface  32 . The monitor-defibrillator  12  will monitor the rapid charge sequence for completion and fault conditions. Successful rapid charge completion is determined by the monitor-defibrillator  12  monitoring the voltage level at the battery pack  18  positive terminal via the A/D converter located in the data storage/processor module  22 . Successful rapid charge completion can also be declared if the monitor-defibrillator  12  detects a defined change in battery pack  18  temperature. The monitor-defibrillator  12  monitors the battery temperature via a temperature sensor located in the battery pack  18  and the A/D converter located in the data storage/processor module  22 . When the monitor-defibrillator  12  detects a successful rapid charge completion, the monitor-defibrillator  12  will configure the charger interface module  34  for float charge operation by activating I/O control lines located in the PBS/M-D interface  32 , reset the monitor-defibrillator  12  runtime parameter to the maximum value, and issue a rapid charge complete communications frame to the patient base station  30  via the PBS/M-D interface  32 . 
     The rapid charge cycle will be aborted if the monitor-defibrillator  12  detects one of the following conditions: a battery pack  18  over voltage condition; a battery pack  18  over temperature condition; or a defined time interval elapsed without a rapid charge completion detected. The limit values are manufacturing parameters that are stored in the monitor-defibrillator  12  data storage/processor module  22 . 
     If the monitor-defibrillator  18  aborts the rapid charge cycle the following operations will be performed: the monitor-defibrillator  12  will configure the charger interface module  34  for float charge operation by activating I/O control lines located in the PBS/M-D interface  32 ; the monitor-defibrillator  12  will set it&#39;s runtime parameter to zero, which will cause patient warning messages on the display  24 ; and the monitor-defibrillator  12  will issue a rapid charge fault communications frame to the patient base station  30  via the PBS/M-D interface  32 . If the patient base station  30  receives a rapid charge fault communications frame from the monitor-defibrillator  12 , the following operations will be performed: the event will be logged in the patient base station  30  operations log file located in the data storage module  42 ; and the patient base station  30  will activate a patient warning message that indicates the monitor-defibrillator  12  should be serviced. 
     During the rapid charge cycle, the patient base station  30  will insure proper charge operation by monitoring various system parameters. The system parameter limit values are stored in the data storage module  42  during the patient base station  30  manufacturing process. 
     The charging current supplied to the battery pack  18  is monitored for proper levels via an A/D converter  64  (FIG. 5) channel connected to the charger interface module  34 . If the measured current is outside the defined limits, the patient base station  30  will abort the rapid charge cycle. 
     The charging voltage on the battery pack  18  is monitored for proper levels via an A/D converter  64  channel connected to the charger interface module  34 . If the measured voltage is outside the defined limits, the patient base station  30  will abort the rapid charge cycle. 
     The patient base station  30  will abort the rapid charge cycle if the counter timer  72  (FIG. 2) indicates the charge cycle exceeded the maximum charge completion interval. 
     If the patient base station  30  determines that a rapid charge cycle abort is required, the following operations will be performed: an abort rapid charge cycle command will be issued to the monitor-defibrillator  12  via the PBS/M-D interface  32 ; the patient base station  30  will configure the charger interface module  34  for float charge operation; the patient base station  30  will issue a command to the monitor-defibrillator  12  to set the runtime parameter to zero, which will cause patient warning messages on the display  24 ; the event will be logged in the patient base station  30  operations log file located in the data storage module  42 ; and the patient base station  30  will activate a patient warning message that indicates the monitor-defibrillator  12  should be serviced. 
     The patient base station  30  may initiate a discharge cycle of the monitor-defibrillator  12  battery pack  18 . The discharge cycle is utilized both during the battery capacity test as well as during the process of reconditioning the battery energy storage capabilities. 
     If the patient base station  30  determines that a discharge cycle is required, a command to initiate a discharge cycle will be sent to the monitor-defibrillator  12  via the PBS/M-D interface  32 . Upon receipt of this command the monitor-defibrillator  12  will set the monitor-defibrillator  12  runtime parameter to zero and configure the charger interface module  34  for discharge operation by activating I/O control lines located in the PBS/M-D interface  32 . The monitor-defibrillator  12  will monitor the discharge sequence for completion and fault conditions. Successful discharge completion is determined by the monitor-defibrillator  12  detecting the defined final discharge voltage threshold on the battery pack  18  positive terminal via the A/D converter located in the data storage/processor module  22 . When the monitor-defibrillator  12  detects a successful discharge completion, the monitor-defibrillator  12  will configure the charger interface module  34  for float charge operation, by activating I/O control lines located in the PBS/M-D interface  32 , and issue a discharge complete communications frame to the patient base station  30  via the PBS/M-D interface  32 . 
     The discharge cycle will be aborted if the monitor-defibrillator  12  detects one of the following conditions: a battery pack  18  over temperature condition; or a defined time interval has elapsed without the detection of the discharge complete condition. The limit values are manufacturing parameters that are stored in the monitor-defibrillator  12  data storage/processor module  22 . 
     If the monitor-defibrillator  12  aborts the discharge cycle the following operations will be performed: the monitor-defibrillator  12  will configure the charger interface module  34  for float charge operation by activating I/O control lines located in the PBS/M-D interface  32 ; and the monitor-defibrillator  12  will issue a discharge fault communications frame to the patient base station  30  via the PBS/M-D interface  32 . If the patient base station  30  receives a discharge fault communications frame from the monitor-defibrillator  12 , the event will be logged in the patient base station  30  operations log file located in the data storage module  42  and a patient warning message will be activated on the PBS display  47  that indicates the monitor-defibrillator  12  should be serviced. 
     During the discharge cycle, the patient base station  30  will insure proper discharge operation by monitoring various system parameters. The system parameter values are stored in the data storage module  42  during the patient base station  30  manufacturing process. 
     The discharge current drawn from the battery pack  18  is monitored for proper levels via an A/D converter  64  channel connected to the charger interface module  34 . If the measured current is outside the defined limits, the patient base station  30  will abort the discharge cycle. 
     The discharge voltage on the battery pack  18  is monitored for proper levels via an A/D converter  64  channel connected to the charger interface module  34 . If the measured voltage is outside the defined limits, the patient base station  30  will abort the discharge cycle. 
     The patient base station  30  will abort the discharge cycle if the counter timer  72  indicates the discharge cycle exceeded the maximum discharge completion interval. 
     If the patient base station  30  determines that a discharge cycle must be terminated, the following operations will be performed: an abort discharge cycle command will be issued to the monitor-defibrillator  12  via the PBS/M-D interface  32 ; the patient base station  30  will configure the charger interface module  34  for float charge operation; the patient base station  30  will issue a command to the monitor-defibrillator  12  to set the runtime parameter to zero, which will cause patient warning messages on the display  24 ; the event will be logged in the patient base station  30  operations log file located in the data storage module  42 ; and the patient base station  30  will activate a patient warning message that indicates the monitor-defibrillator  12  should be serviced. 
     The rapid charge cycle or discharge cycle will not be initiated if the monitor-defibrillator  12  determines that the battery pack  18  temperature is outside a set of defined limits. The limit values are manufacturing parameters that are stored i n the monitor-defibrillator  12  data storage/processor module  22 . 
     If the monitor-defibrillator  12  is removed from the patient base station  30  prior to completion of all battery pack maintenance operations, a message and alarm will be activated on the patient interface module  46 . The message will indicate the monitor-defibrillator maintenance is not complete and to return the monitor-defibrillator to the patient base station. The interrupted maintenance procedure will be continued if the removed monitor-defibrillator  12  is reconnected to the patient base station  30 . 
     The energy delivery capabilities of the battery pack  18  are periodically verified by testing the battery  18  energy capacity and high current delivery capabilities. The patient base station  30  will perform an energy capacity test on the battery pack  18  if the elapsed time from the last capacity test, as indicated by data retrieved from monitor-defibrillator data storage/processor module  22  via the PBS/M-D interface  32 , exceeds the maximum time interval parameter stored in the data storage module  42 , or status data retrieved from monitor-defibrillator data storage/processor module  22  via the PBS/M-D interface  32 , indicates that the battery  18  operational performance was deficient during the previous patient monitoring cycle. 
     The battery  18  energy capacity test procedure consists of the following operations: the patient base station  30  will activate a message on the patient interface  46  visual display  47  that indicates the monitor-defibrillator  12  is being tested and to wait for the test to complete; the patient base station  30  initiates a battery discharge cycle to condition the battery for a full charge cycle; initiate a rapid charge cycle when the discharge cycle is complete to charge the battery  18  to full capacity; the patient base station  30  initiates a second discharge cycle when the rapid charge cycle is complete; and the patient base station  30  initiates a final rapid charge cycle at the completion of the second discharge cycle to ready the battery  18  for service. The duration of the second discharge cycle is timed by a counter timer located in the monitor-defibrillator  12  data storage/processor module  22 . At the completion of the second discharge cycle the monitor-defibrillator  12  will compare the measured battery  18  discharge time with an acceptance parameter stored in storage/processor module  22 . If the capacity discharge time is within the acceptable limit, monitor-defibrillator  12  will issue a capacity discharge pass communications frame to the patient base station  30  via the PBS/M-D interface  32 . 
     If the capacity discharge time is not within the acceptable limit, the monitor-defibrillator  12  will set a battery capacity fault status flag located in the data storage/processor module  22 , and issue a capacity discharge fault communications frame to the patient base station  30  via the PBS/M-D interface  32 . The patient base station  30  will log the event in a log file located in the data storage module  42 . Whenever the patient base station  30  receives a capacity discharge fault indication from the monitor-defibrillator  12 , a patient warning message will be activated which indicates that the monitor-defibrillator  12  should be serviced as soon as possible. Each time a monitor-defibrillator  12  is connected to the patient base station  30 , the patient base station  30  will retrieve the monitor-defibrillator  12  battery capacity fault status flag located in the data storage/processor module  22 . If the battery capacity fault status flag is active, the patient base station  30  will initiate normal battery maintenance operations, with the exception of the battery capacity test which will no longer be performed. The patient base station  30  will also issue a command to the monitor-defibrillator  12  to set the runtime parameter to zero. This will cause repeated patient warning messages on the patient display  24 . 
     If the battery status information indicates that the expiration date of the battery  18  has been exceeded (status information is entered during the initial configuration programming) or if the maximum number of charge cycles has been exceeded, the patient will be notified by the patient base station  30  that the monitor-defibrillator  12  should be serviced. The notification sequence will be activated until the patient acknowledges receipt by pressing a button  57  (FIG. 4) on the patient interface  46 , or the monitor-defibrillator  12  is removed from the patient base station  30 . Normal battery maintenance will continue so that the patient may use the monitor-defibrillator  12 . 
     When a rapid charge cycle or battery discharge cycle is initiated, the patient base station  30  will deactivate the particular one of the battery status LED indicators  51  which is the “READY” LED indicator on the patient interface module  46  and activate the particular one of the battery status LED indicators  51  which is the “CHARGING” LED indicator. During the rapid charge cycle, the patient base station  30  displays a message on the patient interface visual display  47  that the monitor-defibrillator battery  18  is being charged and the monitor-defibrillator  12  is not ready for use. 
     If monitor-defibrillator maintenance operations are complete at the conclusion of a successful rapid charge cycle, the patient base station performs the following: 
     A message is displayed on the PBS display  47  indicating that the monitor-defibrillator  12  is ready for use; the PBS  30  “READY” LED  51  is activated; the “CHARGING” LED  51  is deactivated; and the monitor-defibrillator  12  is powered down. 
     The patient base station  30  logs the following battery maintenance information into a maintenance log: the start and completion times of battery operations; the length of the charge/discharge cycles; any abnormal conditions; and the charge cycle count, and if enabled, the battery voltage measurements taken during charge and discharge cycles. The maintenance log is stored in the data storage module  42 . 
     The patient base station  30  issues various diagnostic test commands to the monitor-defibrillator  12 . These tests are performed on a regular basis. Some tests are performed each time the monitor-defibrillator  12  is connected to the patient base station  30 . Others are performed only as required. The monitor-defibrillator  12  executes the received commands and reports the test results to the patient base station  30 . The patient base station  30  maintains a log of the test results on the mass storage media  42 . If a fault is detected during any diagnostic procedure, the patient is notified of the condition along with the appropriate corrective action. 
     Other variations are also possible. For example, the preferred patient base station  30  utilizes a charger interface module board. Stacked on top of that board are purchased assemblies of PC104 boards which form the CPU module  40  and Ethernet module  52 . These boards are ISA compatible because the expansion bus  54  is an ISA type bus. The stacks of PC104 boards require a great deal of cabling which is very costly. Thus, all of the major system functions could be implemented on a single PC board. This would eliminate much of the cabling. 
     Moreover, alternative embodiments of the battery management system are contemplated. Particularly, referring to FIG. 6, a basic perspective view of an alternative embodiment of a battery management system  110  is shown having a monitor defibrillator  112 , rechargeable battery pack  118  and battery pack recharger  190 . A battery pack receptacle  182  is provided in the monitor-defibrillator  112  wherein the battery pack  118  is adapted to be received for use as a power supply. Also, the recharger  190  includes a battery pack receptacle  184  to receive the battery pack  118  for recharging and, if desired, testing to determine the operational condition of the battery pack  118 . The battery pack  118  memory/processor is configured to exchange information with both a processor in the recharger  190  and the data storage/processor  22  in the monitor-defibrillator  112 . 
     As can be seen in the simplified diagram shown in FIG. 7, all of the heretofore described functions carried out by the patient base station  30 , except for the battery recharging and related functions, can be carried out by an upgraded monitor-defibrillator  112  having increased functional capabilities. Basically, the monitor-defibrillator  112  package has been upgraded/expanded to include the circuitry necessary to perform the functions of not only the previously described monitor-defibrillator  12 , but additionally, the functions formerly performed by the patient base station  30 . Of course, some of the components in the previous embodiments of the monitor-defibrillator  12  and patient base station  30 , are eliminated, for example the respective interface modules  26  and  32 , external power supply  60 , power entry module  36 , power supply  38 , computer  40  and battery charger interface module  34  that are not required for the expanded function monitor-defibrillator  112 . Some of the components are obsoleted by the fact that the monitor-defibrillator  112  no longer interfaces with a base station. Other components, such as those related to battery recharging will be part of the battery charger  190  to be used with the smart battery pack  118 . Thus, the monitor-defibrillator  112  can include maintenance circuitry for providing an indication of the operation condition of the monitor-defibrillator  112  whereas the battery recharger  190  can include battery maintenance circuitry for providing an indication of the operating condition of the rechargeable battery pack  118 . 
     Other elements of the prior embodiment of the battery management system  10 , such as the computer  40 , are redundant with components in the monitor-defibrillator  112 . For example, the data storage/processor  22  is also a “computer.” However, the functioning of the data storage/processor  22  may also be upgraded with regard to memory and processing capabilities in order to handle the added functionality taken over by the monitor-defibrillator  112 . Additionally, another input/output  170  option is an infrared communication module  53 , which can be used in addition to the serial port  50  or ethernet module  52 . 
     The battery management system  110  also contemplates the use of what is known as a “smart battery” pack  118 . A smart battery is a relatively new type of battery which has an internal memory/processor that monitors the condition of the battery and can also communicate with a battery recharger  190  designed to recharge such smart battery packs. The pack recharger  190  also has a processor to read and update the memory/processor in the smart battery pack  118 . Moreover, the recharger  190  can include the battery pack recharging, maintenance and testing functionality previously performed by the patient base station  30 . Additionally, the smart battery pack  118  memory/processor can communicate with data storage/processor  22  in the monitor-defibrillator  112 . A preferred smart battery pack  118  and recharger  190  are described in more detail below, in connection with FIGS. 8 and 9. 
     As explained above, the monitor-defibrillator  112  performs, in addition to the functions previously described for the monitor-defibrillator  12 , all the functions previously associated with the patient base station  30 , except battery recharging. The monitor-defibrillator  112  has a receptacle  182  adapted to receive the smart battery pack  118  for use as a power supply, communicates therewith to ascertain the battery condition stored in the memory of the smart battery  118 , performs test operations thereon, and can update the internal memory regarding the battery condition when appropriate. Both the battery pack  118  and the battery pack receptacle  182  in the monitor-defibrillator  112  are provided with the requisite contacts and interfaces necessary for the monitor-defibrillator to be powered by the battery pack  118  and also for the data storage/processor  22  in the monitor-defibrillator  112  to exchange information with the memory/processor in the smart battery pack  118 . 
     As will be described below in more detail, the smart battery pack  118  is equipped to monitor the battery drain only for the computer circuitry of the monitor-defibrillator  112 , it is not designed to monitor the current drain caused by the high voltage converter. Thus, the upgraded monitor-defibrillator  112  can independently monitor the charge status of the battery. This separate energy monitoring function can be, for example, provided by an “energy monitoring circuit”  180  which very precisely measures the energy output of the converter-defibrillator circuit  19 , which energy is, of course, provided by the smart battery pack  118 . The monitor-defibrillator  112  can then update the memory of the smart battery pack  118  with this information to determine the final condition of the battery regarding the available energy. 
     The smart battery and recharger hardware will supply various diagnostic capabilities to the battery management system. The capabilities will include providing accurate run-time information to the monitor-defibrillator  112 , storage of fault flag information for both the monitor-defibrillator  112 , and storage of information which allows both the battery charger and monitor-defibrillator  112  to adapt operation to different types of smart batteries. 
     Described below are certain software interface and data structures which can preferably be used in the smart battery interface. FIGS. 8 and 9 illustrate certain preferred flow diagrams which can be used as a guide during the design and implementation of both the battery charger  190  and monitor-defibrillator  112  software. 
     Determination and Adjustment of Monitor-Defibrillator Available Run Time 
     The determination of available monitor-defibrillator  112  run time is based upon multiple factors. The design of the monitor-defibrillator smart battery pack  118  preferably includes a BenchMarq™ Model BQ2092 “gas gauge” integrated circuit. The BQ2092 continuously monitors the current being consumed by the monitor-defibrillator  112  and adjusts an internal capacity register. The monitor-defibrillator  112  reads the capacity register to determine available operating time which is displayed to the patient in hours and minutes. The smart battery pack  118  internal circuitry has been designed to particularly monitor the current being drawn by the data storage/processor circuitry of the monitor-defibrillator  112 . However, the current drain caused by operation of the high voltage converter (approximately 8 amps) is not monitored by the BenchMarq gas gauge. Even if it were, the conventional internal circuitry could not measure the current drain with the desired precision. Due to this, the monitor-defibrillator  112  can have, for example, the aforementioned energy monitoring circuit  180  for precisely measuring this current drain and using this information to make an appropriate adjustment to the smart battery pack  118  gas gauge, based on measuring the operation time of the converter. The remaining capacity register of the smart battery pack  118  will be adjusted based on a calculation performed by the monitor-defibrillator  112  after operation of the converter. 
     Additionally, due to the design of the monitor-defibrillator  112 , the remaining capacity register contained in the BenchMarq BQ2092 IC does not provide enough information to accurately determine the remaining run time of the monitor-defibrillator  112 . The monitor defibrillator  112  design specifications indicate that the monitor-defibrillator  112  must be able to operate for a period of 24 hours, and at the end of the 24 hour period, be able to deliver five full energy defibrillation pulses without entering converter foldback mode. Converter foldback mode is a mode of converter operation that is enabled if the battery pack terminal voltage falls below a predefined threshold during operation of the converter interface. As a result of this specification, the smart battery pack  118  must have sufficient reserve capacity to operate the converter interface while maintaining a battery pack voltage which is above this threshold. Due to the five pulse requirement, the smart battery pack  118  must have additional calibration information stored in the battery pack memory which allows the monitor-defibrillator  112  to verify that sufficient reserve capacity exists in the battery to operate the converter at the 24 hour operating point. 
     A reserve battery capacity calibration constant, “ReserveCapacityCutoff,” will be stored in each monitor-defibrillator  112  during manufacturing. The value of ReserveCapacityCutoff must be determined by a battery qualification test which exercises the smart battery pack  118  under simulated current drawings. The monitor-defibrillator  112  software will read this constant during initialization and use it to determine run time based on the following formula: 
     
       
         (RemainingCapacity−ReserveCapacityCutoff)÷SystemCurrent=CurrentRuntime. 
       
     
     In the above formula, the constants ReserveCapacityCutoff and SystemCurrent must be maintained in the monitor-defibrillator  112  data storage/processor  22 . The battery pack  118  will also maintain a RemainingCapacity (command code 0x0F) register which will be used to determine available operating time and which is adjusted by circuitry internal to the battery pack  118  based on actual sensed battery current drain. The monitor-defibrillator  112  software generally decrements its run time counter in a linear fashion. In one method, adjustments to the run time, outside of a straight decrement in time, will only be made if the above calculation indicates a run time less than the decremented time amount or operation of the high voltage converter occurs time amount or operation of the high voltage converter occurs. However, in a presently preferred method, the monitor-defibrillator  112  predicts the amount of operating time remaining based on actual usage. The current drain of the system is measured by hardware/software in the monitor-defibrillator  112 , this is in addition to the smart battery pack  118 , and averaged over a defined interval. When the run time value is needed, e.g. the patient pressing the display button or a periodic system low battery check, the monitor-defibrillator  112  will calculate the estimated run time amount based on the RemainingCapacity value that is maintained in the smart battery pack  118  and the average current consumption measured by the RemainingCapacity (0x0F) register. This run time value is a more realistic prediction of how long the system will operate based on actual usage. The only time the smart battery pack  118  RemainingCapacity register value is adjusted by the monitor-defibrillator  112 , is during converter operation. If an adjustment becomes necessary, the monitor-defibrillator  112  will modify the battery pack  118  RemainingCapacity (0x0F) register with a new capacity value based on the duration of converter operation. 
     When a battery pack  118  is initially inserted into the monitor-defibrillator  112 , the above formula will be used to initialize the initial run time variable CurrentRuntime. The Current/Runtime variable is decremented based on elapsed time after the initial calculation is performed. 
     Periodically, the monitor-defibrillator  112  will recalculate the formula and compare the calculated run time to the run time which is being decremented based upon elapsed time. If the new calculated run time indicates less time available than the CurrentRuntime variable, the variable will be set equal to the calculated time. This situation may occur if the patient display is activated for significant periods of time, causing greater than average current drain from the battery. 
     Monitor Defibrillator Battery Initialization Sequence 
     The flow diagram shown in FIG. 8 illustrates one presently preferred embodiment of software flow during initialization of the monitor-defibrillator  112  when a battery pack  118  is installed. The initial calculation of CurrentRuntime is performed along with a test for charger detected error conditions. A status variable, “BatteryErrorStatus,” maintained in the battery pack is shared by the monitor-defibrillator  112  and charger. Variable BatteryErrorStatus, located in the battery pack  118  ManufacturerAccess (Command code 0x00) register low byte, is used by the monitor-defibrillator  112  to flag the battery charger  190  to perform a capacity test cycle after certain operating conditions are detected such as converter foldback or a low battery voltage state. Detected error conditions and resulting battery charger  190  operations are described later in this document. 
     Battery Capacity Testing and General Charger Functionality 
     In addition to basic battery charging sequences, the battery charger  190  can conduct periodic battery capacity measurements and monitor the integrity of the battery pack  118 . The battery pack  118  capacity test will be initiated based on checking an internal battery pack register value, “TestCycleNumber,” that will be stored in the ManufacturerAccess (Command code 0x00) register high byte of the BQ2092. Variable TestCycleNumber is reset to zero by the charger  190  whenever a battery capacity test cycle has been completed. This value is maintained and updated by the charger  190  whenever the battery pack  118  completes a charge cycle. Manufacturing constant “CyclesPerTestSequence” will be stored in the manufacturing data (command code 0x23) area of the BenchMarq BQ2092 IC. Constant CyclesPerTestSequence will be programmed at the time of manufacturing and will indicate the number of charge cycles between capacity test sequences. 
     When a smart battery pack  118  is inserted into the charger  190 , the charger  190  will read variables TestCycleNumber and CyclesPerTestSequence and determine if a capacity test cycle is required. Prior to commencement of the capacity test it will be necessary for the charger  190  to determine if the patient&#39;s current battery pack  118  is capable of sustaining monitor-defibrillator  112  operations for the duration of the test. The battery charger  190  will not initiate a battery capacity test sequence if the previously charged battery pack  118  has Bit 1 of the BatteryErrorStatus set or does not have sufficient reserve capacity to operate the monitor-defibrillator  112  for the duration of the test. 
     As mentioned in the previous section, it is also possible that the monitor-defibrillator  112  may periodically request a battery capacity test via variable BatteryErrorStatus Bit 0 contained in the BenchMarq BQ2092 ManufacturerAccess (Command code 0x00) register low byte. The following details the bit positions in BatteryErrorStatus and their meaning. 
     BatteryErrorStatus (Low Byte of ManufacturerAccess (0x00) 
     Bit 0: Set by the monitor-defibrillator  112  if converter foldback or low battery voltage condition exists during operation. 
     Bit 1: Set by battery charger if the smart battery pack  118  fails battery capacity test or the battery pack  118  is otherwise defective. 
     If the battery charger  190  detects that Bit 0 of BatteryErrorStatus is set, the charger  190  should proceed to perform a battery capacity test. The charger  190  must keep track of the time when a fully charged battery pack  118  was removed from the charger  190  and assume that it will power the monitor-defibrillator  112  system for a period of twelve hours. The decision to perform the battery capacity test must take into consideration the actual worst case duration of the test and the remaining run time of the last fully charged battery pack  118 . The test should not be initiated if the battery pack  118  which is currently being used by the patient does not have sufficient reserve capacity to power the monitor-defibrillator  112  for the worse case capacity test time or if the battery pack  118  is faulty (Bit 1 is set). 
     Upon completion of the capacity test, the charger  190  should compare the measured battery capacity to battery pack  118  parameter LowLimitCapacity which is stored in the manufacturing data area. If the battery pack  118  capacity is less than this value, the charger  190  should clear Bit 0 &amp; set Bit 1 of variable BatteryErrorStatus. If the test passes, then both error Bits should be cleared. 
     The flow diagram shown in FIG. 9 illustrates one general, presently preferred, method of operation of the battery charger  190 . When a smart battery pack  118  is removed from the system or not installed, all status illuminators should be turned off. 
     Mapping of Defined Variables to BQ2092 Memory 
     The previously defined battery maintenance constants will be mapped into the manufacturing data area and the variables mapped to the registers of the BQ2092. This section defines the storage locations of the variables and constants in the BQ2092. The variables and constants must be initialized to default values during the battery pack manufacturing process. 
     
       
         
               
               
               
             
           
               
                   
               
             
             
               
                 Constant Name 
                 Size in Bytes 
                 Manufacturing String Index 
               
               
                   
               
               
                 
                   Low Limit Capacity 
                 
                 2 
                 BASE ADDRESS+0&amp;1 
               
               
                 
                   CyclesPerTestSequence 
                 
               
               
                 Variable Name 
                 Size in Bytes 
                 Register Location in BenchMarq BQ2092 
               
               
                   
               
               
                 
                   BatteryErrorStatus 
                 
                 1 
                 ManufacturerAccess(0x00) Low Byte 
               
               
                 
                   TestCycleNumber 
                 
                 1 
                 ManufacturerAccess(0x00) High Byte 
               
               
                   
               
             
          
         
       
     
     Regarding the manufacturing string address, the base address indicates the first byte of the manufacturing data string provided by BQ2092 function ManufacturingData (command code 0x23). 
     In accordance with the patent statutes we have described principles of operation and preferred embodiments of our invention. It should be understood, however, that within the scope of the appended claims, the invention may be practiced in a manner other than as illustrated and described.