Patent Publication Number: US-9419462-B2

Title: Method of laser welding the housing of a rechargeable battery

Description:
RELATIONSHIP TO EARLIER FILED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 14/031,380 now U.S. Pat. No. 9,142,292. U.S. patent application Ser. No. 14/031,380 is a divisional of U.S. patent application Ser. No. 12/582,740 filed 21 Oct. 2009, now U.S. Pat. No. 8,564,242. U.S. patent application Ser. No. 12/582,740, is a divisional of U.S. patent application Ser. No. 11/551,335 filed 20 Oct. 2006, now abandoned. U.S. patent application Ser. No. 11/551,335 claims priority under 35 U.S.C. Sec 119 from U.S. Provisional Patent App. No. 60/729,338 filed 21 Oct. 2005. The contents of the priority applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention is related to a system and method for recharging a battery. More particularly, this invention is related to a system and method for both charging a battery and evaluating the state of health of the battery. This invention is further related to a system and method for obtaining data from the power consuming devices to which a battery is connected. 
     BACKGROUND OF THE INVENTION 
     A battery often energizes a powered surgical tool used in an operating room to perform a surgical procedure. The use of a battery eliminates the need to provide a power cord connected to an external power source. The elimination of the power cord offers several benefits over corded surgical tools. Surgical personnel using this type of tool do not have to concern themselves with either sterilizing a cord so that it can be brought into the sterile surgical field surrounding the patient or ensuring that, during surgery, an unsterilized cord is not inadvertently introduced into the surgical field. Moreover, the elimination of the cord results in the like elimination of the physical clutter and field-of-view blockage the cord otherwise brings to a surgical procedure. 
     In an operating room, batteries are used to power more than the tools used to perform the surgical procedure. Batteries are also used to energize the power consuming components integral with a personal protection system surgical personnel sometimes wear when performing a procedure. This system typically includes some type of hooded garment. Internal to the garment is a ventilation unit for circulating air within the garment. Some of these systems also have lights for illuminating the surgical site or radios that facilitate conventional spoken level conversation with other persons involved in performing the procedure. Each of these units, the ventilation unit, the light unit and the radio, requires a source of power. By providing this power from the battery, the need to attach cords to each individual wearing such a unit is eliminated. This, in turn, reduces number of cords in the operating room persons would otherwise have to avoid. Further, eliminating these cords likewise eliminates the restrictions of movement they place on the individual using the system. 
     An integral part of any battery-powered device is, naturally, the battery. Most battery-powered surgical devices used in an operating room are designed to be used with rechargeable batteries. These rechargeable batteries typically include one or more NiCd cells. Once a battery is discharged, it is coupled to a complementary charger. The charger applies a current to the battery&#39;s cells to store energy in the cells. 
     Unlike other rechargeable batteries, a rechargeable battery intended for use with a surgical tool must be sterilizable so that it can be placed in close proximity to the open surgical site on a patient. Often, these batteries are sterilized by placing them in an autoclave wherein the atmosphere is saturated with water vapor (steam), the temperature is approximately 270° F. (132° C.) and the atmospheric pressure is approximately 30 psi (Gage) (1552 mmHg). The repetitive exposure to this environment causes a battery cells&#39; ability to store electric charge to degrade. Often this is referred to as degradation in the “state of health” of the battery. 
     The Applicant&#39;s U.S. Pat. No. 6,018,227, BATTERY CHARGER ESPECIALLY USEFUL WITH STERILIZABLE RECHARGEABLE BATTERY PACKS, issued Jan. 25, 2000 and incorporated herein by reference, discloses a means to determine the voltage at load of a battery. Inferentially, this is a measure of the internal resistance of the battery. Unfortunately, this information alone does not provide a complete measure of the battery state of health. For example, this information alone does not provide information if the stored energy is sufficient to power the device to which the battery is attached for the time required to perform the surgical procedure. This means that, during the performance of a procedure, if the battery&#39;s stored energy appreciably depletes, the procedure is interrupted to replace the battery. This increases the overall time takes to perform the procedure. This interruption runs contrary to one of the goals of modern surgery which is to perform the procedure as quickly as possible so as to lessen the time the patient&#39;s internal organs are exposed, and therefore open to infection, and the amount of time a patient is held under anesthesia. 
     Moreover, there is an interest in having surgical equipment provide data regarding their own operating states to other equipment in the hospital. For example, some motorized surgical tools are provided with internal temperature sensors. In the event a bearing assembly internal to a tool of this type malfunctions, tool temperature will start to rise. This rise in temperature is detected by the complementary sensor. The output signal from the sensor can then be read by a remote device in the hospital. This gives hospital personnel notice that the tool may be approaching a critical malfunction and should be repaired or replaced. 
     Corded surgical devices provide these types of operating state data. These communications systems are relatively simple technically and economical to provide because the signals are forwarded to the complementary control consoles through the cords through which power is supplied to these devices. One can also provide the data from these devices through wireless communications systems. One system is disclosed in the Applicant&#39;s U.S. Patent Application No. 60/694,592, POWERED SURGICAL TOOL WITH SEALED CONTROL MODULE, filed 28 Jun. 2005, the contents of which are published in U.S. Pat. No. 7,638,958 B2, incorporated herein by reference. A disadvantage of the above-mentioned system is that it requires the addition of a wireless communications system into the operating room. The expense of providing such a system limits the locations where they are installed. 
     The Applicant&#39;s Assignee&#39;s U.S. Pat. No. 5,977,746, RECHARGEABLE BATTERY PACK AND METHOD FOR MANUFACTURING SAME, issued 2 Nov. 1999 and incorporated herein by reference, discloses a rechargeable battery especially designed to withstand the rigors of autoclave sterilization. The battery of this invention includes a cluster of cells that are bound together by top and bottom plastic binders. Conductive straps extending between openings formed in the binders connect the cells. One of the straps is a fuse that opens upon a more than a specific current flowing through it. More specifically, the current through the fuse heats the material forming the fuse so a section of the fuse vaporizes. This vaporization of the fuse section separates the rest of the fuse into two sections. 
     The above battery pack has proven useful for storing the charge needed to energize a cordless surgical tool. However, the cells internal to the battery pack can generate significant amounts of heat. This causes the temperature of the cells to rise. Sometimes, the temperature rise between the cells is uneven. This uneven thermal loading of cells can result in an electrical imbalance of the cells. If the cells become so imbalanced, both the immediate utility of the battery to supply energy at a particular time and its useful lifetime may diminish. 
     SUMMARY OF THE INVENTION 
     This invention relates to a new and useful battery and battery charging system. The battery is designed for use in a harsh environment such as in a hospital where the battery is autoclave sterilized. The battery and battery charging system of this invention are further designed to record and transmit data about the devices the battery is used to energize. 
     The battery of this invention includes a set of rechargeable cells. Also internal to the battery are a data recording unit and a temperature sensor. Both the data recording unit and temperature sensor are powered by the battery cells so that they are always on, regardless of whether or not the battery is being used to power a device or is being charged. Collectively, the data recording unit and temperature sensor are configured to record data about the temperature of the battery. 
     The battery charger of this invention includes a current source for charging the battery. Also internal to the battery charger is a processor and a load resistor. The processor regulates the actuation of the current source and connection of the battery to the load resistor. 
     The processor also reads the data stored in the battery data recording unit. Depending on the data indicating the history of the battery, the processor may conduct a state of health evaluation of the battery. For example, a state of health evaluation may be performed if the data in the data recording unit indicates that battery was continually at a temperature above a threshold level for more than a given period of time. To perform a state of health evaluation, the processor both measures the voltage-at-load of the battery and the quantity of energy input to the battery. Often, this last evaluation is made by first fully discharging the battery. The results of the state of health evaluation are displayed. 
     Another feature of this invention is that, while the battery is being used to power a device, the device writes data into the data recording unit. When the battery is attached to the charger, the data recording unit writes out the stored device data to the charger processor. The charger processor, in turn, forwards these data to another device. Thus, information about the operating state of a battery powered device is available to persons charged with maintaining the device. This information is available even though there is no corded link or RF/IR/ultrasonic wireless communications link to the device. 
     The battery of this invention is also configured to foster uniform dissipation of the heat generated by the cells internal to the pack. This minimizes the temperature imbalance of the cells. The minimization of the temperature imbalance reduces the electric imbalance between the cells. The reduction of this electrical imbalance results in a like reduction in the extent to which the cells, if electrically imbalanced, adversely affect battery performance. The battery of this invention is further constructed to have a fuse that will regularly open when a defined amount of current flows through the fuse. The battery of this invention is also economical to manufacture and occupies a relatively small surface area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is pointed out with particularity the in the claims. The above and further features and benefits of the battery, battery charger and method for charging a battery of this invention may be better understood from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a battery and battery charger of this invention; 
         FIG. 2  is a perspective view of the battery; 
         FIG. 3  is an exploded view of the battery of this invention; 
         FIG. 4  is a perspective view of the battery housing; 
         FIG. 5  is a cross sectional view of the battery housing; 
         FIG. 5A  is an enlarged cross sectional view of the top edge of the battery housing; 
         FIG. 6  is an exploded view of the cell cluster internal to the battery; 
         FIG. 7  is an exploded view of the binder assembly, here the top binder assembly, of the cell cluster; 
         FIG. 8  is a plan view of the thermal fuse internal to the top binder assembly; 
         FIG. 9  is a cross sectional view of the battery lid; 
         FIG. 10  is a plan view of the undersurface of the battery lid; 
         FIG. 11  is an enlarged cross sectional view of the bottom lip of the battery lid; 
         FIG. 12  is a schematic drawing of the electrical components internal to the battery; 
         FIG. 13  is a block diagram of some of the sub circuits internal to the battery microcontroller; 
         FIG. 14  depicts some to types of data stored in the memory integral with the battery microcontroller; 
         FIG. 15A  is a plan view illustrating one of the fixtures in which the components forming the cell cluster are placed in order to facilitate assembly of the cluster; 
         FIG. 15B  is side view illustrating how the components forming the cell cluster are fitted in a pair of fixtures; 
         FIG. 16  is a diagrammatic illustration of the welding process used to complete the assembly of the cell cluster 
         FIG. 17  is a cross sectional view of the interface of the battery housing and battery lid prior to the welding of these components together; 
         FIG. 18  is diagrammatic representation of how the battery housing and lid are welded together; 
         FIG. 19  is a cross sectional view of the interface of the battery housing and battery lid after the welding process; 
         FIG. 20  is an exploded view of relationship of the charger base to the charger housing; 
         FIG. 20A  is a perspective view of how the discharger resistors and complementary heat sink are secured to the charger base; 
         FIG. 21  is a cross sectional view of some of the components internal to the charger; 
         FIG. 22  is a block diagram of sub-circuits internal to the charger and a module attached to the charger; 
         FIGS. 23A and 23B  collectively form a flow chart of the process steps performed by the battery microcontroller to monitor the autoclaving of the battery; 
         FIGS. 24A, 24B and 24C  collectively form a flow chart of the process steps executed by the charger in order to charge a batter according to the process of this invention; 
         FIG. 25  is a flow chart of the process steps executed by the processor internal the charger to ensure that the charger temperature does not rise to potentially unsafe levels; 
         FIG. 26  is a block diagram illustrating of the tool communications system of this wherein the battery and charger are used to facilitate the exchange of data between the surgical tool and other components; 
         FIG. 27  is a block diagram of the components of tool of the system of this invention; 
         FIG. 28  is a block diagram of data stored in the tool history file internal to the battery microcontroller; and 
         FIG. 29  is a flow diagram of the process steps executed in the tool communication system of this invention. 
     
    
    
     DETAILED DESCRIPTION 
     I. Overview 
       FIG. 1  illustrates a battery  40  and battery charger  42  constructed in accordance with this invention. Battery  40 , includes a set of rechargeable cells  44  ( FIG. 3 ) a microcontroller  46  and a temperature sensor  48  ( FIG. 12 ). Battery charger  42  includes a housing  50  with a number of pockets  52  ( FIG. 20 ). Each pocket  52  removably receives a module  54  associated with a specific type of battery. The module  54  is shaped to define a complementary socket  56  for receiving the head end of the associated battery  40 . Internal to the battery charger  42  are components for reading the data stored in the battery microcontroller  46  and for charging the battery cells  44 . A plurality of I/O units  58  are attached to the charger  42 . Each I/O unit  58  functions as the sub-assembly through which instructions are entered and charge state information presented about an individual one of the batteries  40  attached to the charger  42 . 
     II. Battery and Method of Battery Assembly 
     As seen in  FIGS. 2 and 3 , a battery  40  of this invention includes a housing  60 . Rechargeable cells  44  are arranged in a cluster  62  seating in housing  60 . A lid  66  is sealing disposed over the open top end of the housing  60 . Lid  66  is formed with a head  68 . The lid  66  is the battery structural component to which the microcontroller  46  and temperature sensor  48  are mounted. In the illustrated version of the invention, the lid head  68  is dimensioned to fit into a complementary socket formed in the power tool  522  ( FIG. 22 ) the battery  40  is intended to power. The lid head  68  is provided with two contacts  70  and a single contact  72 . Contacts  70  are the conductive members through which the charger  42  applies a charging current to the cells  44  and from which the power tool  522  ( FIG. 23 ) draws an energizing current. Contact  72  is the contact through which data and instructions are written into and read out from the microcontroller  46 . Thus, data are exchanged between the charger  42  and battery microcontroller  46  using a one-wire signal exchange protocol. One such protocol is the Dallas Semiconductor One-Wire protocol. 
     Battery housing  60  is formed from a single piece of plastic that is transmissive to light energy emitted at 980 nanometers. By “transmissive” it is understood the plastic is at least “partially” transmissive. In most versions of the invention the plastic is at least 55% percent transmissive. In more preferred versions, the plastic is at least 75% transmissive. In one version of the invention, housing  60  is formed from a polyphenylsulfone plastic. One such plastic from which housing  60  is formed is sold under the brand name RADEL by Solvay Advanced Polymers, of Alpharetta, Ga., United States. This plastic is partially transparent. For aesthetic reasons, the plastic forming housing  60  may be dyed to be opaque at visible wavelengths. If housing  60  is so dyed, the dye should be selected so that it does not appreciably interfere with transmissivity of photonic energy at the 980 nanometer range. As discussed below this is the wavelength at which, in one process lid  66  is laser welded to housing  60 . 
     As seen in  FIGS. 4, 5 and 5A , housing  60  is formed to have a generally rectangular base  76 . Four interconnected walls  78  extend upwardly from the perimeter edges of the base  76 . For aesthetic reasons, the corners of the base  76  and the corners where walls  78  abut are rounded. Housing  60  is further shaped so that walls  78  taper outwardly away from base  76 . The housing  60  is further formed so that ribs  80  extend inwardly from the inner surfaces of the walls  78  from the top surface of the base  76 . Each wall  78  may be formed with one, two or more ribs  80 . Ribs  80  provide structural rigidity to the walls and minimize movement of the cell cluster  62  within the housing  60 . 
     Each housing wall  78  has an inner vertical surface  86 . (In the cross sectional view of  FIG. 5  rib  50  is seen below the top of the inner surface  86 .) Above the inner vertical surface  86  there is a tapered face  88  that angled outwardly relative to the vertical surface  86 . A reveal  90  forms the top most portion of each lip  78 . The reveal  90  has a generally square cross sectional profile. The width of the reveal  90  is less than that of the vertical surface  91  that extends between the top edge of the lip outer surface  85  and the top edge of tapered inner face  88 . Housing  60  is thus formed so that reveal  90  is located inwardly of both the top edge of the lip outer surface and the top edge of the tapered inner face  88 . 
     As seen by reference to  FIG. 6 , the cell cluster  62  includes a plurality of rechargeable cells  44 . As is known from the above-identified, incorporated herein by reference U.S. Pat. No. 5,977,746, the outer cylindrical surface of each cell  44 , which functions as the cell ground, is covered with polyimide tape, (not shown). 
     Cells  44  are arranged in a three abutting rows  92 ,  94  and  96 , such that the cells in one row abut the cells in the adjacent row. In each row  92 - 94 , the adjacent cells  44  abut. The cells  44  are arranged so that there are three cells in the outer rows, rows  92  and  96 , and two cells in the center row, row  94 . This arrangement ensures that each cell has an outer perimeter section of at least 10% and, more preferably at least 20%, that neither abuts an adjacent cell nor is concealed behind an adjacent row of cells. Thus a perimeter section of at least 10%, and more preferably at least 20%, of each cell  44  forms a portion of the outer perimeter of the array of cells forming the cell cluster  62 . 
     The top and bottom orientation, the orientations of, respectively, the positive and negative terminals, of the cells  44  is arranged as a function to the extent the cells are to be connected together in a series or parallel arrangement in order to provide a charge at a particular voltage level and current. 
     The cells  44  are held together to form the cluster  62  by top and bottom binder assemblies  102  and  104 , respectively. Each binder assembly  102  and  104  includes a number of conductive straps  106  that are in the form of thin strips of metal. As seen in  FIG. 7 , which shows the top binder assembly  102 , each binder assembly includes inner and outer binders  108  and  110 , respectively. (For reference, the “inner” binder is understood to be the binder closest to the cells  44 ; the “outer” binder is spaced from the cells.) Each binder  108  and  110  is formed from a flexible plastic material such as a polyester sold under the trademark MYLAR by DuPont. Each binder  108  and  110  is formed with a number of openings  112  and  114 , respectively. Binders  108  and  110  forming the upper binder assembly  102  are further formed so as to define along the outer perimeter thereof aligned notches  116  and  117 , respectively. 
     Conductive straps  106  are sandwiched between the binders  108  and  110 . Each conductive strap  106  is positioned to have one end that extends into the space subtended by aligned pair of binder openings  112  and  114 . Some conductive straps  106  are positioned so that that the second ends of the straps extend into one of the aligned pairs of binder openings  112  and  114 . These conductive straps  106  electrically connect the terminals of adjacent cells  44 . Two of the conductive straps  106  are positioned so that their second ends project beyond the perimeters of the binders  108  and  110 . These two conductive straps  106 , seen in  FIG. 6 , function as the members that provide electrical connections between the cell cluster  62  and the contacts  70 . 
     A fuse  118  is also disposed between the binders  108  and  110  forming top binder assembly  102 . The fuse  118 , best seen in  FIG. 8 , is formed of a conductive metal that when the current flow therethrough causes material heating to the point the metal vaporizes. In one version of the invention, fuse  118  is formed from nickel or a nickel alloy. Fuse  118  is generally in the form of a planar strip. The fuse  118  is further formed so as have notch  120  that extends inwardly from the one of the longitudinal side edges of the metal strip forming the fuse. (The geometries of notch  120  of the fuse of  FIG. 7  and of the fuse  118  of  FIG. 8  are slightly different.) In  FIG. 8 , section  119  of fuse  118 , the narrowest width section, defines the widest portion of notch  120 . 
     A binder assembly  102  or  104  of this invention is assembled by first placing one of the binders  108  and  110  in a jig. More particularly, the jig is formed with a recess designed in which the binders  108  and  110  are designed to precisely seat. Extending into the recess from the base of the jig are spaced apart fingers. The fingers extend through into the spaces subtended by binder openings  112  and  114 . The fingers are spaced so as to define spaces therebetween into which the conductive straps  106  and fuse  118  are seated. 
     The exposed surface of the binder  108  or  110  seated in the jig recess is provided with an adhesive. In some versions of the invention, the adhesive is pre-applied to the binder  108  or  110 . At manufacture, a protective sheet that covers the adhesive is removed. In  FIG. 7 , the adhesive is represented as stippling  124  on inner binder  108 . 
     Once the first binder  108  or  110  is set in the jig, the conductive straps  106  and fuse  118  are set over the binder. More specifically, the conductive straps  106  and fuse  118  are set between the fingers that extend through the binder openings  112  or  114 . The second binder  110  or  108  is then disposed over the partially assembled unit. In some versions of the invention, adhesive material may also disposed over the surface of the second binder that abuts the first binder. 
     As a consequence of the assembly of the binders  108  and  110 , each inner binder opening  112  is aligned with an associated one of the upper binder openings  114 . Inner and outer binder notches  116  and  117 , respectively, are also aligned. It should further be appreciated that, during the assembly of the binder assembly  102 , fuse  118  is positioned so that fuse notch  120  is within the area where the binders  108  and  110  are sandwiched together. The portion of the fuse  118  that defines fuse notch  120  is within the space subtended by binder notches  116  and  117 . In more preferred versions of the invention, the fuse is positioned so that the thinnest section of the fuse, the portion defining the widest section of fuse notch  120 , is spaced from the binders  108  and  110 . 
     The battery lid  66  is now described by reference to  FIGS. 2, 9, and 10 . In one version of the invention, lid  66  is a single component formed from a polyphenelsulfone plastic such as the RADEL R plastic. For aesthetic reasons, the plastic forming the lid may be dyed to be opaque at the visible wavelengths. If the lid  66  is to be secured to the housing  60  by the below discussed laser welding process, the lid should be formed of material that absorbs the photonic energy at the wavelength emitted by the laser. The aesthetic dye can function as this material. Thus, in the described version of the invention, the dye absorbs energy emitted in the 980 nanometer range. Lid  66  is shaped to have a generally rectangular base  126  that has a geometry that subtends the top edges of the housing walls  78 . Four panels  128 ,  130 ,  132  and  134  extend inwardly and upwardly from the sides of the base  126 . The panels  128 - 134  meet at a planar horizontal surface  136  from which the battery head  68  upwardly projects. Panels  128  and  132  are the side panels and are symmetric relative to each other. Panel  130  is the front panel; panel  134  is the rear panel. Relative to the horizontal plane, front panel  130  has a steep upward slope; the slope of rear panel  134  is shallower. 
     Battery head  68  is formed to have a slot  136  and two slots  138 . Each of slots  136  and  138  are open to the front face of the head  68 . Slot  136  is centered along the longitudinal centerline of the battery  40 . Slots  138  are parallel to and located on either side of slot  138 . Contact  72 , the contact through which signals are exchanged with microcontroller  46  extends into slot  136 . Contacts  70 , the contacts through which charge is stored in and drawn from cells  44 , is disposed in slots  138 . 
     A latch  140  is pivotally mounted to the battery head. The latch  140  holds the battery  40  to the power consuming device to which the battery is connected. A pressure relief valve  142  is mounted to horizontal surface under the latch  140 . Not identified are the openings in which latch  140  and valve  142  are mounted and the assembly that pivotally holds the latch to the battery lid  66 . 
     A number of ribs  146  and  148  extend inwardly from the inner surface of lid panels  128 - 134 . The ribs  146  and  148  are generally rectangular in shape and extend into the inner surface of the lid below horizontal surface  135 . Ribs  146  are relatively tall; ribs  148  are short. Two ribs  146  extend inwardly from panels  128 ,  132  and  134 . A single rib  148  extends inwardly from front panel  130 . An additional rib  148  extends inwardly from each of the side panels  128  and  132  immediately adjacent the front panel. Each rib  148  is further formed so that the outer end is downwardly stepped relative to the portion of the rib immediately adjacent the panel from which the rib extends. Ribs  146  and  148  minimize, if not completely block, vertical displacement of the cell cluster  62 . 
     Battery lid  66  also has a lip  152  that extends downwardly from the base  126  around the perimeter of the lid. As seen best in  FIG. 11 , the lip  152  is located inwardly of the outer vertical surface of the base  126 . Lid  66  is formed so that lip  152  has an inner vertical surface  154  that is flush with the adjacent inner surface of the base  126 . The lip  152  has an outer vertical surface  156  located inward of the outer perimeter of the base  126 . The lip  152  is further formed to have a tapered surface  158  that extends below vertical surface  154 . Surface  158  tapers inward toward the center of the lid  66 . A rectangularly shaped flange  160  forms the bottommost portion of lip  152  and, by extension, the bottommost structural feature of the battery lid  66 . The bottommost portion of inner vertical surface  154  forms the inner surface of flange  160 . A parallel vertical surface  164  that is inwardly stepped relative to the adjacent surface  158  forms the outer wall of the flange  160 . 
     Battery lid  66  is further formed to define a rectangular notch  166  that extends upwardly from the bottom surface of base  126 . The base  126  is formed so that notch  166  is located immediately in front of and is partially defined by lip outer vertical surface  156 . In some versions of the invention, the notch is absent from the lid  66 . 
     Returning to  FIG. 3 , it can be seen that a printed circuit board  170  is mounted in the battery lid  66 . Printed circuit board  170  is the component to which battery microcontroller  46  and temperature sensor  48  are mounted (not illustrated). Circuit board  170  is fitted in the lid  66  to seat against the inwardly stepped edges of ribs  148 . A post  172  extends upwardly from the printed circuit board  170 . A screw  174  that extends through lid horizontal surface  135  into post  172  holds the circuit board  170  to the lid. 
     Seen extending from circuit board  170  are two conductors  176 . Conductors  176  provide an electrical connection between the cells  44  and the components on the circuit board  170 . As discussed in more detail below, energization signals are continually applied to microcontroller  46  and temperature sensor  48  of battery  40  regardless of whether or not the battery is being charged, discharged, autoclaved, or simply in storage. 
     Also seen in  FIG. 3  are the wire assemblies  177  that extend from the cell cluster to contacts  70 . Also seen in the Figure but not otherwise described further are the button head fasteners  178  and lock washers  179  that hold the contacts  70  and  72  in position. Also seen is the O-ring  180  disposed around post  172 . 
       FIG. 12  is a schematic of the electrical circuit components integral with the battery  40 . A voltage regulator  182  is connected to the positive output terminal of the cell cluster  62 . In one version of the invention voltage regulator produces a 3.3 VDC signal, the signal present at point  183 . A capacitor  184 , tied between the pin of the voltage converter  182  at which the 3.3 VDC signal is present and ground, filters the 3.3 VDC signal. 
     One of the components to which the 3.3 VDC signal is applied is the microcontroller  46 . One suitable unit that can be used as microcontroller  46  is the P89LPC925 8 bit microcontroller manufactured by Philips Electronics N.V. of the Netherlands. Microcontroller  46  has a number of different sub-circuits, a number of which are now described by reference to  FIG. 13 . A central processing unit (CPU)  185  controls most of the operation of microcontroller  46  and the components connected to the microcontroller. A non volatile flash memory  187  stores instructions executed by the CPU  185 . As discussed below, memory  187  also stores: the instructions used to regulate the charging of the battery; data describing the use history of the battery; and data describing the use history of the tool  522  to which the battery is attached. 
     A random access memory  188  functions as a temporary buffer for data read and generated by microcontroller  46 . A CPU clock  189  supplies the clock signal used to regulate the operation of the CPU  185 . While shown as single block for purposes of simplicity, it should be appreciated that CPU clock  189  includes an on-chip oscillator as well as sub-circuits that convert the output signal from the oscillator into a CPU clock signal. A real time clock  190  generates a clock signal at fixed intervals as discussed below. 
     The output signal from the temperature sensor is applied to both an analog comparator  191  and an analog to digital converter  192 . In  FIG. 13  the above sub-circuits are shown interconnected by a single bus  193 . It should be appreciated that this is for simplicity. In practice, dedicated lines may connect certain of the sub circuits together. Likewise it should be understood microcontroller  46  may have other sub-circuits. These sub-circuits are not specifically relevant to this invention and so are not described in detailed. 
       FIG. 14  illustrates types of data stored in the flash memory  187  in addition to the instructions executed by the microcontroller  46 . These data include, in a field or file  194 , data that identifies the battery. These data, in addition to serial number, lot number and manufacturer identification can include data such as an authorization code. This code is read by the tool  522  or charger  42  to which the battery is connected to determine if, respectively the battery can power the tool or be recharged by the charger. The battery identification data may include data indicating the useful life of the battery. Useful life data are understood to be one or more of the following data types: battery expiration data; number of chargings; and number of autoclavings. Other data in identification file  194  can indicate the nominal open circuit voltage of the signal produced by the battery, the current the battery can produce and the joules of available energy. 
     Charging instructions for the battery are stored in a file  195 . These data can be the types of data described in the memories of the batteries disclosed in incorporated by reference U.S. Pat. Nos. 6,018,227, and 6,184,655. Flash memory  187  also contains data describing the charging and autoclave histories of the battery. In a field  196  data are stored indicating the number of times the battery was charged. A measured post-charge voltages file  197  contains data indicating the measured voltages-at-load of the battery after each charging. In some versions of the invention file  197  only contains these measurements for the last 1 to 10 chargings. In a file  198  data are stored indicating the highest battery temperature measured during its previous chargings. Again, file  198  may only contain data indicating the highest temperatures measured during the last 1 to 10 chargings of the battery. 
     A field  199  stores data indicating the total number of times the battery has been autoclaved. A cumulative autoclave time field  200 , as its name implies, is used to store data indicating the total time the battery has been at temperatures at or above a threshold considered to be the autoclave temperature. 
     A field  201  contains data indicating the number of times the battery has been exposed to potentially excessive autoclavings. Data indicating the cumulative time the battery may have been potentially excessively autoclaved is stored in a field  202 . A peak autoclave temperature field  203  contains data indicating the highest autoclave temperature to which has been exposed. A file  204  contains records of the time the battery has been in the autoclave for each of its autoclavings. In some versions of the invention, time in autoclave file  204  only contains data indicating the time the battery was in the autoclave for each of its last 5 to 100 autoclavings. A file  205  contains data indicating the peak temperatures of the battery that measured during its last 5 to 100 autoclavings. In most versions of the invention, memory  187  stores autoclave time and temperature data for the exact same number of autoclavings. Field  206  contains data indicating the period of the longest single time the battery was subjected to autoclaving. 
     Memory  187  also contains a tool history file  229 . As discussed below, tool history file  229  stores data obtained from the tool  522  that battery  40  is employed to power. 
     Returning to  FIG. 12 , other circuit components internal to battery  40  are now described. Temperature sensor  48  is any suitable temperature sensing device capable of detecting whether or not battery  40  is exposed to autoclave temperatures. In the described versions of the invention, temperature sensor  48  is a thermistor. The 3.3 VDC is applied to one end of the temperature sensor. The opposed end of the temperature sensor  48  is tied to ground through a resistor  207 . A capacitor  208  is tied across resistor  207 . The voltage present at the junction of the temperature sensor  48  and resistor  207  is applied as the T_SENSE signal representative of detected temperature to the noninverting input of microcontroller comparator  191  (connection not specifically shown.) 
     A reference voltage, V TEMP   _   REF , is applied to the inverting input of comparator  191  (connection not specifically shown.) The reference voltage is the signal present at the junction of series connected resistors  209  and  210 . The opposed end of resistor  209  receives a reference voltage from a source internal to microcontroller  46 . The opposed end of resistor  210  is selectively tied to ground through a switch internal to the microcontroller  46  (switch not illustrated). 
     Microcontroller  48  is connected to battery contact  72  by a conductor  211 . A pair of series-connected opposed diodes  212  extend between conductor  211  and ground. 
     As part of the process of assembling battery  40 , cell cluster  62  is assembled. Initially, binder assemblies  102  and  104  are fabricated as described above. Then, a first binder assembly  102  or  104  is placed in a fixture  213   a  or  213   b ,  FIG. 15A  illustrating fixture  213   a , the fixture in which the top binder assembly  102  is seated. Each Fixture  213   a  and  213   b  includes a base plate  214  formed with a number of openings  215 . A block  216  extends upwardly from the fixture base plate. Block  216  is shaped to define a recess  223  dimensioned to slip fit receive the binder assembly  102  or  104  and cells  44 . The block  216  is formed to define the pattern of the rows  92 ,  94  and  96  in which the cells are to be placed. Illustrated fixture  213   a  is further shaped to define two opposed slots  224  that are contiguous with recess  223 . Slots  224  receive the free end of the top binder assembly conductive straps  106  that function as electrical connections. Thus, fixture  213   a  has a supplemental block  216   a  spaced from block  216  so as to define slots  224  therebetween. 
     Fixture openings  215  are formed in the fixture base plate  214  to be concentric with the binder openings  112  and  114 . When a cell is fitted in the fixture  213   a  or  213   b  it should be appreciated the cell is centered with binder openings  112  and  114  and the associated fixture opening  215 . 
     The second binder assembly  104  or  102  is then placed in its associated fixture  213   b  or  213   a , respectively. As seen in  FIG. 15B , the second fixture with fitted binder assembly is then fitted over the fixture assembly in which the binder assembly  102  or  104  and cells  44  are already placed. 
     A robotic welding unit  218 , shown diagrammatically in  FIG. 16 , welds the conductive straps  106  and fuse  118  to the cells  44 . Specifically, robotic welding unit  218  has a base  237  to which an arm  232  is attached. Arm  232  includes two opposed fingers  233  that, when brought together, clamp cells  44  and fixtures  213   a  and  213   b  therebetweeen. A drive mechanism, (not illustrated,) moves arm  232  and the components held thereby both in the X plane (to the left and right in  FIG. 16 ) and in the Y-plane (in and out of the plane of  FIG. 16 ). 
     Robotic welding unit  218  also includes a welding head  230 . Head  230  is attached to a track  234  so as to be able to move in Z-plane, (vertically in  FIG. 16 ). Two opposed electrodes  235  and  236  are attached to and extending downwardly from head  230 . 
     The welding process begins with the placement of the sandwiched-between-fixtures cells  44  and binders  102  and  104  between fingers  233  of arm  232 . Arm  232  is moved so that a first one of the fixture openings  215  is disposed below electrodes  235  and  236 . Welding head  230  is lowered so that the electrodes  235  and  236  pass through the fixture opening  215  and the aligned binder opening  114  to the surface of the exposed conductive strap  106  (or fuse  118 ). Current is flowed between the electrodes  235  and  236  to weld the strap  106  (or fuse  118 ) to the surface of the underlying cell  44 . Once this weld process is complete, head  230  is raised. Arm  232  is slightly repositioned so that when head  230  is again lowered, electrode  235  and  260  can make a second weld joint between the same strap  106  (or fuse  118 ) and cell  44 . 
     After the two weld joints for the first strap (or fuse) cell interface are completed, head  230  is again raised. Arm  232  is again positioned so each strap- (or fuse-) and-cell interface is similarly welded. 
     The final assembly of the battery  40  begins with the seating of a shock absorber  217  seen in  FIG. 3 , in the base of the housing  60 . The shock absorber  217  is formed from a compressible material such as a silicon rubber. Shock absorber  217  subtends the area subtended by the cell cluster  62 . In some versions of the invention, the shock absorber  217  is, in an earlier step bonded to the exposed face of the bottom binder assembly  104 . Cell cluster  62  is placed in the housing. The connections are made between the cell cluster  62  and conductors  176  and wire assemblies  177 . 
     Lid  66  is then welded to the housing  60  to complete the assembly of the battery  40 . In this process, the lid  66  is seated on the housing so that lid tapered surface  158  abuts housing tapered face  88 . As seen in  FIG. 17 , owing to the dimensioning of housing  60  and lid  66 , at this time, the lid is positioned so that the bottom horizontal surface of the lid base  126  is spaced above the housing reveal  90 . 
     The welding process is accomplished by applying a downward force on the lid  66  so that the lid bears against the housing  60 . In  FIG. 18 , this is represented diagrammatically by arrow  225 . More particularly, owing to the angled profile of housing tapered surface  88  and lid tapered surface  158 , these surfaces  88  and  158  abut. Simultaneously with application of the downward force, coherent (laser) light at 980 nanometers is simultaneously applied to the lateral section of the housing that subtends the interface between housing tapered face  88  and lid tapered surface  158 . As represented by plural arrows  219 , this photonic energy is applied simultaneously around the whole of the perimeter of the outer housing. A suitable system capable of performing this welding is available from Branson Ultrasonics of Danbury, Conn. 
     Owing to the transmissivity of the material forming the housing  60  to this wavelength of photonic energy, the energy passes substantially through the housing lip  84  as represented by phantom arrow  220  of  FIG. 17 . This energy is absorbed by the material forming lid lip  152 . The material forming lid lip  152  thus heats to its melting point. This includes the material forming lid tapered surface  158 . Owing to the downward force imposed on the lid  66 , the lid therefore settles downwardly into the open space of the housing  60 . The settling of lid  66  stops by the abutment of the bottom surface of lid base  126  against housing reveal  90 . 
     Moreover, thermal energy is transferred from the lid tapered surface  158  to the adjacent abutting housing tapered surface  88 . As represented to  FIG. 19 , this causes the material forming the housing tapered face  88  to likewise melt. Collectively, the material forming the opposed housing tapered face  88  and lid tapered surface  158  form a hermetic weld joint  221  around and along the interface of the battery housing  60  and lid  66 . 
     It should be appreciated that, as part of the above process, a small amount of the material forming the housing tapered face  88  and lid tapered surface  158  spread away from these two surfaces. Some of this material, flash material  239  in  FIG. 19 , flows into the space immediately inward of housing reveal  90  and the contiguous lid notch  166 . Other of this material, flash material  222 , flows into the space between housing vertical surface  86  and lid lip outer vertical surface  164 . 
     III. Charger 
     The basic structure of the battery charger  42  is now explained by reference to  FIGS. 20, 20A and 21 . Pockets  52  are formed in a front flat portion of the charger housing  50 , (flat portion not identified). The charger housing  50  is further formed to have a back section  242  that is raised relative to the section in which pockets  52  are formed. A rear wall  244  forms the rear end of section  242  and thus, the rear end of the charger housing  50 . Housing rear wall  244  is formed with a set of lower and upper ribs  246  and  248 , respectively. Both ribs  246  and  248  extend vertically. A web  250 , part of housing rear wall  244 , separates ribs  246  and  248  from each other. Ribs  246  are spaced apart from each other to define vertical vents  252  therebetween. Ribs  248  are spaced apart from each other to define vertical vents  254  therebetween. 
     Battery charger  42  also has a metallic, plate shaped base  256 . In one version of the invention, the base  256  is formed from spring steel. Base  256  is disposed in the open end of housing  50 . The base  256  is shaped to have numerous openings  258  that extend therethrough. Base  256  is the structural component internal to the charger to which the majority of other charger components are attached. Not seen are the structural components and fasteners that hold housing  50  and base  256  together. 
     One component attached to base  256  is a heat sink  264 . In some versions of the invention, heat sink  264  is formed from aluminum or other material with good thermal conductivity characteristics. The heat sink  264  is shaped to have a planar base  266 . A number of fins  268  extend perpendicularly outwardly from the base  266 . Fins  268  extend laterally across the base  266 . 
     The heat sink  264  is mounted to base  256  by brackets  265 . More particularly, the heat sink  264  is mounted to the base  256  so that the heat sink is disposed within the space internal to housing back section  242 . More particularly the heat sink  264  is positioned so that there is free space between the outer edges of the fins  268  and housing vents  252  and  254 . 
     A set of discharge resistors  272  are mounted to the face of the heat sink base  266  opposite fins  268 . As discussed below, during certain processes for charging or evaluating a battery  42 , it is necessary to first fully discharge the stored energy in the battery. This process step is executed by connecting the battery to a discharge resistor  272 . In the illustrated version of the invention, each discharge resistor  272  is associated with a separate one of the charger pockets  52 . During the discharging of a battery  40 , each battery is tied to the specific discharge resistor  272  associated with the pocket in which the module  54  to which the battery is coupled is seated. 
     Each discharge resistor  272  generally has a resistance of 15 Ohms or less. In still other versions of the invention, each discharge resistor  272  has resistance of 10 Ohms or less. Each discharge resistor  272  is often encased in its own heat sink, (not illustrated). This resistor heat sink is the resistor component that physically abuts the heat sink base  266 . 
     Also attached to the heat sink base  266  is a temperature sensor  274 . It will be observed there is no fan or other device internal to or otherwise integral with the charger  42  for moving air through the housing  50  or across the heat sink  264 . 
     From  FIG. 1  it is seen that each I/O unit  58  includes an LCD display  278  and two LEDs  280  and  282 . Each I/O unit  58  of charger  40  of this invention further includes two membrane switches  284  and  286 . 
       FIG. 22  is a block diagram of the electric circuit assemblies internal to charger  42 . A power supply  288  converts the line current into signals that can be used to energize the other components internal to the charger  42 . Power supply  288  also produces a signal that is applied, through a module  54  to the battery  40  to charge cells  44 . 
     The charging current is applied to the battery by a current source  290 . In actuality, charger  42  has plural current sources  290 ; one to apply current to a battery through each module  54 . This allows different charging signals to be applied to simultaneously to separate attached batteries. For simplicity, only a single current source  290  is illustrated. Integral to each current source  290  is a resistor  292 . When the battery  40  is seated in module  54 , resistor  292  establishes a connection between the battery positive terminal and ground. Each discharge resistor  272  is associated with a separate one of the current sources. Thus, in  FIG. 22 , the discharge resistor  272  is shown internal to the current source  290 . Each discharge resistor  272  has one end selectively connected to ground. The opposed end of resistor  272  is selectively tied to the battery positive terminal by a switch, typically a FET (switch not shown). 
     Module  54 , one shown as a block element in  FIG. 18 , also includes a resistor  294 . Resistor  294  is selectively connected across the terminals to which battery contacts  70  are connected. A switch, typically a FET (not illustrated) is used to make this connection. Resistor  294  is thus used to measure the voltage at load of the battery  40 . 
     The module  54  also contains a NOVRAM  296 . NOVRAM  296  contains charging sequence and charging parameter data used to regulate the charging of the battery  40  charged through the module. A main processor  298 , also internal to charger  42 , controls the charging of the battery  40 . Main processor  298  further determines, if it is necessary to perform a state of health evaluation of a battery, performs the evaluation and, based on the data generated in the evaluation, generates an indication of the state of health of the battery. Main processor  298  also generates the read/write instructions to obtain data from and load data into the memory integral with battery microcontroller  46  and module NOVRAM  296 . In one version of the invention, the AT91SAM7X256/128 available from Atmel of San Jose, Calif. functions as the main processor  298 . 
     More specifically, the main processor  298  is connected to the current source  290  over a plurality of conductors collectively represented as bus  304 . Main processor  298  outputs a variable CURRENT_CONTROL signal to the current source  290 . In response to the CURRENT_CONTROL signal, current source  290  outputs a charging current, at a select current, through module  54  to the battery cells  44 . The voltage across resistor  292  is output over bus  304  to the main processor  298  as a MEASURED_VOLTAGE signal. This MEASURED_VOLTAGE signal is representative of the voltage across the battery  40 . Also output from the main processor  298  through bus  304  is the signal to the switch that selectively ties resistor  272  to the battery  40 . This connection causes the charge stored in the battery  40  to be discharge by the resistor  272 . 
     Main processor  298  is connected to the module  54  by a plurality of conductors represented as a single-wire bus  260 . Main processor  298  selectively generates the control signal that connects resistor  294  across the positive and negative terminals of the battery  40 . When resistor  294  is so connected, the resistor  294  is connected to resistor  292 . The MEASURED_VOLTAGE signal from the current source  290  thus becomes a measure of the voltage at load of the battery  40 . 
     Bus  260  also functions as the link through which the contents of the module NOVRAM  296  are written to main processor  298 . Data are also read from and written to the battery microcontroller  46  over bus  260 . 
     The output signal produced by temperature sensor  274  is applied to the main processor  298 . 
     Main processor  298  is also connected to a data transceiver head  301 . Transceiver head  301  is the interface internal to the charger connected to bus  586  ( FIG. 26 ). 
     A more detailed description of the components internal to module  54  and current source  290  as well as the processes by which a battery may be charged is disclosed in the incorporated by reference U.S. Pat. No. 6,018,227. Additional description of the processes involved in charging plural batteries and alternative charge assemblies are found in the Applicants&#39; Assignee&#39;s U.S. Pat. No. 6,184,655, Battery Charging System With Internal Power Manager, issued 6 Feb. 2001, the contents of which is incorporated herein by reference. 
     Battery charger  42  also contains an I/O processor  299 . The I/O processor  299 , based on signals output from the main processor  298 , generates the signals that cause LCD display  278  to generate the appropriate image. The I/O processor  60  also regulates actuation of the LEDs  280  and  282 . Membrane switches  284  and  286  are also connected to the I/O processor  299 . Based on the signal generated as a consequence of the opening and closing of switches  284  and  286 , the I/O processor  299  generates the appropriate commands to the main processor  298 . 
     IV. Operation 
     A. Battery 
     Battery microcontroller  46  operates in three different modes. This is to minimize the load the components internal to the battery  40  place on cells  44 . In a normal mode, all subcircuits internal to the microcontroller  46  are energized. In one version of the invention, when microcontroller  46  is in this state, it draws approximately 6 mA. Microcontroller  46  also has a power down, clock on state. When the microcontroller  46  is in this state, CPU  185 , analog comparator  191  and the analog to digital circuit  192  are deactivated. Both the CPU clock  189  and the real time clock  190  are on when microcontroller  46  is in the power down, clock on state. When microcontroller  46  is in the power down, clock on state, the microcontroller draws approximately 3 mA. 
     A power down, clock off state is the lowest power consuming state in which microcontroller  46  operates. In this state, the CPU  185 , the CPU clock  189 , the real time clock  190  and the analog to digital circuit  192  are deactivated. When microcontroller  46  is in this state, the analog comparator  191  is activated. When microcontroller  46  is in the power down, clock off state, it draws approximately 120 to 150 μA. 
     It should further be appreciated that during the states in which the analog comparator  191  is on, switches internal to microcontroller  46  are set so there is current flow through resistors  209  and  210  to ground. This results in a V TEMP   _   REF  signal appearing at the inverting input of the comparator. When the analog comparator  191  is turned off, when battery microcontroller  46  is in the power down, clock on state, the microcontroller switches are set so both resistors  209  and  210  are tied high. This eliminates current draw of these resistors. 
     The operation of microcontroller  46  is now explained by reference to the flow chart of  FIGS. 23A and 23B . For the majority of the time, battery microcontroller  46  is in the power down, clock off state. In  FIG. 21A  this is represented by step  390 , the microcontroller entering the power down, clock off state. When microcontroller  46  is in this state, analog comparator  191  continually compares the V TEMP  to V TEMP   _   REF , step  392 . As long as this comparison indicates that signal from temperature sensor  48  indicates that the battery is not being autoclaved, microcontroller  46  remains in the power down, clock off state. 
     It should be appreciated that the reference signal V TEMP   _   REF  may not be a signal that corresponds to the actual temperature inside the autoclave. Instead to compensate for the thermal insulation of the battery housing  60  and lid  66 , the V TEMP   _   REF  may be at a level that corresponds to a temperature less than that of the actual autoclave temperature. In some versions of the invention, the V TEMP   _   REF  signal is set to level to be representative of an autoclave temperature, generally this is an ambient temperature, of at least 100° C. Often, this is an ambient temperature of between 100 and 150° C. In alternative versions of the invention, it may be desirable to set the V TEMP   _   REF  signal so that the battery is considered in a harsh environment when in environment when the ambient temperature is at least 70° C. The actual level of the V TEMP   _   REF  signal may be determined by thermal modeling and/or empirical analysis. 
     If, in step  392 , the comparison indicates that V TEMP  is above V TEMP   _   REF r  microcontroller  46  interprets V TEMP  signal as indicating that the battery is being subjected to autoclaving. In response to this event, microcontroller  46 , in step  394 , enters the power down, clock on mode. 
     As a result of the microcontroller  46  entering the power down, clock on mode, the real time clock  190  counts down a 30 second time period, step  396 . At the conclusion of this count, the microcontroller  46  transitions to the normal mode, step  398 . Once in the normal mode, in a step  402 , using comparator  191  again compares V TEMP  to V TEMP   _   REF . 
     If the comparison of step  402  indicates that the battery is still being autoclaved, CPU  185  performs a data update step  404 . In step  404 , data stored in RAM  188  are updated. These data include a field that indicates the total time the battery has been at autoclave temperature. In some versions of this invention, the data in this field is simply incremented by a unit count (one unit=30 sec.). Also data in a RAM field that indicates the highest temperature of the current autoclave cycle may be updated. In this part of step  402 , a digital signal representative of the V TEMP  from the analog digital converter  192  are compared to the stored temperature level in the RAM  188 . If the data from converter  192  is representative of a higher temperature than the stored measurement, these data are overwritten into the RAM field. 
     Once step  404  is executed, microcontroller  46  reenters the power down, clock on mode. Thus steps  394 ,  396  and  402  are reexecuted. 
     Upon completion of the autoclave process, battery temperature will drop to below the autoclave temperature. This event will be indicated by a different result in the comparison of step  402 . Battery microcontroller  46  then updates the data stored in memory  187 . This process includes an updating of the basic history data stored in memory  187 , step  408 . As part of step  408 , then count of the number of times the battery has been autoclaved, the data in field  199  is incremented by one. Based on the data in the RAM  188  indicating the total time the battery was autoclaved, the data in the cumulative autoclave time field  200  is likewise revised. Also in step  408 , the data in field  204  is updated to indicate the time the battery was, in this last autoclaving, autoclaved. 
     In step  408 , the data in memory  187  are updated based on the RAM data indicating the total time the battery was, in this autoclaving autoclaved. Specifically, data indicating the total time the battery was autoclaved in this cycle are written into field  205 . The data in field  206  indicating the peak single autoclave time is, if necessary, likewise rewritten. In some versions of the invention these data are first written into the RAM. 
     In a step  410  microcontroller CPU  185  determines if the battery was subjected to a potentially excessive autoclaving. This step is performed by comparing from RAM  188  the time the battery was autoclaved to a boundary time. This boundary time is the limit of the acceptable time for which the battery can be autoclaved and there will not be any potential of damage to its internal components. In some versions of the invention, this boundary time is between 3 and 60 minutes. In still more preferred versions of the invention, this boundary time is between 5 and 30 minutes. 
     If the battery was not subjected to a potentially excessive autoclaving, microcontroller returns to the power down, clock off mode. Step  390  is reexecuted. 
     However, if the comparison of step  410  indicates that the battery may have been subjected to a potentially excessive autoclaving, there are further revisions to the data in a step  412 . In step  412  the data in field  201  indicating the number of potentially excessive autoclaving to which the battery was subjected is incremented. In some versions of this invention these data are first written into the RAM  188 . Then, in a single write-to-flash step, (not illustrated,) all the data written to the RAM  188  in steps  408  and  412  are written to the flash memory  187 . 
     Also in step  412 , the cumulative time to which the battery has been exposed to potentially excessive autoclaving is updated. This time count is first adjusted by subtracting from the total time of the battery was autoclaved the boundary time. Thus, if the battery was autoclaved for 12 minutes and the boundary time was 10 minutes, by subtraction the CPU  185  determines that for this autoclave cycle the battery was subjected to 2 minutes of potentially excessive autoclaving. This is the value added to the cumulative data stored in field  202 . Step  390  is then executed to return battery microcontroller  46  to the power down, clock off state. 
     B. Charger 
     The process by which the charger  42  charges the battery is now  40  is now described by reference to the flow charts of  FIGS. 24A, 24B and 24C . While not illustrated, it should be understood that the depicted process assumes the module  54  is seated in a charger pocket  52 . Upon the seating of each module  54  in a pocket  52 , the data in the module NOVRAM  296  are read to the charger main processor  298 , (step not shown). In a step  452 , main processor  298  continually tests to determine if a battery  42  is seated in a module  54 . This test is performed by monitoring the level of the current source MEASURED_VOLTAGE signal. Specifically, if a battery is not seated in a module  54 , the MEASURED_VOLTAGE signal is the open circuit voltage of the charging signal output by the current source. In some embodiments of the invention, this voltage is 20 VDC. As long as the MEASURED_VOLTAGE signal remains at the open circuit voltage level, main processor  298  continually reexecutes step  452 . 
     The seating of a battery  40  in the module  54  causes the MEASURED_VOLTAGE signal to drop. In response to the drop in this signal level, (the seating of the battery in the module,) in a step  453  main processor  298  causes battery microcontroller  46  to transition from the power down, clock off mode to the normal mode. In one version of this invention, this transition is effected by tying battery contact  70  to ground for a given time period. This pulls the one-wire communication line connected to microcontroller  46  to ground. An interrupt circuit internal to battery microcontroller  46  (circuit not illustrated) continually monitors this communication line. The interrupt circuit interprets the extended low state signal on the communication line as indication that it should transition the microcontroller  46  from the power on clock off state to the normal state. 
     Once the battery microcontroller  46  is in the normal mode, main processor  298  generates an instruction through the module  54  to cause the battery microcontroller  46  to write out to the main processor  298  the contents of the associated memory  187 . These data are written out to the main processor  298 . The data written to the charger processor  298  include the charging sequence instructions and the data describing the use and autoclave history of the battery. Collectively, this read request and data write out are shown as step  456 . 
     Main processor  298  then determines if the data retrieved from memory  187  indicates the battery should be subjected to a full state of health (S_O_H) evaluation. One test made to determine if the battery  40  should be so evaluated is, in step  458 , the determination based on the data retrieved from memory file  204 . The last entry in file  204  indicates the total time the battery was autoclaved in the last autoclaving. Main processor  298 , in step  458  compares this value to the boundary time. If the last autoclaving was for a time more than the boundary time, the main processor  298  considers the battery to be in a state in which it is appropriate to perform a state of health evaluation. 
     As represented by step  460  other data read from the battery memory  187  are also tested to determine if a state of health evaluation is required. For example, in step  460  the data in the fields  196  and  199  are read to determine if, respectively, the battery has been subjected to more than P number of rechargings or Q number of autoclavings. Also in step  460  the data in field  202  are read to determine if, since manufacture, the battery has been subject to R amount of total time of potential excessive autoclave exposure. It should be appreciated that, in step  460 , processor  298  determines it is necessary to perform a complete state of health evaluation if the battery has been subjected to a multiple of P rechargings, Q autoclavings or R total time of potentially excessive autoclave exposure. 
     Also once the charger processor  298  detects the battery is placed in the module socket  56 , the processor may cause a message to be presented on the complementary display  278  asking if a state of health evaluation is wanted, (step not shown). The person responsible for charging the battery  40  indicates if the evaluation is required by depressing an appropriate one of the membrane switches  284  or  286 , step  462 . 
     If a state of health evaluation is not required, the charger executes a standard charging sequence for the battery, step  464 . In step  464 , based on the sequence instructions received from the battery microcontroller memory  187  or module NOVRAM  296 , charger main processor  298  causes the connected current source  290  to apply the appropriate sequence of charging currents to the battery cells  64 . It should be appreciated that the charging currents are also based on the MEASURED_VOLTAGE signals obtained from the current source  290 . 
     Once the charging process is complete, charger  42  performs a voltage at load test on the battery, step  466 . Typically, the voltage at load test is performed by measuring the voltage at load across the battery  40 . Charger main processor  298  performs this evaluation by asserting the appropriate gate signal to FET integral with the module to which resistor  294  is attached (FET not illustrated). This results in the connecting of the module resistor  294  across the positive and negative terminals of the battery. As a result of resistor  294  being so connected to the battery, the MEASURED_VOLTAGE signal from the current source  290  becomes a measure of the voltage-at-load of the battery. Execution of this single test of battery state can be considered the performance of a partial state-of-health evaluation of the battery  42 . 
     In a step  468 , main processor  298 , through I/O processor  299 , causes an image to be presented on display  278  indicating the voltage at load of the battery. This data is sometimes referred to as an indication of the basic state of health of the battery. If the battery voltage at load (basic state of health) is at or above an acceptable level, main processor  298 , again through the I/O processor  299 , causes an appropriate one of the LEDs  280  or  282  to illuminate to indicate the battery is available for use, also part of step  468 . 
     In a step  470 , main processor  298  writes into battery memory  187  data regarding the charging. Specifically, in step  470  the count of the number of chargings stored in memory field  196  is incremented. Also data are added to file  197  to indicate the measured voltage-at-load of the battery after charging. 
     Eventually, the battery  40  is removed from the charger  42 , step  471 . As a consequence of this step, there is no communication over the one-wire line internal to the battery  40 . The signal on this line transitions to a continuous high level state. As discussed above with respect to step  453 , the signal level on this communications line is monitored by an interrupt circuit. The interrupt circuit interrupts the signal level of the communications line being high for an extended period of time as an indication that step  471  was executed. Therefore, in step  472 , the interrupt circuit transitions the battery microcontroller from the normal state back to the power down, clock off state. Charger  42  returns to step  452 . 
     While not shown, it should be understood that after the charging process is completed, main processor  298  also causes one of the LEDs to be appropriately actuated to indicate that the battery is available for use. 
     As represented by step  478 , a battery full state of health evaluation starts with the complete discharging of the battery. Step  478  is executed by the main processor  298  asserting the appropriate gate signal to tie the battery positive terminal to resistor  272 . Periodically, the voltage across the battery is measured, step  480 . This step is executed until it is determined the battery is fully discharged. 
     Once the battery  40  is fully discharged, charger  42  proceeds to charge the battery, step  484 . Step  484  is essentially identical to step  464 . As part of this evaluation, main processor  298 , in step  484 , also monitors the overall length of time it takes for the cells  64  internal to battery to fully charge. As is known in the art, main processor typically determines the cells are full charged by determining when change in voltage over a period time falls to a value less than 0, (negative slope.) Thus, in step  486  during the primary or main state charging of the battery  40 , main processor  298  monitors both the ΔV BATTERY /Δ Time  and the time from the start of the main state charging it takes for this slope to go negative. This time is T FULL   _   CHARGE . 
     Once the main state charging of the battery is complete, charger  42  performs a voltage at load test, step  488 . Step  488  is essentially identical to the voltage at load test of step  466 . 
     Based on the data obtain in steps  486  and  488 , main processor  298  determines if the health of the battery is such that it can supply the amount of power needed to actuate a powered surgical tool. In a step  490 , main processor  298  makes this determination by determining if the overall time it took the battery to fully charge, T FULL   _   CHARGE , is at or above a threshold time, T THRESHOLD . The basis for this evaluation is that the T FULL   _   CHARGE  time is directly proportional to the quantity of charge being stored in the battery. Therefore, if T FULL   _   CHARGE &gt;T THRESHOLD , this is an indication that the quantity of charge in the battery is above that needed to energize a surgical tool for the total time such power is required. Thus, when the above determination tests true, main processor  298  recognizes the battery as being in state in which it most likely can power the surgical instrument as required. 
     If the determination of step  490  tests false, main processor  298  considers the battery to be in the opposite state. In this event, main processor  298  causes the I/O processor  299  to generate the appropriate fault state message, step  492 , regarding the battery  40  on the display  278 . This provides notice the battery may not function appropriately. 
     As part of the state of health evaluation, main processor  298  determines whether or not the voltage at load is above a minimum voltage value, step  494 . If the battery voltage at load is not above this minimum value, the battery is considered to have an internal resistance so high that it cannot appropriately energize the tool to which it is attached. Therefore, if in a step  494  the determination tests false, step  492  is executed. 
     As part of the state of health evaluation, main processor  298  further determines whether or not the battery can deliver sufficient charge based on both T FULL   _   CHARGE  and the measured voltage at load. Specifically, both T FULL   _   CHARGE  and measured voltage at load values are normalized, step  496 . In some version of the invention, each of these values is normalized by quantifying them to a range for example, between 0.0 and 1.0. 
     Then, in a step  498  the normalized T FULLCHARGE  and V ATLOAD  values are used as input variables into an equation. This equation may be a simple summation,
 
 S _ H _ R=T   FULLCHARGE   +V   ATLOAD   (1)
 
Here S_H_R is state of health result. Alternatively, the normalized values are multiplied by coefficients
 
 S _ H _ R=A ( T   FULLCHARGE )+ B ( V   ATLOAD )  (1a)
 
Here, A and B are constants. In some versions of the invention, the variables are multiplied together:
 
 S _ H _ R=C ( T   FULLCHARGE )( V   ATLOAD )+ D   (1b)
 
Here, C and D are constants.
 
     Once S_H_R is calculated, in step  502 , it is compared to a cutoff value, S_H_R CUTOFF . If S_H_R is equal to or greater than S_H_R CUTOFF , the charger main processor  298  recognizes the battery as being in a state in which it will deliver an appropriate charge to a surgical tool. Therefore, a step  504  is executed to cause the appropriate image to be presented on the display  282  and LED activation to indicate the battery is available for use. Also in step  504  the charger presents on display  278  an indication of the above calculated S_H_R result. These data are referred to as an indication of the calibrated state of health of the battery. If, in step  502  it is determined that the calculated S_H_R value is less than S_H_R CUTOFF , step  492  is executed. 
     After either step  492  or  504  is executed, step  470  is executed to complete the charging process. (Not shown is the loop back to step  470 .) 
     Charger  42  of this invention is further configured so that when actuated, temperature sensor  274  provides a signal to main processor  298  representative temperature of the heat sink  264 . As represented by step  508  of  FIG. 25 , main processor  298  monitors the heat sink temperature, T H   _   S . As represented by step  510 , the main processor compares the heat sink temperature to a limit temperature, T H   _   S   _   LMT . 
     When charger  42  of this invention is required as part of a charging process or a state of health evaluation to discharge a battery  40 , the battery charge is discharged through one of the resistors  272 . The heat generated by this resistor is conductively transferred to heat sink  272 . Most of the time air flow into the charger housing through base openings  258  and housing vents  252  has sufficient thermal capacity to sink the heat radiated by heat sink  272 . This warmed air is discharged through housing vents  254 . During such time periods the heat sink temperatures stays below the heat sink limit temperature. 
     However, there may be times the air flow past the heat sink  264  cannot sink all the heat sourced by the heat sink  264 . This may occur if, due to unusual circumstances, the charger simultaneously discharges large amounts of current from plural batteries. If this event occurs, the measured rises heat sink temperature rises. If the heat sink temperature rises above the limit temperature, T H   _   S   _   LMT , there is a possibility that further temperature rise will result in the charger housing  52  being heated to a temperature that makes it unpleasant, or worse, to touch the charger  42 . The limit temperature, T H   _   S   _   LMT , it should be appreciated, is often determined by empirical analysis. 
     Therefore, if the comparison of step  510  indicates the heat sink temperature is above the limit temperature, main processor  298  executes a battery discharge interrupt sequence represented by step  510 . In this sequence, the charger interrupts the discharging of one or more attached batteries  40 . Thus, in step  510 , the discharge step  478  to which one or more of the batteries is presently being subjected may be interrupted. Similarly, if one of the batteries is being discharged as part of the normally charging sequence for that battery, that discharge step may likewise be interrupted. 
     Step  510  is executed until, as a result of a subsequent measurement of heat sink temperature, (step not shown) it is determined heat sink temperature has dropped below a restart temperature, T H   _   S   _   RSTRT , step  512 . Once the heat sink temperature is fallen to this level, additional thermal energy sourced by the discharged resistors  272  can be output without the likelihood of such heat placing the charger in an undesirable state. Therefore, once the heat sink temperature so drops, step  510  is terminated. 
     Battery  40  of this invention provides an indication if its cells may have been damaged. If the battery  40  may be in this state, charger  42  conducts a state of health evaluation on the battery. One immediate advantage of this invention is that, if the battery cells may have been damaged, a state of health evaluation is performed. This substantially reduces the possibility that someone will attempt to use a damaged battery to energize a surgical tool. 
     During the charging or discharging of the battery  40 , the temperature of cells  44  inevitably rises. In this invention, each cell has some surface area that is spaced free of the adjacent cells. This minimizes the uneven heat dissipation and consequential uneven temperature rises of the cells. The reduction of this temperature imbalance results in a like lessening of the extent to which the individual cells  44  can become electrically imbalanced. Reducing the electrical imbalance of the cells reduces the extent to which the cells being so imbalanced can adversely affect either the utility or useful lifetime of the battery. 
     Battery  40  of this invention is also designed so that the narrow section  119  of fuse  118  is spaced from the adjacent binders  108  and  110 . Section  119  is the section of the fuse  118  that vaporizes upon the flow of more than the selected amount of current flow through the fuse. Since fuse section  119  is not in physical contact with another section of the battery, no other section of the battery, such as the binders, serve as sinks for the heat generated by the current flow. Thus when the defined current flows through the fuse  118  the thermal energy generates in the vicinity of fuse section  119  stays in the section. This thermal energy therefore causes the fuse section  119  to rise to the level at which vaporization occurs. Thus, this design feature of the battery of this invention increases the likelihood that, when more than the defined current flows through the fuse, the fuse will open. 
     The charger  42  is further configured that it does not always perform the state of health evaluation, which can be time consuming to perform. Instead, the charger of this invention only performs this evaluation when the environmental history stored in the battery indicates it is desirable to perform the evaluation. By minimizing the number of times the charger performs state of health evaluations, the time it takes the charger to charge batteries is likewise held to a reasonable time period. 
     Still another feature of charger  42  is that the charger discharges batteries as part of a charging sequence or state of health evaluation yet it does not include a fan or other powered ventilation unit to exhaust air heated as a consequence of this discharging. The absence of fan in this charger reduces the noise generated by the charger when it is active. In the event there is an excessive generation of heat, further battery discharging is limited until the heat is dissipated. 
     Also battery  40  invention stores data regarding the environment to which the battery has been exposed. This information can be used to help evaluate why a battery underperforms and further provide feedback with regard to the charging and sterilization processes to which the battery is subjected. 
     Further, the laser welding assembly of the battery lid  60  to the underlying housing  66  eliminates the need to use fasteners to accomplish this attachment. Weld joint  221  formed by this process likewise eliminates the need to provide a separate seal to form an air-tight hermetic barrier between these components. 
     C. Tool Communication 
     As depicted by  FIG. 26 , in a system  520  of this invention, battery  40  is used to energize a cordless powered surgical tool  522 . The depicted tool  522  is a surgical sagittal saw. It should, of course, be recognized that the system of this invention is not limited to this type of tool or only tools with motors.  FIG. 27  is a block diagram of components of tool  522  relevant to system  520  of this invention. Tool  522  has a power generator  524 . The power generator  524  is the component internal tool  522  that actuates a surgical attachment  526 . In the depicted invention, the power generator  524  is a motor; surgical accessory  526  is a saw blade. A coupling assembly  528  removably holds the surgical attachment to the tool  522 . Integral with the attachment is identification component  530 , such as an RFID. An attachment reader  532 , part of tool  522  reads the data stored by the identification component  530 . 
     A power regulator  534  selectively applies the energy output by battery  40  to the power generator  524 . The power regulator  534  applies power to the power generator  524  based on instructions received from a control processor  536 . Control processor  536  generates instructions to the power regulator  534  in part based on the depression of control members integral with the tool; (control members not illustrated). Control processor  536  receives from the attachment reader  532  the data read from the attachment identification on component  530 . 
     Also internal the tool  522  is one or more sensors that monitor the operation of the tool. For simplicity only a single sensor a temperature sensor  538 , is illustrated. When tool  522  includes a motor as the power generating unit, temperature sensor  538  is often placed in close proximity to a bearing assembly integral with the motor. The output signal generated by temperature sensor  538  is applied to tool control processor  536 . 
     Tool  522  also has a data transceiver head  535 . Head  535 , which may be implemented in hardware or software, is designed to communicate with battery microcontroller  46 . In one version of the invention, data transceiver head  535  consists of a software executed by tool controller  536  to exchange signals with battery microcontroller  46  and a contact integral with the tool  522  designed to establish a conductive connection with battery contact  72 . 
     A more detailed description of the structure of a tool  522  integral with system  520  of this invention is found in the Applicants&#39; Assignee&#39;s previously referenced U.S. Patent Application No. 60/694,592, POWERED SURGICAL TOOL WITH SEALED CONTROL MODULE, the contents of which are incorporated herein by reference. 
     During the use of tool  522  and battery  40  of this invention, data regarding the use of the tool are stored in the battery memory  187 . More particularly, these data are stored in memory tool history file  229 .  FIG. 23  depicts in more detail types of data stored in the tool history file  229 . A first file internal to file  229  is a tool identification file  542 . File  542  contains data that identifies the tool  522  to which the battery  40  is attached. 
     Data regarding the total time the tool is run is contained in an overall run time odometer field  544 . Data indicating the times the power generator  524  is run above or below specific operating state(s) is stored in one or more operating mode run time odometer fields  546 . For example, if the tool power generator  524  is a motor, a first field  546  may store data indicating the overall time the motor is run at a particular speed. A second field  546  is used to store data indicating the overall time the motor is run under load. Tool control processor  536  makes a determination of whether or not the motor is run under load based on the current drawn by the motor. If the tool power generator  524  is a part of an ablation tool, an operating mode run time power generator field  546  stores data indicating the total time the tool is used to heat tissue to a particular temperature. 
     Tool history file  229  also contains a sensor output log file  548 . File  548  is used to store data based on the signals generated by the sensor associated with the tool. In some versions of the invention, the data stored in file  548  are signals representative of the actual parameter sensed by the sensor. For example, if one sensor is a temperature sensor, the data in file  548  can include data indicating the peak temperature detected by the sensor. Alternatively, file  548  includes flags that are set as a function of the tool or environmental states sensed by the sensor. Thus, system  520  of this invention is set so that if the sensor  538  detects a temperature above a threshold level, a flag indicating that the tool reached such a temperature is set. 
     Also internal to tool history file  229  is an attachment log file  550 . Accessory log file  550  contains data that identifies the specific attachment(s)  526  attached to the tool  520 . These data are based on the data collected by the tool attachment reader  532 . In some versions of the invention, each attachment file contains for each attachment, total run time odometer data, operating mode run time data and data based on the output from the sensors during use of the attachment. 
     A process by which data are loaded into and retrieved from the battery microcontroller memory  187  are now described by reference to  FIG. 29 . Step  560  is the coupling of the battery to the tool. As a result of this step, there is immediate current flow to the tool and the subsequent actuation of the tool control processor  536 , step  562 . As part of the initial actuation sequence, tool control processor  536  pulls the one-wire communication line internal to the battery low so as to cause battery microcontroller  46  to transition from the power down, clock off state to the normal state, step  564 . Tool control processor  536 , in a step  566 , then writes into battery microcontroller memory file  187  data identifying the tool. 
     Step  568  represents the actuation of the tool. At this time, tool control processor  536  engages in an initial collection of data regarding the operation of the tool, step  570 . Step  570  involves determining from the attachment reader  532  the identity of the specific attachment  526  coupled to the tool. The data obtained in step  570 , as part of the step, are stored in a RAM associated with the tool control processor  536  (RAM not shown). 
     As long as the tool continues to be actuated, tool control processor  536 , in a step  572  acquires and stores data regarding the tool actuation. These data, for example, include total run time odometer data and data indicating run time in one or more states, for example, speed level, running at load or operating at a particular temperature. These data are likewise stored in the microcontroller RAM. 
     In a step  574  the tool is deactuated. In an immediate next step  576 , tool control processor  536 , through data transceiver head  535 , updates the data log of the use of the tool in the battery microcontroller memory tool file  229 . Thus, after each individual actuation of the tool, the data recorded in the odometer logs fields  544  and  546  are updated. It should be appreciated that not all of the data may be updated. For example, if peak temperature is measured during the first actuation of the tool, the temperatures reached in any subsequent actuations are not recorded. 
     Once use of the tool  522  is completed, battery  40  is disconnected, step  578 . This results in battery one-wire communication line going high. This transition is detected by the interrupt circuit internal to the microcontroller  46 . This signal staying high for an extended period of time is interpreted by the microcontroller as indicating the battery has been disconnected from the tool  522 . Therefore, in a step  580 , the microcontroller returns the battery to the low power consuming, power down, clock off state. 
     As discussed above with respect to  FIG. 24A , once the battery is attached to the charger, in step  456 , the data in the battery microcontroller memory  187  are written out to the charger main processor  298 . As part of this process, the data in the tool history file are read out, step  582  of  FIG. 29 . 
     Returning to  FIG. 26 , it can be seen that the charger  42  is connected by a bus  586  to other components at the medical facility at which system  520  is installed. This connection is through charger transceiver head  301 . The transceiver head  301  is the sub-circuit internal to the charger that allows charger processor  298  to exchange data and instructions with other components connected to bus  586 . 
     The additional components connected to bus  586  include, for example, a personal computer  588 . Thus in a step  590 , the charger main processor  298  forwards the data in the battery memory tool history field  229  to another component on the attached network, for example the personal computer  588 . Bus  586  may even have a telecommunication head (not identified). The telecommunications exchanges signal passed over the bus with signals on an external network such as a PSTN or external network. 
     This arrangement provides a log of the use of the cordless surgical tool  522  of the system  520  available to persons charged with maintaining the tool. For example, the data in the tool history file may indicate the tool reached a particular operating temperature. The occurrence of this event is recognized as indication the tool may require maintenance. In this event, a message regarding tool state may be transferred by the external network to an off site repair facility. Upon receipt of this notice, the repair facility can schedule the repair or replacement of the tool prior to the tool becoming inoperable. The data retrieved from tool history file  229  may likewise be used to provide information for warranty purposes or to ensure that, if the tool is approaching the end of useful life time, the relevant individuals receive notice of this fact. 
     V. Alternative Embodiments 
     It should be appreciated that the foregoing description is directed to one specific version of the battery and related components of the system of this invention. Other versions of this invention may have alternative features, constructions and methods of execution. 
     Thus, there is no requirement that each of the above inventive features be found in all embodiments of the invention. 
     For example, in some versions of the invention, the battery may not be sealed from the ambient environment. In these and other versions of the invention, the sensor internal to the battery may be one that is used to determine the exposure to an environmental agent other than temperature that could adversely affect charge storage by the cells  44 . Thus, the sensor internal to the battery could detect humidity. If the sensor detects that the atmosphere within the battery is of relatively high humidity, data logging this event are stored in the battery memory. Another alternative sensor is an accelerometer. Such a device would record a rapid deceleration of the battery if it was dropped. Again, such an event would be logged in the battery memory. Then if the charger  42 , upon reading the stored data, recognizes that the battery was exposed to the unusual environment event, the charger would subject the batter to the complete state-of-health evaluation. 
     Alternatively, an accelerometer or other sensor may be employed to sense whether or not the battery is excessively vibrated. Data regarding the excessive vibration is likewise stored in the battery memory. 
     With regard to the above it should also be understood that occurrence of one of the above environmental events may be the trigger that causes the battery to transition from the power down mode to the normal mode. 
     Further it should be appreciated plural such environmental sensor may be fitted to the battery. 
     Similarly, alternative constructions that come within the scope of the invention are also possible. Thus, a battery may be provided with cells having less or more than the eight (8) cells illustrated in the version of the invention illustrated in  FIG. 6 . For example, to provide a battery with ten (10) cells that has the heat dissipating cell arrangement of this invention, plural middle rows of cells, each having no more than two (2) cells per row may be provided. Also outer rows of cells with fewer or more than the three (3) cells may be provided depending on the number of cells the array is to have. In some versions of the invention, arrays of cells may be stacked one on top of the other. 
     Similarly, there is no requirement that in all versions of the invention the laser welding be performed using a laser that emits photonic energy at 980 nanometers. For example, in some versions of the invention, the laser welding may be performed with a laser that emits coherent light energy at 808 nanometers. Again, this is just exemplary, not limiting. It should likewise be appreciated that other medical equipment, not just batteries, may be laser welded using the process of this invention. 
     In this vein, it is further understood that there is no requirement that in all versions of the invention, the top of the housing always function as the component that is seated in the base and heated by the photonic energy. In other versions of the invention, this relationship may be reversed. Clearly, the laser welding may be used to assemble other components forming the housing together. Thus, the method may be used to secure multiple panels together. 
     Likewise, there is no requirement that the geometries along which the components forming the battery housing meet have the disclosed geometry. In some versions of the invention, either neither or only one of the surfaces along which the weld seam is formed may have a tapered profile. 
     Similarly, in some versions of the invention, the battery may only contain a non-volatile memory. When the battery is attached to the tool, the tool writes data to the memory. Then, when the battery is attached to the charger the charger reads out the data written into the memory by the tool so the data can be forward to the appropriate destination. 
     Clearly, there is no requirement that all versions of the invention be constructed to energize and communicate with powered surgical tools. Thus, the battery of this invention can be used to energize power consuming devices other than surgical tools. The communications system of this invention can be used to obtain data from devices other than cordless surgical tools. 
     It should likewise be appreciated that the components and process steps of this description are only exemplary and not limiting. For example, in some versions of the invention, the multiple components internal to the battery may function as the memory in which data are stored and the device that writes to and reads data from the memory. Likewise, in some versions of the invention, tool control processor  536  may, during actuation, simultaneously log data into the battery memory. 
     Circuit variations are also possible. Thus, in some versions of this invention, the end of resistor  209  opposite the V TEMP   _   REF  junction may be tied to the output pin of voltage converter  182 . In these versions of this invention, the end of resistor  210  opposite V TEMP   _   REF  junction is tied to V SS  or the BATT-terminal. An advantage of this version of the invention is that it results in a V TEMP   _   REF  signal that does not vary with manufacturing differences in microcontroller  46 . 
     There is no requirement that all chargers of this invention be able to simultaneously charge plural batteries. There is no requirement a charger accept different modules so the charger is able to charger different types of batteries. 
     Also, it should be recognized that the power generator  524  need not always be a motor. The power generator may be a device that generates electrical energy, RF energy, ultrasonic energy, thermal energy or photonic energy. 
     Returning to  FIG. 12 , it can be seen that the battery may also be provided with a wireless transceiver  602 . This transceiver may be an RF or IR unit. In some versions of the invention, the transceiver may be a Bluetooth transceiver. When the battery is connected to the tool, transceiver  602  exchanges signals with a complementary transceiver  604  attached to bus  586 . Thus, this version of the invention allows real time communication between the cordless tool  522  and other operating room equipment through battery  40 . For example using this arrangement, a voice actuated control head  606  can be used to regulate tool actuation. Thus, a command entered through control head  606  is packetized and sent over bus  586  to transceiver  604 . Transceiver  604  broadcasts the command to battery transceiver  602 . The command is transferred from the battery transceiver to the battery microcontroller  46 . Microcontroller  46 , in turn, forwards the command through the tool transceiver head  535  to the tool processor  530 . Tool processor  530 , in turn, generates the appropriate commands to the power regulator  534  to cause desired actuation of the power generator  524 . 
     Similarly, a surgical navigation system  610  may likewise be connected to the tool through transceivers  602  and  604 . The surgical navigation system tracks the position of the tool  520  and attachment  526  relative to the surgical site to which the attachment is applied. If the navigation system determines that the attachment is being position at a location at which it should not be used, the attachment would generate a stop command. This command is transmitted through transceiver  604  to transceiver  602  and, from transceiver  602 , to the tool control processor  536 . Tool control processor  536 , upon receipt of the command, at least temporarily deactivates or slows operation of the tool  522 . 
     It should likewise be understood that the not all batteries of this invention may be designed to withstand the rigors of sterilization. Alternatively, the features of this invention may be incorporated into an aseptic battery pack. This type of battery pack includes a sterilizable housing that defines a void space for receiving a removable cell cluster. A sealable lid associated with the housing allows insertion and removal of the cell cluster. With this battery pack, prior to sterilization, the cell cluster is removed from the housing. Thus the cells of an aseptic battery pack are spared the rigors of autoclave sterilization. The Applicants&#39; Assignee&#39;s U.S. patent application Ser. No. 11/341,064, filed 27 Jan. 2006, ASEPTIC BATTERY WITH REMOVABLE CELL CLUSTER, now U.S. Pat. No. 7,705,559 B2, the contents of which are incorporated herein by reference, discloses one such aseptic battery pack. Still, the features of this invention may be built into the housing and or cell cluster of an aseptic battery pack. 
     Thus, it is an object of the appended claims to cover all such variations and modifications that come within the true spirit and scope of this invention.