Abstract:
One embodiment provides an electronic device (for example, a ruggedized laptop computer) which includes a housing, a battery compartment, and a battery cover. The cover can have a thickness sufficient to protect the battery from damage. The cover can include a body, a conductive heat transfer device (for instance a conductive pad), and a convective heat transfer device (for instance, a plurality of fins). The conductive device can be on the inside of the cover and can abut the battery. Together, the conductive heat transfer device, the body of the battery cover, and the convective heat transfer device can form a heat transfer path from the battery to the environment which has a low overall heat transfer coefficient. The convective device can be a plurality of fins recessed into the exterior of the cover. A gusset can be on the interior of the cover and can correspond with the recess.

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/967,421, entitled “System, Method and Apparatus for Battery Cooling and Protection” by Bruce, et al., filed on Sep. 4, 2007, which is hereby fully incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Embodiments of the disclosure relate generally to electronic devices and more particularly to cooling and protecting the batteries of portable electronic devices. 
     BACKGROUND 
     Portable electronic devices often include batteries to power the devices when power outlets may not be available, convenient, or functioning. As portable electronic devices have become more powerful (for example, by inclusion of more features), the batteries used in conjunction with them have tended to grow in capacity as measured by their ampere-hour ratings. Many users of these electronic devices prefer lithium-ion batteries because of their high storage capacity. Moreover, lithium-ion batteries can be re-charged, have high capacity-to-weight ratios, and retain their charges well when not powering the device. Thus, many users power their portable electronic devices (such as laptop computers, telecommunication equipment, entertainment devices, etc.) with lithium-ion batteries. 
     Batteries in general, and more particularly lithium-ion batteries, have certain disadvantages. For instance, some lithium-ion batteries tend to warm during operation due to Joule heating within the batteries. Joule heating arises from the battery generated current flowing through internal features of the battery which offer some resistance to the flow of that current. Joule heating increases in proportion to the square of the current. Thus, when large current draws occur on the battery, Joule heating can increase sharply thereby driving the battery temperature higher. As the temperature of some lithium-ion batteries increases, cells within the batteries can become unstable and begin internally discharging across their negative and positive terminals. This discharge can generate Joule heating and warm the battery further. In turn, the increasing temperature causes further instability, discharge, and (potentially) the loss of the battery. 
     Another disadvantage associated with using batteries to power portable electronic devices arises from various mechanical features of the batteries. More particularly, lithium-ion batteries typically include numerous cells each of which has a layer of carbon and a layer of lithium cobalt oxide separated by a separator. The carbon layer is typically connected to the negative terminal whereas the lithium cobalt layer is typically connected to the positive terminal of the cell. The separator is usually a sheet of insulating material. Should the case of a lithium-ion cell be punctured the separator can be damaged thereby creating an electrical “short” circuit between the electrodes. Short-circuited cells can discharge across their electrodes leading to rapid warming of the cell, possible loss of the cell, and warming of adjacent cells with an attendant possibility that these adjacent cells might also be lost. Yet, as more electronic devices become portable and require increasing amounts of power, the possibility that one or more cells might be subject to mechanical abuse increases. 
     In addition, high storage and operating temperatures can disadvantageously affect batteries too. For instance, battery life tends to decrease with increasing operating and storage temperatures. Indeed, lithium-ion batteries (some of which loose capacity with time regardless of their thermal environment) can lose capacity at an accelerated rate when stored or operated in warm environments. Yet, as more electronic devices become portable, their batteries are becoming increasingly exposed to wide thermal variations. 
     SUMMARY OF THE DESCRIPTION 
     Embodiments of the present disclosure provide systems, methods, and apparatus for cooling and protecting batteries in electronic devices that eliminate, or at least substantially reduce, the shortcomings of previously available systems, methods, and apparatus for cooling and protecting batteries in portable electronic devices. 
     One embodiment provides an electronic device which includes a housing, a battery compartment in the housing, a battery in the battery compartment; and a battery cover coupled to the housing. The battery cover can have an overall thickness (which, in some embodiments, can be about two millimeters) sufficient to protect the battery from mechanical damage. The battery cover can include a body, a conductive heat transfer device, and a convective heat transfer device. Together, the conductive heat transfer device, the body of the battery cover, and the convective heat transfer device can form a heat transfer path from the battery to the environment. In some embodiments, the battery cover can limit the temperature rise experienced by the battery (while the electronic device operates in a 60 degree Celsius environment) to no more than about 8 degrees Celsius and can withstand the mechanical forces, shocks, etc. associated with portable electronic device  100  being dropped from 36 inches on a non yielding surface and on any face, corner, etc. 
     In some embodiments, the conductive heat transfer device can be a conductive pad positioned on the internal surface of the battery cover and abutting the battery. The convective heat transfer device can include a plurality of fins recessed into the external surface of the battery cover. A gusset on the internal surface of the battery cover can be positioned to correspond with the recess on the external surface of the battery cover. A latch assembly can couple the battery cover to the housing. In some embodiments, the electronic device can be a ruggedized personal computer. 
     Battery covers of various embodiments provide both mechanical protection of, and thermal management for, batteries in electronic devices. Batteries in electronic devices of various embodiments can be charged to higher levels at higher charge rates than heretofore possible. Moreover, the charging of batteries of various batteries can occur in warmer environments than was previously possible. 
     These, and other, aspects will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. The following description, while indicating various embodiments and numerous specific details thereof, is given by way of illustration and not of limitation, Many substitutions, modifications, additions, or rearrangements may be made within the scope of the disclosure, and the disclosure includes all such substitutions, modifications, additions, or rearrangements. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       A more complete understanding of the disclosure and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers generally indicate like features. 
         FIG. 1  illustrates a perspective view of one embodiment of a portable electronic device. 
         FIG. 2  illustrates an exploded view of one embodiment of a battery cover. 
         FIG. 3  illustrates a perspective view of one embodiment of a battery cover. 
         FIG. 4  illustrates a cross-sectional view of one embodiment of a battery compartment. 
         FIG. 5  illustrates an exploded view of one embodiment of a latch assembly. 
         FIG. 6  illustrates a perspective view of an embodiment of a latch adaptor. 
         FIG. 7  illustrates a perspective view of an embodiment of a latch adaptor. 
         FIG. 8  illustrates a perspective view of one embodiment of a battery cover. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure are illustrated in the FIGURES, like numerals being generally used to refer to like and corresponding parts of the various drawings. Embodiments of the disclosure provide systems, methods, and apparatus for cooling and protecting batteries in portable electronic devices. 
     As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, article, or apparatus that comprises a list of elements is not necessarily limited only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead, these examples or illustrations are to be regarded as being described with respect to one particular embodiment and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized will encompass other embodiments which may or may not be given therewith or elsewhere in the specification and all such embodiments are intended to be included within the scope of that term or terms. Language designating such nonlimiting examples and illustrations includes, but is not limited to: “for example”, “for instance”, “e.g.”, “in one embodiment”. 
       FIG. 1  illustrates a perspective view of one embodiment of portable electronic device  100 . Portable electronic device  100  can be a laptop computer (e.g., such as a Dell Latitude™ D620 ruggedized laptop computer which are available from the Augmentix Corporation of Austin, Tex.), a piece of telecommunications equipment, an entertainment device, etc. Portable electronic device  100  can operate in, or be stored in, a wide variety of locations and environments. In some cases, portable electronic device  100  can operate in a nominal “shirt-sleeve” environment in which humidity, temperature, potential mechanical abuse, etc. are relatively controlled. In some cases, portable electronic device  100  can be subjected to less moderate environments in which ambient conditions can vary more widely. For instance, portable electronic device  100  can be taken outdoors where temperatures can vary between about minus 18 degrees Celsius (0 degrees Fahrenheit) and about 38 degrees Celsius (100 degrees Fahrenheit). In addition, being portable, portable electronic device  100  can be subjected to drops, collisions with blunt objects, collisions with more sharply pointed objects (i.e. potential penetrations of portable electronic device  100 ), etc. 
     Portable electronic device  100  can be used by consumers, industrial users, law enforcement members, members of the military, members of the Department of Homeland Security, etc. in a wide variety of locations and environments. Some conditions which portable electronic device  100  (and components thereof) can withstand include but are not limited to:
         Drop/Shock   36″ drops to non-yielding surfaces (while not operating) on all faces and corners.   Vibration   Operation under random vibration to, for example, simulate 1000 miles of transport.   Exaggerated Rain   4″ of rain per hour as simulated by 40 psi spraying water pressure at portable electronic device  100  along 6 axes.   Blowing Dust   Dust particles blowing at 8.7 m/s (19.5 mph) with ambient temperatures up to 140° F. (60° C.).   Dust Ingress   Ingress of dust.   Splashing Water   Water spraying at all angles at 10 liters/min at a gage pressure of 80-100 kN/m2 for 5 min.   Humidity   0%-95% non-condensing humidity.   Salt Fog Spray   5% saline solution for 48-hour cycles.   Crash Shock Test   40 g, 11 m/s: 75 g, 6 m/s, terminal saw tooth.   Altitude   15,000 feet, operational and non-operational.   Temperature Extremes (Operating/Non-Operating)   Operation in temperatures from −20° F. to 140° F., (−29° C. to 60° C.) and storage in temperatures from −60° F. to 160° F. (−51° C. to 71° C.).   Temperature Cycling   Temperature shock from −60° F. to 205° F. (−51° C. to 96° C.).       

     Thus, portable electronic device  100  can withstand a wide range of mechanical and thermal environmental conditions. More particular, battery covers of some embodiments can limit the temperature rise experienced by the battery (while the electronic device operates in a 60 degree Celsius environment) to no more than about 8 degrees Celsius and can withstand the mechanical forces, shocks, etc. associated with portable electronic device  100  being dropped from 36 inches on a non yielding surface and on any face, corner, etc. In addition, portable electronic device  100  can be configured to operate in hazardous locations such as those associated the National Electric Code, Class 1, Division 2, Groups A, B, C, and D among others. 
     With continuing reference to  FIG. 1 , portable electronic device  100  can include elements  102  such as displays, keyboards, pointing devices, etc. for user convenience and for use in operating portable electronic device  100 . Portable electronic device  100  can include overmolded bumpers  104  on housing  106  to protect portable electronic device  100  and portions thereof from mechanical forces, shocks, etc. Housing  106  can provide a frame on which various components of portable electronic device  100  can be mounted. Housing  106  can also provide compartments for various components, accessories, etc. of portable electronic device  100 . Portable electronic device  100  can also include various covers such as battery cover  108  to provide access to various components and compartments of portable electronic device  100 . 
       FIG. 2  illustrates portable electronic device  100  including battery cover  108 , conductive heat transfer device  110 , cover recess  112 , convective heat transfer devices  114 , channels  116 , latch assemblies  118 , latch recesses  120 , latch gussets  122 , external surface  124 , bosses  126 , and footrest  130 . Covers such as battery cover  108  can be included on portable electronic device  100  to close and seal various compartments, connectors, openings, etc. Battery cover  108  can serve to protect one or more batteries in housing  106  from mechanical forces, shocks, etc. and provide thermal management for such batteries. Battery cover  108  can also include one or more latch assemblies  118  to removably couple battery cover  108  to housing  106 . In some embodiments, battery cover  108  can be formed from die cast AZ91D magnesium. Moreover, battery cover  108  can weigh as little as 0.0836 kilograms (0.184 pounds) thereby minimizing its contribution to the overall weight of portable electronic device  100 . 
     Battery cover  108  and housing  106  can be configured so that battery cover  108  can withstand higher mechanical forces, shocks, etc. than housing  106  in some embodiments. Battery cover  108  can be strengthened to resist torsional forces which might be applied to battery cover  108  and/or housing  106 . For instance, latch gussets  122  can be shaped, dimensioned, positioned, etc. to resist torsional forces. The configuration, orientation, number, shape, dimensions, positions, etc. of convective heat transfer devices  114  can also be selected to resist torsional forces. In  FIG. 3 , convective heat transfer devices  114  are illustrated as being gussets orientated perpendicularly to the longitudinal axis of battery cover  108 . However, in some embodiments, convective heat transfer devices  114  can be oriented along the longitudinal axis of battery cover  108  or in some other direction. Thus, batteries internal to battery covers  108  can be protected from mechanical forces, shocks, etc. up to (and beyond,) some point at which housing  106  fails. 
     In some embodiments, as illustrated by  FIG. 2 , external surface  124  of battery cover  108  can define one or more areas for various purposes. For instance, cover recess  112  can define areas for convective heat transfer devices  114 . In some embodiments, latch assemblies  118  and associated structures such as latch recess  120  and latch gusset  122  can be included on battery cover  108 . In addition, external surface  124  can include one or more areas to which footrests  130  can be coupled. 
     With continuing reference to  FIG. 2 , latch assemblies  118  can be coupled to battery cover  108  at latch recess  120  and can removable couple battery cover  108  to housing  106  (see  FIG. 1 ). Latch assemblies  118  can extend through the body of battery cover  108  so that, on the internal side of battery cover  108 , latch assemblies  118  can engage corresponding features of housing  106  and, on the external side of battery cover  106 , users can actuate latch assemblies  118 . In engaging housing  106 , latch assemblies  118  can urge battery cover  108  toward bulkhead  141  thereby placing conductive pad  111  and battery  136  in compression against each other and the body of battery cover  108 . Latch gussets  122  can provide structural strength to battery cover  108  in the vicinity of latch recesses  120 . Latch assemblies  118  can be configured to lie within latch recesses  120  so that portable electronic device  100  can rest on various surfaces without interference from latch assemblies  118 . 
     In some embodiments, latch assemblies  118  can be butterfly latch assemblies as discussed with reference to  FIG. 5  although any type of latch, fastener, catch, hasp, clasp, clamp, detent, etc. can be used in lieu of latch assemblies  118 . In addition to latch assemblies  118 , battery cover  108  can include bosses  126  for aligning battery cover  108  with housing  106  and assisting latch assemblies  118  with securing battery cover  108  thereto. 
     Conductive heat transfer device  110  can be coupled to battery cover  108  as illustrated by  FIG. 2 . For instance, conductive heat transfer device  110  may be thermally bonded to battery cover  108  in a variety of manners including soldering, brazing, using a thermal adhesive, etc. Thus, the interface between conductive heat transfer devise  110  and the body of battery cover  108  can present relatively little resistance to conductive heat transfers between conductive heat transfer device  110  and the body of battery cover  108 . 
     Battery cover  108  can include one or more convective heat transfer devices  114  on its external surface  124 . Convective heat transfer devices  114  can be fins which convectively transfer heat from batteries of portable electronic device  100  to the environment. External surface  124  of battery cover  108  can define cover recess  112  in which convective heat transfer devices  114  can be positioned. Convective heat transfer devices  114  can be any type of convective heat transfer devices  114  such as fins, rods, cylinders, etc. which can increase the surface area of external surface  124  of battery cover  108 . With increased surface area due to convective heat transfer devices  114 , external surface  124  can transfer more heat to the environment than would otherwise occur. Cover recess  112  can maximize the portion of external surface  124  for convective heat transfer devices  114  while providing suitable portions for latch assemblies  118 . With convective heat transfer devices  114  in cover recess  112 , cover recess  112  can allow portable electronic device  100  to rest relatively flatly on surfaces such as desks, counters, dashboards, etc. 
     With reference now to  FIG. 3 , the body of battery cover  108 , latch assemblies  118 , latch gusset  122 , bosses  126 , internal surface  128  of battery cover  108 , cover gusset  132 , and gusset portions  134  are illustrated. Cover gusset  132  and gusset portions  134  can extend longitudinally along battery cover  108  and correspond in position, shape, and dimensions to cover recess  112  and channels  116  (see  FIG. 2 ). Latch gusset  122  can correspond in position, shape, and dimensions to latch recess  120 . Either alone, or in combination, latch gusset  122  and cover gusset  132  can reinforce battery cover  108  against torsion and other mechanical forces, shocks, etc. 
       FIG. 4  illustrates a cross-sectional view of one embodiment of battery compartment  139  of portable electronic device  100 .  FIG. 4  illustrates housing  106  of portable electronic device  100 , battery cover  108 , conductive heat transfer device  110 , cover recess  112 , convective heat transfer devices  114 , external surface  124 , internal surface  128 , battery  136 , battery compartment  139 , cell  140 , bulkhead  141 , battery connector  142 , battery package  143 , battery surface  144 , first pad surface  146 , second pad surface  148 , and gasket  150 . 
     Bulkhead  141  can be a portion of a larger component of portable electronic device  100 . In some embodiments, bulkhead  141  can form one or more internal panels of battery compartment  139 . Battery cover  108  can fit in a recess of housing  106  of portable electronic device  100  such that it covers battery compartment  139 . Battery cover  108  can form an external panel of battery compartment  139  and can (in conjunction with gasket  150  and bulkhead  141 ) seal battery compartment  139  against intrusion by water, dust, chemicals, etc. Cover gusset  132  can extend across battery  136  (and conductive pad  111 ) and, in some embodiments, gusset portion  134  can extend longitudinally from the cover gusset  132 . 
     The body of battery cover  108  can have a minimum thickness t 1  of about 2 millimeters which can correspond to the thickness of housing  106 , bulkhead  141 , and other structural components of portable electronic device  100 . By forming battery cover  108  and other structural components (e.g., housing  106  and bulkhead  141 ) from approximately the same material and at approximately the same thickness t 1 , cracking of various structural components (including battery cover  108 ) subject to mechanical forces, shocks, etc. can be minimized if not avoided. Structures of housing  106  such as bulkhead  141  can have thicknesses other than 2 millimeters without departing from the scope of the disclosure. Moreover, thickness t 1  can be selected to provide desired degrees of protection for battery  136  from mechanical forces, shocks, etc. Thus, battery cover  108  can protect battery  136  from damage including the possibility that some object(s) traveling relative to battery cover  108  might puncture battery cover  108  (and possibly batteries  136  housed behind battery cover  108 ). 
     With continuing reference to  FIG. 4 , battery  136  can be positioned within battery compartment  139  in abutting relationship with bulkhead  141 . Gaps can exist between certain internal panels of battery compartment  139  and battery  136 . For instance, gaps can exist between internal panels of battery compartment  139  and the longitudinal ends of battery  136 . Conductive pad  111  can rest on, and can pressed against, battery  136  by the body of battery cover  106  acting in cooperation with bulkhead  141  and latch assemblies  118 . Conductive pad  111  can correspond with battery  136  in shape, dimensions, position, etc. The body of battery cover  108  can extend longitudinally from the vicinity of battery  136 . Such longitudinal extensions of the body of battery cover  108  can, as discussed herein, provide surface area for convective heat transfer from portable electronic device  100  (and more particularly, batteries  136  therein). Longitudinal extensions of battery cover  108  can also provide area for additional convective heat transfer devices  114  beyond those in the general vicinity of battery  136 . 
     In some embodiments, battery  136  can include one or more cells  140  within battery package  143  or some other structure. Cells  140  can generate electric current for portable electronic device  100 . As a result, cells  140  can be prone to Joule heating. Convective heat transfer devices  114  can be positioned on battery cover  108  to correspond in position to cells  140  within battery  136 . Thus, in some embodiments, each particular cell  140  can have one or more particular convective heat transfer devices  114  positioned adjacent thereto and spaced apart there from by the wall of battery package  143 , conductive pad  111 , and the body of battery cover  108 . 
     In some embodiments, battery package  143 , conductive pad  111 , the body of battery cover  108 , and convective heat transfer devices  114  can form a heat transfer path between cells  140  and the environment of portable electronic device  100 . Thus, as heat flows from cells  140  to the environment, it flows through battery package  143  and encounters the interface between battery surface  144  and first pad surface  146 . As discussed herein, battery surface  144  of battery package  143  can be pressed against first pad surface  146  by the combined action of battery cover  108 , latch assemblies  118 , and bulkhead  141 . When conductive pad  111  is formed of a softer material than battery  136 , first pad surface  146  can conform to battery surface  144  even when certain levels of particulates, imperfections, irregularities, foreign objects, etc. might be present on, or between, surfaces  144  and  146 . Conductive pad  111  can be formed from Gap Pad® 2500S20 which is available from the Bergquist Co. of Chanhassen, Minn. or any conductive material softer than battery surface  144 . Thus, thermal contact resistance between surfaces  144  and  146  can be decreased thereby facilitating heat transfer between the two surfaces  144  and  146 . 
     Second pad surface  148  (which can be on the side of conductive pad  111  opposite first pad surface  146 ) can be thermally bonded to the body of battery cover  108  by soldering, brazing, thermal adhesive, etc. More particularly, conductive pad  111  can be bonded to internal surface  128  of battery cover  108  using TIC™ 4000 thermal interface compound which is available from the Bergquist Co. of Chanhassen, Minn. or any method of thermally bonding conductive pad  111  to internal surface  128  of batter cover  108 . Thus, thermal contact resistance between second pad surface  148  and internal surface  128  of battery cover  108  can be reduced, if not eliminated, thereby facilitating heat transfer between surfaces  128  and  148 . Being metallic (or some other thermally conductive material), the body of battery cover  108  can allow heat to flow from external surface  124  to convective heat transfer devices  114  and other portions of external surface  124 . Heat may transfer from convective heat transfer devices  114  (and other portions of external surface  124 ) to the environment by convection when fluid is present at convective heat transfer devices  114 . Heat may also transfer from convective heat transfer devices  114  by conduction when convective heat transfer devices  114  are in thermal contact with solid material (e.g., a countertop, desktop, dashboard, etc.) Thus, battery cover  108  can provide heat transfer paths from cells  140  (and battery  136 ) to corresponding convective heat transfer devices  114  as well as to other portions of external surface  124  of battery cover  108 . 
     With continuing reference to  FIG. 4 , and as discussed herein, operation of portable electronic device  100  can cause Joule heating in cells  140  and other components of battery  136  and portable electronic device  100 . More particularly, as portable electronic device  100  operates, electric current can be drawn form battery  136  via battery connector  142 . In such scenarios, cells  140  develop the electric current and allow the electric current to flow from cells  140  to battery connector  142  and thence to various components of portable electronic device  100 . In flowing from cells  140  to portable electronic device  100 , the electric current can encounter certain components offering electrical resistance thereto. For instance, internal structures, impurities, etc. in cells  140  may offer resistance to the electric current. Wires, conductive paths, contacts, etc. within battery  136  can also offer resistance to the flow of the current. As the electric current flows from battery  136 , battery connector  142  (and a corresponding connector on portable electronic device  100 ) can also offer resistance to the electric current. 
     At each location where some component offers resistance to the electric current, Joule heating can occur. Joule heating can arise from energy losses as the electric current overcomes that resistance. Joule heating varies with both the value of the resistance (typically measured in ohms) and with the square of the current (typically measured in amperes). Thus, while Joule heating can occur when portable electronic device  100  is relatively quiescent, Joule heating can be markedly increased during peak loads imposed on battery  136  by portable electronic device  100 . In addition, components of portable electronic device  100  on the side of bulkhead  141  opposite from battery  136  can be subject to Joule heating also. Thus, heat can flow from the side of bulkhead  141  to battery  136 . In some embodiments, though, bulkhead  141  can be configured to thermally isolate battery  136  from other heat producing components of portable electronic device  100 . 
     Nonetheless, because of Joule heating within battery compartment  139  (including Joule heating within battery  136 ), battery  136  can be subject to temperature increases as portable electronic device  100  operates. Furthermore, portable electronic device  100  can be carried into, or stored in, locations with relatively warm thermal environments. In some situations, the thermal environment of portable electronic device  100  can be as warm as 60 degrees Celsius. In these situations, it can be desirable to limit the temperature experienced by battery  136  to 68 degrees Celsius despite Joule heating, heat transferred from other components of portable electronic device  100 , and the potentially warm thermal environment of portable electronic device  100 . 
     In operation, heat from battery  136  can flow from battery  136  to conductive heat transfer device  110 . More particularly, heat may flow from battery  136  to first pad surface  146 , through conductive pad  111 , and to second pad surface  148 . From second pad surface  148 , heat from battery  136  can flow from conductive pad  111  to battery cover  108 . Heat entering battery cover  108  from conductive heat transfer device  110  can flow through battery cover  108  to convective heat transfer devices  114 . From convective heat transfer devices  114 , heat can flow to the environment by convection (when fluids such as air are present) or by conduction when convective heat transfer devices  114  are in contact with solids, or a combination thereof. Heat may also flow longitudinally from portions of battery cover  108  in the vicinity of battery  136  to portions of battery cover  108  (and convective heat transfer devices  114 ) which are longitudinally spaced apart from battery  136  for transfer to the environment. 
     Thus, battery cover  108  can allow heat to flow from battery  136  to the environment. In some embodiments, battery  136 , conductive heat transfer device  110 , battery cover  108 , and convective heat transfer devices  114  can be selected and assembled so that the heat transfer path described above can have a relatively high overall heat transfer coefficient. 
       FIG. 5  illustrates one embodiment of latch assembly  118 . Latch assemblies  118  can be configured to releasably couple battery cover  108  to housing  106  of portable electronic device  100 . In some embodiments, portable electronic device  100  can include various numbers of latch assemblies  118  including 2 and 4 latch assemblies  118 . Latch assemblies can be shaped and dimensioned to withstand mechanical forces, shocks, etc. such as those generated when portable electronic device  100  (which can weight about 10 pounds) when portable electronic device  100  is dropped on a non yielding surface from about 36 inches. 
     Latch assembly  118  can include toggle  160 , adaptor  162 , gasket  164 , cam  166 , fastener  168 , pin  170 , and latch  172 . Adaptor  162  can extend through an aperture in body cover  108  to align with one or more bosses on toggle  160  such that toggle  160  and adaptor  162  can receive pin  170  generally adjacent to external surface  124  of battery cover  108  (when latch assembly  118  is installed thereon). Fastener  168  can couple cam  166  to adaptor  162  and compress gasket  164  there between thereby sealing the aperture in battery cover  108  through which latch assembly  118  can extend. Cam  166  can be rotated, via toggle  160  and adaptor  162 , between a closed position and an opened position. Cam  166 , in the closed position, can engage corresponding features in bulkhead  142  to couple battery cover  108  to housing  106  through bulkhead  142 . Cam  166  (and the corresponding feature on bulkhead  142 ) can be shaped and dimensioned to urge battery cover  108  toward bulkhead  141  in the closed position. In the opened position, cam  166  can be disengaged from housing  106 , thereby releasing battery cover  108  from housing  106 . Latch assembly  118  can be configured to withstand mechanical forces, shocks, etc. applied to battery cover  108  (or itself). Thus, latch assembly  118  can releasably couple battery cover  108  to housing  106  of portable electronic device  100  even in the presence of various mechanical forces, shocks, etc. 
     With continuing reference to  FIG. 5 , in some embodiments, toggle  160  can be made of PC+ABS GE C7410 (Grade UL 94V-0) plastic, CRCA, nylon, 304 stainless steel, etc. In one embodiment, toggle  160  (made of nylon) can be shaped and dimension to withstand torque up to about 1.796 pound-inches (and a force of about 2.664 pounds applied to develop the torque) when cam  166  is closed (or fully open) and unable to move in response to torque applied to toggle  160 . 
     With reference now to  FIG. 6  one embodiment of adaptor  162  of latch assembly  118  is illustrated. Adaptor  162  can include boss  174  for receiving pin  170 . Boss  174  can be shaped and dimensioned to withstand mechanical forces, shocks, etc. that might be applied directly to it, or transmitted to it by pin  170  and toggle  160 . More particularly, filets  176  can be shaped and dimensioned to withstand forces applied thereto. With reference to  FIG. 7 , adaptor  162  can also include posts  178  on the side of adaptor  162  opposite boss  174 . Posts  178  can space adaptor  162  apart from the external surface of latch recess  120  so that gasket  164  can be compressed by an appropriate amount to seal latch assembly  118  and battery cover  108 . Posts  178  can also slidably engage the external surface of latch recess  120  so that users can turn toggle  160  thereby moving latch assembly  118  between its open and closed positions. Posts  178  can be shaped and dimensioned to withstand mechanical forces, shocks, etc. applied to or transmitted to thereto. More particularly, adaptor  162  can be made from magnesium and can be shaped and dimensioned to withstand torque (transmitted thereto by pin  170  at boss  174 ) up to about 6.75 pound-inches. 
     Cams  166  can be shaped and dimensioned to withstand various mechanical forces, shocks, etc. transmitted thereto. Cams  166  can be made from various stainless steels, corrosion resistant steels, etc. For instance, in one embodiment, portable electronic device  100  can include 4 latch assemblies  118  and can weigh about 10 pounds. Cams  166  of the four latch assemblies of the current embodiment can absorb mechanical forces, shocks etc. developed when portable electronic device  100  is dropped on a non yielding surface from about 36 inches. In some embodiments, cams  166  can be about 1.5 mm to about 1.9 mm thick. 
       FIG. 8  illustrates a perspective view of one embodiment of battery cover  108  with battery  136  removably coupled thereto by brackets  138 . Battery  136  can be secured to battery cover  108  with devices other than brackets  138  such as straps, hooks, detents, bayonet connectors, etc. Conductive heat transfer device  110  can be positioned between the body of battery cover  108  and battery  136  in some embodiments. Thus, brackets  138  can hold battery  136  against conductive heat transfer device  110  thereby compressing conductive heat transfer device  110 ; conforming it to battery surface  144 ; and lowering thermal contact resistance between battery  136  and conductive heat transfer device  110 . Battery cover  108 , with battery  136  coupled thereto by brackets  138 , can be coupled to housing  106  with battery  136  positioned in battery compartment  139 . Portions of brackets  138  passing between battery  136  and bulkhead  141  (see  FIG. 4 ) can create a gap between battery  136  and bulkhead  141  thereby increasing thermal isolation between battery  136  and other heat producing components of portable electric device  100 . 
     Embodiments disclosed herein can both protect batteries from damage and provide enhanced heat transfer there from. Embodiments of battery covers can extend the lives of batteries housed in battery compartments covered by such battery covers. Batteries, when housed in battery compartments disclosed herein, can have greater life and faster recharge capabilities than heretofore possible. Embodiments of portable electronic devices disclosed herein can be operated, and stored, in warmer environments than heretofore possible. 
     Although embodiments have been described in detail herein, it should be understood that the description is by way of example only and is not to be construed in a limiting sense. It is to be further understood, therefore, that numerous changes in the details of the embodiments and additional embodiments will be apparent, and may be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within scope of the claims below and their legal equivalents.